Adaptation of Acoustic Model Experiments of STM via Smartphones and Tablets

ERIC Educational Resources Information Center

Thees, Michael; Hochberg, Katrin; Kuhn, Jochen; Aeschlimann, Martin

2017-01-01

The importance of Scanning Tunneling Microscopy (STM) in today's research and industry leads to the question of how to include such a key technology in physics education. Manfred Euler has developed an acoustic model experiment to illustrate the fundamental measuring principles based on an analogy between quantum mechanics and acoustics. Based on…

Acoustic Propagation Studies For Sperm Whale Phonation Analysis During LADC Experiments

NASA Astrophysics Data System (ADS)

Sidorovskaia, Natalia A.; Ioup, George E.; Ioup, Juliette W.; Caruthers, Jerald W.

2004-11-01

The Littoral Acoustic Demonstration Center (LADC) conducted a series of passive acoustic experiments in the Northern Gulf of Mexico and the Ligurian Sea in 2001 and 2002. Environmental and acoustic moorings were deployed in areas of large concentrations of marine mammals (mainly, sperm whales). Recordings and analysis of whale phonations are among the objectives of the project. Each mooring had a single autonomously recording hydrophone (Environmental Acoustic Recording System (EARS)) obtained from the U.S. Naval Oceanographic Office after modification to record signals up to 5,859 Hz in the Gulf of Mexico and up to 12,500 Hz in the Ligurian Sea. Self-recording environmental sensors, attached to the moorings, and concurrent environmental ship surveys provided the environmental data for the experiments. The results of acoustic simulations of long-range propagation of the broad-band (500-6,000 Hz) phonation pulses from a hypothetical whale location to the recording hydrophone in the experimental environments are presented. The utilization of the simulation results for an interpretation of the spectral features observed in whale clicks and for the development of tracking algorithms from single hydrophone recordings based on the identification of direct and surface and bottom reflected arrivals are discussed. [Research supported by ONR.

Modal processing for acoustic communications in shallow water experiment.

PubMed

Morozov, Andrey K; Preisig, James C; Papp, Joseph

2008-09-01

Acoustical array data from the Shallow Water Acoustics experiment was processed to show the feasibility of broadband mode decomposition as a preprocessing method to reduce the effective channel delay spread and concentrate received signal energy in a small number of independent channels. The data were collected by a vertical array designed at the Woods Hole Oceanographic Institution. Phase-shift Keying (PSK) m-sequence modulated signals with different carrier frequencies were transmitted at a distance 19.2 km from the array. Even during a strong internal waves activity a low bit error rate was achieved.

Transducer Design Experiments for Ground-Penetrating Acoustic Systems

DTIC Science & Technology

1996-03-19

subsurface imaging experiments have utilized a source (Tx) and receiver (Rx) configuration in which signals produced by a transmitter at the soil surface...development in the field of acoustic subsurface imaging are as follows. First, a transmitter designed to minimize the emission of surface waves, while

Acoustic wave propagation and intensity fluctuations in shallow water 2006 experiment

NASA Astrophysics Data System (ADS)

Luo, Jing

Fluctuations of low frequency sound propagation in the presence of nonlinear internal waves during the Shallow Water 2006 experiment are analyzed. Acoustic waves and environmental data including on-board ship radar images were collected simultaneously before, during, and after a strong internal solitary wave packet passed through a source-receiver acoustic track. Analysis of the acoustic wave signals shows temporal intensity fluctuations. These fluctuations are affected by the passing internal wave and agrees well with the theory of the horizontal refraction of acoustic wave propagation in shallow water. The intensity focusing and defocusing that occurs in a fixed source-receiver configuration while internal wave packet approaches and passes the acoustic track is addressed in this thesis. Acoustic ray-mode theory is used to explain the modal evolution of broadband acoustic waves propagating in a shallow water waveguide in the presence of internal waves. Acoustic modal behavior is obtained from the data through modal decomposition algorithms applied to data collected by a vertical line array of hydrophones. Strong interference patterns are observed in the acoustic data, whose main cause is identified as the horizontal refraction referred to as the horizontal Lloyd mirror effect. To analyze this interference pattern, combined Parabolic Equation model and Vertical-mode horizontal-ray model are utilized. A semi-analytic formula for estimating the horizontal Lloyd mirror effect is developed.

Adaptation of acoustic model experiments of STM via smartphones and tablets

NASA Astrophysics Data System (ADS)

Thees, Michael; Hochberg, Katrin; Kuhn, Jochen; Aeschlimann, Martin

2017-10-01

The importance of Scanning Tunneling Microscopy (STM) in today's research and industry leads to the question of how to include such a key technology in physics education. Manfred Euler has developed an acoustic model experiment to illustrate the fundamental measuring principles based on an analogy between quantum mechanics and acoustics. Based on earlier work we applied mobile devices such as smartphones and tablets instead of using a computer to record and display the experimental data and thus converted Euler's experimental setup into a low-cost experiment that is easy to build and handle by students themselves.

Dimensions Underlying the Perceived Similarity of Acoustic Environments

PubMed Central

Aletta, Francesco; Axelsson, Östen; Kang, Jian

2017-01-01

Scientific research on how people perceive or experience and/or understand the acoustic environment as a whole (i.e., soundscape) is still in development. In order to predict how people would perceive an acoustic environment, it is central to identify its underlying acoustic properties. This was the purpose of the present study. Three successive experiments were conducted. With the aid of 30 university students, the first experiment mapped the underlying dimensions of perceived similarity among 50 acoustic environments, using a visual sorting task of their spectrograms. Three dimensions were identified: (1) Distinguishable–Indistinguishable sound sources, (2) Background–Foreground sounds, and (3) Intrusive–Smooth sound sources. The second experiment was aimed to validate the results from Experiment 1 by a listening experiment. However, a majority of the 10 expert listeners involved in Experiment 2 used a qualitatively different approach than the 30 university students in Experiment 1. A third experiment was conducted in which 10 more expert listeners performed the same task as per Experiment 2, with spliced audio signals. Nevertheless, Experiment 3 provided a statistically significantly worse result than Experiment 2. These results suggest that information about the meaning of the recorded sounds could be retrieved in the spectrograms, and that the meaning of the sounds may be captured with the aid of holistic features of the acoustic environment, but such features are still unexplored and further in-depth research is needed in this field. PMID:28747894

Study on model design and dynamic similitude relations of vibro-acoustic experiment for elastic cavity

NASA Astrophysics Data System (ADS)

Shi, Ao; Lu, Bo; Yang, Dangguo; Wang, Xiansheng; Wu, Junqiang; Zhou, Fangqi

2018-05-01

Coupling between aero-acoustic noise and structural vibration under high-speed open cavity flow-induced oscillation may bring about severe random vibration of the structure, and even cause structure to fatigue destruction, which threatens the flight safety. Carrying out the research on vibro-acoustic experiments of scaled down model is an effective means to clarify the effects of high-intensity noise of cavity on structural vibration. Therefore, in allusion to the vibro-acoustic experiments of cavity in wind tunnel, taking typical elastic cavity as the research object, dimensional analysis and finite element method were adopted to establish the similitude relations of structural inherent characteristics and dynamics for distorted model, and verifying the proposed similitude relations by means of experiments and numerical simulation. Research shows that, according to the analysis of scale-down model, the established similitude relations can accurately simulate the structural dynamic characteristics of actual model, which provides theoretic guidance for structural design and vibro-acoustic experiments of scaled down elastic cavity model.

Nonlinear acoustic experiments involving landmine detection: A connection between mesoscopic/nanoscale effects in geomaterials

NASA Astrophysics Data System (ADS)

Korman, Murray S.

2004-05-01

The vibration interaction between the top-plate interface of a buried plastic landmine and the soil above it appears to exhibit many characteristics of the mesoscopic/nanoscale nonlinear effects that are observed in geomaterials like rocks (sandstone) or granular materials. Experiments are performed with an inert VS 1.6 anti-tank mine that is buried 3.6 cm deep in dry sifted loess soil. Airborne sound at two primary frequencies f1=120 Hz and f2=130 Hz undergo acoustic-to-seismic coupling. Interactions with the compliant mine and soil generate combination frequencies that, through scattering, can affect the vibration velocity at the surface. Profiles of the soil surface particle velocity at f1 and f2 and the nonlinearly generated f1-(f2-f1) component are characterized by a single peak. Doubly peaked profiles at 2f1+f2 and 2f2+f1 are attributed to the familiar mode shape of a timpani drum. Near resonance, the bending (a softening) of a family of tuning curves for the soil surface vibration over a landmine exhibits a linear relationship between the peak frequency and the corresponding peak particle velocity, which also exhibit hysteresis effects. [Work supported by U.S. Army Communications-Electronics Command RDEC, NVESD, Fort Belvoir, VA.

Acoustic emissions verification testing of International Space Station experiment racks at the NASA Glenn Research Center Acoustical Testing Laboratory

NASA Astrophysics Data System (ADS)

Akers, James C.; Passe, Paul J.; Cooper, Beth A.

2005-09-01

The Acoustical Testing Laboratory (ATL) at the NASA John H. Glenn Research Center (GRC) in Cleveland, OH, provides acoustic emission testing and noise control engineering services for a variety of specialized customers, particularly developers of equipment and science experiments manifested for NASA's manned space missions. The ATL's primary customer has been the Fluids and Combustion Facility (FCF), a multirack microgravity research facility being developed at GRC for the USA Laboratory Module of the International Space Station (ISS). Since opening in September 2000, ATL has conducted acoustic emission testing of components, subassemblies, and partially populated FCF engineering model racks. The culmination of this effort has been the acoustic emission verification tests on the FCF Combustion Integrated Rack (CIR) and Fluids Integrated Rack (FIR), employing a procedure that incorporates ISO 11201 (``Acoustics-Noise emitted by machinery and equipment-Measurement of emission sound pressure levels at a work station and at other specified positions-Engineering method in an essentially free field over a reflecting plane''). This paper will provide an overview of the test methodology, software, and hardware developed to perform the acoustic emission verification tests on the CIR and FIR flight racks and lessons learned from these tests.

Acoustic interactions between an altitude test facility and jet engine plumes: Theory and experiments

NASA Technical Reports Server (NTRS)

Ahuja, K. K.; Jones, R. R., III; Tam, C. K.; Massey, K. C.; Fleming, A. J.

1992-01-01

The overall objective of the described effort was to develop an understanding of the physical mechanisms involved in the flow/acoustic interactions experienced in full-scale altitude engine test facilities. This is done by conducting subscale experiments and through development of a theoretical model. Model cold jet experiments with an axisymmetric convergent nozzle are performed in a test setup that stimulates a supersonic jet exhausting into a cylindrical diffuser. The measured data consist of detailed flow visualization data and acoustic spectra for a free and a ducted plume. It is shown that duct resonance is most likely responsible by theoretical calculations. Theoretical calculations also indicate that the higher discrete tones observed in the measurements are related to the screech phenomena. Limited experiments on the sensitivity of a free 2-D, C-D nozzle to externally imposed sound are also presented. It is shown that a 2-D, C-D nozzle with a cutback is less excitable than a 2-D C-D nozzle with no cutback. At a pressure ratio of 1.5 unsteady separation from the diverging walls of the nozzle is noticed. This separation switches from one wall to the opposite wall thus providing an unsteady deflection of the plume. It is shown that this phenomenon is related to the venting provided by the cutback section.

Spatial and temporal variation of acoustic backscatter in the STRESS experiment

NASA Astrophysics Data System (ADS)

Dworski, J. George; Jackson, Darrell R.

1994-08-01

Acoustic backscatter measurements were made of the seabed with a bottom mounted, circularly scanning sonar. The placement was at 91 m depth, mid-shelf of Northern California (38° 34'N), site C3 of the experiment STRESS I (1988-1989). Our expectation was that sonar images (70 m radius, 12,000 m 2) would provide a means of observing, over a large field of view, changes in the bottom due to storm-induced sediment transport and due to bioturbation. This expectation was supported in part by towed sonar measurements at 35 kHz over a sandy area in the North Sea, where dramatic spatial variation in the level of the backseattered signal was observed during an Autumn storm on scales of a few km with no concomitant change in sediment grain size [ JACKSONet al. (1986) The Journal of the Acoustical Society of America, 80, 1188-1199]. It appeared possible that storm-driven sediment transport might have been responsible for this patchiness, by altering bottom roughness and by redeposition of suspended material. At the California site, a conventional sonar processing of our data from the STRESS experiment reveals no such dramatic change in backscattered signal level due to storms. The sonar images contain random structures whose time evolution is subtle and difficult to interpret. A much clearer picture of temporal and spatial variations emerges from a processing scheme involving cross-correlation of time-separated acoustic views of the bottom. In effect, the sequence of correlation data images produces a movie in which patches of activity are seen to develop as functions of time. It appears that most of this activity is biological rather than hydrodynamic. A tentative explanation is two-fold. The bottom shear stress might have been considerably greater at the North Sea site (with depth only one-half of the California site). The seafloor at the California site was silty-clayey, and backscatter from such floor is less sensitive to the water-floor interface shape and roughness than

Charged drop dynamics experiment using an electrostatic-acoustic hybrid system

NASA Technical Reports Server (NTRS)

Rhim, W. K.; Chung, S. K.; Trinh, E. H.; Elleman, D. D.

1987-01-01

The design and the performance of an electrostatic-acoustic hybrid system and its application to a charge drop rotation experiment are presented. This system can levitate a charged drop electrostatically and induce drop rotation or oscillation by imposing an acoustic torque or an oscillating acoustic pressure. Using this system, the equilibrium shapes and stability of a rotating charged drop were experimentally investigated. A 3 mm size water drop was rotated as a rigid body and its gyrostatic equilibrium shapes were observed. Families of axisymmetric shapes, two-lobed shapes, and eventual fissioning have been observed. With the assumption of 'effective surface tension' in which the surface charge simply modified the surface tension of neutral liquid, the results agree exceptionally well with the Brown and Scriven's (1980) prediction for uncharged drops.

Using acoustic levitation in synchrotron based laser pump hard x-ray probe experiments

NASA Astrophysics Data System (ADS)

Hu, Bin; Lerch, Jason; Suthar, Kamlesh; Dichiara, Anthony

Acoustic levitation provides a platform to trap and hold a small amount of material by using standing pressure waves without a container. The technique has a potential to be used for laser pump x-ray probe experiments; x-ray scattering and laser distortion from the container can be avoided, sample consumption can be minimized, and unwanted chemistry that may occur at the container interface can be avoided. The method has been used at synchrotron sources for studying protein and pharmaceutical solutions using x-ray diffraction (XRD) and small angle x-ray scattering (SAXS). However, pump-probe experiments require homogeneously excited samples, smaller than the absorption depth of the material that must be held stably at the intersection of both the laser and x-ray beams. We discuss 1) the role of oscillations in acoustic levitation and the optimal acoustic trapping conditions for x-ray/laser experiments, 2) opportunities to automate acoustic levitation for fast sample loading and manipulation, and 3) our experimental results using SAXS to monitor laser induced thermal expansion in gold nanoparticles solution. We also performed Finite Element Analysis to optimize the trapping performance and stability of droplets ranging from 0.4 mm to 2 mm. Our early x-ray/laser demonstrated the potential of the technique for time-resolved X-ray science.

Experiments to Investigate the Acoustic Properties of Sound Propagation

ERIC Educational Resources Information Center

Dagdeviren, Omur E.

2018-01-01

Propagation of sound waves is one of the fundamental concepts in physics. Some of the properties of sound propagation such as attenuation of sound intensity with increasing distance are familiar to everybody from the experiences of daily life. However, the frequency dependence of sound propagation and the effect of acoustics in confined…

Acoustic impulse response method as a source of undergraduate research projects and advanced laboratory experiments.

PubMed

Robertson, W M; Parker, J M

2012-03-01

A straightforward and inexpensive implementation of acoustic impulse response measurement is described utilizing the signal processing technique of coherent averaging. The technique is capable of high signal-to-noise measurements with personal computer data acquisition equipment, an amplifier/speaker, and a high quality microphone. When coupled with simple waveguide test systems fabricated from commercial PVC plumbing pipe, impulse response measurement has proven to be ideal for undergraduate research projects-often of publishable quality-or for advanced laboratory experiments. The technique provides important learning objectives for science or engineering students in areas such as interfacing and computer control of experiments; analog-to-digital conversion and sampling; time and frequency analysis using Fourier transforms; signal processing; and insight into a variety of current research areas such as acoustic bandgap materials, acoustic metamaterials, and fast and slow wave manipulation. © 2012 Acoustical Society of America

The development of acoustic experiments for off-campus teaching and learning

NASA Astrophysics Data System (ADS)

Wild, Graham; Swan, Geoff

2011-05-01

In this article, we show the implementation of a computer-based digital storage oscilloscope (DSO) and function generator (FG) using the computer's soundcard for off-campus acoustic experiments. The microphone input is used for the DSO, and a speaker jack is used as the FG. In an effort to reduce the cost of implementing the experiment, we examine software available for free, online. A small number of applications were compared in terms of their interface and functionality, for both the DSO and the FG. The software was then used to investigate standing waves in pipes using the computer-based DSO. Standing wave theory taught in high school and in first year physics is based on a one-dimensional model. With the use of the DSO's fast Fourier transform function, the experimental uncertainly alone was not sufficient to account for the difference observed between the measure and the calculated frequencies. Hence the original experiment was expanded upon to include the end correction effect. The DSO was also used for other simple acoustics experiments, in areas such as the physics of music.

Acoustic input and efferent activity regulate the expression of molecules involved in cochlear micromechanics

PubMed Central

Lamas, Veronica; Arévalo, Juan C.; Juiz, José M.; Merchán, Miguel A.

2015-01-01

Electromotile activity in auditory outer hair cells (OHCs) is essential for sound amplification. It relies on the highly specialized membrane motor protein prestin, and its interactions with the cytoskeleton. It is believed that the expression of prestin and related molecules involved in OHC electromotility may be dynamically regulated by signals from the acoustic environment. However little is known about the nature of such signals and how they affect the expression of molecules involved in electromotility in OHCs. We show evidence that prestin oligomerization is regulated, both at short and relatively long term, by acoustic input and descending efferent activity originating in the cortex, likely acting in concert. Unilateral removal of the middle ear ossicular chain reduces levels of trimeric prestin, particularly in the cochlea from the side of the lesion, whereas monomeric and dimeric forms are maintained or even increased in particular in the contralateral side, as shown in Western blots. Unilateral removal of the auditory cortex (AC), which likely causes an imbalance in descending efferent activity on the cochlea, also reduces levels of trimeric and tetrameric forms of prestin in the side ipsilateral to the lesion, whereas in the contralateral side prestin remains unaffected, or even increased in the case of trimeric and tetrameric forms. As far as efferent inputs are concerned, unilateral ablation of the AC up-regulates the expression of α10 nicotinic Ach receptor (nAChR) transcripts in the cochlea, as shown by RT-Quantitative real-time PCR (qPCR). This suggests that homeostatic synaptic scaling mechanisms may be involved in dynamically regulating OHC electromotility by medial olivocochlear efferents. Limited, unbalanced efferent activity after unilateral AC removal, also affects prestin and β-actin mRNA levels. These findings support that the concerted action of acoustic and efferent inputs to the cochlea is needed to regulate the expression of major

The Development of Acoustic Experiments for Off-Campus Teaching and Learning

ERIC Educational Resources Information Center

Wild, Graham; Swan, Geoff

2011-01-01

In this article, we show the implementation of a computer-based digital storage oscilloscope (DSO) and function generator (FG) using the computer's soundcard for off-campus acoustic experiments. The microphone input is used for the DSO, and a speaker jack is used as the FG. In an effort to reduce the cost of implementing the experiment, we examine…

Acoustic Modal Patterns and Striations (AMPS) experiment G-325, Norfolk Public Schools

NASA Technical Reports Server (NTRS)

Young, Joy W.

1995-01-01

This paper will describe how high school students with the guidance of volunteer mentors were able to successfully complete an acoustics space experiment. Some of the NORSTAR program strategies used to effectively accomplish this goal will be discussed. The experiment and present status of results will be explained.

Nonlinear acoustic experiments involving landmine detection: Connections with mesoscopic elasticity and slow dynamics in geomaterials

NASA Astrophysics Data System (ADS)

Korman, Murray S.; Fenneman, Douglas J.; Sabatier, James M.

2004-10-01

The vibration interaction between the top-plate of a buried VS 1.6 plastic, anti-tank landmine and the soil above it appears to exhibit similar characteristics to the nonlinear mesoscopic/nanoscale effects that are observed in geomaterials like rocks or granular materials. In nonlinear detection schemes, airborne sound at two primary frequencies f1 and f2 (chosen several Hz apart on either side of resonance) undergo acoustic-to-seismic coupling. Interactions with the compliant mine and soil generate combination frequencies that, through scattering, can effect the vibration velocity at the surface. Profiles at f1, f2, f1-(f2-f1) and f2+(f2-f1) exhibit a single peak while profiles at 2f1-(f2-f1), f1+f2 and 2f2+(f2-f1) are attributed to higher order mode shapes. Near resonance (~125 Hz for a mine buried 3.6 cm deep), the bending (softening) of a family of increasing amplitude tuning curves (involving the surface vibration over the landmine) exhibits a linear relationship between the peak particle velocity and corresponding frequency. Subsequent decreasing amplitude tuning curves exhibit hysteresis effects. Slow dynamics explains the amplitude difference in tuning curves for first sweeping upward and then downward through resonance, provided the soil modulus drops after periods of high strain. [Work supported by U.S. Army RDECOM, CERDEC, NVESD, Fort Belvoir, VA.

Development of an Acoustic Localization Method for Cavitation Experiments in Reverberant Environments

NASA Astrophysics Data System (ADS)

Ranjeva, Minna; Thompson, Lee; Perlitz, Daniel; Bonness, William; Capone, Dean; Elbing, Brian

2011-11-01

Cavitation is a major concern for the US Navy since it can cause ship damage and produce unwanted noise. The ability to precisely locate cavitation onset in laboratory scale experiments is essential for proper design that will minimize this undesired phenomenon. Measuring the cavitation onset is more accurately determined acoustically than visually. However, if other parts of the model begin to cavitate prior to the component of interest the acoustic data is contaminated with spurious noise. Consequently, cavitation onset is widely determined by optically locating the event of interest. The current research effort aims at developing an acoustic localization scheme for reverberant environments such as water tunnels. Currently cavitation bubbles are being induced in a static water tank with a laser, allowing the localization techniques to be refined with the bubble at a known location. The source is located with the use of acoustic data collected with hydrophones and analyzed using signal processing techniques. To verify the accuracy of the acoustic scheme, the events are simultaneously monitored visually with the use of a high speed camera. Once refined testing will be conducted in a water tunnel. This research was sponsored by the Naval Engineering Education Center (NEEC).

Experiments on stress dependent borehole acoustic waves.

PubMed

Hsu, Chaur-Jian; Kane, Michael R; Winkler, Kenneth; Wang, Canyun; Johnson, David Linton

2011-10-01

In the laboratory setup, a borehole traverses a dry sandstone formation, which is subjected to a controlled uniaxial stress in the direction perpendicular to the borehole axis. Measurements are made in a single loading-unloading stress cycle from zero to 10 MPa and then back down to zero stress. The applied stress and the presence of the borehole induce anisotropy in the bulk of the material and stress concentration around the borehole, both azimuthally and radially. Acoustic waves are generated and detected in the water-filled borehole, including compressional and shear headwaves, as well as modes of monopole, dipole, quadrupole, and higher order azimuthal symmetries. The linear and non-linear elastic parameters of the formation material are independently quantified, and utilized in conjunction with elastic theories to predict the characteristics of various borehole waves at zero and finite stress conditions. For example, an analytic theory is developed which is successfully used to estimate the changes of monopole tube mode at low frequency resulted from uniaxial stress, utilizing the measured material third order elasticity parameters. Comparisons between various measurements as well as that between experiments and theories are also presented. © 2011 Acoustical Society of America

Reproducibility experiments on measuring acoustical properties of rigid-frame porous media (round-robin tests).

PubMed

Horoshenkov, Kirill V; Khan, Amir; Bécot, François-Xavier; Jaouen, Luc; Sgard, Franck; Renault, Amélie; Amirouche, Nesrine; Pompoli, Francesco; Prodi, Nicola; Bonfiglio, Paolo; Pispola, Giulio; Asdrubali, Francesco; Hübelt, Jörn; Atalla, Noureddine; Amédin, Celse K; Lauriks, Walter; Boeckx, Laurens

2007-07-01

This paper reports the results of reproducibility experiments on the interlaboratory characterization of the acoustical properties of three types of consolidated porous media: granulated porous rubber, reticulated foam, and fiberglass. The measurements are conducted in several independent laboratories in Europe and North America. The studied acoustical characteristics are the surface complex acoustic impedance at normal incidence and plane wave absorption coefficient which are determined using the standard impedance tube method. The paper provides detailed procedures related to sample preparation and installation and it discusses the dispersion in the acoustical material property observed between individual material samples and laboratories. The importance of the boundary conditions, homogeneity of the porous material structure, and stability of the adopted signal processing method are highlighted.

Oscillating load-induced acoustic emission in laboratory experiment

USGS Publications Warehouse

Ponomarev, Alexander; Lockner, David A.; Stroganova, S.; Stanchits, S.; Smirnov, Vladmir

2010-01-01

Spatial and temporal patterns of acoustic emission (AE) were studied. A pre-fractured cylinder of granite was loaded in a triaxial machine at 160 MPa confining pressure until stick-slip events occurred. The experiments were conducted at a constant strain rate of 10−7 s−1 that was modulated by small-amplitude sinusoidal oscillations with periods of 175 and 570 seconds. Amplitude of the oscillations was a few percent of the total load and was intended to simulate periodic loading observed in nature (e.g., earth tides or other sources). An ultrasonic acquisition system with 13 piezosensors recorded acoustic emissions that were generated during deformation of the sample. We observed a correlation between AE response and sinusoidal loading. The effect was more pronounced for higher frequency of the modulating force. A time-space spectral analysis for a “point” process was used to investigate details of the periodic AE components. The main result of the study was the correlation of oscillations of acoustic activity synchronized with the applied oscillating load. The intensity of the correlated AE activity was most pronounced in the “aftershock” sequences that followed large-amplitude AE events. We suggest that this is due to the higher strain-sensitivity of the failure area when the sample is in a transient, unstable mode. We also found that the synchronization of AE activity with the oscillating external load nearly disappeared in the period immediately after the stick-slip events and gradually recovered with further loading.

Construction of an anechoic chamber for aeroacoustic experiments and examination of its acoustic parameters

NASA Astrophysics Data System (ADS)

Kopiev, V. F.; Palchikovskiy, V. V.; Belyaev, I. V.; Bersenev, Yu. V.; Makashov, S. Yu.; Khramtsov, I. V.; Korin, I. A.; Sorokin, E. V.; Kustov, O. Yu.

2017-01-01

The acoustic parameters of a new anechoic chamber constructed at Perm National Research Polytechnic University (PNRPU) are presented. This chamber is designed to be used, among other things, for measuring noise from aerodynamic sources. Sound-absorbing wedges lining the walls of the chamber were studied in an interferometer with normal wave incidence. The results are compared to the characteristics of sound-absorbing wedges of existing anechoic facilities. Metrological examination of the acoustic parameters of the PNRPU anechoic chamber demonstrates that free field conditions are established in it, which will make it possible to conduct quantitative acoustic experiments.

Student design projects in applied acoustics.

PubMed

Bös, Joachim; Moritz, Karsten; Skowronek, Adam; Thyes, Christian; Tschesche, Johannes; Hanselka, Holger

2012-03-01

This paper describes a series of student projects which are intended to complement theoretical education in acoustics and engineering noise control with practical experience. The projects are also intended to enhance the students' ability to work in a team, to manage a project, and to present their results. The projects are carried out in close cooperation with industrial partners so that the students can get a taste of the professional life of noise control engineers. The organization of such a project, its execution, and some of the results from the most recent student project are presented as a demonstrative example. This latest project involved the creation of noise maps of a production hall, the acoustic analysis of a packaging machine, and the acoustic analysis of a spiral vibratory conveyor. Upon completion of the analysis, students then designed, applied, and verified some simple preliminary noise reduction measures to demonstrate the potential of these techniques. © 2012 Acoustical Society of America

Homogenization-based interval analysis for structural-acoustic problem involving periodical composites and multi-scale uncertain-but-bounded parameters.

PubMed

Chen, Ning; Yu, Dejie; Xia, Baizhan; Liu, Jian; Ma, Zhengdong

2017-04-01

This paper presents a homogenization-based interval analysis method for the prediction of coupled structural-acoustic systems involving periodical composites and multi-scale uncertain-but-bounded parameters. In the structural-acoustic system, the macro plate structure is assumed to be composed of a periodically uniform microstructure. The equivalent macro material properties of the microstructure are computed using the homogenization method. By integrating the first-order Taylor expansion interval analysis method with the homogenization-based finite element method, a homogenization-based interval finite element method (HIFEM) is developed to solve a periodical composite structural-acoustic system with multi-scale uncertain-but-bounded parameters. The corresponding formulations of the HIFEM are deduced. A subinterval technique is also introduced into the HIFEM for higher accuracy. Numerical examples of a hexahedral box and an automobile passenger compartment are given to demonstrate the efficiency of the presented method for a periodical composite structural-acoustic system with multi-scale uncertain-but-bounded parameters.

Biological Significance of Acoustic Impacts on Marine Mammals: Examples Using an Acoustic Recording tag to Define Acoustic Exposure of Sperm Whales, Physeter catodon, Exposed to Airgun Sounds in Controlled Exposure Experiments

NASA Astrophysics Data System (ADS)

Tyack, P. L.; Johnson, M. P.; Madsen, P. T.; Miller, P. J.; Lynch, J.

2006-05-01

There has been considerable debate about how to regulate behavioral disruption in marine mammals. The U.S. Marine Mammal Protection Act prohibits "taking" marine mammals, including harassment, which is defined as injury or disruption of behavioral patterns. A 2005 report by the National Academy of Sciences focuses on the need to analyze acoustic impacts on marine mammal behavior in terms of biological significance. The report develops a model for predicting population consequences of acoustic impacts. One of the key data gaps involves methods to estimate the impact of disruption on an animal's ability to complete life functions critical for growth, survival, and reproduction. One of the few areas where theory and data are available involves foraging energetics. Patrick Miller in the next talk and I will discuss an example study designed to evaluate the impact of exposure to seismic survey on the foraging energetics of sperm whales. As petroleum exploration moves offshore to deep water, there is increasing overlap between seismic exploration and deep diving toothed whales such as the sperm whale which is listed by the US as an endangered species. With support from the US Minerals Management Service and the Industry Research Funding Coalition, we tagged sperm whales with tags that can record sound, orientation, acceleration, temperature and depth. Eight whales tagged in the Gulf of Mexico during 2002-2003 were subjects in 5 controlled experiments involving exposure to sounds of an airgun array. One critical component of evaluating effects involves quantifying exposure at the animal. While the on-axis signature of airgun arrays has been well quantified, there are few broadband calibrated measurements in the water column displaced horizontally away from the downward-directed beam. The acoustic recording tags provide direct data on sounds as received at the animals. Due to multipath propagation, multiple sound pulses were recorded on the tagged whales for each firing of

Acoustic Remote Sensing

NASA Astrophysics Data System (ADS)

Dowling, David R.; Sabra, Karim G.

2015-01-01

Acoustic waves carry information about their source and collect information about their environment as they propagate. This article reviews how these information-carrying and -collecting features of acoustic waves that travel through fluids can be exploited for remote sensing. In nearly all cases, modern acoustic remote sensing involves array-recorded sounds and array signal processing to recover multidimensional results. The application realm for acoustic remote sensing spans an impressive range of signal frequencies (10-2 to 107 Hz) and distances (10-2 to 107 m) and involves biomedical ultrasound imaging, nondestructive evaluation, oil and gas exploration, military systems, and Nuclear Test Ban Treaty monitoring. In the past two decades, approaches have been developed to robustly localize remote sources; remove noise and multipath distortion from recorded signals; and determine the acoustic characteristics of the environment through which the sound waves have traveled, even when the recorded sounds originate from uncooperative sources or are merely ambient noise.

Acoustical experiment of yogurt fermentation process.

PubMed

Ogasawara, H; Mizutani, K; Ohbuchi, T; Nakamura, T

2006-12-22

One of the important factors through food manufacturing is hygienic management. Thus, food manufactures prove their hygienic activities by taking certifications like a Hazard Analysis and Critical Control Point (HACCP). This concept also applies to food monitoring. Acoustical measurements have advantage for other measurement in food monitoring because they make it possible to measure with noncontact and nondestructive. We tried to monitor lactic fermentation of yogurt by a probing sensor using a pair of acoustic transducers. Temperature of the solution changes by the reaction heat of fermentation. Consequently the sound velocity propagated through the solution also changes depending on the temperature. At the same time, the solution change its phase from liquid to gel. The transducers usage in the solution indicates the change of the temperature as the change of the phase difference between two transducers. The acoustic method has advantages of nondestructive measurement that reduces contamination of food product by measuring instrument. The sensor was inserted into milk with lactic acid bacterial stain of 19 degrees C and monitored phase retardation of propagated acoustic wave and its temperature with thermocouples in the mild. The monitoring result of fermentation from milk to Caspian Sea yogurt by the acoustic transducers with the frequency of 3.7 MHz started to show gradient change in temperature caused by reaction heat of fermentation but stop the gradient change at the end although the temperature still change. The gradient change stopped its change because of phase change from liquid to gel. The present method will be able to measure indirectly by setting transducers outside of the measuring object. This noncontact sensing method will have great advantage of reduces risk of food contamination from measuring instrument because the measurement probes are set out of fermentation reactor or food containers. Our proposed method will contribute to the

Propellant injection strategy for suppressing acoustic combustion instability

NASA Astrophysics Data System (ADS)

Diao, Qina

Shear-coaxial injector elements are often used in liquid-propellant-rocket thrust chambers, where combustion instabilities remain a significant problem. A conventional solution to the combustion instability problem relies on passive control techniques that use empirically-developed hardware such as acoustic baffles and tuned cavities. In addition to adding weight and decreasing engine performance, these devices are designed using trial-and-error methods, which do not provide the capability to predict the overall system stability characteristics in advance. In this thesis, two novel control strategies that are based on propellant fluid dynamics were investigated for mitigating acoustic instability involving shear-coaxial injector elements. The new control strategies would use a set of controlled injectors allowing local adjustment of propellant flow patterns for each operating condition, particularly when instability could become a problem. One strategy relies on reducing the oxidizer-fuel density gradient by blending heavier methane with the main fuel, hydrogen. Another strategy utilizes modifying the equivalence ratio to affect the acoustic impedance through mixing and reaction rate changes. The potential effectiveness of these strategies was assessed by conducting unit-physics experiments. Two different model combustors, one simulating a single-element injector test and the other a double-element injector test, were designed and tested for flame-acoustic interaction. For these experiments, the Reynolds number of the central oxygen jet was kept between 4700 and 5500 making the injector flames sufficiently turbulent. A compression driver, mounted on one side of the combustor wall, provided controlled acoustic excitation to the injector flames, simulating the initial phase of flame-acoustic interaction. Acoustic excitation was applied either as band-limited white noise forcing between 100 Hz and 5000 Hz or as single-frequency, fixed-amplitude forcing at 1150 Hz

Intermedius nerve involvement and testing in acoustic neuromas.

PubMed

Thomsen, J; Zilstorff, K

1975-01-01

The clinical findings in 125 patients with surgically confirmed acoustic neuromas are presented, with special regard to the involvement of the intermedius nerve in the diagnosis. In assessing the function of the intermedius nerve the examination of the nasolacrimal reflex and the sensation of taste on the anterior two-thirds of the tongue are used. The methods of investigation are described in detail. The material consisted of 20 medium-sized and 105 large tumours; no intracanalicular tumor was found. Hearing loss was the initial symptom in 85% of the patients, 10% had tinitus and 4% vertigo as the first symptom. Apart from the VIII cranial nerve symptoms, a defective nasolacrimal reflex was the most significant evidence of cerebellopontine angle pathology. The test was positive in 65% of the medium-sized tumours, in the entire material, 85%. The figures are higher than the incidence of trigeminal nerve symptoms. This in contrast to the reports of most authors. The tests described are simple and quick to perform, and it is emphasized that they should be applied to all patients with unilateral hearing loss of unknown origin.

Three-dimensional manipulation of single cells using surface acoustic waves

PubMed Central

Guo, Feng; Mao, Zhangming; Chen, Yuchao; Xie, Zhiwei; Lata, James P.; Li, Peng; Ren, Liqiang; Liu, Jiayang; Yang, Jian; Dao, Ming; Suresh, Subra; Huang, Tony Jun

2016-01-01

The ability of surface acoustic waves to trap and manipulate micrometer-scale particles and biological cells has led to many applications involving “acoustic tweezers” in biology, chemistry, engineering, and medicine. Here, we present 3D acoustic tweezers, which use surface acoustic waves to create 3D trapping nodes for the capture and manipulation of microparticles and cells along three mutually orthogonal axes. In this method, we use standing-wave phase shifts to move particles or cells in-plane, whereas the amplitude of acoustic vibrations is used to control particle motion along an orthogonal plane. We demonstrate, through controlled experiments guided by simulations, how acoustic vibrations result in micromanipulations in a microfluidic chamber by invoking physical principles that underlie the formation and regulation of complex, volumetric trapping nodes of particles and biological cells. We further show how 3D acoustic tweezers can be used to pick up, translate, and print single cells and cell assemblies to create 2D and 3D structures in a precise, noninvasive, label-free, and contact-free manner. PMID:26811444

Three-dimensional manipulation of single cells using surface acoustic waves.

PubMed

Guo, Feng; Mao, Zhangming; Chen, Yuchao; Xie, Zhiwei; Lata, James P; Li, Peng; Ren, Liqiang; Liu, Jiayang; Yang, Jian; Dao, Ming; Suresh, Subra; Huang, Tony Jun

2016-02-09

The ability of surface acoustic waves to trap and manipulate micrometer-scale particles and biological cells has led to many applications involving "acoustic tweezers" in biology, chemistry, engineering, and medicine. Here, we present 3D acoustic tweezers, which use surface acoustic waves to create 3D trapping nodes for the capture and manipulation of microparticles and cells along three mutually orthogonal axes. In this method, we use standing-wave phase shifts to move particles or cells in-plane, whereas the amplitude of acoustic vibrations is used to control particle motion along an orthogonal plane. We demonstrate, through controlled experiments guided by simulations, how acoustic vibrations result in micromanipulations in a microfluidic chamber by invoking physical principles that underlie the formation and regulation of complex, volumetric trapping nodes of particles and biological cells. We further show how 3D acoustic tweezers can be used to pick up, translate, and print single cells and cell assemblies to create 2D and 3D structures in a precise, noninvasive, label-free, and contact-free manner.

Low-intensity ultrasound adjuvant therapy: enhancement of doxorubicin-induced cytotoxicity and the acoustic mechanisms involved.

PubMed

Kondo, Takashi; Yoshida, Toru; Ogawa, Ryohei; Hassan, Mariame A; Furusawa, Yukihiro; Zhao, Qing-Li; Watanabe, Akihiko; Morii, Akihiro; Feril, Loreto B; Tachibana, Katsuro; Kitagawa, Hiroshi; Tabuchi, Yoshiaki; Takasaki, Ichiro; Shehata, Mohammad H; Kudo, Nobuki; Tsukada, Kazuhiro

2009-06-01

In this study, the effects of low-intensity pulsed ultrasound (LIU) as an adjuvant to doxorubicin (DOX) treatment was further investigated in comparison to hyperthermia as another widely used adjuvant. The effects were compared with respect to cell killing and apoptosis induction in U937 cells. Human primary liver cancer (PLC) cells were also used to evaluate the effects of the combinations. The use of an echo contrast agent was investigated for further enhancement of cytotoxicity. Finally, the acoustic mechanisms involved were investigated. The effects of different treatment regimens on cell viability were determined using the Trypan blue dye-exclusion test. Apoptosis induction was detected by flow cytometry using fluorescein isothiocyanate-annexin V and propidium iodide staining. The mechanistic study involved electron paramagnetic spin trapping for detecting free radical formation as an indicator of the occurrence of inertial cavitation and spectrophotometry for sucrose hydrolysis as an indicator for noncavitational effects. The combination treatments exerted synergistic effects on cytotoxicity depending on the acoustic conditions used. The use of LIU as an adjuvant to DOX treatment was shown to be superior to the use of hyperthermia as an adjuvant. Moreover, the combination seems to be promising for other cancer types provided that the acoustic conditions are properly selected with respect to drug concentration. The key ultrasound mechanism responsible for the synergism observed was shown to be the production of free radicals by inertial cavitation. Non-cavitational forces were also shown to contribute to the effect. This study is motivating to engage in in vivo research with various cancer types as a step toward clinical applicability and is emphasizing on the importance of developing therapeutic protocols for setting LIU parameters with respect to other therapeutic conditions.

Translational-circular scanning for magneto-acoustic tomography with current injection.

PubMed

Wang, Shigang; Ma, Ren; Zhang, Shunqi; Yin, Tao; Liu, Zhipeng

2016-01-27

Magneto-acoustic tomography with current injection involves using electrical impedance imaging technology. To explore the potential applications in imaging biological tissue and enhance image quality, a new scan mode for the transducer is proposed that is based on translational and circular scanning to record acoustic signals from sources. An imaging algorithm to analyze these signals is developed in respect to this alternative scanning scheme. Numerical simulations and physical experiments were conducted to evaluate the effectiveness of this scheme. An experiment using a graphite sheet as a tissue-mimicking phantom medium was conducted to verify simulation results. A pulsed voltage signal was applied across the sample, and acoustic signals were recorded as the transducer performed stepped translational or circular scans. The imaging algorithm was used to obtain an acoustic-source image based on the signals. In simulations, the acoustic-source image is correlated with the conductivity at the sample boundaries of the sample, but image results change depending on distance and angular aspect of the transducer. In general, as angle and distance decreases, the image quality improves. Moreover, experimental data confirmed the correlation. The acoustic-source images resulting from the alternative scanning mode has yielded the outline of a phantom medium. This scan mode enables improvements to be made in the sensitivity of the detecting unit and a change to a transducer array that would improve the efficiency and accuracy of acoustic-source images.

PoroTomo Subtask 3.2 Data files from the Distributed Acoustic Sensing experiment at Garner Valley, California

DOE Data Explorer

Chelsea Lancelle

2013-09-11

In September 2013, an experiment using Distributed Acoustic Sensing (DAS) was conducted at Garner Valley, a test site of the University of California Santa Barbara (Lancelle et al., 2014). This submission includes all DAS data recorded during the experiment. The sampling rate for all files is 1000 samples per second. Any files with the same filename but ending in _01, _02, etc. represent sequential files from the same test. Locations of the sources are plotted on the basemap in GDR submission 481, titled: "PoroTomo Subtask 3.2 Sample data from a Distributed Acoustic Sensing experiment at Garner Valley, California (PoroTomo Subtask 3.2)." Lancelle, C., N. Lord, H. Wang, D. Fratta, R. Nigbor, A. Chalari, R. Karaulanov, J. Baldwin, and E. Castongia (2014), Directivity and Sensitivity of Fiber-Optic Cable Measuring Ground Motion using a Distributed Acoustic Sensing Array (abstract # NS31C-3935), AGU Fall Meeting. 
https://agu.confex.com/agu/fm1/meetingapp.cgi#Paper/19828 The e-poster is available at: https://agu.confex.com/data/handout/agu/fm14/Paper_19828_handout_696_0.pdf

Research on Acoustical Scattering, Diffraction Catastrophes, Optics of Bubbles, Photoacoustics, and Acoustical Phase Conjugation.

DTIC Science & Technology

1987-09-15

optical levitation of bubbles; D. Acoustical and optical diffraction catastrophes (theory and optical simulation of transverse cusps, experiments with...35 C. Optical Levitation of Bubbles in Water by the Radiation Pressure of a Laser Beam: An Acoustically Quiet Levitator ...radiation pressure of a laser beam: an acoustically quiet levitator ," J. Acoust . Soc. Am. (submitted July 1987). C. Books (and sections thereof) Published

Shallow Water Acoustic Experiments and Preliminary Planning for FY06 Fieldwork

DTIC Science & Technology

2011-03-21

To) 5/1/2005-12/31/2010 4. TITLE AND SUBTITLE Shallow Water Acoustic Experiments and Preliminary Planning for FY06 Fieldwork 5a. CONTRACT NUMBERS...numerical computations show horizontal interference patterns within the duct. Richly de - tailed sound radiation fields are predicted at locations far...4) for the vertical modal amplitude Tm at x^L is now de - scribed in detail. First, the assumption of total transmission at the open-ended

Cerebellar interaction with the acoustic reflex.

PubMed

Jastreboff, P J

1981-01-01

The involvement of the cerebellar vermis in the acoustic reflex was analyzed in 12 cats, decerebrated or in pentobarbital anesthesia. Anatomical data suggested the existence of a connection of lobules VIII with the ventral cochlear nucleus. Single cell recording and evoked potential techniques demonstrated the existence of the acoustic projection to lobulus VIII. Electrical stimulation of this area changed the tension of the middle ear muscle and caused evoked potential responses in the caudal part of the ventral cochlear nucleus. Electrical stimulation of the motor nucleus of the facial nerve evoked a slow wave in the recording taken from the surrounding of the cochlear round window. A hypothesis is proposed which postulates the involvement of the acoustic reflex in space localization of acoustic stimuli and the action of cerebellar vermis in order to assure the stability and plasticity of the acoustic reflex arc.

Robust acoustic wave manipulation of bubbly liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gumerov, N. A., E-mail: gumerov@umiacs.umd.edu; Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076; Akhatov, I. S.

Experiments with water–air bubbly liquids when exposed to acoustic fields of frequency ∼100 kHz and intensity below the cavitation threshold demonstrate that bubbles ∼30 μm in diameter can be “pushed” away from acoustic sources by acoustic radiation independently from the direction of gravity. This manifests formation and propagation of acoustically induced transparency waves (waves of the bubble volume fraction). In fact, this is a collective effect of bubbles, which can be described by a mathematical model of bubble self-organization in acoustic fields that matches well with our experiments.

Versatile resonance-tracking circuit for acoustic levitation experiments.

PubMed

Baxter, K; Apfel, R E; Marston, P L

1978-02-01

Objects can be levitated by radiation pressure forces in an acoustic standing wave. In many circumstances it is important that the standing wave frequency remain locked on an acoustic resonance despite small changes in the resonance frequency. A self-locking oscillator circuit is described which tracks the resonance frequency by sensing the magnitude of the transducer current. The tracking principle could be applied to other resonant systems.

Results From a Parametric Acoustic Liner Experiment Using P and W GEN1 HSR Mixer/Ejector Model

NASA Technical Reports Server (NTRS)

Boyd, Kathleen C.; Wolter, John D.

2004-01-01

This report documents the results of an acoustic liner test performed using a Gen 1 HSR mixer/ejector model installed on the Jet Exit Rig in the Nozzle Acoustic Test Rig in the Aeroacoustic Propulsion Laboratory or NASA Glenn Research Center. Acoustic liner effectiveness and single-component thrust performance results are discussed. Results from 26 different types of single-degree-of-freedom and bulk material liners are compared with each other and against a hardwall baseline. Design parameters involving all aspects of the facesheet, the backing cavity, and the type of bulk material were varied in order to study the effects of these design features on the acoustic impedance, acoustic effectiveness and on nozzle thrust performance. Overall, the bulk absorber liners are more effective at reducing the jet noise than the single-degree-of-freedom liners. Many of the design parameters had little effect on acoustic effectiveness, such as facesheeet hole diameter and honeycomb cell size. A relatively large variation in the impedance of the bulk absorber in a bulk liner is required to have a significant impact on the noise reduction. The thrust results exhibit a number of consistent trends, supporting the validity of this new addition to the facility. In general, the thrust results indicate that thrust performance benefits from increased facesheet thickness and decreased facesheet porosity.

Sonification of acoustic emission data

NASA Astrophysics Data System (ADS)

Raith, Manuel; Große, Christian

2014-05-01

While loading different specimens, acoustic emissions appear due to micro crack formation or friction of already existing crack edges. These acoustic emissions can be recorded using suitable ultrasonic transducers and transient recorders. The analysis of acoustic emissions can be used to investigate the mechanical behavior of different specimens under load. Our working group has undertaken several experiments, monitored with acoustic emission techniques. Different materials such as natural stone, concrete, wood, steel, carbon composites and bone were investigated. Also the experimental setup has been varied. Fire-spalling experiments on ultrahigh performance concrete and pullout experiments on bonded anchors have been carried out. Furthermore uniaxial compression tests on natural stone and animal bone had been conducted. The analysis tools include not only the counting of events but the analysis of full waveforms. Powerful localization algorithms and automatic onset picking techniques (based on Akaikes Information Criterion) were established to handle the huge amount of data. Up to several thousand events were recorded during experiments of a few minutes. More sophisticated techniques like moment tensor inversion have been established on this relatively small scale as well. Problems are related to the amount of data but also to signal-to-noise quality, boundary conditions (reflections) sensor characteristics and unknown and changing Greens functions of the media. Some of the acoustic emissions recorded during these experiments had been transferred into audio range. The transformation into the audio range was done using Matlab. It is the aim of the sonification to establish a tool that is on one hand able to help controlling the experiment in-situ and probably adjust the load parameters according to the number and intensity of the acoustic emissions. On the other hand sonification can help to improve the understanding of acoustic emission techniques for training

Measurements of Low-Frequency Acoustic Attenuation in Soils.

DTIC Science & Technology

1994-10-13

Engineering Research Laboratory to design an acoustic subsurface imaging system, a set of experiments was conducted in which the attenuation and the velocity...support of the U.S. Army Construction Engineering Research Laboratory’s efforts to design an acoustic subsurface imaging system which would ideally be...of acoustic waves such as those generated by a subsurface imaging system. An experiment reported in the literature characterized the acoustic

Wideband acoustic microscopy of tissue.

PubMed

Daft, C W; Briggs, G D

1989-01-01

A scanning acoustic microscope (SAM) has been used to measure the elastic properties of tissue with a resolution of around 8 mum. This is achieved by broadband excitation of the acoustic lens, and the recording of an undemodulated returning signal. A method of analyzing this information to yield sound velocity, acoustic impedance, section thickness, and acoustic attenuation is described. Results from a sample of skin tissue are presented and compared with data from a computer simulation of the experiment.

A viable method to predict acoustic streaming in presence of cavitation.

PubMed

Louisnard, O

2017-03-01

The steady liquid flow observed under ultrasonic emitters generating acoustic cavitation can be successfully predicted by a standard turbulent flow calculation. The flow is driven by the classical averaged volumetric force density calculated from the acoustic field, but the inertial term in Navier-Stokes equations must be kept, and a turbulent solution must be sought. The acoustic field must be computed with a realistic model, properly accounting for dissipation by the cavitation bubbles [Louisnard, Ultrason. Sonochem., 19, (2012) 56-65]. Comparison with 20kHz experiments, involving the combination of acoustic streaming and a perpendicular forced flow in a duct, shows reasonably good agreement. Moreover, the persistence of the cavitation effects on the wall facing the emitter, in spite of the deflection of the streaming jet, is correctly reproduced by the model. It is also shown that predictions based either on linear acoustics with the correct turbulent solution, or with Louisnard's model with Eckart-Nyborg's theory yields unrealistic results. Copyright © 2016 Elsevier B.V. All rights reserved.

Teaching Musical Acoustics to the Musician.

ERIC Educational Resources Information Center

Kelly, Robert E.

1979-01-01

Gives ideas, suggestions, impressions, and opinions on teaching musical acoustics specifically to musicians both in and out of the classroom. The approach is practical and is intended for physics teachers involved with musical acoustics. (Author/GA)

Acoustic fine structure may encode biologically relevant information for zebra finches.

PubMed

Prior, Nora H; Smith, Edward; Lawson, Shelby; Ball, Gregory F; Dooling, Robert J

2018-04-18

The ability to discriminate changes in the fine structure of complex sounds is well developed in birds. However, the precise limit of this discrimination ability and how it is used in the context of natural communication remains unclear. Here we describe natural variability in acoustic fine structure of male and female zebra finch calls. Results from psychoacoustic experiments demonstrate that zebra finches are able to discriminate extremely small differences in fine structure, which are on the order of the variation in acoustic fine structure that is present in their vocal signals. Results from signal analysis methods also suggest that acoustic fine structure may carry information that distinguishes between biologically relevant categories including sex, call type and individual identity. Combined, our results are consistent with the hypothesis that zebra finches can encode biologically relevant information within the fine structure of their calls. This study provides a foundation for our understanding of how acoustic fine structure may be involved in animal communication.

Arrival Time Tracking of Partially Resolved Acoustic Rays with Application to Ocean Acoustic Tomography

DTIC Science & Technology

1991-03-01

ocean acoustic tomography. A straightforward method of arrival time estimation, based on locating the maximum value of an interpolated arrival, was...used with limited success for analysis of data from the December 1988 Monterey Bay Tomography Experiment. Close examination of the data revealed multiple...estimation of arrival times along an ocean acoustic ray path is an important component of ocean acoustic tomography. A straightforward method of arrival time

The Simplest Demonstration on Acoustic Beats

ERIC Educational Resources Information Center

Ganci, Alessio; Ganci, Salvatore

2015-01-01

The classical demonstration experiment on acoustic beats using two signal generators and a dual trace oscilloscope is an important ingredient in teaching the subject. This short laboratory note aims to point out what may be the simplest demonstrative experiment on acoustic beats to carry out in a classroom without employing any lab apparatus.

Acoustic and Categorical Dissimilarity of Musical Timbre: Evidence from Asymmetries Between Acoustic and Chimeric Sounds

PubMed Central

Siedenburg, Kai; Jones-Mollerup, Kiray; McAdams, Stephen

2016-01-01

This paper investigates the role of acoustic and categorical information in timbre dissimilarity ratings. Using a Gammatone-filterbank-based sound transformation, we created tones that were rated as less familiar than recorded tones from orchestral instruments and that were harder to associate with an unambiguous sound source (Experiment 1). A subset of transformed tones, a set of orchestral recordings, and a mixed set were then rated on pairwise dissimilarity (Experiment 2A). We observed that recorded instrument timbres clustered into subsets that distinguished timbres according to acoustic and categorical properties. For the subset of cross-category comparisons in the mixed set, we observed asymmetries in the distribution of ratings, as well as a stark decay of inter-rater agreement. These effects were replicated in a more robust within-subjects design (Experiment 2B) and cannot be explained by acoustic factors alone. We finally introduced a novel model of timbre dissimilarity based on partial least-squares regression that compared the contributions of both acoustic and categorical timbre descriptors. The best model fit (R2 = 0.88) was achieved when both types of descriptors were taken into account. These findings are interpreted as evidence for an interplay of acoustic and categorical information in timbre dissimilarity perception. PMID:26779086

Effect of gas adsorption on acoustic wave propagation in MFI zeolite membrane materials: experiment and molecular simulation.

PubMed

Manga, Etoungh D; Blasco, Hugues; Da-Costa, Philippe; Drobek, Martin; Ayral, André; Le Clezio, Emmanuel; Despaux, Gilles; Coasne, Benoit; Julbe, Anne

2014-09-02

The present study reports on the development of a characterization method of porous membrane materials which consists of considering their acoustic properties upon gas adsorption. Using acoustic microscopy experiments and atomistic molecular simulations for helium adsorbed in a silicalite-1 zeolite membrane layer, we showed that acoustic wave propagation could be used, in principle, for controlling the membranes operando. Molecular simulations, which were found to fit experimental data, showed that the compressional modulus of the composite system consisting of silicalite-1 with adsorbed He increases linearly with the He adsorbed amount while its shear modulus remains constant in a large range of applied pressures. These results suggest that the longitudinal and Rayleigh wave velocities (VL and VR) depend on the He adsorbed amount whereas the transverse wave velocity VT remains constant.

Digital Controller For Acoustic Levitation

NASA Technical Reports Server (NTRS)

Tarver, D. Kent

1989-01-01

Acoustic driver digitally controls sound fields along three axes. Allows computerized acoustic levitation and manipulation of small objects for such purposes as containerless processing and nuclear-fusion power experiments. Also used for controlling motion of vibration-testing tables in three dimensions.

Acoustic Characterization of Compact Jet Engine Simulator Units

NASA Technical Reports Server (NTRS)

Doty, Michael J.; Haskin, Henry H.

2013-01-01

Two dual-stream, heated jet, Compact Jet Engine Simulator (CJES) units are designed for wind tunnel acoustic experiments involving a Hybrid Wing Body (HWB) vehicle. The newly fabricated CJES units are characterized with a series of acoustic and flowfield investigations to ensure successful operation with minimal rig noise. To limit simulator size, consistent with a 5.8% HWB model, the CJES units adapt Ultra Compact Combustor (UCC) technology developed at the Air Force Research Laboratory. Stable and controllable operation of the combustor is demonstrated using passive swirl air injection and backpressuring of the combustion chamber. Combustion instability tones are eliminated using nonuniform flow conditioners in conjunction with upstream screens. Through proper flow conditioning, rig noise is reduced by more than 20 dB over a broad spectral range, but it is not completely eliminated at high frequencies. The low-noise chevron nozzle concept designed for the HWB test shows expected acoustic benefits when installed on the CJES unit, and consistency between CJES units is shown to be within 0.5 dB OASPL.

Acoustic field modulation in regenerators

NASA Astrophysics Data System (ADS)

Hu, J. Y.; Wang, W.; Luo, E. C.; Chen, Y. Y.

2016-12-01

The regenerator is a key component that transfers energy between heat and work. The conversion efficiency is significantly influenced by the acoustic field in the regenerator. Much effort has been spent to quantitatively determine this influence, but few comprehensive experimental verifications have been performed because of difficulties in modulating and measuring the acoustic field. In this paper, a method requiring two compressors is introduced and theoretically investigated that achieves acoustic field modulation in the regenerator. One compressor outputs the acoustic power for the regenerator; the other acts as a phase shifter. A RC load dissipates the acoustic power out of both the regenerator and the latter compressor. The acoustic field can be modulated by adjusting the current in the two compressors and opening the RC load. The acoustic field is measured with pressure sensors instead of flow-field imaging equipment, thereby greatly simplifying the experiment.

Spectral Characteristics of Continuous Acoustic Emission (AE) Data from Laboratory Rock Deformation Experiments

NASA Astrophysics Data System (ADS)

Flynn, J. William; Goodfellow, Sebastian; Reyes-Montes, Juan; Nasseri, Farzine; Young, R. Paul

2016-04-01

Continuous acoustic emission (AE) data recorded during rock deformation tests facilitates the monitoring of fracture initiation and propagation due to applied stress changes. Changes in the frequency and energy content of AE waveforms have been previously observed and were associated with microcrack coalescence and the induction or mobilisation of large fractures which are naturally associated with larger amplitude AE events and lower-frequency components. The shift from high to low dominant frequency components during the late stages of the deformation experiment, as the rate of AE events increases and the sample approaches failure, indicates a transition from the micro-cracking to macro-cracking regime, where large cracks generated result in material failure. The objective of this study is to extract information on the fracturing process from the acoustic records around sample failure, where the fast occurrence of AE events does not allow for identification of individual AE events and phase arrivals. Standard AE event processing techniques are not suitable for extracting this information at these stages. Instead the observed changes in the frequency content of the continuous record can be used to characterise and investigate the fracture process at the stage of microcrack coalescence and sample failure. To analyse and characterise these changes, a detailed non-linear and non-stationary time-frequency analysis of the continuous waveform data is required. Empirical Mode Decomposition (EMD) and Hilbert Spectral Analysis (HSA) are two of the techniques used in this paper to analyse the acoustic records which provide a high-resolution temporal frequency distribution of the data. In this paper we present the results from our analysis of continuous AE data recorded during a laboratory triaxial deformation experiment using the combined EMD and HSA method.

Determination of the viscous acoustic field for liquid drop positioning/forcing in an acoustic levitation chamber in microgravity

NASA Technical Reports Server (NTRS)

Lyell, Margaret J.

1992-01-01

The development of acoustic levitation systems has provided a technology with which to undertake droplet studies as well as do containerless processing experiments in a microgravity environment. Acoustic levitation chambers utilize radiation pressure forces to position/manipulate the drop. Oscillations can be induced via frequency modulation of the acoustic wave, with the modulated acoustic radiation vector acting as the driving force. To account for tangential as well as radial forcing, it is necessary that the viscous effects be included in the acoustic field. The method of composite expansions is employed in the determination of the acoustic field with viscous effects.

Acoustical standards in engineering acoustics

NASA Astrophysics Data System (ADS)

Burkhard, Mahlon D.

2004-05-01

The Engineering Acoustics Technical Committee is concerned with the evolution and improvement of acoustical techniques and apparatus, and with the promotion of new applications of acoustics. As cited in the Membership Directory and Handbook (2002), the interest areas include transducers and arrays; underwater acoustic systems; acoustical instrumentation and monitoring; applied sonics, promotion of useful effects, information gathering and transmission; audio engineering; acoustic holography and acoustic imaging; acoustic signal processing (equipment and techniques); and ultrasound and infrasound. Evident connections between engineering and standards are needs for calibration, consistent terminology, uniform presentation of data, reference levels, or design targets for product development. Thus for the acoustical engineer standards are both a tool for practices, for communication, and for comparison of his efforts with those of others. Development of many standards depends on knowledge of the way products are put together for the market place and acoustical engineers provide important input to the development of standards. Acoustical engineers and members of the Engineering Acoustics arm of the Society both benefit from and contribute to the Acoustical Standards of the Acoustical Society.

Varieties of Musical Experience

ERIC Educational Resources Information Center

Bharucha, J. Jamshed; Curtis, Meagan; Paroo, Kaivon

2006-01-01

In this paper, we argue that music cognition involves the use of acoustic and auditory codes to evoke a variety of conscious experiences. The variety of domains that are encompassed by music is so diverse that it is unclear whether a single domain of structure or experience is defining. Music is best understood as a form of communication in which…

Generation of thermo-acoustic waves from pulsed solar/IR radiation

NASA Astrophysics Data System (ADS)

Rahman, Aowabin

Acoustic waves could potentially be used in a wide range of engineering applications; however, the high energy consumption in generating acoustic waves from electrical energy and the cost associated with the process limit the use of acoustic waves in industrial processes. Acoustic waves converted from solar radiation provide a feasible way of obtaining acoustic energy, without relying on conventional nonrenewable energy sources. One of the goals of this thesis project was to experimentally study the conversion of thermal to acoustic energy using pulsed radiation. The experiments were categorized into "indoor" and "outdoor" experiments, each with a separate experimental setup. The indoor experiments used an IR heater to power the thermo-acoustic lasers and were primarily aimed at studying the effect of various experimental parameters on the amplitude of sound waves in the low frequency range (below 130 Hz). The IR radiation was modulated externally using a chopper wheel and then impinged on a porous solid, which was housed inside a thermo-acoustic (TA) converter. A microphone located at a certain distance from the porous solid inside the TA converter detected the acoustic signals. The "outdoor" experiments, which were targeted at TA conversion at comparatively higher frequencies (in 200 Hz-3 kHz range) used solar energy to power the thermo-acoustic laser. The amplitudes (in RMS) of thermo-acoustic signals obtained in experiments using IR heater as radiation source were in the 80-100 dB range. The frequency of acoustic waves corresponded to the frequency of interceptions of the radiation beam by the chopper. The amplitudes of acoustic waves were influenced by several factors, including the chopping frequency, magnitude of radiation flux, type of porous material, length of porous material, external heating of the TA converter housing, location of microphone within the air column, and design of the TA converter. The time-dependent profile of the thermo-acoustic signals

KENNEDY SPACE CENTER, FLA. - Research team members work with acoustic cable during underwater acoustic research being conducted in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

NASA Image and Video Library

2003-08-18

KENNEDY SPACE CENTER, FLA. - Research team members work with acoustic cable during underwater acoustic research being conducted in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

KENNEDY SPACE CENTER, FLA. - Research team members roll out acoustic cable to the water's edge during underwater acoustic research being conducted in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

NASA Image and Video Library

2003-08-18

KENNEDY SPACE CENTER, FLA. - Research team members roll out acoustic cable to the water's edge during underwater acoustic research being conducted in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

Acoustic-noise-optimized diffusion-weighted imaging.

PubMed

Ott, Martin; Blaimer, Martin; Grodzki, David M; Breuer, Felix A; Roesch, Julie; Dörfler, Arnd; Heismann, Björn; Jakob, Peter M

2015-12-01

This work was aimed at reducing acoustic noise in diffusion-weighted MR imaging (DWI) that might reach acoustic noise levels of over 100 dB(A) in clinical practice. A diffusion-weighted readout-segmented echo-planar imaging (EPI) sequence was optimized for acoustic noise by utilizing small readout segment widths to obtain low gradient slew rates and amplitudes instead of faster k-space coverage. In addition, all other gradients were optimized for low slew rates. Volunteer and patient imaging experiments were conducted to demonstrate the feasibility of the method. Acoustic noise measurements were performed and analyzed for four different DWI measurement protocols at 1.5T and 3T. An acoustic noise reduction of up to 20 dB(A) was achieved, which corresponds to a fourfold reduction in acoustic perception. The image quality was preserved at the level of a standard single-shot (ss)-EPI sequence, with a 27-54% increase in scan time. The diffusion-weighted imaging technique proposed in this study allowed a substantial reduction in the level of acoustic noise compared to standard single-shot diffusion-weighted EPI. This is expected to afford considerably more patient comfort, but a larger study would be necessary to fully characterize the subjective changes in patient experience.

Turbofan Acoustic Propagation and Radiation

NASA Technical Reports Server (NTRS)

Eversman, Walter

2000-01-01

This document describes progress in the development of finite element codes for the prediction of near and far field acoustic radiation from the inlet and aft fan ducts of turbofan engines. The report consists of nine papers which have appeared in archival journals and conference proceedings, or are presently in review for publication. Topics included are: 1. Aft Fan Duct Acoustic Radiation; 2. Mapped Infinite Wave Envelope Elements for Acoustic Radiation in a Uniformly Moving Medium; 3. A Reflection Free Boundary Condition for Propagation in Uniform Flow Using Mapped Infinite Wave Envelope Elements; 4. A Numerical Comparison Between Multiple-Scales and FEM Solution for Sound Propagation in Lined Flow Ducts; 5. Acoustic Propagation at High Frequencies in Ducts; 6. The Boundary Condition at an Impedance Wall in a Nonuniform Duct with Potential Flow; 7. A Reverse Flow Theorem and Acoustic Reciprocity in Compressible Potential Flows; 8. Reciprocity and Acoustics Power in One Dimensional Compressible Potential Flows; and 9. Numerical Experiments on Acoustic Reciprocity in Compressible Potential Flows.

Tiltrotor Acoustic Flight Test: Terminal Area Operations

NASA Technical Reports Server (NTRS)

SantaMaria, O. L.; Wellman, J. B.; Conner, D. A.; Rutledge, C. K.

1991-01-01

This paper provides a comprehensive description of an acoustic flight test of the XV- 15 Tiltrotor Aircraft with Advanced Technology Blades (ATB) conducted in August and September 1991 at Crows Landing, California. The purpose of this cooperative research effort of the NASA Langley and Ames Research Centers was to obtain a preliminary, high quality database of far-field acoustics for terminal area operations of the XV-15 at a takeoff gross weight of approximately 14,000 lbs for various glide slopes, airspeeds, rotor tip speeds, and nacelle tilt angles. The test also was used to assess the suitability of the Crows Landing complex for full scale far-field acoustic testing. This was the first acoustic flight test of the XV-15 aircraft equipped with ATB involving approach and level flyover operations. The test involved coordination of numerous personnel, facilities and equipment. Considerable effort was made to minimize potential extraneous noise sources unique to the region during the test. Acoustic data from the level flyovers were analyzed, then compared with data from a previous test of the XV-15 equipped with Standard Metal Blades

Droplet Vaporization In A Levitating Acoustic Field

NASA Technical Reports Server (NTRS)

Ruff, G. A.; Liu, S.; Ciobanescu, I.

2003-01-01

Combustion experiments using arrays of droplets seek to provide a link between single droplet combustion phenomena and the behavior of complex spray combustion systems. Both single droplet and droplet array studies have been conducted in microgravity to better isolate the droplet interaction phenomena and eliminate or reduce the effects of buoyancy-induced convection. In most experiments involving droplet arrays, the droplets are supported on fibers to keep them stationary and close together before the combustion event. The presence of the fiber, however, disturbs the combustion process by introducing a source of heat transfer and asymmetry into the configuration. As the number of drops in a droplet array increases, supporting the drops on fibers becomes less practical because of the cumulative effect of the fibers on the combustion process. To eliminate the effect of the fiber, several researchers have conducted microgravity experiments using unsupported droplets. Jackson and Avedisian investigated single, unsupported drops while Nomura et al. studied droplet clouds formed by a condensation technique. The overall objective of this research is to extend the study of unsupported drops by investigating the combustion of well-characterized drop clusters in a microgravity environment. Direct experimental observations and measurements of the combustion of droplet clusters would provide unique experimental data for the verification and improvement of spray combustion models. In this work, the formation of drop clusters is precisely controlled using an acoustic levitation system so that dilute, as well as dense clusters can be created and stabilized before combustion in microgravity is begun. While the low-gravity test facility is being completed, tests have been conducted in 1-g to characterize the effect of the acoustic field on the vaporization of single and multiple droplets. This is important because in the combustion experiment, the droplets will be formed and

Preliminary study of the effect of the turbulent flow field around complex surfaces on their acoustic characteristics

NASA Technical Reports Server (NTRS)

Olsen, W. A.; Boldman, D.

1978-01-01

Fairly extensive measurements have been conducted of the turbulent flow around various surfaces as a basis for a study of the acoustic characteristics involved. In the experiments the flow from a nozzle was directed upon various two-dimensional surface configurations such as the three-flap model. A turbulent flow field description is given and an estimate of the acoustic characteristics is provided. The developed equations are based upon fundamental theories for simple configurations having simple flows. Qualitative estimates are obtained regarding the radiation pattern and the velocity power law. The effect of geometry and turbulent flow distribution on the acoustic emission from simple configurations are discussed.

Large Aperture Acoustic Arrays in Support of Reverberation Studies

DTIC Science & Technology

1990-04-01

Acoustic Reverberation Special Research Program (SRP). Approach We propose the development of several acoustic arrays in preparation for a FY92 experiment...hydrophone array to measure the directional spectrum of seafloor scattered wavefields. Approach As part of the ONT-sponsored, 1987 SVLA experiment, we...scattered energy. Approach Two methods will be described by which vertical and horizontal acoustic arrays can be deployed together for making bottom

Photo-acoustic and video-acoustic methods for sensing distant sound sources

NASA Astrophysics Data System (ADS)

Slater, Dan; Kozacik, Stephen; Kelmelis, Eric

2017-05-01

Long range telescopic video imagery of distant terrestrial scenes, aircraft, rockets and other aerospace vehicles can be a powerful observational tool. But what about the associated acoustic activity? A new technology, Remote Acoustic Sensing (RAS), may provide a method to remotely listen to the acoustic activity near these distant objects. Local acoustic activity sometimes weakly modulates the ambient illumination in a way that can be remotely sensed. RAS is a new type of microphone that separates an acoustic transducer into two spatially separated components: 1) a naturally formed in situ acousto-optic modulator (AOM) located within the distant scene and 2) a remote sensing readout device that recovers the distant audio. These two elements are passively coupled over long distances at the speed of light by naturally occurring ambient light energy or other electromagnetic fields. Stereophonic, multichannel and acoustic beam forming are all possible using RAS techniques and when combined with high-definition video imagery it can help to provide a more cinema like immersive viewing experience. A practical implementation of a remote acousto-optic readout device can be a challenging engineering problem. The acoustic influence on the optical signal is generally weak and often with a strong bias term. The optical signal is further degraded by atmospheric seeing turbulence. In this paper, we consider two fundamentally different optical readout approaches: 1) a low pixel count photodiode based RAS photoreceiver and 2) audio extraction directly from a video stream. Most of our RAS experiments to date have used the first method for reasons of performance and simplicity. But there are potential advantages to extracting audio directly from a video stream. These advantages include the straight forward ability to work with multiple AOMs (useful for acoustic beam forming), simpler optical configurations, and a potential ability to use certain preexisting video recordings. However

Acoustic parametric pumping of spin waves

NASA Astrophysics Data System (ADS)

Keshtgar, Hedyeh; Zareyan, Malek; Bauer, Gerrit E. W.

2014-11-01

Recent experiments demonstrated generation of spin currents by ultrasound. We can understand this acoustically induced spin pumping in terms of the coupling between magnetization and lattice waves. Here we study the parametric excitation of magnetization by longitudinal acoustic waves and calculate the acoustic threshold power. The induced magnetization dynamics can be detected by the spin pumping into an adjacent normal metal that displays the inverse spin Hall effect.

Acoustical and optical backscatter measurements of sediment transport in the 1988 1989 STRESS experiment

NASA Astrophysics Data System (ADS)

Lynch, J. F.; Gross, T. F.; Sherwood, C. R.; Irish, J. D.; Brumley, B. H.

1997-04-01

During the 1988-1989 Sediment Transport Events on Shelves and Slopes (STRESS) experiment, a 1-MHz acoustic backscatter system (ABSS), deployed in 90 m of water off the California coast measured vertical profiles of suspended sediment concentration from 1.5 to (nominally) 26 meters above bottom (m.a.b.). An 8-week-long time series was obtained, showing major sediment transport events (storms) in late December and early January. Comparison of the acoustics measurements from 1.5 m.a.b. are made with optical backscatter system (OBS) concentration estimates lower in the boundary layer (0.25 m.a.b.). Correlations between ABSS and OBS concentration measurements and the boundary layer forcing functions (waves, currents, and their non-linear interaction) provided a variety of insights into the nature of the sediment transport of the STRESS site. Transport rates and integrated transport are seen to be dominated by the largest storm events.

Acoustics

NASA Technical Reports Server (NTRS)

Goodman, Jerry R.; Grosveld, Ferdinand

2007-01-01

The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

Experimental Research Into Generation of Acoustic Emission Signals in the Process of Friction of Hadfield Steel Single Crystals

NASA Astrophysics Data System (ADS)

Lychagin, D. V.; Filippov, A. V.; Novitskaia, O. S.; Kolubaev, E. A.; Sizova, O. V.

2016-08-01

The results of experimental research into dry sliding friction of Hadfield steel single crystals involving registration of acoustic emission are presented in the paper. The images of friction surfaces of Hadfield steel single crystals and wear grooves of the counterbody surface made after completion of three serial experiments conducted under similar conditions and friction regimes are given. The relation of the acoustic emission waveform envelope to the changing friction factor is revealed. Amplitude-frequency characteristics of acoustic emission signal frames are determined on the base of Fast Fourier Transform and Short Time Fourier Transform during the run-in stage of tribounits and in the process of stable friction.

Modeling Nonlinear Acoustic Standing Waves in Resonators: Theory and Experiments

NASA Technical Reports Server (NTRS)

Raman, Ganesh; Li, Xiaofan; Finkbeiner, Joshua

2004-01-01

The overall goal of the cooperative research with NASA Glenn is to fundamentally understand, computationally model, and experimentally validate non-linear acoustic waves in enclosures with the ultimate goal of developing a non-contact acoustic seal. The longer term goal is to transition the Glenn acoustic seal innovation to a prototype sealing device. Lucas and coworkers are credited with pioneering work in Resonant Macrosonic Synthesis (RMS). Several Patents and publications have successfully illustrated the concept of Resonant Macrosonic Synthesis. To utilize this concept in practical application one needs to have an understanding of the details of the phenomenon and a predictive tool that can examine the waveforms produced within resonators of complex shapes. With appropriately shaped resonators one can produce un-shocked waveforms of high amplitude that would result in very high pressures in certain regions. Our goal is to control the waveforms and exploit the high pressures to produce an acoustic seal. Note that shock formation critically limits peak-to-peak pressure amplitudes and also causes excessive energy dissipation. Proper shaping of the resonator is thus critical to the use of this innovation.

Scaling and dimensional analysis of acoustic streaming jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moudjed, B.; Botton, V.; Henry, D.

2014-09-15

This paper focuses on acoustic streaming free jets. This is to say that progressive acoustic waves are used to generate a steady flow far from any wall. The derivation of the governing equations under the form of a nonlinear hydrodynamics problem coupled with an acoustic propagation problem is made on the basis of a time scale discrimination approach. This approach is preferred to the usually invoked amplitude perturbations expansion since it is consistent with experimental observations of acoustic streaming flows featuring hydrodynamic nonlinearities and turbulence. Experimental results obtained with a plane transducer in water are also presented together with amore » review of the former experimental investigations using similar configurations. A comparison of the shape of the acoustic field with the shape of the velocity field shows that diffraction is a key ingredient in the problem though it is rarely accounted for in the literature. A scaling analysis is made and leads to two scaling laws for the typical velocity level in acoustic streaming free jets; these are both observed in our setup and in former studies by other teams. We also perform a dimensional analysis of this problem: a set of seven dimensionless groups is required to describe a typical acoustic experiment. We find that a full similarity is usually not possible between two acoustic streaming experiments featuring different fluids. We then choose to relax the similarity with respect to sound attenuation and to focus on the case of a scaled water experiment representing an acoustic streaming application in liquid metals, in particular, in liquid silicon and in liquid sodium. We show that small acoustic powers can yield relatively high Reynolds numbers and velocity levels; this could be a virtue for heat and mass transfer applications, but a drawback for ultrasonic velocimetry.« less

Theoretical Properties of Acoustical Speckle Interferometry.

DTIC Science & Technology

1980-09-01

an obvious one , since it was first performed in the acoustical holography. An acoustical speckle interferometry study has been demonstrated to be a...experiments in which pulses were used to study the propagation of the circumferential waves on aluminum cylinders immersed in water. In 1969, Bunney...destructive Testing SB. ABTRACT aCdo as revers. NW ass a" Id by block numb") Acoustical speckle interferometry is based locally on the elastodynamic response

Integrated Model for the Acoustics of Sediments

DTIC Science & Technology

2013-09-30

1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Integrated Model for the Acoustics of Sediments...physics, and (3) the development and testing of sediment acoustic models through a series of at-sea experiments. APPROACH The approach may be...assess its impact on acoustic propagation and reverberation models . Practically, all underwater sediments are porous and water-permeable, therefore

Low-cost synchronization of high-speed audio and video recordings in bio-acoustic experiments.

PubMed

Laurijssen, Dennis; Verreycken, Erik; Geipel, Inga; Daems, Walter; Peremans, Herbert; Steckel, Jan

2018-02-27

In this paper, we present a method for synchronizing high-speed audio and video recordings of bio-acoustic experiments. By embedding a random signal into the recorded video and audio data, robust synchronization of a diverse set of sensor streams can be performed without the need to keep detailed records. The synchronization can be performed using recording devices without dedicated synchronization inputs. We demonstrate the efficacy of the approach in two sets of experiments: behavioral experiments on different species of echolocating bats and the recordings of field crickets. We present the general operating principle of the synchronization method, discuss its synchronization strength and provide insights into how to construct such a device using off-the-shelf components. © 2018. Published by The Company of Biologists Ltd.

Acoustic constituents of prosodic typology

NASA Astrophysics Data System (ADS)

Komatsu, Masahiko

Different languages sound different, and considerable part of it derives from the typological difference of prosody. Although such difference is often referred to as lexical accent types (stress accent, pitch accent, and tone; e.g. English, Japanese, and Chinese respectively) and rhythm types (stress-, syllable-, and mora-timed rhythms; e.g. English, Spanish, and Japanese respectively), it is unclear whether these types are determined in terms of acoustic properties, The thesis intends to provide a potential basis for the description of prosody in terms of acoustics. It argues for the hypothesis that the source component of the source-filter model (acoustic features) approximately corresponds to prosody (linguistic features) through several experimental-phonetic studies. The study consists of four parts. (1) Preliminary experiment: Perceptual language identification tests were performed using English and Japanese speech samples whose frequency spectral information (i.e. non-source component) is heavily reduced. The results indicated that humans can discriminate languages with such signals. (2) Discussion on the linguistic information that the source component contains: This part constitutes the foundation of the argument of the thesis. Perception tests of consonants with the source signal indicated that the source component carries the information on broad categories of phonemes that contributes to the creation of rhythm. (3) Acoustic analysis: The speech samples of Chinese, English, Japanese, and Spanish, differing in prosodic types, were analyzed. These languages showed difference in acoustic characteristics of the source component. (4) Perceptual experiment: A language identification test for the above four languages was performed using the source signal with its acoustic features parameterized. It revealed that humans can discriminate prosodic types solely with the source features and that the discrimination is easier as acoustic information increases. The

Deep Water Ocean Acoustics (DWOA): The Philippine Sea, OBSANP, and THAAW Experiments

DTIC Science & Technology

2015-09-30

the travel times. 4 The ocean state estimates were then re-computed to fit the acoustic travel times as integrals of the sound speed, and...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Deep Water Ocean Acoustics (DWOA): The Philippine Sea...deep-water acoustic propagation and ambient noise has been collected in a wide variety of environments over the last few years with ONR support

Safety and clinical performance of acoustic reflex tests.

PubMed

Hunter, L L; Ries, D T; Schlauch, R S; Levine, S C; Ward, W D

1999-12-01

Safety and effectiveness of acoustic reflex tests are important issues because these tests are widely applied to screen for retrocochlear pathology. Previous studies have reported moderately high sensitivity and specificity for detection of acoustic neuroma. However, there have been reports of possible iatrogenic hearing loss resulting from acoustic reflex threshold (ART) and decay (ARD) tests. This study assessed safety and clinical performance of ART tests for detection of acoustic neuroma. We report a case in which ARD testing resulted in a significant bilateral permanent threshold shift. This case was the impetus for us to investigate the clinical utility of ART and ARD tests. We analyzed sensitivity and specificity of ART, as well as asymmetry in pure-tone thresholds (PTT) for detection of acoustic neuroma in 56 tumor and 108 non-tumor ears. Sensitivity and specificity were higher for PTT asymmetry than for ART. Ipsilateral ART at 1000 Hz had poor sensitivity and specificity for detection of acoustic neuroma, and involves some potential risk to residual hearing for presentation levels higher than 115 dB SPL. Approximately half of the acoustic neuroma group had ipsilateral ARTs that would require administration of ARD tests at levels exceeding 115 dB SPL. Therefore, we conclude that PTT asymmetry is a more effective test for detection of acoustic neuroma, and involves no risk to residual hearing. Future studies of contralateral reflex threshold and ARD in combination with PTT asymmetry are recommended.

Perceptual integration of acoustic cues to laryngeal contrasts in Korean fricatives.

PubMed

Lee, Sarah; Katz, Jonah

2016-02-01

This paper provides evidence that multiple acoustic cues involving the presence of low-frequency energy integrate in the perception of Korean coronal fricatives. This finding helps explain a surprising asymmetry between the production and perception of these fricatives found in previous studies: lower F0 onset in the following vowel leads to a response bias for plain [s] over fortis [s*], despite the fact that there is no evidence for a corresponding acoustic asymmetry in the production of [s] and [s*]. A fixed classification task using the Garner paradigm provides evidence that low F0 in a following vowel and the presence of voicing during frication perceptually integrate. This suggests that Korean listeners in previous experiments were responding to an "intermediate perceptual property" of stimuli, despite the fact that the individual acoustic components of that property are not all present in typical Korean fricative productions. The finding also broadens empirical support for the general idea of perceptual integration to a language, a different manner of consonant, and a situation where covariance of the acoustic cues under investigation is not generally present in a listener's linguistic input.

Acoustic Emission Detected by Matched Filter Technique in Laboratory Earthquake Experiment

NASA Astrophysics Data System (ADS)

Wang, B.; Hou, J.; Xie, F.; Ren, Y.

2017-12-01

Acoustic Emission in laboratory earthquake experiment is a fundamental measures to study the mechanics of the earthquake for instance to characterize the aseismic, nucleation, as well as post seismic phase or in stick slip experiment. Compared to field earthquake, AEs are generally recorded when they are beyond threshold, so some weak signals may be missing. Here we conducted an experiment on a 1.1m×1.1m granite with a 1.5m fault and 13 receivers with the same sample rate of 3MHz are placed on the surface. We adopt continues record and a matched filter technique to detect low-SNR signals. We found there are too many signals around the stick-slip and the P- arrival picked by manual may be time-consuming. So, we combined the short-term average to long-tem-average ratio (STA/LTA) technique with Autoregressive-Akaike information criterion (AR-AIC) technique to pick the arrival automatically and found mostly of the P- arrival accuracy can satisfy our demand to locate signals. Furthermore, we will locate the signals and apply a matched filter technique to detect low-SNR signals. Then, we can see if there is something interesting in laboratory earthquake experiment. Detailed and updated results will be present in the meeting.

Improved Calibration Of Acoustic Plethysmographic Sensors

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J.; Davis, David C.

1993-01-01

Improved method of calibration of acoustic plethysmographic sensors involves acoustic-impedance test conditions like those encountered in use. Clamped aluminum tube holds source of sound (hydrophone) inside balloon. Test and reference sensors attached to outside of balloon. Sensors used to measure blood flow, blood pressure, heart rate, breathing sounds, and other vital signs from surfaces of human bodies. Attached to torsos or limbs by straps or adhesives.

KENNEDY SPACE CENTER, FLA. - Research team members roll out acoustic cable to the water's edge as others stand by in a watercraft during underwater acoustic research being conducted in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

NASA Image and Video Library

2003-08-18

KENNEDY SPACE CENTER, FLA. - Research team members roll out acoustic cable to the water's edge as others stand by in a watercraft during underwater acoustic research being conducted in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

Triad Resonance in the Gravity-Acoustic Family

NASA Astrophysics Data System (ADS)

Kadri, U.

2015-12-01

Resonance interactions of waves play a prominent role in energy share among the different wave types involved. Such interactions may significantly contribute, among others, to the evolution of the ocean energy spectrum by exchanging energy between surface-gravity waves; surface and internal gravity waves; or even surface and compression-type waves, that can transfer energy from the upper ocean through the whole water column reaching down to the seafloor. A resonant triad occurs among a triplet of waves, usually involving interaction of nonlinear terms of second order perturbed equations. Until recently, it has been believed that in a homogeneous fluid a resonant triad is possible only when tension forces are included, or at the limit of a shallow water, and that when the compressibility of water is considered, no resonant triads can occur within the family of gravity-acoustic waves. However, more recently it has been proved that, under some circumstances, resonant triads comprising two opposing surface-gravity waves of similar periods (though not identical) and a much longer acoustic-gravity wave, of almost double the frequency, exist [Kadri and Stiassnie 2013, J. Fluid Mech.735 R6]. Here, I report on a new resonant triad involving a gravity wave and two acoustic waves of almost double the length. Interestingly, the two acoustic waves propagate in the same direction with similar wavelengths, that are almost double of that of the gravity wave. The evolution of the wave triad amplitudes is periodic and it is derived analytically, in terms of Jacobian elliptic functions and elliptic integrals. The physical importance of this type of triad interactions is the modulation of pertinent acoustic signals, leading to inaccurate signal perceptions. Enclosed figure: presents an example spatio-temporal evolution of the wave triad amplitudes. The gravity wave (top) remains almost unaltered, while the envelope slowly displaces to the left. However, the prescribed acoustic

Integrated Model for the Acoustics of Sediments

DTIC Science & Technology

2014-09-30

1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Integrated Model for the Acoustics of Sediments Nicholas...physics, and (3) the development and testing of sediment acoustic models through a series of at-sea experiments. APPROACH The approach may be...00-2014 4. TITLE AND SUBTITLE Integrated Model for the Acoustics of Sediments 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6

Acoustic Conditioning System Development and Conditioning Experiments on Black Seabreams in the Xiangshan Bay Sea Ranch

NASA Astrophysics Data System (ADS)

Hu, Qingsong; Rahman, Hafiz Abd ur; Jiang, Yazhou; Zhang, Shouyu; Shentu, Jikang

2018-06-01

Attracting released hatchery-reared fish to designated areas during the growth process is vital to realize the objectives of sea ranching. Based on the bottom artificial reefs and surface kelp culture facilities in the Xiangshan Bay sea ranch, we proposed systematic techniques related to acoustic conditioning of the black seabream ( Sparus macrocephalus). Experiments conducted in 12 m × 10 m × 1.6 m ponds on Xixuan Island showed that black seabream was positively sensitive to 500-600 Hz periodic signals. Conditioned responses were apparent after 8 d. Two to three days were required for recovery of the memory of a conditioned response after a 20-day interval. According to the practical application requirements in the open sea, unattended acoustic conditioning equipment was developed. The ranching equipment was used in 12 m × 12 m × 2.5 m cages, and the behavior of black seabream juveniles was successfully guided after 7 days. Of the 16000 released fish, 82.5% of them were conditioned with a flexible grading net. To avoid inducing a stress response, the juveniles were released into the sea ranch in situ from the net cage. The acoustic conditioning equipments were moved into the open sea and the aggregation phenomenon of the released fish was observed when the sound was played. After 6 months of investigation and based on Sr+ marking, only one acoustically conditioned fish was found outside the 3.5-km2 sea ranch area, thereby reached the goal of guiding activity. The practical effect in the Xiangshan Bay sea ranch showed the validity of the acoustic conditioning system, which may contribute to improve the operation of the sea ranches in the East China Sea.

Ultrasonic power transfer from a spherical acoustic wave source to a free-free piezoelectric receiver: Modeling and experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shahab, S.; Gray, M.; Erturk, A., E-mail: alper.erturk@me.gatech.edu

2015-03-14

Contactless powering of small electronic components has lately received growing attention for wireless applications in which battery replacement or tethered charging is undesired or simply impossible, and ambient energy harvesting is not a viable solution. As an alternative to well-studied methods of contactless energy transfer, such as the inductive coupling method, the use of ultrasonic waves transmitted and received by piezoelectric devices enables larger power transmission distances, which is critical especially for deep-implanted electronic devices. Moreover, energy transfer by means of acoustic waves is well suited in situations where no electromagnetic fields are allowed. The limited literature of ultrasonic acousticmore » energy transfer is mainly centered on proof-of-concept experiments demonstrating the feasibility of this method, lacking experimentally validated modeling efforts for the resulting multiphysics problem that couples the source and receiver dynamics with domain acoustics. In this work, we present fully coupled analytical, numerical, and experimental multiphysics investigations for ultrasonic acoustic energy transfer from a spherical wave source to a piezoelectric receiver bar that operates in the 33-mode of piezoelectricity. The fluid-loaded piezoelectric receiver under free-free mechanical boundary conditions is shunted to an electrical load for quantifying the electrical power output for a given acoustic source strength of the transmitter. The analytical acoustic-piezoelectric structure interaction modeling framework is validated experimentally, and the effects of system parameters are reported along with optimal electrical loading and frequency conditions of the receiver.« less

Acoustic Design of Naval Structures

DTIC Science & Technology

2005-12-01

Ship Signatures Department Research and Development Report NSWCCD-70--TR-2005/149 December 2005 ACOUSTIC DESIGN OF NAVAL STRUCTURES by: S. Nikiforov...NSWCCD-70--TR–2005/149 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) Office of Naval Research ...approach, gained through his research experience on the acoustic characteristics of vibration and radiation of ship structures, sources of the main

A new Strategy to Improve Drug Delivery to the Maxillary Sinuses: The Frequency Sweep Acoustic Airflow.

PubMed

El Merhie, Amira; Navarro, Laurent; Delavenne, Xavier; Leclerc, Lara; Pourchez, Jérémie

2016-05-01

Enhancement of intranasal sinus deposition involves nebulization of a drug superimposed by an acoustic airflow. We investigated the impact of fixed frequency versus frequency sweep acoustic airflow on the improvement of aerosolized drug penetration into maxillary sinuses. Fixed frequency and frequency sweep acoustic airflow were generated using a nebulizing system of variable frequency. The effect of sweep cycle and intensity variation was studied on the intranasal sinus deposition. We used a nasal replica created from CT scans using 3D printing. Sodium fluoride and gentamicin were chosen as markers. Studies performed using fixed frequency acoustic airflow showed that each of maxillary sinuses of the nasal replica required specific frequency for the optimal aerosol deposition. Intranasal sinus drug deposition experiments under the effect of the frequency sweep acoustic airflow showed an optimal aerosol deposition into both maxillary sinus of the nasal replica. Studies on the effect of the duration of the sweep cycle showed that the shorter the cycle the better the deposition. We demonstrate the benefit of frequency sweep acoustic airflow on drug deposition into maxillary sinuses. However further in vivo studies have to be conducted since delivery rates cannot be obviously determined from a nasal replica.

Contrast-enhanced optical coherence microangiography with acoustic-actuated microbubbles

NASA Astrophysics Data System (ADS)

Liu, Yu-Hsuan; Zhang, Jia-Wei; Yeh, Chih-Kuang; Wei, Kuo-Chen; Liu, Hao-Li; Tsai, Meng-Tsan

2017-04-01

In this study, we propose to use gas-filled microbubbles (MBs) simultaneously actuated by the acoustic wave to enhance the imaging contrast of optical coherence tomography (OCT)-based angiography. In the phantom experiments, MBs can result in stronger backscattered intensity, enabling to enhance the contrast of OCT intensity image. Moreover, simultaneous application of low-intensity acoustic wave enables to temporally induce local vibration of particles and MBs in the vessels, resulting in time-variant OCT intensity which can be used for enhancing the contrast of OCT intensitybased angiography. Additionally, different acoustic modes and different acoustic powers to actuate MBs are performed and compared to investigate the feasibility of contrast enhancement. Finally, animal experiments are performed. The findings suggest that acoustic-actuated MBs can effectively enhance the imaging contrast of OCT-based angiography and the imaging depth of OCT angiography is also extended.

In-flight acoustic testing techniques using the YO-3A Acoustic Research Aircraft

NASA Technical Reports Server (NTRS)

Cross, J. L.; Watts, M. E.

1984-01-01

This report discusses the flight testing techniques and equipment employed during air-to-air acoustic testing of helicopters at Ames Research Center. The in flight measurement technique used enables acoustic data to be obtained without the limitations of anechoic chambers or the multitude of variables encountered in ground based flyover testing. The air-to-air testing is made possible by the NASA YO-3A Acoustic Research Aircraft. This "Quiet Aircraft' is an acoustically instrumented version of a quiet observation aircraft manufactured for the military. To date, tests with the following aircraft have been conducted: YO-3A background noise; Hughes 500D; Hughes AH-64; Bell AH-1S; Bell AH-1G. Several system upgrades are being designed and implemented to improve the quality of data. This report will discuss not only the equipment involved and aircraft tested, but also the techniques used in these tests. In particular, formation flying position locations, and the test matrices will be discussed. Examples of data taken will also be presented.

In-flight acoustic testing techniques using the YO-3A acoustic research aircraft

NASA Technical Reports Server (NTRS)

Cross, J. L.; Watts, M. E.

1983-01-01

This report discusses the flight testing techniques and equipment employed during air-to-air acoustic testing of helicopters at Ames Research Center. The in-flight measurement technique used enables acoustic data to be obtained without the limitations of anechoic chambers or the multitude of variables encountered in ground based flyover testing. The air-to-air testing is made possible by the NASA YO-3A Acoustic Research Aircraft. This 'Quiet Aircraft' is an acoustically instrumented version of a quiet observation aircraft manufactured for the military. To date, tests with the following aircraft have been conducted: YO-3A background noise; Hughes 500D; Hughes AH-64; Bell AH-1S; Bell AH-1G. Several system upgrades are being designed and implemented to improve the quality of data. This report will discuss not only the equipment involved and aircraft tested, but also the techniques used in these tests. In particular, formation flying, position locations, and the test matrices will be discussed. Examples of data taken will also be presented.

Dynamics and Instabilities of Acoustically Stressed Interfaces

NASA Astrophysics Data System (ADS)

Shi, William Tao

An intense sound field exerts acoustic radiation pressure on a transitional layer between two continuous fluid media, leading to the unconventional dynamical behavior of the interface in the presence of the sound field. An understanding of this behavior has applications in the study of drop dynamics and surface rheology. Acoustic fields have also been utilized in the generation of interfacial instability, which may further encourage the dispersion or coalescence of liquids. Therefore, the study of the dynamics of the acoustically stressed interfaces is essential to infer the mechanism of the various phenomena related to interfacial dynamics and to acquire the properties of liquid surfaces. This thesis studies the dynamics of acoustically stressed interfaces through a theoretical model of surface interactions on both closed and open interfaces. Accordingly, a boundary integral method is developed to simulate the motions of a stressed interface. The method has been employed to determine the deformation, oscillation and instability of acoustically levitated drops. The generalized computations are found to be in good agreement with available experimental results. The linearized theory is also derived to predict the instability threshold of the flat interface, and is then compared with experiments conducted to observe and measure the unstable motions of the horizontal interface. This thesis is devoted to describing and classifying the simplest mechanisms by which acoustic fields provide a surface interaction with a fluid. A physical picture of the competing processes introduced by the evolution of an interface in a sound field is presented. The development of an initial small perturbation into a sharp form is observed on either a drop surface or a horizontal interface, indicating a strong focusing of acoustic energy at certain spots of the interface. Emphasis is placed on understanding the basic coupling mechanisms, rather than on particular applications that may

Study and application of acoustic emission testing in fault diagnosis of low-speed heavy-duty gears.

PubMed

Gao, Lixin; Zai, Fenlou; Su, Shanbin; Wang, Huaqing; Chen, Peng; Liu, Limei

2011-01-01

Most present studies on the acoustic emission signals of rotating machinery are experiment-oriented, while few of them involve on-spot applications. In this study, a method of redundant second generation wavelet transform based on the principle of interpolated subdivision was developed. With this method, subdivision was not needed during the decomposition. The lengths of approximation signals and detail signals were the same as those of original ones, so the data volume was twice that of original signals; besides, the data redundancy characteristic also guaranteed the excellent analysis effect of the method. The analysis of the acoustic emission data from the faults of on-spot low-speed heavy-duty gears validated the redundant second generation wavelet transform in the processing and denoising of acoustic emission signals. Furthermore, the analysis illustrated that the acoustic emission testing could be used in the fault diagnosis of on-spot low-speed heavy-duty gears and could be a significant supplement to vibration testing diagnosis.

Study and Application of Acoustic Emission Testing in Fault Diagnosis of Low-Speed Heavy-Duty Gears

PubMed Central

Gao, Lixin; Zai, Fenlou; Su, Shanbin; Wang, Huaqing; Chen, Peng; Liu, Limei

2011-01-01

Most present studies on the acoustic emission signals of rotating machinery are experiment-oriented, while few of them involve on-spot applications. In this study, a method of redundant second generation wavelet transform based on the principle of interpolated subdivision was developed. With this method, subdivision was not needed during the decomposition. The lengths of approximation signals and detail signals were the same as those of original ones, so the data volume was twice that of original signals; besides, the data redundancy characteristic also guaranteed the excellent analysis effect of the method. The analysis of the acoustic emission data from the faults of on-spot low-speed heavy-duty gears validated the redundant second generation wavelet transform in the processing and denoising of acoustic emission signals. Furthermore, the analysis illustrated that the acoustic emission testing could be used in the fault diagnosis of on-spot low-speed heavy-duty gears and could be a significant supplement to vibration testing diagnosis. PMID:22346592

Novel Fiber-Optic Ring Acoustic Emission Sensor.

PubMed

Wei, Peng; Han, Xiaole; Xia, Dong; Liu, Taolin; Lang, Hao

2018-01-13

Acoustic emission technology has been applied to many fields for many years. However, the conventional piezoelectric acoustic emission sensors cannot be used in extreme environments, such as those with heavy electromagnetic interference, high pressure, or strong corrosion. In this paper, a novel fiber-optic ring acoustic emission sensor is proposed. The sensor exhibits high sensitivity, anti-electromagnetic interference, and corrosion resistance. First, the principle of a novel fiber-optic ring sensor is introduced. Different from piezoelectric and other fiber acoustic emission sensors, this novel sensor includes both a sensing skeleton and a sensing fiber. Second, a heterodyne interferometric demodulating method is presented. In addition, a fiber-optic ring sensor acoustic emission system is built based on this method. Finally, fiber-optic ring acoustic emission experiments are performed. The novel fiber-optic ring sensor is glued onto the surface of an aluminum plate. The 150 kHz standard continuous sinusoidal signals and broken lead signals are successfully detected by the novel fiber-optic ring acoustic emission sensor. In addition, comparison to the piezoelectric acoustic emission sensor is performed, which shows the availability and reliability of the novel fiber-optic ring acoustic emission sensor. In the future, this novel fiber-optic ring acoustic emission sensor will provide a new route to acoustic emission detection in harsh environments.

Acoustical Properties of Mud Sediments

DTIC Science & Technology

2015-09-30

Acoustical Properties of Mud Sediments Allan D. Pierce Boston University 399 Quaker Meeting House Road P. O. Box 339 East Sandwich, MA 03537...shallow-ocean mud sediments. Other goals are to assess prior data relating to the acoustic properties of mud and to provide guidance in the...development and interpretation of experiments. A related goal is to construct models that will guide inversion techniques for inferring properties of mud

Acoustic Probe for Solid-Gas-Liquid Suspension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tavlarides, L.L.; Sangani, Ashok

The primary objective of the research project during the first funding period was to develop an acoustic probe to measure volume percent solids in solid-liquid slurries in the presence of small amounts of gas bubbles. This problem was addressed because of the great need for a non-invasive, accurate and reliable method for solids monitoring in liquid slurries in the presence of radiolytically generated gases throughout the DOE complex. These measurements are necessary during mobilization of salts and sediments in tanks, transport of these slurries in transfer lines to processing facilities across a site, and, in some instances, during high levelmore » waste processing. Although acoustic probes have been commonly used for monitoring flows in single-phase fluids (McLeod, 1967), their application to monitor two-phase mixtures has not yet fully realized its potential. A number of investigators in recent years have therefore been involved in developing probes for measuring the volume fractions in liquid solid suspensions (Atkinson and Kytomaa, 1993; Greenwood et al., 1993; Martin et al., 1995) and in liquid-liquid suspensions (Bonnet and Tavlarides, 1987; Tavlarides and Bonnet, 1988, Yi and Tavlarides, 1990; Tsouris and Tavlarides, 1993, Tsouris et al., 1995). In particular, Atkinson and Kytomaa (1993) showed that the acoustic technique can be used to determine both the velocity and the volume fraction of solids while Martin et al. (1995) and Spelt et al. (1999) showed that the acoustic probe can also be used to obtain information on the size distribution of the particles. In a recent testing of in-line slurry monitors with radioactive slurries suspended with Pulsair Mixers (Hylton & Bayne, 1999), an acoustic probe did not compare well with other instruments most probably due to presence of entrained gases and improper acoustic frequency range of interrogation. The work of the investigators cited has established the potential of the acoustic probe for characterizing

Acoustic Experiment to Measure the Bulk Viscosity of Near-Critical Xenon in Microgravity

NASA Technical Reports Server (NTRS)

Gillis, K. A.; Shinder, I.; Moldover, M. R.; Zimmerli, G. A.

2002-01-01

We plan a rigorous test of the theory of dynamic scaling by accurately measuring the bulk viscosity of xenon in microgravity 50 times closer to the critical temperature T(sub c) than previous experiments. The bulk viscosity zeta (or "second viscosity" or "dilational viscosity") will be determined by measuring the attenuation length of sound alpha lambda and also measuring the frequency-dependence of the speed of sound. For these measurements, we developed a unique Helmholtz resonator and specialized electro-acoustic transducers. We describe the resonator, the transducers, their performance on Earth, and their expected performance in microgravity.

Pattern-formation under acoustic driving forces

NASA Astrophysics Data System (ADS)

Valverde, Jose Manuel

2015-07-01

Chemical and metallurgical processes enhanced by high intensity acoustic waves, thermoacoustic engines and refrigerators, fuel rods in nuclear reactors, heat exchanger tubes, offshore and vibrating structures, solar thermal collectors, acoustic levitators, microfluidic devices, cycling, musical acoustics, blood flow through veins/arteries, hearing in the mammalian ear, carbon nanotube loudspeakers, etc. The evolution of a myriad of processes involving the oscillation of viscous fluids in the presence of solid boundaries is up to a certain extent influenced by acoustic streaming. In addition to the sound field, viscous energy dissipation at the fluid-solid boundary causes a time-independent fluid circulation, which can lead to a significant enhancement of heat, mass and momentum transfer at large oscillation amplitudes. A particularly relevant phenomenon that can be notably affected by acoustic streaming is the promotion of sound waves by temperature gradients or viceversa (thermoacoustics), which is at the basis of potentially efficient and environmental friendly engines and refrigerators that have attracted a renewed interest in the last years. In the present manuscript, historical developments and the underlying basic physics behind acoustic streaming and thermoacoustics are reviewed from an unifying perspective.

Layered acoustofluidic resonators for the simultaneous optical and acoustic characterisation of cavitation dynamics, microstreaming, and biological effects.

PubMed

Pereno, V; Aron, M; Vince, O; Mannaris, C; Seth, A; de Saint Victor, M; Lajoinie, G; Versluis, M; Coussios, C; Carugo, D; Stride, E

2018-05-01

The study of the effects of ultrasound-induced acoustic cavitation on biological structures is an active field in biomedical research. Of particular interest for therapeutic applications is the ability of oscillating microbubbles to promote both cellular and tissue membrane permeabilisation and to improve the distribution of therapeutic agents in tissue through extravasation and convective transport. The mechanisms that underpin the interaction between cavitating agents and tissues are, however, still poorly understood. One challenge is the practical difficulty involved in performing optical microscopy and acoustic emissions monitoring simultaneously in a biologically compatible environment. Here we present and characterise a microfluidic layered acoustic resonator ( μ LAR) developed for simultaneous ultrasound exposure, acoustic emissions monitoring, and microscopy of biological samples. The μ LAR facilitates in vitro ultrasound experiments in which measurements of microbubble dynamics, microstreaming velocity fields, acoustic emissions, and cell-microbubble interactions can be performed simultaneously. The device and analyses presented provide a means of performing mechanistic in vitro studies that may benefit the design of predictable and effective cavitation-based ultrasound treatments.

Features of CO2 fracturing deduced from acoustic emission and microscopy in laboratory experiments

NASA Astrophysics Data System (ADS)

Ishida, Tsuyoshi; Chen, Youqing; Bennour, Ziad; Yamashita, Hiroto; Inui, Shuhei; Nagaya, Yuya; Naoi, Makoto; Chen, Qu; Nakayama, Yoshiki; Nagano, Yu

2016-11-01

We conducted hydraulic fracturing (HF) experiments on 170 mm cubic granite specimens with a 20 mm diameter central hole to investigate how fluid viscosity affects HF process and crack properties. In experiments using supercritical carbon dioxide (SC-CO2), liquid carbon dioxide (L-CO2), water, and viscous oil with viscosity of 0.051-336.6 mPa · s, we compared the results for breakdown pressure, the distribution and fracturing mechanism of acoustic emission, and the microstructure of induced cracks revealed by using an acrylic resin containing a fluorescent compound. Fracturing with low-viscosity fluid induced three-dimensionally sinuous cracks with many secondary branches, which seem to be desirable pathways for enhanced geothermal system, shale gas recovery, and other processes.

Dynamics of Ultrasound Contrast Agents and Nonlinear Acoustic Waves: Experiments, Modeling, and Theories

NASA Astrophysics Data System (ADS)

Xia, Lang

Bubbles occur in many natural and biological flows as well as in numerous industrial phenomena, such as pumps, propellers, turbines, and chemical processing plants. They have been widely studied in the past leading to a large body of literature. However, bubbles appearing in different situations differ significantly in their physical characteristics and behaviors. Recently, bubbles of diameter less than 10 micrometers have found applications in diagnostic ultrasound imaging. These microbubble-based ultrasound contrast agents (UCA) are intravenously administered in patients before ultrasound imaging. Due to the compressive gas core, they generate substantial ultrasound echoes leading to significant enhancement of image quality and contrast. Free bubbles of a micrometer diameter experience a large surface tension induced Laplace pressure leading to their quick dissolution in milliseconds. UCAs are stabilized by coating them with a shell of lipids, polymers, proteins, and other surface-active materials and changing the gas content from air to a high molecular weight low solubility gas such as perfluorocarbon. The past literature of bubble dynamics are mostly restricted to free bubbles. The stabilizing shell of UCAs, however, critically affects their dynamics. In this thesis, we performed acoustic characterization of several UCAs coated with polymer and lipids. We experimentally measured their acoustic attenuation and scattering, of which the data were used in mathematical models to determine shell properties and nonlinear dynamics. Several different interfacial rheological models were employed. Experimental acoustic characterization was also extended to a novel type of nanoparticle suspension--polymersomes, vesicles encapsulated by amphiphilic polymers. The later part of the thesis is devoted to modeling the effects of the presence of coated microbubbles to the overall effective bulk properties of bubbly liquids. Introduction of microbubbles in the liquids does not

Novel Fiber-Optic Ring Acoustic Emission Sensor

PubMed Central

Han, Xiaole; Xia, Dong; Liu, Taolin; Lang, Hao

2018-01-01

Acoustic emission technology has been applied to many fields for many years. However, the conventional piezoelectric acoustic emission sensors cannot be used in extreme environments, such as those with heavy electromagnetic interference, high pressure, or strong corrosion. In this paper, a novel fiber-optic ring acoustic emission sensor is proposed. The sensor exhibits high sensitivity, anti-electromagnetic interference, and corrosion resistance. First, the principle of a novel fiber-optic ring sensor is introduced. Different from piezoelectric and other fiber acoustic emission sensors, this novel sensor includes both a sensing skeleton and a sensing fiber. Second, a heterodyne interferometric demodulating method is presented. In addition, a fiber-optic ring sensor acoustic emission system is built based on this method. Finally, fiber-optic ring acoustic emission experiments are performed. The novel fiber-optic ring sensor is glued onto the surface of an aluminum plate. The 150 kHz standard continuous sinusoidal signals and broken lead signals are successfully detected by the novel fiber-optic ring acoustic emission sensor. In addition, comparison to the piezoelectric acoustic emission sensor is performed, which shows the availability and reliability of the novel fiber-optic ring acoustic emission sensor. In the future, this novel fiber-optic ring acoustic emission sensor will provide a new route to acoustic emission detection in harsh environments. PMID:29342858

Bioeffects due to acoustic droplet vaporization

NASA Astrophysics Data System (ADS)

Bull, Joseph

2015-11-01

Encapsulated micro- and nano-droplets can be vaporized via ultrasound, a process termed acoustic droplet vaporization. Our interest is primarily motivated by a developmental gas embolotherapy technique for cancer treatment. In this methodology, infarction of tumors is induced by selectively formed vascular gas bubbles that arise from the acoustic vaporization of vascular microdroplets. Additionally, the microdroplets may be used as vehicles for localized drug delivery, with or without flow occlusion. In this talk, we examine the dynamics of acoustic droplet vaporization through experiments and theoretical/computational fluid mechanics models, and investigate the bioeffects of acoustic droplet vaporization on endothelial cells and in vivo. Early timescale vaporization events, including phase change, are directly visualized using ultra-high speed imaging, and the influence of acoustic parameters on droplet/bubble dynamics is discussed. Acoustic and fluid mechanics parameters affecting the severity of endothelial cell bioeffects are explored. These findings suggest parameter spaces for which bioeffects may be reduced or enhanced, depending on the objective of the therapy. This work was supported by NIH grant R01EB006476.

Generation of Artificial Acoustic-Gravity Waves and Traveling Ionospheric Disturbances in HF Heating Experiments

NASA Astrophysics Data System (ADS)

Pradipta, R.; Lee, M. C.; Cohen, J. A.; Watkins, B. J.

2015-10-01

We report the results of our ionospheric HF heating experiments to generate artificial acoustic-gravity waves (AGW) and traveling ionospheric disturbances (TID), which were conducted at the High-frequency Active Auroral Research Program facility in Gakona, Alaska. Based on the data from UHF radar, GPS total electron content, and ionosonde measurements, we found that artificial AGW/TID can be generated in ionospheric modification experiments by sinusoidally modulating the power envelope of the transmitted O-mode HF heater waves. In this case, the modulation frequency needs to be set below the characteristic Brunt-Vaisala frequency at the relevant altitudes. We avoided potential contamination from naturally-occurring AGW/TID of auroral origin by conducting the experiments during geomagnetically quiet time period. We determine that these artificial AGW/TID propagate away from the edge of the heated region with a horizontal speed of approximately 160 m/s.

Acoustic manipulation of bacteria cells suspensions

NASA Astrophysics Data System (ADS)

GutiéRrez-Ramos, Salomé; Hoyos, Mauricio; Aider, Jean Luc; Ruiz, Carlos; Acoustofluidics Team Team; Soft; Bio Group Collaboration

An acoustic contacless manipulation gives advantages in the exploration of the complex dynamics enviroment that active matter exhibits. Our works reports the control confinement and dispersion of Escherichia coliRP437-pZA3R-YFP suspensions (M9Glu-Ca) via acoustic levitation.The manipulation of the bacteria bath in a parallel plate resonator is achieved using the acoustic radiation force and the secondary radiation force. The primary radiation force generates levitation of the bacteria cells at the nodal plane of the ultrasonic standing wave generated inside the resonator. On the other side, secondary forces leads to the consolidation of stable aggregates. All the experiments were performed in the acoustic trap described, where we excite the emission plate with a continuous sinusoidal signal at a frequency in the order of MHz and a quartz slide as the reflector plate. In a typical experiment we observed that, before the input of the signal, the bacteria cells exhibit their typical run and tumble behavior and after the sound is turned on all of them displace towards the nodal plane, and instantaneously the aggregation begins in this region. CNRS French National Space Studies, CONACYT Mexico.

Optimizing piezoelectric receivers for acoustic power transfer applications

NASA Astrophysics Data System (ADS)

Gorostiaga, M.; Wapler, M. C.; Wallrabe, U.

2018-07-01

In this paper, we aim to optimize piezoelectric plate receivers for acoustic power transfer applications by analyzing the influence of the losses and of the acoustic boundary conditions. We derive the analytic expressions of the efficiency of the receiver with the optimal electric loads attached, and analyze the maximum efficiency value and its frequency with different loss and acoustic boundary conditions. To validate the analytical expressions that we have derived, we perform experiments in water with composite transducers of different filling fractions, and see that a lower acoustic impedance mismatch can compensate the influence of large dielectric and acoustic losses to achieve a good performance. Finally, we briefly compare the advantages and drawbacks of composite transducers and pure PZT (lead zirconate titanate) plates as acoustic power receivers, and conclude that 1–3 composites can achieve similar efficiency values in low power applications due to their adjustable acoustic impedance.

Acoustic wayfinding: A method to measure the acoustic contrast of different paving materials for blind people.

PubMed

Secchi, Simone; Lauria, Antonio; Cellai, Gianfranco

2017-01-01

Acoustic wayfinding involves using a variety of auditory cues to create a mental map of the surrounding environment. For blind people, these auditory cues become the primary substitute for visual information in order to understand the features of the spatial context and orient themselves. This can include creating sound waves, such as tapping a cane. This paper reports the results of a research about the "acoustic contrast" parameter between paving materials functioning as a cue and the surrounding or adjacent surface functioning as a background. A number of different materials was selected in order to create a test path and a procedure was defined for the verification of the ability of blind people to distinguish different acoustic contrasts. A method is proposed for measuring acoustic contrast generated by the impact of a cane tip on the ground to provide blind people with environmental information on spatial orientation and wayfinding in urban places. Copyright © 2016 Elsevier Ltd. All rights reserved.

Acoustic intensity calculations for axisymmetrically modeled fluid regions

NASA Technical Reports Server (NTRS)

Hambric, Stephen A.; Everstine, Gordon C.

1992-01-01

An algorithm for calculating acoustic intensities from a time harmonic pressure field in an axisymmetric fluid region is presented. Acoustic pressures are computed in a mesh of NASTRAN triangular finite elements of revolution (TRIAAX) using an analogy between the scalar wave equation and elasticity equations. Acoustic intensities are then calculated from pressures and pressure derivatives taken over the mesh of TRIAAX elements. Intensities are displayed as vectors indicating the directions and magnitudes of energy flow at all mesh points in the acoustic field. A prolate spheroidal shell is modeled with axisymmetric shell elements (CONEAX) and submerged in a fluid region of TRIAAX elements. The model is analyzed to illustrate the acoustic intensity method and the usefulness of energy flow paths in the understanding of the response of fluid-structure interaction problems. The structural-acoustic analogy used is summarized for completeness. This study uncovered a NASTRAN limitation involving numerical precision issues in the CONEAX stiffness calculation causing large errors in the system matrices for nearly cylindrical cones.

Acoustic resonances of fluid-immersed elastic cylinders and spheroids: Theory and experiment

NASA Astrophysics Data System (ADS)

Niemiec, Jan; Überall, Herbert; Bao, X. L.

2002-05-01

Frequency resonances in the scattering of acoustic waves from a target object are caused by the phase matching of surface waves repeatedly encircling the object. This is exemplified here by considering elastic finite cylinders and spheroids, and the phase-matching condition provides a means of calculating the complex resonance frequencies of such objects. Tank experiments carried out at Catholic University, or at the University of Le Havre, France by G. Maze and J. Ripoche, have been interpreted using this approach. The experiments employed sound pulses to measure arrival times, which allowed identification of the surface paths taken by the surface waves, thus giving rise to resonances in the scattering amplitude. A calculation of the resonance frequencies using the T-matrix approach showed satisfactory agreement with the experimental resonance frequencies that were either measured directly (as at Le Havre), or that were obtained by the interpretation of measured arrival times (at Catholic University) using calculated surface wave paths, and the extraction of resonance frequencies therefrom, on the basis of the phase-matching condition. Results for hemispherically endcapped, evacuated steel cylinders obtained in a lake experiment carried out by the NSWC were interpreted in the same fashion.

Hidden acoustic information revealed by intentional nonlinearity

NASA Astrophysics Data System (ADS)

Dowling, David R.

2017-11-01

Acoustic waves are omnipresent in modern life and are well described by the linearized equations of fluid dynamics. Once generated, acoustic waves carry and collect information about their source and the environment through which they propagate, respectively, and this information may be retrieved by analyzing recordings of these waves. Because of this, acoustics is the primary means for observation, surveillance, reconnaissance, and remote sensing in otherwise opaque environments, such as the Earth's oceans and crust, and the interior of the human body. For such information-retrieval tasks, acoustic fields are nearly always interrogated within their recorded frequency range or bandwidth. However, this frequency-range restriction is not general; acoustic fields may also carry (hidden) information at frequencies outside their bandwidth. Although such a claim may seem counter intuitive, hidden acoustic-field information can be revealed by re-introducing a marquee trait of fluid dynamics: nonlinearity. In particular, an intentional quadratic nonlinearity - a form of intra-signal heterodyning - can be used to obtain acoustic field information at frequencies outside a recorded acoustic field's bandwidth. This quadratic nonlinearity enables a variety of acoustic remote sensing applications that were long thought to be impossible. In particular, it allows the detrimental effects of sparse recordings and random scattering to be suppressed when the original acoustic field has sufficient bandwidth. In this presentation, the topic is developed heuristically, with a just brief exposition of the relevant mathematics. Hidden acoustic field information is then revealed from simulated and measured acoustic fields in simple and complicated acoustic environments involving frequencies from a few Hertz to more than 100 kHz, and propagation distances from tens of centimeters to hundreds of kilometers. Sponsored by ONR, NAVSEA, and NSF.

Impact of acoustic airflow on intrasinus drug deposition: New insights into the vibrating mode and the optimal acoustic frequency to enhance the delivery of nebulized antibiotic.

PubMed

Leclerc, Lara; Merhie, Amira El; Navarro, Laurent; Prévôt, Nathalie; Durand, Marc; Pourchez, Jérémie

2015-10-15

We investigated the impact of vibrating acoustic airflow, the high frequency (f≥100 Hz) and the low frequency (f≤45 Hz) sound waves, on the enhancement of intrasinus drug deposition. (81m)Kr-gas ventilation study was performed in a plastinated human cast with and without the addition of vibrating acoustic airflow. Similarly, intrasinus drug deposition in a nasal replica using gentamicin as a marker was studied with and without the superposition of different modes of acoustic airflow. Ventilation experiments demonstrate that no sinus ventilation was observed without acoustic airflow although sinus ventilation occurred whatever the modes of acoustic airflow applied. Intrasinus drug deposition experiments showed that the high frequency acoustic airflow led to 4-fold increase in gentamicin deposition into the left maxillary sinus and to 2-fold deposition increase into the right maxillary sinus. Besides, the low frequency acoustic airflow demonstrated a significant increase of 4-fold and 2-fold in the right and left maxillary sinuses, respectively. We demonstrated the benefit of different modes of vibrating acoustic airflow for maxillary sinus ventilation and intrasinus drug deposition. The degree of gentamicin deposition varies as a function of frequency of the vibrating acoustic airflow and the geometry of the ostia. Copyright © 2015 Elsevier B.V. All rights reserved.

Brain Metabolic Changes in Rats following Acoustic Trauma

PubMed Central

He, Jun; Zhu, Yejin; Aa, Jiye; Smith, Paul F.; De Ridder, Dirk; Wang, Guangji; Zheng, Yiwen

2017-01-01

Acoustic trauma is the most common cause of hearing loss and tinnitus in humans. However, the impact of acoustic trauma on system biology is not fully understood. It has been increasingly recognized that tinnitus caused by acoustic trauma is unlikely to be generated by a single pathological source, but rather a complex network of changes involving not only the auditory system but also systems related to memory, emotion and stress. One obvious and significant gap in tinnitus research is a lack of biomarkers that reflect the consequences of this interactive “tinnitus-causing” network. In this study, we made the first attempt to analyse brain metabolic changes in rats following acoustic trauma using metabolomics, as a pilot study prior to directly linking metabolic changes to tinnitus. Metabolites in 12 different brain regions collected from either sham or acoustic trauma animals were profiled using a gas chromatography mass spectrometry (GC/MS)-based metabolomics platform. After deconvolution of mass spectra and identification of the molecules, the metabolomic data were processed using multivariate statistical analysis. Principal component analysis showed that metabolic patterns varied among different brain regions; however, brain regions with similar functions had a similar metabolite composition. Acoustic trauma did not change the metabolite clusters in these regions. When analyzed within each brain region using the orthogonal projection to latent structures discriminant analysis sub-model, 17 molecules showed distinct separation between control and acoustic trauma groups in the auditory cortex, inferior colliculus, superior colliculus, vestibular nucleus complex (VNC), and cerebellum. Further metabolic pathway impact analysis and the enrichment overview with network analysis suggested the primary involvement of amino acid metabolism, including the alanine, aspartate and glutamate metabolic pathways, the arginine and proline metabolic pathways and the purine

Drag Measurements of Porous Plate Acoustic Liners

NASA Technical Reports Server (NTRS)

Wolter, John D.

2005-01-01

This paper presents the results of direct drag measurements on a variety of porous plate acoustic liners. The existing literature describes numerous studies of drag on porous walls with injection or suction, but relatively few of drag on porous plates with neither injection nor suction. Furthermore, the porosity of the porous plate in existing studies is much lower than typically used in acoustic liners. In the present work, the acoustic liners consisted of a perforated face sheet covering a bulk acoustic absorber material. Factors that were varied in the experiment were hole diameter, hole pattern, face sheet thickness, bulk material type, and size of the gap (if any) between the face sheet and the absorber material.

Effect of acoustic field parameters on arc acoustic binding during ultrasonic wave-assisted arc welding.

PubMed

Xie, Weifeng; Fan, Chenglei; Yang, Chunli; Lin, Sanbao

2016-03-01

As a newly developed arc welding method, power ultrasound has been successfully introduced into arc and weld pool during ultrasonic wave-assisted arc welding process. The advanced process for molten metals can be realized by utilizing additional ultrasonic field. Under the action of the acoustic wave, the plasma arc as weld heat source is regulated and its characteristics make an obvious change. Compared with the conventional arc, the ultrasonic wave-assisted arc plasma is bound significantly and becomes brighter. To reveal the dependence of the acoustic binding force on acoustic field parameters, a two-dimensional acoustic field model for ultrasonic wave-assisted arc welding device is established. The influences of the radiator height, the central pore radius, the radiator radius, and curvature radius or depth of concave radiator surface are discussed using the boundary element method. Then the authors analyze the resonant mode by this relationship curve between acoustic radiation power and radiator height. Furthermore, the best acoustic binding ability is obtained by optimizing the geometric parameters of acoustic radiator. In addition, three concave radiator surfaces including spherical cap surface, paraboloid of revolution, and rotating single curved surface are investigated systematically. Finally, both the calculation and experiment suggest that, to obtain the best acoustic binding ability, the ultrasonic wave-assisted arc welding setup should be operated under the first resonant mode using a radiator with a spherical cap surface, a small central pore, a large section radius and an appropriate curvature radius. Copyright © 2015 Elsevier B.V. All rights reserved.

Laser-induced acoustic imaging of underground objects

NASA Astrophysics Data System (ADS)

Li, Wen; DiMarzio, Charles A.; McKnight, Stephen W.; Sauermann, Gerhard O.; Miller, Eric L.

1999-02-01

This paper introduces a new demining technique based on the photo-acoustic interaction, together with results from photo- acoustic experiments. We have buried different types of targets (metal, rubber and plastic) in different media (sand, soil and water) and imaged them by measuring reflection of acoustic waves generated by irradiation with a CO2 laser. Research has been focused on the signal acquisition and signal processing. A deconvolution method using Wiener filters is utilized in data processing. Using a uniform spatial distribution of laser pulses at the ground's surface, we obtained 3D images of buried objects. The images give us a clear representation of the shapes of the underground objects. The quality of the images depends on the mismatch of acoustic impedance of the buried objects, the bandwidth and center frequency of the acoustic sensors and the selection of filter functions.

High Frequency Acoustic Reflection and Transmission in Ocean Sediments

DTIC Science & Technology

2003-09-30

Development of a physical model of high-frequency acoustic interaction with the ocean floor, including penetration through and reflection from smooth and...experiments and additional laboratory measurements in the ARL:UT sand tank, an improved model of sediment acoustics will be developed that is...distinct areas of concentration: development of a broadband the oretical model to describe the acoustic interaction with the ocean floor in littoral

Reconfigurable origami-inspired acoustic waveguides

PubMed Central

Babaee, Sahab; Overvelde, Johannes T. B.; Chen, Elizabeth R.; Tournat, Vincent; Bertoldi, Katia

2016-01-01

We combine numerical simulations and experiments to design a new class of reconfigurable waveguides based on three-dimensional origami-inspired metamaterials. Our strategy builds on the fact that the rigid plates and hinges forming these structures define networks of tubes that can be easily reconfigured. As such, they provide an ideal platform to actively control and redirect the propagation of sound. We design reconfigurable systems that, depending on the externally applied deformation, can act as networks of waveguides oriented along one, two, or three preferential directions. Moreover, we demonstrate that the capability of the structure to guide and radiate acoustic energy along predefined directions can be easily switched on and off, as the networks of tubes are reversibly formed and disrupted. The proposed designs expand the ability of existing acoustic metamaterials and exploit complex waveguiding to enhance control over propagation and radiation of acoustic energy, opening avenues for the design of a new class of tunable acoustic functional systems. PMID:28138527

Acoustic Noise Prediction of the Amine Swingbed ISS ExPRESS Rack Payload

NASA Technical Reports Server (NTRS)

Welsh, David; Smith, Holly; Wang, Shuo

2010-01-01

Acoustics plays a vital role in maintaining the health, safety, and comfort of crew members aboard the International Space Station (ISS). In order to maintain this livable and workable environment, acoustic requirements have been established to ensure that ISS hardware and payload developers account for the acoustic emissions of their equipment and develop acoustic mitigations as necessary. These requirements are verified by an acoustic emissions test of the integrated hardware. The Amine Swingbed ExPRESS (Expedite the PRocessing of ExperimentS to Space) rack payload creates a unique challenge to the developers in that the payload hardware is transported to the ISS in phases, making an acoustic emissions test on the integrated flight hardware impossible. In addition, the payload incorporates a high back pressure fan and a diaphragm vacuum pump, which are recognized as significant and complex noise sources. In order to accurately predict the acoustic emissions of the integrated payload, the individual acoustic noise sources and paths are first characterized. These characterizations are conducted though a series of acoustic emissions tests on the individual payload components. Secondly, the individual acoustic noise sources and paths are incorporated into a virtual model of the integrated hardware. The virtual model is constructed with the use of hybrid method utilizing the Finite Element Acoustic (FEA) and Statistical Energy Analysis (SEA) techniques, which predict the overall acoustic emissions. Finally, the acoustic model is validated though an acoustic characterization test performed on an acoustically similar mock-up of the flight unit. The results of the validated acoustic model are then used to assess the acoustic emissions of the flight unit and define further acoustic mitigation efforts.

Perception of recorded singing voice quality and expertise: cognitive linguistics and acoustic approaches.

PubMed

Morange, Séverine; Dubois, Danièle; Fontaine, Jean-Marc

2010-07-01

The objective of the present pluridisciplinary study was to contribute to determine how a diversity of audience differently appreciates several versions resulting from different "restoration" treatments of one single original lyrical recording. We present here a joint analysis coupling psychological and linguistic analyses with acoustic descriptions on a unique research object: a Caruso's piece of song diversely remastered on commercial CDs. Thirty-two subjects were selected contrasted on age ("younger than 30 years" and "older than 60 years") related with their different experience of earlier technical recording devices (rendering through devices such as radio, 78rpm records, CD...) and on expertise concerning musical acoustics (acousticians and/or musicians vs ordinary music lovers). Eleven excerpts of reediting of an opera record interpreted by Caruso were selected from what could found on the market. The listening protocol involved a free categorization task and the selection of excerpts on preference judgments. Each task involved subjects' free commentaries about their choices as a joint output from psychological processing. A cluster analysis scaffold by a psycholinguistic processing of the verbal comments of the categories allowed to identify both commonalities and differences in groupings excerpts by the different groups of the subjects, along a diversity of criteria, varying according to age and expertise. Each excerpt can therefore be characterized both according to psychological and to acoustic criteria. This study has enabled us to develop the idea that a lyric voice is a multifaced object (cultural, esthetic, technical, physical), acoustic parameters being linked to the various sensory experiences and expertises of appraisers. Such pluridisciplinary research and the coupling of the correlated multiplicity of methodologies we developed acknowledge for a better understanding of listening practices and music-lover assessments here concerned with a

Environmental Fluctuations and Acoustic Data Communications

DTIC Science & Technology

2015-09-30

July 2011 along with subsequent analysis of the experiment data. KAM11 Experiment (2011) A shallow water acoustic communications experiment...packet and packet-to-packet variability. Algorithm Design and Experiment Data Analysis Communication receiver algorithm design for shallow water is...exhibited substantial daily oceanographic variability. Analysis of the KAM11 experiment data this past year has focused on fixed source transmissions

Optical Sensor/Actuator Locations for Active Structural Acoustic Control

NASA Technical Reports Server (NTRS)

Padula, Sharon L.; Palumbo, Daniel L.; Kincaid, Rex K.

1998-01-01

Researchers at NASA Langley Research Center have extensive experience using active structural acoustic control (ASAC) for aircraft interior noise reduction. One aspect of ASAC involves the selection of optimum locations for microphone sensors and force actuators. This paper explains the importance of sensor/actuator selection, reviews optimization techniques, and summarizes experimental and numerical results. Three combinatorial optimization problems are described. Two involve the determination of the number and position of piezoelectric actuators, and the other involves the determination of the number and location of the sensors. For each case, a solution method is suggested, and typical results are examined. The first case, a simplified problem with simulated data, is used to illustrate the method. The second and third cases are more representative of the potential of the method and use measured data. The three case studies and laboratory test results establish the usefulness of the numerical methods.

Acoustic radiation force on a heated sphere including effects of heat transfer and acoustic streaming

NASA Technical Reports Server (NTRS)

Lee, Chun P.; Wang, Taylor G.

1988-01-01

A previous theoretical result on the subject of the acoustic radiation force on a heated sphere (Lee and Wang, 1984) is reexamined. For a more complete understanding, effects of heat transfer and acoustic streaming are taken into consideration. Essentially, it was found that, at high sound-pressure levels in a steady situation, the force is not affected significantly by the temperature profile, consistent with the result of an experimental work (Leung and Wang, 1985). This resolves the earlier apparent contradiction between the theory and the experiment. If excessive hot air is accumulated around the sphere, which can happen in transient situations, the force can be weakened or reversed in sign. A heat transfer model due to acoustic streaming was also found.

Localization of short-range acoustic and seismic wideband sources: Algorithms and experiments

NASA Astrophysics Data System (ADS)

Stafsudd, J. Z.; Asgari, S.; Hudson, R.; Yao, K.; Taciroglu, E.

2008-04-01

We consider the determination of the location (source localization) of a disturbance source which emits acoustic and/or seismic signals. We devise an enhanced approximate maximum-likelihood (AML) algorithm to process data collected at acoustic sensors (microphones) belonging to an array of, non-collocated but otherwise identical, sensors. The approximate maximum-likelihood algorithm exploits the time-delay-of-arrival of acoustic signals at different sensors, and yields the source location. For processing the seismic signals, we investigate two distinct algorithms, both of which process data collected at a single measurement station comprising a triaxial accelerometer, to determine direction-of-arrival. The direction-of-arrivals determined at each sensor station are then combined using a weighted least-squares approach for source localization. The first of the direction-of-arrival estimation algorithms is based on the spectral decomposition of the covariance matrix, while the second is based on surface wave analysis. Both of the seismic source localization algorithms have their roots in seismology; and covariance matrix analysis had been successfully employed in applications where the source and the sensors (array) are typically separated by planetary distances (i.e., hundreds to thousands of kilometers). Here, we focus on very-short distances (e.g., less than one hundred meters) instead, with an outlook to applications in multi-modal surveillance, including target detection, tracking, and zone intrusion. We demonstrate the utility of the aforementioned algorithms through a series of open-field tests wherein we successfully localize wideband acoustic and/or seismic sources. We also investigate a basic strategy for fusion of results yielded by acoustic and seismic arrays.

Magneto-acoustic imaging by continuous-wave excitation.

PubMed

Shunqi, Zhang; Zhou, Xiaoqing; Tao, Yin; Zhipeng, Liu

2017-04-01

The electrical characteristics of tissue yield valuable information for early diagnosis of pathological changes. Magneto-acoustic imaging is a functional approach for imaging of electrical conductivity. This study proposes a continuous-wave magneto-acoustic imaging method. A kHz-range continuous signal with an amplitude range of several volts is used to excite the magneto-acoustic signal and improve the signal-to-noise ratio. The magneto-acoustic signal amplitude and phase are measured to locate the acoustic source via lock-in technology. An optimisation algorithm incorporating nonlinear equations is used to reconstruct the magneto-acoustic source distribution based on the measured amplitude and phase at various frequencies. Validation simulations and experiments were performed in pork samples. The experimental and simulation results agreed well. While the excitation current was reduced to 10 mA, the acoustic signal magnitude increased up to 10 -7  Pa. Experimental reconstruction of the pork tissue showed that the image resolution reached mm levels when the excitation signal was in the kHz range. The signal-to-noise ratio of the detected magneto-acoustic signal was improved by more than 25 dB at 5 kHz when compared to classical 1 MHz pulse excitation. The results reported here will aid further research into magneto-acoustic generation mechanisms and internal tissue conductivity imaging.

Influence of Acoustic Overstimulation on the Central Auditory System: An Functional Magnetic Resonance Imaging (fMRI) Study.

PubMed

Wolak, Tomasz; Cieśla, Katarzyna; Rusiniak, Mateusz; Piłka, Adam; Lewandowska, Monika; Pluta, Agnieszka; Skarżyński, Henryk; Skarżyński, Piotr H

2016-11-28

BACKGROUND The goal of the fMRI experiment was to explore the involvement of central auditory structures in pathomechanisms of a behaviorally manifested auditory temporary threshold shift in humans. MATERIAL AND METHODS The material included 18 healthy volunteers with normal hearing. Subjects in the exposure group were presented with 15 min of binaural acoustic overstimulation of narrowband noise (3 kHz central frequency) at 95 dB(A). The control group was not exposed to noise but instead relaxed in silence. Auditory fMRI was performed in 1 session before and 3 sessions after acoustic overstimulation and involved 3.5-4.5 kHz sweeps. RESULTS The outcomes of the study indicate a possible effect of acoustic overstimulation on central processing, with decreased brain responses to auditory stimulation up to 20 min after exposure to noise. The effect can be seen already in the primary auditory cortex. Decreased BOLD signal change can be due to increased excitation thresholds and/or increased spontaneous activity of auditory neurons throughout the auditory system. CONCLUSIONS The trial shows that fMRI can be a valuable tool in acoustic overstimulation studies but has to be used with caution and considered complimentary to audiological measures. Further methodological improvements are needed to distinguish the effects of TTS and neuronal habituation to repetitive stimulation.

Influence of Acoustic Overstimulation on the Central Auditory System: An Functional Magnetic Resonance Imaging (fMRI) Study

PubMed Central

Wolak, Tomasz; Cieśla, Katarzyna; Rusiniak, Mateusz; Piłka, Adam; Lewandowska, Monika; Pluta, Agnieszka; Skarżyński, Henryk; Skarżyński, Piotr H.

2016-01-01

Background The goal of the fMRI experiment was to explore the involvement of central auditory structures in pathomechanisms of a behaviorally manifested auditory temporary threshold shift in humans. Material/Methods The material included 18 healthy volunteers with normal hearing. Subjects in the exposure group were presented with 15 min of binaural acoustic overstimulation of narrowband noise (3 kHz central frequency) at 95 dB(A). The control group was not exposed to noise but instead relaxed in silence. Auditory fMRI was performed in 1 session before and 3 sessions after acoustic overstimulation and involved 3.5–4.5 kHz sweeps. Results The outcomes of the study indicate a possible effect of acoustic overstimulation on central processing, with decreased brain responses to auditory stimulation up to 20 min after exposure to noise. The effect can be seen already in the primary auditory cortex. Decreased BOLD signal change can be due to increased excitation thresholds and/or increased spontaneous activity of auditory neurons throughout the auditory system. Conclusions The trial shows that fMRI can be a valuable tool in acoustic overstimulation studies but has to be used with caution and considered complimentary to audiological measures. Further methodological improvements are needed to distinguish the effects of TTS and neuronal habituation to repetitive stimulation. PMID:27893698

Decoding Group Vocalizations: The Acoustic Energy Distribution of Chorus Howls Is Useful to Determine Wolf Reproduction

PubMed Central

López-Bao, José Vicente; Llaneza, Luis; Fernández, Carlos; Font, Enrique

2016-01-01

Population monitoring is crucial for wildlife management and conservation. In the last few decades, wildlife researchers have increasingly applied bioacoustics tools to obtain information on several essential ecological parameters, such as distribution and abundance. One such application involves wolves (Canis lupus). These canids respond to simulated howls by emitting group vocalizations known as chorus howls. These responses to simulated howls reveal the presence of wolf litters during the breeding period and are therefore often used to determine the status of wolf populations. However, the acoustic structure of chorus howls is complex and discriminating the presence of pups in a chorus is sometimes difficult, even for experienced observers. In this study, we evaluate the usefulness of analyses of the acoustic energy distribution in chorus howls to identify the presence of pups in a chorus. We analysed 110 Iberian wolf chorus howls with known pack composition and found that the acoustic energy distribution is concentrated at higher frequencies when there are pups vocalizing. We built predictive models using acoustic energy distribution features to determine the presence of pups in a chorus, concluding that the acoustic energy distribution in chorus howls can be used to determine the presence of wolf pups in a pack. The method we outline here is objective, accurate, easily implemented, and independent of the observer's experience. These advantages are especially relevant in the case of broad scale surveys or when many observers are involved. Furthermore, the analysis of the acoustic energy distribution can be implemented for monitoring other social canids that emit chorus howls such as jackals or coyotes, provides an easy way to obtain information on ecological parameters such as reproductive success, and could be useful to study other group vocalizations. PMID:27144887

Navy Applications of High-Frequency Acoustics

NASA Astrophysics Data System (ADS)

Cox, Henry

2004-11-01

Although the emphasis in underwater acoustics for the last few decades has been in low-frequency acoustics, motivated by long range detection of submarines, there has been a continuing use of high-frequency acoustics in traditional specialized applications such as bottom mapping, mine hunting, torpedo homing and under ice navigation. The attractive characteristics of high-frequency sonar, high spatial resolution, wide bandwidth, small size and relatively low cost must be balanced against the severe range limitation imposed by attenuation that increases approximately as frequency-squared. Many commercial applications of acoustics are ideally served by high-frequency active systems. The small size and low cost, coupled with the revolution in small powerful signal processing hardware has led to the consideration of more sophisticated systems. Driven by commercial applications, there are currently available several commercial-off-the-shelf products including acoustic modems for underwater communication, multi-beam fathometers, side scan sonars for bottom mapping, and even synthetic aperture side scan sonar. Much of the work in high frequency sonar today continues to be focused on specialized applications in which the application is emphasized over the underlying acoustics. Today's vision for the Navy of the future involves Autonomous Undersea Vehicles (AUVs) and off-board ASW sensors. High-frequency acoustics will play a central role in the fulfillment of this vision as a means of communication and as a sensor. The acoustic communication problems for moving AUVs and deep sensors are discussed. Explicit relationships are derived between the communication theoretic description of channel parameters in terms of time and Doppler spreads and ocean acoustic parameters, group velocities, phase velocities and horizontal wavenumbers. Finally the application of synthetic aperture sonar to the mine hunting problems is described.

Sample data from a Distributed Acoustic Sensing experiment at Garner Valley, California (PoroTomo Subtask 3.2)

DOE Data Explorer

Lancelle, Chelsea

2013-09-10

In September 2013, an experiment using Distributed Acoustic Sensing (DAS) was conducted at Garner Valley, a test site of the University of California Santa Barbara (Lancelle et al., 2014). This submission includes one 45 kN shear shaker (called “large shaker” on the basemap) test for three different measurement systems. The shaker swept from a rest, up to 10 Hz, and back down to a rest over 60 seconds. Lancelle, C., N. Lord, H. Wang, D. Fratta, R. Nigbor, A. Chalari, R. Karaulanov, J. Baldwin, and E. Castongia (2014), Directivity and Sensitivity of Fiber-Optic Cable Measuring Ground Motion using a Distributed Acoustic Sensing Array (abstract # NS31C-3935), AGU Fall Meeting. https://agu.confex.com/agu/fm1/meetingapp.cgi#Paper/19828 The e-poster is available at: https://agu.confex.com/data/handout/agu/fm14/Paper_19828_handout_696_0.pdf

Acoustically Enhanced Electroplating Being Developed

NASA Technical Reports Server (NTRS)

Oeftering, Richard C.

2002-01-01

In cooperation with the NASA Glenn Research Center, Alchemitron Corp. is developing the Acoustically Enhanced Electroplating Process (AEEP), a new technique of employing nonlinear ultrasonics to enhance electroplating. The applications range from electroplating full-panel electronic circuit boards to electroplating microelectronics and microelectromechanical systems (MEMS) devices. In a conventional plating process, the surface area to be plated is separated from the nonplated areas by a temporary mask. The mask may take many forms, from a cured liquid coating to a simple tape. Generally, the mask is discarded when the plating is complete, creating a solid waste product that is often an environmental hazard. The labor and materials involved with the layout, fabrication, and tooling of masks is a primary source of recurring and nonrecurring production costs. The objective of this joint effort, therefore, is to reduce or eliminate the need for masks. AEEP improves selective plating processes by using directed beams of high-intensity acoustic waves to create nonlinear effects that alter the fluid dynamic and thermodynamic behavior of the plating process. It relies on two effects: acoustic streaming and acoustic heating. Acoustic streaming is observed when a high-intensity acoustic beam creates a liquid current within the beam. The liquid current can be directed as the beam is directed and, thus, users can move liquid around as desired without using pumps and nozzles. The current of the electroplating electrolyte, therefore, can be directed at distinct target areas where electroplating is desired. The current delivers fresh electrolyte to the target area while flushing away the spent electrolyte. This dramatically increases the plating rate in the target area. In addition, acoustic heating of both the liquid in the beam and the target surface increases the chemical reaction rate, which further increases the plating rate. The combined effects of acoustic streaming and

Location of acoustic emission sources generated by air flow

PubMed

Kosel; Grabec; Muzic

2000-03-01

The location of continuous acoustic emission sources is a difficult problem of non-destructive testing. This article describes one-dimensional location of continuous acoustic emission sources by using an intelligent locator. The intelligent locator solves a location problem based on learning from examples. To verify whether continuous acoustic emission caused by leakage air flow can be located accurately by the intelligent locator, an experiment on a thin aluminum band was performed. Results show that it is possible to determine an accurate location by using a combination of a cross-correlation function with an appropriate bandpass filter. By using this combination, discrete and continuous acoustic emission sources can be located by using discrete acoustic emission sources for locator learning.

Acoustically Driven Magnetized Target Fusion At General Fusion: An Overview

NASA Astrophysics Data System (ADS)

O'Shea, Peter; Laberge, M.; Donaldson, M.; Delage, M.; the Fusion Team, General

2016-10-01

Magnetized Target Fusion (MTF) involves compressing an initial magnetically confined plasma of about 1e23 m-3, 100eV, 7 Tesla, 20 cm radius, >100 μsec life with a 1000x volume compression in 100 microseconds. If near adiabatic compression is achieved, the final plasma of 1e26 m-3, 10keV, 700 Tesla, 2 cm radius, confined for 10 μsec would produce interesting fusion energy gain. General Fusion (GF) is developing an acoustic compression system using pneumatic pistons focusing a shock wave on the CT plasma in the center of a 3 m diameter sphere filled with liquid lead-lithium. Low cost driver, straightforward heat extraction, good tritium breeding ratio and excellent neutron protection could lead to a practical power plant. GF (65 employees) has an active plasma R&D program including both full scale and reduced scale plasma experiments and simulation of both. Although acoustic driven compression of full scale plasmas is the end goal, present compression studies use reduced scale plasmas and chemically accelerated Aluminum liners. We will review results from our plasma target development, motivate and review the results of dynamic compression field tests and briefly describe the work to date on the acoustic driver front.

Method of Adjusting Acoustic Impedances for Impedance-Tunable Acoustic Segments

NASA Technical Reports Server (NTRS)

Jones, Kennie H (Inventor); Nark, Douglas M. (Inventor); Jones, Michael G. (Inventor); Parrott, Tony L. (Inventor); Lodding, Kenneth N. (Inventor)

2012-01-01

A method is provided for making localized decisions and taking localized actions to achieve a global solution. In an embodiment of the present invention, acoustic impedances for impedance-tunable acoustic segments are adjusted. A first acoustic segment through an N-th acoustic segment are defined. To start the process, the first acoustic segment is designated as a leader and a noise-reducing impedance is determined therefor. This is accomplished using (i) one or more metrics associated with the acoustic wave at the leader, and (ii) the metric(s) associated with the acoustic wave at the N-th acoustic segment. The leader, the N-th acoustic segment, and each of the acoustic segments exclusive of the leader and the N-th acoustic segment, are tuned to the noise-reducing impedance. The current leader is then excluded from subsequent processing steps. The designation of leader is then given one of the remaining acoustic segments, and the process is repeated for each of the acoustic segments through an (N-1)-th one of the acoustic segments.

High-bandwidth acoustic detection system (HBADS) for stripmap synthetic aperture acoustic imaging of canonical ground targets using airborne sound and a 16 element receiving array

NASA Astrophysics Data System (ADS)

Bishop, Steven S.; Moore, Timothy R.; Gugino, Peter; Smith, Brett; Kirkwood, Kathryn P.; Korman, Murray S.

2018-04-01

High Bandwidth Acoustic Detection System (HBADS) is an emerging active acoustic sensor technology undergoing study by the US Army's Night Vision and Electronic Sensors Directorate. Mounted on a commercial all-terrain type vehicle, it uses a single source pulse chirp while moving and a new array (two rows each containing eight microphones) mounted horizontally and oriented in a side scan mode. Experiments are performed with this synthetic aperture air acoustic (SAA) array to image canonical ground targets in clutter or foliage. A commercial audio speaker transmits a linear FM chirp having an effective frequency range of 2 kHz to 15 kHz. The system includes an inertial navigation system using two differential GPS antennas, an inertial measurement unit and a wheel coder. A web camera is mounted midway between the two horizontal microphone arrays and a meteorological unit acquires ambient, temperature, pressure and humidity information. A data acquisition system is central to the system's operation, which is controlled by a laptop computer. Recent experiments include imaging canonical targets located on the ground in a grassy field and similar targets camouflaged by natural vegetation along the side of a road. A recent modification involves implementing SAA stripmap mode interferometry for computing the reflectance of targets placed along the ground. Typical strip map SAA parameters are chirp pulse = 10 or 40 ms, slant range resolution c/(2*BW) = 0.013 m, microphone diameter D = 0.022 m, azimuthal resolution (D/2) = 0.01, air sound speed c ≍ 340 m/s and maximum vehicle speed ≍ 2 m/s.

Development of a MEMS device for acoustic emission testing

NASA Astrophysics Data System (ADS)

Ozevin, Didem; Pessiki, Stephen P.; Jain, Akash; Greve, David W.; Oppenheim, Irving J.

2003-08-01

Acoustic emission testing is an important technology for evaluating structural materials, and especially for detecting damage in structural members. Significant new capabilities may be gained by developing MEMS transducers for acoustic emission testing, including permanent bonding or embedment for superior coupling, greater density of transducer placement, and a bundle of transducers on each device tuned to different frequencies. Additional advantages include capabilities for maintenance of signal histories and coordination between multiple transducers. We designed a MEMS device for acoustic emission testing that features two different mechanical types, a hexagonal plate design and a spring-mass design, with multiple detectors of each type at ten different frequencies in the range of 100 kHz to 1 MHz. The devices were fabricated in the multi-user polysilicon surface micromachining (MUMPs) process and we have conducted electrical characterization experiments and initial experiments on acoustic emission detection. We first report on C(V) measurements and perform a comparison between predicted (design) and measured response. We next report on admittance measurements conducted at pressures varying from vacuum to atmospheric, identifying the resonant frequencies and again providing a comparison with predicted performance. We then describe initial calibration experiments that compare the performance of the detectors to other acoustic emission transducers, and we discuss the overall performance of the device as a sensor suite, as contrasted to the single-channel performance of most commercial transducers.

Translational illusion of acoustic sources by transformation acoustics.

PubMed

Sun, Fei; Li, Shichao; He, Sailing

2017-09-01

An acoustic illusion of creating a translated acoustic source is designed by utilizing transformation acoustics. An acoustic source shifter (ASS) composed of layered acoustic metamaterials is designed to achieve such an illusion. A practical example where the ASS is made with naturally available materials is also given. Numerical simulations verify the performance of the proposed device. The designed ASS may have some applications in, e.g., anti-sonar detection.

In-situ acoustic signature monitoring in additive manufacturing processes

NASA Astrophysics Data System (ADS)

Koester, Lucas W.; Taheri, Hossein; Bigelow, Timothy A.; Bond, Leonard J.; Faierson, Eric J.

2018-04-01

Additive manufacturing is a rapidly maturing process for the production of complex metallic, ceramic, polymeric, and composite components. The processes used are numerous, and with the complex geometries involved this can make quality control and standardization of the process and inspection difficult. Acoustic emission measurements have been used previously to monitor a number of processes including machining and welding. The authors have identified acoustic signature measurement as a potential means of monitoring metal additive manufacturing processes using process noise characteristics and those discrete acoustic emission events characteristic of defect growth, including cracks and delamination. Results of acoustic monitoring for a metal additive manufacturing process (directed energy deposition) are reported. The work investigated correlations between acoustic emissions and process noise with variations in machine state and deposition parameters, and provided proof of concept data that such correlations do exist.

Acoustic Seaglider: PhilSea10 Data Analysis

DTIC Science & Technology

2016-06-13

and (simple) Kalman filtering techniques will be explored to utilize the unique time-space sound speed sampling of the Seagliders to generate snapshots... temperature and salinity were deployed (Figure 1). General objectives of the experiment are to understand the acoustic propagation in the...an acoustic recording system (ARS) to record the moored source transmissions, as well as temperature , salinity and pressure sensors (from which

Perturbation measurement of waveguides for acoustic thermometry

NASA Astrophysics Data System (ADS)

Lin, H.; Feng, X. J.; Zhang, J. T.

2013-09-01

Acoustic thermometers normally embed small acoustic transducers in the wall bounding a gas-filled cavity resonator. At high temperature, insulators of transducers loss electrical insulation and degrade the signal-to-noise ratio. One essential solution to this technical trouble is to couple sound by acoustic waveguides between resonator and transducers. But waveguide will break the ideal acoustic surface and bring perturbations(Δf+ig) to the ideal resonance frequency. The perturbation model for waveguides was developed based on the first-order acoustic theory in this paper. The frequency shift Δf and half-width change g caused by the position, length and radius of waveguides were analyzed using this model. Six different length of waveguides (52˜1763 mm) were settled on the cylinder resonator and the perturbation (Δf+ig) were measured at T=332 K and p=250˜500 kPa. The experiment results agreed with the theoretical prediction very well.

Acoustic Levitation Containerless Processing

NASA Technical Reports Server (NTRS)

Whymark, R. R.; Rey, C. A.

1985-01-01

This research program consists of the development of acoustic containerless processing systems with applications in the areas of research in material sciences, as well as the production of new materials, solid forms with novel and unusual microstructures, fusion target spheres, and improved optical fibers. Efforts have been focused on the containerless processing at high temperatures for producing new kinds of glasses. Also, some development has occurred in the areas of containerlessly supporting liquids at room temperature, with applications in studies of fluid dynamics, potential undercooling of liquids, etc. The high temperature area holds the greatest promise for producing new kinds of glasses and ceramics, new alloys, and possibly unusual structural shapes, such as very uniform hollow glass shells for fusion target applications. High temperature acoustic levitation required for containerless processing has been demonstrated in low-g environments as well as in ground-based experiments. Future activities include continued development of the signals axis acoustic levitator.

Ipsilateral masking between acoustic and electric stimulations.

PubMed

Lin, Payton; Turner, Christopher W; Gantz, Bruce J; Djalilian, Hamid R; Zeng, Fan-Gang

2011-08-01

Residual acoustic hearing can be preserved in the same ear following cochlear implantation with minimally traumatic surgical techniques and short-electrode arrays. The combined electric-acoustic stimulation significantly improves cochlear implant performance, particularly speech recognition in noise. The present study measures simultaneous masking by electric pulses on acoustic pure tones, or vice versa, to investigate electric-acoustic interactions and their underlying psychophysical mechanisms. Six subjects, with acoustic hearing preserved at low frequencies in their implanted ear, participated in the study. One subject had a fully inserted 24 mm Nucleus Freedom array and five subjects had Iowa/Nucleus hybrid implants that were only 10 mm in length. Electric masking data of the long-electrode subject showed that stimulation from the most apical electrodes produced threshold elevations over 10 dB for 500, 625, and 750 Hz probe tones, but no elevation for 125 and 250 Hz tones. On the contrary, electric stimulation did not produce any electric masking in the short-electrode subjects. In the acoustic masking experiment, 125-750 Hz pure tones were used to acoustically mask electric stimulation. The acoustic masking results showed that, independent of pure tone frequency, both long- and short-electrode subjects showed threshold elevations at apical and basal electrodes. The present results can be interpreted in terms of underlying physiological mechanisms related to either place-dependent peripheral masking or place-independent central masking.

Application of acoustic imaging techniques on snowmobile pass-by noise.

PubMed

Padois, Thomas; Berry, Alain

2017-02-01

Snowmobile manufacturers invest important efforts to reduce the noise emission of their products. The noise sources of snowmobiles are multiple and closely spaced, leading to difficult source separation in practice. In this study, source imaging results for snowmobile pass-by noise are discussed. The experiments involve a 193-microphone Underbrink array, with synchronization of acoustic with video data provided by a high-speed camera. Both conventional beamforming and Clean-SC deconvolution are implemented to provide noise source maps of the snowmobile. The results clearly reveal noise emission from the engine, exhaust, and track depending on the frequency range considered.

MURI: Impact of Oceanographic Variability on Acoustic Communications

DTIC Science & Technology

2011-09-01

multiplexing ( OFDM ), multiple- input/multiple-output ( MIMO ) transmissions, and multi-user single-input/multiple-output (SIMO) communications. Lastly... MIMO - OFDM communications: Receiver design for Doppler distorted underwater acoustic channels,” Proc. Asilomar Conf. on Signals, Systems, and... MIMO ) will be of particular interest. Validating experimental data will be obtained during the ONR acoustic communications experiment in summer 2008

A hierarchical generalization of the acoustic reciprocity theorem involving higher-order derivatives and interaction quantities.

PubMed

Lin, Ju; Li, Jie; Li, Xiaolei; Wang, Ning

2016-10-01

An acoustic reciprocity theorem is generalized, for a smoothly varying perturbed medium, to a hierarchy of reciprocity theorems including higher-order derivatives of acoustic fields. The standard reciprocity theorem is the first member of the hierarchy. It is shown that the conservation of higher-order interaction quantities is related closely to higher-order derivative distributions of perturbed media. Then integral reciprocity theorems are obtained by applying Gauss's divergence theorem, which give explicit integral representations connecting higher-order interactions and higher-order derivative distributions of perturbed media. Some possible applications to an inverse problem are also discussed.

Linear and Nonlinear Time Reverse Acoustics in Geomaterials

NASA Astrophysics Data System (ADS)

Sutin, A.; Johnson, P. A.; Tencate, J.

2004-12-01

Linear and Nonlinear Time Reverse Acoustics in Geomaterials P. A. Johnson, A.Sutin and J. TenCate Time Reversal Acoustics (TRA) is one of the most interesting topics to have emerged in modern acoustics in the last 40 years. Much of the seminal research in this area has been carried out by the group at the Laboratoire Ondes et Acoustique at the University of Paris 7, who have demonstrated the ability and robustness of TRA (using Time Reversal Mirrors) to provide spatial control and focusing of an ultrasonic beam (e.g. Fink, 1999). The ability to obtain highly focused signals with TRA has numerous applications, including lithotripsy, ultrasonic brain surgery, nondestructive evaluation and underwater acoustic communication. Notably, the study of time reversal in solids and in the earth is still relatively new. The problem is fundamentally different from the purely acoustic one due to the excitation and propagation of both compressional (bulk) and shear waves as well as the scattering and potentially high dissipation of the medium. We conducted series of TRA experiments in different solids using direct-coupled transducers on solids in tandem with a large bandwidth laser vibrometer detector. A typical time reversal experiment was carried out using the following steps (Sutin et al. 2004a). Laboratory experiments were conducted in different geomaterials of different shapes and sizes, including Carrera marble, granite and Berea sandstone. We observed that, in spite of potentially huge numbers of wave conversions (e.g., compressional to shear, shear to compressional, compressional/shear to surface waves, etc.) for each reflection at each free surface, time reversal still provides significant spatial and temporal focusing in these different geophysical materials. The typical size of the focal area is approximately equivalent to the shear wavelength and the focal area, but becomes larger with increasing wave attenuation (Sutin et al. 2004a; Delsanto et al., 2003)). The TR

Microgravity acoustic mixing for particle cloud combustors

NASA Technical Reports Server (NTRS)

Pla, Frederic; Rubinstein, Robert I.

1990-01-01

Experimental and theoretical investigations of acoustic mixing procedures designed to uniformly distribute fuel particles in a combustion tube for application in the proposed Particle Cloud Combustion Experiment (PCCE) are described. Two acoustic mixing methods are investigated: mixing in a cylindrical tube using high frequency spinning modes generated by suitably phased, or quadrature speakers, and acoustic premixing in a sphere. Quadrature mixing leads to rapid circumferential circulation of the powder around the tube. Good mixing is observed in the circulating regions. However, because axial inhomogeneities are necessarily present in the acoustic field, this circulation does not extend throughout the tube. Simultaneous operation of the quadrature-speaker set and the axial-speaker was observed to produce considerably enhanced mixing compared to operation of the quadrature-speaker set alone. Mixing experiments using both types of speakers were free of the longitudinal powder drift observed using axial-speakers alone. Vigorous powder mixing was obtained in the sphere for many normal modes: however, in no case was the powder observed to fill the sphere entirely. Theoretical analysis indicated that mixing under steady conditions cannot fill more than a hemisphere except under very unusual conditions. Premixing in a hemisphere may be satisfactory; otherwise, complete mixing in microgravity might be possible by operating the speaker in short bursts. A general conclusion is that acoustic transients are more likely to produce good mixing than steady state conditions. The reason is that in steady conditions, flow structures like nodal planes are possible and often even unavoidable. These tend to separate the mixing region into cells across which powder cannot be transferred. In contrast, transients not only are free of such structures, they also have the characteristics, desirable for mixing, of randomness and disorder. This conclusion is corroborated by mixing

Arbitrary electron acoustic waves in degenerate dense plasmas

NASA Astrophysics Data System (ADS)

Rahman, Ata-ur; Mushtaq, A.; Qamar, A.; Neelam, S.

2017-05-01

A theoretical investigation is carried out of the nonlinear dynamics of electron-acoustic waves in a collisionless and unmagnetized plasma whose constituents are non-degenerate cold electrons, ultra-relativistic degenerate electrons, and stationary ions. A dispersion relation is derived for linear EAWs. An energy integral equation involving the Sagdeev potential is derived, and basic properties of the large amplitude solitary structures are investigated in such a degenerate dense plasma. It is shown that only negative large amplitude EA solitary waves can exist in such a plasma system. The present analysis may be important to understand the collective interactions in degenerate dense plasmas, occurring in dense astrophysical environments as well as in laser-solid density plasma interaction experiments.

Acoustic emission from composite materials. [nondestructive tests

NASA Technical Reports Server (NTRS)

Visconti, I. C.; Teti, R.

1979-01-01

The two basic areas where the acoustic emission (AE) technique can be applied are materials research and the evaluation of structural reliability. This experimental method leads to a better understanding of fracture mechanisms and is an NDT technique particularly well suited for the study of propagating cracks. Experiments are described in which acoustic emissions were unambiguously correlated with microstructural fracture mechanisms. The advantages and limitations of the AE technique are noted.

Fundamentals of Acoustics. Psychoacoustics and Hearing. Acoustical Measurements

NASA Technical Reports Server (NTRS)

Begault, Durand R.; Ahumada, Al (Technical Monitor)

1997-01-01

These are 3 chapters that will appear in a book titled "Building Acoustical Design", edited by Charles Salter. They are designed to introduce the reader to fundamental concepts of acoustics, particularly as they relate to the built environment. "Fundamentals of Acoustics" reviews basic concepts of sound waveform frequency, pressure, and phase. "Psychoacoustics and Hearing" discusses the human interpretation sound pressure as loudness, particularly as a function of frequency. "Acoustic Measurements" gives a simple overview of the time and frequency weightings for sound pressure measurements that are used in acoustical work.

On resonant coupling of acoustic waves and gravity waves

NASA Astrophysics Data System (ADS)

Millet, Christophe

2017-11-01

Acoustic propagation in the atmosphere is often modeled using modes that are confined within waveguides causing the sound to propagate through multiple paths to the receiver. On the other hand, direct observations in the lower stratosphere show that the gravity wave field is intermittent, and is often dominated by rather well defined large-amplitude wave packets. In the present work, we use normal modes to describe both the gravity wave field and the acoustic field. The gravity wave spectrum is obtained by launching few monochromatic waves whose properties are chosen stochastically to mimic the intermittency. Owing to the disparity of the gravity and acoustic length scales, the interactions between the gravity wave field and each of the acoustic modes can be described using a multiple-scale analysis. The appropriate amplitude evolution equation for the acoustic field involves certain random terms that can be directly related to the gravity wave sources. We will show that the cumulative effect of gravity wave breakings makes the sensitivity of ground-based acoustic signals large, in that small changes in the gravity wave parameterization can create or destroy specific acoustic features.

Passive acoustic measurement of bedload grain size distribution using self-generated noise

NASA Astrophysics Data System (ADS)

Petrut, Teodor; Geay, Thomas; Gervaise, Cédric; Belleudy, Philippe; Zanker, Sebastien

2018-01-01

Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.

Acoustic source for generating an acoustic beam

DOEpatents

Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

2016-05-31

An acoustic source for generating an acoustic beam includes a housing; a plurality of spaced apart piezo-electric layers disposed within the housing; and a non-linear medium filling between the plurality of layers. Each of the plurality of piezoelectric layers is configured to generate an acoustic wave. The non-linear medium and the plurality of piezo-electric material layers have a matching impedance so as to enhance a transmission of the acoustic wave generated by each of plurality of layers through the remaining plurality of layers.

Acoustic levitation: recent developments and emerging opportunities in biomaterials research.

PubMed

Weber, Richard J K; Benmore, Chris J; Tumber, Sonia K; Tailor, Amit N; Rey, Charles A; Taylor, Lynne S; Byrn, Stephen R

2012-04-01

Containerless sample environments (levitation) are useful for study of nucleation, supercooling, and vitrification and for synthesis of new materials, often with non-equilibrium structures. Elimination of extrinsic nucleation by container walls extends access to supercooled and supersaturated liquids under high-purity conditions. Acoustic levitation is well suited to the study of liquids including aqueous solutions, organics, soft materials, polymers, and pharmaceuticals at around room temperature. This article briefly reviews recent developments and applications of acoustic levitation in materials R&D. Examples of experiments yielding amorphous pharmaceutical materials are presented. The implementation and results of experiments on supercooled and supersaturated liquids using an acoustic levitator at a high-energy X-ray beamline are described.

Acoustic calibration apparatus for calibrating plethysmographic acoustic pressure sensors

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J. (Inventor); Davis, David C. (Inventor)

1995-01-01

An apparatus for calibrating an acoustic sensor is described. The apparatus includes a transmission material having an acoustic impedance approximately matching the acoustic impedance of the actual acoustic medium existing when the acoustic sensor is applied in actual in-service conditions. An elastic container holds the transmission material. A first sensor is coupled to the container at a first location on the container and a second sensor coupled to the container at a second location on the container, the second location being different from the first location. A sound producing device is coupled to the container and transmits acoustic signals inside the container.

Acoustic calibration apparatus for calibrating plethysmographic acoustic pressure sensors

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J. (Inventor); Davis, David C. (Inventor)

1994-01-01

An apparatus for calibrating an acoustic sensor is described. The apparatus includes a transmission material having an acoustic impedance approximately matching the acoustic impedance of the actual acoustic medium existing when the acoustic sensor is applied in actual in-service conditions. An elastic container holds the transmission material. A first sensor is coupled to the container at a first location on the container and a second sensor coupled to the container at a second location on the container, the second location being different from the first location. A sound producing device is coupled to the container and transmits acoustic signals inside the container.

North Pacific Acoustic Laboratory and Deep Water Acoustics

DTIC Science & Technology

2015-09-30

range acoustic systems, whether for acoustic surveillance, communication, or remote sensing of the ocean interior . The data from the NPAL network, and...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. North Pacific Acoustic Laboratory and Deep Water... Acoustics PI James A. Mercer Applied Physics Laboratory, University of Washington 1013 NE 40th Street Seattle, WA 98105 phone: (206) 543-1361 fax

Probe beam deflection technique as acoustic emission directionality sensor with photoacoustic emission source.

PubMed

Barnes, Ronald A; Maswadi, Saher; Glickman, Randolph; Shadaram, Mehdi

2014-01-20

The goal of this paper is to demonstrate the unique capability of measuring the vector or angular information of propagating acoustic waves using an optical sensor. Acoustic waves were generated using photoacoustic interaction and detected by the probe beam deflection technique. Experiments and simulations were performed to study the interaction of acoustic emissions with an optical sensor in a coupling medium. The simulated results predict the probe beam and wavefront interaction and produced simulated signals that are verified by experiment.

Acoustic Quality Levels of Mosques in Batu Pahat

NASA Astrophysics Data System (ADS)

Azizah Adnan, Nor; Nafida Raja Shahminan, Raja; Khair Ibrahim, Fawazul; Tami, Hannifah; Yusuff, M. Rizal M.; Murniwaty Samsudin, Emedya; Ismail, Isham

2018-04-01

Every Friday, Muslims has been required to perform a special prayer known as the Friday prayers which involve the delivery of a brief lecture (Khutbah). Speech intelligibility in oral communications presented by the preacher affected all the congregation and determined the level of acoustic quality in the interior of the mosque. Therefore, this study intended to assess the level of acoustic quality of three public mosques in Batu Pahat. Good acoustic quality is essential in contributing towards appreciation in prayers and increasing khusyu’ during the worship, which is closely related to the speech intelligibility corresponding to the actual function of the mosque according to Islam. Acoustic parameters measured includes noise criteria (NC), reverberation time (RT) and speech transmission index (STI), and was performed using the sound level meter and sound measurement instruments. This test is carried out through the physical observation with the consideration of space and volume design as a factor affecting acoustic parameters. Results from all 3 mosques as the showed that the acoustic quality level inside these buildings are slightly poor which is at below 0.45 coefficients based on the standard. Among the factors that influencing the low acoustical quality are location, building materials, installation of sound absorption material and the number of occupants inside the mosque. As conclusion, the acoustic quality level of a mosque is highly depends on physical factors of the mosque such as the architectural design and space volume besides other factors as been identified by this study.

Acoustic simulation in architecture with parallel algorithm

NASA Astrophysics Data System (ADS)

Li, Xiaohong; Zhang, Xinrong; Li, Dan

2004-03-01

In allusion to complexity of architecture environment and Real-time simulation of architecture acoustics, a parallel radiosity algorithm was developed. The distribution of sound energy in scene is solved with this method. And then the impulse response between sources and receivers at frequency segment, which are calculated with multi-process, are combined into whole frequency response. The numerical experiment shows that parallel arithmetic can improve the acoustic simulating efficiency of complex scene.

Degraded Vowel Acoustics and the Perceptual Consequences in Dysarthria

NASA Astrophysics Data System (ADS)

Lansford, Kaitlin L.

Distorted vowel production is a hallmark characteristic of dysarthric speech, irrespective of the underlying neurological condition or dysarthria diagnosis. A variety of acoustic metrics have been used to study the nature of vowel production deficits in dysarthria; however, not all demonstrate sensitivity to the exhibited deficits. Less attention has been paid to quantifying the vowel production deficits associated with the specific dysarthrias. Attempts to characterize the relationship between naturally degraded vowel production in dysarthria with overall intelligibility have met with mixed results, leading some to question the nature of this relationship. It has been suggested that aberrant vowel acoustics may be an index of overall severity of the impairment and not an "integral component" of the intelligibility deficit. A limitation of previous work detailing perceptual consequences of disordered vowel acoustics is that overall intelligibility, not vowel identification accuracy, has been the perceptual measure of interest. A series of three experiments were conducted to address the problems outlined herein. The goals of the first experiment were to identify subsets of vowel metrics that reliably distinguish speakers with dysarthria from non-disordered speakers and differentiate the dysarthria subtypes. Vowel metrics that capture vowel centralization and reduced spectral distinctiveness among vowels differentiated dysarthric from non-disordered speakers. Vowel metrics generally failed to differentiate speakers according to their dysarthria diagnosis. The second and third experiments were conducted to evaluate the relationship between degraded vowel acoustics and the resulting percept. In the second experiment, correlation and regression analyses revealed vowel metrics that capture vowel centralization and distinctiveness and movement of the second formant frequency were most predictive of vowel identification accuracy and overall intelligibility. The third

An acoustic emission study of plastic deformation in polycrystalline aluminium

NASA Technical Reports Server (NTRS)

Bill, R. C.; Frederick, J. R.; Felbeck, D. K.

1979-01-01

Acoustic emission experiments were performed on polycrystalline and single crystal 99.99% aluminum while undergoing tensile deformation. It was found that acoustic emission counts as a function of grain size showed a maximum value at a particular grain size. Furthermore, the slip area associated with this particular grain size corresponded to the threshold level of detectability of single dislocation slip events. The rate of decline in acoustic emission activity as grain size is increased beyond the peak value suggests that grain boundary associated dislocation sources are giving rise to the bulk of the detected acoustic emissions.

International Space Station Acoustics - A Status Report

NASA Technical Reports Server (NTRS)

Allen, Christopher S.

2015-01-01

It is important to control acoustic noise aboard the International Space Station (ISS) to provide a satisfactory environment for voice communications, crew productivity, alarm audibility, and restful sleep, and to minimize the risk for temporary and permanent hearing loss. Acoustic monitoring is an important part of the noise control process on ISS, providing critical data for trend analysis, noise exposure analysis, validation of acoustic analyses and predictions, and to provide strong evidence for ensuring crew health and safety, thus allowing Flight Certification. To this purpose, sound level meter (SLM) measurements and acoustic noise dosimetry are routinely performed. And since the primary noise sources on ISS include the environmental control and life support system (fans and airflow) and active thermal control system (pumps and water flow), acoustic monitoring will reveal changes in hardware noise emissions that may indicate system degradation or performance issues. This paper provides the current acoustic levels in the ISS modules and sleep stations and is an update to the status presented in 2011. Since this last status report, many payloads (science experiment hardware) have been added and a significant number of quiet ventilation fans have replaced noisier fans in the Russian Segment. Also, noise mitigation efforts are planned to reduce the noise levels of the T2 treadmill and levels in Node 3, in general. As a result, the acoustic levels on the ISS continue to improve.

Acoustic Characterization of Fluorinert FC-43 Liquid with Helium Gas Bubbles: Numerical Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanhille, Christian; Pantea, Cristian; Sinha, Dipen N.

In this work, we define the acoustic characteristics of a biphasic fluid consisting of static helium gas bubbles in liquid Fluorinert FC-43 and study the propagation of ultrasound of finite amplitudes in this medium. Very low sound speed and high sound attenuation are found, in addition to a particularly high acoustic nonlinear parameter. This result suggests the possibility of using this medium as a nonlinear enhancer in various applications. In particular, parametric generation of low ultrasonic frequencies is studied in a resonator cavity as a function of driving pressure showing high conversion efficiency. This work suggests that this medium couldmore » be used for applications such as parametric arrays, nondestructive testing, diagnostic medicine, sonochemistry, underwater acoustics, and ultrasonic imaging and to boost the shock formation in fluids.« less

Acoustic Characterization of Fluorinert FC-43 Liquid with Helium Gas Bubbles: Numerical Experiments

DOE PAGES

Vanhille, Christian; Pantea, Cristian; Sinha, Dipen N.

2017-01-19

In this work, we define the acoustic characteristics of a biphasic fluid consisting of static helium gas bubbles in liquid Fluorinert FC-43 and study the propagation of ultrasound of finite amplitudes in this medium. Very low sound speed and high sound attenuation are found, in addition to a particularly high acoustic nonlinear parameter. This result suggests the possibility of using this medium as a nonlinear enhancer in various applications. In particular, parametric generation of low ultrasonic frequencies is studied in a resonator cavity as a function of driving pressure showing high conversion efficiency. This work suggests that this medium couldmore » be used for applications such as parametric arrays, nondestructive testing, diagnostic medicine, sonochemistry, underwater acoustics, and ultrasonic imaging and to boost the shock formation in fluids.« less

Stop-like modification of the dental fricative ∕ð∕: An acoustic analysis

PubMed Central

Zhao, Sherry Y.

2010-01-01

This study concentrates on one of the commonly occurring phonetic variations in English: the stop-like modification of the dental fricative ∕ð∕. The variant exhibits a drastic change from the canonical ∕ð∕; the manner of articulation is changed from one that is fricative to one that is stop-like. Furthermore, the place of articulation of stop-like ∕ð∕ has been a point of uncertainty, leading to confusion between stop-like ∕ð∕ and ∕d/. In this study, acoustic and spectral moment measures were taken from 100 stop-like ∕ð∕ and 102 ∕d/ tokens produced by 59 male and 23 female speakers in the TIMIT corpus. Data analysis indicated that stop-like ∕ð∕ is significantly different from ∕d/ in burst amplitude, burst spectrum shape, burst peak frequency, second formant at following-vowel onset, and spectral moments. Moreover, the acoustic differences from ∕d/ are consistent with those expected for a dental stop-like ∕ð∕. Automatic classification experiments involving these acoustic measures suggested that they are salient in distinguishing stop-like ∕ð∕ from ∕d/. PMID:20968372

Examination of nanosecond laser melting thresholds in refractory metals by shear wave acoustics

NASA Astrophysics Data System (ADS)

Abdullaev, A.; Muminov, B.; Rakhymzhanov, A.; Mynbayev, N.; Utegulov, Z. N.

2017-07-01

Nanosecond laser pulse-induced melting thresholds in refractory (Nb, Mo, Ta and W) metals are measured using detected laser-generated acoustic shear waves. Obtained melting threshold values were found to be scaled with corresponding melting point temperatures of investigated materials displaying dissimilar shearing behavior. The experiments were conducted with motorized control of the incident laser pulse energies with small and uniform energy increments to reach high measurement accuracy and real-time monitoring of the epicentral acoustic waveforms from the opposite side of irradiated sample plates. Measured results were found to be in good agreement with numerical finite element model solving coupled elastodynamic and thermal conduction governing equations on structured quadrilateral mesh. Solid-melt phase transition was handled by means of apparent heat capacity method. The onset of melting was attributed to vanished shear modulus and rapid radial molten pool propagation within laser-heated metal leading to preferential generation of transverse acoustic waves from sources surrounding the molten mass resulting in the delay of shear wave transit times. Developed laser-based technique aims for applications involving remote examination of rapid melting processes of materials present in harsh environment (e.g. spent nuclear fuels) with high spatio-temporal resolution.

Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface.

PubMed

Xie, Yangbo; Wang, Wenqi; Chen, Huanyang; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A

2014-11-24

Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell's law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications.

Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing

NASA Technical Reports Server (NTRS)

Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.

2009-01-01

Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in

Three-dimensional broadband omnidirectional acoustic ground cloak

NASA Astrophysics Data System (ADS)

Zigoneanu, Lucian; Popa, Bogdan-Ioan; Cummer, Steven A.

2014-04-01

The control of sound propagation and reflection has always been the goal of engineers involved in the design of acoustic systems. A recent design approach based on coordinate transformations, which is applicable to many physical systems, together with the development of a new class of engineered materials called metamaterials, has opened the road to the unconstrained control of sound. However, the ideal material parameters prescribed by this methodology are complex and challenging to obtain experimentally, even using metamaterial design approaches. Not surprisingly, experimental demonstration of devices obtained using transformation acoustics is difficult, and has been implemented only in two-dimensional configurations. Here, we demonstrate the design and experimental characterization of an almost perfect three-dimensional, broadband, and, most importantly, omnidirectional acoustic device that renders a region of space three wavelengths in diameter invisible to sound.

Preliminary theoretical acoustic and rf sounding calculations for MILL RACE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warshaw, S.I.; Dubois, P.F.

1981-11-02

As participant in DOE/ISA's Ionospheric Monitoring Program, LLNL has the responsibility of providing theoretical understanding and calculational support for experimental activities carried out by Los Alamos National Laboratory in using ionospheric sounders to remotely detect violent atmospheric phenomena. We have developed a system of interconnected computer codes which simulate the entire range of atmospheric and ionospheric processes involved in this remote detection procedure. We are able to model the acoustic pulse shape from an atmospheric explosion, the subsequent nonlinear transport of this energy to all parts of the immediate atmosphere including the ionosphere, and the propagation of high-frequency ratio wavesmore » through the acoustically perturbed ionosphere. Los Alamos' coverage of DNA's MILL RACE event provided an excellent opportunity to assess the credibility of the calculational system to correctly predict how ionospheric sounders would respond to a surface-based chemical explosion. In this experiment, 600 tons of high explosive were detonated at White Sands Missile Range at 12:35:40 local time on 16 September 1981. Vertical incidence rf phase sounders and bistatic oblique incidence rf sounders fielded by Los Alamos and SRI International throughout New Mexico and southern Colorado detected the ionospheric perturbation that ensued. A brief account of preliminary calculations of the acoustic disturbance and the predicted ionospheric sounder signatures for MILL RACE is presented. (WHK)« less

Zonal Flow Velocimetry in Spherical Couette Flow using Acoustic Modes

NASA Astrophysics Data System (ADS)

Adams, Matthew M.; Mautino, Anthony R.; Stone, Douglas R.; Triana, Santiago A.; Lekic, Vedran; Lathrop, Daniel P.

2015-11-01

We present studies of spherical Couette flows using the technique of acoustic mode Doppler velocimetry. This technique uses rotational splittings of acoustic modes to infer the azimuthal velocity profile of a rotating flow, and is of special interest in experiments where direct flow visualization is impractical. The primary experimental system consists of a 60 cm diameter outer spherical shell concentric with a 20 cm diameter sphere, with air or nitrogen gas serving as the working fluid. The geometry of the system approximates that of the Earth's core, making these studies geophysically relevant. A turbulent shear flow is established in the system by rotating the inner sphere and outer shell at different rates. Acoustic modes of the fluid volume are excited using a speaker and measured via microphones, allowingdetermination of rotational splittings. Preliminary results comparing observed splittings with those predicted by theory are presented. While the majority of these studies were performed in the 60 cm diameter device using nitrogen gas, some work has also been done looking at acoustic modes in the 3 m diameter liquid sodium spherical Couette experiment. Prospects for measuring zonal velocity profiles in a wide variety of experiments are discussed.

The social effects of poor classroom acoustics on students and The District of Columbia Public Schools demonstration of support through mandating the ANSI Classroom Acoustics standard

NASA Astrophysics Data System (ADS)

Ellis, Donna

2002-11-01

The effects that poor acoustics have on students extend beyond the classroom. This paper is to discuss the immediate and long-term results that inadequate acoustical design in the educational setting has on academic and social development and how the District of Columbia Public Schools (DCPS) are contributing to the classroom acoustic movement. DCPS is taking a pro-active stance in educational acoustics by mandating the ANSI Draft S12.60-200X classroom acoustic standard in the transformation of ten schools a year for the next ten to fifteen years. Synthesizing the ANSI S12 standard with the DCPS Design Guidelines describes explanation of how to design for appropriate acoustics in all core-learning spaces. Examples of the existing conditions of the facilities and acoustical remediation for new and historical preservation projects will be demonstrated. In addition, experience will be shared on the International Building Code Council hearings for classroom acoustics.

A new acoustic lens material for large area detectors in photoacoustic breast tomography☆

PubMed Central

Xia, Wenfeng; Piras, Daniele; van Hespen, Johan C.G.; Steenbergen, Wiendelt; Manohar, Srirang

2013-01-01

Objectives We introduce a new acoustic lens material for photoacoustic tomography (PAT) to improve lateral resolution while possessing excellent acoustic acoustic impedance matching with tissue to minimize lens induced image artifacts. Background A large surface area detector due to its high sensitivity is preferable to detect weak signals in photoacoustic mammography. The lateral resolution is then limited by the narrow acceptance angle of such detectors. Acoustic lenses made of acrylic plastic (PMMA) have been used to enlarge the acceptance angle of such detectors and improve lateral resolution. However, such PMMA lenses introduce image artifacts due to internal reflections of ultrasound within the lenses, the result of acoustic impedance mismatch with the coupling medium or tissue. Methods A new lens is proposed based on the 2-component resin Stycast 1090SI. We characterized the acoustic properties of the proposed lens material in comparison with commonly used PMMA, inspecting the speed of sound, acoustic attenuation and density. We fabricated acoustic lenses based on the new material and PMMA, and studied the effect of the acoustic lenses on detector performance comparing finite element (FEM) simulations and measurements of directional sensitivity, pulse-echo response and frequency response. We further investigated the effect of using the acoustic lenses on the image quality of a photoacoustic breast tomography system using k-Wave simulations and experiments. Results Our acoustic characterization shows that Stycast 1090SI has tissue-like acoustic impedance, high speed of sound and low acoustic attenuation. These acoustic properties ensure an excellent acoustic lens material to minimize the acoustic insertion loss. Both acoustic lenses show significant enlargement of detector acceptance angle and lateral resolution improvement from modeling and experiments. However, the image artifacts induced by the presence of an acoustic lens are reduced using the proposed

A comparison of solar wind and ionospheric ion acoustic waves

NASA Technical Reports Server (NTRS)

Kintner, P. M.; Kelley, M. C.

1980-01-01

Ion acoustic waves produced during the Trigger experiment are compared to ion acoustic waves observed in the solar wind. After normalizing to the Debye length the spectra are nearly identical, although the ionospheric wave relative energy density is 100 times larger than the solar wind case.

KENNEDY SPACE CENTER, FLA. - Researchers conduct underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

NASA Image and Video Library

2003-08-18

KENNEDY SPACE CENTER, FLA. - Researchers conduct underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

Acoustic vibration analysis for utilization of woody plant in space environment

NASA Astrophysics Data System (ADS)

Chida, Yukari; Yamashita, Masamichi; Hashimoto, Hirofumi; Sato, Seigo; Tomita-Yokotani, Kaori; Baba, Keiichi; Suzuki, Toshisada; Motohashi, Kyohei; Sakurai, Naoki; Nakagawa-izumi, Akiko

2012-07-01

We are proposing to raise woody plants for space agriculture in Mars. Space agriculture has the utilization of wood in their ecosystem. Nobody knows the real tree shape grown under space environment under the low or micro gravitational conditions such as outer environment. Angiosperm tree forms tension wood for keeping their shape. Tension wood formation is deeply related to gravity, but the details of the mechanism of its formation has not yet been clarified. For clarifying the mechanism, the space experiment in international space station, ISS is the best way to investigate about them as the first step. It is necessary to establish the easy method for crews who examine the experiments at ISS. Here, we are proposing to investigate the possibility of the acoustic vibration analysis for the experiment at ISS. Two types of Japanese cherry tree, weeping and upright types in Prunus sp., were analyzed by the acoustic vibration method. Coefficient-of-variation (CV) of sound speed was calculated by the acoustic vibration analysis. The amount of lignin and decomposed lignin were estimated by both Klason and Py-GC/MS method, respectively. The relationships of the results of acoustic vibration analysis and the inner components in tested woody materials were investigated. After the experiments, we confirm the correlation about them. Our results indicated that the acoustic vibration analysis would be useful for determining the inside composition as a nondestructive method in outer space environment.

Acoustic Tomography in the Canary Basin: Meddies and Tides

NASA Astrophysics Data System (ADS)

Dushaw, Brian D.; Gaillard, Fabienne; Terre, Thierry

2017-11-01

An acoustic propagation experiment over 308 km range conducted in the Canary Basin in 1997-1998 was used to assess the ability of ocean acoustic tomography to measure the flux of Mediterranean water and Meddies. Instruments on a mooring adjacent to the acoustic path measured the southwestward passage of a strong Meddy in temperature, salinity, and current. Over 9 months of transmissions, the acoustic arrival pattern was an initial broad stochastic pulse varying in duration by 250-500 ms, followed eight stable, identified-ray arrivals. Small-scale sound speed fluctuations from Mediterranean water parcels littered around the sound channel axis caused acoustic scattering. Internal waves contributed more modest acoustic scattering. Based on simulations, the main effect of a Meddy passing across the acoustic path is the formation of many early-arriving, near-axis rays, but these rays are thoroughly scattered by the small-scale Mediterranean-water fluctuations. A Meddy decreases the deep-turning ray travel times by 10-30 ms. The dominant acoustic signature of a Meddy is therefore the expansion of the width of the initial stochastic pulse. While this signature appears inseparable from the other effects of Mediterranean water in this region, the acoustic time series indicates the steady passage of Mediterranean water across the acoustic path. Tidal variations caused by the mode-1 internal tides were measured by the acoustic travel times. The observed internal tides were partly predicted using a recent global model for such tides derived from satellite altimetry.

Simultaneous masking between electric and acoustic stimulation in cochlear implant users with residual low-frequency hearing.

PubMed

Krüger, Benjamin; Büchner, Andreas; Nogueira, Waldo

2017-09-01

Ipsilateral electric-acoustic stimulation (EAS) is becoming increasingly important in cochlear implant (CI) treatment. Improvements in electrode designs and surgical techniques have contributed to improved hearing preservation during implantation. Consequently, CI implantation criteria have been expanded toward people with significant residual low-frequency hearing, who may benefit from the combined use of both the electric and acoustic stimulation in the same ear. However, only few studies have investigated the mutual interaction between electric and acoustic stimulation modalities. This work characterizes the interaction between both stimulation modalities using psychophysical masking experiments and cone beam computer tomography (CBCT). Two psychophysical experiments for electric and acoustic masking were performed to measure the hearing threshold elevation of a probe stimulus in the presence of a masker stimulus. For electric masking, the probe stimulus was an acoustic tone while the masker stimulus was an electric pulse train. For acoustic masking, the probe stimulus was an electric pulse train and the masker stimulus was an acoustic tone. Five EAS users, implanted with a CI and ipsilateral residual low-frequency hearing, participated in the study. Masking was determined at different electrodes and different acoustic frequencies. CBCT scans were used to determine the individual place-pitch frequencies of the intracochlear electrode contacts by using the Stakhovskaya place-to-frequency transformation. This allows the characterization of masking as a function of the difference between electric and acoustic stimulation sites, which we term the electric-acoustic frequency difference (EAFD). The results demonstrate a significant elevation of detection thresholds for both experiments. In electric masking, acoustic-tone thresholds increased exponentially with decreasing EAFD. In contrast, for the acoustic masking experiment, threshold elevations were present

Suppression of Helmholtz resonance using inside acoustic liner

NASA Astrophysics Data System (ADS)

Hong, Zhiliang; Dai, Xiwen; Zhou, Nianfa; Sun, Xiaofeng; Jing, Xiaodong

2014-08-01

When a Helmholtz resonator is exposed to grazing flow, an unstable shear layer at the opening can cause the occurrence of acoustic resonance under appropriate conditions. In this paper, in order to suppress the flow-induced resonance, the effects of inside acoustic liners placed on the side wall or the bottom of a Helmholtz resonator are investigated. Based on the one-dimensional sound propagation theory, the time domain impedance model of a Helmholtz resonator with inside acoustic liner is derived, and then combined with a discrete vortex model the resonant behavior of the resonator under grazing flow is simulated. Besides, an experiment is conducted to validate the present model, showing significant reduction of the peak sound pressure level achieved by the use of the side-wall liners. And the simulation results match reasonably well with the experimental data. The present results reveal that the inside acoustic liner can not only absorb the resonant sound pressure, but also suppress the fluctuation motion of the shear layer over the opening of the resonator. In all, the impact of the acoustic liners is to dampen the instability of the flow-acoustic coupled system. This demonstrates that it is a convenient and effective method for suppressing Helmholtz resonance by using inside acoustic liner.

Manipulating Liquids With Acoustic Radiation Pressure Phased Arrays

NASA Technical Reports Server (NTRS)

Oeftering, Richard C.

1999-01-01

High-intensity ultrasound waves can produce the effects of "Acoustic Radiation Pressure" (ARP) and "acoustic streaming." These effects can be used to propel liquid flows and to apply forces that can be used to move or manipulate floating objects or liquid surfaces. NASA's interest in ARP includes the remote-control agitation of liquids and the manipulation of bubbles and drops in liquid experiments and propellant systems. A high level of flexibility is attained by using a high-power acoustic phased array to generate, steer, and focus a beam of acoustic waves. This is called an Acoustic Radiation Pressure Phased Array, or ARPPA. In this approach, many acoustic transducer elements emit wavelets that converge into a single beam of sound waves. Electronically coordinating the timing, or "phase shift," of the acoustic waves makes it possible to form a beam with a predefined direction and focus. Therefore, a user can direct the ARP force at almost any desired point within a liquid volume. ARPPA lets experimenters manipulate objects anywhere in a test volume. This flexibility allow it to be used for multiple purposes, such as to agitate liquids, deploy and manipulate drops or bubbles, and even suppress sloshing in spacecraft propellant tanks.

Bubbles in an acoustic field: an overview.

PubMed

Ashokkumar, Muthupandian; Lee, Judy; Kentish, Sandra; Grieser, Franz

2007-04-01

Acoustic cavitation is the fundamental process responsible for the initiation of most of the sonochemical reactions in liquids. Acoustic cavitation originates from the interaction between sound waves and bubbles. In an acoustic field, bubbles can undergo growth by rectified diffusion, bubble-bubble coalescence, bubble dissolution or bubble collapse leading to the generation of primary radicals and other secondary chemical reactions. Surface active solutes have been used in association with a number of experimental techniques in order to isolate and understand these activities. A strobe technique has been used for monitoring the growth of a single bubble by rectified diffusion. Multibubble sonoluminescence has been used for monitoring the growth of the bubbles as well as coalescence between bubbles. The extent of bubble coalescence has also been monitored using a newly developed capillary technique. An overview of the various experimental results has been presented in order to highlight the complexities involved in acoustic cavitation processes, which on the other hand arise from a simple, mechanical interaction between sound waves and bubbles.

Aeroelastic-Acoustics Simulation of Flight Systems

NASA Technical Reports Server (NTRS)

Gupta, kajal K.; Choi, S.; Ibrahim, A.

2009-01-01

This paper describes the details of a numerical finite element (FE) based analysis procedure and a resulting code for the simulation of the acoustics phenomenon arising from aeroelastic interactions. Both CFD and structural simulations are based on FE discretization employing unstructured grids. The sound pressure level (SPL) on structural surfaces is calculated from the root mean square (RMS) of the unsteady pressure and the acoustic wave frequencies are computed from a fast Fourier transform (FFT) of the unsteady pressure distribution as a function of time. The resulting tool proves to be unique as it is designed to analyze complex practical problems, involving large scale computations, in a routine fashion.

Flow-excited acoustic resonance of a Helmholtz resonator: Discrete vortex model compared to experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Xiwen; Jing, Xiaodong, E-mail: jingxd@buaa.edu.cn; Sun, Xiaofeng

The acoustic resonance in a Helmholtz resonator excited by a low Mach number grazing flow is studied theoretically. The nonlinear numerical model is established by coupling the vortical motion at the cavity opening with the cavity acoustic mode through an explicit force balancing relation between the two sides of the opening. The vortical motion is modeled in the potential flow framework, in which the oscillating motion of the thin shear layer is described by an array of convected point vortices, and the unsteady vortex shedding is determined by the Kutta condition. The cavity acoustic mode is obtained from the one-dimensionalmore » acoustic propagation model, the time-domain equivalent of which is given by means of a broadband time-domain impedance model. The acoustic resistances due to radiation and viscous loss at the opening are also taken into account. The physical processes of the self-excited oscillations, at both resonance and off-resonance states, are simulated directly in the time domain. Results show that the shear layer exhibits a weak flapping motion at the off-resonance state, whereas it rolls up into large-scale vortex cores when resonances occur. Single and dual-vortex patterns are observed corresponding to the first and second hydrodynamic modes. The simulation also reveals different trajectories of the two vortices across the opening when the first and second hydrodynamic modes co-exist. The strong modulation of the shed vorticity by the acoustic feedback at the resonance state is demonstrated. The model overestimates the pressure pulsation amplitude by a factor 2, which is expected to be due to the turbulence of the flow which is not taken into account. The model neglects vortex shedding at the downstream and side edges of the cavity. This will also result in an overestimation of the pulsation amplitude.« less

Challenges in Rotorcraft Acoustic Flight Prediction and Validation

NASA Technical Reports Server (NTRS)

Boyd, D. Douglas, Jr.

2003-01-01

Challenges associated with rotorcraft acoustic flight prediction and validation are examined. First, an outline of a state-of-the-art rotorcraft aeroacoustic prediction methodology is presented. Components including rotorcraft aeromechanics, high resolution reconstruction, and rotorcraft acoustic prediction arc discussed. Next, to illustrate challenges and issues involved, a case study is presented in which an analysis of flight data from a specific XV-15 tiltrotor acoustic flight test is discussed in detail. Issues related to validation of methodologies using flight test data are discussed. Primary flight parameters such as velocity, altitude, and attitude are discussed and compared for repeated flight conditions. Other measured steady state flight conditions are examined for consistency and steadiness. A representative example prediction is presented and suggestions are made for future research.

Extremely Low Loss Phonon-Trapping Cryogenic Acoustic Cavities for Future Physical Experiments

PubMed Central

Galliou, Serge; Goryachev, Maxim; Bourquin, Roger; Abbé, Philippe; Aubry, Jean Pierre; Tobar, Michael E.

2013-01-01

Low loss Bulk Acoustic Wave devices are considered from the point of view of the solid state approach as phonon-confining cavities. We demonstrate effective design of such acoustic cavities with phonon-trapping techniques exhibiting extremely high quality factors for trapped longitudinally-polarized phonons of various wavelengths. Quality factors of observed modes exceed 1 billion, with a maximum Q-factor of 8 billion and Q × f product of 1.6 · 1018 at liquid helium temperatures. Such high sensitivities allow analysis of intrinsic material losses in resonant phonon systems. Various mechanisms of phonon losses are discussed and estimated. PMID:23823569

African American Parental Involvement in Their Children's Middle School Experiences

ERIC Educational Resources Information Center

Archer-Banks, Diane A. M.; Behar-Horenstein, Linda S.

2008-01-01

The purpose of this study was to determine the factors that influence African American parents' involvement in their children's middle school experiences. Two focus group interviews were conducted with African American parents. While the participants viewed parent involvement as important, they reported that family structure and socioeconomic…

Spatio-Temporal Analysis of Urban Acoustic Environments with Binaural Psycho-Acoustical Considerations for IoT-Based Applications.

PubMed

Segura-Garcia, Jaume; Navarro-Ruiz, Juan Miguel; Perez-Solano, Juan J; Montoya-Belmonte, Jose; Felici-Castell, Santiago; Cobos, Maximo; Torres-Aranda, Ana M

2018-02-26

Sound pleasantness or annoyance perceived in urban soundscapes is a major concern in environmental acoustics. Binaural psychoacoustic parameters are helpful to describe generic acoustic environments, as it is stated within the ISO 12913 framework. In this paper, the application of a Wireless Acoustic Sensor Network (WASN) to evaluate the spatial distribution and the evolution of urban acoustic environments is described. Two experiments are presented using an indoor and an outdoor deployment of a WASN with several nodes using an Internet of Things (IoT) environment to collect audio data and calculate meaningful parameters such as the sound pressure level, binaural loudness and binaural sharpness. A chunk of audio is recorded in each node periodically with a microphone array and the binaural rendering is conducted by exploiting the estimated directional characteristics of the incoming sound by means of DOA estimation. Each node computes the parameters in a different location and sends the values to a cloud-based broker structure that allows spatial statistical analysis through Kriging techniques. A cross-validation analysis is also performed to confirm the usefulness of the proposed system.

Spatio-Temporal Analysis of Urban Acoustic Environments with Binaural Psycho-Acoustical Considerations for IoT-Based Applications

PubMed Central

Montoya-Belmonte, Jose; Cobos, Maximo; Torres-Aranda, Ana M.

2018-01-01

Sound pleasantness or annoyance perceived in urban soundscapes is a major concern in environmental acoustics. Binaural psychoacoustic parameters are helpful to describe generic acoustic environments, as it is stated within the ISO 12913 framework. In this paper, the application of a Wireless Acoustic Sensor Network (WASN) to evaluate the spatial distribution and the evolution of urban acoustic environments is described. Two experiments are presented using an indoor and an outdoor deployment of a WASN with several nodes using an Internet of Things (IoT) environment to collect audio data and calculate meaningful parameters such as the sound pressure level, binaural loudness and binaural sharpness. A chunk of audio is recorded in each node periodically with a microphone array and the binaural rendering is conducted by exploiting the estimated directional characteristics of the incoming sound by means of DOA estimation. Each node computes the parameters in a different location and sends the values to a cloud-based broker structure that allows spatial statistical analysis through Kriging techniques. A cross-validation analysis is also performed to confirm the usefulness of the proposed system. PMID:29495407

Theory of acoustic radiation pressure for actual fluids

NASA Astrophysics Data System (ADS)

Doinikov, Alexander A.

1996-12-01

A body irradiated by a sound field is known to experience a steady force that is called the acoustic radiation pressure. This force plays an important role in many physical phenomena, such as cavitation, sonoluminescence, acoustic levitation, etc. The existing theory of acoustic radiation pressure neglects dissipative effects. The present paper develops a theory that takes these effects into account, both dissipative mechanisms, viscous and thermal, being considered. It is shown that, when they are no longer negligible, the dissipative effects drastically change the radiation pressure. As a result, its magnitude and sign become different from those predicted by the ``classical'' theory neglecting losses.

Experimental study on inter-particle acoustic forces.

PubMed

Garcia-Sabaté, Anna; Castro, Angélica; Hoyos, Mauricio; González-Cinca, Ricard

2014-03-01

A method for the experimental measurement of inter-particle forces (secondary Bjerknes force) generated by the action of an acoustic field in a resonator micro-channel is presented. The acoustic radiation force created by an ultrasonic standing wave moves suspended particles towards the pressure nodes and the acoustic pressure induces particle volume oscillations. Once particles are in the levitation plane, transverse and secondary Bjerknes forces become important. Experiments were carried out in a resonator filled with a suspension composed of water and latex particles of different size (5-15 μm) at different concentrations. Ultrasound was generated by means of a 2.5 MHz nominal frequency transducer. For the first time the acoustic force generated by oscillating particles acting on other particles has been measured, and the critical interaction distance in various cases has been determined. Inter-particle forces on the order of 10(-14) N have been measured by using this method.

Left hemisphere lateralization for lexical and acoustic pitch processing in Cantonese speakers as revealed by mismatch negativity.

PubMed

Gu, Feng; Zhang, Caicai; Hu, Axu; Zhao, Guoping

2013-12-01

For nontonal language speakers, speech processing is lateralized to the left hemisphere and musical processing is lateralized to the right hemisphere (i.e., function-dependent brain asymmetry). On the other hand, acoustic temporal processing is lateralized to the left hemisphere and spectral/pitch processing is lateralized to the right hemisphere (i.e., acoustic-dependent brain asymmetry). In this study, we examine whether the hemispheric lateralization of lexical pitch and acoustic pitch processing in tonal language speakers is consistent with the patterns of function- and acoustic-dependent brain asymmetry in nontonal language speakers. Pitch contrast in both speech stimuli (syllable /ji/ in Experiment 1) and nonspeech stimuli (harmonic tone in Experiment 1; pure tone in Experiment 2) was presented to native Cantonese speakers in passive oddball paradigms. We found that the mismatch negativity (MMN) elicited by lexical pitch contrast was lateralized to the left hemisphere, which is consistent with the pattern of function-dependent brain asymmetry (i.e., left hemisphere lateralization for speech processing) in nontonal language speakers. However, the MMN elicited by acoustic pitch contrast was also left hemisphere lateralized (harmonic tone in Experiment 1) or showed a tendency for left hemisphere lateralization (pure tone in Experiment 2), which is inconsistent with the pattern of acoustic-dependent brain asymmetry (i.e., right hemisphere lateralization for acoustic pitch processing) in nontonal language speakers. The consistent pattern of function-dependent brain asymmetry and the inconsistent pattern of acoustic-dependent brain asymmetry between tonal and nontonal language speakers can be explained by the hypothesis that the acoustic-dependent brain asymmetry is the consequence of a carryover effect from function-dependent brain asymmetry. Potential evolutionary implication of this hypothesis is discussed. © 2013.

Role of transient water pressure in quarrying: A subglacial experiment using acoustic emissions

USGS Publications Warehouse

Cohen, D.; Hooyer, T.S.; Iverson, N.R.; Thomason, J.F.; Jackson, M.

2006-01-01

Probably the most important mechanism of glacial erosion is quarrying: the growth and coalescence of cracks in subglacial bedrock and dislodgement of resultant rock fragments. Although evidence indicates that erosion rates depend on sliding speed, rates of crack growth in bedrock may be enhanced by changing stresses on the bed caused by fluctuating basal water pressure in zones of ice-bed separation. To study quarrying in real time, a granite step, 12 cm high with a crack in its stoss surface, was installed at the bed of Engabreen, Norway. Acoustic emission sensors monitored crack growth events in the step as ice slid over it. Vertical stresses, water pressure, and cavity height in the lee of the step were also measured. Water was pumped to the lee of the step several times over 8 days. Pumping initially caused opening of a leeward cavity, which then closed after pumping was stopped and water pressure decreased. During cavity closure, acoustic emissions emanating mostly from the vicinity of the base of the crack in the step increased dramatically. With repeated pump tests this crack grew with time until the step's lee surface was quarried. Our experiments indicate that fluctuating water pressure caused stress thresholds required for crack growth to be exceeded. Natural basal water pressure fluctuations should also concentrate stresses on rock steps, increasing rates of crack growth. Stress changes on the bed due to water pressure fluctuations will increase in magnitude and duration with cavity size, which may help explain the effect of sliding speed on erosion rates. Copyright 2006 by the American Geophysical Union.

Optical generation and detection of gigahertz-frequency longitudinal and shear acoustic waves in liquids: Theory and experiment

NASA Astrophysics Data System (ADS)

Klieber, Christoph; Pezeril, Thomas; Andrieu, Stéphane; Nelson, Keith A.

2012-07-01

We describe an adaptation of picosecond laser ultrasonics tailored for study of GHz-frequency longitudinal and shear acoustic waves in liquids. Time-domain coherent Brillouin scattering is used to detect multicycle acoustic waves after their propagation through variable thickness liquid layers into a solid substrate. A specialized optical pulse shaping method is used to generate sequences of pulses whose repetition rate determines the acoustic frequency. The measurements reveal the viscoelastic liquid properties and also include signatures of the optical and acoustic cavities formed by the multilayer sample assembly. Modeling of the signals allows their features to be distinguished so that liquid properties can be extracted reliably. Longitudinal and shear acoustic wave data from glycerol and from the silicon oil DC704 are presented.

Acoustic levitation for high temperature containerless processing in space

NASA Technical Reports Server (NTRS)

Rey, C. A.; Sisler, R.; Merkley, D. R.; Danley, T. J.

1990-01-01

New facilities for high-temperature containerless processing in space are described, including the acoustic levitation furnace (ALF), the high-temperature acoustic levitator (HAL), and the high-pressure acoustic levitator (HPAL). In the current ALF development, the maximum temperature capabilities of the levitation furnaces are 1750 C, and in the HAL development with a cold wall furnace they will exceed 2000-2500 C. The HPAL demonstrated feasibility of precursor space flight experiments on the ground in a 1 g pressurized-gas environment. Testing of lower density materials up to 1300 C has also been accomplished. It is suggested that advances in acoustic levitation techniques will result in the production of new materials such as ceramics, alloys, and optical and electronic materials.

Acoustic droplet vaporization of vascular droplets in gas embolotherapy

NASA Astrophysics Data System (ADS)

Bull, Joseph

2016-11-01

This work is primarily motivated by a developmental gas embolotherapy technique for cancer treatment. In this methodology, infarction of tumors is induced by selectively formed vascular gas bubbles that arise from the acoustic vaporization of vascular droplets. Additionally, micro- or nano-droplets may be used as vehicles for localized drug delivery, with or without flow occlusion. In this talk, we examine the dynamics of acoustic droplet vaporization through experiments and theoretical/computational fluid mechanics models, and investigate the bioeffects of acoustic droplet vaporization on endothelial cells and in vivo. Functionalized droplets that are targeted to tumor vasculature are examined. The influence of fluid mechanical and acoustic parameters, as well as droplet functionalization, is explored. This work was supported by NIH Grant R01EB006476.

Coherent entropy induced and acoustic noise separation in compact nozzles

NASA Astrophysics Data System (ADS)

Tao, Wenjie; Schuller, Thierry; Huet, Maxime; Richecoeur, Franck

2017-04-01

A method to separate entropy induced noise from an acoustic pressure wave in an harmonically perturbed flow through a nozzle is presented. It is tested on an original experimental setup generating simultaneously acoustic and temperature fluctuations in an air flow that is accelerated by a convergent nozzle. The setup mimics the direct and indirect noise contributions to the acoustic pressure field in a confined combustion chamber by producing synchronized acoustic and temperature fluctuations, without dealing with the complexity of the combustion process. It allows generating temperature fluctuations with amplitude up to 10 K in the frequency range from 10 to 100 Hz. The noise separation technique uses experiments with and without temperature fluctuations to determine the relative level of acoustic and entropy fluctuations in the system and to identify the nozzle response to these forcing waves. It requires multi-point measurements of acoustic pressure and temperature. The separation method is first validated with direct numerical simulations of the nonlinear Euler equations. These simulations are used to investigate the conditions for which the separation technique is valid and yield similar trends as the experiments for the investigated flow operating conditions. The separation method then gives successfully the acoustic reflection coefficient but does not recover the same entropy reflection coefficient as predicted by the compact nozzle theory due to the sensitivity of the method to signal noises in the explored experimental conditions. This methodology provides a framework for experimental investigation of direct and indirect combustion noises originating from synchronized perturbations.

Improving Fidelity of Launch Vehicle Liftoff Acoustic Simulations

NASA Technical Reports Server (NTRS)

Liever, Peter; West, Jeff

2016-01-01

Launch vehicles experience high acoustic loads during ignition and liftoff affected by the interaction of rocket plume generated acoustic waves with launch pad structures. Application of highly parallelized Computational Fluid Dynamics (CFD) analysis tools optimized for application on the NAS computer systems such as the Loci/CHEM program now enable simulation of time-accurate, turbulent, multi-species plume formation and interaction with launch pad geometry and capture the generation of acoustic noise at the source regions in the plume shear layers and impingement regions. These CFD solvers are robust in capturing the acoustic fluctuations, but they are too dissipative to accurately resolve the propagation of the acoustic waves throughout the launch environment domain along the vehicle. A hybrid Computational Fluid Dynamics and Computational Aero-Acoustics (CFD/CAA) modeling framework has been developed to improve such liftoff acoustic environment predictions. The framework combines the existing highly-scalable NASA production CFD code, Loci/CHEM, with a high-order accurate discontinuous Galerkin (DG) solver, Loci/THRUST, developed in the same computational framework. Loci/THRUST employs a low dissipation, high-order, unstructured DG method to accurately propagate acoustic waves away from the source regions across large distances. The DG solver is currently capable of solving up to 4th order solutions for non-linear, conservative acoustic field propagation. Higher order boundary conditions are implemented to accurately model the reflection and refraction of acoustic waves on launch pad components. The DG solver accepts generalized unstructured meshes, enabling efficient application of common mesh generation tools for CHEM and THRUST simulations. The DG solution is coupled with the CFD solution at interface boundaries placed near the CFD acoustic source regions. Both simulations are executed simultaneously with coordinated boundary condition data exchange.

Acoustic levitation and manipulation for space applications

NASA Technical Reports Server (NTRS)

Wang, T. G.

1979-01-01

A wide spectrum of experiments to be performed in space in a microgravity environment require levitation and manipulation of liquid or molten samples. A novel acoustic method has been developed at JPL for controlling liquid samples without physical contacts. This method utilizes the static pressure generated by three orthogonal acoustic standing waves excited within an enclosure. Furthermore, this method will allow the sample to be rotated and/or oscillated by modifying the phase angles and/or the amplitude of the acoustic field. This technique has been proven both in our laboratory and in a microgravity environment provided by KC-135 flights. Samples placed within our chamber driven at (1,0,0), (0,1,0), and (0,0,1), modes were indeed levitated, rotated, and oscillated.

Dynamics of Two Interactive Bubbles in An Acoustic Field - Part II: Experiments

NASA Astrophysics Data System (ADS)

Ashgriz, Nasser; Barbat, Tiberiu; Liu, Ching-Shi

1996-11-01

The motion of two air bubbles levitated in water, in the presence of a high-frequency acoustic field is experimentally studied. The interaction force between them is named "secondary Bjerknes force" and may be significant in microgravity environments; in our experiments the buoyancy effect is compensated through the action of the "primary Bjerknes forces" - interaction between each bubble oscillation and external sound field. The stationary sound field is produced by a piezoceramic tranducer, in the range of 22-24 kHz. The experiments succesfully demonstrate the existence of three patterns of interaction between bubbles of various sizes: attraction, repulsion and oscillation. Bubbles attraction is quantitatively studied using a high speed video, for "large" bubbles (in the range 0.5-2 mm radius); bubbles repulsion and oscillations are only observed with a regular video, for "small" bubbles (around the resonance size at these frequencies, 0.12 mm). Velocities and accelerations of each bubble are computed from the time history of the motion. The theoretical equations of motion are completed with a drag force formula for single bubbles and solved numerically. Experimental results, for the case of two attracting bubbles, are in good agreement with the numerical model, especially for values of the mutual distance greater than 3 large bubble radii.

Estimating animal population density using passive acoustics.

PubMed

Marques, Tiago A; Thomas, Len; Martin, Stephen W; Mellinger, David K; Ward, Jessica A; Moretti, David J; Harris, Danielle; Tyack, Peter L

2013-05-01

Reliable estimation of the size or density of wild animal populations is very important for effective wildlife management, conservation and ecology. Currently, the most widely used methods for obtaining such estimates involve either sighting animals from transect lines or some form of capture-recapture on marked or uniquely identifiable individuals. However, many species are difficult to sight, and cannot be easily marked or recaptured. Some of these species produce readily identifiable sounds, providing an opportunity to use passive acoustic data to estimate animal density. In addition, even for species for which other visually based methods are feasible, passive acoustic methods offer the potential for greater detection ranges in some environments (e.g. underwater or in dense forest), and hence potentially better precision. Automated data collection means that surveys can take place at times and in places where it would be too expensive or dangerous to send human observers. Here, we present an overview of animal density estimation using passive acoustic data, a relatively new and fast-developing field. We review the types of data and methodological approaches currently available to researchers and we provide a framework for acoustics-based density estimation, illustrated with examples from real-world case studies. We mention moving sensor platforms (e.g. towed acoustics), but then focus on methods involving sensors at fixed locations, particularly hydrophones to survey marine mammals, as acoustic-based density estimation research to date has been concentrated in this area. Primary among these are methods based on distance sampling and spatially explicit capture-recapture. The methods are also applicable to other aquatic and terrestrial sound-producing taxa. We conclude that, despite being in its infancy, density estimation based on passive acoustic data likely will become an important method for surveying a number of diverse taxa, such as sea mammals, fish, birds

Estimating animal population density using passive acoustics

PubMed Central

Marques, Tiago A; Thomas, Len; Martin, Stephen W; Mellinger, David K; Ward, Jessica A; Moretti, David J; Harris, Danielle; Tyack, Peter L

2013-01-01

Reliable estimation of the size or density of wild animal populations is very important for effective wildlife management, conservation and ecology. Currently, the most widely used methods for obtaining such estimates involve either sighting animals from transect lines or some form of capture-recapture on marked or uniquely identifiable individuals. However, many species are difficult to sight, and cannot be easily marked or recaptured. Some of these species produce readily identifiable sounds, providing an opportunity to use passive acoustic data to estimate animal density. In addition, even for species for which other visually based methods are feasible, passive acoustic methods offer the potential for greater detection ranges in some environments (e.g. underwater or in dense forest), and hence potentially better precision. Automated data collection means that surveys can take place at times and in places where it would be too expensive or dangerous to send human observers. Here, we present an overview of animal density estimation using passive acoustic data, a relatively new and fast-developing field. We review the types of data and methodological approaches currently available to researchers and we provide a framework for acoustics-based density estimation, illustrated with examples from real-world case studies. We mention moving sensor platforms (e.g. towed acoustics), but then focus on methods involving sensors at fixed locations, particularly hydrophones to survey marine mammals, as acoustic-based density estimation research to date has been concentrated in this area. Primary among these are methods based on distance sampling and spatially explicit capture-recapture. The methods are also applicable to other aquatic and terrestrial sound-producing taxa. We conclude that, despite being in its infancy, density estimation based on passive acoustic data likely will become an important method for surveying a number of diverse taxa, such as sea mammals, fish, birds

Curcumin protects against acoustic trauma in the rat cochlea.

PubMed

Soyalıç, Harun; Gevrek, Fikret; Karaman, Serhat

2017-08-01

In this study we evaluated the therapeutic utility of curcumin in a rodent model of acoustic trauma using histopathology, immunohistochemical, and distortion product otoacoustic emission (DPOAEs) measurements. 28 Wistar albino rats were included in the study and randomly assigned to 4 treatment groups. The first group (group 1) served as the control and was exposed to acoustic trauma alone. Group 2 was the curcumin group. Group 3 was the curcumin plus acoustic trauma group. Group 4 was the saline plus acoustic trauma group. Otoacoustic emission measurements were collected at the end of the experiment and all animals were sacrificed. Cochlea were collected and prepared for TUNEL (TdT-mediated deoxyuridinetriphosphate nick end-labelling) staining assay. Group 3 maintained baseline DPOAEs values at 3000 Hz, 4000 Hz and 8000 Hz on the 3rd and 5th day of the experiment. DPOAEs results were correlated with the immunohistochemical and histopathological findings in all groups. In comparison to the histopathologic control group, Group 1 exhibited a statistically significant increase in apoptotic indices in the organ of Corti, inner hair cell, and outer hair cell areas (p < 0.05). Relative to the control group, rats in Group 3 showed little increase in inner hair cell and outer hair cell apoptotic indices. Our results support the conclusion that curcumin may protect the cochlear tissues from acoustic trauma in rats. Curcumin injection prior to or after an acoustic trauma reduces cochlear hair cell damage and may protect against hearing loss. Copyright © 2017 Elsevier B.V. All rights reserved.

Single beam acoustic trapping

PubMed Central

Lee, Jungwoo; Teh, Shia-Yen; Lee, Abraham; Kim, Hyung Ham; Lee, Changyang; Shung, K. Kirk

2009-01-01

A single beam acoustic device, with its relatively simple scheme and low intensity, can trap a single lipid droplet in a manner similar to optical tweezers. Forces in the order of hundreds of nanonewtons direct the droplet toward the beam focus, within the range of hundreds of micrometers. This trapping method, therefore, can be a useful tool for particle manipulation in areas where larger particles or forces are involved. PMID:19798424

Single beam acoustic trapping.

PubMed

Lee, Jungwoo; Teh, Shia-Yen; Lee, Abraham; Kim, Hyung Ham; Lee, Changyang; Shung, K Kirk

2009-08-17

A single beam acoustic device, with its relatively simple scheme and low intensity, can trap a single lipid droplet in a manner similar to optical tweezers. Forces in the order of hundreds of nanonewtons direct the droplet toward the beam focus, within the range of hundreds of micrometers. This trapping method, therefore, can be a useful tool for particle manipulation in areas where larger particles or forces are involved.

Nonlinear Acoustic Landmine Detection: Profiling Soil Surface Vibrations and Modeling Mesoscopic Elastic Behavior

DTIC Science & Technology

2007-05-04

TITLE AND SUBTITLE Nonlinear Acoustic Landmine Detection: Profiling Soil Surface Vibrations and Modeling Mesoscopic Elastic Behavior 6. AUTHOR(S...project report; no. 352 (2007) NONLINEAR ACOUSTIC LANDMINE DETECTION: PROFILING SOIL SURFACE VIBRATIONS AND MODELING MESOSCOPIC ELASTIC... model (Caughey 1966). Nonlinear acoustic landmine detection experiments are performed in the anechoic chamber facility using both a buried acrylic

Evanescent acoustic waves: Production and scattering by resonant targets

NASA Astrophysics Data System (ADS)

Osterhoudt, Curtis F.

Small targets with acoustic resonances which may be excited by incident acoustic planewaves are shown to possess high-Q modes ("organ-pipe" modes) which may be suitable for ocean-based calibration and ranging purposes. The modes are modeled using a double point-source model; this, along with acoustic reciprocity and inversion symmetry, is shown to adequately model the backscattering form functions of the modes at low frequencies. The backscattering form-functions are extended to apply to any bistatic acoustic experiment using the targets when the target response is dominated by the modes in question. An interface between two fluids which each approximate an unbounded half-space has been produced in the laboratory. The fluids have different sound speeds. When sound is incident on this interface at beyond the critical angle from within the first fluid, the second fluid is made to evince a region dominated by evanescent acoustic energy. Such a system is shown to be an possible laboratory-based proxy for a flat sediment bottom in the ocean, or sloped (unrippled) bottom in littoral environments. The evanescent sound field is characterized and shown to have complicated features despite the simplicity of its production. Notable among these features is the presence of dips in the soundfield amplitude, or "quasi-nulls". These are proposed to be extremely important when considering the return from ocean-based experiments. The soundfield features are also shown to be accurately predicted and characterized by wavenumber-integration software. The targets which exhibit organ-pipe modes in the free-field are shown to also be excited by the evanescent waves, and may be used as soundfield probes when the target returns are well characterized. Alternately, if the soundfield is well-known, the target parameters may be extracted from back- or bistatic-scattering experiments in evanescent fields. It is shown that the spatial decay rate as measured by a probe directly in the evanescent

Ecological Insights from Pelagic Habitats Acquired Using Active Acoustic Techniques.

PubMed

Benoit-Bird, Kelly J; Lawson, Gareth L

2016-01-01

Marine pelagic ecosystems present fascinating opportunities for ecological investigation but pose important methodological challenges for sampling. Active acoustic techniques involve producing sound and receiving signals from organisms and other water column sources, offering the benefit of high spatial and temporal resolution and, via integration into different platforms, the ability to make measurements spanning a range of spatial and temporal scales. As a consequence, a variety of questions concerning the ecology of pelagic systems lend themselves to active acoustics, ranging from organism-level investigations and physiological responses to the environment to ecosystem-level studies and climate. As technologies and data analysis methods have matured, the use of acoustics in ecological studies has grown rapidly. We explore the continued role of active acoustics in addressing questions concerning life in the ocean, highlight creative applications to key ecological themes ranging from physiology and behavior to biogeography and climate, and discuss emerging avenues where acoustics can help determine how pelagic ecosystems function.

Airborne Acoustic Perception by a Jumping Spider.

PubMed

Shamble, Paul S; Menda, Gil; Golden, James R; Nitzany, Eyal I; Walden, Katherine; Beatus, Tsevi; Elias, Damian O; Cohen, Itai; Miles, Ronald N; Hoy, Ronald R

2016-11-07

Jumping spiders (Salticidae) are famous for their visually driven behaviors [1]. Here, however, we present behavioral and neurophysiological evidence that these animals also perceive and respond to airborne acoustic stimuli, even when the distance between the animal and the sound source is relatively large (∼3 m) and with stimulus amplitudes at the position of the spider of ∼65 dB sound pressure level (SPL). Behavioral experiments with the jumping spider Phidippus audax reveal that these animals respond to low-frequency sounds (80 Hz; 65 dB SPL) by freezing-a common anti-predatory behavior characteristic of an acoustic startle response. Neurophysiological recordings from auditory-sensitive neural units in the brains of these jumping spiders showed responses to low-frequency tones (80 Hz at ∼65 dB SPL)-recordings that also represent the first record of acoustically responsive neural units in the jumping spider brain. Responses persisted even when the distances between spider and stimulus source exceeded 3 m and under anechoic conditions. Thus, these spiders appear able to detect airborne sound at distances in the acoustic far-field region, beyond the near-field range often thought to bound acoustic perception in arthropods that lack tympanic ears (e.g., spiders) [2]. Furthermore, direct mechanical stimulation of hairs on the patella of the foreleg was sufficient to generate responses in neural units that also responded to airborne acoustic stimuli-evidence that these hairs likely play a role in the detection of acoustic cues. We suggest that these auditory responses enable the detection of predators and facilitate an acoustic startle response. VIDEO ABSTRACT. Copyright © 2016 Elsevier Ltd. All rights reserved.

Topological Acoustics

NASA Astrophysics Data System (ADS)

Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

2015-03-01

The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

Multisource passive acoustic tracking: an application of random finite set data fusion

NASA Astrophysics Data System (ADS)

Ali, Andreas M.; Hudson, Ralph E.; Lorenzelli, Flavio; Yao, Kung

2010-04-01

Multisource passive acoustic tracking is useful in animal bio-behavioral study by replacing or enhancing human involvement during and after field data collection. Multiple simultaneous vocalizations are a common occurrence in a forest or a jungle, where many species are encountered. Given a set of nodes that are capable of producing multiple direction-of-arrivals (DOAs), such data needs to be combined into meaningful estimates. Random Finite Set provides the mathematical probabilistic model, which is suitable for analysis and optimal estimation algorithm synthesis. Then the proposed algorithm has been verified using a simulation and a controlled test experiment.

Evaluation of bridge cables corrosion using acoustic emission technique

NASA Astrophysics Data System (ADS)

Li, Dongsheng; Ou, Jinping

2010-04-01

Owing to the nature of the stress, corrosion of bridge cable may result in catastrophic failure of the structure. However, using electrochemical techniques isn't fully efficient for the detection and control on line of the corrosion phenomenon. A non-destructive testing method based on acoustic emission technique monitoring bridge cable corrosion was explored. The steel strands were placed at room temperature in 5% NaCl solution. Acoustic emission (AE) characteristic parameters were recorded in the whole corrosion experiment process. Based on the plot of cumulated acoustic activity, the bridge cables corrosion included three stages. It can be clearly seen that different stages have different acoustic emission signal characteristics. The AE characteristic parameters would be increased with cables corrosion development. Finally, the bridge cables corrosion experiment with different stress state and different corrosion environment was performed. The results shows that stress magnitude only affects the bridge cable failure time, however, the AE characteristic parameters value has changed a little. It was verified that AE technique can be used to detect the bridge cable early corrosion, investigating corrosion developing trend, and in monitoring and evaluating corrosion damages.

A Method for Large Eddy Simulation of Acoustic Combustion Instabilities

NASA Astrophysics Data System (ADS)

Wall, Clifton; Pierce, Charles; Moin, Parviz

2002-11-01

A method for performing Large Eddy Simulation of acoustic combustion instabilities is presented. By extending the low Mach number pressure correction method to the case of compressible flow, a numerical method is developed in which the Poisson equation for pressure is replaced by a Helmholtz equation. The method avoids the acoustic CFL condition by using implicit time advancement, leading to large efficiency gains at low Mach number. The method also avoids artificial damping of acoustic waves. The numerical method is attractive for the simulation of acoustic combustion instabilities, since these flows are typically at low Mach number, and the acoustic frequencies of interest are usually low. Both of these characteristics suggest the use of larger time steps than those allowed by an acoustic CFL condition. The turbulent combustion model used is the Combined Conserved Scalar/Level Set Flamelet model of Duchamp de Lageneste and Pitsch for partially premixed combustion. Comparison of LES results to the experiments of Besson et al will be presented.

Acoustic wave generation by microwaves and applications to nondestructive evaluation.

PubMed

Hosten, Bernard; Bacon, Christophe; Guilliorit, Emmanuel

2002-05-01

Although acoustic wave generation by electromagnetic waves has been widely studied in the case of laser-generated ultrasounds, the literature on acoustic wave generation by thermal effects due to electromagnetic microwaves is very sparse. Several mechanisms have been suggested to explain the phenomenon of microwave generation, i.e. radiation pressure, electrostriction or thermal expansion. Now it is known that the main cause is the thermal expansion due to the microwave absorption. This paper will review the recent advances in the theory and experiments that introduce a new way to generate ultrasonic waves without contact for the purpose of nondestructive evaluation and control. The unidirectional theory based on Maxwell's equations, heat equation and thermoviscoelasticity predicts the generation of acoustic waves at interfaces and inside stratified materials. Acoustic waves are generated by a pulsed electromagnetic wave or a burst at a chosen frequency such that materials can be excited with a broad or narrow frequency range. Experiments show the generation of acoustic waves in water, viscoelastic polymers and composite materials shaped as rod and plates. From the computed and measured accelerations at interfaces, the viscoelastic and electromagnetic properties of materials such as polymers and composites can be evaluated (NDE). Preliminary examples of non-destructive testing applications are presented.

Acoustic sensors using microstructures tunable with energy other than acoustic energy

DOEpatents

Datskos, Panagiotis G.

2003-11-25

A sensor for detecting acoustic energy includes a microstructure tuned to a predetermined acoustic frequency and a device for detecting movement of the microstructure. A display device is operatively linked to the movement detecting device. When acoustic energy strikes the acoustic sensor, acoustic energy having a predetermined frequency moves the microstructure, where the movement is detected by the movement detecting device.

Acoustic sensors using microstructures tunable with energy other than acoustic energy

DOEpatents

Datskos, Panagiotis G.

2005-06-07

A sensor for detecting acoustic energy includes a microstructure tuned to a predetermined acoustic frequency and a device for detecting movement of the microstructure. A display device is operatively linked to the movement detecting device. When acoustic energy strikes the acoustic sensor, acoustic energy having a predetermined frequency moves the microstructure, where the movement is detected by the movement detecting device.

What does See the Impulse Acoustic Microscopy inside Nanocomposites?

NASA Astrophysics Data System (ADS)

Levin, V. M.; Petronyuk, Y. S.; Morokov, E. S.; Celzard, A.; Bellucci, S.; Kuzhir, P. P.

The paper presents results of studying bulk microstructure in carbon nanocomposites by impulse acoustic microscopy technique. Nanocomposite materials are in the focus of interest because of their outstanding properties in minimal nanofiller content. Large surface area and high superficial activity cause strong interaction between nanoparticles that can result in formation of fractal conglomerates. This paper involves results of the first direct observation of nanoparticle conglomerates inside the bulk of epoxy-carbon nanocomposites. Diverse types of carbon nanofiller have been under investigation. The impulse acoustic microscope SIAM-1 (Acoustic Microscopy Lab, IBCP RAS) has been employed for 3D imaging bulk microstructure and measuring elastic properties of the nanocomposite specimens. The range of 50-200 MHz allows observing microstructure inside the entire specimen bulk. Acoustic images are obtained in the ultramicroscopic regime; they are formed by the Rayleigh type scattered radiation. It has been found the high-resolution acoustic vision (impulse acoustic microscopy) is an efficient technique to observe mesostructure formed by fractal cluster inside nanocomposites. The clusterization takes its utmost form in nanocomposites with graphite nanoplatelets as nanofiller. The nanoparticles agglomerate into micron-sized conglomerates distributed randomly over the material. Mesostructure in nanocomposites filled with carbon nanotubes is alternation of regions with diverse density of nanotube packing. Regions with alternative density of CNT packing are clearly seen in acoustical images as neighboring pixels of various brightness.

Comprehensive comparisons of geodesic acoustic mode characteristics and dynamics between Tore Supra experiments and gyrokinetic simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Storelli, A., E-mail: alexandre.storelli@lpp.polytechnique.fr; Vermare, L.; Hennequin, P.

2015-06-15

In a dedicated collisionality scan in Tore Supra, the geodesic acoustic mode (GAM) is detected and identified with the Doppler backscattering technique. Observations are compared to the results of a simulation with the gyrokinetic code GYSELA. We found that the GAM frequency in experiments is lower than predicted by simulation and theory. Moreover, the disagreement is higher in the low collisionality scenario. Bursts of non harmonic GAM oscillations have been characterized with filtering techniques, such as the Hilbert-Huang transform. When comparing this dynamical behaviour between experiments and simulation, the probability density function of GAM amplitude and the burst autocorrelation timemore » are found to be remarkably similar. In the simulation, where the radial profile of GAM frequency is continuous, we observed a phenomenon of radial phase mixing of the GAM oscillations, which could influence the burst autocorrelation time.« less

Characteristic of Secondary Flow Caused by Local Density Change in Standing Acoustic Fields

NASA Astrophysics Data System (ADS)

Tonsho, Kazuyuki; Hirosawa, Takuya; Kusakawa, Hiroshi; Kuwahara, Takuo; Tanabe, Mitsuaki

Secondary flow is a flow which is caused by the interference between standing acoustic fields and local density change. The behavior of the secondary flow depends on the location of the given local density change in the standing acoustic fields. When the density change is given at the middle of a velocity node and the neighboring velocity anti-node (middle point) or when it is given at the velocity anti-node in standing acoustic fields, the secondary flow shows particular behavior. Characteristic of the secondary flow at the two positions was predicted by numerical simulations. It was examined from these simulations whether the driving mechanism of the flow can be explained by the kind of acoustic radiation force that has been proposed so far. The predicted secondary flow was verified by experiments. For both the simulations and experiments, the standing acoustic fields generated in a cylinder are employed. In the experiments, the acoustic fields are generated by two loud speakers that are vibrated in same phase in a chamber. The employed resonance frequency is about 1000 Hz. The chamber is filled with air of room temperature and atmospheric pressure. In the numerical simulations and experiments, the local density change is given by heating or cooling. Because the secondary flow is influenced by buoyancy, the numerical simulations were done without taking gravity force into account and a part of the experiments were done by the microgravity condition using a drop tower. As a result of the simulations, at the middle point, the heated air was blown toward the node and the cooled air was blown toward the anti-node. It is clarified that the secondary flow is driven by the expected kind of acoustic radiation force. At the anti-node, both the heated and cooled air expands perpendicular to the traveling direction of the sound wave. The driving mechanism of the secondary flow can not be explained by the acoustic radiation force, and a detailed analysis is done. Through the

Acoustic dispersive prism.

PubMed

Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R

2016-01-07

The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz-1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium.

Modeling of Structural-Acoustic Interaction Using Coupled FE/BE Method and Control of Interior Acoustic Pressure Using Piezoelectric Actuators

NASA Technical Reports Server (NTRS)

Mei, Chuh; Shi, Yacheng

1997-01-01

A coupled finite element (FE) and boundary element (BE) approach is presented to model full coupled structural/acoustic/piezoelectric systems. The dual reciprocity boundary element method is used so that the natural frequencies and mode shapes of the coupled system can be obtained, and to extend this approach to time dependent problems. The boundary element method is applied to interior acoustic domains, and the results are very accurate when compared with limited exact solutions. Structural-acoustic problems are then analyzed with the coupled finite element/boundary element method, where the finite element method models the structural domain and the boundary element method models the acoustic domain. Results for a system consisting of an isotropic panel and a cubic cavity are in good agreement with exact solutions and experiment data. The response of a composite panel backed cavity is then obtained. The results show that the mass and stiffness of piezoelectric layers have to be considered. The coupled finite element and boundary element equations are transformed into modal coordinates, which is more convenient for transient excitation. Several transient problems are solved based on this formulation. Two control designs, a linear quadratic regulator (LQR) and a feedforward controller, are applied to reduce the acoustic pressure inside the cavity based on the equations in modal coordinates. The results indicate that both controllers can reduce the interior acoustic pressure and the plate deflection.

Fault growth and acoustic emissions in confined granite

USGS Publications Warehouse

Lockner, David A.; Byerlee, James D.

1992-01-01

The failure process in a brittle granite was studied by using acoustic emission techniques to obtain three dimensional locations of the microfracturing events. During a creep experiment the nucleation of faulting coincided with the onset of tertiary creep, but the development of the fault could not be followed because the failure occurred catastrophically. A technique has been developed that enables the failure process to be stabilized by controlling the axial stress to maintain a constant acoustic emission rate. As a result the post-failure stress-strain curve has been followed quasi-statically, extending to hours the fault growth process that normally would occur violently in a fraction of a second. The results from the rate-controlled experiments show that the fault plane nucleated at a point on the sample surface after the stress-strain curve reached its peak. Before nucleation, the microcrack growth was distributed throughout the sample. The fault plane then grew outward from the nucleation site and was accompanied by a gradual drop in stress. Acoustic emission locations showed that the fault propagated as a fracture front (process zone) with dimensions of 1 to 3 cm. As the fracture front passed by a given fixed point on the fault plane, the subsequent acoustic emission would drop. When growth was allowed to progress until the fault bisected the sample, the stress dropped to the frictional strength. These observations are in accord with the behavior predicted by Rudnicki and Rice's bifurcation analysis but conflict with experiments used to infer that shear localization would occur in brittle rock while the material is still hardening.

Velocity measurement by vibro-acoustic Doppler.

PubMed

Nabavizadeh, Alireza; Urban, Matthew W; Kinnick, Randall R; Fatemi, Mostafa

2012-04-01

We describe the theoretical principles of a new Doppler method, which uses the acoustic response of a moving object to a highly localized dynamic radiation force of the ultrasound field to calculate the velocity of the moving object according to Doppler frequency shift. This method, named vibro-acoustic Doppler (VAD), employs two ultrasound beams separated by a slight frequency difference, Δf, transmitting in an X-focal configuration. Both ultrasound beams experience a frequency shift because of the moving objects and their interaction at the joint focal zone produces an acoustic frequency shift occurring around the low-frequency (Δf) acoustic emission signal. The acoustic emission field resulting from the vibration of the moving object is detected and used to calculate its velocity. We report the formula that describes the relation between Doppler frequency shift of the emitted acoustic field and the velocity of the moving object. To verify the theory, we used a string phantom. We also tested our method by measuring fluid velocity in a tube. The results show that the error calculated for both string and fluid velocities is less than 9.1%. Our theory shows that in the worst case, the error is 0.54% for a 25° angle variation for the VAD method compared with an error of -82.6% for a 25° angle variation for a conventional continuous wave Doppler method. An advantage of this method is that, unlike conventional Doppler, it is not sensitive to angles between the ultrasound beams and direction of motion.

Graph-based sensor fusion for classification of transient acoustic signals.

PubMed

Srinivas, Umamahesh; Nasrabadi, Nasser M; Monga, Vishal

2015-03-01

Advances in acoustic sensing have enabled the simultaneous acquisition of multiple measurements of the same physical event via co-located acoustic sensors. We exploit the inherent correlation among such multiple measurements for acoustic signal classification, to identify the launch/impact of munition (i.e., rockets, mortars). Specifically, we propose a probabilistic graphical model framework that can explicitly learn the class conditional correlations between the cepstral features extracted from these different measurements. Additionally, we employ symbolic dynamic filtering-based features, which offer improvements over the traditional cepstral features in terms of robustness to signal distortions. Experiments on real acoustic data sets show that our proposed algorithm outperforms conventional classifiers as well as the recently proposed joint sparsity models for multisensor acoustic classification. Additionally our proposed algorithm is less sensitive to insufficiency in training samples compared to competing approaches.

Political Involvement. Community Involvement/Career Education: An Experience-based Social Studies Program, Volume III.

ERIC Educational Resources Information Center

Kyle, James; And Others

This collection of materials and ideas is designed for the high school student who wants to try to influence society. The guide provides background information and descriptions of experience-based learning activities for use by students as they explore political involvement opportunities in their communities. The purposes of the materials are to…

Measurement of acoustic attenuation in South Pole ice

NASA Astrophysics Data System (ADS)

IceCube Collaboration; Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bissok, M.; Blaufuss, E.; Boersma, D. J.; Bohm, C.; Böser, S.; Botner, O.; Bradley, L.; Braun, J.; Buitink, S.; Carson, M.; Chirkin, D.; Christy, B.; Clem, J.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; D'Agostino, M. V.; Danninger, M.; de Clercq, C.; Demirörs, L.; Depaepe, O.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; Deyoung, T.; Díaz-Vélez, J. C.; Dreyer, J.; Dumm, J. P.; Duvoort, M. R.; Ehrlich, R.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Feusels, T.; Filimonov, K.; Finley, C.; Foerster, M. M.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Ganugapati, R.; Geisler, M.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gunasingha, R. M.; Gurtner, M.; Gustafsson, L.; Ha, C.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Helbing, K.; Herquet, P.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Homeier, A.; Hoshina, K.; Hubert, D.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Imlay, R. L.; Ishihara, A.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Joseph, J. M.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kelley, J. L.; Kemming, N.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Knops, S.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Krings, T.; Kroll, G.; Kuehn, K.; Kuwabara, T.; Labare, M.; Lafebre, S.; Laihem, K.; Landsman, H.; Lauer, R.; Lehmann, R.; Lennarz, D.; Lünemann, J.; Madsen, J.; Majumdar, P.; Maruyama, R.; Mase, K.; Matis, H. S.; Matusik, M.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Middell, E.; Milke, N.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nießen, P.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; Ono, M.; Panknin, S.; Paul, L.; Pérez de Los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Prikockis, M.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Rizzo, A.; Rodrigues, J. P.; Roth, P.; Rothmaier, F.; Rott, C.; Roucelle, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Sarkar, S.; Schatto, K.; Schlenstedt, S.; Schmidt, T.; Schneider, D.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Slipak, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stephens, G.; Stezelberger, T.; Stokstad, R. G.; Stoyanov, S.; Strahler, E. A.; Straszheim, T.; Sullivan, G. W.; Swillens, Q.; Taboada, I.; Tamburro, A.; Tarasova, O.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Tosi, D.; Turčan, D.; van Eijndhoven, N.; Vandenbroucke, J.; van Overloop, A.; van Santen, J.; Voigt, B.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Wikström, G.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Woschnagg, K.; Xu, C.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; IceCube Collaboration

2011-01-01

Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient α = 3.20 ± 0.57 km-1 between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for λ ≡ 1/α of ˜300 m with 20% uncertainty. No significant depth or frequency dependence has been found.

High efficiency and broadband acoustic diodes

NASA Astrophysics Data System (ADS)

Fu, Congyi; Wang, Bohan; Zhao, Tianfei; Chen, C. Q.

2018-01-01

Energy transmission efficiency and working bandwidth are the two major factors limiting the application of current acoustic diodes (ADs). This letter presents a design of high efficiency and broadband acoustic diodes composed of a nonlinear frequency converter and a linear wave filter. The converter consists of two masses connected by a bilinear spring with asymmetric tension and compression stiffness. The wave filter is a linear mass-spring lattice (sonic crystal). Both numerical simulation and experiment show that the energy transmission efficiency of the acoustic diode can be improved by as much as two orders of magnitude, reaching about 61%. Moreover, the primary working band width of the AD is about two times of the cut-off frequency of the sonic crystal filter. The cut-off frequency dependent working band of the AD implies that the developed AD can be scaled up or down from macro-scale to micro- and nano-scale.

Pulse analysis of acoustic emission signals

NASA Technical Reports Server (NTRS)

Houghton, J. R.; Packman, P. F.

1977-01-01

A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio were examined in the frequency domain analysis and pulse shape deconvolution was developed for use in the time domain analysis. Comparisons of the relative performance of each analysis technique are made for the characterization of acoustic emission pulses recorded by a measuring system. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameter values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emission associated with (a) crack propagation, (b) ball dropping on a plate, (c) spark discharge, and (d) defective and good ball bearings. Deconvolution of the first few micro-seconds of the pulse train is shown to be the region in which the significant signatures of the acoustic emission event are to be found.

Pulse analysis of acoustic emission signals

NASA Technical Reports Server (NTRS)

Houghton, J. R.; Packman, P. F.

1977-01-01

A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio were examined in the frequency domain analysis, and pulse shape deconvolution was developed for use in the time domain analysis. Comparisons of the relative performance of each analysis technique are made for the characterization of acoustic emission pulses recorded by a measuring system. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameters values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emissions associated with: (1) crack propagation, (2) ball dropping on a plate, (3) spark discharge and (4) defective and good ball bearings. Deconvolution of the first few micro-seconds of the pulse train are shown to be the region in which the significant signatures of the acoustic emission event are to be found.

Seismo-acoustic ray model benchmarking against experimental tank data.

PubMed

Camargo Rodríguez, Orlando; Collis, Jon M; Simpson, Harry J; Ey, Emanuel; Schneiderwind, Joseph; Felisberto, Paulo

2012-08-01

Acoustic predictions of the recently developed traceo ray model, which accounts for bottom shear properties, are benchmarked against tank experimental data from the EPEE-1 and EPEE-2 (Elastic Parabolic Equation Experiment) experiments. Both experiments are representative of signal propagation in a Pekeris-like shallow-water waveguide over a non-flat isotropic elastic bottom, where significant interaction of the signal with the bottom can be expected. The benchmarks show, in particular, that the ray model can be as accurate as a parabolic approximation model benchmarked in similar conditions. The results of benchmarking are important, on one side, as a preliminary experimental validation of the model and, on the other side, demonstrates the reliability of the ray approach for seismo-acoustic applications.

Development of a MEMS acoustic emission sensor system

NASA Astrophysics Data System (ADS)

Greve, David W.; Oppenheim, Irving J.; Wu, Wei; Wright, Amelia P.

2007-04-01

An improved multi-channel MEMS chip for acoustic emission sensing has been designed and fabricated in 2006 to create a device that is smaller in size, superior in sensitivity, and more practical to manufacture than earlier designs. The device, fabricated in the MUMPS process, contains four resonant-type capacitive transducers in the frequency range between 100 kHz and 500 kHz on a chip with an area smaller than 2.5 sq. mm. The completed device, with its circuit board, electronics, housing, and connectors, possesses a square footprint measuring 25 mm x 25 mm. The small footprint is an important attribute for an acoustic emission sensor, because multiple sensors must typically be arrayed around a crack location. Superior sensitivity was achieved by a combination of four factors: the reduction of squeeze film damping, a resonant frequency approximating a rigid body mode rather than a bending mode, a ceramic package providing direct acoustic coupling to the structural medium, and high-gain amplifiers implemented on a small circuit board. Manufacture of the system is more practical because of higher yield (lower unit costs) in the MUMPS fabrication task and because of a printed circuit board matching the pin array of the MEMS chip ceramic package for easy assembly and compactness. The transducers on the MEMS chip incorporate two major mechanical improvements, one involving squeeze film damping and one involving the separation of resonance modes. For equal proportions of hole area to plate area, a triangular layout of etch holes reduces squeeze film damping as compared to the conventional square layout. The effect is modeled analytically, and is verified experimentally by characterization experiments on the new transducers. Structurally, the transducers are plates with spring supports; a rigid plate would be the most sensitive transducer, and bending decreases the sensitivity. In this chip, the structure was designed for an order-of-magnitude separation between the first

Characterisation of bubbles in liquids using acoustic techniques

NASA Astrophysics Data System (ADS)

Ramble, David Gary

1997-12-01

This thesis is concerned with the characterisation of air bubbles in a liquid through the use of a range of acoustic techniques, with the ultimate aim of minimising the ambiguity of the result and the complexity of the task. A bubble is particularly amenable to detection by using acoustical methods because there usually exists a large acoustic impedance mismatch between the gas/vapour inside the bubble and that of the surrounding liquid. The bubble also behaves like a single degree-of-freedom oscillator when excited, and as such exhibits a well-defined resonance frequency which is related to its radius. Though techniques which exploit this resonance property of the bubble are straightforward to apply, the results are prone to ambiguities as larger bubbles can geometrically scatter more sound than a smaller resonant bubble. However, these drawbacks can be overcome by using acoustical methods which make use of the nonlinear behaviour of bubbles. A particular nonlinear technique monitors the second harmonic emission of the bubble which is a global maximum at resonance. In addition, a two- frequency excitation technique is used which involves exciting the bubble with a fixed high frequency signal (the imaging signal, ωi) of the order of megahertz, and a lower variable frequency (the pumping signal, ωp) which is tuned to the bubble's resonance. The bubble couples these two sound fields together to produce sum-and-difference terms which peak at resonance. The two most promising combination frequency signals involve the coupling of the bubble's fundamental with the imaging frequency to give rise to a ωi+ωp signal, and the coupling of a subharmonic signal at half the resonance frequency of the bubble to give rise to a ωi/pmωp/2 signal. Initially, theory is studied which outlines the advantages and disadvantages of each of the acoustic techniques available. Experiments are then conducted in a large tank of water on simple bubble populations, ranging from stationary

Acoustic energy harvesting based on a planar acoustic metamaterial

NASA Astrophysics Data System (ADS)

Qi, Shuibao; Oudich, Mourad; Li, Yong; Assouar, Badreddine

2016-06-01

We theoretically report on an innovative and practical acoustic energy harvester based on a defected acoustic metamaterial (AMM) with piezoelectric material. The idea is to create suitable resonant defects in an AMM to confine the strain energy originating from an acoustic incidence. This scavenged energy is converted into electrical energy by attaching a structured piezoelectric material into the defect area of the AMM. We show an acoustic energy harvester based on a meta-structure capable of producing electrical power from an acoustic pressure. Numerical simulations are provided to analyze and elucidate the principles and the performances of the proposed system. A maximum output voltage of 1.3 V and a power density of 0.54 μW/cm3 are obtained at a frequency of 2257.5 Hz. The proposed concept should have broad applications on energy harvesting as well as on low-frequency sound isolation, since this system acts as both acoustic insulator and energy harvester.

Experimental studies of applications of time-reversal acoustics to noncoherent underwater communications.

PubMed

Heinemann, M; Larraza, A; Smith, K B

2003-06-01

The most difficult problem in shallow underwater acoustic communications is considered to be the time-varying multipath propagation because it impacts negatively on data rates. At high data rates the intersymbol interference requires adaptive algorithms on the receiver side that lead to computationally intensive and complex signal processing. A novel technique called time-reversal acoustics (TRA) can environmentally adapt the acoustic propagation effects of a complex medium in order to focus energy at a particular target range and depth. Using TRA, the multipath structure is reduced because all the propagation paths add coherently at the intended target location. This property of time-reversal acoustics suggests a potential application in the field of noncoherent acoustic communications. This work presents results of a tank scale experiment using an algorithm for rapid transmission of binary data in a complex underwater environment with the TRA approach. A simple 15-symbol code provides an example of the simplicity and feasibility of the approach. Covert coding due to the inherent scrambling induced by the environment at points other than the intended receiver is also investigated. The experiments described suggest a high potential in data rate for the time-reversal approach in underwater acoustic communications while keeping the computational complexity low.

Panel acoustic contribution analysis.

PubMed

Wu, Sean F; Natarajan, Logesh Kumar

2013-02-01

Formulations are derived to analyze the relative panel acoustic contributions of a vibrating structure. The essence of this analysis is to correlate the acoustic power flow from each panel to the radiated acoustic pressure at any field point. The acoustic power is obtained by integrating the normal component of the surface acoustic intensity, which is the product of the surface acoustic pressure and normal surface velocity reconstructed by using the Helmholtz equation least squares based nearfield acoustical holography, over each panel. The significance of this methodology is that it enables one to analyze and rank relative acoustic contributions of individual panels of a complex vibrating structure to acoustic radiation anywhere in the field based on a single set of the acoustic pressures measured in the near field. Moreover, this approach is valid for both interior and exterior regions. Examples of using this method to analyze and rank the relative acoustic contributions of a scaled vehicle cabin are demonstrated.

Improving Classroom Acoustics (ICA): A Three-Year FM Sound Field Classroom Amplification Study.

ERIC Educational Resources Information Center

Rosenberg, Gail Gegg; Blake-Rahter, Patricia; Heavner, Judy; Allen, Linda; Redmond, Beatrice Myers; Phillips, Janet; Stigers, Kathy

1999-01-01

The Improving Classroom Acoustics (ICA) special project was designed to determine if students' listening and learning behaviors improved as a result of an acoustical environment enhanced through the use of FM sound field classroom amplification. The 3-year project involved 2,054 students in 94 general education kindergarten, first-, and…

Anisotropic Dispersion and Partial Localization of Acoustic Surface Plasmons on an Atomically Stepped Surface: Au(788)

NASA Astrophysics Data System (ADS)

Smerieri, M.; Vattuone, L.; Savio, L.; Langer, T.; Tegenkamp, C.; Pfnür, H.; Silkin, V. M.; Rocca, M.

2014-10-01

Understanding acoustic surface plasmons (ASPs) in the presence of nanosized gratings is necessary for the development of future devices that couple light with ASPs. We show here by experiment and theory that two ASPs exist on Au(788), a vicinal surface with an ordered array of monoatomic steps. The ASPs propagate across the steps as long as their wavelength exceeds the terrace width, thereafter becoming localized. Our investigation identifies, for the first time, ASPs coupled with intersubband transitions involving multiple surface-state subbands.

From flying wheel to square flow: Dynamics of a flow driven by acoustic forcing

NASA Astrophysics Data System (ADS)

Cambonie, Tristan; Moudjed, Brahim; Botton, Valéry; Henry, Daniel; Ben Hadid, Hamda

2017-12-01

Acoustic streaming designates the ability to drive quasisteady flows by acoustic propagation in dissipative fluids and results from an acoustohydrodynamics coupling. It is a noninvasive way of putting a fluid into motion using the volumetric acoustic force and can be used for different applications such as mixing purposes. We present an experimental investigation of a kind of square flow driven by acoustic streaming, with the use of beam reflections, in a water tank. Time-resolved experiments using particle image velocimetry have been performed to investigate the velocity field in the reference plane of the experiments for six powers: 0.5, 1, 2, 4, 6, and 8 W. The evolution of the flow regime from almost steady to strongly unsteady states is characterized using different tools: the plot of time-averaged and instantaneous velocity fields, the calculation of presence density maps for vortex positions and for the maximal velocity and vorticity crest lines, and the use of spatiotemporal maps of the waving observed on the jets created by acoustic streaming. A transition is observed between two regimes at moderate and high acoustic forcing.

Is dust acoustic wave a new plasma acoustic mode?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dwivedi, C.B.

1997-09-01

In this Brief Communication, the claim of the novelty of the dust acoustic wave in a dusty plasma within the constant dust charge model is questioned. Conceptual lacunas behind the claim have been highlighted and appropriate physical arguments have been forwarded against the claim. It is demonstrated that the so-called dust acoustic wave could better be termed as a general acoustic fluctuation response with a dominant characteristic feature of the acoustic-like mode (ALM) fluctuation response reported by Dwivedi {ital et al.} [J. Plasma Phys. {bold 41}, 219 (1989)]. It is suggested that both correct and more usable nomenclature of themore » ALM should be the so-called acoustic mode. {copyright} {ital 1997 American Institute of Physics.}« less

Numerical Simulations of Acoustically Driven, Burning Droplets

NASA Technical Reports Server (NTRS)

Kim, H.-C.; Karagozian, A. R.; Smith, O. I.; Urban, Dave (Technical Monitor)

1999-01-01

This computational study focuses on understanding and quantifying the effects of external acoustical perturbations on droplet combustion. A one-dimensional, axisymmetric representation of the essential diffusion and reaction processes occurring in the vicinity of the droplet stagnation point is used here in order to isolate the effects of the imposed acoustic disturbance. The simulation is performed using a third order accurate, essentially non-oscillatory (ENO) numerical scheme with a full methanol-air reaction mechanism. Consistent with recent microgravity and normal gravity combustion experiments, focus is placed on conditions where the droplet is situated at a velocity antinode in order for the droplet to experience the greatest effects of fluid mechanical straining of flame structures. The effects of imposed sound pressure level and frequency are explored here, and conditions leading to maximum burning rates are identified.

Acoustic Neuroma Mimicking Orofacial Pain: A Unique Case Report

PubMed Central

Srinivas, Naveen; Mendigeri, Vijaylaxmi; Puranik, Surekha R.

2016-01-01

Acoustic neuroma (AN), also called vestibular schwannoma, is a tumor composed of Schwann cells that most frequently involve the vestibular division of the VII cranial nerve. The most common symptoms include orofacial pain, facial paralysis, trigeminal neuralgia, tinnitus, hearing loss, and imbalance that result from compression of cranial nerves V–IX. Symptoms of acoustic neuromas can mimic and present as temporomandibular disorder. Therefore, a thorough medical and dental history, radiographic evaluation, and properly conducted diagnostic testing are essential in differentiating odontogenic pain from pain that is nonodontogenic in nature. This article reports a rare case of a young pregnant female patient diagnosed with an acoustic neuroma located in the cerebellopontine angle that was originally treated for musculoskeletal temporomandibular joint disorder. PMID:28053796

Numerical Investigations of High Pressure Acoustic Waves in Resonators

NASA Technical Reports Server (NTRS)

Athavale, Mahesh; Pindera, Maciej; Daniels, Christopher C.; Steinetz, Bruce M.

2004-01-01

This presentation presents work on numerical investigations of nonlinear acoustic phenomena in resonators that can generate high-pressure waves using acoustic forcing of the flow. Time-accurate simulations of the flow in a closed cone resonator were performed at different oscillation frequencies and amplitudes, and the numerical results for the resonance frequency and fluid pressure increase match the GRC experimental data well. Work on cone resonator assembly simulations has started and will involve calculations of the flow through the resonator assembly with and without acoustic excitation. A new technique for direct calculation of resonance frequency of complex shaped resonators is also being investigated. Script-driven command procedures will also be developed for optimization of the resonator shape for maximum pressure increase.

Feasibility study of complex wavefield retrieval in off-axis acoustic holography employing an acousto-optic sensor

PubMed Central

Rodríguez, Guillermo López; Weber, Joshua; Sandhu, Jaswinder Singh; Anastasio, Mark A.

2011-01-01

We propose and experimentally demonstrate a new method for complex-valued wavefield retrieval in off-axis acoustic holography. The method involves use of an intensity-sensitive acousto-optic (AO) sensor, optimized for use at 3.3 MHz, to record the acoustic hologram and a computational method for reconstruction of the object wavefield. The proposed method may circumvent limitations of conventional implementations of acoustic holography and may facilitate the development of acoustic-holography-based biomedical imaging methods. PMID:21669451

Characterization of blocks impacts from acoustic emissions: insights from laboratory experiments

NASA Astrophysics Data System (ADS)

Farin, Maxime; Mangeney, Anne; de Rosny, Julien; Toussaint, Renaud; Shapiro, Nikolaï

2014-05-01

Rockfalls, debris flows and rock avalanches represent a major natural hazard for the population in mountainous, volcanic and coastal areas but their direct observation on the field is very dangerous. Recent studies showed that gravitational instabilities can be detected and characterized (volume, duration,...) thanks to the seismic signal they generate. In an avalanche, individual block bouncing and rolling on the ground are expected to generated signals of higher frequencies than the main flow spreading. The identification of the time/frequency signature of individual blocks in the recorded signal remains however difficult. Laboratory experiments were conducted to investigate the acoustic signature of diverse simple sources corresponding to grains falling over thin plates of plexiglas and glass and over rock blocks. The elastic energy emitted by a single bouncing bead into the support was first quantitatively estimated and compared to the potential energy of fall and to the potential energy change during the shock. We obtained simple scaling laws relating the impactor characteristics (size, height of fall, material,...) to the elastic energy and spectral content. Next, we consider the collapse of granular columns made of steel spherical beads onto hard substrates. Initially, these columns were held by a magnetic field allowing to suppress suddenly the cohesion between the beads, and thus to minimize friction effects that would arise from side walls. We varied systematically the column volume, the column aspect ratio (height over length) and the grain size. This is shown to affect the signal envelope and frequency content. In the experiments, accelerometers (1 Hz to 56 kHz) were used to record the signals in a wide frequency range. The experiments were also monitored optically using fast cameras. Eventually, we looked at what types of features in the signal are affected by individual impacts, rolling of beads or by the large scale geometry of the avalanche.

Nonlinear Acoustics in Cicada Mating Calls Enhance Sound Propagation

DTIC Science & Technology

2009-03-01

NUWC-NPT Reprint Report 11,907 1 March 2009 Nonlinear Acoustics in Cicada Mating Calls Enhance Sound Propagation Derke R. Hughes Albert H...vol. 125, no. 2, February 2009. Nonlinear acoustics in cicada mating calls enhance sound propagation Derke R. Hughes,3 Albert H. Nuttall,h Richard A...2008; revised 31 October 2008; accepted 15 November 2008) An analysis of cicada mating calls, measured in field experiments, indicates that the very

Acoustic scattering on spheroidal shapes near boundaries

NASA Astrophysics Data System (ADS)

Miloh, Touvia

2016-11-01

A new expression for the Lamé product of prolate spheroidal wave functions is presented in terms of a distribution of multipoles along the axis of the spheroid between its foci (generalizing a corresponding theorem for spheroidal harmonics). Such an "ultimate" singularity system can be effectively used for solving various linear boundary-value problems governed by the Helmholtz equation involving prolate spheroidal bodies near planar or other boundaries. The general methodology is formally demonstrated for the axisymmetric acoustic scattering problem of a rigid (hard) spheroid placed near a hard/soft wall or inside a cylindrical duct under an axial incidence of a plane acoustic wave.

REMORA 3: The first instrumented fuel experiment with on-line gas composition measurement by acoustic sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lambert, T.; Muller, E.; Federici, E.

With the aim to improve the knowledge of nuclear fuel behaviour, the development of advanced instrumentation used during in-pile experiments in Material Testing Reactor (MTR) is necessary. To obtain data on high Burn-Up MOX fuel performance under transient operating conditions, especially in order to differentiate between the kinetics of fission gas and helium releases and to acquire data on the degradation of the fuel conductivity, a highly instrumented in-pile experiment called REMORA 3 has been conducted by CEA and IES (Southern Electronic Inst. - CNRS - Montpellier 2 Univ.). A rodlet extracted from a fuel rod base irradiated for fivemore » cycles in a French EDF commercial PWR has been re-instrumented with a fuel centerline thermocouple, a pressure transducer and an advanced acoustic sensor. This latter, patented by CEA and IES, is 1 used in addition to pressure measurement to determine the composition of the gases located in the free volume and the molar fractions of fission gas and helium. This instrumented fuel rodlet has been re-irradiated in a specific rig, GRIFFONOS, located in the periphery of the OSIRIS experimental reactor core at CEA Saclay. First of all, an important design stage and test phases have been performed before the irradiation in order to optimize the response and the accuracy of the sensors: - To control the influence of the temperature on the acoustic sensor behaviour, a thermal mock-up has been built. - To determine the temperature of the gas located in the acoustic cavity as a function of the coolant temperature, and the average temperature of the gases located in the rodlet free volume as a function of the linear heat rate, thermal calculations have been achieved. The former temperature is necessary to calculate the molar fractions of the gases and the latter is used to calculate the total amount of released gas from the internal rod pressure measurements. - At the end of the instrumented rod manufacturing, specific internal free

Application of optical interferometry in focused acoustic field measurement

NASA Astrophysics Data System (ADS)

Wang, Yuebing; Sun, Min; Cao, Yonggang; Zhu, Jiang

2018-07-01

Optical interferometry has been successfully applied in measuring acoustic pressures in plane-wave fields and spherical-wave fields. In this paper, the "effective" refractive index for focused acoustic fields was developed, through numerical simulation and experiments, the feasibility of the optical method in measuring acoustic fields of focused transducers was proved. Compared with the results from a membrane hydrophone, it was concluded that the optical method has good spatial resolution and is suitable for detecting focused fields with fluctuant distributions. The influences of a few factors (the generated lamb wave, laser beam directivity, etc.) were analyzed, and corresponding suggestions were proposed for effective application of this technology.

[Adolescents previously involved in Satanism: mental health problems experience].

PubMed

Heathcote, H; Gmeiner, A; Poggenpoel, M

1998-03-01

As far as the phenomena of adolescents previously involved with satanism that experience obstacles in the strive for mental health, no research has previously been done. Adolescents previously involved in satanism, presents behaviour problems like aggressive outbursts depression, "psychosis", or suicide attempts that can even lead to suicide. In the phenomena-analysis semi-structured, phenomenological interviews with the respondents and their parents, were performed. The respondents were requested to write a naive sketch about there life. After the data-control was done, guidelines for nursing staff had been set. The guidelines are set for the management of adolescents that has previously been involved in satanism, and experiences obstacles in their strive for mental health. Interviews with experts in satanism was done, literature in the form of books, magazines and newsclippings were used to verify the findings in the research. The most important guidelines are that: the caregivers have to be reborn Christians; they are not allowed to show, any fear or sympathy; they have to have sufficient knowledge about satanism; the adolescent has to be unconditionally accepted; the caregivers have to work in a team; the adolescents have to be taught to deal with their emotions.

Acoustic landmarks contain more information about the phone string than other frames for automatic speech recognition with deep neural network acoustic model

NASA Astrophysics Data System (ADS)

He, Di; Lim, Boon Pang; Yang, Xuesong; Hasegawa-Johnson, Mark; Chen, Deming

2018-06-01

Most mainstream Automatic Speech Recognition (ASR) systems consider all feature frames equally important. However, acoustic landmark theory is based on a contradictory idea, that some frames are more important than others. Acoustic landmark theory exploits quantal non-linearities in the articulatory-acoustic and acoustic-perceptual relations to define landmark times at which the speech spectrum abruptly changes or reaches an extremum; frames overlapping landmarks have been demonstrated to be sufficient for speech perception. In this work, we conduct experiments on the TIMIT corpus, with both GMM and DNN based ASR systems and find that frames containing landmarks are more informative for ASR than others. We find that altering the level of emphasis on landmarks by re-weighting acoustic likelihood tends to reduce the phone error rate (PER). Furthermore, by leveraging the landmark as a heuristic, one of our hybrid DNN frame dropping strategies maintained a PER within 0.44% of optimal when scoring less than half (45.8% to be precise) of the frames. This hybrid strategy out-performs other non-heuristic-based methods and demonstrate the potential of landmarks for reducing computation.

Non-Data Aided Doppler Shift Estimation for Underwater Acoustic Communication

DTIC Science & Technology

2014-05-01

in underwater acoustic wireless sensor networks . We analyzed the data collected from our experiments using non-data aided (blind) techniques such as...investigated different methods for blind Doppler shift estimation and compensation for a single carrier in underwater acoustic wireless sensor ...distributed underwater sensor networks . Detailed experimental and simulated results based on second order cyclostationary features of the received signals

Acoustic Seal

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Inventor)

2006-01-01

The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

Acoustic seal

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Inventor)

2006-01-01

The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

The Northern Experience of Street-Involved Youth: A Narrative Inquiry

ERIC Educational Resources Information Center

George, Serena D.; O'Neill, Linda K.

2011-01-01

This research explored the experiences of 8 street-involved youth (4 male, 4 female) between the ages of 20 and 27 living in north-central British Columbia. The analysis was carried out in 3 phases based on the narrative approach developed by Lieblich, Tuval-Mashiach, and Zilber (1998). The narratives represented the holistic experiences of the…

Effect of acoustic streaming on the mass transfer from a sublimating sphere

NASA Astrophysics Data System (ADS)

Kawahara, N.; Yarin, A. L.; Brenn, G.; Kastner, O.; Durst, F.

2000-04-01

The effect of the acoustic streaming on the mass transfer from the surface of a sphere positioned in an ultrasonic acoustic levitator is studied both experimentally and theoretically. Acoustic levitation using standing ultrasonic waves is an experimental tool for studying the heat and mass transfer from small solid or liquid samples, because it allows an almost steady positioning of a sample at a fixed location in space. However, the levitator introduces some difficulties. One of the main problems with acoustic levitation is that an acoustic streaming is induced near the sample surface, which affects the heat and mass transfer rates, as characterized by increased Nusselt and Sherwood numbers. The transfer rates are not uniform along the sample surface, and the aim of the present study is to quantify the spatial Sherwood number distribution over the surface of a sphere. The experiments are based on the measurement of the surface shape of a sphere layered with a solid substance as a function of time using a charge-coupled device (CCD) camera with backlighting. The sphere used in this research is a glass sphere layered with a volatile solid substance (naphthalene or camphor). The local mass transfer from the surface both with and without an ultrasonic acoustic field is investigated in order to evaluate the effect of the acoustic streaming. The experimental results are compared with predictions following from the theory outlined [A. L. Yarin, M. Pfaffenlehner, and C. Tropea, J. Fluid Mech. 356, 65 (1998); A. L. Yarin, G. Brenn, O. Kastner, D. Rensink, and C. Tropea, ibid. 399, 151 (1999)] which describes the acoustic field and the resulting acoustic streaming, and the mass transfer at the surface of particles and droplets located in an acoustic levitator. The results are also compared with the experimental data and with the theoretical predictions of Burdukov and Nakoryakov [J. Appl. Mech. Tech. Phys. 6, 51 (1965)], which are valid only in the case of spherical

Speaker verification system using acoustic data and non-acoustic data

DOEpatents

Gable, Todd J [Walnut Creek, CA; Ng, Lawrence C [Danville, CA; Holzrichter, John F [Berkeley, CA; Burnett, Greg C [Livermore, CA

2006-03-21

A method and system for speech characterization. One embodiment includes a method for speaker verification which includes collecting data from a speaker, wherein the data comprises acoustic data and non-acoustic data. The data is used to generate a template that includes a first set of "template" parameters. The method further includes receiving a real-time identity claim from a claimant, and using acoustic data and non-acoustic data from the identity claim to generate a second set of parameters. The method further includes comparing the first set of parameters to the set of parameters to determine whether the claimant is the speaker. The first set of parameters and the second set of parameters include at least one purely non-acoustic parameter, including a non-acoustic glottal shape parameter derived from averaging multiple glottal cycle waveforms.

High-acoustic-impedance tantalum oxide layers for insulating acoustic reflectors.

PubMed

Capilla, Jose; Olivares, Jimena; Clement, Marta; Sangrador, Jesús; Iborra, Enrique; Devos, Arnaud

2012-03-01

This work describes the assessment of the acoustic properties of sputtered tantalum oxide films intended for use as high-impedance films of acoustic reflectors for solidly mounted resonators operating in the gigahertz frequency range. The films are grown by sputtering a metallic tantalum target under different oxygen and argon gas mixtures, total pressures, pulsed dc powers, and substrate biases. The structural properties of the films are assessed through infrared absorption spectroscopy and X-ray diffraction measurements. Their acoustic impedance is assessed by deriving the mass density from X-ray reflectometry measurements and the acoustic velocity from picosecond acoustic spectroscopy and the analysis of the frequency response of the test resonators.

Acousto-optic modulation and opto-acoustic gating in piezo-optomechanical circuits

PubMed Central

Balram, Krishna C.; Davanço, Marcelo I.; Ilic, B. Robert; Kyhm, Ji-Hoon; Song, Jin Dong; Srinivasan, Kartik

2017-01-01

Acoustic wave devices provide a promising chip-scale platform for efficiently coupling radio frequency (RF) and optical fields. Here, we use an integrated piezo-optomechanical circuit platform that exploits both the piezoelectric and photoelastic coupling mechanisms to link 2.4 GHz RF waves to 194 THz (1550 nm) optical waves, through coupling to propagating and localized 2.4 GHz acoustic waves. We demonstrate acousto-optic modulation, resonant in both the optical and mechanical domains, in which waveforms encoded on the RF carrier are mapped to the optical field. We also show opto-acoustic gating, in which the application of modulated optical pulses interferometrically gates the transmission of propagating acoustic pulses. The time-domain characteristics of this system under both pulsed RF and pulsed optical excitation are considered in the context of the different physical pathways involved in driving the acoustic waves, and modelled through the coupled mode equations of cavity optomechanics. PMID:28580373

A Method for Large Eddy Simulation of Acoustic Combustion Instabilities

NASA Astrophysics Data System (ADS)

Wall, Clifton; Moin, Parviz

2003-11-01

A method for performing Large Eddy Simulation of acoustic combustion instabilities is presented. By extending the low Mach number pressure correction method to the case of compressible flow, a numerical method is developed in which the Poisson equation for pressure is replaced by a Helmholtz equation. The method avoids the acoustic CFL condition by using implicit time advancement, leading to large efficiency gains at low Mach number. The method also avoids artificial damping of acoustic waves. The numerical method is attractive for the simulation of acoustics combustion instabilities, since these flows are typically at low Mach number, and the acoustic frequencies of interest are usually low. Additionally, new boundary conditions based on the work of Poinsot and Lele have been developed to model the acoustic effect of a long channel upstream of the computational inlet, thus avoiding the need to include such a channel in the computational domain. The turbulent combustion model used is the Level Set model of Duchamp de Lageneste and Pitsch for premixed combustion. Comparison of LES results to the reacting experiments of Besson et al. will be presented.

Feedback control of acoustic musical instruments: collocated control using physical analogs.

PubMed

Berdahl, Edgar; Smith, Julius O; Niemeyer, Günter

2012-01-01

Traditionally, the average professional musician has owned numerous acoustic musical instruments, many of them having distinctive acoustic qualities. However, a modern musician could prefer to have a single musical instrument whose acoustics are programmable by feedback control, where acoustic variables are estimated from sensor measurements in real time and then fed back in order to influence the controlled variables. In this paper, theory is presented that describes stable feedback control of an acoustic musical instrument. The presentation should be accessible to members of the musical acoustics community who may have limited or no experience with feedback control. First, the only control strategy guaranteed to be stable subject to any musical instrument mobility is described: the sensors and actuators must be collocated, and the controller must emulate a physical analog system. Next, the most fundamental feedback controllers and the corresponding physical analog systems are presented. The effects that these controllers have on acoustic musical instruments are described. Finally, practical design challenges are discussed. A proof explains why changing the resonance frequency of a musical resonance requires much more control power than changing the decay time of the resonance. © 2012 Acoustical Society of America.

On the relationship between acoustic energy density flux near the jet axis and far field acoustic intensity

NASA Technical Reports Server (NTRS)

Maestrello, L.

1973-01-01

By measurement and analysis, the relationship between the distribution of the outflow of acoustic energy over the jet boundary and the far-field intensity is considered. The physical quantity used is the gradient of the pressure evaluated on a geometrical plane at the smallest possible radial distance from the jet axis, but outside the vortical region, in the area where the homogeneous wave equation is reasonably well satisfied. The numerical and experimental procedures involved have been checked out by using a known source. Results indicate that the acoustic power output per unit length of the jet, in the region from which the sound emanates, peaks at approximately 9 diameters downstream. The acoustic emission for a jet Strouhal number of about 0.3 exceeds the emission for all other Strouhal numbers nearly everywhere along the measurement plane. However, the far-field peak intensity distribution obtained from the contribution of each station was found to depend on the spatial extent of the region where sound emanates from the jet, which, in turn, depends more on the far-field angle than on the Strouhal number.

A realization of sound focused personal audio system using acoustic contrast control.

PubMed

Chang, Ji-Ho; Lee, Chan-Hui; Park, Jin-Young; Kim, Yang-Hann

2009-04-01

A personal audio system that does not use earphone or any wire would have great interest and potential impact on the audio industries. In this study, a line array speaker system is used to localize sound in the listening zone. The contrast control [Choi, J.-W. and Kim, Y.-H. (2002). J. Acoust. Soc. Am. 111, 1695-1700] is applied, which is a method to make acoustically bright zone around the user and acoustically dark zone in other regions by maximizing the ratio of acoustic potential energy density between the bright and the dark zone. This ratio is regarded as acoustic contrast, analogous with what is used for optical devices. For the evaluation of the performance of acoustic contrast control, experiments are performed and the results are compared with those of uncontrolled case and time reversal array.

Potential for application of an acoustic camera in particle tracking velocimetry.

PubMed

Wu, Fu-Chun; Shao, Yun-Chuan; Wang, Chi-Kuei; Liou, Jim

2008-11-01

We explored the potential and limitations for applying an acoustic camera as the imaging instrument of particle tracking velocimetry. The strength of the acoustic camera is its usability in low-visibility environments where conventional optical cameras are ineffective, while its applicability is limited by lower temporal and spatial resolutions. We conducted a series of experiments in which acoustic and optical cameras were used to simultaneously image the rotational motion of tracer particles, allowing for a comparison of the acoustic- and optical-based velocities. The results reveal that the greater fluctuations associated with the acoustic-based velocities are primarily attributed to the lower temporal resolution. The positive and negative biases induced by the lower spatial resolution are balanced, with the positive ones greater in magnitude but the negative ones greater in quantity. These biases reduce with the increase in the mean particle velocity and approach minimum as the mean velocity exceeds the threshold value that can be sensed by the acoustic camera.

Acoustic perfect absorption and broadband insulation achieved by double-zero metamaterials

NASA Astrophysics Data System (ADS)

Wang, Xiaole; Luo, Xudong; Zhao, Hui; Huang, Zhenyu

2018-01-01

We report the mechanism for simultaneous realization of acoustic perfect absorption (PA) and broadband insulation (BI) in the acoustic free field by a layered acoustic metamaterial (LAM). The proposed LAM comprises two critically coupled membrane-type acoustic metamaterials sandwiching a porous material layer. Both theoretical and experimental results verify that the proposed LAM sample can achieve nearly PA (98.4% in experiments) at 312 Hz with a thickness of 15 mm (1/73 of wavelength) and BI in the frequency range of 200-1000 Hz with an areal density of 2.2 kg/m2. In addition, the real parts of both the effective dynamic density and bulk modulus reach zero precisely at the critical frequency of 312 Hz, arising from the monopolar eigenmode of LAM. Our work advances the concept of synthetic design of sound absorption and insulation properties of multi-impedance-coupled acoustic systems and promotes membrane-type acoustic metamaterials to more practical engineering applications.

Ultrasound imparted air-recoil resonance (UIAR) method for acoustic power estimation: theory and experiment.

PubMed

Kaiplavil, Sreekumar; Rivens, Ian; ter Haar, Gail

2013-07-01

Ultrasound imparted air-recoil resonance (UIAR), a new method for acoustic power estimation, is introduced with emphasis on therapeutic high-intensity focused ultrasound (HIFU) monitoring applications. Advantages of this approach over existing practices include fast response; electrical and magnetic inertness, and hence MRI compatibility; portability; high damage threshold and immunity to vibration and interference; low cost; etc. The angle of incidence should be fixed for accurate measurement. However, the transducer-detector pair can be aligned in any direction with respect to the force of gravity. In this sense, the operation of the device is orientation independent. The acoustic response of a pneumatically coupled pair of Helmholtz resonators, with one of them acting as the sensor head, is used for the estimation of acoustic power. The principle is valid in the case of pulsed/ burst as well as continuous ultrasound exposure, the former being more sensitive and accurate. An electro-acoustic theory has been developed for describing the dynamics of pressure flow and resonance in the system considering various thermo- viscous loss mechanisms. Experimental observations are found to be in agreement with theoretical results. Assuming the window damage threshold (~10 J·mm(-2)) and accuracy of RF power estimation are the upper and lower scale-limiting factors, the performance of the device was examined for an RF power range of 5 mW to 100 W with a HIFU transducer operating at 1.70 MHz, and an average nonlinearity of ~1.5% was observed. The device is also sensitive to sub-milliwatt powers. The frequency response was analyzed at 0.85, 1.70, 2.55, and 3.40 MHz and the results are presented with respective theoretical estimates. Typical response time is in the millisecond regime. Output drift is about 3% for resonant and 5% for nonresonant modes. The principle has been optimized to demonstrate a general-purpose acoustic power meter.

NORSTAR Project: Norfolk public schools student team for acoustical research

NASA Technical Reports Server (NTRS)

Fortunato, Ronald C.

1987-01-01

Development of the NORSTAR (Norfolk Public Student Team for Acoustical Research) Project includes the definition, design, fabrication, testing, analysis, and publishing the results of an acoustical experiment. The student-run program is based on a space flight organization similar to the Viking Project. The experiment will measure the scattering transfer of momentum from a sound field to spheres in a liquid medium. It is hoped that the experimental results will shed light on a difficult physics problem - the difference in scattering cross section (the overall effect of the sound wave scattering) for solid spheres and hollow spheres of differing wall thicknesses.

Acoustic/infrasonic rocket engine signatures

NASA Astrophysics Data System (ADS)

Tenney, Stephen M.; Noble, John M.; Whitaker, Rodney W.; ReVelle, Douglas O.

2003-09-01

Infrasonics offers the potential of long-range acoustic detection of explosions, missiles and even sounds created by manufacturing plants. The atmosphere attenuates acoustic energy above 20 Hz quite rapidly, but signals below 10 Hz can propagate to long ranges. Space shuttle launches have been detected infrasonically from over 1000 km away and the Concorde airliner from over 400 km. This technology is based on microphones designed to respond to frequencies from .1 to 300 Hz that can be operated outdoors for extended periods of time with out degrading their performance. The US Army Research Laboratory and Los Alamos National Laboratory have collected acoustic and infrasonic signatures of static engine testing of two missiles. Signatures were collected of a SCUD missile engine at Huntsville, AL and a Minuteman engine at Edwards AFB. The engines were fixed vertically in a test stand during the burn. We will show the typical time waveform signals of these static tests and spectrograms for each type. High resolution, 24-bit data were collected at 512 Hz and 16-bit acoustic data at 10 kHz. Edwards data were recorded at 250 Hz and 50 Hz using a Geotech Instruments 24 bit digitizer. Ranges from the test stand varied from 1 km to 5 km. Low level and upper level meteorological data was collected to provide full details of atmospheric propagation during the engine test. Infrasonic measurements were made with the Chaparral Physics Model 2 microphone with porous garden hose attached for wind noise suppression. A B&K microphone was used for high frequency acoustic measurements. Results show primarily a broadband signal with distinct initiation and completion points. There appear to be features present in the signals that would allow identification of missile type. At 5 km the acoustic/infrasonic signal was clearly present. Detection ranges for the types of missile signatures measured will be predicted based on atmospheric modeling. As part of an experiment conducted by ARL

Technical challenges involved in supporting the Lambda Point Experiment

NASA Technical Reports Server (NTRS)

Petrac, D.; Israelsson, U.; Otth, D.; Simmons, L.; Staats, J.; Thompson, A.

1990-01-01

The Lambda Point Experiment (LPE) is one of the instruments included in the U.S. Microgravity Payload Mission 1 planned for one of the Space Shuttle flights in 1992. The objective of the experiment is to measure the heat capacity of liquid helium within a narrow interval around the transition between superfluid and normal helium (the lambda point) with an unprecedented temperature resolution of about 10 to the -10th. Multiple technical challenges are presented in the areas of structural support, safety analysis, and modal frequency tests. This paper describes the technical challenges of JPL's multidisciplinary involvement in support of these experiments in microgravity.

Computational Acoustic Beamforming for Noise Source Identification for Small Wind Turbines.

PubMed

Ma, Ping; Lien, Fue-Sang; Yee, Eugene

2017-01-01

This paper develops a computational acoustic beamforming (CAB) methodology for identification of sources of small wind turbine noise. This methodology is validated using the case of the NACA 0012 airfoil trailing edge noise. For this validation case, the predicted acoustic maps were in excellent conformance with the results of the measurements obtained from the acoustic beamforming experiment. Following this validation study, the CAB methodology was applied to the identification of noise sources generated by a commercial small wind turbine. The simulated acoustic maps revealed that the blade tower interaction and the wind turbine nacelle were the two primary mechanisms for sound generation for this small wind turbine at frequencies between 100 and 630 Hz.

Computational Acoustic Beamforming for Noise Source Identification for Small Wind Turbines

PubMed Central

Lien, Fue-Sang

2017-01-01

This paper develops a computational acoustic beamforming (CAB) methodology for identification of sources of small wind turbine noise. This methodology is validated using the case of the NACA 0012 airfoil trailing edge noise. For this validation case, the predicted acoustic maps were in excellent conformance with the results of the measurements obtained from the acoustic beamforming experiment. Following this validation study, the CAB methodology was applied to the identification of noise sources generated by a commercial small wind turbine. The simulated acoustic maps revealed that the blade tower interaction and the wind turbine nacelle were the two primary mechanisms for sound generation for this small wind turbine at frequencies between 100 and 630 Hz. PMID:28378012

Detection of impulsive sources from an aerostat-based acoustic array data collection system

NASA Astrophysics Data System (ADS)

Prather, Wayne E.; Clark, Robert C.; Strickland, Joshua; Frazier, Wm. Garth; Singleton, Jere

2009-05-01

An aerostat based acoustic array data collection system was deployed at the NATO TG-53 "Acoustic Detection of Weapon Firing" Joint Field Experiment conducted in Bourges, France during the final two weeks of June 2008. A variety of impulsive sources including mortar, artillery, gunfire, RPG, and explosive devices were fired during the test. Results from the aerostat acoustic array will be presented against the entire range of sources.

Impact of Acoustic Standing Waves on Structural Responses: Reverberant Acoustic Testing (RAT) vs. Direct Field Acoustic Testing (DFAT)

NASA Technical Reports Server (NTRS)

Kolaini, Ali R.; Doty, Benjamin; Chang, Zensheu

2012-01-01

Loudspeakers have been used for acoustic qualification of spacecraft, reflectors, solar panels, and other acoustically responsive structures for more than a decade. Limited measurements from some of the recent speaker tests used to qualify flight hardware have indicated significant spatial variation of the acoustic field within the test volume. Also structural responses have been reported to differ when similar tests were performed using reverberant chambers. To address the impact of non-uniform acoustic field on structural responses, a series of acoustic tests were performed using a flat panel and a 3-ft cylinder exposed to the field controlled by speakers and repeated in a reverberant chamber. The speaker testing was performed using multi-input-single-output (MISO) and multi-input-multi-output (MIMO) control schemes with and without the test articles. In this paper the spatial variation of the acoustic field due to acoustic standing waves and their impacts on the structural responses in RAT and DFAT (both using MISO and MIMO controls for DFAT) are discussed in some detail.

Experiences of User Involvement in Mental Health Settings: User Motivations and Benefits.

PubMed

Neech, Sophie G B; Scott, Helen; Priest, Helena M; Bradley, Eleanor J; Tweed, Alison E

2018-05-12

Despite guidance promoting user involvement, meaningful involvement continues to be debated within services. To effectively implement involvement, it is important to acknowledge why users devote time to such activities. This study explores user representatives' experiences of involvement, including motivations and personal benefits. Thirteen user representatives involved in activities such as staff training and interviews were recruited from a UK National Health Service mental health Trust during 2015. Themes within semi-structured interviews were developed using constructivist grounded theory analysis. Memo-writing, process and focused coding, and core categories supported development of the conceptual framework of being a user representative. Being a user representative was inextricably linked to wellness, yet staff governed opportunities. Making a difference to others and giving back were initial motivating factors. Experiences depended on feeling valued, and the theme of transition captured shifts in identity. User representatives reported increased confidence and wellbeing when supported by staff. However, involvement triggered mental health difficulties, and identified need for regular monitoring and reflection of involvement activities and practice. Services should consider coproduction, where users and staff agree together on involvement definitions. Dedicated involvement workers are crucial to supporting individual wellbeing and monitoring involvement. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Two-dimensional water acoustic waveguide based on pressure compensation method

NASA Astrophysics Data System (ADS)

Zheng, Mingye; Chen, Yi; Liu, Xiaoning; Hu, Gengkai

2018-02-01

A two-dimensional (2D) waveguide is a basic facility for experiment measurement due to a much more simplified wave field pattern than that in free space. A waveguide for airborne sound is easily achieved with almost any solid plates. However, the design of a 2D water acoustic waveguide is still challenging because of unavailable solids with a sufficient large impedance difference from water. In this work, a new method of constructing a 2D water acoustic waveguide is proposed based on pressure compensation and has been verified by numerical simulation. A prototype of the water acoustic waveguide is fabricated and complemented by an acoustic pressure scanning system; the measured scattered pressure fields by air and aluminum cylinders both agree quite well with numerical simulations. Most acoustic pressure fields within a frequency range 7 kHz-15 kHz can be measured in this waveguide when the required scanning region is smaller than the aluminum plate area (1800 mm × 800 mm).

An acoustic switch.

PubMed

Vanhille, Christian; Campos-Pozuelo, Cleofé

2014-01-01

The benefits derived from the development of acoustic transistors which act as switches or amplifiers have been reported in the literature. Here we propose a model of acoustic switch. We theoretically demonstrate that the device works: the input signal is totally restored at the output when the switch is on whereas the output signal nulls when the switch is off. The switch, on or off, depends on a secondary acoustic field capable to manipulate the main acoustic field. The model relies on the attenuation effect of many oscillating bubbles on the main travelling wave in the liquid, as well as on the capacity of the secondary acoustic wave to move the bubbles. This model evidences the concept of acoustic switch (transistor) with 100% efficiency. Copyright © 2013 Elsevier B.V. All rights reserved.

KENNEDY SPACE CENTER, FLA. - Researchers are positioned on one of the watercraft being utilized to conduct underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

NASA Image and Video Library

2003-08-19

KENNEDY SPACE CENTER, FLA. - Researchers are positioned on one of the watercraft being utilized to conduct underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

KENNEDY SPACE CENTER, FLA. - Researchers utilize several types of watercraft to conduct underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

NASA Image and Video Library

2003-08-18

KENNEDY SPACE CENTER, FLA. - Researchers utilize several types of watercraft to conduct underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

KENNEDY SPACE CENTER, FLA. - Researchers utilize several types of watercraft to conduct underwater acoustic research in the Launch Complex 39 turn basin near Launch Pad 39A. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

NASA Image and Video Library

2003-08-18

KENNEDY SPACE CENTER, FLA. - Researchers utilize several types of watercraft to conduct underwater acoustic research in the Launch Complex 39 turn basin near Launch Pad 39A. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

KENNEDY SPACE CENTER, FLA. - Dr. Grant Gilmore (left), Dynamac Corp., talks to another member of the research team conducting underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

NASA Image and Video Library

2003-08-18

KENNEDY SPACE CENTER, FLA. - Dr. Grant Gilmore (left), Dynamac Corp., talks to another member of the research team conducting underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

KENNEDY SPACE CENTER, FLA. - Research team members take their places on one of the watercraft being utilized to conduct underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

NASA Image and Video Library

2003-08-19

KENNEDY SPACE CENTER, FLA. - Research team members take their places on one of the watercraft being utilized to conduct underwater acoustic research in the Launch Complex 39 turn basin. Several government agencies, including NASA, NOAA, the Navy, the Coast Guard, and the Florida Fish and Wildlife Commission are involved in the testing. The research involves demonstrations of passive and active sensor technologies, with applications in fields ranging from marine biological research to homeland security. The work is also serving as a pilot project to assess the cooperation between the agencies involved. Equipment under development includes a passive acoustic monitor developed by NASA’s Jet Propulsion Laboratory, and mobile robotic sensors from the Navy’s Mobile Diving and Salvage Unit.

An Inorganic Laboratory Experiment Involving Photochemistry, Liquid Chromatography, and Infrared Spectroscopy.

ERIC Educational Resources Information Center

Post, Elroy W.

1980-01-01

Presents an experiment involving photochemical legand displacement on a metal carbonyl, separation of the product mixture by chromotography, and identification of the components by use of infrared spectroscopy and group theory. The chromatography and spectroscopy are combined as complementary tools in this experiment. (Author/JN)

Acoustic measurements of the spatial and temporal structure of the near-bottom boundary layer in the 1990-1991 STRESS experiment

NASA Astrophysics Data System (ADS)

Lynch, James F.; Irish, James D.; Gross, Thomas F.; Wiberg, Patricia L.; Newhall, Arthur E.; Traykovski, Peter A.; Warren, Joseph D.

1997-08-01

As part of the 1990-1991 Sediment TRansport Events on Shelves and Slopes (STRESS) experiment, a 5 MHz Acoustic BackScatter System (ABSS) was deployed in 90 m of water to measure vertical profiles of near-bottom suspended sediment concentration. By looking at the vertical profile of concentration from 0 to 50 cm above bottom (cmab) with 1 cm vertical resolution, the ABSS was able to examine the detailed structure of the bottom boundary layer created by combined wave and current stresses. The acoustic profiles clearly showed the wave-current boundary layer, which extends to (order) 10 cmab. The profiles also showed evidence of an "intermediate" boundary layer, also influenced by combined wave and current stresses, just above the wave-current boundary layer. This paper examines the boundary-layer structure by comparing acoustic data obtained by the authors to a 1-D eddy viscosity model formulation. Specifically, these data are compared to a simple extension of the Grant-Glenn-Madsen model formulation. Also of interest is the appearance of apparently 3-D "advective plume" structures in these data. This is an interesting feature in a site which was initially chosen to be a good example of (temporally averaged) 1-D bottom boundary-layer dynamics. Computer modeling and sector-scanning sonar images are presented to justify the plausibility of observing 3-D structure at the STRESS site. 1997 Elsevier Science Ltd

Acoustic tweezers via sub-time-of-flight regime surface acoustic waves.

PubMed

Collins, David J; Devendran, Citsabehsan; Ma, Zhichao; Ng, Jia Wei; Neild, Adrian; Ai, Ye

2016-07-01

Micrometer-scale acoustic waves are highly useful for refined optomechanical and acoustofluidic manipulation, where these fields are spatially localized along the transducer aperture but not along the acoustic propagation direction. In the case of acoustic tweezers, such a conventional acoustic standing wave results in particle and cell patterning across the entire width of a microfluidic channel, preventing selective trapping. We demonstrate the use of nanosecond-scale pulsed surface acoustic waves (SAWs) with a pulse period that is less than the time of flight between opposing transducers to generate localized time-averaged patterning regions while using conventional electrode structures. These nodal positions can be readily and arbitrarily positioned in two dimensions and within the patterning region itself through the imposition of pulse delays, frequency modulation, and phase shifts. This straightforward concept adds new spatial dimensions to which acoustic fields can be localized in SAW applications in a manner analogous to optical tweezers, including spatially selective acoustic tweezers and optical waveguides.

Considerations for acoustic emission monitoring of spherical Kevlar/epoxy composite pressure vessels

NASA Technical Reports Server (NTRS)

Hamstad, M. A.; Patterson, R. G.

1977-01-01

We are continuing to research the applications of acoustic emission testing for predicting burst pressure of filament-wound Kevlar 49/epoxy pressure vessels. This study has focused on three specific areas. The first area involves development of an experimental technique and the proper instrumentation to measure the energy given off by the acoustic emission transducer per acoustic emission burst. The second area concerns the design of a test fixture in which to mount the composite vessel so that the acoustic emission transducers are held against the outer surface of the composite. Included in this study area is the calibration of the entire test setup including couplant, transducer, electronics, and the instrument measuring the energy per burst. In the third and final area of this study, we consider the number, location, and sensitivity of the acoustic emission transducers used for proof testing composite pressure vessels.

Acoustic Full Waveform Inversion to Characterize Near-surface Chemical Explosions

NASA Astrophysics Data System (ADS)

Kim, K.; Rodgers, A. J.

2015-12-01

Recent high-quality, atmospheric overpressure data from chemical high-explosive experiments provide a unique opportunity to characterize near-surface explosions, specifically estimating yield and source time function. Typically, yield is estimated from measured signal features, such as peak pressure, impulse, duration and/or arrival time of acoustic signals. However, the application of full waveform inversion to acoustic signals for yield estimation has not been fully explored. In this study, we apply a full waveform inversion method to local overpressure data to extract accurate pressure-time histories of acoustics sources during chemical explosions. A robust and accurate inversion technique for acoustic source is investigated using numerical Green's functions that take into account atmospheric and topographic propagation effects. The inverted pressure-time history represents the pressure fluctuation at the source region associated with the explosion, and thus, provides a valuable information about acoustic source mechanisms and characteristics in greater detail. We compare acoustic source properties (i.e., peak overpressure, duration, and non-isotropic shape) of a series of explosions having different emplacement conditions and investigate the relationship of the acoustic sources to the yields of explosions. The time histories of acoustic sources may refine our knowledge of sound-generation mechanisms of shallow explosions, and thereby allow for accurate yield estimation based on acoustic measurements. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Acoustic levitation of an object larger than the acoustic wavelength.

PubMed

Andrade, Marco A B; Okina, Fábio T A; Bernassau, Anne L; Adamowski, Julio C

2017-06-01

Levitation and manipulation of objects by sound waves have a wide range of applications in chemistry, biology, material sciences, and engineering. However, the current acoustic levitation techniques are mainly restricted to particles that are much smaller than the acoustic wavelength. In this work, it is shown that acoustic standing waves can be employed to stably levitate an object much larger than the acoustic wavelength in air. The levitation of a large slightly curved object weighting 2.3 g is demonstrated by using a device formed by two 25 kHz ultrasonic Langevin transducers connected to an aluminum plate. The sound wave emitted by the device provides a vertical acoustic radiation force to counteract gravity and a lateral restoring force that ensure horizontal stability to the levitated object. In order to understand the levitation stability, a numerical model based on the finite element method is used to determine the acoustic radiation force that acts on the object.

A single-scattering correction for the seismo-acoustic parabolic equation.

PubMed

Collins, Michael D

2012-04-01

An efficient single-scattering correction that does not require iterations is derived and tested for the seismo-acoustic parabolic equation. The approach is applicable to problems involving gradual range dependence in a waveguide with fluid and solid layers, including the key case of a sloping fluid-solid interface. The single-scattering correction is asymptotically equivalent to a special case of a single-scattering correction for problems that only have solid layers [Küsel et al., J. Acoust. Soc. Am. 121, 808-813 (2007)]. The single-scattering correction has a simple interpretation (conservation of interface conditions in an average sense) that facilitated its generalization to problems involving fluid layers. Promising results are obtained for problems in which the ocean bottom interface has a small slope.

Some limitations on processing materials in acoustic levitation devices

NASA Technical Reports Server (NTRS)

Oran, W. A.; Witherow, W. K.; Ross, B. B.; Rush, J. E.

1979-01-01

The spot heating of samples, suspended in an acoustic field, was investigated to determine if the technique could be used to process materials. A single axis resonance device operating in air at 25 C with an rms pressure maximum of 160 to 170 db was used in the experiments. The heat flow from a hot object suspended in a levitation node is dominated by the effects of the field, with the heat loss approximately 20 times larger than that due to natural convection. The acoustic forces which suspend the body at a node also serve to eject the heated air. The coupling between the locally heated region around the body and the acoustic field results in instabilities in both the pressure wave and force field. The investigations indicated the extreme difficulties in developing a materials processing device based on acoustic/spot heating for use in a terrestrial environment.

Broadband acoustic properties of a murine skull.

PubMed

Estrada, Héctor; Rebling, Johannes; Turner, Jake; Razansky, Daniel

2016-03-07

It has been well recognized that the presence of a skull imposes harsh restrictions on the use of ultrasound and optoacoustic techniques in the study, treatment and modulation of the brain function. We propose a rigorous modeling and experimental methodology for estimating the insertion loss and the elastic constants of the skull over a wide range of frequencies and incidence angles. A point-source-like excitation of ultrawideband acoustic radiation was induced via the absorption of nanosecond duration laser pulses by a 20 μm diameter microsphere. The acoustic waves transmitted through the skull are recorded by a broadband, spherically focused ultrasound transducer. A coregistered pulse-echo ultrasound scan is subsequently performed to provide accurate skull geometry to be fed into an acoustic transmission model represented in an angular spectrum domain. The modeling predictions were validated by measurements taken from a glass cover-slip and ex vivo adult mouse skulls. The flexible semi-analytical formulation of the model allows for seamless extension to other transducer geometries and diverse experimental scenarios involving broadband acoustic transmission through locally flat solid structures. It is anticipated that accurate quantification and modeling of the skull transmission effects would ultimately allow for skull aberration correction in a broad variety of applications employing transcranial detection or transmission of high frequency ultrasound.

Cruise Report: Long-Range Ocean Acoustic Propagation EXperiment (LOAPEX)

DTIC Science & Technology

2005-04-01

starboard side was used. Both ends of the slip line shown ran through the crane hook to keep them vertical; a strip of masking tape was put around the...2150-3550 m nominal) with a 20-element, 700-in long array (3570- 4270 m nominal) to span the lower caustics in the acoustic arrival pattern with a...during the cruise. The critical equipment belonging to the ship included the stem A-frame, starboard A-frame, both of the ship’s cranes , CTD/rosette

Simulation of Acoustic Scattering from a Trailing Edge

NASA Technical Reports Server (NTRS)

Singer, Bart A.; Brentner, Kenneth S.; Lockard, David P.; Lilley, Geoffrey M.

1999-01-01

Three model problems were examined to assess the difficulties involved in using a hybrid scheme coupling flow computation with the the Ffowcs Williams and Hawkings equation to predict noise generated by vortices passing over a sharp edge. The results indicate that the Ffowcs Williams and Hawkings equation correctly propagates the acoustic signals when provided with accurate flow information on the integration surface. The most difficult of the model problems investigated inviscid flow over a two-dimensional thin NACA airfoil with a blunt-body vortex generator positioned at 98 percent chord. Vortices rolled up downstream of the blunt body. The shed vortices possessed similarities to large coherent eddies in boundary layers. They interacted and occasionally paired as they convected past the sharp trailing edge of the airfoil. The calculations showed acoustic waves emanating from the airfoil trailing edge. Acoustic directivity and Mach number scaling are shown.

Acoustically excited heated jets. 1: Internal excitation

NASA Technical Reports Server (NTRS)

Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Salikuddin, M.; Morris, P. J.

1988-01-01

The effects of relatively strong upstream acoustic excitation on the mixing of heated jets with the surrounding air are investigated. To determine the extent of the available information on experiments and theories dealing with acoustically excited heated jets, an extensive literature survey was carried out. The experimental program consisted of flow visualization and flowfield velocity and temperature measurements for a broad range of jet operating and flow excitation conditions. A 50.8-mm-diam nozzle was used for this purpose. Parallel to the experimental study, an existing theoretical model of excited jets was refined to include the region downstream of the jet potential core. Excellent agreement was found between theory and experiment in moderately heated jets. However, the theory has not yet been confirmed for highly heated jets. It was found that the sensitivity of heated jets to upstream acoustic excitation varies strongly with the jet operating conditions and that the threshold excitation level increases with increasing jet temperature. Furthermore, the preferential Strouhal number is found not to change significantly with a change of the jet operating conditions. Finally, the effects of the nozzle exit boundary layer thickness appear to be similar for both heated and unheated jets at low Mach numbers.

ACOUSTICS IN ARCHITECTURAL DESIGN, AN ANNOTATED BIBLIOGRAPHY ON ARCHITECTURAL ACOUSTICS.

ERIC Educational Resources Information Center

DOELLE, LESLIE L.

THE PURPOSE OF THIS ANNOTATED BIBLIOGRAPHY ON ARCHITECTURAL ACOUSTICS WAS--(1) TO COMPILE A CLASSIFIED BIBLIOGRAPHY, INCLUDING MOST OF THOSE PUBLICATIONS ON ARCHITECTURAL ACOUSTICS, PUBLISHED IN ENGLISH, FRENCH, AND GERMAN WHICH CAN SUPPLY A USEFUL AND UP-TO-DATE SOURCE OF INFORMATION FOR THOSE ENCOUNTERING ANY ARCHITECTURAL-ACOUSTIC DESIGN…

Comment on "Acoustical observation of bubble oscillations induced by bubble popping"

NASA Astrophysics Data System (ADS)

Blanc, É.; Ollivier, F.; Antkowiak, A.; Wunenburger, R.

2015-03-01

We have reproduced the experiment of acoustic monitoring of spontaneous popping of single soap bubbles standing in air reported by Ding et al. [2aa Phys. Rev. E 75, 041601 (2007), 10.1103/PhysRevE.75.041601]. By using a single microphone and two different signal acquisition systems recording in parallel the signal at the microphone output, among them the system used by Ding et al., we have experimentally evidenced that the acoustic precursors of bubble popping events detected by Ding et al. actually result from an acausal artifact of the signal processing performed by their acquisition system which lies outside of its prescribed working frequency range. No acoustic precursor of popping could be evidenced with the microphone used in these experiments, whose sensitivity is 1 V Pa-1 and frequency range is 500 Hz-100 kHz.

Acoustic richness modulates the neural networks supporting intelligible speech processing.

PubMed

Lee, Yune-Sang; Min, Nam Eun; Wingfield, Arthur; Grossman, Murray; Peelle, Jonathan E

2016-03-01

The information contained in a sensory signal plays a critical role in determining what neural processes are engaged. Here we used interleaved silent steady-state (ISSS) functional magnetic resonance imaging (fMRI) to explore how human listeners cope with different degrees of acoustic richness during auditory sentence comprehension. Twenty-six healthy young adults underwent scanning while hearing sentences that varied in acoustic richness (high vs. low spectral detail) and syntactic complexity (subject-relative vs. object-relative center-embedded clause structures). We manipulated acoustic richness by presenting the stimuli as unprocessed full-spectrum speech, or noise-vocoded with 24 channels. Importantly, although the vocoded sentences were spectrally impoverished, all sentences were highly intelligible. These manipulations allowed us to test how intelligible speech processing was affected by orthogonal linguistic and acoustic demands. Acoustically rich speech showed stronger activation than acoustically less-detailed speech in a bilateral temporoparietal network with more pronounced activity in the right hemisphere. By contrast, listening to sentences with greater syntactic complexity resulted in increased activation of a left-lateralized network including left posterior lateral temporal cortex, left inferior frontal gyrus, and left dorsolateral prefrontal cortex. Significant interactions between acoustic richness and syntactic complexity occurred in left supramarginal gyrus, right superior temporal gyrus, and right inferior frontal gyrus, indicating that the regions recruited for syntactic challenge differed as a function of acoustic properties of the speech. Our findings suggest that the neural systems involved in speech perception are finely tuned to the type of information available, and that reducing the richness of the acoustic signal dramatically alters the brain's response to spoken language, even when intelligibility is high. Copyright © 2015 Elsevier

Design and Performance of AN Electrostrictive-Polymer Acoustic Actuator

NASA Astrophysics Data System (ADS)

Heydt, R.; Kornbluh, R.; Pelrine, R.; Mason, V.

1998-08-01

This paper discusses a novel electroacoustic transducer that uses the electrostrictive response of a polymer film. The active element of the transducer is a thin silicone-rubber film, with graphite powder electrodes on each side, that forms an array of bubble-like radiating elements. In experiments, radiated acoustic pressure and harmonic distortion of the electrostrictive-film actuator were measured in the frequency band 50-2000 Hz. A simple acoustic model was also developed to study the effect of various design and operating parameters on the actuator performance. Preliminary results from the experiments and simulations show that the electrostrictive-polymer-film actuator has the potential to be an efficient, compact, and lightweight electroacoustic transducer.

AST Launch Vehicle Acoustics

NASA Technical Reports Server (NTRS)

Houston, Janice; Counter, D.; Giacomoni, D.

2015-01-01

The liftoff phase induces acoustic loading over a broad frequency range for a launch vehicle. These external acoustic environments are then used in the prediction of internal vibration responses of the vehicle and components which result in the qualification levels. Thus, predicting these liftoff acoustic (LOA) environments is critical to the design requirements of any launch vehicle. If there is a significant amount of uncertainty in the predictions or if acoustic mitigation options must be implemented, a subscale acoustic test is a feasible pre-launch test option to verify the LOA environments. The NASA Space Launch System (SLS) program initiated the Scale Model Acoustic Test (SMAT) to verify the predicted SLS LOA environments and to determine the acoustic reduction with an above deck water sound suppression system. The SMAT was conducted at Marshall Space Flight Center and the test article included a 5% scale SLS vehicle model, tower and Mobile Launcher. Acoustic and pressure data were measured by approximately 250 instruments. The SMAT liftoff acoustic results are presented, findings are discussed and a comparison is shown to the Ares I Scale Model Acoustic Test (ASMAT) results.

Acoustic neuroma

MedlinePlus

... Cerebellopontine angle tumor; Angle tumor; Hearing loss - acoustic; Tinnitus - acoustic ... that makes it hard to hear conversations Ringing ( tinnitus ) in the affected ear Less common symptoms include: ...

Educational Support System for Experiments Involving Construction of Sound Processing Circuits

ERIC Educational Resources Information Center

Takemura, Atsushi

2012-01-01

This paper proposes a novel educational support system for technical experiments involving the production of practical electronic circuits for sound processing. To support circuit design and production, each student uses a computer during the experiments, and can learn circuit design, virtual circuit making, and real circuit making. In the…

Double negative acoustic metastructure for attenuation of acoustic emissions

NASA Astrophysics Data System (ADS)

Kumar, Sanjay; Bhushan, Pulak; Prakash, Om; Bhattacharya, Shantanu

2018-03-01

Acoustic metamaterials hold great potential for attenuation of low frequency acoustic emissions. However, a fundamental challenge is achieving high transmission loss over a broad frequency range. In this work, we report a double negative acoustic metastructure for absorption of low frequency acoustic emissions in an aircraft. This is achieved by utilizing a periodic array of hexagonal cells interconnected with a neck and mounted with an elastic membrane on both ends. An average transmission loss of 56 dB under 500 Hz and an overall absorption of over 48% have been realized experimentally. The negative mass density is derived from the dipolar resonances created as a result of the in-phase movement of the membranes. Further, the negative bulk modulus is ascribed to the combined effect of out-of-phase acceleration of the membranes and the Helmholtz resonator. The proposed metastructure enables absorption of low frequency acoustic emissions with improved functionality that is highly desirable for varied applications.

Nonlinear acoustic experiments for landmine detection: the significance of the top-plate normal modes

NASA Astrophysics Data System (ADS)

Korman, Murray S.; Alberts, W. C. K., II; Sabatier, James M.

2004-09-01

In nonlinear acoustic detection experiments involving a buried inert VS 2.2 anti-tank landmine, airborne sound at two closely spaced primary frequencies f1 and f2 couple into the ground and interact nonlinearly with the soil-top pressure plate interface. Scattering generates soil vibration at the surface at the combination frequencies | m f1 +- n f2 | , where m and n are integers. The normal component of the particle velocity at the soil surface has been measured with a laser Doppler velocimeter (LDV) and with a geophone by Sabatier et. al. [SPIE Proceedings Vol. 4742, (695-700), 2002; Vol. 5089, (476-486), 2003] at the gravel lane test site. Spatial profiles of the particle velocity measured for both primary components and for various combination frequencies indicate that the modal structure of the mine is playing an important role. Here, an experimental modal analysis is performed on a VS 1.6 inert anti-tank mine that is resting on sand but is not buried. Five top-plate mode shapes are described. The mine is then buried in dry finely sifted natural loess soil and excited at f1 = 120 Hz and f2 = 130 Hz. Spatial profiles at the primary components and the nonlinearly generated f1 - (f2 - f1) component are characterized by a single peak. For the 2f1+f2 and 2f2 + f1 components, the doubly peaked profiles can be attributed to the familiar mode shape of a timpani drum (that is shifted lower in frequency due to soil mass loading). Other nonlinear profiles appear to be due to a mixture of modes. This material is based upon work supported by the U. S. Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate under Contract DAAB15-02-C-0024.

Acoustic and perceptual cues for compound-phrasal contrasts in Vietnamese.

PubMed

Nguyen, Anh-Thu T; Ingram, John C L

2007-09-01

This paper reports two series of experiments that examined the phonetic correlates of lexical stress in Vietnamese compounds in comparison to their phrasal constructions. In the first series of experiments, acoustic and perceptual characteristics of Vietnamese compound words and their phrasal counterparts were investigated on five likely acoustic correlates of stress or prominence (f0 range and contour, duration, intensity and spectral slope, vowel reduction), elicited under two distinct speaking conditions: a "normal speaking" condition and a "maximum contrast" condition which encouraged speakers to employ prosodic strategies for disambiguation. The results suggested that Vietnamese lacks phonetic resources for distinguishing compounds from phrases lexically and that native speakers may employ a phrase-level prosodic disambiguation strategy (juncture marking), when required to do so. However, in a second series of experiments, minimal pairs of bisyllabic coordinative compounds with reversible syllable positions were examined for acoustic evidence of asymmetrical prominence relations. Clear evidence of asymmetric prominences in coordinative compounds was found, supporting independent results obtained from an analysis of reduplicative compounds and tone sandhi in Vietnamese [Nguye;n and Ingram, 2006]. A reconciliation of these apparently conflicting findings on word stress in Vietnamese is presented and discussed.

Study Acoustic Emissions from Composites

NASA Technical Reports Server (NTRS)

Walker, James L.; Workman, Gary L.

1997-01-01

The nondestructive evaluation (NDE) of future propulsion systems utilizing advanced composite structures for the storage of cryogenic fuels, such as liquid hydrogen or oxygen, presents many challenges. Economic justification for these structures requires, light weight, reusable components with an infrastructure allowing periodic evaluation of structural integrity after enduring demanding stresses during operation. A major focus has been placed on the use of acoustic emission NDE to detect propagating defects, in service, necessitating an extensive study into characterizing the nature of acoustic signal propagation at very low temperatures and developing the methodology of applying AE sensors to monitor cryogenic components. This work addresses the question of sensor performance in the cryogenic environment. Problems involving sensor mounting, spectral response and durability are addressed. The results of this work provides a common point of measure from which sensor selection can be made when testing composite components at cryogenic temperatures.

Reducing the dimensions of acoustic devices using anti-acoustic-null media

NASA Astrophysics Data System (ADS)

Li, Borui; Sun, Fei; He, Sailing

2018-02-01

An anti-acoustic-null medium (anti-ANM), a special homogeneous medium with anisotropic mass density, is designed by transformation acoustics (TA). Anti-ANM can greatly compress acoustic space along the direction of its main axis, where the size compression ratio is extremely large. This special feature can be utilized to reduce the geometric dimensions of classic acoustic devices. For example, the height of a parabolic acoustic reflector can be greatly reduced. We also design a brass-air structure on the basis of the effective medium theory to materialize the anti-ANM in a broadband frequency range. Numerical simulations verify the performance of the proposed anti-ANM.

North Pacific Acoustic Laboratory: Deep Water Acoustic Propagation in the Philippine Sea

DTIC Science & Technology

2016-06-21

the "Special Issue on Deep-water Ocean Acoustics" in the Journal of the Acoustical Society of America (Vol. 134, No . 4, Pt. 2 of 2 , October20 13...also listed. Fourteen (14) of these publications appeared in the " Special Issue on Deep-water Ocean Acoustics" in the Journal of the Acoustical

Relationships between objective acoustic indices and acoustic comfort evaluation in nonacoustic spaces

NASA Astrophysics Data System (ADS)

Kang, Jian

2004-05-01

Much attention has been paid to acoustic spaces such as concert halls and recording studios, whereas research on nonacoustic buildings/spaces has been rather limited, especially from the viewpoint of acoustic comfort. In this research a series of case studies has been carried out on this topic, considering various spaces including shopping mall atrium spaces, library reading rooms, football stadia, swimming spaces, churches, dining spaces, as well as urban open public spaces. The studies focus on the relationships between objective acoustic indices such as sound pressure level and reverberation time and perceptions of acoustic comfort. The results show that the acoustic atmosphere is an important consideration in such spaces and the evaluation of acoustic comfort may vary considerably even if the objective acoustic indices are the same. It is suggested that current guidelines and technical regulations are insufficient in terms of acoustic design of these spaces, and the relationships established from the case studies between objective and subjective aspects would be useful for developing further design guidelines. [Work supported partly by the British Academy.

Shear dilatancy and acoustic emission in dry and saturated granular materials

NASA Astrophysics Data System (ADS)

Brodsky, E. E.; Siman-Tov, S.

2017-12-01

Shearing of granular materials plays a strong role in naturally sheared systems as landslides and faults. Many works on granular flows have concentrated on dry materials, but relatively little work has been done on water saturated sands. Here we experimentally investigate dry versus saturated quartz-rich sand to understand the effect of the fluid medium on the rheology and acoustic waves emission of the sheared sand. The sand was sheared in a rotary shear rheometer under applied constant normal stress boundary at low (100 µm/s) to high (1 m/s) velocities. Mechanical, acoustic data and deformation were continuously recorded and imaged. For dry and water saturated experiments the granular volume remains constant for low shear velocities ( 10-3 m/s) and increases during shearing at higher velocities ( 1 m/s). Continuous imaging of the sheared sand show that the steady state shear band thickness is thicker during the high velocity steps. No significant change observed in the shear band thickness between dry and water saturated experiments. In contrast, the amount of dilation during water saturated experiments is about half the value measured for dry material. The measured decrease cannot be explained by shear band thickness change as such is not exist. However, the reduced dilation is supported by our acoustic measurements. In general, the event rate and acoustic event amplitudes increase with shear velocity. While isolated events are clearly detected during low velocities at higher the events overlap, resulting in a noisy signal. Although detection is better for saturated experiments, during the high velocity steps the acoustic energy measured from the signal is lower compared to that recorded for dry experiments. We suggest that the presence of fluid suppresses grain motion and particles impacts leading to mild increase in the internal pressure and therefore for the reduced dilation. In addition, the viscosity of fluids may influence the internal pressure via

Acoustic Microfluidics for Bioanalytical Application

NASA Astrophysics Data System (ADS)

Lopez, Gabriel

2013-03-01

This talk will present new methods the use of ultrasonic standing waves in microfluidic systems to manipulate microparticles for the purpose of bioassays and bioseparations. We have recently developed multi-node acoustic focusing flow cells that can position particles into many parallel flow streams and have demonstrated the potential of such flow cells in the development of high throughput, parallel flow cytometers. These experiments show the potential for the creation of high throughput flow cytometers in applications requiring high flow rates and rapid detection of rare cells. This talk will also present the development of elastomeric capture microparticles and their use in acoustophoretic separations. We have developed simple methods to form elastomeric particles that are surface functionalized with biomolecular recognition reagents. These compressible particles exhibit negative acoustic contrast in ultrasound when suspended in aqueous media, blood serum or diluted blood. These particles can be continuously separated from cells by flowing them through a microfluidic device that uses an ultrasonic standing wave to align the blood cells, which exhibit positive acoustic contrast, at a node in the acoustic pressure distribution while aligning the negative acoustic contrast elastomeric particles at the antinodes. Laminar flow of the separated particles to downstream collection ports allows for collection of the separated negative contrast particles and cells. Separated elastomeric particles were analyzed via flow cytometry to demonstrate nanomolar detection for prostate specific antigen in aqueous buffer and picomolar detection for IgG in plasma and diluted blood samples. This approach has potential applications in the development of rapid assays that detect the presence of low concentrations of biomarkers (including biomolecules and cells) in a number of biological sample types. We acknowledge support through the NSF Research Triangle MRSEC.

Embedded and conventional ultrasonic sensors for monitoring acoustic emission during thermal fatigue

NASA Astrophysics Data System (ADS)

Trujillo, Blaine; Zagrai, Andrei

2016-04-01

Acoustic emission is widely used for monitoring pressure vessels, pipes, critical infrastructure, as well as land, sea and air vehicles. It is one of dominant approaches to explore material degradation under fatigue and events leading to material fracture. Addressing a recent interest in structural health monitoring of space vehicles, a need has emerged to evaluate material deterioration due to thermal fatigue during spacecraft atmospheric reentry. Thermal fatigue experiments were conducted, in which aluminum plates were subjected to localized heating and acoustic emission was monitoring by embedded and conventional acoustic emission sensors positioned at various distances from a heat source. At the same time, surface temperature of aluminum plates was monitored using an IR camera. Acoustic emission counts collected by embedded sensors were compared to counts measured with conventional acoustic emission sensors. Both types of sensors show noticeable increase of acoustic emission activity as localized heating source was applied to aluminum plates. Experimental data demonstrate correlation between temperature increase on the surface of the plates and increase in measured acoustic emission activity. It is concluded that under particular conditions, embedded piezoelectric wafer active sensors can be used for acoustic emission monitoring of thermally-induced structural degradation.

Virtual acoustics displays

NASA Astrophysics Data System (ADS)

Wenzel, Elizabeth M.; Fisher, Scott S.; Stone, Philip K.; Foster, Scott H.

1991-03-01

The real time acoustic display capabilities are described which were developed for the Virtual Environment Workstation (VIEW) Project at NASA-Ames. The acoustic display is capable of generating localized acoustic cues in real time over headphones. An auditory symbology, a related collection of representational auditory 'objects' or 'icons', can be designed using ACE (Auditory Cue Editor), which links both discrete and continuously varying acoustic parameters with information or events in the display. During a given display scenario, the symbology can be dynamically coordinated in real time with 3-D visual objects, speech, and gestural displays. The types of displays feasible with the system range from simple warnings and alarms to the acoustic representation of multidimensional data or events.

Virtual acoustics displays

NASA Technical Reports Server (NTRS)

Wenzel, Elizabeth M.; Fisher, Scott S.; Stone, Philip K.; Foster, Scott H.

1991-01-01

The real time acoustic display capabilities are described which were developed for the Virtual Environment Workstation (VIEW) Project at NASA-Ames. The acoustic display is capable of generating localized acoustic cues in real time over headphones. An auditory symbology, a related collection of representational auditory 'objects' or 'icons', can be designed using ACE (Auditory Cue Editor), which links both discrete and continuously varying acoustic parameters with information or events in the display. During a given display scenario, the symbology can be dynamically coordinated in real time with 3-D visual objects, speech, and gestural displays. The types of displays feasible with the system range from simple warnings and alarms to the acoustic representation of multidimensional data or events.

Modulated acoustic radiation pressure and stress-coupling projections

NASA Astrophysics Data System (ADS)

Marston, Philip L.; Thiessen, David B.

2005-09-01

Low-frequency deformation can be induced at a single frequency using radiation stress oscillations of double-sideband suppressed-carrier ultrasound [P. L. Marston and R. E. Apfel, J. Acoust. Soc. Am. 67, 27 (1980)]. The transducer voltage is proportional to a product of low- and high-frequency sine waves. To anticipate the shape and magnitude of induced deformations, it is helpful to expand the distribution of the radiation stress on the object to be deformed as a series of projections [P. L. Marston, J. Acoust. Soc. Am. 67, 15 (1980)]. Stress projections are also useful for unmodulated waves: the radiation force is an example. In addition to spherical and nearly spherical objects, recent experiments and calculations have concerned cylindrical objects [S. F. Morse, D. B. Thiessen, and P. L. Marston, Phys. Fluids 8, 3 (1996); W. Wei, D. B. Thiessen, and P. L. Marston, J. Acoust. Soc. Am. 116, 202 (2004)]. In standing waves the following projections are nonvanishing in the low acoustic frequency limit for appropriately situated dense objects: radial projection [M. J. Marr-Lyon, D. B. Thiessen, and P. L. Marston, Phys. Rev. Lett. 86, 2293 (2001)] and quadrupole projection [P. L. Marston et al., J. Acoust. Soc. Am. 69, 1499 (1981)].

Acoustics and hydrodynamics of a drop impact on a water surface

NASA Astrophysics Data System (ADS)

Chashechkin, Yu. D.; Prokhorov, V. E.

2017-01-01

Hydrodynamic and acoustic processes associated with a drop impact on a water surface were studied experimentally. Acoustic signals were detected underwater (with a hydrophone) and in air (with a microphone), the flow pattern was recorded with a high-speed camera, and the surface perturbation was monitored with a laser detector. The dimensionless parameters of flows (Reynolds, Froude, and Weber numbers) induced by the impact varied with fall height within the ranges of 5000 < Re < 20000, 20 < Fr < 350, and 70 < We < 1000. The sequence of acoustic signals incorporated an impact pulse at the moment of contact between a drop and the surface and a series of acoustic packets attributable to the resonance emission of gas cavities. The top of the impact pulse, which was detected clearly in the entire fall height range, had a complex structure with short high-frequency and longer low-frequency oscillations. The total number and the parameters of emitted acoustic packets depended to a considerable extent on the fall height. The cases of lacking, one-time, and repeated emission of packets were noted in a series of experiments performed at a constant fall height. The analysis of video data showed that the signal variability was induced by considerable differences in the scenarios of water entry of a drop, which assumed an ovoid shape at the end trajectory segment, in the mentioned experiments.

Simulation of Acoustics for Ares I Scale Model Acoustic Tests

NASA Technical Reports Server (NTRS)

Putnam, Gabriel; Strutzenberg, Louise L.

2011-01-01

The Ares I Scale Model Acoustics Test (ASMAT) is a series of live-fire tests of scaled rocket motors meant to simulate the conditions of the Ares I launch configuration. These tests have provided a well documented set of high fidelity acoustic measurements useful for validation including data taken over a range of test conditions and containing phenomena like Ignition Over-Pressure and water suppression of acoustics. To take advantage of this data, a digital representation of the ASMAT test setup has been constructed and test firings of the motor have been simulated using the Loci/CHEM computational fluid dynamics software. Results from ASMAT simulations with the rocket in both held down and elevated configurations, as well as with and without water suppression have been compared to acoustic data collected from similar live-fire tests. Results of acoustic comparisons have shown good correlation with the amplitude and temporal shape of pressure features and reasonable spectral accuracy up to approximately 1000 Hz. Major plume and acoustic features have been well captured including the plume shock structure, the igniter pulse transient, and the ignition overpressure.

Generation and control of sound bullets with a nonlinear acoustic lens.

PubMed

Spadoni, Alessandro; Daraio, Chiara

2010-04-20

Acoustic lenses are employed in a variety of applications, from biomedical imaging and surgery to defense systems and damage detection in materials. Focused acoustic signals, for example, enable ultrasonic transducers to image the interior of the human body. Currently however the performance of acoustic devices is limited by their linear operational envelope, which implies relatively inaccurate focusing and low focal power. Here we show a dramatic focusing effect and the generation of compact acoustic pulses (sound bullets) in solid and fluid media, with energies orders of magnitude greater than previously achievable. This focusing is made possible by a tunable, nonlinear acoustic lens, which consists of ordered arrays of granular chains. The amplitude, size, and location of the sound bullets can be controlled by varying the static precompression of the chains. Theory and numerical simulations demonstrate the focusing effect, and photoelasticity experiments corroborate it. Our nonlinear lens permits a qualitatively new way of generating high-energy acoustic pulses, which may improve imaging capabilities through increased accuracy and signal-to-noise ratios and may lead to more effective nonintrusive scalpels, for example, for cancer treatment.

Escaping the maze: micro-swimmers using acoustic forces to navigate

NASA Astrophysics Data System (ADS)

Louf, Jean-Francois; Dollet, Benjamin; Stephan, Olivier; Marmottant, Philippe

2017-11-01

The goal of this study is to make 3D micro-swimmers containing a bubble that can be stimulated with acoustic waves emitted by a transducer, and whose direction is accurately controlled. By using 3D micro-fabrication techniques, we designed 40x40 μm swimmers with a trapped air bubble. We then applied acoustic vibration to the bubble, which generates a strong steady flow (1-100 mm/s) behind it, an effect referred as acoustic streaming. However, independently from the orientation of the bubble and thus from the flow, the motion of the swimmer is found to be towards the transducer. This suggests that primary Bjerknes forces, i.e. acoustic radiation forces, are involved. Subsequently, using different transducers located at different points, we could be able to navigate the swimmer in a chosen direction. The next step of our study is to use a stationary wave and Bjerknes forces to bring encapsulated objects in a pressure node. Without bubbles, the effect of acoustic streaming on big objects of more than a micrometer is not sufficient to generate motion. However, with the presence of bubbles, our swimmers should be able to move. ERC BUBBLEBOOST.

APL - North Pacific Acoustic Laboratory

DTIC Science & Technology

2011-09-01

including marine mammals ) measurements in the NE Pacific Ocean. The Laboratory consists of the legacy SOSUS hydrophone receiver network in the...exposure in the marine environment. Philippine Sea- Ambient noise levels measured during the 2010-2011 Philippine Sea experiment on the Scripps...sound speed perturbations and the characteristics of the ambient acoustic noise field. Scattering and diffraction resulting from internal waves and

The Nature of Exhibits About Acoustics in Science and Technology Centres

NASA Astrophysics Data System (ADS)

Afonso, Ana S.; Gilbert, John K.

2008-11-01

This is a study of the opportunities currently provided by interactive science and technology centres for visitors’ engagement in the field of acoustics. E-mails, requesting a description of exhibits on acoustics (sound and hearing) in use, were sent to members of staff of interactive science and technology centres around the world as well as to companies that design and sell exhibits. Eighty-seven descriptions of distinctive interactive exhibits were received and analysed. Results show that: there are few analogy-based exhibits concerning the more complex aspects of acoustics; narratives involving visitors’ everyday lives, that might provide continuity between and beyond the situations presented by exhibits, are not generally provided; science is emphasised at the expense of technology; the risks, benefits and ethical implications of relevant technological artefacts are rarely mentioned; the majority of the exhibits are concerned with the fields of fundamental acoustics, hearing, and psychoacoustics. It is suggested that interactive science and technology centres need to rethink the design of exhibits about acoustics if their mission includes some appreciation of this important branch of science and technology.

Perceptual aspects of reproduced sound in car cabin acoustics.

PubMed

Kaplanis, Neofytos; Bech, Søren; Tervo, Sakari; Pätynen, Jukka; Lokki, Tapio; van Waterschoot, Toon; Jensen, Søren Holdt

2017-03-01

An experiment was conducted to determine the perceptual effects of car cabin acoustics on the reproduced sound field. In-car measurements were conducted whilst the cabin's interior was physically modified. The captured sound fields were recreated in the laboratory using a three-dimensional loudspeaker array. A panel of expert assessors followed a rapid sensory analysis protocol, the flash profile, to perceptually characterize and evaluate 12 acoustical conditions of the car cabin using individually elicited attributes. A multivariate analysis revealed the panel's consensus and the identified perceptual constructs. Six perceptual constructs characterize the differences between the acoustical conditions of the cabin, related to bass, ambience, transparency, width and envelopment, brightness, and image focus. The current results indicate the importance of several acoustical properties of a car's interior on the perceived sound qualities. Moreover, they signify the capacity of the applied methodology in assessing spectral and spatial properties of automotive environments in laboratory settings using a time-efficient and flexible protocol.

Feasibility of detecting orthopaedic screw overtightening using acoustic emission.

PubMed

Pullin, Rhys; Wright, Bryan J; Kapur, Richard; McCrory, John P; Pearson, Matthew; Evans, Sam L; Crivelli, Davide

2017-03-01

A preliminary study of acoustic emission during orthopaedic screw fixation was performed using polyurethane foam as the bone-simulating material. Three sets of screws, a dynamic hip screw, a small fragment screw and a large fragment screw, were investigated, monitoring acoustic-emission activity during the screw tightening. In some specimens, screws were deliberately overtightened in order to investigate the feasibility of detecting the stripping torque in advance. One set of data was supported by load cell measurements to directly measure the axial load through the screw. Data showed that acoustic emission can give good indications of impending screw stripping; such indications are not available to the surgeon at the current state of the art using traditional torque measuring devices, and current practice relies on the surgeon's experience alone. The results suggest that acoustic emission may have the potential to prevent screw overtightening and bone tissue damage, eliminating one of the commonest sources of human error in such scenarios.

Effect of Forcing Function on Nonlinear Acoustic Standing Waves

NASA Technical Reports Server (NTRS)

Finkheiner, Joshua R.; Li, Xiao-Fan; Raman, Ganesh; Daniels, Chris; Steinetz, Bruce

2003-01-01

Nonlinear acoustic standing waves of high amplitude have been demonstrated by utilizing the effects of resonator shape to prevent the pressure waves from entering saturation. Experimentally, nonlinear acoustic standing waves have been generated by shaking an entire resonating cavity. While this promotes more efficient energy transfer than a piston-driven resonator, it also introduces complicated structural dynamics into the system. Experiments have shown that these dynamics result in resonator forcing functions comprised of a sum of several Fourier modes. However, previous numerical studies of the acoustics generated within the resonator assumed simple sinusoidal waves as the driving force. Using a previously developed numerical code, this paper demonstrates the effects of using a forcing function constructed with a series of harmonic sinusoidal waves on resonating cavities. From these results, a method will be demonstrated which allows the direct numerical analysis of experimentally generated nonlinear acoustic waves in resonators driven by harmonic forcing functions.

Observation of ice nucleation in acoustically levitated water drops

NASA Astrophysics Data System (ADS)

Lü, Y. J.; Xie, W. J.; Wei, B.

2005-10-01

The supercooling and nucleation of acoustically levitated water drops were investigated at two different sound pressure levels (SPL). These water drops were supercooled by 13to16K at the low SPL of 160.6dB, whereas their supercoolings varied from 5to11K at the high SPL of 164.4dB. The maximum supercooling obtained in the experiments is 32K. Statistical analyses based on the classical nucleation theory reveal that the occurrence of ice nucleation in water drops is mainly confined to the surface region under acoustic levitation conditions and the enlargement of drop surface area caused by the acoustic radiation pressure reduces water supercoolability remarkably. A comparison of the nucleation rates at the two SPLs indicates that the sound pressure can strengthen the surface-dominated nucleation of water drops. The acoustic stream around levitated water drops and the cavitation effect associated with ultrasonic field are the main factors that induce surface-dominated nucleation.

Acoustic multipath arrivals in the horizontal plane due to approaching nonlinear internal waves.

PubMed

Badiey, Mohsen; Katsnelson, Boris G; Lin, Ying-Tsong; Lynch, James F

2011-04-01

Simultaneous measurements of acoustic wave transmissions and a nonlinear internal wave packet approaching an along-shelf acoustic path during the Shallow Water 2006 experiment are reported. The incoming internal wave packet acts as a moving frontal layer reflecting (or refracting) sound in the horizontal plane. Received acoustic signals are filtered into acoustic normal mode arrivals. It is shown that a horizontal multipath interference is produced. This has previously been called a horizontal Lloyd's mirror. The interference between the direct path and the refracted path depends on the mode number and frequency of the acoustic signal. A mechanism for the multipath interference is shown. Preliminary modeling results of this dynamic interaction using vertical modes and horizontal parabolic equation models are in good agreement with the observed data.

A contrast source method for nonlinear acoustic wave fields in media with spatially inhomogeneous attenuation.

PubMed

Demi, L; van Dongen, K W A; Verweij, M D

2011-03-01

Experimental data reveals that attenuation is an important phenomenon in medical ultrasound. Attenuation is particularly important for medical applications based on nonlinear acoustics, since higher harmonics experience higher attenuation than the fundamental. Here, a method is presented to accurately solve the wave equation for nonlinear acoustic media with spatially inhomogeneous attenuation. Losses are modeled by a spatially dependent compliance relaxation function, which is included in the Westervelt equation. Introduction of absorption in the form of a causal relaxation function automatically results in the appearance of dispersion. The appearance of inhomogeneities implies the presence of a spatially inhomogeneous contrast source in the presented full-wave method leading to inclusion of forward and backward scattering. The contrast source problem is solved iteratively using a Neumann scheme, similar to the iterative nonlinear contrast source (INCS) method. The presented method is directionally independent and capable of dealing with weakly to moderately nonlinear, large scale, three-dimensional wave fields occurring in diagnostic ultrasound. Convergence of the method has been investigated and results for homogeneous, lossy, linear media show full agreement with the exact results. Moreover, the performance of the method is demonstrated through simulations involving steered and unsteered beams in nonlinear media with spatially homogeneous and inhomogeneous attenuation. © 2011 Acoustical Society of America

Environmental Support for Project WEAP (Weapons Environmental Acoustic Program), East of Montauk Point, New York, 7-28 May 1982.

DTIC Science & Technology

1983-10-01

scatterer of acoustic energy. During May, the * The objective of Project WEAP (Weapons sound speed gradient would be slightly Environmental Acoustics...remotely collected box site the experiment in a homogeneous cores for small macrofaunal animals. area or at least in an area where heter- Megafauna must...variety of sediment types. bation by both megafauna and macrofauna. DThis data may be required to understand During or after the acoustic experiment, the

Stresses in acoustically excited panels and shuttle insulation tiles

NASA Technical Reports Server (NTRS)

Otalvo, I. U.

1976-01-01

Natural vibration and acoustic response results are presented for a 36 x 18 inch panel with 18 6 x 6-inch tiles of 1.0, 1.6 and 2.3 inch thicknesses. Computed results for an untiled panel are compared with experiments performed earlier. Natural frequency and acoustic response comparisons are also given for independent analyses performed upon tiled and untiled panels. The results indicate the general applicability of the computer programs developed for use as shuttle design and analysis tools.

A comparison of auditory evoked potentials to acoustic beats and to binaural beats.

PubMed

Pratt, Hillel; Starr, Arnold; Michalewski, Henry J; Dimitrijevic, Andrew; Bleich, Naomi; Mittelman, Nomi

2010-04-01

The purpose of this study was to compare cortical brain responses evoked by amplitude modulated acoustic beats of 3 and 6 Hz in tones of 250 and 1000 Hz with those evoked by their binaural beats counterparts in unmodulated tones to indicate whether the cortical processes involved differ. Event-related potentials (ERPs) were recorded to 3- and 6-Hz acoustic and binaural beats in 2000 ms duration 250 and 1000 Hz tones presented with approximately 1 s intervals. Latency, amplitude and source current density estimates of ERP components to beats-evoked oscillations were determined and compared across beat types, beat frequencies and base (carrier) frequencies. All stimuli evoked tone-onset components followed by oscillations corresponding to the beat frequency, and a subsequent tone-offset complex. Beats-evoked oscillations were higher in amplitude in response to acoustic than to binaural beats, to 250 than to 1000 Hz base frequency and to 3 Hz than to 6 Hz beat frequency. Sources of the beats-evoked oscillations across all stimulus conditions located mostly to left temporal lobe areas. Differences between estimated sources of potentials to acoustic and binaural beats were not significant. The perceptions of binaural beats involve cortical activity that is not different than acoustic beats in distribution and in the effects of beat- and base frequency, indicating similar cortical processing. Copyright 2010 Elsevier B.V. All rights reserved.

Dan Poskevich demonstrates experiment for STS student involvement project

NASA Technical Reports Server (NTRS)

1984-01-01

Dan Poskevich, a college student, demonstrates an experiment he developed for the Space Transportation System (STS) student involvement project. In the aluminum box are thousands of honeybees constructing a honeycomb. Poskevich gave a brief demonstration for news media representatives in the Space Shuttle one-G trainer in JSC's mockup and integration lab.

Three-Dimensional Phenomena in Microbubble Acoustic Streaming

NASA Astrophysics Data System (ADS)

Marin, Alvaro; Rossi, Massimiliano; Rallabandi, Bhargav; Wang, Cheng; Hilgenfeldt, Sascha; Kähler, Christian J.

2015-04-01

Ultrasound-driven oscillating microbubbles are used as active actuators in microfluidic devices to perform manifold tasks such as mixing, sorting, and manipulation of microparticles. A common configuration consists of side bubbles created by trapping air pockets in blind channels perpendicular to the main channel direction. This configuration consists of acoustically excited bubbles with a semicylindrical shape that generate significant streaming flow. Because of the geometry of the channels, such flows are generally considered as quasi-two-dimensional. Similar assumptions are often made in many other microfluidic systems based on flat microchannels. However, in this Letter we show that microparticle trajectories actually present a much richer behavior, with particularly strong out-of-plane dynamics in regions close to the microbubble interface. Using astigmatism particle-tracking velocimetry, we reveal that the apparent planar streamlines are actually projections of a stream surface with a pseudotoroidal shape. We, therefore, show that acoustic streaming cannot generally be assumed as a two-dimensional phenomenon in confined systems. The results have crucial consequences for most of the applications involving acoustic streaming such as particle trapping, sorting, and mixing.

Effect of sound-related activities on human behaviours and acoustic comfort in urban open spaces.

PubMed

Meng, Qi; Kang, Jian

2016-12-15

Human activities are important to landscape design and urban planning; however, the effect of sound-related activities on human behaviours and acoustic comfort has not been considered. The objective of this study is to explore how human behaviours and acoustic comfort in urban open spaces can be changed by sound-related activities. On-site measurements were performed at a case study site in Harbin, China, and an acoustic comfort survey was simultaneously conducted. In terms of effect of sound activities on human behaviours, music-related activities caused 5.1-21.5% of persons who pass by the area to stand and watch the activity, while there was a little effect on the number of persons who performed excises during the activity. Human activities generally have little effect on the behaviour of pedestrians when only 1 to 3 persons are involved in the activities, while a deep effect on the behaviour of pedestrians is noted when >6 persons are involved in the activities. In terms of effect of activities on acoustic comfort, music-related activities can increase the sound level from 10.8 to 16.4dBA, while human activities such RS and PC can increase the sound level from 9.6 to 12.8dBA; however, they lead to very different acoustic comfort. The acoustic comfort of persons can differ with activities, for example the acoustic comfort of persons who stand watch can increase by music-related activities, while the acoustic comfort of persons who sit and watch can decrease by human sound-related activities. Some sound-related activities can show opposite trend of acoustic comfort between visitors and citizens. Persons with higher income prefer music sound-related activities, while those with lower income prefer human sound-related activities. Copyright © 2016 Elsevier B.V. All rights reserved.

Design, characterization, and experimental use of the second generation MEMS acoustic emission device

NASA Astrophysics Data System (ADS)

Ozevin, Didem; Greve, David W.; Oppenheim, Irving J.; Pessiki, Stephen

2005-05-01

We describe the design, fabrication, testing and application (in structural experiments) of our 2004 (second generation) MEMS device, designed for acoustic emission sensing based upon experiments with our 2002 (first generation) device. Both devices feature a suite of resonant-type transducers in the frequency range between 100 kHz and 1 MHz. The 2002 device was designed to operate in an evacuated housing because of high squeeze film damping, as confirmed in our earlier experiments. In additional studies involving the 2002 device, experimental simulation of acoustic emissions in a steel plate, using pencil lead break or ball impact loading, showed that the transducers in the frequency range of 100 kHz-500 kHz presented clearer output signals than the transducers with frequencies higher than 500 kHz. Using the knowledge gained from the 2002 device, we designed and fabricated our second generation device in 2004 using the multi-user polysilicon surface micromachining (MUMPs) process. The 2004 device has 7 independent capacitive type transducers, compared to 18 independent transducers in the 2002 device, including 6 piston type transducers in the frequency range of 100 kHz to 500 kHz and 1 piston type transducer at 1 MHz to capture high frequency information. Piston type transducers developed in our research have two uncoupled modes so that twofold information can be acquired from a single transducer. In addition, the piston shape helps to reduce residual stress effect of surface micromachining process. The center to center distance between etch holes in the vibrating plate was reduced from 30 μm to 13 μm, in order to reduce squeeze film damping. As a result, the Q factor under atmospheric pressure for the 100 kHz transducer was increased to 2.37 from 0.18, and therefore the vacuum housing has been eliminated from the 2004 device. Sensitivities of transducers were also increased, by enlarging transducer area, in order to capture significant small amplitude acoustic

Acoustic signals of baby black caimans.

PubMed

Vergne, Amélie L; Aubin, Thierry; Taylor, Peter; Mathevon, Nicolas

2011-12-01

In spite of the importance of crocodilian vocalizations for the understanding of the evolution of sound communication in Archosauria and due to the small number of experimental investigations, information concerning the vocal world of crocodilians is limited. By studying black caimans Melanosuchus niger in their natural habitat, here we supply the experimental evidence that juvenile crocodilians can use a graded sound system in order to elicit adapted behavioral responses from their mother and siblings. By analyzing the acoustic structure of calls emitted in two different situations ('undisturbed context', during which spontaneous calls of juvenile caimans were recorded without perturbing the group, and a simulated 'predator attack', during which calls were recorded while shaking juveniles) and by testing their biological relevance through playback experiments, we reveal the existence of two functionally different types of juvenile calls that produce a different response from the mother and other siblings. Young black caimans can thus modulate the structure of their vocalizations along an acoustic continuum as a function of the emission context. Playback experiments show that both mother and juveniles discriminate between these 'distress' and 'contact' calls. Acoustic communication is thus an important component mediating relationships within family groups in caimans as it is in birds, their archosaurian relatives. Although probably limited, the vocal repertoire of young crocodilians is capable of transmitting the information necessary for allowing siblings and mother to modulate their behavior. Copyright © 2011 Elsevier GmbH. All rights reserved.

Acoustical imaging of high-frequency elastic responses of targets

NASA Astrophysics Data System (ADS)

Morse, Scot F.; Hefner, Brian T.; Marston, Philip L.

2002-05-01

Acoustical imaging was used to investigate high-frequency elastic responses to sound of two targets in water. The backscattering of broadband bipolar acoustic pulses by a truncated cylindrical shell was recorded over a wide range of tilt angles [S. F. Morse and P. L. Marston, ``Backscattering of transients by tilted truncated cylindrical shells: time-frequency identification of ray contributions from measurements,'' J. Acoust. Soc. Am. (in press)]. This data set was used to form synthetic aperture images of the target based on the data within different angular apertures. Over a range of viewing angles, the visibility of the cylinder's closest rear corner was significantly enhanced by the meridional flexural wave contribution to the backscattering. In another experiment, the time evolution of acoustic holographic images was used to explore the response of tilted elastic circular disks to tone bursts having frequencies of 250 and 300 kHz. For different tilt angles, specific responses that enhance the backscattering were identified from the time evolution of the images [B. T. Hefner and P. L. Marston, Acoust. Res. Lett. Online 2, 55-60 (2001)]. [Work supported by ONR.

Complete de-Dopplerization and acoustic holography for external noise of a high-speed train.

PubMed

Yang, Diange; Wen, Junjie; Miao, Feng; Wang, Ziteng; Gu, Xiaoan; Lian, Xiaomin

2016-09-01

Identification and measurement of moving sound sources are the bases for vehicle noise control. Acoustic holography has been applied in successfully identifying the moving sound source since the 1990s. However, due to the high demand for the accuracy of holographic data, currently the maximum velocity achieved by acoustic holography is just above 100 km/h. The objective of this study was to establish a method based on the complete Morse acoustic model to restore the measured signal in high-speed situations, and to propose a far-field acoustic holography method applicable for high-speed moving sound sources. Simulated comparisons of the proposed far-field acoustic holography with complete Morse model, the acoustic holography with simplified Morse model and traditional delay-and-sum beamforming were conducted. Experiments with a high-speed train running at the speed of 278 km/h validated the proposed far-field acoustic holography. This study extended the applications of acoustic holography to high-speed situations and established the basis for quantitative measurements of far-field acoustic holography.

Subwavelength diffractive acoustics and wavefront manipulation with a reflective acoustic metasurface

NASA Astrophysics Data System (ADS)

Wang, Wenqi; Xie, Yangbo; Popa, Bogdan-Ioan; Cummer, Steven A.

2016-11-01

Acoustic metasurfaces provide useful wavefront shaping capabilities, such as beam steering, acoustic focusing, and asymmetric transmission, in a compact structure. Most acoustic metasurfaces described in the literature are transmissive devices and focus their performance on steering sound beam of the fundamental diffractive order. In addition, the range of incident angles studied is usually below the critical incidence predicted by generalized Snell's law of reflection. In this work, we comprehensively analyze the wave interaction with a generic periodic phase-modulating structure in order to predict the behavior of all diffractive orders, especially for cases beyond critical incidence. Under the guidance of the presented analysis, a broadband reflective metasurface is designed based on an expanded library of labyrinthine acoustic metamaterials. Various local and nonlocal wavefront shaping properties are experimentally demonstrated, and enhanced absorption of higher order diffractive waves is experimentally shown for the first time. The proposed methodology provides an accurate approach for predicting practical diffracted wave behaviors and opens a new perspective for the study of acoustic periodic structures. The designed metasurface extends the functionalities of acoustic metasurfaces and paves the way for the design of thin planar reflective structures for broadband acoustic wave manipulation and extraordinary absorption.

Computation of Sound Generated by Flow Over a Circular Cylinder: An Acoustic Analogy Approach

NASA Technical Reports Server (NTRS)

Brentner, Kenneth S.; Cox, Jared S.; Rumsey, Christopher L.; Younis, Bassam A.

1997-01-01

The sound generated by viscous flow past a circular cylinder is predicted via the Lighthill acoustic analogy approach. The two dimensional flow field is predicted using two unsteady Reynolds-averaged Navier-Stokes solvers. Flow field computations are made for laminar flow at three Reynolds numbers (Re = 1000, Re = 10,000, and Re = 90,000) and two different turbulent models at Re = 90,000. The unsteady surface pressures are utilized by an acoustics code that implements Farassat's formulation 1A to predict the acoustic field. The acoustic code is a 3-D code - 2-D results are found by using a long cylinder length. The 2-D predictions overpredict the acoustic amplitude; however, if correlation lengths in the range of 3 to 10 cylinder diameters are used, the predicted acoustic amplitude agrees well with experiment.

Air-ground interface: Surface waves, surface impedance and acoustic-to-seismic coupling coefficient

NASA Technical Reports Server (NTRS)

Daigle, Gilles; Embleton, Tony

1990-01-01

In atmospheric acoustics, the subject of surface waves has been an area of discussion for many years. The existence of an acoustic surface wave is now well established theoretically. The mathematical solution for spherical wave propagation above an impedance boundary includes the possibility of a contribution that possesses all the standard properties for a surface wave. Surface waves exist when the surface is sufficiently porous, relative to its acoustical resistance, that it can influence the airborne particle velocity near the surface and reduce the phase velocity of sound waves in air at the surface. This traps some of the sound energy in the air to remain near the surface as it propagates. Above porous grounds, the existence of surface waves has eluded direct experimental confirmation (pulse experiments have failed to show a separate arrival expected from the reduced phase speed) and indirect evidence for its existence has appeared contradictory. The experimental evidence for the existence of an acoustical surface wave above porous boundaries is reviewed. Recent measurements including pulse experiments are also described. A few years ago the acoustic impedance of a grass-covered surface was measured in the frequency range 30 to 300 Hz. Here, further measurements on the same site are discussed. These measurements include core samples, a shallow refractive survey to determine the seismic velocities, and measurements of the acoustic-to-seismic coupling coefficient.

Induced clustering of Escherichia coli by acoustic fields.

PubMed

Gutiérrez-Ramos, Salomé; Hoyos, Mauricio; Ruiz-Suárez, J C

2018-03-16

Brownian or self-propelled particles in aqueous suspensions can be trapped by acoustic fields generated by piezoelectric transducers usually at frequencies in the megahertz. The obtained confinement allows the study of rich collective behaviours like clustering or spreading dynamics in microgravity-like conditions. The acoustic field induces the levitation of self-propelled particles and provides secondary lateral forces to capture them at nodal planes. Here, we give a step forward in the field of confined active matter, reporting levitation experiments of bacterial suspensions of Escherichia coli. Clustering of living bacteria is monitored as a function of time, where different behaviours are clearly distinguished. Upon the removal of the acoustic signal, bacteria rapidly spread, impelled by their own swimming. Nevertheless, long periods of confinement result in irreversible bacteria entanglements that could act as seeds for levitating bacterial aggregates.

Imaging and detection of mines from acoustic measurements

NASA Astrophysics Data System (ADS)

Witten, Alan J.; DiMarzio, Charles A.; Li, Wen; McKnight, Stephen W.

1999-08-01

A laboratory-scale acoustic experiment is described where a buried target, a hockey puck cut in half, is shallowly buried in a sand box. To avoid the need for source and receiver coupling to the host sand, an acoustic wave is generated in the subsurface by a pulsed laser suspended above the air-sand interface. Similarly, an airborne microphone is suspended above this interface and moved in unison with the laser. After some pre-processing of the data, reflections for the target, although weak, could clearly be identified. While the existence and location of the target can be determined by inspection of the data, its unique shape can not. Since target discrimination is important in mine detection, a 3D imaging algorithm was applied to the acquired acoustic data. This algorithm yielded a reconstructed image where the shape of the target was resolved.

Femtosecond imaging of nonlinear acoustics in gold.

PubMed

Pezeril, Thomas; Klieber, Christoph; Shalagatskyi, Viktor; Vaudel, Gwenaelle; Temnov, Vasily; Schmidt, Oliver G; Makarov, Denys

2014-02-24

We have developed a high-sensitivity, low-noise femtosecond imaging technique based on pump-probe time-resolved measurements with a standard CCD camera. The approach used in the experiment is based on lock-in acquisitions of images generated by a femtosecond laser probe synchronized to modulation of a femtosecond laser pump at the same rate. This technique allows time-resolved imaging of laser-excited phenomena with femtosecond time resolution. We illustrate the technique by time-resolved imaging of the nonlinear reshaping of a laser-excited picosecond acoustic pulse after propagation through a thin gold layer. Image analysis reveals the direct 2D visualization of the nonlinear acoustic propagation of the picosecond acoustic pulse. Many ultrafast pump-probe investigations can profit from this technique because of the wealth of information it provides over a typical single diode and lock-in amplifier setup, for example it can be used to image ultrasonic echoes in biological samples.

Effects of Nanoparticulate Additives on Acoustically Coupled Fuel Droplet Combustion

NASA Astrophysics Data System (ADS)

Vargas, Andres; Plascencia, Miguel; Sim, Hyung Sub; Smith, Owen; Karagozian, Ann

2017-11-01

The present study investigates interactions between applied acoustic perturbations and burning ethanol droplets containing nano particulate additives. Reactive nanoscale aluminum (nAl) as well as inert silica (nSiO2), each with an 80 nm average diameter. Continuously-fed fuel droplet combustion experiments were conducted in the vicinity of a pressure node created in a closed acoustic waveguide, with a range of applied forcing frequencies, pressure or velocity perturbation amplitudes, and particle loading concentrations. Simultaneous phase-locked OH* chemiluminescence and high-speed visible imaging enabled quantification of the influences of nanoparticle concentration on burning rate constant K and combustion-acoustic coupling. Results indicated that nAl particles in ethanol yielded measurable increases in K with increasing applied perturbation amplitudes, as compared to pure ethanol in the presence of acoustic excitation. Droplets with nAl exposed to moderate acoustic excitation exhibited sustained combustion for much longer periods of time than for unforced conditions. Post analysis of particulate matter collected from residue via electron microscopy aids in interpreting these trends and findings. Supported by AFOSR Grant FA9550-15-1-0339.

Multi-carrier Communications over Time-varying Acoustic Channels

NASA Astrophysics Data System (ADS)

Aval, Yashar M.

Acoustic communication is an enabling technology for many autonomous undersea systems, such as those used for ocean monitoring, offshore oil and gas industry, aquaculture, or port security. There are three main challenges in achieving reliable high-rate underwater communication: the bandwidth of acoustic channels is extremely limited, the propagation delays are long, and the Doppler distortions are more pronounced than those found in wireless radio channels. In this dissertation we focus on assessing the fundamental limitations of acoustic communication, and designing efficient signal processing methods that cam overcome these limitations. We address the fundamental question of acoustic channel capacity (achievable rate) for single-input-multi-output (SIMO) acoustic channels using a per-path Rician fading model, and focusing on two scenarios: narrowband channels where the channel statistics can be approximated as frequency- independent, and wideband channels where the nominal path loss is frequency-dependent. In each scenario, we compare several candidate power allocation techniques, and show that assigning uniform power across all frequencies for the first scenario, and assigning uniform power across a selected frequency-band for the second scenario, are the best practical choices in most cases, because the long propagation delay renders the feedback information outdated for power allocation based on the estimated channel response. We quantify our results using the channel information extracted form the 2010 Mobile Acoustic Communications Experiment (MACE'10). Next, we focus on achieving reliable high-rate communication over underwater acoustic channels. Specifically, we investigate orthogonal frequency division multiplexing (OFDM) as the state-of-the-art technique for dealing with frequency-selective multipath channels, and propose a class of methods that compensate for the time-variation of the underwater acoustic channel. These methods are based on multiple

Physical mechanism of coherent acoustic phonons generation and detection in GaAs semiconductor

NASA Astrophysics Data System (ADS)

Babilotte, P.; Morozov, E.; Ruello, P.; Mounier, D.; Edely, M.; Breteau, J.-M.; Bulou, A.; Gusev, V.

2007-12-01

We first describe the picosecond acoustic interferometry study of GaAs with two-colors pump-probe laser pulses. The dependence of the generation process on the pump wavelength and the detection process on the probe wavelength both can cause the shift in the phase of the Brillouin signal. Secondly, in order to distinguish the short high frequency wideband acoustic pulse from low frequency Brillouin contribution, we accomplished experiments with (100)GaAs semiconductor coated by a transparent and photoelastically inactive thin film, serving a delay line for the acoustic pulse. Even with highly penetrating pump light (approx 680nm), short acoustic disturbances of approx 7ps of duration have been registered.

Tuning Coler Magnetic Current Apparatus with Magneto-Acoustic Resonance

NASA Astrophysics Data System (ADS)

Ludwig, Thorsten

An attempt was made to tune the Coler magnetic current apparatus with the magneto acoustic resonance of the magnetic rods. Measurements with a replica of the famous Coler "Magnetstromapparat" were conducted. In order to tune the acoustic, magnetic and electric resonance circuits of the Coler device the magneto-acoustic resonance was measured with a frequency scan through a function generator and a lock-in amplifier. The frequency generator was powering a driving coil, while the lock-in was connected to a pickup coil. Both coils were placed on a magnetic rod. Resonances were observed up to the 17th harmonic. The quality Q of the observed resonances was 270. To study the magneto-acoustic resonance in the time domain a pair of Permendur rods were employed. The magneto-acoustic resonances of the Permendur rods were observed with an oscilloscope. Spectra of the magneto acoustic resonance were measured for the Permendur rods and for a Coler replica magnet in the frequency range from 25 kHz to 380 kHz. The next step was to bring the resonances of the Permendur rods close together so that they overlap. The 10thharmonic was chosen because it was close to the 180 kHz that Hans Coler related to ferromagnetism. Further more magneto-acoustic coupling between the Permendur rods was studied. Finally the question was explored if Hans Coler converted vacuum fluctuations via magnetic and acoustic resonance into electricity. There is a strong connection between magnetism and quantum field zero point energy (ZPE). An outlook is given on next steps in the experiments to unveil the working mechanism of the Coler magnetic current apparatus.

Fluids and Combustion Facility Acoustic Emissions Controlled by Aggressive Low-Noise Design Process

NASA Technical Reports Server (NTRS)

Cooper, Beth A.; Young, Judith A.

2004-01-01

The Fluids and Combustion Facility (FCF) is a dual-rack microgravity research facility that is being developed by Northrop Grumman Information Technology (NGIT) for the International Space Station (ISS) at the NASA Glenn Research Center. As an on-orbit test bed, FCF will host a succession of experiments in fluid and combustion physics. The Fluids Integrated Rack (FIR) and the Combustion Integrated Rack (CIR) must meet ISS acoustic emission requirements (ref. 1), which support speech communication and hearing-loss-prevention goals for ISS crew. To meet these requirements, the NGIT acoustics team implemented an aggressive low-noise design effort that incorporated frequent acoustic emission testing for all internal noise sources, larger-scale systems, and fully integrated racks (ref. 2). Glenn's Acoustical Testing Laboratory (ref. 3) provided acoustical testing services (see the following photograph) as well as specialized acoustical engineering support as part of the low-noise design process (ref. 4).

Changes in room acoustics elicit a Mismatch Negativity in the absence of overall interaural intensity differences.

PubMed

Frey, Johannes Daniel; Wendt, Mike; Löw, Andreas; Möller, Stephan; Zölzer, Udo; Jacobsen, Thomas

2017-02-15

Changes in room acoustics provide important clues about the environment of sound source-perceiver systems, for example, by indicating changes in the reflecting characteristics of surrounding objects. To study the detection of auditory irregularities brought about by a change in room acoustics, a passive oddball protocol with participants watching a movie was applied in this study. Acoustic stimuli were presented via headphones. Standards and deviants were created by modelling rooms of different sizes, keeping the values of the basic acoustic dimensions (e.g., frequency, duration, sound pressure, and sound source location) as constant as possible. In the first experiment, each standard and deviant stimulus consisted of sequences of three short sounds derived from sinusoidal tones, resulting in three onsets during each stimulus. Deviant stimuli elicited a Mismatch Negativity (MMN) as well as two additional negative deflections corresponding to the three onset peaks. In the second experiment, only one sound was used; the stimuli were otherwise identical to the ones used in the first experiment. Again, an MMN was observed, followed by an additional negative deflection. These results provide further support for the hypothesis of automatic detection of unattended changes in room acoustics, extending previous work by demonstrating the elicitation of an MMN by changes in room acoustics. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Are ion acoustic waves supported by high-density plasmas in the Large Plasma Device (LaPD)?

NASA Astrophysics Data System (ADS)

Roycroft, Rebecca; Dorfman, Seth; Carter, Troy A.; Gekelman, Walter; Tripathi, Shreekrishna

2012-10-01

Ion acoustic waves are a type of longitudinal wave in a plasma, propagating though the motion of the ions. The wave plays a key role in a parametric decay process thought to be responsible for the spectrum of turbulence observed in the solar wind. In recent LaPD experiments aimed at studying this process, modes thought to be ion acoustic waves are strongly damped when the pump Alfven waves are turned off. This observation motivates an experiment focused on directly launching ion acoustic waves under similar conditions. Our first attempt to launch ion acoustic waves using a metal grid in the plasma was unsuccessful at high magnetic fields and densities due to electrons shorting out the bias applied between the grid and the wall. Results from a new device based on [1] to launch ion acoustic waves will be presented; this device will consist of a small chamber with a plasma source separated from the main chamber by two biased grids. The plasma created inside the small device will be held at a different potential from the main plasma; modulation of this difference should affect the ions, allowing ion acoustic waves to be launched and their properties compared to the prior LaPD experiments.[4pt] [1] W. Gekelman and R. L. Stenzel, Phys. Fluids 21, 2014 (1978).

Acoustic sounding in the planetary boundary layer

NASA Technical Reports Server (NTRS)

Kelly, E. H.

1974-01-01

Three case studies are presented involving data from an acoustic radar. The first two cases examine data collected during the passage of a mesoscale cold-air intrusion, probably thunderstorm outflow, and a synoptic-scale cold front. In these studies the radar data are compared to conventional meteorological data obtained from the WKY tower facility for the purpose of radar data interpretation. It is shown that the acoustic radar echoes reveal the boundary between warm and cold air and other areas of turbulent mixing, regions of strong vertical temperature gradients, and areas of weak or no wind shear. The third case study examines the relationship between the nocturnal radiation inversion and the low-level wind maximum or jet in the light of conclusions presented by Blackadar (1957). The low-level jet is seen forming well above the top of the inversion. Sudden rapid growth of the inversion occurs which brings the top of the inversion to a height equal that of the jet. Coincident with the rapid growth of the inversion is a sudden decrease in the intensity of the acoustic radar echoes in the inversion layer. It is suggested that the decrease in echo intensity reveals a decrease in turbulent mixing in the inversion layer as predicted by Blackadar. It is concluded that the acoustic radar can be a valuable tool for study in the lower atmosphere.

Acoustic Neuroma

MedlinePlus

An acoustic neuroma is a benign tumor that develops on the nerve that connects the ear to the brain. ... can press against the brain, becoming life-threatening. Acoustic neuroma can be difficult to diagnose, because the ...

Single-droplet evaporation kinetics and particle formation in an acoustic levitator. Part 1: evaporation of water microdroplets assessed using boundary-layer and acoustic levitation theories.

PubMed

Schiffter, Heiko; Lee, Geoffrey

2007-09-01

The suitability of a single droplet drying acoustic levitator as a model for the spray drying of aqueous, pharmaceutically-relevant solutes used to produce protein-loaded particles has been examined. The acoustic levitator was initially evaluated by measuring the drying rates of droplets of pure water in dependence of drying-air temperature and flow rate. The measured drying rates were higher than those predicted by boundary layer theory because of the effects of primary acoustic streaming. Sherwood numbers of 2.6, 3.6, and 4.4 at drying-air temperatures of 25 degrees C, 40 degrees C, and 60 degrees C were determined, respectively. Acoustic levitation theory could predict the measured drying rates and Sherwood numbers only when a forced-convection drying-air stream was used to neuralize the retarding effect of secondary acoustic streaming on evaporation rate. At still higher drying-air flow rates, the Ranz-Marshall correlation accurately predicts Sherwood number, provided a stable droplet position in the standing acoustic wave is maintained. The measured Sherwood numbers and droplet Reynolds numbers show that experiments performed in the levitator in still air are taking place effectively under conditions of substantial forced convection. The similitude of these values to those occurring in spray dryers is fortuitous for the suitability of the acoustic levitator as a droplet evaporation model for spray drying. (c) 2007 Wiley-Liss, Inc. and the American Pharmacists Association.

Acoustic levitation technique for containerless processing at high temperatures in space

NASA Technical Reports Server (NTRS)

Rey, Charles A.; Merkley, Dennis R.; Hammarlund, Gregory R.; Danley, Thomas J.

1988-01-01

High temperature processing of a small specimen without a container has been demonstrated in a set of experiments using an acoustic levitation furnace in the microgravity of space. This processing technique includes the positioning, heating, melting, cooling, and solidification of a material supported without physical contact with container or other surface. The specimen is supported in a potential energy well, created by an acoustic field, which is sufficiently strong to position the specimen in the microgravity environment of space. This containerless processing apparatus has been successfully tested on the Space Shuttle during the STS-61A mission. In that experiment, three samples wer successfully levitated and processed at temperatures from 600 to 1500 C. Experiment data and results are presented.

Acoustic suspension system

NASA Technical Reports Server (NTRS)

Lee, M. C.; Wang, T. G. (Inventor)

1983-01-01

An acoustic levitation system is described, with single acoustic source and a small reflector to stably levitate a small object while the object is processed as by coating or heating it. The system includes a concave acoustic source which has locations on opposite sides of its axis that vibrate towards and away from a focal point to generate a converging acoustic field. A small reflector is located near the focal point, and preferably slightly beyond it, to create an intense acoustic field that stably supports a small object near the reflector. The reflector is located about one-half wavelength from the focal point and is concavely curved to a radius of curvature (L) of about one-half the wavelength, to stably support an object one-quarter wavelength (N) from the reflector.

Acoustic modes in fluid networks

NASA Technical Reports Server (NTRS)

Michalopoulos, C. D.; Clark, Robert W., Jr.; Doiron, Harold H.

1992-01-01

Pressure and flow rate eigenvalue problems for one-dimensional flow of a fluid in a network of pipes are derived from the familiar transmission line equations. These equations are linearized by assuming small velocity and pressure oscillations about mean flow conditions. It is shown that the flow rate eigenvalues are the same as the pressure eigenvalues and the relationship between line pressure modes and flow rate modes is established. A volume at the end of each branch is employed which allows any combination of boundary conditions, from open to closed, to be used. The Jacobi iterative method is used to compute undamped natural frequencies and associated pressure/flow modes. Several numerical examples are presented which include acoustic modes for the Helium Supply System of the Space Shuttle Orbiter Main Propulsion System. It should be noted that the method presented herein can be applied to any one-dimensional acoustic system involving an arbitrary number of branches.

Liver haemostasis using microbubble-enhanced ultrasound at a low acoustic intensity.

PubMed

Zhao, Xiaochen; Li, Lu; Zhao, Hongzhi; Li, Tao; Wu, Shengzheng; Zhong, Yu; Zhao, Yang; Liu, Zheng

2012-02-01

To explore the haemostatic effects of microbubble-enhanced ultrasound (MEUS) at a very low acoustic intensity on the bleeding liver of rabbits. Liver incisions made on 20 rabbits were treated with a pulsed therapeutic ultrasound transducer. The transducer was operated at 831 KHz with an acoustic intensity of 0.4 W/cm(2). The treatment was coordinated with intravenous injection of microbubbles. Ultrasound only and sham treatment served as the controls. Visual bleeding score and 10-min bleeding volume were evaluated for haemostatic efficacy. Contrast-enhanced ultrasound (CEUS) was performed to assess the liver perfusion. Nine treated livers were harvested for acute histological examination. Regarding the bleeding incisions made on rabbit livers, the haemorrhage stopped immediately after 2 min of MEUS treatment but bleeding continued in the controls treated by ultrasound or microbubble injection alone. The bleeding scores and the 10-min haemorrhagic volumes dropped significantly in the MEUS group compared with those of the controls (p < 0.01). The mechanism of MEUS haemostasis appears to involve the extensive swelling of hepatocytes and the haemorrhage of the portal area, which formed a joint compression on the regional liver circulation. Low acoustic intensity MEUS might provide a novel method for liver haemostasis. • This animal experiment demonstrates a novel method of controlling hepatic haemorrhage • The treatment uses therapeutic ultrasound during enhancement with intravenous microbubbles • This combined therapy was more effective than ultrasound or intravenous microbubbles alone • More work is required with larger animals before potential human trials.

Acoustic evaluation of wood quality in standing trees. Part I, Acoustic wave behavior

Treesearch

Xiping Wang; Robert J. Ross; Peter Carter

2007-01-01

Acoustic wave velocities in standing trees or live softwood species were measured by the time-of-flight (TOF) method. Tree velocities were compared with acoustic velocities measured in corresponding butt logs through a resonance acoustic method. The experimental data showed a skewed relationship between tree and log acoustic measurements. For most trees tested,...

High-frequency combustion instability control through acoustic modulation at the inlet boundary for liquid rocket engine applications

NASA Astrophysics Data System (ADS)

Bennewitz, John William

This research investigation encompasses experimental tests demonstrating the control of a high-frequency combustion instability by acoustically modulating the propellant flow. A model rocket combustor burned gaseous oxygen and methane using a single-element, pentad-style injector. Flow conditions were established that spontaneously excited a 2430 Hz first longitudinal combustion oscillation at an amplitude up to p'/pc ≈ 6%. An acoustic speaker was placed at the base of the oxidizer supply to modulate the flow and alter the oscillatory behavior of the combustor. Two speaker modulation approaches were investigated: (1) Bands of white noise and (2) Pure sinusoidal tones. The first approach adjusted 500 Hz bands of white noise ranging from 0-500 Hz to 2000-2500 Hz, while the second implemented single-frequency signals with arbitrary phase swept from 500-2500 Hz. The results showed that above a modulation signal amplitude threshold, both approaches suppressed 95+% of the spontaneous combustion oscillation. By increasing the applied signal amplitude, a wider frequency range of instability suppression became present for these two acoustic modulation approaches. Complimentary to these experiments, a linear modal analysis was undertaken to investigate the effects of acoustic modulation at the inlet boundary on the longitudinal instability modes of a dump combustor. The modal analysis employed acoustically consistent matching conditions with a specific impedance boundary condition at the inlet to represent the acoustic modulation. From the modal analysis, a naturally unstable first longitudinal mode was predicted in the absence of acoustic modulation, consistent with the spontaneously excited 2430 Hz instability observed experimentally. Subsequently, a detailed investigation involving variation of the modulation signal from 0-2500 Hz and mean combustor temperature from 1248-1685 K demonstrated the unstable to stable transition of a 2300-2500 Hz first longitudinal mode. The

A hybrid finite element-transfer matrix model for vibroacoustic systems with flat and homogeneous acoustic treatments.

PubMed

Alimonti, Luca; Atalla, Noureddine; Berry, Alain; Sgard, Franck

2015-02-01

Practical vibroacoustic systems involve passive acoustic treatments consisting of highly dissipative media such as poroelastic materials. The numerical modeling of such systems at low to mid frequencies typically relies on substructuring methodologies based on finite element models. Namely, the master subsystems (i.e., structural and acoustic domains) are described by a finite set of uncoupled modes, whereas condensation procedures are typically preferred for the acoustic treatments. However, although accurate, such methodology is computationally expensive when real life applications are considered. A potential reduction of the computational burden could be obtained by approximating the effect of the acoustic treatment on the master subsystems without introducing physical degrees of freedom. To do that, the treatment has to be assumed homogeneous, flat, and of infinite lateral extent. Under these hypotheses, simple analytical tools like the transfer matrix method can be employed. In this paper, a hybrid finite element-transfer matrix methodology is proposed. The impact of the limiting assumptions inherent within the analytical framework are assessed for the case of plate-cavity systems involving flat and homogeneous acoustic treatments. The results prove that the hybrid model can capture the qualitative behavior of the vibroacoustic system while reducing the computational effort.

Room Acoustics

NASA Astrophysics Data System (ADS)

Kuttruff, Heinrich; Mommertz, Eckard

The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.

A binaural Web-based tour of the acoustics of Troy Music Hall

NASA Astrophysics Data System (ADS)

Torres, Rendell R.; Cooney, James; Shimizu, Yasushi

2004-05-01

For classical music to become more widely enjoyed, it must sound exciting. We hypothesize that if people could hear examples of truly exciting acoustics, classical music would be perceived less as a rarefied delicacy and more as a viscerally engaging listening experience. The Troy Savings Bank Music Hall in Troy, New York, is a legendary 1200-seat concert hall famous for its acoustics. Such landmarks are commonly documented architecturally but with few attempts to document their acoustics in a way that it is listenable. Thus, the goal is to capture and sonically disseminate the hall's acoustics through a Web-based acoustical tour, where one can click on various seats to hear binaural auralizations of different instruments and see corresponding views of the stage. The hope is that these auralizations will not only sonically document the acoustics of the hall but also tantalize even geographically distant listeners with binaural samples of how exciting music can be in excellent acoustics. The fun and challenges of devising (let alone standardizing) such an auralization-based system of documentation will be discussed, and a demonstration given. This process can be applied to other historically and acoustically significant spaces. [Work supported by the National Endowment for the Arts.

Acoustic scaling: A re-evaluation of the acoustic model of Manchester Studio 7

NASA Astrophysics Data System (ADS)

Walker, R.

1984-12-01

The reasons for the reconstruction and re-evaluation of the acoustic scale mode of a large music studio are discussed. The design and construction of the model using mechanical and structural considerations rather than purely acoustic absorption criteria is described and the results obtained are given. The results confirm that structural elements within the studio gave rise to unexpected and unwanted low-frequency acoustic absorption. The results also show that at least for the relatively well understood mechanisms of sound energy absorption physical modelling of the structural and internal components gives an acoustically accurate scale model, within the usual tolerances of acoustic design. The poor reliability of measurements of acoustic absorption coefficients, is well illustrated. The conclusion is reached that such acoustic scale modelling is a valid and, for large scale projects, financially justifiable technique for predicting fundamental acoustic effects. It is not appropriate for the prediction of fine details because such small details are unlikely to be reproduced exactly at a different size without extensive measurements of the material's performance at both scales.

Acoustic Test Characterization of Melamine Foam for Usage in NASA's Payload Fairing Acoustic Attenuation Systems

NASA Technical Reports Server (NTRS)

Hughes, William O.; McNelis, Anne M.; McNelis, Mark E.

2014-01-01

The external acoustic liftoff levels predicted for NASA's future heavy lift launch vehicles are expected to be significantly higher than the environment created by today's commercial launch vehicles. This creates a need to develop an improved acoustic attenuation system for future NASA payload fairings. NASA Glenn Research Center initiated an acoustic test series to characterize the acoustic performance of melamine foam, with and without various acoustic enhancements. This testing was denoted as NEMFAT, which stands for NESC Enhanced Melamine Foam Acoustic Test, and is the subject of this paper. Both absorption and transmission loss testing of numerous foam configurations were performed at the Riverbank Acoustical Laboratory in July 2013. The NEMFAT test data provides an initial acoustic characterization and database of melamine foam for NASA. Because of its acoustic performance and lighter mass relative to fiberglass blankets, melamine foam is being strongly considered for use in the acoustic attenuation systems of NASA's future launch vehicles.

From Kratzenstein to Wheatstone: Episodes in the early history of free reed acoustics

NASA Astrophysics Data System (ADS)

Cottingham, James P.

2002-05-01

In 1780 C. G. Kratzenstein published a paper in St. Petersburg describing a machine which produced vowel sounds using free reeds with resonators of various shapes. This marks a convenient, if arbitrary, starting point for the history of the free reed musical instruments of European origin. These instruments developed rapidly, and by 1850 the accordion, concertina, harmonica, reed organ, and harmonium all had been invented and developed into more or less final form. A key figure in this period is Charles Wheatstone, who not only published papers on acoustical research but was also an inventor and commercially successful manufacturer of musical instruments, most notably the Wheatstone English concertina. Much of Wheatstone's research in acoustics and almost all of his work as an inventor of musical instruments involved free reeds. This paper presents some episodes in the development of the free reed instruments and some examples of acoustical research involving free reeds during the 18th and 19th centuries.

From prosodic structure to acoustic saliency: A fMRI investigation of speech rate, clarity, and emphasis

NASA Astrophysics Data System (ADS)

Golfinopoulos, Elisa

Acoustic variability in fluent speech can arise at many stages in speech production planning and execution. For example, at the phonological encoding stage, the grouping of phonemes into syllables determines which segments are coarticulated and, by consequence, segment-level acoustic variation. Likewise phonetic encoding, which determines the spatiotemporal extent of articulatory gestures, will affect the acoustic detail of segments. Functional magnetic resonance imaging (fMRI) was used to measure brain activity of fluent adult speakers in four speaking conditions: fast, normal, clear, and emphatic (or stressed) speech. These speech manner changes typically result in acoustic variations that do not change the lexical or semantic identity of productions but do affect the acoustic saliency of phonemes, syllables and/or words. Acoustic responses recorded inside the scanner were assessed quantitatively using eight acoustic measures and sentence duration was used as a covariate of non-interest in the neuroimaging analysis. Compared to normal speech, emphatic speech was characterized acoustically by a greater difference between stressed and unstressed vowels in intensity, duration, and fundamental frequency, and neurally by increased activity in right middle premotor cortex and supplementary motor area, and bilateral primary sensorimotor cortex. These findings are consistent with right-lateralized motor planning of prosodic variation in emphatic speech. Clear speech involved an increase in average vowel and sentence durations and average vowel spacing, along with increased activity in left middle premotor cortex and bilateral primary sensorimotor cortex. These findings are consistent with an increased reliance on feedforward control, resulting in hyper-articulation, under clear as compared to normal speech. Fast speech was characterized acoustically by reduced sentence duration and average vowel spacing, and neurally by increased activity in left anterior frontal

[Visual input affects the expression of the early genes c-Fos and ZENK in auditory telencephalic centers of pied flycatcher nestlings during the acoustically-guided freezing].

PubMed

Korneeva, E V; Tiunova, A A; Aleksandrov, L I; Golubeva, T B; Anokhin, K V

2014-01-01

The present study analyzed expression of transcriptional factors c-Fos and ZENK in 9-day-old pied flycatcher nestlings' (Ficedula hypoleuca) telencephalic auditory centers (field L, caudomedial nidopallium and caudomedial mesopallium) involved in the acoustically-guided defense behavior. Species-typical alarm call was presented to the young in three groups: 1--intact group (sighted control), 2--nestlings visually deprived just before the experiment for a short time (unsighted control) 3--nestlings visually deprived right after hatching (experimental deprivation). Induction of c-Fos as well as ZENK in nestlings from the experimental deprivation group was decreased in both hemispheres as compared with intact group. In the group of unsighted control, only the decrease of c-Fos induction was observed exclusively in the right hemisphere. These findings suggest that limitation of visual input changes the population of neurons involved into the acoustically-guided behavior, the effect being dependant from the duration of deprivation.

Acoustic Liner Drag: Measurements on Novel Facesheet Perforate Geometries

NASA Technical Reports Server (NTRS)

Howerton, Brian M.; Jones, Michael G.

2016-01-01

Interest in characterization of the aerodynamic drag of acoustic liners has increased in the past several years. This paper details experiments in the NASA Langley Grazing Flow Impedance Tube to quantify the relative drag of several perforate-over-honeycomb liner configurations at flow speeds of centerline flow Mach number equals 0.3 and 0.5. Various perforate geometries and orientations are investigated to determine their resistance factors using a static pressure drop approach. Comparison of these resistance factors gives a relative measurement of liner drag. For these same flow conditions, acoustic measurements are performed with tonal excitation from 400 to 3000 hertz at source sound pressure levels of 140 and 150 decibels. Educed impedance and attenuation spectra are used to determine the impact of variations in perforate geometry on acoustic performance.

Theoretical and experimental examination of near-field acoustic levitation.

PubMed

Nomura, Hideyuki; Kamakura, Tomoo; Matsuda, Kazuhisa

2002-04-01

A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense.

Theoretical and experimental examination of near-field acoustic levitation

NASA Astrophysics Data System (ADS)

Nomura, Hideyuki; Kamakura, Tomoo; Matsuda, Kazuhisa

2002-04-01

A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense.

Analysis of existing data from a Distributed Acoustic Sensing experiment at Garner Valley, California using noise correlation functions (PoroTomo Substask 3.2)

DOE Data Explorer

Zeng, Xiangfang

2015-03-26

In September 2013, an experiment using Distributed Acoustic Sensing (DAS) was conducted at Garner Valley, a test site of the University of California Santa Barbara (Lancelle et al., 2014). This submission includes noise cross-correlation functions (NCF) . Each file includes a NCF between two channels. The name of each channel denotes the distance in meters from starting point of the fiber-optic cable. Lancelle, C., N. Lord, H. Wang, D. Fratta, R. Nigbor, A. Chalari, R. Karaulanov, J. Baldwin, and E. Castongia (2014), Directivity and Sensitivity of Fiber-Optic Cable Measuring Ground Motion using a Distributed Acoustic Sensing Array (abstract # NS31C-3935), AGU Fall Meeting. https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/19828 The e-poster is available at: https://agu.confex.com/data/handout/agu/fm14/Paper_19828_handout_696_0.pdf

Low-frequency acoustic pressure, velocity, and intensity thresholds in a bottlenose dolphin (Tursiops truncatus) and white whale (Delphinapterus leucas)

NASA Astrophysics Data System (ADS)

Finneran, James J.; Carder, Donald A.; Ridgway, Sam H.

2002-01-01

The relative contributions of acoustic pressure and particle velocity to the low-frequency, underwater hearing abilities of the bottlenose dolphin (Tursiops truncatus) and white whale (Delphinapterus leucas) were investigated by measuring (masked) hearing thresholds while manipulating the relationship between the pressure and velocity. This was accomplished by varying the distance within the near field of a single underwater sound projector (experiment I) and using two underwater sound projectors and an active sound control system (experiment II). The results of experiment I showed no significant change in pressure thresholds as the distance between the subject and the sound source was changed. In contrast, velocity thresholds tended to increase and intensity thresholds tended to decrease as the source distance decreased. These data suggest that acoustic pressure is a better indicator of threshold, compared to particle velocity or mean active intensity, in the subjects tested. Interpretation of the results of experiment II (the active sound control system) was difficult because of complex acoustic conditions and the unknown effects of the subject on the generated acoustic field; however, these data also tend to support the results of experiment I and suggest that odontocete thresholds should be reported in units of acoustic pressure, rather than intensity.

Transformative Parents: Facilitating Transformative Experiences and Interest with a Parent Involvement Intervention

ERIC Educational Resources Information Center

Heddy, Benjamin C.; Sinatra, Gale M.

2017-01-01

This study reports the implementation of a parental involvement intervention coupled with small group discussions aimed at facilitating transformative experiences (TEs) in science courses (biology and chemistry) in an all-girls middle and high school. Specifically, the goal was to generate parental involvement, TE, and interest. Analyses showed…

Estimation of Fine and Oversize Particle Ratio in a Heterogeneous Compound with Acoustic Emissions.

PubMed

Nsugbe, Ejay; Ruiz-Carcel, Cristobal; Starr, Andrew; Jennions, Ian

2018-03-13

The final phase of powder production typically involves a mixing process where all of the particles are combined and agglomerated with a binder to form a single compound. The traditional means of inspecting the physical properties of the final product involves an inspection of the particle sizes using an offline sieving and weighing process. The main downside of this technique, in addition to being an offline-only measurement procedure, is its inability to characterise large agglomerates of powders due to sieve blockage. This work assesses the feasibility of a real-time monitoring approach using a benchtop test rig and a prototype acoustic-based measurement approach to provide information that can be correlated to product quality and provide the opportunity for future process optimisation. Acoustic emission (AE) was chosen as the sensing method due to its low cost, simple setup process, and ease of implementation. The performance of the proposed method was assessed in a series of experiments where the offline quality check results were compared to the AE-based real-time estimations using data acquired from a benchtop powder free flow rig. A designed time domain based signal processing method was used to extract particle size information from the acquired AE signal and the results show that this technique is capable of estimating the required ratio in the washing powder compound with an average absolute error of 6%.

Generation and control of sound bullets with a nonlinear acoustic lens

PubMed Central

Spadoni, Alessandro; Daraio, Chiara

2010-01-01

Acoustic lenses are employed in a variety of applications, from biomedical imaging and surgery to defense systems and damage detection in materials. Focused acoustic signals, for example, enable ultrasonic transducers to image the interior of the human body. Currently however the performance of acoustic devices is limited by their linear operational envelope, which implies relatively inaccurate focusing and low focal power. Here we show a dramatic focusing effect and the generation of compact acoustic pulses (sound bullets) in solid and fluid media, with energies orders of magnitude greater than previously achievable. This focusing is made possible by a tunable, nonlinear acoustic lens, which consists of ordered arrays of granular chains. The amplitude, size, and location of the sound bullets can be controlled by varying the static precompression of the chains. Theory and numerical simulations demonstrate the focusing effect, and photoelasticity experiments corroborate it. Our nonlinear lens permits a qualitatively new way of generating high-energy acoustic pulses, which may improve imaging capabilities through increased accuracy and signal-to-noise ratios and may lead to more effective nonintrusive scalpels, for example, for cancer treatment. PMID:20368461

Reflected wave manipulation by inhomogeneous impedance via varying-depth acoustic liners

NASA Astrophysics Data System (ADS)

Guo, Jingwen; Zhang, Xin; Fang, Yi; Fattah, Ryu

2018-05-01

Acoustic liners, consisting of a perforated panel affixed to a honeycomb core with a rigid back plate, are widely used for noise attenuation purpose. In this study, by exploiting inhomogeneous impedance properties, we report an experimental and numerical study on a liner-type acoustic metasurface, which possesses the functionality of both reflected wave manipulation and sound energy attenuation simultaneously. To realize the inhomogeneous acoustic impedance, an acoustic metasurface constructed by varying-depth acoustic liners is designed and fabricated. The reflected sound pressure fields induced by the metasurface are obtained in both experiments and simulations. A complete characterization of this metasurface is performed, including the effects of depth gradient, incident angle, and incident frequency. Anomalous reflection, apparent negative reflection, and conversion from an incident wave to a surface wave with strong energy dissipation are achieved by the structure. Moreover, our proposed structure can overcome the single frequency performance limitation that exists in conventional metasurfaces and performs well in a broadband frequency range. The proposed acoustic metasurface offers flexibility in controlling the direction of sound wave propagation with energy dissipation property and holds promise for various applications of noise reduction.

Acoustic Propagation Modeling in Shallow Water

DTIC Science & Technology

1996-10-01

Oceanography La Jolla, California 92093-0701 (Received April 15, 1996) This paper provides references for the Navy’s existing databases . Various...a compilation of many aspects of high-frequency (OAML) contains a description of Navy models and acoustics. databases . The Navy’s use of shallow...become significant because the propagation path may involve many tens of bounces. A description of a reflectivity database is (b) Geometry for the

Acoustic sources of opportunity in the marine environment - Applied to source localization and ocean sensing

NASA Astrophysics Data System (ADS)

Verlinden, Christopher M.

Controlled acoustic sources have typically been used for imaging the ocean. These sources can either be used to locate objects or characterize the ocean environment. The processing involves signal extraction in the presence of ambient noise, with shipping being a major component of the latter. With the advent of the Automatic Identification System (AIS) which provides accurate locations of all large commercial vessels, these major noise sources can be converted from nuisance to beacons or sources of opportunity for the purpose of studying the ocean. The source localization method presented here is similar to traditional matched field processing, but differs in that libraries of data-derived measured replicas are used in place of modeled replicas. In order to account for differing source spectra between library and target vessels, cross-correlation functions are compared instead of comparing acoustic signals directly. The library of measured cross-correlation function replicas is extrapolated using waveguide invariant theory to fill gaps between ship tracks, fully populating the search grid with estimated replicas allowing for continuous tracking. In addition to source localization, two ocean sensing techniques are discussed in this dissertation. The feasibility of estimating ocean sound speed and temperature structure, using ship noise across a drifting volumetric array of hydrophones suspended beneath buoys, in a shallow water marine environment is investigated. Using the attenuation of acoustic energy along eigenray paths to invert for ocean properties such as temperature, salinity, and pH is also explored. In each of these cases, the theory is developed, tested using numerical simulations, and validated with data from acoustic field experiments.

Concurrent Ultrasonic Tomography and Acoustic Emission in Solid Materials

NASA Astrophysics Data System (ADS)

Chow, Thomas M.

A series of experiments were performed to detect stress induced changes in the elastic properties of various solid materials. A technique was developed where these changes were monitored concurrently by two methods, ultrasonic tomography and acoustic emission monitoring. This thesis discusses some experiments in which acoustic emission (AE) and ultrasonic tomography were performed on various samples of solid materials including rocks, concrete, metals, and fibre reinforced composites. Three separate techniques were used to induce stress in these samples. Disk shaped samples were subject to stress via diametral loading using an indirect tensile test geometry. Cylindrical samples of rocks and concrete were subject to hydraulic fracture tests, and rectangular samples of fibre reinforced composite were subject to direct tensile loading. The majority of the samples were elastically anisotropic. Full waveform acoustic emission and tomographic data were collected while these samples were under load to give information concerning changes in the structure of the material as it was undergoing stress change and/or failure. Analysis of this data indicates that AE and tomographic techniques mutually compliment each other to give a view of the stress induced elastic changes in the tested samples.

Effects of subsampling of passive acoustic recordings on acoustic metrics.

PubMed

Thomisch, Karolin; Boebel, Olaf; Zitterbart, Daniel P; Samaran, Flore; Van Parijs, Sofie; Van Opzeeland, Ilse

2015-07-01

Passive acoustic monitoring is an important tool in marine mammal studies. However, logistics and finances frequently constrain the number and servicing schedules of acoustic recorders, requiring a trade-off between deployment periods and sampling continuity, i.e., the implementation of a subsampling scheme. Optimizing such schemes to each project's specific research questions is desirable. This study investigates the impact of subsampling on the accuracy of two common metrics, acoustic presence and call rate, for different vocalization patterns (regimes) of baleen whales: (1) variable vocal activity, (2) vocalizations organized in song bouts, and (3) vocal activity with diel patterns. To this end, above metrics are compared for continuous and subsampled data subject to different sampling strategies, covering duty cycles between 50% and 2%. The results show that a reduction of the duty cycle impacts negatively on the accuracy of both acoustic presence and call rate estimates. For a given duty cycle, frequent short listening periods improve accuracy of daily acoustic presence estimates over few long listening periods. Overall, subsampling effects are most pronounced for low and/or temporally clustered vocal activity. These findings illustrate the importance of informed decisions when applying subsampling strategies to passive acoustic recordings or analyses for a given target species.

Elastic versus acoustic inversion for marine surveys

NASA Astrophysics Data System (ADS)

Mora, Peter; Wu, Zedong

2018-04-01

Full Wavefield Inversion (FWI) is a powerful and elegant approach for seismic imaging that is on the way to becoming the method of choice when processing exploration or global seismic data. In the case of processing marine survey data, one may be tempted to assume acoustic FWI is sufficient given that only pressure waves exist in the water layer. In this paper, we pose the question as to whether or not in theory - at least for a hard water bottom case - it should be possible to resolve the shear modulus or S-wave velocity in a marine setting using large offset data. We therefore conduct numerical experiments with idealized marine data calculated with the elastic wave equation. We study two cases, FWI of data due to a diffractor model, and FWI of data due to a fault model. We find that at least in idealized situation, elastic FWI of hard waterbottom data is capable of resolving between the two Lamé parameters λ and μ. Another numerical experiment with a soft waterbottom layer gives the same result. In contrast, acoustic FWI of the synthetic elastic data results in a single image of the first Lamé parameter λ which contains severe artefacts for diffraction data and noticable artefacts for layer reflection data. Based on these results, it would appear that at least, inversions of large offset marine data should be fully elastic rather than acoustic unless it has been demonstrated that for the specific case in question (offsets, model and water depth, practical issues such as soft sediment attenuation of shear waves or computational time), that an acoustic only inversion provides a reasonably good quality of image comparable to that of an elastic inversion. Further research with real data is required to determine the degree to which practical issues such as shear wave attenuation in soft sediments may affect this result.

Elastic versus acoustic inversion for marine surveys

NASA Astrophysics Data System (ADS)

Mora, Peter; Wu, Zedong

2018-07-01

Full wavefield inversion (FWI) is a powerful and elegant approach for seismic imaging that is on the way to becoming the method of choice when processing exploration or global seismic data. In the case of processing marine survey data, one may be tempted to assume that acoustic FWI is sufficient given that only pressure waves exist in the water layer. In this paper, we pose the question as to whether or not in theory—at least for a hard waterbottom case—it should be possible to resolve the shear modulus or S-wave velocity in a marine setting using large offset data. We, therefore, conduct numerical experiments with idealized marine data calculated with the elastic wave equation. We study two cases, FWI of data due to a diffractor model, and FWI of data due to a fault model. We find that at least in idealized situation, elastic FWI of hard waterbottom data is capable of resolving between the two Lamé parameters λ and μ. Another numerical experiment with a soft waterbottom layer gives the same result. In contrast, acoustic FWI of the synthetic elastic data results in a single image of the first Lamé parameter λ which contains severe artefacts for diffraction data and notable artefacts for layer reflection data. Based on these results, it would appear that at least the inversions of large offset marine data should be fully elastic rather than acoustic, unless it has been demonstrated that for the specific case in question (offsets, model and water depth, practical issues such as soft sediment attenuation of shear waves or computational time), an acoustic-only inversion provides a reasonably good quality of image comparable to that of an elastic inversion. Further research with real data is required to determine the degree to which practical issues such as shear wave attenuation in soft sediments may affect this result.

Outcomes Measurement in Voice Disorders: Application of an Acoustic Index of Dysphonia Severity

ERIC Educational Resources Information Center

Awan, Shaheen N.; Roy, Nelson

2009-01-01

Purpose: The purpose of this experiment was to assess the ability of an acoustic model composed of both time-based and spectral-based measures to track change following voice disorder treatment and to serve as a possible treatment outcomes measure. Method: A weighted, four-factor acoustic algorithm consisting of shimmer, pitch sigma, the ratio of…

Producing acoustic 'Frozen Waves': simulated experiments with diffraction/attenuation resistant beams in lossy media.

PubMed

Prego-Borges, José L; Zamboni-Rached, Michel; Recami, Erasmo; Costa, Eduardo Tavares

2014-08-01

The so-called Localized Waves (LW), and the "Frozen Waves" (FW), have raised significant attention in the areas of Optics and Ultrasound, because of their surprising energy localization properties. The LWs resist the effects of diffraction for large distances, and possess an interesting self-reconstruction -self-healing- property (after obstacles with size smaller than the antenna's); while the FWs, a sub-class of LWs, offer the possibility of arbitrarily modeling the longitudinal field intensity pattern inside a prefixed interval, for instance 0⩽z⩽L, of the wave propagation axis. More specifically, the FWs are localized fields "at rest", that is, with a static envelope (within which only the carrier wave propagates), and can be endowed moreover with a high transverse localization. In this paper we investigate, by simulated experiments, various cases of generation of ultrasonic FW fields, with the frequency of f0=1 MHz in a water-like medium, taking account of the effects of attenuation. We present results of FWs for distances up to L=80 mm, in attenuating media with absorption coefficient α in the range 70⩽α⩽170 dB/m. Such simulated FW fields are constructed by using a procedure developed by us, via appropriate finite superpositions of monochromatic ultrasonic Bessel beams. We pay due attention to the selection of the FW parameters, constrained by the rather tight restrictions imposed by experimental Acoustics, as well as to some practical implications of the transducer design. The energy localization properties of the Frozen Waves can find application even in many medical apparatus, such as bistouries or acoustic tweezers, as well as for treatment of diseased tissues (in particular, for the destruction of tumor cells, without affecting the surrounding tissues; also for kidney stone shuttering, etc.). Copyright © 2014 Elsevier B.V. All rights reserved.

Analyzing panel acoustic contributions toward the sound field inside the passenger compartment of a full-size automobile.

PubMed

Wu, Sean F; Moondra, Manmohan; Beniwal, Ravi

2015-04-01

The Helmholtz equation least squares (HELS)-based nearfield acoustical holography (NAH) is utilized to analyze panel acoustic contributions toward the acoustic field inside the interior region of an automobile. Specifically, the acoustic power flows from individual panels are reconstructed, and relative contributions to sound pressure level and spectrum at any point of interest are calculated. Results demonstrate that by correlating the acoustic power flows from individual panels to the field acoustic pressure, one can correctly locate the panel allowing the most acoustic energy transmission into the vehicle interior. The panel on which the surface acoustic pressure amplitude is the highest should not be used as indicative of the panel responsible for the sound field in the vehicle passenger compartment. Another significant advantage of this HELS-based NAH is that measurements of the input data only need to be taken once by using a conformal array of microphones in the near field, and ranking of panel acoustic contributions to any field point can be readily performed. The transfer functions between individual panels of any vibrating structure to the acoustic pressure anywhere in space are calculated not measured, thus significantly reducing the time and effort involved in panel acoustic contributions analyses.

Laser Generated Leaky Acoustic Waves for Needle Visualization.

PubMed

Wu, Kai-Wen; Wang, Yi-An; Li, Pai-Chi

2018-04-01

Ultrasound (US)-guided needle operation is usually used to visualize both tissue and needle position such as tissue biopsy and localized drug delivery. However, the transducer-needle orientation is limited due to reflection of the acoustic waves. We proposed a leaky acoustic wave method to visualize the needle position and orientation. Laser pulses are emitted on top of the needle to generate acoustic waves; then, these acoustic waves propagate along the needle surface. Leaky wave signals are detected by the US array transducer. The needle position can be calculated by phase velocities of two different wave modes and their corresponding emission angles. In our experiments, a series of needles was inserted into a tissue mimicking phantom and porcine tissue to evaluate the accuracy of the proposed method. The results show that the detection depth is up to 51 mm and the insertion angle is up to 40° with needles of different diameters. It is demonstrated that the proposed approach outperforms the conventional B-mode US-guided needle operation in terms of the detection range while achieving similar accuracy. The proposed method reveals the potentials for further clinical applications.

Mid-Frequency Environmental and Acoustic Studies from SW06, and Applications to Asian Littoral Waters

DTIC Science & Technology

2009-09-30

Development (ADD), Hanyang University ( HYU ), to undertake collaborative research programs in shallow water acoustics in Asian littoral waters...coast of Korea with the U.S. NRL, ADD and HYU that occurred in August 2008, as part of the Transverse Acoustic Variability Experiment (TAVEX

A Secure Communication Suite for Underwater Acoustic Sensor Networks

PubMed Central

Dini, Gianluca; Duca, Angelica Lo

2012-01-01

In this paper we describe a security suite for Underwater Acoustic Sensor Networks comprising both fixed and mobile nodes. The security suite is composed of a secure routing protocol and a set of cryptographic primitives aimed at protecting the confidentiality and the integrity of underwater communication while taking into account the unique characteristics and constraints of the acoustic channel. By means of experiments and simulations based on real data, we show that the suite is suitable for an underwater networking environment as it introduces limited, and sometimes negligible, communication and power consumption overhead. PMID:23202204

Plant Ethylene Detection Using Laser-Based Photo-Acoustic Spectroscopy.

PubMed

Van de Poel, Bram; Van Der Straeten, Dominique

2017-01-01

Analytical detection of the plant hormone ethylene is an important prerequisite in physiological studies. Real-time and super sensitive detection of trace amounts of ethylene gas is possible using laser-based photo-acoustic spectroscopy. This Chapter will provide some background on the technique, compare it with conventional gas chromatography, and provide a detailed user-friendly hand-out on how to operate the machine and the software. In addition, this Chapter provides some tips and tricks for designing and performing physiological experiments suited for ethylene detection with laser-based photo-acoustic spectroscopy.

A Numerical Method of Calculating Propeller Noise Including Acoustic Nonlinear Effects

NASA Technical Reports Server (NTRS)

Korkan, K. D.

1985-01-01

Using the transonic flow fields(s) generated by the NASPROP-E computer code for an eight blade SR3-series propeller, a theoretical method is investigated to calculate the total noise values and frequency content in the acoustic near and far field without using the Ffowcs Williams - Hawkings equation. The flow field is numerically generated using an implicit three dimensional Euler equation solver in weak conservation law form. Numerical damping is required by the differencing method for stability in three dimensions, and the influence of the damping on the calculated acoustic values is investigated. The acoustic near field is solved by integrating with respect to time the pressure oscillations induced at a stationary observer location. The acoustic far field is calculated from the near field primitive variables as generated by NASPROP-E computer code using a method involving a perturbation velocity potential as suggested by Hawkings in the calculation of the acoustic pressure time-history at a specified far field observed location. the methodologies described are valid for calculating total noise levels and are applicable to any propeller geometry for which a flow field solution is available.

Spectral and temporal resolutions of information-bearing acoustic changes for understanding vocoded sentencesa)

PubMed Central

Stilp, Christian E.; Goupell, Matthew J.

2015-01-01

Short-time spectral changes in the speech signal are important for understanding noise-vocoded sentences. These information-bearing acoustic changes, measured using cochlea-scaled entropy in cochlear implant simulations [CSECI; Stilp et al. (2013). J. Acoust. Soc. Am. 133(2), EL136–EL141; Stilp (2014). J. Acoust. Soc. Am. 135(3), 1518–1529], may offer better understanding of speech perception by cochlear implant (CI) users. However, perceptual importance of CSECI for normal-hearing listeners was tested at only one spectral resolution and one temporal resolution, limiting generalizability of results to CI users. Here, experiments investigated the importance of these informational changes for understanding noise-vocoded sentences at different spectral resolutions (4–24 spectral channels; Experiment 1), temporal resolutions (4–64 Hz cutoff for low-pass filters that extracted amplitude envelopes; Experiment 2), or when both parameters varied (6–12 channels, 8–32 Hz; Experiment 3). Sentence intelligibility was reduced more by replacing high-CSECI intervals with noise than replacing low-CSECI intervals, but only when sentences had sufficient spectral and/or temporal resolution. High-CSECI intervals were more important for speech understanding as spectral resolution worsened and temporal resolution improved. Trade-offs between CSECI and intermediate spectral and temporal resolutions were minimal. These results suggest that signal processing strategies that emphasize information-bearing acoustic changes in speech may improve speech perception for CI users. PMID:25698018

Acoustical and optical radiation pressure and the development of single beam acoustical tweezers

NASA Astrophysics Data System (ADS)

Thomas, Jean-Louis; Marchiano, Régis; Baresch, Diego

2017-07-01

Studies on radiation pressure in acoustics and optics have enriched one another and have a long common history. Acoustic radiation pressure is used for metrology, levitation, particle trapping and actuation. However, the dexterity and selectivity of single-beam optical tweezers are still to be matched with acoustical devices. Optical tweezers can trap, move and position micron size particles, biological samples or even atoms with subnanometer accuracy in three dimensions. One limitation of optical tweezers is the weak force that can be applied without thermal damage due to optical absorption. Acoustical tweezers overcome this limitation since the radiation pressure scales as the field intensity divided by the speed of propagation of the wave. However, the feasibility of single beam acoustical tweezers was demonstrated only recently. In this paper, we propose a historical review of the strong similarities but also the specificities of acoustical and optical radiation pressures, from the expression of the force to the development of single-beam acoustical tweezers.

Broadband acoustic focusing by Airy-like beams based on acoustic metasurfaces

NASA Astrophysics Data System (ADS)

Chen, Di-Chao; Zhu, Xing-Feng; Wei, Qi; Wu, Da-Jian; Liu, Xiao-Jun

2018-01-01

An acoustic metasurface (AM) composed of space-coiling subunits is proposed to generate acoustic Airy-like beams (ALBs) by manipulating the transmitted acoustic phase. The self-accelerating, self-healing, and non-diffracting features of ALBs are demonstrated using finite element simulations. We further employ two symmetrical AMs to realize two symmetrical ALBs, resulting in highly efficient acoustic focusing. At the working frequency, the focal intensity can reach roughly 20 times that of the incident wave. It is found that the highly efficient acoustic focusing can circumvent obstacles in the propagating path and can be maintained in a broad frequency bandwidth. In addition, simply changing the separation between the two AMs can modulate the focal length of the proposed AM lens. ALBs generated by AMs and the corresponding AM lens may benefit applications in medical ultrasound imaging, biomedical therapy, and particle trapping and manipulation.

Acoustic characterization of a nonlinear vibroacoustic absorber at low frequencies and high sound levels

NASA Astrophysics Data System (ADS)

Chauvin, A.; Monteil, M.; Bellizzi, S.; Côte, R.; Herzog, Ph.; Pachebat, M.

2018-03-01

A nonlinear vibroacoustic absorber (Nonlinear Energy Sink: NES), involving a clamped thin membrane made in Latex, is assessed in the acoustic domain. This NES is here considered as an one-port acoustic system, analyzed at low frequencies and for increasing excitation levels. This dynamic and frequency range requires a suitable experimental technique, which is presented first. It involves a specific impedance tube able to deal with samples of sufficient size, and reaching high sound levels with a guaranteed linear response thank's to a specific acoustic source. The identification method presented here requires a single pressure measurement, and is calibrated from a set of known acoustic loads. The NES reflection coefficient is then estimated at increasing source levels, showing its strong level dependency. This is presented as a mean to understand energy dissipation. The results of the experimental tests are first compared to a nonlinear viscoelastic model of the membrane absorber. In a second step, a family of one degree of freedom models, treated as equivalent Helmholtz resonators is identified from the measurements, allowing a parametric description of the NES behavior over a wide range of levels.

Microfibrous metallic cloth for acoustic isolation of a MEMS gyroscope

NASA Astrophysics Data System (ADS)

Dean, Robert; Burch, Nesha; Black, Meagan; Beal, Aubrey; Flowers, George

2011-04-01

The response of a MEMS device that is exposed to a harsh environment may range from an increased noise floor to a completely erroneous output to temporary or even permanent device failure. One such harsh environment is high power acoustic energy possessing high frequency components. This type of environment sometimes occurs in small aerospace vehicles. In this type of operating environment, high frequency acoustic energy can be transferred to a MEMS gyroscope die through the device packaging. If the acoustic noise possesses a sufficiently strong component at the resonant frequency of the gyroscope, it will overexcite the motion of the proof mass, resulting in the deleterious effect of corrupted angular rate measurement. Therefore if the device or system packaging can be improved to sufficiently isolate the gyroscope die from environmental acoustic energy, the sensor may find new applications in this type of harsh environment. This research effort explored the use of microfibrous metallic cloth for isolating the gyroscope die from environmental acoustic excitation. Microfibrous cloth is a composite of fused, intermingled metal fibers and has a variety of typical uses involving chemical processing applications and filtering. Specifically, this research consisted of experimental evaluations of multiple layers of packed microfibrous cloth composed of sintered nickel material. The packed cloth was used to provide acoustic isolation for a test MEMS gyroscope, the Analog Devices ADXRS300. The results of this investigation revealed that the intermingling of the various fibers of the metallic cloth provided a significant contact area between the fiber strands and voids, which enhanced the acoustic damping of the material. As a result, the nickel cloth was discovered to be an effective acoustic isolation material for this particular MEMS gyroscope.

A Hybrid Acoustic and Pronunciation Model Adaptation Approach for Non-native Speech Recognition

NASA Astrophysics Data System (ADS)

Oh, Yoo Rhee; Kim, Hong Kook

In this paper, we propose a hybrid model adaptation approach in which pronunciation and acoustic models are adapted by incorporating the pronunciation and acoustic variabilities of non-native speech in order to improve the performance of non-native automatic speech recognition (ASR). Specifically, the proposed hybrid model adaptation can be performed at either the state-tying or triphone-modeling level, depending at which acoustic model adaptation is performed. In both methods, we first analyze the pronunciation variant rules of non-native speakers and then classify each rule as either a pronunciation variant or an acoustic variant. The state-tying level hybrid method then adapts pronunciation models and acoustic models by accommodating the pronunciation variants in the pronunciation dictionary and by clustering the states of triphone acoustic models using the acoustic variants, respectively. On the other hand, the triphone-modeling level hybrid method initially adapts pronunciation models in the same way as in the state-tying level hybrid method; however, for the acoustic model adaptation, the triphone acoustic models are then re-estimated based on the adapted pronunciation models and the states of the re-estimated triphone acoustic models are clustered using the acoustic variants. From the Korean-spoken English speech recognition experiments, it is shown that ASR systems employing the state-tying and triphone-modeling level adaptation methods can relatively reduce the average word error rates (WERs) by 17.1% and 22.1% for non-native speech, respectively, when compared to a baseline ASR system.

Child-Mother Agreement on Experiences of School Bullying Involvement in Children With ADHD.

PubMed

Hu, Huei-Fan; Yen, Chia-Nan; Wu, Yu-Yu; Hsiao, Ray C; Yen, Cheng-Fang; Cheng, Chung-Ping

2018-03-01

To examine the levels of agreement between the reports of 452 children and their mothers on children's experiences of bullying involvement at school and investigate the factors influencing the levels of agreement in children with ADHD. The levels of agreement between children's and mothers' reports were examined. The influence of age, sex, ADHD symptoms, and psychiatric comorbidities on the levels of agreement was also examined. The results indicated low agreement on the experiences of bullying involvement in child-mother ADHD dyads. Age and hyperactivity-impulsivity, oppositional, depressive, and anxiety symptoms significantly influenced the levels of agreement on the victimization of physical bullying. Age significantly influenced the levels of agreement on the perpetration of physical bullying. Multiple sources of information are required when clinicians assess the experiences of bullying involvement at school in children with ADHD. The factors influencing the levels of agreement should be considered.

Acoustic integrated extinction.

PubMed

Norris, Andrew N

2015-05-08

The integrated extinction (IE) is defined as the integral of the scattering cross section as a function of wavelength. Sohl et al. (2007 J. Acoust. Soc. Am. 122 , 3206-3210. (doi:10.1121/1.2801546)) derived an IE expression for acoustic scattering that is causal, i.e. the scattered wavefront in the forward direction arrives later than the incident plane wave in the background medium. The IE formula was based on electromagnetic results, for which scattering is causal by default. Here, we derive a formula for the acoustic IE that is valid for causal and non-causal scattering. The general result is expressed as an integral of the time-dependent forward scattering function. The IE reduces to a finite integral for scatterers with zero long-wavelength monopole and dipole amplitudes. Implications for acoustic cloaking are discussed and a new metric is proposed for broadband acoustic transparency.

Acoustic levitation of liquid drops: Dynamics, manipulation and phase transitions.

PubMed

Zang, Duyang; Yu, Yinkai; Chen, Zhen; Li, Xiaoguang; Wu, Hongjing; Geng, Xingguo

2017-05-01

The technique of acoustic levitation normally produces a standing wave and the potential well of the sound field can be used to trap small objects. Since no solid surface is involved it has been widely applied for the study of fluid physics, nucleation, bio/chemical processes, and various forms of soft matter. In this article, we survey the works on drop dynamics in acoustic levitation, focus on how the dynamic behavior is related to the rheological properties and discuss the possibility to develop a novel rheometer based on this technique. We review the methods and applications of acoustic levitation for the manipulation of both liquid and solid samples and emphasize the important progress made in the study of phase transitions and bio-chemical analysis. We also highlight the possible open areas for future research. Copyright © 2017 Elsevier B.V. All rights reserved.

Spatiotemporal Imaging of the Acoustic Field Emitted by a Single Copper Nanowire

NASA Astrophysics Data System (ADS)

Jean, Cyril; Belliard, Laurent; Cornelius, Thomas W.; Thomas, Olivier; Pennec, Yan; Cassinelli, Marco; Toimil-Molares, Maria Eugenia; Perrin, Bernard

2016-10-01

The monochromatic and geometrically anisotropic acoustic field generated by 400 nm and 120 nm diameter copper nanowires simply dropped on a 10 $\\mu$m silicon membrane is investigated in transmission using three-dimensional time-resolved femtosecond pump-probe experiments. Two pump-probe time-resolved experiments are carried out at the same time on both side of the silicon substrate. In reflection, the first radial breathing mode of the nanowire is excited and detected. In transmission, the longitudinal and shear waves are observed. The longitudinal signal is followed by a monochromatic component associated with the relaxation of the nanowire's first radial breathing mode. Finite Difference Time Domain (FDTD) simulations are performed and accurately reproduce the diffracted field. A shape anisotropy resulting from the large aspect ratio of the nanowire is detected in the acoustic field. The orientation of the underlying nanowires is thus acoustically deduced.

Case study of restaurant successfully designed, constructed, and operated for excellent dining acoustics

NASA Astrophysics Data System (ADS)

Bollard, Paul; Des Jardins, Stephen

2005-09-01

Prior to the construction of La Provence Restaurant in Roseville, California in 2004, the owner, Stephen Des Jardins, traveled with his cook, architect, and engineer to the Provence Region of France to study the cuisine, architecture, and acoustics of the local restaurants. This information was incorporated into the design, construction, and operation of his restaurant, with acoustical design assistance provided by the author, Paul Bollard. The result of the owner's painstaking attention to detail is a restaurant which has received very positive reviews for its architecture, quality of food, service, and acoustic ambience. This paper documents the measures included in the construction of the restaurant to ensure that the building acoustics enhance the dining experience, rather than detract from it. Photographs of acoustic treatments are included, as are reverberation time (RT60) test results and ambient noise level measurement results.

Acoustic Signal Processing in Photorefractive Optical Systems.

NASA Astrophysics Data System (ADS)

Zhou, Gan

This thesis discusses applications of the photorefractive effect in the context of acoustic signal processing. The devices and systems presented here illustrate the ideas and optical principles involved in holographic processing of acoustic information. The interest in optical processing stems from the similarities between holographic optical systems and contemporary models for massively parallel computation, in particular, neural networks. An initial step in acoustic processing is the transformation of acoustic signals into relevant optical forms. A fiber-optic transducer with photorefractive readout transforms acoustic signals into optical images corresponding to their short-time spectrum. The device analyzes complex sound signals and interfaces them with conventional optical correlators. The transducer consists of 130 multimode optical fibers sampling the spectral range of 100 Hz to 5 kHz logarithmically. A physical model of the human cochlea can help us understand some characteristics of human acoustic transduction and signal representation. We construct a life-sized cochlear model using elastic membranes coupled with two fluid-filled chambers, and use a photorefractive novelty filter to investigate its response. The detection sensitivity is determined to be 0.3 angstroms per root Hz at 2 kHz. Qualitative agreement is found between the model response and physiological data. Delay lines map time-domain signals into space -domain and permit holographic processing of temporal information. A parallel optical delay line using dynamic beam coupling in a rotating photorefractive crystal is presented. We experimentally demonstrate a 64 channel device with 0.5 seconds of time-delay and 167 Hz bandwidth. Acoustic signal recognition is described in a photorefractive system implementing the time-delay neural network model. The system consists of a photorefractive optical delay-line and a holographic correlator programmed in a LiNbO_3 crystal. We demonstrate the recognition

Interacting Multiscale Acoustic Vortices as Coherent Excitations in Dust Acoustic Wave Turbulence

NASA Astrophysics Data System (ADS)

Lin, Po-Cheng; I, Lin

2018-03-01

In this work, using three-dimensional intermittent dust acoustic wave turbulence in a dusty plasma as a platform and multidimensional empirical mode decomposition into different-scale modes in the 2 +1 D spatiotemporal space, we demonstrate the experimental observation of the interacting multiscale acoustic vortices, winding around wormlike amplitude hole filaments coinciding with defect filaments, as the basic coherent excitations for acoustic-type wave turbulence. For different decomposed modes, the self-similar rescaled stretched exponential lifetime histograms of amplitude hole filaments, and the self-similar power spectra of dust density fluctuations, indicate that similar dynamical rules are followed over a wide range of scales. In addition to the intermode acoustic vortex pair generation, propagation, or annihilation, the intra- and intermode interactions of acoustic vortices with the same or opposite helicity, their entanglement and synchronization, are found to be the key dynamical processes in acoustic wave turbulence, akin to the interacting multiscale vortices around wormlike cores observed in hydrodynamic turbulence.

Acoustic Test Results of Melamine Foam with Application to Payload Fairing Acoustic Attenuation Systems

NASA Technical Reports Server (NTRS)

Hughes, William O.; McNelis, Anne M.

2014-01-01

A spacecraft at launch is subjected to a harsh acoustic and vibration environment resulting from the passage of acoustic energy, created during the liftoff of a launch vehicle, through the vehicle's payload fairing. In order to ensure the mission success of the spacecraft it is often necessary to reduce the resulting internal acoustic sound pressure levels through the usage of acoustic attenuation systems. Melamine foam, lining the interior walls of the payload fairing, is often utilized as the main component of such a system. In order to better understand the acoustic properties of melamine foam, with the goal of developing improved acoustic attenuation systems, NASA has recently performed panel level testing on numerous configurations of melamine foam acoustic treatments at the Riverbank Acoustical Laboratory. Parameters assessed included the foam's thickness and density, as well as the effects of a top outer cover sheet material and mass barriers embedded within the foam. This testing followed the ASTM C423 standard for absorption and the ASTM E90 standard for transmission loss. The acoustic test data obtained and subsequent conclusions are the subjects of this paper.

A Computational Study of the Flow Physics of Acoustic Liners

NASA Technical Reports Server (NTRS)

Tam, Christopher

2006-01-01

The present investigation is a continuation of a previous joint project between the Florida State University and the NASA Langley Research Center Liner Physics Team. In the previous project, a study of acoustic liners, in two dimensions, inside a normal incidence impedance tube was carried out. The study consisted of two parts. The NASA team was responsible for the experimental part of the project. This involved performing measurements in an impedance tube with a large aspect ratio slit resonator. The FSU team was responsible for the computation part of the project. This involved performing direct numerical simulation (DNS) of the NASA experiment in two dimensions using CAA methodology. It was agreed that upon completion of numerical simulation, the computed values of the liner impedance were to be sent to NASA for validation with experimental results. On following this procedure good agreements were found between numerical results and experimental measurements over a wide range of frequencies and sound-pressure-level. Broadband incident sound waves were also simulated numerically and measured experimentally. Overall, good agreements were also found.

Controllable Solid Propulsion Combustion and Acoustic Knowledge Base Improvements

NASA Technical Reports Server (NTRS)

McCauley, Rachel; Fischbach, Sean; Fredrick, Robert

2012-01-01

Controllable solid propulsion systems have distinctive combustion and acoustic environments that require enhanced testing and analysis techniques to progress this new technology from development to production. In a hot gas valve actuating system, the movement of the pintle through the hot gas exhibits complex acoustic disturbances and flow characteristics that can amplify induced pressure loads that can damage or detonate the rocket motor. The geometry of a controllable solid propulsion gas chamber can set up unique unsteady flow which can feed acoustic oscillations patterns that require characterization. Research in this area aids in the understanding of how best to design, test, and analyze future controllable solid rocket motors using the lessons learned from past government programs as well as university research and testing. This survey paper will give the reader a better understanding of the potentially amplifying affects propagated by a controllable solid rocket motor system and the knowledge of the tools current available to address these acoustic disturbances in a preliminary design. Finally the paper will supply lessons learned from past experiences which will allow the reader to come away with understanding of what steps need to be taken when developing a controllable solid rocket propulsion system. The focus of this survey will be on testing and analysis work published by solid rocket programs and from combustion and acoustic books, conference papers, journal articles, and additionally from subject matter experts dealing currently with controllable solid rocket acoustic analysis.

Acoustic Suppression Systems and Related Methods

NASA Technical Reports Server (NTRS)

Kolaini, Ali R. (Inventor); Kern, Dennis L. (Inventor)

2013-01-01

An acoustic suppression system for absorbing and/or scattering acoustic energy comprising a plurality of acoustic targets in a containment is described, the acoustic targets configured to have resonance frequencies allowing the targets to be excited by incoming acoustic waves, the resonance frequencies being adjustable to suppress acoustic energy in a set frequency range. Methods for fabricating and implementing the acoustic suppression system are also provided.

School Experiences of an Adolescent with Medical Complexities Involving Incontinence

ERIC Educational Resources Information Center

Filce, Hollie Gabler; Bishop, John B.

2014-01-01

The educational implications of chronic illnesses which involve incontinence are not well represented in the literature. The experiences of an adolescent with multiple complex illnesses, including incontinence, were explored via an intrinsic case study. Data were gathered from the adolescent, her mother, and teachers through interviews, email…

Introducing passive acoustic filter in acoustic based condition monitoring: Motor bike piston-bore fault identification

NASA Astrophysics Data System (ADS)

Jena, D. P.; Panigrahi, S. N.

2016-03-01

Requirement of designing a sophisticated digital band-pass filter in acoustic based condition monitoring has been eliminated by introducing a passive acoustic filter in the present work. So far, no one has attempted to explore the possibility of implementing passive acoustic filters in acoustic based condition monitoring as a pre-conditioner. In order to enhance the acoustic based condition monitoring, a passive acoustic band-pass filter has been designed and deployed. Towards achieving an efficient band-pass acoustic filter, a generalized design methodology has been proposed to design and optimize the desired acoustic filter using multiple filter components in series. An appropriate objective function has been identified for genetic algorithm (GA) based optimization technique with multiple design constraints. In addition, the sturdiness of the proposed method has been demonstrated in designing a band-pass filter by using an n-branch Quincke tube, a high pass filter and multiple Helmholtz resonators. The performance of the designed acoustic band-pass filter has been shown by investigating the piston-bore defect of a motor-bike using engine noise signature. On the introducing a passive acoustic filter in acoustic based condition monitoring reveals the enhancement in machine learning based fault identification practice significantly. This is also a first attempt of its own kind.

New Acoustic Arena Qualified at NASA Glenn's Aero-Acoustic Propulsion Laboratory

NASA Technical Reports Server (NTRS)

Wnuk, Stephen P.

2004-01-01

A new acoustic arena has been qualified in the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center. This arena is outfitted specifically for conducting fan noise research with the Advanced Noise Control Fan (ANCF) test rig. It features moveable walls with large acoustic wedges (2 by 2 by 1 ft) that create an acoustic environment usable at frequencies as low as 250 Hz. The arena currently uses two dedicated microphone arrays to acquire fan inlet and exhaust far-field acoustic data. It was used successfully in fiscal year 2003 to complete three ANCF tests. It also allowed Glenn to improve the operational efficiency of the four test rigs at AAPL and provided greater flexibility to schedule testing. There were a number of technical challenges to overcome in bringing the new arena to fruition. The foremost challenge was conflicting acoustic requirements of four different rigs. It was simply impossible to construct a static arena anywhere in the facility without intolerably compromising the acoustic test environment of at least one of the test rigs. This problem was overcome by making the wall sections of the new arena movable. Thus, the arena can be reconfigured to meet the operational requirements of any particular rig under test. Other design challenges that were encountered and overcome included structural loads of the large wedges, personnel access requirements, equipment maintenance requirements, and typical time and budget constraints. The new acoustic arena improves operations at the AAPL facility in several significant ways. First, it improves productivity by allowing multiple rigs to operate simultaneously. Second, it improves research data quality by providing a unique test area within the facility that is optimal for conducting fan noise research. Lastly, it reduces labor and equipment costs by eliminating the periodic need to transport the ANCF into and out of the primary AAPL acoustic arena. The investment to design, fabricate, and

Acoustic cooling engine

DOEpatents

Hofler, Thomas J.; Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

1988-01-01

An acoustic cooling engine with improved thermal performance and reduced internal losses comprises a compressible fluid contained in a resonant pressure vessel. The fluid has a substantial thermal expansion coefficient and is capable of supporting an acoustic standing wave. A thermodynamic element has first and second ends and is located in the resonant pressure vessel in thermal communication with the fluid. The thermal response of the thermodynamic element to the acoustic standing wave pumps heat from the second end to the first end. The thermodynamic element permits substantial flow of the fluid through the thermodynamic element. An acoustic driver cyclically drives the fluid with an acoustic standing wave. The driver is at a location of maximum acoustic impedance in the resonant pressure vessel and proximate the first end of the thermodynamic element. A hot heat exchanger is adjacent to and in thermal communication with the first end of the thermodynamic element. The hot heat exchanger conducts heat from the first end to portions of the resonant pressure vessel proximate the hot heat exchanger. The hot heat exchanger permits substantial flow of the fluid through the hot heat exchanger. The resonant pressure vessel can include a housing less than one quarter wavelength in length coupled to a reservoir. The housing can include a reduced diameter portion communicating with the reservoir. The frequency of the acoustic driver can be continuously controlled so as to maintain resonance.

Neural Correlates of Sound Localization in Complex Acoustic Environments

PubMed Central

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

2013-01-01

Listening to and understanding people in a “cocktail-party situation” is a remarkable feature of the human auditory system. Here we investigated the neural correlates of the ability to localize a particular sound among others in an acoustically cluttered environment with healthy subjects. In a sound localization task, five different natural sounds were presented from five virtual spatial locations during functional magnetic resonance imaging (fMRI). Activity related to auditory stream segregation was revealed in posterior superior temporal gyrus bilaterally, anterior insula, supplementary motor area, and frontoparietal network. Moreover, the results indicated critical roles of left planum temporale in extracting the sound of interest among acoustical distracters and the precuneus in orienting spatial attention to the target sound. We hypothesized that the left-sided lateralization of the planum temporale activation is related to the higher specialization of the left hemisphere for analysis of spectrotemporal sound features. Furthermore, the precuneus − a brain area known to be involved in the computation of spatial coordinates across diverse frames of reference for reaching to objects − seems to be also a crucial area for accurately determining locations of auditory targets in an acoustically complex scene of multiple sound sources. The precuneus thus may not only be involved in visuo-motor processes, but may also subserve related functions in the auditory modality. PMID:23691185