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Sample records for sound antarctica local

  1. Sounding rockets in Antarctica

    NASA Technical Reports Server (NTRS)

    Alford, G. C.; Cooper, G. W.; Peterson, N. E.

    1982-01-01

    Sounding rockets are versatile tools for scientists studying the atmospheric region which is located above balloon altitudes but below orbital satellite altitudes. Three NASA Nike-Tomahawk sounding rockets were launched from Siple Station in Antarctica in an upper atmosphere physics experiment in the austral summer of 1980-81. The 110 kg payloads were carried to 200 km apogee altitudes in a coordinated project with Arcas rocket payloads and instrumented balloons. This Siple Station Expedition demonstrated the feasibility of launching large, near 1,000 kg, rocket systems from research stations in Antarctica. The remoteness of research stations in Antarctica and the severe environment are major considerations in planning rocket launching expeditions.

  2. Monaural Sound Localization Revisited

    NASA Technical Reports Server (NTRS)

    Wightman, Frederic L.; Kistler, Doris J.

    1997-01-01

    Research reported during the past few decades has revealed the importance for human sound localization of the so-called 'monaural spectral cues.' These cues are the result of the direction-dependent filtering of incoming sound waves accomplished by the pinnae. One point of view about how these cues are extracted places great emphasis on the spectrum of the received sound at each ear individually. This leads to the suggestion that an effective way of studying the influence of these cues is to measure the ability of listeners to localize sounds when one of their ears is plugged. Numerous studies have appeared using this monaural localization paradigm. Three experiments are described here which are intended to clarify the results of the previous monaural localization studies and provide new data on how monaural spectral cues might be processed. Virtual sound sources are used in the experiments in order to manipulate and control the stimuli independently at the two ears. Two of the experiments deal with the consequences of the incomplete monauralization that may have contaminated previous work. The results suggest that even very low sound levels in the occluded ear provide access to interaural localization cues. The presence of these cues complicates the interpretation of the results of nominally monaural localization studies. The third experiment concerns the role of prior knowledge of the source spectrum, which is required if monaural cues are to be useful. The results of this last experiment demonstrate that extraction of monaural spectral cues can be severely disrupted by trial-to-trial fluctuations in the source spectrum. The general conclusion of the experiments is that, while monaural spectral cues are important, the monaural localization paradigm may not be the most appropriate way to study their role.

  3. Active localization of virtual sounds

    NASA Astrophysics Data System (ADS)

    Loomis, Jack M.; Hebert, C.; Cicinelli, J. G.

    1991-06-01

    We describe a virtual sound display built around a 12 MHz 80286 microcomputer and special purpose analog hardware. The display implements most of the primary cues for sound localization in the ear-level plane. Static information about direction is conveyed by interaural time differences and, for frequencies above 1800 Hz, by head sound shadow (interaural intensity differences) and pinna sound shadow. Static information about distance is conveyed by variation in sound pressure (first power law) for all frequencies, by additional attenuation in the higher frequencies (simulating atmospheric absorption), and by the proportion of direct to reverberant sound. When the user actively locomotes, the changing angular position of the source occasioned by head rotations provides further information about direction and the changing angular velocity produced by head translations (motion parallax) provides further information about distance. Judging both from informal observations by users and from objective data obtained in an experiment on homing to virtual and real sounds, we conclude that simple displays such as this are effective in creating the perception of external sounds to which subjects can home with accuracy and ease.

  4. Active localization of virtual sounds

    NASA Technical Reports Server (NTRS)

    Loomis, Jack M.; Hebert, C.; Cicinelli, J. G.

    1991-01-01

    We describe a virtual sound display built around a 12 MHz 80286 microcomputer and special purpose analog hardware. The display implements most of the primary cues for sound localization in the ear-level plane. Static information about direction is conveyed by interaural time differences and, for frequencies above 1800 Hz, by head sound shadow (interaural intensity differences) and pinna sound shadow. Static information about distance is conveyed by variation in sound pressure (first power law) for all frequencies, by additional attenuation in the higher frequencies (simulating atmospheric absorption), and by the proportion of direct to reverberant sound. When the user actively locomotes, the changing angular position of the source occasioned by head rotations provides further information about direction and the changing angular velocity produced by head translations (motion parallax) provides further information about distance. Judging both from informal observations by users and from objective data obtained in an experiment on homing to virtual and real sounds, we conclude that simple displays such as this are effective in creating the perception of external sounds to which subjects can home with accuracy and ease.

  5. Sound localization in the alligator.

    PubMed

    Bierman, Hilary S; Carr, Catherine E

    2015-11-01

    In early tetrapods, it is assumed that the tympana were acoustically coupled through the pharynx and therefore inherently directional, acting as pressure difference receivers. The later closure of the middle ear cavity in turtles, archosaurs, and mammals is a derived condition, and would have changed the ear by decoupling the tympana. Isolation of the middle ears would then have led to selection for structural and neural strategies to compute sound source localization in both archosaurs and mammalian ancestors. In the archosaurs (birds and crocodilians) the presence of air spaces in the skull provided connections between the ears that have been exploited to improve directional hearing, while neural circuits mediating sound localization are well developed. In this review, we will focus primarily on directional hearing in crocodilians, where vocalization and sound localization are thought to be ecologically important, and indicate important issues still awaiting resolution. PMID:26048335

  6. Sound localization by echolocating bats

    NASA Astrophysics Data System (ADS)

    Aytekin, Murat

    Echolocating bats emit ultrasonic vocalizations and listen to echoes reflected back from objects in the path of the sound beam to build a spatial representation of their surroundings. Important to understanding the representation of space through echolocation are detailed studies of the cues used for localization, the sonar emission patterns and how this information is assembled. This thesis includes three studies, one on the directional properties of the sonar receiver, one on the directional properties of the sonar transmitter, and a model that demonstrates the role of action in building a representation of auditory space. The general importance of this work to a broader understanding of spatial localization is discussed. Investigations of the directional properties of the sonar receiver reveal that interaural level difference and monaural spectral notch cues are both dependent on sound source azimuth and elevation. This redundancy allows flexibility that an echolocating bat may need when coping with complex computational demands for sound localization. Using a novel method to measure bat sonar emission patterns from freely behaving bats, I show that the sonar beam shape varies between vocalizations. Consequently, the auditory system of a bat may need to adapt its computations to accurately localize objects using changing acoustic inputs. Extra-auditory signals that carry information about pinna position and beam shape are required for auditory localization of sound sources. The auditory system must learn associations between extra-auditory signals and acoustic spatial cues. Furthermore, the auditory system must adapt to changes in acoustic input that occur with changes in pinna position and vocalization parameters. These demands on the nervous system suggest that sound localization is achieved through the interaction of behavioral control and acoustic inputs. A sensorimotor model demonstrates how an organism can learn space through auditory-motor contingencies

  7. Mezozooplankton Beneath the Summer Sea Ice in McMurdo Sound, Antarctica: Abundance, Species Composition, and DMSP content

    EPA Science Inventory

    The Ross Sea Phaeocystis antarctica bloom contributes to a summer increase in under-ice planton biomass in McMurdo Sound, Antarctica. Due to difficulties of under-ice sampling, information on the mesozooplankton in McMurdo Sound is limited. We measured the abundance of mesooopl...

  8. Material sound source localization through headphones

    NASA Astrophysics Data System (ADS)

    Dunai, Larisa; Peris-Fajarnes, Guillermo; Lengua, Ismael Lengua; Montaña, Ignacio Tortajada

    2012-09-01

    In the present paper a study of sound localization is carried out, considering two different sounds emitted from different hit materials (wood and bongo) as well as a Delta sound. The motivation of this research is to study how humans localize sounds coming from different materials, with the purpose of a future implementation of the acoustic sounds with better localization features in navigation aid systems or training audio-games suited for blind people. Wood and bongo sounds are recorded after hitting two objects made of these materials. Afterwards, they are analysed and processed. On the other hand, the Delta sound (click) is generated by using the Adobe Audition software, considering a frequency of 44.1 kHz. All sounds are analysed and convolved with previously measured non-individual Head-Related Transfer Functions both for an anechoic environment and for an environment with reverberation. The First Choice method is used in this experiment. Subjects are asked to localize the source position of the sound listened through the headphones, by using a graphic user interface. The analyses of the recorded data reveal that no significant differences are obtained either when considering the nature of the sounds (wood, bongo, Delta) or their environmental context (with or without reverberation). The localization accuracies for the anechoic sounds are: wood 90.19%, bongo 92.96% and Delta sound 89.59%, whereas for the sounds with reverberation the results are: wood 90.59%, bongo 92.63% and Delta sound 90.91%. According to these data, we can conclude that even when considering the reverberation effect, the localization accuracy does not significantly increase.

  9. An Isotopic Map of Dust Source Areas in the McMurdo Sound Sector of Antarctica

    NASA Astrophysics Data System (ADS)

    Blakowski, M. A.; Aciego, S.; Delmonte, B.; Baroni, C.; Salvatore, M. C.

    2014-12-01

    The McMurdo Sound sector of Antarctica features a unique, polar desert ecosystem characterized by low temperatures, hyper-aridity, and high-speed winds. These climatic conditions result in limited water sources, sparse vegetation, underdeveloped soils, and abundant unconsolidated sediment easily influenced by wind-driven transport. Radiogenic isotopes (87Sr/86Sr, 143Nd/144Nd) provide constant signatures of dust from source- to sink-areas. Accordingly, aeolian dust derived from arid regions has been recognized in many studies as an important tracer of atmospheric circulation, as well as a tool for deciphering past climatic conditions in dust source regions. However, while major global dust sources (e.g. from South America, Africa, and Asia) are well studied and easily identifiable via distinct isotopic signatures when encountered in different depositional environments (e.g. Antarctic ice cores), local material from sources in and around the ice-free Dry Valleys and surrounding areas have remained in need of further documentation. We analyzed 40 samples of silt, sand, glacial drift, and weathered regolith material in both fine (<5μm) and coarse fractions collected from Victoria Land and the McMurdo Sound sector, including Cape Royds, Cape Bird, and the McMurdo Ice Shelf. Here we present an ArcGIS-generated, high-precision geochemical map of Antarctic PSAs synthesized from our data and combined with geomorphological and stratigraphic information on the studied sites. We believe that our expanded isotopic catalogue and map can be used to enhance and/or prompt regional studies in a variety of disciplines, such as by providing greater constraints on models of regional dust variability and transport pathways and of the melting history of the Antarctic ice sheet, and by determining the provenance of dust archived in ice cores, lake sediment, soil records, and impurities in Antarctic sea-ice.

  10. Hearing in three dimensions: Sound localization

    NASA Technical Reports Server (NTRS)

    Wightman, Frederic L.; Kistler, Doris J.

    1990-01-01

    The ability to localize a source of sound in space is a fundamental component of the three dimensional character of the sound of audio. For over a century scientists have been trying to understand the physical and psychological processes and physiological mechanisms that subserve sound localization. This research has shown that important information about sound source position is provided by interaural differences in time of arrival, interaural differences in intensity and direction-dependent filtering provided by the pinnae. Progress has been slow, primarily because experiments on localization are technically demanding. Control of stimulus parameters and quantification of the subjective experience are quite difficult problems. Recent advances, such as the ability to simulate a three dimensional sound field over headphones, seem to offer potential for rapid progress. Research using the new techniques has already produced new information. It now seems that interaural time differences are a much more salient and dominant localization cue than previously believed.

  11. Influence of sound source width on human sound localization.

    PubMed

    Greene, Nathaniel T; Paige, Gary D

    2012-01-01

    Free-field sound localization experiments generally assume that a loudspeaker can be approximated by a point-source; however, a large loudspeaker may extend beyond the width that two sources can be discriminated. Humans can accurately discriminate sound source locations within a few degrees, thus one might expect localization precision to decrease as a function of sound source diameter, much as precision is lower for localizing the center of a wide, blurry light source. In order to test the degree to which humans differentially localize small and large sound sources, auditory targets were presented using a single 25.4 cm by 10.2 cm elliptical loudspeaker with the primary axis oriented both horizontally and vertically in different sessions. Subjects were seated with their heads fixed by a bite bar in a darkened, echo-attenuating room facing a cylindrical, acoustically transparent screen at a distance of 2 meters. Auditory targets consisted of repeating bursts (5 Hz) of low frequency band-pass noise (0.2 - 1 kHz, 75 dB SPL). Subjects were instructed to quickly and accurately guide a laser pointer mounted on a cylindrical joystick towards targets, presented randomly within a field ± 40° in azimuth by ± 10° in elevation, with oversampled points located every ten degrees along the primary meridians. Localization accuracy and precision (mean and standard deviation of localization error at oversampled locations) were not significantly different between speaker orientations, and were comparable to baseline measurements recorded using a 7.6 cm circular speaker. We conclude that low frequency sound localization performance is not dependent upon the size of the sound source as predicted theoretically, and is well approximated by a point source. PMID:23367407

  12. The upper lithostratigraphic unit of ANDRILL AND-2A core (Southern McMurdo Sound, Antarctica): Local Pleistocene volcanic sources, paleoenvironmental implications and subsidence in the southern Victoria Land Basin

    NASA Astrophysics Data System (ADS)

    Del Carlo, P.; Panter, K. S.; Bassett, K.; Bracciali, L.; Di Vincenzo, G.; Rocchi, S.

    2009-11-01

    We report results from the study of the uppermost 37 m of the Southern McMurdo Sound (SMS) AND-2A drill core, corresponding to the lithostratigraphic unit 1 (LSU 1), the most volcanogenic unit within the core. We present data on the age, composition, volcanological and depositional features of the volcanic sedimentary and tephra deposits of LSU 1 and discuss their source, mechanisms of emplacement and environment of deposition. Sedimentary features and compositional data indicate shallow water sedimentation for the whole of LSU 1. Most of LSU 1 deposits are a mixture of near primary volcanic material with minor exotic clasts derived from the Paleozoic crystalline basement rocks. Among volcanic materials, glassy particles are the most abundant. They were produced by mildly explosive basaltic eruptions occurring in subaerial and subaqueous environments. The Dailey Islands group, 13 km south-southwest of the SMS drill-site, has been identified as a possible source for the volcanics on the basis of similarity in composition and age. 40Ar- 39Ar laser step-heating analyses on a lava sample from Juergens Island yields an age of 775 ± 22 ka. Yet because of the minimal reworking features of vitriclasts, preservation of fragile structures in volcaniclastic sediments and evidence for volcanic seamounts to the north of the Dailey Islands, it is likely that some of the material originated also from vents close to the drill-site. Evidence for local volcanic sources and for deposition of sediments in a shallow marine environment provides indications about the local paleogeography and implications for the subsidence history of the southern Victoria Land Basin from Pleistocene to Recent.

  13. Judging sound rotation when listeners and sounds rotate: Sound source localization is a multisystem process.

    PubMed

    Yost, William A; Zhong, Xuan; Najam, Anbar

    2015-11-01

    In four experiments listeners were rotated or were stationary. Sounds came from a stationary loudspeaker or rotated from loudspeaker to loudspeaker around an azimuth array. When either sounds or listeners rotate the auditory cues used for sound source localization change, but in the everyday world listeners perceive sound rotation only when sounds rotate not when listeners rotate. In the everyday world sound source locations are referenced to positions in the environment (a world-centric reference system). The auditory cues for sound source location indicate locations relative to the head (a head-centric reference system), not locations relative to the world. This paper deals with a general hypothesis that the world-centric location of sound sources requires the auditory system to have information about auditory cues used for sound source location and cues about head position. The use of visual and vestibular information in determining rotating head position in sound rotation perception was investigated. The experiments show that sound rotation perception when sources and listeners rotate was based on acoustic, visual, and, perhaps, vestibular information. The findings are consistent with the general hypotheses and suggest that sound source localization is not based just on acoustics. It is a multisystem process. PMID:26627802

  14. Antarctica

    Atmospheric Science Data Center

    2013-04-16

    ... Twilight in Antarctica, February 24, 2000 . Nearly 15 times every 24 hours, the Terra spacecraft, traveling southward, crosses from ... D.C. The Terra spacecraft is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. The MISR data were obtained from the NASA Langley ...

  15. The upper lithostratigraphic unit of ANDRILL AND-2A core (Southern McMurdo Sound, Antarctica): local Pleistocene volcanic sources, paleoenvironmental implications and subsidence in the southern Victoria Land Basin

    NASA Astrophysics Data System (ADS)

    Del Carlo, P.; Panter, K. S.; Bassett, K. N.; Bracciali, L.; di Vincenzo, G.; Rocchi, S.

    2009-12-01

    We report results from the study of the uppermost 37 meters of the Southern McMurdo Sound (SMS) AND-2A drillcore, corresponding to the lithostratigraphic unit 1 (LSU 1), the most volcanogenic unit within the core. Nearly all of LSU 1 consists of volcanic breccia and sandstone that is a mixture of near primary volcanic material dominated by lava and vitric clasts with minor exotic material derived from distal basement sources. Lava clasts and glass are mafic and range from strongly alkaline (basanite, tephrite) to moderately alkaline (alkali basalt, hawaiite) compositions that are similar to nearby land deposits. 40Ar-39Ar laser step-heating analyses on groundmass separated from lava clasts yield Pleistocene ages (692±38 and 793±63, ±2σ internal errors). Volcanoes of the Dailey Island group, located ~13 km SW of the drillsite, are a possible source for the volcanic materials based on their close proximity, similar composition and age. A basanite lava flow on Juergens Island yields a comparable Pleistocene age of 775±22 ka. Yet there is evidence to suggest that the volcanic source is much closer to the drillsite and that the sediments were deposited in much shallower water relative to the present-day water depth of 384 mbsl. Evidence for local volcanic activity is based in part on the common occurrence of delicate vitriclasts (e.g. glass shards and Pele’s hair) and a minimally reworked ~2 meter thick monomict breccia that is interpreted to have formed by autobrecciating lava. In addition, conical-shaped seamounts and high frequency magnetic anomalies encompass the drillsite and extend south including the volcanoes of the Dailey Islands. Sedimentary features and structures indicate shallow water sedimentation for the whole of LSU 1. Rippled asymmetric cross-laminated sands and hummocky cross-stratification occur intermittently throughout LSU 1 and indicate water depths shallower than 100 meters. The occurrence of ooliths and layers containing siderite and Fe

  16. A probabilistic model for binaural sound localization.

    PubMed

    Willert, Volker; Eggert, Julian; Adamy, Jürgen; Stahl, Raphael; Körner, Edgar

    2006-10-01

    This paper proposes a biologically inspired and technically implemented sound localization system to robustly estimate the position of a sound source in the frontal azimuthal half-plane. For localization, binaural cues are extracted using cochleagrams generated by a cochlear model that serve as input to the system. The basic idea of the model is to separately measure interaural time differences and interaural level differences for a number of frequencies and process these measurements as a whole. This leads to two-dimensional frequency versus time-delay representations of binaural cues, so-called activity maps. A probabilistic evaluation is presented to estimate the position of a sound source over time based on these activity maps. Learned reference maps for different azimuthal positions are integrated into the computation to gain time-dependent discrete conditional probabilities. At every timestep these probabilities are combined over frequencies and binaural cues to estimate the sound source position. In addition, they are propagated over time to improve position estimation. This leads to a system that is able to localize audible signals, for example human speech signals, even in reverberating environments. PMID:17036807

  17. Marine record of Holocene climate, ocean, and cryosphere interactions: Herbert Sound, James Ross Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Minzoni, Rebecca Totten; Anderson, John B.; Fernandez, Rodrigo; Wellner, Julia Smith

    2015-12-01

    The sediment record offshore James Ross Island, northeast Antarctic Peninsula presents an unparalleled opportunity to directly compare marine and terrestrial climate records spanning the Holocene in maritime Antarctica. An 11 m drill core was collected between Herbert Sound and Croft Bay as part of the SHALDRIL NBP-0502 initiative and produced the southernmost sediment record from the eastern side of the AP. Thirty-eight radiocarbon ages are used to construct an age model of centennial-scale resolution. Multi-proxy records, including magnetic susceptibility, pebble content, particle size, total organic carbon, and diatom assemblages, were interrogated in the context of nearby Holocene-age ice core, lake, and drift records from James Ross Island. Differences in the timing and expression of Holocene events reflect marine controls on tidewater glaciers, such as water mass configurations and sea ice. Glacial behavior mimics ice core paleotemperatures during the Holocene, with the exception of distinct ocean warming events. Herbert Sound was fully occupied by grounded ice during the Last Glacial Maximum, and experienced rapid lift-off, followed by a floating ice phase. The canopy of floating ice receded by 10 ± 2.4 cal kyr BP, presumably in response to Early Holocene warming. Herbert Sound and Croft Bay fully deglaciated by 7.2 cal kyr BP, when the Mid Holocene Hypsithermal commenced and the sound became open and productive. An extreme peak in productivity ˜6.1 cal kyr BP indicates an oceanic warming event that is not reflected in atmospheric temperature or lacustrine sediment records. Increase in sea ice cover and ice rafting mark the onset of the Neoglacial ˜2.5 cal kyr BP, when pronounced atmospheric cooling is documented in the James Ross Island ice core. Our comparison facilitates more holistic understanding of atmosphere-ocean-cryosphere interactions that may aid predictions of glacial response to future warming and sea-level scenarios.

  18. Sound Localization Strategies in Three Predators.

    PubMed

    Carr, Catherine E; Christensen-Dalsgaard, Jakob

    2015-09-01

    In this paper, we compare some of the neural strategies for sound localization and encoding interaural time differences (ITDs) in three predatory species of Reptilia, alligators, barn owls and geckos. Birds and crocodilians are sister groups among the extant archosaurs, while geckos are lepidosaurs. Despite the similar organization of their auditory systems, archosaurs and lizards use different strategies for encoding the ITDs that underlie localization of sound in azimuth. Barn owls encode ITD information using a place map, which is composed of neurons serving as labeled lines tuned for preferred spatial locations, while geckos may use a meter strategy or population code composed of broadly sensitive neurons that represent ITD via changes in the firing rate. PMID:26398572

  19. [Sound localization cues of binaural hearing].

    PubMed

    Paulus, E

    2003-04-01

    The ability to localize sound sources in space is of considerable importance to the human safety- and survival-system. Consequently the current scientific interest in improving the safety-standard i. e. in air-traffic control has provided a new momentum for investigating spatial hearing. This review deals with the nature and the relative salience of the localization cues. Localization refers to judgements of the direction and distance of a sound source but here we will deal with direction only. We begin with a short introduction into the so-called Duplex theory which dates back to John William Strutt (later Lord Rayleigh). The idea is that sound localization is based on interaural time differences (ITD) at low frequencies and interaural level differences (ILD) at high frequencies. If the head remains stationary neither a given ITD nor an ILD can sufficiently define the position of a sound source in space. On such a theoretical basis cones of confusion which open outward from each ear can be predicted ambiguously projecting any source on the surface of such a cone onto an interaural axis. Our restricted ability at localizing sound sources in the vertical median plane is another example of possible ambiguity. At the end of the 19th century scientists already realized that occlusion of the pinnae cavities decreases localization competence. As a result of later achievements in physics and signal-theory it became more obvious that the pinnae may provide an additional cue for spatial hearing and that the outer ear together with the head and the upper torso form a sophisticated direction-dependent filter. The action of such a filter is mathematically described by the so-called Anatomical Transfer Function (ATF). The spectral patterning of the sound produced by the pinnae and the head is most effective when the source has spectral energy over a wide range and contains frequencies above 6 kHz, that is it contains wavelengths short enough to interact with the anatomical

  20. Comparing near-regional and local measurements of infrasound from Mount Erebus, Antarctica: Implications for monitoring

    NASA Astrophysics Data System (ADS)

    Dabrowa, A. L.; Green, D. N.; Johnson, J. B.; Phillips, J. C.; Rust, A. C.

    2014-11-01

    Local (100 s of metres from vent) monitoring of volcanic infrasound is a common tool at volcanoes characterized by frequent low-magnitude eruptions, but it is generally not safe or practical to have sensors so close to the vent during more intense eruptions. To investigate the potential and limitations of monitoring at near-regional ranges (10 s of km) we studied infrasound detection and propagation at Mount Erebus, Antarctica. This site has both a good local monitoring network and an additional International Monitoring System infrasound array, IS55, located 25 km away. We compared data recorded at IS55 with a set of 117 known Strombolian events that were recorded with the local network in January 2006. 75% of these events were identified at IS55 by an analyst looking for a pressure transient coincident with an F-statistic detection, which identifies coherent infrasound signals. With the data from January 2006, we developed and calibrated an automated signal-detection algorithm based on threshold values of both the F-statistic and the correlation coefficient. Application of the algorithm across IS55 data for all of 2006 identified infrasonic signals expected to be Strombolian explosions, and proved reliable for indicating trends in eruption frequency. However, detectability at IS55 of known Strombolian events depended strongly on the local signal amplitude: 90% of events with local amplitudes > 25 Pa were identified at IS55, compared to only 26% of events with local amplitudes < 25 Pa. Event detection was also affected by considerable variation in amplitude decay rates between the local and near-regional sensors. Amplitudes recorded at IS55 varied between 3% and 180% of the amplitude expected assuming hemispherical spreading, indicating that amplitudes recorded at near-regional ranges to Erebus are unreliable indicators of event magnitude. Comparing amplitude decay rates with locally collected radiosonde data indicates a close relationship between recorded

  1. An Antarctica-to-Spain HF ionospheric radio link: Sounding results

    NASA Astrophysics Data System (ADS)

    Vilella, C.; Miralles, D.; Pijoan, J. L.

    2008-08-01

    Our research group in Electromagnetism and Communications is involved in a project dealing with the channel characterization of an ionospheric radio link from the Spanish Antarctic Base (62.6°S, 60.4°W) to the Observatori de l'Ebre (40.8°N, 0.5°E) in Spain. Since the link was established for the first time on December 2003, the sounder and measurement techniques have been improved on the basis of the preliminary results. In this paper, the final results of the project corresponding to the 2006/2007 sounding survey are presented. First the hardware and measurement techniques used to probe the channel are described. Then the results in terms of channel availability (and its daily, hourly, and frequency variation), multipath and Doppler spreads, and signal-to-noise ratio are discussed. These results are being used to design the physical layer of a low data rate transmission system intended to send the information acquired by a geomagnetic sensor in the Antarctica.

  2. Surface Clutter Removal in Airborne Radar Sounding Data from the Dry Valleys, Antarctica

    NASA Technical Reports Server (NTRS)

    Holt, J. W.; Blankenship, D. D.; Morse, D. L.; Peters, M. E.; Kempf, S. D.

    2005-01-01

    We have collected roughly 1,000 line-km of airborne radar sounding data over glaciers, rock/ice glaciers, permafrost, subsurface ice bodies, ice-covered saline lakes, and glacial deposits in Taylor and Beacon Valley. These data are being analyzed in order to develop techniques for discriminating between subsurface and off-nadir echoes and for detecting and characterizing subsurface interfaces. The identification of features on Mars exhibiting morphologies consistent with ice/rock mixtures, near-surface ice bodies and near-surface liquid water, and the importance of such features to the search for water on Mars, highlights the need for appropriate terrestrial analogs and analysis techniques in order to prepare for radar sounder missions to Mars. Climatic, hydrological, and geological conditions in the Dry Valleys of Antarctica are analogous in many ways to those on Mars. A crucial first step in the data analysis process is the discrimination of echo sources in the radar data. The goal is to identify all returns from the surface of off-nadir topography in order to positively identify subsurface echoes. This process will also be critical for radar data that will be collected in areas of Mars exhibiting significant topography, so that subsurface echoes are identified unambiguously. The positive detection and characterization of subsurface (including sub-ice) water is a primary goal of NASA's Mars exploration program. Our data over the Dry Valleys provides an opportunity to implement techniques we are developing to accomplish these goals.

  3. Evolving subglacial water systems in East Antarctica from airborne radar sounding

    NASA Astrophysics Data System (ADS)

    Carter, Sasha Peter

    The cold, lightless, and high pressure aquatic environment at the base of the East Antarctic Ice Sheet is of interest to a wide range of disciplines. Stable subglacial lakes and their connecting channels remain perennially liquid three kilometers below some of the coldest places on Earth. The presence of subglacial water impacts flow of the overlying ice and provides clues to the geologic properties of the bedrock below, and may harbor unique life forms which have evolved out of contact with the atmosphere for millions of years. Periodic release of water from this system may impact ocean circulation at the margins of the ice sheet. This research uses airborne radar sounding, with its unique ability to infer properties within and at the base of the ice sheet over large spatial scales, to locate and characterize this unique environment. Subglacial lakes, the primary storage mechanism for subglacial water, have been located and classified into four categories on the basis of the radar reflection properties from the sub-ice interface: Definite lakes are brighter than their surroundings by at least two decibels (relatively bright), and are both consistently reflective (specular) and have a reflection coefficient greater than -10 decibels (absolutely bright). Dim lakes are relatively bright and specular but not absolutely bright, possibly indicating non-steady dynamics in the overlying ice. Fuzzy lakes are both relatively and absolutely bright, but not specular, and may indicate saturated sediments or high frequency spatially heterogeneous distributions of sediment and liquid water (i.e. a braided steam). Indistinct lakes are absolutely bright and specular but no brighter than their surroundings. Lakes themselves and the different classes of lakes are not arranged randomly throughout Antarctica but are clustered around ice divides, ice stream onsets and prominent bedrock troughs, with each cluster demonstrating a different characteristic lake classification distribution

  4. Comparative study of heart sound localization algorithms

    NASA Astrophysics Data System (ADS)

    Moukadem, A.; Dieterlen, A.; Hueber, N.; Brandt, C.; Raymond, P.

    2011-05-01

    The purpose of this document is to present a comparative study of five algorithms of heart sound localization, one of which, is a method based on radial basis function networks applied in a novel approach. The advantages and disadvantages of each method are evaluated according to a data base of 50 subjects in which there are 25 healthy subjects selected from the University Hospital of Strasbourg (HUS) and from theMARS500 project (Moscow) and 25 subjects with cardiac pathologies selected from the HUS. This study is made under the control of an experienced cardiologist. The performance of each method is evaluated by calculating the area under a receiver operating curve (AUC) and the robustness is shown against different levels of additive white Gaussian noise.

  5. Millennial-scale variability of the George VI Sound Ice Shelf, Antarctica

    NASA Astrophysics Data System (ADS)

    Roberts, S.; Bentley, M.; Hodgson, D.; Bryant, C.; Carmicheal, E.; Noon, P.; Smith, J.; Sugden, D.; Verleyen, E.

    2003-04-01

    This project provides a Late Quaternary perspective of Antarctic ice shelf variability by examining sediment records from epishelf lakes dammed on the eastern side of Alexander Island by George VI Ice Shelf. In recent decades, vast areas of ice shelves on the east coast of the Antarctic Peninsula have fragmented in a series of large break-up events, while others have disintegrated progressively. The global significance of current ice shelf loss is difficult to judge as similar variations may be a feature of the last 10,000 years. George VI Ice Shelf is currently close to the limit for ice shelf stability; hence, a two-season sediment-coring programme was undertaken to establish its palaeo-stability record. Recent results are presented from two principal study sites, Moutonnée and Ablation, with preliminary data from Cannonball and Citadel Bastion. These lakes are almost unique in Antarctica because they possess a continuous palaeolacustrine record of ice shelf history that can be linked to a geomorphological record of ice shelf variability. Most significant thus far, is the discovery of benthic foram-rich zones in the Moutonnée basin cores, representing at least one occasion when the ice shelf withdrew and open marine conditions existed in the sound. To determine when this occurred, mono-specific radiocarbon ages and oxygen and carbon isotope data are being obtained from forams, algal mat material and sediments. Physical, chemical and isotope analysis of cores reveals cyclic patterns that potentially match sections of ice core records.

  6. Airborne Radar Sounding and Ice Thickness Measurements over Lake Vostok, East Antarctica

    NASA Astrophysics Data System (ADS)

    Peters, M. E.; Blankenship, D. D.; Morse, D. L.; Holt, J. W.; Kempf, S. D.; Richter, T. G.; Falola, B.; Oliason, S.

    2002-05-01

    Lake Vostok was discovered using airborne ice-sounding radar in East Antarctica during the mid 1970's, but interest in this largest known subglacial lake has increased in recent years. Frozen microbial discoveries from ice cores taken just above Lake Vostok suggest its potential for being an isolated biological ecosystem. Also, the lake's unique combination of glaciologic, hydrologic and geological processes make it a possible terrestrial analogue for sub-ice water on other planetary bodies. Satellite radar has mapped the spatial extent of the lake from surface topography, and Russian ground traverses have gathered radar and seismic data along select profiles, but the full subglacial environment has remained uncharted. In response to a proposal by R.E. Bell and M. Studinger at Lamont Doherty Earth Observatory, the University of Texas Institute for Geophysics (UTIG) conducted an airborne geophysical survey over Lake Vostok and its surroundings during the 2000/01 field season. The survey included 21,000 line-km of geophysical observations with a line spacing of 7.5 km and a tie-line spacing of 11.25 or 22.5 km. The instrument suite included incoherent ice-sounding radar, laser altimetry, and precise GPS positioning and navigation, as well as airborne gravity and magnetics measurements. The radar system consisted of a 60 MHz, 8000 watt peak power transmitter operating in pulsed continuous-wave mode at 12.5 kHz (with 250 ns pulse width), a log-detection incoherent receiver (with 80 dB dynamic range), and a signal digitizer with a unique capability to average signals rapidly. Incoherent radar observations constructed from 2048 averaged transmissions occurred roughly every 12 m along-track. Ice thicknesses in excess of 4000 m were routinely sounded over Lake Vostok using this system. In addition to the incoherent radar, a new acquisition system was developed on an experimental basis to coherently integrate radar signals utilizing synthetic aperture radar techniques

  7. Sound source localization identification accuracy: Level and duration dependencies.

    PubMed

    Yost, William A

    2016-07-01

    Sound source localization accuracy for noises was measured for sources in the front azimuthal open field mainly as a function of overall noise level and duration. An identification procedure was used in which listeners identify which loudspeakers presented a sound. Noises were filtered and differed in bandwidth and center frequency. Sound source localization accuracy depended on the bandwidth of the stimuli, and for the narrow bandwidths, accuracy depended on the filter's center frequency. Sound source localization accuracy did not depend on overall level or duration. PMID:27475204

  8. SoundCompass: a distributed MEMS microphone array-based sensor for sound source localization.

    PubMed

    Tiete, Jelmer; Domínguez, Federico; da Silva, Bruno; Segers, Laurent; Steenhaut, Kris; Touhafi, Abdellah

    2014-01-01

    Sound source localization is a well-researched subject with applications ranging from localizing sniper fire in urban battlefields to cataloging wildlife in rural areas. One critical application is the localization of noise pollution sources in urban environments, due to an increasing body of evidence linking noise pollution to adverse effects on human health. Current noise mapping techniques often fail to accurately identify noise pollution sources, because they rely on the interpolation of a limited number of scattered sound sensors. Aiming to produce accurate noise pollution maps, we developed the SoundCompass, a low-cost sound sensor capable of measuring local noise levels and sound field directionality. Our first prototype is composed of a sensor array of 52 Microelectromechanical systems (MEMS) microphones, an inertial measuring unit and a low-power field-programmable gate array (FPGA). This article presents the SoundCompass's hardware and firmware design together with a data fusion technique that exploits the sensing capabilities of the SoundCompass in a wireless sensor network to localize noise pollution sources. Live tests produced a sound source localization accuracy of a few centimeters in a 25-m2 anechoic chamber, while simulation results accurately located up to five broadband sound sources in a 10,000-m2 open field. PMID:24463431

  9. SoundCompass: A Distributed MEMS Microphone Array-Based Sensor for Sound Source Localization

    PubMed Central

    Tiete, Jelmer; Domínguez, Federico; da Silva, Bruno; Segers, Laurent; Steenhaut, Kris; Touhafi, Abdellah

    2014-01-01

    Sound source localization is a well-researched subject with applications ranging from localizing sniper fire in urban battlefields to cataloging wildlife in rural areas. One critical application is the localization of noise pollution sources in urban environments, due to an increasing body of evidence linking noise pollution to adverse effects on human health. Current noise mapping techniques often fail to accurately identify noise pollution sources, because they rely on the interpolation of a limited number of scattered sound sensors. Aiming to produce accurate noise pollution maps, we developed the SoundCompass, a low-cost sound sensor capable of measuring local noise levels and sound field directionality. Our first prototype is composed of a sensor array of 52 Microelectromechanical systems (MEMS) microphones, an inertial measuring unit and a low-power field-programmable gate array (FPGA). This article presents the SoundCompass’s hardware and firmware design together with a data fusion technique that exploits the sensing capabilities of the SoundCompass in a wireless sensor network to localize noise pollution sources. Live tests produced a sound source localization accuracy of a few centimeters in a 25-m2 anechoic chamber, while simulation results accurately located up to five broadband sound sources in a 10,000-m2 open field. PMID:24463431

  10. The Avian Head Induces Cues for Sound Localization in Elevation

    PubMed Central

    Schnyder, Hans A.; Vanderelst, Dieter; Bartenstein, Sophia; Firzlaff, Uwe; Luksch, Harald

    2014-01-01

    Accurate sound source localization in three-dimensional space is essential for an animal’s orientation and survival. While the horizontal position can be determined by interaural time and intensity differences, localization in elevation was thought to require external structures that modify sound before it reaches the tympanum. Here we show that in birds even without external structures like pinnae or feather ruffs, the simple shape of their head induces sound modifications that depend on the elevation of the source. Based on a model of localization errors, we show that these cues are sufficient to locate sounds in the vertical plane. These results suggest that the head of all birds induces acoustic cues for sound localization in the vertical plane, even in the absence of external ears. PMID:25390036

  11. Male advantage in sound localization at cocktail parties.

    PubMed

    Zündorf, Ida C; Karnath, Hans-Otto; Lewald, Jörg

    2011-06-01

    Sex differences exist in the structural organization of the human brain and are related to cognitive abilities. Females usually outperform men in verbal fluency, verbal memory, perceptual speed, numerical calculation, and fine motor skills, whereas males are superior in visuospatial abilities, throwing accuracy, and mathematical reasoning. Here we demonstrated a male advantage in spatial abilities for the auditory modality. We employed a sound localization task based on the so-called "cocktail party situation", requiring extraction of auditory information of a specific sound source when multiple competing sound sources were present. The results indicated better performance of males than females for localizing target sounds in a multi-source sound environment. This finding suggests a sex difference in the attentional mechanisms extracting spatial information of one acoustic event of interest from an auditory scene composed of multiple sound sources. It seems that the known male superiority in spatial abilities may be supramodal, rather than a specificity of the visual modality. PMID:20828679

  12. Onset of deglacial warming in West Antarctica driven by local orbital forcing

    USGS Publications Warehouse

    WAIS Divide Project Members; Steig, Eric J.; Markle, Bradley R.; Schoenemann, Spruce W.; Ding, Qinghua; Taylor, Kendrick C.; McConnell, Joseph R.; Brook, Edward J.; Sowers, Todd; White, James W. C.; Alley, Richard B.; Chen, Hai; Clow, Gary D.; Cole-Dai, Jihong; Conway, Howard; Fitzpatrick, Joan J.; Hargreaves, Geoffrey; and others

    2013-01-01

    The cause of warming in the Southern Hemisphere during the most recent deglaciation remains a matter of debate. Hypotheses for a Northern Hemisphere trigger, through oceanic redistributions of heat, are based in part on the abrupt onset of warming seen in East Antarctic ice cores and dated to 18,000 years ago, which is several thousand years after high-latitude Northern Hemisphere summer insolation intensity began increasing from its minimum, approximately 24,000 years ago. An alternative explanation is that local solar insolation changes cause the Southern Hemisphere to warm independently. Here we present results from a new, annually resolved ice-core record from West Antarctica that reconciles these two views. The records show that 18,000 years ago snow accumulation in West Antarctica began increasing, coincident with increasing carbon dioxide concentrations, warming in East Antarctica and cooling in the Northern Hemisphere associated with an abrupt decrease in Atlantic meridional overturning circulation. However, significant warming in West Antarctica began at least 2,000 years earlier. Circum-Antarctic sea-ice decline, driven by increasing local insolation, is the likely cause of this warming. The marine-influenced West Antarctic records suggest a more active role for the Southern Ocean in the onset of deglaciation than is inferred from ice cores in the East Antarctic interior, which are largely isolated from sea-ice changes.

  13. Onset of deglacial warming in West Antarctica driven by local orbital forcing.

    PubMed

    2013-08-22

    The cause of warming in the Southern Hemisphere during the most recent deglaciation remains a matter of debate. Hypotheses for a Northern Hemisphere trigger, through oceanic redistributions of heat, are based in part on the abrupt onset of warming seen in East Antarctic ice cores and dated to 18,000 years ago, which is several thousand years after high-latitude Northern Hemisphere summer insolation intensity began increasing from its minimum, approximately 24,000 years ago. An alternative explanation is that local solar insolation changes cause the Southern Hemisphere to warm independently. Here we present results from a new, annually resolved ice-core record from West Antarctica that reconciles these two views. The records show that 18,000 years ago snow accumulation in West Antarctica began increasing, coincident with increasing carbon dioxide concentrations, warming in East Antarctica and cooling in the Northern Hemisphere associated with an abrupt decrease in Atlantic meridional overturning circulation. However, significant warming in West Antarctica began at least 2,000 years earlier. Circum-Antarctic sea-ice decline, driven by increasing local insolation, is the likely cause of this warming. The marine-influenced West Antarctic records suggest a more active role for the Southern Ocean in the onset of deglaciation than is inferred from ice cores in the East Antarctic interior, which are largely isolated from sea-ice changes. PMID:23945585

  14. Is the cochlea coiled to provide sound localization?

    NASA Astrophysics Data System (ADS)

    Huang, Xun; Xu, Chi; Bai, Long

    2012-06-01

    The potential physical effect of the cochlear shape on sound localization is studied from the perspective of signal processing. The sensory hair cells are taken to form a sensor array, and a numerical model is used to simulate the external sound pressure perceived by the sensory hair cells directly, that is, via bone conduction. The cognitive process is thus approximated as a signal processing array. The sound localization capabilities of a straight cochlea and a spiral cochlea are compared by examining the simulated acoustic images. The results demonstrate that the spiral shape can achieve better vertical sound localization. The analysis therefore indicates that the cochlear spiral shape might not only have evolved for space conservation reasons but also for possible perceptual benefits.

  15. Echo Source Discrimination in Airborne Radar Sounding Data for Mars Analog Studies, Dry Valleys, Antarctica

    NASA Technical Reports Server (NTRS)

    Holt, J. W.; Blankenship, D. D.; Peters, M. E.; Kempf, S. D.; Morse, D. L.; Williams, B. J.

    2003-01-01

    The recent identification of features on Mars exhibiting morphologies consistent with ice/rock mixtures, near-surface ice bodies and near-surface liquid water [1,2], and the importance of such features to the search for water on Mars, highlights the need for appropriate terrestrial analogs in order to prepare for upcoming radar missions targeting these and other water-related features. Climatic, hydrological, and geological conditions in the McMurdo Dry Valleys of Antarctica are analogous in many ways to those on Mars, and a number of ice-related features in the Dry Valleys may have direct morphologic and compositional counterparts on Mars.

  16. Localizing heart sounds in respiratory signals using singular spectrum analysis.

    PubMed

    Ghaderi, Foad; Mohseni, Hamid R; Sanei, Saeid

    2011-12-01

    Respiratory sounds are always contaminated by heart sound interference. An essential preprocessing step in some of the heart sound cancellation methods is localizing primary heart sound components. Singular spectrum analysis (SSA), a powerful time series analysis technique, is used in this paper. Despite the frequency overlap of the heart and lung sound components, two different trends in the eigenvalue spectra are recognizable, which leads to find a subspace that contains more information about the underlying heart sound. Artificially mixed and real respiratory signals are used for evaluating the performance of the method. Selecting the appropriate length for the SSA window results in good decomposition quality and low computational cost for the algorithm. The results of the proposed method are compared with those of well-established methods, which use the wavelet transform and entropy of the signal to detect the heart sound components. The proposed method outperforms the wavelet-based method in terms of false detection and also correlation with the underlying heart sounds. Performance of the proposed method is slightly better than that of the entropy-based method. Moreover, the execution time of the former is significantly lower than that of the latter. PMID:21788177

  17. Biology-inspired acoustic sensors for sound source localization

    NASA Astrophysics Data System (ADS)

    Liu, Haijun; Chen, Zhong; Yu, Miao

    2008-03-01

    In this article, the design of a biology-inspired miniature directional microphone is presented. This microphone consists of two clamped circular diaphragms, which are mechanically coupled by a connecting bridge that is pivoted at its center. A theoretical model is constructed to determine the microphone response to sound incident from an arbitrary direction. Both the simulation and preliminary experimental results show that the proposed microphone provides a remarkable amplification of the time delay associated with the sound induced diaphragm responses. This study should be relevant to various sound source localization applications.

  18. Vertical and oblique ionospheric soundings over the long haul HF link between Antarctica and Spain

    NASA Astrophysics Data System (ADS)

    Ads, A. G.; Bergadà, P.; Regué, J. R.; Alsina-Pagès, R. M.; Pijoan, J. L.; Altadill, D.; Badia, D.; Graells, S.

    2015-09-01

    This paper presents a comparative study between the oblique sounding results, the International Telecommunication Union Rec533 HF prediction model, and the vertical sounding results of a transequatorial long haul link. The long haul link is a 12,760 km link between the Spanish Antarctic Station, SAS, located in the Livingston Island and the Ebro Observatory (OE) in Spain. The data were collected during three consecutive surveys (2009/2010, 2010/2011, and 2011/2012). The ionospheric channel from the SAS to the OE is studied in terms of frequency availability as function of time using the measurements of an oblique incidence sounder (OIS) and measurements of several vertical incidence sounding stations (VIS) placed near the estimated radiopropagation path. The results obtained show promising correlations between VIS and OIS measurements and led us to think that the frequency of largest availability for this particular long haul radio link can be estimated from the VIS sounding measurements.

  19. Monaural sound localization based on structure-induced acoustic resonance.

    PubMed

    Kim, Keonwook; Kim, Youngwoong

    2015-01-01

    A physical structure such as a cylindrical pipe controls the propagated sound spectrum in a predictable way that can be used to localize the sound source. This paper designs a monaural sound localization system based on multiple pyramidal horns around a single microphone. The acoustic resonance within the horn provides a periodicity in the spectral domain known as the fundamental frequency which is inversely proportional to the radial horn length. Once the system accurately estimates the fundamental frequency, the horn length and corresponding angle can be derived by the relationship. The modified Cepstrum algorithm is employed to evaluate the fundamental frequency. In an anechoic chamber, localization experiments over azimuthal configuration show that up to 61% of the proper signal is recognized correctly with 30% misfire. With a speculated detection threshold, the system estimates direction 52% in positive-to-positive and 34% in negative-to-positive decision rate, on average. PMID:25668214

  20. Local non-Gaussianity from rapidly varying sound speeds

    SciTech Connect

    Emery, Jon; Tasinato, Gianmassimo; Wands, David E-mail: gianmassimo.tasinato@port.ac.uk

    2012-08-01

    We study the effect of non-trivial sound speeds on local-type non-Gaussianity during multiple-field inflation. To this end, we consider a multiple-DBI model and use the δN formalism to track the super-horizon evolution of perturbations. By adopting a sum separable Hubble parameter we derive analytic expressions for the relevant quantities in the two-field case, valid beyond slow variation. We find that non-trivial sound speeds can, in principle, curve the trajectory in such a way that significant local-type non-Gaussianity is produced. Deviations from slow variation, such as rapidly varying sound speeds, enhance this effect. To illustrate our results we consider two-field inflation in the tip regions of two warped throats and find large local-type non-Gaussianity produced towards the end of the inflationary process.

  1. Monaural Sound Localization Based on Structure-Induced Acoustic Resonance

    PubMed Central

    Kim, Keonwook; Kim, Youngwoong

    2015-01-01

    A physical structure such as a cylindrical pipe controls the propagated sound spectrum in a predictable way that can be used to localize the sound source. This paper designs a monaural sound localization system based on multiple pyramidal horns around a single microphone. The acoustic resonance within the horn provides a periodicity in the spectral domain known as the fundamental frequency which is inversely proportional to the radial horn length. Once the system accurately estimates the fundamental frequency, the horn length and corresponding angle can be derived by the relationship. The modified Cepstrum algorithm is employed to evaluate the fundamental frequency. In an anechoic chamber, localization experiments over azimuthal configuration show that up to 61% of the proper signal is recognized correctly with 30% misfire. With a speculated detection threshold, the system estimates direction 52% in positive-to-positive and 34% in negative-to-positive decision rate, on average. PMID:25668214

  2. Impact of hearing protection devices on sound localization performance

    PubMed Central

    Zimpfer, Véronique; Sarafian, David

    2014-01-01

    Hearing Protection Devices (HPDs) can protect the ear against loud potentially damaging sounds while allowing lower-level sounds such as speech to be perceived. However, the impact of these devices on the ability to localize sound sources is not well known. To address this question, we propose two different methods: one behavioral and one dealing with acoustical measurements. For the behavioral method, sound localization performance was measured with, and without, HPDs on 20 listeners. Five HPDs, including both passive (non-linear attenuation) and three active (talk-through) systems were evaluated. The results showed a significant increase in localization errors, especially front-back and up-down confusions relative to the “naked ear” test condition for all of the systems tested, especially for the talk-through headphone system. For the acoustic measurement method, Head-Related Transfer Functions (HRTFs) were measured on an artificial head both without, and with the HPDs in place. The effects of the HPDs on the spectral cues for the localization of different sound sources in the horizontal plane were analyzed. Alterations of the Interaural Spectral Difference (ISD) cues were identified, which could explain the observed increase in front-back confusions caused by the talk-through headphone protectors. PMID:24966807

  3. A robust method for heart sounds localization using lung sounds entropy.

    PubMed

    Yadollahi, Azadeh; Moussavi, Zahra M K

    2006-03-01

    Heart sounds are the main unavoidable interference in lung sound recording and analysis. Hence, several techniques have been developed to reduce or cancel heart sounds (HS) from lung sound records. The first step in most HS cancellation techniques is to detect the segments including HS. This paper proposes a novel method for HS localization using entropy of the lung sounds. We investigated both Shannon and Renyi entropies and the results of the method using Shannon entropy were superior. Another HS localization method based on multiresolution product of lung sounds wavelet coefficients adopted from was also implemented for comparison. The methods were tested on data from 6 healthy subjects recorded at low (7.5 ml/s/kg) and medium 115 ml/s/kg) flow rates. The error of entropy-based method using Shannon entropy was found to be 0.1 +/- 0.4% and 1.0 +/- 0.7% at low and medium flow rates, respectively, which is significantly lower than that of multiresolution product method and those of other methods reported in previous studies. The proposed method is fully automated and detects HS included segments in a completely unsupervised manner. PMID:16532776

  4. Feasibility report: Operation of light air cushion vehicle at McMurdo Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Dibbern, J. S.

    1987-02-01

    This report explores the viability of the use of an air cushion vehicle (ACV) or hovercraft to perform logistic and scientific support in the area of McMurdo Station, Antarctica. After a review of personnel assets and facilities at McMurdo Station to support the ACV plus a reconnaissance of the five major routes selected, it appears that an air cushion vehicle in the 1 to 1 1/2 ton payload class would be of significant value to support operations. It would reduce transit times for surface vehicle traverses on the routes selected and reduce requirements for expenditure of helicopter flight time in others. Of major significance is the ability to handle passenger/shuttle requirements between the Scott Base transition and Williams Field Skiway. Use of the ACV for high frequency passenger operations would help preserve the snow road for cargo operations during periods of road deterioration.

  5. Binaural Sound Localizer for Azimuthal Movement Detection Based on Diffraction

    PubMed Central

    Kim, Keonwook; Choi, Anthony

    2012-01-01

    Sound localization can be realized by utilizing the physics of acoustics in various methods. This paper investigates a novel detection architecture for the azimuthal movement of sound source based on the interaural level difference (ILD) between two receivers. One of the microphones in the system is surrounded by barriers of various heights in order to cast the direction dependent diffraction of the incoming signal. The gradient analysis of the ILD between the structured and unstructured microphone demonstrates the rotation directions as clockwise, counter clockwise, and no rotation of the sound source. Acoustic experiments with different types of sound source over a wide range of target movements show that the average true positive and false positive rates are 67% and 16%, respectively. Spectral analysis demonstrates that the low frequency delivers decreased true and false positive rates and the high frequency presents increases of both rates, overall. PMID:23112617

  6. Localization of sound sources by means of unidirectional microphones

    NASA Astrophysics Data System (ADS)

    Rizzo, Piervincenzo; Bordoni, Giacomo; Marzani, Alessandro; Vipperman, Jeffrey

    2009-05-01

    This paper describes the results of a new approach devoted to the localization of ground borne acoustic sources. It is demonstrated that an array made of at least three unidirectional microphones can be exploited to identify the position of the source. Sound features extracted either in the time domain or in the frequency domain are used to localize the direction of the incoming sound. This information is then fed into a semi-analytical algorithm aimed at identifying the source location. The novelty of the method presented here consists in the use of unidirectional microphones rather than omnidirectional microphones and in the ability to extract the sound direction by considering features like sound amplitude rather than the time of arrival. Experimental tests have been undertaken in a closed environment and have demonstrated the feasibility of the proposed approach. It is believed that this method may pave the road toward a new generation of reduced-size sound detectors and localizers, and future work is described in the conclusions.

  7. Modeling the utility of binaural cues for underwater sound localization.

    PubMed

    Schneider, Jennifer N; Lloyd, David R; Banks, Patchouly N; Mercado, Eduardo

    2014-06-01

    The binaural cues used by terrestrial animals for sound localization in azimuth may not always suffice for accurate sound localization underwater. The purpose of this research was to examine the theoretical limits of interaural timing and level differences available underwater using computational and physical models. A paired-hydrophone system was used to record sounds transmitted underwater and recordings were analyzed using neural networks calibrated to reflect the auditory capabilities of terrestrial mammals. Estimates of source direction based on temporal differences were most accurate for frequencies between 0.5 and 1.75 kHz, with greater resolution toward the midline (2°), and lower resolution toward the periphery (9°). Level cues also changed systematically with source azimuth, even at lower frequencies than expected from theoretical calculations, suggesting that binaural mechanical coupling (e.g., through bone conduction) might, in principle, facilitate underwater sound localization. Overall, the relatively limited ability of the model to estimate source position using temporal and level difference cues underwater suggests that animals such as whales may use additional cues to accurately localize conspecifics and predators at long distances. PMID:24727491

  8. Preliminary results of a radio echo sounding survey of the Recovery Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Humbert, Angelika; Kleiner, Thomas; Steinhage, Daniel

    2014-05-01

    The Recovery Glacier is draining about 8% of the East Antarctic ice sheet and feeds into the Filchner Ice Shelf. This ice shelf might be subjected in future to increasing basal melting (Hellmer et al., 2012) forcing potentially grounding line retreat. Compared to other areas in Antarctica this glacier is been surveyed very sparse and hence does not allow modeling studies yet. As many large and small subglacial lakes are present underneath this ice stream at different locations along the flow, the question of the influence of the lakes on ice stream genesis and ice stream dynamics arose. For investigating this influence by observation and subsequent modelling, an airborne campaign of the Alfred Wegener Institute was carried out in January 2014, covering the Recovery Ice Stream and two smaller glaciers merging with it, the Ramp Glacier and the Blackwall Glacier. The radar system uses a carrier frequency of 150MHz and a 600ns pulse. The survey includes several flights along flow lines in order to assess the basal roughness of the ice stream. Here we present the first preliminary data analysis.

  9. A comprehensive sounding of the ionospheric HF radio link from Antarctica to Spain

    NASA Astrophysics Data System (ADS)

    Ads, A. G.; Bergadã, P.; Vilella, C.; Regué, J. R.; Pijoan, J. L.; Bardají, R.; Mauricio, J.

    2013-01-01

    Since 2003, our group has been investigating the performance of different transmission techniques for low-power low-interference High Frequency (HF) ionospheric communication systems. Specifically, we have focused on the link between the Spanish Antarctic Station (SAS) Juan Carlos I in Livingston Island and Ebro Observatory (OE) in Spain, in order to transmit the data gathered from some geomagnetic sensors. These transmission techniques require a valuable knowledge of the channel behavior, thus a comprehensive narrowband and wideband sounding of the ionospheric channel is needed. Some significant improvements both in the system and in the signal processing have been done to achieve this goal. The analysis time and the frequency band have been extended to 24 hours per day and to the whole HF band (2-30 MHz). Moreover, new measurements of the absolute propagation time and the Doppler frequency shift are introduced. In this paper, the sounding results obtained using the new system are presented.

  10. Extension of an Ice Shelf Water plume model beneath sea ice with application in McMurdo Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Hughes, K. G.; Langhorne, P. J.; Leonard, G. H.; Stevens, C. L.

    2014-12-01

    A one-dimensional, frazil-laden plume model predicts the properties of Ice Shelf Water (ISW) as it evolves beneath sea ice beyond the ice shelf edge. An idealized background ocean circulation, which moves parallel to the plume, imitates forcings other than the plume's own buoyancy. The size distribution and concentration of the plume's suspended frazil ice crystals are affected by the background circulation velocity, the root-mean square tidal velocity, the drag coefficient, and the efficiency of secondary nucleation. Consequently, these variables are the key physical controls on the survival of supercooled water with distance from the ice shelf, which is predicted using several realistic parameter choices. Starting at 65 m thick, the in situ supercooled layer thins to 11 ± 5 and 4 ± 3 m at distances of 50 and 100 km, respectively. We apply the extended model in McMurdo Sound, Antarctica, along the expected path of the coldest water. Three late-winter oceanographic stations along this path, in conjunction with historical data, provide initial conditions and evaluation of the simulations. Near the ice shelf in the western Sound, the water column consisted entirely of ISW, and the subice platelet layer thickness exceeded 5 m with platelet crystals dominating the sea ice structure suggesting that ISW persisted throughout winter. Presuming a constant ISW flux, the model predicts that the plume increases thermodynamic growth of sea ice by approximately 0.1 m yr-1 (˜5% of the average growth rate) even as far as 100 km beyond the ice shelf edge.

  11. Aeromagnetic and radio echo ice-sounding measurements show much greater area of the Dufek intrusion, Antarctica

    USGS Publications Warehouse

    Behrendt, John C.; Drewry, D.J.; Jankowski, E.; Grim, M.S.

    1980-01-01

    A combined aeromagnetic and radio echo ice-sounding survey made in 1978 in Antarctica over the Dufek layered mafic intrusion suggests a minimum area of the intrusion of about 50,000 square kilometers, making it comparable in size with the Bushveld Complex of Africa. Comparisons of the magnetic and subglacial topographic profiles illustrate the usefulness of this combination of methods in studying bedrock geology beneath ice-covered areas. Magnetic anomalies range in peak-to-trough amplitude from about 50 nanoteslas over the lowermost exposed portion of the section in the Dufek Massif to about 3600 nanoteslas over the uppermost part of the section in the Forrestal Range. Theoretical magnetic anomalies, computed from a model based on the subice topography fitted to the highest amplitude observed magnetic anomalies, required normal and reversed magnetizations ranging from 10-3 to 10-2 electromagnetic units per cubic centimeter. This result is interpreted as indicating that the Dufek intrusion cooled through the Curie isotherm during one or more reversals of the earth's magnetic field. Copyright ?? 1980 AAAS.

  12. Evolution of mammalian sound localization circuits: A developmental perspective.

    PubMed

    Nothwang, Hans Gerd

    2016-06-01

    Localization of sound sources is a central aspect of auditory processing. A unique feature of mammals is the smooth, tonotopically organized extension of the hearing range to high frequencies (HF) above 10kHz, which likely induced positive selection for novel mechanisms of sound localization. How this change in the auditory periphery is accompanied by changes in the central auditory system is unresolved. I will argue that the major VGlut2(+) excitatory projection neurons of sound localization circuits (dorsal cochlear nucleus (DCN), lateral and medial superior olive (LSO and MSO)) represent serial homologs with modifications, thus being paramorphs. This assumption is based on common embryonic origin from an Atoh1(+)/Wnt1(+) cell lineage in the rhombic lip of r5, same cell birth, a fusiform cell morphology, shared genetic components such as Lhx2 and Lhx9 transcription factors, and similar projection patterns. Such a parsimonious evolutionary mechanism likely accelerated the emergence of neurons for sound localization in all three dimensions. Genetic analyses indicate that auditory nuclei in fish, birds, and mammals receive contributions from the same progenitor lineages. Anatomical and physiological differences and the independent evolution of tympanic ears in vertebrate groups, however, argue for convergent evolution of sound localization circuits in tetrapods (amphibians, reptiles, birds, and mammals). These disparate findings are discussed in the context of the genetic architecture of the developing hindbrain, which facilitates convergent evolution. Yet, it will be critical to decipher the gene regulatory networks underlying development of auditory neurons across vertebrates to explore the possibility of homologous neuronal populations. PMID:27032475

  13. Transversal Anderson localization of sound in acoustic waveguide arrays.

    PubMed

    Ye, Yangtao; Ke, Manzhu; Feng, Junheng; Wang, Mudi; Qiu, Chunyin; Liu, Zhengyou

    2015-04-22

    We present designs of one-dimensional acoustic waveguide arrays and investigate wave propagation inside. Under the condition of single identical waveguide mode and weak coupling, the acoustic wave motion in waveguide arrays can be modeled with a discrete mode-coupling theory. The coupling constants can be retrieved from simulations or experiments as the function of neighboring waveguide separations. Sound injected into periodic arrays gives rise to the discrete diffraction, exhibiting ballistic or extended transport in transversal direction. But sound injected into randomized waveguide arrays readily leads to Anderson localization transversally. The experimental results show good agreement with simulations and theoretical predictions. PMID:25812602

  14. High Resolution Magnetic Anomaly Imaging of Southern McMurdo Sound (Antarctica)

    NASA Astrophysics Data System (ADS)

    Chiappini, M.; Gaya Pique, L. R.; Pignatelli, A.; Wilson, T.

    2004-12-01

    During the 2003-04 austral summer season, a low-altitude, high-resolution airborne magnetic survey was conducted in the area of Southern McMurdo Sound, western Ross Sea, in the framework of the joint Italian-US initiative called GEOIMAG (GEOphysical IMAGing of Antarctic tectonic and volcanic units in the Transantarctic Mountains and Ross Sea area). The survey was flown by helicopter from McMurdo Station, at a constant terrain clearance of 70 m. Profile spacing was 350 m. The resolution of the survey, the accuracy of the data acquisition, and a preliminary digital enhancement of the processed magnetic data have contributed to highlight the short-wavelength component of the regional magnetic anomaly field, resolving volcanic bodies and faults. A broad positive anomaly tapers northward from the volcanic Brown Peninsula. The breadth and low amplitude of the anomaly suggests this may mark relatively thin deposits of volcanic material on or near the seafloor. High-frequency and high-amplitude anomalies are associated with the volcanic Daily Islands at the edge of the Ross Ice Shelf. Anomalies of similar amplitude and size in adjacent areas indicate additional volcanic cones occur on the seafloor and beneath the ice sheet. Low-amplitude, curvilinear anomalies with a convex shape toward McMurdo Sound occur offshore of the outlet of Ferrar Glacier and extending southward parallel to the coastline. The new data are being integrated with a multi-source database (magnetic, digital terrain data, bathymetry, regional structural trends) to obtain an unprecedented view of the magnetic signature of the major tectonic elements in the area. The structural and volcanic framework resulting from this investigation will provide important site survey information for the proposed ANDRILL drill sites in southern McMurdo Sound.

  15. Flexural controls on late Neogene basin evolution in southern McMurdo Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Aitken, Alan R. A.; Wilson, Gary S.; Jordan, Thomas; Tinto, Kirsty; Blakemore, Hamish

    2012-01-01

    The basins of southern McMurdo Sound have evolved under the influence of lithospheric flexure induced by the loads of the Erebus Volcanic Province. To characterise these basins, it is important to investigate the lithosphere's flexural properties, and estimate their influence on basin architecture and evolution. Seismic and gravity data are used to constrain 3D forward modelling of the progressive development of accommodation space within the flexural basins. Elastic plate flexure was calculated for a range of effective elastic thicknesses (T e) from 0.5 to 25 km using a spectral method. Models with low, but nonzero, T e values (2 km < T e < 5 km) produce the best fit to the gravity data, although uncertainty is high due to inaccuracies in the Digital Elevation Model. The slopes of flexural horizons revealed in seismic reflection lines are consistent with this, indicating a T e of 2 km to 5 km, although the depths to these horizons are not consistent, perhaps due to a northwards slope, or step, in the pre-flexural surface. These results indicate that the lithospheric strength of southern McMurdo Sound is significantly less than estimates of the regional average (T e ~ 20 km). This low strength may reflect the weakening effects of the Terror Rift, and perhaps also the Discovery Accommodation Zone, a region of major transverse faulting. A low T e model (T e = 3) for southern McMurdo Sound predicts the development of two discrete flexural depressions, each 2-2.5 km deep. The predicted stratigraphy of the northern basin reflects flexure due to Ross Island, predominantly erupted since ca. 1.8 Ma. The predicted stratigraphy of the southern basin reflects more gradual flexure from ca. 10 Ma to ca. 2 Ma, due to the more dispersed volcanoes of the Discovery subprovince. Collectively, these two basins have the potential to preserve a remarkable stratigraphic record of Antarctic climate change through the late Neogene.

  16. Reprint of: Flexural controls on late Neogene basin evolution in southern McMurdo Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Aitken, Alan R. A.; Wilson, Gary S.; Jordan, Tom; Tinto, Kirsty; Blakemore, Hamish

    2012-10-01

    The basins of southern McMurdo Sound have evolved under the influence of lithospheric flexure induced by the loads of the Erebus Volcanic Province. To characterise these basins, it is important to investigate the lithosphere's flexural properties, and estimate their influence on basin architecture and evolution. Seismic and gravity data are used to constrain 3D forward modelling of the progressive development of accommodation space within the flexural basins. Elastic plate flexure was calculated for a range of effective elastic thicknesses (Te) from 0.5 to 25 km using a spectral method. Models with low, but nonzero, Te values (2 km < Te < 5 km) produce the best fit to the gravity data, although uncertainty is high due to inaccuracies in the Digital Elevation Model. The slopes of flexural horizons revealed in seismic reflection lines are consistent with this, indicating a Te of 2 km to 5 km, although the depths to these horizons are not consistent, perhaps due to a northwards slope, or step, in the pre-flexural surface. These results indicate that the lithospheric strength of southern McMurdo Sound is significantly less than estimates of the regional average (Te ~ 20 km). This low strength may reflect the weakening effects of the Terror Rift, and perhaps also the Discovery Accommodation Zone, a region of major transverse faulting. A low Te model (Te = 3) for southern McMurdo Sound predicts the development of two discrete flexural depressions, each 2-2.5 km deep. The predicted stratigraphy of the northern basin reflects flexure due to Ross Island, predominantly erupted since ca. 1.8 Ma. The predicted stratigraphy of the southern basin reflects more gradual flexure from ca. 10 Ma to ca. 2 Ma, due to the more dispersed volcanoes of the Discovery subprovince. Collectively, these two basins have the potential to preserve a remarkable stratigraphic record of Antarctic climate change through the late Neogene.

  17. 75 FR 16700 - Special Local Regulation, Swim Across the Sound, Long Island Sound, Port Jefferson, NY to Captain...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-02

    ... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulation, Swim Across the Sound, Long... Long Island Sound between Port Jefferson, NY and Captain's Cove Seaport, Bridgeport, CT due to the..., Prevention Department, USCG Sector Long Island Sound at 203-468-4459, e-mail christie.m.dixon@uscg.mil ....

  18. Design of laser monitoring and sound localization system

    NASA Astrophysics Data System (ADS)

    Liu, Yu-long; Xu, Xi-ping; Dai, Yu-ming; Qiao, Yang

    2013-08-01

    In this paper, a novel design of laser monitoring and sound localization system is proposed. It utilizes laser to monitor and locate the position of the indoor conversation. In China most of the laser monitors no matter used in labor in an instrument uses photodiode or phototransistor as a detector at present. At the laser receivers of those facilities, light beams are adjusted to ensure that only part of the window in photodiodes or phototransistors received the beams. The reflection would deviate from its original path because of the vibration of the detected window, which would cause the changing of imaging spots in photodiode or phototransistor. However, such method is limited not only because it could bring in much stray light in receivers but also merely single output of photocurrent could be obtained. Therefore a new method based on quadrant detector is proposed. It utilizes the relation of the optical integral among quadrants to locate the position of imaging spots. This method could eliminate background disturbance and acquired two-dimensional spots vibrating data pacifically. The principle of this whole system could be described as follows. Collimated laser beams are reflected from vibrate-window caused by the vibration of sound source. Therefore reflected beams are modulated by vibration source. Such optical signals are collected by quadrant detectors and then are processed by photoelectric converters and corresponding circuits. Speech signals are eventually reconstructed. In addition, sound source localization is implemented by the means of detecting three different reflected light sources simultaneously. Indoor mathematical models based on the principle of Time Difference Of Arrival (TDOA) are established to calculate the twodimensional coordinate of sound source. Experiments showed that this system is able to monitor the indoor sound source beyond 15 meters with a high quality of speech reconstruction and to locate the sound source position accurately.

  19. Sound localization of aerial broadband noise in pinnipeds

    NASA Astrophysics Data System (ADS)

    Holt, Marla M.; Schusterman, Ronald J.; Kastak, David; Southall, Brandon L.

    2003-04-01

    Pinnipeds (seals, sea lions, and walruses) emit broadband calls on land as part of their communication system in order to coordinate their reproductive activities. How well do they localize these types of signals? In this study, the aerial sound localization acuities of a harbor seal (Phoca vitulina), a California sea lion (Zalophus californianus), and a northern elephant seal (Mirounga angustirostris) were measured in the horizontal plane with a broadband white noise stimulus. Testing was conducted in a hemi-anechoic chamber using a left/right forced choice procedure to measure the minimum audible angle (MAA) for each subject. MAAs were defined as half the angular separation of two sound sources relative to a subject's midline that corresponded to 75% correct discrimination. MAAs were 3.6, 4.2, and 4.7 deg for the harbor seal, California sea lion, and northern elephant seal, respectively. These results demonstrate that these pinniped species had sound localization abilities comparable to the domestic cat and rhesus macaques. The acuity differences between our subjects were small, were not predicted by head size, and therefore likely reflect the relatively acute abilities of other pinniped species to localize aerial broadband signals.

  20. Microphones' directivity for the localization of sound sources

    NASA Astrophysics Data System (ADS)

    Rizzo, Piervincenzo; Tajari, Mahdi; Spada, Antonino

    2011-06-01

    In a recent paper [P. Rizzo, G. Bordoni, A. Marzani, and J. Vipperman, "Localization of Sound Sources by Means of Unidirectional Microphones, Meas. Sci. Tech., 20, 055202 (12pp), 2009] the proof-of-concept of an approach for the localization of acoustic sources was presented. The method relies on the use of unidirectional microphones and amplitude-based signals' features to extract information about the direction of the incoming sound. By intersecting the directions identified by a pair of microphones, the position of the emitting source can be identified. In this paper we expand the work presented previously by assessing the effectiveness of the approach for the localization of an acoustic source in an indoor setting. As the method relies on the accurate knowledge of the microphones directivity, analytical expression of the acoustic sensors polar pattern were derived by testing them in an anechoic chamber. Then an experiment was conducted in an empty laboratory by using an array of three unidirectional microphones. The ability to locate the position of a commercial speaker placed at different positions in the room is discussed. The objective of this study is to propose a valid alternative to the common application of spaced arrays and therefore to introduce a new generation of reduced size sound detectors and localizers. The ability of the proposed methodology to locate the position of a commercial speaker placed at different positions in the room was evaluated and compared to the accuracy provided by a conventional time delay estimate algorithm.

  1. Jun Jaegyu Volcano: A Recently Discovered Alkali Basalt Volcano in Antarctic Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Hatfield, A.; Bailey, D.; Domack, E.; Brachfeld, S.; Gilbert, R.; Ishman, S.; Krahmann, G.; Leventer, A.

    2004-12-01

    Jun Jaegyu is a young volcanic construct discovered in May 2004 by researchers aboard the National Science Foundation (NSF) vessel Laurence M. Gould (LMG04-04). The volcano is located on the Antarctic continental shelf in Antarctic Sound, approximately 9 km due north of the easternmost point of Andersson Island. Swath bathymetry (NBP01-07) indicates that the volcano stands 700 meters above the seafloor, yet remains 275 meters short of the ocean surface. The seamount lies along a northwest-southeast oriented fault scarp and contains at least 1.5 km3 of volcanic rock. Video recording of the volcano's surface revealed regions nearly devoid of submarine life. These areas are associated with a thermal anomaly of up to 0.052° C higher than the surrounding ocean water. A rock dredge collected ~13 kg of material, over 80% of which was fresh volcanic rock; the remainder was glacial IRD. These observations, along with reports by mariners of discolored water in this region of Antarctic Sound, suggest that the volcano has been recently active. The basalt samples are generally angular, glassy and vesicular. Preliminary petrographic observations indicate that plagioclase, olivine, and clinopyroxene are all present as phenocryst phases, and that small (<1cm) rounded xenoliths are common. A comprehensive study of the volcano's petrography and whole-rock chemistry is currently underway. Jun Jaegyu is the northernmost volcanic center of the James Ross Island Volcanic Group (JRIVG), and the only center in this region of the Antarctic Peninsula with evidence of recent activity. It lies along the boundary between the Late Cenozoic JRIVG and the Upper Paleozoic rocks of the Trinity Peninsula Formation. While the tectonic setting of the region is complex, volcanism appears to be associated with active faults related to within-plate extension.

  2. Atypical vertical sound localization and sound-onset sensitivity in people with autism spectrum disorders

    PubMed Central

    Visser, Eelke; Zwiers, Marcel P.; Kan, Cornelis C.; Hoekstra, Liesbeth; van Opstal, A. John; Buitelaar, Jan K.

    2013-01-01

    Background Autism spectrum disorders (ASDs) are associated with auditory hyper- or hyposensitivity; atypicalities in central auditory processes, such as speech-processing and selective auditory attention; and neural connectivity deficits. We sought to investigate whether the low-level integrative processes underlying sound localization and spatial discrimination are affected in ASDs. Methods We performed 3 behavioural experiments to probe different connecting neural pathways: 1) horizontal and vertical localization of auditory stimuli in a noisy background, 2) vertical localization of repetitive frequency sweeps and 3) discrimination of horizontally separated sound stimuli with a short onset difference (precedence effect). Results Ten adult participants with ASDs and 10 healthy control listeners participated in experiments 1 and 3; sample sizes for experiment 2 were 18 adults with ASDs and 19 controls. Horizontal localization was unaffected, but vertical localization performance was significantly worse in participants with ASDs. The temporal window for the precedence effect was shorter in participants with ASDs than in controls. Limitations The study was performed with adult participants and hence does not provide insight into the developmental aspects of auditory processing in individuals with ASDs. Conclusion Changes in low-level auditory processing could underlie degraded performance in vertical localization, which would be in agreement with recently reported changes in the neuroanatomy of the auditory brainstem in individuals with ASDs. The results are further discussed in the context of theories about abnormal brain connectivity in individuals with ASDs. PMID:24148845

  3. Vertical-plane sound localization with distorted spectral cues

    PubMed Central

    Macpherson, Ewan A.; Sabin, Andrew T.

    2014-01-01

    For human listeners, the primary cues for localization in the vertical plane are provided by the direction-dependent filtering of the pinnae, head, and upper body. Vertical-plane localization generally is accurate for broadband sounds, but when such sounds are presented at near-threshold levels or at high levels with short durations (<20 ms), the apparent location is biased toward the horizontal plane (i.e., elevation gain <1). We tested the hypothesis that these effects result in part from distorted peripheral representations of sound spectra. Human listeners indicated the apparent position of 100-ms, 50–60dB SPL, wideband noise-burst targets by orienting their heads. The targets were synthesized in virtual auditory space and presented over headphones. Faithfully synthesized targets were interleaved with targets for which the directional transfer function spectral notches were filled in, peaks were levelled off, or the spectral contrast of the entire profile was reduced or expanded. As notches were filled in progressively or peaks levelled progressively, elevation gain decreased in a graded manner similar to that observed as sensation level is reduced below 30dB or, for brief sounds, increased above 45dB. As spectral contrast was reduced, gain dropped only at the most extreme reduction (25% of normal). Spectral contrast expansion had little effect. The results are consistent with the hypothesis that loss of representation of spectral features contributes to reduced elevation gain at low and high sound levels. The results also suggest that perceived location depends on a correlation-like spectral matching process that is sensitive to the relative, rather than absolute, across-frequency shape of the spectral profile. PMID:24076423

  4. Decadal Trends in Abundance, Size and Condition of Antarctic Toothfish in McMurdo Sound, Antarctica, 1972-2010

    NASA Technical Reports Server (NTRS)

    Ainley, David G.; Nur, Nadav; Eastman, Joseph T.; Ballard. Grant; Parkinson, Claire L; Evans, Clive W.; DeVries, Arthur L.

    2012-01-01

    We report analyses of a dataset spanning 38 years of near-annual fishing for Antarctic toothfish Dissostichus mawsoni, using a vertical setline through the fast ice of McMurdo Sound, Antarctica, 1972-2010. This constitutes one of the longest biological time series in the Southern Ocean, and certainly the longest for any fish. Fish total length, condition and catch per unit effort (CPUE) were derived from the more than 5500 fish caught. Contrary to expectation, length-frequency was dominated by fish in the upper half of the industrial catch. The discrepancy may be due to biases in the sampling capabilities of vertical (this study) versus benthic (horizontal) fishing gear (industry long lines), related to the fact that only large Antarctic toothfish (more than 100 cm TL) are neutrally buoyant and occur in the water column. Fish length and condition increased from the early 1970s to the early 1990s and then decreased, related to sea ice cover, with lags of 8 months to 5 years, and may ultimately be related to the fishery (which targets large fish) and changes in the Southern Annular Mode through effects on toothfish main prey, Antarctic silverfish Pleuragramma antarcticum. CPUE was constant through 2001 and then decreased dramatically, likely related to the industrial fishery, which began in 1996 and which concentrates effort over the Ross Sea slope, where tagged McMurdo fish have been found. Due to limited prey choices and, therefore, close coupling among mesopredators of the Ross Sea, Antarctic toothfish included, the fishery may be altering the trophic structure of the Ross Sea.

  5. Radio-echo sounding at Dome C, East Antarctica: A comparison of measured and modeled data

    NASA Astrophysics Data System (ADS)

    Winter, Anna; Eisen, Olaf; Steinhage, Daniel; Zirizzotti, Achille; Urbini, Stefano; Cavitte, Marie; Blankenship, Donald D.; Wolff, Eric

    2016-04-01

    The internal layering architecture of ice sheets, detected with radio-echo sounding (RES), contains clues to past ice-flow dynamics and mass balance. A common way of relating the recorded travel time of RES reflections to depth is by integrating a wave-speed distribution. This results in an increasing absolute error with depth. We present a synchronization of RES-internal layers of different radar systems (Alfred Wegener Institute, Center for Remote Sensing of Ice Sheets, Istituto Nazionale di Geofisica e Vulcanologia, British Antarctic Survey and University of Texas Institute for Geophysics) with ice-core records from the Antarctic deep drill site Dome C. Synthetic radar traces are obtained from measurements of ice-core density and conductivity with a 1D model of Maxwell's equations. The reflection peaks of the different radar systems' measurements are shifted by a wiggle-matching algorithm, so they match the synthetic trace. In this way, we matched pronounced internal reflections in the RES data to conductivity peaks with considerably smaller depth uncertainties, and assigned them with the ice-core age. We examine the differences in shifts and resolution of the different RES data to address the question of their comparability and combined analysis for an extensive age-depth distribution.

  6. Magneto-stratigraphic studies in Neogene deposits of Taylor Valley and McMurdo Sound, Antarctica.

    USGS Publications Warehouse

    Elston, D.P.; Bressler, S.L.

    1981-01-01

    Magnetic polarity and susceptibility zonations obtained from drill cores have served to refine temporal correlations in glaciogenic sections cored in eastern Taylor Valley. The zonations have led to a better understanding of the glacial and structural history for an interval of time that extends from the late Miocene (about 7Ma) to perhaps near the end of the Pliocene (approx 2.4-1.8Ma). However polarity data from a core drilled in McMurdo Sound (hole MSSTS-1) were found to be less useful. In this core, normal and reverse polarity deposits of Holocene, Pleistocene, and Pliocene age are nearly 40m thick and appear to uncomformably overlie strata assigned to the middle Miocene on the basis of a reworked fauna and flora. Gaps in the stratigraphic coverage of the Miocene strata, and two intervals in which the magnetisation post-dates deposition, however, have made development of a reliable polarity zonation impossible, and no firm correlation could be made with the magnetic polarity time scale. -Authors

  7. Foraminiferal Record From Drillcore AND-2A, Southern McMurdo Sound, Antarctica.

    NASA Astrophysics Data System (ADS)

    Ishman, S.; Johnson, K.; Sprovieri, M.; Lirer, F.

    2008-12-01

    ANDRILL's Southern McMurdo Sound Project (SMS) recovered a 1138.54 meter cored interval in drill core AND-2A. A total of four hundred and fifty-nine samples from lithostratigraphic units (LSUs) 1-14 of AND-2A were collected for initial foraminiferal analyses, of which 219 yielded foraminifera. Preliminary analyses resulted in the recognition of 25 taxonomic groups including 4 genera of planktonic and 21 genera of benthic foraminifera. Planktonic foraminifera are rare, occurring in LSUs 1, 2, 5, 7 and 12. Benthic foraminifera were recovered from LSUs 2-9, 11, 12, and 14 with diversity ranging from 1 to 10 taxa. Preservation ranges from Good to Poor with the best preservation of Good to Fair in LSUs 1, 2 and 3. The remaining intervals are represented by Fair to Poor preservation. Broad benthic foraminiferal zonations are observed. Zone 1 includes LSU 1 through LSU 5 and contains benthic foraminifera common to the late Miocene and mid- Pliocene assemblages of DVDP 10 and 11 from Taylor Valley. Zone 2 is restricted to LSU 7 and includes foraminifera indicating a possible early to mid-Miocene age and change in depositional environment. Foraminiferal Zone 3 is comprised of LSU 8.1 through 14. With the exception of LSU 9, this zone has the lowest diversity, poorest preservation and recovery in AND-2A. The foraminiferal assemblages reported are consistent with the current age model of the core, having affinities to early Miocene through mid- Pliocene assemblages from the Victoria Land Basin and its margins. Further analyses will increase the resolution of the foraminiferal zonations and allow for better correlation to not only DVDP 10 and 11 but to the additional drill cores from the Victoria Land Basin and its margin.

  8. Interpretation of Ice Sheet Stratigraphy: a Radio - Sounding Study of the Dyer Plateau, Antarctica.

    NASA Astrophysics Data System (ADS)

    Weertman, Bruce Randall

    Determining the flow history of ice sheets is an issue central to glaciology. Stratigraphic ice horizons provide the only known natural markers for inferring velocity at depth. Stratigraphy can be detected by radio-echo sounding (RES, also called radar) and dated by coring, which together determine the age field in the ice. In this thesis it is shown for the first time how ice flow can be deduced from stratigraphy. As a first step a method is given for the deduction of the spatial pattern of accumulation from shallow dated stratigraphy. The effects of densification and horizontal divergence are determined. It is then shown how, and when, internal motion can be deduced from dated stratigraphy. A theory is developed to deduce streamlines assuming steady-state flow and mass conservation. The theory does not require rheological assumptions or a spatial accumulation rate pattern. The theory can be used to determine internal deformation rates, accumulation rate history and whether or not observed stratigraphy is consistent with steady-state flow. As part of a collaborative program involving the British Antarctic Survey, the Byrd Polar Research Center, the Polar Ice Coring Office and the University of Washington, the author has used a newly devised RES system to measure the geometry of internal stratigraphy and ice thickness on the Dyer Plateau Ice Sheet, Antarctic Peninsula. RES -determined stratigraphy was dated by comparison to ice core stratigraphy. A prominent shallow RES horizon probably associated with the eruption of Tambora (1815) was used for estimating the spatial accumulation rate pattern. The estimated pattern is consistent with the pattern measured from burial markers indicating that the new method is accurate and that the recent accumulation rate pattern is not different from the 175 year average. An analysis of ice core stratigraphy indicates that over the past 500 years the accumulation rate has varied and over the past 50 years has had an increasing

  9. A Benthic Invertebrate Survey of Jun Jaegyu Volcano: An active undersea volcano in Antarctic Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Quinones, G.; Brachfeld, S.; Gorring, M.; Prezant, R. S.; Domack, E.

    2005-12-01

    Jun Jaegyu volcano, an Antarctic submarine volcano, was dredged in May 2004 during cruise 04-04 of the RV Laurence M. Gould to determine rock, sediment composition and marine macroinvertebrate diversity. The objectives of this study are to examine the benthic assemblages and biodiversity present on a young volcano. The volcano is located on the continental shelf of the northeastern Antarctic Peninsula, where recent changes in surface temperature and ice shelf stability have been observed. This volcano was originally swath-mapped during cruise 01-07 of the Research Vessel-Ice Breaker Nathaniel B. Palmer. During LMG04-04 we also studied the volcano using a SCUD video camera, and performed temperature surveys along the flanks and crest. Both the video and the dredge indicate a seafloor surface heavily colonized by benthic organisms. Indications of fairly recent lava flows are given by the absence of marine life on regions of the volcano. The recovered dredge material was sieved, and a total of thirty-three invertebrates were extracted. The compilation of invertebrate community data can subsequently be compared to other benthic invertebrate studies conducted along the peninsula, which can determine the regional similarity of communities over time, their relationship to environmental change and health, if any, and their relationship to geologic processes in Antarctic Sound. Twenty-two rock samples, all slightly weathered and half bearing encrusted organisms, were also analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES). Except for one conglomerate sample, all are alkali basalts and share similar elemental compositions with fresh, unweathered samples from the volcano. Two of the encrusted basalt samples have significantly different compositions than the rest. We speculate this difference could be due to water loss during sample preparation, loss of organic carbon trapped within the vesicles of the samples and/or elemental uptake by the

  10. How to generate a sound-localization map in fish

    NASA Astrophysics Data System (ADS)

    van Hemmen, J. Leo

    2015-03-01

    How sound localization is represented in the fish brain is a research field largely unbiased by theoretical analysis and computational modeling. Yet, there is experimental evidence that the axes of particle acceleration due to underwater sound are represented through a map in the midbrain of fish, e.g., in the torus semicircularis of the rainbow trout (Wubbels et al. 1997). How does such a map arise? Fish perceive pressure gradients by their three otolithic organs, each of which comprises a dense, calcareous, stone that is bathed in endolymph and attached to a sensory epithelium. In rainbow trout, the sensory epithelia of left and right utricle lie in the horizontal plane and consist of hair cells with equally distributed preferred orientations. We model the neuronal response of this system on the basis of Schuijf's vector detection hypothesis (Schuijf et al. 1975) and introduce a temporal spike code of sound direction, where optimality of hair cell orientation θj with respect to the acceleration direction θs is mapped onto spike phases via a von-Mises distribution. By learning to tune in to the earliest synchronized activity, nerve cells in the midbrain generate a map under the supervision of a locally excitatory, yet globally inhibitory visual teacher. Work done in collaboration with Daniel Begovic. Partially supported by BCCN - Munich.

  11. What Avian and Mammalian Sound Localization Have in Common

    NASA Astrophysics Data System (ADS)

    van Hemmen, J. Leo

    2004-03-01

    The barn owl has long been considered to be the canonical example of how azimuthal sound localization works: In the laminar nucleus, the first station (nucleus) where excitatory signals from both ears come together, each neuron encodes a specific direction in space through a maximal firing rate, i.e., maximal activity. In small mammals such as gerbils a completely different mechanism has been found to hold in that all neurons in the MSO, the equivalent (homolog) of the avian laminar nucleus, respond in the same way by means of a firing rate that is a monotone function of the stimulus direction. In so doing they exploit a subtle interplay of precisely timed excitation and inhibition. We present a theory [1] that fully explains both the avian and the mammalian auditory map through spike-timing-dependent synaptic plasticity (STDP) [2] of excitatory and inhibitory synapses during ontogeny. Hence we propose STDP as a universal principle underlying azimuthal sound localization. Refs: [1] C. Leibold and J.L. van Hemmen, TU Munich preprint (2003); [2] W. Gerstner, R. Kempter, J.L. van Hemmen, and H. Wagner, Nature 383 (1996) 76-78.

  12. Adaptive Sound Localization with a Silicon Cochlea Pair

    PubMed Central

    Chan, Vincent Yue-Sek; Jin, Craig T.; van Schaik, André

    2010-01-01

    A neuromorphic sound localization system is presented. It employs two microphones and a pair of silicon cochleae with address event interface for front-end processing. The system is based the extraction of interaural time difference from a far-field source. At each frequency channel, a soft-winner-takes-all network is used to preserve timing information before it is processed by a simple neural network to estimate auditory activity at all bearing positions. The estimates are then combined across channels to produce the final estimate. The proposed algorithm is adaptive and supports online learning, enabling the system to compensate for circuit mismatch and environmental changes. Its localization capability was tested with white noise and pure tone stimuli, with an average error of around 3° in the −45° to 45° range. PMID:21152257

  13. Interaction of katabatic wind and local surface mass balance at Scharffenbergbotnen Blue Ice Area, Antarctica

    NASA Astrophysics Data System (ADS)

    Zwinger, T.; Malm, T.; Schäfer, M.; Stenberg, R.; Moore, J. C.

    2015-04-01

    We model the wind causing the formation of a blue ice area in Scharffenbergbotnen valley, Antarctica, using the finite element code Elmer. The high resolution numerical simulations of the local wind flow from katabatic wind fronts show highly spatially variable wind impact patterns and good congruence between places of enhanced wind-impact and the blue ice area. The results were fortuitously confirmed by the destruction of a field camp located in a high wind speed area and its subsequent redistribution to low velocity areas. In addition we perform wind simulations on an altered glacier geometry that resembles the thicker ice cover at the Late Glacial Maximum (LGM). These simulations indicate that the pronounced spatial wind-impact patterns depend on present day geometry and did not occur during the LGM. This leads to the conclusion that the formation of the blue ice area that is situated more inside the valley of Scharffenbergbotnen started only after the lowering of the ice surface, later than the LGM. Experiments with smoothed surface topography suggest that detailed positions of the high wind regions and hence individual blue ice fields, may have varied as the ice sheet lowered. The experiments and the field observations are consistent with localized violent katabatic events, rather than synoptic scale storms, playing the dominant role in the formation and maintenance of this, and perhaps many blue ice areas.

  14. Sound localization and auditory response capabilities in round goby (Neogobius melanostomus)

    NASA Astrophysics Data System (ADS)

    Rollo, Audrey K.; Higgs, Dennis M.

    2005-04-01

    A fundamental role in vertebrate auditory systems is determining the direction of a sound source. While fish show directional responses to sound, sound localization remains in dispute. The species used in the current study, Neogobius melanostomus (round goby) uses sound in reproductive contexts, with both male and female gobies showing directed movement towards a calling male. The two-choice laboratory experiment was used (active versus quiet speaker) to analyze behavior of gobies in response to sound stimuli. When conspecific male spawning sounds were played, gobies moved in a direct path to the active speaker, suggesting true localization to sound. Of the animals that responded to conspecific sounds, 85% of the females and 66% of the males moved directly to the sound source. Auditory playback of natural and synthetic sounds showed differential behavioral specificity. Of gobies that responded, 89% were attracted to the speaker playing Padogobius martensii sounds, 87% to 100 Hz tone, 62% to white noise, and 56% to Gobius niger sounds. Swimming speed, as well as mean path angle to the speaker, will be presented during the presentation. Results suggest a strong localization of the round goby to a sound source, with some differential sound specificity.

  15. Visual capture of a stereo sound: Interactions between cue reliability, sound localization variability, and cross-modal bias.

    PubMed

    Montagne, Christopher; Zhou, Yi

    2016-07-01

    Multisensory interactions involve coordination and sometimes competition between multiple senses. Vision usually dominates audition in spatial judgments when light and sound stimuli are presented from two different physical locations. This study investigated the influence of vision on the perceived location of a phantom sound source placed in a stereo sound field using a pair of loudspeakers emitting identical signals that were delayed or attenuated relative to each other. Results show that although a similar horizontal range (+/-45°) was reported for timing-modulated and level-modulated signals, listeners' localization performance showed greater variability for the timing signals. When visual stimuli were presented simultaneously with the auditory stimuli, listeners showed stronger visual bias for timing-modulated signals than level-modulated and single-speaker control signals. Trial-to-trial errors remained relatively stable over time, suggesting that sound localization uncertainty has an immediate and long-lasting effect on the across-modal bias. Binaural signal analyses further reveal that interaural differences of time and intensity-the two primary cues for sound localization in the azimuthal plane-are inherently more ambiguous for signals placed using timing. These results suggest that binaural ambiguity is intrinsically linked with localization variability and the strength of cross-modal bias in sound localization. PMID:27475171

  16. Echo Source Discrimination in Airborne Radar Sounding Data From the Dry Valleys, Antarctica, for Mars Analog Studies

    NASA Astrophysics Data System (ADS)

    Holt, J. W.; Blankenship, D. D.; Peters, M. E.; Kempf, S. D.; Williams, B. J.

    2003-12-01

    The identification of features on Mars exhibiting morphologies consistent with ice/rock mixtures, near-surface ice bodies and near-surface liquid water, and the importance of such features to the search for water on Mars highlights the need for appropriate terrestrial analogs in order to prepare for upcoming radar missions targeting these and other water-related features. Climatic, hydrological, and geological conditions in the McMurdo Dry Valleys of Antarctica are analogous in many ways to those on Mars, and a number of ice-related features in the Dry Valleys may have direct morphologic and compositional counterparts on Mars. We have collected roughly 1,000 line-km of airborne radar sounding data in the Dry Valleys for Mars analog studies. A crucial first step in the data analysis process is the discrimination of echo sources in the radar data. The goal is to identify all returns from the surface of surrounding topography in order to positively identify subsurface echoes. This process will also be critical for radar data that will be collected in areas of Mars exhibiting significant topography, so that subsurface echoes are identified unambiguously. Using a Twin Otter airborne platform, data were collected in three separate flights during the austral summers of 1999-2000 and 2001-2002 using multiple systems, including a chirped 52.5 - 67.5 MHz coherent radar operating at 750 W and 8 kW peak power (with multiple receivers) and 1 - 2 microsecond pulse width, and a 60 MHz pulsed, incoherent radar operating at 8 kW peak power with 60 ns and 250 ns pulse width. The chirped, coherent data are suitable for the implementation of advanced pulse compression algorithms and SAR focusing. Flight elevation was nominally 500 m above the surface. Targets included permafrost, subsurface ice bodies, rock/ice glaciers, ice-covered saline lakes, and glacial deposits in Taylor and Beacon Valleys. A laser altimeter (fixed relative to the aircraft frame) was also used during both

  17. Manual of Suggested Activities for the Development of Sound Localization Skills.

    ERIC Educational Resources Information Center

    Brothers, Roy J.; Huff, Roger A.

    The manual is intended to provide teachers of young blind children with activities to develop sound localization skills. Both group and individual activities are suggested for the following four categories: activities in which both child and sound are stationary, activities in which the child is stationary but the sound is moving, activities in…

  18. Sensitive and critical periods for visual calibration of sound localization by barn owls.

    PubMed

    Knudsen, E I; Knudsen, P F

    1990-01-01

    This study describes developmental changes in the capacity of owls to adjust sound localization in response to chronic prismatic displacement of the visual field and to recover accurate sound localization following the restoration of normal vision. Matched, binocular displacing prisms were mounted over the eyes of 19 barn owls (Tyto alba) beginning at ages ranging from 10 to 272 d. In nearly all cases, the visual field was shifted 23 degrees to the right. Sound localization was assessed on the basis of head orientations to sound sources, measured in a darkened sound chamber with a search coil system. Chronic exposure to a displaced visual field caused the owls to alter sound localization in the direction of the visual field displacement, thereby inducing a sound-localization error. The size of the sound-localization error that resulted depended on the age of the animal when prism experience began. Maximal errors of about 20 degrees were induced only when prism experience began by 21 d of age. As prism experience began at later ages, the magnitude of induced errors decreased. A bird that wore prisms beginning at 102 d of age, altered sound localization by only 6 degrees. An adult owl, when exposed chronically to a displaced visual field, altered sound localization by about 3 degrees. We refer to the early period in life when displaced vision induces exceptionally large sound-localization errors (relative to those induced in the adult) as a sensitive period. The capacity to recover accurate sound localization following restoration of normal vision was tested in 7 owls that had been raised wearing prisms. Four owls that had prisms removed by 182 d of age recovered accurate localization rapidly (over a period of weeks), whereas 3 owls that were older when the prisms were removed did not recover accurate localization when tested for up to 7 months after prism removal. Adjustment of sound localization slowed greatly or ceased at about 200 days of age, referred to here as

  19. Comparative physiology of sound localization in four species of owls.

    PubMed

    Volman, S F; Konishi, M

    1990-01-01

    Bilateral ear asymmetry is found in some, but not all, species of owls. We investigated the neural basis of sound localization in symmetrical and asymmetrical species, to deduce how ear asymmetry might have evolved from the ancestral condition, by comparing the response properties of neurons in the external nucleus of the inferior colliculus (ICx) of the symmetrical burrowing owl and asymmetrical long-eared owl with previous findings in the symmetrical great horned owl and asymmetrical barn owl. In the ICx of all of these owls, the neurons had spatially restricted receptive fields, and auditory space was topographically mapped. In the symmetrical owls, ICx units were not restricted in elevation, and only azimuth was mapped in ICx. In the barn owl, the space map is two-dimensional, with elevation forming the second dimension. Receptive fields in the long-eared owl were somewhat restricted in elevation, but their tuning was not sharp enough to determine if elevation is mapped. In every species, the primary cue for azimuth was interaural time difference, although ICx units were also tuned for interaural intensity difference (IID). In the barn owl, the IIDs of sounds with frequencies between about 5 and 8 kHz vary systematically with elevation, and the IID selectivity of ICx neurons primarily encodes elevation. In the symmetrical owls, whose ICx neurons do not respond to frequencies above about 5 kHz, IID appears to be a supplementary cue for azimuth. We hypothesize that ear asymmetry can be exploited by owls that have evolved the higher-frequency hearing necessary to generate elevation cues. Thus, the IID selectivity of ICx neurons in symmetrical owls may preadapt them for asymmetry; the neural circuitry that underlies IID selectivity is already present in symmetrical owls, but because IID is not absolutely required to encode azimuth it can come to encode elevation in asymmetrical owls. PMID:2279234

  20. Skin microbial flora and effectiveness of aseptic technique for deep muscle biopsies in Weddell seals (Leptonychotes weddellii ) in McMurdo Sound, Antarctica.

    PubMed

    Mellish, J; Tuomi, P; Hindle, A; Jang, S; Horning, M

    2010-04-01

    Deep muscle biopsies were collected from the pectoralis and longissimus dorsi of wild Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarctica, during October-December 2007. Sterile swabs were collected from the surface of each skin site before biopsy and from the deep-needle path after biopsy. No growth occurred in two of six pectoralis and three of six longissimus skin sites, or in four of 10 pectoralis deep biopsy and eight of 12 longissimus deep-biopsy sites. Positive skin culture was not predictive of deep-biopsy contamination, nor did contamination at one body location correlate with contamination at the second site. Psychrobacter species were most common in one or more samples from each of the four sample types. Only one of the eight documented bacteria exhibited resistance to commonly used antibiotics. PMID:20688668

  1. Spatial resolution limits for the localization of noise sources using direct sound mapping

    NASA Astrophysics Data System (ADS)

    Fernandez Comesaña, D.; Holland, K. R.; Fernandez-Grande, E.

    2016-08-01

    One of the main challenges arising from noise and vibration problems is how to identify the areas of a device, machine or structure that produce significant acoustic excitation, i.e. the localization of main noise sources. The direct visualization of sound, in particular sound intensity, has extensively been used for many years to locate sound sources. However, it is not yet well defined when two sources should be regarded as resolved by means of direct sound mapping. This paper derives the limits of the direct representation of sound pressure, particle velocity and sound intensity by exploring the relationship between spatial resolution, noise level and geometry. The proposed expressions are validated via simulations and experiments. It is shown that particle velocity mapping yields better results for identifying closely spaced sound sources than sound pressure or sound intensity, especially in the acoustic near-field.

  2. Sound localization with bilateral cochlear implants in noise: how much do head movements contribute to localization?

    PubMed

    Mueller, Martin F; Meisenbacher, Katrin; Lai, Wai-Kong; Dillier, Norbert

    2014-01-01

    Bilateral cochlear implant (CI) users encounter difficulties in localizing sound sources in everyday environments, especially in the presence of background noise and reverberation. They tend to show large directional errors and front-back confusions compared to normal hearing (NH) subjects in the same conditions. In this study, the ability of bilateral CI users to use head movements to improve sound source localization was evaluated. Speech sentences of 0.5, 2, and 4.5 seconds were presented in noise to the listeners in conditions with and without head movements. The results show that for middle and long signal durations, the CI users could significantly reduce the number of front-back confusions. The angular accuracy, however, did not improve. Analysis of head trajectories showed that the CI users had great difficulties in moving their head towards the position of the source, whereas the NH listeners targeted the source loudspeaker correctly. PMID:23684420

  3. Organized flow from the South Pole to the Filchner-Ronne ice shelf: An assessment of balance velocities in interior East Antarctica using radio echo sounding data

    NASA Astrophysics Data System (ADS)

    Bingham, Robert G.; Siegert, Martin J.; Young, Duncan A.; Blankenship, Donald D.

    2007-09-01

    Ice flow through central Antarctica has the potential to transmit accumulation changes from deep-interior East Antarctica rapidly to the shelf, but it is poorly constrained owing to a dearth of ice-velocity observations. We use parameters derived from airborne radio echo sounding (RES) data to examine the onset, areal extent, and englacial conditions of an organized flow network (tributaries feeding an ice stream) draining from the South Pole to the Filchner-Ronne Ice Shelf. We classified RES flight tracks covering the region according to whether englacial stratigraphy was disrupted (i.e., internal layers diverged significantly from the surface and bed echoes) or undisrupted (i.e., internal layers closely parallel surface and basal topography), and we calculated subglacial roughness along basal reflectors. Where satellite-measured surface ice-flow speeds are available (covering 39% of the study region), regions of fast and tributary flow correspond with RES flight tracks that exhibit more disrupted internal layers and smoother subglacial topography than their counterparts in regions of slow flow. This suggests that disrupted internal layering and smooth subglacial topography identified from RES profiles can be treated as indicators of past or present enhanced-flow tributaries where neither satellite nor ground-based ice-flow measurements are available. We therefore use these RES-derived parameters to assess the balance-flux-modeled steady state flow regime between the South Pole and Filchner-Ronne Ice Shelf. The RES analysis confirms that an organized flow network drains a wide region around the South Pole into the Filchner-Ronne Ice Shelf. However, the spatial extent of this network, as delineated by the RES data, diverges from that predicted by currently available balance-flux models.

  4. Horizontal sound localization in cochlear implant users with a contralateral hearing aid.

    PubMed

    Veugen, Lidwien C E; Hendrikse, Maartje M E; van Wanrooij, Marc M; Agterberg, Martijn J H; Chalupper, Josef; Mens, Lucas H M; Snik, Ad F M; John van Opstal, A

    2016-06-01

    Interaural differences in sound arrival time (ITD) and in level (ILD) enable us to localize sounds in the horizontal plane, and can support source segregation and speech understanding in noisy environments. It is uncertain whether these cues are also available to hearing-impaired listeners who are bimodally fitted, i.e. with a cochlear implant (CI) and a contralateral hearing aid (HA). Here, we assessed sound localization behavior of fourteen bimodal listeners, all using the same Phonak HA and an Advanced Bionics CI processor, matched with respect to loudness growth. We aimed to determine the availability and contribution of binaural (ILDs, temporal fine structure and envelope ITDs) and monaural (loudness, spectral) cues to horizontal sound localization in bimodal listeners, by systematically varying the frequency band, level and envelope of the stimuli. The sound bandwidth had a strong effect on the localization bias of bimodal listeners, although localization performance was typically poor for all conditions. Responses could be systematically changed by adjusting the frequency range of the stimulus, or by simply switching the HA and CI on and off. Localization responses were largely biased to one side, typically the CI side for broadband and high-pass filtered sounds, and occasionally to the HA side for low-pass filtered sounds. HA-aided thresholds better than 45 dB HL in the frequency range of the stimulus appeared to be a prerequisite, but not a guarantee, for the ability to indicate sound source direction. We argue that bimodal sound localization is likely based on ILD cues, even at frequencies below 1500 Hz for which the natural ILDs are small. These cues are typically perturbed in bimodal listeners, leading to a biased localization percept of sounds. The high accuracy of some listeners could result from a combination of sufficient spectral overlap and loudness balance in bimodal hearing. PMID:27178443

  5. Challenges to Airborne and Orbital Radar Sounding in the Presence of Surface Clutter: Lessons Learned (so far) from the Dry Valleys of Antarctica

    NASA Astrophysics Data System (ADS)

    Holt, J. W.; Peters, M. E.; Kempf, S. D.; Morse, D. L.; Blankenship, D. D.

    2005-12-01

    The search for life and in-situ resources for exploration on Mars targets both liquid and solid water, whether distributed or in reservoirs. Massive surface ice may cover potential habitats or other features of great interest. Ice-rich layering in the high latitudes holds clues to the climatic history of the planet. Multiple geophysical methods will clearly be necessary to fully characterize these various states of water (and other forms of ice), but radar sounding will be a critical component of the effort. Orbital radar sounders are already being employed and plans for surface-based and suborbital, above-surface radar sounders are being discussed. The difficulties in interpreting data from each type of platform are quite different. Given the lack of existing orbital radar sounding data from any planetary body, the analysis of airborne radar sounding data is quite useful for assessing the advantages and disadvantages of above-surface radar sounding on Mars. In addition to over 300,000 line-km of data collected over the Antarctic ice sheet by airborne radar sounding, we have recently analyzed data from the Dry Valleys of Antarctica where conditions and features emulate Mars in several respects. These airborne radar sounding data were collected over an ice-free area of Taylor Valley, ice-covered lakes, Taylor Glacier, and Beacon Valley. The pulsed radar (52.5 - 67.5 MHz chirp) was coherently recorded. Pulse compression and unfocused SAR processing were applied. One of the most challenging aspects of above-surface radar sounding is the determination of echo sources. This can, of course, be problematic for surface-based radar sounders given possible subsurface scattering geometries, but it is most severe for above-surface sounders because echoes from cross-track surface topography (surface clutter) can have similar time delays to those from the subsurface. We have developed two techniques to accomplish the identification of this surface clutter in single-pass airborne

  6. Spike-Timing-Based Computation in Sound Localization

    PubMed Central

    Goodman, Dan F. M.; Brette, Romain

    2010-01-01

    Spike timing is precise in the auditory system and it has been argued that it conveys information about auditory stimuli, in particular about the location of a sound source. However, beyond simple time differences, the way in which neurons might extract this information is unclear and the potential computational advantages are unknown. The computational difficulty of this task for an animal is to locate the source of an unexpected sound from two monaural signals that are highly dependent on the unknown source signal. In neuron models consisting of spectro-temporal filtering and spiking nonlinearity, we found that the binaural structure induced by spatialized sounds is mapped to synchrony patterns that depend on source location rather than on source signal. Location-specific synchrony patterns would then result in the activation of location-specific assemblies of postsynaptic neurons. We designed a spiking neuron model which exploited this principle to locate a variety of sound sources in a virtual acoustic environment using measured human head-related transfer functions. The model was able to accurately estimate the location of previously unknown sounds in both azimuth and elevation (including front/back discrimination) in a known acoustic environment. We found that multiple representations of different acoustic environments could coexist as sets of overlapping neural assemblies which could be associated with spatial locations by Hebbian learning. The model demonstrates the computational relevance of relative spike timing to extract spatial information about sources independently of the source signal. PMID:21085681

  7. Infants' Perception of Illusions in Sound Localization: Reaching to Sounds in the Dark.

    ERIC Educational Resources Information Center

    Hillier, Loretta; And Others

    1992-01-01

    Infants between four and eight months of age were tested for their ability to reach for visible and unseen toys that made sounds. Infants reached for toys in the dark under two auditory illusion conditions, the Haas effect and the midline illusion. Results indicated that, by four months of age, infants perceived the Haas effect and the midline…

  8. 76 FR 42542 - Special Local Regulations for Marine Events, Bogue Sound; Morehead City, NC

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-19

    ... for Marine Events, Bogue Sound; Morehead City, North Carolina in the Federal Register (76 FR 30887... establishing Special Local Regulations for ``The Crystal Coast Grand Prix'' powerboat race, to be held on the... sponsor ``The Crystal Coast Grand Prix'' powerboat race on the waters of Bogue Sound adjacent to...

  9. A SOUND SOURCE LOCALIZATION TECHNIQUE TO SUPPORT SEARCH AND RESCUE IN LOUD NOISE ENVIRONMENTS

    NASA Astrophysics Data System (ADS)

    Yoshinaga, Hiroshi; Mizutani, Koichi; Wakatsuki, Naoto

    At some sites of earthquakes and other disasters, rescuers search for people buried under rubble by listening for the sounds which they make. Thus developing a technique to localize sound sources amidst loud noise will support such search and rescue operations. In this paper, we discuss an experiment performed to test an array signal processing technique which searches for unperceivable sound in loud noise environments. Two speakers simultaneously played a noise of a generator and a voice decreased by 20 dB (= 1/100 of power) from the generator noise at an outdoor space where cicadas were making noise. The sound signal was received by a horizontally set linear microphone array 1.05 m in length and consisting of 15 microphones. The direction and the distance of the voice were computed and the sound of the voice was extracted and played back as an audible sound by array signal processing.

  10. Detection and localization of sounds: Virtual tones and virtual reality

    NASA Astrophysics Data System (ADS)

    Zhang, Peter Xinya

    IPD-meter or an ITD-meter. Listeners estimated the lateral positions of 50 sine tones with IPDs ranging from -150° to +150° and with different frequencies, all in the range where signal fine structure supports lateralization. The estimates indicated that listeners lateralize sine tones on the basis of ITD and not IPD. In order to distinguish between sound sources in front and in back, listeners use spectral cues caused by the diffraction by pinna, head, neck and torso. To study this effect, the VRX technique was developed based on transaural technology. The technique was successful in presenting desired spectra into listeners' ears with high accuracy up to 16 kHz. When presented with real source and simulated virtual signal, listeners in an anechoic room could not distinguish between them. Eleven experiments on discrimination between front and back sources were carried out in an anechoic room. The results show several findings. First, the results support a multiple band comparison model, and disfavor a necessary band(s) model. Second, it was found that preserving the spectral dips was more important than preserving the spectral peaks for successful front/back discrimination. Moreover, it was confirmed that neither monaural cues nor interaural spectral level difference cues were adequate for front/back discrimination. Furthermore, listeners' performance did not deteriorate when presented with sharpened spectra. Finally, when presented with an interaural delay less than 200 mus, listeners could succeed to discriminate front from back, although the image was pulled to the side, which suggests that the localizations in azimuthal plane and in sagittal plane are independent within certain limits.

  11. Issues in Humanoid Audition and Sound Source Localization by Active Audition

    NASA Astrophysics Data System (ADS)

    Nakadai, Kazuhiro; Okuno, Hiroshi G.; Kitano, Hiroaki

    In this paper, we present an active audition system which is implemented on the humanoid robot "SIG the humanoid". The audition system for highly intelligent humanoids localizes sound sources and recognizes auditory events in the auditory scene. Active audition reported in this paper enables SIG to track sources by integrating audition, vision, and motor movements. Given the multiple sound sources in the auditory scene, SIG actively moves its head to improve localization by aligning microphones orthogonal to the sound source and by capturing the possible sound sources by vision. However, such an active head movement inevitably creates motor noises.The system adaptively cancels motor noises using motor control signals and the cover acoustics. The experimental result demonstrates that active audition by integration of audition, vision, and motor control attains sound source tracking in variety of conditions.onditions.

  12. Decoding neural responses to temporal cues for sound localization

    PubMed Central

    Goodman, Dan FM; Benichoux, Victor; Brette, Romain

    2013-01-01

    The activity of sensory neural populations carries information about the environment. This may be extracted from neural activity using different strategies. In the auditory brainstem, a recent theory proposes that sound location in the horizontal plane is decoded from the relative summed activity of two populations in each hemisphere, whereas earlier theories hypothesized that the location was decoded from the identity of the most active cells. We tested the performance of various decoders of neural responses in increasingly complex acoustical situations, including spectrum variations, noise, and sound diffraction. We demonstrate that there is insufficient information in the pooled activity of each hemisphere to estimate sound direction in a reliable way consistent with behavior, whereas robust estimates can be obtained from neural activity by taking into account the heterogeneous tuning of cells. These estimates can still be obtained when only contralateral neural responses are used, consistently with unilateral lesion studies. DOI: http://dx.doi.org/10.7554/eLife.01312.001 PMID:24302571

  13. Effect of local cooling on skin temperature and blood flow of men in Antarctica

    NASA Astrophysics Data System (ADS)

    Naidu, M.; Sachdeva, U.

    1993-12-01

    Alterations to the finger skin temperature (Tsk) and blood flow (FBF) before and after cold immersion on exposure to an Antarctic environment for 8 weeks were studied in 64 subjects. There was a significant fall in Tsk and increase in finger blood flow after 1 week of Antarctic exposure. The Tsk did not further change even after 8 weeks of stay in Antarctica but a significant increase in FBF was obtained after 8 weeks. The cold immersion test was performed at non-Antarctic and Antarctic conditions by immersing the hand for 2 min in 0 4° C cold water. In the non-Antarctic environment the Tsk and FBF dropped significantly ( P < 0.001) indicating a vasoconstriction response. Interestingly after 8 weeks of stay in Antarctic conditions, the skin temperature dropped ( P < 0.001) but the cold induced fall in FBF was inhibited. Based on these observations it may be hypothesized that continuous cold exposure in Antarctica results in vasodilatation, which overrides the stronger vasoactive response of acute cold exposure and thus prevents cold injuries.

  14. Airborne and ground based measurements in McMurdo Sound, Antarctica, for the validation of satellite derived ice thickness

    NASA Astrophysics Data System (ADS)

    Rack, Wolfgang; Haas, Christian; Langhorne, Pat; Leonard, Greg; Price, Dan; Barnsdale, Kelvin; Soltanzadeh, Iman

    2014-05-01

    Melting and freezing processes in the ice shelf cavities of the Ross and McMurdo Ice Shelves significantly influence the sea ice formation in McMurdo Sound. Between 2009 and 2013 we used a helicopter-borne laser and electromagnetic induction sounder (EM bird) to measure thickness and freeboard profiles across the ice shelf and the landfast sea ice, which was accompanied by extensive field validation, and coordinated with satellite altimeter overpasses. Using freeboard and thickness, the bulk density of all ice types was calculated assuming hydrostatic equilibrium. Significant density steps were detected between first-year and multi-year sea ice, with higher values for the younger sea ice. Values are overestimated in areas with abundance of sub-ice platelets because of overestimation in both ice thickness and freeboard. On the ice shelf, bulk ice densities were sometimes higher than that of pure ice, which can be explained by both the accretion of marine ice and glacial sediments. For thin ice, the freeboard to thickness conversion critically depends on the knowledge of snow properties. Our measurements allow tuning and validation of snow cover simulations using the Weather Research Forecasting (WRF) model. The simulated snowcover is used to calculate ice thickness from satellite derived freeboard. The results of our measurements, which are supported by the New Zealand Antarctic programme, draw a picture of how oceanographic processes influence the ice shelf morphology and sea ice formation in McMurdo Sound, and how satellite derived freeboard of ICESat and CryoSat together with information on snow cover can potentially capture the signature of these processes.

  15. Localization of virtual sound sources with bilateral hearing aids in realistic acoustical scenes.

    PubMed

    Mueller, Martin F; Kegel, Andrea; Schimmel, Steven M; Dillier, Norbert; Hofbauer, Markus

    2012-06-01

    Sound localization with hearing aids has traditionally been investigated in artificial laboratory settings. These settings are not representative of environments in which hearing aids are used. With individual Head-Related Transfer Functions (HRTFs) and room simulations, realistic environments can be reproduced and the performance of hearing aid algorithms can be evaluated. In this study, four different environments with background noise have been implemented in which listeners had to localize different sound sources. The HRTFs were measured inside the ear canals of the test subjects and by the microphones of Behind-The-Ear (BTEs) hearing aids. In the first experiment the system for virtual acoustics was evaluated by comparing perceptual sound localization results for the four scenes in a real room with a simulated one. In the second experiment, sound localization with three BTE algorithms, an omnidirectional microphone, a monaural cardioid-shaped beamformer and a monaural noise canceler, was examined. The results showed that the system for generating virtual environments is a reliable tool to evaluate sound localization with hearing aids. With BTE hearing aids localization performance decreased and the number of front-back confusions was at chance level. The beamformer, due to its directivity characteristics, allowed the listener to resolve the front-back ambiguity. PMID:22712946

  16. Representation of sound localization cues in the auditory thalamus of the barn owl.

    PubMed

    Proctor, L; Konishi, M

    1997-09-16

    Barn owls can localize a sound source using either the map of auditory space contained in the optic tectum or the auditory forebrain. The auditory thalamus, nucleus ovoidalis (N.Ov), is situated between these two auditory areas, and its inactivation precludes the use of the auditory forebrain for sound localization. We examined the sources of inputs to the N.Ov as well as their patterns of termination within the nucleus. We also examined the response of single neurons within the N.Ov to tonal stimuli and sound localization cues. Afferents to the N.Ov originated with a diffuse population of neurons located bilaterally within the lateral shell, core, and medial shell subdivisions of the central nucleus of the inferior colliculus. Additional afferent input originated from the ipsilateral ventral nucleus of the lateral lemniscus. No afferent input was provided to the N.Ov from the external nucleus of the inferior colliculus or the optic tectum. The N.Ov was tonotopically organized with high frequencies represented dorsally and low frequencies ventrally. Although neurons in the N.Ov responded to localization cues, there was no apparent topographic mapping of these cues within the nucleus, in contrast to the tectal pathway. However, nearly all possible types of binaural response to sound localization cues were represented. These findings suggest that in the thalamo-telencephalic auditory pathway, sound localization is subserved by a nontopographic representation of auditory space. PMID:9294226

  17. Sound

    NASA Astrophysics Data System (ADS)

    Capstick, J. W.

    2013-01-01

    1. The nature of sound; 2. Elasticity and vibrations; 3. Transverse waves; 4. Longitudinal waves; 5. Velocity of longitudinal waves; 6. Reflection and refraction. Doppler's principle; 7. Interference. Beats. Combination tones; 8. Resonance and forced vibrations; 9. Quality of musical notes; 10. Organ pipes; 11. Rods. Plates. Bells; 12. Acoustical measurements; 13. The phonograph, microphone and telephone; 14. Consonance; 15. Definition of intervals. Scales. Temperament; 16. Musical instruments; 17. Application of acoustical principles to military purposes; Questions; Answers to questions; Index.

  18. Sound source localization by hearing preservation patients with and without symmetric, low-frequency acoustic hearing

    PubMed Central

    Loiselle, Louise H.; Dorman, Michael F.; Yost, William A.; Gifford, Rene H.

    2015-01-01

    The aim of this paper was to study sound source localization by cochlear implant (CI) listeners with low-frequency (LF) acoustic hearing in both the operated ear and in the contralateral ear. Eight CI listeners had symmetrical LF acoustic hearing (symm) and four had asymmetric LF acoustic hearing (asymm). The effects of two variables were assessed: (i) the symmetry of the LF thresholds in the two ears and (ii) the presence/absence of bilateral acoustic amplification. Stimuli consisted of low-pass, high pass, and wide-band noise bursts presented in the frontal horizontal plane. Localization accuracy was 23 degrees of error for the symm listeners and 76 degrees of error for the asymm listeners. The presence of a unilateral CI used in conjunction with bilateral LF acoustic hearing does not impair sound source localization accuracy, but amplification for acoustic hearing can be detrimental to sound source localization accuracy. PMID:25832907

  19. Abiotic versus Biotic Drivers of Ocean pH Variation under Fast Sea Ice in McMurdo Sound, Antarctica

    PubMed Central

    Matson, Paul G.; Washburn, Libe; Martz, Todd R.; Hofmann, Gretchen E.

    2014-01-01

    Ocean acidification is expected to have a major effect on the marine carbonate system over the next century, particularly in high latitude seas. Less appreciated is natural environmental variation within these systems, particularly in terms of pH, and how this natural variation may inform laboratory experiments. In this study, we deployed sensor-equipped moorings at 20 m depths at three locations in McMurdo Sound, comprising deep (bottom depth>200 m: Hut Point Peninsula) and shallow environments (bottom depth ∼25 m: Cape Evans and New Harbor). Our sensors recorded high-frequency variation in pH (Hut Point and Cape Evans only), tide (Cape Evans and New Harbor), and water mass properties (temperature and salinity) during spring and early summer 2011. These collective observations showed that (1) pH differed spatially both in terms of mean pH (Cape Evans: 8.009±0.015; Hut Point: 8.020±0.007) and range of pH (Cape Evans: 0.090; Hut Point: 0.036), and (2) pH was not related to the mixing of two water masses, suggesting that the observed pH variation is likely not driven by this abiotic process. Given the large daily fluctuation in pH at Cape Evans, we developed a simple mechanistic model to explore the potential for biotic processes – in this case algal photosynthesis – to increase pH by fixing carbon from the water column. For this model, we incorporated published photosynthetic parameters for the three dominant algal functional groups found at Cape Evans (benthic fleshy red macroalgae, crustose coralline algae, and sea ice algal communities) to estimate oxygen produced/carbon fixed from the water column underneath fast sea ice and the resulting pH change. These results suggest that biotic processes may be a primary driver of pH variation observed under fast sea ice at Cape Evans and potentially at other shallow sites in McMurdo Sound. PMID:25221950

  20. Abiotic versus biotic drivers of ocean pH variation under fast sea ice in McMurdo Sound, Antarctica.

    PubMed

    Matson, Paul G; Washburn, Libe; Martz, Todd R; Hofmann, Gretchen E

    2014-01-01

    Ocean acidification is expected to have a major effect on the marine carbonate system over the next century, particularly in high latitude seas. Less appreciated is natural environmental variation within these systems, particularly in terms of pH, and how this natural variation may inform laboratory experiments. In this study, we deployed sensor-equipped moorings at 20 m depths at three locations in McMurdo Sound, comprising deep (bottom depth>200 m: Hut Point Peninsula) and shallow environments (bottom depth ∼25 m: Cape Evans and New Harbor). Our sensors recorded high-frequency variation in pH (Hut Point and Cape Evans only), tide (Cape Evans and New Harbor), and water mass properties (temperature and salinity) during spring and early summer 2011. These collective observations showed that (1) pH differed spatially both in terms of mean pH (Cape Evans: 8.009±0.015; Hut Point: 8.020±0.007) and range of pH (Cape Evans: 0.090; Hut Point: 0.036), and (2) pH was not related to the mixing of two water masses, suggesting that the observed pH variation is likely not driven by this abiotic process. Given the large daily fluctuation in pH at Cape Evans, we developed a simple mechanistic model to explore the potential for biotic processes--in this case algal photosynthesis--to increase pH by fixing carbon from the water column. For this model, we incorporated published photosynthetic parameters for the three dominant algal functional groups found at Cape Evans (benthic fleshy red macroalgae, crustose coralline algae, and sea ice algal communities) to estimate oxygen produced/carbon fixed from the water column underneath fast sea ice and the resulting pH change. These results suggest that biotic processes may be a primary driver of pH variation observed under fast sea ice at Cape Evans and potentially at other shallow sites in McMurdo Sound. PMID:25221950

  1. Sound localization with head movement: implications for 3-d audio displays

    PubMed Central

    McAnally, Ken I.; Martin, Russell L.

    2014-01-01

    Previous studies have shown that the accuracy of sound localization is improved if listeners are allowed to move their heads during signal presentation. This study describes the function relating localization accuracy to the extent of head movement in azimuth. Sounds that are difficult to localize were presented in the free field from sources at a wide range of azimuths and elevations. Sounds remained active until the participants' heads had rotated through windows ranging in width of 2, 4, 8, 16, 32, or 64° of azimuth. Error in determining sound-source elevation and the rate of front/back confusion were found to decrease with increases in azimuth window width. Error in determining sound-source lateral angle was not found to vary with azimuth window width. Implications for 3-d audio displays: the utility of a 3-d audio display for imparting spatial information is likely to be improved if operators are able to move their heads during signal presentation. Head movement may compensate in part for a paucity of spectral cues to sound-source location resulting from limitations in either the audio signals presented or the directional filters (i.e., head-related transfer functions) used to generate a display. However, head movements of a moderate size (i.e., through around 32° of azimuth) may be required to ensure that spatial information is conveyed with high accuracy. PMID:25161605

  2. Perceptual factors contribute more than acoustical factors to sound localization abilities with virtual sources

    PubMed Central

    Andéol, Guillaume; Savel, Sophie; Guillaume, Anne

    2015-01-01

    Human sound localization abilities rely on binaural and spectral cues. Spectral cues arise from interactions between the sound wave and the listener's body (head-related transfer function, HRTF). Large individual differences were reported in localization abilities, even in young normal-hearing adults. Several studies have attempted to determine whether localization abilities depend mostly on acoustical cues or on perceptual processes involved in the analysis of these cues. These studies have yielded inconsistent findings, which could result from methodological issues. In this study, we measured sound localization performance with normal and modified acoustical cues (i.e., with individual and non-individual HRTFs, respectively) in 20 naïve listeners. Test conditions were chosen to address most methodological issues from past studies. Procedural training was provided prior to sound localization tests. The results showed no direct relationship between behavioral results and an acoustical metrics (spectral-shape prominence of individual HRTFs). Despite uncertainties due to technical issues with the normalization of the HRTFs, large acoustical differences between individual and non-individual HRTFs appeared to be needed to produce behavioral effects. A subset of 15 listeners then trained in the sound localization task with individual HRTFs. Training included either visual correct-answer feedback (for the test group) or no feedback (for the control group), and was assumed to elicit perceptual learning for the test group only. Few listeners from the control group, but most listeners from the test group, showed significant training-induced learning. For the test group, learning was related to pre-training performance (i.e., the poorer the pre-training performance, the greater the learning amount) and was retained after 1 month. The results are interpreted as being in favor of a larger contribution of perceptual factors than of acoustical factors to sound localization

  3. Sound localization in reverberant environments: physiological bases of the precedence effect

    NASA Astrophysics Data System (ADS)

    Paterson, Miles Andrew McLean

    Localization dominance, a phenomenon of the precedence effect, refers to the dominance of directional cues conveyed by sound arriving directly from the source over cues conveyed by reflected copies on the perception of sound source location. One theory of localization dominance is that leading sounds suppress neural responses to lagging sounds (Yin, 1994 Litovsky & Yin, 1998 a, b). Neurons in auditory nuclei respond best to a leading sound and have a reduced response to a lagging sound, supporting this hypothesis. It has been proposed that GABA-ergic or glycinergic inhibition suppresses neural responses to lagging sounds (Yin, 1994 Fitzpatrick et al. 1995 Pollack & Burger, 2002). An alternative hypothesis states that cochlear processing in low-frequency hearing animals alters directional cues conveyed by the leading and lagging sound, emphasising those present in the leading sound (Tollin, 1998 Hartung & Trahiotis 2001). Responses of single neurons in the inferior colliculus (IC) of anaesthetised guinea pigs were recorded to binaural click pair stimuli. Responses of some neurons were recorded before, during, and after iontophoresis of either the GABAa receptor antagonist gabazine, or the glycine receptor antagonist strychnine. Blocking glycine did not decrease neural suppression of the lagging click in 8/10 neurons. Blocking GAB A did not decrease neural suppression of the lagging click in 11/16 neurons. The neural representation of directional cues in the output of low-frequency neurons to the leading click of a binaural click pair differed from those actually conveyed by the stimulus in 20/20 neurons. Examination of the responses of several such neurons indicated responses to the leading click represented a direction between that conveyed by the leading and lagging click. The results supported the hypothesis that cochlear processing of binaural click pairs alters directional cues conveyed by the stimulus. Limited support was also found for the hypothesis that

  4. Sound attenuation in ducts using locally resonant periodic aluminum patches.

    PubMed

    Farooqui, Maaz; Elnady, Tamer; Akl, Wael

    2016-06-01

    In recent years, the control of low frequency noise has received a lot of attention for several applications. Traditional passive noise control techniques using Helmholtz resonators have size limitations in the low frequency range because of the long wavelength. Promising noise reductions, with flush mounted aluminum patches with no size problems can be obtained using local resonance phenomenon implemented in acoustic metamaterial techniques. The objective of this work is to introduce locally resonant thin aluminum patches flush mounted to a duct walls aiming at creating frequency stop bands in a specific frequency range. Green's function is used within the framework of interface response theory to predict the amount of attenuation of the local resonant patches. The two-port theory and finite elements are also used to predict the acoustic performance of these patches. No flow measurements were conducted and show good agreement with the models. The effect of varying the damping and the masses of the patches are used to expand the stop bandwidth and the effect of both Bragg scattering and the locally resonant mechanisms was demonstrated using mathematical models. The effect of the arrays of patches on the effective dynamic density and bulk modulus has also been investigated. PMID:27369152

  5. Sound localization in noise by normal-hearing listeners and cochlear implant users

    PubMed Central

    Kerber, Stefan; Seeber, Bernhard U.

    2012-01-01

    Objectives This study aimed to characterize horizontal-plane sound localization in interfering noise at different signal-to-noise ratios (SNRs) and to compare performance across normal-hearing listeners and users of unilateral and bilateral cochlear implants (CIs). CI users report difficulties with listening in noisy environments. While their difficulties with speech understanding have been investigated in several studies, the ability to localize sounds in background noise has not extensively been examined, despite the benefits of binaural hearing being greatest in noisy situations. Sound localization is a measure of binaural processing and is thus well suited to assessing the benefit of bilateral implantation. The results will inform clinicians and implant manufacturers how to focus their efforts to improve localization with CIs in noisy situations. Design Six normal-hearing listeners, four unilateral and ten bilateral CI users indicated the perceived location of sound sources using a light pointer method. Target sounds were noise pulses played from one of 11 loudspeakers placed between −80° and +80° in the frontal horizontal plane in the free-field. Localization was assessed in quiet and in diffuse background noise at SNRs between +10 and −7 dB. Speech reception thresholds were measured and their relation to the localization results examined. Results Localization performance declined with decreasing SNR: Target sounds were perceived closer to the median plane and the standard deviation of responses increased. Localization performance across groups was compared using a measure of “Spatial Resolvability” (SR). This measure gives the angular separation between two sound sources that would enable an ideal observer to correctly distinguish them 69.1% of the time. For all participants SR increased with decreasing SNR, i.e. at low SNRs the spatial separation between sound sources remained distinguishable only when it was larger. Normal-hearing participants

  6. Human sound localization: measurements in untrained, head-unrestrained subjects using gaze as a pointer.

    PubMed

    Populin, Luis C

    2008-09-01

    Studies of sound localization in humans have used various behavioral measures to quantify the observers' perceptions; a non-comprehensive list includes verbal reports, head pointing, gun pointing, stylus pointing, and laser aiming. Comparison of localization performance reveals that in humans, just as in animals, different results are obtained with different experimental tasks. Accordingly, to circumvent problems associated with task selection and training, this study used gaze, an ethologically valid behavior for spatial pointing in species with a specialized area of the fovea, to measure sound localization perception of human subjects. Orienting using gaze as a pointer does not require training, preserves the natural link between perception and action, and allows for direct behavioral comparisons across species. The results revealed, unexpectedly, a large degree of variability across subjects in both accuracy and precision. The magnitude of the average angular localization errors for the most eccentric horizontal targets, however, were very similar to those documented in studies that used head pointing, whereas the magnitude of the localization errors for the frontal targets were considerably larger. In addition, an overall improvement in sound localization in the context of the memory-saccade task, as well as a lack of effect of initial eye and head position on perceived sound location were documented. PMID:18575853

  7. Physiological correlates of sound localization in a parasitoid fly, Ormia ochracea

    NASA Astrophysics Data System (ADS)

    Oshinsky, Michael Lee

    A major focus of research in the nervous system is the investigation of neural circuits. The question of how neurons connect to form functional units has driven modern neuroscience research from its inception. From the beginning, the neural circuits of the auditory system and specifically sound localization were used as a model system for investigating neural connectivity and computation. Sound localization lends itself to this task because there is no mapping of spatial information on a receptor sheet as in vision. With only one eye, an animal would still have positional information for objects. Since the receptor sheet in the ear is frequency oriented and not spatially oriented, positional information for a sound source does not exist with only one ear. The nervous system computes the location of a sound source based on differences in the physiology of the two ears. In this study, I investigated the neural circuits for sound localization in a fly, Ormia ochracea (Diptera, Tachinidae, Ormiini), which is a parasitoid of crickets. This fly possess a unique mechanically coupled hearing organ. The two ears are contained in one air sac and a cuticular bridge, that has a flexible spring-like structure at its center, connects them. This mechanical coupling preprocesses the sound before it is detected by the nervous system and provides the fly with directional information. The subject of this study is the neural coding of the location of sound stimuli by a mechanically coupled auditory system. In chapter 1, I present the natural history of an acoustic parasitoid and I review the peripheral processing of sound by the Ormian ear. In chapter 2, I describe the anatomy and physiology of the auditory afferents. I present this physiology in the context of sound localization. In chapter 3, I describe the directional dependent physiology for the thoracic local and ascending acoustic interneurons. In chapter 4, I quantify the threshold and I detail the kinematics of the phonotactic

  8. [Effect of cochlear implantation on sound localization for patients with unilateral sensorineural hearing loss].

    PubMed

    Liu, J F; Dai, J S; Wang, N Y

    2016-08-01

    The aim of this review was to examine the current literature regarding application of cochlear implantation on patients with unilateral sensorineural hearing loss (USNHL) for improvement on sound localization. The literature were searched in the PubMed database with 'cochlear implantation AND single-sided deafness' or 'cochlear implantation AND unilateral deafness' as keywords. The publication date of the articles was up to 2015-2-12. A total of 12 articles were included. The results show that the ability of sound localization for most of the USNHL subjects (90%) with cochlear implantation was significantly improved than that without CI, which suggests that CI is a superior auditory rehabilitation treatment than BAHA and CROS hearing aids for patients with USNHL, because of the re-establishment of the benefits of binaural hearing. In addition, the benefit of CI for USNHL requires a period of auditory experience or training. About 30% subjects showed significantly improvement on sound localization ability after CI worked for three months. For most of the patients (90%), the sound localization ability improved after CI worked for six months. When CI worked for nine months, all the subjects would show improvement on sound localization ability. Sound localization of the USNHL subjects with a CI is based primarily on interaural level differences (ILD) while interaural time differences (ITD) provide little advantage or probably not perceptible at all. The younger subject suffers from USNHL, the stronger the plasticity of the auditory center shows, which results in more obvious degeneration of the affected side and adaptive enhancement of the contralateral side of the auditory pathway. Similarly, the longer duration of USNHL lead to more obvious degeneration of the affected side and adaptive enhancement of the contralateral side. An adaptive enhancement of auditory pathway corresponding to the healthy ear will rely more on the monaural spatial cues that available to the

  9. A biomimetic coupled circuit based microphone array for sound source localization.

    PubMed

    Xu, Huping; Xu, Xiangyuan; Jia, Han; Guan, Luyang; Bao, Ming

    2015-09-01

    An equivalent analog circuit is designed to mimic the coupled ears of the fly Ormia ochracea for sound source localization. This coupled circuit receives two signals with tiny phase difference from a space closed two-microphone array, and produces two signals with obvious intensity difference. The response sensitivity can be adjusted through the coupled circuit parameters. The directional characteristics of the coupled circuit have been demonstrated in the experiment. The miniature microphone array can localize the sound source with low computational burden by using the intensity difference. This system has significant advantages in various applications where the array size is limited. PMID:26428825

  10. Puget Sound Area Electric Reliability Plan. Appendix B : Local Generation Evaluation : Draft Environmental Impact Statement.

    SciTech Connect

    United States. Bonneville Power Administration.

    1991-09-01

    The information and data contained in this Appendix was extracted from numerous sources. The principle sources used for technical data were Bonneville Power Administration's 1990 Resource Program along with its technical appendix, and Chapter 8 of the Draft 1991 Northwest Conservation and Electric Power Plan. All cost data is reported 1988 dollars unless otherwise noted. This information was supplemented by other data developed by Puget Sound utilities who participated on the Local Generation Team. Identifying generating resources available to the Puget Sound area involved a five step process: (1) listing all possible resources that might contribute power to the Puget Sound area, (2) characterizing the technology/resource status, cost and operating characteristics of these resources, (3) identifying exclusion criteria based on the needs of the overall Puget Sound Electric Reliability Plan study, (4) applying these criteria to the list of resources, and (5) summarizing of the costs and characteristics of the final list of resources. 15 refs., 20 tabs.

  11. Sound source localization inspired by the ears of the Ormia ochracea

    NASA Astrophysics Data System (ADS)

    Kuntzman, Michael L.; Hall, Neal A.

    2014-07-01

    The parasitoid fly Ormia ochracea has the remarkable ability to locate crickets using audible sound. This ability is, in fact, remarkable as the fly's hearing mechanism spans only 1.5 mm which is 50× smaller than the wavelength of sound emitted by the cricket. The hearing mechanism is, for all practical purposes, a point in space with no significant interaural time or level differences to draw from. It has been discovered that evolution has empowered the fly with a hearing mechanism that utilizes multiple vibration modes to amplify interaural time and level differences. Here, we present a fully integrated, man-made mimic of the Ormia's hearing mechanism capable of replicating the remarkable sound localization ability of the special fly. A silicon-micromachined prototype is presented which uses multiple piezoelectric sensing ports to simultaneously transduce two orthogonal vibration modes of the sensing structure, thereby enabling simultaneous measurement of sound pressure and pressure gradient.

  12. Non-line-of-sight sound source localization using matched-field processing.

    PubMed

    Singh, Victor; Knisely, Katherine E; Yönak, Serdar H; Grosh, Karl; Dowling, David R

    2012-01-01

    Acoustic diffraction allows sound to travel around opaque objects and therefore may allow beyond-line-of-sight sensing of remote sound sources. This paper reports simulated and experimental results for localizing sound sources based on fully shadowed microphone array measurements. The generic geometry includes a point source, a solid 90° wedge, and a receiving array that lies entirely in the shadow defined by the source location and the wedge. Source localization performance is assessed via matched-field (MF) ambiguity surfaces as a function of receiving array configuration, and received signal-to-noise ratio for the Bartlett and minimum variance distortionless (MVD) MF processors. Here, the sound propagation model is developed from a Green's function integral treatment. A simple 16 element line array of microphones is tested in three mutually orthogonal orientations. The experiments were conducted using an approximate 50-to-1-scaled tabletop model of a blind city-street intersection and produced ambiguity surfaces from source frequencies between 17.5 and 19 kHz that were incoherently summed. The experimental results suggest that a sound source may be localized by the MVD processor when using fully shadowed arrays that have significant aperture parallel to the edge of the wedge. However, this performance is reduced significantly for signal-to-noise ratios below 40 dB. PMID:22280592

  13. Biomimetic ears for a sensor agent robot to localize sound sources

    NASA Astrophysics Data System (ADS)

    Marin, Daniel J.; Mita, Akira

    2011-04-01

    Our current environment and architecture are mainly static even though our surrounding society is constantly changing. This is why the Biofication of Living Spaces field was created, to get more adaptive and suitable living spaces. On the other hand, human was naturally empowered with a lot of features responding to the environment. His/her 2 ears are powerful tools from which he/she can acquire a lot of information such as the source localization of a sound. Interaural (between both ears) time differences enable a lateral localization and this function can be technologically reproduced. However, the sound localization in the median plane of the head provided amongst others by our external ear called the pinna is yet to be imitated in robotics. The idea of this paper is to build some biomimetic ear prototypes and to analyze theirs influences on a transfer function called Interaural Transfer Function (ITF). Once achieved, attaching these prototyped ears to a sensor agent robot, we aim particularly at a sound localization in the median plane of the robot. However, we will have a quick look at the horizontal sound localization too. Finally, these "ears" on the sensor agent robot will be convenient to get a" much accurate and useful information as possible with only 2 microphones and to use this agent for biofication of living spaces issues.

  14. The contribution of high frequencies to human brain activity underlying horizontal localization of natural spatial sounds

    PubMed Central

    Leino, Sakari; May, Patrick JC; Alku, Paavo; Liikkanen, Lassi A; Tiitinen, Hannu

    2007-01-01

    Background In the field of auditory neuroscience, much research has focused on the neural processes underlying human sound localization. A recent magnetoencephalography (MEG) study investigated localization-related brain activity by measuring the N1m event-related response originating in the auditory cortex. It was found that the dynamic range of the right-hemispheric N1m response, defined as the mean difference in response magnitude between contralateral and ipsilateral stimulation, reflects cortical activity related to the discrimination of horizontal sound direction. Interestingly, the results also suggested that the presence of realistic spectral information within horizontally located spatial sounds resulted in a larger right-hemispheric N1m dynamic range. Spectral cues being predominant at high frequencies, the present study further investigated the issue by removing frequencies from the spatial stimuli with low-pass filtering. This resulted in a stepwise elimination of direction-specific spectral information. Interaural time and level differences were kept constant. The original, unfiltered stimuli were broadband noise signals presented from five frontal horizontal directions and binaurally recorded for eight human subjects with miniature microphones placed in each subject's ear canals. Stimuli were presented to the subjects during MEG registration and in a behavioral listening experiment. Results The dynamic range of the right-hemispheric N1m amplitude was not significantly affected even when all frequencies above 600 Hz were removed. The dynamic range of the left-hemispheric N1m response was significantly diminished by the removal of frequencies over 7.5 kHz. The subjects' behavioral sound direction discrimination was only affected by the removal of frequencies over 600 Hz. Conclusion In accord with previous psychophysical findings, the current results indicate that frontal horizontal sound localization and related right-hemispheric cortical processes are

  15. 3-D inversion of airborne electromagnetic data parallelized and accelerated by local mesh and adaptive soundings

    NASA Astrophysics Data System (ADS)

    Yang, Dikun; Oldenburg, Douglas W.; Haber, Eldad

    2014-03-01

    Airborne electromagnetic (AEM) methods are highly efficient tools for assessing the Earth's conductivity structures in a large area at low cost. However, the configuration of AEM measurements, which typically have widely distributed transmitter-receiver pairs, makes the rigorous modelling and interpretation extremely time-consuming in 3-D. Excessive overcomputing can occur when working on a large mesh covering the entire survey area and inverting all soundings in the data set. We propose two improvements. The first is to use a locally optimized mesh for each AEM sounding for the forward modelling and calculation of sensitivity. This dedicated local mesh is small with fine cells near the sounding location and coarse cells far away in accordance with EM diffusion and the geometric decay of the signals. Once the forward problem is solved on the local meshes, the sensitivity for the inversion on the global mesh is available through quick interpolation. Using local meshes for AEM forward modelling avoids unnecessary computing on fine cells on a global mesh that are far away from the sounding location. Since local meshes are highly independent, the forward modelling can be efficiently parallelized over an array of processors. The second improvement is random and dynamic down-sampling of the soundings. Each inversion iteration only uses a random subset of the soundings, and the subset is reselected for every iteration. The number of soundings in the random subset, determined by an adaptive algorithm, is tied to the degree of model regularization. This minimizes the overcomputing caused by working with redundant soundings. Our methods are compared against conventional methods and tested with a synthetic example. We also invert a field data set that was previously considered to be too large to be practically inverted in 3-D. These examples show that our methodology can dramatically reduce the processing time of 3-D inversion to a practical level without losing resolution

  16. Development of Sound Localization Strategies in Children with Bilateral Cochlear Implants

    PubMed Central

    Zheng, Yi; Godar, Shelly P.; Litovsky, Ruth Y.

    2015-01-01

    Localizing sounds in our environment is one of the fundamental perceptual abilities that enable humans to communicate, and to remain safe. Because the acoustic cues necessary for computing source locations consist of differences between the two ears in signal intensity and arrival time, sound localization is fairly poor when a single ear is available. In adults who become deaf and are fitted with cochlear implants (CIs) sound localization is known to improve when bilateral CIs (BiCIs) are used compared to when a single CI is used. The aim of the present study was to investigate the emergence of spatial hearing sensitivity in children who use BiCIs, with a particular focus on the development of behavioral localization patterns when stimuli are presented in free-field horizontal acoustic space. A new analysis was implemented to quantify patterns observed in children for mapping acoustic space to a spatially relevant perceptual representation. Children with normal hearing were found to distribute their responses in a manner that demonstrated high spatial sensitivity. In contrast, children with BiCIs tended to classify sound source locations to the left and right; with increased bilateral hearing experience, they developed a perceptual map of space that was better aligned with the acoustic space. The results indicate experience-dependent refinement of spatial hearing skills in children with CIs. Localization strategies appear to undergo transitions from sound source categorization strategies to more fine-grained location identification strategies. This may provide evidence for neural plasticity, with implications for training of spatial hearing ability in CI users. PMID:26288142

  17. Development of Sound Localization Strategies in Children with Bilateral Cochlear Implants.

    PubMed

    Zheng, Yi; Godar, Shelly P; Litovsky, Ruth Y

    2015-01-01

    Localizing sounds in our environment is one of the fundamental perceptual abilities that enable humans to communicate, and to remain safe. Because the acoustic cues necessary for computing source locations consist of differences between the two ears in signal intensity and arrival time, sound localization is fairly poor when a single ear is available. In adults who become deaf and are fitted with cochlear implants (CIs) sound localization is known to improve when bilateral CIs (BiCIs) are used compared to when a single CI is used. The aim of the present study was to investigate the emergence of spatial hearing sensitivity in children who use BiCIs, with a particular focus on the development of behavioral localization patterns when stimuli are presented in free-field horizontal acoustic space. A new analysis was implemented to quantify patterns observed in children for mapping acoustic space to a spatially relevant perceptual representation. Children with normal hearing were found to distribute their responses in a manner that demonstrated high spatial sensitivity. In contrast, children with BiCIs tended to classify sound source locations to the left and right; with increased bilateral hearing experience, they developed a perceptual map of space that was better aligned with the acoustic space. The results indicate experience-dependent refinement of spatial hearing skills in children with CIs. Localization strategies appear to undergo transitions from sound source categorization strategies to more fine-grained location identification strategies. This may provide evidence for neural plasticity, with implications for training of spatial hearing ability in CI users. PMID:26288142

  18. Acoustic space learning for sound-source separation and localization on binaural manifolds.

    PubMed

    Deleforge, Antoine; Forbes, Florence; Horaud, Radu

    2015-02-01

    In this paper, we address the problems of modeling the acoustic space generated by a full-spectrum sound source and using the learned model for the localization and separation of multiple sources that simultaneously emit sparse-spectrum sounds. We lay theoretical and methodological grounds in order to introduce the binaural manifold paradigm. We perform an in-depth study of the latent low-dimensional structure of the high-dimensional interaural spectral data, based on a corpus recorded with a human-like audiomotor robot head. A nonlinear dimensionality reduction technique is used to show that these data lie on a two-dimensional (2D) smooth manifold parameterized by the motor states of the listener, or equivalently, the sound-source directions. We propose a probabilistic piecewise affine mapping model (PPAM) specifically designed to deal with high-dimensional data exhibiting an intrinsic piecewise linear structure. We derive a closed-form expectation-maximization (EM) procedure for estimating the model parameters, followed by Bayes inversion for obtaining the full posterior density function of a sound-source direction. We extend this solution to deal with missing data and redundancy in real-world spectrograms, and hence for 2D localization of natural sound sources such as speech. We further generalize the model to the challenging case of multiple sound sources and we propose a variational EM framework. The associated algorithm, referred to as variational EM for source separation and localization (VESSL) yields a Bayesian estimation of the 2D locations and time-frequency masks of all the sources. Comparisons of the proposed approach with several existing methods reveal that the combination of acoustic-space learning with Bayesian inference enables our method to outperform state-of-the-art methods. PMID:25164245

  19. Neogene ice sheet, paleoclimatic and geological history of the McMurdo Sound region, Victoria Land Basin, Antarctica: overview of ANDRILL's first two drilling projects

    NASA Astrophysics Data System (ADS)

    Powell, R.; Naish, T.; Harwood, D.; Florindo, F.; Levy, R.; Teams, M. S.

    2008-12-01

    The ANtarctic geological DRILLing Program (ANDRILL), an international collaboration within IPY, has recovered 2 cores: from under the Ross Ice Shelf (McMurdo Ice Shelf Project (MIS) - AND-1B), and from the land-fast sea-ice of McMurdo Sound (Southern McMurdo Sound Project (SMS) - AND-2A). Drill cores reached respective total depths of 1285mbsf in c. 850m of water (MIS) and 1138.54mbsf in c. 380m of water (SMS). Repetitive facies successions in AND-1B core imply at least 60 fluctuations, of probable Milankovitch- duration, between subglacial, ice proximal and ice distal open marine environments. These are grouped into 3 types of facies cycles corresponding to glacial-interglacial variability during climatically distinct periods of Late Neogene: (1) cold-polar climate and ice (late Miocene and Pleistocene); (2) relatively warmer climate, polythermal ice and interglacials dominated by pelagic diatomite (Pliocene); (3) warmer climate, polythermal ice with interglacials dominated by hemipelagites (early late Miocene). A c. 80m-thick interval of diatomite of mid to late Pliocene age shows no apparent glacial cyclicity and represents an extended period of ice-free conditions indicating reduced or absent WAIS. Late Pliocene glacial-interglacial cycles characterized by abrupt alternations between subglacial/ice-proximal facies and open marine diatomite units imply significant WAIS dynamism, and contribution to global ice volume changes coeval with the initiation of Northern Hemisphere glaciations. A c. 4m-thick interval of diatomaceous mudstone in the mid-Pleistocene also represents warm-interglacial ice-free conditions. Intriguingly, glacial deposits interrupted by periodic, small- scale grounding-line retreats dominate the last 1m.y. Inter-hemispheric ice sheet coupling was probably controlled by Northern Hemispheric insolation and consequent glacial eustasy to account for much of the orbital-scale WAIS variability since 2.5Ma. A further expansion of WAIS occurred across

  20. The Offshore New Harbor (ONH) Seismic Expedition: Revealing the Stratigraphic History in the Southern McMurdo Sound Region, Ross Sea, Antarctica from the Greenhouse to Icehouse Worlds

    NASA Astrophysics Data System (ADS)

    Pekar, S. F.; Speece, M. A.; Wilson, G. S.; Sunwall, D. A.; Tinto, K. J.

    2010-12-01

    In the austral spring 2008, the ANDRILL (ANtarctic geological DRILLing) Program’s Offshore New Harbor Expedition successfully collected over 48 km of multi-channel seismic (MCS) data to investigate the stratigraphic and tectonic history of westernmost Southern McMurdo Sound during the Greenhouse World (Eocene) and the start of the Icehouse World (Oligocene). This survey represents an important step for identifying future drilling targets for ANDRILL, which is a multinational program, with the aim to recover stratigraphic intervals for interpreting Antarctica’s climate and glacial history over the past 50 million years. The goal of the Offshore New Harbor Project is to recover proximal archives from two widely recognized but unresolved time intervals regarding Antarctica’s history: 1) the mid-Paleogene cryospheric development on Antarctica; and 2) the abrupt climate shift across the Eocene/Oligocene transition. The ONH seismic survey used methods successfully employed by previous ANDRILL’s surveys in Southern McMurdo Sound (2005) and in Mackay Sea Valley (2007), which included deploying a Generator Injector (G.I.) airgun through holes drilled through the ice and a 1.5 km long streamer that used 60 gimbled geophones to measure the returning reflected seismic energy. Processing of the seismic data was successfully able to remove the bottom water multiple, permitting deeper seismic reflectors to be identified for the first time in this area. Since one of the two seismic lines crossed close to the previously drilled CIROS-1, correlation was possible between the seismic reflectors and the entire stratigraphic section at CIROS-1, which has been dated as old as Late Eocene (~37 Ma). Additionally, seismic and gravity data indicated that a thick sedimentary wedge of up to 5 km lie immediately east of CIROS-1. With the Devonian Beacon Sandstone Formation having been observed to be no thicker than 2 km on land, an additional 3 km of Cenozoic sediments may lie below and

  1. Simulation and testing of a multichannel system for 3D sound localization

    NASA Astrophysics Data System (ADS)

    Matthews, Edward Albert

    Three-dimensional (3D) audio involves the ability to localize sound anywhere in a three-dimensional space. 3D audio can be used to provide the listener with the perception of moving sounds and can provide a realistic listening experience for applications such as gaming, video conferencing, movies, and concerts. The purpose of this research is to simulate and test 3D audio by incorporating auditory localization techniques in a multi-channel speaker system. The objective is to develop an algorithm that can place an audio event in a desired location by calculating and controlling the gain factors of each speaker. A MATLAB simulation displays the location of the speakers and perceived sound, which is verified through experimentation. The scenario in which the listener is not equidistant from each of the speakers is also investigated and simulated. This research is envisioned to lead to a better understanding of human localization of sound, and will contribute to a more realistic listening experience.

  2. Two-Dimensional Classical Wave Localization in a Third Sound System

    SciTech Connect

    Luhman, D. R.; Herrmann, J. C.; Hallock, R. B.

    2006-09-07

    Patterned calcium fluoride deposited on glass creates an effective two-dimensional scatterer of third sound propagating on a thin 4He film. We have utilized a substrate with a periodic arrangement of scatterers and a substrate with a random arrangement of scatterers to investigate classical wave propagation and localization using third sound. We observe pass bands on the periodic substrate while only low frequency modes are observed in the disordered case. The presence of high frequency modes on the ordered substrate and the absence of high frequency modes on the disordered substrate indicates we are observing localization on the disordered substrate. We compare the disordered data to the two-dimensional localization theory of Cohen and Machta and find reasonable agreement.

  3. Use of unidirectional microphones and signal processing for the localization of sound sources

    NASA Astrophysics Data System (ADS)

    Rizzo, Piervincenzo; Bordoni, Giacomo; Marzani, Alessandro

    2009-05-01

    Targeting people or objects by passive acoustic sensors is of relevant interest in several military and civil applications, spanning from surveillance and patrolling systems to teleconferencing and human-robot interaction. To date methods and patents focused solely on the use of beamforming algorithms to compute the time of arrival of sounds detected by using omnidirectional microphones (OM) sparsely deployed. This paper describes the preliminary results of a novel approach devoted to the localization of ground borne acoustic sources. It is demonstrated that an array made of at least three unidirectional microphones can be exploited to detect the position the source. Pulse features extracted either in the time domain or in the frequency domain are used to identify the direction of the incoming sound. This information is then fed into a semi-analytical algorithm devoted to the identification of the source location. The novelty of the method presented here consists on the use of unidirectional microphones rather than omnidirectional microphones and on the ability to extract the sound direction by considering features like the pulse amplitude rather than the pulse arrival time. It is believed that this method may pave the road toward a new generation of reduced size sound detectors and localizers.

  4. Localization of a sound source in a noisy environment by hyperbolic curves in quefrency domain

    NASA Astrophysics Data System (ADS)

    Park, Choon-Su; Jeon, Jong-Hoon; Kim, Yang-Hann

    2014-10-01

    Time Difference of Arrivals (TDOAs) of sound waves between microphones have to do with source localization. How well a sound source can be localized depends on how precisely the TDOAs are estimated. Although many ways to estimate TDOA have been proposed, noise always prevents us from finding exact time differences more or less in practice. Cross correlation has been the most prevalent way to estimate time difference, and various cross correlations robust to noise have also been developed. Nevertheless, much remains to be done for exact TDOA estimation under noisy environments. A novel way to show time delays in quefrency domain by removing noise has been proposed, which is called Minimum Variance Cepstrum (MVC). In particular, it is practically desirable to visualize source position with as few number of sensors as possible. Once TDOAs are obtained precisely, it is enough to show the source position in a 2-D plane using hyperbolic curves with only three sensors. In this work, the MVC is adopted to accurately estimate TDOAs under noise, and a way to localize an acoustic source by intersecting hyperbolic curves using the TDOAs between three microphones is proposed. Numerical simulations on TDOA estimation and source localization with white Gaussian noise demonstrated that the proposed method worked well under the noisy environment, and we compared the results with those of other old but well-established cross correlation estimators. In addition, experiments to detect a leaking point on a pipe successfully showed where the leak sound was generated.

  5. Cosmogenic Ne-21 exposure ages of glacial boulders constrained by local bedrock erosion rates in Ong Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Morgan, D. J.; Balco, G.; Putkonen, J.; Bibby, T.; Giusti, C.; Ball, A. E.; Hedberg, C. P.; Diamond, M. S.; Ringger, K. C.

    2013-12-01

    In order to accurately determine the exposure age of glacial boulders with cosmogenic nuclides, we need to know something about the erosion rate of the rock and any previous exposure the boulder may have had. Commonly, the erosion rate is simply assumed, and inheritance is dealt with by both sampling strategy and removing outliers from the data. In this study, we determine the rock erosion rate by measuring the concentration of cosmogenic Ne-21 in granite bedrock samples. This is used to constrain the exposure age of glacial boulders of the same lithology from the same locale. Ong Valley, Antarctica, (157.5 East, 83.25 South) is an ice-free valley in the Miller Range of the Central Transantarctic Mountains. The valley contains three distinct glacial drifts, and the oldest of these is well defined by an end moraine. We collected samples from six boulders on this end moraine, and six additional samples from the surrounding bedrock that is composed of the same lithology, the Hope Granite. The bedrock samples were collected from the ridge bordering the valley, well above the glacial limit. Because the bedrock samples have not been shielded by ice and have been exposed for millions of years, the concentration of cosmogenic Ne-21 in these samples reflects only the erosion rate of the granite. We separated quartz from the granite samples following standard laboratory methods and measured the concentration of cosmogenic Ne-21 in the quartz at the BGC Noble Gas Thermochronometry Lab. The concentration of cosmogenic Ne-21 in the bedrock samples is interpreted as reflecting only the erosion rate. We can then assume that the erosion rate of the bedrock is equal to the erosion rate of the glacial boulders on the end moraine because they have the same lithology and have been subjected to the same climate conditions during their exposure. With this information, we can better constrain the exposure age of the glacial boulders in Ong Valley.

  6. A Method for Direct Localized Sound Speed Estimates Using Registered Virtual Detectors

    PubMed Central

    Byram, Brett C.; Trahey, Gregg E.; Jensen, Jørgen A.

    2012-01-01

    Accurate sound speed estimates are desirable in a number of fields. In an effort to increase the spatial resolution of sound speed estimates, a new method is proposed for direct measurement of sound speed between arbitrary spatial locations. The method uses the sound speed estimator developed by Anderson and Trahey. Their least squares fit of the received waveform’s curvature provides an estimate of the wave’s point of origin. The point of origin and the delay profile calculated from the fit are used to arrive at a spatially registered virtual detector. Between a pair of registered virtual detectors, a spherical wave is propagated. By beamforming the data, the time-of-flight between the two virtual sources can be calculated. From this information, the local sound speed can be estimated. Validation of the estimator is made using phantom and simulation data. The set of test phantoms consisted of both homogeneous and inhomogeneous media. Several different inhomogeneous phantom configurations were used for the physical validation. The simulation validation focused on the limits of target depth and signal-to-noise ratio on virtual detector registration. The simulations also compare the impact of two- and three-layer inhomogeneous media. The phantom results varied based on signal-to-noise ratio and geometry. The results for all cases were generally less than 1% mean error and standard deviation. The simulation results varied somewhat with depth and F/#, but primarily, they varied with signal-to-noise ratio and geometry. With two-layer geometries, the algorithm has a worst-case spatial registration bias of 0.02%. With three-layer geometries, the axial registration error gets worse with a bias magnitude up to 2.1% but is otherwise relatively stable over depth. The stability over depth of the bias in a given medium still allows for accurate sound speed estimates with a mean relative error less than 0.2%. PMID:22972913

  7. Do you hear where I hear?: isolating the individualized sound localization cues

    PubMed Central

    Romigh, Griffin D.; Simpson, Brian D.

    2014-01-01

    It is widely acknowledged that individualized head-related transfer function (HRTF) measurements are needed to adequately capture all of the 3D spatial hearing cues. However, many perceptual studies have shown that localization accuracy in the lateral dimension is only minimally decreased by the use of non-individualized head-related transfer functions. This evidence supports the idea that the individualized components of an HRTF could be isolated from those that are more general in nature. In the present study we decomposed the HRTF at each location into average, lateral and intraconic spectral components, along with an ITD in an effort to isolate the sound localization cues that are responsible for the inter-individual differences in localization performance. HRTFs for a given listener were then reconstructed systematically with components that were both individualized and non-individualized in nature, and the effect of each modification was analyzed via a virtual localization test where brief 250 ms noise bursts were rendered with the modified HRTFs. Results indicate that the cues important for individualization of HRTFs are contained almost exclusively in the intraconic portion of the HRTF spectra and localization is only minimally affected by introducing non-individualized cues into the other HRTF components. These results provide new insights into what specific inter-individual differences in head-related acoustical features are most relevant to sound localization, and provide a framework for how future human-machine interfaces might be more effectively generalized and/or individualized. PMID:25520607

  8. Eight-choice sound localization by manatees: performance abilities and head related transfer functions.

    PubMed

    Colbert-Luke, Debborah E; Gaspard, Joseph C; Reep, Roger L; Bauer, Gordon B; Dziuk, Kimberly; Cardwell, Adrienne; Mann, David A

    2015-02-01

    Two experiments investigated the ability and means by which two male Florida manatees (Trichechus manatus latirostris) may determine the direction of a sound source. An eight-choice discrimination paradigm was used to determine the subjects' sound localization abilities of five signal conditions covering a range of frequencies, durations, and levels. Subjects performed above the 12.5% chance level for all broadband frequencies and were able to localize sounds over a large level range. Errors were typically located to either side of the signal source location when presented in the front 180° but were more dispersed when presented from locations behind the subject. Front-to-back confusions were few and accuracy was greater when signals originated from the front 180°. Head-related transfer functions were measured to determine if frequencies were filtered by the manatee body to create frequency-specific interaural level differences (ILDs). ILDs were found for all frequencies as a function of source location, although they were largest with frequencies above 18 kHz and when signals originated to either side of the subjects. Larger ILDs were found when the signals originated behind the subjects. A shadowing-effect produced by the body may explain the relatively low occurrence of front-back confusions in the localization study. PMID:25533765

  9. Monitoring the environment: sound localization equipment for deaf-blind people.

    PubMed

    Borg, E; Rönnberg, J; Neovius, L; Kjellander, M

    1999-03-01

    The problems that deaf-blind subjects have with monitoring the environment and the strategies they use were identified using structured interviews. The use of the vibratory sense did not appear to be highly developed, but some individuals indicated that it has great potential. We describe here the design of a computerized laboratory device for sound localization, based on a three-microphone system with a cross correlation algorithm. It was found to have reasonable precision and sufficient reliability to allow the detection and localization of a person approaching a deaf-blind subject in an ordinary room. The next step is to miniaturize the equipment and build a portable prototype. PMID:10320064

  10. Inhibiting the inhibition: a neuronal network for sound localization in reverberant environments.

    PubMed

    Pecka, Michael; Zahn, Thomas P; Saunier-Rebori, Bernadette; Siveke, Ida; Felmy, Felix; Wiegrebe, Lutz; Klug, Achim; Pollak, George D; Grothe, Benedikt

    2007-02-14

    The precedence effect describes the phenomenon whereby echoes are spatially fused to the location of an initial sound by selectively suppressing the directional information of lagging sounds (echo suppression). Echo suppression is a prerequisite for faithful sound localization in natural environments but can break down depending on the behavioral context. To date, the neural mechanisms that suppress echo directional information without suppressing the perception of echoes themselves are not understood. We performed in vivo recordings in Mongolian gerbils of neurons of the dorsal nucleus of the lateral lemniscus (DNLL), a GABAergic brainstem nucleus that targets the auditory midbrain, and show that these DNLL neurons exhibit inhibition that persists tens of milliseconds beyond the stimulus offset, so-called persistent inhibition (PI). Using in vitro recordings, we demonstrate that PI stems from GABAergic projections from the opposite DNLL. Furthermore, these recordings show that PI is attributable to intrinsic features of this GABAergic innervation. Implementation of these physiological findings into a neuronal model of the auditory brainstem demonstrates that, on a circuit level, PI creates an enhancement of responsiveness to lagging sounds in auditory midbrain cells. Moreover, the model revealed that such response enhancement is a sufficient cue for an ideal observer to identify echoes and to exhibit echo suppression, which agrees closely with the percepts of human subjects. PMID:17301185

  11. The natural history of sound localization in mammals – a story of neuronal inhibition

    PubMed Central

    Grothe, Benedikt; Pecka, Michael

    2014-01-01

    Our concepts of sound localization in the vertebrate brain are widely based on the general assumption that both the ability to detect air-borne sounds and the neuronal processing are homologous in archosaurs (present day crocodiles and birds) and mammals. Yet studies repeatedly report conflicting results on the neuronal circuits and mechanisms, in particular the role of inhibition, as well as the coding strategies between avian and mammalian model systems. Here we argue that mammalian and avian phylogeny of spatial hearing is characterized by a convergent evolution of hearing air-borne sounds rather than by homology. In particular, the different evolutionary origins of tympanic ears and the different availability of binaural cues in early mammals and archosaurs imposed distinct constraints on the respective binaural processing mechanisms. The role of synaptic inhibition in generating binaural spatial sensitivity in mammals is highlighted, as it reveals a unifying principle of mammalian circuit design for encoding sound position. Together, we combine evolutionary, anatomical and physiological arguments for making a clear distinction between mammalian processing mechanisms and coding strategies and those of archosaurs. We emphasize that a consideration of the convergent nature of neuronal mechanisms will significantly increase the explanatory power of studies of spatial processing in both mammals and birds. PMID:25324726

  12. Evaluation of Speech Intelligibility and Sound Localization Abilities with Hearing Aids Using Binaural Wireless Technology

    PubMed Central

    Ibrahim, Iman; Parsa, Vijay; Macpherson, Ewan; Cheesman, Margaret

    2012-01-01

    Wireless synchronization of the digital signal processing (DSP) features between two hearing aids in a bilateral hearing aid fitting is a fairly new technology. This technology is expected to preserve the differences in time and intensity between the two ears by co-ordinating the bilateral DSP features such as multichannel compression, noise reduction, and adaptive directionality. The purpose of this study was to evaluate the benefits of wireless communication as implemented in two commercially available hearing aids. More specifically, this study measured speech intelligibility and sound localization abilities of normal hearing and hearing impaired listeners using bilateral hearing aids with wireless synchronization of multichannel Wide Dynamic Range Compression (WDRC). Twenty subjects participated; 8 had normal hearing and 12 had bilaterally symmetrical sensorineural hearing loss. Each individual completed the Hearing in Noise Test (HINT) and a sound localization test with two types of stimuli. No specific benefit from wireless WDRC synchronization was observed for the HINT; however, hearing impaired listeners had better localization with the wireless synchronization. Binaural wireless technology in hearing aids may improve localization abilities although the possible effect appears to be small at the initial fitting. With adaptation, the hearing aids with synchronized signal processing may lead to an improvement in localization and speech intelligibility. Further research is required to demonstrate the effect of adaptation to the hearing aids with synchronized signal processing on different aspects of auditory performance. PMID:26557339

  13. Acoustical cues for sound localization by the Mongolian gerbil, Meriones unguiculatus

    NASA Astrophysics Data System (ADS)

    Maki, Katuhiro; Furukawa, Shigeto

    2005-08-01

    The present study measured the head-related transfer functions (HRTFs) of the Mongolian gerbil for various sound-source directions, and explored acoustical cues for sound localization that could be available to the animals. The HRTF exhibited spectral notches for frequencies above 25 kHz. The notch frequency varied systematically with source direction, and thereby characterized the source directions well. The frequency dependence of the acoustical axis, the direction for which the HRTF amplitude was maximal, was relatively irregular and inconsistent between ears and animals. The frequency-by-frequency plot of the interaural level difference (ILD) exhibited positive and negative peaks, with maximum values of 30 dB at around 30 kHz. The ILD peak frequency had a relatively irregular spatial distribution, implying a poor sound localization cue. The binaural acoustical axis (the direction with the maximum ILD magnitude) showed relatively orderly clustering around certain frequencies, the pattern being fairly consistent among animals. The interaural time differences (ITDs) were also measured and fell in a +/-120 μs range. When two different animal postures were compared (i.e., the animal was standing on its hind legs and prone), small but consistent differences were found for the lower rear directions on the HRTF amplitudes, the ILDs, and the ITDs.

  14. Near-Field Sound Localization Based on the Small Profile Monaural Structure.

    PubMed

    Kim, Youngwoong; Kim, Keonwook

    2015-01-01

    The acoustic wave around a sound source in the near-field area presents unconventional properties in the temporal, spectral, and spatial domains due to the propagation mechanism. This paper investigates a near-field sound localizer in a small profile structure with a single microphone. The asymmetric structure around the microphone provides a distinctive spectral variation that can be recognized by the dedicated algorithm for directional localization. The physical structure consists of ten pipes of different lengths in a vertical fashion and rectangular wings positioned between the pipes in radial directions. The sound from an individual direction travels through the nearest open pipe, which generates the particular fundamental frequency according to the acoustic resonance. The Cepstral parameter is modified to evaluate the fundamental frequency. Once the system estimates the fundamental frequency of the received signal, the length of arrival and angle of arrival (AoA) are derived by the designed model. From an azimuthal distance of 3-15 cm from the outer body of the pipes, the extensive acoustic experiments with a 3D-printed structure show that the direct and side directions deliver average hit rates of 89% and 73%, respectively. The closer positions to the system demonstrate higher accuracy, and the overall hit rate performance is 78% up to 15 cm away from the structure body. PMID:26580618

  15. Cue Reliability Represented in the Shape of Tuning Curves in the Owl's Sound Localization System

    PubMed Central

    Fischer, Brian J.; Peña, Jose L.

    2016-01-01

    Optimal use of sensory information requires that the brain estimates the reliability of sensory cues, but the neural correlate of cue reliability relevant for behavior is not well defined. Here, we addressed this issue by examining how the reliability of spatial cue influences neuronal responses and behavior in the owl's auditory system. We show that the firing rate and spatial selectivity changed with cue reliability due to the mechanisms generating the tuning to the sound localization cue. We found that the correlated variability among neurons strongly depended on the shape of the tuning curves. Finally, we demonstrated that the change in the neurons' selectivity was necessary and sufficient for a network of stochastic neurons to predict behavior when sensory cues were corrupted with noise. This study demonstrates that the shape of tuning curves can stand alone as a coding dimension of environmental statistics. SIGNIFICANCE STATEMENT In natural environments, sensory cues are often corrupted by noise and are therefore unreliable. To make the best decisions, the brain must estimate the degree to which a cue can be trusted. The behaviorally relevant neural correlates of cue reliability are debated. In this study, we used the barn owl's sound localization system to address this question. We demonstrated that the mechanisms that account for spatial selectivity also explained how neural responses changed with degraded signals. This allowed for the neurons' selectivity to capture cue reliability, influencing the population readout commanding the owl's sound-orienting behavior. PMID:26888922

  16. Near-Field Sound Localization Based on the Small Profile Monaural Structure

    PubMed Central

    Kim, Youngwoong; Kim, Keonwook

    2015-01-01

    The acoustic wave around a sound source in the near-field area presents unconventional properties in the temporal, spectral, and spatial domains due to the propagation mechanism. This paper investigates a near-field sound localizer in a small profile structure with a single microphone. The asymmetric structure around the microphone provides a distinctive spectral variation that can be recognized by the dedicated algorithm for directional localization. The physical structure consists of ten pipes of different lengths in a vertical fashion and rectangular wings positioned between the pipes in radial directions. The sound from an individual direction travels through the nearest open pipe, which generates the particular fundamental frequency according to the acoustic resonance. The Cepstral parameter is modified to evaluate the fundamental frequency. Once the system estimates the fundamental frequency of the received signal, the length of arrival and angle of arrival (AoA) are derived by the designed model. From an azimuthal distance of 3–15 cm from the outer body of the pipes, the extensive acoustic experiments with a 3D-printed structure show that the direct and side directions deliver average hit rates of 89% and 73%, respectively. The closer positions to the system demonstrate higher accuracy, and the overall hit rate performance is 78% up to 15 cm away from the structure body. PMID:26580618

  17. In vivo coincidence detection in mammalian sound localization generates phase delays.

    PubMed

    Franken, Tom P; Roberts, Michael T; Wei, Liting; Golding, Nace L; Joris, Philip X

    2015-03-01

    Sound localization critically depends on detection of differences in arrival time of sounds at the two ears (acoustic delay). The fundamental mechanisms are debated, but all proposals include a process of coincidence detection and a separate source of internal delay that offsets the acoustic delay and determines neural tuning. We used in vivo patch-clamp recordings of binaural neurons in the Mongolian gerbil and pharmacological manipulations to directly compare neuronal input to output and to separate excitation from inhibition. Our results cannot be accounted for by existing models and reveal that coincidence detection is not an instantaneous process, but is instead shaped by the interaction of intrinsic conductances with preceding synaptic activity. This interaction generates an internal delay as an intrinsic part of the process of coincidence detection. The multiplication and time-shifting stages thought to extract synchronous activity in many brain areas can therefore be combined in a single operation. PMID:25664914

  18. Inhibition in the balance: binaurally coupled inhibitory feedback in sound localization circuitry

    PubMed Central

    Fukui, Iwao; Ohmori, Harunori; Rubel, Edwin W.

    2011-01-01

    Interaural time differences (ITDs) are the primary cue animals, including humans, use to localize low-frequency sounds. In vertebrate auditory systems, dedicated ITD processing neural circuitry performs an exacting task, the discrimination of microsecond differences in stimulus arrival time at the two ears by coincidence-detecting neurons. These neurons modulate responses over their entire dynamic range to sounds differing in ITD by mere hundreds of microseconds. The well-understood function of this circuitry in birds has provided a fruitful system to investigate how inhibition contributes to neural computation at the synaptic, cellular, and systems level. Our recent studies in the chicken have made significant progress in bringing together many of these findings to provide a cohesive picture of inhibitory function. PMID:21525367

  19. The influence of vision on sound localization abilities in both the horizontal and vertical planes.

    PubMed

    Tabry, Vanessa; Zatorre, Robert J; Voss, Patrice

    2013-01-01

    Numerous recent reports have suggested that individuals deprived of vision are able to develop heightened auditory spatial abilities. However, most such studies have compared the blind to blindfolded sighted individuals, a procedure that might introduce a strong performance bias. Indeed, while blind individuals have had their whole lives to adapt to this condition, sighted individuals might be put at a severe disadvantage when having to localize sounds without visual input. To address this unknown, we compared the sound localization ability of eight sighted individuals with and without a blindfold in a hemi-anechoic chamber. Sound stimuli were broadband noise delivered via two speaker arrays: a horizontal array with 25 loudspeakers (ranging from -90° to +90°; 7.5°) and a vertical array with 16 loudspeakers (ranging from -45° to +67.5°). A factorial design was used, where we compared two vision conditions (blindfold vs. non-blindfold), two sound planes (horizontal vs. vertical) and two pointing methods (hand vs. head). Results show that all three factors significantly interact with one another with regards to the average absolute deviation error. Although blindfolding significantly affected all conditions, it did more so for head-pointing in the horizontal plane. Moreover, blindfolding was found to increase the tendency to undershoot more eccentric spatial positions for head-pointing, but not hand-pointing. Overall, these findings suggest that while proprioceptive cues appear to be sufficient for accurate hand pointing in the absence of visual feedback, head pointing relies more heavily on visual cues in order to provide a precise response. It also strongly argues against the use of head pointing methodologies with blindfolded sighted individuals, particularly in the horizontal plane, as it likely introduces a bias when comparing them to blind individuals. PMID:24376430

  20. The influence of vision on sound localization abilities in both the horizontal and vertical planes

    PubMed Central

    Tabry, Vanessa; Zatorre, Robert J.; Voss, Patrice

    2013-01-01

    Numerous recent reports have suggested that individuals deprived of vision are able to develop heightened auditory spatial abilities. However, most such studies have compared the blind to blindfolded sighted individuals, a procedure that might introduce a strong performance bias. Indeed, while blind individuals have had their whole lives to adapt to this condition, sighted individuals might be put at a severe disadvantage when having to localize sounds without visual input. To address this unknown, we compared the sound localization ability of eight sighted individuals with and without a blindfold in a hemi-anechoic chamber. Sound stimuli were broadband noise delivered via two speaker arrays: a horizontal array with 25 loudspeakers (ranging from −90° to +90°; 7.5°) and a vertical array with 16 loudspeakers (ranging from −45° to +67.5°). A factorial design was used, where we compared two vision conditions (blindfold vs. non-blindfold), two sound planes (horizontal vs. vertical) and two pointing methods (hand vs. head). Results show that all three factors significantly interact with one another with regards to the average absolute deviation error. Although blindfolding significantly affected all conditions, it did more so for head-pointing in the horizontal plane. Moreover, blindfolding was found to increase the tendency to undershoot more eccentric spatial positions for head-pointing, but not hand-pointing. Overall, these findings suggest that while proprioceptive cues appear to be sufficient for accurate hand pointing in the absence of visual feedback, head pointing relies more heavily on visual cues in order to provide a precise response. It also strongly argues against the use of head pointing methodologies with blindfolded sighted individuals, particularly in the horizontal plane, as it likely introduces a bias when comparing them to blind individuals. PMID:24376430

  1. Excitation by Axon Terminal GABA Spillover in a Sound Localization Circuit

    PubMed Central

    Weisz, Catherine J.C.; Rubio, Maria E.; Givens, Richard S.

    2016-01-01

    Synapses from neurons of the medial nucleus of the trapezoid body (MNTB) onto neurons of the lateral superior olive (LSO) in the auditory brainstem are glycinergic in maturity, but also GABAergic and glutamatergic in development. The role for this neurotransmitter cotransmission is poorly understood. Here we use electrophysiological recordings in brainstem slices from P3-P21 mice to demonstrate that GABA release evoked from MNTB axons can spill over to neighboring MNTB axons and cause excitation by activating GABAAR. This spillover excitation generates patterns of staggered neurotransmitter release from different MNTB axons resulting in characteristic “doublet” postsynaptic currents in LSO neurons. Postembedding immunogold labeling and electron microscopy provide evidence that GABAARs are localized at MNTB axon terminals. Photolytic uncaging of p-hydroxyphenacyl (pHP) GABA demonstrates backpropagation of GABAAR-mediated depolarizations from MNTB axon terminals to the soma, some hundreds of microns away. These somatic depolarizations enhanced somatic excitability by increasing the probability of action potential generation. GABA spillover excitation between MNTB axon terminals may entrain neighboring MNTB neurons, which may play a role in the developmental refinement of the MNTB-LSO pathway. Axonal spillover excitation persisted beyond the second postnatal week, suggesting that this mechanism may play a role in sound localization, by providing new avenues of communication between MNTB neurons via their distal axonal projections. SIGNIFICANCE STATEMENT In this study, a new mechanism of neuronal communication between auditory synapses in the mammalian sound localization pathway is described. Evidence is provided that the inhibitory neurotransmitter GABA can spill over between axon terminals to cause excitation of nearby synapses to further stimulate neurotransmitter release. Excitatory GABA spillover between inhibitory axon terminals may have important

  2. Excitation by Axon Terminal GABA Spillover in a Sound Localization Circuit.

    PubMed

    Weisz, Catherine J C; Rubio, Maria E; Givens, Richard S; Kandler, Karl

    2016-01-20

    Synapses from neurons of the medial nucleus of the trapezoid body (MNTB) onto neurons of the lateral superior olive (LSO) in the auditory brainstem are glycinergic in maturity, but also GABAergic and glutamatergic in development. The role for this neurotransmitter cotransmission is poorly understood. Here we use electrophysiological recordings in brainstem slices from P3-P21 mice to demonstrate that GABA release evoked from MNTB axons can spill over to neighboring MNTB axons and cause excitation by activating GABAAR. This spillover excitation generates patterns of staggered neurotransmitter release from different MNTB axons resulting in characteristic "doublet" postsynaptic currents in LSO neurons. Postembedding immunogold labeling and electron microscopy provide evidence that GABAARs are localized at MNTB axon terminals. Photolytic uncaging of p-hydroxyphenacyl (pHP) GABA demonstrates backpropagation of GABAAR-mediated depolarizations from MNTB axon terminals to the soma, some hundreds of microns away. These somatic depolarizations enhanced somatic excitability by increasing the probability of action potential generation. GABA spillover excitation between MNTB axon terminals may entrain neighboring MNTB neurons, which may play a role in the developmental refinement of the MNTB-LSO pathway. Axonal spillover excitation persisted beyond the second postnatal week, suggesting that this mechanism may play a role in sound localization, by providing new avenues of communication between MNTB neurons via their distal axonal projections. Significance statement: In this study, a new mechanism of neuronal communication between auditory synapses in the mammalian sound localization pathway is described. Evidence is provided that the inhibitory neurotransmitter GABA can spill over between axon terminals to cause excitation of nearby synapses to further stimulate neurotransmitter release. Excitatory GABA spillover between inhibitory axon terminals may have important implications

  3. A Pulse-type Hardware Level Difference Detection Model Based on Sound Source Localization Mechanism in Barn Owl

    NASA Astrophysics Data System (ADS)

    Sakurai, Tsubasa; Sekine, Yoshifumi

    Auditory information processing is very important in the darkness where vision information is extremely limited. Barn owls have excellent hearing information processing function. Barn owls can detect a sound source in the high accuracy of less than two degrees in both of the vertical and horizontal directions. When they perform the sound source localization, the barn owls use the interaural time difference for localization in the horizontal plane, and the interaural level difference for localization in the vertical plane. We are constructing the two-dimensional sound source localization model using pulse-type hardware neuron models based on sound source localization mechanism of barn owl for the purpose of the engineering application. In this paper, we propose a pulse-type hardware model for level difference detection based on sound source localization mechanism of barn owl. Firstly, we discuss the response characteristics of the mathematical model for level difference detection. Next we discuss the response characteristics of the hardware mode. As a result, we show clearly that this proposal model can be used as a sound source localization model of vertical direction.

  4. Front-back confusion resolution in three-dimensional sound localization using databases built with a dummy head.

    PubMed

    Ovcharenko, Alexander; Cho, Sang Jin; Chong, Ui-Pil

    2007-07-01

    Sound localization plays an important role in everyday life. It helps us to separate sounds coming from different sources and thus to acquire acoustic information. This paper describes an algorithm for localizing the position of a sound source, as recorded by dummy head microphones. The recorded signals are considered to be basic, random signals within an imaginary round room. The goal of this research is to localize random signals produced from different positions using information about basic signals. The method used is based on the identification of similarities between basic and random signals. It includes an interaural time difference comparison at the beginning, and continues with further analysis of the differences in signal spectrums. One of the main issues arising in sound localization is the problem of front-back confusion, and this paper shows how it was resolved by the use of reference signals. PMID:17614506

  5. A Sr-Nd-Hf isotope characterization of dust source areas in Victoria Land and the McMurdo Sound sector of Antarctica

    NASA Astrophysics Data System (ADS)

    Blakowski, Molly A.; Aciego, Sarah M.; Delmonte, Barbara; Baroni, Carlo; Salvatore, Maria Cristina; Sims, Kenneth W. W.

    2016-06-01

    Determining the geographical provenance of dust provides crucial insight into the global dust cycle. For the East Antarctic Ice Sheet (EAIS), the importance of Southern hemisphere potential dust sources has been thoroughly investigated using radiogenic isotopes, whereas proximal dust source areas located on the periphery of the ice sheet remain poorly documented from a geochemical standpoint. In this work, we expand the existing isotopic (Srsbnd Nd) catalogue of dust and sand-sized sediments from Victoria Land and the McMurdo Sound sector, and incorporate Hf isotopic data to place additional constraints on dust source identification. The isotopic field for materials considered in this study is characterized by 87Sr/86Sr ratios ranging from 0.703 to 0.783, εNd between -12.01 and 6.36, and εHf from -16.77 to 6.89. As reported in previous works, the data reveal close relationships between Antarctic sediments and distinct parent lithologies; in addition, our findings emphasize the background presence of very fine dusts originating from dominant global sources and regional volcanic activity as barriers to direct source-to-sink comparison of isotopic signatures. Thus, geochemical characterizations of dust sources to the Antarctic ice sheet involving multiple size fractions, including coarser-grained particles more susceptible to short-range transport, can help us to rule out global sources of dust when examining local sediment cores and ice cores.

  6. A Sr-Nd-Hf isotope characterization of dust source areas in Victoria Land and the McMurdo Sound sector of Antarctica

    NASA Astrophysics Data System (ADS)

    Blakowski, Molly A.; Aciego, Sarah M.; Delmonte, Barbara; Baroni, Carlo; Salvatore, Maria Cristina; Sims, Kenneth W. W.

    2016-06-01

    Determining the geographical provenance of dust provides crucial insight into the global dust cycle. For the East Antarctic Ice Sheet (EAIS), the importance of Southern hemisphere potential dust sources has been thoroughly investigated using radiogenic isotopes, whereas proximal dust source areas located on the periphery of the ice sheet remain poorly documented from a geochemical standpoint. In this work, we expand the existing isotopic (Srsbnd Nd) catalogue of dust and sand-sized sediments from Victoria Land and the McMurdo Sound sector, and incorporate Hf isotopic data to place additional constraints on dust source identification. The isotopic field for materials considered in this study is characterized by 87Sr/86Sr ratios ranging from 0.703 to 0.783, εNd between -12.01 and 6.36, and εHf from -16.77 to 6.89. As reported in previous works, the data reveal close relationships between Antarctic sediments and distinct parent lithologies; in addition, our findings emphasize the background presence of very fine dusts originating from dominant global sources and regional volcanic activity as barriers to direct source-to-sink comparison of isotopic signatures. Thus, geochemical characterizations of dust sources to the Antarctic ice sheet involving multiple size fractions, including coarser-grained particles more susceptible to short-range transport, can help us to rule out global sources of dust when examining local sediment cores and ice cores.

  7. Hovercraft experience in Antarctica

    NASA Astrophysics Data System (ADS)

    Cook, Harvey C.

    The Model 1500 TD air-cushion vehicle (ACV) has been modified for the extreme conditions encountered in Antarctic operations; these operations began in the 1988-1989 austral summer. Performance evaluations covering 300 hours of engine operations have been obtained which demonstrate the basic soundness of this ACV's design and construction, and its applicability to Antarctic operations, where it was able to reduce travel time and fuel consumption in excess of 40 percent. In addition, passenger comfort was increased manyfold over wheeled and tracked vehicles for comparable missions. The ACV is judged capable of solving many of the transportation problems experienced in Antarctica.

  8. Integrated provenance-detrital thermochronology studies in ANDRILL AND-2A drill core: first evidence of an Oligocene exhumation episode (McMurdo Sound, Antarctica)

    NASA Astrophysics Data System (ADS)

    Zattin, M.; Talarico, F. M.; Sandroni, S.

    2009-12-01

    An integrated investigation including provenance analysis of the gravel-fraction and detrital apatite fission-track (AFT) thermochronology on the AND-2A core provides new results to constrain the exhumation history of source regions and the reconstruction of sediment provenance models in the Ross Embayment in Late Cenozoic time. All the AFT ages, from 20 samples, evenly distributed in the uppermost 1000 m of the core, indicate that the entire succession originated from a source that exhumed in the Oligocene/Late Eocene time. In fact, most of the grains in nearly all the samples can be grouped into a youngest grain-age component (P1) in the range between 21.7 Ma and 43.4 Ma. However, most of the samples show more than one population, documenting the presence of multiple source areas in some periods of the basin history. On the other hand, the presence in some of the samples of a unique peak suggests a limited drainage system, as indicated by the petrographic data. The AFT data indicate the presence of active tectonics at the end of the Oligocene, therefore suggesting a source of sediments located along the Transantarctic Mountains (TAM) south of the Dry Valleys Block, where bedrock AFT ages indicate an older (Eocene) exhumation phase. Hence, the idea of a structural segmentation of the TAM during the Cenozoic (Wilson, Glob. Plan. Change, 1999) is well supported by these data. Provenance analysis of the gravel fraction highlights significant down-core modal and compositional variations and the occurrence of two main basement clast assemblages, diagnostic of specific source regions and occurring in distinct core sections: a) including marbles, garnet micaschists and diopside schists, suggesting oscillation of "local" glaciers in the on-shore area close to the AND-2A drill site, and b) low-grade metasediments and alkaline granites, indicating oscillations of a most extensive ice sheet/shelf with a clear provenance from the Skelton-Mulock glacier area. These data agree

  9. Detection of the Third Heart Sound Based on Nonlinear Signal Decomposition and Time-Frequency Localization.

    PubMed

    Barma, Shovan; Chen, Bo-Wei; Ji, Wen; Rho, Seungmin; Chou, Chih-Hung; Wang, Jhing-Fa

    2016-08-01

    This study presents a precise way to detect the third ( S3 ) heart sound, which is recognized as an important indication of heart failure, based on nonlinear single decomposition and time-frequency localization. The detection of the S3 is obscured due to its significantly low energy and frequency. Even more, the detected S3 may be misunderstood as an abnormal second heart sound with a fixed split, which was not addressed in the literature. To detect such S3, the Hilbert vibration decomposition method is applied to decompose the heart sound into a certain number of subcomponents while intactly preserving the phase information. Thus, the time information of all of the decomposed components are unchanged, which further expedites the identification and localization of any module/section of a signal properly. Next, the proposed localization step is applied to the decomposed subcomponents by using smoothed pseudo Wigner-Ville distribution followed by the reassignment method. Finally, based on the positional information, the S3 is distinguished and confirmed by measuring time delays between the S2 and S3. In total, 82 sets of cardiac cycles collected from different databases including Texas Heart Institute database are examined for evaluation of the proposed method. The result analysis shows that the proposed method can detect the S3 correctly, even when the normalized temporal energy of S3 is larger than 0.16, and the frequency of those is larger than 34 Hz. In a performance analysis, the proposed method demonstrates that the accuracy rate of S3 detection is as high as 93.9%, which is significantly higher compared with the other methods. Such findings prove the robustness of the proposed idea for detecting substantially low-energized S3 . PMID:26584485

  10. Sound localization with communications headsets: comparison of passive and active systems.

    PubMed

    Abel, Sharon M; Tsang, Suzanne; Boyne, Stephen

    2007-01-01

    Studies have demonstrated that conventional hearing protectors interfere with sound localization. This research examines possible benefits from advanced communications devices. Horizontal plane sound localization was compared in normal-hearing males with the ears unoccluded and fitted with Peltor H10A passive attenuation earmuffs, Racal Slimgard II communications muffs in active noise reduction (ANR) and talk-through-circuitry (TTC) modes and Nacre QUIETPRO TM communications earplugs in off (passive attenuation) and push-to-talk (PTT) modes. Localization was assessed using an array of eight loudspeakers, two in each spatial quadrant. The stimulus was 75 dB SPL, 300-ms broadband noise. One block of 120 forced-choice loudspeaker identification trials was presented in each condition. Subjects responded using a laptop response box with a set of eight microswitches in the same configuration as the speaker array. A repeated measures ANOVA was applied to the dataset. The results reveal that the overall percent correct response was highest in the unoccluded condition (94%). A significant reduction of 24% was observed for the communications devices in TTC and PTT modes and a reduction of 49% for the passive muff and plug and muff with ANR. Disruption in performance was due to an increase in front-back reversal errors for mirror image spatial positions. The results support the conclusion that communications devices with advanced technologies are less detrimental to directional hearing than conventional, passive, limited amplification and ANR devices. PMID:18087116

  11. Efficient Approximation of Head-Related Transfer Functions in Subbands for Accurate Sound Localization

    PubMed Central

    Marelli, Damián; Baumgartner, Robert; Majdak, Piotr

    2015-01-01

    Head-related transfer functions (HRTFs) describe the acoustic filtering of incoming sounds by the human morphology and are essential for listeners to localize sound sources in virtual auditory displays. Since rendering complex virtual scenes is computationally demanding, we propose four algorithms for efficiently representing HRTFs in subbands, i.e., as an analysis filterbank (FB) followed by a transfer matrix and a synthesis FB. All four algorithms use sparse approximation procedures to minimize the computational complexity while maintaining perceptually relevant HRTF properties. The first two algorithms separately optimize the complexity of the transfer matrix associated to each HRTF for fixed FBs. The other two algorithms jointly optimize the FBs and transfer matrices for complete HRTF sets by two variants. The first variant aims at minimizing the complexity of the transfer matrices, while the second one does it for the FBs. Numerical experiments investigate the latency-complexity trade-off and show that the proposed methods offer significant computational savings when compared with other available approaches. Psychoacoustic localization experiments were modeled and conducted to find a reasonable approximation tolerance so that no significant localization performance degradation was introduced by the subband representation. PMID:26681930

  12. Sound Source Localization for HRI Using FOC-Based Time Difference Feature and Spatial Grid Matching.

    PubMed

    Li, Xiaofei; Liu, Hong

    2013-08-01

    In human-robot interaction (HRI), speech sound source localization (SSL) is a convenient and efficient way to obtain the relative position between a speaker and a robot. However, implementing a SSL system based on TDOA method encounters many problems, such as noise of real environments, the solution of nonlinear equations, switch between far field and near field. In this paper, fourth-order cumulant spectrum is derived, based on which a time delay estimation (TDE) algorithm that is available for speech signal and immune to spatially correlated Gaussian noise is proposed. Furthermore, time difference feature of sound source and its spatial distribution are analyzed, and a spatial grid matching (SGM) algorithm is proposed for localization step, which handles some problems that geometric positioning method faces effectively. Valid feature detection algorithm and a decision tree method are also suggested to improve localization performance and reduce computational complexity. Experiments are carried out in real environments on a mobile robot platform, in which thousands of sets of speech data with noise collected by four microphones are tested in 3D space. The effectiveness of our TDE method and SGM algorithm is verified. PMID:26502430

  13. Encoding of natural sounds by variance of the cortical local field potential.

    PubMed

    Ding, Nai; Simon, Jonathan Z; Shamma, Shihab A; David, Stephen V

    2016-06-01

    Neural encoding of sensory stimuli is typically studied by averaging neural signals across repetitions of the same stimulus. However, recent work has suggested that the variance of neural activity across repeated trials can also depend on sensory inputs. Here we characterize how intertrial variance of the local field potential (LFP) in primary auditory cortex of awake ferrets is affected by continuous natural sound stimuli. We find that natural sounds often suppress the intertrial variance of low-frequency LFP (<16 Hz). However, the amount of the variance reduction is not significantly correlated with the amplitude of the mean response at the same recording site. Moreover, the variance changes occur with longer latency than the mean response. Although the dynamics of the mean response and intertrial variance differ, spectro-temporal receptive field analysis reveals that changes in LFP variance have frequency tuning similar to multiunit activity at the same recording site, suggesting a local origin for changes in LFP variance. In summary, the spectral tuning of LFP intertrial variance and the absence of a correlation with the amplitude of the mean evoked LFP suggest substantial heterogeneity in the interaction between spontaneous and stimulus-driven activity across local neural populations in auditory cortex. PMID:26912594

  14. Dynamic binaural sound localization based on variations of interaural time delays and system rotations.

    PubMed

    Baumann, Claude; Rogers, Chris; Massen, Francis

    2015-08-01

    This work develops the mathematical model for a steerable binaural system that determines the instantaneous direction of a sound source in space. The model combines system angular speed and interaural time delays (ITDs) in a differential equation, which allows monitoring the change of source position in the binaural reference frame and therefore resolves the confusion about azimuth and elevation. The work includes the analysis of error propagation and presents results from a real-time application that was performed on a digital signal processing device. Theory and experiments demonstrate that the azimuthal angle to the sound source is accurately yielded in the case of horizontal rotations, whereas the elevation angle is estimated with large uncertainty. This paper also proves the equivalence of the ITD derivative and the Doppler shift appearing between the binaurally captured audio signals. The equation of this Doppler shift is applicable for any kind of motion. It shows that weak binaural pitch differences may represent an additional cue in localization of sound. Finally, the paper develops practical applications from this relationship, such as the synthesizing of binaural images of pure and complex tones emitted by a moving source, and the generation of multiple frequency images for binaural beat experiments. PMID:26328682

  15. A Robust Sound Source Localization Approach for Microphone Array with Model Errors

    NASA Astrophysics Data System (ADS)

    Xiao, Hua; Shao, Huai-Zong; Peng, Qi-Cong

    In this paper, a robust sound source localization approach is proposed. The approach retains good performance even when model errors exist. Compared with previous work in this field, the contributions of this paper are as follows. First, an improved broad-band and near-field array model is proposed. It takes array gain, phase perturbations into account and is based on the actual positions of the elements. It can be used in arbitrary planar geometry arrays. Second, a subspace model errors estimation algorithm and a Weighted 2-Dimension Multiple Signal Classification (W2D-MUSIC) algorithm are proposed. The subspace model errors estimation algorithm estimates unknown parameters of the array model, i. e., gain, phase perturbations, and positions of the elements, with high accuracy. The performance of this algorithm is improved with the increasing of SNR or number of snapshots. The W2D-MUSIC algorithm based on the improved array model is implemented to locate sound sources. These two algorithms compose the robust sound source approach. The more accurate steering vectors can be provided for further processing such as adaptive beamforming algorithm. Numerical examples confirm effectiveness of this proposed approach.

  16. How Internally Coupled Ears Generate Temporal and Amplitude Cues for Sound Localization

    NASA Astrophysics Data System (ADS)

    Vedurmudi, A. P.; Goulet, J.; Christensen-Dalsgaard, J.; Young, B. A.; Williams, R.; van Hemmen, J. L.

    2016-01-01

    In internally coupled ears, displacement of one eardrum creates pressure waves that propagate through air-filled passages in the skull and cause displacement of the opposing eardrum, and conversely. By modeling the membrane, passages, and propagating pressure waves, we show that internally coupled ears generate unique amplitude and temporal cues for sound localization. The magnitudes of both these cues are directionally dependent. The tympanic fundamental frequency segregates a low-frequency regime with constant time-difference magnification from a high-frequency domain with considerable amplitude magnification.

  17. How Internally Coupled Ears Generate Temporal and Amplitude Cues for Sound Localization.

    PubMed

    Vedurmudi, A P; Goulet, J; Christensen-Dalsgaard, J; Young, B A; Williams, R; van Hemmen, J L

    2016-01-15

    In internally coupled ears, displacement of one eardrum creates pressure waves that propagate through air-filled passages in the skull and cause displacement of the opposing eardrum, and conversely. By modeling the membrane, passages, and propagating pressure waves, we show that internally coupled ears generate unique amplitude and temporal cues for sound localization. The magnitudes of both these cues are directionally dependent. The tympanic fundamental frequency segregates a low-frequency regime with constant time-difference magnification from a high-frequency domain with considerable amplitude magnification. PMID:26824568

  18. Sound source localization and speech understanding in complex listening environments by single-sided deaf listeners after cochlear implantation

    PubMed Central

    Zeitler, Daniel M.; Dorman, Michael F.; Natale, Sarah J.; Loiselle, Louise; Yost, William A.; Gifford, Rene H.

    2015-01-01

    Objective To assess improvements in sound source localization and speech understanding in complex listening environments following unilateral cochlear implantation for single-sided deafness (SSD). Study Design Non-randomized, open, prospective case series Setting Tertiary referral center Patients Nine subjects with a unilateral cochlear implant (CI) for SSD (SSD-CI) were tested. Reference groups for the task of sound source localization included young (n=45) and older (n=12) normal hearing (NH) subjects and 27 bilateral CI (BCI) subjects. Intervention Unilateral cochlear implantation Main outcome measures Sound source localization was tested with 13 loudspeakers in a 180 arc in front of the subject. Speech understanding was tested with the subject seated in an 8-loudspeaker sound system arrayed in a 360-degree pattern. Directionally appropriate noise, originally recorded in a restaurant, was played from each loudspeaker. Speech understanding in noise was tested using the Azbio sentence test and sound source localization quantified using root mean square error. Results All CI subjects showed poorer-than-normal sound source localization. SSD-CI subjects showed a bimodal distribution of scores - six subjects had scores near the mean of those obtained by BCI subjects, while three had scores just outside the 95th percentile of NH listeners. Speech understanding improved significantly in the restaurant environment when the signal was presented to the side of the CI. Conclusions Cochlear implantation for SSD can offer improved speech understanding in complex listening environments and improved sound source localization in both children and adults. On tasks of sound source localization, SSD-CI patients typically perform as well as BCI patients and, in some cases, achieve scores at the upper boundary of normal performance. PMID:26375967

  19. The Relative Contribution of Interaural Time and Magnitude Cues to Dynamic Sound Localization

    NASA Technical Reports Server (NTRS)

    Wenzel, Elizabeth M.; Null, Cynthia H. (Technical Monitor)

    1995-01-01

    This paper presents preliminary data from a study examining the relative contribution of interaural time differences (ITDs) and interaural level differences (ILDs) to the localization of virtual sound sources both with and without head motion. The listeners' task was to estimate the apparent direction and distance of virtual sources (broadband noise) presented over headphones. Stimuli were synthesized from minimum phase representations of nonindividualized directional transfer functions; binaural magnitude spectra were derived from the minimum phase estimates and ITDs were represented as a pure delay. During dynamic conditions, listeners were encouraged to move their heads; the position of the listener's head was tracked and the stimuli were synthesized in real time using a Convolvotron to simulate a stationary external sound source. ILDs and ITDs were either correctly or incorrectly correlated with head motion: (1) both ILDs and ITDs correctly correlated, (2) ILDs correct, ITD fixed at 0 deg azimuth and 0 deg elevation, (3) ITDs correct, ILDs fixed at 0 deg, 0 deg. Similar conditions were run for static conditions except that none of the cues changed with head motion. The data indicated that, compared to static conditions, head movements helped listeners to resolve confusions primarily when ILDs were correctly correlated, although a smaller effect was also seen for correct ITDs. Together with the results for static conditions, the data suggest that localization tends to be dominated by the cue that is most reliable or consistent, when reliability is defined by consistency over time as well as across frequency bands.

  20. Adaptation in sound localization: from GABA(B) receptor-mediated synaptic modulation to perception.

    PubMed

    Stange, Annette; Myoga, Michael H; Lingner, Andrea; Ford, Marc C; Alexandrova, Olga; Felmy, Felix; Pecka, Michael; Siveke, Ida; Grothe, Benedikt

    2013-12-01

    Across all sensory modalities, the effect of context-dependent neural adaptation can be observed at every level, from receptors to perception. Nonetheless, it has long been assumed that the processing of interaural time differences, which is the primary cue for sound localization, is nonadaptive, as its outputs are mapped directly onto a hard-wired representation of space. Here we present evidence derived from in vitro and in vivo experiments in gerbils indicating that the coincidence-detector neurons in the medial superior olive modulate their sensitivity to interaural time differences through a rapid, GABA(B) receptor-mediated feedback mechanism. We show that this mechanism provides a gain control in the form of output normalization, which influences the neuronal population code of auditory space. Furthermore, psychophysical tests showed that the paradigm used to evoke neuronal GABA(B) receptor-mediated adaptation causes the perceptual shift in sound localization in humans that was expected on the basis of our physiological results in gerbils. PMID:24141311

  1. ECC (Electrochemical Concentration Cell) ozonesonde observations at Mirny, Antarctica, during 1988

    NASA Technical Reports Server (NTRS)

    Komhyr, W. D.; Lathrop, J. A.; Arbuzova, V. N.; Khattatov, V. U.; Nureyev, P. G.; Rudakov, V. V.; Zamyshlayev, I. V.

    1989-01-01

    Atmospheric ozone vertical distributions, air temperatures, and wind speed and direction data are presented for 40 balloon electrochemical concentration cell ozone soundings made at Mirny, Antarctica, in 1988.

  2. The role of envelope shape in the localization of multiple sound sources and echoes in the barn owl.

    PubMed

    Baxter, Caitlin S; Nelson, Brian S; Takahashi, Terry T

    2013-02-01

    Echoes and sounds of independent origin often obscure sounds of interest, but echoes can go undetected under natural listening conditions, a perception called the precedence effect. How does the auditory system distinguish between echoes and independent sources? To investigate, we presented two broadband noises to barn owls (Tyto alba) while varying the similarity of the sounds' envelopes. The carriers of the noises were identical except for a 2- or 3-ms delay. Their onsets and offsets were also synchronized. In owls, sound localization is guided by neural activity on a topographic map of auditory space. When there are two sources concomitantly emitting sounds with overlapping amplitude spectra, space map neurons discharge when the stimulus in their receptive field is louder than the one outside it and when the averaged amplitudes of both sounds are rising. A model incorporating these features calculated the strengths of the two sources' representations on the map (B. S. Nelson and T. T. Takahashi; Neuron 67: 643-655, 2010). The target localized by the owls could be predicted from the model's output. The model also explained why the echo is not localized at short delays: when envelopes are similar, peaks in the leading sound mask corresponding peaks in the echo, weakening the echo's space map representation. When the envelopes are dissimilar, there are few or no corresponding peaks, and the owl localizes whichever source is predicted by the model to be less masked. Thus the precedence effect in the owl is a by-product of a mechanism for representing multiple sound sources on its map. PMID:23175801

  3. The role of envelope shape in the localization of multiple sound sources and echoes in the barn owl

    PubMed Central

    Baxter, Caitlin S.; Takahashi, Terry T.

    2013-01-01

    Echoes and sounds of independent origin often obscure sounds of interest, but echoes can go undetected under natural listening conditions, a perception called the precedence effect. How does the auditory system distinguish between echoes and independent sources? To investigate, we presented two broadband noises to barn owls (Tyto alba) while varying the similarity of the sounds' envelopes. The carriers of the noises were identical except for a 2- or 3-ms delay. Their onsets and offsets were also synchronized. In owls, sound localization is guided by neural activity on a topographic map of auditory space. When there are two sources concomitantly emitting sounds with overlapping amplitude spectra, space map neurons discharge when the stimulus in their receptive field is louder than the one outside it and when the averaged amplitudes of both sounds are rising. A model incorporating these features calculated the strengths of the two sources' representations on the map (B. S. Nelson and T. T. Takahashi; Neuron 67: 643–655, 2010). The target localized by the owls could be predicted from the model's output. The model also explained why the echo is not localized at short delays: when envelopes are similar, peaks in the leading sound mask corresponding peaks in the echo, weakening the echo's space map representation. When the envelopes are dissimilar, there are few or no corresponding peaks, and the owl localizes whichever source is predicted by the model to be less masked. Thus the precedence effect in the owl is a by-product of a mechanism for representing multiple sound sources on its map. PMID:23175801

  4. Adjustment of interaural time difference in head related transfer functions based on listeners' anthropometry and its effect on sound localization

    NASA Astrophysics Data System (ADS)

    Suzuki, Yôiti; Watanabe, Kanji; Iwaya, Yukio; Gyoba, Jiro; Takane, Shouichi

    2005-04-01

    Because the transfer functions governing subjective sound localization (HRTFs) show strong individuality, sound localization systems based on synthesis of HRTFs require suitable HRTFs for individual listeners. However, it is impractical to obtain HRTFs for all listeners based on measurements. Improving sound localization by adjusting non-individualized HRTFs to a specific listener based on that listener's anthropometry might be a practical method. This study first developed a new method to estimate interaural time differences (ITDs) using HRTFs. Then correlations between ITDs and anthropometric parameters were analyzed using the canonical correlation method. Results indicated that parameters relating to head size, and shoulder and ear positions are significant. Consequently, it was attempted to express ITDs based on listener's anthropometric data. In this process, the change of ITDs as a function of azimuth angle was parameterized as a sum of sine functions. Then the parameters were analyzed using multiple regression analysis, in which the anthropometric parameters were used as explanatory variables. The predicted or individualized ITDs were installed in the nonindividualized HRTFs to evaluate sound localization performance. Results showed that individualization of ITDs improved horizontal sound localization.

  5. The bat head-related transfer function reveals binaural cues for sound localization in azimuth and elevation

    NASA Astrophysics Data System (ADS)

    Aytekin, Murat; Grassi, Elena; Sahota, Manjit; Moss, Cynthia F.

    2004-12-01

    Directional properties of the sound transformation at the ear of four intact echolocating bats, Eptesicus fuscus, were investigated via measurements of the head-related transfer function (HRTF). Contributions of external ear structures to directional features of the transfer functions were examined by remeasuring the HRTF in the absence of the pinna and tragus. The investigation mainly focused on the interactions between the spatial and the spectral features in the bat HRTF. The pinna provides gain and shapes these features over a large frequency band (20-90 kHz), and the tragus contributes gain and directionality at the high frequencies (60 to 90 kHz). Analysis of the spatial and spectral characteristics of the bat HRTF reveals that both interaural level differences (ILD) and monaural spectral features are subject to changes in sound source azimuth and elevation. Consequently, localization cues for horizontal and vertical components of the sound source location interact. Availability of multiple cues about sound source azimuth and elevation should enhance information to support reliable sound localization. These findings stress the importance of the acoustic information received at the two ears for sound localization of sonar target position in both azimuth and elevation. .

  6. Global Effects of Local Sound-Speed Perturbations in the Sun: A Theoretical Study

    NASA Astrophysics Data System (ADS)

    Hanasoge, S. M.; Larson, T. P.

    2008-09-01

    We study the effect of localized sound-speed perturbations on global mode frequencies by applying techniques of global helioseismology to numerical simulations of the solar acoustic wave field. Extending the method of realization-noise subtraction ( e.g., Hanasoge, Duvall, and Couvidat, Astrophys. J. 664, 1234, 2007) to global modes and exploiting the luxury of full spherical coverage, we are able to achieve very highly resolved frequency differences that are then used to study sensitivities and the signatures of the thermal asphericities. We find that i) global modes are almost twice as sensitive to sound-speed perturbations at the bottom of the convection zone in comparison to anomalies well inside the radiative interior ( r≲0.55 R ⊙), ii) the m degeneracy is lifted ever so slightly, as seen in the a coefficients, and iii) modes that propagate in the vicinity of the perturbations show small amplitude shifts. Through comparisons with error estimates obtained from Michelson Doppler Imager (MDI; Scherrer et al., Solar Phys. 162, 129, 1995) observations, we find that the frequency differences are detectable with a sufficiently long time series (70 642 days).

  7. Comparing Sound Localization Deficits in Bilateral Cochlear-Implant Users and Vocoder Simulations With Normal-Hearing Listeners

    PubMed Central

    Kan, Alan; Litovsky, Ruth Y.

    2014-01-01

    Bilateral cochlear-implant (BiCI) users are less accurate at localizing free-field (FF) sound sources than normal-hearing (NH) listeners. This performance gap is not well understood but is likely due to a combination of compromises in acoustic signal representation by the two independent speech processors and neural degradation of auditory pathways associated with a patient’s hearing loss. To exclusively investigate the effect of CI speech encoding on horizontal-plane sound localization, the present study measured sound localization performance in NH subjects listening to vocoder processed and nonvocoded virtual acoustic space (VAS) stimuli. Various aspects of BiCI stimulation such as independently functioning devices, variable across-ear channel selection, and pulsatile stimulation were simulated using uncorrelated noise (Nu), correlated noise (N0), or Gaussian-enveloped tone (GET) carriers during vocoder processing. Additionally, FF sound localization in BiCI users was measured in the same testing environment for comparison. Distinct response patterns across azimuthal locations were evident for both listener groups and were analyzed using a multilevel regression analysis. Simulated implant speech encoding, regardless of carrier, was detrimental to NH localization and the GET vocoder best simulated BiCI FF performance in NH listeners. Overall, the detrimental effect of vocoder processing on NH performance suggests that sound localization deficits may persist even for BiCI patients who have minimal neural degradation associated with their hearing loss and indicates that CI speech encoding plays a significant role in the sound localization deficits experienced by BiCI users. PMID:25385244

  8. Comparing sound localization deficits in bilateral cochlear-implant users and vocoder simulations with normal-hearing listeners.

    PubMed

    Jones, Heath; Kan, Alan; Litovsky, Ruth Y

    2014-01-01

    Bilateral cochlear-implant (BiCI) users are less accurate at localizing free-field (FF) sound sources than normal-hearing (NH) listeners. This performance gap is not well understood but is likely due to a combination of compromises in acoustic signal representation by the two independent speech processors and neural degradation of auditory pathways associated with a patient's hearing loss. To exclusively investigate the effect of CI speech encoding on horizontal-plane sound localization, the present study measured sound localization performance in NH subjects listening to vocoder processed and nonvocoded virtual acoustic space (VAS) stimuli. Various aspects of BiCI stimulation such as independently functioning devices, variable across-ear channel selection, and pulsatile stimulation were simulated using uncorrelated noise (Nu), correlated noise (N0), or Gaussian-enveloped tone (GET) carriers during vocoder processing. Additionally, FF sound localization in BiCI users was measured in the same testing environment for comparison. Distinct response patterns across azimuthal locations were evident for both listener groups and were analyzed using a multilevel regression analysis. Simulated implant speech encoding, regardless of carrier, was detrimental to NH localization and the GET vocoder best simulated BiCI FF performance in NH listeners. Overall, the detrimental effect of vocoder processing on NH performance suggests that sound localization deficits may persist even for BiCI patients who have minimal neural degradation associated with their hearing loss and indicates that CI speech encoding plays a significant role in the sound localization deficits experienced by BiCI users. PMID:25385244

  9. Low-frequency sound propagation modeling over a locally-reacting boundary using the parabolic approximation

    NASA Technical Reports Server (NTRS)

    Robertson, J. S.; Siegman, W. L.; Jacobson, M. J.

    1989-01-01

    There is substantial interest in the analytical and numerical modeling of low-frequency, long-range atmospheric acoustic propagation. Ray-based models, because of frequency limitations, do not always give an adequate prediction of quantities such as sound pressure or intensity levels. However, the parabolic approximation method, widely used in ocean acoustics, and often more accurate than ray models for lower frequencies of interest, can be applied to acoustic propagation in the atmosphere. Modifications of an existing implicit finite-difference implementation for computing solutions to the parabolic approximation are discussed. A locally-reacting boundary is used together with a one-parameter impedance model. Intensity calculations are performed for a number of flow resistivity values in both quiescent and windy atmospheres. Variations in the value of this parameter are shown to have substantial effects on the spatial variation of the acoustic signal.

  10. Petroleum geology of western Antarctica

    SciTech Connect

    Kingston, J. )

    1990-05-01

    Antarctica's geology is mostly obscured by thick, moving ice that covers 95% of the land and continental shelf. Reconnaissance investigations of outcrops, shallow boreholes, and geophysical surveys are limited and peripheral owing to ice coverage. However, it is possible to outline substantial elements of the regional geology. Further insight is gained by comparison to analogous sedimentary provinces, especially provinces once adjoined within the framework of the Gondwana supercontinent until middle Cretaceous. The petroleum potential of Antarctica, as in the case of the other related high-standing Gondwana continental fragments, is in Early Cretaceous rifts associated with the Gondwana breakup and with the Pacific convergence in the west Antarctica back arc. The Pacific-facing western Antarctica includes two structural provinces: (1) the Cretaceous and younger interior rift system on the east side of the Weddell and Ross Sea embayment, which contain aulacogens that form the boundary with East Antarctica and (2) the back-arc and fore-arc basins adjoining the Antarctica Peninsula and extending into Marie Byrd Land and the Bellingshausen Sea which are associated with the eastward convergence of the Pacific plate. The petroleum potential of the rifts may be assessed by analogies with related rifts of Australia, India, and South Africa; assessment of the convergent basins of western Antarctica depends upon analogy with similar basins of South America, New Zealand, and Indonesia. An estimate of the petroleum potential of western Antarctica generally is comparable with oil and gas occurrences (both in overall quantity and in field sizes) in the other Gondwana continental fragments. However, in view of the thict moving ice cover, the remote locale, and severe climate, petroleum production is largely beyond technology at this time and probably is economically unfeasible.

  11. High frequency source localization in a shallow ocean sound channel using frequency difference matched field processing.

    PubMed

    Worthmann, Brian M; Song, H C; Dowling, David R

    2015-12-01

    Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, particularly those involving high frequency signals, imperfect knowledge of the actual propagation environment prevents accurate propagation modeling and source localization via MFP fails. For beamforming applications, this actual-to-model mismatch problem was mitigated through a frequency downshift, made possible by a nonlinear array-signal-processing technique called frequency difference beamforming [Abadi, Song, and Dowling (2012). J. Acoust. Soc. Am. 132, 3018-3029]. Here, this technique is extended to conventional (Bartlett) MFP using simulations and measurements from the 2011 Kauai Acoustic Communications MURI experiment (KAM11) to produce ambiguity surfaces at frequencies well below the signal bandwidth where the detrimental effects of mismatch are reduced. Both the simulation and experimental results suggest that frequency difference MFP can be more robust against environmental mismatch than conventional MFP. In particular, signals of frequency 11.2 kHz-32.8 kHz were broadcast 3 km through a 106-m-deep shallow ocean sound channel to a sparse 16-element vertical receiving array. Frequency difference MFP unambiguously localized the source in several experimental data sets with average peak-to-side-lobe ratio of 0.9 dB, average absolute-value range error of 170 m, and average absolute-value depth error of 10 m. PMID:26723312

  12. Vertical-plane sound localization probed with ripple-spectrum noise.

    PubMed

    Macpherson, Ewan A; Middlebrooks, John C

    2003-07-01

    Ripple-spectrum stimuli were used to investigate the scale of spectral detail used by listeners in interpreting spectral cues for vertical-plane localization. In three experiments, free-field localization judgments were obtained for 250-ms, 0.6-16-kHz noise bursts with log-ripple spectra that varied in ripple density, peak-to-trough depth, and phase. When ripple density was varied and depth was held constant at 40 dB, listeners' localization error rates increased most (relative to rates for flat-spectrum targets) for densities of 0.5-2 ripples/oct. When depth was varied and density was held constant at 1 ripple/oct, localization accuracy was degraded only for ripple depths > or = 20 dB. When phase was varied and density was held constant at 1 ripple/oct and depth at 40 dB, three of five listeners made errors at consistent locations unrelated to the ripple phase, whereas two listeners made errors at locations systematically modulated by ripple phase. Although the reported upper limit for ripple discrimination is 10 ripples/oct [Supin et al., J. Acoust. Soc. Am. 106, 2800-2804 (1999)], present results indicate that details finer than 2 ripples/oct or coarser than 0.5 ripples/oct do not strongly influence processing of spectral cues for sound localization. The low spectral-frequency limit suggests that broad-scale spectral variation is discounted, even though components at this scale are among those contributing the most to the shapes of directional transfer functions. PMID:12880054

  13. Input-Specific Gain Modulation by Local Sensory Context Shapes Cortical and Thalamic Responses to Complex Sounds.

    PubMed

    Williamson, Ross S; Ahrens, Misha B; Linden, Jennifer F; Sahani, Maneesh

    2016-07-20

    Sensory neurons are customarily characterized by one or more linearly weighted receptive fields describing sensitivity in sensory space and time. We show that in auditory cortical and thalamic neurons, the weight of each receptive field element depends on the pattern of sound falling within a local neighborhood surrounding it in time and frequency. Accounting for this change in effective receptive field with spectrotemporal context improves predictions of both cortical and thalamic responses to stationary complex sounds. Although context dependence varies among neurons and across brain areas, there are strong shared qualitative characteristics. In a spectrotemporally rich soundscape, sound elements modulate neuronal responsiveness more effectively when they coincide with sounds at other frequencies, and less effectively when they are preceded by sounds at similar frequencies. This local-context-driven lability in the representation of complex sounds-a modulation of "input-specific gain" rather than "output gain"-may be a widespread motif in sensory processing. PMID:27346532

  14. Three-dimensional sound localization from a compact non-coplanar array of microphones using tree-based learning.

    PubMed

    Weng, J; Guentchev, K Y

    2001-07-01

    One of the various human sensory capabilities is to identify the direction of perceived sounds. The goal of this work is to study sound source localization in three dimensions using some of the most important cues the human uses. In an attempt to satisfy the requirements of portability and miniaturization in robotics, this approach employs a compact sensor structure that can be placed on a mobile platform. The objective is to estimate the relative sound source position in three-dimensional space without imposing excessive restrictions on its spatio-temporal characteristics and the environment structure. Two types of features are considered, interaural time and level differences. Their relative effectiveness for localization is studied, as well as a practical way of using these complementary parameters. A two-stage procedure was used. In the training stage, sound samples are produced from points with known coordinates and then are stored. In the recognition stage, unknown sounds are processed by the trained system to estimate the 3D location of the sound source. Results from the experiments showed under +/-3 degrees in average angular error and less than +/-20% in average radial distance error. PMID:11508957

  15. 77 FR 33967 - Special Local Regulations; OPSAIL 2012 Connecticut, Niantic Bay, Long Island Sound, Thames River...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-08

    ... Sound, Thames River and New London Harbor, New London, CT'' in the Federal Register (77 FR 15981). We... Connecticut DHS Department of Homeland Security FR Federal Register SLIS Sector Long Island Sound A..., Niantic Bay, Long Island Sound, Thames River and New London Harbor, New London, CT AGENCY: Coast...

  16. Effects of congruency on localization of audiovisual three-dimensional speech sounds Part IIa

    NASA Astrophysics Data System (ADS)

    Riederer, Klaus A. J.

    2003-10-01

    Part two of the current study [J. Acoust. Soc. Am., this issue] investigated localization of virtual audiovisual speech under exactly the same conditions. Perceived directions were signified by pushing keypad-buttons. Inside-the-head localization occurred almost only for the median-plane stimuli, being insignificant of the stimulus type (7.62% congruent, 9.38% incongruent, and 6.54% auditory-only) and disregarded from further analyses. The mean of correct answers was 46.81%. Factorial within-subjects ANOVA showed no significance on acoustic stimuli (/ipi/, /iti/) or stimulus type but showed strong dependence on direction (p=0.000015) and its interactions with acoustic stimuli (p=0.015374) and stimulus type (p=0.00812). Reaction times were highly dependent on direction (p=0.000002). From the 384 frontal location answers (azimuths 0°, +/-40°) 25.52% congruent, 28.39% incongruent, and 28.65% auditory-only were perceived as backward confused, for 0° azimuth only the corresponding values were 28.13%, 28.13%, and 35.94%. Back-front confusions were 13.80%, 9.64%, and 8.85% (azimuths 180°, +/-130°), and 18.75%, 14.06%, and 14.06% (azimuth 180°). Seeing the (congruently) talking face biased the localization more to the front, especially for the median-backward sounds. Obviously, vision overcomes weaker monaural localization cues as in the ventriloquism effect [Driver, Nature (London) 381, 66-68 (1996)]. [Work supported by Graduate School of Electronics, Telecommunication and Automation.

  17. Moving Sound Source Localization Based on Sequential Subspace Estimation in Actual Room Environments

    NASA Astrophysics Data System (ADS)

    Tsuji, Daisuke; Suyama, Kenji

    This paper presents a novel method for moving sound source localization and its performance evaluation in actual room environments. The method is based on the MUSIC (MUltiple SIgnal Classification) which is one of the most high resolution localization methods. When using the MUSIC, a computation of eigenvectors of correlation matrix is required for the estimation. It needs often a high computational costs. Especially, in the situation of moving source, it becomes a crucial drawback because the estimation must be conducted at every the observation time. Moreover, since the correlation matrix varies its characteristics due to the spatial-temporal non-stationarity, the matrix have to be estimated using only a few observed samples. It makes the estimation accuracy degraded. In this paper, the PAST (Projection Approximation Subspace Tracking) is applied for sequentially estimating the eigenvectors spanning the subspace. In the PAST, the eigen-decomposition is not required, and therefore it is possible to reduce the computational costs. Several experimental results in the actual room environments are shown to present the superior performance of the proposed method.

  18. Slowly emerging glycinergic transmission enhances inhibition in the sound localization pathway of the avian auditory system

    PubMed Central

    Fischl, Matthew J.; Weimann, Sonia R.; Kearse, Michael G.

    2013-01-01

    Localization of low-frequency acoustic stimuli is processed in dedicated neural pathways where coincidence-detecting neurons compare the arrival time of sound stimuli at the two ears, or interaural time disparity (ITD). ITDs occur in the submillisecond range, and vertebrates have evolved specialized excitatory and inhibitory circuitry to compute these differences. Glycinergic inhibition is a computationally significant and prominent component of the mammalian ITD pathway. However, evidence for glycinergic transmission is limited in birds, where GABAergic inhibition has been thought to be the dominant or exclusive inhibitory transmitter. Indeed, previous work showed that GABA antagonists completely eliminate inhibition in avian nuclei specialized for processing temporal features of sound, nucleus magnocellularis (NM) and nucleus laminaris (NL). However, more recent work shows that glycine is coexpressed with GABA in synaptic terminals apposed to neurons in both nuclei (Coleman WL, Fischl MJ, Weimann SR, Burger RM. J Neurophysiol 105: 2405–2420, 2011; Kuo SP, Bradley LA, Trussell LO. J Neurosci 29: 9625–9634, 2009). Here we show complementary evidence of functional glycine receptor (GlyR) expression in NM and NL. Additionally, we show that glycinergic input can be evoked under particular stimulus conditions. Stimulation at high but physiologically relevant rates evokes a slowly emerging glycinergic response in NM and NL that builds over the course of the stimulus. Glycinergic response magnitude was stimulus rate dependent, representing 18% and 7% of the total inhibitory current in NM and NL, respectively, at the end of the 50-pulse, 200-Hz stimulus. Finally, we show that the glycinergic component is functionally relevant, as its elimination reduced inhibition of discharges evoked by current injection into NM neurons. PMID:24198323

  19. Four-choice sound localization abilities of two Florida manatees, Trichechus manatus latirostris.

    PubMed

    Colbert, Debborah E; Gaspard, Joseph C; Reep, Roger; Mann, David A; Bauer, Gordon B

    2009-07-01

    The absolute sound localization abilities of two Florida manatees (Trichechus manatus latirostris) were measured using a four-choice discrimination paradigm, with test locations positioned at 45 deg., 90 deg., 270 deg. and 315 deg. angles relative to subjects facing 0 deg. Three broadband signals were tested at four durations (200, 500, 1000, 3000 ms), including a stimulus that spanned a wide range of frequencies (0.2-20 kHz), one stimulus that was restricted to frequencies with wavelengths shorter than their interaural time distances (6-20 kHz) and one that was limited to those with wavelengths longer than their interaural time distances (0.2-2 kHz). Two 3000 ms tonal signals were tested, including a 4 kHz stimulus, which is the midpoint of the 2.5-5.9 kHz fundamental frequency range of manatee vocalizations and a 16 kHz stimulus, which is in the range of manatee best-hearing sensitivity. Percentage correct within the broadband conditions ranged from 79% to 93% for Subject 1 and from 51% to 93% for Subject 2. Both performed above chance with the tonal signals but had much lower accuracy than with broadband signals, with Subject 1 at 44% and 33% and Subject 2 at 49% and 32% at the 4 kHz and 16 kHz conditions, respectively. These results demonstrate that manatees are able to localize frequency bands with wavelengths that are both shorter and longer than their interaural time distances and suggest that they have the ability to localize both manatee vocalizations and recreational boat engine noises. PMID:19525437

  20. 76 FR 39292 - Special Local Regulations & Safety Zones; Marine Events in Captain of the Port Long Island Sound...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-06

    ...The Coast Guard is establishing fourteen temporary special local regulations and safety zones for marine events and fireworks displays within the Captain of the Port (COTP) Long Island Sound Zone. This action is necessary to provide for the safety of life on navigable waters during the events. Entry into, transit through, mooring or anchoring within these zones is prohibited unless authorized......

  1. Sound localization in common vampire bats: acuity and use of the binaural time cue by a small mammal.

    PubMed

    Heffner, Rickye S; Koay, Gimseong; Heffner, Henry E

    2015-01-01

    Passive sound-localization acuity and the ability to use binaural time and intensity cues were determined for the common vampire bat (Desmodus rotundus). The bats were tested using a conditioned suppression/avoidance procedure in which they drank defibrinated blood from a spout in the presence of sounds from their right, but stopped drinking (i.e., broke contact with the spout) whenever a sound came from their left, thereby avoiding a mild shock. The mean minimum audible angle for three bats for a 100-ms noise burst was 13.1°-within the range of thresholds for other bats and near the mean for mammals. Common vampire bats readily localized pure tones of 20 kHz and higher, indicating they could use interaural intensity-differences. They could also localize pure tones of 5 kHz and lower, thereby demonstrating the use of interaural time-differences, despite their very small maximum interaural distance of 60 μs. A comparison of the use of locus cues among mammals suggests several implications for the evolution of sound localization and its underlying anatomical and physiological mechanisms. PMID:25618037

  2. Sound localization in common vampire bats: Acuity and use of the binaural time cue by a small mammal

    PubMed Central

    Heffner, Rickye S.; Koay, Gimseong; Heffner, Henry E.

    2015-01-01

    Passive sound-localization acuity and the ability to use binaural time and intensity cues were determined for the common vampire bat (Desmodus rotundus). The bats were tested using a conditioned suppression/avoidance procedure in which they drank defibrinated blood from a spout in the presence of sounds from their right, but stopped drinking (i.e., broke contact with the spout) whenever a sound came from their left, thereby avoiding a mild shock. The mean minimum audible angle for three bats for a 100-ms noise burst was 13.1°—within the range of thresholds for other bats and near the mean for mammals. Common vampire bats readily localized pure tones of 20 kHz and higher, indicating they could use interaural intensity-differences. They could also localize pure tones of 5 kHz and lower, thereby demonstrating the use of interaural time-differences, despite their very small maximum interaural distance of 60 μs. A comparison of the use of locus cues among mammals suggests several implications for the evolution of sound localization and its underlying anatomical and physiological mechanisms. PMID:25618037

  3. 33 CFR 100.100 - Special Local Regulations; Regattas and Boat Races in the Coast Guard Sector Long Island Sound...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Special Local Regulations; Regattas and Boat Races in the Coast Guard Sector Long Island Sound Captain of the Port Zone. 100.100 Section 100.100 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY REGATTAS AND MARINE PARADES SAFETY OF LIFE ON...

  4. 76 FR 53337 - Special Local Regulation and Safety Zones; Marine Events in Captain of the Port Long Island Sound...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    ...The Coast Guard is establishing temporary special local regulations and safety zones for marine events within the Captain of the Port (COTP) Long Island Sound Zone for regattas, fireworks displays and swim events. This action is necessary to provide for the safety of life on navigable waters during the events. Entry into, transit through, mooring or anchoring within this zone is prohibited......

  5. 33 CFR 100.100 - Special Local Regulations; Regattas and Boat Races in the Coast Guard Sector Long Island Sound...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Special Local Regulations; Regattas and Boat Races in the Coast Guard Sector Long Island Sound Captain of the Port Zone. 100.100 Section 100.100 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY REGATTAS AND MARINE PARADES SAFETY OF LIFE ON...

  6. 33 CFR 100.1308 - Special Local Regulation; Hydroplane Races within the Captain of the Port Puget Sound Area of...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... hydroplane event in accordance with 33 CFR 100. The Captain of the Port will provide notice of the...; Hydroplane Races within the Captain of the Port Puget Sound Area of Responsibility. 100.1308 Section 100.1308... SAFETY OF LIFE ON NAVIGABLE WATERS § 100.1308 Special Local Regulation; Hydroplane Races within...

  7. A Spiking Neural Network Model of the Medial Superior Olive Using Spike Timing Dependent Plasticity for Sound Localization

    PubMed Central

    Glackin, Brendan; Wall, Julie A.; McGinnity, Thomas M.; Maguire, Liam P.; McDaid, Liam J.

    2010-01-01

    Sound localization can be defined as the ability to identify the position of an input sound source and is considered a powerful aspect of mammalian perception. For low frequency sounds, i.e., in the range 270 Hz–1.5 KHz, the mammalian auditory pathway achieves this by extracting the Interaural Time Difference between sound signals being received by the left and right ear. This processing is performed in a region of the brain known as the Medial Superior Olive (MSO). This paper presents a Spiking Neural Network (SNN) based model of the MSO. The network model is trained using the Spike Timing Dependent Plasticity learning rule using experimentally observed Head Related Transfer Function data in an adult domestic cat. The results presented demonstrate how the proposed SNN model is able to perform sound localization with an accuracy of 91.82% when an error tolerance of ±10° is used. For angular resolutions down to 2.5°, it will be demonstrated how software based simulations of the model incur significant computation times. The paper thus also addresses preliminary implementation on a Field Programmable Gate Array based hardware platform to accelerate system performance. PMID:20802855

  8. Changes in ice cover thickness and lake level of Lake Hoare, Antarctica - Implications for local climatic change

    NASA Technical Reports Server (NTRS)

    Wharton, Robert A., Jr.; Mckay, Christopher P.; Clow, Gary D.; Andersen, Dale T.; Simmons, George M., Jr.; Love, F. G.

    1992-01-01

    Results are reported from 10 years of ice-thickness measurements at perennially ice-covered Lake Hoare in southern Victoria Land, Antarctica. The ice cover of this lake had been thinning steadily at a rate exceeding 20 cm/yr during the last decade but seems to have recently stabilized at a thickness of 3.3 m. Data concerning lake level and degree-days above freezing are presented to show the relationship between peak summer temperatures and the volume of glacier-derived meltwater entering Lake Hoare each summer. From these latter data it is inferred that peak summer temperatures have been above 0 C for a progressively longer period of time each year since 1972. Possible explanations for the thinning of the lake ice are considered. The thickness of the ice cover is determined by the balance between freezing during the winter and ablation that occurs all year but maximizes in summer. It is suggested that the term most likely responsible for the change in the ice cover thickness at Lake Hoare is the extent of summer melting, consistent with the rising lake levels.

  9. Median-plane sound localization as a function of the number of spectral channels using a channel vocoder

    PubMed Central

    Goupell, Matthew J.; Majdak, Piotr; Laback, Bernhard

    2010-01-01

    Using a vocoder, median-plane sound localization performance was measured in eight normal-hearing listeners as a function of the number of spectral channels. The channels were contiguous and logarithmically spaced in the range from 0.3 to 16 kHz. Acutely testing vocoded stimuli showed significantly worse localization compared to noises and 100 pulse∕s click trains, both of which were tested after feedback training. However, localization for the vocoded stimuli was better than chance. A second experiment was performed using two different 12-channel spacings for the vocoded stimuli, now including feedback training. One spacing was from experiment 1. The second spacing (called the speech-localization spacing) assigned more channels to the frequency range associated with speech. There was no significant difference in localization between the two spacings. However, even with training, localizing 12-channel vocoded stimuli remained worse than localizing virtual wideband noises by 4.8° in local root-mean-square error and 5.2% in quadrant error rate. Speech understanding for the speech-localization spacing was not significantly different from that for a typical spacing used by cochlear-implant users. These experiments suggest that current cochlear implants have a sufficient number of spectral channels for some vertical-plane sound localization capabilities, albeit worse than normal-hearing listeners, without loss of speech understanding. PMID:20136221

  10. Fast and persistent adaptation to new spectral cues for sound localization suggests a many-to-one mapping mechanism.

    PubMed

    Trapeau, Régis; Aubrais, Valérie; Schönwiesner, Marc

    2016-08-01

    The adult human auditory system can adapt to changes in spectral cues for sound localization. This plasticity was demonstrated by changing the shape of the pinna with earmolds. Previous results indicate that participants regain localization accuracy after several weeks of adaptation and that the adapted state is retained for at least one week without earmolds. No aftereffect was observed after mold removal, but any aftereffect may be too short to be observed when responses are averaged over many trials. This work investigated the lack of aftereffect by analyzing single-trial responses and modifying visual, auditory, and tactile information during the localization task. Results showed that participants localized accurately immediately after mold removal, even at the first stimulus presentation. Knowledge of the stimulus spectrum, tactile information about the absence of the earmolds, and visual feedback were not necessary to localize accurately after adaptation. Part of the adaptation persisted for one month without molds. The results are consistent with the hypothesis of a many-to-one mapping of the spectral cues, in which several spectral profiles are simultaneously associated with one sound location. Additionally, participants with acoustically more informative spectral cues localized sounds more accurately, and larger acoustical disturbances by the molds reduced adaptation success. PMID:27586720

  11. Tuning Neuronal Hardware with Microsecond Precision: Sound Localization in the Barn Owl

    NASA Astrophysics Data System (ADS)

    van Hemmen, J. Leo

    1998-03-01

    In auditory and electrosensory neuronal systems, there seems to exist an unresolved paradox: They encode behaviorally relevant signals in the range of a few microseconds with neurons that are at least one order of magnitude slower. The barn owl's auditory system is a prominent example that may serve to provide a solution(W. Gerstner, R. Kempter, J.L. van Hemmen, and H. Wagner, Nature 383) (1996) 76--78 to the above paradox. First, neuronal output is much more accurate than the input, phprovided the presynaptic spikes arrive coherently on the average -- as they do in the adult animal. Second, this coherence in signal arrival times can be attained through unsupervised Hebbian learning (`tuning') during ontogenetic development. The learning rule governing the strength of a synapse is based on the precise timing of input as compared to output spikes. Third, the learning rule also selects the correct delays from two independent groups of input, for example, from the left and right ear and, thus, can explain the tuning to interaural time differences in the microsecond range that underlies sound localization. The relation to stochastic resonance is indicated.

  12. MEMS Biomimetic Acoustic Pressure Gradient Sensitive Structure for Sound Source Localization

    PubMed Central

    An, Peng; Yuan, Weizheng; Ren, Sen

    2009-01-01

    The parasitoid fly Ormia ochracea shows an astonishing localization ability with its tiny hearing organ. A novel MEMS biomimetic acoustic pressure gradient sensitive structure was designed and fabricated by mimicking the mechanically coupled tympana of the fly. Firstly, the analytic representation formulas of the resultant force and resultant moment of the incoming plane wave acting on the structure were derived. After that, structure modal analysis was performed and the results show that the structure has out-of-phase and in-phase vibration modes, and the corresponding eigenfrequency is decided by the stiffness of vertical torsional beam and horizontal beam respectively. Acoustic-structural coupled analysis was performed and the results show that phase difference and amplitude difference between the responses of the two square diaphragms of the sensitive structure are effectively enlarged through mechanical coupling beam. The phase difference and amplitude difference increase with increasing incident angle and can be used to distinguish the direction of sound arrival. At last, the fabrication process and results of the device is also presented. PMID:22346718

  13. Impulsive sound source localization using peak and RMS estimation of the time-domain beamformer output

    NASA Astrophysics Data System (ADS)

    Seo, Dae-Hoon; Choi, Jung-Woo; Kim, Yang-Hann

    2014-12-01

    This paper presents a beamforming technique for locating impulsive sound source. The conventional frequency-domain beamformer is advantageous for localizing noise sources for a certain frequency band of concern, but the existence of many frequency components in the wide-band spectrum of impulsive noise makes the beamforming image less clear. In contrast to a frequency-domain beamformer, it has been reported that a time-domain beamformer can be better suited for transient signals. Although both frequency- and time-domain beamformers produce the same result for the beamforming power, which is defined as the RMS value of its output, we can use alternative directional estimators such as the peak value to enhance the performance of a time-domain beamformer. In this study, the performance of two different directional estimators, the peak and RMS output values, are investigated and compared with the incoherent measurement noise embedded in multiple microphone signals. The impulsive noise source is modeled as a triangular pulse, and the beamwidth and side lobe level of the time-domain beamformer are formulated as functions of the pulse duration, the microphone spacing, and the number of microphones. The proposed formula is verified via experiments in an anechoic chamber using a uniformly spaced linear array, and the results show that the peak estimation of beamformer output determines the location with better spatial resolution and a lower side lobe level than RMS estimation.

  14. Sound localization in the presence of multiple reflections using a binaurally integrated cross-correlation/auto-correlation mechanism.

    PubMed

    Braasch, Jonas

    2016-07-01

    A precedence effect model is described that can use a binaural signal to robustly localize a sound source in the presence of multiple reflections for the frontal horizontal plane. The model also estimates a room impulse response from a running binaural signal and determines the spatial locations and delays of early reflections, without any prior or additional knowledge of the source. A dual-layer cross-correlation/auto-correlation algorithm is used to determine the interaural time difference of the direct sound source component and to estimate a binaural activity pattern. PMID:27475205

  15. Provenance Investigations Using Magnetic Susceptibility of Pebble- to Cobble-Sized Clasts in the AND-2A Core, ANDRILL Southern McMurdo Sound Project, Antarctica

    NASA Astrophysics Data System (ADS)

    Strada, E.; Florindo, F.; Sandroni, S.; Talarico, F.; Acton, G.; Jovane, L.; Ohneiser, C.; Sagnotti, L.; Verosub, K. L.; Wilson, G. S.; Science Team

    2008-12-01

    Magnetic susceptibilities of pebble- to cobble-sized clasts recovered in the ANDRILL SMS core (site AND-2A: 77° 45.488'S, 165° 16.605'E) (McMurdo Sound, Ross Sea) were measured on ice with a Bartington MS-2B susceptibility meter. Measurements were made on thin section billets or on clasts themselves when they were of suitable size for the instrument. The variability of the magnetic susceptibility is related both to variations in the primary magnetic mineral content of the source rocks as well as to secondary magnetic mineral formation/dissolution prior to and during the diagenetic process. Volcanic clasts, the dominant clast type thoughout the core, display the highest susceptibility values, but there is extreme heterogeneity of values within the same compositional type (i.e. felsic, intermediate, mafic). Given this, the susceptibilities of volcanic clasts in the AND-2A core are poorly suited for provenance studies. In contrast, the basement clasts (consisting of a variety of metasedimentary and intrusive rocks) can play an important role in defining ice provenance and dynamics. The textures and mineralogical compositions of intrusive and metamorphic rocks indicate the region between the Ferrar Glacier and the Mulock Glacier as the most likely provenance region. In order to better understand this result, we chose to undertake a magnetic petrology study on the most magnetic (Low-Field mass susceptibility, χ > 90*10-8 m3/kg) basement clasts sampled on ice. A comparison of the magnetic susceptibilities of our AND-2A clasts with samples collected from the outcrops of Southern Victoria Land (SVL) indicate that there is a good correlation between the highly magnetic metamorphic rocks of the region south of Ferrar Glacier and the most magnetic basement clasts in the core. In particular, the petrographic and magnetic features of metasedimentary clasts closely match both metasandstones from Baronick Glacier (Skelton Glacier area) and gneisses and schists from Hobbs Peak

  16. Numerical calculation of listener-specific head-related transfer functions and sound localization: Microphone model and mesh discretization

    PubMed Central

    Ziegelwanger, Harald; Majdak, Piotr; Kreuzer, Wolfgang

    2015-01-01

    Head-related transfer functions (HRTFs) can be numerically calculated by applying the boundary element method on the geometry of a listener’s head and pinnae. The calculation results are defined by geometrical, numerical, and acoustical parameters like the microphone used in acoustic measurements. The scope of this study was to estimate requirements on the size and position of the microphone model and on the discretization of the boundary geometry as triangular polygon mesh for accurate sound localization. The evaluation involved the analysis of localization errors predicted by a sagittal-plane localization model, the comparison of equivalent head radii estimated by a time-of-arrival model, and the analysis of actual localization errors obtained in a sound-localization experiment. While the average edge length (AEL) of the mesh had a negligible effect on localization performance in the lateral dimension, the localization performance in sagittal planes, however, degraded for larger AELs with the geometrical error as dominant factor. A microphone position at an arbitrary position at the entrance of the ear canal, a microphone size of 1 mm radius, and a mesh with 1 mm AEL yielded a localization performance similar to or better than observed with acoustically measured HRTFs. PMID:26233020

  17. Effects of Active and Passive Hearing Protection Devices on Sound Source Localization, Speech Recognition, and Tone Detection.

    PubMed

    Brown, Andrew D; Beemer, Brianne T; Greene, Nathaniel T; Argo, Theodore; Meegan, G Douglas; Tollin, Daniel J

    2015-01-01

    Hearing protection devices (HPDs) such as earplugs offer to mitigate noise exposure and reduce the incidence of hearing loss among persons frequently exposed to intense sound. However, distortions of spatial acoustic information and reduced audibility of low-intensity sounds caused by many existing HPDs can make their use untenable in high-risk (e.g., military or law enforcement) environments where auditory situational awareness is imperative. Here we assessed (1) sound source localization accuracy using a head-turning paradigm, (2) speech-in-noise recognition using a modified version of the QuickSIN test, and (3) tone detection thresholds using a two-alternative forced-choice task. Subjects were 10 young normal-hearing males. Four different HPDs were tested (two active, two passive), including two new and previously untested devices. Relative to unoccluded (control) performance, all tested HPDs significantly degraded performance across tasks, although one active HPD slightly improved high-frequency tone detection thresholds and did not degrade speech recognition. Behavioral data were examined with respect to head-related transfer functions measured using a binaural manikin with and without tested HPDs in place. Data reinforce previous reports that HPDs significantly compromise a variety of auditory perceptual facilities, particularly sound localization due to distortions of high-frequency spectral cues that are important for the avoidance of front-back confusions. PMID:26313145

  18. Effects of Active and Passive Hearing Protection Devices on Sound Source Localization, Speech Recognition, and Tone Detection

    PubMed Central

    Brown, Andrew D.; Beemer, Brianne T.; Greene, Nathaniel T.; Argo, Theodore; Meegan, G. Douglas; Tollin, Daniel J.

    2015-01-01

    Hearing protection devices (HPDs) such as earplugs offer to mitigate noise exposure and reduce the incidence of hearing loss among persons frequently exposed to intense sound. However, distortions of spatial acoustic information and reduced audibility of low-intensity sounds caused by many existing HPDs can make their use untenable in high-risk (e.g., military or law enforcement) environments where auditory situational awareness is imperative. Here we assessed (1) sound source localization accuracy using a head-turning paradigm, (2) speech-in-noise recognition using a modified version of the QuickSIN test, and (3) tone detection thresholds using a two-alternative forced-choice task. Subjects were 10 young normal-hearing males. Four different HPDs were tested (two active, two passive), including two new and previously untested devices. Relative to unoccluded (control) performance, all tested HPDs significantly degraded performance across tasks, although one active HPD slightly improved high-frequency tone detection thresholds and did not degrade speech recognition. Behavioral data were examined with respect to head-related transfer functions measured using a binaural manikin with and without tested HPDs in place. Data reinforce previous reports that HPDs significantly compromise a variety of auditory perceptual facilities, particularly sound localization due to distortions of high-frequency spectral cues that are important for the avoidance of front-back confusions. PMID:26313145

  19. The representation of sound localization cues in the barn owl's inferior colliculus.

    PubMed

    Singheiser, Martin; Gutfreund, Yoram; Wagner, Hermann

    2012-01-01

    The barn owl is a well-known model system for studying auditory processing and sound localization. This article reviews the morphological and functional organization, as well as the role of the underlying microcircuits, of the barn owl's inferior colliculus (IC). We focus on the processing of frequency and interaural time (ITD) and level differences (ILD). We first summarize the morphology of the sub-nuclei belonging to the IC and their differentiation by antero- and retrograde labeling and by staining with various antibodies. We then focus on the response properties of neurons in the three major sub-nuclei of IC [core of the central nucleus of the IC (ICCc), lateral shell of the central nucleus of the IC (ICCls), and the external nucleus of the IC (ICX)]. ICCc projects to ICCls, which in turn sends its information to ICX. The responses of neurons in ICCc are sensitive to changes in ITD but not to changes in ILD. The distribution of ITD sensitivity with frequency in ICCc can only partly be explained by optimal coding. We continue with the tuning properties of ICCls neurons, the first station in the midbrain where the ITD and ILD pathways merge after they have split at the level of the cochlear nucleus. The ICCc and ICCls share similar ITD and frequency tuning. By contrast, ICCls shows sigmoidal ILD tuning which is absent in ICCc. Both ICCc and ICCls project to the forebrain, and ICCls also projects to ICX, where space-specific neurons are found. Space-specific neurons exhibit side peak suppression in ITD tuning, bell-shaped ILD tuning, and are broadly tuned to frequency. These neurons respond only to restricted positions of auditory space and form a map of two-dimensional auditory space. Finally, we briefly review major IC features, including multiplication-like computations, correlates of echo suppression, plasticity, and adaptation. PMID:22798945

  20. The representation of sound localization cues in the barn owl's inferior colliculus

    PubMed Central

    Singheiser, Martin; Gutfreund, Yoram; Wagner, Hermann

    2012-01-01

    The barn owl is a well-known model system for studying auditory processing and sound localization. This article reviews the morphological and functional organization, as well as the role of the underlying microcircuits, of the barn owl's inferior colliculus (IC). We focus on the processing of frequency and interaural time (ITD) and level differences (ILD). We first summarize the morphology of the sub-nuclei belonging to the IC and their differentiation by antero- and retrograde labeling and by staining with various antibodies. We then focus on the response properties of neurons in the three major sub-nuclei of IC [core of the central nucleus of the IC (ICCc), lateral shell of the central nucleus of the IC (ICCls), and the external nucleus of the IC (ICX)]. ICCc projects to ICCls, which in turn sends its information to ICX. The responses of neurons in ICCc are sensitive to changes in ITD but not to changes in ILD. The distribution of ITD sensitivity with frequency in ICCc can only partly be explained by optimal coding. We continue with the tuning properties of ICCls neurons, the first station in the midbrain where the ITD and ILD pathways merge after they have split at the level of the cochlear nucleus. The ICCc and ICCls share similar ITD and frequency tuning. By contrast, ICCls shows sigmoidal ILD tuning which is absent in ICCc. Both ICCc and ICCls project to the forebrain, and ICCls also projects to ICX, where space-specific neurons are found. Space-specific neurons exhibit side peak suppression in ITD tuning, bell-shaped ILD tuning, and are broadly tuned to frequency. These neurons respond only to restricted positions of auditory space and form a map of two-dimensional auditory space. Finally, we briefly review major IC features, including multiplication-like computations, correlates of echo suppression, plasticity, and adaptation. PMID:22798945

  1. Mapping of saltwater intrusions into the McMurdo Ice Shelf, Antarctica, using electromagnetic induction sounding and ground penetrating radar measurements

    NASA Astrophysics Data System (ADS)

    Rack, Wolfgang; Haas, Christian; Krützmann, Nikolai

    2010-05-01

    Ice Shelves, interacting with both the ocean and the atmosphere, are a sensitive indicator of a changing environment. The repeated observation of ice shelf thickness as a result of surface and bottom mass balance and ice shelf dynamics yields insight into this sensitive balance. Ice shelf thickness is normally measured by radar, or derived from freeboard height using knowledge about ice density and sea level height. Seismic methods may also be used but are usually limited to smaller areas. In general, melting at the underside of the ice shelf is expected to be highest near the grounding line, and the rise and outflow of diluted undercooled water may result in bottom freezing. In the presence of saline ice at the ice shelf bottom the use of radar for ice thickness measurements is limited, as the radar energy is effectively absorbed. This is also the case near the ice shelf edge where saltwater intrusions may be observed. In November 2009 we conducted helicopter-borne electromagnetic induction measurements in the McMurdo Sound to measure sea ice and ice shelf thickness within a validation experiment for the CryoSat-2 satellite. The instrument used was an "EM bird", which is more frequently operated in the Arctic to map sea ice thickness. The thickness of the ice shelf could be detected for values less than about 50 m, with a strong gradient perpendicular to the ice shelf front and significant undulations parallel to the ice shelf front. At the same time, we used a ground penetrating radar system in order to detect the transition depth between fresh water and saline ice. In this contribution we present the results of this combined airborne and ground based method, which could be further developed to a fully airborne or ground based technology detecting larger ice shelf thickness and ice shelf morphology in the presence of marine ice.

  2. The impact of glacier retreat from the Ross Sea on local climate: Characterization of mineral dust in the Taylor Dome ice core, East Antarctica

    NASA Astrophysics Data System (ADS)

    Aarons, S. M.; Aciego, S. M.; Gabrielli, P.; Delmonte, B.; Koornneef, J. M.; Wegner, A.; Blakowski, M. A.

    2016-06-01

    Recent declines in ice shelf and sea ice extent experienced in polar regions highlight the importance of evaluating variations in local weather patterns in response to climate change. Airborne mineral particles (dust) transported through the atmosphere and deposited on ice sheets and glaciers in Antarctica and Greenland can provide a robust set of tools for resolving the evolution of climatic systems through time. Here we present the first high time resolution radiogenic isotope (strontium and neodymium) data for Holocene dust in a coastal East Antarctic ice core, accompanied by rare earth element composition, dust concentration, and particle size distribution during the last deglaciation. We aim to use these combined ice core data to determine dust provenance, with variations indicative of shifts in either dust production, sources, and/or transport pathways. We analyzed a series of 17 samples from the Taylor Dome (77°47‧47″S, 158°43‧26″E) ice core, 113-391 m in depth from 1.1-31.4 ka. Radiogenic isotopic and rare earth element compositions of dust during the last glacial period are in good agreement with previously measured East Antarctic ice core dust records. In contrast, the Holocene dust dataset displays a broad range in isotopic and rare earth element compositions, suggesting a shift from long-range transported dust to a more variable, local input that may be linked to the retreat of the Ross Ice Shelf during the last deglaciation. Observed changes in the dust cycle inferred from a coastal East Antarctic ice core can thus be used to infer an evolving local climate.

  3. Microstructural records of multiple retrograde local H2O supplement in the pelitic gneiss, Lützow-Holm Complex at Akarui Point, East Antarctica

    NASA Astrophysics Data System (ADS)

    Nakamura, Aya; Kitamura, Masao; Kawakami, Tetsuo

    2014-04-01

    The alkali-feldspar and biotite in the sillimanite-biotite-garnet gneiss from East Antarctica preserves characteristic microstructural evidence of multi-stage H2O supplement during the retrograde metamorphism. The first microstructural evidence is the "zoned feldspar," in which the mesoperthitic zone, the anti-perthitic zone, and lamella-free plagioclase zone coexist within a single crystal. They are occasionally found next to biotite, and are always depleted in orthoclase (Or) component toward the biotite. The formation process of this microstructure could be explained by the diffusion that oversteps the solvus. The second microstructural evidence is the serrate boundary between alkali-feldspar and biotite. The projections of biotite are selectively developed next to Or lamellae of alkali-feldspar every 3-5 μm. These two microstructures would have formed as the biotite grew by consuming potash in alkali-feldspar when H2O-bearing fluid locally passed through the grain boundaries. The former microstructure was formed at 825-900 °C before lamella formation, and the latter microstructure was formed after the lamella formation. These microstructures are the indicators of fluid pathways formed under two different temperature conditions. The common coexistence of these microstructures implies that the fluid used similar pathways during the retrograde metamorphism.

  4. Comparing Local-Time and Storm-Phase Distributions of EMIC Waves Observed by Van Allen Probes A, GOES-13, and Halley, Antarctica

    NASA Astrophysics Data System (ADS)

    Ohnsted, M.; Engebretson, M. J.; Posch, J. L.; Lessard, M.; Singer, H. J.; Kletzing, C.; Smith, C. W.; Horne, R. B.

    2015-12-01

    Electromagnetic ion cyclotron (EMIC) waves are expected to be highly efficient in depleting the ring current and in removing outer radiation belt electrons. However, the distribution of these waves in subauroral regions has not been well characterized. In this study we present 0-5 Hz magnetic field data from the Van Allen Probes A (RBSP A) spacecraft (in elliptical equatorial orbit with apogee at 5.8 RE), 0-1 Hz data from GOES-13 (in geosynchronous orbit), and 0-5 Hz data from Halley, Antarctica (L ~4.6), during the first full local-time precession of the Van Allen Probes from October 2012 through July 2014. The considerably different hourly local time vs. L distributions observed point to distinct locations and geomagnetic activity-dependent patterns of EMIC wave activity. GOES-13 wave occurrences exhibited a broad peak in the noon-to-dusk sector. He+ band events peaked near dusk, while H+ band waves peaked near noon, with a secondary peak centered near dawn. More EMIC waves occurred during storm main phase in the He+ band (5%) than in the H+ band (1%), and 80% and 89% of the He+ and H+ band waves, respectively, occurred under late storm recovery or quiet conditions. During all storm phases the local time occurrence patterns of < 0.4 Hz and 0.4-1.0 Hz events at Halley resembled those of He+ and H+ band waves, respectively, at GOES-13. The relatively few wave events at Halley with f > 1.0 Hz occurred at all local times, but with a modest, broad peak near dawn. Roughly 90% of both the 1570 Halley events < 1.0 Hz and the 142 Halley events > 1.0 Hz occurred during late storm recovery and quiet conditions. Events during compressions at GOES-13 (10%), Halley (6%), and RBSP A (6%) peaked near local noon, but with a secondary peak near midnight. Waves observed by RBSP A were distributed rather evenly in local time in all L shell ranges between 3 and 6, and the percentage occurring during late storm recovery or quiet conditions was only 65%. We interpret the difference in

  5. Geochemical record of Miocene sediment provenance and continental weathering in the McMurdo Sound, ANDRILL AND-2A, Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Hoffmann, S.; von Eynatten, H.; Kuhn, G.

    2010-12-01

    Geochemical whole rock analyses have been carried out on the AND-2A core during the drilling campaign 2007 with an Avaatech XRF-Core Scanner (XRF-CS). After the on-ice season, about 500 samples were prepared for conventional XRF measurements on fused glass discs to complete the semi-quantitative XRF-CS dataset. Based on this geochemical dataset we (i) indentify the dominant source rock pattern and (ii) constrain the corresponding paleoclimate conditions by the degree of chemical weathering. A multivariate statistical approach was applied to recognize the source rock composition of the AND-2A sediments. Hierarchical cluster analysis on the conventional XRF dataset provides clear evidence for four different clusters within both the diamicties (D1, D2, D3, D4) and mudstones (M1, M2, M3, M4). Element ratios of these four clusters were compared with literature data for potential source rocks from the McMurdo Sound area. For both lithologies the first cluster (D1 and M1) is strongly dominated by rocks from the Transantartic Mountains (TAM). All other clusters show a stepwise increase of the McMurdo Volcanic Group (MVG) with increasing cluster number. According to this, cluster D4 and M4 are close to the endmember composition of the MVG. These results subdivide the AND-2A core into three main provenance sections, seprated by major breaks at ~665 and ~225 meter below seafloor (mbsf). The lower section between ~1138 to 665 mbsf is dominated by high cluster numbers (D3-D4 and M3-M4) which corresponds to a predominance of volcanics from the MVG. In contrast, the middle section between ~665 to 225 mbsf is characterized by a strong TAM influence (cluster numbers D1-D2 and M1-M2). Above ~225 mbsf the provenance is again dominated by the MVG (cluster numbers D3-D4). The Chemical Index of Alteration (CIA) is one of the widest used proxies to determine the influence of climate changes on bulk sediment composition. This index uses the major oxides ratios of Al2O3, Na2O, CaO and K2O

  6. Spatial hearing in Cope's gray treefrog: I. Open and closed loop experiments on sound localization in the presence and absence of noise.

    PubMed

    Caldwell, Michael S; Bee, Mark A

    2014-04-01

    The ability to reliably locate sound sources is critical to anurans, which navigate acoustically complex breeding choruses when choosing mates. Yet, the factors influencing sound localization performance in frogs remain largely unexplored. We applied two complementary methodologies, open and closed loop playback trials, to identify influences on localization abilities in Cope's gray treefrog, Hyla chrysoscelis. We examined localization acuity and phonotaxis behavior of females in response to advertisement calls presented from 12 azimuthal angles, at two signal levels, in the presence and absence of noise, and at two noise levels. Orientation responses were consistent with precise localization of sound sources, rather than binary discrimination between sources on either side of the body (lateralization). Frogs were unable to discriminate between sounds arriving from forward and rearward directions, and accurate localization was limited to forward sound presentation angles. Within this region, sound presentation angle had little effect on localization acuity. The presence of noise and low signal-to-noise ratios also did not strongly impair localization ability in open loop trials, but females exhibited reduced phonotaxis performance consistent with impaired localization during closed loop trials. We discuss these results in light of previous work on spatial hearing in anurans. PMID:24504182

  7. Spatial hearing in Cope’s gray treefrog: I. Open and closed loop experiments on sound localization in the presence and absence of noise

    PubMed Central

    Caldwell, Michael S.; Bee, Mark A.

    2014-01-01

    The ability to reliably locate sound sources is critical to anurans, which navigate acoustically complex breeding choruses when choosing mates. Yet, the factors influencing sound localization performance in frogs remain largely unexplored. We applied two complementary methodologies, open and closed loop playback trials, to identify influences on localization abilities in Cope’s gray treefrog, Hyla chrysoscelis. We examined localization acuity and phonotaxis behavior of females in response to advertisement calls presented from 12 azimuthal angles, at two signal levels, in the presence and absence of noise, and at two noise levels. Orientation responses were consistent with precise localization of sound sources, rather than binary discrimination between sources on either side of the body (lateralization). Frogs were unable to discriminate between sounds arriving from forward and rearward directions, and accurate localization was limited to forward sound presentation angles. Within this region, sound presentation angle had little effect on localization acuity. The presence of noise and low signal-to-noise ratios also did not strongly impair localization ability in open loop trials, but females exhibited reduced phonotaxis performance consistent with impaired localization during closed loop trials. We discuss these results in light of previous work on spatial hearing in anurans. PMID:24504182

  8. Dichotic sound localization properties of duration-tuned neurons in the inferior colliculus of the big brown bat

    PubMed Central

    Sayegh, Riziq; Aubie, Brandon; Faure, Paul A.

    2014-01-01

    Electrophysiological studies on duration-tuned neurons (DTNs) from the mammalian auditory midbrain have typically evoked spiking responses from these cells using monaural or free-field acoustic stimulation focused on the contralateral ear, with fewer studies devoted to examining the electrophysiological properties of duration tuning using binaural stimulation. Because the inferior colliculus (IC) receives convergent inputs from lower brainstem auditory nuclei that process sounds from each ear, many midbrain neurons have responses shaped by binaural interactions and are selective to binaural cues important for sound localization. In this study, we used dichotic stimulation to vary interaural level difference (ILD) and interaural time difference (ITD) acoustic cues and explore the binaural interactions and response properties of DTNs and non-DTNs from the IC of the big brown bat (Eptesicus fuscus). Our results reveal that both DTNs and non-DTNs can have responses selective to binaural stimulation, with a majority of IC neurons showing some type of ILD selectivity, fewer cells showing ITD selectivity, and a number of neurons showing both ILD and ITD selectivity. This study provides the first demonstration that the temporally selective responses of DTNs from the vertebrate auditory midbrain can be selective to binaural cues used for sound localization in addition to having spiking responses that are selective for stimulus frequency, amplitude, and duration. PMID:24959149

  9. Southern McMurdo Sound Project (SMS- ANDRILL): overview of Mid Miocene Climatic Optima events and correlations in western Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Harwood, D. M.; Florindo, F.; Levy, R. H.; Talarico, F.; Fielding, C.; Fischbein, S.; Sms Science Team

    2009-04-01

    The ANtarctic geological DRILLing Program (ANDRILL), an international collaboration between Antarctic research programs of Germany, Italy, New Zealand and the United States, successfully cored in late 2007 (with 98% recovery) a 1138 meter drill hole that documents an excellent history of high latitude paleoenvironmental conditions and climate/glacial variation during Miocene climatic optimum periods. In addition, fracture mapping, core orientation success, and borehole hydrofracture experiments reveal details regarding the history and current stress regime in the western Ross Sea. We present initial correlations of the AND-2A drillcore to global proxies of sea-level and deep-sea geochemical stratigraphy, guided by a robust chronostrati-graphic framework for the early and middle Miocene. Changes evident in stratigraphic sequences, physical properties (borehole and core), and geochemical logs, record fine details of glacial, climatic, tectonic and eustatic influence in the western Ross Sea help establish through correlation to existing records how local changes evident in the drillcore relate to regional and global events. These records combined with paleontological and geochemical evidence for terrestrial - marine paleotemperatures provide important data input for climate and ice-sheet model reconstructions and testing. An abundance of volcanic materials reveals evolution of the McMurdo Volcanic Group, including episodes of explosive volcanism. Substantial subsidence occurred within the last 2 Ma associated with volcanic loading from Ross Island, reversing the persistent littoral to shallow neritic depths evident through most of the cored sequence. Persistent sediment supply into western Victoria Land Basin during a steady phase of thermal subsidence produced a thick stratigraphic sequence from which we are reconstructing the details of paleoclimatic, eustatic and glacial variations on the shallow marine coast of the Transantarctic Mountains.

  10. Behavioural sensitivity to binaural spatial cues in ferrets: evidence for plasticity in the duplex theory of sound localization

    PubMed Central

    Keating, Peter; Nodal, Fernando R; King, Andrew J

    2014-01-01

    For over a century, the duplex theory has guided our understanding of human sound localization in the horizontal plane. According to this theory, the auditory system uses interaural time differences (ITDs) and interaural level differences (ILDs) to localize low-frequency and high-frequency sounds, respectively. Whilst this theory successfully accounts for the localization of tones by humans, some species show very different behaviour. Ferrets are widely used for studying both clinical and fundamental aspects of spatial hearing, but it is not known whether the duplex theory applies to this species or, if so, to what extent the frequency range over which each binaural cue is used depends on acoustical or neurophysiological factors. To address these issues, we trained ferrets to lateralize tones presented over earphones and found that the frequency dependence of ITD and ILD sensitivity broadly paralleled that observed in humans. Compared with humans, however, the transition between ITD and ILD sensitivity was shifted toward higher frequencies. We found that the frequency dependence of ITD sensitivity in ferrets can partially be accounted for by acoustical factors, although neurophysiological mechanisms are also likely to be involved. Moreover, we show that binaural cue sensitivity can be shaped by experience, as training ferrets on a 1-kHz ILD task resulted in significant improvements in thresholds that were specific to the trained cue and frequency. Our results provide new insights into the factors limiting the use of different sound localization cues and highlight the importance of sensory experience in shaping the underlying neural mechanisms. PMID:24256073

  11. Trade-off in the sound localization abilities of early blind individuals between the horizontal and vertical planes.

    PubMed

    Voss, Patrice; Tabry, Vanessa; Zatorre, Robert J

    2015-04-15

    There is substantial evidence that sensory deprivation leads to important cross-modal brain reorganization that is paralleled by enhanced perceptual abilities. However, it remains unclear how widespread these enhancements are, and whether they are intercorrelated or arise at the expense of other perceptual abilities. One specific area where such a trade-off might arise is that of spatial hearing, where blind individuals have been shown to possess superior monaural localization abilities in the horizontal plane, but inferior localization abilities in the vertical plane. While both of these tasks likely involve the use of monaural cues due to the absence of any relevant binaural signal, there is currently no proper explanation for this discrepancy, nor has any study investigated both sets of abilities in the same sample of blind individuals. Here, we assess whether the enhancements observed in the horizontal plane are related to the deficits observed in the vertical plane by testing sound localization in both planes in groups of blind and sighted persons. Our results show that the blind individuals who displayed the highest accuracy at localizing sounds monaurally in the horizontal plane are also the ones who exhibited the greater deficit when localizing in the vertical plane. These findings appear to argue against the idea of generalized perceptual enhancements in the early blind, and instead suggest the possibility of a trade-off in the localization proficiency between the two auditory spatial planes, such that learning to use monaural cues for the horizontal plane comes at the expense of using those cues to localize in the vertical plane. PMID:25878278

  12. Joint inversion for transponder localization and sound-speed profile temporal variation in high-precision acoustic surveys.

    PubMed

    Li, Zhao; Dosso, Stan E; Sun, Dajun

    2016-07-01

    This letter develops a Bayesian inversion for localizing underwater acoustic transponders using a surface ship which compensates for sound-speed profile (SSP) temporal variation during the survey. The method is based on dividing observed acoustic travel-time data into time segments and including depth-independent SSP variations for each segment as additional unknown parameters to approximate the SSP temporal variation. SSP variations are estimated jointly with transponder locations, rather than calculated separately as in existing two-step inversions. Simulation and sea-trial results show this localization/SSP joint inversion performs better than two-step inversion in terms of localization accuracy, agreement with measured SSP variations, and computational efficiency. PMID:27475210

  13. Sound source localization on an axial fan at different operating points

    NASA Astrophysics Data System (ADS)

    Zenger, Florian J.; Herold, Gert; Becker, Stefan; Sarradj, Ennes

    2016-08-01

    A generic fan with unskewed fan blades is investigated using a microphone array method. The relative motion of the fan with respect to the stationary microphone array is compensated by interpolating the microphone data to a virtual rotating array with the same rotational speed as the fan. Hence, beamforming algorithms with deconvolution, in this case CLEAN-SC, could be applied. Sound maps and integrated spectra of sub-components are evaluated for five operating points. At selected frequency bands, the presented method yields sound maps featuring a clear circular source pattern corresponding to the nine fan blades. Depending on the adjusted operating point, sound sources are located on the leading or trailing edges of the fan blades. Integrated spectra show that in most cases leading edge noise is dominant for the low-frequency part and trailing edge noise for the high-frequency part. The shift from leading to trailing edge noise is strongly dependent on the operating point and frequency range considered.

  14. The distribution of basal water between Antarctic subglacial lakes from radar sounding.

    PubMed

    Young, D A; Schroeder, D M; Blankenship, D D; Kempf, Scott D; Quartini, E

    2016-01-28

    Antarctica's subglacial lakes have two end member geophysical expressions: as hydraulically flat, radar reflective regions highlighted in ice surface topography and radar sounding profiles ('definite lakes'), and as localized sites of elevation change identified from repeat elevation observations ('active lakes') that are often found in fast flowing ice streams or enhanced ice flow tributaries. While 'definite lakes' can be identified readily by high bed reflectivity in radar sounding, the identification and characterization of less distinct subglacial lakes and water systems with radar sounding are complicated by variable radio-wave attenuation in the overlying ice. When relying on repeat elevation observations, the relatively short times series and biased distribution of elevation observations, along with the episodic nature of 'active lake' outflow and replenishment, limit our understanding of how water flows under the ice sheet. Using recently developed methods for quantifying the radar scattering behaviour of the basal interface of the ice, we can avoid the problem of attenuation, and observe the plumbing of the subglacial landscape. In West Antarctica's Ross Sea Embayment, we confirm that extensive distributed water systems underlie these ice streams. Distributed water sheets are upstream in the onset regions of fast flow, while canal systems underly downstream regions of fast flow. In East Antarctica, we use specularity analysis to recover substantial hydraulic connectivity extending beyond previous knowledge, connecting the lakes already delineated by traditional radar sounding or surface elevation transients. PMID:26667910

  15. Relating large-scale climate variability to local species abundance: ENSO forcing and shrimp in Breton Sound, Louisiana, USA

    USGS Publications Warehouse

    Piazza, Bryan P.; LaPeyre, Megan K.; Keim, B.D.

    2010-01-01

    Climate creates environmental constraints (filters) that affect the abundance and distribution of species. In estuaries, these constraints often result from variability in water flow properties and environmental conditions (i.e. water flow, salinity, water temperature) and can have significant effects on the abundance and distribution of commercially important nekton species. We investigated links between large-scale climate variability and juvenile brown shrimp Farfantepenaeus aztecus abundance in Breton Sound estuary, Louisiana (USA). Our goals were to (1) determine if a teleconnection exists between local juvenile brown shrimp abundance and the El Niño Southern Oscillation (ENSO) and (2) relate that linkage to environmental constraints that may affect juvenile brown shrimp recruitment to, and survival in, the estuary. Our results identified a teleconnection between winter ENSO conditions and juvenile brown shrimp abundance in Breton Sound estuary the following spring. The physical connection results from the impact of ENSO on winter weather conditions in Breton Sound (air pressure, temperature, and precipitation). Juvenile brown shrimp abundance effects lagged ENSO by 3 mo: lower than average abundances of juvenile brown shrimp were caught in springs following winter El Niño events, and higher than average abundances of brown shrimp were caught in springs following La Niña winters. Salinity was the dominant ENSO-forced environmental filter for juvenile brown shrimp. Spring salinity was cumulatively forced by winter river discharge, winter wind forcing, and spring precipitation. Thus, predicting brown shrimp abundance requires incorporating climate variability into models.

  16. Effect of long-term training on sound localization performance with spectrally warped and band-limited head-related transfer functions.

    PubMed

    Majdak, Piotr; Walder, Thomas; Laback, Bernhard

    2013-09-01

    Sound localization in the sagittal planes, including the ability to distinguish front from back, relies on spectral features caused by the filtering effects of the head, pinna, and torso. It is assumed that important spatial cues are encoded in the frequency range between 4 and 16 kHz. In this study, in a double-blind design and using audio-visual training covering the full 3-D space, normal-hearing listeners were trained 2 h per day over three weeks to localize sounds which were either band limited up to 8.5 kHz or spectrally warped from the range between 2.8 and 16 kHz to the range between 2.8 and 8.5 kHz. The training effect for the warped condition exceeded that for procedural task learning, suggesting a stable auditory recalibration due to the training. After the training, performance with band-limited sounds was better than that with warped ones. The results show that training can improve sound localization in cases where spectral cues have been reduced by band-limiting or remapped by warping. This suggests that hearing-impaired listeners, who have limited access to high frequencies, might also improve their localization ability when provided with spectrally warped or band-limited sounds and adequately trained on sound localization. PMID:23967945

  17. The local--global analysis of the stimulated Brillouin scattering in the regime of nonlinear sound waves

    SciTech Connect

    Rozmus, W.; Casanova, M.; Pesme, D.; Heron, A.; Adam, J. )

    1992-03-01

    The effect of ion sound wave (ISW) nonlinearities on the stimulated Brillouin scattering (SBS) in long plasmas is investigated within the framework of the Korteweg--de Vries--Maxwell equations. The nonlinear evolution of the driven ISW results in the localization of the ion density on a scale shorter than the wavelength ({lambda}{sub {ital s}}) of the resonant ISW satisfying SBS three-wave matching conditions. Since the transverse wave amplitudes vary on a much longer scale, a local--global modeling of SBS is proposed in which this scale separation is exploited. The local part of the procedure includes a solution to the damped KdV equation with periodic boundary conditions and driven by a constant amplitude ponderomotive force. In the global part of the analysis approximate solutions for the transverse waves in long plasmas are constructed using the results from the local part. Particle-in-cell simulations have been performed in order to investigate the importance of kinetic effects for the local model. Numerical results obtained from the solutions to the KdV--Maxwell equations are well approximated by the local--global modeling. They are also compared with the results of a harmonic decomposition approximation.

  18. Parallel pathways mediating both sound localization and gaze control in the forebrain and midbrain of the barn owl.

    PubMed

    Knudsen, E I; Knudsen, P F; Masino, T

    1993-07-01

    The hypothesis that sound localization and gaze control are mediated in parallel in the midbrain and forebrain was tested in the barn owl. The midbrain pathway for gaze control was interrupted by reversible inactivation (muscimol injection) or lesion of the optic tectum. Auditory input to the forebrain was disrupted by reversible inactivation or lesion of the primary thalamic auditory nucleus, nucleus ovoidalis (homolog of the medial geniculate nucleus). Barn owls were trained to orient their gaze toward auditory or visual stimuli presented from random locations in a darkened sound chamber. Auditory and visual test stimuli were brief so that the stimulus was over before the orienting response was completed. The accuracy and kinetics of the orienting responses were measured with a search coil attached to the head. Unilateral inactivation of the optic tectum had immediate and long-lasting effects on auditory orienting behavior. The owls failed to respond on a high percentage of trials when the auditory test stimulus was located on the side contralateral to the inactivated tectum. When they did respond, the response was usually (but not always) short of the target, and the latency of the response was abnormally long. When the auditory stimulus was located on the side ipsilateral to the inactivated tectum, responses were reliable and accurate, and the latency of responses was shorter than normal. In a tectally lesioned animal, response probability and latency to contralateral sounds returned to normal within 2 weeks, but the increase in response error (due to undershooting) persisted for at least 12 weeks. Despite abnormalities in the response, all of the owls were capable of localizing and orienting to contralateral auditory stimuli on some trials with the optic tectum inactivated or lesioned. This was not true for contralateral visual stimuli. Immediately following tectal inactivation, the owls exhibited complete neglect for visual stimuli located more than 20

  19. Enhanced Soundings for Local Coupling Studies: 2015 ARM Climate Research Facility Field Campaign

    SciTech Connect

    Ferguson, CR; Santanello, JA; Gentine, P

    2015-11-01

    Matching observed diurnal cycles is a fundamental yet extremely complex test for models. High temporal resolution measurements of surface turbulent heat fluxes and boundary layer properties are required to evaluate the daytime evolution of the boundary layer and its sensitivity to land-atmosphere coupling. To address this need, (12) one-day intensive observing periods (IOP) with enhanced radiosonding will be carried out at the ARM Southern Great Plains (SGP) Central Facility (CF) during summer 2015. Each IOP will comprise a single launch to correspond with the nighttime overpass of the A-Train of satellites (~0830 UTC) and hourly launches during daytime beginning from 1130 UTC and ending at 2130 UTC. At 3-hourly intervals (i.e., 1140 UTC, 1440 UTC, 1740 UTC, and 2040 UTC) a duplicate second radiosonde will be launched 10 minutes subsequent to launch of the on-hour radiosonde for the purpose of assessing horizontal atmospheric variability. In summary, each IOP will have a 14-sounding supplement to the 6-hourly operational sounding schedule at the ARM-SGP CF. The IOP days will be decided before sunset on the preceding day, according to the judgment of the PI’s and taking into consideration daily weather forecasts and the operability of complimentary ARM-SGP CF instrumentation. An overarching goal of the project is to address how ARM could better observe land-atmosphere coupling to support the evaluation and refinement of coupled weather and climate models.

  20. Inverse problem with beamforming regularization matrix applied to sound source localization in closed wind-tunnel using microphone array

    NASA Astrophysics Data System (ADS)

    Padois, Thomas; Gauthier, Philippe-Aubert; Berry, Alain

    2014-12-01

    Microphone arrays have become a standard technique to localize and quantify source in aeroacoustics. The simplest approach is the beamforming that provides noise source maps with large main lobe and strong side lobes at low frequency. Since a decade, the focus is set on deconvolution techniques such as DAMAS or Clean-SC. While the source map is clearly improved, these methods require a large computation time. In this paper, we propose a sound source localization technique based on an inverse problem with beamforming regularization matrix called Hybrid Method. With synthetic data, we show that the side lobes are removed and the main lobe is narrower. Moreover, if the sound noise source map provided by this method is used as input in the DAMAS process, the number of DAMAS iterations is highly reduced. The Hybrid Method is applied to experimental data obtained in a closed wind-tunnel. In both cases of acoustic or aeroacoustic data, the source is correctly detected. The proposed Hybrid Method is found simple to implement and the computation time is low if the number of scan points is reasonable.

  1. Solar Wind Charge Exchange and Local Hot Bubble X-Ray Emission with the DXL Sounding Rocket Experiment

    NASA Technical Reports Server (NTRS)

    Galeazzi, M.; Collier, M. R.; Cravens, T.; Koutroumpa, D.; Kuntz, K. D.; Lepri, S.; McCammon, D.; Porter, F. S.; Prasai, K.; Robertson, I.; Snowden, S.; Thomas, N. E.; Uprety, Y.

    2012-01-01

    The Diffuse X-ray emission from the Local Galaxy (DXL) sounding rocket is a NASA approved mission with a scheduled first launch in December 2012. Its goal is to identify and separate the X-ray emission of the SWCX from that of the Local Hot Bubble (LHB) to improve our understanding of both. To separate the SWCX contribution from the LHB. DXL will use the SWCX signature due to the helium focusing cone at 1=185 deg, b=-18 deg, DXL uses large area propostionai counters, with an area of 1.000 sq cm and grasp of about 10 sq cm sr both in the 1/4 and 3/4 keY bands. Thanks to the large grasp, DXL will achieve in a 5 minule flight what cannot be achieved by current and future X-ray satellites.

  2. Geoethical approach to mineral activities in Antarctica

    NASA Astrophysics Data System (ADS)

    Talalay, Pavel

    2013-04-01

    severe not only permanent, local impact on the environment, but also will have implications for other Earth's systems as a whole. Mineral prospecting and exploration in Antarctica need to be reflected and respected in any concept of environmental sustainability. Anyway, first stage of the geological surveying should be carried purely scientific and not designed to explore for and identify mineral deposits. It's obvious that although various countries claim sovereignty in certain regions of Antarctica, the continent should be continued to be politically neutral. Efforts of scientists and politicians should respect their own responsibility for the protection of the fragile Antarctic environment and of our planet in the whole taking care for future generations.

  3. ECC (electrochemical concentration cell) ozonesonde observations at South Pole, Antarctica, during 1987. Data report

    SciTech Connect

    Komhyr, W.D.; Franchois, P.R.; Kuester, S.E.; Reitelback, P.J.; Fanning, M.L.

    1988-03-01

    Atmospheric ozone vertical distributions, air temperatures, and wind speed and wind direction data are presented for 76 balloon electrochemical concentration cell (ECC) ozonesonde soundings made at South Pole, Antarctica, in 1987.

  4. Bringing Antarctica Home

    ERIC Educational Resources Information Center

    Constible, Juanita; Williams, Lauren; Faure, Jaime; Lee, Richard E., Jr.

    2012-01-01

    When one thinks of the amazing creatures of Antarctica, an insect probably does not come to mind. But this unlikely animal, and a scientific expedition to Antarctica, was the foundation for a learning event that created a community of learners spanning kindergarten through sixth grade and extended beyond the classroom. Miami University's Antarctic…

  5. Estimation of seismic wave velocity at seafloor surface and sound source localization based on transmitted wave observation with an ocean bottom seismometer offshore of Kamaishi, Japan

    NASA Astrophysics Data System (ADS)

    Iwase, Ryoichi

    2016-07-01

    An in situ method of estimating the seismic wave velocity at the seafloor surface by observing the particle motion of a wave transmitted into the sediment is presented; this method uses a sound source whose location is known. Conversely, a sound source localization method using the obtained seismic velocities and involving particle motion observation is also presented. Although this method is applicable only when the sound source exists within the critical incidence angle range, it is expected to contribute to the tracing of vocalizing baleen whales, which are unknown around Japanese waters.

  6. Deconvolution for the localization of sound sources using a circular microphone array.

    PubMed

    Tiana-Roig, Elisabet; Jacobsen, Finn

    2013-09-01

    During the last decade, the aeroacoustic community has examined various methods based on deconvolution to improve the visualization of acoustic fields scanned with planar sparse arrays of microphones. These methods assume that the beamforming map in an observation plane can be approximated by a convolution of the distribution of the actual sources and the beamformer's point-spread function, defined as the beamformer's response to a point source. By deconvolving the resulting map, the resolution is improved, and the side-lobes effect is reduced or even eliminated compared to conventional beamforming. Even though these methods were originally designed for planar sparse arrays, in the present study, they are adapted to uniform circular arrays for mapping the sound over 360°. This geometry has the advantage that the beamforming output is practically independent of the focusing direction, meaning that the beamformer's point-spread function is shift-invariant. This makes it possible to apply computationally efficient deconvolution algorithms that consist of spectral procedures in the entire region of interest, such as the deconvolution approach for the mapping of the acoustic sources 2, the Fourier-based non-negative least squares, and the Richardson-Lucy. This investigation examines the matter with computer simulations and measurements. PMID:23967939

  7. 76 FR 30887 - Special Local Regulations for Marine Events, Bogue Sound; Morehead City, NC

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-27

    ... FR 3316). Public Meeting We do not now plan to hold a public meeting. But you may submit a request... proposes establishing of Special Local Regulations for ``The Crystal Coast Grand Prix'' powerboat race, to... 20-21, 2011 from 10 a.m. to 4 p.m. East Coast Extreme Corporation will sponsor ``The Crystal...

  8. An investigation of matching symmetry in the human pinnae with possible implications for 3D ear recognition and sound localization.

    PubMed

    Claes, Peter; Reijniers, Jonas; Shriver, Mark D; Snyders, Jonatan; Suetens, Paul; Nielandt, Joachim; De Tré, Guy; Vandermeulen, Dirk

    2015-01-01

    The human external ears, or pinnae, have an intriguing shape and, like most parts of the human external body, bilateral symmetry is observed between left and right. It is a well-known part of our auditory sensory system and mediates the spatial localization of incoming sounds in 3D from monaural cues due to its shape-specific filtering as well as binaural cues due to the paired bilateral locations of the left and right ears. Another less broadly appreciated aspect of the human pinna shape is its uniqueness from one individual to another, which is on the level of what is seen in fingerprints and facial features. This makes pinnae very useful in human identification, which is of great interest in biometrics and forensics. Anatomically, the type of symmetry observed is known as matching symmetry, with structures present as separate mirror copies on both sides of the body, and in this work we report the first such investigation of the human pinna in 3D. Within the framework of geometric morphometrics, we started by partitioning ear shape, represented in a spatially dense way, into patterns of symmetry and asymmetry, following a two-factor anova design. Matching symmetry was measured in all substructures of the pinna anatomy. However, substructures that 'stick out' such as the helix, tragus, and lobule also contained a fair degree of asymmetry. In contrast, substructures such as the conchae, antitragus, and antihelix expressed relatively stronger degrees of symmetric variation in relation to their levels of asymmetry. Insights gained from this study were injected into an accompanying identification setup exploiting matching symmetry where improved performance is demonstrated. Finally, possible implications of the results in the context of ear recognition as well as sound localization are discussed. PMID:25382291

  9. 77 FR 52604 - Special Local Regulations; Safety Zones; Recurring Events in Captain of the Port Long Island Sound

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-30

    ... of the Port Long Island Sound AGENCY: Coast Guard, DHS. ACTION: Notice of enforcement of regulation. SUMMARY: The Coast Guard will enforce two fireworks display safety zones in the Sector Long Island Sound... Port (COTP) Sector Long Island Sound or designated representative. DATES: The regulations in 33 CFR...

  10. Mineral resources of Antarctica

    SciTech Connect

    Rowley, P.D.; Williams, P.L.; Pride, D.E.

    1983-01-01

    Metallic and nonmetallic mineral occurrences are abundant in Antarctica. The most significant known deposits are of iron, copper, and coal. In the Precambrian shield of East Antarctica, for example, iron is present as banded iron-formation and as magnetite in veins, pods, and schist. The largest deposits of iron are in the Prince Charles Mountains, where bodies of banded iron-formation at least as thick as 400 m extend, mostly under the ice for at least 120 km. Widely scattered morainal boulders and outcrops of iron-rich rock suggest that undiscovered iron deposits are also distributed over many other parts of East Antarctica. Gondwana reconstructions suggest that many more mineral deposits occur in Antarctica. However, ice covers nearly 98 percent of the continent, and few of the bedrock areas have even been prospected or geologically, geophysically, or geochemically mapped in detail.

  11. Antarctica: up for grabs

    SciTech Connect

    Shapley, D.

    1982-11-01

    Antarctica is viewed as a special area, requiring meticulous diplomacy to develop international agreements for exploiting its resources. Little exploration has been accomplished, but oil, gas, and marine krill resources are protected by a 14-nation treaty dating from 1961. The treaty fixed national claims on specific territories and launched scientific activities that reflect national interests. Studies of meteorology, climatology, oceanography, upper-atmospheric physics, and territorial biology have revealed Antarctica's resource potential for krill, minerals, and even ice. 4 figures. (DCK)

  12. Further Investigations of Cosmogenic Ne-21 Exposure Ages of Glacial Boulders Constrained by Local Bedrock Erosion Rates in Ong Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Hedberg, C. P.; Morgan, D. J.; Cox, J.; Balco, G.; Putkonen, J.; Bibby, T.

    2014-12-01

    A history of glaciation can be tracked by determining the exposure age of boulders found in glacial drifts using the concentration of the cosmogenic nuclide Ne-21. In order to calculate exposure age, the erosion rate and previous exposure must be taken into consideration. In this study, we measured cosmogenic Ne-21 concentrations in quartz from samples of bedrock and samples taken from distinct glacial drifts in Antarctica. We determined the erosion rate using the concentrations of Ne-21 in the bedrock and then used this rate to calculate the exposure ages of the samples taken from the glacial drifts. The samples were collected from the Ong Valley, Antarctica (157.5 East, 83.25 South), an ice-free valley in the Miller Range of the Central Transantarctic Mountains that contains three distinct glacial drifts. We analyzed samples from the oldest and the youngest of these drifts, from moraines from a small alpine glacier to the east of the main valley, and from the surrounding bedrock of the valley walls above the glacial limit. The average erosion rate we calculated was 23 cm/Myrs. The six samples from the oldest glacial drift have an average exposure age of 2.1 Myrs, but have a range of 4.4 Myrs. The exposure age of samples from the middle of the youngest drift on the valley floor average 90.1 kyrs, with a range of 13.4 kyrs. Samples from a lateral moraine of this youngest drift have an average exposure age of 145 kyrs, with a range of 134 kyrs. The 7 samples taken from the alpine glacier east of Ong Valley have an average age of 1.10 Myrs, but a range of 3.87 Myrs. The high variability in ages among samples from the same glacial drift arises from prior exposure and postdepositional movement of the rocks.

  13. Living and Working in Antarctica.

    ERIC Educational Resources Information Center

    Kemp, Noel

    This source book, designed for 11- to 14-year-old students, seeks to describe what life is like in Antarctica. In spite of extreme weather conditions, people go to Antarctica to work every summer. Some of them stay there during the winter as well. This book seeks to supply answers to such questions as: How do people get to Antarctica? Why do they…

  14. 33 CFR 100.1308 - Special Local Regulation; Hydroplane Races within the Captain of the Port Puget Sound Area of...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... event in accordance with 33 CFR 100. The Captain of the Port will provide notice of the enforcement of...; Hydroplane Races within the Captain of the Port Puget Sound Area of Responsibility. 100.1308 Section 100.1308... Captain of the Port Puget Sound Area of Responsibility. (a) Location. The following areas are...

  15. 33 CFR 100.1308 - Special Local Regulation; Hydroplane Races within the Captain of the Port Puget Sound Area of...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... event in accordance with 33 CFR 100. The Captain of the Port will provide notice of the enforcement of...; Hydroplane Races within the Captain of the Port Puget Sound Area of Responsibility. 100.1308 Section 100.1308... Captain of the Port Puget Sound Area of Responsibility. (a) Location. The following areas are...

  16. 76 FR 17339 - Special Local Regulation; Hydroplane Races Within the Captain of the Port Puget Sound Area of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-29

    ... the Captain of the Port Puget Sound Area of Responsibility in the Federal Register (75 FR 2833). On... Captain of the Port Puget Sound Area of Responsibility AGENCY: Coast Guard, DHS. ACTION: Final rule... CFR part 100 in the Federal Register (76 FR 3057). We did not receive any comments on the NPRM...

  17. 76 FR 3057 - Special Local Regulation; Hydroplane Races Within the Captain of the Port Puget Sound Area of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-19

    ... Captain of the Port Puget Sound Area of Responsibility AGENCY: Coast Guard, DHS. ACTION: Supplemental... designated hydroplane race areas within the Captain of the Port, Puget Sound area of responsibility. When... Federal Register (73 FR 3316). Public Meeting We do not now plan to hold a public meeting. But you...

  18. Geographic names of Antarctica

    USGS Publications Warehouse

    U.S. Board on Geographic Names; Department of the Interior; Burrill, Meredith F.; Bertrand, Kenneth J.; Alberts, Fred G.

    1956-01-01

    The geographic nomenclature of Antarctica was long in need of an overall systematic treatment, objective in approach and based upon thorough examination of all the evidence. The results of such treatment over a period of about three years were presented in Geographical Names of Antarctica, Special Publication No. 86 of the Board on Geographical Names, in May 1947, two supplements to which were issued in 1949 and 1951. The continuing program since that publication has now covered most of the geographic naming in Antarctica. As research has filled in many of the previous gaps in knowledge, a number of names have been modified and minor amendments have been made in the policies. This revised publication brings together the greatly enlarged body of names officially standardized for use by the United States Government, together with new pertinent background information.

  19. Antarctica, why so Blue?

    NASA Astrophysics Data System (ADS)

    Reif, C.; Williams, Q.; Manners, U.

    2006-12-01

    Are all fast seismic anomalies at the core-mantle boundary (CMB) created alike? Much attention has been paid to the relative variations of seismic wave speeds in slow regions of the lowermost mantle, but there is a wealth of information in the fast anomalies as well. Here we systematically characterize fast regions at the CMB in terms of their shear, compressional, and bulk wave speed anomalies and Poisson's ratio using the largest long-period catalog to date of S, ScS, Sdiff, P, and Pdiff arrival times. The fastest regions at the CMB occur beneath Antarctica, Central America, and eastern Asia. The latter two have been active subduction zones for more than 200 Ma. However, Antarctica is an exception in that subduction has not occurred there in the last 100 Ma. And, during the final stages of subduction, young oceanic lithosphere may be positively buoyant compared to the mantle and not be likely to sink all the way to the CMB. Therefore, the youngest (and thus coldest) material beneath Antarctica near the CMB is around 130 Ma in age. It is puzzling why the region beneath Antarctica would have one of the fastest seismic signals since plate reconstructions indicate that for the last 200 Ma, the greatest volume of material has been subducted under the northern Pacific. However, outside of Antarctica, the strongest fast anomalies at the CMB are geographically coincident with the current pattern of subduction, not that of the distant past. It has been noted that the seismic anomalies at the CMB do not fit those predicted by past plate reconstructions, and this mismatch has been explained in terms of the presence of the thermal boundary layer. Here, we examine thermal and compositional effects that could be produced by the interaction of subducted material with a basal thermal boundary layer, and probe how strong fast anomalies can be produced in both unexpected (Antarctica) and expected regions (eastern Asia), while fast anomalies anticipated elsewhere (northern Pacific

  20. Abdominal sounds

    MedlinePlus

    ... sounds by listening to the abdomen with a stethoscope ( auscultation ). Most bowel sounds are normal. However, there ... sounds can sometimes be heard even without a stethoscope. Hyperactive bowel sounds mean there is an increase ...

  1. Comparison between bilateral cochlear implants and Neurelec Digisonic(®) SP Binaural cochlear implant: speech perception, sound localization and patient self-assessment.

    PubMed

    Bonnard, Damien; Lautissier, Sylvie; Bosset-Audoit, Amélie; Coriat, Géraldine; Beraha, Max; Maunoury, Antoine; Martel, Jacques; Darrouzet, Vincent; Bébéar, Jean-Pierre; Dauman, René

    2013-01-01

    An alternative to bilateral cochlear implantation is offered by the Neurelec Digisonic(®) SP Binaural cochlear implant, which allows stimulation of both cochleae within a single device. The purpose of this prospective study was to compare a group of Neurelec Digisonic(®) SP Binaural implant users (denoted BINAURAL group, n = 7) with a group of bilateral adult cochlear implant users (denoted BILATERAL group, n = 6) in terms of speech perception, sound localization, and self-assessment of health status and hearing disability. Speech perception was assessed using word recognition at 60 dB SPL in quiet and in a 'cocktail party' noise delivered through five loudspeakers in the hemi-sound field facing the patient (signal-to-noise ratio = +10 dB). The sound localization task was to determine the source of a sound stimulus among five speakers positioned between -90° and +90° from midline. Change in health status was assessed using the Glasgow Benefit Inventory and hearing disability was evaluated with the Abbreviated Profile of Hearing Aid Benefit. Speech perception was not statistically different between the two groups, even though there was a trend in favor of the BINAURAL group (mean percent word recognition in the BINAURAL and BILATERAL groups: 70 vs. 56.7% in quiet, 55.7 vs. 43.3% in noise). There was also no significant difference with regard to performance in sound localization and self-assessment of health status and hearing disability. On the basis of the BINAURAL group's performance in hearing tasks involving the detection of interaural differences, implantation with the Neurelec Digisonic(®) SP Binaural implant may be considered to restore effective binaural hearing. Based on these first comparative results, this device seems to provide benefits similar to those of traditional bilateral cochlear implantation, with a new approach to stimulate both auditory nerves. PMID:23548561

  2. Antarctica: Discovery & Exploration.

    ERIC Educational Resources Information Center

    Gascoigne, Toss; Collett, Peter

    An examination of Antarctica, from the first sightings to the heroic explorations of the late 18th and early 19th centuries to modern-day research, is presented in this book. Twelve chapters are as follows: (1) The search begins; (2) Whalers and sealers: bites and nibbles; (3) The new continent: first sight; (4) Wintering: the first party; (5)…

  3. Getting Antarctica down Cold!

    ERIC Educational Resources Information Center

    Sandmeier, Kay; Greeson, Linda

    1990-01-01

    Outlines learning activities for applying geography's five fundamental themes to studying Antarctica and points out the learning potential, for studying the economic, historical, and political geography of the continent. Groups activities for grades K-5, 6-8, and 8-12. Stresses cooperative learning in general, and includes a role play activity for…

  4. Married to Antarctica.

    ERIC Educational Resources Information Center

    Monastersky, Richard

    1991-01-01

    A novel theory about Earth's ancient history is presented. It is proposed that North America and Antarctica once lay side by side for perhaps as long as a billion years. The importance of these continental connections to geology and other disciplines is discussed. (KR)

  5. Complex Wind-Induced Variations of Surface Snow Accumulation Rates over East Antarctica

    NASA Astrophysics Data System (ADS)

    Das, I.; Scambos, T. A.; Koenig, L.; van den Broeke, M.; Lenaerts, J.

    2015-12-01

    Accurate quantification of surface snow-accumulation over Antarctica is important for mass balance estimates and climate studies based on ice core records. Using airborne radar, lidar and thresholds of surface slope, modeled surface mass balance (SMB) and wind fields, we have predicted continent-wide distribution of wind-scour zones over Antarctica. These zones are located over relatively steep ice surfaces formed by ice flow over bedrock topography. Near-surface winds accelerate over these steeper slopes and erode and sublimate the snow. This results in numerous localized regions (typically ≤ 200 km2) with reduced or negative surface accumulation. Although small zones of re-deposition occur at the base of the steeper slope areas, the redeposited mass is small relative to the ablation loss. Total losses from wind-scour and wind-glaze areas amounts to tens of gigatons annually. Near the coast, winds often blow significant amounts of surface snow from these zones into the ocean. Large uncertainties remain in SMB estimates over East Antarctica as climate models do not adequately represent the small-scale physical processes that lead to mass loss or redistribution over the wind-scour zones. In this study, we also use Operation IceBridge's snow radar data to provide evidence for a gradual ablation of ~16-18 m of firn (~200 years of accumulation) from wind-scour zones over the upper Recovery Ice Stream catchment. The maximum ablation rates observed in this region are ~ -54 kg m-2 a-1 (-54 mm water equivalent a-1). Our airborne radio echo-sounding analysis show snow redeposition downslope of the wind-scour zones is <10% of the cumulative mass loss. Our study shows that the local mass loss is dominated by sublimation to water vapor rather than wind-transport of snow.

  6. Antarctica and Its Ice Sheet: Knowledge Gained During the IGY/IGC

    NASA Astrophysics Data System (ADS)

    Bentley, C. R.

    2006-12-01

    At the end of World War II, the interior of Antarctica, with the exception of the mountains south of the Ross Ice Shelf, was still terra incognita. It was described simply as a nearly continuous high plateau. Even less was known about the ice thickness; the eminent glacial geologist, Richard Foster Flint, believed it "unlikely that the ice thickness exceeds 2000 feet except very locally; probably its average thickness is considerably less." Then in the late 1940's and early 1950's, seismic sounding in Greenland by the Expéditions Polaires Françaises and in Queen Maud Land by the Norwegian-British-Swedish Antarctic Expedition, 1949-52, revealed that, inland of the coastal mountains, the beds in both regions lie close to sea level. This led to a reappraisal of the Antarctic ice sheet, such that the prescient glaciologist, Robert P. Sharp, could predict, on the eve of the IGY, that "between 3000 and 4000 meters of ice will be found" in East Antarctica and that "work during IGY will establish an average thickness for Antarctic inland ice in excess of 1600 m." Seismic and gravity soundings on oversnow traverses conducted by eight countries during the IGY and the succeeding IGC showed Sharp to be basically correct, but there were major surprises, such as the vast Gamburtsev Subglacial Mountains, completely hidden by the ice in central East Antarctica, and the equally vast Byrd Subglacial Basin beneath much of the West Antarctic ice sheet, so deep that roughly half the ice in the region lies below sea level. There were major discoveries on and above the surface too, such as the huge size of the Filchner/Ronne Ice Shelf, and the very existence of the Ellsworth and Pensacola Mountains, the former including the highest peak on the continent. Further, the fundamental difference between the crustal structures of East and West Antarctica became clear. A summary paper published in 1960, looking primarily at West Antarctica where the main U.S. activity lay, could conclude that

  7. DXL: A Sounding Rocket Mission for the Study of Solar Wind Charge Exchange and Local Hot Bubble X-Ray Emission

    NASA Technical Reports Server (NTRS)

    Galeazzi, M.; Prasai, K.; Uprety, Y.; Chiao, M.; Collier, M. R.; Koutroumpa, D.; Porter, F. S.; Snowden, S.; Cravens, T.; Robertson, I.; Kuntz, K. D.; Lepri, S.; McCammon, D.

    2011-01-01

    The Diffuse X-rays from the Local galaxy (DXL) mission is an approved sounding rocket project with a first launch scheduled around December 2012. Its goal is to identify and separate the X-ray emission generated by solar wind charge exchange from that of the local hot bubble to improve our understanding of both. With 1,000 square centimeters proportional counters and grasp of about 10 square centimeters sr both in the 1/4 and 3/4 keV bands, DXL will achieve in a 5-minute flight what cannot be achieved by current and future X-ray satellites.

  8. Extreme wind-ice interaction over Recovery Ice Stream, East Antarctica

    NASA Astrophysics Data System (ADS)

    Das, Indrani; Scambos, Ted A.; Koenig, Lora S.; Broeke, Michiel R.; Lenaerts, Jan T. M.

    2015-10-01

    Surface snow accumulation over East Antarctica is an important climate indicator but a difficult parameter to constrain. Surface mass ablation dominates over persistent wind-scour zones as near-surface katabatic winds accelerate over locally steeper ice surface topography, and sublimate and redistribute snow. Here we quantify ablation rates and downwind redeposition of snow over wind-scour zones in the upper Recovery Ice Stream catchment. Airborne radio echo-soundings show a gradual ablation of ~16-18 m of firn, corresponding to ~200 years of accumulation, over these zones and ablation rates of ~54 kg m-2 a-1 (54 mm water equivalent a-1). We conclude that mass loss is dominated by sublimation and mass is transported downwind as water vapor, because snow redeposition downslope of the wind-scour zones constitutes only a small fraction (<10%) of the cumulative mass loss.

  9. Experimental localization of an acoustic sound source in a wind-tunnel flow by using a numerical time-reversal technique.

    PubMed

    Padois, Thomas; Prax, Christian; Valeau, Vincent; Marx, David

    2012-10-01

    The possibility of using the time-reversal technique to localize acoustic sources in a wind-tunnel flow is investigated. While the technique is widespread, it has scarcely been used in aeroacoustics up to now. The proposed method consists of two steps: in a first experimental step, the acoustic pressure fluctuations are recorded over a linear array of microphones; in a second numerical step, the experimental data are time-reversed and used as input data for a numerical code solving the linearized Euler equations. The simulation achieves the back-propagation of the waves from the array to the source and takes into account the effect of the mean flow on sound propagation. The ability of the method to localize a sound source in a typical wind-tunnel flow is first demonstrated using simulated data. A generic experiment is then set up in an anechoic wind tunnel to validate the proposed method with a flow at Mach number 0.11. Monopolar sources are first considered that are either monochromatic or have a narrow or wide-band frequency content. The source position estimation is well-achieved with an error inferior to the wavelength. An application to a dipolar sound source shows that this type of source is also very satisfactorily characterized. PMID:23039435

  10. Ozone Hole Over Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    These images from the Total Ozone Mapping Spectrometer (TOMS) show the progressive depletion of ozone over Antarctica from 1979 to 1999. This 'ozone hole' has extended to cover an area as large as 10.5 million square miles in September 1998. The previous record of 10.0 million square miles was set in 1996. The Antarctic ozone hole develops each year between late August and early October. Regions with higher levels of ozone are shown in red. NASA and NOAA instruments have been measuring Antarctic ozone levels since the early 1970s. Large regions of depleted ozone began to develop over Antarctica in the early 1980s. Ozone holes of substantial size and depth are likely to continue to form during the next few years, scientists hope to see a reduction in ozone loss as levels of ozone-destroying CFCs (chlorofluorocarbons) are gradually reduced. Credit: Images by Greg Shirah, NASA Goddard Space Flight Center Scientific Visualization Studio

  11. Earth - Antarctica Mosaic

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This color picture of the limb of the Earth, looking north past Antarctica, is a mosaic of 11 images taken during a ten-minute period near 5:45 p.m. PST Dec. 8, 1990, by Galileo's imaging system. Red, green and violet filters were used. The picture spans about 1,600 miles across the south polar latitudes of our planet. The morning day/night terminator is toward the right. The South Pole is out of sight below the picture; the visible areas of Antarctica are those lying generally south of South America. The violet-blue envelope of Earth's atmosphere is prominent along the limb to the left. At lower left, the dark blue Amundsen Sea lies to the left of the Walgreen and Bakutis Coasts. Beyond it, Peter Island reacts with the winds to produce a striking pattern of atmospheric waves.

  12. Breath sounds

    MedlinePlus

    The lung sounds are best heard with a stethoscope. This is called auscultation. Normal lung sounds occur ... the bottom of the rib cage. Using a stethoscope, the doctor may hear normal breathing sounds, decreased ...

  13. Tectonic structure of East Antarctica

    NASA Astrophysics Data System (ADS)

    Leychenkov, German; Grikurov, Garrik; Golynsky, Alexander

    2013-04-01

    First overviews of tectonic structure of the Southern Continent were made by the pioneers of Antarctic earth science investigations almost 100 years ago. Despite rapidly advancing international geological studies under the Antarctic Treaty, the presentations of Antarctic tectonic structure remained largely speculative until the end of the past century when implementation of modern analytical and remote-sensing research technologies enabled compilation of more credible tectonic models of Antarctica. The East Antarctic bedrock consists mainly of the Precambrian crystalline complexes and the Paleozoic-Early Mesozoic platform units. Crystalline Shield is locally complicated by Neoproterozoic aulacogenes and Late Paleozoic to Mesozoic rifts. Shield assemblages reliably recognized in coastal outcrops indicate the predominant occurrence of Archean cratonic nuclei and Mesoproterozoic mobile belts. The undisturbed platform cover strata are exposed in East Antarctica mainly along its boundary with West Antarctica. Tectonic structure of ice-covered regions (more that 99% of the East Antarctic territory) is interpreted using mostly magnetic and bedrock topography data, but other geophysical and geological information (satellite, airborne and over-ice gravity; seismology; active seismics; erratics; detrital zircons dates; etc.) is also important. Archean cratons are geologically documented in western Dronning Maud Land, Enderby Land, Princess Elizabeth Land and in the southern Prince Charles Mts. Their distribution under the ice is marked by a specific magnetic pattern including low-amplitude mosaic and/or high-amplitude long-wavelength anomalies. The most extensive ancient craton being 1000 km across is believed to extend from the southern Prince Charles Mts. to the Gamburtsev Mts. Mesoproterozoic mobile belts are distinguished by elongated high-amplitude magnetic anomalies and are mapped along the costal area as the zone of 250-600 km wide. The Gamburtsev Mts. area is also

  14. Princess Astrid Coast, Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The continent of Antarctica is almost completely covered by a thick blanket of ice, punctuated only by steep mountain peaks and a handful of dry valleys. Antarctica is also ringed by a permanent ice shelf, and that is surrounded by seasonal sea ice. The image above, acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS) on September 26, 2001, shows many of the types of ice found in Antarctica. At the bottom of the image is the ice of the continental glacier, which is up to 4,000 meters thick in the interior. These thick glaciers are held in place by coastal mountain ranges. Some ice does flow through the mountains, spilling onto the relatively flat land of the Princess Astrid Coast. Cold air also spills over the mountains, creating very strong and persistent 'katabatic' winds. These scour the snow off the tops of the glaciers, leaving pale blue patches of bare ice. Above the coastline is the ice shelf, which is much smoother. There, glacial ice actually floats on the sea surface. Beyond that is the chaotic surface of the sea ice, which has been solidifying all winter long. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  15. Calibrating the cosmic distance scale ladder: the role of the sound-horizon scale and the local expansion rate as distance anchors

    NASA Astrophysics Data System (ADS)

    Cuesta, Antonio J.; Verde, Licia; Riess, Adam; Jimenez, Raul

    2015-04-01

    We exploit cosmological model-independent measurements of the expansion history of the Universe to provide a cosmic distance ladder. These are supernovae Type Ia used as standard candles (at redshift between 0.01 and 1.3) and baryon acoustic oscillations (at redshifts between 0.1 and 0.8) as standard rulers. We calibrate (anchor) the ladder in two ways: first using the local H0 value as an anchor at z = 0 (effectively calibrating the standard candles) and secondly using the cosmic microwave background-inferred sound-horizon scale as an anchor (giving the standard ruler length) as an inverse distance ladder. Both methods are consistent, but the uncertainty in the expansion history H(z) is smaller if the sound-horizon scale is used. We present inferred values for the sound horizon at radiation drag rd which do not rely on assumptions about the early expansion history nor on cosmic microwave background measurements but on the cosmic distance ladder and baryon acoustic oscillations measurements. We also present derived values of H0 from the inverse distance ladder and we show that they are in very good agreement with the extrapolated value in a Λ cold dark matter model from Planck cosmic microwave background data.

  16. Sound Symbolism.

    ERIC Educational Resources Information Center

    Hinton, Leanne, Ed.; And Others

    Sound symbolism is the study of the relationship between the sound of an utterance and its meaning. In this interdisciplinary collection of new studies, 24 leading scholars discuss the role of sound symbolism in a theory of language. Contributions and authors include the following: "Sound-Symbolic Processes" (Leanne Hinton, Johanna Nichols, John…

  17. Informal STEM Education in Antarctica

    NASA Astrophysics Data System (ADS)

    Chell, K.

    2010-12-01

    Tourism in Antarctica has increased dramatically with tens of thousands of tourists visiting the White Continent each year. Tourism cruises to Antarctica offer a unique educational experience for lay people through informal science-technology-engineering-mathematics (STEM) education. Passengers attend numerous scientific lectures that cover topics such as the geology of Antarctica, plate tectonics, glaciology, and climate change. Furthermore, tourists experience the geology and glaciology first hand during shore excursions. Currently, the grand challenges facing our global society are closely connected to the Earth sciences. Issues such as energy, climate change, water security, and natural hazards, are consistently on the legislative docket of policymakers around the world. However, the majority of the world’s population is uninformed about the role Earth sciences play in their everyday lives. Tourism in Antarctica provides opportunities for informal STEM learning and, as a result, tourists leave with a better understanding and greater appreciation for both Antarctica and Earth sciences.

  18. How isolated is Antarctica?

    PubMed

    Clarke, Andrew; Barnes, David K A; Hodgson, Dominic A

    2005-01-01

    The traditional view of Antarctica and the surrounding Southern Ocean as an isolated system is now being challenged by the recent discovery at the Antarctic Peninsula of adult spider crabs Hyas areneus from the North Atlantic and of larvae of subpolar marine invertebrates. These observations question whether the well described biogeographical similarities between the benthic fauna of the Antarctic Peninsula and the Magellan region of South America result from history (the two regions were once contiguous), or from a previously unrecognized low level of faunal exchange. Such exchange might be influenced by regional climate change, and also exacerbated by changes in human impact. PMID:16701330

  19. Antarctica Day: An International Celebration

    NASA Astrophysics Data System (ADS)

    Pope, A.; Hambrook Berkman, J.; Berkman, P. A.

    2013-12-01

    For more than half a century, the 1959 Antarctic Treaty continues to shine as a rare beacon of international cooperation. To celebrate this milestone of peace in our civilization with hope and inspiration for future generations, Antarctica Day is celebrated each year on December 1st , the anniversary of the Antarctic Treaty signing. As an annual event - initiated by the Foundation for the Good Governance of International Spaces (www.internationalspaces.org/) in collaboration with the Association of Polar Early Carer Scientists (www.apecs.is) - Antarctica Day encourages participation from around the world. The Antarctic Treaty set aside 10% of the earth, 'forever to be used exclusively for peaceful purposes in the interest of mankind.' It was the first nuclear arms agreement and the first institution to govern all human activities in an international region beyond sovereign jurisdictions. In this spirit, Antarctica Day aims to: - Demonstrate how diverse nations can work together peacefully, using science as a global language of cooperation for decision making beyond national boundaries, - Provide strategies for students learning about Antarctica through art, science and history at all school levels, - Increase collaboration and communication between classrooms, communities, researchers and government officials around the world, and - Provide a focus for polar educators to build on each year. Through close collaboration with a number of partners. Antarctica Day activities have included: a Polar Film Festival convened by The Explorers Club; live sessions connecting classrooms with scientists in Antarctica thanks to PolarTREC and ARCUS; an international activity that involved children from 13 countries who created over 600 flags which exemplify Antarctica Day (these were actually flown in Antarctica with signed certificates then returned to the classes); a map where Antarctica Day participants all over the world could share what they were doing; an Antarctic bird count

  20. Sequence stratigraphy of the ANDRILL Southern McMurdo Sound (SMS) project drillcore, Antarctica: an expanded, near-field record of Antarctic Early to Middle Miocene climate and relative sea-level change

    NASA Astrophysics Data System (ADS)

    Fielding, C. R.; Browne, G. H.; Field, B.; Florindo, F.; Harwood, D. M.; Krissek, L. A.; Levy, R. H.; Panter, K.; Passchier, S.; Pekar, S. F.; SMS Science Team

    2008-12-01

    Present understanding of Antarctic climate change during the Early to Middle Miocene, including definition of major cycles of glacial expansion and contraction, relies in large part on stable isotope proxy records from Ocean Drilling Program cores. Here, we present a sequence stratigraphic analysis of the Southern McMurdo Sound drillcore (AND-2A), which was acquired during the Austral Spring of 2007. This core offers a hitherto unavailable ice-proximal stratigraphic archive of the Early to Middle Miocene from a high-accommodation Antarctic continental margin setting, and provides clear evidence of repeated fluctuations in climate, ice expansion/contraction and attendant sea-level change over the period 20-14 Ma, with a more fragmentary record of the post-14 Ma period. A succession of seventy sequences is recognized, each bounded by a significant facies dislocation (sequence boundary), composed internally of deposits of glacimarine to open shallow marine environments, and each typically dominated by the transgressive systems tract. From changes in facies abundances and sequence character, a series of long-term (m.y.) changes in climate and relative sea-level is identified. The lithostratigraphy can be correlated confidently to glacial events Mi1b and Mi2, to the Miocene Climatic Optimum, and to the global eustatic sea-level curve. SMS provides a detailed, direct, ice-proximal reference point from which to evaluate stable isotope proxy records for Neogene Antarctic paleoclimate.

  1. 40Ar-39Ar dating of volcanogenic products from the AND-2A core (ANDRILL Southern McMurdo Sound Project, Antarctica): correlations with the Erebus Volcanic Province and implications for the age model of the core

    NASA Astrophysics Data System (ADS)

    di Vincenzo, Gianfranco; Bracciali, Laura; Del Carlo, Paola; Panter, Kurt; Rocchi, Sergio

    2010-05-01

    The AND-2A drillcore (Antarctic Drilling Program—ANDRILL) was successfully completed in late 2007 on the Antarctic continental margin (Southern McMurdo Sound, Ross Sea) with the aim of tracking ice proximal to shallow marine environmental fluctuations and to document the 20-Ma evolution of the Erebus Volcanic Province. Lava clasts and tephra layers from the AND-2A drillcore were investigated from a petrographic and stratigraphic point of view and analyzed by the 40Ar-39Ar laser technique in order to constrain the age model of the core and to gain information on the style and nature of sediment deposition in the Victoria Land Basin since Early Miocene. Ten out of 17 samples yielded statistically robust 40Ar-39Ar ages, indicating that the AND-2A drillcore recovered ≤230 m of Middle Miocene (˜128-358 m below sea floor, ˜11.5-16.0 Ma) and >780 m of Early Miocene (˜358-1093 m below sea floor, ˜16.0-20.1 Ma). Results also highlight a nearly continuous stratigraphic record from at least 358 m below sea floor down hole, characterized by a mean sedimentation rate of ˜19 cm/ka, possible oscillations of no more than a few hundreds of ka and a break within ˜17.5-18.1 Ma. Comparison with available data from volcanic deposits on land, suggests that volcanic rocks within the AND-2A core were supplied from the south, possibly with source areas closer to the drill site for the upper core levels, and from 358 m below sea floor down hole, with the “proto-Mount Morning” as the main source.

  2. Development of a precise and accurate age-depth model based on 40Ar/39Ar dating of volcanic material in the ANDRILL (1B) drill core, Southern McMurdo Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Ross, J. I.; McIntosh, W. C.; Dunbar, N. W.

    2012-10-01

    High precision 40Ar/39Ar dates on a variety of volcanic materials from the AND-1B drill core provide pinning points for defining the chronostratigraphy for the core. The volcanic materials dated include 1) felsic and basaltic tephra, 2) interior of a ~ 3 m thick intermediate submarine lava flow, and 3) felsic and basaltic volcanic clasts. In the upper 600 m of the core, two felsic tephra, two basaltic tephra and the intermediate laval flow yield precise and depositional ages, with further maximum age constraints from volcanic clasts. Below 600 m in the core, tephric intervals are significantly altered and maximum age constraints only are available from volcanic clasts. The ages for eight stratigraphic intervals are 1) 17.17-17.18 mbsf, basaltic clast (maximum depositional age 0.310 ± 0.039 Ma, all errors quoted at 2σ), 2) 52.80-52.82 mbsf, three basaltic clasts (maximum depositional age 0.726 ± 0.052 Ma), 3) 85.27-85.87 mbsf felsic tephra (1.014 ± 0.008 Ma), 4) ~ 112-145 mbsf sequence of basaltic tephra (1.633 ± 0.057 to 1.683 ± 0.055 Ma), 5) 480.97-481.96 mbsf pumice-rich mudstone (4.800 ± 0.076 Ma), 6) 646.30-649.34 mbsf intermediate lava flow (6.48 ± 0.13 Ma), 7) 822.78 mbsf kaersutite phenocrysts from volcanic clasts (maximum depositional age 8.53 ± 0.53 Ma) and 8) ~ 1280 mbsf, three volcanic clasts (maximum depositional age 13.57 ± 0.13 Ma). Minimum average sediment accumulation rates or 102 and 87 m/Ma for the upper and lower 650 m of core, respectively were calculated using the 40Ar/39Ar analyses. The volcanic material recovered from AND-1B also reveals a general northward progression of volcanism in Southern McMurdo Sound.

  3. Abdominal sounds

    MedlinePlus

    ... during sleep. They also occur normally for a short time after the use of certain medicines and after abdominal surgery. Decreased or absent bowel sounds often indicate constipation. Increased ( hyperactive ) bowel sounds ...

  4. Airborne laser scanning for high-resolution mapping of Antarctica

    NASA Astrophysics Data System (ADS)

    Csatho, Bea; Schenk, Toni; Krabill, William; Wilson, Terry; Lyons, William; McKenzie, Garry; Hallam, Cheryl; Manizade, Serdar; Paulsen, Timothy

    In order to evaluate the potential of airborne laser scanning for topographic mapping in Antarctica and to establish calibration/validation sites for NASA's Ice, Cloud and land Elevation Satellite (ICESat) altimeter mission, NASA, the U.S. National Science Foundation (NSF), and the U.S. Geological Survey (USGS) joined forces to collect high-resolution airborne laser scanning data.In a two-week campaign during the 2001-2002 austral summer, NASA's Airborne Topographic Mapper (ATM) system was used to collect data over several sites in the McMurdo Sound area of Antarctica (Figure 1a). From the recorded signals, NASA computed laser points and The Ohio State University (OSU) completed the elaborate computation/verification of high-resolution Digital Elevation Models (DEMs) in 2003. This article reports about the DEM generation and some exemplary results from scientists using the geomorphologic information from the DEMs during the 2003-2004 field season.

  5. Auditory cortical and hippocampal local-field potentials to frequency deviant tones in urethane-anesthetized rats: An unexpected role of the sound frequencies themselves.

    PubMed

    Ruusuvirta, Timo; Lipponen, Arto; Pellinen, Eeva-Kaarina; Penttonen, Markku; Astikainen, Piia

    2015-06-01

    The human brain can automatically detect auditory changes, as indexed by the mismatch negativity of event-related potentials. The mechanisms that underlie this response are poorly understood. We recorded primary auditory cortical and hippocampal (dentate gyrus, CA1) local-field potentials to serial tones in urethane-anesthetized rats. In an oddball condition, a rare (deviant) tone (p=0.11) randomly replaced a repeated (standard) tone. The deviant tone was either lower (2200, 2700, 3200, 3700Hz) or higher (4300, 4800, 5300, 5800Hz) in frequency than the standard tone (4000Hz). In an equiprobability control condition, all nine tones were presented at random (p=0.11). Differential responses to deviant tones relative to the standard tone were found in the auditory cortex and the dentate gyrus but not in CA1. Only in the dentate gyrus, the responses were found to be standard- (i.e., oddball condition-) specific. In the auditory cortex, the sound frequencies themselves sufficed to explain their generation. These findings tentatively suggest dissociation among non-contextual afferent, contextual afferent and auditory change detection processes. Most importantly, they remind us about the importance of strict control of physical sound features in mismatch negativity studies in animals. PMID:25911953

  6. Characteristic sounds facilitate visual search.

    PubMed

    Iordanescu, Lucica; Guzman-Martinez, Emmanuel; Grabowecky, Marcia; Suzuki, Satoru

    2008-06-01

    In a natural environment, objects that we look for often make characteristic sounds. A hiding cat may meow, or the keys in the cluttered drawer may jingle when moved. Using a visual search paradigm, we demonstrated that characteristic sounds facilitated visual localization of objects, even when the sounds carried no location information. For example, finding a cat was faster when participants heard a meow sound. In contrast, sounds had no effect when participants searched for names rather than pictures of objects. For example, hearing "meow" did not facilitate localization of the word cat. These results suggest that characteristic sounds cross-modally enhance visual (rather than conceptual) processing of the corresponding objects. Our behavioral demonstration of object-based cross-modal enhancement complements the extensive literature on space-based cross-modal interactions. When looking for your keys next time, you might want to play jingling sounds. PMID:18567253

  7. The model of the Uzon-Geizernaya volcano-tectonic depression and Kikhpinych volcano, Kamchatka, from the joint analysis of microseismic sounding data and local geodynamic activity

    NASA Astrophysics Data System (ADS)

    Kugaenko, Yu. A.; Saltykov, V. A.; Gorbatikov, A. V.; Stepanova, M. Yu.

    2015-05-01

    The model of the magmatic system beneath the Uzon-Geizernaya volcano-tectonic depression and adjacent Kikhpinych volcano in Kamchatka is constructed to a depth of 30 km based on the microseismic sounding data. For doing this, measurements of the natural microseismic field by the Guralp CMG-6TD portable broadband seismometer were carried out at 60 points along three profiles with a total length of about 28 km. The revealed structural heterogeneities were interpreted in the common context with the previous geological, geological-morphological, and petrological results. The area of a shallow crystallized magmatic reservoir is identified and spatially localized below the depression. The zones of the presumed concentration of the basaltic melts probably responsible for the local geodynamic activation of the region during the past 15 years are revealed as the peripheral magmatic chamber of the Kikhpinych volcano at a depth of 5-12 km and a deeper (15-20 km) magma storage. The geometry of the identified deep structures is consistent with the local microseismicity and the model of the contemporary magmatic intrusion into the upper crustal layers, which is based on the data of satellite interferometry.

  8. Adaptive adjustment of unit tuning to sound localization cues in response to monaural occlusion in developing owl optic tectum.

    PubMed

    Mogdans, J; Knudsen, E I

    1992-09-01

    Bimodal units in the barn owl's optic tectum are tuned to the location of auditory and visual stimuli, and are systematically organized according to their spatial tuning to form mutually aligned maps of auditory and visual space. Map alignment results from the fact that, normally, units are tuned to the values of interaural level difference (ILD) and interaural time difference (ITD) produced by a sound source at the location of their visual receptive fields (VRFs). Monaural occlusion alters the correspondence of ILD and ITD values with locations in space. We investigated the effect that raising owls with a chronic monaural occlusion has on the tuning of tectal units to ILD and ITD. Owls were monaurally occluded beginning at 1 month of age. The effects of monaural occlusion were assessed 2-4 months later by comparing the ILD and ITD tuning of units in monaurally occluded owls with the ILD and ITD tuning of units with equivalent VRFs in normal owls. ILD and ITD tuning was shifted substantially and in the direction of the unoccluded ear (the adaptive direction) in owls raised with a monaural occlusion. In most tecta, the mapped representations of ILD and ITD were shifted systematically. In addition, in some tecta, monaural occlusion induced a change in the topography of the ILD map such that ILD tuning remained essentially constant at values near 0 dB over abnormally large portions of the tectum. Across all recording sites, the average shift in ILD tuning was 9 dB (n = 396) and the average shift in ITD tuning was 40 microseconds (n = 414). In four of five animals, the magnitude of the effect was not equivalent on the two sides of the brain, the adjustments being significantly larger and more systematic on the side ipsilateral to the occlusion. Such differences in the altered ILD and ITD maps on the two sides of the brain in individual animals indicate that, although a component of the adaptive adjustment might be due to regulation of the gain and phase response of the

  9. Sound Absorbers

    NASA Astrophysics Data System (ADS)

    Fuchs, H. V.; Möser, M.

    Sound absorption indicates the transformation of sound energy into heat. It is, for instance, employed to design the acoustics in rooms. The noise emitted by machinery and plants shall be reduced before arriving at a workplace; auditoria such as lecture rooms or concert halls require a certain reverberation time. Such design goals are realised by installing absorbing components at the walls with well-defined absorption characteristics, which are adjusted for corresponding demands. Sound absorbers also play an important role in acoustic capsules, ducts and screens to avoid sound immission from noise intensive environments into the neighbourhood.

  10. An emission inventory of sulfur from anthropogenic sources in Antarctica

    NASA Astrophysics Data System (ADS)

    Shirsat, S. V.; Graf, H. F.

    2009-05-01

    This paper presents first results of a comprehensive emission inventory of chemical species from anthropogenic activities (power generation, vehicles, ships and aircraft) in Antarctica, covering the 2004-2005 period. The inventory is based on estimated emission rates of fuel consumption provided by some of the Antarctic research stations. Since the emission sources have different modes of operation and use a variety of fuel, the emission flux rate of chemical species is calculated by multiplying the fuel consumption value with the density of fuel and appropriate emission factors. A separate inventory is prepared for each anthropogenic emission source in Antarctica. Depending on the type of operation, emission rates of SO2, and BC (Black Carbon, from shipping only) have been calculated using the above technique. However, only results of SO2 emissions from each source are presented here. Emission inventory maps of SO2 depicting the track/path taken by each mobile source are shown. The total annual SO2 is 158 Mg from power generation and vehicle operations, 3873 Mg from ships and 56 Mg from aircraft for 2004-2005 and these values undergo strong seasonality following the human activity in Antarctica. Though these figures are small when compared to the emissions at most other regions of the world, they are an indication that human presence in Antarctica leads to at least local pollution. The sources are mainly line and point sources and thus the local pollution potentially is relatively strong.

  11. An emission inventory of sulfur from anthropogenic sources in Antarctica

    NASA Astrophysics Data System (ADS)

    Shirsat, S. V.; Graf, H. F.

    2009-01-01

    This paper presents first results of a comprehensive emission inventory of chemical species from anthropogenic activities (power generation, vehicles, ships and aircraft) in Antarctica, covering the 2004-2005 period. The inventory is based on estimated emission rates of fuel consumption provided by some of the Antarctic research stations. Since the emission sources have different modes of operation and use a variety of fuel, the emission flux rate of chemical species is calculated by multiplying the fuel consumption value with the density of fuel and appropriate emission factors. A separate inventory is prepared for each anthropogenic emission source in Antarctica. Depending on the type of operation, emission rates of SO2, and BC (Black Carbon, from shipping only) have been calculated using the above technique. However, only results of SO2 emissions from each source are presented here. Emission inventory maps of SO2 depicting the track/path taken by each mobile source are shown. The total annual SO2 is 158 Mg from power generation and vehicle operations, 3873 Mg from ships and 56 Mg from aircraft for 2004-2005 and these values undergo strong seasonality following the human activity in Antarctica. Though these figures are small when compared to the emissions at most other regions of the world, they are an indication that human presence in Antarctica leads to at least local pollution. The sources are mainly line and point sources and thus the local pollution potentially is relatively strong.

  12. My IGY in Antarctica

    NASA Technical Reports Server (NTRS)

    Bentley, Charles

    2012-01-01

    Dr Charles Bentley is the A.P. Crary Professor Emeritus of Geophysics, Department of Geology and Geophysics, University of Wisconsin-Madison. Dr. Bentley joined the Arctic Institute of North America in 1956 to participate in International Geophysical Year (IGY)-related activities in the Antarctic. He wintered over consecutively in 1957 and 1958 at Byrd Station, a station in the interior of West Antarctica that housed 24 men each winter - 12 Navy support people and 12 civilian scientists/technicians. During the austral summers, he also participated in over-snow traverses, first as co-leader, then leader (the other coleader went home after the first year). These traverses consisted of six men and three vehicles, and lasted several months. These traverses covered more than 1609 kilometers (1000 miles) of largely unmapped and unphotographed terrain. During these traverses, connections to Byrd Station were by radio (daily, when the transmission conditions were good enough) and roughly every 2 weeks by resupply flight.

  13. GOCE and Antarctica

    NASA Astrophysics Data System (ADS)

    Forsberg, Rene

    2015-03-01

    GOCE has mapped the gravity field of the planet with unprecedented accuracy, and will leave a legacy gravity field measurement unmatched for many years to come. GOCE data in Antarctica demonstrate the mapping of significant crustal anomalies and deep subglacial valleys, and give for the first time a unified overlook of the gravitation field north of 83.3°S, and the accuracy and high resolution of GOCE is confirmed by comparison to recent airborne gravity data. A “beauty spot” of the global GOCE gravity field map is, however, the lack of data at the polar gaps, beyond 83.5 latitude. Although GRACE fills the polar gaps at medium to long wavelengths, the crucial wavelength band around harmonic degrees 120-240 will remain unmapped, unless terrestrial data are used. The gravity data coverage of the Arctic is pretty much done, thanks to major US, European and Russian airborne and surface surveys carried out since the early 1990’s. In the Antarctic, however, the situation is the opposite: virtually no surface or airborne data exist in the polar gap; therefore an international effort to fill in this gap by airborne gravity would be timely now, to make the final GOCE legacy gravity field models truly global. It is possible to fill this gap at a sufficient accuracy level in one field season, and plans for doing exactly that in a European-US cooperation 2015/16 are outlined.

  14. Solar Eclipses Observed from Antarctica

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.

    2013-01-01

    Aspects of the solar corona are still best observed during totality of solar eclipses, and other high-resolution observations of coronal active regions can be observed with radio telescopes by differentiation of occultation observations, as we did with the Jansky Very Large Array for the annular solar eclipse of 2012 May 20 in the US. Totality crossing Antarctica included the eclipse of 2003 November 23, and will next occur on 2021 December 4; annularity crossing Antarctica included the eclipse of 2008 February 7, and will next occur on 2014 April 29. Partial phases as high as 87% coverage were visible and were imaged in Antarctica on 2011 November 25, and in addition to partial phases of the total and annular eclipses listed above, partial phases were visible in Antarctica on 2001 July 2011, 2002 December 4, 2004 April 19, 2006 September 22, 2007 September 11, and 2009 January 26, and will be visible on 2015 September 13, 2016 September 1, 2017 February 26, 2018 February 15, and 2020 December 14. On behalf of the Working Group on Solar Eclipses of the IAU, the poster showed the solar eclipses visible from Antarctica and this article shows a subset (see www.eclipses.info for the full set). A variety of investigations of the Sun and of the response of the terrestrial atmosphere and ionosphere to the abrupt solar cutoff can be carried out at the future eclipses, making the Antarctic observations scientifically useful.

  15. The crustal thickness of West Antarctica

    NASA Astrophysics Data System (ADS)

    Chaput, J.; Aster, R. C.; Huerta, A.; Sun, X.; Lloyd, A.; Wiens, D.; Nyblade, A.; Anandakrishnan, S.; Winberry, J. P.; Wilson, T.

    2014-01-01

    P-to-S receiver functions (PRFs) from the Polar Earth Observing Network (POLENET) GPS and seismic leg of POLENET spanning West Antarctica and the Transantarctic Mountains deployment of seismographic stations provide new estimates of crustal thickness across West Antarctica, including the West Antarctic Rift System (WARS), Marie Byrd Land (MBL) dome, and the Transantarctic Mountains (TAM) margin. We show that complications arising from ice sheet multiples can be effectively managed and further information concerning low-velocity subglacial sediment thickness may be determined, via top-down utilization of synthetic receiver function models. We combine shallow structure constraints with the response of deeper layers using a regularized Markov chain Monte Carlo methodology to constrain bulk crustal properties. Crustal thickness estimates range from 17.0±4 km at Fishtail Point in the western WARS to 45±5 km at Lonewolf Nunataks in the TAM. Symmetric regions of crustal thinning observed in a transect deployment across the West Antarctic Ice Sheet correlate with deep subice basins, consistent with pure shear crustal necking under past localized extension. Subglacial sediment deposit thicknesses generally correlate with trough/dome expectations, with the thickest inferred subice low-velocity sediment estimated as ˜0.4 km within the Bentley Subglacial Trench. Inverted PRFs from this study and other published crustal estimates are combined with ambient noise surface wave constraints to generate a crustal thickness map for West Antarctica south of 75°S. Observations are consistent with isostatic crustal compensation across the central WARS but indicate significant mantle compensation across the TAM, Ellsworth Block, MBL dome, and eastern and western sectors of thinnest WARS crust, consistent with low density and likely dynamic, low-viscosity high-temperature mantle.

  16. Tectonic development of West Antarctica and its relation to East Antarctica

    SciTech Connect

    Dalziel, I.W.D. )

    1987-09-01

    Over several years, the author has compiled data and conducted field research to gain an understanding of the relationship between East and West Antarctica through geologic time. The investigations have focused on the Scotia Arc and the region at the base of the Antarctic Peninsula extending to the Ellsworth, Thiel, and Whitmore mountains. During the 1983-1984 austral summer, US and British geologists began an intensive investigation in the Ellsworth Mountains and Martin Hills, at Mount Smart, and near Siple Station. Field work includes geology, paleomagnetism, geochronology, and geophysics, with radio-echo sounding and aeromagnetic surveys conducted by British geophysicists. This investigation attempts to define the limits of the crustal blocks and determine the tectonic nature of the ice-covered area between them.

  17. Total ozone, ozone vertical distributions, and stratospheric temperatures at South Pole, Antarctica, in 1986 and 1987

    NASA Technical Reports Server (NTRS)

    Komhyr, W. D.; Grass, R. D.; Reitelbach, P. J.; Franchois, P. R.; Kuester, S. E.

    1988-01-01

    Seventy-six electrochemical cell (ECC) ozonesondes were flown at South Pole, Antarctica, during 1987 in a continuing program to document year-round changes in Antarctica ozone that are dynamically and photochemically induced. Dobson spectrophotometer total ozone observations were also made. For the twilight months of March and September when Dobson instrument observations cannot be made at South Pole, total ozone amounts were deduced from the ECC ozonesonde soundings. ECC sonde total ozone data obtained during the polar night (April to August), supplemented the sparse total ozone data obtained from Dobson instrument moon observations. Similar ozone profile and total ozone observations were made at South Pole in 1986.

  18. Data report for the Siple Coast (Antarctica) project

    NASA Technical Reports Server (NTRS)

    Bindschadler, R. A.; Stephenson, S. N.; Roberts, E. P.; Macayeal, D. R.; Lindstrom, D. R.

    1988-01-01

    This report presents data collected during three field seasons of glaciological studies in the Antarctica and describes the methods employed. The region investigated covers the mouths of Ice Streams B and C (the Siple Coast) and Crary Ice Rise on the Ross Ice Shelf. Measurements included in the report are as follows: surface velocity and deformation from repeated satellite geoceiver positions; surface topography from optical levelling; radar sounding of ice thickness; accumulation rates; near-surface densities and temperature profiles; and mapping from aerial photography.

  19. Practical analysis of tide gauges records from Antarctica

    NASA Astrophysics Data System (ADS)

    Galassi, Gaia; Spada, Giorgio

    2015-04-01

    We have collected and analyzed in a basic way the currently available time series from tide gauges deployed along the coasts of Antarctica. The database of the Permanent Service for Mean Sea Level (PSMSL) holds relative sea level information for 17 stations, which are mostly concentrated in the Antarctic Peninsula (8 out of 17). For 7 of the PSMSL stations, Revised Local Reference (RLR) monthly and yearly observations are available, spanning from year 1957.79 (Almirante Brown) to 2013.95 (Argentine Islands). For the remaining 11 stations, only metric monthly data can be obtained during the time window 1957-2013. The record length of the available time series is not generally exceeding 20 years. Remarkable exceptions are the RLR station of Argentine Island, located in the Antarctic Peninsula (AP) (time span: 1958-2013, record length: 54 years, completeness=98%), and the metric station of Syowa in East Antarctica (1975-2012, 37 years, 92%). The general quality (geographical coverage and length of record) of the time series hinders a coherent geophysical interpretation of the relative sea-level data along the coasts of Antarctica. However, in an attempt to characterize the relative sea level signals available, we have stacked (i.e., averaged) the RLR time series for the AP and for the whole Antarctica. The so obtained time series have been analyzed using simple regression in order to estimate a trend and a possible sea-level acceleration. For the AP, the the trend is 1.8 ± 0.2 mm/yr and for the whole Antarctica it is 2.1 ± 0.1 mm/yr (both during 1957-2013). The modeled values of Glacial Isostatic Adjustment (GIA) obtained with ICE-5G(VM2) using program SELEN, range between -0.7 and -1.6 mm/yr, showing that the sea-level trend recorded by tide gauges is strongly influenced by GIA. Subtracting the average GIA contribution (-1.1 mm/yr) to observed sea-level trend from the two stacks, we obtain 3.2 and 2.9 mm/yr for Antarctica and AP respectively, which are interpreted

  20. Soil Microorganisms of the McMurdo Sound Area, Antarctica

    PubMed Central

    Boyd, William L.; Boyd, Josephine W.

    1963-01-01

    A study of soil microorganisms of Ross Island and the adjacent mainland was carried out during the brief austral summer of 1961-1962. In some cases, seasonal changes in microbial numbers were observed, although microorganisms could not be detected in some soils. Bacterial species common to temperate regions were isolated from a number of different samples. Thermophilic bacteria were present in some of the soils, and a significant portion of the bacterial population was capable of growth at 2 C. The soil microflora were capable of carrying out certain reactions of the nitrogen cycle at a very slow rate. In addition to temperature, other environmental factors which might influence growth and metabolic activity were discussed. PMID:14014701

  1. Antarctica as a Martian model.

    NASA Technical Reports Server (NTRS)

    Vishniac, W. V.; Mainzer, S. E.

    1973-01-01

    Results of a survey of a variety of environments in the dry valleys of Antarctica, ranging from mountain crests to valley floors. The main purpose of the investigation was the determination of active microbial multiplication in the soil. A series of techniques was employed which permitted the detection of bacterial growth in situ. All evidence points to an active growth of micro-organisms in the Antarctic soil in all locations examined. The measurements were supported by electron micrographs of soil films which showed colonial growth covering soil particles. These findings suggest that Antarctica does not serve as a useful model for the Martian environment in evaluating quarantine standards.

  2. The Sounds of Sentences: Differentiating the Influence of Physical Sound, Sound Imagery, and Linguistically Implied Sounds on Physical Sound Processing.

    PubMed

    Dudschig, Carolin; Mackenzie, Ian Grant; Strozyk, Jessica; Kaup, Barbara; Leuthold, Hartmut

    2016-10-01

    Both the imagery literature and grounded models of language comprehension emphasize the tight coupling of high-level cognitive processes, such as forming a mental image of something or language understanding, and low-level sensorimotor processes in the brain. In an electrophysiological study, imagery and language processes were directly compared and the sensory associations of processing linguistically implied sounds or imagined sounds were investigated. Participants read sentences describing auditory events (e.g., "The dog barks"), heard a physical (environmental) sound, or had to imagine such a sound. We examined the influence of the 3 sound conditions (linguistic, physical, imagery) on subsequent physical sound processing. Event-related potential (ERP) difference waveforms indicated that in all 3 conditions, prime compatibility influenced physical sound processing. The earliest compatibility effect was observed in the physical condition, starting in the 80-110 ms time interval with a negative maximum over occipital electrode sites. In contrast, the linguistic and the imagery condition elicited compatibility effects starting in the 180-220 ms time window with a maximum over central electrode sites. In line with the ERPs, the analysis of the oscillatory activity showed that compatibility influenced early theta and alpha band power changes in the physical, but not in the linguistic and imagery, condition. These dissociations were further confirmed by dipole localization results showing a clear separation between the source of the compatibility effect in the physical sound condition (superior temporal area) and the source of the compatibility effect triggered by the linguistically implied sounds or the imagined sounds (inferior temporal area). Implications for grounded models of language understanding are discussed. PMID:27473463

  3. Surface winds over West Antarctica

    NASA Technical Reports Server (NTRS)

    Bromwich, David

    1993-01-01

    Five winter months (April-August 1988) of thermal infrared satellite images were examined to investigate the occurrence of dark (warm) signatures across the Ross Ice Shelf in the Antarctic continent. These features are inferred to be generated by katabatic winds that descend from southern Marie Byrd Land and then blow horizontally across the ice shelf. Significant mass is added to this airstream by katabatic winds blowing from the major glaciers that flow through the Transantarctic Mountains from East Antarctica. These negatively buoyant katabatic winds can reach the northwestern edge of the shelf - a horizontal propagation distance of up to 1,000 km - 14 percent of the time. Where the airstream crosses from the ice shelf to the ice-covered Ross Sea, a prominent coastal polynya is formed. Because the downslope buoyancy force is near zero over the Ross Ice Shelf, the northwestward propagation of the katabatic air mass requires pressure gradient support. The study shows that the extended horizontal propagation of this atmospheric density current occurred in conjunction with the passage of synoptic cyclones over the southern Amundsen Sea. These cyclones can strengthen the pressure gradient in the interior of West Antarctica and make the pressure field favorable for northwestward movement of the katabatic winds from West Antarctica across the ice shelf in a geostrophic direction. The glacier winds from East Antarctica are further accelerated by the synoptic pressure gradient, usually undergo abrupt adjustment beyond the exit to the glacier valley, and merge into the mountain-parallel katabatic air mass.

  4. Landsat Image Mosaic of Antarctica

    USGS Publications Warehouse

    U.S. Geological Survey

    2007-01-01

    Description Fact sheet introduces the Landsat Image Mosaic of Antarctica (LIMA) with images from a section of the mosaic over McMurdo Station, descriptions of the four versions of LIMA, where to access and download LIMA, and a brief explanation of the Antarctic Web portal.

  5. Intrinsic plasticity induced by group II metabotropic glutamate receptors via enhancement of high-threshold KV currents in sound localizing neurons.

    PubMed

    Hamlet, W R; Lu, Y

    2016-06-01

    Intrinsic plasticity has emerged as an important mechanism regulating neuronal excitability and output under physiological and pathological conditions. Here, we report a novel form of intrinsic plasticity. Using perforated patch clamp recordings, we examined the modulatory effects of group II metabotropic glutamate receptors (mGluR II) on voltage-gated potassium (KV) currents and the firing properties of neurons in the chicken nucleus laminaris (NL), the first central auditory station where interaural time cues are analyzed for sound localization. We found that activation of mGluR II by synthetic agonists resulted in a selective increase of the high-threshold KV currents. More importantly, synaptically released glutamate (with reuptake blocked) also enhanced the high-threshold KV currents. The enhancement was frequency-coding region dependent, being more pronounced in low-frequency neurons compared to middle- and high-frequency neurons. The intracellular mechanism involved the Gβγ signaling pathway associated with phospholipase C and protein kinase C. The modulation strengthened membrane outward rectification, sharpened action potentials, and improved the ability of NL neurons to follow high-frequency inputs. These data suggest that mGluR II provides a feedforward modulatory mechanism that may regulate temporal processing under the condition of heightened synaptic inputs. PMID:26964678

  6. Lyman-alpha observations of the interplanetary hydrogen: support of a NASA sounding rocket program and study of the local interstellar medium

    NASA Astrophysics Data System (ADS)

    Vincent, Frederic

    2013-10-01

    Our proposal is to use the Hubble Space Telescope Imaging Spectrograph {HST /STIS} over a single orbit to make Lyman-alpha observations of the interplanetary hydrogen {IPH} during the April period of this year {2014}.These measurements will provide wavelength and flux calibration, in order to support the HYPE instrument {Hydrogen Polarimetric Explorer} that is planned to make spectro-polarimetric observations in April during a suborbital flight of a NASA sounding rocket {grant NNX08AI98G}. Cross-calibration will also be made with the SWAN instrument {Solar Wind Anisotropies} on the SOHO satellite {Solar and Heliospheric Observatory}. SWAN can provide flux calibration but without any spectral information, so only HST/STIS can provide the wavelength calibration.Moreover the scientific controversy on the physical properties of the local interstellar medium {LISM} is still going on. The recent observations of interstellar helium atoms by IBEX {Interstellar Boundaries Explorer} suggest that the LISM velocity vector may vary over time. Such a change should impact the bulk velocity of interplanetary hydrogen and should be detected by HST /STIS.

  7. Pine Island Glacier, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This pair of MISR images of the Pine Island Glacier in western Antarctica was acquired on December 12, 2000 during Terra orbit 5246. At left is a conventional, true-color image from the downward-looking (nadir) camera. The false-color image at right is a composite of red band data taken by the MISR forward 60-degree, nadir, and aftward 60-degree cameras, displayed in red, green, and blue colors, respectively. Color variations in the left (true-color) image highlight spectral differences. In the multi-angle composite, on the other hand, color variations act as a proxy for differences in the angular reflectance properties of the scene. In this representation, clouds show up as light purple. Blue to orange gradations on the surface indicate a transition in ice texture from smooth to rough. For example, the bright orange 'carrot-like' features are rough crevasses on the glacier's tongue. In the conventional nadir view, the blue ice labeled 'rough crevasses' and 'smooth blue ice' exhibit similar coloration, but the multi-angle composite reveals their different textures, with the smoother ice appearing dark purple instead of orange. This could be an indicator of different mechanisms by which this ice is exposed. The multi-angle view also reveals subtle roughness variations on the frozen sea ice between the glacier and the open water in Pine Island Bay.

    To the left of the 'icebergs' label are chunks of floating ice. Additionally, smaller icebergs embedded in the frozen sea ice are visible below and to the right of the label. These small icebergs are associated with dark streaks. Analysis of the illumination geometry suggests that these streaks are surface features, not shadows. Wind-driven motion and thinning of the sea ice in the vicinity of the icebergs is one possible explanation.

    Recently, Robert Bindschadler, a glaciologist at the NASA Goddard Space Flight Center discovered in Landsat 7 imagery a newly-formed crack traversing the Pine Island Glacier. This crack

  8. Breath sounds

    MedlinePlus

    ... Rales can be further described as moist, dry, fine, and coarse. Rhonchi. Sounds that resemble snoring. They ... notice them. The following tests may be done: Analysis of a sputum sample ( sputum culture , sputum Gram ...

  9. Sound Guard

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Lubrication technology originally developed for a series of NASA satellites has produced a commercial product for protecting the sound fidelity of phonograph records. Called Sound Guard, the preservative is a spray-on fluid that deposits a microscopically thin protective coating which reduces friction and prevents the hard diamond stylus from wearing away the softer vinyl material of the disc. It is marketed by the Consumer Products Division of Ball Corporation, Muncie, Indiana. The lubricant technology on which Sound Guard is based originated with NASA's Orbiting Solar Observatory (OSO), an Earth-orbiting satellite designed and built by Ball Brothers Research Corporation, Boulder, Colorado, also a division of Ball Corporation. Ball Brothers engineers found a problem early in the OSO program: known lubricants were unsuitable for use on satellite moving parts that would be exposed to the vacuum of space for several months. So the company conducted research on the properties of materials needed for long life in space and developed new lubricants. They worked successfully on seven OSO flights and attracted considerable attention among other aerospace contractors. Ball Brothers now supplies its "Vac Kote" lubricants and coatings to both aerospace and non-aerospace industries and the company has produced several hundred variations of the original technology. Ball Corporation expanded its product line to include consumer products, of which Sound Guard is one of the most recent. In addition to protecting record grooves, Sound Guard's anti-static quality also retards particle accumulation on the stylus. During comparison study by a leading U.S. electronic laboratory, a record not treated by Sound Guard had to be cleaned after 50 plays and the stylus had collected a considerable number of small vinyl particles. The Sound Guard-treated disc was still clean after 100 plays, as was its stylus.

  10. Ocean current observations near McMurdo Station, Antarctica from 1991 to 1993: Relation to wastewater discharge dispersal

    SciTech Connect

    Barry, J.P.

    1994-08-01

    Analyses of ocean currents in the vicinity of McMurdo Station, Antarctica, are relevant to the transport and dispersal of wastewater from the McMurdo Station sewage outfall pipe. Observations of ocean currents during the initial phases of this study have been presented by Howington and McFeters. These studies, using coliform bacterial counts as an indicator of dispersion of the wastewater plume and current meters to measure flow patterns, indicated that dispersal of the plume by local currents does not effectively remove the plume from the vicinity of McMurdo Sound, under the present outfall pipe location. Moreover, these studies suggest that, although the flow pattern is generally consistent with transport of the plume away from McMurdo Station, episodes of current reversal are sufficient to transport the wastewater plume along the shore toward the southeast, eventually overlapping the seawater intake area near the McMurdo jetty. Several concerns included (a) impacts of wastewater inputs to nearshore benthic and pelagic habitats adjacent to McMurdo Station, (b) effects of wastewater input to the McMurdo Station fresh water intake source, and (c) reduction in human impacts on the McMurdo Sound ecosystem. These concerns motivated studies to characterize nearshore currents more extensively in relation to dispersal of the wastewater plume. This report discusses analysis results of current observations from November 1992 to November 1993.

  11. Measurements of Refractory Black Carbon (rBC) Aerosols in the McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Khan, A. L.; McMeeking, G. R.; Lyons, W. B.; Schwarz, J. P.; Welch, K. A.; McKnight, D. M.

    2015-12-01

    Measurements of light absorbing particles in the boundary layer of the high southern latitudes are scarce. During the 2013-2014 austral summer field season refractory black carbon (rBC) aerosols were quantified by a single particle soot photometer (SP2) in the McMurdo Dry Valleys, Antarctica. The dark rBC particles absorb more radiation thereby increasing atmospheric heating, as well as reducing surface albedo and enhancing hydrologic melt when deposited on highly reflective surfaces such as snow and ice. Quantifying both local and long-range atmospheric transport of rBC to this region of a remote continent mostly covered by ice and snow would be useful in understanding meltwater generation as climate changes. Although the Dry Valleys are the largest ice-free region of Antarctica, they contain many alpine glaciers, some of which are fed from the East Antarctic Ice Sheet (EAIS). Continuous rBC measurements were collected at Lake Hoare Camp in the Taylor Valley for two months, along with shorter periods at more remote locations within the Dry Valleys. Conditions at the Lake Hoare Camp were dominated by up-valley winds from McMurdo Sound, however, winds also brought air down-valley from the EAIS polar plateau. Here we investigated periods dominated by both up and down-valley winds to explore differences in rBC concentrations, size distributions, and scattering properties. The average background rBC mass concentration was 1ng/m3, though concentrations as high as 50 ng/m3 were observed at times, likely due to local sources.

  12. Geophysical Sounding

    NASA Astrophysics Data System (ADS)

    Blake, E.

    1998-01-01

    Of the many geophysical remote-sensing techniques available today, a few are suitable for the water ice-rich, layered material expected at the north martian ice cap. Radio echo sounding has been used for several decades to determine ice thickness and internal structure. Selection of operating frequency is a tradeoff between signal attenuation (which typically increases with frequency and ice temperature) and resolution (which is proportional to wavelength). Antenna configuration and size will be additional considerations for a mission to Mars. Several configurations for ice-penetrating radar systems are discussed: these include orbiter-borne sounders, sounding antennas trailed by balloons and penetrators, and lander-borne systems. Lander-borne systems could include short-wave systems capable of resolving fine structure and layering in the upper meters beneath the lander. Spread-spectrum and deconvolution techniques can be used to increase the depth capability of a radar system. If soundings over several locations are available (e.g., with balloons, rovers, or panning short-wave systems), then it will be easier to resolve internal layering, variations in basal reflection coefficient (from which material properties may be inferred), and the geometry of nonhorizontal features. Sonic sounding has a long history in oil and gas exploration. It is, however, unlikely that large explosive charges, or even swept-frequency techniques such as Vibroseis, would be suitable for a Polar lander -- these systems are capable of penetrating several kilometers of material at frequencies of 10-200 Hz, but the energy required to generate the sound waves is large and potentially destructive. The use of audio-frequency and ultrasonic sound generated by piezoelectric crystals is discussed as a possible method to explore layering and fine features in the upper meters of the ice cap. Appropriate choice of transducer(s) will permit operation over a range of fixed or modulated frequencies

  13. Site-testing in Antarctica

    NASA Astrophysics Data System (ADS)

    Storey, J. W. V.; Lawrence, J. S.; Ashley, M. C. B.

    2007-10-01

    Sites on the Antarctic Plateau such as Dome A, Dome C and South Pole, offer unique and exceptionally favourable conditions for astronomy. Site testing over the past decade has revealed extremely low infrared backgrounds, low water vapour, excellent infrared transmission and very low levels of atmospheric turbulence. Although several large facilities have already been built in Antarctica and plans for many more are well underway, there is still much to learn about this unique and beautiful place.

  14. Newborns' Head Orientation toward Sounds Within Hemifields.

    ERIC Educational Resources Information Center

    Fenwick, Kimberley; And Others

    This experiment examined the accuracy with which newborn infants orient their heads toward a sound positioned off midline within hemifields. The study also evaluated newborns' ability to update the angle of their head turn to match a change in localization of an ongoing sound. Alert newborns were held in a supine position and presented a sound at…

  15. Characteristic Surface Processes Between Atmosphere, Cryosphere and Oceanic Environment Inferred from Infrasound Array Observations in Lützow-Holm Bay, East Antarctica

    NASA Astrophysics Data System (ADS)

    Ishihara, Y.; Kanao, M.; Yamamoto, M. Y.; Kakinami, Y.; Murayama, T.; Okada, K.; Toda, S.; Matsushima, T.

    2014-12-01

    Infrasound is sub-audible sound whose frequency range is about 3 mHz to 20 Hz. Because this frequency is common between atmospheric, oceanic and solid earth vibrations, those waves are interacting with each other and interaction itself generates infrasound. At polar region, cryosphere also play an important role for generation and propagation of infrasound. The Japanese Antarctic infrasound observation started at April 2008. A sensor was installed at Syowa Station (SYO) in Lützow-Holm Bay (LHB) of East Antarctica, as a part of the International Polar Year. Characteristic infrasound waves observed at SYO demonstrate physical interaction involving environmental changes in the Antarctic region. Continuous recordings of infrasound clearly indicate existence of the hums generated by ocean-atmosphere interaction (microbaroms) with peaks of 0.1 to 0.25 Hz. Because larger amount of sea-ice extending around the LHB near SYO suppress ocean wave, the microbaroms become weak during austral winter. Following success of pilot observation, in austral summer in 2013, we extended one-sensor observation at SYO to 3-sensor arrayed observations, and installed a few field stations along the coast of the LHB. Newly established SYO array clearly detected the propagating directions and frequency contents of the microbaroms from Southern Ocean. In addition, we found harmonic signals around lowermost human audible band, however, currently unclear how and what generating hamonic signals. Those signals are recorded under windy condition. Since our system has no mechanical resonance at those frequency ranges, we speculate that the characteristic harmonic signals are probably related to local surficial phenomena such as ice sheet vibration generated by katabatic winds. Infrasound measurement at Antarctica could be a new proxy for monitoring a regional environmental change in high southern latitude. In such point of view, we will continue and improve the observations at and around SYO

  16. An extensive subglacial lake and canyon system in Princess Elizabeth Land, East Antarctica

    NASA Astrophysics Data System (ADS)

    Jamieson, Stewart; Ross, Neil; Greenbaum, Jamin; Young, Duncan; Aitken, Alan; Roberts, Jason; Blankenship, Donald; Bo, Sun; Siegert, Martin

    2016-04-01

    The subglacial landscape of Princess Elizabeth Land (PEL) in East Antarctica is poorly known due to a paucity of ice thickness measurements. This is problematic given its importance for understanding ice sheet dynamics and landscape and climate evolution. To address this issue, we describe the topography beneath the ice sheet by assuming that ice surface expressions in satellite imagery relate to large-scale subglacial features. We find evidence that a large, previously undiscovered subglacial drainage network is hidden beneath the ice sheet in PEL. We interpret a discrete feature that is 140 × 20 km in plan form, and multiple narrow sinuous features that extend over a distance of ~1100 km. We hypothesize that these are tectonically controlled and relate to a large subglacial basin containing a deep-water lake in the interior of PEL linked to a series of long, deep canyons. The presence of 1-km-deep canyons is confirmed at a few localities by radio-echo sounding data, and drainage analysis suggests that these canyons will direct subglacial meltwater to the coast between the Vestfold Hills and the West Ice Shelf.

  17. Topographic and hydrological controls on Subglacial Lake Ellsworth, West Antarctica

    NASA Astrophysics Data System (ADS)

    Vaughan, David G.; Rivera, Andrés; Woodward, John; Corr, Hugh F. J.; Wendt, Jens; Zamora, Rodrigo

    2007-09-01

    Subglacial Lake Ellsworth (SLE) was identified using reconnaissance data collected in the 1970s, here we present more detailed surveys. SLE lies beneath 3.2 km of ice in a subglacial valley in West Antarctica. It has an area of only ~18 km2, is dissimilar to the large tectonically-controlled lakes beneath East Antarctica and is a strong candidate for in situ exploration. Our analysis indicates that the ice above SLE is floating on a fluid whose density is 950-1013 kg m-3. This could indicate freshwater, but certainly precludes seawater, or high salt, acid, or clathrate content. The water in the lake is unlikely to be produced solely by local melt; it is more likely delivered via subglacial drainage. Our surveys show no identifiable hydrological barrier to outflow, meaning SLE is effectively full; new water entering the lake is likely balanced by outflow, which would drain into another lake that we have also identified.

  18. Sound Solutions

    ERIC Educational Resources Information Center

    Starkman, Neal

    2007-01-01

    Poor classroom acoustics are impairing students' hearing and their ability to learn. However, technology has come up with a solution: tools that focus voices in a way that minimizes intrusive ambient noise and gets to the intended receiver--not merely amplifying the sound, but also clarifying and directing it. One provider of classroom audio…

  19. Early opening of Australia and Antarctica: New inferences and regional consequences

    NASA Astrophysics Data System (ADS)

    Jacob, Jensen; Dyment, Jérôme

    2014-12-01

    Both continental margins of Australia and Antarctica exhibit a very clear gravity anomaly on the satellite free-air gravity data. The detailed sinuosity of these first-order conjugate features matches perfectly, suggesting that they are the signature of the initial continental breakup and mark the ocean-continent boundary. Another weaker, still clearly deciphered, pair of symmetrical gravity anomalies is identified oceanward. These anomalies are considered as pseudo-isochrons F and G and tentatively dated 128 and 94 Ma. Precise reconstructions of pseudo-isochron F are achieved over three sections of the margin, denoting the relative motion of Australia and East Antarctica, the Polda Block and East Antarctica, and Tasmania and West Antarctica. The Polda Block and Tasmania are transient micro-continents. Tasmania and Australia are reconstructed to align their linear eastern margin. The eastern margins of reconstructed Australia, Tasmania, and West Antarctica on one hand, the western margin of reconstructed Lord Howe Rise and Campbell Plateau on the other hand, fit a small circle of radius 15°, which suggests a transform motion between 128 and 83 Ma along this plate boundary. The reconstruction predicts a gap between East and West Antarctica, probably filled by non-cratonic continental crust compressively deformed and thickened by the SW motion of East Antarctica and participating to the formation of the Trans-Antarctic Mountains. The initial extension between Australia and East Antarctica may be related to the inception of the Kerguelen hotspot, ~ 1000 km to the west. The different rheology of cratons and orogenic terranes has played a role in the style and localization of both extensional and compressional deformations.

  20. Human Activity and Pollution in Antarctica

    NASA Astrophysics Data System (ADS)

    Graf, H.-F.; Shirsat, S. V.; Podzun, R.

    2009-04-01

    A regional climate chemistry model is used to determine the level of pollution of the Antarctic continent due to anthropogenic and natural emission of sulphur species. Based on an emission inventory for the year 2004/2005 including emissions from energy use and ground traffic at and between Antarctic research stations, flight activity, tourist and scientific ship operations, and emissions from the Mt. Erebus volcano, atmospheric concentration and deposition rates of sulphur species and black carbon were simulated at 0.5 degree resolution for the whole Antarctic continent. The biggest anthropogenic source of pollution is ship operations. These concentrate near the Antarctic Peninsula and close to the big scientific stations at Queen Maud Land and in the Ross sea area. The prevailing winds guarantee that most of the anthropogenic emissions from sources near the coast will be blown to lower latitudes and do not affect the continent. While atmospheric concentrations over vast areas remain extremely low, in some places locally concentrations and deposition rates are reached that may be detectable by in-situ measurements and give rise to concern. Especially at the Peninsula atmospheric concentrations and surface deposition of sulphur and soot are dominated by ship emissions. The largest part of shipping activity in this region is from tourist ships, a strongly increasing business. The by far biggest source of sulphur species in Antarctica is the Mt. Erebus volcano. It is also the only source that remains equally strong in polar winter. However, due to its high altitude and the long life time of SO2, especially in winter resulting in long range transport and dilution, Erebus emissions contribute relatively little to deposition of sulphur in the most anthropogenic polluted areas while they dominate the sulphur deposition in central Antarctica.

  1. Geometric Constraints on Human Speech Sound Inventories.

    PubMed

    Dunbar, Ewan; Dupoux, Emmanuel

    2016-01-01

    We investigate the idea that the languages of the world have developed coherent sound systems in which having one sound increases or decreases the chances of having certain other sounds, depending on shared properties of those sounds. We investigate the geometries of sound systems that are defined by the inherent properties of sounds. We document three typological tendencies in sound system geometries: economy, a tendency for the differences between sounds in a system to be definable on a relatively small number of independent dimensions; local symmetry, a tendency for sound systems to have relatively large numbers of pairs of sounds that differ only on one dimension; and global symmetry, a tendency for sound systems to be relatively balanced. The finding of economy corroborates previous results; the two symmetry properties have not been previously documented. We also investigate the relation between the typology of inventory geometries and the typology of individual sounds, showing that the frequency distribution with which individual sounds occur across languages works in favor of both local and global symmetry. PMID:27462296

  2. Geometric Constraints on Human Speech Sound Inventories

    PubMed Central

    Dunbar, Ewan; Dupoux, Emmanuel

    2016-01-01

    We investigate the idea that the languages of the world have developed coherent sound systems in which having one sound increases or decreases the chances of having certain other sounds, depending on shared properties of those sounds. We investigate the geometries of sound systems that are defined by the inherent properties of sounds. We document three typological tendencies in sound system geometries: economy, a tendency for the differences between sounds in a system to be definable on a relatively small number of independent dimensions; local symmetry, a tendency for sound systems to have relatively large numbers of pairs of sounds that differ only on one dimension; and global symmetry, a tendency for sound systems to be relatively balanced. The finding of economy corroborates previous results; the two symmetry properties have not been previously documented. We also investigate the relation between the typology of inventory geometries and the typology of individual sounds, showing that the frequency distribution with which individual sounds occur across languages works in favor of both local and global symmetry. PMID:27462296

  3. PREFACE: Aerodynamic sound Aerodynamic sound

    NASA Astrophysics Data System (ADS)

    Akishita, Sadao

    2010-02-01

    The modern theory of aerodynamic sound originates from Lighthill's two papers in 1952 and 1954, as is well known. I have heard that Lighthill was motivated in writing the papers by the jet-noise emitted by the newly commercialized jet-engined airplanes at that time. The technology of aerodynamic sound is destined for environmental problems. Therefore the theory should always be applied to newly emerged public nuisances. This issue of Fluid Dynamics Research (FDR) reflects problems of environmental sound in present Japanese technology. The Japanese community studying aerodynamic sound has held an annual symposium since 29 years ago when the late Professor S Kotake and Professor S Kaji of Teikyo University organized the symposium. Most of the Japanese authors in this issue are members of the annual symposium. I should note the contribution of the two professors cited above in establishing the Japanese community of aerodynamic sound research. It is my pleasure to present the publication in this issue of ten papers discussed at the annual symposium. I would like to express many thanks to the Editorial Board of FDR for giving us the chance to contribute these papers. We have a review paper by T Suzuki on the study of jet noise, which continues to be important nowadays, and is expected to reform the theoretical model of generating mechanisms. Professor M S Howe and R S McGowan contribute an analytical paper, a valuable study in today's fluid dynamics research. They apply hydrodynamics to solve the compressible flow generated in the vocal cords of the human body. Experimental study continues to be the main methodology in aerodynamic sound, and it is expected to explore new horizons. H Fujita's study on the Aeolian tone provides a new viewpoint on major, longstanding sound problems. The paper by M Nishimura and T Goto on textile fabrics describes new technology for the effective reduction of bluff-body noise. The paper by T Sueki et al also reports new technology for the

  4. Landsat Image Mosaic of Antarctica (LIMA)

    USGS Publications Warehouse

    U.S. Geological Survey

    2007-01-01

    For most of us, Antarctica was at best a distant acquaintance. Now, with the Landsat Image Mosaic of Antarctica (LIMA), we are on intimate terms. In stunning, up-close and personal detail, LIMA brings Antarctica to life. Explore this virtually cloudless, seamless, most geometrically accurate, and highest resolution satellite mosaic of Antarctica. A team of scientists from the U.S. Geological Survey, the British Antarctic Survey, and the National Aeronautics and Space Administration, with funding from the National Science Foundation, created LIMA in support of the International Polar Year (IPY; 2007?08). As the first major scientific outcome of the IPY, LIMA truly fulfills the IPY goals. LIMA is an international effort, supports current scientific polar research, encourages new projects, and helps the general public visualize Antarctica and changes happening in this southernmost environment. Researchers and the general public can download LIMA and all component Landsat scenes at no charge.

  5. Potential methane reservoirs beneath Antarctica.

    PubMed

    Wadham, J L; Arndt, S; Tulaczyk, S; Stibal, M; Tranter, M; Telling, J; Lis, G P; Lawson, E; Ridgwell, A; Dubnick, A; Sharp, M J; Anesio, A M; Butler, C E H

    2012-08-30

    Once thought to be devoid of life, the ice-covered parts of Antarctica are now known to be a reservoir of metabolically active microbial cells and organic carbon. The potential for methanogenic archaea to support the degradation of organic carbon to methane beneath the ice, however, has not yet been evaluated. Large sedimentary basins containing marine sequences up to 14 kilometres thick and an estimated 21,000 petagrams (1 Pg equals 10(15) g) of organic carbon are buried beneath the Antarctic Ice Sheet. No data exist for rates of methanogenesis in sub-Antarctic marine sediments. Here we present experimental data from other subglacial environments that demonstrate the potential for overridden organic matter beneath glacial systems to produce methane. We also numerically simulate the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model and show that pressure/temperature conditions favour methane hydrate formation down to sediment depths of about 300 metres in West Antarctica and 700 metres in East Antarctica. Our results demonstrate the potential for methane hydrate accumulation in Antarctic sedimentary basins, where the total inventory depends on rates of organic carbon degradation and conditions at the ice-sheet bed. We calculate that the sub-Antarctic hydrate inventory could be of the same order of magnitude as that of recent estimates made for Arctic permafrost. Our findings suggest that the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage. PMID:22932387

  6. The discovery of kimberlites in Antarctica extends the vast Gondwanan Cretaceous province.

    PubMed

    Yaxley, Gregory M; Kamenetsky, Vadim S; Nichols, Geoffrey T; Maas, Roland; Belousova, Elena; Rosenthal, Anja; Norman, Marc

    2013-01-01

    Kimberlites are a volumetrically minor component of the Earth's volcanic record, but are very important as the major commercial source of diamonds and as the deepest samples of the Earth's mantle. They were predominantly emplaced from ≈2,100 Ma to ≈10 ka ago, into ancient, stable regions of continental crust (cratons), but are also known from continental rifts and mobile belts. Kimberlites have been reported from almost all major cratons on all continents except for Antarctica. Here we report the first bona fide Antarctic kimberlite occurrence, from the northern Prince Charles Mountains, emplaced during the reactivation of the Lambert Graben associated with rifting of India from Australia-Antarctica. The samples are texturally, mineralogically and geochemically typical of Group I kimberlites from more classical localities. Their ≈120 Ma ages overlap with those of many kimberlites from other world-wide localities, extending a vast Cretaceous, Gondwanan kimberlite province, for the first time, into Antarctica. PMID:24346162

  7. Ocean current observations near McMurdo Station, Antarctica, 1993 to 1994: Relation to wastewater discharge dispersal

    SciTech Connect

    Barry, J.P.

    1995-09-01

    This report presents analyses of current measurements from McMurdo Sound, Antarctica during December, 1993 to November, 1994, in relation to dispersal of the McMurdo Station wastewater plume. Data collected from 1991 to 1993 are also discussed here. Six current meters were deployed near McMurdo Station, Antarctica, from December 1993 to November 1994. Five functioned properly throughout the observation period, and one failed. Analyses of 5 data series include: (1) summaries of current speed and direction, (2) directional analyses of flow, (3) time series current vectors averaged over 1, 3, 6, 12, and 24 h, (4) principal axes of flow, (5) maps of mean seasonal flow, (6) progressive vector plots, (7) spectral analyses, and (8) low-pass filtered (30h) time series of currents at McMurdo Station. Observations of flow near McMurdo Station during 1994 were generally similar to 1993. Short term variation in flow was related principally to diurnal tidal motions. Longer period oscillations in flow such as seasonal shifts, and non-periodic changes in current speed and direction were likely related to changes in ice cover and wind stress in the vicinity of McMurdo Station or over much larger scales or both. Three distinct oceanographic {open_quote}seasons{close_quote} were apparent in time series from 1992 to 1994, from stations furthest offshore, where the effects of local topography are minimal. The spring-summer (Oct.-Jan.) period of both years was dominated by regional southward flow, which generates a counter-clockwise eddy (McMurdo Gyre) adjacent to McMurdo Station. With regard to dispersal of the wastewater plume from McMurdo Station, observations of currents during 1994 generally corroborate those from 1993, and the recommendation that the outfall pipe should be repositioned offshore of the McMurdo Gyre is supported.

  8. Ice megadunes on Mars: analogy with Antarctica

    NASA Astrophysics Data System (ADS)

    Herny, Clémence; Massé, Marion; Bourgeois, Olivier; Carpy, Sabrina; Le Mouélic, Stéphane; Appéré, Thomas; Smith, Isaac; Spiga, Aymeric; Rodriguez, Sébastien

    2014-05-01

    Mass and energy balance of ice sheets are driven by complex interactions between the atmosphere and the cryosphere. Feedbacks between katabatic winds and the cryosphere may lead to the formation of sedimentation waves, so-called megadunes, at the surface of ice sheets. These have been first described in Antarctica. Here we use topographic data, optical images, and spectroscopic data acquired by Mars orbiters. We show that the surface of the Martian North Polar Cap displays two superimposed sets of sedimentation waves with differing wavelengths. These sedimentation waves have similarities with Antarctic ice megadunes regarding their surface morphology, texture, grain size, and internal stratigraphic architecture. Their shallow-dipping upwind sides, their tops and the intervening troughs are covered by young ice and occasional sastrugi fields, indicative of net accumulation. On the other hand, their steep-dipping downwind sides either expose exhumed layers of dusty old ice or correspond to smooth surfaces of coarse-grained ice, indicative of net ablation or reduced net accumulation associated with sublimation and metamorphism. These surface characteristics and the internal stratigraphic architecture revealed by radar sounding are consistent with the interpretation that both sets of Martian sedimentation waves grow and migrate upwind in response to the development of periodic accumulation/ablation patterns controlled by katabatic winds. The smaller waves, characterized by reduced net accumulation on their downwind sides, are probably analogous to the Antarctic megadunes that have been described so far. On the other hand, a terrestrial equivalent remains to be discovered for the larger ones, characterized by net ablation on their downwind sides. The recognition of these sedimentation waves provides the basis for the development of a common model of ice/wind interaction at the surface of Martian and terrestrial ice sheets and for future investigations on the respective

  9. Influence of Persistent Wind Scour on the Surface Mass Balance of Antarctica

    NASA Technical Reports Server (NTRS)

    Das, Indrani; Bell, Robin E.; Scambos, Ted A.; Wolovick, Michael; Creyts, Timothy T.; Studinger, Michael; Fearson, Nicholas; Nicolas, Julien P.; Lenaerts, Jan T. M.; vandenBroeke, Michiel R.

    2013-01-01

    Accurate quantification of surface snow accumulation over Antarctica is a key constraint for estimates of the Antarctic mass balance, as well as climatic interpretations of ice-core records. Over Antarctica, near-surface winds accelerate down relatively steep surface slopes, eroding and sublimating the snow. This wind scour results in numerous localized regions (< or = 200 sq km) with reduced surface accumulation. Estimates of Antarctic surface mass balance rely on sparse point measurements or coarse atmospheric models that do not capture these local processes, and overestimate the net mass input in wind-scour zones. Here we combine airborne radar observations of unconformable stratigraphic layers with lidar-derived surface roughness measurements to identify extensive wind-scour zones over Dome A, in the interior of East Antarctica. The scour zones are persistent because they are controlled by bedrock topography. On the basis of our Dome A observations, we develop an empirical model to predict wind-scour zones across the Antarctic continent and find that these zones are predominantly located in East Antarctica. We estimate that approx. 2.7-6.6% of the surface area of Antarctica has persistent negative net accumulation due to wind scour, which suggests that, across the continent, the snow mass input is overestimated by 11-36.5 Gt /yr in present surface-mass-balance calculations.

  10. Natural sound archives: past, present and future.

    PubMed

    Ranft, Richard

    2004-06-01

    Recordings of wild animals were first made in the Palearctic in 1900, in the Nearctic in 1929, in Antarctica in 1934, in Asia in 1937, and in the Neotropics in the 1940s. However, systematic collecting did not begin until the 1950s. Collections of animal sound recordings serve many uses in education, entertainment, science and nature conservation. In recent years, technological developments have transformed the ways in which sounds can be sampled, stored and accessed. Now the largest collections between them hold altogether around 0.5 million recordings with their associated data. The functioning of a major archive will be described with reference to the British Library Sound Archive. Preserving large collections for the long term is a primary concern in the digital age. While digitization and digital preservation has many advantages over analogue methods, the rate of technology change and lack of standardization are a serious problem for the world's major audio archives. Another challenge is to make collections more easily and widely accessible via electronic networks. On-line catalogues and access to the actual sounds via the internet are already available for some collections. Case studies describing the establishment and functioning of sound libraries in Mexico, Colombia and Brazil are given in individually authored sections in an Appendix. PMID:15258666

  11. Sounds of Space

    NASA Astrophysics Data System (ADS)

    Gurnett, D. A.

    2005-12-01

    Starting in the early 1960s, spacecraft-borne plasma wave instruments revealed that space is filled with an astonishing variety of radio and plasma wave sounds, which have come to be called "sounds of space." For over forty years these sounds have been collected and played to a wide variety of audiences, often as the result of press conferences or press releases involving various NASA projects for which the University of Iowa has provided plasma wave instruments. This activity has led to many interviews on local and national radio programs, and occasionally on programs haviang world-wide coverage, such as the BBC. As a result of this media coverage, we have been approached many times by composers requesting copies of our space sounds for use in their various projects, many of which involve electronic synthesis of music. One of these collaborations led to "Sun Rings," which is a musical event produced by the Kronos Quartet that has played to large audiences all over the world. With the availability of modern computer graphic techniques we have recently been attempting to integrate some of these sound of space into an educational audio/video web site that illustrates the scientific principles involved in the origin of space plasma waves. Typically I try to emphasize that a substantial gas pressure exists everywhere in space in the form of an ionized gas called a plasma, and that this plasma can lead to a wide variety of wave phenomenon. Examples of some of this audio/video material will be presented.

  12. Sound source tracking device for telematic spatial sound field reproduction

    NASA Astrophysics Data System (ADS)

    Cardenas, Bruno

    This research describes an algorithm that localizes sound sources for use in telematic applications. The localization algorithm is based on amplitude differences between various channels of a microphone array of directional shotgun microphones. The amplitude differences will be used to locate multiple performers and reproduce their voices, which were recorded at close distance with lavalier microphones, spatially corrected using a loudspeaker rendering system. In order to track multiple sound sources in parallel the information gained from the lavalier microphones will be utilized to estimate the signal-to-noise ratio between each performer and the concurrent performers.

  13. Hydrogeochemistry of sulfate-affected landscapes in Keller Peninsula, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    de Souza, José João L. L.; Schaefer, Carlos Ernesto G. R.; Abrahão, Walter Antônio P.; de Mello, Jaime Wilson V.; Simas, Felipe N. B.; da Silva, Juscimar; Francelino, Márcio R.

    2012-06-01

    Keller Peninsula, located in King George Island, has a typical Maritime Antarctica climatic regime, with higher temperatures and rainfall than other areas in Continental Antarctica. The main outcropping rocks are pyritized andesites, volcaniclastics and basalts. Recent pedological investigation indicated that the presence of sulfides in Keller Peninsula accelerates the weathering process. The aim of this work was the determination of the geochemical background in water channels following geomorphological gradients in Keller Peninsula, Maritime Antarctica. We delimited and mapped all catchments in Keller Peninsula using GIS techniques and field observations. Water samples were analyzed for twenty-nine elements by ICP-OES and IEC, after the proper treatments. Eight catchments were identified as sulfide-affected, although water pH was nearly neutral. The ionic concentration in solution was high, both in non-affected and sulfide-affected catchments, with a trend of greater values in the latter, and changing downslope. Concentration values are above the range of other hydrogeochemical studies from elsewhere in Antarctica. The values of molar ratio HCO3-:(Ca + Mg)2 + and Na+:Cl- indicated the absence of carbonate-bearing rocks. Local precipitation of evaporites, as gypsum and epsomite was confirmed by the Ca2 +:SO42 - and Mg2 +:SO42 - molar ratios. The high ionic concentration in sulfide-affected areas illustrates the role of sulfate soil formation in this part of Antarctica.

  14. Wind profiler installed in Antarctica

    NASA Astrophysics Data System (ADS)

    Balsley, B. B.; Carey, J.; Woodman, R. F.; Sarango, M.; Urbina, J.; Rodriguez, R.; Ragaini, E.

    A VHF (50 MHz) wind profiler was installed in Antarctica at the Peruvian Base “Machu Picchu” on King George Island from January 21 to 26. The wind profiler will provide a first look at atmospheric dynamics over the region.The profiler—the first of its kind in Antarctica—is a National Science Foundationsponsored cooperative project of the University of Colorado, the Geophysical Institute of Peru, the University of Piura (Peru), and the Peruvian Navy. This venture was also greatly facilitated by Peru's Comision Nacional de Asuntos Antartidos and Consejo Nacional de Ciencias y Tecnologia, with additional logis tics support provided by the Argentinean Navy and the Uruguayan Air Force.

  15. Statistics of Natural Binaural Sounds

    PubMed Central

    Młynarski, Wiktor; Jost, Jürgen

    2014-01-01

    Binaural sound localization is usually considered a discrimination task, where interaural phase (IPD) and level (ILD) disparities at narrowly tuned frequency channels are utilized to identify a position of a sound source. In natural conditions however, binaural circuits are exposed to a stimulation by sound waves originating from multiple, often moving and overlapping sources. Therefore statistics of binaural cues depend on acoustic properties and the spatial configuration of the environment. Distribution of cues encountered naturally and their dependence on physical properties of an auditory scene have not been studied before. In the present work we analyzed statistics of naturally encountered binaural sounds. We performed binaural recordings of three auditory scenes with varying spatial configuration and analyzed empirical cue distributions from each scene. We have found that certain properties such as the spread of IPD distributions as well as an overall shape of ILD distributions do not vary strongly between different auditory scenes. Moreover, we found that ILD distributions vary much weaker across frequency channels and IPDs often attain much higher values, than can be predicted from head filtering properties. In order to understand the complexity of the binaural hearing task in the natural environment, sound waveforms were analyzed by performing Independent Component Analysis (ICA). Properties of learned basis functions indicate that in natural conditions soundwaves in each ear are predominantly generated by independent sources. This implies that the real-world sound localization must rely on mechanisms more complex than a mere cue extraction. PMID:25285658

  16. The seismic noise environment of Antarctica

    DOE PAGESBeta

    Anthony, Robert E.; Aster, Richard C.; Wiens, Douglas; Nyblade, Andrew; Anandakrishnan, Sridhar; Huerta, Audrey; Winberry, J. Paul; Wilson, Terry; Rowe, Charlotte

    2014-11-26

    Seismographic coverage of Antarctica prior to 2007 consisted overwhelmingly of a handful of long running and sporadically deployed transient stations, many of which were principally collocated with scientific research stations. Thus, despite very cold temperatures, sunless winters, challenging logistics, and extreme storms, recent developments in polar instrumentation driven by new scientific objectives have opened up the entirety of Antarctica to year–round and continuous seismological observation (e.g., Nyblade et al., 2012).

  17. Method of sound synthesis

    DOEpatents

    Miner, Nadine E.; Caudell, Thomas P.

    2004-06-08

    A sound synthesis method for modeling and synthesizing dynamic, parameterized sounds. The sound synthesis method yields perceptually convincing sounds and provides flexibility through model parameterization. By manipulating model parameters, a variety of related, but perceptually different sounds can be generated. The result is subtle changes in sounds, in addition to synthesis of a variety of sounds, all from a small set of models. The sound models can change dynamically according to changes in the simulation environment. The method is applicable to both stochastic (impulse-based) and non-stochastic (pitched) sounds.

  18. Focused view of bedrock structures nearby EPICA drilling (Dome C, Antarctica)

    NASA Astrophysics Data System (ADS)

    Urbini, Stefano; Cafarella, Lili; Tabacco, Ignazio; Baskaradas, James; Zirizzotti, Achille

    2013-04-01

    In the last decades the study of Dome Concordia (Antarctica, 123° 20' E, 75° 20" S) represented a turning point especially for glaciology and climatology studies. Geophysical surveys played a fundamental role on several important issues like as the positioning of the EPICA drilling (European Project for Ice Coring in Antarctica) and revealing the physical assessment of the bedrock in the surrounding area. In this presentation, we show the last results pointed out by Radio Echo Sounding (RES) data collected during 2009, 2011 and 2012 Italian Antarctic Expeditions. The aim of these short-range campaigns was to obtain a high resolution image of the area surrounding the EPICA drilling site in order to enhance the knowledge on physical condition of ice bottom. The results revealed the presence of small scale bedrock structures. Nevertheless, the data acquired in 2011 and 2012 campaigns, showed unexpected characteristics that provide additional information on the nature of the interface between ice bottom and bedrock.

  19. Zero sound in dipolar Fermi gases

    SciTech Connect

    Ronen, Shai; Bohn, John L.

    2010-03-15

    We study the propagation of sound in a homogeneous dipolar gas at zero temperature, which is known as zero sound. We find that undamped zero sound propagation is possible only in a range of solid angles around the direction of polarization of the dipoles. Above a critical dipole moment, we find an unstable mode, by which the gas collapses locally perpendicular to the dipoles' direction.

  20. Precise analysis of ICESat altimetry data and assessment of the hydrostatic equilibrium for subglacial Lake Vostok, East Antarctica

    NASA Astrophysics Data System (ADS)

    Ewert, H.; Popov, S. V.; Richter, A.; Schwabe, J.; Scheinert, M.; Dietrich, R.

    2012-09-01

    Based on the Ice, Cloud and Land Elevation Satellite (ICESat) laser altimetry data, the hydrostatic equilibrium (HE) condition for the subglacial Lake Vostok, East Antarctica, is evaluated. A digital elevation model (DEM) of the ice surface is derived by a regional crossover adjustment. The analysis of the DEM and its comparison with GPS derived ice-surface elevations and an ice-surface DEM based on radar altimetry data reveal an overall accuracy of better than ± 0.7 m for the lake area. The DEM is combined with an ice-thickness model and a regional geoid model to determine the deviation of the local ice-surface height from HE. For large parts of the lake, the ice sheet fulfils the HE. Our results reveal a strong positive deviation of about 10 m along the lake shoreline. In addition, positive deviations are found in the northern part of the lake which coincide with ice rumples detected by radio-echo sounding. In the southern part of the lake, we find a linear negative deviation (-4.0 m) which coincides with the convoy route from Vostok station to Mirny base. In addition to the DEM, relative biases for the ICESat laser operational periods are determined in the regional crossover adjustment.

  1. Holocene glacial discharge fluctuations and recent instability in East Antarctica

    NASA Astrophysics Data System (ADS)

    Crespin, Julien; Yam, Ruth; Crosta, Xavier; Massé, Guillaume; Schmidt, Sabine; Campagne, Philippine; Shemesh, Aldo

    2014-05-01

    Antarctica holds the largest ice sheet in the world, the East Antarctic Ice Sheet (EAIS), and plays a significant role in both local and global climate through the interactions between ice sheets, ocean, sea ice, and atmosphere. Our understanding of East Antarctica Holocene climate variability relies mainly on ice cores that however do not document glacial discharge history. Here, we present the first high resolution δ18Odiatom record derived from two marine sediment cores retrieved on the East Antarctic continental shelf to reconstruct glacial discharge off Adélie Land and George V Land (AL-GVL) over the last 11,000 years from decadal to centennial resolution. Our results suggest multi-centennial glacier advances and retreats until 2000 cal yr BP, followed by a period of relative instability marked by two major glacial retreats centered at ˜1700 cal yr BP and ˜1980 CE. We suggest that the multi-centennial oscillations during the Early/Mid-Holocene reflect glacier fluctuations in response to long-term local seasonal insolation and short-term solar variability. We also propose that δ18Odiatom variability over the last 2000 years was the result of a recent change in the AL-GVL region to increasing atmospheric influence, linked to ENSO intensification and teleconnections strengthening between low and high latitudes.

  2. Detection and Analysis of Complex Patterns of Ice Dynamics in Antarctica from ICESat Laser Altimetry

    NASA Astrophysics Data System (ADS)

    Babonis, Gregory Scott

    There remains much uncertainty in estimating the amount of Antarctic ice mass change, its dynamic component, and its spatial and temporal patterns. This work remedies the limitations of previous studies by generating the first detailed reconstruction of total and dynamic ice thickness and mass changes across Antarctica, from ICESat satellite altimetry observations in 2003-2009 using the Surface Elevation Reconstruction and Change Detection (SERAC) method. Ice sheet thickness changes are calculated with quantified error estimates for each time when ICESat flew over a ground-track crossover region, at approximately 110,000 locations across the Antarctic Ice Sheet. The time series are partitioned into changes due to surficial processes and ice dynamics. The new results markedly improve the spatial and temporal resolution of surface elevation, volume, and mass change rates for the AIS, and can be sampled at annual temporal resolutions. The results indicate a complex spatiotemporal pattern of dynamic mass loss in Antarctica, especially along individual outlet glaciers, and allow for the quantification of the annual contribution of Antarctic ice loss to sea level rise. Over 5000 individual locations exhibit either strong dynamic ice thickness change patterns, accounting for approximately 500 unique spatial clusters that identify regions likely influenced by subglacial hydrology. The spatial distribution and temporal behavior of these regions reveal the complexity and short-time scale variability in the subglacial hydrological system. From the 500 unique spatial clusters, over 370 represent newly identified, and not previously published, potential subglacial water bodies indicating an active subglacial hydrological system over a much larger region than previously observed. These numerous new observations of dynamic changes provide more than simply a larger set of data. Examination of both regional and local scale dynamic change patterns across Antarctica shows newly

  3. Korotkoff Sounds.

    PubMed

    Shennan; Halligan

    1996-12-01

    We were interested in the historical perspective that Arabidze et al. [1] brought to the subject of Korotkoff's auscultatory method of measuring blood pressure. The original description by the Reverend Stephen Hales performing the very first blood pressure measurement (which was actually published in 1733) does not make reference to a column of water as the authors suggest [2]. Hales wrote: 'Then untying the Ligature on the Artery, the Blood rose in the Tube eight Feet three Inches.'. He goes on to state that, 'When it was at its full Height, it would rise and fall at and after each Pulse two, three, or four Inches, and sometimes it would fall twelve or fourteen Inches, and have there for a time the same vibrations up and down at and after each Pulse, as it had, when it was at its full Height; to which it would rise again, after forty or fifty Pulses'. We believe this fall of '12 or 14 in' to have been the first description of blood pressure variability, which has wrongly been attributed to respirations by subsequent authors [3]. The mare's pulse rate was described to be about 50 beats per minute; therefore an unanaesthetized horse would not be likely to have a respiration rate of once per minute. One further important point of error concerning the Korotkoff sounds is their reproducibility. We have demonstrated recently that phase IV is reproduced or identified poorly, both in adults and even during pregnancy, when it has been recommended to be used in favour of phase V. We have also demonstrated that phase I (systolic blood pressure) is perceived to be significantly clearer than phase V [4]. PMID:10226281

  4. Surface layer response to topographic solar shading in Antarctica's dry valleys

    NASA Astrophysics Data System (ADS)

    Katurji, Marwan; Zawar-Reza, Peyman; Zhong, Shiyuan

    2013-11-01

    The effects of topographic shading on local flow transitioning and atmospheric surface layer properties are investigated using observational data from the Miers Valley, one of the dry valleys of Antarctica. A unique data set was collected during a 9 day period in the summer of 2012 using an eddy covariance system and a sound detection and ranging that provided vertical profiles of wind and turbulence characteristics in the surface layer and the lower part of the boundary layer within the Miers Valley. This data set is ideal for investigating the dynamics of flow transitioning due to topographic shading, without the atmosphere experiencing complete darkness. The lack of atmospheric humidity, soil moisture, and surface vegetation in the dry valleys creates an atmosphere within which the microclimatic responses are amplified, and as a result, the valley atmosphere is extremely sensitive to solar radiation. The entire measured valley boundary layer (up to 250 m above ground level) feels the transition from an unstable to a stable stratification as the surface temperature drops by 10°C in response to the topographic shading. Wavelet analysis reveals the dynamics of flow deceleration, stagnation, and oscillations as the flow transitions from an unstable to a stable boundary layer. The larger air mass (along valley) scales to the longer terrain fetch, and as the shade is cast over the valley, it retains some of the longer wavelengths of the flow. The cross-valley component influenced by the slopes is quicker to adjust to short-period oscillations and takes around three more hours before it couples with the oscillatory pattern of the along-valley flow.

  5. NORTHERN PUGET SOUND MARINE MAMMALS

    EPA Science Inventory

    A baseline study of the marine mammals of northern Puget Sound and the Strait of Juan de Fuca was undertaken from November 1977 to September 1979 emphasizing certain aspects of the biology of the harbor seal, which is the most abundant marine mammal in this area. The local abunda...

  6. Tracking human footprints in Antarctica through passive sampling of polycyclic aromatic hydrocarbons in inland lakes.

    PubMed

    Yao, Yao; Meng, Xiang-Zhou; Wu, Chen-Chou; Bao, Lian-Jun; Wang, Feng; Wu, Feng-Chang; Zeng, Eddy Y

    2016-06-01

    Freely dissolved polycyclic aromatic hydrocarbons (PAHs) were monitored in seven inland lakes of Antarctica by a polyethylene (PE)-based passive sampling technique, with the objective of tracking human footprints. The measured concentrations of PAHs were in the range of 14-360 ng L(-1) with the highest values concentrated around the Russian Progress II Station, indicating the significance of human activities to the loading of PAHs in Antarctica. The concentrations of PAHs in the inland lakes were in the upper part of the PAHs levels in aquatic environments from remote and background regions across the globe. The composition profiles of PAHs indicated that PAHs in the inland lakes were derived mainly from local oil spills, which was corroborated by a large number of fuel spillage reports from ship and plane crash incidents in Antarctica during recent years. Clearly, local human activities, rather than long-range transport, are the dominant sources of PAH contamination to the inland lakes. Finally, the present study demonstrates the efficacy of PE-based passive samplers for investigating PAHs in the aquatic environment of Antarctica under complex field conditions. PMID:26946176

  7. Yukimarimo at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Petenko, Igor

    2015-04-01

    Natural frostballs called "yukimarimo" were observed at at Dome C, Antarctica, during the winter of 2014. Frostballs have spheroidal or lightly oblate form. Four cases of the yukimarimo were observed in the period April - August. The characteristics concerning their sizes, density, distribution over the surface varied for different cases. The diameters ranged from several millimetres to 120 mm, the density ranged from 15 to 60 kg/m3 . The heaviest one weighted 14 g and had a diameter of ≈90 mm. The initial "material" from which they formed resembles candy floss or fluff. In one case, only the initial stage of the small-yukimarimo formation was observed; the further development was interrupted. The meteorological conditions observed diuring the yukimarimo were not particular. The near-surface temperature varied between -70° and -60°C. Winds favouring to the yukimarimo formation were low, but not less than 2 m/s^1. A two-step mechanism of their formation and development is assumed: 1) at the initial stage, an electrostatic attraction favours the clumping of ice crystals to form some ice mass resembling floss structured in spherical pieces; 2) some pieces of ice floss are rolled by the wind and collect more ice crystals and increase in size like to a tumbleweed. Special comprehensive studies of electrical properties of the frost during the initial stage are necessary. Videos of moving yukimarimo at different stages of their formation are available.

  8. Terra Nova Bay Polynya, Antarctica

    NASA Technical Reports Server (NTRS)

    2007-01-01

    In Terra Nova Bay, off the Scott Coast of Victoria Land, Antarctica, a large pocket of open water persists throughout most of the Southern Hemisphere winter, even while most of the rest of the Antarctic coastline is firmly embraced by the frozen Southern Ocean. This pocket of open water--a polynya--results from exceptionally strong winds that blow downslope from the Trans-Antarctic Mountains. These fierce katabatic winds drive the sea ice eastward. Since the dominant ice drift pattern in the area is northward, the Drygalski Ice Tongue prevents the bay from being re-populated with sea ice. This image of the Terra Nova Bay polynya was captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite on October 16, 2007. Sea ice sits over the Ross Sea like a cracked and crumbling windshield. Blue-tinged glaciers flow down from the Trans-Antarctic Mountains. Although glaciers can appear blue because of melt water, they can also get that tint when the wind scours and polishes the ice surface. Given the strength of the katabatic winds along this part of the Antarctic coast, it is likely that the blue color of these glaciers is a result of their having been swept clean of snow. The large image has a spatial resolution (level of detail) of 250 meters per pixel.

  9. Space analogue studies in Antarctica

    NASA Astrophysics Data System (ADS)

    Lugg, D.; Shepanek, M.

    1999-09-01

    Medical research has been carried out on the Australian National Antarctic Research Expeditions (ANARE) for 50 years. As an extension of this program collaborative Australian/United States research on immunology, microbiology, psychology and remote medicine has produced important data and insight on how humans adapt to the stress of extreme isolation, confinement and the harsh environment of Antarctica. An outstanding analogue for the isolation and confinement of space missions (especially planetary outposts), ANARE has been used as an international research platform by Australia and the United States since 1993. Collaborative research has demonstrated a lowered responsiveness of the immune system under the isolation and confinement of Antarctic winter-over; a reduction of almost 50% in T cell proliferation to mltogen phytohaemogglutinin, as well as changes in latent herpesvirus states and the expansion of the polyclonal latent Epstein-Barr virus infected B cell populations. Although no clinically significant disease has been found to result from these immune changes, research is currently assessing the effects of psychological factors on the immune system. This and associated research performed to date and its relevance to both organisations is discussed, and comment made on possible extensions to the program in both medical and other fields.

  10. Space analogue studies in Antarctica

    NASA Technical Reports Server (NTRS)

    Lugg, D.; Shepanek, M.

    1999-01-01

    Medical research has been carried out on the Australian National Antarctic Research Expeditions (ANARE) for 50 years. As an extension of this program collaborative Australian/United States research on immunology, microbiology, psychology and remote medicine has produced important data and insight on how humans adapt to the stress of extreme isolation, confinement and the harsh environment of Antarctica. An outstanding analogue for the isolation and confinement of space missions (especially planetary outposts), ANARE has been used as an international research platform by Australia and the United States since 1993. Collaborative research has demonstrated a lowered responsiveness of the immune system under the isolation and confinement of Antarctic winter-over; a reduction of almost 50% in T cell proliferation to mitogen phytohaemogglutinin, as well as changes in latent herpesvirus states and the expansion of the polyclonal latent Epstein-Barr virus infected B cell populations. Although no clinically significant disease has been found to result from these immune changes, research is currently assessing the effects of psychological factors on the immune system. This and associated research performed to date and its relevance to both organisations is discussed, and comment made on possible extensions to the program in both medical and other fields.

  11. Soils of the Galindez Island, Argentine archipelago, Western Antarctica

    NASA Astrophysics Data System (ADS)

    Abakumov, Evgeny; Parnikoza, Ivan

    2015-04-01

    Antarctic Peninsula is a part of Antarctica which is characterized by increased soil diversity, caused by specific of parent materials and diversity of non-vascular and vascular plants. Soils of Galindez Island have been investigated during the 18-th Ukranian Antarctic Expedition 2013/14. This Island situated in Argentine archipelago (coastal part of Antarctic Peninsula). Soils of Galindez Island presented by following types: Leptosols, Lithosols, Histic Lithosols and Leptosols and some Gleyic soils, located in lowlands and coastal parts. An average solum profile thickness is 3-19 cm which result from the small depth of debris's, underplayed by massive crystallic rocks. The permafrost layer is located within the massive rock, but not in coarse friable parent material. The soils with bird influence are widely spread both in coastal and central part of Island. In the coastal parts we can find typical Ornithosols in the penguin rockeries areas. The main aim of our investigation was characterization of soils formed under vegetation, exactly under Deschampsia antarctica Desv. localities. Argentine Islands is the central part of D. antarctica spreading area in region of Antarctic peninsula. Probably, these islands colonized by hairgrass mainly due to ornitogenic activity. So, coastal population appearance related with Larus dominicanus nest areas and feeding activity. Thus, we found typical post ornithogenic soils here. This kind of soils we also observed in population of hairgrass of Galindez mainland where it was connected with the other Antarctic bird - Catharacta maccormicki activity. Thus, the soil diversity and soil geochemistry of the Galindez Island are closely related to the activity of birds. The spatial pattern of soils, their chemistry and organic matter quality is discussed in relation with distribution of bird nesting and feeding activity.

  12. Antarctica: Scientific Journeys from McMurdo to the Pole.

    ERIC Educational Resources Information Center

    Brand, Judith, Ed.

    2002-01-01

    This issue of Exploratorium Magazine focuses on Antarctica. Antarctica has one of the most extreme climates in the world with an untouched environment inviting researchers with great opportunities for study. This issue describes the journey of four Exploratorium staff members to frozen Antarctica. Chapters include: (1) "Life at the Bottom of the…

  13. Soils of Marie Byrd Land, West Antarctica

    NASA Astrophysics Data System (ADS)

    Lupachev, A. V.; Abakumov, E. V.

    2013-10-01

    Soils of Marie Byrd Land-one of the remotest and difficultly accessible regions of Antarctica-were investigated in the area of the mothballed Russkaya station located to the south of 74° S. Despite the extremely severe wind regime (the average wind velocity is 13 m/s, and the maximum wind velocity is up to 60 m/s), the projective cover of vegetation in the area of the station averages 25-40% and reaches 60-80% in some places. The phenomena of physical weathering of the bedrock-exfoliation, stone pavements, residual rocks exposed by wind (hoodoos), and others-are clearly manifested. In most of the described soils, normal organic and organomineral horizons are absent. The soil profiles represent the mixture of the residues of mosses and lichens and the gravelly eluvium. The fine earth material is blown out of the surface horizons by strong winds; its residual accumulation takes place in the middle and lower parts of the profiles. The classification position of these soils is open to argument; they are close to Petrozems and Lithozems. Most of the profiles are underlain by the massive or slightly disintegrated bedrock with dry permafrost at a depth of 20 to 50 cm. Soils with dry permafrost comprise about 75% of the surveyed area. In separate loci in the depressions of the local mesorelief and on gentle slopes, the soils with clearly expressed cryoturbation features are developed; their profiles are underlain by the ice-rich permafrost and compose about 15% of the surveyed area. Anthropogenically disturbed soils and soils polluted with petroleum hydrocarbons, heavy metals, and other pollutants occupy about 10% of the surveyed area.

  14. Making Sound Connections

    ERIC Educational Resources Information Center

    Deal, Walter F., III

    2007-01-01

    Sound provides and offers amazing insights into the world. Sound waves may be defined as mechanical energy that moves through air or other medium as a longitudinal wave and consists of pressure fluctuations. Humans and animals alike use sound as a means of communication and a tool for survival. Mammals, such as bats, use ultrasonic sound waves to…

  15. The Sound of Science

    ERIC Educational Resources Information Center

    Merwade, Venkatesh; Eichinger, David; Harriger, Bradley; Doherty, Erin; Habben, Ryan

    2014-01-01

    While the science of sound can be taught by explaining the concept of sound waves and vibrations, the authors of this article focused their efforts on creating a more engaging way to teach the science of sound--through engineering design. In this article they share the experience of teaching sound to third graders through an engineering challenge…

  16. Sounds Exaggerate Visual Shape

    ERIC Educational Resources Information Center

    Sweeny, Timothy D.; Guzman-Martinez, Emmanuel; Ortega, Laura; Grabowecky, Marcia; Suzuki, Satoru

    2012-01-01

    While perceiving speech, people see mouth shapes that are systematically associated with sounds. In particular, a vertically stretched mouth produces a /woo/ sound, whereas a horizontally stretched mouth produces a /wee/ sound. We demonstrate that hearing these speech sounds alters how we see aspect ratio, a basic visual feature that contributes…

  17. The Landsat Image Mosaic of Antarctica (LIMA): A Cutting-Edge Way for Students and Teachers to Learn about Antarctica

    ERIC Educational Resources Information Center

    Campbell, Brian; Bindschadler, Robert

    2009-01-01

    By studying Antarctica via satellite and through ground-truthing research, we can learn where the ice is melting and why. The Landsat Image Mosaic of Antarctica (LIMA), a new and cutting-edge way for scientists, researchers, educators, students, and the public to look at Antarctica, supports this research and allows for unprecedented views of our…

  18. Frictionless Telescopes in Antarctica: Why and How?

    NASA Astrophysics Data System (ADS)

    Quattri, M.

    Seeing quality in Antarctica is in the hundredth arcseconds range out of the boundary layer. To take advantage of this quality telescopes should be in thermal equilibrium with the outside environment and should minimize the non linearity's like limit cycles which will deteriorate tracking. At the ESO Very Large Telescope (VLT) 8m telescopes this is realized using oil bearings and direct drives on the axes to avoid slip stick effects on the motion. In Antarctica this could be realized using magnetic bearings, possibly combined with motors, on the axes, with also advantages concerning power consumptions and maintenance of the system.

  19. Live from Antarctica: Then and now

    NASA Astrophysics Data System (ADS)

    This real-time educational video series, featuring Camille Jennings from Maryland Public Television, includes information from Antarctic scientists and interactive discussion between the scientists and school children from both Maryland and Hawaii. This is part of a 'Passport to Knowledge Special' series. In this part of the four part Antarctic series, the history of Antarctica from its founding to the present, its mammals, plants, and other life forms are shown and discussed. The importance of Antarctica as a research facility is explained, along with different experiments and research that the facilities there perform.

  20. Live from Antarctica: Then and Now

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This real-time educational video series, featuring Camille Jennings from Maryland Public Television, includes information from Antarctic scientists and interactive discussion between the scientists and school children from both Maryland and Hawaii. This is part of a 'Passport to Knowledge Special' series. In this part of the four part Antarctic series, the history of Antarctica from its founding to the present, its mammals, plants, and other life forms are shown and discussed. The importance of Antarctica as a research facility is explained, along with different experiments and research that the facilities there perform.

  1. Acting Antarctica: science on stage

    NASA Astrophysics Data System (ADS)

    Ciceri, Piera; Tizzoni, Paola; Pierro, Luigia

    2016-04-01

    Key-words: Polar science, Earth science, Theatre, Hands on activities The legendary Antarctic Expedition of sir E. Shackleton and his crew of 27 aboard the Endurance (1914/16) trapped in the Antarctic ice has become the starting point to learn about Polar Science and Climate Change. While the students were involved into this incredible adventure by the astonishing images of the Australian photographer Frank Hurley (who joined the crew), they discovered the world in which this story happened. Students were then involved in hands-on activities and role plays and have become the writers of the play "Uomini a scienza ai confini del mondo". They act the story of Shackelton's expedition and they tell at the same time to the audience about ice pack, ice cores and their role in understanding the past of the climate, physical and geographical characteristic of polar regions, thermal phenomena related to adaptations of polar animals, solar radiation at different latitude, day/night duration. The theater was the place to "stage" some scientific experiments and to explain the current research carried out in polar regions and their importance in climate change studies and to stress some similarities between Antarctica and space. The project was carried out from teachers of science, letters and geography and was born in collaboration with the "Piccolo Teatro di Milano" and the association "Science Under 18" with the support of a professional actor and director and was played for other schools at "EXPO 2015" in Milano (Italy). In our opinion drama activities improve reading comprehension, and both verbal and non-verbal communication skills. To be able to write and to act, students need a deep understanding of contents. Arts, including theatre, are a good key to involve emotionally students. To have an audience different from their own teachers and classmates offers a real task and the opportunity to play and let grow real skills.

  2. Temporal weighting in sound localizationa

    PubMed Central

    Stecker, G. Christopher; Hafter, Ervin R.

    2010-01-01

    The dynamics of sound localization were studied using a free-field direct localization task (pointing to sound sources) and an observer-weighting analysis that assessed the relative influence of each click in a click-train stimulus. In agreement with previous studies of the precedence effect and binaural adaptation, weighting functions showed increased influence of the onset click when the interclick interval (ICI) was short (<5 ms). For longer ICIs, all clicks in a train contributed roughly the same amount to listeners’ localization responses. Finally, when a short gap was introduced in the middle of a train, the influence of the click immediately following the gap increased, in agreement with the “restarting” results obtained by Hafter and Buell PMID:12243153

  3. What is that mysterious booming sound?

    USGS Publications Warehouse

    Hill, David P.

    2011-01-01

    The residents of coastal North Carolina are occasionally treated to sequences of booming sounds of unknown origin. The sounds are often energetic enough to rattle windows and doors. A recent sequence occurred in early January 2011 during clear weather with no evidence of local thunder storms. Queries by a local reporter (Colin Hackman of the NBC affiliate WETC in Wilmington, North Carolina, personal communication 2011) seemed to eliminate common anthropogenic sources such as sonic booms or quarry blasts. So the commonly asked question, “What's making these booming sounds?” remained (and remains) unanswered.

  4. NASA sounding rockets, 1958 - 1968: A historical summary

    NASA Technical Reports Server (NTRS)

    Corliss, W. R.

    1971-01-01

    The development and use of sounding rockets is traced from the Wac Corporal through the present generation of rockets. The Goddard Space Flight Center Sounding Rocket Program is discussed, and the use of sounding rockets during the IGY and the 1960's is described. Advantages of sounding rockets are identified as their simplicity and payload simplicity, low costs, payload recoverability, geographic flexibility, and temporal flexibility. The disadvantages are restricted time of observation, localized coverage, and payload limitations. Descriptions of major sounding rockets, trends in vehicle usage, and a compendium of NASA sounding rocket firings are also included.

  5. Antarctica--the Ultimate Summer Institute.

    ERIC Educational Resources Information Center

    Van Wey, Nate J.

    1995-01-01

    Describes personal experiences of a participant in the National Science Foundation program, Teachers Experiencing Antarctica. Uses the study of the temperature history of Taylor Dome to provide teachers with the experience of research and help other teachers recognize that there are opportunities outside the classroom for personal and professional…

  6. Antarctica: What Shall We Do with It?

    ERIC Educational Resources Information Center

    Branson, Margaret S.; Long, Cathryn J.

    1977-01-01

    Describes a role playing exercise in which students act as delegates to a meeting at which they will revise the Antarctic Treaty. Background information is presented about Antarctica, the Antarctic Treaty, and positions of 19 nations with regard to the Treaty. (Author/DB)

  7. CyberHunt: Head Off to Antarctica.

    ERIC Educational Resources Information Center

    Kloza, Brad

    2001-01-01

    Explains how to take an elementary class on a cyber visit to the continent of Antarctica, the highest, driest, and coldest continent on earth. A student reproducible page presents eight web sites to visit in this quest as well as questions to answer about each site. Answers to the questions are included. (SM)

  8. Read--and Walk--to Antarctica

    ERIC Educational Resources Information Center

    Harr, Natalie; Doneyko, Kathleen; Lee, Richard E., Jr.

    2012-01-01

    The students at Crestwood Primary School proved that they have what it takes to exercise their bodies and their minds. In an effort to support their teacher's scientific expedition to Antarctica, students from kindergarten to second grade pledged to read books and do physical activity that equated to the 12,900 km (8,000-mile) journey to the…

  9. Lystrosaurus zone (triassic) fauna from antarctica.

    PubMed

    Kitching, J W; Collinson, J W; Elliot, D H; Colbert, E H

    1972-02-01

    Tetrapod skeletons recently found in the Fremouw Formation in the Shackleton Glacier area, Transantarctic Mountains, include several forms that closely compare to South African species. Faunal similarities that confirm a close connection between Antarctica and Africa during the Triassic Period lend further support to the concept of Gondwanaland and continental drift. PMID:17755654

  10. Antarctica: Is It More Than Just Ice?

    ERIC Educational Resources Information Center

    Johnson, Cheryl; Gutierrez, Melida

    2009-01-01

    The authors introduced polar science in a fourth-grade classroom by means of 3 hands-on activities that addressed (1) the melting of glaciers and ice, (2) the differences between the North and the South Pole, and (3) the geography and landforms of Antarctica. An assessment 4 months after the original activity showed that students remembered the…

  11. The atmospheric hydrologic cycle over the Southern Ocean and Antarctica from operational numerical analyses

    SciTech Connect

    Bromwich, D.H.; Robasky, F.M.; Cullather, R.I.; Van Woert, M.L.

    1995-12-01

    Moisture budget calculations for Antarctica and the Southern Ocean are performed using operational numerical analyses from several sources. The analyses are compared for an 8-yr period and evaluated against rawinsonde sites. The comparisons to East Antarctic and Macquarie Island rawinsondes show the European Centre for Medium-Range Weather Forecasts (ECMWF) analyses to be superior in reproducing sounding values at each level. While results are highly variable, agreement of the ECMWF analyses to zonally averaged sounding moisture flux values along the East Antarctic coast is very close. The National Meteorological Center (NMC) and Australian Bureau of Meteorology analyses generally underestimate transport at each level; error cancellation occurs during vertical integration however. A comparison of moisture convergence for East Antarctica with values calculated from rawinsonde data indicates the ECMWF analysis is within 5 mm per yr of the observed value, while the NMC result is severely deficient. Comparison of the moisture transport convergence derived from the numerical analyses with previous moisture flux studies over the Southern Ocean reveals general agreement in the location of the boundary between the moisture source and sink. The ECMWF and NMC analyses place the convergence maximum slightly farther south than has been previously found. It is inferred that this results from the blocking effect of the Antarctic coastal topography. At full resolution this point is at approximately 64{degree}S. Long-term net precipitation derived from analyses is somewhat smaller than values determined by glaciological methods. Net precipitation varies interannually by 25%, with most of the variation concentrated in the South Pacific sector. The results offer a positive outlook for determining continental-scale precipitation trends in Antarctica through atmospheric methods and demonstrate that the ECMWF analyses provide generally good estimates. 56 refs., 21 figs., 3 tabs.

  12. Sound wave transmission (image)

    MedlinePlus

    When sounds waves reach the ear, they are translated into nerve impulses. These impulses then travel to the brain where they are interpreted by the brain as sound. The hearing mechanisms within the inner ear, can ...

  13. VAS sounding data evaluation

    NASA Technical Reports Server (NTRS)

    Scoggins, J. R.

    1984-01-01

    The VAS soundings derived by NOAA personnel and NASA personnel and rawinsonde soundings are compared: (1) directly by plotting on Skew t-log p diagrams; (2) by pairing rawinsonde soundings with the closest satellite soundings and calculating the mean and standard deviations of differences between the two data sets; and (3) by constructing synoptic and subsynoptic scale analyses with rawinsonde and satellite data. Differences for various parameters are discussed.

  14. Records of past ice sheet fluctuations in interior East Antarctica

    USGS Publications Warehouse

    Liu, Xiaohan; Huang, Feixin; Kong, Ping; Fang, Aimin; Li, Xiaoli

    2007-01-01

    The results of a land-based multi-disciplinary study of the past ice surface elevation in the Grove Mountains of interior East Antarctica support a dynamic evolution of the East Antarctic Ice Sheet (EAIS). Moraine boulders of sedimentary rocks and spore pollen assemblage imply a significant shrinkage of the EAIS, with its margin retreating south of the Grove Mountains (~450 km south of recent coast line) before the middle Pliocene. The exposure ages indicate that the ice sheet subsequently re-advanced, with the ice surface rising locally at least 450 m higher than today. It then went back down constantly from before 2.3 Ma to 1.6 Ma. The glacial topography and existence of soil show that the ice surface fluctuation continued since the early Quaternary, but with highest levels never exceeding ~100 m higher than today.

  15. Accelerated sea-level rise from West Antarctica.

    PubMed

    Thomas, R; Rignot, E; Casassa, G; Kanagaratnam, P; Acuña, C; Akins, T; Brecher, H; Frederick, E; Gogineni, P; Krabill, W; Manizade, S; Ramamoorthy, H; Rivera, A; Russell, R; Sonntag, J; Swift, R; Yungel, J; Zwally, J

    2004-10-01

    Recent aircraft and satellite laser altimeter surveys of the Amundsen Sea sector of West Antarctica show that local glaciers are discharging about 250 cubic kilometers of ice per year to the ocean, almost 60% more than is accumulated within their catchment basins. This discharge is sufficient to raise sea level by more than 0.2 millimeters per year. Glacier thinning rates near the coast during 2002-2003 are much larger than those observed during the 1990s. Most of these glaciers flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates, providing exit routes for ice from further inland if ice-sheet collapse is under way. PMID:15388895

  16. Enlarge Your Sound Repertory

    ERIC Educational Resources Information Center

    Carle, Irmgard Lehrer; Martin, Isaiah

    1975-01-01

    Authors served up a variety of techniques for investigating sound sources and sound patterns. Have you considered creating a composition from breathing sounds? Or constructing a conversation in percussion? These ideas are included along with step-by-step directions for making nine percussion instruments. (Editor)

  17. The Sounds of Mandarin.

    ERIC Educational Resources Information Center

    Yen, Isabella Y.

    This phonology workbook on the sounds of Mandarin Chinese accompanies a 3-volume set of textbooks for the language. The workbook provides illustrations of the articulation of the sounds and offers exercises and drills for practicing each sound. For related documents in this series, see FL 002 773, FL 002 774, FL 002 776, and FL 002 777. (VM)

  18. Multiple meteoroid impact in Antarctica

    NASA Astrophysics Data System (ADS)

    Weihoupt, J. W.; Rice, A.; van der Hoeven, F.

    2006-12-01

    In the late 1950's, geophysical field parties undertaking gravity surveys across Antarctica observed over a large area of Wilkes Land (> 240km across) an exceptionally pronounced negative free air anomaly ((to -158.3 mgal). This area was later interpreted as a possible meteor impact site because the gravity profiles were similar to those of known impact sites (apparent rim structures, circular basins, central peaks or rings), they possessed appropriate aspect ratios (e.g., crater diameter vs crater depth), anomalously steep negative free air gravity anomaly gradients (to 4.71 mgal/km) were characteristic of impact craters and uncharacteristic of solely mantle-related or geologic crustal variations, etc. The condition of the ice covering the anomaly (heavily crevassed), the apparent lack of isostatic compensation with surrounding environs, etc suggested the impact was geologically recent and that perhaps a tektite strewn field was associated with it. The distance from the postulated impact to the Australian strewn field was appropriate as are the ages of the tektites there. This early work has been augmented with the detection of a dominant cluster of negative free air gravity anomalies crossing the continental-oceanic boundary, and the East and West Antarctic structural boundary (i.e., Transantarctic Mountains). These anomalies are coincident with complex subglacial craterform topographic features inferred from radiosounding (to -500m below MSL). The major interior positive free air gravity anomalies are associated with subglacial topographic highs. The elliptical distribution of the negative gravity anomalies resemble known multiple impact distributions (scatter ellipses with the larger anomalies forward and the lesser ones aft). This more recent information favors expanding the original proposal to that of a multiple meteoroid impact. The multiple impact hypotheses would explain aeromagnetic surveys revealing ring-shaped structures in the subglacial rock surface

  19. Neural realignment of spatially separated sound components.

    PubMed

    Salminen, Nelli H; Takanen, Marko; Santala, Olli; Alku, Paavo; Pulkki, Ville

    2015-06-01

    Natural auditory scenes often consist of several sound sources overlapping in time, but separated in space. Yet, location is not fully exploited in auditory grouping: spatially separated sounds can get perceptually fused into a single auditory object and this leads to difficulties in the identification and localization of concurrent sounds. Here, the brain mechanisms responsible for grouping across spatial locations were explored in magnetoencephalography (MEG) recordings. The results show that the cortical representation of a vowel spatially separated into two locations reflects the perceived location of the speech sound rather than the physical locations of the individual components. In other words, the auditory scene is neurally rearranged to bring components into spatial alignment when they were deemed to belong to the same object. This renders the original spatial information unavailable at the level of the auditory cortex and may contribute to difficulties in concurrent sound segregation. PMID:26093425

  20. National Report on the NASA Sounding Rocket and Balloon Programs

    NASA Technical Reports Server (NTRS)

    Eberspeaker, Philip; Fairbrother, Debora

    2013-01-01

    The U. S. National Aeronautics and Space Administration (NASA) Sounding Rockets and Balloon Programs conduct a total of 30 to 40 missions per year in support of the NASA scientific community and other users. The NASA Sounding Rockets Program supports the science community by integrating their experiments into the sounding rocket payloads, and providing both the rocket vehicle and launch operations services. Activities since 2011 have included two flights from Andoya Rocket Range, more than eight flights from White Sands Missile Range, approximately sixteen flights from Wallops Flight Facility, two flights from Poker Flat Research Range, and four flights from Kwajalein Atoll. Other activities included the final developmental flight of the Terrier-Improved Malemute launch vehicle, a test flight of the Talos-Terrier-Oriole launch vehicle, and a host of smaller activities to improve program support capabilities. Several operational missions have utilized the new Terrier-Malemute vehicle. The NASA Sounding Rockets Program is currently engaged in the development of a new sustainer motor known as the Peregrine. The Peregrine development effort will involve one static firing and three flight tests with a target completion data of August 2014. The NASA Balloon Program supported numerous scientific and developmental missions since its last report. The program conducted flights from the U.S., Sweden, Australia, and Antarctica utilizing standard and experimental vehicles. Of particular note are the successful test flights of the Wallops Arc Second Pointer (WASP), the successful demonstration of a medium-size Super Pressure Balloon (SPB), and most recently, three simultaneous missions aloft over Antarctica. NASA continues its successful incremental design qualification program and will support a science mission aboard WASP in late 2013 and a science mission aboard the SPB in early 2015. NASA has also embarked on an intra-agency collaboration to launch a rocket from a balloon to

  1. Study of Vertical Sound Image Control Using Parametric Loudspeakers

    NASA Astrophysics Data System (ADS)

    Shimizu, Kazuhiro; Itou, Kouki; Aoki, Shigeaki

    A parametric loudspeaker is known as a super-directivity loudspeaker. So far, the applications have been limited monaural reproduction sound system. We had discussed characteristics of stereo reproduction with two parametric loudspeakers. In this paper, the sound localization in the vertical direction using the parametric loudspeakers was confirmed. The direction of sound localization was able to be controlled. The results were similar as in using ordinary loudspeakers. However, by setting the parametric loudspeaker 5 degrees rightward, the direction of sound localization moved about 20 degrees rightward. The measured ILD (Interaural Level Difference) using a dummy head were analyzed.

  2. Vision-independent adjustment of unit tuning to sound localization cues in response to monaural occlusion in developing owl optic tectum.

    PubMed

    Knudsen, E I; Mogdans, J

    1992-09-01

    Neurons in the developing optic tectum adjust their tuning to auditory localization cues in response to chronic monaural occlusion so that auditory spatial fields align with visual receptive fields (VRFs). We tested whether this adaptive adjustment of auditory tuning requires visual instruction. Both eyelids were sutured closed at the same time that one ear was occluded in two barn owls that were 1 month old. After 70 and 100 d, respectively, the tuning of units to interaural level difference (ILD) and to interaural time difference (ITD) was measured. These data were compared with equivalent data from 15 normal owls. Unit tuning to ITD was shifted from normal in both of the monaurally occluded owls. In one owl, ILD tuning was also clearly shifted. In the other owl, the map of ILD was flipped upside down and adaptive adjustments in ILD tuning could not be assessed. Instead, adjustments in ILD tuning were observed following removal of the earplug with the eyelids kept closed. Unit tuning was monitored at several sites in the tectum for 1 month after earplug removal using chronically implanted electrodes. Then, ILD tuning was resampled across the entire tectum. Both measures indicated shifts in ILD tuning in response to removal of the earplug in the second blind owl. In both animals, the magnitude of the shifts in ILD tuning and ITD tuning was smaller than has been observed previously in monaurally occluded but sighted owls. The results demonstrate that the brain can make adaptive adjustments in ILD and ITD tuning in response to early monaural occlusion even without the guiding influence of vision. PMID:1527592

  3. Errors in Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) Kinetic Temperature Caused by Non-Local Thermodynamic Equilibrium Model Parameters

    NASA Technical Reports Server (NTRS)

    Garcia-Comas, Maya; Lopez-Puertas, M.; Funke, B.; Bermejo-Pantaleon, D.; Marshall, Benjamin T.; Mertens, Christopher J.; Remsberg, Ellis E.; Mlynczak, Martin G.; Gordley, L. L.; Russell, James M.

    2008-01-01

    The vast set of near global and continuous atmospheric measurements made by the SABER instrument since 2002, including daytime and nighttime kinetic temperature (T(sub k)) from 20 to 105 km, is available to the scientific community. The temperature is retrieved from SABER measurements of the atmospheric 15 micron CO2 limb emission. This emission separates from local thermodynamic equilibrium (LTE) conditions in the rarefied mesosphere and thermosphere, making it necessary to consider the CO2 vibrational state non-LTE populations in the retrieval algorithm above 70 km. Those populations depend on kinetic parameters describing the rate at which energy exchange between atmospheric molecules take place, but some of these collisional rates are not well known. We consider current uncertainties in the rates of quenching of CO2 (v2 ) by N2 , O2 and O, and the CO2 (v2 ) vibrational-vibrational exchange to estimate their impact on SABER T(sub k) for different atmospheric conditions. The T(sub k) is more sensitive to the uncertainty in the latter two and their effects depend on altitude. The T(sub k) combined systematic error due to non-LTE kinetic parameters does not exceed +/- 1.5 K below 95 km and +/- 4-5 K at 100 km for most latitudes and seasons (except for polar summer) if the Tk profile does not have pronounced vertical structure. The error is +/- 3 K at 80 km, +/- 6 K at 84 km and +/- 18 K at 100 km under the less favourable polar summer conditions. For strong temperature inversion layers, the errors reach +/- 3 K at 82 km and +/- 8 K at 90 km. This particularly affects tide amplitude estimates, with errors of up to +/- 3 K.

  4. Priming Gestures with Sounds

    PubMed Central

    Lemaitre, Guillaume; Heller, Laurie M.; Navolio, Nicole; Zúñiga-Peñaranda, Nicolas

    2015-01-01

    We report a series of experiments about a little-studied type of compatibility effect between a stimulus and a response: the priming of manual gestures via sounds associated with these gestures. The goal was to investigate the plasticity of the gesture-sound associations mediating this type of priming. Five experiments used a primed choice-reaction task. Participants were cued by a stimulus to perform response gestures that produced response sounds; those sounds were also used as primes before the response cues. We compared arbitrary associations between gestures and sounds (key lifts and pure tones) created during the experiment (i.e. no pre-existing knowledge) with ecological associations corresponding to the structure of the world (tapping gestures and sounds, scraping gestures and sounds) learned through the entire life of the participant (thus existing prior to the experiment). Two results were found. First, the priming effect exists for ecological as well as arbitrary associations between gestures and sounds. Second, the priming effect is greatly reduced for ecologically existing associations and is eliminated for arbitrary associations when the response gesture stops producing the associated sounds. These results provide evidence that auditory-motor priming is mainly created by rapid learning of the association between sounds and the gestures that produce them. Auditory-motor priming is therefore mediated by short-term associations between gestures and sounds that can be readily reconfigured regardless of prior knowledge. PMID:26544884

  5. Electrophonic sounds in meteors

    NASA Astrophysics Data System (ADS)

    Wu, Guangjie

    2003-06-01

    Recordings about the sounds of meteors existed in ancient Chinese literature before Christ. During recent two hundreds years, especially, recent twenty years, reports and investigations about Electrophonic meteors and Electrophonic sounds have been developed largely. Electrophonic sounds are defined as sounds produced by direct conversion of electromagnetic radiation into audible sounds. It is thought that Electrophonic sounds may be induced in events of bolide, very bright auroral display, nearby strong lightning, earthquake and nuclear explosion. However, on account of its unusually rare chance and its particular physical course, no matter in observations or in theoretical study, there are many difficult and unresolved problems. The historical and present situations about Electrophonic sounds are summarized in this paper.

  6. Live from Antarctica, volume 4

    NASA Astrophysics Data System (ADS)

    In this fourth video of a four part 'Passport to Knowledge Special', hosted by Camille Moody Jennings from Maryland Public Television, children from Maryland and Alaska public schools had the opportunity to directly interact with and ask questions of scientists and researchers from the Antarctic, and learn about the different geological and meteorological research going on in the Antarctic and McMurdo Base at McMurdo Sound. The scientists questioned included: Donal Manahan (biologist from Un. of So. California), who described some of the geological features from Hut Point, the historic hut built by Capt. Scott in 1902; Sridar Anandakrishnan (Penn State Un.) whose research includes ice plate movement of the central ice sheet and earthquakes and how they affect the sheet; and Lt. j.g. Kate McNitt, who spends her winters investigating the trace gases, aerosols, CFC's and ozone levels over the Antarctic area that are affecting the seasonal ozone hole that appears in that region. Historical film footage of Capt. Scott's exploration of the Antarctic is included.

  7. Live from Antarctica, Volume 4

    NASA Technical Reports Server (NTRS)

    1994-01-01

    In this fourth video of a four part 'Passport to Knowledge Special', hosted by Camille Moody Jennings from Maryland Public Television, children from Maryland and Alaska public schools had the opportunity to directly interact with and ask questions of scientists and researchers from the Antarctic, and learn about the different geological and meteorological research going on in the Antarctic and McMurdo Base at McMurdo Sound. The scientists questioned included: Donal Manahan (biologist from Un. of So. California), who described some of the geological features from Hut Point, the historic hut built by Capt. Scott in 1902; Sridar Anandakrishnan (Penn State Un.) whose research includes ice plate movement of the central ice sheet and earthquakes and how they affect the sheet; and Lt. j.g. Kate McNitt, who spends her winters investigating the trace gases, aerosols, CFC's and ozone levels over the Antarctic area that are affecting the seasonal ozone hole that appears in that region. Historical film footage of Capt. Scott's exploration of the Antarctic is included.

  8. 45 CFR 674.4 - Restrictions on collection of meteorites in Antarctica.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... SCIENCE FOUNDATION ANTARCTIC METEORITES § 674.4 Restrictions on collection of meteorites in Antarctica. No person may collect meteorites in Antarctica for other than scientific research purposes....

  9. 45 CFR 674.4 - Restrictions on collection of meteorites in Antarctica.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... SCIENCE FOUNDATION ANTARCTIC METEORITES § 674.4 Restrictions on collection of meteorites in Antarctica. No person may collect meteorites in Antarctica for other than scientific research purposes....

  10. Planetary geomorphology field studies: Iceland and Antarctica

    NASA Technical Reports Server (NTRS)

    Malin, M. C.

    1984-01-01

    Field studies of terrestrial landforms and the processes that shape them provide new directions to the study of planetary features. These studies, conducted in Iceland and in Antarctica, investigated physical and chemical weathering mechanisms and rates, eolitan processes, mudflow phenomena, drainage development, and catastrophic fluvial and volcanic phenomena. Continuing investigations in Iceland fall in three main catagories: (1) catastrophic floods of the Jokulsa a Fjollum, (2) lahars associated with explosive volcanic eruptions of Askja caldera, and (3) rates of eolian abrasion in cold, volcanic deserts. The ice-free valleys of Antarctica, in particular those in South Victoria Land, have much is common with the surface of Mars. In addition to providing independent support for the application of the Iceland findings to consideration of the martian erosional system, the Antarctic observations also provide analogies to other martian phenomena. For example, a family of sand dunes in Victoria Valley are stabilized by the incorporation of snow as beds.

  11. Antarctica - Lessons for a Mars exploration program

    NASA Technical Reports Server (NTRS)

    Mckay, C. P.

    1985-01-01

    The history of exploration and the international system of control of Antarctica has often been cited as a paradigm for the exploration of space. The small isolated research stations have been used to model the psychological stresses of future space missions. In addition, the programmatic structure of the U.S. Antarctic Research Program provides several possible analogs to future Mars Programs presently under discussion. These are: (1) Continued presence; (2) Civilian, military and private sector involvement; (3) Scientific activities; (4) Risk assessment and logistical support; (5) Accessibility for non-specialists; (6) Political and strategic motivations; (7) International cooperation/competition. Survival in Antarctica is contingent on advanced technology and the active transport of supplies. The scientific exploration of this remote and barren expanse without, of course, the aid and guidance of indigenous people certainly provides one of the closest analogs available to future science activities on the Martian surface.

  12. Intercomparison of ozone measurements over Antarctica

    NASA Technical Reports Server (NTRS)

    Margitan, J. J.; Farmer, C. B.; Toon, G. C.; Brothers, G. A.; Browell, E. V.; Gregory, G. L.; Hypes, W.; Larsen, J. C.; Mccormick, M. P.; Krueger, A. J.

    1989-01-01

    Measurements of the abundances of ozone over Antarctica in August and September 1987 obtained during the Airborne Antarctic Ozone Experiment are intercompared. These measurements of ozone concentrations and total column abundance were obtained by three satellite instruments, two IR and one UV column-measuring instruments aboard the DC-8, one in situ DC-8, and two in situ ER-2 instruments, an upward looking lidar aboard the DC-8, and ozone sondes from four sites in Antarctica. This paper presents a summary of the ozone data, using the data and accuracies given by the individual investigators in the individual papers in this issue, without any attempt to critically review or evaluate the data. In general, very good agreement (within about 10-20 percent, limited by natural variability) among the various techniques was found, with no systematic biases detected. These observations confirm the low ozone amounts reported in the Antarctic stratosphere.

  13. The Landsat Image Mosaic of Antarctica

    NASA Astrophysics Data System (ADS)

    Bindschadler, R.; Vornberger, P.; Fleming, A.; Fox, A.; Morin, P.

    2008-12-01

    The first-ever true-color, high-resolution digital mosaic of Antarctica has been produced from nearly 1100 Landsat-7 ETM+ images collected between 1999 and 2003. The Landsat Image Mosaic of Antarctica (LIMA) project was an early benchmark data set of the International Polar Year and represents a close and successful collaboration between NASA, USGS, the British Antarctic Survey and the National Science Foundation. The mosaic was successfully merged with lower resolution MODIS data south of Landsat coverage to produce a complete true-color data set of the entire continent. LIMA is being used as a platform for a variety of education and outreach activities. Central to this effort is the NASA website 'Faces of Antarctica' that offers the web visitor the opportunity to explore the data set and to learn how these data are used to support scientific research. Content is delivered through a set of mysteries designed to pique the user's interest and to motivate them to delve deeper into the website where there are various videos and scientific articles for downloading. Detailed lesson plans written by teachers are provided for classroom use and Java applets let the user track the motion of ice in sequential Landsat images. Web links take the user to other sites where they can roam over the imagery using standard pan and zoom functions, or search for any named feature in the Antarctic Geographic Names data base that returns to the user a centered true-color view of any named feature. LIMA also has appeared is a host of external presentations from museum exhibits, to postcards and large posters. It has attracted various value-added providers that increase LIMA's accessibility by allowing users to specify subsets of the very large data set for individual downloads. The ultimate goal of LIMA in the public and educational sector is to enable everyone to become more familiar with Antarctica.

  14. Life on ice, Antarctica and Mars

    NASA Technical Reports Server (NTRS)

    Anderson, D. T.; Mckay, C. P.; Wharton, Robert A., Jr.; Sagan, C.; Squyres, S. W.; Simmons, G. M.

    1991-01-01

    The study of the origin of life and the prospects for human exploration of Mars are two themes developed in a new 57-minute film, Life on Ice, Antarctica, and Mars, produced by the InnerSpace Foundation and WHRO Television for broadcast by the Public Broadcasting System (PBS). A brief explanation of the film and how it relates to the future human exploration of space is presented.

  15. The Ice: A Journey to Antarctica

    NASA Astrophysics Data System (ADS)

    Ford, Arthur B.

    The title is misleading for a non—“OAE” (Old Antarctic Explorer, to whom “The Ice” is Antarctica) because The Ice is about far more than just ice. It does indeed cover just about all you'd want to know (or more) about Antarctic ice, from the vast south polar sheets and glaciers to the great tabular bergs, bergy bits, brash ice, pancake ice, frazil ice, and the pack of the polar seas; but it also explores nearly every aspect of this “Last of Lands” in an unusually comprehensive coverage. From the “Heroic Ages” of early 20th-century explorers Robert Scott, Ernest Shackleton, and Roald Amundsen to the present “Cruise Ship Age,”Antarctica has produced a wealth of literature in the “Journey to…” style — which Pyne's is not. Instead, his product from one short (3-month) visit under a National Endowment for the Humanities fellowship takes all readers o n a webwork journey through time, space, ice, and rocks for an appreciation of “ The Ice” in a way found in no other book. This, his fifth book (another one is Fire in America, Princeton University Press, Princeton, N.J., 1982), is a significant contribution to the literature of Antarctica. Pyne's prose cannot be paraphrased for a review, as the reader will be able to appreciate from the excerpts to follow.

  16. Observatio of HF noise in an intense aurora by the sounding rocket S-310JA-7

    NASA Astrophysics Data System (ADS)

    Nakamura, Y.; Nomura, Y.

    1982-09-01

    Observation of noise in the frequency range from 0.6 to 7.6 MHz has been made in an auroral plasma up to approximately 220 km by an instrument (PWN-H) on board the S-310JA-7 sounding rocket. This rocket was launched at 1915:50 UT on March 27, 1978 from Syowa Station in Antarctica, just prior to an intense auroral substorm (magnetic H component decrease = -700 nT and 30 MHz CNA = -5 dB). The observed HF emissions are classified into three types according to their frequency ranges and spectral shape; (1) High level and narrow band signals whose frequencies are nearly equal to nf(ce) or (n + 1/2)f(ce), where n is an integer and f(ce) is the electron gyrofrequency. (2) A low level broad band emission whose upper-limiting frequency is below the local electron plasma frequency. (3) Signals at frequencies below f(ce). Excitation mechanism of these waves in the aurora is discussed.

  17. The sound of distance.

    PubMed

    Rabaglia, Cristina D; Maglio, Sam J; Krehm, Madelaine; Seok, Jin H; Trope, Yaacov

    2016-07-01

    Human languages may be more than completely arbitrary symbolic systems. A growing literature supports sound symbolism, or the existence of consistent, intuitive relationships between speech sounds and specific concepts. Prior work establishes that these sound-to-meaning mappings can shape language-related judgments and decisions, but do their effects generalize beyond merely the linguistic and truly color how we navigate our environment? We examine this possibility, relating a predominant sound symbolic distinction (vowel frontness) to a novel associate (spatial proximity) in five studies. We show that changing one vowel in a label can influence estimations of distance, impacting judgment, perception, and action. The results (1) provide the first experimental support for a relationship between vowels and spatial distance and (2) demonstrate that sound-to-meaning mappings have outcomes that extend beyond just language and can - through a single sound - influence how we perceive and behave toward objects in the world. PMID:27062226

  18. Present-day climate of Antarctica : A study with a regional atmospheric climate model

    NASA Astrophysics Data System (ADS)

    van de Berg, W. J.

    2008-02-01

    The present-day climate of Antarctica is studied with a regional climate model. In this research, foci are the surface mass balance, i.e. the accumulation of snow on the ice cap, and the heat budget of the atmosphere above Antarctica. Insight in the surface mass balance of the Antarctic ice cap is gained by explanation, evaluation and subsequently calibration of model-simulated surface mass balance patterns using more than 1900 in situ observations. Furthermore, a method is developed to quantify the uncertainty in the local and spatially integrated surface mass balance estimate. In our study, a good correlation between the observations and model results is found, giving reliability to the results presented. The final surface mass balance estimate primarily deviates in the coastal zones of Antarctica from earlier estimates. Our results strongly suggest much higher accumulation rates than previously assumed, leading to a 15% higher overall accumulation. Unfortunately, the coastal zone is poorly covered by observations, which makes a final assessment difficult. Analysis of the heat budget of the Antarctic atmosphere clarifies the dynamics of the Antarctic boundary layer and shows the coupling to the global climate. Our results show how the boundary layer develops from the interior of Antarctica to the coast; from shallow and extremely stable to deeper, mixed but still stable. Furthermore, the effect of surface undulations on the local near surface temperature is explained. Domes and ridges have a weakening effect on the surface inversion of the temperature through enhanced divergence of the near-surface wind field. Oppositely, valleys strengthen the surface inversion. This coupling of topography and temperature causes the spatial variability of surface temperatures on scales of typical a few hundred kilometers.

  19. Early sound symbolism for vowel sounds

    PubMed Central

    Spector, Ferrinne; Maurer, Daphne

    2013-01-01

    Children and adults consistently match some words (e.g., kiki) to jagged shapes and other words (e.g., bouba) to rounded shapes, providing evidence for non-arbitrary sound–shape mapping. In this study, we investigated the influence of vowels on sound–shape matching in toddlers, using four contrasting pairs of nonsense words differing in vowel sound (/i/ as in feet vs. /o/ as in boat) and four rounded–jagged shape pairs. Crucially, we used reduplicated syllables (e.g., kiki vs. koko) rather than confounding vowel sound with consonant context and syllable variability (e.g., kiki vs. bouba). Toddlers consistently matched words with /o/ to rounded shapes and words with /i/ to jagged shapes (p < 0.01). The results suggest that there may be naturally biased correspondences between vowel sound and shape. PMID:24349684

  20. Sound radiation by a plane localized vortex

    NASA Astrophysics Data System (ADS)

    Yakovlev, P. G.

    2012-07-01

    A classical problem on small-scale fluctuations of the Rankine vortex in a compressible gas has been numerically simulated. Euler equations for a compressible gas have been solved by the CABARET method. Simulation results well predict the value of the eigenfrequency of the boundary fluctuations for the azimuthal harmonic n = 2 and almost coincide with the analytic solution. The value of the acoustic instability increment has been quantitatively predicted despite the fact that it is small and it has been revealed at a fluctuation number higher than 100.

  1. The Sound and the Fury: Adding Sound to Your PC.

    ERIC Educational Resources Information Center

    Crawford, Walt

    1996-01-01

    Addresses the concept of adding sound to existing personal computers. Describes hardware and software options and explores uses of computers equipped with sound. Sidebars summarize the development of stereo sound in multimedia products and describe the two major forms of computer sound: Musical Instrument Digital Interface and digital sound waves.…

  2. PUTATIVE STRESS REGULATED GENES OF THE ANTARCTIC MIDGE, BELGICA ANTARCTICA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Antarctica presents one of the earth’s most inhospitable environments. Though an abundance of animals have adapted to life associated with the sea in this part of the world, few animals have adapted to the rigors of a terrestrial existence. One exception is the flightless midge Belgica antarctica ...

  3. STRESS PROTEINS OF THE ANTARCTIC MIDGE, BELGICA ANTARCTICA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Antarctica presents one of the earth’s most inhospitable environments. Though an abundance of animals have adapted to life associated with the sea in this part of the world, few animals have adapted to the rigors of a terrestrial existence. One exception is the flightless midge Belgica antarctica ...

  4. Antarctica Research in the Polar Research Center of China

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Li, Y.; Liu, S.; Cole-Dai, J.

    2003-12-01

    The Polar Research Center of China (PRCC) was established in the early 1990s (formerly Polar Research Institute of China) to serve as the leading national organization for Antarctica-related research in China. Current research areas of center staff scientists include glaciology and paleoclimatology, upper atmospheric physics, polar and marine biology, and oceanagrphy. In addition to its own active research, PRCC on behalf of the China Antarctic and Arctic Administration coordinates and provides logistical support to Antarctica research activities by all Chinese scientists. The center organizes and manages the annual Chinese Research Expedition to Antarctica with participation from many other national and academic institutions. In its first decade of existence, PRCC has accumulated valuable experience in conducting and facilitating research in Antarctica, particularly in the areas of logistic support for field programs, staffing and managing the two permanent stations in Antarctica (Great Wall and Zhongshan). The successful operation of the Chinese Antarctica research program has benefitted from generous assistance from several more established national (for example, Australia, Japan and the United States) Antarctica programs and from frequent contact with international colleagues working on Antarctica research. Among the many issues and problems frequently encountered in the last decade are: (1) The scale of research activities is often seriously constrained by logistic capabilities and funding; (2) Limited computer network and library resources hamper speedy and timely access to relevant international scientific literature; (3) Acquisition of high quality scientific (field and laboratory) equipment and special supplies can be limited by funding and access to suppliers.

  5. Online estimation of lower and upper bounds for heart sound boundaries in chest sound using Convex-hull algorithm.

    PubMed

    Çağlar, F; Ozbek, I Y

    2012-01-01

    Heart sound localization in chest sound is an essential part for many heart sound cancellation algorithms. The main difficulty for heart sound localization methods is the precise determination of the onset and offset boundaries of the heart sound segment. This paper presents a novel method to estimate lower and upper bounds for the onset and offset of the heart sound segment, which can be used as anchor points for more precise estimation. For this purpose, first chest sound is divided into frames and then entropy and smoothed entropy features of these frames are extracted, and used in the Convex-hull algorithm to estimate the upper and lower bounds for heart sound boundaries. The Convex-hull algorithm constructs a special type of envelope function for entropy features and if the maximal difference between the envelope function and the entropy is larger than a certain threshold, this point is considered as a heart sound bound. The results of the proposed method are compared with a baseline method which is a modified version of a well-known heart sound localization method. The results show that the proposed method outperforms the baseline method in terms of accuracy and detection error rate. Also, the experimental results show that smoothing entropy features significantly improves the performance of both baseline and proposed methods. PMID:23366867

  6. Categorization of Sounds

    ERIC Educational Resources Information Center

    Smits, Roel; Sereno, Joan; Jongman, Allard

    2006-01-01

    The authors conducted 4 experiments to test the decision-bound, prototype, and distribution theories for the categorization of sounds. They used as stimuli sounds varying in either resonance frequency or duration. They created different experimental conditions by varying the variance and overlap of 2 stimulus distributions used in a training phase…

  7. Breaking the Sound Barrier

    ERIC Educational Resources Information Center

    Brown, Tom; Boehringer, Kim

    2007-01-01

    Students in a fourth-grade class participated in a series of dynamic sound learning centers followed by a dramatic capstone event--an exploration of the amazing Trashcan Whoosh Waves. It's a notoriously difficult subject to teach, but this hands-on, exploratory approach ignited student interest in sound, promoted language acquisition, and built…

  8. School Sound Level Study.

    ERIC Educational Resources Information Center

    California State Dept. of Education, Sacramento.

    California has conducted on-site sound surveys of 36 different schools to determine the degree of noise, and thus disturbance, within the learning environment. This report provides the methodology and results of the survey, including descriptive charts and graphs illustrating typical desirable and undesirable sound levels. Results are presented…

  9. The Bosstown Sound.

    ERIC Educational Resources Information Center

    Burns, Gary

    Based on the argument that (contrary to critical opinion) the musicians in the various bands associated with Bosstown Sound were indeed talented, cohesive individuals and that the bands' lack of renown was partially a result of ill-treatment by record companies and the press, this paper traces the development of the Bosstown Sound from its…

  10. Exploring Noise: Sound Pollution.

    ERIC Educational Resources Information Center

    Rillo, Thomas J.

    1979-01-01

    Part one of a three-part series about noise pollution and its effects on humans. This section presents the background information for teachers who are preparing a unit on sound. The next issues will offer learning activities for measuring the effects of sound and some references. (SA)

  11. Antarctica: measuring glacier velocity from satellite images

    SciTech Connect

    Lucchitta, B.K.; Ferguson, H.M.

    1986-11-28

    Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

  12. Antarctica: Measuring glacier velocity from satellite images

    USGS Publications Warehouse

    Lucchitta, B.K.; Ferguson, H.M.

    1986-01-01

    Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

  13. Low deuterium content of Lake Vanda, Antarctica

    USGS Publications Warehouse

    Ragotzkie, R.A.; Friedman, I.

    1965-01-01

    Lake Vanda in Victoria Land, Antarctica, is permanently ice-covered and permanently stratified, with warm, salty water near the bottom. Deuterium analyses of lake water from several levels indicate that the lake has a low deuterium content, and that it is stratified with respect to this isotope. This low deuterium content supports the evidence from the lake's ionic content that the saline layer is not of marine origin, and it indicates that evaporation from the ice surface has taken place. The stratification of the lake with respect to deuterium suggests that the upper and lower layers of water were formed at different times from different sources of glacial melt water.

  14. Exhumation of the Shackleton Range, Antarctica

    NASA Astrophysics Data System (ADS)

    Lucka, Nicole; Lisker, Frank; Läufer, Andreas; Spiegel, Cornelia

    2013-04-01

    The Shackleton Range is situated between 80° - 81°S and 19° - 31°W, where it forms the continuation of the Transantarctic Mountains in the Weddell Sea sector of Antarctica. There, Precambrian igneous and metamorphic basement is overlain by (meta-) sedimentary rocks of an Early Paleozoic nappe stack and post-orogenic red beds. Nappe stacking resulted from the collision of East and West Gondwana due to the closure of the Mozambique Ocean in pan-African times. The uplift and exhumation history of the Shackleton Range has been analysed earlier based on a series of vertical fission track profiles (Schäfer, 1998; Lisker et al., 1999). Zircon ages range from ~160 to 210 Ma while apatite ages between ~95 and ~170 Ma comprise a break in slope of the altitude regression at ~110 Ma, and are accompanied by mean track lengths of 12.7 - 14.1 µm (standard deviation 1.0 - 1.4 µm). These data have been interpreted qualitatively in terms of two cooling/ exhumation stages during Jurassic and mid-Cretaceous times. However, the recognition of Jurassic volcaniclastic rocks associated with the ~180 Ma Ferrar event in the vicinity of the sample locations (Buggisch et al., 1994) challenges this exhumation concept. Moreover, new fission track proxy data (Dpar) and apatite (U-Th-Sm)/He ages between 88 and 171 Ma allow thermal history modelling of the combined thermochronological data. First tentative thermal history models suggest early Mesozoic cooling followed by (post-) Jurassic heating and final cooling since the Late Cretaceous. This scenario requires burial of the Shackleton Range region, and therefore the existence of a sedimentary basin at least during the Jurassic-Early Cretaceous, and subsequent basin inversion. The thickness of the now vanished sedimentary strata did unlikely exceed 2 - 3 km. Future work including additional apatite fission track analyses will help to quantifying geometry, depth and timing of this depocentre and evaluating potential links with the coeval

  15. Boundary layer halogens in coastal Antarctica.

    PubMed

    Saiz-Lopez, Alfonso; Mahajan, Anoop S; Salmon, Rhian A; Bauguitte, Stephane J-B; Jones, Anna E; Roscoe, Howard K; Plane, John M C

    2007-07-20

    Halogens influence the oxidizing capacity of Earth's troposphere, and iodine oxides form ultrafine aerosols, which may have an impact on climate. We report year-round measurements of boundary layer iodine oxide and bromine oxide at the near-coastal site of Halley Station, Antarctica. Surprisingly, both species are present throughout the sunlit period and exhibit similar seasonal cycles and concentrations. The springtime peak of iodine oxide (20 parts per trillion) is the highest concentration recorded anywhere in the atmosphere. These levels of halogens cause substantial ozone depletion, as well as the rapid oxidation of dimethyl sulfide and mercury in the Antarctic boundary layer. PMID:17641195

  16. Long-term persistence enhances uncertainty about anthropogenic warming of Antarctica

    NASA Astrophysics Data System (ADS)

    Ludescher, Josef; Bunde, Armin; Franzke, Christian L. E.; Schellnhuber, Hans Joachim

    2016-01-01

    Previous estimates of the strength and the uncertainty of the observed Antarctic temperature trends assumed that the natural annual temperature fluctuations can be represented by an auto-regressive process of first order [AR(1)]. Here we find that this hypothesis is inadequate. We consider the longest observational temperature records in Antarctica and show that their variability is better represented by a long-term persistent process that has a propensity of large and enduring natural excursions from the mean. As a consequence, the statistical significance of the recent (presumably anthropogenic) Antarctic warming trend is lower than hitherto reported, while the uncertainty about its magnitude is enhanced. Indeed, all records except for one (Faraday/Vernadsky) fail to show a significant trend. When increasing the signal-to-noise ratio by considering appropriate averages of the local temperature series, we find that the warming trend is still not significant in East Antarctica and the Antarctic Peninsula. In West Antarctica, however, the significance of the trend is above 97.4 %, and its magnitude is between 0.08 and 0.96 °C per decade. We argue that the persistent temperature fluctuations not only have a larger impact on regional warming uncertainties than previously thought but also may provide a potential mechanism for understanding the transient weakening ("hiatus") of the regional and global temperature trends.

  17. Relative sea-level rise around East Antarctica during Oligocene glaciation

    NASA Astrophysics Data System (ADS)

    Stocchi, Paolo; Escutia, Carlota; Houben, Alexander J. P.; Vermeersen, Bert L. A.; Bijl, Peter K.; Brinkhuis, Henk; Deconto, Robert M.; Galeotti, Simone; Passchier, Sandra; Pollard, David; Brinkhuis, Henk; Escutia, Carlota; Klaus, Adam; Fehr, Annick; Williams, Trevor; Bendle, James A. P.; Bijl, Peter K.; Bohaty, Steven M.; Carr, Stephanie A.; Dunbar, Robert B.; Flores, Jose Abel; Gonzàlez, Jhon J.; Hayden, Travis G.; Iwai, Masao; Jimenez-Espejo, Francisco J.; Katsuki, Kota; Kong, Gee Soo; McKay, Robert M.; Nakai, Mutsumi; Olney, Matthew P.; Passchier, Sandra; Pekar, Stephen F.; Pross, Jörg; Riesselman, Christina; Röhl, Ursula; Sakai, Toyosaburo; Shrivastava, Prakash Kumar; Stickley, Catherine E.; Sugisaki, Saiko; Tauxe, Lisa; Tuo, Shouting; van de Flierdt, Tina; Welsh, Kevin; Yamane, Masako

    2013-05-01

    During the middle and late Eocene (~ 48-34Myr ago), the Earth's climate cooled and an ice sheet built up on Antarctica. The stepwise expansion of ice on Antarctica induced crustal deformation and gravitational perturbations around the continent. Close to the ice sheet, sea level rose despite an overall reduction in the mass of the ocean caused by the transfer of water to the ice sheet. Here we identify the crustal response to ice-sheet growth by forcing a glacial-hydro isostatic adjustment model with an Antarctic ice-sheet model. We find that the shelf areas around East Antarctica first shoaled as upper mantle material upwelled and a peripheral forebulge developed. The inner shelf subsequently subsided as lithosphere flexure extended outwards from the ice-sheet margins. Consequently the coasts experienced a progressive relative sea-level rise. Our analysis of sediment cores from the vicinity of the Antarctic ice sheet are in agreement with the spatial patterns of relative sea-level change indicated by our simulations. Our results are consistent with the suggestion that near-field processes such as local sea-level change influence the equilibrium state obtained by an ice-sheet grounding line.

  18. A network of autonomous surface ozone monitors in Antarctica: technical description and first results

    NASA Astrophysics Data System (ADS)

    Bauguitte, S. J.-B.; Brough, N.; Frey, M. M.; Jones, A. E.; Maxfield, D. J.; Roscoe, H. K.; Rose, M. C.; Wolff, E. W.

    2011-04-01

    A suite of 10 autonomous ozone monitoring units, each powered using renewable energy, was developed and built to study surface ozone in Antarctica during the International Polar Year (2007-2009). The monitoring systems were deployed in a network around the Weddell Sea sector of coastal Antarctica with a transect up onto the Antarctic Plateau. The aim was to measure for a full year, thus gaining a much-improved broader view of boundary layer ozone seasonality at different locations as well as of factors affecting the budget of surface ozone in Antarctica. Ozone mixing ratios were measured based on UV photometry using a modified version of the commercial 2B Technologies Inc. Model 202 instrument. All but one of the autonomous units measured successfully within its predefined duty cycle throughout the year, with some differences in performance dependent on power availability and ambient temperature. Mean data recovery after removal of outliers was on average 70% (range 44-83%) and precision varied between 1.5 and 8 ppbv, thus was sufficiently good to resolve year-round the main ozone features of scientific interest. We conclude that, with adequate power, and noting a minor communication problem, our units would be able to operate successfully at ambient temperatures down to -60 °C. Systems such as the one described in this paper, or derivatives of it, could therefore be deployed either as local or regional networks elsewhere in the Arctic or Antarctic. Here we present technical information and first results from the experiment.

  19. A network of autonomous surface ozone monitors in Antarctica: technical description and first results

    NASA Astrophysics Data System (ADS)

    Bauguitte, S. J.-B.; Brough, N.; Frey, M. M.; Jones, A. E.; Maxfield, D. J.; Roscoe, H. K.; Rose, M. C.; Wolff, E. W.

    2010-12-01

    A suite of 10 autonomous ozone monitors, each powered using renewable energy, was developed and built to study surface ozone in Antarctica during the International Polar Year (2007-2009). The monitoring systems were deployed in a network around the Weddell Sea sector of coastal Antarctica with a transect up onto the Antarctic Plateau. The aim was to measure for a full year, thus gaining a much-improved broader view of boundary layer ozone seasonality at different locations as well as of factors affecting the budget of surface ozone in Antarctica. Ozone mixing ratios were measured based on UV photometry using a modified version of the commercial 2B Technologies Inc. Model 202 instrument. All but one of the autonomous units measured successfully within its predefined duty cycle throughout the year, with some differences in performance dependent on power availability and ambient temperature. Mean data recovery after removal of outliers was on average 70% (range 44-83%) and precision varied between 1.5 and 8 ppbv, thus was sufficiently good to resolve year-round the main ozone features of scientific interest. We conclude that, with adequate power, and noting a minor communication problem, our units would be able to operate successfully at ambient temperatures down to -60 °C. Systems such as the one described in this paper, or derivatives of it, could therefore be deployed either as local or regional networks elsewhere in the Arctic or Antarctic. Here we present technical information and first results from the experiment.

  20. Analysis of continuous GPS measurements from southern Victoria Land, Antarctica

    USGS Publications Warehouse

    Willis, Michael J.

    2007-01-01

    Several years of continuous data have been collected at remote bedrock Global Positioning System (GPS) sites in southern Victoria Land, Antarctica. Annual to sub-annual variations are observed in the position time-series. An atmospheric pressure loading (APL) effect is calculated from pressure field anomalies supplied by the European Centre for Medium-Range Weather Forecasts (ECMWF) model loading an elastic Earth model. The predicted APL signal has a moderate correlation with the vertical position time-series at McMurdo, Ross Island (International Global Navigation Satellite System Service (IGS) station MCM4), produced using a global solution. In contrast, a local solution in which MCM4 is the fiducial site generates a vertical time series for a remote site in Victoria Land (Cape Roberts, ROB4) which exhibits a low, inverse correlation with the predicted atmospheric pressure loading signal. If, in the future, known and well modeled geophysical loads can be separated from the time-series, then local hydrological loading, of interest for glaciological and climate applications, can potentially be extracted from the GPS time-series.

  1. GIS representation of coal-bearing areas in Antarctica

    USGS Publications Warehouse

    Merrill, Matthew D.

    2016-01-01

    Understanding the distribution of coal-bearing geologic units in Antarctica provides information that can be used in sedimentary, geomorphological, paleontological, and climatological studies. This report is a digital compilation of information on Antarctica’s coal-bearing geologic units found in the literature. It is intended to be used in small-scale spatial geographic information system (GIS) investigations and as a visual aid in the discussion of Antarctica’s coal resources or in other coal-based geologic investigations. Instead of using spatially insignificant point markers to represent large coal-bearing areas, this dataset uses polygons to represent actual coal-bearing lithologic units. Specific locations of coal deposits confirmed from the literature are provided in the attribution for the coal-bearing unit polygons. Coal-sample-location data were used to confirm some reported coal-bearing geology. The age and extent of the coal deposits indicated in the literature were checked against geologic maps ranging from local scale at 1:50,000 to Antarctic continental scale at 1:5,000,000; if satisfactory, the map boundaries were used to generate the polygons for the coal-bearing localities.

  2. Hexabromocyclododecane flame retardant in Antarctica: Research stations as sources.

    PubMed

    Chen, Da; Hale, Robert C; La Guardia, Mark J; Luellen, Drew; Kim, Stacy; Geisz, Heidi N

    2015-11-01

    Historical persistent organic pollutants (POPs) are banned from Antarctica under international treaty; but contemporary-use POPs can enter as additives within polymer and textile products. Over their useful lives these products may release additives in-situ. Indeed, we observed 226 and 109 ng/g dry weight (dw) of the total concentrations of α-, β- and γ-hexabromocyclododecane (HBCD) in indoor dust from McMurdo Station (U.S.) and Scott Station (New Zealand), respectively. Sewage sludge collected from wastewater treatment facilities at these stations exhibited ∑HBCD of 45 and 69 ng/g dw, respectively. Contaminants originally within the bases may exit to the local outdoor environment via wastewaters. Near McMurdo, maximum ∑HBCD levels in surficial marine sediments and aquatic biota (invertebrates and fish) were 2350 ng/g (total organic carbon basis) and 554 ng/g lipid weight, respectively. Levels declined with distance from McMurdo. Our results illustrate that Antarctic research stations serve as local HBCD sources to the pristine Antarctic environment. PMID:26312743

  3. Sparse Spectrotemporal Coding of Sounds

    NASA Astrophysics Data System (ADS)

    Klein, David J.; König, Peter; Körding, Konrad P.

    2003-12-01

    Recent studies of biological auditory processing have revealed that sophisticated spectrotemporal analyses are performed by central auditory systems of various animals. The analysis is typically well matched with the statistics of relevant natural sounds, suggesting that it produces an optimal representation of the animal's acoustic biotope. We address this topic using simulated neurons that learn an optimal representation of a speech corpus. As input, the neurons receive a spectrographic representation of sound produced by a peripheral auditory model. The output representation is deemed optimal when the responses of the neurons are maximally sparse. Following optimization, the simulated neurons are similar to real neurons in many respects. Most notably, a given neuron only analyzes the input over a localized region of time and frequency. In addition, multiple subregions either excite or inhibit the neuron, together producing selectivity to spectral and temporal modulation patterns. This suggests that the brain's solution is particularly well suited for coding natural sound; therefore, it may prove useful in the design of new computational methods for processing speech.

  4. Sedimentation Waves on the Martian North Polar Cap: Analogy with Megadunes in Antarctica

    NASA Astrophysics Data System (ADS)

    Herny, C.; Masse, M.; Bourgeois, O.; Carpy, S.; Le Mouelic, S.; Appéré, T.; Smith, I. B.; Spiga, A.; Perret, L.; Rodriguez, S.; Piquet, T.; Gaudin, D.; Le Menn, E.

    2014-12-01

    Complex feedbacks between katabatic winds and the cryosphere may lead to the development of sedimentation waves at the surface of ice sheets. These have been first described and named megadunes in Antarctica. Here we use topographic data, optical images, spectroscopic data and radar soundings, acquired by Mars orbiters, to show that the surface of the Martian North Polar Cap displays two superimposed sets of sedimentation waves with differing wavelengths. These sedimentation waves grow and migrate upwind in response to the development of periodic accumulation/ablation patterns controlled by katabatic winds. They have similarities with Antarctic megadunes regarding their surface morphology, texture, grain size, and internal stratigraphic architecture. Based on this analogy, we are currently developing a model of ice/wind interaction at the surface of ice sheets. In Antarctica the accumulation processes on megadunes fields is generally attributed to the wind-blown snow transport while on sedimentation waves of the North Polar Cap of Mars the accumulation seems to be dominated by sublimation/condensation processes at the surface. The model is designed to explore the implication of the water vapor mass transfer and heat transfer on the development of sedimentation waves both on Mars and Earth.

  5. Ocean access to a cavity beneath Totten Glacier in East Antarctica

    NASA Astrophysics Data System (ADS)

    Greenbaum, J. S.; Blankenship, D. D.; Young, D. A.; Richter, T. G.; Roberts, J. L.; Aitken, A. R. A.; Legresy, B.; Schroeder, D. M.; Warner, R. C.; van Ommen, T. D.; Siegert, M. J.

    2015-04-01

    Totten Glacier, the primary outlet of the Aurora Subglacial Basin, has the largest thinning rate in East Antarctica. Thinning may be driven by enhanced basal melting due to ocean processes, modulated by polynya activity. Warm modified Circumpolar Deep Water, which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the nearby continental shelf beneath 400 to 500 m of cool Antarctic Surface Water. Here we derive the bathymetry of the sea floor in the region from gravity and magnetics data as well as ice-thickness measurements. We identify entrances to the ice-shelf cavity below depths of 400 to 500 m that could allow intrusions of warm water if the vertical structure of inflow is similar to nearby observations. Radar sounding reveals a previously unknown inland trough that connects the main ice-shelf cavity to the ocean. If thinning trends continue, a larger water body over the trough could potentially allow more warm water into the cavity, which may, eventually, lead to destabilization of the low-lying region between Totten Glacier and the similarly deep glacier flowing into the Reynolds Trough. We estimate that at least 3.5 m of eustatic sea level potential drains through Totten Glacier, so coastal processes in this area could have global consequences.

  6. Lateral isotopic discontinuity in the lower crust: an example from Antarctica

    SciTech Connect

    Kalamarides, R.I.; Berg, J.H.; Hank, R.A.

    1987-09-04

    The lower continental crust is one of the least known variables in the crust-mantle evolutionary equation. In order to study the nature and compositional heterogeneity of the lower crust, more than 20 inclusions of lower crustal granulites in volcanic rocks from the McMurdo Sound region of Antarctica were analyzed for strontium and oxygen isotopes. These inclusions were erupted from volcanic centers covering an area of 12,000 square kilometers. Along with results from analyses of major and trace elements, the isotopic data reveal a profound discontinuity in the composition and probably the age of the lower crust that coincides with the boundary between the Transantarctic Mountains and the Ross Embayment. Although this topographic boundary between East and West Antarctica is largely a Cenozoic development, which apparently reflects a simple subvertical faulting relationship due to crustal rifting, the isotopic differences in the lower crust across the boundary suggest that the current faulting and rifting may coincide with an older crustal suture, the age of which is uncertain.

  7. Sound-Imitation Word Recognition for Environmental Sounds

    NASA Astrophysics Data System (ADS)

    Ishihara, Kazushi; Komatani, Kazunori; Ogata, Tetsuya; Okuno, Hiroshi G.

    Environmental sounds are very helpful in understanding environmental situations and in telling the approach of danger, and sound-imitation words (sound-related onomatopoeia) are important expressions to inform such sounds in human communication, especially in Japanese language. In this paper, we design a method to recognize sound-imitation words (SIWs) for environmental sounds. Critical issues in recognizing SIW are how to divide an environmental sound into recognition units and how to resolve representation ambiguity of the sounds. To solve these problems, we designed three-stage procedure that transforms environmental sounds into sound-imitation words, and phoneme group expressions that can represent ambiguous sounds. The three-stage procedure is as follows: (1) a whole waveform is divided into some chunks, (2) the chunks are transformed into sound-imitation syllables by phoneme recognition, (3) a sound-imitation word is constructed from sound-imitation syllables according to the requirements of the Japanese language. Ambiguity problem is that an environmental sound is often recognized differently by different listeners even under the same situation. Phoneme group expressions are new phonemes for environmental sounds, and they can express multiple sound-imitation words by one word. We designed two sets of phoneme groups: ``a set of basic phoneme group'' and ``a set of articulation-based phoneme group'' to absorb the ambiguity. Based on subjective experiments, the set of basic phoneme groups proved more appropriate to represent environmental sounds than the articulation-based one or a set of normal Japaneses phonemes.

  8. The sound manifesto

    NASA Astrophysics Data System (ADS)

    O'Donnell, Michael J.; Bisnovatyi, Ilia

    2000-11-01

    Computing practice today depends on visual output to drive almost all user interaction. Other senses, such as audition, may be totally neglected, or used tangentially, or used in highly restricted specialized ways. We have excellent audio rendering through D-A conversion, but we lack rich general facilities for modeling and manipulating sound comparable in quality and flexibility to graphics. We need coordinated research in several disciplines to improve the use of sound as an interactive information channel. Incremental and separate improvements in synthesis, analysis, speech processing, audiology, acoustics, music, etc. will not alone produce the radical progress that we seek in sonic practice. We also need to create a new central topic of study in digital audio research. The new topic will assimilate the contributions of different disciplines on a common foundation. The key central concept that we lack is sound as a general-purpose information channel. We must investigate the structure of this information channel, which is driven by the cooperative development of auditory perception and physical sound production. Particular audible encodings, such as speech and music, illuminate sonic information by example, but they are no more sufficient for a characterization than typography is sufficient for characterization of visual information. To develop this new conceptual topic of sonic information structure, we need to integrate insights from a number of different disciplines that deal with sound. In particular, we need to coordinate central and foundational studies of the representational models of sound with specific applications that illuminate the good and bad qualities of these models. Each natural or artificial process that generates informative sound, and each perceptual mechanism that derives information from sound, will teach us something about the right structure to attribute to the sound itself. The new Sound topic will combine the work of computer

  9. Phylogeography of microbial phototrophs in the dry valleys of the high Himalayas and Antarctica

    PubMed Central

    Schmidt, S. K.; Lynch, R. C.; King, A. J.; Karki, D.; Robeson, M. S.; Nagy, L.; Williams, M. W.; Mitter, M. S.; Freeman, K. R.

    2011-01-01

    High-elevation valleys in dry areas of the Himalayas are among the most extreme, yet least explored environments on Earth. These barren, rocky valleys are subjected to year-round temperature fluctuations across the freezing point and very low availability of water and nutrients, causing previous workers to hypothesize that no photoautotrophic life (primary producers) exists in these locations. However, there has been no work using modern biogeochemical or culture-independent molecular methods to test the hypothesis that photoautotrophs are absent from high Himalayan soil systems. Here, we show that although microbial biomass levels are as low as those of the Dry Valleys of Antarctica, there are abundant microbial photoautotrophs, displaying unexpected phylogenetic diversity, in barren soils from just below the permanent ice line of the central Himalayas. Furthermore, we discovered that one of the dominant algal clades from the high Himalayas also contains the dominant algae in culture-independent surveys of both soil and ice samples from the Dry Valleys of Antarctica, revealing an unexpected link between these environmentally similar but geographically very distant systems. Phylogenetic and biogeographic analyses demonstrated that although this algal clade is globally distributed to other high-altitude and high-latitude soils, it shows significant genetic isolation by geographical distance patterns, indicating local adaptation and perhaps speciation in each region. Our results are the first to demonstrate the remarkable similarities of microbial life of arid soils of Antarctica and the high Himalayas. Our findings are a starting point for future comparative studies of the dry valleys of the Himalayas and Antarctica that will yield new insights into the cold and dry limits to life on Earth. PMID:20826485

  10. Heart murmurs and other sounds

    MedlinePlus

    Chest sounds - murmurs; Heart sounds - abnormal; Murmur - innocent; Innocent murmur; Systolic heart murmur; Diastolic heart murmur ... classified ("graded") depending on how loud the murmur sounds with a stethoscope. The grading is on a ...

  11. Sound as artifact

    NASA Astrophysics Data System (ADS)

    Benjamin, Jeffrey L.

    A distinguishing feature of the discipline of archaeology is its reliance upon sensory dependant investigation. As perceived by all of the senses, the felt environment is a unique area of archaeological knowledge. It is generally accepted that the emergence of industrial processes in the recent past has been accompanied by unprecedented sonic extremes. The work of environmental historians has provided ample evidence that the introduction of much of this unwanted sound, or "noise" was an area of contestation. More recent research in the history of sound has called for more nuanced distinctions than the noisy/quiet dichotomy. Acoustic archaeology tends to focus upon a reconstruction of sound producing instruments and spaces with a primary goal of ascertaining intentionality. Most archaeoacoustic research is focused on learning more about the sonic world of people within prehistoric timeframes while some research has been done on historic sites. In this thesis, by way of a meditation on industrial sound and the physical remains of the Quincy Mining Company blacksmith shop (Hancock, MI) in particular, I argue for an acceptance and inclusion of sound as artifact in and of itself. I am introducing the concept of an individual sound-form, or sonifact , as a reproducible, repeatable, representable physical entity, created by tangible, perhaps even visible, host-artifacts. A sonifact is a sound that endures through time, with negligible variability. Through the piecing together of historical and archaeological evidence, in this thesis I present a plausible sonifactual assemblage at the blacksmith shop in April 1916 as it may have been experienced by an individual traversing the vicinity on foot: an 'historic soundwalk.' The sensory apprehension of abandoned industrial sites is multi-faceted. In this thesis I hope to make the case for an acceptance of sound as a primary heritage value when thinking about the industrial past, and also for an increased awareness and acceptance

  12. Ozone and temperature profiles over McMurdo Station Antarctica in the Spring of 1989

    SciTech Connect

    Deshler, T.; Hofmann, D.J.; Hereford, J.V.; Sutter, C.B. )

    1990-02-01

    Ozone and temperature were measured in 39 balloon soundings at McMurdo station Antarctica (78{degree}S) in the spring of 1989. Compared to 1986 and 1988 the stratosphere was colder and ozone depletion worse. Compared to 1987 the stratosphere warmed earlier but ozone depletion was similar, both in the magnitude and rate of depletion. Within regions of the atmosphere in 1989 ozone depletion was between 80 and 98% complete. This was again similar to 1987 and suggests that conditions observed in 1987 exceeded the minimum required for rapid and complete ozone depletion. As in previous years ozone was destroyed primarily between 12 and 20 km and there were several short periods, < 5 days, when rapid depletion was observed.

  13. Applications of Subspace Seismicity Detection in Antarctica

    NASA Astrophysics Data System (ADS)

    Myers, E. K.; Aster, R. C.; Benz, H.; McMahon, N. D.; McNamara, D. E.; Lough, A. C.; Wiens, D. A.; Wilson, T. J.

    2014-12-01

    Subspace detection can improve event recognition by enhancing the completeness of earthquake catalogs and by improving the characterization and interpretation of seismic events, particularly in regions of clustered seismicity. Recent deployments of dense networks of seismometers enable subspace detection methods to be more broadly applied to intraplate Antarctica, where historically very limited and sporadic network coverage has inhibited understanding of dynamic glacial, volcanic, and tectonic processes. In particular, recent broad seismographic networks such as POLENET/A-Net and AGAP provide significant new opportunities for characterizing and understanding the low seismicity rates of this continent. Our methodology incorporates three-component correlation to detect events in a statistical and adaptive framework. Detection thresholds are statistically assessed using phase-randomized template correlation levels. As new events are detected and the set of subspace basis vectors is updated, the algorithm can also be directed to scan back in a search for weaker prior events that have significant correlations with the updated basis vectors. This method has the resolving power to identify previously undetected areas of seismic activity under very low signal-to-noise conditions, and thus holds promise for revealing new seismogenic phenomena within and around Antarctica. In this study we investigate two intriguing seismogenic regions and demonstrate the methodology, reporting on a subspace detection-based study of recently identified clusters of deep long-period magmatic earthquakes in Marie Byrd Land, and on shallow icequakes that are dynamically triggered by teleseismic surface waves.

  14. Cenozoic motion between East and West Antarctica

    PubMed

    Cande; Stock; Muller; Ishihara

    2000-03-01

    The West Antarctic rift system is the result of late Mesozoic and Cenozoic extension between East and West Antarctica, and represents one of the largest active continental rift systems on Earth. But the timing and magnitude of the plate motions leading to the development of this rift system remain poorly known, because of a lack of magnetic anomaly and fracture zone constraints on seafloor spreading. Here we report on magnetic data, gravity data and swath bathymetry collected in several areas of the south Tasman Sea and northern Ross Sea. These results enable us to calculate mid-Cenozoic rotation parameters for East and West Antarctica. These rotations show that there was roughly 180 km of separation in the western Ross Sea embayment in Eocene and Oligocene time. This episode of extension provides a tectonic setting for several significant Cenozoic tectonic events in the Ross Sea embayment including the uplift of the Transantarctic Mountains and the deposition of large thicknesses of Oligocene sediments. Inclusion of this East-West Antarctic motion in the plate circuit linking the Australia, Antarctic and Pacific plates removes a puzzling gap between the Lord Howe rise and Campbell plateau found in previous early Tertiary reconstructions of the New Zealand region. Determination of this East-West Antarctic motion also resolves a long standing controversy regarding the contribution of deformation in this region to the global plate circuit linking the Pacific to the rest of the world. PMID:10724159

  15. The Landsat Image Mosaic of Antarctica

    USGS Publications Warehouse

    Bindschadler, R.; Vornberger, P.; Fleming, A.; Fox, A.; Mullins, J.; Binnie, D.; Paulsen, S.J.; Granneman, B.; Gorodetzky, D.

    2008-01-01

    The Landsat Image Mosaic of Antarctica (LIMA) is the first true-color, high-spatial-resolution image of the seventh continent. It is constructed from nearly 1100 individually selected Landsat-7 ETM+ scenes. Each image was orthorectified and adjusted for geometric, sensor and illumination variations to a standardized, almost seamless surface reflectance product. Mosaicing to avoid clouds produced a high quality, nearly cloud-free benchmark data set of Antarctica for the International Polar Year from images collected primarily during 1999-2003. Multiple color composites and enhancements were generated to illustrate additional characteristics of the multispectral data including: the true appearance of the surface; discrimination between snow and bare ice; reflectance variations within bright snow; recovered reflectance values in regions of sensor saturation; and subtle topographic variations associated with ice flow. LIMA is viewable and individual scenes or user defined portions of the mosaic are downloadable at http://lima.usgs.gov. Educational materials associated with LIMA are available at http://lima.nasa.gov.

  16. Exploring Noise: Sound Pollution.

    ERIC Educational Resources Information Center

    Rillo, Thomas J.

    1979-01-01

    The second part of a three-part series, this article describes sound measurement, effects, and indoor learning activities. Thirty elementary school activities are described with appropriate grade levels specified. (Author/CS)

  17. The sound of activism.

    PubMed

    Sandstrom, B; Vetter, C

    2001-01-01

    ABSTRACT A longtime advocate for female empowerment and equality, Boden Sandstrom has worked for political change in many arenas. In the 1960s, she began a career as a librarian, but soon made activism her full-time job, working for feminist, leftist and socialist causes. In the 1970s, she found a way to turn her lifelong passion for music into a career as a sound engineer. Once established in that profession, she began donating her services to political events, marches, demonstrations, and rallies. After thirteen years of running her own company, called Woman Sound,Inc. (later City Sound Productions,Inc.), she turned to the study of ethnomusicology. She is now Program Manager and Lecturer for the Ethnomusicology Program at the University of Maryland, where she is also working on her doctorate in that subject. She continues to freelance as a sound engineer and serve as a technical producer for major events. PMID:24802836

  18. Sound Visualization and Holography

    ERIC Educational Resources Information Center

    Kock, Winston E.

    1975-01-01

    Describes liquid surface holograms including their application to medicine. Discusses interference and diffraction phenomena using sound wave scanning techniques. Compares focussing by zone plate to holographic image development. (GH)

  19. Velocity of Sound

    ERIC Educational Resources Information Center

    Gillespie, A.

    1975-01-01

    Describes a method for the determination of the velocity of sound using a dual oscilloscope on which is displayed the sinusoidal input into a loudspeaker and the signal picked up by a microphone. (GS)

  20. Active sound attenuation across a double wall structure

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.; Shepherd, Kevin P.

    1991-01-01

    The possibility of achieving significant local and global sound attenuation across a flat double wall is demonstrated. It is also shown that sound can be prevented from entering the interior of a cabinlike environment. The approach used is unlike established active noise control techniques.

  1. Sound speed in downhole flow measurement.

    PubMed

    Ünalmis, Ö Haldun

    2016-07-01

    This paper describes the use of sound speed in flow measurement applications in the high-pressure/high-temperature downhole environment. The propagation speed of a sound wave is a powerful tool to extract useful information from a flowing fluid medium in pipe whether the medium consists of a single-phase or multiphase flow. Considering the complex nature of the flow patterns and changing phase fractions from reservoir to surface, utilizing the propagation speed of sound of a fluid mixture is not a trivial task, especially if the interest is real-time flow measurement. The demanding applications span a wide spectrum from noisy medium originating from fast-moving gas/liquid flows to quiet medium originating from slow-moving liquid/liquid flows. In the current work, multiple flow loop tests are conducted in different facilities to evaluate the direct use of sound speed in flow rate measurement and the results are associated with real-life field examples. A tool analysis map is developed that addresses the use of sound speed for flow measurement under different scenarios. Although most examples are based on strain-based local sensing of the flow, the use of sound speed is independent of the methodology and can be implemented by other methods such as acoustic-based distributed sensing. PMID:27475167

  2. Sound Stuff? Naïve materialism in middle-school students' conceptions of sound

    NASA Astrophysics Data System (ADS)

    Eshach, Haim; Schwartz, Judah L.

    2006-06-01

    Few studies have dealt with students’ preconceptions of sounds. The current research employs Reiner et al. (2000) substance schema to reveal new insights about students’ difficulties in understanding this fundamental topic. It aims not only to detect whether the substance schema is present in middle school students’ thinking, but also examines how students use the schema’s properties. It asks, moreover, whether the substance schema properties are used as islands of local consistency or whether one can identify more global coherent consistencies among the properties that the students use to explain the sound phenomena. In-depth standardized open-ended interviews were conducted with ten middle school students. Consistent with the substance schema, sound was perceived by our participants as being pushable, frictional, containable, or transitional. However, sound was also viewed as a substance different from the ordinary with respect to its stability, corpuscular nature, additive properties, and inertial characteristics. In other words, students’ conceptions of sound do not seem to fit Reiner et al.’s schema in all respects. Our results also indicate that students’ conceptualization of sound lack internal consistency. Analyzing our results with respect to local and global coherence, we found students’ conception of sound is close to diSessa’s “loosely connected, fragmented collection of ideas.” The notion that sound is perceived only as a “sort of a material,” we believe, requires some revision of the substance schema as it applies to sound. The article closes with a discussion concerning the implications of the results for instruction.

  3. Ecological sounds affect breath duration more than artificial sounds.

    PubMed

    Murgia, Mauro; Santoro, Ilaria; Tamburini, Giorgia; Prpic, Valter; Sors, Fabrizio; Galmonte, Alessandra; Agostini, Tiziano

    2016-01-01

    Previous research has demonstrated that auditory rhythms affect both movement and physiological functions. We hypothesized that the ecological sounds of human breathing can affect breathing more than artificial sounds of breathing, varying in tones for inspiration and expiration. To address this question, we monitored the breath duration of participants exposed to three conditions: (a) ecological sounds of breathing, (b) artificial sounds of breathing having equal temporal features as the ecological sounds, (c) no sounds (control). We found that participants' breath duration variability was reduced in the ecological sound condition, more than in the artificial sound condition. We suggest that ecological sounds captured the timing of breathing better than artificial sounds, guiding as a consequence participants' breathing. We interpreted our results according to the Theory of Event Coding, providing further support to its validity, and suggesting its possible extension in the domain of physiological functions which are both consciously and unconsciously controlled. PMID:25637249

  4. Major Subglacial Meltwater Channels Reveal Former Dynamic Ice Sheet in West Antarctica

    NASA Astrophysics Data System (ADS)

    Rose, Kathryn; Ross, Neil; Bingham, Robert; Corr, Hugh; Ferraccioli, Fausto; Jordan, Tom; LeBrocq, Anne; Rippin, David; Siegert, Martin

    2014-05-01

    The Eocene-Oligocene boundary (ca. 34 Ma) marks the onset of widespread, continental-scale glaciation in Antarctica, due to declining atmospheric carbon dioxide levels and the opening of the Drake Passage. The marine-based West Antarctic Ice Sheet (WAIS) is considered highly susceptible to change, experiencing numerous oscillations since its formation. In order to assess how past changes to the WAIS are relevant for understanding its future behaviour, it is important to comprehend the glaciological processes involved in those changes. Central to this is an appreciation of climate and ice flow regimes, in particular the extent to which former ice sheets have experienced surface melting (as in Greenland today). Geomorphic analysis of subglacial topography has played a key role in reconstructing the nature of former ice masses in Antarctica, as landscape form can be linked to glacial process. While radio-echo sounding (RES) is the primary tool used to map boundary conditions beneath ice sheets, recent developments have demonstrated that satellite imagery of the ice surface can provide insights into subglacial topography, where RES is unavailable. Using this combination of datasets, we have identified a series of major, elongate subglacial features, which we interpret as preserved subglacial channels, developed through the action of water. They are incised into a subglacial plateau in the region between the Möller and Foundation ice streams (MIS and FIS, respectively), in West Antarctica. The channels are observed across an area of ~17,700 km2 and extend 200 km inland from the grounding line. They are located below sea level and track over present-day reverse slopes, indicating a subglacial (rather than pre-glacial) fluvial origin. In order to form, these channels require significant, probably periodic (seasonal), meltwater inputs to the base of the ice sheet. We suggest the channels are the result of meltwater inputs to the subglacial environment from the ice surface

  5. Climatological observations and predicted sublimation rates at Lake Hoare, Antarctica.

    USGS Publications Warehouse

    Clow, G.D.; McKay, C.P.; Simmons, G.M., Jr.; Wharton, R.A., Jr.

    1988-01-01

    In December 1985, an automated meteorological station was established at Lake Hoare in the dry valley region of Antarctica. Here, we report on the first year-round observations available for any site in Taylor Valley. This dataset augments the year-round data obtained at Lake Vanda (Wright Valley) by winter-over crews during the late 1960s and early 1970s. The mean annual solar flux at Lake Hoare was 92 W m-2 during 1986, the mean air temperature -17.3 degrees C, and the mean 3-m wind speed 3.3 m s-1. The local climate is controlled by the wind regime during the 4-month sunless winter and by seasonal and diurnal variations in the incident solar flux during the remainder of the year. Temperature increases of 20 degrees-30 degrees C are frequently observed during the winter due to strong fo??hn winds descending from the Polar Plateau. A model incorporating nonsteady molecular diffusion into Kolmogorov-scale eddies in the interfacial layer and similarity-theory flux-profiles in the surface sublayer, is used to determine the rate of ice sublimation from the acquired meteorological data. Despite the frequent occurrence of strong winter fo??hns, the bulk of the annual ablation occurs during the summer due to elevated temperatures and persistent moderate winds. The annual ablation from Lake Hoare is estimated to have been 35.0 +/- 6.3 cm for 1986.

  6. Turbulent Mixing in the Ocean and Shelf Seas Surrounding Antarctica

    NASA Astrophysics Data System (ADS)

    Padman, L.

    2006-12-01

    Ocean turbulence and mixing data have been collected from the Southern Ocean and coastal seas surrounding Antarctica since the early 1990's. I summarize these observations, discuss their implications for parameterization of diapycnal mixing in southern seas, and identify regions and processes deserving of further study. Mixing data have been acquired from: the western Weddell Sea; Maud Rise in the eastern Weddell Sea; the Bellingshausen Sea continental shelf; the northwest Ross Sea; the shelf break and inner shelf near the Mertz Glacier Tongue; Drake Passage; the region surrounding the South Scotia Ridge; and locations near the Kerguelen Plateau and the adjacent Antarctic coastal zone. Vertical diffusivities estimated for these diverse regions span at least three orders of magnitude. The different regions exhibit a variety of primary mechanisms for mixing including shear-driven instabilities, nonlinear equation-of-state effects (cabbeling and thermobaricity), double diffusion, and boundary-layer stresses and buoyancy exchange. Energy sources include density flows, extreme surface forcing by cold coastal katabatic winds, tide-driven mixing in the benthic layer, and in the pycnocline due to locally strong baroclinic tides; downward propagation of wind-forced near-inertial waves, and flow interactions with large-scale topographic features. From this review I identify regions and processes for which we presently have little information on which to base mixing parameterizations, and suggest field and analysis activities to overcome these limitations in the representation of mixing in Southern Ocean and global models.

  7. Biodiversity of air-borne microorganisms at Halley Station, Antarctica.

    PubMed

    Pearce, David A; Hughes, K A; Lachlan-Cope, T; Harangozo, S A; Jones, A E

    2010-03-01

    A study of air-borne microbial biodiversity over an isolated scientific research station on an ice-shelf in continental Antarctica was undertaken to establish the potential source of microbial colonists. The study aimed to assess: (1) whether microorganisms were likely to have a local (research station) or distant (marine or terrestrial) origin, (2) the effect of changes in sea ice extent on microbial biodiversity and (3) the potential human impact on the environment. Air samples were taken above Halley Research Station during the austral summer and austral winter over a 2-week period. Overall, a low microbial biodiversity was detected, which included many sequence replicates. No significant patterns were detected in the aerial biodiversity between the austral summer and the austral winter. In common with other environmental studies, particularly in the polar regions, many of the sequences obtained were from as yet uncultivated organisms. Very few marine sequences were detected irrespective of the distance to open water, and around one-third of sequences detected were similar to those identified in human studies, though both of these might reflect prevailing wind conditions. The detected aerial microorganisms were markedly different from those obtained in earlier studies over the Antarctic Peninsula in the maritime Antarctic. PMID:20091326

  8. Postspreading rifting in the Adare Basin, Antarctica: Regional tectonic consequences

    NASA Astrophysics Data System (ADS)

    Granot, R.; Cande, S. C.; Stock, J. M.; Davey, F. J.; Clayton, R. W.

    2010-08-01

    Extension during the middle Cenozoic (43-26 Ma) in the north end of the West Antarctic rift system (WARS) is well constrained by seafloor magnetic anomalies formed at the extinct Adare spreading axis. Kinematic solutions for this time interval suggest a southward decrease in relative motion between East and West Antarctica. Here we present multichannel seismic reflection and seafloor mapping data acquired within and near the Adare Basin on a recent geophysical cruise. We have traced the ANTOSTRAT seismic stratigraphic framework from the northwest Ross Sea into the Adare Basin, verified and tied to DSDP drill sites 273 and 274. Our results reveal three distinct periods of tectonic activity. An early localized deformational event took place close to the cessation of seafloor spreading in the Adare Basin (˜24 Ma). It reactivated a few normal faults and initiated the formation of the Adare Trough. A prominent pulse of rifting in the early Miocene (˜17 Ma) resulted in normal faulting that initiated tilted blocks. The overall trend of structures was NE-SW, linking the event with the activity outside the basin. It resulted in major uplift of the Adare Trough and marks the last extensional phase of the Adare Basin. Recent volcanic vents (Pliocene to present day) tend to align with the early Miocene structures and the on-land Hallett volcanic province. This latest phase of tectonic activity also involves near-vertical normal faulting (still active in places) with negligible horizontal consequences. The early Miocene extensional event found within the Adare Basin does not require a change in the relative motion between East and West Antarctica. However, the lack of subsequent rifting within the Adare Basin coupled with the formation of the Terror Rift and an on-land and subice extension within the WARS require a pronounced change in the kinematics of the rift. These observations indicate that extension increased southward, therefore suggesting that a major change in

  9. India-East Antarctica conjugate margins: rift-shear tectonic setting inferred from gravity and bathymetry data

    NASA Astrophysics Data System (ADS)

    Chand, Shyam; Radhakrishna, M.; Subrahmanyam, C.

    2001-02-01

    The Eastern Continental Margin of India (ECMI) has evolved as a consequence of breakup of India from East Antarctica during the Early Cretaceous (ca. 130 Ma). The conjugate margin of ECMI in East Antarctica is represented by the margin extending from Gunneris Ridge in the west to about 95°E in the east. To understand the isostatic compensation mechanism operating beneath these conjugate margins, we have examined the cross spectral correlation between gravity and bathymetry along 21 profiles across the ECMI and 16 profiles across the conjugate East Antarctica Margin using both ship and satellite-derived gravity data. The ECMI is considered as a composite of two segments, one north of 16°N extending beyond 20°N, which is based on its rifted margin character, and the other, south of 16°N extending up to Sri Lanka, which has a transform-rift character. Similarly, the conjugate margin of East Antarctica is also considered to be a composite of two segments, west and east of the central bulge at 50-55°E. Admittance analysis and comparison with various isostatic models suggest a flexural plate model with an elastic thickness of 10-25 km for the northern segment of ECMI and its conjugate segment which is the east Enderby land Margin, comparable to results obtained from the eastern North American Margin. For the southern segment of ECMI, low elastic plate thickness of less than 5 km or a local compensation is obtained with matching results for the west Enderby land Margin. These, in turn, appear comparable to the low Te values inferred for the Ghana transform margin of North Africa and Grand Banks Margin of eastern Canada, thereby indicating that the southern segment of ECMI and its conjugate in East Antarctica have developed as a consequence of shearing rather than rifting in the early stages of continental separation.

  10. Occurrence and turnover of DMSP and DMS in deep waters of the Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Rellinger, Alison N.; Kiene, Ronald P.; del Valle, Daniela A.; Kieber, David J.; Slezak, Doris; Harada, Hyakubun; Bisgrove, John; Brinkley, Jordan

    2009-05-01

    High concentrations of the phytoplankton metabolite dimethylsulfoniopropionate (DMSP) and its degradation product dimethylsulfide (DMS) are associated with blooms of Phaeocystis antarctica in the Ross Sea, Antarctica. Episodic and rapid vertical export of Phaeocystis biomass to deep water has been reported for the Ross Sea, therefore we examined the distribution and microbial consumption rates of DMSP and DMS throughout the sub-euphotic water column. Total DMSP (dissolved+particulate; DMSPt) was present at 0.5-22 nM at depths between 70 and 690 m during both the early bloom (November) and the late bloom (January). Sub-euphotic peaks of DMSP were sometimes associated with mid-water temperature maxima, and elevated DMSP below 70 m was found mainly in water masses characterized as Modified Circumpolar Deep Water or Antarctic Shelf Water. Overall, 50-94% of the integrated water-column DMSPt was found below the euphotic zone. At one station during the early bloom, local maxima of DMSPt (14 nM) and DMS (20 nM) were observed between 113 and 240 m and these maxima corresponded with high chlorophyll a concentrations, P. antarctica cell numbers, and Fv/Fm (the quantum yield of photosystem II). During the late bloom, a sub-euphotic maximum of DMSPt (15.8 nM) at 250 m cooccurred with peaks of chlorophyll a concentration, DMSP lyase activity, bacterial production and dissolved DMSP consumption rates. DMSP turnover contributed ˜12% of the bacterial carbon demand between 200 and 400 m. DMS concentrations peaked at 286 m but the maximum concentration (0.42 nM) was far lower than observed during the early bloom, probably because of relatively rapid biological consumption of DMS (1-3 turnovers per day) which, in turn, contributed to elevated dissolved dimethylsulfoxide (DMSO) concentrations. Relatively stable DMSPt distributions at some sites suggest that rapid sinking of Phaeocystis biomass is probably not the major mechanism responsible for mesopelagic DMSP accumulations. Rather

  11. Proposal to protect marine areas around Antarctica

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2012-05-01

    Forty percent of Antarctica's Southern Ocean should be protected in a network of marine protected areas (MPAs) and no-take marine reserves, according to a 21 May report by the Antarctic Ocean Alliance, which is composed of about 20 environmental groups. The protected areas should include the 19 Antarctic marine habitats outlined in the report, along with existing MPAs and areas identified through previous conservation and planning analyses, the report notes. Protected areas should include the Antarctic Peninsula, the Weddell and Ross seas, the Indian Ocean Benthic Environment, and Pacific seamounts, according to the report. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which manages living resources for the Southern Ocean, has already agreed to establish an initial network of Antarctic MPAs this year, the report states.

  12. Ice-shelf melting around Antarctica.

    PubMed

    Rignot, E; Jacobs, S; Mouginot, J; Scheuchl, B

    2013-07-19

    We compare the volume flux divergence of Antarctic ice shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and mass balance. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making ice-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne ice shelves covering two-thirds of the total ice-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific ice shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic ice shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines. PMID:23765278

  13. Ice-Shelf Melting Around Antarctica

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Jacobs, S.; Mouginot, J.; Scheuchl, B.

    2013-07-01

    We compare the volume flux divergence of Antarctic ice shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and mass balance. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making ice-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne ice shelves covering two-thirds of the total ice-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific ice shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic ice shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines.

  14. Volcanic earthquake swarms at Mt. Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Kaminuma, Katsutada; Ueki, Sadato; Juergen, Kienle

    1985-04-01

    Mount Erebus is an active volcano in Antarctica located on Ross Island. A convecting lava lake occupies the summit crater of Mt. Erebus. Since December 1980 the seismic activity of Mt. Erebus has been continuously monitored using a radio-telemetered network of six seismic stations. The seismic activity observed by the Ross Island network during the 1982-1983 field season shows that: (1)Strombolian eruptions occur frequently at the Erebus summit lava lake at rates of 2-5 per day; (2)centrally located earthquakes map out a nearly vertical, narrow conduit system beneath the lava lake; (3)there are other source regions of seismicity on Ross Island, well removed from Mt. Erebus proper. An intense earthquake swarm recorded in October 1982 near Abbott Peak, 10 km northwest of the summit of Mt. Erebus, and volcanic tremor accompanying the swarm, may have been associated with new dike emplacement at depth.

  15. Iceberg B-15, Ross Ice Shelf, Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Iceberg B-15 broke from the Ross Ice Shelf in Antarctica in late March. Among the largest ever observed, the new iceberg is approximately 170 miles long x 25 miles wide. Its 4,250 square-mile area is nearly as large as the state of Connecticut. The iceberg was formed from glacial ice moving off the Antarctic continent and calved along pre-existing cracks in the Ross Ice Shelf near Roosevelt Island. The calving of the iceberg essentially moves the northern boundary of the ice shelf about 25 miles to the south, a loss that would normally take the ice shelf as long as 50-100 years to replace. This infrared image was acquired by the DMSP (Defense Meteorological Satellite Program) F-13 satellite on April 13, 2000. For more images see Antarctic Meteorological Research Center Image courtesy of the University of Wisconsin - Madison, Space Science and Engineering Center, Antarctic Meteorological Research Center

  16. Recovery of Neonatal Head Turning to Decreased Sound Pressure Level.

    ERIC Educational Resources Information Center

    Tarquinio, Nancy; And Others

    1990-01-01

    Investigated newborns' responses to decreased sound pressure level (SPL) by means of a localized head turning habituation procedure. Findings, which demonstrated recovery of neonatal head turning to decreased SPL, were inconsistent with the selective receptor adaptation model. (RH)

  17. Occurrence and diversity of marine yeasts in Antarctica environments

    NASA Astrophysics Data System (ADS)

    Zhang, Xue; Hua, Mingxia; Song, Chunli; Chi, Zhenming

    2012-03-01

    A total of 28 yeast strains were obtained from the sea sediment of Antarctica. According to the results of routine identification and molecular characterization, the strains belonged to species of Yarrowia lipolytica, Debaryomyces hansenii, Rhodotorula slooffiae, Rhodotorula mucilaginosa, Sporidiobolus salmonicolor, Aureobasidium pullulans, Mrakia frigida and Guehomyces pullulans, respectively. The Antarctica yeasts have wide potential applications in biotechnology, for some of them can produce β-galactosidase and killer toxins.

  18. Oxygen isotope studies and compilation of isotopic dates from Antarctica

    SciTech Connect

    Grootes, P.M.; Stuiver, M.

    1986-01-01

    The Quaternary Isotope Laboratory, alone or in collaboration with other investigators, is currently involved in a number of oxygen-isotope studies mainly in Antarctica. Studies of a drill core from the South Pole, seasonal oxygen-18 signals preserved in the Dominion Range, isotope dating of the Ross Ice Shelf, oxygen-18 profiles of the Siple Coast, McMurdo Ice Shelf sampling, and a data compilation of radiometric dates from Antarctica are discussed.

  19. Ice-shelf melting around Antarctica

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Jacobs, S.

    2008-12-01

    The traditional view on the mass balance of Antarctic ice shelves is that they loose mass principally from iceberg calving with bottom melting a much lower contributing factor. Because ice shelves are now known to play a fundamental role in ice sheet evolution, it is important to re-evaluate their wastage processes from a circumpolar perspective using a combination of remote sensing techniques. We present area average rates deduced from grounding line discharge, snow accumulation, firn depth correction and ice shelf topography. We find that ice shelf melting accounts for roughly half of ice-shelf ablation, with a total melt water production of 1027 Gt/yr. The attrition fraction due to in-situ melting varies from 9 to 90 percent around Antarctica. High melt producers include the Ronne, Ross, Getz, Totten, Amery, George VI, Pine Island, Abbot, Dotson/Crosson, Shackleton, Thwaites and Moscow University Ice Shelves. Low producers include the Larsen C, Princess Astrid and Ragnhild coast, Fimbul, Brunt and Filchner. Correlation between melt water production and grounding line discharge is low (R2 = 0.65). Correlation with thermal ocean forcing from the ocean are highest in the northern parts of West Antarctica where regressions yield R2 of 0.93-0.97. Melt rates in the Amundsen Sea exhibit a quadratic sensitivity to thermal ocean forcing. We conclude that ice shelf melting plays a dominant role in ice shelf mass balance, with a potential to change rapidly in response to altered ocean heat transport onto the Antarctic continental shelf.

  20. IT’S GOOD TO BE BIG—PHAEOCYSTIS ANTARCTICA COLONY SIZE UNDER THE INFLUENCE OF ZOOPLANKTON GRAZERS

    EPA Science Inventory

    The haptophyte Phaeocystis antarctica forms extremely dense accumulations in the Ross Sea, Antarctica, and accounts for over 60% of the seasonal primary production. Similar to the Phaeocystis species in the northern hemisphere, P. antarctica exists as solitary cells and mucilagin...

  1. It’s good to be big--- Phaeocystis antarctica colony size under the influence of zooplankton grazers

    EPA Science Inventory

    The haptophyte Phaeocystis antarctica forms extremely dense accumulations in the Ross Sea, Antarctica, and accounts for over 60% of the seasonal primary production. Similar to the Phaeocystis species in the northern hemisphere, P. antarctica exists as solitary cells and mucilagin...

  2. Sound modes in holographic superfluids

    SciTech Connect

    Herzog, Christopher P.; Yarom, Amos

    2009-11-15

    Superfluids support many different types of sound waves. We investigate the relation between the sound waves in a relativistic and a nonrelativistic superfluid by using hydrodynamics to calculate the various sound speeds. Then, using a particular holographic scalar gravity realization of a strongly interacting superfluid, we compute first, second, and fourth sound speeds as a function of the temperature. The relativistic low temperature results for second sound differ from Landau's well known prediction for the nonrelativistic, incompressible case.

  3. Radio Sounding Science at High Powers

    NASA Technical Reports Server (NTRS)

    Green, J. L.; Reinisch, B. W.; Song, P.; Fung, S. F.; Benson, R. F.; Taylor, W. W. L.; Cooper, J. F.; Garcia, L.; Markus, T.; Gallagher, D. L.

    2004-01-01

    Future space missions like the Jupiter Icy Moons Orbiter (JIMO) planned to orbit Callisto, Ganymede, and Europa can fully utilize a variable power radio sounder instrument. Radio sounding at 1 kHz to 10 MHz at medium power levels (10 W to kW) will provide long-range magnetospheric sounding (several Jovian radii) like those first pioneered by the radio plasma imager instrument on IMAGE at low power (less than l0 W) and much shorter distances (less than 5 R(sub E)). A radio sounder orbiting a Jovian icy moon would be able to globally measure time-variable electron densities in the moon ionosphere and the local magnetospheric environment. Near-spacecraft resonance and guided echoes respectively allow measurements of local field magnitude and local field line geometry, perturbed both by direct magnetospheric interactions and by induced components from subsurface oceans. JIMO would allow radio sounding transmissions at much higher powers (approx. 10 kW) making subsurface sounding of the Jovian icy moons possible at frequencies above the ionosphere peak plasma frequency. Subsurface variations in dielectric properties, can be probed for detection of dense and solid-liquid phase boundaries associated with oceans and related structures in overlying ice crusts.

  4. Magnetostratigraphy of ANDRILL Core AND-2A, Southern McMurdo Sound, Antarctica

    NASA Astrophysics Data System (ADS)

    Florindo, F.; Acton, G.; Harwood, D. M.; Jovane, L.; Levy, R. H.; Ohneiser, C.; Sagnotti, L.; Strada, E.; Verosub, K. L.; Wilson, G. S.

    2010-12-01

    Paleomagnetic data from ANDRILL Site AND-2A (77°45.488’S, 165°16.605’E, ~383.57 m water depth) are used to construct a magnetostratigraphy that is integrated with other age constraints in order to provide a robust chronostratigraphy, which is being used to date climatic and environmental change in the Ross Sea since the early Miocene. A total of 951 discrete samples (~10 cm3) were collected roughly every meter or two along the core from the top of the section down to the base at 1138.54 mbsf. In addition, 11 U-channel samples (1.5-m long strips of core) were collected from a fine-grained, laminated interval from 1016 to 1040 mbsf to examine short-term geomagnetic field variability. This study gives an updated magnetostratigraphy based on the ~680 discrete samples published in the initial report (Acton et al., Terra Antartica, 2009a, b: http://www.mna.it/english/Publications/TAP/volume15.html) along with new results from an additional ~270 discrete samples and from the 1573 intervals measured every 1 cm along the U-channel samples. Our new study focuses mainly on Lithostratigraphic Units 6 through 14 (296.34-1138.54 mbsf), where the most continuous stratigraphy occurs and where the paleomagnetic data provide a relatively good magnetostratigraphy. Sediments within this interval lie within Chrons C5B to C6A (~15-20 Ma). Because discontinuities exist in the stratigraphic section that may represent significant hiatuses, we develop several end member age models that provide feasible best age estimates and give insights into the age uncertainties. http://www.mna.it/english/Publications/TAP/volume15.html

  5. Aeromagnetic and radio echo ice-sounding measurements over the Dufek intrusion, Antarctica.

    USGS Publications Warehouse

    Behrendt, John C.; Drewry, D.J.; Jankowski, E.; Grim, M.S.

    1981-01-01

    Comparisons of the magnetic and subglacial topographic profiles illustrate the usefulness of this combination of methods in studying bedrock geology beneath ice-covered areas. Rocks are exposed in only 3% of the inferred area of the intrusion.-from Authors

  6. The Neural Correlates of Broad Bandwidth and Narrow Bandwidth Elevated Sound

    NASA Astrophysics Data System (ADS)

    Cumming, Amanda

    The present study aimed to investigate the N1 response for both narrow band and broadband sound in order to better understand auditory spatial localization, as well as the role of the "where" stream for localizing elevated sound. Electroencephalographic recordings were obtained from subjects as they listened to broadband or narrowband sounds, with center frequencies of either 4 kHz or 10 kHz, presented from five vertical loud speakers, +/-40°, +/-20° and 0°. The data did not reveal any clusters that identified differences in neuronal processing across time for sound type. The auditory evoked responses demonstrated that, under monaural conditions, narrow band and broadband sounds are differentially processed in A1. Overall, we could not confirm the use of different or similar brain resources for horizontal and vertical sound localization, nor could we demonstrate involvement of the dorsal stream regarding elevated sound localization.

  7. On categorizing sounds

    NASA Astrophysics Data System (ADS)

    Lockhead, Gregory R.

    1991-08-01

    Context is important when people judge sounds, or attributes of sounds, or other stimuli. It is shown how judgments depend on what sounds recently occurred (sequence effects), on how those sounds differ from one another (range effects), on the distribution of those differences (set effects), on what subjects are told about the situation (task effects), and on what subjects are told about their performance (feedback effects). Each of these factors determines the overall mean and variability of response times and response choices, which are the standard measures, when people judge attribute amounts. Trial-by-trial analysis of the data show these factors also determine performance on individual trials. Moreover, these momentary data cannot be predicted from the overall data. The opposite is not true; the averaged data can be predicted from the momentary details. These results are consistent with a model having two simple assumptions: successive sounds (not just their attributes) assimilate toward one another in memory, and judgments are based on comparisons of these remembered events. It is suggested that relations between attributes, rather than the magnitudes of the attributes themselves, are the basis for judgment.

  8. Meteor fireball sounds identified

    NASA Technical Reports Server (NTRS)

    Keay, Colin

    1992-01-01

    Sounds heard simultaneously with the flight of large meteor fireballs are electrical in origin. Confirmation that Extra/Very Low Frequency (ELF/VLF) electromagnetic radiation is produced by the fireball was obtained by Japanese researchers. Although the generation mechanism is not fully understood, studies of the Meteorite Observation and Recovery Project (MORP) and other fireball data indicate that interaction with the atmosphere is definitely responsible and the cut-off magnitude of -9 found for sustained electrophonic sounds is supported by theory. Brief bursts of ELF/VLF radiation may accompany flares or explosions of smaller fireballs, producing transient sounds near favorably placed observers. Laboratory studies show that mundane physical objects can respond to electrical excitation and produce audible sounds. Reports of electrophonic sounds should no longer be discarded. A catalog of over 300 reports relating to electrophonic phenomena associated with meteor fireballs, aurorae, and lightning was assembled. Many other reports have been cataloged in Russian. These may assist the full solution of the similar long-standing and contentious mystery of audible auroral displays.

  9. Commissural Gain Control Enhances the Midbrain Representation of Sound Location

    PubMed Central

    Orton, Llwyd David; Papasavvas, Christoforos A.

    2016-01-01

    Accurate localization of sound sources is essential for survival behavior in many species. The inferior colliculi (ICs) are the first point in the auditory pathway where cues used to locate sounds, ie, interaural time differences (ITDs), interaural level differences (ILDs), and pinna spectral cues, are all represented in the same location. These cues are first extracted separately on each side of the midline in brainstem nuclei that project to the ICs. Because of this segregation, each IC predominantly represents stimuli in the contralateral hemifield. We tested the hypothesis that commissural connections between the ICs mediate gain control that enhances sound localization acuity. We recorded IC neurons sensitive to either ITDs or ILDs in anesthetized guinea pig, before, during, and following recovery from deactivation of the contralateral IC by cryoloop cooling or microdialysis of procaine. During deactivation, responses were rescaled by divisive gain change and additive shifts, which reduced the dynamic range of ITD and ILD response functions and the ability of neurons to signal changes in sound location. These data suggest that each IC exerts multiplicative gain control and subtractive shifts over the other IC that enhances the neural representation of sound location. Furthermore, this gain control operates in a similar manner on both ITD- and ILD-sensitive neurons, suggesting a shared mechanism operates across localization cues. Our findings reveal a novel dependence of sound localization on commissural processing. SIGNIFICANCE STATEMENT Sound localization, a fundamental process in hearing, is dependent on bilateral computations in the brainstem. How this information is transmitted from the brainstem to the auditory cortex, through several stages of processing, without loss of signal fidelity, is not clear. We show that the ability of neurons in the auditory midbrain to encode azimuthal sound location is dependent on gain control mediated by the commissure of

  10. Radio-echo sounding of 'active' Antarctic subglacial lakes

    NASA Astrophysics Data System (ADS)

    Siegert, M. J.; Ross, N.; Blankenship, D. D.; Young, D. A.; Greenbaum, J. S.; Richter, T.; Rippin, D. M.; Le Brocq, A. M.; Wright, A.; Bingham, R.; Corr, H.; Ferraccioli, F.; Jordan, T. A.; Smith, B. E.; Payne, A. J.; Dowdeswell, J. A.; Bamber, J. L.

    2013-12-01

    Repeat-pass satellite altimetry has revealed 124 discrete surface height changes across the Antarctic Ice Sheet, interpreted to be caused by subglacial lake discharges (surface lowering) and inputs (surface uplift). Few of these active lakes have been confirmed by radio-echo sounding (RES) despite several attempts, however. Over the last 5 years, major geophysical campaigns have acquired RES data from several 'active' lake sites, including the US-UK-Australian ICECAP programme in East Antactica and the UK survey of the Institute Ice Stream in West Antarctica. In the latter case, a targeted RES survey of one 'active' lake was undertaken. RES evidence of the subglacial bed beneath 'active' lakes in both East and West Antarctica will be presented, and the evidence for pooled subglacial water from these data will be assessed. Based on this assessment, the nature of 'active' subglacial lakes, and their associated hydrology and relationship with surrounding topography will be discussed, as will the likelihood of further 'active' lakes in Antarctica. Hydraulic potential map of the Byrd Glacier catchment with contours at 5 MPa intervals. Predicted subglacial flowpaths are shown in blue. Subglacial lakes known from previous geophysical surveys are shown as black triangles while the newly discovered 'Three-tier lakes' are shown in dashed black outline. Surface height change features within the Byrd subglacial catchment are shown in outline and are shaded to indicate whether they were rising or falling during the ICESat campaign. Those features are labelled in-line with the numbering system of Smith et al. (J. Glac. 2009).

  11. Atmospheric sound propagation

    NASA Technical Reports Server (NTRS)

    Cook, R. K.

    1969-01-01

    The propagation of sound waves at infrasonic frequencies (oscillation periods 1.0 - 1000 seconds) in the atmosphere is being studied by a network of seven stations separated geographically by distances of the order of thousands of kilometers. The stations measure the following characteristics of infrasonic waves: (1) the amplitude and waveform of the incident sound pressure, (2) the direction of propagation of the wave, (3) the horizontal phase velocity, and (4) the distribution of sound wave energy at various frequencies of oscillation. Some infrasonic sources which were identified and studied include the aurora borealis, tornadoes, volcanos, gravity waves on the oceans, earthquakes, and atmospheric instability waves caused by winds at the tropopause. Waves of unknown origin seem to radiate from several geographical locations, including one in the Argentine.

  12. Wind Forced Circulation in Long Island Sound

    NASA Astrophysics Data System (ADS)

    O'Donnell, J.; Bohlen, W. F.; Houk, A. E.

    2008-12-01

    Western Long Island Sound is connected to the New York Harbor and the Hudson River through the East River, a sea level canal. Though the time mean, cross-sectional average flow in the Sound is thought to be westward into the Harbor, there is near-surface layer which transports fresh water into the Sound. This buoyancy flux has a significant influence on the vertical stratification which inhibits vertical mixing and exacerbates the extent and duration of summertime hypoxia. Recent work has revealed interment periods of enhanced vertical mixing. Using measurements from an array of vertically profiling current meters and wind observations, we show how the local and remotely forced circulation modulates the vertical stratification leading and influences the rate of decline of dissolved oxygen in the near bottom waters.

  13. The Imagery of Sound

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Automated Analysis Corporation's COMET is a suite of acoustic analysis software for advanced noise prediction. It analyzes the origin, radiation, and scattering of noise, and supplies information on how to achieve noise reduction and improve sound characteristics. COMET's Structural Acoustic Foam Engineering (SAFE) module extends the sound field analysis capability of foam and other materials. SAFE shows how noise travels while airborne, how it travels within a structure, and how these media interact to affect other aspects of the transmission of noise. The COMET software reduces design time and expense while optimizing a final product's acoustical performance. COMET was developed through SBIR funding and Langley Research Center for Automated Analysis Corporation.

  14. The heart sound preprocessor

    NASA Technical Reports Server (NTRS)

    Chen, W. T.

    1972-01-01

    Technology developed for signal and data processing was applied to diagnostic techniques in the area of phonocardiography (pcg), the graphic recording of the sounds of the heart generated by the functioning of the aortic and ventricular valves. The relatively broad bandwidth of the PCG signal (20 to 2000 Hz) was reduced to less than 100 Hz by the use of a heart sound envelope. The process involves full-wave rectification of the PCG signal, envelope detection of the rectified wave, and low pass filtering of the resultant envelope.

  15. Lake Hoare, Antarctica: sedimentation through a thick perennial ice cover

    NASA Technical Reports Server (NTRS)

    Squyres, S. W.; Andersen, D. W.; Nedell, S. S.; Wharton, R. A. Jr; Wharton RA, J. r. (Principal Investigator)

    1991-01-01

    Lake Hoare in the Dry Valleys of Antarctica is covered with a perennial ice cover more than 3 m thick, yet there is a complex record of sedimentation and of growth of microbial mats on the lake bottom. Rough topography on the ice covering the lake surface traps sand that is transported by the wind. In late summer, vertical conduits form by melting and fracturing, making the ice permeable to both liquid water and gases. Cross-sections of the ice cover show that sand is able to penetrate into and apparently through it by descending through these conduits. This is the primary sedimentation mechanism in the lake. Sediment traps retrieved from the lake bottom indicate that rates of deposition can vary by large amounts over lateral scales as small as 1 m. This conclusion is supported by cores taken in a 3 x 3 grid with a spacing of 1.5 m. Despite the close spacing of the cores, the poor stratigraphic correlation that is observed indicates substantial lateral variability in sedimentation rate. Apparently, sand descends into the lake from discrete, highly localized sources in the ice that may in some cases deposit a large amount of sand into the lake in a very short time. In some locations on the lake bottom, distinctive sand mounds have been formed by this process. They are primary sedimentary structures and appear unique to the perennially ice-covered lacustrine environment. In some locations they are tens of centimetres high and gently rounded with stable slopes; in others they reach approximately 1 m in height and have a conical shape with slopes at angle of repose. A simple formation model suggests that these differences can be explained by local variations in water depth and sedimentation rate. Rapid colonization of fresh sand surfaces by microbial mats composed of cyanobacteria, eukaryotic algae, and heterotrophic bacteria produces a complex intercalation of organic and sandy layers that are a distinctive form of modern stromatolites.

  16. Extraterrestrial sound for planetaria: A pedagogical study.

    PubMed

    Leighton, T G; Banda, N; Berges, B; Joseph, P F; White, P R

    2016-08-01

    The purpose of this project was to supply an acoustical simulation device to a local planetarium for use in live shows aimed at engaging and inspiring children in science and engineering. The device plays audio simulations of estimates of the sounds produced by natural phenomena to accompany audio-visual presentations and live shows about Venus, Mars, and Titan. Amongst the simulated noise are the sounds of thunder, wind, and cryo-volcanoes. The device can also modify the speech of the presenter (or audience member) in accordance with the underlying physics to reproduce those vocalizations as if they had been produced on the world under discussion. Given that no time series recordings exist of sounds from other worlds, these sounds had to be simulated. The goal was to ensure that the audio simulations were delivered in time for a planetarium's launch show to enable the requested outreach to children. The exercise has also allowed an explanation of the science and engineering behind the creation of the sounds. This has been achieved for young children, and also for older students and undergraduates, who could then debate the limitations of that method. PMID:27586771

  17. Auditory performance in an open sound field

    NASA Astrophysics Data System (ADS)

    Fluitt, Kim F.; Letowski, Tomasz; Mermagen, Timothy

    2003-04-01

    Detection and recognition of acoustic sources in an open field are important elements of situational awareness on the battlefield. They are affected by many technical and environmental conditions such as type of sound, distance to a sound source, terrain configuration, meteorological conditions, hearing capabilities of the listener, level of background noise, and the listener's familiarity with the sound source. A limited body of knowledge about auditory perception of sources located over long distances makes it difficult to develop models predicting auditory behavior on the battlefield. The purpose of the present study was to determine the listener's abilities to detect, recognize, localize, and estimate distances to sound sources from 25 to 800 m from the listing position. Data were also collected for meteorological conditions (wind direction and strength, temperature, atmospheric pressure, humidity) and background noise level for each experimental trial. Forty subjects (men and women, ages 18 to 25) participated in the study. Nine types of sounds were presented from six loudspeakers in random order; each series was presented four times. Partial results indicate that both detection and recognition declined at distances greater than approximately 200 m and distance estimation was grossly underestimated by listeners. Specific results will be presented.

  18. Surface contributions to radiated sound power.

    PubMed

    Marburg, Steffen; Lösche, Eric; Peters, Herwig; Kessissoglou, Nicole

    2013-06-01

    This paper presents a method to identify the surface areas of a vibrating structure that contribute to the radiated sound power. The surface contributions of the structure are based on the acoustic radiation modes and are computed for all boundaries of the acoustic domain. The surface contributions are compared to the acoustic intensity, which is a common measure for near-field acoustic energy. Sound intensity usually has positive and negative values that correspond to energy sources and sinks on the surface of the radiating structure. Sound from source and sink areas partially cancel each other and only a fraction of the near-field acoustic energy reaches the far-field. In contrast to the sound intensity, the surface contributions are always positive and no cancelation effects exist. The technique presented here provides a method to localize the relevant radiating surface areas on a vibrating structure. To illustrate the method, the radiated sound power from a baffled square plate is presented. PMID:23742325

  19. Balloon-borne observations of stratospheric aerosol in Antarctica from 1972 to 1984

    NASA Technical Reports Server (NTRS)

    Hofmann, D. J.

    1985-01-01

    Stratospheric levels of particles with r or = 0.15 microns were monitored with optical particle counters in approximately monthly balloon soundings at Laramie, Wyoming (41 deg N) since 1971. These measurements were used to characterize the background stratospheric aerosol layer and the disturbed layer following major volcanic eruptions. Levels of particles with r or = 0.01 microns have also been measured with balloon-borne counters since 1973. The latter are collectively called condensation nuclei (CN) as they are characteristic of aerosol in the early stages of growth. While they dominate the size distribution in the tropsophere, they are a trace species in the undisturbed stratosphere. From 1972 until 1980, annual balloon soundings from McMurdo Station (78 deg S) and/or Amundsen-Scott Station (90 deg S), in Antarctica, have also been conducted to crudely monitor Southern Hemisphere aerosol levels. These measurements were continued in 1983 and 1984. Profiles of r 0.15 microns aerosol concentrations as measured during January at the south pole from 1972 to 1975 and in 1980 are given. The former are typical of undisturbed conditions and indicate the small degree of variability under these conditions. The latter indicates the effect of minor volcanic activity, visible in the 10 to 15 km region.

  20. Site testing for submillimetre astronomy at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Tremblin, P.; Minier, V.; Schneider, N.; Durand, G. Al.; Ashley, M. C. B.; Lawrence, J. S.; Luong-van, D. M.; Storey, J. W. V.; Durand, G. An.; Reinert, Y.; Veyssiere, C.; Walter, C.; Ade, P.; Calisse, P. G.; Challita, Z.; Fossat, E.; Sabbatini, L.; Pellegrini, A.; Ricaud, P.; Urban, J.

    2011-11-01

    Aims: Over the past few years a major effort has been put into the exploration of potential sites for the deployment of submillimetre astronomical facilities. Amongst the most important sites are Dome C and Dome A on the Antarctic Plateau, and the Chajnantor area in Chile. In this context, we report on measurements of the sky opacity at 200 μm over a period of three years at the French-Italian station, Concordia, at Dome C, Antarctica. We also present some solutions to the challenges of operating in the harsh polar environment. Methods: The 200-μm atmospheric opacity was measured with a tipper. The forward atmospheric model MOLIERE (Microwave Observation LIne Estimation and REtrieval) was used to calculate the atmospheric transmission and to evaluate the precipitable water vapour content (PWV) from the observed sky opacity. These results have been compared with satellite measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on Metop-A, with balloon humidity sondes and with results obtained by a ground-based microwave radiometer (HAMSTRAD). In addition, a series of experiments has been designed to study frost formation on surfaces, and the temporal and spatial evolution of thermal gradients in the low atmosphere. Results: Dome C offers exceptional conditions in terms of absolute atmospheric transmission and stability for submillimetre astronomy. Over the austral winter the PWV exhibits long periods during which it is stable and at a very low level (0.1 to 0.3 mm). Higher values (0.2 to 0.8 mm) of PWV are observed during the short summer period. Based on observations over three years, a transmission of around 50% at 350 μm is achieved for 75% of the time. The 200-μm window opens with a typical transmission of 10% to 15% for 25% of the time. Conclusions: Dome C is one of the best accessible sites on Earth for submillimetre astronomy. Observations at 350 or 450 μm are possible all year round, and the 200-μm window opens long enough and with a

  1. Sounds of the Desert.

    ERIC Educational Resources Information Center

    McCullough-Brabson, Ellen; Achilles, Elayne; Ashcraft, Joan

    1997-01-01

    Discusses the program called "Sounds of the Desert" that celebrates the Southwest indigenous culture and focuses on understanding music in relation to history and culture. Emphasizes the study of Mariachi music that is being taught alongside band, orchestra, and chorus from the third grade to senior high in many Tucson (Arizona) schools. (CMK)

  2. Sunny Norton Sound

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A clear day over Norton Sound in the Bering Sea allowed SeaWiFS to capture this image of the phytoplankton bloom off the coast of Alaska. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  3. Sound level measurements

    NASA Astrophysics Data System (ADS)

    1981-07-01

    This report describes procedures for measuring the sound levels of developmental and production materiel as a means of evaluating personnel safety, recognition and community annoyance (by a drive-by test). It covers tests for steady-state noise from military vehicles and general equipment, and impulse noise from weapon systems and explosive ordnance material.

  4. Exploring Sound with Insects

    ERIC Educational Resources Information Center

    Robertson, Laura; Meyer, John R.

    2010-01-01

    Differences in insect morphology and movement during singing provide a fascinating opportunity for students to investigate insects while learning about the characteristics of sound. In the activities described here, students use a free online computer software program to explore the songs of the major singing insects and experiment with making…

  5. Creative Sound Dramatics

    ERIC Educational Resources Information Center

    Hendrix, Rebecca; Eick, Charles

    2014-01-01

    Sound propagation is not easy for children to understand because of its abstract nature, often best represented by models such as wave drawings and particle dots. Teachers Rebecca Hendrix and Charles Eick wondered how science inquiry, when combined with an unlikely discipline like drama, could produce a better understanding among their…

  6. Exploring Noise: Sound Pollution.

    ERIC Educational Resources Information Center

    Rillo, Thomas J.

    1980-01-01

    This article is the last of a three-part series dealing with sound measurement, effects, pollution, and indoor/door learning activities. This section focuses on outdoor activities and equipment that students can make to assist them in data collection. (Author/SA)

  7. Sounds Like Fun.

    ERIC Educational Resources Information Center

    Lucas, Linda M.

    1991-01-01

    Presents hands-on science activities that help students learn the concepts of hearing and sound while allowing students to practice science process skills. Students investigate the use of alternative phonograph speakers and needles and apply the knowledge learned to the construction of one-string banjos. (MDH)

  8. Object localization using a biosonar beam: how opening your mouth improves localization

    PubMed Central

    Arditi, G.; Weiss, A. J.; Yovel, Y.

    2015-01-01

    Determining the location of a sound source is crucial for survival. Both predators and prey usually produce sound while moving, revealing valuable information about their presence and location. Animals have thus evolved morphological and neural adaptations allowing precise sound localization. Mammals rely on the temporal and amplitude differences between the sound signals arriving at their two ears, as well as on the spectral cues available in the signal arriving at a single ear to localize a sound source. Most mammals rely on passive hearing and are thus limited by the acoustic characteristics of the emitted sound. Echolocating bats emit sound to perceive their environment. They can, therefore, affect the frequency spectrum of the echoes they must localize. The biosonar sound beam of a bat is directional, spreading different frequencies into different directions. Here, we analyse mathematically the spatial information that is provided by the beam and could be used to improve sound localization. We hypothesize how bats could improve sound localization by altering their echolocation signal design or by increasing their mouth gape (the size of the sound emitter) as they, indeed, do in nature. Finally, we also reveal a trade-off according to which increasing the echolocation signal's frequency improves the accuracy of sound localization but might result in undesired large localization errors under low signal-to-noise ratio conditions. PMID:26361552

  9. Object localization using a biosonar beam: how opening your mouth improves localization.

    PubMed

    Arditi, G; Weiss, A J; Yovel, Y

    2015-08-01

    Determining the location of a sound source is crucial for survival. Both predators and prey usually produce sound while moving, revealing valuable information about their presence and location. Animals have thus evolved morphological and neural adaptations allowing precise sound localization. Mammals rely on the temporal and amplitude differences between the sound signals arriving at their two ears, as well as on the spectral cues available in the signal arriving at a single ear to localize a sound source. Most mammals rely on passive hearing and are thus limited by the acoustic characteristics of the emitted sound. Echolocating bats emit sound to perceive their environment. They can, therefore, affect the frequency spectrum of the echoes they must localize. The biosonar sound beam of a bat is directional, spreading different frequencies into different directions. Here, we analyse mathematically the spatial information that is provided by the beam and could be used to improve sound localization. We hypothesize how bats could improve sound localization by altering their echolocation signal design or by increasing their mouth gape (the size of the sound emitter) as they, indeed, do in nature. Finally, we also reveal a trade-off according to which increasing the echolocation signal's frequency improves the accuracy of sound localization but might result in undesired large localization errors under low signal-to-noise ratio conditions. PMID:26361552

  10. Understanding the Role of Wind in Reducing the Surface Mass Balance Estimates over East Antarctica

    NASA Astrophysics Data System (ADS)

    Das, I.; Scambos, T. A.; Koenig, L.; Creyts, T. T.; Bell, R. E.; van den Broeke, M. R.; Lenaerts, J.; Paden, J. D.

    2014-12-01

    Accurate quantification of surface snow-accumulation over Antarctica is important for mass balance estimates and climate studies based on ice core records. An improved estimate of surface mass balance must include the significant role near-surface wind plays in the sublimation and redistribution of snow across Antarctica. We have developed an empirical model based on airborne radar and lidar observations, and modeled surface mass balance and wind fields to produce a continent-wide prediction of wind-scour zones over Antarctica. These zones have zero to negative surface mass balance, are located over locally steep ice sheet areas (>0.002) and controlled by bedrock topography. The near-surface winds accelerate over these zones, eroding and sublimating the surface snow. This scouring results in numerous localized regions (≤ 200 km2) with reduced surface accumulation. Each year, tens of gigatons of snow on the Antarctic ice sheet are ablated by persistent near-surface katabatic winds over these wind-scour zones. Large uncertainties remain in the surface mass balance estimates over East Antarctica as climate models do not adequately represent the small-scale physical processes that lead to mass loss through sublimation or redistribution over the wind-scour zones. In this study, we integrate Operation IceBridge's snow radar over the Recovery Ice Stream with a series of ice core dielectric and depth-density profiles for improved surface mass balance estimates that reflect the mass loss over the wind-scour zones. Accurate surface mass balance estimates from snow radars require spatially variable depth-density profiles. Using an ensemble of firn cores, MODIS-derived surface snow grain size, modeled accumulation rates and surface temperatures from RACMO2, we assemble spatially variable depth-density profiles and use our mapping of snow density variations to estimate layer mass and net accumulation rates from snow radar layer data. Our study improves the quantification of

  11. Codes for sound-source location in nontonotopic auditory cortex.

    PubMed

    Middlebrooks, J C; Xu, L; Eddins, A C; Green, D M

    1998-08-01

    We evaluated two hypothetical codes for sound-source location in the auditory cortex. The topographical code assumed that single neurons are selective for particular locations and that sound-source locations are coded by the cortical location of small populations of maximally activated neurons. The distributed code assumed that the responses of individual neurons can carry information about locations throughout 360 degrees of azimuth and that accurate sound localization derives from information that is distributed across large populations of such panoramic neurons. We recorded from single units in the anterior ectosylvian sulcus area (area AES) and in area A2 of alpha-chloralose-anesthetized cats. Results obtained in the two areas were essentially equivalent. Noise bursts were presented from loudspeakers spaced in 20 degrees intervals of azimuth throughout 360 degrees of the horizontal plane. Spike counts of the majority of units were modulated >50% by changes in sound-source azimuth. Nevertheless, sound-source locations that produced greater than half-maximal spike counts often spanned >180 degrees of azimuth. The spatial selectivity of units tended to broaden and, often, to shift in azimuth as sound pressure levels (SPLs) were increased to a moderate level. We sometimes saw systematic changes in spatial tuning along segments of electrode tracks as long as 1.5 mm but such progressions were not evident at higher sound levels. Moderate-level sounds presented anywhere in the contralateral hemifield produced greater than half-maximal activation of nearly all units. These results are not consistent with the hypothesis of a topographic code. We used an artificial-neural-network algorithm to recognize spike patterns and, thereby, infer the locations of sound sources. Network input consisted of spike density functions formed by averages of responses to eight stimulus repetitions. Information carried in the responses of single units permitted reasonable estimates of sound

  12. Radiometric sounding system

    SciTech Connect

    Whiteman, C.D.; Anderson, G.A.; Alzheimer, J.M.; Shaw, W.J.

    1995-04-01

    Vertical profiles of solar and terrestrial radiative fluxes are key research needs for global climate change research. These fluxes are expected to change as radiatively active trace gases are emitted to the earth`s atmosphere as a consequence of energy production and industrial and other human activities. Models suggest that changes in the concentration of such gases will lead to radiative flux divergences that will produce global warming of the earth`s atmosphere. Direct measurements of the vertical variation of solar and terrestrial radiative fluxes that lead to these flux divergences have been largely unavailable because of the expense of making such measurements from airplanes. These measurements are needed to improve existing atmospheric radiative transfer models, especially under the cloudy conditions where the models have not been adequately tested. A tethered-balloon-borne Radiometric Sounding System has been developed at Pacific Northwest Laboratory to provide an inexpensive means of making routine vertical soundings of radiative fluxes in the earth`s atmospheric boundary layer to altitudes up to 1500 m above ground level. Such vertical soundings would supplement measurements being made from aircraft and towers. The key technical challenge in the design of the Radiometric Sounding System is to develop a means of keeping the radiometers horizontal while the balloon ascends and descends in a turbulent atmospheric environment. This problem has been addressed by stabilizing a triangular radiometer-carrying platform that is carried on the tetherline of a balloon sounding system. The platform, carried 30 m or more below the balloon to reduce the balloon`s effect on the radiometric measurements, is leveled by two automatic control loops that activate motors, gears and pulleys when the platform is off-level. The sensitivity of the automatic control loops to oscillatory motions of various frequencies and amplitudes can be adjusted using filters.

  13. New aerogeophysical survey targets crustal architecture and tectonic evolution of East Antarctica in the Recovery frontier

    NASA Astrophysics Data System (ADS)

    Ferraccioli, F.; Forsberg, R.; Jordan, T. A.; Matsuoka, K.; Olesen, A. V.; Ghidella, M. E.

    2013-12-01

    East Antarctica is the size of the conterminous US; it represents the least known continent on Earth despite being regarded as a keystone in Gondwana, Rodinia and possibly even earlier Columbia/Nuna supercontinents. Significant progress has however been made in recent years in the exploration of East Antarctica using airborne geophysical techniques. Spurred by the International Polar Year major collaborative international aerogeophysical campaigns have been performed over the Wilkes Subglacial Basin, the Aurora Subglacial Basin and the Gamburtsev Mountains in recent years, and these are continuing to provide fundamental new glimpses into the crustal architecture in interior East Antarctica, as well as several new interpretations regarding its linkages with tectonic and geodynamic evolution from Precambrian to Mesozoic/Cenozoic times. Here we present the first results of a major reconnaissance aerogeophysical survey over the largely unexplored Recovery ice stream catchment in East Antarctica completed during the IceGRAV 2012-13 field campaign, as part of an international Danish, Norwegian, UK and Argentine collaboration. Over 29,000 line km of new radio-echo sounding, laser altimetry, gravity and magnetic data were acquired using a British Antarctic Survey Twin Otter that surveyed the region. We focus primarily on the new potential field datasets for the area. Specifically, we present the first aeromagnetic anomaly maps, free air and Bouguer and isostatic residual maps obtained for the region. These images provide new geophysical perspectives that are required in order to address a cascade of open questions over this region. Where are the major tectonic boundaries between the Coats Land Block, the Shackleton Range, and the collage of different provinces recently proposed from aeromagnetic studies in Dronning Maud Land (Mieth and Jokat, 2013, GR)? Is the Coats Land crustal block a tectonic tracer for Laurentia (Loewy et al., 2011, Geology), and how and when was this

  14. Heart murmurs and other sounds

    MedlinePlus

    Chest sounds - murmurs; Heart sounds - abnormal; Murmur - innocent; Innocent murmur; Systolic heart murmur; Diastolic heart murmur ... The heart has four chambers: Two upper chambers (atria) Two lower chambers (ventricles) The heart has valves that close ...

  15. Modeling the Transmission of Sound.

    ERIC Educational Resources Information Center

    Palmer, David H.

    2003-01-01

    Introduces a functional model of sound transmission through solids and gases. Describes procedures of an activity to model how sound travels faster through solid materials than gases. Use dominoes to represent the particles of solids and gases. (KHR)

  16. Light aircraft sound transmission study

    NASA Technical Reports Server (NTRS)

    Heitman, K.; Bernhard, R. J.

    1983-01-01

    The plausibility of using the two microphone sound intensity technique to study noise transmission into light aircraft was investigated. In addition, a simple model to predict the interior sound pressure level of the cabin was constructed.

  17. Hydrogen emissions from Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Moussallam, Yves; Oppenheimer, Clive; Aiuppa, Alessandro; Giudice, Gaetano; Moussallam, Manuel; Kyle, Philip

    2012-11-01

    The continuous measurement of molecular hydrogen (H2) emissions from passively degassing volcanoes has recently been made possible using a new generation of low-cost electrochemical sensors. We have used such sensors to measure H2, along with SO2, H2O and CO2, in the gas and aerosol plume emitted from the phonolite lava lake at Erebus volcano, Antarctica. The measurements were made at the crater rim between December 2010 and January 2011. Combined with measurements of the long-term SO2 emission rate for Erebus, they indicate a characteristic H2 flux of 0.03 kg s-1 (2.8 Mg day-1). The observed H2 content in the plume is consistent with previous estimates of redox conditions in the lava lake inferred from mineral compositions and the observed CO2/CO ratio in the gas plume (˜0.9 log units below the quartz-fayalite-magnetite buffer). These measurements suggest that H2 does not combust at the surface of the lake, and that H2 is kinetically inert in the gas/aerosol plume, retaining the signature of the high-temperature chemical equilibrium reached in the lava lake. We also observe a cyclical variation in the H2/SO2 ratio with a period of ˜10 min. These cycles correspond to oscillatory patterns of surface motion of the lava lake that have been interpreted as signs of a pulsatory magma supply at the top of the magmatic conduit.

  18. Icebergs in the Ross Sea, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Two large icebergs, designated B-15A and C-16, are captured in this MISR nadir camera view of the Ross Ice Shelf and Ross Sea in Antarctica. The image was acquired on December 10, 2000 during Terra orbit 5220.

    Iceberg C-16 calved off the ice shelf in late September and is nearly 50 kilometers in length. It is seen here having migrated to the vicinity of Cape Bird on Ross Island. The initial letter designation in an iceberg's name denotes the longitudinal quadrant in which it is first seen, and new icebergs sighted in that quadrant are sequentially numbered. B-15 divided from the ice shelf last March, and initially was nearly as large as the state of Connecticut. It has since broken up into several pieces, hence the final letter designation in the berg shown in this image.

    Ross Island lies between 77 and 78 degrees south latitude, and consists of several volcanic peaks, of which the still active Mt. Erebus is the tallest (3794 meters). It overlooks McMurdo Station, a U.S. research facility located near the tip of the island's Hut Point Peninsula.

    MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

  19. Odd cloud in the Ross Sea, Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    On January 28, 2002, MODIS captured this image of an interesting cloud formation in the boundary waters between Antarctica's Ross Sea and the Southern Ocean. A dragon? A snake? A fish? No, but it is an interesting example of the atmospheric physics of convection. The 'eye' of this dragon-looking cloud is likely a small spot of convection, the process by which hot moist air rises up into the atmosphere, often producing big, fluffy clouds as moisture in the air condenses as rises into the colder parts of the atmosphere. A false color analysis that shows different kinds of clouds in different colors reveals that the eye is composed of ice crystals while the 'body' is a liquid water cloud. This suggests that the eye is higher up in the atmosphere than the body. The most likely explanation for the eye feature is that the warm, rising air mass had enough buoyancy to punch through the liquid water cloud. As a convective parcel of air rises into the atmosphere, it pushes the colder air that is higher up out of its way. That cold air spills down over the sides of the convective air mass, and in this case has cleared away part of the liquid cloud layer below in the process. This spilling over of cold air from higher up in the atmosphere is the reason why thunderstorms are often accompanied by a cool breeze. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  20. Sedimentary basins in Ross Sea, Antarctica

    SciTech Connect

    Cooper, A.K.; Davey, F.J.

    1986-07-01

    The Ross Sea lies in the Pacific sector of the Antarctic continental margin. Three major sedimentary basins (from east to west, the Eastern, Central, and Victoria Land basins) lie beneath the broad, deep continental shelf of the Ross Sea. These north-south-trending basins occur in the extensionally deformed region between East and West Antarctica. Multichannel seismic reflection (MCS) surveys have been conducted over these basins since 1980 by West German, French, Japanese, and US expeditions. The MCS and previous geophysical surveys have shown that the three basins contain 5-6 km of sedimentary rock, possibly Late Cretaceous and younger. An additional 6-8 km of sedimentary and volcanic rock lies within the deeper parts of the Victoria Land basin. The basins are separated by uplifted and eroded basement ridges covered by thin sedimentary sections. Each basin has distinct characteristics, commonly related to its extensional origin. Petroleum hydrocarbons are unknown from the Ross Sea region, with the possible exception of ethane gas recovered by the Deep Sea Drilling Project. Previous model studies, based on estimated sediment thickness, assumed temperature gradients, and postulated seismostratigraphy, indicate that hydrocarbons could be generated at depths of 3.5-6km within the sedimentary section. However, this hypothesis cannot be verified without further geologic and geophysical data from the Ross Sea region.

  1. Fabric and texture at Siple Dome, Antarctica

    USGS Publications Warehouse

    Diprinzio, C.L.; Wilen, L.A.; Alley, R.B.; Fitzpatrick, J.J.; Spencer, M.K.; Gow, A.J.

    2005-01-01

    Preferred c-axis orientations are present in the firn at Siple Dome, West Antarctica, and recrystallization begins as shallow as 200 m depth in ice below -20??C, based on digital analysis of c-axis fabrics, grain-sizes and other characteristics of 52 vertical thin sections prepared in the field from the kilometer-long Siple Dome ice core. The shallowest section analyzed, from 22 m, shows clustering of c axes toward the vertical. By 200 m depth, girdle fabric and other features of recrystallized ice are evident in layers (or regions), separated by layers (regions) of typically finer-grained ice lacking evidence of recrystallization. Ice from about 700-780 m depth, which was deposited during the last ice age, is especially fine-grained, with strongly vertical c axes, but deeper ice shows much larger crystals and strong evidence of recrystallization. Azimuthal asymmetry of some c-axis fabrics, trends in grain-size, and other indicators reveal additional information on processes and history of ice flow at Siple Dome.

  2. Social, occupational and cultural adaptation in Antarctica

    NASA Astrophysics Data System (ADS)

    Nicolas, Michel; Bishop, Sheryl; Weiss, Karine; Gaudino, Marvin

    2016-07-01

    Life in isolated and confined environments (ICEs, e.g., polar stations, submarine or space missions), is subject to important constraints which can generate psychosociological impaired outcomes. This study investigated psychological, social, occupational and cultural variables which are among the most important determinants in adaptation to a one-year wintering in Antarctica with 13 international participants. Our findings confirm and give further insight into the role of social (Cohesiveness, Social Support) and occupational (Implementation / Preparedness, Counterproductive Activity, Decision Latitude and Psychological Job Demands) dimensions of adaptation to ICE environments. Relationships between various social and occupational dimensions studies reflected detrimental effects ranging from decrements in cohesiveness, social support and work performance which differed across professional status and multicultural factors. These psychosocial issues have important implications for pre-mission selection and training, monitoring and support of crews during the mission and post-mission readaptation. Operational recommendations are suggested to improve adaptation, success and well-being for long-term ICE missions, e.g., to Mars and beyond.

  3. A magnetospheric substorm observed at Sanae, Antarctica

    SciTech Connect

    Gledhill, J.A.; Dore, I.S.; Haggard, R. ); Goertz, C.K. ); Hughes, W.J. ); Scourfield, M.W.J.; Wakerley, P.A.; Walker, A.D.M. ); Smits, D.P.; Sutcliffe, P.R. ); Stoker, P.H. )

    1987-03-01

    A magnetospheric substorm that occurred at Sanae, Antarctica, on July 27, 1979, was observed by a variety of techniques. A synthesis of the observations is presented, and an attempt made to deduce details of the behavior of the magnetosphere-ionosphere system during the event. While there was some evidence of a growth phase, it was inconclusive. At the onset there was a rapid change in the tail field, which assumed a more dipolar form, accompanied by Pi 2 oscillations and the precipitation of 6-keV electrons, with brightening of the auroral arc, auroral-type sporadic E ionization, and riometer absorption. A positive spike was observed in the D magnetic component, instead of the expected negative one. There was no evidence of the usual westward traveling surge at the beginning of the expansion phase during which the precipitation region, auroral arc, and electrojet moved rapidly poleward, though it may have occurred outside the field of view from Sanae. The H{beta} emission increased by a factor of less than 2, whereas the oxygen and nitrogen emissions monitored increased by 3-4. During the recovery phase, phenomena were consistent with a return of the tail field to an elongated form; a very high ratio of 557.7-nm/630-nm emissions, exceeding 10, was observed; and the electrojet lagged noticeably behind the photon emission regions.

  4. Seismic Tomography of Erebus Volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Zandomeneghi, Daria; Kyle, Philip; Miller, Pnina; Snelson, Catherine; Aster, Richard

    2010-02-01

    Mount Erebus (77°32'S, 167°10'E elevation 3794 meters) is the most active volcano in Antarctica and is well known for its persistent lava lake. The lake constitutes an “open window” into the conduit and underlying feeding system and offers a rare opportunity to observe a shallow convecting magmatic system. Imaging and modeling of the internal structure of Erebus volcano are best done through compiling information from arrays of seismometers positioned strategically around the volcano. From these data, the three-dimensional (3-D) structure of the conduit can be pieced together. Building this 3-D model of Erebus was a main goal of the seismic tomographic experiment Tomo Erebus (TE). During the 2007-2008 austral field season, 23 intermediate-period seismometers were installed to contribute data, through the winter, for the passive-source aspect of the experiment. One year later, 100 three-component short-period stations were deployed to record 16 chemical blasts (see Figure 1).

  5. Intercomparison of ozone measurements over Antarctica

    SciTech Connect

    Margitan, J.J.; Farmer, C.B.; Toon, G.C. ); Brothers, G.A. ); Browell, E.V.; Gregory, G.L.; Hypes, W.; Larsen, J.C.; McCormick, M.P. ); Cariolle, D. ); Coffey, M.T.; Mankin, W. ); Farman, J.C. ); Harder, J.W.; Mount, G.H.; Ravishankara, A.R.; Schemeltekopf, A.L.; Tuck, A.F. ); Hofmann, D.J. ); Ismail, S.; Kooi, S. ); Jakoubek, R.O.; Proffitt, M.H.; Wahner, A.; Watterson, I. Univ. of Colorado, Boulder ); Komhyr, W. (NOAA Air Resources La

    1989-11-30

    Measurements of the abundances of ozone over Antarctic in August and September 1987 obtained during the Airborne Antarctic Ozone Experiment are intercompared. These measurements of ozone concentrations and total column abundance were obtained by three satellite instruments, two IR and one UV column-measuring instruments aboard the DC-8, one in situ DC-8, and two in situ ER-2 instruments, an upward looking lidar aboard the DC-8, and ozonesondes from four sites in Antarctica. Given the natural variability of ozone in the Antarctic and the fact that the data were not truly coincident spatially and temporally, this intercomparison is suitable only for identifying gross disparities among the techniques, rather than confirming the accuracies as rigorously as is normally done in an intercomparison. This paper presents a summary of the ozone data, using the data and accuracies given by the individual investigators in the individual papers in this issue, without any attempt to critically review or evaluate the data. In general, very good agreement (within about 10-20%, limited by natural variability) among the various techniques was found, with no systematic biases detected. These observations confirm the low ozone amounts reported in the Antarctic stratosphere.

  6. Ozone profiles above Palmer Station, Antarctica

    NASA Technical Reports Server (NTRS)

    Torres, Arnold L.; Brothers, George

    1988-01-01

    NASA's Goddard Space Flight Center/Wallops Flight Facility conducted a series of 52 balloon-borne measurements of vertical ozone profiles over the National Science Foundation (NSF) research facility at Palmer Station, Antarctica (64 deg 46 S, 64 deg 3 W) between August 9 and October 24, 1987. High resolution measurements were made from ground level to an average of 10 mb. While much variation was seen in the profile amounts of ozone, it is clear that a progressive depletion of ozone occurred during the measurement period, with maximum depletion taking place in the 17 to 19 km altitude region. Ozone partial pressures dropped by about 95 percent in this region. Shown here are plotted time dependences of ozone amounts observed at 17 km and at arbitrarily selected altitudes below (13 km) and above (24 km) the region of maximum depletion. Ozone partial pressure at 17 km is about 150nb in early August, and has decreased to less than 10nb in the minimums in October. The loss rate is of the order of 1.5 percent/day. In summary, a progressive depletion in stratospheric ozone over Palmer Station was observed from August to October, 1987. Maximum depletion occurred in the 17 to 19 km range, and amounted to 95 percent. Total ozone overburden decreased by up to 50 percent during the same period.

  7. The Center for Astrophysics in Antarctica

    NASA Technical Reports Server (NTRS)

    Pernic, Robert J.; Harper, D. AL, Jr.; Bausch, Judith A.

    1995-01-01

    Nowhere on Earth are the infrared skies clearer, darker, or more stable than on the high Antarctic Plateau. At some wavelengths, Antarctic telescopes may be more than one to two orders of magnitude more efficient than at other sites. However, exploiting these advantages requires first addressing the formidable practical difficulties of working in the remote and frigid polar environment. This was the motivation for the Center for Astrophysical Research in Antarctica (CARA), one of twenty-five National Science Foundation Science and Technology Centers. At its inception, the Center organized its research into four projects. Three - AST/RO, COBRA, and SPIREX - address key problems in star formation, evolution of galaxies, and the distribution of matter in the early universe. They feature surveys which can be conducted effectively with moderate-size telescopes operated in a highly automated mode. They also explore the potential of the Antarctic Plateau for a broad range of astrophysical research over a spectral range extending from the near-infrared to millimeter wavelengths. A fourth, ATP, was created to obtain quantitative data on the qualities of the South Pole site and to plan for future scientific projects. During the next five years, AST/RO, COBRA, and SPIREX will become operational, and the Center will begin to build a second generation of telescopes which can address a broader range of problems and accommodate a larger community of users.

  8. Mass casualty incident response and aeromedical evacuation in antarctica.

    PubMed

    Mills, Christopher N; Mills, Gregory H

    2011-02-01

    Antarctica is one of the most remote regions on Earth. Mass casualty incident (MCI) responses in Antarctica are prone to complications from multiple environmental and operational challenges. This review of the current status of MCI risks and response strategies for Antarctica focuses on aeromedical evacuation, a critical component of many possible MCI scenarios. Extreme cold and weather, a lack of medical resources and a multitude of disparate international bases all exert unique demands on MCI response planning. Increasing cruise ship traffic is also escalating the risk of MCI occurrence. To be successful, MCI response must be well coordinated and undertaken by trained rescuers, especially in the setting of Antarctica. Helicopter rescue or aeromedical evacuation of victims to off-continent facilities may be necessary. Currently, military forces have the greatest capacity for mass air evacuation. Specific risks that are likely to occur include structure collapses, vehicle incapacitations, vehicle crashes and fires. All of these events pose concomitant risks of hypothermia among both victims and rescuers. Antarctica's unique environment requires flexible yet robust MCI response planning among the many entities in operation on the continent. PMID:21691470

  9. Response of pioneer soil microalgal colonists to environmental change in Antarctica.

    PubMed

    Wynn-Williams, D D

    1996-03-01

    There is increasing evidence of climate change in Antarctica, especially elevated temperature and ultraviolet B (UVB) flux within the ozone "hole." Its origins are debatable, but the effects on ice recession, water availability, and summer growth conditions are demonstrable. Light-dependent, temperature-sensitive, fast-growing organisms respond to these physical and biogeographical changes. Microalgae (cyanobacteria and eukaryotic algae), which are pioneer colonists of Antarctic mineral fellfield soils, are therefore highly suitable biological indicators of such changes. In frost-heaved soil polygons containing naturally sorted fine mineral particles, microalgal growth is restricted to a shallow zone of light penetration. By virtue of this light requirement, microalgae are exposed to extreme seasonal fluctuations in temperature (air and black-body radiation), photosynthetically active radiation, UV radiation, and desiccation. Dominance of conspicuous autofluorescent indicator species with distinctive morphology allowed quantification of responses using epifluorescence microscopy, and image analysis of undisturbed, unstained communities. However, the physical changes in climate, although significant in the long term, are gradual. The changes were therefore amplified experimentally by enclosing the communities at a fellfield site on Signy Island, maritime Antarctica, in cloches (small greenhouses). These were made of polystyrene of either UV transparent or UV opaque acrylic plastic, with or without walls. During a 6-year period, statistically significant changes were observed in microalgal colonization of the soil surface and in the morphology of filamentous populations. Evidence of community succession correlated with measured changes in local environment was found. Results from Signy Island and at continental sites on Alexander Island suggested that rates of microalgal colonization and community development might change significantly during current climate changes

  10. Tectonic evolution of west Antarctica and its relation to east Antarctica

    SciTech Connect

    Dalziel, I.W.D.

    1987-05-01

    West Antarctica consists of five major blocks of continental crust separated by deep sub-ice basins. Marie Byrd Land appears to have been rifted off the adjacent margin of the East Antarctic craton along the line of the Transantarctic Mountains during the Mesozoic. Ellsworth-Whitmore mountains and Haag Nunataks blocks were also rifted from the margin of the craton. They appear to have moved together with the Antarctic Peninsula and Thurston Island blocks, segments of a Pacific margin Mesozoic-Cenozoic magmatic arc, during the Mesozoic opening of the Weddell Sea basin. Paleomagnetic data suggest that all four of these blocks remained attached to western Gondwanaland (South America-Africa) until approximately 125 m.y. ago, and that the present geographic configuration of the Antarctic continent was essentially complete by the mid-Cretaceous, although important Cenozoic rifting has also occurred. Fragmentation of the Gondwanaland supercontinent was preceded in the Middle to Late Jurassic by an important and widespread thermal event of uncertain origin that resulted in the emplacement of an extensive bimodal igneous suite in South America, Africa, Antarctica, and Australia. This was associated with the development of the composite back-arc basin along the western margin of South America. Inversion of this basin in the mid-Cretaceous initiated Andean orogenesis. The presentation will include new data from the joint US-UK West Antarctic Tectonics Project.

  11. Evaluation of four global reanalysis products using in situ observations in the Amundsen Sea Embayment, Antarctica

    NASA Astrophysics Data System (ADS)

    Jones, R. W.; Renfrew, I. A.; Orr, A.; Webber, B. G. M.; Holland, D. M.; Lazzara, M. A.

    2016-06-01

    The glaciers within the Amundsen Sea Embayment (ASE), West Antarctica, are amongst the most rapidly retreating in Antarctica. Meteorological reanalysis products are widely used to help understand and simulate the processes causing this retreat. Here we provide an evaluation against observations of four of the latest global reanalysis products within the ASE region—the European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-I), Japanese 55-year Reanalysis (JRA-55), Climate Forecast System Reanalysis (CFSR), and Modern Era Retrospective-Analysis for Research and Applications (MERRA). The observations comprise data from four automatic weather stations (AWSs), three research vessel cruises, and a new set of 38 radiosondes all within the period 2009-2014. All four reanalyses produce 2 m temperature fields that are colder than AWS observations, with the biases varying from approximately -1.8°C (ERA-I) to -6.8°C (MERRA). Over the Amundsen Sea, spatially averaged summertime biases are between -0.4°C (JRA-55) and -2.1°C (MERRA) with notably larger cold biases close to the continent (up to -6°C) in all reanalyses. All four reanalyses underestimate near-surface wind speed at high wind speeds (>15 m s-1) and exhibit dry biases and relatively large root-mean-square errors (RMSE) in specific humidity. A comparison to the radiosonde soundings shows that the cold, dry bias at the surface extends into the lower troposphere; here ERA-I and CFSR reanalyses provide the most accurate profiles. The reanalyses generally contain larger temperature and humidity biases, (and RMSE) when a temperature inversion is observed, and contain larger wind speed biases (~2 to 3 m s-1), when a low-level jet is observed.

  12. SeaWiFS: Summer in Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Ross Sea has been somewhat cloud free lately, providing SeaWiFS with views such as this one from December 26, 2001. Note the deep green water; this is a highly productive part of the world'd oceans. Also note the ice gathered around McMurdo Sound. The ice is making it difficult for penguins to reach their food supply. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  13. THE SOUND PATTERN OF ENGLISH.

    ERIC Educational Resources Information Center

    CHOMSKY, NOAM; HALLE, MORRIS

    "THE SOUND PATTERN OF ENGLISH" PRESENTS A THEORY OF SOUND STRUCTURE AND A DETAILED ANALYSIS OF THE SOUND STRUCTURE OF ENGLISH WITHIN THE FRAMEWORK OF GENERATIVE GRAMMAR. IN THE PREFACE TO THIS BOOK THE AUTHORS STATE THAT THEIR "WORK IN THIS AREA HAS REACHED A POINT WHERE THE GENERAL OUTLINES AND MAJOR THEORETICAL PRINCIPLES ARE FAIRLY CLEAR" AND…

  14. Data sonification and sound visualization.

    SciTech Connect

    Kaper, H. G.; Tipei, S.; Wiebel, E.; Mathematics and Computer Science; Univ. of Illinois

    1999-07-01

    Sound can help us explore and analyze complex data sets in scientific computing. The authors describe a digital instrument for additive sound synthesis (Diass) and a program to visualize sounds in a virtual reality environment (M4Cave). Both are part of a comprehensive music composition environment that includes additional software for computer-assisted composition and automatic music notation.

  15. Just How Does Sound Wave?

    ERIC Educational Resources Information Center

    Shipman, Bob

    2006-01-01

    When children first hear the term "sound wave" perhaps they might associate it with the way a hand waves or perhaps the squiggly line image on a television monitor when sound recordings are being made. Research suggests that children tend to think sound somehow travels as a discrete package, a fast-moving invisible thing, and not something that…

  16. Sounds Alive: A Noise Workbook.

    ERIC Educational Resources Information Center

    Dickman, Donna McCord

    Sarah Screech, Danny Decibel, Sweetie Sound and Neil Noisy describe their experiences in the world of sound and noise to elementary students. Presented are their reports, games and charts which address sound measurement, the effects of noise on people, methods of noise control, and related areas. The workbook is intended to stimulate students'…

  17. Exploring Subglacial Lake Connectivity via Groundwater Aquifers in the Dome C Region, East Antarctica

    NASA Astrophysics Data System (ADS)

    Gooch, B. T.; Carter, S. P.; Blankenship, D. D.

    2011-12-01

    Subglacial lakes lying under the Antarctic Ice Sheet form part of a dynamic, interconnected hydraulic system. Most research exploring the nature of this system has focused on flow along the ice-bed interface, neglecting the effects of groundwater transport, as such systems are thought to lack the transmissivity necessary to accommodate the inferred meltwater volume. In the Dome C region of East Antarctica, however, inferred melt water volumes are relatively low due to proximity to the ice divide and hydraulic gradients are relatively high due to steep subglacial bedrock topography, such that groundwater flow might be viable as a dominant means of water transport. This region contains many small subglacial lakes residing in bedrock depressions of steep basal topography. Preliminary analysis of radar sounding data does not always reveal an obvious hydraulic connection between these lakes despite readily apparent sources of melt feeding these bodies. Here we test several simple models for groundwater flow, including both fractured rock and porous media systems using ice-surface and bedrock geometry inferred from radio-echo sounding data and a published map of melt rates, with the purpose of defining a region in which a groundwater system can account for the majority of the water budget. We then compare these results against maps of basal reflectivity and subglacial lake distribution, as determined from radar sounding data. Areas in which groundwater flow is the dominant process will lack basal lubrication and demonstrate low basal reflectivities, but could still contain small subglacial lakes. While not spatially extensive with respect to the ice sheet, these groundwater-dominated areas could occupy the headwaters of most glacial catchments representing a unique and relatively stable subglacial environment.

  18. Discovery of new hydrothermal vent sites in Bransfield Strait, Antarctica

    NASA Astrophysics Data System (ADS)

    Klinkhammer, G. P.; Chin, C. S.; Keller, R. A.; Dählmann, A.; Sahling, H.; Sarthou, G.; Petersen, S.; Smith, F.; Wilson, C.

    2001-12-01

    We carried out a search for hydrothermal vents in the Central Basin of Bransfield Strait, Antarctica. The ZAPS (zero angle photon spectrometer) chemical sensor and instrument package (Oregon State University), OFOS (ocean-floor observation system) camera sled and TVG (TV-grab) (GEOMAR) were used to explore the water column and underlying seafloor. These operations were supplemented with a series of dredges. Hydrothermal plumes over Hook Ridge at the eastern end of the basin are confined to the E ridge crest and SE flank. The plumes are complex and sometimes contain two turbidity maxima one widespread feature centered at 1150 m and a smaller, more localized but broad maximum at 600-800 m. We traced the source of the shallower plume to a sunken crater near the ridge crest using sensors on the ZAPS instrument package. Subsequently two TV-grabs from the crater brought back hot, soupy sediment (42-49°C) overlain by hard, siliceous crusts and underlain by a thick layer of volcanic ash. We also recovered chimney fragments whose texture and mineralogy indicate venting temperatures in excess of 250°C. Native sulfur and Fe-sulfides occur in fractures and porous layers in sediment from throughout the area. Pore water data from the crater site are consistent with venting into a thin sediment layer and indicate phase separation of fluids beneath Hook Ridge. The source of the deeper plumes at Hook Ridge has yet to be located. We also explored a series of three parallel volcanic ridges west of Hook Ridge called Three Sisters. We detected water column anomalies indicative of venting with the ZAPS package and recovered hydrothermal barites and sulfides from Middle Sister. We spent considerable time photographing Middle Sister and Hook Ridge but did not identify classic vent fauna at either location. We either missed small areas with our photography or typical MOR vent fauna are absent at these sites.

  19. Environmental controls of marine productivity hot spots around Antarctica

    NASA Astrophysics Data System (ADS)

    Arrigo, Kevin R.; van Dijken, Gert L.; Strong, Aaron L.

    2015-08-01

    Antarctic coastal polynyas are biologically rich ecosystems that support large populations of mammals and birds and are globally significant sinks of atmospheric carbon dioxide. To support local phytoplankton blooms, these highly productive ecosystems require a large input of iron (Fe), the sources of which are poorly known. Here we assess the relative importance of six different environmental factors in controlling the amount of phytoplankton biomass and rates of net primary production (NPP) in 46 coastal polynyas around Antarctica. Data presented here suggest that melting ice shelves are a primary supplier of Fe to coastal polynyas, with basal melt rates explaining 59% of the between-polynya variance in mean chlorophyll a (Chl a) concentration. In a multiple regression analysis, which explained 78% of the variance in chlorophyll a (Chl a) between polynyas, basal melt rate explained twice as much of the variance as the next most important variable. Fe upwelled from sediments, which is partly controlled by continental shelf width, was also important in some polynyas. Of secondary importance to phytoplankton abundance and NPP were sea surface temperature and polynya size. Surprisingly, differences in light availability and the length of the open water season explained little or none of the variance in either Chl a or NPP between polynyas. If the productivity of coastal polynyas is indeed sensitive to the release of Fe from melting ice shelves, future changes in ice shelf melt rates could dramatically influence Antarctic coastal ecosystems and the ability of continental shelf waters to sequester atmospheric carbon dioxide. This article was corrected on 26 AUG 2015. See the end of the full text for details.

  20. Deviant sounds yield distraction irrespective of the sounds' informational value.

    PubMed

    Parmentier, Fabrice B R

    2016-06-01

    Oddball studies show that rare and unexpected changes in an otherwise repetitive or structured sequence of task-irrelevant sounds (deviant sounds among standard sounds) ineluctably break through attentional filters and yield longer response times in an ongoing task. Although this deviance distraction effect has generally been thought of as an involuntary and adaptive phenomenon, recent studies questioned this view by reporting that deviance distraction is observed when sounds predict the occurrence of a target stimulus (informative sounds) but that it disappears when sounds do not convey this information (uninformative sounds). Here, I challenge this conclusion and suggest that the apparent absence of deviance distraction with uninformative sounds results in fact from 2 opposite effects: deviance distraction when the previous trial involved a target and required responding, and a speeding up of responses by deviant sound following trials involving no target and requiring the withholding of responses. Data from a new experiment, new analyses of the data from 3 earlier studies, and the modeling of these data all converge in suggesting the existence of deviance distraction impervious to the sounds' informational value. These results undermine the proposition of a late top-down control mechanism gating behavioral distraction as a function of the sounds' informative value. (PsycINFO Database Record PMID:26727016