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Sample records for acoustic transmission loss

  1. Noise transmission loss of aircraft panels using acoustic intensity methods

    NASA Technical Reports Server (NTRS)

    Mcgary, M. C.

    1982-01-01

    The two-microphone, cross-spectral, acoustic intensity measurement technique was used to determine the acoustic transmission loss of three different aircraft panels. The study was conducted in the transmission loss apparatus in the Langley aircraft noise reduction laboratory.

  2. Determining Transmission Loss from Measured External and Internal Acoustic Environments

    NASA Technical Reports Server (NTRS)

    Scogin, Tyler; Smith, A. M.

    2012-01-01

    An estimate of the internal acoustic environment in each internal cavity of a launch vehicle is needed to ensure survivability of Space Launch System (SLS) avionics. Currently, this is achieved by using the noise reduction database of heritage flight vehicles such as the Space Shuttle and Saturn V for liftoff and ascent flight conditions. Marshall Space Flight Center (MSFC) is conducting a series of transmission loss tests to verify and augment this method. For this test setup, an aluminum orthogrid curved panel representing 1/8th of the circumference of a section of the SLS main structure was mounted in between a reverberation chamber and an anechoic chamber. Transmission loss was measured across the panel using microphones. Data measured during this test will be used to estimate the internal acoustic environments for several of the SLS launch vehicle internal spaces.

  3. Measurement of transmission loss characteristics using acoustic intensity techniques at the KU-FRL Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Roskam, J.

    1983-01-01

    The transmission loss characteristics of panels using the acoustic intensity technique is presented. The theoretical formulation, installation of hardware, modifications to the test facility, and development of computer programs and test procedures are described. A listing of all the programs is also provided. The initial test results indicate that the acoustic intensity technique is easily adapted to measure transmission loss characteristics of panels. Use of this method will give average transmission loss values. The fixtures developed to position the microphones along the grid points are very useful in plotting the intensity maps of vibrating panels.

  4. Efficient Acoustic Uncertainty Estimation for Transmission Loss Calculations

    DTIC Science & Technology

    2011-09-01

    Soc. Am. Vol. 129, 589-592. PUBLICATIONS [1] Kundu , P.K., Cohen, I.M., and Dowling, D.R., Fluid Mechanics , 5th Ed. (Academic Press, Oxford, 2012), 891 pages. ...Transmission Loss Calculations Kevin R. James Department of Mechanical Engineering University of Michigan Ann Arbor, MI 48109-2133 phone: (734) 998...1807 fax: (734) 764-4256 email: krj@umich.edu David R. Dowling Department of Mechanical Engineering University of Michigan Ann Arbor, MI

  5. Bayesian hindcast of acoustic transmission loss in the western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Palmsten, Margaret; Paquin Fabre, J.

    2016-09-01

    A Bayesian network is developed to demonstrate the feasibility of using environmental acoustic feature vectors (EAFVs) to predict underwater acoustic transmission loss (TL) versus range at two locations for a single acoustic source depth and frequency. Features for the networks are chosen based on a sensitivity analysis. The final network design resulted in a well-trained network, with high skill, little gain error, and low bias. The capability presented here shows promise for expansion to a more generalized approach, which could be applied at varying locations, depths and frequencies to estimate acoustic performance over a highly variable oceanographic area in real-time or near-real-time.

  6. Loss-induced Enhanced Transmission in Anisotropic Density-near-zero Acoustic Metamaterials

    PubMed Central

    Shen, Chen; Jing, Yun

    2016-01-01

    Anisotropic density-near-zero (ADNZ) acoustic metamaterials are investigated theoretically and numerically in this paper and are shown to exhibit extraordinary transmission enhancement when material loss is induced. The enhanced transmission is due to the enhanced propagating and evanescent wave modes inside the ADNZ medium thanks to the interplay of near-zero density, material loss, and high wave impedance matching in the propagation direction. The equi-frequency contour (EFC) is used to reveal whether the propagating wave mode is allowed in ADNZ metamaterials. Numerical simulations based on plate-type acoustic metamaterials with different material losses were performed to demonstrate collimation and subwavelength imaging enabled by the induced loss in ADNZ media. This work provides a different way for manipulating acoustic waves. PMID:27885268

  7. Loss-induced Enhanced Transmission in Anisotropic Density-near-zero Acoustic Metamaterials

    NASA Astrophysics Data System (ADS)

    Shen, Chen; Jing, Yun

    2016-11-01

    Anisotropic density-near-zero (ADNZ) acoustic metamaterials are investigated theoretically and numerically in this paper and are shown to exhibit extraordinary transmission enhancement when material loss is induced. The enhanced transmission is due to the enhanced propagating and evanescent wave modes inside the ADNZ medium thanks to the interplay of near-zero density, material loss, and high wave impedance matching in the propagation direction. The equi-frequency contour (EFC) is used to reveal whether the propagating wave mode is allowed in ADNZ metamaterials. Numerical simulations based on plate-type acoustic metamaterials with different material losses were performed to demonstrate collimation and subwavelength imaging enabled by the induced loss in ADNZ media. This work provides a different way for manipulating acoustic waves.

  8. WaveQ3D: Fast and accurate acoustic transmission loss (TL) eigenrays, in littoral environments

    NASA Astrophysics Data System (ADS)

    Reilly, Sean M.

    This study defines a new 3D Gaussian ray bundling acoustic transmission loss model in geodetic coordinates: latitude, longitude, and altitude. This approach is designed to lower the computation burden of computing accurate environmental effects in sonar training application by eliminating the need to transform the ocean environment into a collection of Nx2D Cartesian radials. This approach also improves model accuracy by incorporating real world 3D effects, like horizontal refraction, into the model. This study starts with derivations for a 3D variant of Gaussian ray bundles in this coordinate system. To verify the accuracy of this approach, acoustic propagation predictions of transmission loss, time of arrival, and propagation direction are compared to analytic solutions and other models. To validate the model's ability to predict real world phenomena, predictions of transmission loss and propagation direction are compared to at-sea measurements, in an environment where strong horizontal refraction effect have been observed. This model has been integrated into U.S. Navy active sonar training system applications, where testing has demonstrated its ability to improve transmission loss calculation speed without sacrificing accuracy.

  9. Acoustic propagation through anisotropic internal wave fields: transmission loss, cross-range coherence, and horizontal refraction.

    PubMed

    Oba, Roger; Finette, Steven

    2002-02-01

    Results of a computer simulation study are presented for acoustic propagation in a shallow water, anisotropic ocean environment. The water column is characterized by random volume fluctuations in the sound speed field that are induced by internal gravity waves, and this variability is superimposed on a dominant summer thermocline. Both the internal wave field and resulting sound speed perturbations are represented in three-dimensional (3D) space and evolve in time. The isopycnal displacements consist of two components: a spatially diffuse, horizontally isotropic component and a spatially localized contribution from an undular bore (i.e., a solitary wave packet or solibore) that exhibits horizontal (azimuthal) anisotropy. An acoustic field is propagated through this waveguide using a 3D parabolic equation code based on differential operators representing wide-angle coverage in elevation and narrow-angle coverage in azimuth. Transmission loss is evaluated both for fixed time snapshots of the environment and as a function of time over an ordered set of snapshots which represent the time-evolving sound speed distribution. Horizontal acoustic coherence, also known as transverse or cross-range coherence, is estimated for horizontally separated points in the direction normal to the source-receiver orientation. Both transmission loss and spatial coherence are computed at acoustic frequencies 200 and 400 Hz for ranges extending to 10 km, a cross-range of 1 km, and a water depth of 68 m. Azimuthal filtering of the propagated field occurs for this environment, with the strongest variations appearing when propagation is parallel to the solitary wave depressions of the thermocline. A large anisotropic degradation in horizontal coherence occurs under the same conditions. Horizontal refraction of the acoustic wave front is responsible for the degradation, as demonstrated by an energy gradient analysis of in-plane and out-of-plane energy transfer. The solitary wave packet is

  10. Sound Transmission Loss Through a Corrugated-Core Sandwich Panel with Integrated Acoustic Resonators

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Allen, Albert R.; Zalewski, Bart F; Beck, Benjamin S.

    2014-01-01

    The goal of this study is to better understand the effect of structurally integrated resonators on the transmission loss of a sandwich panel. The sandwich panel has facesheets over a corrugated core, which creates long aligned chambers that run parallel to the facesheets. When ports are introduced through the facesheet, the long chambers within the core can be used as low-frequency acoustic resonators. By integrating the resonators within the structure they contribute to the static load bearing capability of the panel while also attenuating noise. An analytical model of a panel with embedded resonators is derived and compared with numerical simulations. Predictions show that acoustic resonators can significantly improve the transmission loss of the sandwich panel around the natural frequency of the resonators. In one configuration with 0.813 m long internal chambers, the diffuse field transmission loss is improved by more than 22 dB around 104 Hz. The benefit is achieved with no added mass or volume relative to the baseline structure. The embedded resonators are effective because they radiate sound out-of-phase with the structure. This results in destructive interference, which leads to less transmitted sound power.

  11. Evaluation of composite materials providing improved acoustic transmission loss for UAVs

    NASA Astrophysics Data System (ADS)

    Callicoat, Jeffrey R.

    With the proliferation of Unmanned Aerial Vehicles (UAVs) in civilian airspace in the near future, community noise will be a major issue of concern. Numerous studies have shown a direct link between community noise pollution (i.e., road traffic noise and airport noise) and serious health problems. There exists, therefore, a pressing need to create quiet UAVs, and this drives the need for noise-attenuating materials and structures suitable for UAV airframe fabrication. By shrouding predominant noise sources such as the engine, exhaust, and even the propeller (in the case of a ducted fan) with the airframe structure, the airframe can serve as a noise transmission barrier and substantially reduce UAV noise profiles. The present research effort is an experimental investigation of light-weight fiber-reinforced composite materials to provide high acoustic transmission loss (TL) for use in fabricating UAV airframes. A transmission loss tube acoustic test system was designed, fabricated, and validated, and extensive testing was done on numerous composite layups of interest for UAV fabrication. Composites under study included carbon fiber, fiberglass, and Kevlar fabrics as skin materials along with vinyl foam, Nomex honeycomb, and balsawood as core materials. Results from testing small 3"x3" samples in the TL tube led to the selection of four composite sandwich panels of interest for further study. Larger 36"x36" test samples of these selected layups were then fabricated and tested using a 2-room methodology. Whereas the TL tube yielded results in the stiffness-controlled region of acoustic behavior, the 2-room tests produced results in the mass-controlled region for these materials, enabling relative performance comparisons over both acoustic regimes. Recognizing that a good material for airframe fabrication should possess not only high TL, but also low weight and high stiffness, load-deflection tests were conducted and overall material performance was compared in terms of

  12. Broadband Transmission Loss Due to Reverberant Excitation

    NASA Technical Reports Server (NTRS)

    Barisciano, Lawrence P. Jr.

    1999-01-01

    The noise transmission characteristics of candidate curved aircraft sidewall panel constructions is examined analytically using finite element models of the selected panel geometries. The models are validated by experimental modal analyses and transmission loss testing. The structural and acoustic response of the models are then examined when subjected to random or reverberant excitation, the simulation of which is also discussed. For a candidate curved honeycomb panel, the effect of add-on trim panel treatments is examined. Specifically, two different mounting configurations are discussed and their effect on the transmission loss of the panel is presented. This study finds that the add-on acoustical treatments do improve on the primary structures transmission loss characteristics, however, much more research is necessary to draw any valid conclusions about the optimal configuration for the maximum noise transmission loss. This paper describes several directions for the extension of this work.

  13. Long Term Statistical Measurements of Environmental Acoustics Parameters in the Arctic. AEAS Report Number 2. Low Frequency Transmission Loss Measurements in the Central Arctic Ocean.

    DTIC Science & Technology

    2014-09-26

    RD-RI56 576 LONG TERM STATISTICAL MEASUREMENTS OF ENVIRONMENTAL 1/2 ACOUSTICS PRAMETERS I..(U) POLRR RESEARCH LAB INC CARPINTERIA CA B M BUCK 15 JAN...BUREAU Of STANDARDS-1963-A I l I E ".-.’ .’ In :j: Lona Term Statistical Measurements of Environmental Acoustics Parameters in the Arctic - AEAS...No - Lo Frequency Transmission ’>:--’.-’- , .- ’ ,. ’.*- Lona Term Statistical Measurements ofcean Environmental Acoustics Parameters ,..-’, in the

  14. Acoustic Power Transmission Through a Ducted Fan

    NASA Technical Reports Server (NTRS)

    Envia, Ed

    2016-01-01

    For high-speed ducted fans, when the rotor flowfield is shock-free, the main contribution to the inlet radiated acoustic power comes from the portion of the rotor stator interaction sound field that is transmitted upstream through the rotor. As such, inclusion of the acoustic transmission is an essential ingredient in the prediction of the fan inlet noise when the fan tip relative speed is subsonic. This paper describes a linearized Euler based approach to computing the acoustic transmission of fan tones through the rotor. The approach is embodied in a code called LINFLUX was applied to a candidate subsonic fan called the Advanced Ducted Propulsor (ADP). The results from this study suggest that it is possible to make such prediction with sufficient fidelity to provide an indication of the acoustic transmission trends with the fan tip speed.

  15. Extraordinary transmission of gigahertz surface acoustic waves

    PubMed Central

    Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H.; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H.; Wright, Oliver B.

    2016-01-01

    Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3–50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging. PMID:27640998

  16. Asymmetric acoustic transmission in multiple frequency bands

    SciTech Connect

    Sun, Hong-xiang; Yuan, Shou-qi; Zhang, Shu-yi

    2015-11-23

    We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices.

  17. Acoustic energy transmission in cast iron pipelines

    NASA Astrophysics Data System (ADS)

    Kiziroglou, Michail E.; Boyle, David E.; Wright, Steven W.; Yeatman, Eric M.

    2015-12-01

    In this paper we propose acoustic power transfer as a method for the remote powering of pipeline sensor nodes. A theoretical framework of acoustic power propagation in the ceramic transducers and the metal structures is drawn, based on the Mason equivalent circuit. The effect of mounting on the electrical response of piezoelectric transducers is studied experimentally. Using two identical transducer structures, power transmission of 0.33 mW through a 1 m long, 118 mm diameter cast iron pipe, with 8 mm wall thickness is demonstrated, at 1 V received voltage amplitude. A near-linear relationship between input and output voltage is observed. These results show that it is possible to deliver significant power to sensor nodes through acoustic waves in solid structures. The proposed method may enable the implementation of acoustic - powered wireless sensor nodes for structural and operation monitoring of pipeline infrastructure.

  18. Noise transmission through an acoustically treated and honeycomb stiffened aircraft sidewall

    NASA Astrophysics Data System (ADS)

    Grosveld, F. W.; Mixson, J. S.

    1984-10-01

    The noise transmission characteristics of test panels and acoustic treatments representative of an aircraft sidewall are experimentally investigated in the NASA Langley Research Center transmission loss apparatus. The test panels were built to represent a segment sidewall in the propeller plane of a twin-engine, turboprop light aircraft. It is shown that an advanced treatment, which uses honeycomb for structural stiffening of skin panels, has better noise transmission loss characteristics than a conventional treatment. An alternative treatment, using the concept of limp mass and vibration isolation, provides more transmission loss than the advanced treatment for the same total surface mass. Effects on transmission loss of a variety of acoustic treatment materials (acoustic blankets, septa, damping tape, and trim panels) are presented. Damping tape does not provide additional benefit when the other treatment provides a high level of damping. Window units representative of aircraft installations are shown to have low transmission loss relative to a completely treated sidewall.

  19. Theoretical vibro-acoustic modeling of acoustic noise transmission through aircraft windows

    NASA Astrophysics Data System (ADS)

    Aloufi, Badr; Behdinan, Kamran; Zu, Jean

    2016-06-01

    In this paper, a fully vibro-acoustic model for sound transmission across a multi-pane aircraft window is developed. The proposed model is efficiently applied for a set of window models to perform extensive theoretical parametric studies. The studied window configurations generally simulate the passenger window designs of modern aircraft classes which have an exterior multi-Plexiglas pane, an interior single acrylic glass pane and a dimmable glass ("smart" glass), all separated by thin air cavities. The sound transmission loss (STL) characteristics of three different models, triple-, quadruple- and quintuple-paned windows identical in size and surface density, are analyzed for improving the acoustic insulation performances. Typical results describing the influence of several system parameters, such as the thicknesses, number and spacing of the window panes, on the transmission loss are then investigated. In addition, a comparison study is carried out to evaluate the acoustic reduction capability of each window model. The STL results show that the higher frequencies sound transmission loss performance can be improved by increasing the number of window panels, however, the low frequency performance is decreased, particularly at the mass-spring resonances.

  20. Acoustic data transmission through a drillstring

    DOEpatents

    Drumheller, D.S.

    1992-07-07

    A method and apparatus for acoustically transmitting data along a drillstring are presented. In accordance with one embodiment of the present invention, acoustic data signals are conditioned to counteract distortions caused by the drillstring. Preferably, this conditioning step comprises multiplying each frequency component of the data signal by exp ([minus]ikL) where L is the transmission length of the drillstring, k is the wave number in the drillstring at the frequency of each component and i is ([minus]1)[sup 1/2]. In another embodiment of this invention, data signals having a frequency content in at least one passband of the drillstring are generated preferably traveling in only one direction (e.g., up the drillstring) while echoes in the drillstring resulting from the data transmission are suppressed. 20 figs.

  1. Acoustic data transmission through a drillstring

    DOEpatents

    Drumheller, Douglas S.

    1992-01-01

    A method and apparatus for acoustically transmitting data along a drillstring is presented. In accordance with one embodiment of the present invention, acoustic data signals are conditioned to counteract distortions caused by the drillstring. Preferably, this conditioning step comprises multiplying each frequency component of the data signal by exp (-ikL) where L is the transmission length of the drillstring, k is the wave number in the drillstring at the frequency of each component and i is (-1).sup.1/2. In another embodiment of this invention, data signals having a frequency content in at least one passband of the drillstring are generated preferably traveling in only one direction (e.g., up the drillstring) while echoes in the drillstring resulting from the data transmission are suppressed.

  2. Modified acoustic transmission tube apparatus incorporating an active downstream termination.

    PubMed

    Machuca-Tzili, F Arturo; Orduña-Bustamante, Felipe; Pérez-López, Antonio; Pérez-Ruiz, Santiago J; Pérez-Matzumoto, Andrés E

    2017-02-01

    Current techniques for measuring normal incidence sound transmission loss with a modified impedance tube, or transmission tube, require setting up two different absorbing termination loads at the end of the downstream tube [ASTM E2611-09, Standard Test Method for Measurement of Normal Incidence Sound Transmission of Acoustical Materials Based on the Transfer Matrix Method (American Society for Testing and Materials, West Conshohocken, 2009)]. The process of physically handling the two required passive absorbing loads is a possible source of measurement errors, which are mainly due to changes in sample test position, or in test setup re-assembly, between measurements. In this paper, a modified transmission tube apparatus is proposed for non-intrusively changing the downstream acoustic load by means of a combined passive-active termination. It provides a controlled variable sound absorption which simplifies the setup of standard two-load techniques, without the need of physically handling the apparatus during the tests. This virtually eliminates the risk of errors associated with the physical manipulation of the two passive terminations. Transmission loss measurements in some representative test conditions are reported, showing improvements over current implementations, in reducing by approximately 50% the measurement variations associated with the setup of the two required absorbing terminations. Measurement results agree within 0.4 dB (maximum difference in high resolution broadband), and 0.04 dB (mean difference in 1/3-octave bands), with those obtained using standard passive two-load methods.

  3. Acoustic asymmetric transmission based on time-dependent dynamical scattering

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Yang, Yang; Ni, Xu; Xu, Ye-Long; Sun, Xiao-Chen; Chen, Ze-Guo; Feng, Liang; Liu, Xiao-Ping; Lu, Ming-Hui; Chen, Yan-Feng

    2015-06-01

    An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrate a new acoustic frequency conversion process in a time-varying system, consisting of a rotating blade and the surrounding air. The scattered acoustic waves from this time-varying system experience frequency shifts, which are linearly dependent on the blade’s rotating frequency. Such scattering mechanism can be well described theoretically by an acoustic linear time-varying perturbation theory. Combining such time-varying scattering effects with highly efficient acoustic filtering, we successfully develop a tunable acoustic unidirectional device with 20 dB power transmission contrast ratio between two counter propagation directions at audible frequencies.

  4. Acoustic asymmetric transmission based on time-dependent dynamical scattering

    PubMed Central

    Wang, Qing; Yang, Yang; Ni, Xu; Xu, Ye-Long; Sun, Xiao-Chen; Chen, Ze-Guo; Feng, Liang; Liu, Xiao-ping; Lu, Ming-Hui; Chen, Yan-Feng

    2015-01-01

    An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrate a new acoustic frequency conversion process in a time-varying system, consisting of a rotating blade and the surrounding air. The scattered acoustic waves from this time-varying system experience frequency shifts, which are linearly dependent on the blade’s rotating frequency. Such scattering mechanism can be well described theoretically by an acoustic linear time-varying perturbation theory. Combining such time-varying scattering effects with highly efficient acoustic filtering, we successfully develop a tunable acoustic unidirectional device with 20 dB power transmission contrast ratio between two counter propagation directions at audible frequencies. PMID:26038886

  5. Extraordinary acoustic transmission mediated by Helmholtz resonators

    NASA Astrophysics Data System (ADS)

    Koju, Vijay; Rowe, Ebony; Robertson, William M.

    2014-07-01

    We demonstrate perfect transmission of sound through a rigid barrier embedded with Helmholtz resonators. The resonators are confined within a waveguide and they are oriented such that one neck protrudes onto each side of the barrier. Perfect sound transmission occurs even though the open area of the necks is less than 3% of the barrier area. Maximum transmission occurs at the resonant frequency of the Helmholtz resonator. Because the dimensions of the Helmholtz resonators are much smaller than the resonant wavelength, the transmission is independent of the direction of sound on the barrier and of the relative placement of the necks. Further, we show that the transmitted sound experiences a continuous phase transition of π radians as a function of frequency through resonance. In simulations of adjacent resonators with slightly offset resonance frequencies, the phase difference leads to destructive interference. By expanding the simulation to a linear array of tuned Helmholtz resonators we show that it is possible to create an acoustic lens. The ability of Helmholtz resonator arrays to manipulate the phase of a plane acoustic wave enables a new class of sonic beam-forming devices analogous to diffractive optics.

  6. Extraordinary acoustic transmission mediated by Helmholtz resonators

    SciTech Connect

    Koju, Vijay; Rowe, Ebony; Robertson, William M.

    2014-07-15

    We demonstrate perfect transmission of sound through a rigid barrier embedded with Helmholtz resonators. The resonators are confined within a waveguide and they are oriented such that one neck protrudes onto each side of the barrier. Perfect sound transmission occurs even though the open area of the necks is less than 3% of the barrier area. Maximum transmission occurs at the resonant frequency of the Helmholtz resonator. Because the dimensions of the Helmholtz resonators are much smaller than the resonant wavelength, the transmission is independent of the direction of sound on the barrier and of the relative placement of the necks. Further, we show that the transmitted sound experiences a continuous phase transition of π radians as a function of frequency through resonance. In simulations of adjacent resonators with slightly offset resonance frequencies, the phase difference leads to destructive interference. By expanding the simulation to a linear array of tuned Helmholtz resonators we show that it is possible to create an acoustic lens. The ability of Helmholtz resonator arrays to manipulate the phase of a plane acoustic wave enables a new class of sonic beam-forming devices analogous to diffractive optics.

  7. Asymmetric acoustic transmission in graded beam

    NASA Astrophysics Data System (ADS)

    Jing, Li; Wu, Jiu Hui; Guan, Dong; Lu, Kuan; Gao, Nansha; Songhua, Cao

    2016-12-01

    We demonstrate the dynamic effective material parameters and vibration performance of a graded beam. The structure of the beam was composed of several unit cells with different fill factors. The dispersion relations and energy band structures of each unit cell were calculated using the finite element method (FEM). The dynamic effective material parameters in each unit cell of the graded beam were determined by the dispersion relations and energy band structures. Longitudinal wave propagation was investigated using a numerical method and FEM. The results show that the graded beam allows asymmetric acoustic transmission over a wide range of frequencies.

  8. Theoretical analysis of sound transmission loss through graphene sheets

    SciTech Connect

    Natsuki, Toshiaki; Ni, Qing-Qing

    2014-11-17

    We examine the potential of using graphene sheets (GSs) as sound insulating materials that can be used for nano-devices because of their small size, super electronic, and mechanical properties. In this study, a theoretical analysis is proposed to predict the sound transmission loss through multi-layered GSs, which are formed by stacks of GS and bound together by van der Waals (vdW) forces between individual layers. The result shows that the resonant frequencies of the sound transmission loss occur in the multi-layered GSs and the values are very high. Based on the present analytical solution, we predict the acoustic insulation property for various layers of sheets under both normal incident wave and acoustic field of random incidence source. The scheme could be useful in vibration absorption application of nano devices and materials.

  9. Broadband enhanced transmission of acoustic waves through serrated metal gratings

    NASA Astrophysics Data System (ADS)

    Qi, Dong-Xiang; Deng, Yu-Qiang; Xu, Di-Hu; Fan, Ren-Hao; Peng, Ru-Wen; Chen, Ze-Guo; Lu, Ming-Hui; Huang, X. R.; Wang, Mu

    2015-01-01

    In this letter, we have demonstrated that serrated metal gratings, which introduce gradient coatings, can give rise to broadband transmission enhancement of acoustic waves. Here, we have experimentally and theoretically studied the acoustic transmission properties of metal gratings with or without serrated boundaries. The average transmission is obviously enhanced for serrated metal gratings within a wide frequency range, while the Fabry-Perot resonance is significantly suppressed. An effective medium hypothesis with varying acoustic impedance is proposed to analyze the mechanism, which was verified through comparison with finite-element simulation. The serrated boundary supplies gradient mass distribution and gradient normal acoustic impedance, which could efficiently reduce the boundary reflection. Further, by increasing the region of the serrated boundary, we present a broadband high-transmission grating for wide range of incident angle. Our results may have potential applications to broadband acoustic imaging, acoustic sensing, and acoustic devices.

  10. Comparison of Computational Aeroacoustics Prediction of Acoustic Transmission Through a 3D Stator with Experiment

    NASA Technical Reports Server (NTRS)

    Hixon, Ray; Envia, Edmane; Dahl, Milo; Sutliff, Daniel

    2014-01-01

    In this paper, numerical predictions of acoustic transmission through a 3D stator obtained using the NASA BASS code are compared with experimentally measured data. The influence of vane count and stagger as well as frequency and mode order on the transmission loss is investigated. The data-theory comparisons indicate that BASS can predict all the important trends observed in the experimental data.

  11. Comparison of Computational Aeroacoustics Prediction of Acoustic Transmission Through a 3D Stator With Experiment

    NASA Technical Reports Server (NTRS)

    Hixon, Ray; Envia, Edmane; Dahl, Milo; Sutliff, Daniel L.

    2014-01-01

    In this paper, numerical predictions of acoustic transmission through a 3D stator obtained using the NASA BASS code are compared with experimentally measured data. The influence of vane count and stagger as well as frequency and mode order on the transmission loss is investigated. The data-theory comparisons indicate that BASS can predict all the important trends observed in the experimental data.

  12. Acoustic data transmission through a drill string

    DOEpatents

    Drumheller, D.S.

    1988-04-21

    Acoustical signals are transmitted through a drill string by canceling upward moving acoustical noise and by preconditioning the data in recognition of the comb filter impedance characteristics of the drill string. 5 figs.

  13. Broadband enhanced transmission of acoustic waves through serrated metal gratings

    NASA Astrophysics Data System (ADS)

    Qi, Dong-Xiang; Fan, Ren-Hao; Deng, Yu-Qiang; Peng, Ru-Wen; Wang, Mu; Jiangnan University Collaboration

    In this talk, we present our studies on broadband properties of acoustic waves through metal gratings. We have demonstrated that serrated metal gratings, which introduce gradient coatings, can give rise to broadband transmission enhancement of acoustic waves. Here, we have experimentally and theoretically studied the acoustic transmission properties of metal gratings with or without serrated boundaries. The average transmission is obviously enhanced for serrated metal gratings within a wide frequency range, while the Fabry-Perot resonance is significantly suppressed. An effective medium hypothesis with varying acoustic impedance is proposed to analyze the mechanism, which was verified through comparison with finite-element simulation. The serrated boundary supplies gradient mass distribution and gradient normal acoustic impedance, which could efficiently reduce the boundary reflection. Further, by increasing the region of the serrated boundary, we present a broadband high-transmission grating for wide range of incident angle. Our results may have potential applications to broadband acoustic imaging, acoustic sensing and new acoustic devices. References: [1] Dong-Xiang Qi, Yu-Qiang Deng, Di-Hu Xu, Ren-Hao Fan, Ru-Wen Peng, Ze-Guo Chen, Ming-Hui Lu, X. R. Huang and Mu Wang, Appl. Phys. Lett. 106, 011906 (2015); [2] Dong-Xiang Qi, Ren-Hao Fan, Ru-Wen Peng, Xian-Rong Huang, Ming-Hui Lu, Xu Ni, Qing Hu, and Mu Wang, Applied Physics Letters 101, 061912 (2012).

  14. Analytical models for use in fan inflow control structure design. Inflow distortion and acoustic transmission models

    NASA Technical Reports Server (NTRS)

    Gedge, M. R.

    1979-01-01

    Analytical models were developed to study the effect of flow contraction and screening on inflow distortions to identify qualitative design criteria. Results of the study are that: (1) static testing distortions are due to atmospheric turbulence, nacelle boundary layer, exhaust flow reingestion, flow over stand, ground plane, and engine casing; (2) flow contraction suppresses, initially, turbulent axial velocity distortions and magnifies turbulent transverse velocity distortions; (3) perforated plate and gauze screens suppress axial components of velocity distortions to a degree determined by the screen pressure loss coefficient; (4) honeycomb screen suppress transverse components of velocity distortions to a degree determined by the length to diameter ratio of the honeycomb; (5) acoustic transmission loss of perforated plate is controlled by the reactance of its acoustic impedance; (6) acoustic transmission loss of honeycomb screens is negligible; and (7) a model for the direction change due to a corner between honeycomb panels compares favorably with measured data.

  15. Flooding in ephemeral streams: incorporating transmission losses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stream flow in semiarid lands commonly occurs as a form of flash floods in dry ephemeral stream beds. The goal of this research is to couple hydrological and hydraulic models treats channel transmission losses and test the methodology in the USDA-ARS Walnut Gulch Experimental Watershed (WGEW). For h...

  16. Broadband asymmetric acoustic transmission in a single medium by an array of heat sources

    NASA Astrophysics Data System (ADS)

    Guan, Yi-Jun; Sun, Hong-Xiang; Xia, Jian-Ping; Yuan, Shou-Qi

    2017-04-01

    We report the realization of a broadband asymmetric acoustic transmission with six different-temperature heat sources in air. This exotic effect arises from the desired refractive index in propagation paths induced from heat sources of different temperatures and asymmetrical distribution, which avoids acoustic impedance differences between the heat sources and air and has no reflection energy loss. In addition, the influence of the viscosity of air, the thermal convection, and the temperature and length of the heat sources on the asymmetric transmission effect is investigated in detail. The results show that the proposed device has the advantages of broad bandwidth, high transmission contrast, and simple structure, which enable it to provide more schemes for sound manipulation. It has excellent potential applications in acoustic devices.

  17. Experimental realization of extraordinary acoustic transmission using Helmholtz resonators

    NASA Astrophysics Data System (ADS)

    Crow, Brian C.; Cullen, Jordan M.; McKenzie, William W.; Koju, Vijay; Robertson, William M.

    2015-02-01

    The phenomenon of extraordinary acoustic transmission through a solid barrier with an embedded Helmholtz resonator (HR) is demonstrated. The Helmholtz resonator consists of an embedded cavity and two necks that protrude, one on each side of the barrier. Extraordinary transmission occurs for a narrow spectral range encompassing the resonant frequency of the Helmholtz resonator. We show that an amplitude transmission of 97.5% is achieved through a resonator whose neck creates an open area of 6.25% of the total barrier area. In addition to the enhanced transmission, we show that there is a smooth, continuous phase transition in the transmitted sound as a function of frequency. The frequency dependent phase transition is used to experimentally realize slow wave propagation for a narrow-band Gaussian wave packet centered at the maximum transmission frequency. The use of parallel pairs of Helmholtz resonators tuned to different resonant frequencies is experimentally explored as a means of increasing the transmission bandwidth. These experiments show that because of the phase transition, there is always a frequency between the two Helmholtz resonant frequencies at which destructive interference occurs whether the resonances are close or far apart. Finally, we explain how the phase transition associated with Helmholtz-resonator-mediated extraordinary acoustic transmission can be exploited to produce diffractive acoustic components including sub-wavelength thickness acoustic lenses.

  18. Experimental realization of extraordinary acoustic transmission using Helmholtz resonators

    SciTech Connect

    Crow, Brian C.; Cullen, Jordan M.; McKenzie, William W.; Koju, Vijay; Robertson, William M.

    2015-02-15

    The phenomenon of extraordinary acoustic transmission through a solid barrier with an embedded Helmholtz resonator (HR) is demonstrated. The Helmholtz resonator consists of an embedded cavity and two necks that protrude, one on each side of the barrier. Extraordinary transmission occurs for a narrow spectral range encompassing the resonant frequency of the Helmholtz resonator. We show that an amplitude transmission of 97.5% is achieved through a resonator whose neck creates an open area of 6.25% of the total barrier area. In addition to the enhanced transmission, we show that there is a smooth, continuous phase transition in the transmitted sound as a function of frequency. The frequency dependent phase transition is used to experimentally realize slow wave propagation for a narrow-band Gaussian wave packet centered at the maximum transmission frequency. The use of parallel pairs of Helmholtz resonators tuned to different resonant frequencies is experimentally explored as a means of increasing the transmission bandwidth. These experiments show that because of the phase transition, there is always a frequency between the two Helmholtz resonant frequencies at which destructive interference occurs whether the resonances are close or far apart. Finally, we explain how the phase transition associated with Helmholtz-resonator-mediated extraordinary acoustic transmission can be exploited to produce diffractive acoustic components including sub-wavelength thickness acoustic lenses.

  19. AC Losses of Prototype HTS Transmission Cables

    SciTech Connect

    Demko, J.A.; Dresner, L.; Hughey, R.L.; Lue, J.W.; Olsen, S.K.; Sinha, U.; Tolbert, J.C.

    1998-09-13

    Since 1995 Southwire Company and Oak Ridge National Laboratory (ORNL) have jointly designed, built, and tested nine, l-m long, high temperature superconducting (HTS) transmission cable prototypes. This paper summarizes the AC loss measurements of five of the cables not reported elsewhere, and compares the losses with each other and with theory developed by Dresner. Losses were measured with both a calorimetric and an electrical technique. Because of the broad resistive transition of the HTS tapes, the cables can be operated stably beyond their critical currents. The AC losses were measured in this region as well as below critical currents. Dresner's theory takes into account the broad resistive transition of the HTS tapes and calculates the AC losses both below and above the critical current. The two sets of AC 10SS data agree with each other and with the theory quite welL In particular, at low currents of incomplete penetration, the loss data agree with the theoretical prediction of hysteresis loss based on only the outer two Iayers carrying the total current.

  20. Characteristics of the transmission loss apparatus at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Grosveld, F. W.

    1983-01-01

    A description of the Transmission Loss Apparatus at NASA Langley Research Center, which is specifically designed to accommodate general aviation type aircraft structures, is presented. The measurement methodology, referred to as the Plate Reference Method, is discussed and compared with the classical method as described in the Standard of the American Society for Testing and Materials. This measurement procedure enables reliable and accurate noise transmission loss measurements down to the 50 Hz one-third octave band. The transmission loss characteristics of add-on acoustical treatments, applied to the basic structure, can be established by inclusion of appropriate absorption corrections for the treatment.

  1. Sound radiation and transmission loss characteristics of a honeycomb sandwich panel with composite facings: Effect of inherent material damping

    NASA Astrophysics Data System (ADS)

    Arunkumar, M. P.; Jagadeesh, M.; Pitchaimani, Jeyaraj; Gangadharan, K. V.; Babu, M. C. Lenin

    2016-11-01

    This paper presents the results of numerical studies carried out on vibro-acoustic and sound transmission loss behaviour of aluminium honeycomb core sandwich panel with fibre reinforced plastic (FRP) facings. Layered structural shell element with equivalent orthotropic elastic properties of core and orthotropic properties of FRP facing layer is used to predict the free and forced vibration characteristics. Followed by this, acoustic response and transmission loss characteristics are obtained using Rayleigh integral. Vibration and acoustic characteristics of FRP sandwich panels are compared with aluminium sandwich panels. The result reveals that FRP panel has better vibro-acoustic and transmission loss characteristics due to high stiffness and inherent material damping associated with them. Resonant amplitudes of the response are fully controlled by modal damping factors calculated based on modal strain energy. It is also demonstrated that FRP panel can be used to replace the aluminium panel without losing acoustic comfort with nearly 40 percent weight reduction.

  2. Modal analysis and acoustic transmission through offset-core honeycomb sandwich panels

    NASA Astrophysics Data System (ADS)

    Mathias, Adam Dustin

    The work presented in this thesis is motivated by an earlier research that showed that double, offset-core honeycomb sandwich panels increased thermal resistance and, hence, decreased heat transfer through the panels. This result lead to the hypothesis that these panels could be used for acoustic insulation. Using commercial finite element modeling software, COMSOL Multiphysics, the acoustical properties, specifically the transmission loss across a variety of offset-core honeycomb sandwich panels, is studied for the case of a plane acoustic wave impacting the panel at normal incidence. The transmission loss results are compared with those of single-core honeycomb panels with the same cell sizes. The fundamental frequencies of the panels are also computed in an attempt to better understand the vibrational modes of these particular sandwich-structured panels. To ensure that the finite element analysis software is adequate for the task at hand, two relevant benchmark problems are solved and compared with theory. Results from these benchmark results compared well to those obtained from theory. Transmission loss results from the offset-core honeycomb sandwich panels show increased transmission loss, especially for large cell honeycombs when compared to single-core honeycomb panels.

  3. Light transmission loss in liquid crystal waveguides

    NASA Astrophysics Data System (ADS)

    Nowinowski-Kruszelnicki, Edward; Walczak, Andrzej; Kiezun, Aleksander; Jaroszewicz, Leszek R.

    1998-02-01

    The investigation results of the propagation loss due to light scattering in electrically induced channel in planar waveguides are presented. The channel structure was obtained by means of electric driven stripe electrode made by photolithographic process. Planar waveguiding cell has been fabricated using ITO/SiO2/polyimide-coated glass plates and LC film 20 micrometers thick. A nematic liquid crystal layer with 90 degrees-twisted nematic orientation was studied. The He-Ne light beam was endfire coupled into an input edge of a waveguide using an objective lens. The propagation loss have been evaluated from the spatial variation intensity of light scattered out perpendicularly to the waveguide surface along the light propagation direction measured with CCD camera. Loss measurements have been made in room temperature. Waveguiding channel effect has been observed above 2.5 Vrms of applied voltage with the loss of about 17 +/- 1 dB. Increased driving voltage up to 100 Vrms reduces the loss to minimum value of 12 +/- 1 dB/cm. As a result of the experiments one may conclude that transmission loss in thick nematic waveguide have bulk character caused by imperfection of molecular alignment.

  4. Finite Element Development of Honeycomb Panel Configurations with Improved Transmission Loss

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.; Palumbo, Daniel L.; Klos, Jacob; Castle, William D.

    2006-01-01

    The higher stiffness-to-mass ratio of a honeycomb panel compared to a homogeneous panel results in a lower acoustic critical frequency. Above the critical frequency the panel flexural wave speed is acoustically fast and the structure becomes a more efficient radiator with associated lower sound transmission loss. Finite element models of honeycomb sandwich structures are presented featuring areas where the core is removed from the radiating face sheet disrupting the supersonic flexural and shear wave speeds that exist in the baseline honeycomb panel. These modified honeycomb panel structures exhibit improved transmission loss for a pre-defined diffuse field sound excitation. The models were validated by the sound transmission loss of honeycomb panels measured in the Structural Acoustic Loads and Transmission (SALT) facility at the NASA Langley Research Center. A honeycomb core panel configuration is presented exhibiting a transmission loss improvement of 3-11 dB compared to a honeycomb baseline panel over a frequency range from 170 Hz to 1000 Hz. The improved transmission loss panel configuration had a 5.1% increase in mass over the baseline honeycomb panel, and approximately twice the deflection when excited by a static force.

  5. Acoustic contributions of a sound absorbing blanket placed in a double panel structure: absorption versus transmission.

    PubMed

    Doutres, Olivier; Atalla, Noureddine

    2010-08-01

    The objective of this paper is to propose a simple tool to estimate the absorption vs. transmission loss contributions of a multilayered blanket unbounded in a double panel structure and thus guide its optimization. The normal incidence airborne sound transmission loss of the double panel structure, without structure-borne connections, is written in terms of three main contributions; (i) sound transmission loss of the panels, (ii) sound transmission loss of the blanket and (iii) sound absorption due to multiple reflections inside the cavity. The method is applied to four different blankets frequently used in automotive and aeronautic applications: a non-symmetric multilayer made of a screen in sandwich between two porous layers and three symmetric porous layers having different pore geometries. It is shown that the absorption behavior of the blanket controls the acoustic behavior of the treatment at low and medium frequencies and its transmission loss at high frequencies. Acoustic treatment having poor sound absorption behavior can affect the performance of the double panel structure.

  6. Frequency Spreading in Underwater Acoustic Signal Transmission.

    DTIC Science & Technology

    1980-04-15

    acoustic signal transmitted and received underwater J-2 J.2 Signal spectrum computing block diagram. J-3 Chapter I. Frequency spreading 1.0 Introduction... transmitted frequency can be expected in the received signal [1] - [18]. This frequency spreading behavior is the result of the amplitude and phase...result of phase modulation of the transmitted sinusoid by the moving surface, and the separation between the spectral lines at the receiving point is

  7. Waveform-preserved unidirectional acoustic transmission based on impedance-matched acoustic metasurface and phononic crystal

    NASA Astrophysics Data System (ADS)

    Song, Ai-Ling; Chen, Tian-Ning; Wang, Xiao-Peng; Wan, Le-Le

    2016-08-01

    The waveform distortion happens in most of the unidirectional acoustic transmission (UAT) devices proposed before. In this paper, a novel type of waveform-preserved UAT device composed of an impedance-matched acoustic metasurface (AMS) and a phononic crystal (PC) structure is proposed and numerically investigated. The acoustic pressure field distributions and transmittance are calculated by using the finite element method. The subwavelength AMS that can modulate the wavefront of the transmitted wave at will is designed and the band structure of the PC structure is calculated and analyzed. The sound pressure field distributions demonstrate that the unidirectional acoustic transmission can be realized by the proposed UAT device without changing the waveforms of the output waves, which is the distinctive feature compared with the previous UAT devices. The physical mechanism of the unidirectional acoustic transmission is discussed by analyzing the refraction angle changes and partial band gap map. The calculated transmission spectra show that the UAT device is valid within a relatively broad frequency range. The simulation results agree well with the theoretical predictions. The proposed UAT device provides a good reference for designing waveform-preserved UAT devices and has potential applications in many fields, such as medical ultrasound, acoustic rectifiers, and noise insulation.

  8. Recent Enhancements to the NASA Langley Structural Acoustics Loads and Transmission (SALT) Facility

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Cabell, Randolph H.; Allen, Albert R.

    2013-01-01

    The Structural Acoustics Loads and Transmission (SALT) facility at the NASA Langley Research Center is comprised of an anechoic room and a reverberant room, and may act as a transmission loss suite when test articles are mounted in a window connecting the two rooms. In the latter configuration, the reverberant room acts as the noise source side and the anechoic room as the receiver side. The noise generation system used for qualification testing in the reverberant room was previously shown to achieve a maximum overall sound pressure level of 141 dB. This is considered to be marginally adequate for generating sound pressure levels typically required for launch vehicle payload qualification testing. Recent enhancements to the noise generation system increased the maximum overall sound pressure level to 154 dB, through the use of two airstream modulators coupled to 35 Hz and 160 Hz horns. This paper documents the acoustic performance of the enhanced noise generation system for a variety of relevant test spectra. Additionally, it demonstrates the capability of the SALT facility to conduct transmission loss and absorption testing in accordance with ASTM and ISO standards, respectively. A few examples of test capabilities are shown and include transmission loss testing of simple unstiffened and built up structures and measurement of the diffuse field absorption coefficient of a fibrous acoustic blanket.

  9. Impedance matched joined drill pipe for improved acoustic transmission

    DOEpatents

    Moss, William C.

    2000-01-01

    An impedance matched jointed drill pipe for improved acoustic transmission. A passive means and method that maximizes the amplitude and minimize the temporal dispersion of acoustic signals that are sent through a drill string, for use in a measurement while drilling telemetry system. The improvement in signal transmission is accomplished by replacing the standard joints in a drill string with joints constructed of a material that is impedance matched acoustically to the end of the drill pipe to which it is connected. Provides improvement in the measurement while drilling technique which can be utilized for well logging, directional drilling, and drilling dynamics, as well as gamma-ray spectroscopy while drilling post shot boreholes, such as utilized in drilling post shot boreholes.

  10. Active control of harmonic sound transmission into an acoustic enclosure using both structural and acoustic actuators

    PubMed

    Kim; Brennan

    2000-05-01

    This paper describes an analytical and experimental investigation into the active control of harmonic sound transmission in a structural-acoustic coupled system. A rectangular enclosure is considered that has five acoustically rigid walls and a flexible plate on the remaining side through which a harmonic sound wave is transmitted into the enclosure. The control system is designed to globally reduce the sound field inside the enclosure, and the roles of structural and acoustic actuators are of particular interest. Three control configurations, classified by the type of actuators, are compared and discussed. They are: (i) use of a single point-force actuator, (ii) use of a single acoustic piston source, and (iii) simultaneous use of both a point-force actuator and an acoustic piston source. It is shown both analytically and experimentally that the point-force actuator is effective in controlling plate-dominated modes while the acoustic source is effective in controlling cavity-dominated modes. Since the transmitted sound field is governed by both plate- and cavity-dominated modes, the hybrid use of both types of actuators is shown to be a desirable configuration for the active control of sound transmission into a structural-acoustic coupled system.

  11. Asymmetric wave transmission in a diatomic acoustic/elastic metamaterial

    NASA Astrophysics Data System (ADS)

    Li, Bing; Tan, K. T.

    2016-08-01

    Asymmetric acoustic/elastic wave transmission has recently been realized using nonlinearity, wave diffraction, or bias effects, but always at the cost of frequency distortion, direction shift, large volumes, or external energy. Based on the self-coupling of dual resonators, we propose a linear diatomic metamaterial, consisting of several small-sized unit cells, to realize large asymmetric wave transmission in low frequency domain (below 1 kHz). The asymmetric transmission mechanism is theoretically investigated, and numerically verified by both mass-spring and continuum models. This passive system does not require any frequency conversion or external energy, and the asymmetric transmission band can be theoretically predicted and mathematically controlled, which extends the design concept of unidirectional transmission devices.

  12. Acoustic Trauma - Hearing Loss in Teenagers

    MedlinePlus

    ... hearing loss. Kids expose themselves to noise through electronic media that often is louder than what is ... caused by exposure to loud noises, such as music played through headphones. The authors of another study ...

  13. Reflection and transmission of acoustic waves from a moving layer

    NASA Technical Reports Server (NTRS)

    Steinmetz, G. G.; Singh, J. J.

    1972-01-01

    The refraction of acoustic waves by a moving medium layer is theoretically treated and the expressions for reflection and transmission coefficients are determined. The moving medium layer velocity is assumed to have a space dependence in one direction. A partitioning of the moving medium layer into constant-velocity sublayers is introduced and the number of sublayers is allowed to increase until the reflection and transmission coefficients converage to their respective values. Numerical results for several sublayer approximations of Poiseuille's flow are presented as functions of the moving layer velocity for several angles of incidence of the acoustic wave. The degenerate case of single constant-velocity layer is also treated, both theoretically and by a numerical analysis.

  14. Transport composite fuselage technology: Impact dynamics and acoustic transmission

    NASA Technical Reports Server (NTRS)

    Jackson, A. C.; Balena, F. J.; Labarge, W. L.; Pei, G.; Pitman, W. A.; Wittlin, G.

    1986-01-01

    A program was performed to develop and demonstrate the impact dynamics and acoustic transmission technology for a composite fuselage which meets the design requirements of a 1990 large transport aircraft without substantial weight and cost penalties. The program developed the analytical methodology for the prediction of acoustic transmission behavior of advanced composite stiffened shell structures. The methodology predicted that the interior noise level in a composite fuselage due to turbulent boundary layer will be less than in a comparable aluminum fuselage. The verification of these analyses will be performed by NASA Langley Research Center using a composite fuselage shell fabricated by filament winding. The program also developed analytical methodology for the prediction of the impact dynamics behavior of lower fuselage structure constructed with composite materials. Development tests were performed to demonstrate that the composite structure designed to the same operating load requirement can have at least the same energy absorption capability as aluminum structure.

  15. Comparison of Transmission Line Methods for Surface Acoustic Wave Modeling

    NASA Technical Reports Server (NTRS)

    Wilson, William; Atkinson, Gary

    2009-01-01

    Surface Acoustic Wave (SAW) technology is low cost, rugged, lightweight, extremely low power and can be used to develop passive wireless sensors. For these reasons, NASA is investigating the use of SAW technology for Integrated Vehicle Health Monitoring (IVHM) of aerospace structures. To facilitate rapid prototyping of passive SAW sensors for aerospace applications, SAW models have been developed. This paper reports on the comparison of three methods of modeling SAWs. The three models are the Impulse Response Method (a first order model), and two second order matrix methods; the conventional matrix approach, and a modified matrix approach that is extended to include internal finger reflections. The second order models are based upon matrices that were originally developed for analyzing microwave circuits using transmission line theory. Results from the models are presented with measured data from devices. Keywords: Surface Acoustic Wave, SAW, transmission line models, Impulse Response Method.

  16. Noise transmission loss of a rectangular plate in an infinite baffle

    NASA Technical Reports Server (NTRS)

    Roussos, L. A.

    1985-01-01

    An improved analytical procedure was developed that allows for the efficient calculation of the noise transmission characteristics of a finite rectangular plate. Both isotropic and symmetrically laminated composite plates are considered. The plate is modeled with classic thin-plate theory and is assumed to be simply supported on all four sides. The incident acoustic pressure is assumed to be a plane wave impinging on the plate at an arbitrary angle. The reradiated pressure is assumed to be negligible compared with the blocked pressure, and the plate vibrations are calculated by a normal-mode approach. A Green's function integral equation is used to link the plate vibrations to be transmitted far-field sound waves, and transmission loss is calculated from the ratio of incident to transmitted acoustic powers. The result is a versatile research and engineering analysis tool that predicts noise transmission loss and enables the determination of the modal behavior of the plate.

  17. High Frequency Acoustic Reflection and Transmission in Ocean Sediments

    DTIC Science & Technology

    2011-09-01

    scattering in ocean environments with special emphasis on propagation in shallow water waveguides and scattering from ocean sediments. 3 ) Development of...TYPE 3 . DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE High Frequency Acoustic Reflection and Transmission in Ocean Sediments...REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 2 3

  18. Sound transmission loss of windows on high speed trains

    NASA Astrophysics Data System (ADS)

    Zhang, Yumei; Xiao, Xinbiao; Thompson, David; Squicciarini, Giacomo; Wen, Zefeng; Li, Zhihui; Wu, Yue

    2016-09-01

    The window is one of the main components of the high speed train car body structure through which noise can be transmitted. To study the windows’ acoustic properties, the vibration of one window of a high speed train has been measured for a running speed of 250 km/h. The corresponding interior noise and the noise in the wheel-rail area have been measured simultaneously. The experimental results show that the window vibration velocity has a similar spectral shape to the interior noise. Interior noise source identification further indicates that the window makes a contribution to the interior noise. Improvement of the window's Sound Transmission Loss (STL) can reduce the interior noise from this transmission path. An STL model of the window is built based on wave propagation and modal superposition methods. From the theoretical results, the window's STL property is studied and several factors affecting it are investigated, which provide indications for future low noise design of high speed train windows.

  19. Refinement and application of acoustic impulse technique to study nozzle transmission characteristics

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.; Brown, W. H.; Ramakrishnan, R.; Tanna, H. K.

    1983-01-01

    An improved acoustic impulse technique was developed and was used to study the transmission characteristics of duct/nozzle systems. To accomplish the above objective, various problems associated with the existing spark-discharge impulse technique were first studied. These included (1) the nonlinear behavior of high intensity pulses, (2) the contamination of the signal with flow noise, (3) low signal-to-noise ratio at high exhaust velocities, and (4) the inability to control or shape the signal generated by the source, specially when multiple spark points were used as the source. The first step to resolve these problems was the replacement of the spark-discharge source with electroacoustic driver(s). These included (1) synthesizing on acoustic impulse with acoustic driver(s) to control and shape the output signal, (2) time domain signal averaging to remove flow noise from the contaminated signal, (3) signal editing to remove unwanted portions of the time history, (4) spectral averaging, and (5) numerical smoothing. The acoustic power measurement technique was improved by taking multiple induct measurements and by a modal decomposition process to account for the contribution of higher order modes in the power computation. The improved acoustic impulse technique was then validated by comparing the results derived by an impedance tube method. The mechanism of acoustic power loss, that occurs when sound is transmitted through nozzle terminations, was investigated. Finally, the refined impulse technique was applied to obtain more accurate results for the acoustic transmission characteristics of a conical nozzle and a multi-lobe multi-tube supressor nozzle.

  20. Some recent developments in the theory of acoustic transmission in tube bundles

    NASA Astrophysics Data System (ADS)

    Heckl, Maria A.; Mulholland, L. S.

    1995-01-01

    A comprehensive theoretical model for acoustic transmission in a tube bundle is presented. The tube bundle is considered as a series of diffraction gratings. Each grating consists of periodically spaced cylindrical tubes which obey the equations of motion of a cylindrical shell. Fluid loading is included. The model can be used for numerical simulations to calculate the sound field at any point in a tube bundle. Various phenomena can be predicted which are of interest for the development of acoustic diagnostics in heat exchangers. These include diffraction of a plane incident wave into several directions, the occurrence of passing and stopping bands in the transmission spectrum, features specific to oblique waves and the effect of dissipative losses. Tube bundles with baffle plates are also examined. The validity of the theoretical model is confirmed by comparison with experimental results.

  1. Enhanced acoustic transmission into dissipative solid materials through the use of inhomogeneous plane waves

    NASA Astrophysics Data System (ADS)

    Woods, D. C.; Bolton, J. S.; Rhoads, J. F.

    2016-09-01

    A number of applications, for instance ultrasonic imaging and nondestructive testing, involve the transmission of acoustic energy across fluid-solid interfaces into dissipative solids. However, such transmission is generally hindered by the large impedance mismatch at the interface. In order to address this problem, inhomogeneous plane waves were investigated in this work for the purpose of improving the acoustic energy transmission. To this end, under the assumption of linear hysteretic damping, models for fluid-structure interaction were developed that allow for both homogeneous and inhomogeneous incident waves. For low-loss solids, the results reveal that, at the Rayleigh angle, a unique value of the wave inhomogeneity can be found which minimizes the reflection coefficient, and consequently maximizes the transmission. The results also reveal that with sufficient dissipation levels in the solid material, homogeneous incident waves yield lower reflection values than inhomogeneous waves, due to the large degrees of inhomogeneity inherent in the transmitted waves. Analytical conditions have also been derived which predict the dependence of the optimal incident wave type on the dissipation level and wave speeds in the solid medium. Finally, implications related to the use of acoustic beams of limited spatial extent are discussed.

  2. Quasilossless acoustic transmission in an arbitrary pathway of a network

    NASA Astrophysics Data System (ADS)

    Dai, Hongqing; Liu, Tingting; Xia, Baizhan; Yu, Dejie

    2017-02-01

    Acoustic metamaterials have exhibited extraordinary potential for manipulating the propagation of sound waves. To date, it has been a challenge to control the propagation of a sound wave through arbitrary pathways in a network. Here, we design a symmetry-breaking, cross-shaped metamaterial comprising Helmholtz resonant cells and a square column. The square column is eccentrically arranged. The sound wave can be transmitted in a quasilossless manner through the channels along the eccentric direction with compressed spaces, which breaks through the general transmission phenomenon. This exotic propagation characteristic is verified by the band structure and the mode of the metamaterial. Two acoustic networks, including a 2 ×2 network and an 8 ×8 network, demonstrate the quasilossless propagation of the sound wave along various arbitrarily shaped pathways, which include a Great Wall shape, a stairway shape, and a serpentine shape, by reconfiguring the eccentric directions. This ability opens up a new method for routing sound waves and exhibits promising applications ranging from acoustic communication to energy transmission.

  3. INSTRUMENTATION FOR SURVEYING ACOUSTIC SIGNALS IN NATURAL GAS TRANSMISSION LINES

    SciTech Connect

    John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra

    2003-09-01

    In the U.S. natural gas is distributed through more than one million miles of high-pressure transmission pipelines. If all leaks and infringements could be detected quickly, it would enhance safety and U.S. energy security. Only low frequency acoustic waves appear to be detectable over distances up to 60 km where pipeline shut-off valves provide access to the inside of the pipeline. This paper describes a Portable Acoustic Monitoring Package (PAMP) developed to record and identify acoustic signals characteristic of: leaks, pump noise, valve and flow metering noise, third party infringement, manual pipeline water and gas blow-off, etc. This PAMP consists of a stainless steel 1/2 inch NPT plumbing tree rated for use on 1000 psi pipelines. Its instrumentation is designed to measure acoustic waves over the entire frequency range from zero to 16,000 Hz by means of four instruments: (1) microphone, (2) 3-inch water full range differential pressure transducer with 0.1% of range sensitivity, (3) a novel 3 inch to 100 inch water range amplifier, using an accumulator with needle valve and (4) a line-pressure transducer. The weight of the PAMP complete with all accessories is 36 pounds. This includes a remote control battery/switch box assembly on a 25-foot extension chord, a laptop data acquisition computer on a field table and a sun shield.

  4. Sound transmission through a high-temperature acoustic probe tube

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Zorumski, William E.

    1990-01-01

    An investigation was conducted of acoustic transmission through a tube subjected to an intense thermal gradient along its axis. The results are of interest in the interpretation of acoustic data from probe tube configurations designed to measure fluctuating pressures in high temperature environments. The measured transfer function across a localized heated region in the tube was compared to a computed transfer function based on a theoretical analysis of propagation through strong temperature gradients. Over the frequency range 0.4 kHz to 6.0 kHz, generally good agreement was obtained between the measured and calculated attenuation across the heated region with some discrepancy occurring at the attenuation minima. Agreement between measured and calculated phase difference was excellent to within the measurement resolution.

  5. Controls of pass-bands in asymmetric acoustic transmission

    NASA Astrophysics Data System (ADS)

    Sun, Hong-Xiang; Zhang, Shu-Yi; Yuan, Shou-Qi

    2016-12-01

    The controls of the pass-bands in an asymmetric acoustic transmission system are investigated numerically and experimentally, and the system consists of a periodical rectangular grating and two uniform brass plates in water. We reveal that the pass-band of the asymmetric acoustic transmission is closely related to the grating period, but is affected slightly by the brass plate thickness. Moreover, the transmittance can be improved by adjusting the grating period and other structural parameters simultaneously. The control method of the system has the advantages of wider frequency range and simple operation, which has great potential applications in ultrasonic devices. Project supported by the National Basic Research Program of China (Grant No. 2012CB921504), the Major Program of the National Natural Science Foundation of China (Grant No. 51239005), the National Natural Science Foundation of China (Grant Nos. 11174142 and 11404147), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20140519), the China Postdoctoral Science Foundation (Grant No. 2015M571672), the Training Project of Young Backbone Teachers of Jiangsu University, China, and the Research Fund for Advanced Talents of Jiangsu University, China (Grant No. 13JDG106).

  6. Boundary-Layer Effects on Acoustic Transmission Through Narrow Slit Cavities

    NASA Astrophysics Data System (ADS)

    Ward, G. P.; Lovelock, R. K.; Murray, A. R. J.; Hibbins, A. P.; Sambles, J. R.; Smith, J. D.

    2015-07-01

    We explore the slit-width dependence of the resonant transmission of sound in air through both a slit array formed of aluminum slats and a single open-ended slit cavity in an aluminum plate. Our experimental results accord well with Lord Rayleigh's theory concerning how thin viscous and thermal boundary layers at a slit's walls affect the acoustic wave across the whole slit cavity. By measuring accurately the frequencies of the Fabry-Perot-like cavity resonances, we find a significant 5% reduction in the effective speed of sound through the slits when an individual viscous boundary layer occupies only 5% of the total slit width. Importantly, this effect is true for any airborne slit cavity, with the reduction being achieved despite the slit width being on a far larger scale than an individual boundary layer's thickness. This work demonstrates that the recent prevalent loss-free treatment of narrow slit cavities within acoustic metamaterials is unrealistic.

  7. Boundary-Layer Effects on Acoustic Transmission Through Narrow Slit Cavities.

    PubMed

    Ward, G P; Lovelock, R K; Murray, A R J; Hibbins, A P; Sambles, J R; Smith, J D

    2015-07-24

    We explore the slit-width dependence of the resonant transmission of sound in air through both a slit array formed of aluminum slats and a single open-ended slit cavity in an aluminum plate. Our experimental results accord well with Lord Rayleigh's theory concerning how thin viscous and thermal boundary layers at a slit's walls affect the acoustic wave across the whole slit cavity. By measuring accurately the frequencies of the Fabry-Perot-like cavity resonances, we find a significant 5% reduction in the effective speed of sound through the slits when an individual viscous boundary layer occupies only 5% of the total slit width. Importantly, this effect is true for any airborne slit cavity, with the reduction being achieved despite the slit width being on a far larger scale than an individual boundary layer's thickness. This work demonstrates that the recent prevalent loss-free treatment of narrow slit cavities within acoustic metamaterials is unrealistic.

  8. Subwavelength acoustic focusing by surface-wave-resonance enhanced transmission in doubly negative acoustic metamaterials

    SciTech Connect

    Zhou, Xiaoming; Badreddine Assouar, M. Oudich, Mourad

    2014-11-21

    We present analytical and numerical analyses of a yet unseen lensing paradigm that is based on a solid metamaterial slab in which the wave excitation source is attached. We propose and demonstrate sub-diffraction-limited acoustic focusing induced by surface resonant states in doubly negative metamaterials. The enhancement of evanescent waves across the metamaterial slab produced by their resonant coupling to surface waves is evidenced and quantitatively determined. The effect of metamaterial parameters on surface states, transmission, and wavenumber bandwidth is clearly identified. Based on this concept consisting of a wave source attached on the metamaterial, a high resolution of λ/28.4 is obtained with the optimum effective physical parameters, opening then an exciting way to design acoustic metamaterials for ultrasonic focused imaging.

  9. Analysis of different techniques to improve sound transmission loss in cylindrical shells

    NASA Astrophysics Data System (ADS)

    Oliazadeh, Pouria; Farshidianfar, Anooshiravan

    2017-02-01

    In this study, sound transmission through double- and triple-walled shells is investigated. The structure-acoustic equations based on Donnell's shell theory are presented and transmission losses calculated by this approach are compared with the transmission losses obtained according to Love's theory. An experimental set-up is also constructed to compare natural frequencies obtained from Donnell and Love's theories with experimental results in the high frequency region. Both comparisons show that Donnell's theory predicts the sound transmission characteristics and vibrational behavior better than Love's theory in the high frequency region. The transmission losses of the double- and triple-walled construction are then presented for various radii and thicknesses. Then the effects of air gap size as an important design parameter are studied. Sound transmission characteristics through a circular cylindrical shell are also computed along with consideration of the effects of material damping. Modest absorption is shown to greatly reduce the sound transmission at ring frequency and coincidence frequency. Also the effects of five common gases that are used for filling the gap are investigated.

  10. General analytical approach for sound transmission loss analysis through a thick metamaterial plate

    SciTech Connect

    Oudich, Mourad; Zhou, Xiaoming; Badreddine Assouar, M.

    2014-11-21

    We report theoretically and numerically on the sound transmission loss performance through a thick plate-type acoustic metamaterial made of spring-mass resonators attached to the surface of a homogeneous elastic plate. Two general analytical approaches based on plane wave expansion were developed to calculate both the sound transmission loss through the metamaterial plate (thick and thin) and its band structure. The first one can be applied to thick plate systems to study the sound transmission for any normal or oblique incident sound pressure. The second approach gives the metamaterial dispersion behavior to describe the vibrational motions of the plate, which helps to understand the physics behind sound radiation through air by the structure. Computed results show that high sound transmission loss up to 72 dB at 2 kHz is reached with a thick metamaterial plate while only 23 dB can be obtained for a simple homogeneous plate with the same thickness. Such plate-type acoustic metamaterial can be a very effective solution for high performance sound insulation and structural vibration shielding in the very low-frequency range.

  11. Acoustic solitons in waveguides with Helmholtz resonators: transmission line approach.

    PubMed

    Achilleos, V; Richoux, O; Theocharis, G; Frantzeskakis, D J

    2015-02-01

    We report experimental results and study theoretically soliton formation and propagation in an air-filled acoustic waveguide side loaded with Helmholtz resonators. We propose a theoretical modeling of the system, which relies on a transmission-line approach, leading to a nonlinear dynamical lattice model. The latter allows for an analytical description of the various soliton solutions for the pressure, which are found by means of dynamical systems and multiscale expansion techniques. These solutions include Boussinesq-like and Korteweg-de Vries pulse-shaped solitons that are observed in the experiment, as well as nonlinear Schrödinger envelope solitons, that are predicted theoretically. The analytical predictions are in excellent agreement with direct numerical simulations and in qualitative agreement with the experimental observations.

  12. Transmission Loss and Absorption of Corrugated Core Sandwich Panels With Embedded Resonators

    NASA Technical Reports Server (NTRS)

    Allen, Albert R.; Schiller, Noah H.; Zalewski, Bart F.; Rosenthal, Bruce N.

    2014-01-01

    The effect of embedded resonators on the diffuse field sound transmission loss and absorption of composite corrugated core sandwich panels has been evaluated experimentally. Two 1.219 m × 2.438 m panels with embedded resonator arrangements targeting frequencies near 100 Hz were evaluated using non-standard processing of ASTM E90-09 acoustic transmission loss and ASTM C423-09a room absorption test measurements. Each panel is comprised of two composite face sheets sandwiching a corrugated core with a trapezoidal cross section. When inlet openings are introduced in one face sheet, the chambers within the core can be used as embedded acoustic resonators. Changes to the inlet and chamber partition locations allow this type of structure to be tuned for targeted spectrum passive noise control. Because the core chambers are aligned with the plane of the panel, the resonators can be tuned for low frequencies without compromising the sandwich panel construction, which is typically sized to meet static load requirements. Absorption and transmission loss performance improvements attributed to opening the inlets were apparent for some configurations and inconclusive for others.

  13. Transmission and Incidence Losses for a Slotted Plate

    NASA Technical Reports Server (NTRS)

    Wilson, Jack; Chima, Rodrick V.; Skews, Beric W.

    1998-01-01

    The objective of this work is to find a model of the stagnation pressure loss resulting from flow through a slotted plate, which is effectively a cascade of flat plate airfoils, particularly at very large angles of incidence. Data from a published experiment is examined, and compared with control volume analysis, and CFD code calculations. An assumption that the loss can be separated into a transmission loss and an incidence loss seems to be justified by the data. Both the data and the CFD code results are consistent with an incidence loss model in which the flow component normal to the slot axis is lost. However, the experimental transmission loss is much larger than calculated values.

  14. Ionospheric Transmission Losses Associated with Mars-orbiting Radars

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.

    2005-01-01

    There are a number of obstacles to radar sounding of the deep Martian subsurface from orbit, including signal losses from the medium conductivity, layer reflective losses, and ground clutter. Another adverse process is signal loss as radio waves propagate through the ionospheric plasma medium. The ionosphere is a plasma consisting of free electrons, ions and neutrals that can effectively damp/attenuate radar signals via electrodneutral collisions. The effect is most severe for transmissions at lower frequencies, which, unfortunately, are also favorable transmissions for deep penetration into the subsurface.

  15. Statistical Modeling of Large-Scale Signal Path Loss in Underwater Acoustic Networks

    PubMed Central

    Llor, Jesús; Malumbres, Manuel Perez

    2013-01-01

    In an underwater acoustic channel, the propagation conditions are known to vary in time, causing the deviation of the received signal strength from the nominal value predicted by a deterministic propagation model. To facilitate a large-scale system design in such conditions (e.g., power allocation), we have developed a statistical propagation model in which the transmission loss is treated as a random variable. By applying repetitive computation to the acoustic field, using ray tracing for a set of varying environmental conditions (surface height, wave activity, small node displacements around nominal locations, etc.), an ensemble of transmission losses is compiled and later used to infer the statistical model parameters. A reasonable agreement is found with log-normal distribution, whose mean obeys a log-distance increases, and whose variance appears to be constant for a certain range of inter-node distances in a given deployment location. The statistical model is deemed useful for higher-level system planning, where simulation is needed to assess the performance of candidate network protocols under various resource allocation policies, i.e., to determine the transmit power and bandwidth allocation necessary to achieve a desired level of performance (connectivity, throughput, reliability, etc.). PMID:23396190

  16. Validation of a Polyimide Foam Model for Use in Transmission Loss Applications

    NASA Technical Reports Server (NTRS)

    Hong, Kwanwoo; Bolton, J. Stuart; Cano, Roberto J.; Weiser, Erik S.; Jensen, Brian J.; Silcox, Rich; Howerton, Brian M.; Maxon, John; Wang, Tongan; Lorenzi, Tyler

    2010-01-01

    The work described in this paper was focused on the use of a new polyimide foam in a double wall sound transmission loss application. Recall that polyimide foams are functionally attractive, compared to polyurethane foams, for example, owing to their fire resistance. The foam considered here was found to have a flow resistivity that was too high for conventional acoustical applications, and as a result, it was processed by partial crushing to lower the flow resistivity into an acceptable range. Procedures for measuring the flow resistivity and Young s modulus of the material have been described, as was an inverse characterization procedure for estimating the remaining Biot parameters based on standing wave tube measurements of transmission loss and absorption coefficient. The inverse characterization was performed using a finite element model implementation of the Biot poro-elastic material theory. Those parameters were then used to predict the sound transmission loss of a double panel system lined with polyimide foam, and the predictions were compared with full-scale transmission loss measurements. The agreement between the two was reasonable, especially in the high and low frequency limits; however, it was found that the SEA model resulted in an under-prediction of the transmission loss in the mid-frequency range. Nonetheless, it was concluded that the performance of polyimide foam could be predicted using conventional poro-elastic material models and that polyimide foam may offer an attractive alternative to other double wall linings in certain situations: e.g., when fire resistance is a key issue. Future work will concentrate on reducing the density of the foam to values similar to those used in current aircraft sidewall treatments, and developing procedures to improve the performance of the foam in transmission loss applications.

  17. Acoustical transmission-line model of the middle-ear cavities and mastoid air cells

    PubMed Central

    Keefe, Douglas H.

    2015-01-01

    An acoustical transmission line model of the middle-ear cavities and mastoid air cell system (MACS) was constructed for the adult human middle ear with normal function. The air-filled cavities comprised the tympanic cavity, aditus, antrum, and MACS. A binary symmetrical airway branching model of the MACS was constructed using an optimization procedure to match the average total volume and surface area of human temporal bones. The acoustical input impedance of the MACS was calculated using a recursive procedure, and used to predict the input impedance of the middle-ear cavities at the location of the tympanic membrane. The model also calculated the ratio of the acoustical pressure in the antrum to the pressure in the middle-ear cavities at the location of the tympanic membrane. The predicted responses were sensitive to the magnitude of the viscothermal losses within the MACS. These predicted input impedance and pressure ratio functions explained the presence of multiple resonances reported in published data, which were not explained by existing MACS models. PMID:25920840

  18. Transmission line corona losses under hoar frost conditions

    SciTech Connect

    Lahti, K.; Nousiainen, K.; Lahtinen, M.

    1997-04-01

    Transmission line corona losses under hoar frost conditions were studied in the climate room of the high voltage laboratory of Tampere University of Technology. The measurements were performed using a coaxial measurement arrangement with different bundle and conductor types. The effects of conductor and bundle type, temperature, applied voltage and hoar frost thickness on corona losses were investigated. A two-conductor bundle had corona losses about 2.5--5 times higher than a three-conductor bundle. Relatively thin hoar frosts were used in the tests. Even the thinnest hoar frost resulted in remarkable corona losses and the losses were very sensitive to changes in the hoar frost thickness. The ambient temperature had a strong influence on the measured losses.

  19. A Numerical Investigation of Turbine Noise Source Hierarchy and Its Acoustic Transmission Characteristics

    NASA Technical Reports Server (NTRS)

    VanZante, Dale; Envia, Edmane

    2008-01-01

    Understanding the relative importance of the various turbine noise generation mechanisms and the characteristics of the turbine acoustic transmission loss are essential ingredients in developing robust reduced-order models for predicting the turbine noise signature. A computationally based investigation has been undertaken to help guide the development of a turbine noise prediction capability that does not rely on empiricism. The investigation relies on highly detailed numerical simulations of the unsteady flowfield inside a modern high-pressure turbine (HPT). The simulations are developed using TURBO, which is an unsteady Reynolds-averaged Navier-Stokes (URANS) code capable of multi-stage simulations. The purpose of this study is twofold. First, to determine an estimate of the relative importance of the contributions to the coherent part of the acoustic signature of a turbine from the three potential sources of turbine noise generation, namely, blade-row viscous interaction, potential field interaction, and entropic source associated with the interaction of the blade rows with the temperature nonuniformities caused by the incomplete mixing of the hot fluid and the cooling flow. Second, to develop an understanding of the turbine acoustic transmission characteristics and to assess the applicability of existing empirical and analytical transmission loss models to realistic geometries and flow conditions for modern turbine designs. The investigation so far has concentrated on two simulations: (1) a single-stage HPT and (2) a two-stage HPT and the associated inter-turbine duct/strut segment. The simulations are designed to resolve up to the second harmonic of the blade passing frequency tone in accordance with accepted rules for second order solvers like TURBO. The calculations include blade and vane cooling flows and a radial profile of pressure and temperature at the turbine inlet. The calculation can be modified later to include the combustor pattern factor at the

  20. Resonant mechanical meta-interface suppressing transmission of acoustic waves without mode conversion

    NASA Astrophysics Data System (ADS)

    Gusev, Vitalyi E.

    2015-02-01

    Physical principles for the creation of meta-interfaces between two elastic media supporting transmission of only mode-converted acoustic waves by use of arrays of resonant mechanical elements that transfer shear and compression/dilatation forces are revealed. Analytical modelling of mechanical structural vibrations according to a lumped-element approximation for mechanical elements oriented obliquely to the interface shows that such meta-interfaces can be applied to the directional transmission of the acoustic waves between solids and liquids. Applications include the acoustic isolation of solid objects in a liquid environment and the reduction of the detection efficiency of solid-object vibrations.

  1. Experimental realization of a variable index transmission line metamaterial as an acoustic leaky-wave antenna

    NASA Astrophysics Data System (ADS)

    Naify, Christina J.; Layman, Christopher N.; Martin, Theodore P.; Nicholas, Michael; Calvo, David C.; Orris, Gregory J.

    2013-05-01

    Development and experimental realization of an acoustic leaky wave antenna are presented. The antenna uses a one-dimensional composite right/left hand transmission line approach to tune radiation angle continually from backfire-to-endfire, including broadside, as a function of input frequency. An array of acoustically loaded membranes and open channels form a structure with negative, zero, or positive refractive index, depending on excitation frequency. The fast-wave radiation band of the antenna is determined using acoustic circuit analysis. Based on the designs specified by circuit and finite element analysis, an acoustic leaky wave antenna was fabricated, and the radiation direction measured at discrete frequencies.

  2. Acoustic guide for noise-transmission testing of aircraft

    NASA Technical Reports Server (NTRS)

    Vaicaitis, Rimas (Inventor)

    1987-01-01

    Selective testing of aircraft or other vehicular components without requiring disassembly of the vehicle or components was accomplished by using a portable guide apparatus. The device consists of a broadband noise source, a guide to direct the acoustic energy, soft sealing insulation to seal the guide to the noise source and to the vehicle component, and noise measurement microphones, both outside the vehicle at the acoustic guide output and inside the vehicle to receive attenuated sound. By directing acoustic energy only to selected components of a vehicle via the acoustic guide, it is possible to test a specific component, such as a door or window, without picking up extraneous noise which may be transmitted to the vehicle interior through other components or structure. This effect is achieved because no acoustic energy strikes the vehicle exterior except at the selected component. Also, since the test component remains attached to the vehicle, component dynamics with vehicle frame are not altered.

  3. Active control of transmission loss with smart foams.

    PubMed

    Kundu, Abhishek; Berry, Alain

    2011-02-01

    Smart foams combine the complimentary advantages of passive foam material and spatially distributed piezoelectric actuator embedded in it for active noise control applications. In this paper, the problem of improving the transmission loss of smart foams using active control strategies has been investigated both numerically and experimentally inside a waveguide under the condition of plane wave propagation. The finite element simulation of a coupled noise control system has been undertaken with three different smart foam designs and their effectiveness in cancelling the transmitted wave downstream of the smart foam have been studied. The simulation results provide insight into the physical phenomenon of active noise cancellation and explain the impact of the smart foam designs on the optimal active control results. Experimental studies aimed at implementing the real-time control for transmission loss optimization have been performed using the classical single input/single output filtered-reference least mean squares algorithm. The active control results with broadband and single frequency primary source inputs demonstrate a good improvement in the transmission loss of the smart foams. The study gives a comparative description of the transmission and absorption control problems in light of the modification of the vibration response of the piezoelectric actuator under active control.

  4. Underwater asymmetric acoustic transmission structure using the medium with gradient change of impedance

    NASA Astrophysics Data System (ADS)

    Bo, Hu; Jie, Shi; Sheng-Guo, Shi; Yu, Sun; Zhong-Rui, Zhu

    2016-02-01

    We propose an underwater asymmetric acoustic transmission structure comprised of two media each with a gradient change of acoustic impedance. By gradually increasing the acoustic impedances of the media, the propagating direction of the acoustic wave can be continuously bent, resulting in allowing the acoustic wave to pass through along the positive direction and blocking acoustic waves from the negative one. The main advantages of this structure are that the asymmetric transmission effect of this structure can be realized and enhanced more easily in water. We investigate both numerically and experimentally the asymmetric transmission effect. The experimental results show that a highly efficient asymmetric acoustic transmission can be yielded within a remarkable broadband frequency range, which agrees well with the numerical prediction. It is of potential practical significance for various underwater applications such as reducing vibration and noise. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204049 and 11204050), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT1228), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant Nos. 20122304120023 and 20122304120011).

  5. Multi-band asymmetric acoustic transmission in a bended waveguide with multiple mechanisms

    NASA Astrophysics Data System (ADS)

    Huang, Yu-lei; Sun, Hong-xiang; Xia, Jian-ping; Yuan, Shou-qi; Ding, Xin-lei

    2016-07-01

    We report the realization of a multi-band device of the asymmetric acoustic transmission by placing a phononic crystal inside a bended waveguide immersed in water, as determined both experimentally and numerically. The asymmetric acoustic transmission exists in three frequency bands below 500 kHz induced by multiple mechanisms. Besides the band gap of the phononic crystal, we also introduce the deaf mode and interaction between the phononic crystal and waveguide. More importantly, this asymmetric transmission can be systematically controlled by mechanically rotating the square rods of the phononic crystal. The device has the advantages of multiple band, broader bandwidth, and adjustable property, showing promising applications in ultrasonic devices.

  6. Feedforward control of sound transmission using an active acoustic metamaterial

    NASA Astrophysics Data System (ADS)

    Cheer, Jordan; Daley, Stephen; McCormick, Cameron

    2017-02-01

    Metamaterials have received significant interest in recent years due to their potential ability to exhibit behaviour not found in naturally occurring materials. This includes the generation of band gaps, which are frequency regions with high levels of wave attenuation. In the context of acoustics, these band gaps can be tuned to occur at low frequencies where the acoustic wavelength is large compared to the material, and where the performance of traditional passive noise control treatments is limited. Therefore, such acoustic metamaterials have been shown to offer a significant performance advantage compared to traditional passive control treatments, however, due to their resonant behaviour, the band gaps tend to occur over a relatively narrow frequency range. A similar long wavelength performance advantage can be achieved using active noise control, but the systems in this case do not rely on resonant behaviour. This paper demonstrates how the performance of an acoustic metamaterial, consisting of an array of Helmholtz resonators, can be significantly enhanced by the integration of an active control mechanism that is facilitated by embedding loudspeakers into the resonators. Crucially, it is then also shown how the active acoustic metamaterial significantly outperforms an equivalent traditional active noise control system. In both cases a broadband feedforward control strategy is employed to minimise the transmitted pressure in a one-dimensional acoustic control problem and a new method of weighting the control effort over a targeted frequency range is described.

  7. Transmission Loss Calculation using A and B Loss Coefficients in Dynamic Economic Dispatch Problem

    NASA Astrophysics Data System (ADS)

    Jethmalani, C. H. Ram; Dumpa, Poornima; Simon, Sishaj P.; Sundareswaran, K.

    2016-04-01

    This paper analyzes the performance of A-loss coefficients while evaluating transmission losses in a Dynamic Economic Dispatch (DED) Problem. The performance analysis is carried out by comparing the losses computed using nominal A loss coefficients and nominal B loss coefficients in reference with load flow solution obtained by standard Newton-Raphson (NR) method. Density based clustering method based on connected regions with sufficiently high density (DBSCAN) is employed in identifying the best regions of A and B loss coefficients. Based on the results obtained through cluster analysis, a novel approach in improving the accuracy of network loss calculation is proposed. Here, based on the change in per unit load values between the load intervals, loss coefficients are updated for calculating the transmission losses. The proposed algorithm is tested and validated on IEEE 6 bus system, IEEE 14 bus, system IEEE 30 bus system and IEEE 118 bus system. All simulations are carried out using SCILAB 5.4 (www.scilab.org) which is an open source software.

  8. LOSS ESTIMATE FOR ITER ECH TRANSMISSION LINE INCLUDING MULTIMODE PROPAGATION

    SciTech Connect

    Shapiro, Michael; Bigelow, Tim S; Caughman, John B; Rasmussen, David A

    2010-01-01

    The ITER electron cyclotron heating (ECH) transmission lines (TLs) are 63.5-mm-diam corrugated waveguides that will each carry 1 MW of power at 170 GHz. The TL is defined here as the corrugated wave guide system connecting the gyrotron mirror optics unit (MO U) to the entrance of the ECH launcher and includes miter bends and other corrugated wave guide components. The losses on the ITER TL have been calculated for four possible cases corresponding to having HE(11) mode purity at the input of the TL of 100, 97, 90, and 80%. The losses due to coupling, ohmic, and mode conversion loss are evaluated in detail using a numerical code and analytical approaches. Estimates of the calorimetric loss on the line show that the output power is reduced by about 5, +/- 1% because of ohmic loss in each of the four cases. Estimates of the mode conversion loss show that the fraction of output power in the HE(11) mode is similar to 3% smaller than the fraction of input power in the HE(11) mode. High output mode purity therefore can be achieved only with significantly higher input mode purity. Combining both ohmic and mode conversion loss, the efficiency of the TL from the gyrotron MOU to the ECH launcher can be roughly estimated in theory as 92% times the fraction of input power in the HE(11) mode.

  9. Sediment Acoustics: Wideband Model, Reflection Loss and Ambient Noise Inversion

    DTIC Science & Technology

    2011-09-01

    grain contact in water- saturated sand," J. Acoust. Soc. Am., vol. 124, pp. EL296-301, (2008). N. P. Chotiros, and M. J. Isakson. "Shear and...34Frame bulk modulus of porous granular marine sediments," J. Acoust. Soc. Am. 120, 699-710, (2006). B. J. Kraft and C. P. de Moustier, "Detailed

  10. High transmission acoustic focusing by impedance-matched acoustic meta-surfaces

    NASA Astrophysics Data System (ADS)

    Al Jahdali, Rasha; Wu, Ying

    2016-01-01

    Impedance is an important issue in the design of acoustic lenses because mismatched impedance is detrimental to real focusing applications. Here, we report two designs of acoustic lenses that focus acoustic waves in water and air, respectively. They are tailored by acoustic meta-surfaces, which are rigid thin plates decorated with periodically distributed sub-wavelength slits. Their respective building blocks are constructed from the coiling-up spaces in water and the layered structures in air. Analytic analysis based on coupled-mode theory and transfer matrix reveals that the impedances of the lenses are matched to those of the background media. With these impedance-matched acoustic lenses, we demonstrate the acoustic focusing effect by finite-element simulations.

  11. A channel transmission losses model for different dryland rivers

    NASA Astrophysics Data System (ADS)

    Costa, A. C.; Bronstert, A.; de Araújo, J. C.

    2011-10-01

    Channel transmission losses in drylands take place normally in extensive alluvial channels or streambeds underlain by fractured rocks. They can play an important role in flood prediction, groundwater recharge, freshwater supply and channel-associated ecosystems. We aim to develop a semi-distributed channel transmission losses model, a coupling of formulations which are more suitable for data-scarce dryland environments, applicable for both hydraulically disconnected losing streams and hydraulically connected losing(/gaining) streams. Hence, this approach should be able to cover a large variation in climate and hydro-geologic controls, which are typically found in dryland regions of the world. Traditionally, channel transmission losses models have been developed for site specific conditions. Our model was firstly evaluated for a losing/gaining, hydraulically connected 30 km reach of the Jaguaribe River, Ceará, Brazil, which controls a catchment area of 20 000 km2. Secondly, we applied it to a small losing, hydraulically disconnected 1.5 km channel reach in the Walnut Gulch Experimental Watershed (WGEW), Arizona, USA. The model based on the perceptual hydrological models of the reaches was able to predict reliably the stream flow for the both case studies. For the larger river reach, the evaluation of the hypotheses on the dominant hydrological processes was fundamental for reducing structural model uncertainties and improving the stream flow prediction, showing that both lateral stream-aquifer water fluxes and groundwater flow in the underlying alluvium parallel to the river course are necessary to predict stream flow and channel transmission losses, the former process being more relevant than the latter. The sensitivity analysis showed that even if the parameters can "potentially" produce large flow exchanges between model units in the saturated part of the modelling, large flow exchanges do not happen because they are restricted by the actual hydraulic gradient

  12. A transmission-loss monitor using current transformers

    SciTech Connect

    Power, J.F.; Gilpatrick, J.D.; Jason, A.J.

    1993-12-01

    A system for measuring the amount of beam-charge loss in a linear-accelerator structure has been developed that uses a pair of beam-current transformers, otherwise used to monitor the linac beam current. This system is necessary to enable the Ground Test Accelerator (GTA) fast-protect system to shut off the accelerated beam in the event of a beam loss that would deposit sufficient energy to damage the accelerator structure. The present GTA accelerator consists of a 2.5-MeV, H{sup {minus}} RFQ, an intermediate matching section (IMS) and a single DTL cavity with an output energy of 3.2-MeV and transmitted current of 35 mA. Based on the RFQ output beam, melting of the copper structures will occur when about 40 nC of beam is deposited in a point loss. For a grazing angle of 30 mrad, up to 640 nC may be tolerated. The beam-current-transmission-loss monitor (BCTLM) system in conjunction with the fast-protect system measures the amount of beam loss between two toroidal beam-current monitors and automatically terminates the macropulse when the integrated loss reaches a predetermined set point. The design and operation of the BCTLM system used in the IMS and DTL section of the accelerator is described.

  13. Empirical dependence of acoustic transmission scintillation statistics on bandwidth, frequency, and range in New Jersey continental shelf.

    PubMed

    Andrews, Mark; Chen, Tianrun; Ratilal, Purnima

    2009-01-01

    The scintillation statistics of broadband acoustic transmissions are determined as a function of signal bandwidth B, center frequency f(c), and range with experimental data in the New Jersey continental shelf. The received signal intensity is shown to follow the Gamma distribution implying that the central limit theorem has led to a fully saturated field from independent multimodal propagation contributions. The Gamma distribution depends on the mean intensity and the number of independent statistical fluctuations or coherent cells micro of the received signal. The latter is calculated for the matched filter, the Parseval sum, and the bandpassed center frequency, all of which are standard ocean acoustic receivers. The number of fluctuations mu of the received signal is found to be an order of magnitude smaller than the time-bandwidth product TB of the transmitted signal, and to increase monotonically with relative bandwidth Bfc. A computationally efficient numerical approach is developed to predict the mean intensity and the corresponding broadband transmission loss of a fluctuating, range-dependent ocean waveguide by range and depth averaging the output of a time-harmonic stochastic propagation model. This model enables efficient and accurate estimation of transmission loss over wide areas, which has become essential in wide-area sonar imaging applications.

  14. Effects of construction changes in the teeth of a gear transmission on acoustic properties.

    PubMed

    Wieczorek, Andrzej

    2012-01-01

    This paper presents results of experimental research on the acoustic properties of gear wheels with high-profile teeth with differentiated tooth height. Those results showed that gear transmissions with high-profile teeth have the best acoustic properties, with the value of the transverse contact ratio εα ≈ 2.0. They also showed that a reduction in tooth height, and thereby in contact ratio, increased the sound pressure level.

  15. The Use of Drugs to Reduce Hearing Loss Following Acute Acoustic Trauma

    DTIC Science & Technology

    2013-10-15

    1 AD_________________ Award Number: W81XWH-10-1-0485 TITLE: The Use of Drugs to Reduce Hearing Loss Following Acute Acoustic...Final 25 June 2010 – 24 October 2013 3. DATES COVERED 4. TITLE AND SUBTITLE The Use of Drugs to Reduce Hearing Loss Following Acute Acoustic Trauma...was to apply the same drug administration protocol to groups of animals exposed to a lower level continuous noise. Data from the treated and control

  16. Peculiar transmission property of acoustic waves in a one-dimensional layered phononic crystal

    NASA Astrophysics Data System (ADS)

    Zhao, Degang; Wang, Wengang; Liu, Zhengyou; Shi, Jing; Wen, Weijia

    2007-03-01

    In this article, we report both theoretical calculation and experimental observation of acoustic waves abnormally through a one-dimensional layered transmitted phononic crystal at frequencies within the band gap into a material of large acoustic impedance mismatch, with an efficiency as high as unity. The transmission peaks can be interpreted as a result of the interference of acoustic waves reflected from all periodically aligned interfaces. The condition for the appearance of peaks is analyzed in detail and the optimized layer number is given for different configurations.

  17. Ensuring quality of service for image transmission: hybrid loss protection.

    PubMed

    Grangetto, Marco; Magli, Enrico; Olmo, Gabriella

    2004-06-01

    We present hybrid loss protection as a new channel coding and packetization scheme for image transmission over nonprioritized lossy packet networks. The scheme employs an interleaver-based structure, and attempts to maximize the expected peak signal-to-noise ratio (PSNR) at the receiver given the constraint that the probability of failure, i.e., the probability that the PSNR of the decoded image is below a given threshold, is upper-bounded by a user-defined value. A new code-allocation algorithm is proposed, which employs Gilbert-Elliot modeling of the network statistics. Experimental results are provided in the case of transmission of images encoded by SPIHT and JPEG 2000 over a wireline, as well as a wireless UMTS-based Internet connection.

  18. Some sound transmission loss characteristics of typical general aviation structural materials

    NASA Technical Reports Server (NTRS)

    Roskam, J.; Van Dam, C.; Grosveld, F.; Durenberger, D.

    1978-01-01

    Experimentally measured sound transmission loss characteristics of flat aluminum panels with and without damping and stiffness treatment are presented and discussed. The effect of pressurization on sound transmission loss of flat aluminum panels is shown to be significant.

  19. Call transmission efficiency in native and invasive anurans: competing hypotheses of divergence in acoustic signals.

    PubMed

    Llusia, Diego; Gómez, Miguel; Penna, Mario; Márquez, Rafael

    2013-01-01

    Invasive species are a leading cause of the current biodiversity decline, and hence examining the major traits favouring invasion is a key and long-standing goal of invasion biology. Despite the prominent role of the advertisement calls in sexual selection and reproduction, very little attention has been paid to the features of acoustic communication of invasive species in nonindigenous habitats and their potential impacts on native species. Here we compare for the first time the transmission efficiency of the advertisement calls of native and invasive species, searching for competitive advantages for acoustic communication and reproduction of introduced taxa, and providing insights into competing hypotheses in evolutionary divergence of acoustic signals: acoustic adaptation vs. morphological constraints. Using sound propagation experiments, we measured the attenuation rates of pure tones (0.2-5 kHz) and playback calls (Lithobates catesbeianus and Pelophylax perezi) across four distances (1, 2, 4, and 8 m) and over two substrates (water and soil) in seven Iberian localities. All factors considered (signal type, distance, substrate, and locality) affected transmission efficiency of acoustic signals, which was maximized with lower frequency sounds, shorter distances, and over water surface. Despite being broadcast in nonindigenous habitats, the advertisement calls of invasive L. catesbeianus were propagated more efficiently than those of the native species, in both aquatic and terrestrial substrates, and in most of the study sites. This implies absence of optimal relationship between native environments and propagation of acoustic signals in anurans, in contrast to what predicted by the acoustic adaptation hypothesis, and it might render these vertebrates particularly vulnerable to intrusion of invasive species producing low frequency signals, such as L. catesbeianus. Our findings suggest that mechanisms optimizing sound transmission in native habitat can play a less

  20. Call Transmission Efficiency in Native and Invasive Anurans: Competing Hypotheses of Divergence in Acoustic Signals

    PubMed Central

    Llusia, Diego; Gómez, Miguel; Penna, Mario; Márquez, Rafael

    2013-01-01

    Invasive species are a leading cause of the current biodiversity decline, and hence examining the major traits favouring invasion is a key and long-standing goal of invasion biology. Despite the prominent role of the advertisement calls in sexual selection and reproduction, very little attention has been paid to the features of acoustic communication of invasive species in nonindigenous habitats and their potential impacts on native species. Here we compare for the first time the transmission efficiency of the advertisement calls of native and invasive species, searching for competitive advantages for acoustic communication and reproduction of introduced taxa, and providing insights into competing hypotheses in evolutionary divergence of acoustic signals: acoustic adaptation vs. morphological constraints. Using sound propagation experiments, we measured the attenuation rates of pure tones (0.2–5 kHz) and playback calls (Lithobates catesbeianus and Pelophylax perezi) across four distances (1, 2, 4, and 8 m) and over two substrates (water and soil) in seven Iberian localities. All factors considered (signal type, distance, substrate, and locality) affected transmission efficiency of acoustic signals, which was maximized with lower frequency sounds, shorter distances, and over water surface. Despite being broadcast in nonindigenous habitats, the advertisement calls of invasive L. catesbeianus were propagated more efficiently than those of the native species, in both aquatic and terrestrial substrates, and in most of the study sites. This implies absence of optimal relationship between native environments and propagation of acoustic signals in anurans, in contrast to what predicted by the acoustic adaptation hypothesis, and it might render these vertebrates particularly vulnerable to intrusion of invasive species producing low frequency signals, such as L. catesbeianus. Our findings suggest that mechanisms optimizing sound transmission in native habitat can play a

  1. Errors in transmission loss prediction—the bispectrum and kurtosis approaches

    NASA Astrophysics Data System (ADS)

    Barbieri, Nilson; Barbieri, Renato; de Lima, Key Fonseca

    2004-03-01

    The measurements of the acoustic performance of automotive mufflers are influenced by the wave propagation with reflection and absorption. This way, the measured signal can have linear and non-linear interactions of the wave components. The bispectrum, which is the measure of the phase relationship between three spectral components, has been shown to be a useful tool in the study of linear and non-linear wave interactions. The bicoherence spectrum may be used to discriminate between non-linearly coupled waves and spontaneously excited waves. At the same time, the kurtosis parameter is used as an indicative of the signals of microphones. The performances of two different physical models (bipartite chamber and a chamber with concentric perforated tube) are analysed considering the transmission loss. The experimental data are obtained through a two microphone method and the numerical values through the finite element method.

  2. Long range transmission loss of broadband seismic pulses in the Arctic under ice-free conditions.

    PubMed

    Thode, Aaron; Kim, Katherine H; Greene, Charles R; Roth, Ethan

    2010-10-01

    In 2008 the Louis S. St-Laurent (LSSL) surveyed deep Arctic waters using a three-airgun seismic source. Signals from the seismic survey were detected between 400 km and 1300 km range on a directional autonomous acoustic recorder deployed in water 53 m deep off the Alaskan North Slope. Observations of received signal levels between 10-450 Hz versus LSSL range roughly fit a cylindrical transmission loss model plus 0.01 dB/km attenuation in deep ice-free waters, and fit previous empirical models in ice-covered waters. The transition between ice-free and ice-covered propagation conditions shifted 200 km closer to the recorder during the survey.

  3. Resonant transmission and mode modulation of acoustic waves in H-shaped metallic gratings

    SciTech Connect

    Deng, Yu-Qiang; Fan, Ren-Hao; Zhang, Kun; Peng, Ru-Wen E-mail: dongxiang87@gmail.com; Qi, Dong-Xiang E-mail: dongxiang87@gmail.com

    2015-04-15

    In this work, we demonstrate that resonant full transmission of acoustic waves exists in subwavelength H-shaped metallic gratings, and transmission peaks can be efficiently tuned by adjusting the grating geometry. We investigate this phenomenon through both numerical simulations and theoretical calculations based on rigorous-coupled wave analysis. The transmission peaks are originated from Fabry-Perot resonances together with the couplings between the diffractive wave on the surface and the multiple guided modes in the slits. Moreover, the transmission modes can be efficiently tuned by adjusting the cavity geometry, without changing the grating thickness. The mechanism is analyzed based on an equivalent circuit model and verified by both the theoretical calculations and the numerical simulations. This research has potential application in acoustic-device miniaturization over a wide range of wavelengths.

  4. Acoustic neuroma

    MedlinePlus

    Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor; Hearing loss - acoustic; Tinnitus - acoustic ... Acoustic neuromas have been linked with the genetic disorder neurofibromatosis type 2 (NF2). Acoustic neuromas are uncommon.

  5. Tonpilz piezoelectric transducers with acoustic matching plates for underwater color image transmission.

    PubMed

    Inoue, T; Nada, T; Tsuchiya, T; Nakanishi, T; Miyama, T; Konno, M

    1993-01-01

    Tonpilz piezoelectric transducers with multiple acoustic matching plates are suitable for color image acoustic transmission, to achieve wideband low-ripple characteristics as well as high-efficiency high-power transmitting capability. The design method for the transducers was investigated on the basis of multiple-mode filter synthesis theory. For transducers with single, double, and triple matching plates, optimum specific acoustic impedances and lengths were calculated. Moreover, based on this design method, a 24 kHz array comprising nine identical transducers with single matching plates was built and evaluated. As a result, this array showed high-efficiency, low-ripple, and wideband characteristics. Excellent agreement between theoretical values and experimental results was obtained. A field test was carried out on color image transmission from a 3500 m sea depth, using the fabricated array, during which good color images were received.

  6. Tunable broadband unidirectional acoustic transmission based on a waveguide with phononic crystal

    NASA Astrophysics Data System (ADS)

    Song, Ailing; Chen, Tianning; Wang, Xiaopeng; Wan, Lele

    2016-08-01

    In this paper, a tunable broadband unidirectional acoustic transmission (UAT) device composed of a bended tube and a superlattice with square columns is proposed and numerically investigated by using finite element method. The UAT is realized in the proposed UAT device within two wide frequency ranges. And the effectiveness of the UAT device is demonstrated by analyzing the sound pressure distributions when the acoustic waves are incident from different directions. The unidirectional band gaps can be effectively tuned by mechanically rotating the square columns, which is a highlight of this paper. Besides, a bidirectional acoustic isolation (BAI) device is obtained by placing two superlattices in the bended tube, in which the acoustic waves cannot propagate along any directions. The physical mechanisms of the proposed UAT device and BAI device are simply discussed. The proposed models show potential applications in some areas, such as unidirectional sonic barrier or noise insulation.

  7. Estimating uncertainty in subsurface glider position using transmissions from fixed acoustic tomography sources.

    PubMed

    Van Uffelen, Lora J; Nosal, Eva-Marie; Howe, Bruce M; Carter, Glenn S; Worcester, Peter F; Dzieciuch, Matthew A; Heaney, Kevin D; Campbell, Richard L; Cross, Patrick S

    2013-10-01

    Four acoustic Seagliders were deployed in the Philippine Sea November 2010 to April 2011 in the vicinity of an acoustic tomography array. The gliders recorded over 2000 broadband transmissions at ranges up to 700 km from moored acoustic sources as they transited between mooring sites. The precision of glider positioning at the time of acoustic reception is important to resolve the fundamental ambiguity between position and sound speed. The Seagliders utilized GPS at the surface and a kinematic model below for positioning. The gliders were typically underwater for about 6.4 h, diving to depths of 1000 m and traveling on average 3.6 km during a dive. Measured acoustic arrival peaks were unambiguously associated with predicted ray arrivals. Statistics of travel-time offsets between received arrivals and acoustic predictions were used to estimate range uncertainty. Range (travel time) uncertainty between the source and the glider position from the kinematic model is estimated to be 639 m (426 ms) rms. Least-squares solutions for glider position estimated from acoustically derived ranges from 5 sources differed by 914 m rms from modeled positions, with estimated uncertainty of 106 m rms in horizontal position. Error analysis included 70 ms rms of uncertainty due to oceanic sound-speed variability.

  8. Asymmetric transmission of acoustic waves in a layer thickness distribution gradient structure using metamaterials

    NASA Astrophysics Data System (ADS)

    Chen, Jung-San; Chang, I.-Ling; Huang, Wan-Ting; Chen, Lien-Wen; Huang, Guan-Hua

    2016-09-01

    This research presents an innovative asymmetric transmission design using alternate layers of water and metamaterial with complex mass density. The directional transmission behavior of acoustic waves is observed numerically inside the composite structure with gradient layer thickness distribution and the rectifying performance of the present design is evaluated. The layer thickness distributions with arithmetic and geometric gradients are considered and the effect of gradient thickness on asymmetric wave propagation is systematically investigated using finite element simulation. The numerical results indicate that the maximum pressure density and transmission through the proposed structure are significantly influenced by the wave propagation direction over a wide range of audible frequencies. Tailoring the thickness of the layered structure enables the manipulation of asymmetric wave propagation within the desired frequency range. In conclusion, the proposed design offers a new possibility for developing directional-dependent acoustic devices.

  9. Energy transmission in a mechanically-linked double-wall structure coupled to an acoustic enclosure

    NASA Astrophysics Data System (ADS)

    Cheng, L.; Li, Y. Y.; Gao, J. X.

    2005-05-01

    The energy transmission in a mechanically linked double-wall structure into an acoustic enclosure is studied in this paper. Based on a fully coupled vibro-acoustic formulation, focus is put on investigating the effect of the air gap and mechanical links between the two panels on the energy transmission and noise insulation properties of such structures. An approximate formula reflecting the gap effect on the lower-order coupled frequencies of the system is proposed. A criterion, based on the ratio between the aerostatic stiffness of the gap cavity and the stiffness of the link, is proposed to predict the dominant transmitting path, with a view to provide guidelines for the design of appropriate control strategies. Numerical results reveal the existence of three distinct zones, within which energy transmission takes place following different mechanisms and transmitting paths. Corresponding effects on noise insulation properties of the double-wall structure are also investigated. .

  10. Control strategies and mechanisms for active control of sound transmission into a vibro-acoustic enclosure

    NASA Astrophysics Data System (ADS)

    Jin, Guoyong; Feng, Na; Yang, Tiejun

    2011-06-01

    An analytical study was presented on active control of sound transmission into a vibro-acoustic enclosure comprising two flexible plates. Two types of actuators were used, i.e. acoustic actuator and distributed lead zirconate titanate piezoelectric (PZT) actuator instead of point force actuator. Using the modal acoustic transfer impedance-mobility matrices, the excitation and interaction in the coupled sound transmission system can be described with clear physical significance. With the control system designed to globally reduce the sound field, different control system configurations were considered, including the structural actuator on the incident plate, actuator on the receiving plate, acoustic actuator on the cavity, and their combinations. The effectiveness and performance of the control strategy corresponding to each system configuration were compared and discussed. The role and control mechanism of each type of actuator were of particular interest. It was shown that the incident plate actuator is effective in controlling the cavity-dominated modes and the structural modes dominated by the incident plate and receiving plate. Two main control mechanisms are involved in this control configuration, i.e., modal suppressing and modal rearrangement. For control system configuration with only acoustic actuator in the enclosure, the mechanism involved in this arrangement is purely modal suppression. Desirable placements of structural actuators in terms of total potential energy reduction were also discussed.

  11. Smaller-loss planar SPP transmission line than conventional microstrip in microwave frequencies

    PubMed Central

    Zhang, Hao Chi; Zhang, Qian; Liu, Jun Feng; Tang, Wenxuan; Fan, Yifeng; Cui, Tie Jun

    2016-01-01

    Transmission line is a basic component in all passive devices, integrated circuits, and systems. Microstrip is the most popular transmission line in the microwave and millimeter-wave frequencies, and has been widely used in current electronic devices, circuits, and systems. One of the important issues to be solved in such applications is the relatively large transmission loss of microstrip. Here, we propose a method to reduce the loss of microwave transmission line based on the designable wavenumber of spoof surface plasmon polaritons (SPPs). Using this characteristic, we analyze and experimentally demonstrate the low-loss feature of the SPP transmission line through the perturbation method and S-parameter measurements, respectively. Both simulation and experimental results show that the SPP transmission line has much smaller transmission loss than traditional microstrip with the same size in the microwave frequencies. Hence, the spoof SPP transmission line may make a big step forward in the low-loss circuits and systems. PMID:26983911

  12. Smaller-loss planar SPP transmission line than conventional microstrip in microwave frequencies.

    PubMed

    Zhang, Hao Chi; Zhang, Qian; Liu, Jun Feng; Tang, Wenxuan; Fan, Yifeng; Cui, Tie Jun

    2016-03-17

    Transmission line is a basic component in all passive devices, integrated circuits, and systems. Microstrip is the most popular transmission line in the microwave and millimeter-wave frequencies, and has been widely used in current electronic devices, circuits, and systems. One of the important issues to be solved in such applications is the relatively large transmission loss of microstrip. Here, we propose a method to reduce the loss of microwave transmission line based on the designable wavenumber of spoof surface plasmon polaritons (SPPs). Using this characteristic, we analyze and experimentally demonstrate the low-loss feature of the SPP transmission line through the perturbation method and S-parameter measurements, respectively. Both simulation and experimental results show that the SPP transmission line has much smaller transmission loss than traditional microstrip with the same size in the microwave frequencies. Hence, the spoof SPP transmission line may make a big step forward in the low-loss circuits and systems.

  13. Smaller-loss planar SPP transmission line than conventional microstrip in microwave frequencies

    NASA Astrophysics Data System (ADS)

    Zhang, Hao Chi; Zhang, Qian; Liu, Jun Feng; Tang, Wenxuan; Fan, Yifeng; Cui, Tie Jun

    2016-03-01

    Transmission line is a basic component in all passive devices, integrated circuits, and systems. Microstrip is the most popular transmission line in the microwave and millimeter-wave frequencies, and has been widely used in current electronic devices, circuits, and systems. One of the important issues to be solved in such applications is the relatively large transmission loss of microstrip. Here, we propose a method to reduce the loss of microwave transmission line based on the designable wavenumber of spoof surface plasmon polaritons (SPPs). Using this characteristic, we analyze and experimentally demonstrate the low-loss feature of the SPP transmission line through the perturbation method and S-parameter measurements, respectively. Both simulation and experimental results show that the SPP transmission line has much smaller transmission loss than traditional microstrip with the same size in the microwave frequencies. Hence, the spoof SPP transmission line may make a big step forward in the low-loss circuits and systems.

  14. Resonant coupling of Rayleigh waves through a narrow fluid channel causing extraordinary low acoustic transmission.

    PubMed

    Garcia-Chocano, Victor M; Nagaraj; Lòpez-Rios, Tomàs; Gumen, Lyudmila; Sànchez-Dehesa, Josè; Krokhin, Arkadii

    2012-10-01

    Coupling of Rayleigh waves propagating along two metal surfaces separated by a narrow fluid channel is predicted and experimentally observed. Although the coupling through a fluid (water) is weak, a strong synchronization in propagation of Rayleigh waves even for the metals with sufficiently high elastic contrast (brass and aluminum) is observed. Dispersion equation for two polarizations of the coupled Rayleigh waves is derived and experimentally confirmed. Excitation of coupled Rayleigh waves in a channel of finite length leads to anomalously low transmission of acoustic energy at discrete set of resonant frequencies. This effect may find useful applications in the design of acoustic metamaterial screens and reflectors.

  15. Progress in Acoustic Transmission of Power through Walls

    NASA Technical Reports Server (NTRS)

    Sherrit,Stewart; Coty, Benjamin; Bao, Xiaoqi; Bar-Cohen, Yoseph; Badescu, Mircea; Chang, Zensheu

    2008-01-01

    A document presents updated information on implementation of the wireless acoustic-electric feed-through (WAEF) concept, which was reported in Using Piezoelectric Devices To Transmit Power Through Walls (NPO-41157), NASA Tech Briefs, Vol. 32, No. 6 (June 2008), page 70. To recapitulate: In a basic WAEF setup, a transmitting piezoelectric transducer on one side of a wall is driven at resonance to excite ultrasonic vibrations in the wall. A receiving piezoelectric transducer on the opposite side of the wall converts the vibrations back to an ultrasonic AC electric signal, which is then detected and otherwise processed in a manner that depends on the modulation (if any) applied to the signal and whether the signal is used to transmit power, data, or both. The present document expands upon the previous information concerning underlying physical principles, advantages, and potential applications of WAEF. It discusses the design and construction of breadboard prototype piezoelectric transducers for WAEF. It goes on to present results of computational simulations of performance and results of laboratory tests of the prototypes. In one notable test, a 100-W light bulb was lit by WAEF to demonstrate the feasibility of powering a realistic load.

  16. An acoustic transmission sensor for the longitudinal viscosity of fluids.

    PubMed

    Antlinger, Hannes; Clara, Stefan; Beigelbeck, Roman; Cerimovic, Samir; Keplinger, Franz; Jakoby, Bernhard

    2013-11-01

    Physical fluid parameters like viscosity, mass density and sound velocity can be determined utilizing ultrasonic sensors. We introduce the concept of a recently devised transmission based sensor utilizing pressure waves to determine the longitudinal viscosity, bulk viscosity, and second coefficient of viscosity of a sample fluid in a test chamber. A model is presented which allows determining these parameters from measurement values by means of a fit. The setup is particularly suited for liquids featuring higher viscosities for which measurement data are scarcely available to date. The setup can also be used to estimate the sound velocity in a simple manner from the phase of the transfer function.

  17. An acoustic transmission sensor for the longitudinal viscosity of fluids

    PubMed Central

    Antlinger, Hannes; Clara, Stefan; Beigelbeck, Roman; Cerimovic, Samir; Keplinger, Franz; Jakoby, Bernhard

    2013-01-01

    Physical fluid parameters like viscosity, mass density and sound velocity can be determined utilizing ultrasonic sensors. We introduce the concept of a recently devised transmission based sensor utilizing pressure waves to determine the longitudinal viscosity, bulk viscosity, and second coefficient of viscosity of a sample fluid in a test chamber. A model is presented which allows determining these parameters from measurement values by means of a fit. The setup is particularly suited for liquids featuring higher viscosities for which measurement data are scarcely available to date. The setup can also be used to estimate the sound velocity in a simple manner from the phase of the transfer function. PMID:25844023

  18. Energy loss to intravalley acoustic modes in nano-dimensional wire structures at low temperatures

    NASA Astrophysics Data System (ADS)

    Nag, S.; Das, B.; Basu, A.; Das, J.; Bhattacharya, D. P.; Sarkar, C. K.

    2017-03-01

    The theory of rate of loss of energy of non-equilibrium electrons due to inelastic interaction with the intravalley acoustic phonons in a nano-dimensional semiconductor wire has been developed under the condition of low lattice temperature, when the approximations of the well known traditional theory are not valid. Numerical results are obtained for narrow-channel GaAs-GaAlAs wires structures. On comparison with other available results it is revealed that the finite energy of the intravalley acoustic phonons and, the use of the full form of the phonon distribution without truncation to the equipartition law, produce significant changes in the energy loss characteristics at low temperatures.

  19. 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.

  20. The effect of habitat acoustics on common marmoset vocal signal transmission.

    PubMed

    Morrill, Ryan J; Thomas, A Wren; Schiel, Nicola; Souto, Antonio; Miller, Cory T

    2013-09-01

    Noisy acoustic environments present several challenges for the evolution of acoustic communication systems. Among the most significant is the need to limit degradation of spectro-temporal signal structure in order to maintain communicative efficacy. This can be achieved by selecting for several potentially complementary processes. Selection can act on behavioral mechanisms permitting signalers to control the timing and occurrence of signal production to avoid acoustic interference. Likewise, the signal itself may be the target of selection, biasing the evolution of its structure to comprise acoustic features that avoid interference from ambient noise or degrade minimally in the habitat. Here, we address the latter topic for common marmoset (Callithrix jacchus) long-distance contact vocalizations, known as phee calls. Our aim was to test whether this vocalization is specifically adapted for transmission in a species-typical forest habitat, the Atlantic forests of northeastern Brazil. We combined seasonal analyses of ambient habitat acoustics with experiments in which pure tones, clicks, and vocalizations were broadcast and rerecorded at different distances to characterize signal degradation in the habitat. Ambient sound was analyzed from intervals throughout the day and over rainy and dry seasons, showing temporal regularities across varied timescales. Broadcast experiment results indicated that the tone and click stimuli showed the typically inverse relationship between frequency and signaling efficacy. Although marmoset phee calls degraded over distance with marked predictability compared with artificial sounds, they did not otherwise appear to be specially designed for increased transmission efficacy or minimal interference in this habitat. We discuss these data in the context of other similar studies and evidence of potential behavioral mechanisms for avoiding acoustic interference in order to maintain effective vocal communication in common marmosets.

  1. Characterization of the Reverberation Chamber at the NASA Langley Structural Acoustics Loads and Transmission (SALT) Facility

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    2013-01-01

    In 2011 the noise generating capabilities in the reverberation chamber of the Structural Acoustic Loads and Transmission (SALT) facility at NASA Langley Research Center were enhanced with two fiberglass reinforced polyester resin exponential horns, each coupled to Wyle Acoustic Source WAS-3000 airstream modulators. This report describes the characterization of the reverberation chamber in terms of the background noise, diffusivity, sound pressure levels, the reverberation times and the related overall acoustic absorption in the empty chamber and with the acoustic horn(s) installed. The frequency range of interest includes the 80 Hz to 8000 Hz one-third octave bands. Reverberation time and sound pressure level measurements were conducted and standard deviations from the mean were computed. It was concluded that a diffuse field could be produced above the Schroeder frequency in the 400 Hz one-third octave band and higher for all applications. This frequency could be lowered by installing panel diffusers or moving vanes to improve the acoustic modal overlap in the chamber. In the 80 Hz to 400 Hz one-third octave bands a successful measurement will be dependent on the type of measurement, the test configuration, the source and microphone locations and the desired accuracy. It is recommended that qualification measurements endorsed in the International Standards be conducted for each particular application.

  2. Reflection and transmission of acoustical waves from a layer with space-dependent velocity.

    NASA Technical Reports Server (NTRS)

    Steinmetz, G. G.; Singh, J. J.

    1972-01-01

    The refraction of acoustical waves by a moving medium layer is theoretically treated and the reflection and transmission coefficients are determined. The moving-medium-layer velocity is uniform but with a space dependence in one direction. A partitioning of the moving medium layer into constant-velocity sublayers is introduced and numerical results for a three-sublayer approximation of Poiseuille flow are presented. The degenerate case of a single constant-velocity layer is also treated theoretically and numerically. The numerical results show the reflection and transmission coefficients as functions of the peak moving-medium-layer normalized velocity for several angles of incidence.

  3. Nonlinear behavior of electric power transmission through an elastic wall by acoustic waves and piezoelectric transducers.

    PubMed

    Yang, Zengtao; Yang, Jiashi; Hu, Yuantai

    2008-11-01

    Weakly nonlinear behavior of electric power transmission through an elastic wall by piezoelectric transducers and acoustic waves near resonance is studied based on the cubic theory of nonlinear electroelasticity. An approximate analytical solution is obtained. Output voltage is calculated and plotted. Basic nonlinear behaviors of the power transmission structure are examined. It is found that near nonlinear resonance the electrical input-output relation loses its linearity, becomes multi-valued, and experiences jumps due to large mechanical deformations. The behavior below and above resonance is qualitatively different and is qualitatively material dependent.

  4. Characterization of Sound Transmission Loss of Laminated Glass with Analytical and Experimental Approaches

    SciTech Connect

    Sun, Xin; Simmons, Kevin L.; Khaleel, Mohammad A.

    2005-11-30

    In this project, we have developed the general formation for calculating transmission loss of sound waves through multi-layered structures. Full factorial design method has also been used to investigate the relative effect of various geometric and material parameters on the transmission loss. It was found that within the range of practical interest, the most effect way of increasing transmission loss is by increasing either the glass thickness or increasing the inner layer mass density. Experimental measurements of sound transmission loss (in decibels) for four laminated glass samples have been made in accordance to SAE J1400, in third-octave bands between 125 Hz and 8 kHz.

  5. Contributions of rapid neuromuscular transmission to the fine control of acoustic parameters of birdsong.

    PubMed

    Mencio, Caitlin; Kuberan, Balagurunathan; Goller, Franz

    2017-02-01

    Neural control of complex vocal behaviors, such as birdsong and speech, requires integration of biomechanical nonlinearities through muscular output. Although control of airflow and tension of vibrating tissues are known functions of vocal muscles, it remains unclear how specific muscle characteristics contribute to specific acoustic parameters. To address this gap, we removed heparan sulfate chains using heparitinases to perturb neuromuscular transmission subtly in the syrinx of adult male zebra finches (Taeniopygia guttata). Infusion of heparitinases into ventral syringeal muscles altered their excitation threshold and reduced neuromuscular transmission changing their ability to modulate airflow. The changes in muscle activation dynamics caused a reduction in frequency modulation rates and elimination of many high-frequency syllables but did not alter the fundamental frequency of syllables. Sound amplitude was reduced and sound onset pressure was increased, suggesting a role of muscles in the induction of self-sustained oscillations under low-airflow conditions, thus enhancing vocal efficiency. These changes were reversed to preinfusion levels by 7 days after infusion. These results illustrate complex interactions between the control of airflow and tension and further define the importance of syringeal muscle in the control of a variety of acoustic song characteristics. In summary, the findings reported here show that altering neuromuscular transmission can lead to reversible changes to the acoustic structure of song. Understanding the full extent of muscle involvement in song production is critical in decoding the motor program for the production of complex vocal behavior, including our search for parallels between birdsong and human speech motor control.

  6. Auditory nerve synapses persist in ventral cochlear nucleus long after loss of acoustic input in mice with early-onset progressive hearing loss.

    PubMed

    McGuire, Brian; Fiorillo, Benjamin; Ryugo, David K; Lauer, Amanda M

    2015-04-24

    Perceptual performance in persons with hearing loss, especially those using devices to restore hearing, is not fully predicted by traditional audiometric measurements designed to evaluate the status of peripheral function. The integrity of auditory brainstem synapses may vary with different forms of hearing loss, and differential effects on the auditory nerve-brain interface may have particularly profound consequences for the transfer of sound from ear to brain. Loss of auditory nerve synapses in ventral cochlear nucleus (VCN) has been reported after acoustic trauma, ablation of the organ of Corti, and administration of ototoxic compounds. The effects of gradually acquired forms deafness on these synapses are less well understood. We investigated VCN gross morphology and auditory nerve synapse integrity in DBA/2J mice with early-onset progressive sensorineural hearing loss. Hearing status was confirmed using auditory brainstem response audiometry and acoustic startle responses. We found no change in VCN volume, number of macroneurons, or number of VGLUT1-positive auditory nerve terminals between young adult and older, deaf DBA/2J. Cell-type specific analysis revealed no difference in the number of VGLUT1 puncta contacting bushy and multipolar cell body profiles, but the terminals were smaller in deaf DBA/2J mice. Transmission electron microscopy confirmed the presence of numerous healthy, vesicle-filled auditory nerve synapses in older, deaf DBA/2J mice. The present results suggest that synapses can be preserved over a relatively long time-course in gradually acquired deafness. Elucidating the mechanisms supporting survival of central auditory nerve synapses in models of acquired deafness may reveal new opportunities for therapeutic intervention.

  7. A Numerical Investigation of Turbine Noise Source Hierarchy and Its Acoustic Transmission Characteristics: Proof-of-Concept Progress

    NASA Technical Reports Server (NTRS)

    VanZante, Dale; Envia, Edmane

    2008-01-01

    A CFD-based simulation of single-stage turbine was done using the TURBO code to assess its viability for determining acoustic transmission through blade rows. Temporal and spectral analysis of the unsteady pressure data from the numerical simulations showed the allowable Tyler-Sofrin modes that are consistent with expectations. This indicated that high-fidelity acoustic transmission calculations are feasible with TURBO.

  8. Acoustic minor losses in high amplitude resonators with single-sided junctions

    NASA Astrophysics Data System (ADS)

    Doller, Andrew J.

    Steady flow engineering handbooks like Idelchik20 do not exist for investigators interested in acoustic (oscillating) fluid flows in complex resonators. Measurements of acoustic minor loss coefficients are presented in this dissertation for a limited number of resonator configurations having single-sided junctions. While these results may be useful, the greater purpose of this work is to provide a set of controlled measurements that can be used to benchmark computational models of acoustic flows used for more complicated resonator structures. The experiments are designed around a driver operating at 150 Hz enabling acoustic pressures in excess of 10k Pa in liquid cooled, temperature controlled resonators with 90°, 45° and 25° junctions. These junctions join a common 109 cm long 4.7 cm diameter section to a section of 8.4 mm diameter tube making two sets of resonators: one set with a small diameter length approximately a quarter-wavelength (45 cm), the other approximately a half-wavelength (112 cm). The long resonators have a velocity node at the junction; the short resonators have a velocity anti-node generating the greatest minor losses. Input power is measured by an accelerometer and a pressure transducer at the driver. A pressure sensor at the rigid termination measures radiation pressure from the driver and static junction pressure, as well as the acoustic pressure used to calculate linear thermal and viscous resonator wall losses. At the largest amplitudes, the 90° junction was found to dissipate as much as 0.3 Watt, 1/3 the power of linear losses alone. For each junction, the power dissipation depends on acoustic pressure differently: pressure cubed for the 90°, pressure to the 3.76 for the 45° and pressure to the 4.48 for the 25°. Common among all resonators, blowing acoustic half-cycle minor losses (KB) are excited at lower amplitudes than the suction half-cycle (KS) minor losses. Data collected for the 90° junction shows KB reaches an asymptotic

  9. Prevention of Acoustic Trauma-Induced Hearing Loss by N-acetylcysteine Administration in Rabbits

    PubMed Central

    Motalebi Kashani, Masoud; Saberi, Hamidreza; Hannani, Mitra

    2013-01-01

    Background Acoustic trauma is an injury to the hearing mechanisms in the inner ear due to excessive noise. This injury is the most prevalent cause of sensorineural hearing loss in humans, especially from occupational exposure. Previous studies have shown the essential role of free radical formation in the inner ear hearing loss caused by acoustic trauma. Objectives This study was performed to determine the effect of N-acetylcysteine (NAC) administration for reducing acute acoustic trauma in rabbits. Materials and Methods Twenty four rabbits were assigned to four groups including: control, noise plus saline, noise plus NAC administration (325 mg/kg body weight by intraperitoneal injection (IP), three days before exposure to noise and three days after noise exposure), and NAC alone. Auditory brain stem response (ABR) threshold was measured before exposure and one hour and 14 days after exposure. Results The saline plus noise group had on average a 49 decibel (dB) temporary threshold shift (TTS) and 23.9 dB permanent threshold shift (PTS) at the studied frequencies, while rabbits in the NAC administration plus noise group had a 31.5 dB TTS and 10.7 dB PTS averaged across the frequencies. Conclusions Administration of NAC can provide appropriate protection against acoustic trauma-induced hearing loss in rabbits at all studied frequencies. PMID:24396768

  10. Observation of low-loss broadband supermode propagation in coupled acoustic waveguide complex

    PubMed Central

    Shen, Ya-Xi; Peng, Yu-Gui; Chen, Xin-Cheng; Zhao, De-Gang; Zhu, Xue-Feng

    2017-01-01

    We investigate analytically, numerically, and experimentally the low-loss supermode propagation in a coupled acoustic waveguide complex within a broadband. The waveguide complex is implemented with air channels coupled via an ultrathin metafluid layer. We analytically derive the field distribution of incident sound needed for producing acoustic supermodes, and verify the periodically revival propagation in coupled waveguide systems numerically and experimentally. We find out that the supermode wavelength becomes longer for higher mode order or lower frequency. We have also demonstrated the robust propagation of supermodes in broadband. Our scheme can in principle be extended to three dimensions and the ultrasound regime with simplicity and may promote applications of high-fidelity signal transfer in complicated acoustic networks. PMID:28349953

  11. Observation of low-loss broadband supermode propagation in coupled acoustic waveguide complex.

    PubMed

    Shen, Ya-Xi; Peng, Yu-Gui; Chen, Xin-Cheng; Zhao, De-Gang; Zhu, Xue-Feng

    2017-03-28

    We investigate analytically, numerically, and experimentally the low-loss supermode propagation in a coupled acoustic waveguide complex within a broadband. The waveguide complex is implemented with air channels coupled via an ultrathin metafluid layer. We analytically derive the field distribution of incident sound needed for producing acoustic supermodes, and verify the periodically revival propagation in coupled waveguide systems numerically and experimentally. We find out that the supermode wavelength becomes longer for higher mode order or lower frequency. We have also demonstrated the robust propagation of supermodes in broadband. Our scheme can in principle be extended to three dimensions and the ultrasound regime with simplicity and may promote applications of high-fidelity signal transfer in complicated acoustic networks.

  12. Analyzing the validity of a DFT-based improved acoustic OFDM transmission along rotating simulated drillstring

    NASA Astrophysics Data System (ADS)

    Cheng, Li; Jinfeng, Chang; Shangchun, Fan; Jun, Yang

    2016-12-01

    In the oil industry, drillstring can be used as a transmission medium to send downhole information via a modulated compressional acoustic wave. However, the accompanied reverberation is a major constraint in the transmission rate and distance because of the multipath fading caused by the heterogeneous drillstring. In combination with discrete Fourier transform-spread (DFT-S) mapping/demapping, high-power amplitude squeezing and DFT-based least squares channel estimation methods, an improved orthogonal frequency division multiplexing (OFDM) scheme is proposed in this paper to overcome the symbol interference inherent in the drillstring multipath channel and reduce the peak-to-average power ratio of the signal. Then an experimental rig is established by using a rotatable electromagnetic vibration exciter and a piezoelectric accelerometer arranged at the position closer to acoustic impedance terminal along a 6.3-m periodic simulated drillstring. The OFDM data sequences at a data rate of 200 bit/s over a limited bandwidth of 140 Hz are applied to the rotating simulated drillstring. The experimental results show that the proposed scheme using QPSK modulation can offer an error-free acoustic communication at rotation speeds up to 90 r/min.

  13. Novel binary PSO algorithm based optimization of transmission expansion planning considering power losses

    NASA Astrophysics Data System (ADS)

    Astuty; Haryono, T.

    2016-04-01

    Transmission expansion planning (TEP) is one of the issue that have to be faced caused by addition of large scale power generation into the existing power system. Optimization need to be conducted to get optimal solution technically and economically. Several mathematic methods have been applied to provide optimal allocation of new transmission line such us genetic algorithm, particle swarm optimization and tabu search. This paper proposed novel binary particle swarm optimization (NBPSO) to determine which transmission line should be added to the existing power system. There are two scenerios in this simulation. First, considering transmission power losses and the second is regardless transmission power losses. NBPSO method successfully obtain optimal solution in short computation time. Compare to the first scenario, the number of new line in second scenario which regardless power losses is less but produces high power losses that cause the cost becoming extremely expensive.

  14. Numerical Study of Transmission Loss Through a Slow Gas Layer Adjacent to a Plate

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Beck, Benjamin S.; Slagle, Adam C.

    2013-01-01

    This paper describes a systematic numerical investigation of the sound transmission loss through a multilayer system consisting of a bagged gas and lightweight panel. The goal of the study is to better understand the effect of the gas on transmission loss and determine whether a gas with a slow speed of sound is beneficial for noise control applications. As part of the study, the density and speed of sound of the gas are varied independently to assess the impact of each on transmission loss. Results show that near grazing incidence the plane wave transmission loss through the multilayer system is more sensitive to the speed of sound than the density of the gas. In addition, it was found that a slow wave speed in the bagged gas provides more low-frequency transmission loss benefit than a fast wave speed. At low angles of incidence, close to the plate normal, the benefit is due to the reduction of the characteristic impedance of the gas. At high angles of incidence, the benefit is attributed to the fact that the incident waves at the air/gas interface are bent towards the surface normal. Since transmission loss is angle dependent, refraction in the slow gas layer results in a significant improvement in the transmission loss at high angles of incidence.

  15. The therapeutic effect of thymoquinone on acoustic trauma-induced hearing loss in rats.

    PubMed

    Ogurlu, Mahmut; Celebi Erdivanli, Ozlem; Tumkaya, Levent; Ozgur, Abdulkadir; Ozergin Coskun, Zerrin; Terzi, Suat; Demirci, Munir; Dursun, Engin

    2017-02-01

    Thymoquinone has antioxidant properties. We hypothesized that thymoquinone may prevent or alleviate hearing loss induced by acoustic trauma. We aimed to study thymoquinone's effect on hearing function with distortion-product otoacoustic emissions and auditory brainstem response. Thirty adult Spraque Dawley rats were randomized into four groups following exposure to acoustic trauma for 4 h. Control group (n = 7) did not receive further treatment. Thymoquinone-20 (n = 8) and Thymoquinone-40 (n = 8) received 20 and 40 mg/kg of intraperitoneal thymoquinone, respectively. Corn-oil group (n = 7) received 1 ml of corn oil intraperitoneally. Hearing function of both ears was tested with distortion-product otoacoustic emission and auditory brainstem response before, and shortly after acoustic trauma, and 96 h following acoustic trauma. Post-trauma signal/noise ratios and wave V amplitude/latencies of all groups were significantly low compared with pre-trauma values, which indicate no preventive effect of thymoquinone. Rats in Thymoquinone-20 showed a significantly improved distortion-product otoacoustic emission and auditory brainstem response results at 4000 frequency and above in post-treatment tests (p < 0.05). Improvement in Thymoquinone-40 at the same frequencies was insignificantly inferior to Thymoquinone-20, yet superior to control and corn-oil groups (p < 0.05). We conclude that thymoquinone may not prevent acoustic trauma-induced hearing loss, however, at 20 mg/kg for 96 h, may repair the damage.

  16. Splice loss requirements in multi-mode fiber mode-division-multiplex transmission links.

    PubMed

    Warm, Stefan; Petermann, Klaus

    2013-01-14

    We investigate numerically the influence of fiber splices and fiber connectors to the statistics of mode dependent loss (MDL) and multiple-input multiple-output (MIMO) outage capacity in mode multiplexed multi-mode fiber links. Our results indicate required splice losses much lower than currently feasible to achieve a reasonable outage capacity in long-haul transmission systems. Splice losses as low as 0.03dB may effectively lead to an outage of MIMO channels after only a few hundred kilometers transmission length. In a first approximation, the relative capacity solely depends on the accumulated splice loss and should be less than ≈ 2dB to ensure a relative capacity of 90%. We also show that discrete mode permutation (mixing) within the transmission line may effectively increase the maximum transmission distance by a factor of 5 for conventional splice losses.

  17. Modeling of systems wireless data transmission based on antenna arrays in underwater acoustic channels

    NASA Astrophysics Data System (ADS)

    Fedosov, V. P.; Lomakina, A. V.; Legin, A. A.; Voronin, V. V.

    2016-05-01

    In this paper the system of wireless transmission of data based on the use an adaptive algorithm for processing spatial-time signals using antenna arrays is presented. In the transmission of data in a multipath propagation of signals have been used such technologies as a MIMO (Multiple input-Multiple output) and OFDM (Orthogonal frequency division multiplexing) to solve the problem of increasing the maximum speed of data transfer and the low probability of errors. The adaptation process is based on the formation of the directional pattern equivalent to the amplitude antenna array in the signal arrival direction with the highest capacity on one of propagation paths in the channel. The simulation results showed that the use of an adaptive algorithm on the reception side can significantly reduce the probability of bit errors, thus to increase throughput in an underwater acoustic data channel.

  18. Acoustic phonon transmission spectra in piezoelectric AlN/GaN Fibonacci phononic crystals

    NASA Astrophysics Data System (ADS)

    Sesion, P. D., Jr.; Albuquerque, E. L.; Chesman, C.; Freire, V. N.

    2007-08-01

    We study the acoustic-phonon transmission spectra in periodic and quasiperiodic (Fibonacci type) superlattices made up from the III-V nitride materials AlN and GaN. The phonon dynamics is described by a coupled elastic and electromagnetic equations within the static field approximation model, stressing the importance of the piezoelectric polarization field in a strained condition. We use a transfer-matrix treatment to simplify the algebra, which would be otherwise quite complicated, allowing a neat analytical expressions for the phonon transmission coefficients. Numerical results, for the normal incidence case, show a strike self-similar pattern for both hexagonal (class 6 mm) and cubic symmetries crystalizations of the nitrides.

  19. Tunability of acoustic phonon transmission and thermal conductance in three dimensional quasi-periodically stubbed waveguides

    NASA Astrophysics Data System (ADS)

    Xie, Zhong-Xiang; Liu, Jing-Zhong; Yu, Xia; Wang, Hai-Bin; Deng, Yuan-Xiang; Li, Ke-Min; Zhang, Yong

    2015-03-01

    We investigate acoustic phonon transmission and thermal conductance in three dimensional (3D) quasi-periodically stubbed waveguides according to the Fibonacci sequence. Results show that the transmission coefficient exhibits the periodic oscillation upon varying the length of stub/waveguide at low frequency, and the period of such oscillation is tunably decreased with increasing the Fibonacci number N. Interestingly, there also exist some anti-resonant dips that gradually develop into wide stop-frequency gaps with increasing N. As the temperature goes up, a transition of the thermal conductance from the decrease to the increase occurs in these systems. When N is increased, the thermal conductance is approximately decreased with a linear trend. Moreover, the decreasing degree sensitively depends on the variation of temperature. A brief analysis of these results is given.

  20. Multiplex transmission system for gate drive signals of inverter circuit using surface acoustic wave filters

    NASA Astrophysics Data System (ADS)

    Suzuki, Akifumi; Ueda, Kensuke; Goka, Shigeyoshi; Wada, Keiji; Kakio, Shoji

    2016-07-01

    We propose and fabricate a multiplexed transmission system based on frequency-division multiple access (FDMA) with surface acoustic wave (SAW) filters. SAW filters are suitable for use in wide-gap switching devices and multilevel inverters because of their capability to operate at high temperatures, good electrical isolation, low cost, and high reliability. Our proposed system reduces the number of electrical signal wires needed to control each switching device and eliminates the need for isolation circuits, simplifying the transmission system and gate drive circuits. We successfully controlled two switching devices with a single coaxial line and confirmed the operation of a single-phase half-bridge inverter at a supply voltage of 100 V, and the total delay time to control the switching devices was less than 2.5 µs. Our experimental results validated our proposed system.

  1. The ecological and evolutionary consequences of noise-induced acoustic habitat loss

    NASA Astrophysics Data System (ADS)

    Tennessen, Jennifer Beissinger

    Anthropogenic threats are facilitating rapid environmental change and exerting novel pressures on the integrity of ecological patterns and processes. Currently, habitat loss is the leading factor contributing to global biodiversity loss. Noise created by human activities is nearly ubiquitous in terrestrial and marine systems, and causes acoustic habitat loss by interfering with species' abilities to freely send and receive critical acoustic biological information. My dissertation investigates how novel sounds from human activities affect ecological and evolutionary processes in space and time in marine and terrestrial systems, and how species may cope with this emerging novel pressure. Using species from both marine and terrestrial systems, I present results from a theoretical investigation, and four acoustic playback experiments combining laboratory studies and field trials, that reveal a range of eco-evolutionary consequences of noiseinduced acoustic habitat loss. First, I use sound propagation modeling to assess how marine shipping noise reduces communication space between mother-calf pairs of North Atlantic right whales (Eubalaena glacialis ), an important unit of an endangered species. I show that shipping noise poses significant challenges for mother-calf pairs, but that vocal compensation strategies can substantially improve communication space. Next, in a series of acoustic playback experiments I show that road traffic noise impairs breeding migration behavior and physiology of wood frogs (Lithobates sylvaticus ). This work reveals the first evidence that traffic noise elicits a physiological stress response and suppresses production of antimicrobial peptides (a component of the innate immune response) in anurans. Further, wood frogs from populations with a history of inhabiting noisy sites mounted reduced physiological stress responses to continuous traffic noise exposure. This research using wood frogs suggests that chronic traffic noise exposure has

  2. A collimated focused ultrasound beam of high acoustic transmission and minimum diffraction achieved by using a lens with subwavelength structures

    SciTech Connect

    Lin, Zhou; Tu, Juan; Cheng, Jianchun; Guo, Xiasheng E-mail: dzhang@nju.edu.cn; Wu, Junru; Huang, Pingtong; Zhang, Dong E-mail: dzhang@nju.edu.cn

    2015-09-14

    An acoustic focusing lens incorporated with periodically aligned subwavelength grooves corrugated on its spherical surface has been developed. It is demonstrated theoretically and experimentally that acoustic focusing achieved by using the lens can suppress the relative side-lobe amplitudes, enhance the focal gain, and minimize the shifting of the focus. Use of the lens coupled with a planar ultrasound transducer can generate an ultrasound beam with enhanced acoustic transmission and collimation effect, which offers the capability of improving the safety, efficiency, and accuracy of targeted surgery implemented by high intensity focused ultrasound.

  3. Environmental Effects on Low Frequency Transmission Loss in the Gulf of Mexico

    DTIC Science & Technology

    1980-09-01

    1979. Ini- tial comparisons of observed transmission loss data, with pre- exercise model predictions made using the ASTRAL model with historical...description of the seafloor. Good agreement was attained for detailed structure comparisons. Estimates made using thE model ASTRAL , together with a bottom...67 Hz (U) Figure 12 (C). Comparison of ASTRAL transmission loss model predictions 13 and CHURCH STROKE III measurements (U) Figure 13 (C). Comparison

  4. Method and apparatus for low-loss signal transmission

    NASA Technical Reports Server (NTRS)

    Siegel, Peter (Inventor); Yeh, Cavour (Inventor); Shimabukuro, Fred (Inventor); Fraser, Scott (Inventor)

    2008-01-01

    The present invention relates to the field of radio-frequency (RF) waveguides. More specifically, the present invention pertains to a method and apparatus that provides ultra-low-loss RF waveguide structures targeted between approximately 300 GHz and approximately 30 THz. The RF waveguide includes a hollow core and a flexible honeycomb, periodic-bandgap structure surrounding the hollow core. The flexible honeycomb, periodic-bandgap structure is formed of a plurality of tubes formed of a dielectric material such as of low-loss quartz, polyethylene, or high-resistivity silicon. Using the RF waveguide, a user may attach a terahertz signal source to the waveguide and pass signals through the waveguide, while a terahertz signal receiver receives the signals.

  5. Loss resilience for two-qubit state transmission using distributed phase sensitive amplification

    DOE PAGES

    Dailey, James; Agarwal, Anjali; Toliver, Paul; ...

    2015-11-12

    We transmit phase-encoded non-orthogonal quantum states through a 5-km long fibre-based distributed optical phase-sensitive amplifier (OPSA) using telecom-wavelength photonic qubit pairs. The gain is set to equal the transmission loss to probabilistically preserve input states during transmission. While neither state is optimally aligned to the OPSA, each input state is equally amplified with no measurable degradation in state quality. These results promise a new approach to reduce the effects of loss by encoding quantum information in a two-qubit Hilbert space which is designed to benefit from transmission through an OPSA.

  6. Loss resilience for two-qubit state transmission using distributed phase sensitive amplification

    PubMed Central

    Dailey, James M.; Agarwal, Anjali; Toliver, Paul; Peters, Nicholas A.

    2015-01-01

    We transmit phase-encoded non-orthogonal quantum states through a 5-km long fibre-based distributed optical phase-sensitive amplifier (OPSA) using telecom-wavelength photonic qubit pairs. The gain is set to equal the transmission loss to probabilistically preserve input states during transmission. While neither state is optimally aligned to the OPSA, each input state is equally amplified with no measurable degradation in state quality. These results promise a new approach to reduce the effects of loss by encoding quantum information in a two-qubit Hilbert space which is designed to benefit from transmission through an OPSA. PMID:26559465

  7. Jump chaotic behaviour of ultra low loss bulk acoustic wave cavities

    NASA Astrophysics Data System (ADS)

    Goryachev, Maxim; Farr, Warrick G.; Galliou, Serge; Tobar, Michael E.

    2014-08-01

    We demonstrate a previously unobserved nonlinear phenomenon in an ultra-low loss quartz bulk acoustic wave cavity ( Q > 3 > 10 9), which only occurs below 20 mK in temperature and under relatively weak pumping. The phenomenon reveals the emergence of several stable equilibria (at least two foci and two nodes) and jumps between these quasi states at random times. The degree of this randomness as well as separations between levels can be controlled by the frequency of the incident carrier signal. It is demonstrated that the nature of the effect lies beyond the standard Duffing model.

  8. Jump chaotic behaviour of ultra low loss bulk acoustic wave cavities

    SciTech Connect

    Goryachev, Maxim Farr, Warrick G.; Tobar, Michael E.; Galliou, Serge

    2014-08-11

    We demonstrate a previously unobserved nonlinear phenomenon in an ultra-low loss quartz bulk acoustic wave cavity (Q>3>10{sup 9}), which only occurs below 20 mK in temperature and under relatively weak pumping. The phenomenon reveals the emergence of several stable equilibria (at least two foci and two nodes) and jumps between these quasi states at random times. The degree of this randomness as well as separations between levels can be controlled by the frequency of the incident carrier signal. It is demonstrated that the nature of the effect lies beyond the standard Duffing model.

  9. Experimental study of structure-borne sound transmission loss of mechanical joints.

    PubMed

    Feng, L; Liu, M; Nilsson, A

    2001-09-01

    A mechanical joint is one of the most effective ways to reduce the transmission of structure-borne sound. In order to increase the transmission loss, heavily damped joints are often used, which, in many cases, will reduce the structure integrity and hence can only be used in limited cases. In this study attention is focused on a type of resonant joint, i.e., a joint which will increase the transmission loss but will not reduce the structure integrity. The study is based on experiments in a one-dimensional structure. It is found that by adjusting the overlap of the joint, the transmission loss of 30 dB can be obtained at a certain frequency range without adding any dissipative materials. The mechanism of this high transmission loss is the cantilever-type resonance. The resonant frequency can be predicted precisely. The influence of extra dissipative material is investigated. The performance of the same joint in a finite structure is also examined by using the concept of vibrational insertion loss. When there is a certain damping in a finite system, a rather high insertion loss can still be achieved by using the above-mentioned joint, but the resonant frequency is shifted to higher end. It seems that the effective length of the cantilever is shortened by the finiteness.

  10. Binaural Simulation Experiments in the NASA Langley Structural Acoustics Loads and Transmission Facility

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.; Silcox, Richard (Technical Monitor)

    2001-01-01

    A location and positioning system was developed and implemented in the anechoic chamber of the Structural Acoustics Loads and Transmission (SALT) facility to accurately determine the coordinates of points in three-dimensional space. Transfer functions were measured between a shaker source at two different panel locations and the vibrational response distributed over the panel surface using a scanning laser vibrometer. The binaural simulation test matrix included test runs for several locations of the measuring microphones, various attitudes of the mannequin, two locations of the shaker excitation and three different shaker inputs including pulse, broadband random, and pseudo-random. Transfer functions, auto spectra, and coherence functions were acquired for the pseudo-random excitation. Time histories were acquired for the pulse and broadband random input to the shaker. The tests were repeated with a reflective surface installed. Binary data files were converted to universal format and archived on compact disk.

  11. The Search for Acoustically-Driven Mass-Loss in Evolved Stars

    NASA Astrophysics Data System (ADS)

    Stencel, R. E.; Brown, A.; Carpenter, K. G.; Cuntz, M.; Judge, P.

    1992-12-01

    Recent ab-initio calculations of stochastic stellar wind models by Cuntz (1992 in Cool Stars VII, ASP Conf. Ser. 26, p.383) have proven remarkably robust in predicting observed chromospheric flow patterns including possible variabilities with time in selected cool, evolved stars. The calculations solve the equations of hydrodynamics using the method of characteristics and assume: (i) saw-tooth shock wave profiles, and (ii) wave periods were changed stochastically while keeping the wave amplitudes constant (see Cuntz 1990 Ap.J. 349, p.141). Among the results of fitting chromospheric flow velocities is the implication that the permitted range of acoustic wave periods for a given star is constrained. We made use of the IUE satellite during August and September 1992 to repeatedly observe two stars, the yellow giant Aldebaran (K5 III) and the red supergiant, Betelgeuse (M2 Iab), in order to sample variations in their atmospheres on timescales of ~ 10(4) to ~ 10(6) seconds, which bracket the predicted mean acoustic wave periods for these objects. In particular, we obtained deep exposures in order to measure density-sensitive line ratios within the C II] intercombination features near 2325A (cf. Lennon et al. 1985 Ap.J. 294, p.200) to test the hypothesis that density fluctuations could be measured as a consequence of these acoustic waves. The results of these observations will be presented and discussed in terms of the number and amplitude of acoustic waves contributing to chromospheric heating and mass loss from these stars, as well as the wave origins in the evolving oscillatory structure of these stellar interiors. We are pleased to acknowledge IUE--NASA grant NAG5-2103 for partial support of this effort.

  12. Measurement of Insertion Loss of an Acoustic Treatment in the Presence of Additional Uncorrelated Sound Sources

    NASA Technical Reports Server (NTRS)

    Klos, Jacob; Palumbo, Daniel L.

    2003-01-01

    A method to intended for measurement of the insertion loss of an acoustic treatment applied to an aircraft fuselage in-situ is documented in this paper. Using this method, the performance of a treatment applied to a limited portion of an aircraft fuselage can be assessed even though the untreated fuselage also radiates into the cabin, corrupting the intensity measurement. This corrupting noise in the intensity measurement incoherent with the panel vibration of interest is removed by correlating the intensity to reference transducers such as accelerometers. Insertion loss of the acoustic treatments is estimated from the ratio of correlated intensity measurements with and without a treatment applied. In the case of turbulent boundary layer excitation of the fuselage, this technique can be used to assess the performance of noise control methods without requiring treatment of the entire fuselage. Several experimental studies and numerical simulations have been conducted, and results from three case studies are documented in this paper. Conclusions are drawn about the use of this method to study aircraft sidewall treatments.

  13. The Effectiveness of the Aquaflex Gel Pad in the Transmission of Acoustic Energy

    PubMed Central

    Klucinec, Brian

    1996-01-01

    Objective: The purpose of this study was to assess the effectiveness of the Aquaflex Gel Pad in the transmission of acoustic energy. Design and Setting: This was a comparative study that utilized descriptive statistics for result interpretation. The independent variables included ultrasound intensity, interposed materials, and trials. The dependent variable was peak-to-peak voltage output recorded via an oscilloscope. The study was conducted in a ventilated research laboratory. Measurements: Three trials were conducted with six combinations of material interposed between a conducting (1 MHz) and a receiving sound head. The interposed materials were as follows: 1) ultrasound gel, 2) gel plus a gel pad, 3) gel plus a gel pad and pig tissue sample (0.90 cm of subcutaneous fat), 4) gel plus a gel pad and a pig tissue sample (1.8 cm of subcutaneous fat), 5) gel plus thin pig tissue sample, and 6) gel plus thick pig tissue sample. Each interposed material combination was tested at the intensities (W/cm2) as follows: 0.10, 0.25, 0.50, 1.00, 1.50, and 2.50. Results: The gel pad proved to be an efficient couplant in the delivery of high-frequency acoustic energy. Using ultrasound gel as the base line (100% transmissivity) it was concluded that the gel pad transmitted more acoustic energy at every intensity except at 0.1 W/cm2. The gel pad used with the two thicknesses of subcutaneous fat gave comparable results. Gel used with the two thicknesses of subcutaneous fat yielded results that warrant further investigation. Conclusions: I believe gel pads are a practical choice for clinical applications of ultrasound over uneven surfaces. The reusable gel pads offer the clinician a convenient and reliable method for delivering ultrasound energy to the patient. I believe it is preferable to use the gel pad with ultrasound gel directly applied to the patient and at the sound head-gel pad interface as opposed to using the traditional water bath immersion method. ImagesFig 1. PMID

  14. The use of streambed temperatures to estimate transmission losses on an experimental channel.

    SciTech Connect

    Ramon C. Naranjo; Michael H. Young; Richard Niswonger; Julianne J. Miller; Richard H. French

    2001-10-18

    Quantifying channel transmission losses in arid environments is important for a variety of reasons, from engineering design of flood control structures to evaluating recharge. To quantify the losses in an alluvial channel, an experiment was performed on a 2-km reach of an alluvial fan located on the Nevada Test Site. The channel was subjected to three separate flow events. Transmission losses were estimated using standard discharge monitoring and subsurface temperature modeling approach. Four stations were equipped to continuously monitor stage, temperature, and water content. Streambed temperatures measured at 0, 30, 50 and 100 cm depths were used to calibrate VS2DH, a two-dimensional, variably saturated flow model. Average losses based on the difference in flow between each station indicate that 21 percent, 27 percent, and 53 percent of the flow was reduced downgradient of the source. Results from the temperature monitoring identified locations with large thermal gradients, suggesting a conduction-dominated heat transfer on streambed sediments where caliche-cemented surfaces were present. Transmission losses at the lowermost segment corresponded to the smallest thermal gradient, suggesting an advection-dominated heat transfer. Losses predicted by VS2DH are within an order of magnitude of the estimated losses based on discharge measurements. The differences in losses are a result of the spatial extent to which the modeling results are applied and lateral subsurface flow.

  15. Acoustic Reflection and Transmission of 2-Dimensional Rotors and Stators, Including Mode and Frequency Scattering Effects

    NASA Technical Reports Server (NTRS)

    Hanson, Donald B.

    1999-01-01

    A reduced order modeling scheme has been developed for the unsteady acoustic and vortical coupling between blade rows of a turbomachine. The essential behavior of the system is governed by modal scattering coefficients (i.e., reflection and transmission coefficients) of the rotor, stator, inlet and nozzle, which are calculated as if they were connected to non-reflecting ducts. The objective of this report is to identify fundamental behavior of these scattering coefficients for a better understanding of the role of blade row reflection and transmission in noise generation. A 2D flat plate unsteady cascade model is used for the analysis with the expectation that the general behavior presented herein will carry over to models that include more realistic flow and geometry. It is shown that stators scatter input waves into many modes at the same frequency whereas rotors scatter on frequency, or harmonic order. Important cases are shown here the rotor reflection coefficient is greater than unity; a mode at blade passing frequency (BPF) traveling from the stator with unit sound power is reflected by the rotor with more than unit power at 2xBPF and 3xBPE Analysis is presented to explain this unexpected phenomenon. Scattering curves are presented in a format chosen for design use and for physical interpretation. To aid in interpretation of the curves, formulas are derived for special condition where waveforms are parallel to perpendicular to the rotor.

  16. Plasmonic analog of microstrip transmission line and effect of thermal annealing on its propagation loss.

    PubMed

    Chen, Yiting; Wang, Jing; Chen, Xi; Yan, Min; Qiu, Min

    2013-01-28

    We fabricated a plasmonic analog of the microwave microstrip transmission line and measured its propagation loss before and after thermal annealing. It is found that its propagation loss at 980 nm wavelength can be reduced by more than 50%, from 0.45 to 0.20 dB/μm, after thermal annealing at 300 °C. The reduction in loss can be attributed to the improved gold surface condition and probably also to the change in the metal's inner structure. Less evident loss reduction is noticed at 1550 nm, which is owing to extremely small portion of the modal electric field located in the metal regions at this wavelength.

  17. The Acoustic Change Complex in Young Children with Hearing Loss: A Preliminary Study.

    PubMed

    Martinez, Amy S; Eisenberg, Laurie S; Boothroyd, Arthur

    2013-01-01

    The acoustic change complex (ACC) is a cortical auditory evoked potential elicited in response to a change in an ongoing sound. The ACC may have promise for assessing speech perception in infants and toddlers. In this preliminary study, the ACC was elicited in adults and young children in response to changes in speech stimuli representing vowel height /u/-/a/ and vowel place /u/-/i/ contrasts. The participants were adults with normal hearing (n = 3), children with normal hearing (n = 5), and children with mild to moderately severe bilateral sensorineural hearing loss (n = 5). The children with hearing loss were hearing aid users. The ages ranged from 2 years 3 months to 6 years 3months for the children and 44 to 55 years for the adults. Robust P1-N1-P2 responses were present for the adults and P1-N2 responses were present for all but the youngest child with hearing loss. The ACC response for the vowel place contrast was less robust than that for the vowel height contrast in one child with substantial hearing loss. The findings from this preliminary study support the conclusion that the ACC can be used successfully to assess auditory resolution in most young children.

  18. Investigation of acoustic changes resulting from contrast enhancement in through-transmission ultrasonic imaging.

    PubMed

    Rothstein, Tamara; Gaitini, Diana; Gallimidi, Zahava; Azhari, Haim

    2010-09-01

    Through-transmitted ultrasonic waves can be used for computed projection imaging of the breast. The goal of this research was to analyze the acoustic properties changes associated with the propagation of ultrasonic waves through media before and after ultrasound contrast agent (UCA) injection and to study the feasibility of a new imaging method combining projection imaging and UCA. Two transmission techniques were examined: Gaussian pulses and pulse inversion. In the latter, three different double inverted pulses were studied: double Gaussian, double square and double sine. A computerized automatic ultrasonic scanning system was used for imaging. To simulate blood vessels, a phantom, consisting of a latex tube through which saline was circulated, was assembled. The phantom was placed within the scanner and sets of acoustic projection images were acquired. Then, a suspension of the UCA Definitely was added to the saline and a new set of images was obtained. The pre and postcontrast images were quantitatively compared in terms of amplitude and time-of-flight (TOF). In addition, nonlinearity was evaluated by comparing the relative alteration of the positive and negative parts of the signal. Statistically significant (p < 0.001) changes in the projection images resulting from the UCA injection were observed in wave amplitude (22% +/- 13%), TOF (7.9 ns +/- 6.3 ns) and nonlinear properties (35% +/- 32% and 56% +/- 17% for Gausian pulses and pulse inversion, respectively). One in vivo study of a female breast is also presented and its preliminary outcomes discussed. Together, these results indicate the technical feasibility of the suggested method and its potential to detect breast tumors.

  19. 1KW Power Transmission Using Wireless Acoustic-Electric Feed-Through (WAEF)

    NASA Technical Reports Server (NTRS)

    Sherrit, S.; Bao, X.; Badescu, M.; Aldrich, J.; Bar-Cohen, Y.; Biederman, W.

    2008-01-01

    A variety of space applications require the delivery of power into sealed structures. Since the structural integrity can be degraded by holes for cabling we present an alternative method of delivering power and information using stress waves to the internal space of a sealed structure. One particular application of this technology is in sample return missions where it is critical to preserve the sample integrity and to prevent earth contamination. Therefore, the container has to be hermetically sealed and the integrity of the seal must be monitored in order to insure to a high degree of reliability the integrity of the sample return vessel. In this study we investigated the use of piezoelectric acoustic-electric power feed-through devices to transfer electric power wirelessly through a solid wall by using elastic or acoustic waves. The technology is applicable to a range of space and terrestrial applications where power is required by electronic equipment inside sealed containers, vacuum or pressure vessels, etc., where holes in the wall are prohibitive or may result in significant structural performance degradation or unnecessarily complex designs. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was investigated. Pre-stressed longitudinal piezoelectric feed-through devices were analyzed by finite element models and an equivalent circuit model was developed to predict the power transfer characteristics to different electric loads. Based on the results of the analysis a prototype device was designed, fabricated and a demonstration of the transmission of electric power up to 1.068-kW was successfully conducted. Efficiencies in the 80-90% range were also demonstrated and methods to increase the efficiency further are currently being considered.

  20. Statistical Polarization Mode Dispersion/Polarization Dependent Loss Emulator for Polarization Division Multiplexing Transmission Testing

    NASA Astrophysics Data System (ADS)

    Perlicki, Krzysztof

    2010-03-01

    A low-cost statistical polarization mode dispersion/polarization dependent loss emulator is presented in this article. The emulator was constructed by concatenating 15 highly birefringence optical-fiber segments and randomly varying the mode coupling between them by rotating the polarization state. The impact of polarization effects on polarization division multiplexing transmission quality was measured. The designed polarization mode dispersion/polarization dependent loss emulator was applied to mimic the polarization effects of real optical-fiber links.

  1. Weighting of Acoustic Cues to a Manner Distinction by Children With and Without Hearing Loss

    PubMed Central

    Lowenstein, Joanna H.

    2015-01-01

    Purpose Children must develop optimal perceptual weighting strategies for processing speech in their first language. Hearing loss can interfere with that development, especially if cochlear implants are required. The three goals of this study were to measure, for children with and without hearing loss: (a) cue weighting for a manner distinction, (b) sensitivity to those cues, and (c) real-world communication functions. Method One hundred and seven children (43 with normal hearing [NH], 17 with hearing aids [HAs], and 47 with cochlear implants [CIs]) performed several tasks: labeling of stimuli from /bɑ/-to-/wɑ/ continua varying in formant and amplitude rise time (FRT and ART), discrimination of ART, word recognition, and phonemic awareness. Results Children with hearing loss were less attentive overall to acoustic structure than children with NH. Children with CIs, but not those with HAs, weighted FRT less and ART more than children with NH. Sensitivity could not explain cue weighting. FRT cue weighting explained significant amounts of variability in word recognition and phonemic awareness; ART cue weighting did not. Conclusion Signal degradation inhibits access to spectral structure for children with CIs, but cannot explain their delayed development of optimal weighting strategies. Auditory training could strengthen the weighting of spectral cues for children with CIs, thus aiding spoken language acquisition. PMID:25813201

  2. Performing broadband optical transmission links by appropriate spectral combination of broadband SOA gain, Raman amplification and transmission fiber losses

    NASA Astrophysics Data System (ADS)

    Motaweh, T.; Sharaiha, A.; Ghisa, L.; Morel, P.; Guégan, M.; Brenot, R.; Verdier, A.

    2017-02-01

    We present the principle of a broadband optical transmission link based on the appropriate combination of the spectral profiles of broadband SOA gain, Raman amplification and transmission fiber losses. We show that, thanks to this principle, a bandwidth as wide as 89 nm (defined at -1 dB) over 75.5 km can be obtained. This bandwidth remains better than 80 nm over a wide range of optical input powers and broadband SOA bias currents, by optimizing the Raman pump. We also show theoretically that the bandwidth of our link is nearly constant for a fiber length from 25 to 100 km optimizing the SOA current. Our broadband transmission link, extended by 24.5 km of fiber, is then validated by achieving the transmission of five CWDM channels modulated at 10 Gbit/s. All five channels were transmitted over 100 km with a minimum received power sensibility of about -15.5 dBm for a reference BER of 10-3.

  3. Propagation of narrow-band-high-frequency clicks: measured and modeled transmission loss of porpoise-like clicks in porpoise habitats.

    PubMed

    DeRuiter, Stacy L; Hansen, Michael; Koopman, Heather N; Westgate, Andrew J; Tyack, Peter L; Madsen, Peter T

    2010-01-01

    Estimating the range at which harbor porpoises can detect prey items and environmental objects is integral to understanding their biosonar. Understanding the ranges at which they can use echolocation to detect and avoid obstacles is particularly important for strategies to reduce bycatch. Transmission loss (TL) during acoustic propagation is an important determinant of those detection ranges, and it also influences animal detection functions used in passive acoustic monitoring. However, common assumptions regarding TL have rarely been tested. Here, TL of synthetic porpoise clicks was measured in porpoise habitats in Canada and Denmark, and field data were compared with spherical spreading law and ray-trace (Bellhop) model predictions. Both models matched mean observations quite well in most cases, indicating that a spherical spreading law can usually provide an accurate first-order estimate of TL for porpoise sounds in porpoise habitat. However, TL varied significantly (+/-10 dB) between sites and over time in response to variability in seafloor characteristics, sound-speed profiles, and other short-timescale environmental fluctuations. Such variability should be taken into account in estimates of the ranges at which porpoises can communicate acoustically, detect echolocation targets, and be detected via passive acoustic monitoring.

  4. Experimental study on guide friction contribution in global power loss of a tooth chain transmission

    NASA Astrophysics Data System (ADS)

    Velicu, R.; Papuc, R.; Gavrila, C. C.; Popa, S.

    2017-02-01

    The subject of the paper is the friction between a tooth chain and the guide. An experimental study is developed with the aim of determining the contribution of chain-guide friction on the global friction of a basic tooth chain transmission. The measurements have been made on a chain friction rig, testing a basic tooth chain transmission with transmission ratio equal to 1, with a controlled tensioning device. The following parameters can be adjusted and measured: rotational speed, tensioning force in the chain, position of the guide, temperature and pressure of the oil used for lubrication. Friction torque at the input shaft is a sum of friction torques coming from bearings, chain and guide. The paper presents the contribution of the guide in the power loss by friction, as percent of the power loss from friction in chain and guide together. Influences of speed, tensioning force and oil temperature are presented.

  5. Monitoring of global acoustic transmissions: Signal processing and preliminary data analysis

    NASA Astrophysics Data System (ADS)

    Frogner, Gary R.

    1991-09-01

    A great deal of controversy exists concerning the possible global warming trend which may occur as a result of a documented increase in atmospheric greenhouse gasses. The 1991 Heard Island Feasibility Experiment tested the feasibility of using transmissions of acoustic energy through major ocean basins of the world to monitor spatially averaged global temperature trends. This thesis documents the Naval Postgraduate School's reception of the phase encoded signal transmitted from the Southern Indian Ocean, development of real-time signal processing software, and preliminary data analysis. Data, received from a 32-channel vertical array suspended in the deep sound channel off the coast of Monterey, CA, was processed using real-time capable software. Data processing to reduce noise, determine SNR, and remove the m-sequence coding was found to be quite sensitive to Doppler frequency shifts. Although the SNR of the raw data was only about -27.5 dB for individual hydrophones, the transmitted signal was detected in both the frequency and time domains. However, the maximum processed signal peak in the time domain had an SNR of only +9 dB which is insufficient for use in a long term global temperature monitoring project. The hydrophone provides inadequate arrival time resolution.

  6. 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.

  7. Self-Characterization of Commercial Ultrasound Probes in Transmission Acoustic Inverse Scattering: Transducer Model and Volume Integral Formulation

    PubMed Central

    Haynes, Mark; Verweij, Sacha A. M.; Moghaddam, Mahta; Carson, Paul L.

    2014-01-01

    A self-contained source characterization method for commercial ultrasound probes in transmission acoustic inverse scattering is derived and experimentally tested. The method is based on modified scattered field volume integral equations that are linked to the source-scattering transducer model. The source-scattering parameters are estimated via pair-wise transducer measurements and the nonlinear inversion of an acoustic propagation model that is derived. This combination creates a formal link between the transducer characterization and the inverse scattering algorithm. The method is tested with two commercial ultrasound probes in a transmission geometry including provisions for estimating the probe locations and aligning a robotic rotator. The transducer characterization results show that the nonlinear inversion fit the measured data well. The transducer calibration and inverse scattering algorithm are tested on simple targets. Initial images show that the recovered contrasts are physically consistent with expected values. PMID:24569251

  8. Reduction of radiation loss at small-radius bend using spoof surface plasmon polariton transmission line

    NASA Astrophysics Data System (ADS)

    Tang, Wen Xuan; Zhang, Hao Chi; Liu, Jun Feng; Xu, Jie; Cui, Tie Jun

    2017-01-01

    Spoof surface plasmon polariton (SPP) has been realized at low frequencies through corrugated metallic structures. As two-dimensional application, the ultrathin SPP transmission lines (TLs) have been proposed with great potentials for microwave compact circuits due to the strong field confinement and enhancement, as well as controllable dispersive properties. In this paper, we examine the radiation loss at small-radius bend, which may cause severe crosstalk in highly-integrated circuits or systems, for the SPP TLs. We theoretically analyze that the SPP TL has essential merit of low radiation loss, and show better performance of SPP TL than the conventional microstrip line through numerical simulations and experiments. Both simulated and measured results demonstrate that the new type of transmission line can efficiently suppress the radiation loss at small-radius bend, and hence reduce the crosstalk in circuits and systems.

  9. Reduction of radiation loss at small-radius bend using spoof surface plasmon polariton transmission line

    PubMed Central

    Tang, Wen Xuan; Zhang, Hao Chi; Liu, Jun Feng; Xu, Jie; Cui, Tie Jun

    2017-01-01

    Spoof surface plasmon polariton (SPP) has been realized at low frequencies through corrugated metallic structures. As two-dimensional application, the ultrathin SPP transmission lines (TLs) have been proposed with great potentials for microwave compact circuits due to the strong field confinement and enhancement, as well as controllable dispersive properties. In this paper, we examine the radiation loss at small-radius bend, which may cause severe crosstalk in highly-integrated circuits or systems, for the SPP TLs. We theoretically analyze that the SPP TL has essential merit of low radiation loss, and show better performance of SPP TL than the conventional microstrip line through numerical simulations and experiments. Both simulated and measured results demonstrate that the new type of transmission line can efficiently suppress the radiation loss at small-radius bend, and hence reduce the crosstalk in circuits and systems. PMID:28112238

  10. Reduction of radiation loss at small-radius bend using spoof surface plasmon polariton transmission line.

    PubMed

    Tang, Wen Xuan; Zhang, Hao Chi; Liu, Jun Feng; Xu, Jie; Cui, Tie Jun

    2017-01-23

    Spoof surface plasmon polariton (SPP) has been realized at low frequencies through corrugated metallic structures. As two-dimensional application, the ultrathin SPP transmission lines (TLs) have been proposed with great potentials for microwave compact circuits due to the strong field confinement and enhancement, as well as controllable dispersive properties. In this paper, we examine the radiation loss at small-radius bend, which may cause severe crosstalk in highly-integrated circuits or systems, for the SPP TLs. We theoretically analyze that the SPP TL has essential merit of low radiation loss, and show better performance of SPP TL than the conventional microstrip line through numerical simulations and experiments. Both simulated and measured results demonstrate that the new type of transmission line can efficiently suppress the radiation loss at small-radius bend, and hence reduce the crosstalk in circuits and systems.

  11. Measured and calculated transmission losses of sound waves through a helium layer

    NASA Technical Reports Server (NTRS)

    Norum, T. D.

    1973-01-01

    An experiment was performed to measure the transmission losses of sound waves traversing an impedance layer. The sound emanated from a point source and the impedance layer was created by a low-speed helium jet. The transmission losses measured were of the order of 12 db for frequencies of the source between 4 and 12 kHz. These losses are greater than those predicted from analysis when the observer angle is less than about 35 deg, but less than those predicted for larger observer angles. The experimental results indicate that appreciable noise reductions can be realized for an observer shielded by an impedance layer, irrespective of his position relative to the source of sound.

  12. A single measurement approach for the determination of the normal incidence transmission loss.

    PubMed

    Bonfiglio, Paolo; Pompoli, Francesco

    2008-09-01

    Several techniques for the determination of the normal incidence complex transmission coefficient and transmission loss have been proposed in literature. It has been shown that two different measurements have to be carried out for a correct evaluation of the above-mentioned quantities. However, single measurement approaches can be used at the condition that energy contributions are correctly included in the implemented formulation. This paper presents a single measurement approach based on a transfer matrix formulation, taking into account reflection contribution from the end termination and phase shift introduced by the material. The transmission performances of different kinds of layered porous materials are investigated by means of a four microphone technique in a plane wave tube. By using the decomposition technique, incident, reflected, and transmitted contributions are separated and transmission coefficient is easily calculated. Results are discussed and compared with similar techniques and with the two-load method.

  13. Mathematical Modeling of Space-time Variations in Acoustic Transmission and Scattering from Schools of Swim Bladder Fish (FY14 Annual Report)

    DTIC Science & Technology

    2014-09-30

    Mathematical modeling of space-time variations in acoustic transmission and scattering from schools of swim bladder fish (FY14 Annual Report...domain theory of acoustic scattering from, and propagation through, schools of swim bladder fish at and near the swim bladder resonance frequency...coupled differential equations. It incorporates a verified swim bladder scattering kernel for the individual fish, includes multiple scattering

  14. A unique method to study acoustic transmission through ducts using signal synthesis and averaging of acoustic pulses

    NASA Technical Reports Server (NTRS)

    Salikuddin, M.; Ramakrishnan, R.; Ahuja, K. K.; Brown, W. H.

    1981-01-01

    An acoustic impulse technique using a loudspeaker driver is developed to measure the acoustic properties of a duct/nozzle system. A signal synthesis method is used to generate a desired single pulse with a flat spectrum. The convolution of the desired signal and the inverse Fourier transform of the reciprocal of the driver's response are then fed to the driver. A signal averaging process eliminates the jet mixing noise from the mixture of jet noise and the internal noise, thereby allowing very low intensity signals to be measured accurately, even for high velocity jets. A theoretical analysis is carried out to predict the incident sound field; this is used to help determine the number and locations of the induct measurement points to account for the contributions due to higher order modes present in the incident tube method. The impulse technique is validated by comparing experimentally determined acoustic characteristics of a duct-nozzle system with similar results obtained by the impedance tube method. Absolute agreement in the comparisons was poor, but the overall shapes of the time histories and spectral distributions were much alike.

  15. Parabolic equation modeling of high frequency acoustic transmission with an evolving sea surface.

    PubMed

    Senne, J; Song, A; Badiey, M; Smith, K B

    2012-09-01

    The present paper examines the temporal evolution of acoustic fields by modeling forward propagation subject to sea surface dynamics with time scales of less than a second to tens of seconds. A time-evolving rough sea surface model is combined with a rough surface formulation of a parabolic equation model for predicting time-varying acoustic fields. Surface waves are generated from surface wave spectra, and stepped in time using a Runge-Kutta integration technique applied to linear evolution equations. This evolving, range-dependent surface information is combined with other environmental parameters and input to the acoustic model, giving an approximation of the time-varying acoustic field. The wide-angle parabolic equation model manages the rough sea surfaces by molding them into the boundary conditions for calculations of the near-surface acoustic field. This merged acoustic model is validated using concurrently-collected acoustic and environmental information, including surface wave spectra. Data to model comparisons demonstrate that the model is able to approximate the ensemble-averaged acoustic intensity at ranges of about a kilometer for acoustic signals of around 15 kHz. Furthermore, the model is shown to capture variations due to surface fluctuations occurring over time scales of less than a second to tens of seconds.

  16. A more fundamental approach to the derivation of nonlinear acoustic wave equations with fractional loss operators (L).

    PubMed

    Prieur, Fabrice; Vilenskiy, Gregory; Holm, Sverre

    2012-10-01

    A corrected derivation of nonlinear wave propagation equations with fractional loss operators is presented. The fundamental approach is based on fractional formulations of the stress-strain and heat flux definitions but uses the energy equation and thermodynamic identities to link density and pressure instead of an erroneous fractional form of the entropy equation as done in Prieur and Holm ["Nonlinear acoustic wave equations with fractional loss operators," J. Acoust. Soc. Am. 130(3), 1125-1132 (2011)]. The loss operator of the obtained nonlinear wave equations differs from the previous derivations as well as the dispersion equation, but when approximating for low frequencies the expressions for the frequency dependent attenuation and velocity dispersion remain unchanged.

  17. Antenna Gain Loss and Pattern Degradation due to Transmission Through Dielectric Radomes

    DTIC Science & Technology

    1993-03-01

    Antenna Gain Loss and Pattern Degradation due to Transmission Through Dielectric Radomes by Lieutenant, United States Naval Reserve B.S., University...In order to analyze the system. the spherical coordinates of Figure 2.1 are used. The tot,, electric field in the direction of unit vectors (0.o) is...directivity used interchangeably. Radiation intensity is the time-averaged power per unit solid angle, and is proportional to the magnitude of the

  18. Transmission loss of multilayer panels containing a fluid using progressive wave model: Comparison with impedance progressive model and experiments

    NASA Astrophysics Data System (ADS)

    Mohammadi, N.; Mahjoob, M. J.

    2009-04-01

    The progressive wave model is applied to calculate transmission loss (TL) of triple layer panels. Theoretical values are then compared with impedance progressive model and experimental results. The triple layer panel comprises two solid layers with a middle layer of air or liquid. An impedance tube is employed to measure the TL values experimentally. The comparison of the two analytical models shows that the results of both models are relatively close. However, the progressive wave model leads to slightly larger values for a wide range of frequencies. Also, for the case of an air middle layer, a shift of the resonances to higher frequencies is observed in the results of the progressive wave model. Computational results also demonstrate that applying a liquid middle layer (replacing air) significantly improves the performance of the acoustic panel particularly at frequencies below 4000 rad/s (640 Hz). Shifting resonance frequencies to higher frequencies is another advantage of incorporating the liquid layer. Good agreement was also found between theoretical and experimental results. To cite this article: N. Mohammadi, M.J. Mahjoob, C. R. Mecanique 337 (2009).

  19. Simultaneous backward data transmission and power harvesting in an ultrasonic transcutaneous energy transfer link employing acoustically dependent electric impedance modulation.

    PubMed

    Ozeri, Shaul; Shmilovitz, Doron

    2014-09-01

    The advancement and miniaturization of body implanted medical devices pose several challenges to Ultrasonic Transcutaneous Energy Transfer (UTET), such as the need to reduce the size of the piezoelectric resonator, and the need to maximize the UTET link power-transfer efficiency. Accordingly, the same piezoelectric resonator that is used for energy harvesting at the body implant, may also be used for ultrasonic backward data transfer, for instance, through impedance modulation. This paper presents physical considerations and design guidelines of the body implanted transducer of a UTET link with impedance modulation for a backward data transfer. The acoustic matching design procedure was based on the 2×2 transfer matrix chain analysis, in addition to the Krimholtz Leedom and Matthaei KLM transmission line model. The UTET power transfer was carried out at a frequency of 765 kHz, continuous wave (CW) mode. The backward data transfer was attained by inserting a 9% load resistance variation around its matched value (550 Ohm), resulting in a 12% increase in the acoustic reflection coefficient. A backward data transmission rate of 1200 bits/s was experimentally demonstrated using amplitude shift keying, simultaneously with an acoustic power transfer of 20 mW to the implant.

  20. Studies of acoustic-electric feed-throughs for power transmission through structures

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Doty, Benjamin; Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph; Aldrich, Jack; Chang, Zensheu

    2006-01-01

    There are numerous engineering design problems where the use of wires to transfer power and communicate data thru the walls of a structure is prohibitive or significantly difficult that it may require a complex design. Using physical feedthroughs in such systems may make them susceptible to leakage of chemicals or gasses, loss of pressure or vacuum, as well as difficulties in providing adequate thermal or electrical insulation. Moreover, feeding wires thru a wall of a structure reduces the strength of the structure and makes the structure prone to cracking due to fatigue that can result from cyclic loading and stress concentrations. One area that has already been identified to require a wireless alternative to electrical feedthroughs is the container of the Mars Sample Return Mission, which will need wireless sensors to sense a pressure leak and to avoid potential contamination. The idea of using elastic or acoustic waves to transfer power was suggested recently by [Y. Hu, et al., July 2003]. This system allows for the avoidance of cabling or wiring. The technology is applicable to the transfer of power for actuation, sensing and other tasks inside any sealed container or vacuum/pressure vessel. An alternative approach to the modeling presented previously [Sherrit et a., 2005] used network analysis to solve the same problem in a clear and expandable manner. Experimental tests on three different designs of these devices were performed. The three designs used different methods of coupling the piezoelectric element to the wall. In the first test the piezoelectric material was bolted using a backing structure. In the second test the piezoelectric was clamped after the application of grease and finally the piezoelectric element was attached using a conductive epoxy. The mechanical clamp with grease produced the highest measured efficiency of 53% however this design was the least practical from a fabrication viewpoint. The power transfer efficiency of conductive epoxy

  1. Effectiveness of T-shaped acoustic resonators in low-frequency sound transmission control of a finite double-panel partition

    NASA Astrophysics Data System (ADS)

    Li, Deyu; Zhang, Xiao-Hong; Cheng, Li; Yu, Ganghua

    2010-10-01

    Double-panel partitions are widely used for sound insulation purposes. Their insulation efficiency is, however, deteriorated at low frequencies due to the structural and acoustic resonances. To tackle this problem, this paper proposes the use of long T-shaped acoustic resonators in a double-panel partition embedded along the edges. In order to facilitate the design and assess the performance of the structure, a general vibro-acoustic model, characterizing the interaction between the panels, air cavity, and integrated acoustic resonators, is developed. The effectiveness of the technique as well as the optimal locations of the acoustic resonators is examined at various frequencies where the system exhibits different coupling characteristics. The measured optimal locations are also compared with the predicted ones to verify the developed theory. Finally, the performance of the acoustic resonators in broadband sound transmission control is demonstrated.

  2. Wireless acoustic-electric feed-through for power and signal transmission

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart (Inventor); Bar-Cohen, Yoseph (Inventor); Bao, Xiaoqi (Inventor); Doty, Benjamin (Inventor); Badescu, Mircea (Inventor); Chang, Zensheu (Inventor)

    2011-01-01

    An embodiment provides electrical energy from a source on one side of a medium to a load on the other side of the medium, the embodiment including a first piezoelectric to generate acoustic energy in response to electrical energy from the source, and a second piezoelectric to convert the received acoustic energy to electrical energy used by the load. Other embodiments are described and claimed.

  3. Automatic Assessment of Acquisition and Transmission Losses in Indian Remote Sensing Satellite Data

    NASA Astrophysics Data System (ADS)

    Roy, D.; Purna Kumari, B.; Manju Sarma, M.; Aparna, N.; Gopal Krishna, B.

    2016-06-01

    The quality of Remote Sensing data is an important parameter that defines the extent of its usability in various applications. The data from Remote Sensing satellites is received as raw data frames at the ground station. This data may be corrupted with data losses due to interferences during data transmission, data acquisition and sensor anomalies. Thus it is important to assess the quality of the raw data before product generation for early anomaly detection, faster corrective actions and product rejection minimization. Manual screening of raw images is a time consuming process and not very accurate. In this paper, an automated process for identification and quantification of losses in raw data like pixel drop out, line loss and data loss due to sensor anomalies is discussed. Quality assessment of raw scenes based on these losses is also explained. This process is introduced in the data pre-processing stage and gives crucial data quality information to users at the time of browsing data for product ordering. It has also improved the product generation workflow by enabling faster and more accurate quality estimation.

  4. Laboratory tests on an aircraft fuselage to determine the insertion loss of various acoustic add-on treatments

    NASA Technical Reports Server (NTRS)

    Heitman, K. E.; Mixson, J. S.

    1984-01-01

    This paper describes a laboratory study of add-on acoustic treatments for a propeller-driven light aircraft fuselage. The treatments included: no treatment (i.e., baseline fuselage); a production-type double-wall interior; and various amounts of high density fiberglass added to the baseline fuselage. The sound source was a pneumatic-driver with attached exponential horn, supplied with a broadband signal. Data were acquired at the approximate head positions of the six passenger seats. The results were analyzed on space-averaged narrowband, one-third octave band and overall insertion loss basis. In addition, insertion loss results for the different configurations at specific frequencies representing propeller tone spectra are presented. The propeller tone data includes not only the space-averaged insertion loss, but also the variation of insertion loss at these particular frequencies across the six microphone positions.

  5. Acoustic fatigue and sound transmission characteristics of a ram composite panel design

    NASA Technical Reports Server (NTRS)

    Cockburn, J. A.; Chang, K. Y.; Kao, G. C.

    1972-01-01

    An experimental study to determine the acoustic fatigue characteristics of a flat multi-layered structural panel is described. The test panel represented a proposed design for the outer skin of a research application module to be housed within the space shuttle orbiter vehicle. The test specimen was mounted in one wall of the Wyle 100,000 cu ft reverberation room and exposed to a broadband acoustic environment having an overall level of 145 db. The test panel was exposed to nine separate applications of the acoustic environment, each application consisting of 250 seconds duration. Upon completion of the ninth test run, the specimen was exposed to a simulated micrometeoroid impact near the panel center. One additional test run of 250 seconds duration was then performed to complete the overall simulation of 50 flight missions. The experimental results show that no significant fatigue damage occurred until the test specimen was exposed to a simulated micrometeoroid impact. The intermediate foam layer forming the core of the test specimen suffered considerable damage due to this impact, causing a marked variation in the dynamic characteristics of the overall test panel. During the final application of the acoustic environment, the strain and acceleration response spectra showed considerable variation from those spectra obtained prior to impact of the panel. Fatigue damage from acoustic loading however, was limited to partial de-bonding around the edges of the composite panel.

  6. Analysis of transmission loss, signal gain, and coherence in shallow water

    NASA Astrophysics Data System (ADS)

    Rozenfeld, Ilya

    2001-08-01

    Experiments in the Strait of Korea were performed to study sound propagation in an oceanographically complex shallow water environment. First a geoacoustic model is developed based on narrowband transmission loss measurements and using estimated profiles and measured bathymetry. The comparisons between measured and calculated transmission loss are made through an effective attenuation coefficient, which measures the rate of change of mean transmission loss with range. Environmental model parameters are selected to achieve the best agreement in the comparisons. Nonlinear frequency dependence in the sediment attenuation profiles permits good agreement between the calculations and measured data. The developed geoacoustic model is then used to obtain predictions of broadband transmission loss and signal energy spread. Very good agreement between these predictions and corresponding independent measurements validates the geoacoustic model. Next signal gain measurements taken during the experiment are examined. Using the previously developed environmental profiles the signal gain is computed. The calculations are in agreement with measurements for shorter ranges. For longer ranges and higher frequencies disagreement is found between the calculations and measurements. The cause is random fluctuations in the signal induced by the random medium. These effects can be included into the signal gain through the coherence function. Using a previously developed theory preliminary calculations of coherence are made. By choosing physically reasonable parameters of the random fluctuations in the medium, close agreement with measurements is achieved. Next this theory is extended to include scattering from inhomogeneities with arbitrary correlation functions. This allows a treatment of random fluctuations described by physically based spectra. The correlation functions corresponding to these spectra for mechanisms such as internal waves, turbulence, and wind driven sea surface

  7. PSO for Multiobjective Economic Load Dispatch (MELD) for Minimizing Generation Cost and Transmission Losses

    NASA Astrophysics Data System (ADS)

    Jain, Narender Kumar; Nangia, Uma; Jain, Aishwary

    2016-06-01

    In this paper, multiobjective economic load dispatch (MELD) problem considering generation cost and transmission losses has been formulated using priority goal programming (PGP) technique. In this formulation, equality constraint has been considered by inclusion of penalty parameter K. It has been observed that fixing its value to 1,000 keeps the equality constraint within limits. The non-inferior set for IEEE 5, 14 and 30-bus systems has been generated by Particle Swarm Optimization (PSO) technique. The best compromise solution has been chosen as the one which gives equal percentage saving for both the objectives.

  8. Percolation Model of Sensory Transmission and Loss of Consciousness Under General Anesthesia.

    PubMed

    Zhou, David W; Mowrey, David D; Tang, Pei; Xu, Yan

    2015-09-04

    Neurons communicate with each other dynamically; how such communications lead to consciousness remains unclear. Here, we present a theoretical model to understand the dynamic nature of sensory activity and information integration in a hierarchical network, in which edges are stochastically defined by a single parameter p representing the percolation probability of information transmission. We validate the model by comparing the transmitted and original signal distributions, and we show that a basic version of this model can reproduce key spectral features clinically observed in electroencephalographic recordings of transitions from conscious to unconscious brain activities during general anesthesia. As p decreases, a steep divergence of the transmitted signal from the original was observed, along with a loss of signal synchrony and a sharp increase in information entropy in a critical manner; this resembles the precipitous loss of consciousness during anesthesia. The model offers mechanistic insights into the emergence of information integration from a stochastic process, laying the foundation for understanding the origin of cognition.

  9. Percolation Model of Sensory Transmission and Loss of Consciousness under General Anesthesia

    PubMed Central

    Zhou, David W.; Mowrey, David D.; Tang, Pei; Xu, Yan

    2015-01-01

    Neurons communicate with each other dynamically. How such communications lead to consciousness remains unclear. Here, we present a theoretical model to understand the dynamic nature of sensory activity and information integration in a hierarchical network, in which edges are stochastically defined by a single parameter, p, representing percolation probability of information transmission. We validate the model by comparing the transmitted and original signal distributions and show that a basic version of this model can reproduce key spectral features clinically observed in electroencephalographic recordings of transitions from conscious to unconscious brain activities during general anesthesia. As p decreases, a steep divergence of the transmitted signal from the original was observed, along with a loss of signal synchrony and a sharp increase in information entropy in a critical manner, resembling the precipitous loss of consciousness during anesthesia. The model offers mechanistic insights into the emergence of information integration from a stochastic process, laying the foundation to understand the origin of cognition. PMID:26382705

  10. Percolation Model of Sensory Transmission and Loss of Consciousness Under General Anesthesia

    NASA Astrophysics Data System (ADS)

    Zhou, David W.; Mowrey, David D.; Tang, Pei; Xu, Yan

    2015-09-01

    Neurons communicate with each other dynamically; how such communications lead to consciousness remains unclear. Here, we present a theoretical model to understand the dynamic nature of sensory activity and information integration in a hierarchical network, in which edges are stochastically defined by a single parameter p representing the percolation probability of information transmission. We validate the model by comparing the transmitted and original signal distributions, and we show that a basic version of this model can reproduce key spectral features clinically observed in electroencephalographic recordings of transitions from conscious to unconscious brain activities during general anesthesia. As p decreases, a steep divergence of the transmitted signal from the original was observed, along with a loss of signal synchrony and a sharp increase in information entropy in a critical manner; this resembles the precipitous loss of consciousness during anesthesia. The model offers mechanistic insights into the emergence of information integration from a stochastic process, laying the foundation for understanding the origin of cognition.

  11. Generation of Acoustic Gravity Waves by Periodic Radio Transmissions from a High-Power Ionospheric Heater

    NASA Astrophysics Data System (ADS)

    Frolov, Vladimir; Chernogor, Leonid; Rozumenko, Victor

    The Radiophysical Research Institute (Nizhny Novgorod, Russia) and Kharkiv V. N. Karazin National University (Kharkiv, Ukraine) have studied opportunities for the effective generation of acoustic gravity waves (AGWs) in 3 - 180-min period range. The excitation of such waves was conducted for the last several years using the SURA heating facility (Nizhny Novgorod). The detection of the HF-induced AGWs was carried out in the Radiophysical Observatory located near Kharkiv City at a distance of about 960 km from the SURA. A coherent radar for vertical sounding, an ionosonde, and magnetometer chains were used in our measurements. The main results are the following (see [1-5]): 1. Infrasound oscillation trains with a period of 6 min are detected during periodic SURA heater turn-on and -off. Similar oscillation trains are detected after long time pumping, during periodic transmissions with a period of 20 s, as well as after pumping turn-off. The train recordings begin 28 - 54 min after the heater turn-on or -off, and the train propagation speeds are about 300 - 570 m/s, the value of which is close to the sound speed at upper atmospheric altitudes. The amplitude of the Doppler shift frequency is of 10 - 40 mHz, which fits to the 0.1 - 0.3% electron density disturbances at ionospheric altitudes. The amplitude of the infrasound oscillations depends on the SURA mode of operation and the state of the upper atmosphere and ionosphere. 2. High-power radio transmissions stimulate the generation (or enhancement) of waves at ionospheric altitudes in the range of internal gravity wave periods. The HF-induced waves propagate with speeds of 360 - 460 m/s and produce changes in electron density with amplitudes of 2 - 3%. The generation of such periodic perturbations is more preferable with periods of 10 - 60 minutes. Their features depend significantly on the heater mode of operation. It should be stressed that perturbation intensity increases when a pumping wave frequency approaches

  12. Transmission of acoustic waves through mixing layers and 2D isotropic turbulence

    NASA Astrophysics Data System (ADS)

    Juve, D.; Blanc-Benon, P.; Comte-Bellot, G.

    Ray tracing and parabolic equation methods have been used to study the properties of acoustic waves transmitted through turbulent velocity fields. A numerical simulation permits individual realizations of the turbulent field, which then allow, if desired, an ensemble averaging of the fields. Two flows have been considered, 2D isotropic turbulence and a 2D mixing layer. The following complementary aspects are developed: the occurrence of caustics, the reinforced or weakened zones of the acoustic field, the eigenrays between a source and a receiver, and the associated travel times, variances, and scintillation index.

  13. A study of methods of prediction and measurement of the transmission of sound through the walls of light aircraft

    NASA Technical Reports Server (NTRS)

    Forssen, B.; Wang, Y. S.; Raju, P. K.; Crocker, M. J.

    1981-01-01

    The acoustic intensity technique was applied to the sound transmission loss of panel structures (single, composite, and stiffened). A theoretical model of sound transmission through a cylindrical shell is presented.

  14. Disease dynamics of Porites bleaching with tissue loss: prevalence, virulence, transmission, and environmental drivers.

    PubMed

    Sudek, M; Williams, G J; Runyon, C; Aeby, G S; Davy, S K

    2015-02-10

    The prevalence, number of species affected, and geographical extent of coral diseases have been increasing worldwide. We present ecological data on the coral disease Porites bleaching with tissue loss (PBTL) from Kaneohe Bay, Oahu (Hawaii, USA), affecting P. compressa. This disease is prevalent throughout the year, although it shows spatio-temporal variability with peak prevalence during the warmer summer months. Temporal variability in disease prevalence showed a strong positive relationship with elevated water temperature. Spatially, PBTL prevalence peaked in clearer waters (lower turbidity) with higher water flow and higher densities of parrotfish, together explaining approximately 26% of the spatial variability in PBTL prevalence. However, the relatively poor performance of the spatial model suggests that other, unmeasured factors may be more important in driving spatial prevalence. PBTL was not transmissible through direct contact or the water column in controlled aquaria experiments, suggesting that this disease may not be caused by a pathogen, is not highly infectious, or perhaps requires a vector for transmission. In general, PBTL results in partial tissue mortality of affected colonies; on average, one-third of the tissue is lost. This disease can affect the same colonies repeatedly, suggesting a potential for progressive damage which could cause increased tissue loss over time. P. compressa is the main framework-building species in Kaneohe Bay; PBTL therefore has the potential to negatively impact the structure of the reefs at this location.

  15. Transmission of wave energy in curved ducts. [acoustic propagation within rigid walls

    NASA Technical Reports Server (NTRS)

    Rostafinski, W.

    1974-01-01

    Investigation of the ability of circular bends to transmit acoustic energy flux. A formulation of wave-energy flow is developed for motion in curved ducts. A parametric study over a range of frequencies shows the ability of circular bends to transmit energy in the case of perfectly rigid walls.

  16. Model distinguishability and inference robustness in mechanisms of cholera transmission and loss of immunity.

    PubMed

    Lee, Elizabeth C; Kelly, Michael R; Ochocki, Brad M; Akinwumi, Segun M; Hamre, Karen E S; Tien, Joseph H; Eisenberg, Marisa C

    2017-01-24

    Mathematical models of cholera and waterborne disease vary widely in their structures, in terms of transmission pathways, loss of immunity, and a range of other features. These differences can affect model dynamics, with different models potentially yielding different predictions and parameter estimates from the same data. Given the increasing use of mathematical models to inform public health decision-making, it is important to assess model distinguishability (whether models can be distinguished based on fit to data) and inference robustness (whether inferences from the model are robust to realistic variations in model structure). In this paper, we examined the effects of uncertainty in model structure in the context of epidemic cholera, testing a range of models with differences in transmission and loss of immunity structure, based on known features of cholera epidemiology. We fit these models to simulated epidemic and long-term data, as well as data from the 2006 Angola epidemic. We evaluated model distinguishability based on fit to data, and whether the parameter values, model behavior, and forecasting ability can accurately be inferred from incidence data. In general, all models were able to successfully fit to all data sets, both real and simulated, regardless of whether the model generating the simulated data matched the fitted model. However, in the long-term data, the best model fits were achieved when the loss of immunity structures matched those of the model that simulated the data. Two parameters, one representing person-to-person transmission and the other representing the reporting rate, were accurately estimated across all models, while the remaining parameters showed broad variation across the different models and data sets. The basic reproduction number (R0) was often poorly estimated even using the correct model, due to practical unidentifiability issues in the waterborne transmission pathway which were consistent across all models. Forecasting

  17. Measurements of the Ech Power and of the Transmission Line Losses on Diii-D

    NASA Astrophysics Data System (ADS)

    Cengher, M.; Lohr, J.; Gorelov, I. A.; Grosnickle, W. H.; Ponce, D.; Johnson, P.

    2009-04-01

    The measurement of the power injected by the electron cyclotron heating (ECH) system in the DIII-D tokamak is a critical requirement for analysis of experiments, for tuning the gyrotrons for maximum power and efficiency, for tracking long-term operational trends and for providing a warning of problems with the system. The ECH system at General Atomics consists of six 110 GHz, 1 MW class gyrotrons. The rf power generated by each gyrotron is determined from calorimetry, using the relevant temperature and flow measurements from the cooling circuits of cavity, matching optics unit and dummy loads. The rf pulse length and time dependence are measured using an rf monitor at the first miter bend in the transmission line. The direct measurement of the efficiencies of four of the transmission lines was performed using a high power, small dummy load (SDL) placed alternately in 2 positions of each DIII-D waveguide line, at accessible points close the beginning and the end of each line. Total losses in the transmission lines range from 21.2% to 30.7%. Experimental results are compared to theoretical predictions of the performance of the components and waveguide lines.

  18. [The audiological phenotype and the prevalence of GJB2-related sensorineural loss of hearing in the infants suffering acoustic disturbances].

    PubMed

    Lalaiants, M R; Markova, T G; Bakhshinian, V V; Bliznets, E A; Poliakov, A V; Tavartikiladze, G A

    2014-01-01

    The objective of the present work was to study specific features of the audiological phenotype and the prevalence of GJB2-related sensorineural hearing loss (SNHL) in the infants suffering acoustic disturbances. The study included 264 children with bilateral non-syndromic sensorineural loss of hearing diagnosed during the first year of life by means of detailed audiological examination that included tympanometry, registration of short-latency auditory action potentials (SLAAP), delayed evoked otoacoustic emission (DEOAE), distortion product-frequency otoacoustic emission (DPFOAE), and auditory brain-stem response (ABR). In addition, stationary acoustically evoked responses (SAER) were recorded in 38 children presenting with hearing impairment associated with GJB2-related sensorineural loss of hearing. The follow-up dynamic study involved 113 children subjected to repeated audiological examination. The study revealed the genotype with pathological mutations in 182 (69.0%) children including 171 (64.8%) ones with biallelic mutations and 11 (4.2%) with a single mutation (heterozygous genotype). Eighty two (31.0%) children had genotype without mutations. A total of 21 different mutations and 30 different genotypes were identified. Analysis of the family histories of the children showed that neither the absence of relatives suffering from hearing impairment nor the presence of risk factors of acquired hearing impairment excludes the possibility of GJB2-related sensorineural loss of hearing in the infants. Otoacoustic emission fails to be registered in the majority of the children with the altered genotype (87%) during the stay in the maternity house. Mutations in the GJB2 gene are most frequently diagnosed in the patients with the moderate, moderately severe, and severe loss of hearing. At the same time, almost half of the infants presenting with the mild loss of hearing were found to exhibit changes in the GJB2 gene. The thresholds of registration of short

  19. Transmission loss of orthogonally rib-stiffened double-panel structures with cavity absorption.

    PubMed

    Xin, F X; Lu, T J

    2011-04-01

    The transmission loss of sound through infinite orthogonally rib-stiffened double-panel structures having cavity-filling fibrous sound absorptive materials is theoretically investigated. The propagation of sound across the fibrous material is characterized using an equivalent fluid model, and the motions of the rib-stiffeners are described by including all possible vibrations, i.e., flexural displacements, bending, and torsional rotations. The effects of fluid-structure coupling are account for by enforcing velocity continuity conditions at fluid-panel interfaces. By taking full advantage of the periodic nature of the double-panel, the space-harmonic approach and virtual work principle are applied to solve the sets of resultant governing equations, which are eventually truncated as a finite system of simultaneous algebraic equations and numerically solved insofar as the solution converges. To validate the proposed model, a comparison between the present model predictions and existing numerical and experimental results for a simplified version of the double-panel structure is carried out, with overall agreement achieved. The model is subsequently employed to explore the influence of the fluid-structure coupling between fluid in the cavity and the two panels on sound transmission across the orthogonally rib-stiffened double-panel structure. Obtained results demonstrate that this fluid-structure coupling affects significantly sound transmission loss (STL) at low frequencies and cannot be ignored when the rib-stiffeners are sparsely distributed. As a highlight of this research, an integrated optimal algorithm toward lightweight, high-stiffness and superior sound insulation capability is proposed, based on which a preliminary optimal design of the double-panel structure is performed.

  20. Acoustical Properties of Mud Sediments

    DTIC Science & Technology

    2015-09-30

    transmission loss and array response in shallow water over mud sediments and of acoustic detection, localization, and classification of objects buried...classification of objects buried in mud; and improvement of shallow water sonar systems and predictions with mud sediments. RELATED PROJECTS...Characterization Experiment. Collaboration is planned with colleagues at Woods Hole Oceanographic Institution (Jim Lynch, Tim Duda, and Ying-Tsong Lin

  1. A high transmission broadband gradient index lens using elastic shell acoustic metamaterial elements

    NASA Astrophysics Data System (ADS)

    Titovich, Alexey S.; Norris, Andrew N.; Haberman, Michael R.

    2016-06-01

    The use of cylindrical elastic shells as elements in acoustic metamaterial devices is demonstrated through simulations and underwater measurements of a cylindrical-to-plane wave lens. Transformation acoustics (TA) of a circular region to a square dictates that the effective density in the lens remain constant and equal to that of water. Piecewise approximation to the desired effective compressibility is achieved using a square array with elements based on the elastic shell metamaterial concept developed in [30]. The size of the elements are chosen based on availability of shells, minimizing fabrication difficulties. The tested device is neutrally buoyant comprising 48 elements of nine different types of commercial shells made from aluminum, brass, copper, and polymers. Simulations indicate a broadband range in which the device acts as a cylindrical to plane wave lens. The experimental findings confirm the broadband quadropolar response from approximately 20 to 40 kHz, with positive gain of the radiation pattern in the four plane wave directions.

  2. Reduced acoustic startle response and peripheral hearing loss in the 5xFAD mouse model of Alzheimer's disease.

    PubMed

    O'Leary, Timothy P; Shin, Sooyoun; Fertan, Emre; Dingle, Rachel N; Almuklass, Awad; Gunn, Rhian K; Yu, Zhiping; Wang, Jian; Brown, Richard E

    2017-01-29

    Hearing dysfunction has been associated with Alzheimer's disease in humans, but there is little data on the auditory function of mouse models of Alzheimer's disease. Furthermore, characterization of hearing ability in mouse models is needed to ensure that tests of cognition that use auditory stimuli are not confounded by hearing dysfunction. Therefore we assessed acoustic startle response and pre-pulse inhibition in the double transgenic 5xFAD mouse model of Alzheimer's disease from 3-4 to 16 months of age. The 5xFAD mice demonstrated an age-related decline in acoustic startle as early as 3-4 months of age. We subsequently tested Auditory Brainstem Response (ABR) thresholds at 4 and 13-14 months of age using tone-bursts at frequencies of 2- 32 kHz. The 5xFAD mice showed increased ABR thresholds for tone-bursts between 8 and 32Khz at 13-14 months of age. Finally, cochleae were extracted and basilar membranes were dissected to count hair cell loss across the cochlea. The 5xFAD mice showed significantly greater loss of both inner and outer hair cells at the apical and basal ends of the basilar membrane than wildtype mice at 15-16 months of age. These results indicate that the 5xFAD mouse model of Alzheimer's disease shows age-related decreases in acoustic startle responses, which are at least partially due to age-related peripheral hearing loss. Therefore, we caution against the use of cognitive tests that rely on audition in 5xFAD mice over 3-4 months of age, without first confirming that performance is not confounded by hearing dysfunction.

  3. A high transmission broadband gradient index lens using elastic shell acoustic metamaterial elements.

    PubMed

    Titovich, Alexey S; Norris, Andrew N; Haberman, Michael R

    2016-06-01

    The use of cylindrical elastic shells as elements in acoustic metamaterial devices is demonstrated through simulations and underwater measurements of a cylindrical-to-plane wave lens. Transformation acoustics of a circular region to a square dictate that the effective density in the lens remain constant and equal to that of water. Piecewise approximation to the desired effective compressibility is achieved using a square array with elements based on the elastic shell metamaterial concept developed by Titovich and Norris [J. Acoust. Soc. Am. 136(4), 1601-1609 (2014)]. The sizes of the elements are chosen based on availability of shells, minimizing fabrication difficulties. The tested device is neutrally buoyant comprising 48 elements of nine different types of commercial shells made from aluminum, brass, copper, and polymers. Simulations indicate a broadband range in which the device acts as a cylindrical to plane wave lens. The experimental findings confirm the broadband quadropolar response from approximately 20 to 40 kHz, with positive gain of the radiation pattern in the four plane wave directions.

  4. Assessment of Transmission in Trachoma Programs over Time Suggests No Short-Term Loss of Immunity

    PubMed Central

    Liu, Fengchen; Porco, Travis C.; Ray, Kathryn J.; Bailey, Robin L.; Mkocha, Harran; Muñoz, Beatriz; Quinn, Thomas C.; Lietman, Thomas M.; West, Sheila K.

    2013-01-01

    Trachoma programs have dramatically reduced the prevalence of the ocular chlamydia that cause the disease. Some have hypothesized that immunity to the infection may be reduced because of program success in reducing the incidence of infection, and transmission may then increase. Longitudinal studies of multiple communities would be necessary to test this hypothesis. Here, we quantify transmission using an estimated basic reproduction number based on 32 communities during the first, second, and third years of an antibiotic treatment program. We found that there is little to no increase in the basic reproduction number over time. The estimated linear trend in the basic reproduction number, , was found to be −0.025 per year, 95% CI −0.167 to 0.117 per year. We are unable to find evidence supporting any loss of immunity over the course of a 3-year program. This is encouraging, as it allows the possibility that repeated mass antibiotic distributions may eliminate infection from even the most severely affected areas. PMID:23875038

  5. Frequency modulation at a moving material interface and a conservation law for wave number. [acoustic wave reflection and transmission

    NASA Technical Reports Server (NTRS)

    Kleinstein, G. G.; Gunzburger, M. D.

    1976-01-01

    An integral conservation law for wave numbers is considered. In order to test the validity of the proposed conservation law, a complete solution for the reflection and transmission of an acoustic wave impinging normally on a material interface moving at a constant speed is derived. The agreement between the frequency condition thus deduced from the dynamic equations of motion and the frequency condition derived from the jump condition associated with the integral equation supports the proposed law as a true conservation law. Additional comparisons such as amplitude discontinuities and Snells' law in a moving media further confirm the stated proposition. Results are stated concerning frequency and wave number relations across a shock front as predicted by the proposed conservation law.

  6. Acoustic puncture assist device™ versus conventional loss of resistance technique for thoracic paravertebral space identification: Clinical and ultrasound evaluation

    PubMed Central

    Ali, Monaz Abdulrahman; Abdellatif, Ashraf Abualhasan

    2017-01-01

    Background: Acoustic puncture assist device (APAD™) is a pressure measurement combined with a related acoustic signal that has been successfully used to facilitate epidural punctures. The principal of loss of resistance (LOR) is similar when performing paravertebral block (PVB). We investigated the usefulness of APAD™ by comparing it with the conventional LOR techniques for identifying paravertebral space (PVS). Subjects and Methods: A total of 100 women who were scheduled for elective breast surgery under general anesthesia with PVB were randomized into two equal groups. The first group (APAD group) was scheduled for PVB using APAD™. The second group (C group) was scheduled for PVB using conventional LOR technique. We recorded the success rate assessed by clinical and ultrasound findings, the time required to identify the PVS, the depth of the PVS and the number of attempts. The attending anesthesiologist was also questioned about the usefulness of the acoustic signal for detection of the PVS. Results: The incidence of successful PVB was (49) in APAD group compared to (42) in C group P < 0.05. The time required to do PVB was significantly shorter in APAD group than in C group (3.5 ± 1.35 vs. 4.1 ± 1.42) minutes. Two patients in APAD group needed two or more attempts compared to four patients in C group. The attending anesthesiologist found the acoustic signal valuable in all patients in APAD group. Conclusion: Using APAD™ compared to the conventional LOR technique showed a lower failure rate and a shorter time to identify the PVS. PMID:28217050

  7. NEMS With Broken T Symmetry: Graphene Based Unidirectional Acoustic Transmission Lines

    PubMed Central

    Zanjani, Mehdi B.; Davoyan, Arthur R.; Engheta, Nader; Lukes, Jennifer R.

    2015-01-01

    In this work we discuss the idea of one-way acoustic signal isolation in low dimensional nanoelectromechanical oscillators. We report a theoretical study showing that one-way conversion between in-phase and anti-phase vibrational modes of a double layer graphene nanoribbon is achieved by introducing spatio-temporal modulation of system properties. The required modulation length in order to reach full conversion between the two modes is subsequently calculated. Generalization of the method beyond graphene nanoribbons and realization of a NEMS signal isolator are also discussed. PMID:25993637

  8. Practical spatial resolution of electron energy loss spectroscopy in aberration corrected scanning transmission electron microscopy.

    PubMed

    Shah, A B; Ramasse, Q M; Wen, J G; Bhattacharya, A; Zuo, J M

    2011-08-01

    The resolution of electron energy loss spectroscopy (EELS) is limited by delocalization of inelastic electron scattering rather than probe size in an aberration corrected scanning transmission electron microscope (STEM). In this study, we present an experimental quantification of EELS spatial resolution using chemically modulated 2×(LaMnO(3))/2×(SrTiO(3)) and 2×(SrVO(3))/2×(SrTiO(3)) superlattices by measuring the full width at half maxima (FWHM) of integrated Ti M(2,3), Ti L(2,3), V L(2,3), Mn L(2,3), La N(4,5), La N(2,3) La M(4,5) and Sr L(3) edges over the superlattices. The EELS signals recorded using large collection angles are peaked at atomic columns. The FWHM of the EELS profile, obtained by curve-fitting, reveals a systematic trend with the energy loss for the Ti, V, and Mn edges. However, the experimental FWHM of the Sr and La edges deviates significantly from the observed experimental tendency.

  9. Acoustically Tailored Composite Rotorcraft Fuselage Panels

    DTIC Science & Technology

    2015-07-02

    Abstract A rotorcraft roof sandwich panel has been redesigned to optimize sound power transmission loss (TL) and minimize structure-borne sound for...loss improvement, and 6-15 dB of structure-borne sound reduction at critical rotorcraft transmission tonal frequencies. Analytic panel TL theory...accurately, and also simulates structure-borne sound well. Applied Research Laboratory Technical Report Acoustically Tailored Composite Rotorcraft

  10. Low-loss unidirectional transducer for high frequency surface acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Biryukov, S. V.; Martin, G.; Schmidt, H.; Wall, B.

    2011-10-01

    A multi-track unidirectional transducer for surface acoustic wave devices is presented. This transducer consists of periodic cells containing in each of the multiple tracks, only two electrodes and two gaps with quarter period width. So the structure has maximal possible dimensions of its elements for a cell period equal to one wavelength. In spite of current technological limitations this permits to implement unidirectional transducers in GHz range. In contrast to known structures with active tracks only, the structure contains alternating both active transducer tracks and passive reflector tracks with different apertures comparable to surface acoustic wave (SAW) wavelength. The tracks strongly interact due to diffraction of waves excited by such electrode structure on a piezoelectric substrate. A structure analysis by means of finite element method shows that complete unidirectionality can be reached. First experimental results are given.

  11. Acoustic pathways revealed: simulated sound transmission and reception in Cuvier's beaked whale (Ziphius cavirostris).

    PubMed

    Cranford, Ted W; Krysl, Petr; Hildebrand, John A

    2008-03-01

    The finite element modeling (FEM) space reported here contains the head of a simulated whale based on CT data sets as well as physical measurements of sound-propagation characteristics of actual tissue samples. Simulated sound sources placed inside and outside of an adult male Cuvier's beaked whale (Ziphius cavirostris) reveal likely sound propagation pathways into and out of the head. Two separate virtual sound sources that were located at the left and right phonic lips produced beams that converged just outside the head. This result supports the notion that dual sound sources can interfere constructively to form a biologically useful and, in fact, excellent sonar beam in front of the animal. The most intriguing FEM results concern pathways by which sounds reach the ears. The simulations reveal a previously undescribed 'gular pathway' for sound reception in Ziphius. Propagated sound pressure waves enter the head from below and between the lower jaws, pass through an opening created by the absence of the medial bony wall of the posterior mandibles, and continue toward the bony ear complexes through the internal mandibular fat bodies. This new pathway has implications for understanding the evolution of underwater hearing in odontocetes. Our model also provides evidence for receive beam directionality, off-axis acoustic shadowing and a plausible mechanism for the long-standing orthodox sound reception pathway in odontocetes. The techniques developed for this study can be used to study acoustic perturbation in a wide variety of marine organisms.

  12. Transmission and reflection of acoustic and entropy waves through a stator-rotor stage

    NASA Astrophysics Data System (ADS)

    Bauerheim, Michael; Duran, Ignacio; Livebardon, Thomas; Wang, Gaofeng; Moreau, Stéphane; Poinsot, Thierry

    2016-07-01

    The propagation of acoustic, entropy and vorticity waves through turbine stages is of significant interest in the field of core noise. In particular, entropy spots have been shown to generate significant noise when accelerated through turbine stages: the so-called indirect combustion noise. Analytical models for the propagation of acoustic, vorticity and entropy waves through a stator vane, developed since the seventies, are generally based on restrictive assumptions such as low frequency waves. In order to analyze such assumptions, the theory of Cumpsty and Marble is extended to rotating rows and applied to a 2D stator-rotor turbine stage. The theoretical transfer functions are then compared with numerical predictions from forced compressible Large-Eddy Simulations of a 2D stator-rotor configuration, using a fluid-fluid coupling strategy with an overset-grid method. The comparisons between the analytical model and the simulations are in good agreement. To improve the analytical predictions, the attenuation due to the entropy spot deformation through the stator vane or the rotor blade is then included, modeled either analytically or extracted from the mean flow of the simulations. The complete analytical model reveals a good agreement with 2D simulations, which allows the prediction and minimization of both direct and indirect noise at the design-stage without computation.

  13. Tunable acoustic waveguide based on vibro-acoustic metamaterials with shunted piezoelectric unit cells

    NASA Astrophysics Data System (ADS)

    Kwon, Byung-Jin; Jung, Jin-Young; Lee, Dooho; Park, Kwang-Chun; Oh, Il-Kwon

    2015-10-01

    We propose a new class of acoustic waveguides with tunable bandgaps (TBs) by using vibro-acoustic metamaterials with shunted periodic piezoelectric unit cells. The unit metamaterial cells that consist of a single crystal piezoelectric transducer and an electrical shunt circuit are designed to induce a strong vibro-acousto-electrical coupling, resulting in a tunable acoustic bandgap as well as local structural resonance and Bragg scattering bandgaps. The present results show that the TB frequency can be actively controlled and the transmission loss of the acoustic wave can be greatly improved by simply changing the inductance values in the shunt circuit.

  14. Structural Acoustic Response of Shape Memory Alloy Hybrid Composite Panels

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.

    1996-01-01

    A method has been developed to predict the structural acoustic response of shape memory alloy hybrid composite panels subjected to acoustic excitation. The panel is modeled by a finite element analysis and the radiated field is predicted using Rayleigh's integral. Transmission loss predictions for the case of an aluminum panel excited by a harmonic acoustic pressure are shown to compare very well with a classical analysis. Predictions of the normal velocity response and transmitted acoustic pressure for a clamped aluminum panel show excellent agreement with experimental measurements. Predicted transmission loss performance for a composite panel with and without shape memory alloy reinforcement are also presented. The preliminary results demonstrate that the transmission loss can be significantly increased with shape memory alloy reinforcement.

  15. A Spectral Analysis Approach for Acoustic Radiation from Composite Panels

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Singh, Mahendra P.; Mei, Chuh

    2004-01-01

    A method is developed to predict the vibration response of a composite panel and the resulting far-field acoustic radiation due to acoustic excitation. The acoustic excitation is assumed to consist of obliquely incident plane waves. The panel is modeled by a finite element analysis and the radiated field is predicted using Rayleigh's integral. The approach can easily include other effects such as shape memory alloy (SMA) ber reinforcement, large detection thermal postbuckling, and non-symmetric SMA distribution or lamination. Transmission loss predictions for the case of an aluminum panel excited by a harmonic acoustic pressure are shown to compare very well with a classical analysis. Results for a composite panel with and without shape memory alloy reinforcement are also presented. The preliminary results demonstrate that the transmission loss can be significantly increased with shape memory alloy reinforcement. The mechanisms for further transmission loss improvement are identified and discussed.

  16. Experimental study using Nearfield Acoustical Holography of sound transmission fuselage sidewall structures

    NASA Technical Reports Server (NTRS)

    Maynard, J. D.

    1983-01-01

    This project involves the development of the Nearfield Acoustic Holography (NAH) technique (in particular its extension from single frequency to wideband noise measurement) and its application in a detailed study of the noise radiation characteristics of several samples of aircraft sidewall panels. With the extensive amount of information provided by the NAH technique, the properties of the sound field radiated by the panels may be correlated with their structure, mounting, and excitation (single frequency or wideband, spatially correlated or uncorrelated, structure-borne). The work accomplished at the beginning of this grant period included: (1) Calibration of the 256 microphone array and test of its accuracy. (2) extension of the facility to permit measurements on wideband noise sources. The extensions incuded the addition of high-speed data acquisition hardware and an array processor, and the development of new software. (3) Installation of motion picture graphics for correlating panel motion with structure, mounting, radiation, etc. (4) Development of new holographic data processing techniques.

  17. Acoustic echo cancellation for full-duplex voice transmission on fading channels

    NASA Technical Reports Server (NTRS)

    Park, Sangil; Messer, Dion D.

    1990-01-01

    This paper discusses the implementation of an adaptive acoustic echo canceler for a hands-free cellular phone operating on a fading channel. The adaptive lattice structure, which is particularly known for faster convergence relative to the conventional tapped-delay-line (TDL) structure, is used in the initialization stage. After convergence, the lattice coefficients are converted into the coefficients for the TDL structure which can accommodate a larger number of taps in real-time operation due to its computational simplicity. The conversion method of the TDL coefficients from the lattice coefficients is derived and the DSP56001 assembly code for the lattice and TDL structure is included, as well as simulation results and the schematic diagram for the hardware implementation.

  18. Acoustic streaming related to minor loss phenomenon in differentially heated elements of thermoacoustic devices

    NASA Astrophysics Data System (ADS)

    Mironov, Mikhail; Gusev, Vitalyi; Auregan, Yves; Lotton, Pierrick; Bruneau, Michel; Piatakov, Pavel

    2002-08-01

    It is demonstrated that the differentially heated stack, the heart of all thermoacoustic devices, provides a source of streaming additional to those associated with Reynolds stresses in quasi-unidirectional gas flow. This source of streaming is related to temperature-induced asymmetry in the generation of vortices and turbulence near the stack ends. The asymmetry of the hydrodynamic effects in an otherwise geometrically symmetric stack is due to the temperature difference between stack ends. The proposed mechanism of streaming excitation in annular thermoacoustic devices operates even in the absence of thermo-viscous interaction of sound waves with resonator walls. copyright 2002 Acoustical Society of America.

  19. Weighting of Acoustic Cues to a Manner Distinction by Children with and without Hearing Loss

    ERIC Educational Resources Information Center

    Nittrouer, Susan; Lowenstein, Joanna H.

    2015-01-01

    Purpose: Children must develop optimal perceptual weighting strategies for processing speech in their first language. Hearing loss can interfere with that development, especially if cochlear implants are required. The three goals of this study were to measure, for children with and without hearing loss: (a) cue weighting for a manner distinction,…

  20. Quasiperfect absorption by subwavelength acoustic panels in transmission using accumulation of resonances due to slow sound

    NASA Astrophysics Data System (ADS)

    Jiménez, Noé; Romero-García, Vicent; Pagneux, Vincent; Groby, Jean-Philippe

    2017-01-01

    We theoretically and experimentally report subwavelength resonant panels for low-frequency quasiperfect sound absorption including transmission by using the accumulation of cavity resonances due to the slow sound phenomenon. The subwavelength panel is composed of periodic horizontal slits loaded by identical Helmholtz resonators (HRs). Due to the presence of the HRs, the propagation inside each slit is strongly dispersive, with near-zero phase velocity close to the resonance of the HRs. In this slow sound regime, the frequencies of the cavity modes inside the slit are down-shifted and the slit behaves as a subwavelength resonator. Moreover, due to strong dispersion, the cavity resonances accumulate at the limit of the band gap below the resonance frequency of the HRs. Near this accumulation frequency, simultaneously symmetric and antisymmetric quasicritical coupling can be achieved. In this way, using only monopolar resonators quasiperfect absorption can be obtained in a material including transmission.

  1. Charge-state-dependent energy loss of slow ions. I. Experimental results on the transmission of highly charged ions

    NASA Astrophysics Data System (ADS)

    Wilhelm, Richard A.; Gruber, Elisabeth; Smejkal, Valerie; Facsko, Stefan; Aumayr, Friedrich

    2016-05-01

    We report on energy loss measurements of slow (v ≪v0 ), highly charged (Q >10 ) ions upon transmission through a 1-nm-thick carbon nanomembrane. We emphasize here the scaling of the energy loss with the velocity and charge exchange or loss. We show that a weak linear velocity dependence exists, whereas charge exchange dominates the kinetic energy loss, especially in the case of a large charge capture. A universal scaling of the energy loss with the charge exchange and velocity is found and discussed in this paper. A model for charge-state-dependent energy loss for slow ions is presented in paper II in this series [R. A. Wilhelm and W. Möller, Phys. Rev. A 93, 052709 (2016), 10.1103/PhysRevA.93.052709].

  2. Prediction of conductive hearing loss based on acoustic ear-canal response using a multivariate clinical decision theory.

    PubMed

    Piskorski, P; Keefe, D H; Simmons, J L; Gorga, M P

    1999-03-01

    This study evaluated the accuracy of acoustic response tests in predicting conductive hearing loss in 161 ears of subjects from the age of 2 to 10 yr, using as a "gold standard" the air-bone gap to classify ears as normal or impaired. The acoustic tests included tympanometric peak-compensated static admittance magnitude (SA) and tympanometric gradient at 226 Hz, and admittance-reflectance (YR) measurements from 0.5 to 8 kHz. The performance of individual, frequency-specific, YR test variables as predictors was assessed. By applying logistic regression (LR) and discriminant analysis (DA) techniques to the multivariate YR response, two univariate functions were calculated as the linear combinations of YR variables across frequency that best separated normal and impaired ears. The tympanometric and YR tests were also combined in a multivariate manner to test whether predictive efficacy improved when 226-Hz tympanometry was added to the predictor set. Conductive hearing loss was predicted based on air-bone gap thresholds at 0.5 and 2 kHz, and on a maximum air-bone gap at any octave frequency from 0.5 to 4 kHz. Each air-bone gap threshold ranged from 5 to 30 dB in 5-dB steps. Areas under the relative operating characteristic curve for DA and LR were larger than for reflectance at 2 kHz, SA and Gr. For constant hit rates of 80% and 90%, both DA and LR scores had lower false-alarm rates than tympanometric tests-LR achieved a false-alarm rate of 6% for a sensitivity of 90%. In general, LR outperformed DA as the multivariate technique of choice. In predicting an impairment at 0.5 kHz, the reflectance scores at 0.5 kHz were less accurate predictors than reflectance at 2 and 4 kHz. This supports the hypothesis that the 2-4-kHz range is a particularly sensitive indicator of middle-ear status, in agreement with the spectral composition of the output predictor from the multivariate analyses. When tympanometric and YR tests were combined, the resulting predictor performed

  3. Effect of applied magnetic field on sound transmission loss of MR-based sandwich panels

    NASA Astrophysics Data System (ADS)

    Hemmatian, Masoud; Sedaghati, Ramin

    2017-02-01

    This study aims to investigate the sound transmission loss (STL) capability of sandwich panels treated with Magnetorheological (MR) fluids at low frequencies. An experimental setup has been designed to investigate the effect of the intensity of applied magnetic field on the natural frequencies and STL of a clamped circular panel. It is shown that the fundamental natural frequency of the MR sandwich panel increases in proportion to the applied magnetic field. In addition, the STL of the panel at the resonance frequency increases as the magnetic field is amplified. Furthermore, the classical plate theory and Ritz method have been utilized to develop the governing equations of motion of the finite multilayered circular panels comprising two elastic face sheets and MR fluid core layer. The radiated sound power from the panel is derived using Rayleigh integral as a function of the transverse velocity of the panel which is subsequently used to evaluate the STL. The theoretical study is validated comparing the simulation results with the experimental measurements. Experimental and analytical parametric study have also been conducted to study the effect of the core layers’ thickness on the natural frequency and the STL of sandwich panel.

  4. Sound Transmission Loss Prediction of the Composite Fuselage with Different Methods

    NASA Astrophysics Data System (ADS)

    Yuan, Chongxin; Bergsma, Otto; Beukers, Adriaan

    2012-12-01

    Increase of sound transmission loss(TL) of the fuselage is vital to build a comfortable cabin environment. In this paper, to find a convenient and accurate means for predicting the fuselage TL, the fuselage is modeled as a composite cylinder, and its TL is predicted with the analytical, the statistic energy analysis (SEA) and the hybrid FE&SEA method. The TL results predicted by the three methods are compared to each other and they show good agreement, but in terms of model building the SEA method is the most convenient one. Therefore, the parameters including the layup, the materials, the geometry, and the structure type are studied with the SEA method. It is observed that asymmetric laminates provide better sound insulation in general. It is further found that glass fiber laminates result in the best sound insulation as compared with graphite and aramid fiber laminates. In addition, the cylinder length has little influence on the sound insulation, while an increase of the radius considerably reduces the TL at low frequencies. Finally, by a comparison among an unstiffened laminate, a sandwich panel and a stiffened panel, the sandwich panel presents the largest TL at high frequencies and the stiffened panel demonstrates the poorest sound insulation at all frequencies.

  5. Acoustically tunable optical transmission through a subwavelength hole with a bubble

    NASA Astrophysics Data System (ADS)

    Maksymov, Ivan S.; Greentree, Andrew D.

    2017-03-01

    Efficient manipulation of light with sound in subwavelength-sized volumes is important for applications in photonics, phononics, and biophysics, but remains elusive. We theoretically demonstrate the control of light with MHz-range ultrasound in a subwavelength, 300-nm-wide water-filled hole with a 100-nm-radius air bubble. Ultrasound-driven pulsations of the bubble modulate the effective refractive index of the hole aperture, which gives rise to spectral tuning of light transmission through the hole. This control mechanism opens up novel opportunities for tunable acousto-optic and optomechanical metamaterials, and all-optical ultrasound transduction.

  6. A membrane-type acoustic metamaterial with adjustable acoustic properties

    NASA Astrophysics Data System (ADS)

    Langfeldt, F.; Riecken, J.; Gleine, W.; von Estorff, O.

    2016-07-01

    A new realization of a membrane-type acoustic metamaterial (MAM) with adjustable sound transmission properties is presented. The proposed design distinguishes itself from other realizations by a stacked arrangement of two MAMs which is inflated using pressurized air. The static pressurization leads to large nonlinear deformations and, consequently, geometrical stiffening of the MAMs which is exploited to adjust the eigenmodes and sound transmission loss of the structure. A theoretical analysis of the proposed inflatable MAM design using numerical and analytical models is performed in order to identify two important mechanisms, namely the shifting of the eigenfrequencies and modal residuals due to the pressurization, responsible for the transmission loss adjustment. Analytical formulas are provided for predicting the eigenmode shifting and normal incidence sound transmission loss of inflated single and double MAMs using the concept of effective mass. The investigations are concluded with results from a test sample measurement inside an impedance tube, which confirm the theoretical predictions.

  7. Influence of the airflow speed along transmission lines on the DC corona discharge loss, using finite element approach

    SciTech Connect

    Shemshadi, A.; Akbari, A.; Niayesh, K.

    2012-07-15

    Corona discharge is of great interest from the physical point of view and due to its numerous practical applications in industry and especially one of the most important sources of loss in the high voltage transmission lines. This paper provides guidelines for the amount of electric loss caused by corona phenomenon occurred around a DC high voltage wire placed between two flat plates and influence of wind speed rate on the amount of corona loss using COMSOL Multiphysics. So electric potential distribution patterns and charge density diffusion around the wire are studied in this article.

  8. Loss of acoustic black hole effect in a structure of finite size

    NASA Astrophysics Data System (ADS)

    Tang, Liling; Cheng, Li

    2016-07-01

    The Acoustic Black Hole (ABH) effect takes place in thin-walled structures with diminishing thickness as a result of the reduction in the bending wave speed. It was shown to exist as a broadband phenomenon, based on wave propagation theory in structures of semi-infinite size. The ABH effect exhibits appealing features for various applications, such as passive vibration control, energy harvesting, and sound radiation control. In this paper, we demonstrate the disappearance of the ABH effect in a finite beam at specific frequency ranges above the cut-on frequency, both experimentally and theoretically. Analyses show that the phenomenon takes place at frequencies which are close to the low order local resonant frequencies of the portion of the beam demarcated by the position of the excitation force. These frequencies can be predicted so that the phenomenon can be avoided for the targeted frequency ranges in ABH applications.

  9. The effect of fluid streams in porous media on acoustic compression wave propagation, transmission, and reflection

    NASA Astrophysics Data System (ADS)

    Madeo, A.; Djeran-Maigre, I.; Rosi, G.; Silvani, C.

    2013-03-01

    In geomechanics, a relevant role is played by coupling phenomena between compressible fluid seepage flow and deformation of the solid matrix. The behavior of complex porous materials can be greatly influenced by such coupling phenomena. A satisfactorily theoretical framework for their description is not yet completely attained. In this paper, we discuss how the model developed in dell'Isola et al. (Int J Solids Struct 46:3150-3164, 2009) can describe how underground flows or, more generally, confined streams of fluid in deformable porous matrices affect compression wave propagation and their reflection and transmission at a solid-material discontinuity surface. Further work will investigate the effect of stream flow in porous media on shear waves, generalizing what done in Djeran Maigre and Kuznetsov (Comptes Rendus Mécanique 336(1-2):102-107, 2008) for shear waves in one-constituent orthotropic two-layered plates. The presented treatment shows that the presence of fluid streams considerably affect reflection and transmission phenomena in porous media.

  10. Mathematical Modeling of Space-Time Variations in Acoustic Transmission and Scattering from Schools of Swim Bladder Fish

    DTIC Science & Technology

    2015-09-30

    1996 (Ref. 1), based upon the harmonic solution of sets of coupled differential equations, each describing scattering from one fish. The Love swim...side of the empty core, thus reducing the acoustic interactions between them. REFERENCES (1) C. Feuillade, R. W. Nero and R. H. Love , "A low...frequency acoustic scattering model for small schools offish," J. Acoust. Soc. Am., 99, 196-208 (1996). (2) R. H. Love , "Resonant acoustic scattering by

  11. Extremely low material loss and dispersion flattened TOPAS based circular porous fiber for long distance terahertz wave transmission

    NASA Astrophysics Data System (ADS)

    Islam, Md. Saiful; Sultana, Jakeya; Rana, Sohel; Islam, Mohammad Rakibul; Faisal, Mohammad; Kaijage, Shubi F.; Abbott, Derek

    2017-03-01

    In this paper, we present a porous-core circular photonic crystal fiber (PC-CPCF) with ultra-low material loss for efficient terahertz wave transmission. The full vector finite element method with an ideally matched layer boundary condition is used to characterize the wave guiding properties of the proposed fiber. At an operating frequency of 1 THz, simulated results exhibit an extremely low effective material loss of 0.043 cm-1, higher core power fraction of 47% and ultra-flattened dispersion variation of 0.09 ps/THz/cm. The effects of important design properties such as single mode operation, confinement loss and effective area of the fiber are investigated in the terahertz regime. Moreover, the proposed fiber can be fabricated using the capillary stacking or sol-gel technique and be useful for long distance transmission of terahertz waves.

  12. Subwavelength slit acoustic metamaterial barrier

    NASA Astrophysics Data System (ADS)

    Rubio, Constanza; Candelas, Pilar; Belmar, Francisco; Gomez-Lozano, Vicente; Uris, Antonio

    2015-10-01

    Reduction of noise in the transmission path is a very important environmental problem. The standard method to reduce this noise level is the use of acoustic barriers. In this paper, an acoustic metamaterial based on sound transmission through subwavelength slits, is tailored to be used as an acoustic barrier. This system consists of two rows of periodic repetition of vertical rigid pickets separated by a slit of subwavelength width, embedded in air. Here, both the experimental and the numerical analyses are presented. These analyses have facilitated the identification of the parameters that affect the insertion loss performance. The results demonstrated that the proposed barrier can be tuned to mitigate a band noise in a mechanical plant for buildings where openings for air flow are required as well as industrial noise, without excessive barrier thickness.

  13. Controlled exploration of the effects of conductive hearing loss on wideband acoustic immittance in human cadaveric preparations.

    PubMed

    Merchant, Gabrielle R; Merchant, Saumil N; Rosowski, John J; Nakajima, Hideko Heidi

    2016-11-01

    Current clinical practice cannot distinguish, with any degree of certainty, the multiple pathologies that produce conductive hearing loss in patients with an intact tympanic membrane and a well-aerated middle ear without exploratory surgery. The lack of an effective non-surgical diagnostic procedure leads to unnecessary surgery and limits the accuracy of information available during pre-surgical consultations with the patient. A non-invasive measurement to determine the pathology responsible for a conductive hearing loss prior to surgery would be of great value. This work investigates the utility of wideband acoustic immittance (WAI), a non-invasive measure of middle-ear mobility, in the differential diagnosis of pathologies responsible for conductive hearing loss. We focus on determining whether power reflectance (PR), a derivative of WAI, is a possible solution to this problem. PR is a measure of the fraction of sound power reflected from the middle ear when a sound stimulus is presented to the ear canal. PR and other metrics of middle-ear performance (such as ossicular motion via laser Doppler vibrometry) were measured in well-controlled human temporal bone preparations with simulated pathologies. We report measurements before and after simulation of stapes fixation (n = 8), malleus fixation (n = 10), ossicular disarticulation (n = 10), and superior canal dehiscence (n = 8). Our results are consistent with the small set of previously published reflectance measurements made in temporal bones and patients. In this present study, these temporal bone experiments with different middle- and inner-ear pathologies were compared to the initial normal state by analyzing both WAI and ossicular motion, demonstrating that WAI can be a valuable tool in the diagnosis of conductive hearing loss.

  14. Correlation between propagation loss and silicon dioxide film properties for surface acoustic wave devices.

    PubMed

    Matsuda, Satoru; Miura, Michio; Matsuda, Takashi; Ueda, Masanori; Satoh, Yoshio; Hashimoto, Ken-Ya

    2013-05-01

    The correlation between the propagation loss and SiO2 film properties has been studied for temperature-compensated SAW devices using the SiO2/LiNbO3 structure. The SAW devices were prepared under different deposition temperatures for SiO2 film. Although they possessed excellent temperature coefficient of elasticity characteristics, devices prepared at lower temperature showed lower Q-factors. The SiO2 films were also deposited on a Si substrate under the same deposition conditions used for the SAW device preparation. Optical characterization was performed with Fourier transform infrared spectroscopy (FT-IR), spectrometer measurement, and Raman spectroscopy. IR absorbance spectra were almost same in the FT-IR measurement. However, optical attenuation in the UV region decreased with the deposition temperature in the spectrometer measurement. The optical attenuation is caused by the increase of the extinction coefficient in the SiO2 layer, and its optical wavelength dependence indicated that observed excess attenuation is caused by Rayleigh scattering. The Raman scattering also decreased with the deposition temperature in the Raman spectroscopy. The scattering is caused by the distortion of the SiO2 network. These results indicate that the Rayleigh scattering caused by the distortion of the SiO2 network is the main contributor to the excess SAW propagation loss in this case.

  15. Thermal analysis of a planetary transmission with spherical roller bearings operating after complete loss of oil

    NASA Technical Reports Server (NTRS)

    Coe, H. H.

    1984-01-01

    Planetsys and Spherbean, two computer programs developed for the analysis of rolling element bearings, were used to simulate the thermal performance of an OH-58 helicopter main rotor transmission. A steady state and a transient thermal analysis were made and temperatures thus calculated were compared with experimental data obtained from a transmission that was operated to destruction, which occurred about 30 min after all the oil was drained from the transmission. Temperatures predicted by Spherbean were within 3% of the corresponding measured values at 15 min elapsed time and within 9% at 25 min. Spherbean also indicates a potential for high bearing cage temperatures with misalignment and outer ring rotation.

  16. Enhancing active and passive remote sensing in the ocean using broadband acoustic transmissions and coherent hydrophone arrays

    NASA Astrophysics Data System (ADS)

    Tran, Duong Duy

    The statistics of broadband acoustic signal transmissions in a random continental shelf waveguide are characterized for the fully saturated regime. The probability distribution of broadband signal energies after saturated multi-path propagation is derived using coherence theory. The frequency components obtained from Fourier decomposition of a broadband signal are each assumed to be fully saturated, where the energy spectral density obeys the exponential distribution with 5.6 dB standard deviation and unity scintillation index. When the signal bandwidth and measurement time are respectively larger than the correlation bandwidth and correlation time of its energy spectral density components, the broadband signal energy obtained by integrating the energy spectral density across the signal bandwidth then follows the Gamma distribution with standard deviation smaller than 5.6 dB and scintillation index less than unity. The theory is verified with broadband transmissions in the Gulf of Maine shallow water waveguide in the 300-1200 Hz frequency range. The standard deviations of received broadband signal energies range from 2.7 to 4.6 dB for effective bandwidths up to 42 Hz, while the standard deviations of individual energy spectral density components are roughly 5.6 dB. The energy spectral density correlation bandwidths of the received broadband signals are found to be larger for signals with higher center frequency. Sperm whales in the New England continental shelf and slope were passively localized, in both range and bearing using a single low-frequency (< 2500 Hz), densely sampled, towed horizontal coherent hydrophone array system. Whale bearings were estimated using time-domain beamforming that provided high coherent array gain in sperm whale click signal-to-noise ratio. Whale ranges from the receiver array center were estimated using the moving array triangulation technique from a sequence of whale bearing measurements. The dive profile was estimated for a sperm

  17. Bending, longitudinal and torsional wave transmission on Euler-Bernoulli and Timoshenko beams with high propagation losses.

    PubMed

    Wang, X; Hopkins, C

    2016-10-01

    Advanced Statistical Energy Analysis (ASEA) is used to predict vibration transmission across coupled beams which support multiple wave types up to high frequencies where Timoshenko theory is valid. Bending-longitudinal and bending-torsional models are considered for an L-junction and rectangular beam frame. Comparisons are made with measurements, Finite Element Methods (FEM) and Statistical Energy Analysis (SEA). When beams support at least two local modes for each wave type in a frequency band and the modal overlap factor is at least 0.1, measurements and FEM have relatively smooth curves. Agreement between measurements, FEM, and ASEA demonstrates that ASEA is able to predict high propagation losses which are not accounted for with SEA. These propagation losses tend to become more important at high frequencies with relatively high internal loss factors and can occur when there is more than one wave type. At such high frequencies, Timoshenko theory, rather than Euler-Bernoulli theory, is often required. Timoshenko theory is incorporated in ASEA and SEA using wave theory transmission coefficients derived assuming Euler-Bernoulli theory, but using Timoshenko group velocity when calculating coupling loss factors. The changeover between theories is appropriate above the frequency where there is a 26% difference between Euler-Bernoulli and Timoshenko group velocities.

  18. Enhanced GABA Transmission Drives Bradykinesia Following Loss of Dopamine D2 Receptor Signaling.

    PubMed

    Lemos, Julia C; Friend, Danielle M; Kaplan, Alanna R; Shin, Jung Hoon; Rubinstein, Marcelo; Kravitz, Alexxai V; Alvarez, Veronica A

    2016-05-18

    Bradykinesia is a prominent phenotype of Parkinson's disease, depression, and other neurological conditions. Disruption of dopamine (DA) transmission plays an important role, but progress in understanding the exact mechanisms driving slowness of movement has been impeded due to the heterogeneity of DA receptor distribution on multiple cell types within the striatum. Here we show that selective deletion of DA D2 receptors (D2Rs) from indirect-pathway medium spiny neurons (iMSNs) is sufficient to impair locomotor activity, phenocopying DA depletion models of Parkinson's disease, despite this mouse model having intact DA transmission. There was a robust enhancement of GABAergic transmission and a reduction of in vivo firing in striatal and pallidal neurons. Mimicking D2R signaling in iMSNs with Gi-DREADDs restored the level of tonic GABAergic transmission and rescued the motor deficit. These findings indicate that DA, through D2R activation in iMSNs, regulates motor output by constraining the strength of GABAergic transmission.

  19. The development and evaluation of a method for understanding the impact of transmission loss on the overall noise attenuation of finite barriers

    NASA Astrophysics Data System (ADS)

    Upasani, Ashwin Arvind

    The purpose of this study is to evaluate the impact of transmission loss on the overall noise reduction obtained from finite barriers. The noise attenuation ability of barriers is understood to be a consequence of sound waves diffracting around their edges. Although the presence of transmission loss is acknowledged, its significance in affecting noise attenuation is usually not considered a priority in barrier design. This study incorporates the Fresnel Number concept for predicting theoretical insertion loss of a finite barrier and compares these predictions to experimental observations. The experiments performed in this study offer a method to isolate the transmission loss component from diffraction based noise attenuation. This isolation allows the comparison of these two factors in the overall barrier performance. The influence of transmission loss is found to be significant and the findings encourage its consideration in designing solutions to modern noise control challenges.

  20. Transmission Acoustic Vibration Testing.

    DTIC Science & Technology

    1985-07-01

    DRVENO Fiue6 xeimna eroCosScin HOUIN The baeiehuig(iue7 sasn odZ4Amgei umalycsigwihn 5 pud ro omciig h hosn isteoiihmcie.ndwih 0 ons h mahie catnosfte...tooth load, P is power, and the suL- scripts indicate reference level. These relationships reflect that doubling the speed, load or power increases...USAAVRACON-TR-83-D-34 UNCLASSIFIED D AAK5I92- - 82-CSSF/61/3 NL I0013EI sonl*.lf.~fmommmmoii-m NNNNNEl 1.8. 1111L2 111. NATION -W EUO TNAOS-16 *~)fl 11111

  1. Transmission

    SciTech Connect

    Sugano, K.

    1988-12-27

    A transmission is described which consists of: an input shaft; an output shaft; a first planetary gear set including a first sun gear selectively connectable by a first clutch to the input shaft, a first carrier selectively connectable by a second clutch to the input shaft and a first ring gear connected to the output shaft. The first sun gear selectively held stationary by a first brake, the first carrier is allowed to rotate in the same forward direction as the input shaft when the second clutch is engaged, but prevented from rotating in a reverse direction opposite to the forward direction by a first one-way clutch, the first carrier being selectively held stationary by a second brake; a second planetary gear set including a second sun gear connected to the input shaft, a second carrier connected to the first ring gear and also the the output shaft, and a second ring gear.

  2. Acoustic propagation under tidally driven, stratified flow.

    PubMed

    Finette, Steven; Oba, Roger; Shen, Colin; Evans, Thomas

    2007-05-01

    Amplitude and phase variability in acoustic fields are simulated within a canonical shelf-break ocean environment using sound speed distributions computed from hydrodynamics. The submesoscale description of the space and time varying environment is physically consistent with tidal forcing of stratified flows over variable bathymetry and includes the generation, evolution and propagation of internal tides and solibores. For selected time periods, two-dimensional acoustic transmission examples are presented for which signal gain degradation is computed between 200 and 500 Hz on vertical arrays positioned both on the shelf and beyond the shelf break. Decorrelation of the field is dominated by the phase contribution and occurs over 2-3 min, with significant recorrelation often noted for selected frequency subbands. Detection range is also determined in this frequency band. Azimuth-time variations in the acoustic field are illustrated for 100 Hz sources by extending the acoustic simulations to three spatial dimensions. The azimuthal and temporal structure of both the depth-averaged transmission loss and temporal correlation of the acoustic fields under different environmental conditions are considered. Depth-averaged transmission loss varies up to 4 dB, depending on a combination of source depth, location relative to the slope and tidally induced volumetric changes in the sound speed distribution.

  3. Mapping of valence energy losses via energy-filtered annular dark-field scanning transmission electron microscopy.

    PubMed

    Gu, Lin; Sigle, Wilfried; Koch, Christoph T; Nelayah, Jaysen; Srot, Vesna; van Aken, Peter A

    2009-08-01

    The advent of electron monochromators has opened new perspectives on electron energy-loss spectroscopy at low energy losses, including phenomena such as surface plasmon resonances or electron transitions from the valence to the conduction band. In this paper, we report first results making use of the combination of an energy filter and a post-filter annular dark-field detector. This instrumental design allows us to obtain energy-filtered (i.e. inelastic) annular dark-field images in scanning transmission electron microscopy of the 2-dimensional semiconductor band-gap distribution of a GaN/Al(45)Ga(55)N structure and of surface plasmon resonances of silver nanoprisms. In comparison to other approaches, the technique is less prone to inelastic delocalization and relativistic artefacts. The mixed contribution of elastic and inelastic contrast is discussed.

  4. Implementation of subcellular water mapping by electron energy loss spectroscopy in a medium-voltage scanning transmission electron microscope.

    PubMed

    Terryn, C; Michel, J; Thomas, X; Laurent-Maquin, D; Balossier, G

    2004-07-01

    The water concentration in biological cells plays a predominant role in cellular life. Using electron energy loss spectroscopy, the feasibility to measure the water content in cells has already been demonstrated. In this paper, we present an upgrade of water measurement in hydrated cryosections by spectrum imaging mode in a medium-voltage scanning transmission electron microscope. The electron energy loss spectra are recorded in spectrum imaging mode in a 2(n)x2(n) pixels array. Each spectrum is processed in order to determine the water mass content in the corresponding pixel. Then a parametric image is obtained in which grey levels are related to water concentration. In this image, it is possible to recognize the different subcellular compartments. By averaging the water concentration over the relevant pixels, we can determine the water mass content in the concerned subcellular compartment. As an example, we present water mass content measurement at subcellular level in rat hepatocytes.

  5. Acoustic metamaterials for sound mitigation

    NASA Astrophysics Data System (ADS)

    Assouar, Badreddine; Oudich, Mourad; Zhou, Xiaoming

    2016-05-01

    We provide theoretical and numerical analyses of the behavior of a plate-type acoustic metamaterial considered in an air-borne sound environment in view of sound mitigation application. Two configurations of plate are studied, a spring-mass one and a pillar system-based one. The acoustic performances of the considered systems are investigated with different approaches and show that a high sound transmission loss (STL) up to 82 dB is reached with a metamaterial plate with a thickness of 0.5 mm. The physical understanding of the acoustic behavior of the metamaterial partition is discussed based on both air-borne and structure-borne approaches. Confrontation between the STL, the band structure, the displacement fields and the effective mass density of the plate metamaterial is made to have a complete physical understanding of the different mechanisms involved.

  6. Multi-stage pulse tube cryocooler with acoustic impedance constructed to reduce transient cool down time and thermal loss

    NASA Technical Reports Server (NTRS)

    Gedeon, David R. (Inventor); Wilson, Kyle B. (Inventor)

    2008-01-01

    The cool down time for a multi-stage, pulse tube cryocooler is reduced by configuring at least a portion of the acoustic impedance of a selected stage, higher than the first stage, so that it surrounds the cold head of the selected stage. The surrounding acoustic impedance of the selected stage is mounted in thermally conductive connection to the warm region of the selected stage for cooling the acoustic impedance and is fabricated of a high thermal diffusivity, low thermal radiation emissivity material, preferably aluminum.

  7. Finite Element Development and Specifications of a Patched, Recessed Nomex Core Honeycomb Panel for Increased Sound Transmission Loss

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    2007-01-01

    This informal report summarizes the development and the design specifications of a recessed nomex core honeycomb panel in fulfillment of the deliverable in Task Order 13RBE, Revision 10, Subtask 17. The honeycomb panel, with 0.020-inch thick aluminum face sheets, has 0.016-inch thick aluminum patches applied to twenty-five, 6 by 6 inch, quarter inch thick recessed cores. A 10 dB higher transmission loss over the frequency range 250 - 1000 Hz was predicted by a MSC/NASTRAN finite element model when compared with the transmission loss of the base nomex core honeycomb panel. The static displacement, due to a unit force applied at either the core or recessed core area, was of the same order of magnitude as the static displacement of the base honeycomb panel when exposed to the same unit force. The mass of the new honeycomb design is 5.1% more than the base honeycomb panel. A physical model was constructed and is being tested.

  8. Morphological Correlates of Hearing Loss after Cochlear Implantation and Electro-Acoustic Stimulation in a Hearing-Impaired Guinea Pig Model

    PubMed Central

    Reiss, Lina A.J.; Stark, Gemaine; Nguyen-Huynh, Anh T.; Spear, Kayce A.; Zhang, Hongzheng; Tanaka, Chiemi; Li, Hongzhe

    2016-01-01

    Hybrid or electro-acoustic stimulation (EAS) cochlear implants (CIs) are designed to provide high-frequency electric hearing together with residual low-frequency acoustic hearing. However, 30-50% of EAS CI recipients lose residual hearing after implantation. The objective of this study was to determine the mechanisms of EAS-induced hearing loss in an animal model with high-frequency hearing loss. Guinea pigs were exposed to 24 hours of noise (12-24 kHz at 116 dB) to induce a high-frequency hearing loss. After recovery, two groups of animals were implanted (n=6 per group), with one group receiving chronic acoustic and electric stimulation for 10 weeks, and the other group receiving no stimulation during this time frame. A third group (n=6) was not implanted, but received chronic acoustic stimulation. Auditory brainstem responses were recorded biweekly to monitor changes in hearing. The organ of Corti was immunolabeled with phalloidin, anti-CtBP2, and anti-GluR2 to quantify hair cells, ribbons and post-synaptic receptors. The lateral wall was immunolabeled with phalloidin and lectin to quantify stria vascularis capillary diameters. Bimodal or trimodal diameter distributions were observed; the number and location of peaks were objectively determined using the Aikake Information Criterion and Expectation Maximization algorithm. Noise exposure led to immediate hearing loss at 16-32 kHz for all groups. Cochlear implantation led to additional hearing loss at 4-8 kHz; this hearing loss was negatively and positively correlated with minimum and maximum peaks of the bimodal or trimodal distributions of stria vascularis capillary diameters, respectively. After chronic stimulation, no significant group changes in thresholds were seen; however, elevated thresholds at 1 kHz in implanted, stimulated animals were significantly correlated with decreased presynaptic ribbon and postsynaptic receptor counts. Inner and outer hair cell counts did not differ between groups and were not

  9. Morphological correlates of hearing loss after cochlear implantation and electro-acoustic stimulation in a hearing-impaired Guinea pig model.

    PubMed

    Reiss, Lina A J; Stark, Gemaine; Nguyen-Huynh, Anh T; Spear, Kayce A; Zhang, Hongzheng; Tanaka, Chiemi; Li, Hongzhe

    2015-09-01

    Hybrid or electro-acoustic stimulation (EAS) cochlear implants (CIs) are designed to provide high-frequency electric hearing together with residual low-frequency acoustic hearing. However, 30-50% of EAS CI recipients lose residual hearing after implantation. The objective of this study was to determine the mechanisms of EAS-induced hearing loss in an animal model with high-frequency hearing loss. Guinea pigs were exposed to 24 h of noise (12-24 kHz at 116 dB) to induce a high-frequency hearing loss. After recovery, two groups of animals were implanted (n = 6 per group), with one group receiving chronic acoustic and electric stimulation for 10 weeks, and the other group receiving no stimulation during this time frame. A third group (n = 6) was not implanted, but received chronic acoustic stimulation. Auditory brainstem responses were recorded biweekly to monitor changes in hearing. The organ of Corti was immunolabeled with phalloidin, anti-CtBP2, and anti-GluR2 to quantify hair cells, ribbons and post-synaptic receptors. The lateral wall was immunolabeled with phalloidin and lectin to quantify stria vascularis capillary diameters. Bimodal or trimodal diameter distributions were observed; the number and location of peaks were objectively determined using the Aikake Information Criterion and Expectation Maximization algorithm. Noise exposure led to immediate hearing loss at 16-32 kHz for all groups. Cochlear implantation led to additional hearing loss at 4-8 kHz; this hearing loss was negatively and positively correlated with minimum and maximum peaks of the bimodal or trimodal distributions of stria vascularis capillary diameters, respectively. After chronic stimulation, no significant group changes in thresholds were seen; however, elevated thresholds at 1 kHz in implanted, stimulated animals were significantly correlated with decreased presynaptic ribbon and postsynaptic receptor counts. Inner and outer hair cell counts did not differ between groups and

  10. 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.

  11. 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.

  12. Loss of Predominant Shank3 Isoforms Results in Hippocampus-Dependent Impairments in Behavior and Synaptic Transmission

    PubMed Central

    Kouser, Mehreen; Speed, Haley E.; Dewey, Colleen M.; Reimers, Jeremy M.; Widman, Allie J.; Gupta, Natasha; Liu, Shunan; Jaramillo, Thomas C.; Bangash, Muhammad; Xiao, Bo; Worley, Paul F.

    2013-01-01

    The Shank3 gene encodes a scaffolding protein that anchors multiple elements of the postsynaptic density at the synapse. Previous attempts to delete the Shank3 gene have not resulted in a complete loss of the predominant naturally occurring Shank3 isoforms. We have now characterized a homozygous Shank3 mutation in mice that deletes exon 21, including the Homer binding domain. In the homozygous state, deletion of exon 21 results in loss of the major naturally occurring Shank3 protein bands detected by C-terminal and N-terminal antibodies, allowing us to more definitively examine the role of Shank3 in synaptic function and behavior. This loss of Shank3 leads to an increased localization of mGluR5 to both synaptosome and postsynaptic density-enriched fractions in the hippocampus. These mice exhibit a decrease in NMDA/AMPA excitatory postsynaptic current ratio in area CA1 of the hippocampus, reduced long-term potentiation in area CA1, and deficits in hippocampus-dependent spatial learning and memory. In addition, these mice also exhibit motor-coordination deficits, hypersensitivity to heat, novelty avoidance, altered locomotor response to novelty, and minimal social abnormalities. These data suggest that Shank3 isoforms are required for normal synaptic transmission/plasticity in the hippocampus, as well as hippocampus-dependent spatial learning and memory. PMID:24259569

  13. Low-loss light transmission in a rectangular-shaped hybrid metal trench at 1550 nm.

    PubMed

    Yang, Pengfei; Di, Zhigang; Xu, Hongxing

    2013-07-15

    A hybrid plasmonic waveguide consisting of a high-index dielectric core embedded inside a rectangular-shaped metallic trench is proposed and its guiding properties are investigated at the wavelength of 1550 nm. Numerical simulations based on the finite element method have demonstrated that the introduced dielectric core could greatly reduce the modal loss of the metal trench while maintaining strong confinement of light. The effects of dielectric core size, material of the cladding and the dielectric core on the modal properties have been systematically investigated. The proposed hybrid plasmonic structure can be realized employing fabrication techniques of the traditional metal trench waveguides and could be leveraged as important elements for highly-integrated photonic circuits.

  14. Sound isolation performance of interior acoustical sash

    NASA Astrophysics Data System (ADS)

    Tocci, Gregory

    2002-05-01

    In existing, as well as new buildings, an interior light of glass mounted on the inside of a prime window is used to improve the sound transmission loss otherwise obtained by the prime window alone. Interior acoustical sash is most often 1/4 in. (6 mm) monolithic or laminated glass, and is typically spaced 3 in. to 6 in. from the glass of the prime window. This paper presents TL data measured at Riverbank Acoustical Laboratories by Solutia (formerly Monsanto) for lightweight prime windows of various types, with and without interior acoustical sash glazed with 1/4 in. laminated glass. The TL data are used to estimate the A-weighted insertion loss of interior acoustical sash when applied to prime windows glazed with lightweight glass for four transportation noise source types-highway traffic, aircraft, electric rail, and diesel rail. The analysis also has been extended to determine the insertion loss expressed as a change in OITC. The data also exhibit the reductions in insertion loss that can result from short-circuiting the interior acoustical sash with the prime window. [Work supported by Solutia, Inc.

  15. Synaptic Transmission from Horizontal Cells to Cones Is Impaired by Loss of Connexin Hemichannels

    PubMed Central

    Klaassen, Lauw J.; Sun, Ziyi; Steijaert, Marvin N.; Bolte, Petra; Fahrenfort, Iris; Sjoerdsma, Trijntje; Klooster, Jan; Claassen, Yvonne; Shields, Colleen R.; Ten Eikelder, Huub M. M.; Janssen-Bienhold, Ulrike; Zoidl, Georg; McMahon, Douglas G.; Kamermans, Maarten

    2011-01-01

    long-standing debate about the unusual form of (ephaptic) synaptic transmission between horizontal cells and cones in the vertebrate retina. PMID:21811399

  16. High-energy-resolution monochromator for aberration-corrected scanning transmission electron microscopy/electron energy-loss spectroscopy.

    PubMed

    Krivanek, Ondrej L; Ursin, Jonathan P; Bacon, Neil J; Corbin, George J; Dellby, Niklas; Hrncirik, Petr; Murfitt, Matthew F; Own, Christopher S; Szilagyi, Zoltan S

    2009-09-28

    An all-magnetic monochromator/spectrometer system for sub-30 meV energy-resolution electron energy-loss spectroscopy in the scanning transmission electron microscope is described. It will link the energy being selected by the monochromator to the energy being analysed by the spectrometer, without resorting to decelerating the electron beam. This will allow it to attain spectral energy stability comparable to systems using monochromators and spectrometers that are raised to near the high voltage of the instrument. It will also be able to correct the chromatic aberration of the probe-forming column. It should be able to provide variable energy resolution down to approximately 10 meV and spatial resolution less than 1 A.

  17. Sound transmission loss through metamaterial plate with lateral local resonators in the presence of external mean flow.

    PubMed

    Wang, Ting; Sheng, Meiping; Qin, Qinghua

    2017-02-01

    In the context of sound incident upon a metamaterial plate, explicit formulas for sound transmission loss (STL) are derived in the presence of external mean flow. Metamaterial plate, consisting of homogeneous plate and lateral local resonators (LLRs), is homogenized by using effective medium method to obtain the effective mass density and facilitate the calculation of STL. Results show that (a) vigorously oscillating LLRs lead to higher STL compared with bare plate, (b) increasing Mach number of the external mean flow helps obtain higher STL below the coincidence frequency but decreases STL above the coincidence frequency due to the added mass effect of light fluid loading and aerodynamic damping effect, (c) the coincidence frequency shifts to higher frequency range for the refracted effect of the external mean flow. However, effects of the flow on STL within negative mass density range can be neglected because of the lateral local resonance occurring. Moreover, hysteretic damping from metamaterial can only smooth the transmission curves by lowering higher peaks and filling dips. Effects of incident angles on STL are also examined. It is demonstrated that increasing elevation angle can improve the sound insulation, while the azimuth angle does not.

  18. Coupled Ocean-Acoustic Prediction of Transmission Loss in a Continental Shelfbreak Region: Predictive Skill, Uncertainty Quantification and Dynamical Sensitivities

    DTIC Science & Technology

    2010-01-01

    DRAFT 21 Pierre F.J. Lermusiaux received B.&M. in Mech. Eng. degrees (highest honors and Jurybs congratulations) from Liege University, Liege , Belgium...awarded a Doherty Associate Professorship in Ocean Utilization by MIT in 2009. He is a member of the Association of Engineers of Liege University...Friends of the University of Liege , Royal Meteorological Society, American Geophysical Union, Oceanography Society, American Association for the

  19. Acoustic Propagation Loss Predictions for a Site on the Bermuda Rise at Low and Very Low Frequencies

    DTIC Science & Technology

    1992-06-01

    Specialized Conference, edited by A. Lara, C. Ranz and C. Carbo (Consejo Superior de Investigaciones Cientificas , Madrid, 1987). 2. R. E. Christensen, J. A...Conference, edited by A. Lara, C. Ranz and C. Carbo (Con- sejo Superior de Investigaciones Cientificas , Madrid, 1987). 16. E. L. Hamilton, "Geo-acoustic

  20. Studies of the acoustic transmission characteristics of coaxial nozzles with inverted velocity profiles, volume 1. [jet engine noise radiation through coannular exhaust nozzles

    NASA Technical Reports Server (NTRS)

    Dean, P. D.; Salikuddin, M.; Ahuja, K. K.; Plumblee, H. E.; Mungur, P.

    1979-01-01

    The efficiency of internal noise radiation through coannular exhaust nozzle with an inverted velocity profile was studied. A preliminary investigation was first undertaken to: (1) define the test parameters which influence the internal noise radiation; (2) develop a test methodology which could realistically be used to examine the effects of the test parameters; (3) and to validate this methodology. The result was the choice of an acoustic impulse as the internal noise source in the in the jet nozzles. Noise transmission characteristics of a nozzle system were then investigated. In particular, the effects of fan nozzle convergence angle, core extention length to annulus height ratio, and flow Mach number and temperatures were studied. The results are presented as normalized directivity plots.

  1. 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.

  2. Broadband acoustic properties of a murine skull

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  3. The influence of oceanic internal waves on the phase stability of broadband acoustic transmission at long range

    NASA Astrophysics Data System (ADS)

    Viechnicki, John Thomas

    1999-12-01

    Instantaneous phase stability in acoustic wavefields measured during the 1994 Acoustic Engineering Test (AET) is examined. AET is one of several preliminary Acoustic Thermometry of Ocean Climate (ATOC) experiments conducted in the past several years. Internal waves are assumed to be the mechanism responsible for phase decorrelation over time scales of ten to thirty minutes. The AET experiment had a center frequency of 75 Hz and a 3 megameter path length. Comparison of numerical simulations to experimental results provide insight into how internal waves scatter sound and can be used to constrain statistical descriptors of realistic deep ocean internal wave fields. Ray-based wavefield simulations are performed using both Deterministic Ray Theory (DRT) and Stochastic Ray Theory (SRT), while full wave simulations are performed using the co insensitive parabolic equation model. This work complements recent similar inference studies of Colosi et al. (1994) and Heaney (1997) on other preliminary ATOC experiments. Working within the framework of the Garrett- Munk internal wave spectrum, phase coherence time, which was observed to be roughly ten to fifteen minutes in the AET experiment, is found to be dependent on the vertically integrated potential energy density, ɛ, and the bounds on the horizontal wavenumber spectrum, k min and kmax. Results suggest that phase coherence is insensitive to mode number cutoff, jmax . Two manifestations of the phase decorrelation observed in simulations are studied. Temporal wavefront wander as defined by Flatté et al. (1979) is examined over the decorrelation period as a function of the horizontal wavenumber spectrum. Intermittent structure that appears and disappears throughout the wavefront on time scales of ten to thirty minutes is examined. This intermittent structure is observed in both full wave modeling and DRT but not SRT.

  4. Acoustical and anatomical determination of sound production and transmission in West Indian (Trichechus manatus) and Amazonian (T. inunguis) manatees.

    PubMed

    Landrau-Giovannetti, Nelmarie; Mignucci-Giannoni, Antonio A; Reidenberg, Joy S

    2014-10-01

    West Indian (Trichechus manatus) and Amazonian (T. inunguis) manatees are vocal mammals, with most sounds produced for communication between mothers and calves. While their hearing and vocalizations have been well studied, the actual mechanism of sound production is unknown. Acoustical recordings and anatomical examination were used to determine the source of sound generation. Recordings were performed on live captive manatees from Puerto Rico, Cuba and Colombia (T. manatus) and from Peru (T. inunguis) to determine focal points of sound production. The manatees were recorded using two directional hydrophones placed on the throat and nasal region and an Edirol-R44 digital recorder. The average sound intensity level was analyzed to evaluate the sound source with a T test: paired two sample for means. Anatomical examinations were conducted on six T. manatus carcasses from Florida and Puerto Rico. During necropsies, the larynx, trachea, and nasal areas were dissected, with particular focus on identifying musculature and soft tissues capable of vibrating or constricting the airway. From the recordings we found that the acoustical intensity was significant (P < 0.0001) for both the individuals and the pooled manatees in the ventral throat region compared to the nasal region. From the dissection we found two raised areas of tissue in the lateral walls of the manatee's laryngeal lumen that are consistent with mammalian vocal folds. They oppose each other and may be able to regulate airflow between them when they are adducted or abducted by muscular control of arytenoid cartilages. Acoustic and anatomical evidence taken together suggest vocal folds as the mechanism for sound production in manatees.

  5. Acoustic Optimization of Automotive Exhaust Heat Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Su, C. Q.; Ye, B. Q.; Guo, X.; Hui, P.

    2012-06-01

    The potential for thermoelectric exhaust heat recovery in vehicles has been increasing with recent advances in the efficiency of thermoelectric generators (TEGs). This study analyzes the acoustic attenuation performance of exhaust-based TEGs. The acoustic characteristics of two different thermal designs of exhaust gas heat exchanger in TEGs are discussed in terms of transmission loss and acoustic insertion loss. GT-Power simulations and bench tests on a dynamometer with a high-performance production engine are carried out. Results indicate that the acoustic attenuation of TEGs could be determined and optimized. In addition, the feasibility of integration of exhaust-based TEGs and engine mufflers into the exhaust line is tested, which can help to reduce space and improve vehicle integration.

  6. Conditions for reflection and transmission of an ion acoustic soliton in a dusty plasma with variable charge dust

    SciTech Connect

    Malik, Hitendra K.; Tomar, Renu; Dahiya, Raj P.

    2014-07-15

    Modified Korteweg-de Vries (mKdV) equations are derived for the incident, reflected, and transmitted waves in order to examine the soliton reflection and its transmission through an inhomogeneous plasma comprising ions, dust grains with fluctuating charge and two types of electrons, namely nonisothermal electrons and isothermal electrons. All the mKdV equations are coupled at the point of reflection and solved for the reflected soliton. Unlike others, a relation is established between the velocity shifts of the incident, reflected and transmitted solitons, and based on a critical value of the shift of incident soliton the strengths of the soliton reflection and transmission are talked about. Conditions are obtained for the soliton reflection and its transmission, and a comparative study is made for the two cases of fixed and fluctuating charges on the dust grains.

  7. Geant4 Monte Carlo simulation of energy loss and transmission and ranges for electrons, protons and ions

    NASA Astrophysics Data System (ADS)

    Ivantchenko, Vladimir

    Geant4 is a toolkit for Monte Carlo simulation of particle transport originally developed for applications in high-energy physics with the focus on experiments at the Large Hadron Collider (CERN, Geneva). The transparency and flexibility of the code has spread its use to other fields of research, e.g. radiotherapy and space science. The tool provides possibility to simulate complex geometry, transportation in electric and magnetic fields and variety of physics models of interaction of particles with media. Geant4 has been used for simulation of radiation effects for number of space missions. Recent upgrades of the toolkit released in December 2009 include new model for ion electronic stopping power based on the revised version of ICRU'73 Report increasing accuracy of simulation of ion transport. In the current work we present the status of Geant4 electromagnetic package for simulation of particle energy loss, ranges and transmission. This has a direct implication for simulation of ground testing setups at existing European facilities and for simulation of radiation effects in space. A number of improvements were introduced for electron and proton transport, followed by a thorough validation. It was the aim of the present study to validate the range against reference data from the United States National Institute of Standards and Technologies (NIST) ESTAR, PSTAR and ASTAR databases. We compared Geant4 and NIST ranges of electrons using different Geant4 models. The best agreement was found for Penelope, except at very low energies in heavy materials, where the Standard package gave better results. Geant4 proton ranges in water agreed with NIST within 1 The validation of the new ion model is performed against recent data on Bragg peak position in water. The data from transmission of carbon ions via various absorbers following Bragg peak in water demonstrate that the new Geant4 model significantly improves precision of ion range. The absolute accuracy of ion range

  8. 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.

  9. Acoustic characteristics and the design of two-layered soundproof plates

    NASA Astrophysics Data System (ADS)

    Chonan, S.; Kugo, Y.

    1989-03-01

    This paper presents exact solutions for the coincidence frequency and the sound transmission loss of two-layered infinite plates excited by a plane acoustic wave. The problem is studied based on the two-dimensional elasticity theory wih the use of the Lame potential functions . A simple design method for a soundproof sheet with high transmission loss and high coincidence frequency is presented and illustrated with some examples. The results obtained are also compared with those from the thick plate theory.

  10. Channel Transmission Loss Studies During Ephemeral Flow Events: ER-5-3 Channel and Cambric Ditch, Nevada Test Site, Nye County, Nevada

    SciTech Connect

    J.J. Miller; S.A. Mizell; R.H. French; D.G. Meadows; M.H. Young

    2005-10-01

    Transmission losses along ephemeral channels are an important, yet poorly understood, aspect of rainfall-runoff prediction. Losses occur as flow infiltrates channel bed, banks, and floodplains. Estimating transmission losses in arid environments is difficult because of the variability of surficial geomorphic characteristics and infiltration capacities of soils and near-surface low-permeability geologic layers (e.g., calcrete). Transmission losses in ephemeral channels are nonlinear functions of discharge and time (Lane, 1972), and vary spatially along the channel reach and with soil antecedent moisture conditions (Sharma and Murthy, 1994). Rainfall-runoff models used to estimate peak discharge and runoff volume for flood hazard assessment are not designed specifically for ephemeral channels, where transmission loss can be significant because of the available storage volume in channel soils. Accuracy of the flow routing and rainfall-runoff models is dependent on the transmission loss estimate. Transmission loss rate is the most uncertain parameter in flow routing through ephemeral channels. This research, sponsored by the U.S. Department of Energy, National Nuclear Security Administration (DOE/NNSA) and conducted at the Nevada Test Site (NTS), is designed to improve understanding of the impact of transmission loss on ephemeral flood modeling and compare various methodologies for predicting runoff from rainfall events. Various applications of this research to DOE projects include more site-specific accuracy in runoff prediction; possible reduction in size of flood mitigation structures at the NTS; and a better understanding of expected infiltration from runoff losses into landfill covers. Two channel transmission loss field experiments were performed on the NTS between 2001 and 2003: the first was conducted in the ER-5-3 channel (Miller et al., 2003), between March and June 2001, and the second was conducted in the Cambric Ditch (Mizell et al., 2005), between April

  11. Hybrid Dielectric-loaded Nanoridge Plasmonic Waveguide for Low-Loss Light Transmission at the Subwavelength Scale

    NASA Astrophysics Data System (ADS)

    Zhang, Bin; Bian, Yusheng; Ren, Liqiang; Guo, Feng; Tang, Shi-Yang; Mao, Zhangming; Liu, Xiaomin; Sun, Jinju; Gong, Jianying; Guo, Xiasheng; Huang, Tony Jun

    2017-01-01

    The emerging development of the hybrid plasmonic waveguide has recently received significant attention owing to its remarkable capability of enabling subwavelength field confinement and great transmission distance. Here we report a guiding approach that integrates hybrid plasmon polariton with dielectric-loaded plasmonic waveguiding. By introducing a deep-subwavelength dielectric ridge between a dielectric slab and a metallic substrate, a hybrid dielectric-loaded nanoridge plasmonic waveguide is formed. The waveguide features lower propagation loss than its conventional hybrid waveguiding counterpart, while maintaining strong optical confinement at telecommunication wavelengths. Through systematic structural parameter tuning, we realize an efficient balance between confinement and attenuation of the fundamental hybrid mode, and we demonstrate the tolerance of its properties despite fabrication imperfections. Furthermore, we show that the waveguide concept can be extended to other metal/dielectric composites as well, including metal-insulator-metal and insulator-metal-insulator configurations. Our hybrid dielectric-loaded nanoridge plasmonic platform may serve as a fundamental building block for various functional photonic components and be used in applications such as sensing, nanofocusing, and nanolasing.

  12. Hybrid Dielectric-loaded Nanoridge Plasmonic Waveguide for Low-Loss Light Transmission at the Subwavelength Scale

    PubMed Central

    Zhang, Bin; Bian, Yusheng; Ren, Liqiang; Guo, Feng; Tang, Shi-Yang; Mao, Zhangming; Liu, Xiaomin; Sun, Jinju; Gong, Jianying; Guo, Xiasheng; Huang, Tony Jun

    2017-01-01

    The emerging development of the hybrid plasmonic waveguide has recently received significant attention owing to its remarkable capability of enabling subwavelength field confinement and great transmission distance. Here we report a guiding approach that integrates hybrid plasmon polariton with dielectric-loaded plasmonic waveguiding. By introducing a deep-subwavelength dielectric ridge between a dielectric slab and a metallic substrate, a hybrid dielectric-loaded nanoridge plasmonic waveguide is formed. The waveguide features lower propagation loss than its conventional hybrid waveguiding counterpart, while maintaining strong optical confinement at telecommunication wavelengths. Through systematic structural parameter tuning, we realize an efficient balance between confinement and attenuation of the fundamental hybrid mode, and we demonstrate the tolerance of its properties despite fabrication imperfections. Furthermore, we show that the waveguide concept can be extended to other metal/dielectric composites as well, including metal-insulator-metal and insulator-metal-insulator configurations. Our hybrid dielectric-loaded nanoridge plasmonic platform may serve as a fundamental building block for various functional photonic components and be used in applications such as sensing, nanofocusing, and nanolasing. PMID:28091583

  13. Hybrid Dielectric-loaded Nanoridge Plasmonic Waveguide for Low-Loss Light Transmission at the Subwavelength Scale.

    PubMed

    Zhang, Bin; Bian, Yusheng; Ren, Liqiang; Guo, Feng; Tang, Shi-Yang; Mao, Zhangming; Liu, Xiaomin; Sun, Jinju; Gong, Jianying; Guo, Xiasheng; Huang, Tony Jun

    2017-01-16

    The emerging development of the hybrid plasmonic waveguide has recently received significant attention owing to its remarkable capability of enabling subwavelength field confinement and great transmission distance. Here we report a guiding approach that integrates hybrid plasmon polariton with dielectric-loaded plasmonic waveguiding. By introducing a deep-subwavelength dielectric ridge between a dielectric slab and a metallic substrate, a hybrid dielectric-loaded nanoridge plasmonic waveguide is formed. The waveguide features lower propagation loss than its conventional hybrid waveguiding counterpart, while maintaining strong optical confinement at telecommunication wavelengths. Through systematic structural parameter tuning, we realize an efficient balance between confinement and attenuation of the fundamental hybrid mode, and we demonstrate the tolerance of its properties despite fabrication imperfections. Furthermore, we show that the waveguide concept can be extended to other metal/dielectric composites as well, including metal-insulator-metal and insulator-metal-insulator configurations. Our hybrid dielectric-loaded nanoridge plasmonic platform may serve as a fundamental building block for various functional photonic components and be used in applications such as sensing, nanofocusing, and nanolasing.

  14. Measurement of vibrational spectrum of liquid using monochromated scanning transmission electron microscopy-electron energy loss spectroscopy.

    PubMed

    Miyata, Tomohiro; Fukuyama, Mao; Hibara, Akihide; Okunishi, Eiji; Mukai, Masaki; Mizoguchi, Teruyasu

    2014-10-01

    Investigations on the dynamic behavior of molecules in liquids at high spatial resolution are greatly desired because localized regions, such as solid-liquid interfaces or sites of reacting molecules, have assumed increasing importance with respect to improving material performance. In application to liquids, electron energy loss spectroscopy (EELS) observed with transmission electron microscopy (TEM) is a promising analytical technique with the appropriate resolutions. In this study, we obtained EELS spectra from an ionic liquid, 1-ethyl-3-methylimidazolium bis (trifluoromethyl-sulfonyl) imide (C2mim-TFSI), chosen as the sampled liquid, using monochromated scanning TEM (STEM). The molecular vibrational spectrum and the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap of the liquid were investigated. The HOMO-LUMO gap measurement coincided with that obtained from the ultraviolet-visible spectrum. A shoulder in the spectrum observed ∼0.4 eV is believed to originate from the molecular vibration. From a separately performed infrared observation and first-principles calculations, we found that this shoulder coincided with the vibrational peak attributed to the C-H stretching vibration of the [C2mim(+)] cation. This study demonstrates that a vibrational peak for a liquid can be observed using monochromated STEM-EELS, and leads one to expect observations of chemical reactions or aids in the analysis of the dynamic behavior of molecules in liquid.

  15. Effect of Coversheet Materials on the Acoustic Performance of Melamine Foam

    NASA Technical Reports Server (NTRS)

    McNelis, Anne M.; Hughes, William O.

    2015-01-01

    Melamine foam is a highly absorptive material that is often used inside the payload fairing walls of a launch vehicle. This foam reduces the acoustic excitation environment that the spacecraft experiences during launch. Often, the melamine foam is enclosed by thin coversheet materials for contamination protection, thermal protection, and electrostatic discharge control. Previous limited acoustic testing by NASA Glenn Research Center has shown that the presence of a coversheet material on the melamine foam can have a significant impact on the absorption coefficient and the transmission loss. As a result of this preliminary finding a more extensive acoustic test program using several different coversheet materials on melamine foam was performed. Those test results are summarized in this paper. Additionally, a method is provided to use the acoustic absorption and transmission loss data obtained from panel level testing to predict their combined effect for the noise reduction of a launch vehicle payload fairing.

  16. Development and Application of a Three-dimensional Seismo-acoustic Coupled-mode Model

    DTIC Science & Technology

    2014-09-30

    of coral reef fish need to locate a reef , and sound emanating from reefs may act as a cue to guide them. Using acoustic data collected from Bahia...Almirante on the north coast of Panama, this study examines the distances from potential settlement sites for which reef sounds can be detected by reef ...fish larvae. Maps of signal excess are created using source levels measured at the reef , transmission loss calculated with range-dependent acoustic

  17. The room acoustic rendering equation.

    PubMed

    Siltanen, Samuel; Lokki, Tapio; Kiminki, Sami; Savioja, Lauri

    2007-09-01

    An integral equation generalizing a variety of known geometrical room acoustics modeling algorithms is presented. The formulation of the room acoustic rendering equation is adopted from computer graphics. Based on the room acoustic rendering equation, an acoustic radiance transfer method, which can handle both diffuse and nondiffuse reflections, is derived. In a case study, the method is used to predict several acoustic parameters of a room model. The results are compared to measured data of the actual room and to the results given by other acoustics prediction software. It is concluded that the method can predict most acoustic parameters reliably and provides results as accurate as current commercial room acoustic prediction software. Although the presented acoustic radiance transfer method relies on geometrical acoustics, it can be extended to model diffraction and transmission through materials in future.

  18. Aeroelastic structural acoustic control.

    PubMed

    Clark, R L; Frampton, K D

    1999-02-01

    Static, constant-gain, output-feedback control compensators were designed to increase the transmission loss across a panel subjected to mean flow on one surface and a stationary, acoustic half-space on the opposite surface. The multi-input, multi-output control system was based upon the use of an array of colocated transducer pairs. The performance of the static-gain, output-feedback controller was compared to that of the full state-feedback controller using the same control actuator arrays, and was found to yield comparable levels of performance for practical limitations on control effort. Additionally, the resulting static compensators proved to be dissipative in nature, and thus the design varied little as a function of the aeroelastic coupling induced by the fluid-structure interaction under subsonic flow conditions. Several parametric studies were performed, comparing the effects of control-effort penalty as well as the number of transducer pairs used in the control system.

  19. Quantifying loss of acoustic communication space for right whales in and around a U.S. National Marine Sanctuary.

    PubMed

    Hatch, Leila T; Clark, Christopher W; Van Parijs, Sofie M; Frankel, Adam S; Ponirakis, Dimitri W

    2012-12-01

    The effects of chronic exposure to increasing levels of human-induced underwater noise on marine animal populations reliant on sound for communication are poorly understood. We sought to further develop methods of quantifying the effects of communication masking associated with human-induced sound on contact-calling North Atlantic right whales (Eubalaena glacialis) in an ecologically relevant area (~10,000 km(2) ) and time period (peak feeding time). We used an array of temporary, bottom-mounted, autonomous acoustic recorders in the Stellwagen Bank National Marine Sanctuary to monitor ambient noise levels, measure levels of sound associated with vessels, and detect and locate calling whales. We related wind speed, as recorded by regional oceanographic buoys, to ambient noise levels. We used vessel-tracking data from the Automatic Identification System to quantify acoustic signatures of large commercial vessels. On the basis of these integrated sound fields, median signal excess (the difference between the signal-to-noise ratio and the assumed recognition differential) for contact-calling right whales was negative (-1 dB) under current ambient noise levels and was further reduced (-2 dB) by the addition of noise from ships. Compared with potential communication space available under historically lower noise conditions, calling right whales may have lost, on average, 63-67% of their communication space. One or more of the 89 calling whales in the study area was exposed to noise levels ≥120 dB re 1 μPa by ships for 20% of the month, and a maximum of 11 whales were exposed to noise at or above this level during a single 10-min period. These results highlight the limitations of exposure-threshold (i.e., dose-response) metrics for assessing chronic anthropogenic noise effects on communication opportunities. Our methods can be used to integrate chronic and wide-ranging noise effects in emerging ocean-planning forums that seek to improve management of cumulative effects

  20. Influence of viscosity on the reflection and transmission of an acoustic wave by a periodic array of screens. The general 3-D problem

    PubMed Central

    Homentcovschi, Dorel; Miles, Ronald N.

    2008-01-01

    An analysis is presented of the diffraction of a pressure wave by a periodic grating including the influence of the air viscosity. The direction of the incoming pressure wave is arbitrary. As opposed to the classical nonviscous case, the problem cannot be reduced to a plane problem having a definite 3-D character. The system of partial differential equations used for solving the problem consists of the compressible Navier-Stokes equations associated with no-slip boundary conditions on solid surfaces. The problem is reduced to a system of two hypersingular integral equations for determining the velocity components in the slits’ plane and a hypersingular integral equation for the normal component of velocity. These equations are solved by using Galerkin’s method with some special trial functions. The results can be applied in designing protective screens for miniature microphones realized in MEMS technology. In this case, the physical dimensions of the device are on the order of the viscous boundary layer so that the viscosity cannot be neglected. The analysis indicates that the openings in the screen should be on the order of 10 microns in order to avoid excessive attenuation of the signal. This paper also provides the variation of the transmission coefficient with frequency in the acoustical domain. PMID:19122753

  1. PRSEUS Acoustic Panel Fabrication

    NASA Technical Reports Server (NTRS)

    Nicolette, Velicki; Yovanof, Nicolette P.; Baraja, Jaime; Mathur, Gopal; Thrash, Patrick; Pickell, Robert

    2011-01-01

    This report describes the development of a novel structural concept, Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS), that addresses the demanding fuselage loading requirements for the Hybrid Wing or Blended Wing Body (BWB) airplane configuration with regards to acoustic response. A PRSEUS panel was designed and fabricated and provided to NASA-LaRC for acoustic response testing in the Structural Acoustics Loads and Transmission (SALT) facility). Preliminary assessments of the sound transmission characteristics of a PRSEUS panel subjected to a representative Hybrid Wing Body (HWB) operating environment were completed for the NASA Environmentally Responsible Aviation (ERA) Program.

  2. Low-Frequency Acoustic Propagation Loss in the Arctic Ocean: Results of the Arctic Climate Observations using Underwater Sound Experiment

    DTIC Science & Technology

    2004-03-05

    experiment on the Turpan-SIMI path, but much smaller than those measured on the Turpan- Narwhal path which was almost coincident with the 1000-km section of...the ACOUS path from the Nansen Basin to the Lincoln Sea. The integral propagation loss on the path to Narwhal was about 30 dB for mode 1 and 10-13 dB

  3. Scaling of membrane-type locally resonant acoustic metamaterial arrays.

    PubMed

    Naify, Christina J; Chang, Chia-Ming; McKnight, Geoffrey; Nutt, Steven R

    2012-10-01

    Metamaterials have emerged as promising solutions for manipulation of sound waves in a variety of applications. Locally resonant acoustic materials (LRAM) decrease sound transmission by 500% over acoustic mass law predictions at peak transmission loss (TL) frequencies with minimal added mass, making them appealing for weight-critical applications such as aerospace structures. In this study, potential issues associated with scale-up of the structure are addressed. TL of single-celled and multi-celled LRAM was measured using an impedance tube setup with systematic variation in geometric parameters to understand the effects of each parameter on acoustic response. Finite element analysis was performed to predict TL as a function of frequency for structures with varying complexity, including stacked structures and multi-celled arrays. Dynamic response of the array structures under discrete frequency excitation was investigated using laser vibrometry to verify negative dynamic mass behavior.

  4. Preparation and transmission loss of the nano-crystal and polymer composite Bi4Ti3O12/PEK-c films

    NASA Astrophysics Data System (ADS)

    Yang, Hongliang; Ji, Wei; Ren, Quan; Zhang, Fujun; Wang, Xinqiang; Zhang, Guanghui

    2008-11-01

    Bismuth titanate, Bi4Ti3O12 (BTO), is a typical ferroelectric material with useful properties for optical memory, piezoelectric and electro-optic devices. Its nano-crystals were compounded by the chemical solution decomposition (CSD) technique. The structure and size of BTO were analyzed by X-ray diffraction (XRD) and transmissive electron microscopy (TEM). Three sorts of composite films BTO/PEK-c with different BTO concentration were prepared by spin-coating method at certain conditions. In this article, the scattering losses in thin films were obtained using the photographic technique. The losses in the films with different BTO weight ratios were compared and analyzed.

  5. High extinction ratio and low transmission loss thin-film terahertz polarizer with a tunable bilayer metal wire-grid structure.

    PubMed

    Huang, Zhe; Parrott, Edward P J; Park, Hongkyu; Chan, Hau Ping; Pickwell-MacPherson, Emma

    2014-02-15

    A thin-film terahertz polarizer is proposed and realized via a tunable bilayer metal wire-grid structure to achieve high extinction ratios and good transmission. The polarizer is fabricated on top of a thin silica layer by standard micro-fabrication techniques to eliminate the multireflection effects. The tunable alignment of the bilayer aluminum-wire grid structure enables tailoring of the extinction ratio and transmission characteristics. Using terahertz time-domain spectroscopy (THz-TDS), a fabricated polarizer is characterized, with extinction ratios greater than 50 dB and transmission losses below 1 dB reported in the 0.2-1.1 THz frequency range. These characteristics can be improved by further tuning the polarizer parameters such as the pitch, metal film thickness, and lateral displacement.

  6. In Situ Environmental Cell-Transmission Electron Microscopy Study of Microbial Reduction of Chromium(VI) Using Electron Energy Loss Spectroscopy.

    PubMed

    Daulton, Tyrone L.; Little, Brenda J.; Lowe, Kristine; Jones-Meehan, Joanne

    2001-11-01

    Reduction of Cr(VI) by the bacterium, Shewanella oneidensis (previously classified Shewanella putrefaciens strain MR-1), was studied by absorption spectrophotometry and in situ, environmental cell-transmission electron microscopy (EC-TEM) coupled with electron energy loss spectroscopy (EELS). Bacteria from rinsed cultures were placed directly in the environmental cell of the transmission electron microscope and examined under 100 Torr pressure. Bright field EC-TEM images show two distinct populations of S. oneidensis in incubated cultures containing Cr(VI)O2- 4: those that exhibit low image contrast and heavily precipitate-encrusted cells exhibiting high image contrast. Several EELS techniques were applied to determine the oxidation state of Cr associated with encrusted cells. The encrusted cells are shown to contain a reduced form of Cr in oxidation state +3 or lower. These results demonstrate the capability to determine the chemistry and valence state of reduction products associated with unfixed, hydrated bacteria in an environmental cell transmission electron microscope.

  7. 5-{mu}m-wide YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} coplanar line with low transmission loss

    SciTech Connect

    Hattori, W.; Yoshitake, T.; Tahara, S.

    1997-06-01

    Narrow and low-loss YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) transmission lines for use in multichip modules have been attempted to be developed. 18-cm-long YBCO coplanar transmission lines with widths down to 5 {mu}m were prepared by a composite patterning process combining Ar-ion milling and wet-etching. The transmission losses of the packaged 5-, 10-, and 25-{mu}m-wide lines, respectively, were {minus}1.57, {minus}0.85, and {minus}0.55 dB at 20 GHz and 55 K. These values provide similar surface resistances of 0.59{endash}0.80 m{Omega} at 20 GHz and 55 K. This indicates successful fabrication of a 5-{mu}m-wide YBCO coplanar line without notable extrinsic loss increase resulting from process damage. The attenuation constants of these lines are approximately two orders of magnitude lower than for 10-{mu}m-wide Cu microstrip lines. These results show that the YBCO coplanar lines with widths down to 5 {mu}m have great potential for use in multi-chip modules. {copyright} {ital 1997 American Institute of Physics.}

  8. Seabed acoustics of a sand ridge on the New Jersey continental shelf.

    PubMed

    Knobles, D P; Wilson, P S; Goff, J A; Cho, S E

    2008-09-01

    Acoustic measurements were made on a sand ridge on the New Jersey continental shelf. Data collected on two L arrays separated by 20 km from a single multi-frequency tow suggest small horizontal environmental variability. Values for the sound speed structure of the seabed are extracted by first applying a geo-acoustic inversion method to broadband and narrowband acoustic data from short-range sources. Then, a parabolic equation algorithm is used to properly include the bathymetry and sub-bottom layering. Finally, the frequency dependence of the seabed attenuation is inferred by optimizing the model fit to long-range transmission loss data in the 50-3000 Hz band.

  9. Acoustic characteristics of the clothes used for a wearable recording device.

    PubMed

    VanDam, Mark

    2014-10-01

    There has been increasing attention in the literature to wearable acoustic recording devices, particularly to examine naturalistic speech in disordered and child populations. Recordings are typically analyzed using automatic procedures that critically depend on the reliability of the collected signal. This work describes the acoustic amplitude response characteristics and the possibility of acoustic transmission loss using several shirts designed for wearable recorders. No difference was observed between the response characteristics of different shirt types or between shirts and the bare-microphone condition. Results are relevant for research, clinical, educational, and home applications in both practical and theoretical terms.

  10. [Impact of the Overlap Region Between Acoustic and Electric Stimulation].

    PubMed

    Baumann, Uwe; Mocka, Moritz

    2017-02-08

    Patients with residual hearing in the low frequencies and ski-slope hearing loss with partial deafness at medium and high frequencies receive a cochlear implant treatment with electric-acoustic stimulation (EAS, "hybrid" stimulation). In the border region between electric and acoustic stimulation a superposition of the 2 types of stimulation is expected. The area of overlap is determined by the insertion depth of the stimulating electrode and the lower starting point of signal transmission provided by the CI speech processor. The study examined the influence of the variation of the electric-acoustic overlap area on speech perception in noise, whereby the width of the "transmission gap" between the 2 different stimulus modalities was varied by 2 different methods. The results derived from 9 experienced users of the MED-EL Duet 2 speech processor show that the electric-acoustic overlapping area and with it the crossover frequency between the acoustic part and the CI should be adjusted individually. Overall, speech reception thresholds (SRT) showed a wide variation of results in between subjects. Further studies shall investigate whether generalized procedures about the setting of the overlap between electric and acoustic stimulation are reasonable, whereby an increased number of subjects and a longer period of acclimatization prior to the conduction of hearing tests deemed necessary.

  11. Tuned Chamber Core Panel Acoustic Test Results

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Allen, Albert R.

    2016-01-01

    This report documents acoustic testing of tuned chamber core panels, which can be used to supplement the low-frequency performance of conventional acoustic treatment. The tuned chamber core concept incorporates low-frequency noise control directly within the primary structure and is applicable to sandwich constructions with a directional core, including corrugated-, truss-, and fluted-core designs. These types of sandwich structures have long, hollow channels (or chambers) in the core. By adding small holes through one of the facesheets, the hollow chambers can be utilized as an array of low-frequency acoustic resonators. These resonators can then be used to attenuate low-frequency noise (below 400 Hz) inside a vehicle compartment without increasing the weight or size of the structure. The results of this test program demonstrate that the tuned chamber core concept is effective when used in isolation or combined with acoustic foam treatments. Specifically, an array of acoustic resonators integrated within the core of the panels was shown to improve both the low-frequency absorption and transmission loss of the structure in targeted one-third octave bands.

  12. Tailoring the Acoustic Properties of Truss-Core Sandwich Structure

    NASA Astrophysics Data System (ADS)

    Lee, Richard

    Undesirable cabin noise has an adverse physiological effect on passengers and crews in an aircraft. In order to reduce the noise level, a passive approach using a truss-core sandwich (TCS) panel as a sound insulator is proposed. Design guidelines and analysis methodologies were developed in order to explore the vibro-acoustic characteristics of TCS structure. Its sound isolation properties can be thereby assessed. Theoretical analyses show that the transmission-loss and sound radiation properties of a TCS structure can be represented by the root-mean-square velocity of its surface, and a beam structure analysis is sufficient to reveal many of the important aspects of TCS panel design. Using finite element analysis, a sensitivity study was performed to create design guidelines for TCS structures. Transmission-loss experiments show that the analytical and numerical analyses correctly predict the trend of TCS structure's vibro-acoustic performance.

  13. Modeling signal loss in surficial marine sediments containing occluded gas

    NASA Astrophysics Data System (ADS)

    Gardner, Trevor

    2003-03-01

    The presence of occluded gas in inland lakes, harbor muds, and surficial marine sediments is well documented. Surficial gassy sediments cause underlying beds to be acoustically impenetrable to seismic surveys; therefore, the modeling of signal loss arising from mudline reflection and transmission absorption is of particular interest. The Anderson and Hampton [J. Acoust. Soc. Am. 67, 1890-1903 (1980)] model for attenuation in gassy sediments was evaluated against the physical and acoustical properties of eight laboratory silty clay soils containing different amounts of occluded gas in bubbles of 0.2- to 1.8-mm diameter. The model was shown to give good agreement with measured data over the lower frequencies of bubble resonance and above resonance. It did not agree with measured data at frequencies below resonance, for which the model did not simulate the bulk properties of the gassy soils. The Mackenzie [J. Acoust. Soc. Am. 32, 221-231 (1960)] model for reflection loss was also examined for the gassy soils. The maximum reflection losses of 6 dB, at a grazing angle of 40°, does not wholly support speculation by Levin [Geophysics 27, 35-47 (1962)] of highly reflective pressure-release boundaries arising from substantial reflection and absorption losses in gassy sediments. It was found that mudlines formed from sediments with significant occluded gas may be successfully penetrated, although the substantial absorption loss arising from signal transmission through the sediment prevents penetration of the surficial layers to much beyond a meter in depth.

  14. Experimentally-Based Ocean Acoustic Propagation and Coherence Studies

    DTIC Science & Technology

    2012-01-01

    water, where sound is highly bottom interacting, and the temperate deep -ocean sound channel. Acoustic field fluctuations have time scales varying from...that has been observed in both shallow and deep regimes. For shallow water, we seek to understand the mean and variability of transmission loss and...phase at frequencies from 50 to 3000 Hz. For the deep -ocean sound channel, the objective is to better characterize coupled-mode propagation at 50 to 100

  15. Acoustic dispersive prism

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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.

  16. 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.

  17. Acoustic dispersive prism

    PubMed Central

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

    2016-01-01

    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. PMID:26739504

  18. Microstructure of highly strained BiFeO{sub 3} thin films: Transmission electron microscopy and electron-energy loss spectroscopy studies

    SciTech Connect

    Heon Kim, Young; Bhatnagar, Akash; Pippel, Eckhard; Hesse, Dietrich; Alexe, Marin

    2014-01-28

    Microstructure and electronic structure of highly strained bismuth ferrite (BiFeO{sub 3}) thin films grown on lanthanum aluminate substrates are studied using high-resolution transmission and scanning transmission electron microscopies and electron energy loss spectroscopy (EELS). Monoclinic and tetragonal phases were observed in films grown at different temperatures, and a mix of both phases was detected in a film grown at intermediate temperature. In this film, a smooth transition of the microstructure was found between the monoclinic and the tetragonal phases. A considerable increase in the c-axis parameters was observed in both phases compared with the rhombohedral bulk phase. The off-center displacement of iron (Fe) ions was increased in the monoclinic phase as compared with the tetragonal phase. EEL spectra show different electronic structures in the monoclinic and the tetragonal phases. These experimental observations are well consistent with the results of theoretical first-principle calculations performed.

  19. Microstructure of highly strained BiFeO3 thin films: Transmission electron microscopy and electron-energy loss spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Heon Kim, Young; Bhatnagar, Akash; Pippel, Eckhard; Alexe, Marin; Hesse, Dietrich

    2014-01-01

    Microstructure and electronic structure of highly strained bismuth ferrite (BiFeO3) thin films grown on lanthanum aluminate substrates are studied using high-resolution transmission and scanning transmission electron microscopies and electron energy loss spectroscopy (EELS). Monoclinic and tetragonal phases were observed in films grown at different temperatures, and a mix of both phases was detected in a film grown at intermediate temperature. In this film, a smooth transition of the microstructure was found between the monoclinic and the tetragonal phases. A considerable increase in the c-axis parameters was observed in both phases compared with the rhombohedral bulk phase. The off-center displacement of iron (Fe) ions was increased in the monoclinic phase as compared with the tetragonal phase. EEL spectra show different electronic structures in the monoclinic and the tetragonal phases. These experimental observations are well consistent with the results of theoretical first-principle calculations performed.

  20. Vehicular sources in acoustic propagation experiments

    NASA Technical Reports Server (NTRS)

    Prado, Gervasio; Fitzgerald, James; Arruda, Anthony; Parides, George

    1990-01-01

    One of the most important uses of acoustic propagation models lies in the area of detection and tracking of vehicles. Propagation models are used to compute transmission losses in performance prediction models and to analyze the results of past experiments. Vehicles can also provide the means for cost effective experiments to measure acoustic propagation conditions over significant ranges. In order to properly correlate the information provided by the experimental data and the propagation models, the following issues must be taken into consideration: the phenomenology of the vehicle noise sources must be understood and characterized; the vehicle's location or 'ground truth' must be accurately reproduced and synchronized with the acoustic data; and sufficient meteorological data must be collected to support the requirements of the propagation models. The experimental procedures and instrumentation needed to carry out propagation experiments are discussed. Illustrative results are presented for two cases. First, a helicopter was used to measure propagation losses at a range of 1 to 10 Km. Second, a heavy diesel-powered vehicle was used to measure propagation losses in the 300 to 2200 m range.

  1. Perforated membrane-type acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Langfeldt, F.; Kemsies, H.; Gleine, W.; von Estorff, O.

    2017-04-01

    This letter introduces a modified design of membrane-type acoustic metamaterials (MAMs) with a ring mass and a perforation so that an airflow through the membrane is enabled. Simplified analytical investigations of the perforated MAM (PMAM) indicate that the perforation introduces a second anti-resonance, where the effective surface mass density of the PMAM is much higher than the static value. The theoretical results are validated using impedance tube measurements, indicating good agreement between the theoretical predictions and the measured data. The anti-resonances yield high low-frequency sound transmission loss values with peak values over 25 dB higher than the corresponding mass-law.

  2. Acoustic Neuroma

    MedlinePlus

    ... search IRSA's site Unique Hits since January 2003 Acoustic Neuroma Click Here for Acoustic Neuroma Practice Guideline ... to microsurgery. One doctor's story of having an acoustic neuroma In August 1991, Dr. Thomas F. Morgan ...

  3. A Stratified Acoustic Model Accounting for Phase Shifts for Underwater Acoustic Networks

    PubMed Central

    Wang, Ping; Zhang, Lin; Li, Victor O. K.

    2013-01-01

    Accurate acoustic channel models are critical for the study of underwater acoustic networks. Existing models include physics-based models and empirical approximation models. The former enjoy good accuracy, but incur heavy computational load, rendering them impractical in large networks. On the other hand, the latter are computationally inexpensive but inaccurate since they do not account for the complex effects of boundary reflection losses, the multi-path phenomenon and ray bending in the stratified ocean medium. In this paper, we propose a Stratified Acoustic Model (SAM) based on frequency-independent geometrical ray tracing, accounting for each ray's phase shift during the propagation. It is a feasible channel model for large scale underwater acoustic network simulation, allowing us to predict the transmission loss with much lower computational complexity than the traditional physics-based models. The accuracy of the model is validated via comparisons with the experimental measurements in two different oceans. Satisfactory agreements with the measurements and with other computationally intensive classical physics-based models are demonstrated. PMID:23669708

  4. Study of semiconductor valence plasmon line shapes via electron energy-loss spectroscopy in the transmission electron microscope

    SciTech Connect

    Kundmann, M.K.

    1988-11-01

    Electron energy-loss spectra of the semiconductors Si, AlAs, GaAs, InAs, InP, and Ge are examined in detail in the regime of outer-shell and plasmon energy losses (0--100eV). Particular emphasis is placed on modeling and analyzing the shapes of the bulk valence plasmon lines. A line shape model based on early work by Froehlich is derived and compared to single-scattering probability distributions extracted from the measured spectra. Model and data are found to be in excellent agreement, thus pointing the way to systematic characterization of the plasmon component of EELS spectra. The model is applied to three separate investigations. 82 refs.

  5. Acoustic modelling and testing of diesel particulate filters

    NASA Astrophysics Data System (ADS)

    Allam, Sabry; Åbom, Mats

    2005-11-01

    The use of Diesel Particulate Filters (DPFs) on automobiles to reduce the harmful effects of diesel exhaust gases is becoming a standard in many countries. Although the main purpose of a DPF is to reduce harmful emission of soot particles it also affects the acoustic emission. This paper presents a first attempt to describe the acoustic behavior of DPFs and to present models which allow the acoustic two-port to be calculated. The simplest model neglects wave propagation and treats the filter as an equivalent acoustic resistance modeled via a lumped impedance element. This simple model gives a constant frequency-independent transmission loss and agrees within 1 dB with measured data on a typical filter (length 250 mm) up to 200-300 Hz (at 20 °C). In the second model, the ceramic filter monolith is described as a system of coupled porous channels carrying plane waves. The coupling between the channels through the porous walls is described via Darcy's law. This model gives a frequency-dependent transmission loss and agrees well with measured data in the entire plane wave range.

  6. Effect of in-material losses on terahertz absorption, transmission, and reflection in photonic crystals made of polar dielectrics

    SciTech Connect

    Serebryannikov, Andriy E.; Nojima, S.; Alici, K. B.; Ozbay, Ekmel

    2015-10-07

    The effect of the material absorption factor on terahertz absorption (A), transmittance (T), and reflectance (R) for slabs of PhC that comprise rods made of GaAs, a polar dielectric, is studied. The main goal was to illustrate how critical a choice of the absorption factor for simulations is and to indicate the importance of the possible modification of the absorption ability by using either active or lossy impurities. The spectra of A, T, and R are strongly sensitive to the location of the polaritonic gap with respect to the photonic pass and stop bands connected with periodicity that enables the efficient combination of the effects of material and structural parameters. It will be shown that the spectra can strongly depend on the utilized value of the material absorption factor. In particular, both narrow and wide absorption bands may appear owing to a variation of the material parameters with a frequency in the vicinity of the polaritonic gap. The latter are often achieved at wideband suppression of transmission, so that an ultra-wide stop band can appear as a result of adjustment of the stop bands having different origin. The results obtained at simultaneous variation of the absorption factor and frequency, and angle of incidence and frequency, indicate the possibility of the existence of wide ranges of tolerance, in which the basic features do remain. This allows for mitigating the accuracy requirements for the absorption factor in simulations and promises the efficient absorption of nonmonochromatic waves and beams with a wide angular spectrum. Suppression of narrowband effects in transmission is demonstrated at rather large values of the absorption factor, when they appear due to either the defect modes related to structural defects or dispersion inspired variations of the material parameters in the vicinity of the polaritonic gap. Comparison with auxiliary structures helps one to detect the common features and differences of homogeneous slabs and slabs of a

  7. Optimal Siting and Sizing of Multiple DG Units for the Enhancement of Voltage Profile and Loss Minimization in Transmission Systems Using Nature Inspired Algorithms.

    PubMed

    Ramamoorthy, Ambika; Ramachandran, Rajeswari

    2016-01-01

    Power grid becomes smarter nowadays along with technological development. The benefits of smart grid can be enhanced through the integration of renewable energy sources. In this paper, several studies have been made to reconfigure a conventional network into a smart grid. Amongst all the renewable sources, solar power takes the prominent position due to its availability in abundance. Proposed methodology presented in this paper is aimed at minimizing network power losses and at improving the voltage stability within the frame work of system operation and security constraints in a transmission system. Locations and capacities of DGs have a significant impact on the system losses in a transmission system. In this paper, combined nature inspired algorithms are presented for optimal location and sizing of DGs. This paper proposes a two-step optimization technique in order to integrate DG. In a first step, the best size of DG is determined through PSO metaheuristics and the results obtained through PSO is tested for reverse power flow by negative load approach to find possible bus locations. Then, optimal location is found by Loss Sensitivity Factor (LSF) and weak (WK) bus methods and the results are compared. In a second step, optimal sizing of DGs is determined by PSO, GSA, and hybrid PSOGSA algorithms. Apart from optimal sizing and siting of DGs, different scenarios with number of DGs (3, 4, and 5) and PQ capacities of DGs (P alone, Q alone, and P and Q both) are also analyzed and the results are analyzed in this paper. A detailed performance analysis is carried out on IEEE 30-bus system to demonstrate the effectiveness of the proposed methodology.

  8. Optimal Siting and Sizing of Multiple DG Units for the Enhancement of Voltage Profile and Loss Minimization in Transmission Systems Using Nature Inspired Algorithms

    PubMed Central

    Ramamoorthy, Ambika; Ramachandran, Rajeswari

    2016-01-01

    Power grid becomes smarter nowadays along with technological development. The benefits of smart grid can be enhanced through the integration of renewable energy sources. In this paper, several studies have been made to reconfigure a conventional network into a smart grid. Amongst all the renewable sources, solar power takes the prominent position due to its availability in abundance. Proposed methodology presented in this paper is aimed at minimizing network power losses and at improving the voltage stability within the frame work of system operation and security constraints in a transmission system. Locations and capacities of DGs have a significant impact on the system losses in a transmission system. In this paper, combined nature inspired algorithms are presented for optimal location and sizing of DGs. This paper proposes a two-step optimization technique in order to integrate DG. In a first step, the best size of DG is determined through PSO metaheuristics and the results obtained through PSO is tested for reverse power flow by negative load approach to find possible bus locations. Then, optimal location is found by Loss Sensitivity Factor (LSF) and weak (WK) bus methods and the results are compared. In a second step, optimal sizing of DGs is determined by PSO, GSA, and hybrid PSOGSA algorithms. Apart from optimal sizing and siting of DGs, different scenarios with number of DGs (3, 4, and 5) and PQ capacities of DGs (P alone, Q alone, and  P and Q both) are also analyzed and the results are analyzed in this paper. A detailed performance analysis is carried out on IEEE 30-bus system to demonstrate the effectiveness of the proposed methodology. PMID:27057557

  9. Development of an analytical solution of modified Biot's equations for the optimization of lightweight acoustic protection.

    PubMed

    Kanfoud, Jamil; Ali Hamdi, Mohamed; Becot, François-Xavier; Jaouen, Luc

    2009-02-01

    During lift-off, space launchers are submitted to high-level of acoustic loads, which may damage sensitive equipments. A special acoustic absorber has been previously integrated inside the fairing of space launchers to protect the payload. A new research project has been launched to develop a low cost fairing acoustic protection system using optimized layers of porous materials covered by a thin layer of fabric. An analytical model is used for the analysis of acoustic wave propagation within the multilayer porous media. Results have been validated by impedance tube measurements. A parametric study has been conducted to determine optimal mechanical and acoustical properties of the acoustic protection under dimensional thickness constraints. The effect of the mounting conditions has been studied. Results reveal the importance of the lateral constraints on the absorption coefficient particularly in the low frequency range. A transmission study has been carried out, where the fairing structure has been simulated by a limp mass layer. The transmission loss and noise reduction factors have been computed using Biot's theory and the local acoustic impedance approximation to represent the porous layer effect. Comparisons between the two models show the frequency domains for which the local impedance model is valid.

  10. Martensitic transformation of Ni2FeGa ferromagnetic shape-memory alloy studied via transmission electron microscopy and electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, H. R.; Ma, C.; Tian, H. F.; Wu, G. H.; Li, J. Q.

    2008-06-01

    The structural properties of Ni2FeGa Heusler alloy synthesized by melt-spinning technique have been systematically studied by means of in situ heating and cooling transmission electron microscopy. It was found that the Ni2FeGa alloy was annealed into a well-defined L21 structure at around 980 K, and complex microstructural domains appeared along with lowering temperature. At room temperature (293 K), a rich variety of micromodulated domains were observed. The domain structures were aligned along the ⟨110⟩ or ⟨100⟩ directions resulting to complex tweed structures. Below martensitic transformation (MT) temperature (Ms,˜142K) , the cubic parent phase transformed into unmodulated martensitic variants and modulated martensitic variants. The variants were alternated along the ⟨100⟩ direction with various arrangements and steplike incommensurate boundaries. The modulated martensitic variants were composed of lamellar structures that have predominately a 5M modulation structure along the ⟨110⟩ directions. The electron energy-loss spectroscopy analysis of the low-loss region and the electron energy-loss near-edge fine structure revealed a visible change of the electronic structure along with MT, which can be well interpreted by means of intra-atomic or intraband charge redistribution due to spd orbital hybridization among the Ni-Fe-Ga atoms.

  11. Enhanced sensitivity of hippocampal pyramidal neurons from mdx mice to hypoxia-induced loss of synaptic transmission.

    PubMed Central

    Mehler, M F; Haas, K Z; Kessler, J A; Stanton, P K

    1992-01-01

    The gene at the Duchenne/Becker muscular dystrophy locus encodes dystrophin, a member of a protein superfamily that links the actin cytoskeleton to transmembrane plasmalemmal proteins. In mature skeletal myocytes, the absence of dystrophin is associated with decreased membrane stability, altered kinetics of several calcium channels, and increased intracellular calcium concentration. In the central nervous system, dystrophin is restricted to specific neuronal populations that show heightened susceptibility to excitotoxic damage and is localized in proximal dendrites and the neuronal somata. We report that CA1 pyramidal neurons in a hippocampal slice preparation from a dystrophin-deficient mouse genetic model of Duchenne muscular dystrophy (the mdx mouse) exhibit significant increased susceptibility to hypoxia-induced damage to synaptic transmission. This selective vulnerability was substantially ameliorated by pretreatment with diphenylhydantoin, an anticonvulsant that blocks both sodium-dependent action potentials and low-threshold transient calcium conductances. These findings suggest that dystrophin deficiency could predispose susceptible neuronal populations to cumulative hypoxic insults that may contribute to the development of cognitive deficits in Duchenne/Becker muscular dystrophy patients and that the effects of such periods of hypoxia may be pharmacologically remediable. PMID:1549609

  12. Acoustic imaging system

    DOEpatents

    Smith, Richard W.

    1979-01-01

    An acoustic imaging system for displaying an object viewed by a moving array of transducers as the array is pivoted about a fixed point within a given plane. A plurality of transducers are fixedly positioned and equally spaced within a laterally extending array and operatively directed to transmit and receive acoustic signals along substantially parallel transmission paths. The transducers are sequentially activated along the array to transmit and receive acoustic signals according to a preestablished sequence. Means are provided for generating output voltages for each reception of an acoustic signal, corresponding to the coordinate position of the object viewed as the array is pivoted. Receptions from each of the transducers are presented on the same display at coordinates corresponding to the actual position of the object viewed to form a plane view of the object scanned.

  13. Distributions of hafnia and titania cores in EUV metal resists evaluated by scanning transmission electron microscopy and electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Toriumi, Minoru; Sato, Yuta; Koshino, Masanori; Suenaga, Kazu; Itani, Toshiro

    2016-11-01

    The morphologies of hafnia (HfO x ) and titania (TiO x ) cores and their distributions in metal resists for EUV lithography were characterized at the atomic level by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). The HfO x cores show a higher affinity to organic components, such as methacrylic acid and benzoic acid, than the TiO x cores, and the same core-shell state as in a solution is almost completely maintained in the HfO x resist film. Furthermore, it was found that the surface modification of the TiO x cores by silylation is effective for preventing their aggregation and improves the postcoating delay (PCD) of the resist.

  14. Loss of neuronal GSK3β reduces dendritic spine stability and attenuates excitatory synaptic transmission via β-catenin

    PubMed Central

    Ochs, S M; Dorostkar, M M; Aramuni, G; Schön, C; Filser, S; Pöschl, J; Kremer, A; Van Leuven, F; Ovsepian, S V; Herms, J

    2015-01-01

    Central nervous glycogen synthase kinase 3β (GSK3β) is implicated in a number of neuropsychiatric diseases, such as bipolar disorder, depression, schizophrenia, fragile X syndrome or anxiety disorder. Many drugs employed to treat these conditions inhibit GSK3β either directly or indirectly. We studied how conditional knockout of GSK3β affected structural synaptic plasticity. Deletion of the GSK3β gene in a subset of cortical and hippocampal neurons in adult mice led to reduced spine density. In vivo imaging revealed that this was caused by a loss of persistent spines, whereas stabilization of newly formed spines was reduced. In electrophysiological recordings, these structural alterations correlated with a considerable drop in the frequency and amplitude of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-dependent miniature excitatory postsynaptic currents. Expression of constitutively active β-catenin caused reduction in spine density and electrophysiological alterations similar to GSK3β knockout, suggesting that the effects of GSK3β knockout were mediated by the accumulation of β-catenin. In summary, changes of dendritic spines, both in quantity and in morphology, are correlates of experience-dependent synaptic plasticity; thus, these results may help explain the mechanism of action of psychotropic drugs inhibiting GSK3β. PMID:24912492

  15. Guided acoustic wave inspection system

    SciTech Connect

    Chinn, Diane J.

    2004-10-05

    A system for inspecting a conduit for undesirable characteristics. A transducer system induces guided acoustic waves onto said conduit. The transducer system detects the undesirable characteristics of the conduit by receiving guided acoustic waves that contain information about the undesirable characteristics. The conduit has at least two sides and the transducer system utilizes flexural modes of propagation to provide inspection using access from only the one side of the conduit. Cracking is detected with pulse-echo testing using one transducer to both send and receive the guided acoustic waves. Thinning is detected in through-transmission testing where one transducer sends and another transducer receives the guided acoustic waves.

  16. Transition section for acoustic waveguides

    DOEpatents

    Karplus, H.H.B.

    1975-10-28

    A means of facilitating the transmission of acoustic waves with minimal reflection between two regions having different specific acoustic impedances is described comprising a region exhibiting a constant product of cross-sectional area and specific acoustic impedance at each cross-sectional plane along the axis of the transition region. A variety of structures that exhibit this feature is disclosed, the preferred embodiment comprising a nested structure of doubly reentrant cones. This structure is useful for monitoring the operation of nuclear reactors in which random acoustic signals are generated in the course of operation.

  17. Estimation of Effective Transmission Loss Due to Subtropical Hydrometeor Scatters using a 3D Rain Cell Model for Centimeter and Millimeter Wave Applications

    NASA Astrophysics Data System (ADS)

    Ojo, J. S.; Owolawi, P. A.

    2014-12-01

    The problem of hydrometeor scattering on microwave radio communication down links continues to be of interest as the number of the ground and earth space terminals continually grows The interference resulting from the hydrometeor scattering usually leads to the reduction in the signal-to-noise ratio ( SNR) at the affected terminal and at worst can even end up in total link outage. In this paper, an attempt has been made to compute the effective transmission loss due to subtropical hydrometeors on vertically polarized signals in Earth-satellite propagation paths in the Ku, Ka and V band frequencies based on the modified Capsoni 3D rain cell model. The 3D rain cell model has been adopted and modified using the subtropical log-normal distributions of raindrop sizes and introducing the equivalent path length through rain in the estimation of the attenuation instead of the usual specific attenuation in order to account for the attenuation of both wanted and unwanted paths to the receiver. The co-channels, interference at the same frequency is very prone to the higher amount of unwanted signal at the elevation considered. The importance of joint transmission is also considered.

  18. Detection of local chemical states of lithium and their spatial mapping by scanning transmission electron microscopy, electron energy-loss spectroscopy and hyperspectral image analysis.

    PubMed

    Muto, Shunsuke; Tatsumi, Kazuyoshi

    2017-02-08

    Advancements in the field of renewable energy resources have led to a growing demand for the analysis of light elements at the nanometer scale. Detection of lithium is one of the key issues to be resolved for providing guiding principles for the synthesis of cathode active materials, and degradation analysis after repeated use of those materials. We have reviewed the different techniques currently used for the characterization of light elements such as high-resolution transmission electron microscopy, scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). In the present study, we have introduced a methodology to detect lithium in solid materials, particularly for cathode active materials used in lithium-ion battery. The chemical states of lithium were isolated and analyzed from the overlapping multiple spectral profiles, using a suite of STEM, EELS and hyperspectral image analysis. The method was successfully applied in the chemical state analyses of hetero-phases near the surface and grain boundary regions of the active material particles formed by chemical reactions between the electrolyte and the active materials.

  19. PORTABLE ACOUSTIC MONITORING PACKAGE (PAMP)

    SciTech Connect

    John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Patrick Browning

    2004-07-20

    The Portable Acoustic Monitoring Package (PAMP) has been designed to record and monitor the acoustic signal in natural gas transmission lines. In particular the three acoustic signals associated with a line leak. The system is portable ({approx}30 lbs) and is designed for line pressures up to 1000 psi. It has become apparent that cataloging of the various background acoustic signals in natural gas transmission line is very important if a system to identify leak signals is to be developed. The low-pressure (0-200 psig) laboratory test phase has been completed and a number of field trials have been conducted. Before the cataloging phase could begin, a few problems identified in field trials identified had to be corrected such as: (1) Decreased microphone sensitivity at line pressures above 250 psig. (2) The inability to deal with large data sets collected when cataloging the variety of signals in a transmission line. (3) The lack of an available online acoustic calibration system. These problems have been solved and the WVU PAMP is now fully functional over the entire pressure range found in the Natural Gas transmission lines in this region. Field portability and reliability have been greatly improved. Data collection and storage have also improved to the point were the full acoustic spectrum of acoustic signals can be accurately cataloged, recorded and described.

  20. Effect of Vacuum on the Occurrence of UV-Induced Surface Photoluminescence, Transmission Loss, and Catastrophic Surface Damage

    SciTech Connect

    Burnham, A K; Runkel, M; Demos, S G; Kozlowski, M R; Wegner, P J

    2000-07-20

    Vacuum degrades the transmittance and catastrophic damage performance of fused-silica surfaces, both bare and silica-sol anti-reflective coated. These effects may be important in certain space application of photonics devices. When exposed to hundreds of 355-rim, 10-ns laser pulses with fluences in the 2-15 J/cm{sup 2} range, transmittance loss is due to both increased reflectance and absorption at the surface. Spectroscopic measurements show that the absorbed light induces broadband fluorescence from the visible to infrared and that the peak photoluminescence wavelength depends cumulative fluence. The effect appears to be consistent with the formation of surface SiO{sub x} (x<2) with progressively lower x as cumulative fluence increases. Conversely, low fluence CW UV irradiation of fluorescent sites in air reduces the fluorescence signal, which suggests a photochemical oxidation reaction back to Si0{sub 2}. The occurrence of catastrophic damage (craters that grow on each subsequent pulse) also increases in a vacuum relative to air for both coated and uncoated samples. In both cases, the 50% damage probability for 100 one-mm sites decreases from about 45 to 35 J/cm{sup 2} for superpolished fused silica at pressures in the 10{sup -6} Torr range. The damage probability distribution in 10 Torr of air is close to that at one atmosphere of air. The damage morphology of the crater formed in vacuum differs substantially from that in air and has a more melted appearance and does not show cracking and flaking. These differences are possibly due to more coupling of the plasma shock wave into the surface with air present but slower heat dissipation in a vacuum. While it is attractive to propose that formation of sub-stoichiometric silica on the surface in a vacuum environment enhances the probability of catastrophic damage, initial experiments have not yet been able to establish a mechanistic link between the two phenomena.

  1. Passive acoustic threat detection in estuarine environments

    NASA Astrophysics Data System (ADS)

    Borowski, Brian; Sutin, Alexander; Roh, Heui-Seol; Bunin, Barry

    2008-04-01

    The Maritime Security Laboratory (MSL) at Stevens Institute of Technology supports research in a range of areas relevant to harbor security, including passive acoustic detection of underwater threats. The difficulties in using passive detection in an urban estuarine environment include intensive and highly irregular ambient noise and the complexity of sound propagation in shallow water. MSL conducted a set of tests in the Hudson River near Manhattan in order to measure the main parameters defining the detection distance of a threat: source level of a scuba diver, transmission loss of acoustic signals, and ambient noise. The source level of the diver was measured by comparing the diver's sound with a reference signal from a calibrated emitter placed on his path. Transmission loss was measured by comparing noise levels of passing ships at various points along their routes, where their distance from the hydrophone was calculated with the help of cameras and custom software. The ambient noise in the Hudson River was recorded under varying environmental conditions and amounts of water traffic. The passive sonar equation was then applied to estimate the range of detection. Estimations were done for a subset of the recorded noise levels, and we demonstrated how variations in the noise level, attenuation, and the diver's source level influence the effective range of detection. Finally, we provided analytic estimates of how an array improves upon the detection distance calculated by a single hydrophone.

  2. Loss to Followup: A Major Challenge to Successful Implementation of Prevention of Mother-to-Child Transmission of HIV-1 Programs in Sub-Saharan Africa.

    PubMed

    Kalembo, Fatch W; Zgambo, Maggie

    2012-07-31

    Purpose. The purpose of this paper was to explore how loss to followup (LFTU) has affected the successful implementation of prevention of mother to child transmission of HIV-1 (PMTCT) programs in sub-Saharan Africa. Methods. We conducted an electronic search from the following databases PubMed, ScienceDirect, Directory of Open Access Journals (DOAJs), and PyscINFO. Additional searches were made in WHO, UNAIDS, UNICEF, Google, and Google scholar websites for (1) peer-reviewed published research, (2) scientific and technical reports, and (3) papers presented on scientific conferences. Results. A total of 678 articles, published from 1990 to 2011, were retrieved. Only 44 articles met our inclusion criteria and were included in the study. The rates of LTFU of mother-child pairs ranged from 19% to 89.4 in the reviewed articles. Health facility factors, fear of HIV-1 test, stigma and discrimination, home deliveries and socioeconomic factors were identified as reasons for LTFU. Conclusion. There is a great loss of mother-child pairs to follow up in PMTCT programs in sub-Saharan Africa. There is need for more research studies to develop public health models of care that can help to improve followup of mother-child pairs in PMTCT programs in Sub-Saharan Africa.

  3. Incidence of Avian Influenza in Adamawa State, Nigeria: The Epidemiology, Economic Losses and the Possible Role of Wild Birds in the Transmission of the Disease

    NASA Astrophysics Data System (ADS)

    Ja`Afar-Furo, M. R.; Balla, H. G.; Tahir, A. S.; Haskainu, C.

    Reducing the huge economic losses due to diseases in poultry as the second largest industry in Nigeria after oil means improving the protein intake of the majority. Similarly, this will also promotes a steady income for the teeming farmers. This study investigated the incidence of the lethal avian influenza in Adamawa State, Nigeria, with particular emphasis on the socio-economic and cultural activities of the poultry farmers, economic losses and the possible role of wild birds in the transmission of the disease. Data were collected from 316 and 458 direct and indirect respondents, respectively, from 6 affected villages and a town in 2 Local Government Areas (LGAs): Girei and Yola-North. Results revealed that a larger (25.71%) proportion of the respondents fell within the age range of 31-40 years, with majority (54.91%) as females. While the bulk (54.65%) of the respondents were illiterates, 95.47% of the direct respondents derived their incomes from crop production, whereas 59.17% of the indirect respondents from livestock rearing. About 26,049 birds worth N13, 454,800.00 was cumulative economic loss incurred by the poultry farmers, whereas that of the government was put at N1, 119,781.10. Of the mortalities experienced in the wildlife before the outbreak of the disease, Bubulcus ibis (64.29) and Tadarida nigeriae (86.36) were the highest. The study recommends a massive rural extension on Poultry Production with absolute biosecurity, involving all stakeholders (Veterinary Surgeons, Animal Scientists/health workers, wildlife specialists, Agricultural Economists, Information Officers etc.) in a collaborative form for high synergistic effects.

  4. Transmission eigenvalues

    NASA Astrophysics Data System (ADS)

    Cakoni, Fioralba; Haddar, Houssem

    2013-10-01

    In inverse scattering theory, transmission eigenvalues can be seen as the extension of the notion of resonant frequencies for impenetrable objects to the case of penetrable dielectrics. The transmission eigenvalue problem is a relatively late arrival to the spectral theory of partial differential equations. Its first appearance was in 1986 in a paper by Kirsch who was investigating the denseness of far-field patterns for scattering solutions of the Helmholtz equation or, in more modern terminology, the injectivity of the far-field operator [1]. The paper of Kirsch was soon followed by a more systematic study by Colton and Monk in the context of developing the dual space method for solving the inverse scattering problem for acoustic waves in an inhomogeneous medium [2]. In this paper they showed that for a spherically stratified media transmission eigenvalues existed and formed a discrete set. Numerical examples were also given showing that in principle transmission eigenvalues could be determined from the far-field data. This first period of interest in transmission eigenvalues was concluded with papers by Colton et al in 1989 [3] and Rynne and Sleeman in 1991 [4] showing that for an inhomogeneous medium (not necessarily spherically stratified) transmission eigenvalues, if they existed, formed a discrete set. For the next seventeen years transmission eigenvalues were ignored. This was mainly due to the fact that, with the introduction of various sampling methods to determine the shape of an inhomogeneous medium from far-field data, transmission eigenvalues were something to be avoided and hence the fact that transmission eigenvalues formed at most a discrete set was deemed to be sufficient. In addition, questions related to the existence of transmission eigenvalues or the structure of associated eigenvectors were recognized as being particularly difficult due to the nonlinearity of the eigenvalue problem and the special structure of the associated transmission

  5. 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.

  6. Acoustic telemetry.

    SciTech Connect

    Drumheller, Douglas Schaeffer; Kuszmaul, Scott S.

    2003-08-01

    Broadcasting messages through the earth is a daunting task. Indeed, broadcasting a normal telephone conversion through the earth by wireless means is impossible with todays technology. Most of us don't care, but some do. Industries that drill into the earth need wireless communication to broadcast navigation parameters. This allows them to steer their drill bits. They also need information about the natural formation that they are drilling. Measurements of parameters such as pressure, temperature, and gamma radiation levels can tell them if they have found a valuable resource such as a geothermal reservoir or a stratum bearing natural gas. Wireless communication methods are available to the drilling industry. Information is broadcast via either pressure waves in the drilling fluid or electromagnetic waves in the earth and well tubing. Data transmission can only travel one way at rates around a few baud. Given that normal Internet telephone modems operate near 20,000 baud, these data rates are truly very slow. Moreover, communication is often interrupted or permanently blocked by drilling conditions or natural formation properties. Here we describe a tool that communicates with stress waves traveling through the steel drill pipe and production tubing in the well. It's based on an old idea called Acoustic Telemetry. But what we present here is more than an idea. This tool exists, it's drilled several wells, and it works. Currently, it's the first and only acoustic telemetry tool that can withstand the drilling environment. It broadcasts one way over a limited range at much faster rates than existing methods, but we also know how build a system that can communicate both up and down wells of indefinite length.

  7. Classroom Acoustics: Understanding Barriers to Learning.

    ERIC Educational Resources Information Center

    Crandell, Carl C., Ed.; Smaldino, Joseph J., Ed.

    2001-01-01

    This booklet explores classroom acoustics and their importance on the learning potential of children with hearing loss and related disabilities. The booklet also reviews research on classroom acoustics and the need for the development of classroom acoustics standards. Chapters examine: 1) a speech-perception model demonstrating the linkage between…

  8. Acoustic scattering by a spliced turbofan inlet duct liner at supersonic fan speeds

    NASA Astrophysics Data System (ADS)

    McAlpine, A.; Wright, M. C. M.

    2006-05-01

    Fan noise is one of the principal noise sources generated by a turbofan aero-engine. At supersonic fan speeds, fan tones are generated by the "rotor-alone" pressure field. In general, these tones can be well absorbed by an inlet duct acoustic liner, apart from at high supersonic fan speeds. However, in practice inlet duct liners contain acoustically hard longitudinal splices which cause scattering. This leads to acoustic energy being scattered into a range of different azimuthal mode orders, similar to the modal content resulting from rotor-stator interactions. The effectiveness of an inlet duct lining is reduced because acoustic energy is scattered into modes that are poorly absorbed by the liner. In this article, the effect of this acoustic scattering is examined by three-dimensional finite-element simulations of sound transmission in a turbofan inlet duct. Results include predictions of the sound power transmission loss with different splice widths, and at different supersonic fan speeds. These results demonstrate how acoustic scattering by liner splices can adversely affect fan tone noise levels at low supersonic fan speeds, but have little adverse affect on noise levels at high supersonic fan speeds. The potential noise benefit that could be achieved by manufacturing thinner splices is also examined.

  9. 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 ...

  10. Acoustic Seaglider

    DTIC Science & Technology

    2008-03-07

    a national naval responsibility. Acoustic sensors on mobile, autonomous platforms will enable basic research topics on temporal and spatial...problem and acoustic navigation and communications within the context of distributed autonomous persistent undersea surveillance sensor networks...Acoustic sensors on mobile, autonomous platforms will enable basic research topics on temporal and spatial coherence and the description of ambient

  11. 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.

  12. 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.

  13. Where does all the water go? Partitioning water transmission losses in a data-sparse, multi-channel and low-gradient dryland river system using modelling and remote sensing

    NASA Astrophysics Data System (ADS)

    Jarihani, Abdollah A.; Larsen, Joshua R.; Callow, John N.; McVicar, Tim R.; Johansen, Kasper

    2015-10-01

    Drylands cover approximately one-third of the Earth's surface, are home to nearly 40% of the Earth's population and are characterised by limited water resources and ephemeral river systems with an extremely variable flow regime and high transmission losses. These losses include actual evaporation, infiltration to the soil and groundwater and residual (terminal) water remaining after flood events. These critical components of the water balance of dryland river systems remain largely unknown due to the scarcity of observational data and the difficulty in accurately accounting for the flow distribution in such large multi-channel floodplain systems. While hydrodynamic models can test hypotheses concerning the water balance of infrequent flood events, the scarcity of flow measurement data inhibits model calibration, constrains model accuracy and therefore utility. This paper provides a novel approach to this problem by combining modelling, remotely-sensed data, and limited field measurements, to investigate the partitioning of flood transmissions losses based on seven flood events between February 2006 and April 2012 along a 180 km reach of the Diamantina River in the Lake Eyre Basin, Australia. Transmission losses were found to be high, on average 46% of total inflow within 180 km reach segment or 7 GL/km (range: 4-10 GL/km). However, in 180 km reach, transmission losses vary non-linearly with flood discharge, with smaller flows resulting in higher losses (up to 68%), which diminish in higher flows (down to 24%) and in general there is a minor increase in losses with distance downstream. Partitioning these total losses into the major components shows that actual evaporation was the most significant component (21.6% of total inflow), followed by infiltration (13.2%) and terminal water storage (11.2%). Lateral inflow can be up to 200% of upstream inflow (mean = 86%) and is therefore a critical parameter in the water balance and transmission loss calculations. This study

  14. The Acoustic Model Evaluation Committee (AMEC) Reports. Volume 2. The Evaluation of the FACT PL9D Transmission Loss Model. Book 1

    DTIC Science & Technology

    1982-09-01

    from a Survey of FACT Users 2.3b (U) Additional Problems and Deficiencies 19 of the FACT Model 3.0 (U) Runnin, Time 24 4.0 (U) Core Storage 25 5.0 (U...parameters [.• under user control. e A list of systems (e.g., sonar predic- u s t tion, engagement model, etc.) supported e What default values or...guide; a response to comparison of model outputs with experi - SECNAVINST 3560.1, Tactical Digital Sys- mental data or the output of a reference "tems

  15. The Acoustic Model Evaluation Committee (AMEC) Reports. Volume 2. The Evaluation of the FACT PL9D Transmission Loss Model. Book 3. Appendices E-H

    DTIC Science & Technology

    1982-09-01

    is a Generic Ocean Research and Development Activity FACT CZ width which is two to three Report No. 34. CONFIDENTIAL times narrower than LORAD’s. Cases...XD 0D L.) II4 LA W 0 LA E-4 GII o ls ULA LA) C’J’ A I~N 0 00 E-37 CO FIEN IA ......... CON FIDENTIAL 0U) U) ~U)j cQ) Uoat4+ * ~o pLf) GoGoI cli zZ r

  16. Fine-Scale Variability in Temperature, Salinity, and pH in the Upper-Ocean and the Effects on Acoustic Transmission Loss in the Western Arctic Ocean.

    DTIC Science & Technology

    2010-03-01

    150m. 47 D. RAY MODEL The ray model used was based on an Eigenray model developed by Prof. John Colosi and modified by Ben Jones from the Naval...possible eigenrays , sixty launch angles were selected for the model runs, from -15˚ to +15˚. Three source depths (50m, 100m, and 150m) were evaluated in

  17. Influence of panel fastening on the acoustic performance of light-weight building elements: Study by sound transmission and laser scanning vibrometry

    NASA Astrophysics Data System (ADS)

    Roozen, N. B.; Muellner, H.; Labelle, L.; Rychtáriková, M.; Glorieux, C.

    2015-06-01

    Structural details and workmanship can cause considerable differences in sound insulation properties of timber frame partitions. In this study, the influence of panel fastening is investigated experimentally by means of standardized sound reduction index measurements, supported by detailed scanning laser Doppler vibrometry. In particular the effect of the number of screws used to fasten the panels to the studs, and the tightness of the screws, is studied using seven different configurations of lightweight timber frame building elements. In the frequency range from 300 to 4000 Hz, differences in the weighted sound reduction index RW as large as 10 dB were measured, suggesting that the method of fastening can have a large impact on the acoustic performance of building elements. Using the measured vibrational responses of the element, its acoustic radiation efficiency was computed numerically by means of a Rayleigh integral. The increased radiation efficiency partly explains the reduced sound reduction index. Loosening the screws, or reducing the number of screws, lowers the radiation efficiency, and significantly increases the sound reduction index of the partition.

  18. Modelling acoustic propagation beneath Antarctic sea ice using measured environmental parameters

    NASA Astrophysics Data System (ADS)

    Alexander, Polly; Duncan, Alec; Bose, Neil; Williams, Guy

    2016-09-01

    Autonomous underwater vehicles are improving and expanding in situ observations of sea ice for the validation of satellite remote sensing and climate models. Missions under sea ice, particularly over large distances (up to 100 km) away from the immediate vicinity of a ship or base, require accurate acoustic communication for monitoring, emergency response and some navigation systems. We investigate the propagation of acoustic signals in the Antarctic seasonal ice zone using the BELLHOP model, examining the influence of ocean and sea ice properties. We processed available observations from around Antarctica to generate input variables such as sound speed, surface reflection coefficient (R) and roughness parameters. The results show that changes in the sound speed profile make the most significant difference to the propagation of the direct path signal. The inclusion of the surface reflected signals from a flat ice surface was found to greatly decrease the transmission loss with range. When ice roughness was added, the transmission loss increased with roughness, in a manner similar to the direct path transmission loss results. The conclusions of this work are that: (1) the accuracy of acoustic modelling in this environment is greatly increased by using realistic sound speed data; (2) a risk averse ranging model would use only the direct path signal transmission; and (3) in a flat ice scenario, much greater ranges can be achieved if the surface reflected transmission paths are included. As autonomous missions under sea ice increase in scale and complexity, it will be increasingly important for operational procedures to include effective modelling of acoustic propagation with representative environmental data.

  19. Report on the GC-MBS method for correcting NaI spectra for transmission loss in hand-held instruments

    SciTech Connect

    Rawool-Sullivan, M.

    1997-10-08

    The goals of this project were (1) to develop a capability to study the scattered components in the NaI spectra of attenuated sources and (2) to evaluate the effectiveness of the gross count material basis set (GC-MBS) method in quantifying transmission losses from the shapes of measured NaI spectra. These goals are related, as the GC-MBS method involves a linear log-spectrum decomposition into MBS component spectra, and scattered gamma rays represent a significant nonlinear interference. Eventually, the authors hope to understand the effect of the scattered components on the MBS decomposition and to develop ways to correct for inaccuracies. As of this writing the authors have not reached that long-term objective, so the two halves of this project are treated here as separate topics, with a separate section for each. They have substantially achieved both of the project goals and are collecting additional data for two publications at the upcoming IEEE conference in Albuquerque, NM--one paper about their work on scattering and another on the GC-MBS method. This project report will contain preliminary portions of those two papers.

  20. Experimental determination of blast-wave pressure loading, thermal radiation protection, and electrical transmission loss for parabolic antenna models in simulated nuclear blast environments

    SciTech Connect

    George, J.H.

    1991-01-01

    A twelve-inch-diameter parabolic antenna model instrumented with eleven differential pressure sensors was tested at the Ballistics Research Laboratory, Aberdeen Proving Ground, Maryland. Transient pressure loading was determined for 37 different antenna model angular positions with respect to the direction of the blast wave at a peak overpressure of 3.0 pounds per square inch; limited data at 4.5 and 6.0 pounds per square inch were also investigated. The first millisecond of shock-wave interaction with the antenna features the most prominent fully reversed triangular pressure pulse. A blast function, F, was developed that accurately approximates the transient behavior of the blast wave resultant force and moment loading on the antenna model. The resultant blast force on the antenna model is minimized when the axis of the paraboloid of the model is rotated 82{degree} with respect to the direction of the blast wave. Four different thermal protective coatings were tested to evaluate the effects of coating color and thickness. Transmission-loss measurements were completed on eight different quartz-polyimide antenna models coated with Caapcoat and Ocean 477 thermal protective coatings.

  1. Active control of sound transmission through partitions composed of discretely controlled modules

    NASA Astrophysics Data System (ADS)

    Leishman, Timothy W.

    This thesis provides a detailed theoretical and experimental investigation of active segmented partitions (ASPs) for the control of sound transmission. ASPs are physically segmented arrays of interconnected acoustically and structurally small modules that are discretely controlled using electronic controllers. Theoretical analyses of the thesis first address physical principles fundamental to ASP modeling and experimental measurement techniques. Next, they explore specific module configurations, primarily using equivalent circuits. Measured normal-incidence transmission losses and related properties of experimental ASPs are determined using plane wave tubes and the two-microphone transfer function technique. A scanning laser vibrometer is also used to evaluate distributed transmitting surface vibrations. ASPs have the inherent potential to provide excellent active sound transmission control (ASTC) through lightweight structures, using very practical control strategies. The thesis analyzes several unique ASP configurations and evaluates their abilities to produce high transmission losses via global minimization of normal transmitting surface vibrations. A novel dual diaphragm configuration is shown to employ this strategy particularly well. It uses an important combination of acoustical actuation and mechano-acoustical segmentation to produce exceptionally high transmission loss (e.g., 50 to 80 dB) over a broad frequency range-including lower audible frequencies. Such performance is shown to be comparable to that produced by much more massive partitions composed of thick layers of steel or concrete and sand. The configuration uses only simple localized error sensors and actuators, permitting effective use of independent single-channel controllers in a decentralized format. This work counteracts the commonly accepted notion that active vibration control of partitions is an ineffective means of controlling sound transmission. With appropriate construction, actuation

  2. Excellent low-frequency sound absorption of radial membrane acoustic metamaterial

    NASA Astrophysics Data System (ADS)

    Gao, Nansha; Wu, Jiu Hui; Hou, Hong; Yu, Lie

    2017-01-01

    This paper proposes a new radial membrane acoustic metamaterial (RMAM) structure, wherein a layer membrane substrate is covered with a rigid ring (polymethyl methacrylate frame and aluminum lump). The dispersion relationships, transmission spectra and displacement fields of the eigenmodes of this radial membrane acoustic metamaterial are studied with FEM. In contrast to the traditional radial phononic crystals (RPCs), the proposed structures can open bandgaps (BGs) in lower frequency range (0-300 Hz). Simulation results show that the physical mechanism behind the bandgaps is the coupling effects between the rotational vibration of aluminum lump and the transverse vibration of membrane. Geometrical parameters which can adjust the bandgaps’ widths or positions are analyzed. Finally, we investigate the axial sound transmission loss of this acoustic metamaterial structure, and discuss the effects of factor loss, membrane thickness and the number of layers of unit cell on the axial sound transmission loss. Dynamic effective density proves the accuracy of the FEM results. This kind of structure has potential application in pipe or circular ring structure for damping/noise reduction.

  3. Design and optimization of membrane-type acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Blevins, Matthew Grant

    One of the most common problems in noise control is the attenuation of low frequency noise. Typical solutions require barriers with high density and/or thickness. Membrane-type acoustic metamaterials are a novel type of engineered material capable of high low-frequency transmission loss despite their small thickness and light weight. These materials are ideally suited to applications with strict size and weight limitations such as aircraft, automobiles, and buildings. The transmission loss profile can be manipulated by changing the micro-level substructure, stacking multiple unit cells, or by creating multi-celled arrays. To date, analysis has focused primarily on experimental studies in plane-wave tubes and numerical modeling using finite element methods. These methods are inefficient when used for applications that require iterative changes to the structure of the material. To facilitate design and optimization of membrane-type acoustic metamaterials, computationally efficient dynamic models based on the impedance-mobility approach are proposed. Models of a single unit cell in a waveguide and in a baffle, a double layer of unit cells in a waveguide, and an array of unit cells in a baffle are studied. The accuracy of the models and the validity of assumptions used are verified using a finite element method. The remarkable computational efficiency of the impedance-mobility models compared to finite element methods enables implementation in design tools based on a graphical user interface and in optimization schemes. Genetic algorithms are used to optimize the unit cell design for a variety of noise reduction goals, including maximizing transmission loss for broadband, narrow-band, and tonal noise sources. The tools for design and optimization created in this work will enable rapid implementation of membrane-type acoustic metamaterials to solve real-world noise control problems.

  4. Acoustic metamaterials capable of both sound insulation and energy harvesting

    NASA Astrophysics Data System (ADS)

    Li, Junfei; Zhou, Xiaoming; Huang, Guoliang; Hu, Gengkai

    2016-04-01

    Membrane-type acoustic metamaterials are well known for low-frequency sound insulation. In this work, by introducing a flexible piezoelectric patch, we propose sound-insulation metamaterials with the ability of energy harvesting from sound waves. The dual functionality of the metamaterial device has been verified by experimental results, which show an over 20 dB sound transmission loss and a maximum energy conversion efficiency up to 15.3% simultaneously. This novel property makes the metamaterial device more suitable for noise control applications.

  5. Acoustically Tailored Composite Rotorcraft Fuselage Panels

    NASA Technical Reports Server (NTRS)

    Hambric, Stephen; Shepherd, Micah; Koudela, Kevin; Wess, Denis; Snider, Royce; May, Carl; Kendrick, Phil; Lee, Edward; Cai, Liang-Wu

    2015-01-01

    A rotorcraft roof sandwich panel has been redesigned to optimize sound power transmission loss (TL) and minimize structure-borne sound for frequencies between 1 and 4 kHz where gear meshing noise from the transmission has the most impact on speech intelligibility. The roof section, framed by a grid of ribs, was originally constructed of a single honeycomb core/composite face sheet panel. The original panel has coincidence frequencies near 700 Hz, leading to poor TL across the frequency range of 1 to 4 kHz. To quiet the panel, the cross section was split into two thinner sandwich subpanels separated by an air gap. The air gap was sized to target the fundamental mass-spring-mass resonance of the double panel system to less than 500 Hz. The panels were designed to withstand structural loading from normal rotorcraft operation, as well as 'man-on-the-roof' static loads experienced during maintenance operations. Thin layers of VHB 9469 viscoelastomer from 3M were also included in the face sheet ply layups, increasing panel damping loss factors from about 0.01 to 0.05. Measurements in the NASA SALT facility show the optimized panel provides 6-11 dB of acoustic transmission loss improvement, and 6-15 dB of structure-borne sound reduction at critical rotorcraft transmission tonal frequencies. Analytic panel TL theory simulates the measured performance quite well. Detailed finite element/boundary element modeling of the baseline panel simulates TL slightly more accurately, and also simulates structure-borne sound well.

  6. Experimental study of acoustical characteristics of honeycomb sandwich structures

    NASA Astrophysics Data System (ADS)

    Peters, Portia Renee

    Loss factor measurements were performed on sandwich panels to determine the effects of different skin and core materials on the acoustical properties. Results revealed inserting a viscoelastic material in the core's mid-plane resulted in the highest loss factor. Panels constructed with carbon-fiber skins exhibited larger loss factors than glass-fiber skins. Panels designed to achieve subsonic wave speed did not show a significant increase in loss factor above the coincidence frequency. The para-aramid core had a larger loss factor value than the meta-aramid core. Acoustic absorption coefficients were measured for honeycomb sandwiches designed to incorporate multiple sound-absorbing devices, including Helmholtz resonators and porous absorbers. The structures consisted of conventional honeycomb cores filled with closed-cell polyurethane foams of various densities and covered with perforated composite facesheets. Honeycomb cores filled with higher density foam resulted in higher absorption coefficients over the frequency range of 50 -- 1250 Hz. However, this trend was not observed at frequencies greater than 1250 Hz, where the honeycomb filled with the highest density foam yielded the lowest absorption coefficient among samples with foam-filled cores. The energy-recycling semi-active vibration suppression method (ERSA) was employed to determine the relationship between vibration suppression and acoustic damping for a honeycomb sandwich panel. Results indicated the ERSA method simultaneously reduced the sound transmitted through the panel and the panel vibration. The largest reduction in sound transmitted through the panel was 14.3% when the vibrations of the panel were reduced by 7.3%. The influence of different design parameters, such as core density, core material, and cell size on wave speeds of honeycomb sandwich structures was experimentally analyzed. Bending and shear wave speeds were measured and related to the transmission loss performance for various material

  7. Membrane-constrained acoustic metamaterials for low frequency sound insulation

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    We present a constrained membrane-type acoustic metamaterial (CMAM) that employs constraint sticks to add out-of-plane dimensions in the design space of MAM. A CMAM sample, which adopts constraint sticks to suppress vibrations at the membrane center, was fabricated to achieve a sound transmission loss (STL) peak of 26 dB at 140 Hz, with the static areal density of 6.0 kg/m2. The working mechanism of the CMAM as an acoustic metamaterial is elucidated by calculating the averaged normal displacement, the equivalent areal density, and the effective dynamic mass of a unit cell through finite element simulations. Furthermore, the vibration modes of the CMAM indicate that the eigenmodes related to STL dips are shifted into high frequencies, thus broadening its effective bandwidth significantly. Three samples possessing the same geometry and material but different constraint areas were fabricated to illustrate the tunability of STL peaks at low frequencies.

  8. Modeling and optimization of an acoustic diode based on micro-bubble nonlinearity.

    PubMed

    Guo, Xiasheng; Lin, Zhou; Tu, Juan; Liang, Bin; Cheng, Jianchun; Zhang, Dong

    2013-02-01

    The first acoustic diode (AD), which is composed by integrating a super lattice (SL) with a nonlinear medium (NLM), has recently been proposed to make a one-way street for the acoustic energy flux. This device prohibits the acoustic waves from one direction, but allows the transmission of the second harmonic wave (generated from the NLM) from the other direction. To improve its performance, it is crucial to transfer more acoustic energy from the stop-band of the acoustic filter (i.e., the SL) to its pass-band with the help of the NLM. In this work, a finite difference time domain model is developed to study the dynamic behaviors of the AD, in which a micro-bubble suspension takes the role of the NLM. Based on this model, the method of optimizing the nonlinearity-based AD is investigated by examining its performance with respect to several parameters, such as the periodicity number of the SL, the bubble size distribution, the bubble shell parameters, and the bubble concentration. It is also suggested that, instead of the rectification ratio, it might be more reasonable to characterize the performance of the AD with the energy attenuation coefficients (or transmission loss) for both incident directions.

  9. Acoustic Microscopy at Cryogenic Temperatures.

    DTIC Science & Technology

    1982-01-01

    intensities are used, and quantitatitvely acount for the onset of nonlinear excess attenuation. Aooeuuaiol For DTIC TAB Unaranounc ed Just if icat to By...to acoustic power is a reasonable value and can be acounted for by assuming a one-way transducer conversion loss of 5 dB, a lens illumination loss of

  10. Musical Acoustics

    NASA Astrophysics Data System (ADS)

    Gough, Colin

    This chapter provides an introduction to the physical and psycho-acoustic principles underlying the production and perception of the sounds of musical instruments. The first section introduces generic aspects of musical acoustics and the perception of musical sounds, followed by separate sections on string, wind and percussion instruments.

  11. Gallium nitride electro-acoustic devices and acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Rais-Zadeh, Mina

    2016-05-01

    Gallium nitride (GaN) being one of a few piezoelectric semiconductors with low acoustic loss is a perfect material for electro-acoustic applications. Interactions of electrons and phonons are facilitated by the piezoelectric effect in addition to the deformation coupling in GaN, a property that can be used to implement a variety of very interesting devices and metamaterials, such as resonant transistors, acoustic amplifiers, circulators, and couplers. This talk covers theoretical basis of such devices and overviews recent advances in this technology.

  12. Multi-Point Hermes Acoustic Modem for High-Speed, High-Frequency Acoustic Communications with Low-Frequency Acoustic Control Loop for Real-Time Transmission of AUV-Carried High-Resolution Images and Navigation Data in Support of Ship Hulls Inspection

    DTIC Science & Technology

    2013-08-31

    Message synchronization using the downlink synchronization pulse . ....................... 27 Figure 12: Constellation diagrams for the transmitted and...acoustic downlink, assuming a single reference sequence following the synchronization pulse ...68 Table 12: Signal-to-Noise Ratio per Mission and per Receiver

  13. Spatially resolved chemical mapping of dry and hydrated polymer morphology by electron energy-loss spectroscopy in the scanning transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Sousa, Alioscka A. C. A.

    Electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) is a technique that allows compositional analysis to be performed at high spatial resolution in thin TEM specimens, and here we implement and apply this technique to quantitatively study the morphology of unstained dry and frozen-hydrated polymer films. While water can play a controlling role that determines many of the important properties of polymers, there has not yet been much experimental work performed to correlate water spatial distribution with variations in underlying polymer morphology. We show how a quantitative map of the nanoscale spatial distribution of water can be generated from frozen-hydrated polymer thin films using EELS in the STEM. We find that hydrated polymers are very sensitive to the incident electron irradiation, and there is a trade off between the spatial resolution that a compositional map can display and its signal-to-noise ratio. The identification of minor fluctuations in composition within small regions across a given water map is therefore challenging because one must distinguish the fluctuations that are significant from those within noise. We implement a methodology using scatter diagrams in combination with noise simulations to threshold water maps and separate real pixel-by-pixel compositional fluctuations from noise. We study a model system comprised of hydrophilic poly(vinyl pyrrolidone) and hydrophobic poly(styrene), and we show that the thresholding approach enables us to quantitatively identify statistically significant single-pixel fluctuations in water content. We also apply EELS in the STEM to characterize the morphology of a dry, solvent-cast thin-film biopolymer blend comprised of poly(caprolactone) and poly(DTE carbonate). We quantitatively show the effect that solvent evaporation rate has on the morphology development of this blend and how the underlying morphology can dramatically influence the spatial distribution of

  14. Acoustic trauma caused by lightning.

    PubMed

    Mora-Magaña, I; Collado-Corona, M A; Toral-Martiñòn, R; Cano, A

    1996-03-01

    Lesions produced by exposure to noise are frequent in everyday life. Injuries may be found in all systems of the human body, from the digestive to the endocrine, from the cardiovascular to the nervous system. Many organs may be damaged, the ear being one of them. It is known that noise produced by factories, airports, musical instruments and even toys can cause auditory loss. Noises in nature can also cause acoustic trauma. This report is the case history of acoustic trauma caused by lightning. The patient was studied with CAT scan, electroencephalogram, and brain mapping, impedance audiometry with tympanogram and acoustic reflex, audiometry and evoked otoacoustics emissions: distortion products and transients.

  15. Finite element analysis of true and pseudo surface acoustic waves in one-dimensional phononic crystals

    SciTech Connect

    Graczykowski, B. Alzina, F.; Gomis-Bresco, J.; Sotomayor Torres, C. M.

    2016-01-14

    In this paper, we report a theoretical investigation of surface acoustic waves propagating in one-dimensional phononic crystal. Using finite element method eigenfrequency and frequency response studies, we develop two model geometries suitable to distinguish true and pseudo (or leaky) surface acoustic waves and determine their propagation through finite size phononic crystals, respectively. The novelty of the first model comes from the application of a surface-like criterion and, additionally, functional damping domain. Exemplary calculated band diagrams show sorted branches of true and pseudo surface acoustic waves and their quantified surface confinement. The second model gives a complementary study of transmission, reflection, and surface-to-bulk losses of Rayleigh surface waves in the case of a phononic crystal with a finite number of periods. Here, we demonstrate that a non-zero transmission within non-radiative band gaps can be carried via leaky modes originating from the coupling of local resonances with propagating waves in the substrate. Finally, we show that the transmission, reflection, and surface-to-bulk losses can be effectively optimised by tuning the geometrical properties of a stripe.

  16. Lightweight acoustic treatments for aerospace applications

    NASA Astrophysics Data System (ADS)

    Naify, Christina Jeanne

    2011-12-01

    Increase in the use of composites for aerospace applications has the benefit of decreased structural weight, but at the cost of decreased acoustic performance. Stiff, lightweight structures (such as composites) are traditionally not ideal for acoustic insulation applications because of high transmission loss at low frequencies. A need has thus arisen for effective sound insulation materials for aerospace and automotive applications with low weight addition. Current approaches, such as the addition of mass law dominated materials (foams) also perform poorly when scaled to small thickness and low density. In this dissertation, methods which reduce sound transmission without adding significant weight are investigated. The methods presented are intended to be integrated into currently used lightweight structures such as honeycomb sandwich panels and to cover a wide range of frequencies. Layering gasses of differing acoustic impedances on a panel substantially reduced the amount of sound energy transmitted through the panel with respect to the panel alone or an equivalent-thickness single species gas layer. The additional transmission loss derives from successive impedance mismatches at the interfaces between gas layers and the resulting inefficient energy transfer. Attachment of additional gas layers increased the transmission loss (TL) by as much as 17 dB at high (>1 kHz) frequencies. The location and ordering of the gasses with respect to the panel were important factors in determining the magnitude of the total TL. Theoretical analysis using a transfer matrix method was used to calculate the frequency dependence of sound transmission for the different configurations tested. The method accurately predicted the relative increases in TL observed with the addition of different gas layer configurations. To address low-frequency sound insulation, membrane-type locally resonant acoustic materials (LRAM) were fabricated, characterized, and analyzed to understand their

  17. Echolocation-Based Foraging by Harbor Porpoises and Sperm Whales, Including Effects on Noise and Acoustic Propagation

    DTIC Science & Technology

    2008-09-01

    pulses recorded on tagged sperm whales 25 1.5.5 Chapter 5 - Modeling Sperm Whale Response to Airgun Sounds 26 1.5.6 Chapter 6-Conclusions 26 1.5.7...Modeled Transmission Loss 112 3.4 Discussion 115 Acknowledgements 123 References 123 Chapter 4. Modeling acoustic propagation of airgun array pulses ...include the lower-frequency, broadband, multi- pulsed clicks of sperm whales (Zimmer et al., 2005b), the high-frequency, broadband, impulsive clicks

  18. A research program to reduce interior noise in general aviation airplanes. Design of an acoustic panel test facility

    NASA Technical Reports Server (NTRS)

    Roskam, J.; Muirhead, V. U.; Smith, H. W.; Henderson, T. D.

    1977-01-01

    The design, construction, and costs of a test facility for determining the sound transmission loss characteristics of various panels and panel treatments are described. The pressurization system and electronic equipment used in experimental testing are discussed as well as the reliability of the facility and the data gathered. Tests results are compared to pertinent acoustical theories for panel behavior and minor anomalies in the data are examined. A method for predicting panel behavior in the stiffness region is also presented.

  19. Application of piezoelectric macro-fiber-composite actuators to the suppression of noise transmission through curved glass plates.

    PubMed

    Nováková, Katerina; Mokrý, Pavel; Václavík, Jan

    2012-09-01

    This paper analyzes the possibility of increasing the acoustic transmission loss of sound transmitted through planar or curved glass shells using attached piezoelectric macro fiber composite (MFC) actuators shunted by active circuits with a negative capacitance. The key features that control the sound transmission through the curved glass shells are analyzed using an analytical approximative model. A detailed analysis of the particular arrangement of MFC actuators on the glass shell is performed using a finite element method (FEM) model. The FEM model takes into account the effect of a flexible frame that clamps the glass shell at its edges. A method is presented for the active control of the Young's modulus and the bending stiffness coefficient of the composite sandwich structure that consists of a glass plate and the attached piezoelectric MFC actuator. The predictions of the acoustic transmission loss frequency dependencies obtained by the FEM model are compared with experimental data. The results indicate that it is possible to increase the acoustic transmission loss by 20 and 25 dB at the frequencies of the first and second resonant modes of the planar and curved glass shells, respectively, using the effect of the shunt circuit with a negative capacitance.

  20. Density-near-zero using the acoustically induced transparency of a Fano acoustic resonator

    NASA Astrophysics Data System (ADS)

    Elayouch, A.; Addouche, M.; Farhat, M.; Amin, M.; Bağcı, H.; Khelif, A.

    2016-11-01

    We report experimental results of near-zero mass density involving an acoustic metamaterial supporting Fano resonance. For this, we designed and fabricated an acoustic resonator with two closely coupled modes and measured its transmission properties. Our study reveals that the phenomenon of acoustically induced transparency is accompanied by an effect of near-zero density. Indeed, the dynamic effective parameters obtained from experimental data show the presence of a frequency band where the effective mass density is close to zero, with high transmission levels reaching 0.7. Furthermore, we demonstrate that such effective parameters lead to wave guiding in a 90-degrees-bent channel. This kind of acoustic metamaterial can, therefore, give rise to acoustic functions like controlling the wavefront, which may lead to very promising applications in acoustic cloacking or imaging.

  1. Autonomous Adaptive Acoustic Relay Positioning

    DTIC Science & Technology

    2013-09-01

    species as well as uncover underwater archaeological sites [21]. Remotely-operated vehicles (ROVs) are designed for remote human control and use with a...distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT We consider the problem of maximizing underwater acoustic data transmission by...practical method of underwater wireless communication and improving channel throughput and reliability is key to improving the capabilities of underwater

  2. Transducer Arrays Suitable for Acoustic Imaging

    DTIC Science & Technology

    1978-06-01

    attention is placed on achieving high transduction efficiency and angular beam - widths of at least ±15°• T. Design techniques based on the transmission line...approximation so that the acoustic beam is caused to come to a focus in the exact analogue to a normal lens. The reference phase delays necessary to...fccus the acoustic beam are provided by a tapped surface acoustic wave delay line. A surface Ji acoustic wave is launched down the delay line with a

  3. Loss-improved electroacoustical modeling of small Helmholtz resonators.

    PubMed

    Starecki, Tomasz

    2007-10-01

    Modeling of small Helmholtz resonators based on electroacoustical analogies often results in significant disagreement with measurements, as existing models do not take into account some losses that are observed in practical implementations of such acoustical circuits, e.g., in photoacoustic Helmholtz cells. The paper presents a method which introduces loss corrections to the transmission line model, resulting in substantial improvement of simulations. Values of the loss corrections obtained from comparison of frequency responses of practically implemented resonators with computer simulations are presented in tabular and graphical form. A simple analytical function that can be used for interpolation or extrapolation of the loss corrections for other dimensions of the Helmholtz resonators is also given. Verification of such a modeling method against an open two-cavity Helmholtz structure shows very good agreement between measurements and simulations.

  4. Sound transmission through finite lightweight multilayered structures with thin air layers.

    PubMed

    Dijckmans, A; Vermeir, G; Lauriks, W

    2010-12-01

    The sound transmission loss (STL) of finite lightweight multilayered structures with thin air layers is studied in this paper. Two types of models are used to describe the vibro-acoustic behavior of these structures. Standard transfer matrix method assumes infinite layers and represents the plane wave propagation in the layers. A wave based model describes the direct sound transmission through a rectangular structure placed between two reverberant rooms. Full vibro-acoustic coupling between rooms, plates, and air cavities is taken into account. Comparison with double glazing measurements shows that this effect of vibro-acoustic coupling is important in lightweight double walls. For infinite structures, structural damping has no significant influence on STL below the coincidence frequency. In this frequency region, the non-resonant transmission or so-called mass-law behavior dominates sound transmission. Modal simulations suggest a large influence of structural damping on STL. This is confirmed by experiments with double fiberboard partitions and sandwich structures. The results show that for thin air layers, the damping induced by friction and viscous effects at the air gap surfaces can largely influence and improve the sound transmission characteristics.

  5. The Acoustic Model Evaluation Committee (AMEC) Reports. Volume 3. Evaluation of the RAYMODE X Propagation Loss Model. Book 2. Appendices A-D

    DTIC Science & Technology

    1982-09-01

    2 of 3 The Acasstic Model Evaluation Committee (AMEC) Reports Vodlme III, Appendices A-i) Elakiaie of Me RAYAODE X f*W#ton Loss Model (U) Prepared by...Richard B. Laer, NORDP Numerical Modefa Division 11N Pylos of RAYNONE X (g) ’T evy •u v ,ap,.,,.,.nDTiC hpWor 1984;& AELE TEfTE Aft 12 W~ LAJ...Activity NSTL Station, Mississippi 39529 84 04 06 511 CONFIDENTIAL .%.. CONFIDENTIAL Appendix IliA. Accuracy Assessment of RAYMODE X Compared to SUDS

  6. Membrane-type Acoustic Metamaterials

    NASA Astrophysics Data System (ADS)

    Ma, Guancong

    Resonant-base membrane-type acoustic metamaterials (MAMs) are investigated with experiments and simulations. Three exotic phenomena, including negative effective mass density, negative effective bulk modulus, and total absorption are demonstrated. As a start, a single-membrane resonator, which consists of a tightened piece of elastic membrane with a relatively rigid weight attached to the center, is studied in detail. It is shown that due to the anti-resonance, such structure is capable of totally reflecting low-frequency airborne sound. With the help of the simulations, we further reveal that the anti-resonance results in extremely large effective mass density, further explaining the large transmission loss. By establishing coupling between two MAMs via a sealed section of air, we discovered that the system displays clear monopolar resonance. Consequently, negativity in effective bulk modulus is achieved. The third kind of MAM is intended to be a perfect absorber for low-frequency sound. The task is accomplished by using asymmetric rigid platelets. We show that the eigenmodes' displacement profiles have large curvatures around the platelets' perimeters, implying highly concentrated elastic bending energy. Also, the broken symmetry introduces rotational freedom into our MAM. Consequently, the eigenmodes' coupling to far-field radiation is effectively reduced, thereby giving rise to strong absorption.

  7. Structural Acoustics and Vibrations

    NASA Astrophysics Data System (ADS)

    Chaigne, Antoine

    This structural chapter is devoted to vibrations of structures and to their coupling with the acoustic field. Depending on the context, the radiated sound can be judged as desirable, as is mostly the case for musical instruments, or undesirable, like noise generated by machinery. In architectural acoustics, one main goal is to limit the transmission of sound through walls. In the automobile industry, the engineers have to control the noise generated inside and outside the passenger compartment. This can be achieved by means of passive or active damping. In general, there is a strong need for quieter products and better sound quality generated by the structures in our daily environment.

  8. Acoustical evaluation of carbonized and activated cotton nonwovens.

    PubMed

    Jiang, N; Chen, J Y; Parikh, D V

    2009-12-01

    An activated carbon fiber nonwoven (ACF) was manufactured from a cotton nonwoven fabric. For the ACF acoustic application, a nonwoven composite of ACF with cotton nonwoven as a base layer was developed. Also produced were the composites of the cotton nonwoven base layer with a layer of glassfiber nonwoven, and the cotton nonwoven base layer with a layer of cotton fiber nonwoven. Their noise absorption coefficients and sound transmission loss were measured using the Brüel and Kjaer impedance tube instrument. Statistical significance of the differences between the composites was tested using the method of Duncan's grouping. The study concluded that the ACF composite exhibited a greater ability to absorb normal incidence sound waves than the composites with either glassfiber or cotton fiber. The analysis of sound transmission loss revealed that the three composites still obeyed the mass law of transmission loss. The composite with the surface layer of cotton fiber nonwoven possessed a higher fabric density and therefore showed a better sound insulation than the composites with glassfiber and ACF.

  9. Holograms for acoustics

    NASA Astrophysics Data System (ADS)

    Melde, Kai; Mark, Andrew G.; Qiu, Tian; Fischer, Peer

    2016-09-01

    Holographic techniques are fundamental to applications such as volumetric displays, high-density data storage and optical tweezers that require spatial control of intricate optical or acoustic fields within a three-dimensional volume. The basis of holography is spatial storage of the phase and/or amplitude profile of the desired wavefront in a manner that allows that wavefront to be reconstructed by interference when the hologram is illuminated with a suitable coherent source. Modern computer-generated holography skips the process of recording a hologram from a physical scene, and instead calculates the required phase profile before rendering it for reconstruction. In ultrasound applications, the phase profile is typically generated by discrete and independently driven ultrasound sources; however, these can only be used in small numbers, which limits the complexity or degrees of freedom that can be attained in the wavefront. Here we introduce monolithic acoustic holograms, which can reconstruct diffraction-limited acoustic pressure fields and thus arbitrary ultrasound beams. We use rapid fabrication to craft the holograms and achieve reconstruction degrees of freedom two orders of magnitude higher than commercial phased array sources. The technique is inexpensive, appropriate for both transmission and reflection elements, and scales well to higher information content, larger aperture size and higher power. The complex three-dimensional pressure and phase distributions produced by these acoustic holograms allow us to demonstrate new approaches to controlled ultrasonic manipulation of solids in water, and of liquids and solids in air. We expect that acoustic holograms will enable new capabilities in beam-steering and the contactless transfer of power, improve medical imaging, and drive new applications of ultrasound.

  10. Applications of surface acoustic and shallow bulk acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Campbell, Colin K.

    1989-10-01

    Surface acoustic wave (SAW) device coverage includes delay lines and filters operating at selected frequencies in the range from about 10 MHz to 11 GHz; modeling with single-crystal piezoelectrics and layered structures; resonators and low-loss filters; comb filters and multiplexers; antenna duplexers; harmonic devices; chirp filters for pulse compression; coding with fixed and programmable transversal filters; Barker and quadraphase coding; adaptive filters; acoustic and acoustoelectric convolvers and correlators for radar, spread spectrum, and packet radio; acoustooptic processors for Bragg modulation and spectrum analysis; real-time Fourier-transform and cepstrum processors for radar and sonar; compressive receivers; Nyquist filters for microwave digital radio; clock-recovery filters for fiber communications; fixed-, tunable-, and multimode oscillators and frequency synthesizers; acoustic charge transport; and other SAW devices for signal processing on gallium arsenide. Shallow bulk acoustic wave device applications include gigahertz delay lines, surface-transverse-wave resonators employing energy-trapping gratings, and oscillators with enhanced performance and capability.

  11. New transmission line analogy applied to single and multilayered piezoelectric transducers.

    PubMed

    Dion, J L

    1993-01-01

    It is shown that a piezoelectric element vibrating in an extensional or shear mode can be modeled rigorously by systematic use of the transmission line analogy and the superposition theorem. A schematic representation of such an element which is in a way more intuitive than others representations is introduced. The stresses on the electroded faces are considered as sources of stress applied at the two ends of an acoustic transmission line, since the acoustical perturbations may be considered as originating on these faces. Using transmission line theory, a complete set of expressions is found for electrical impedance, acoustic stresses, and velocities. Computed results are exactly the same as those given by the classical method, even if the computation sequence is almost entirely different. An intuitive graphical model for a piezoelectric element is proposed. It is also shown that the acoustic velocities on opposite faces of an asymmetrical loaded piezoelectric plate are exactly equal at the antiresonance frequency when internal losses are neglected. The programs developed can be used efficiently for practical multilayered transducer design.

  12. Detecting Structural Failures Via Acoustic Impulse Responses

    NASA Technical Reports Server (NTRS)

    Bayard, David S.; Joshi, Sanjay S.

    1995-01-01

    Advanced method of acoustic pulse reflectivity testing developed for use in determining sizes and locations of failures within structures. Used to detect breaks in electrical transmission lines, detect faults in optical fibers, and determine mechanical properties of materials. In method, structure vibrationally excited with acoustic pulse (a "ping") at one location and acoustic response measured at same or different location. Measured acoustic response digitized, then processed by finite-impulse-response (FIR) filtering algorithm unique to method and based on acoustic-wave-propagation and -reflection properties of structure. Offers several advantages: does not require training, does not require prior knowledge of mathematical model of acoustic response of structure, enables detection and localization of multiple failures, and yields data on extent of damage at each location.

  13. Reducing Thermal Conduction In Acoustic Levitators

    NASA Technical Reports Server (NTRS)

    Lierke, Ernst G.; Leung, Emily W.; Bhat, Balakrishna T.

    1991-01-01

    Acoustic transducers containing piezoelectric driving elements made more resistant to heat by reduction of effective thermal-conductance cross sections of metal vibration-transmitting rods in them, according to proposal. Used to levitate small objects acoustically for noncontact processing in furnaces. Reductions in cross sections increase amplitudes of transmitted vibrations and reduce loss of heat from furnaces.

  14. Estimating suspended solids concentrations from backscatter intensity measured by acoustic Doppler current profiler in San Francisco Bay, California

    USGS Publications Warehouse

    Gartner, J.W.

    2004-01-01

    The estimation of mass concentration of suspended solids is one of the properties needed to understand the characteristics of sediment transport in bays and estuaries. However, useful measurements or estimates of this property are often problematic when employing the usual methods of determination from collected water samples or optical sensors. Analysis of water samples tends to undersample the highly variable character of suspended solids, and optical sensors often become useless from biological fouling in highly productive regions. Acoustic sensors, such as acoustic Doppler current profilers that are now routinely used to measure water velocity, have been shown to hold promise as a means of quantitatively estimating suspended solids from acoustic backscatter intensity, a parameter used in velocity measurement. To further evaluate application of this technique using commercially available instruments, profiles of suspended solids concentrations are estimated from acoustic backscatter intensity recorded by 1200- and 2400-kHz broadband acoustic Doppler current profilers located at two sites in San Francisco Bay, California. ADCP backscatter intensity is calibrated using optical backscatterance data from an instrument located at a depth close to the ADCP transducers. In addition to losses from spherical spreading and water absorption, calculations of acoustic transmission losses account for attenuation from suspended sediment and correction for nonspherical spreading in the near field of the acoustic transducer. Acoustic estimates of suspended solids consisting of cohesive and noncohesive sediments are found to agree within about 8-10% (of the total range of concentration) to those values estimated by a second optical backscatterance sensor located at a depth further from the ADCP transducers. The success of this approach using commercially available Doppler profilers provides promise that this technique might be appropriate and useful under certain conditions in

  15. Controlling sound with acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Cummer, Steven A.; Christensen, Johan; Alù, Andrea

    2016-03-01

    Acoustic metamaterials can manipulate and control sound waves in ways that are not possible in conventional materials. Metamaterials with zero, or even negative, refractive index for sound offer new possibilities for acoustic imaging and for the control of sound at subwavelength scales. The combination of transformation acoustics theory and highly anisotropic acoustic metamaterials enables precise control over the deformation of sound fields, which can be used, for example, to hide or cloak objects from incident acoustic energy. Active acoustic metamaterials use external control to create effective material properties that are not possible with passive structures and have led to the development of dynamically reconfigurable, loss-compensating and parity-time-symmetric materials for sound manipulation. Challenges remain, including the development of efficient techniques for fabricating large-scale metamaterial structures and converting laboratory experiments into useful devices. In this Review, we outline the designs and properties of materials with unusual acoustic parameters (for example, negative refractive index), discuss examples of extreme manipulation of sound and, finally, provide an overview of future directions in the field.

  16. The acoustic environment of the Florida manatee: Correlation with level of habitat use

    NASA Astrophysics Data System (ADS)

    Miksis-Olds, Jennifer L.; Miller, James H.; Tyack, Peter L.

    2004-05-01

    The Florida manatee is regularly exposed to high volumes of vessel traffic and other human-related noise pollutants because of their coastal distribution. Quantifying specific aspects of the manatees' acoustic environment will allow for a better understanding of how these animals are responding to both natural and human induced changes in their environment. Acoustic recordings and transmission loss measurements were made in two critical manatee habitats: seagrass beds and dredged basins. Twenty-four sampling sites were chosen based on the frequency of manatee presence in specific areas from 2000-2003. Recordings were composed of both ambient noise levels and transient noise sources. The Monterey-Miami Parabolic Equation Model (MMPE) was used to relate environmental parameters to transmission loss, and model outputs were verified by field tests at all sites. Preliminary results indicate that high-use grassbeds have higher levels of transmission loss compared to low-use sites. Additionally, high-use grassbeds have lower ambient noise in the early morning and later afternoon hours compared to low-use grassbeds. The application of noise measurements and model results can now be used to predict received levels, signal-to-noise ratios, and reliable detection of biologically relevant signals in manatee habitats and in the many different environments that marine mammals live.

  17. The acoustic environment of the Florida manatee: Correlation with level of habitat use

    NASA Astrophysics Data System (ADS)

    Miksis-Olds, Jennifer L.; Miller, James H.; Tyack, Peter L.

    2001-05-01

    The Florida manatee is regularly exposed to high volumes of vessel traffic and other human-related noise pollutants because of their coastal distribution. Quantifying specific aspects of the manatees' acoustic environment will allow for a better understanding of how these animals are responding to both natural and human induced changes in their environment. Acoustic recordings and transmission loss measurements were made in two critical manatee habitats: seagrass beds and dredged basins. Twenty-four sampling sites were chosen based on the frequency of manatee presence in specific areas from 2000-2003. Recordings were composed of both ambient noise levels and transient noise sources. The Monterey-Miami Parabolic Equation Model (MMPE) was used to relate environmental parameters to transmission loss, and model outputs were verified by field tests at all sites. Preliminary results indicate that high-use grassbeds have higher levels of transmission loss compared to low-use sites. Additionally, high-use grassbeds have lower ambient noise in the early morning and later afternoon hours compared to low-use grassbeds. The application of noise measurements and model results can now be used to predict received levels, signal-to-noise ratios, and reliable detection of biologically relevant signals in manatee habitats and in the many different environments that marine mammals live.

  18. Acoustic biosensors

    PubMed Central

    Fogel, Ronen; Seshia, Ashwin A.

    2016-01-01

    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors. PMID:27365040

  19. Acoustic biosensors.

    PubMed

    Fogel, Ronen; Limson, Janice; Seshia, Ashwin A

    2016-06-30

    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors.

  20. Vibro-acoustic modelling of aircraft double-walls with structural links using Statistical Energy Analysis

    NASA Astrophysics Data System (ADS)

    Campolina, Bruno L.

    The prediction of aircraft interior noise involves the vibroacoustic modelling of the fuselage with noise control treatments. This structure is composed of a stiffened metallic or composite panel, lined with a thermal and acoustic insulation layer (glass wool), and structurally connected via vibration isolators to a commercial lining panel (trim). The goal of this work aims at tailoring the noise control treatments taking design constraints such as weight and space optimization into account. For this purpose, a representative aircraft double-wall is modelled using the Statistical Energy Analysis (SEA) method. Laboratory excitations such as diffuse acoustic field and point force are addressed and trends are derived for applications under in-flight conditions, considering turbulent boundary layer excitation. The effect of the porous layer compression is firstly addressed. In aeronautical applications, compression can result from the installation of equipment and cables. It is studied analytically and experimentally, using a single panel and a fibrous uniformly compressed over 100% of its surface. When compression increases, a degradation of the transmission loss up to 5 dB for a 50% compression of the porous thickness is observed mainly in the mid-frequency range (around 800 Hz). However, for realistic cases, the effect should be reduced since the compression rate is lower and compression occurs locally. Then the transmission through structural connections between panels is addressed using a four-pole approach that links the force-velocity pair at each side of the connection. The modelling integrates experimental dynamic stiffness of isolators, derived using an adapted test rig. The structural transmission is then experimentally validated and included in the double-wall SEA model as an equivalent coupling loss factor (CLF) between panels. The tested structures being flat, only axial transmission is addressed. Finally, the dominant sound transmission paths are

  1. PORTABLE ACOUSTIC MONITORING PACKAGE (PAMP)

    SciTech Connect

    John l. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra

    2003-07-01

    The 1st generation acoustic monitoring package was designed to detect and analyze weak acoustic signals inside natural gas transmission lines. Besides a microphone it housed a three-inch diameter aerodynamic acoustic signal amplifier to maximize sensitivity to leak induced {Delta}p type signals. The theory and test results of this aerodynamic signal amplifier was described in the master's degree thesis of our Research Assistant Deepak Mehra who is about to graduate. To house such a large three-inch diameter sensor required the use of a steel 300-psi rated 4 inch weld neck flange, which itself weighed already 29 pounds. The completed 1st generation Acoustic Monitoring Package weighed almost 100 pounds. This was too cumbersome to mount in the field, on an access port at a pipeline shut-off valve. Therefore a 2nd generation and truly Portable Acoustic Monitor was built. It incorporated a fully self-contained {Delta}p type signal sensor, rated for line pressures up to 1000 psi with a base weight of only 6 pounds. This is the Rosemont Inc. Model 3051CD-Range 0, software driven sensor, which is believed to have industries best total performance. Its most sensitive unit was purchased with a {Delta}p range from 0 to 3 inch water. This resulted in the herein described 2nd generation: Portable Acoustic Monitoring Package (PAMP) for pipelines up to 1000 psi. Its 32-pound total weight includes an 18-volt battery. Together with a 3 pound laptop with its 4-channel data acquisition card, completes the equipment needed for field acoustic monitoring of natural gas transmission pipelines.

  2. Broadband Metamaterial for Nonresonant Matching of Acoustic Waves

    DTIC Science & Technology

    2012-03-28

    transmission (EOT)5–8. Lately, it has been extended to acoustic waves, as extraordinary acoustic transmission ( EAT )9–11. Usually these phenomena are achieved... EAT limitations. To this goal, we show a way to manipulate the effective constitutive properties (density reff and sound velocity ceff) of an...obtained. Most EAT phenomena rely on resonance effects that are inherently narrow-band, and for which large transmission is usually hindered by

  3. Radiosurgery of acoustic neurinomas

    SciTech Connect

    Flickinger, J.C.; Lunsford, L.D.; Coffey, R.J.; Linskey, M.E.; Bissonette, D.J.; Maitz, A.H.; Kondziolka, D. )

    1991-01-15

    Eighty-five patients with acoustic neurinomas underwent stereotactic radiosurgery with the gamma unit at the University of Pittsburgh (Pittsburgh, PA) during its first 30 months of operation. Neuroimaging studies performed in 40 patients with more than 1 year follow-up showed that tumors were smaller in 22 (55%), unchanged in 17 (43%), and larger in one (2%). The 2-year actuarial rates for preservation of useful hearing and any hearing were 46% and 62%, respectively. Previously undetected neuropathies of the trigeminal (n = 12) and facial nerves (n = 14) occurred 1 week to 1 year after radiosurgery (median, 7 and 6 months, respectively), and improved at median intervals of 13 and 8 months, respectively, after onset. Hearing loss was significantly associated with increasing average tumor diameter (P = 0.04). No deterioration of any cranial nerve function has yet developed in seven patients with average tumor diameters less than 10 mm. Radiosurgery is an important treatment alternative for selected acoustic neurinoma patients.

  4. Evaluation of Parallel-Element, Variable-Impedance, Broadband Acoustic Liner Concepts

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Howerton, Brian M.; Ayle, Earl

    2012-01-01

    Recent trends in aircraft engine design have highlighted the need for acoustic liners that provide broadband sound absorption with reduced liner thickness. Three such liner concepts are evaluated using the NASA normal incidence tube. Two concepts employ additive manufacturing techniques to fabricate liners with variable chamber depths. The first relies on scrubbing losses within narrow chambers to provide acoustic resistance necessary for sound absorption. The second employs wide chambers that provide minimal resistance, and relies on a perforated sheet to provide acoustic resistance. The variable-depth chambers used in both concepts result in reactance spectra near zero. The third liner concept employs mesh-caps (resistive sheets) embedded at variable depths within adjacent honeycomb chambers to achieve a desired impedance spectrum. Each of these liner concepts is suitable for use as a broadband sound absorber design, and a transmission line model is presented that provides good comparison with their respective acoustic impedance spectra. This model can therefore be used to design acoustic liners to accurately achieve selected impedance spectra. Finally, the effects of increasing the perforated facesheet thickness are demonstrated, and the validity of prediction models based on lumped element and wave propagation approaches is investigated. The lumped element model compares favorably with measured results for liners with thin facesheets, but the wave propagation model provides good comparisons for a wide range of facesheet thicknesses.

  5. Physical-space refraction-corrected transmission ultrasound computed tomography made computationally practical.

    PubMed

    Li, Shengying; Mueller, Klaus; Jackowski, Marcel; Dione, Donald; Staib, Lawrence

    2008-01-01

    Transmission Ultrasound Computed Tomography (CT) is strongly affected by the acoustic refraction properties of the imaged tissue, and proper modeling and correction of these effects is crucial to achieving high-quality image reconstructions. A method that can account for these refractive effects solves the governing Eikonal equation within an iterative reconstruction framework, using a wave-front tracking approach. Excellent results can be obtained, but at considerable computational expense. Here, we report on the acceleration of three Eikonal solvers (Fast Marching Method (FMM), Fast Sweeping Method (FSM), Fast Iterative Method (FIM)) on three computational platforms (commodity graphics hardware (GPUs), multi-core and cluster CPUs), within this refractive Transmission Ultrasound CT framework. Our efforts provide insight into the capabilities of the various architectures for acoustic wave-front tracking, and they also yield a framework that meets the interactive demands of clinical practice, without a loss in reconstruction quality.

  6. NW-MILO Acoustic Data Collection

    SciTech Connect

    Matzner, Shari; Myers, Joshua R.; Maxwell, Adam R.; Jones, Mark E.

    2010-02-17

    signatures of small vessels. The sampling rate of 8 kHz and low pass filtering to 2 kHz results in an alias-free signal in the frequency band that is appropriate for small vessels. Calibration was performed using a Lubell underwater speaker so that the raw data signal levels can be converted to sound pressure. Background noise is present due to a nearby pump and as a result of tidal currents. More study is needed to fully characterize the noise, but it does not pose an obstacle to using the acoustic data for the purposes of vessel detection and signature analysis. The detection range for a small vessel was estimated using the calibrated voltage response of the system and a cylindrical spreading model for transmission loss. The sound pressure of a typical vessel with an outboard motor was found to be around 140 dB mPa, and could theoretically be detected from 10 km away. In practical terms, a small vessel could reliably be detected from 3 - 5 km away. The data is archived in netCDF files, a standard scientific file format that is "self describing". This means that each data file contains the metadata - timestamps, units, origin, etc. - needed to make the data meaningful and portable. Other file formats, such as XML, are also supported. A visualization tool has been developed to view the acoustic data in the form of spectrograms, along with the coincident radar track data and camera images.

  7. SU-8 photoresist and SU-8 based nanocomposites for broadband acoustical matching at 1 GHz

    NASA Astrophysics Data System (ADS)

    Ndieguene, A.; Campistron, P.; Carlier, J.; Wang, S.; Callens-Debavelaere, D.; Nongaillard, B.

    2009-11-01

    So as to integrate acoustic functions in BioMEMS using 1 GHz ZnO transducers deposited on silicon substrates, acoustic waves propagation through the silicon substrate and its transmission in water needs to be maximized (the insertion losses at the Si / water interface are about 6dB). In the context of integration, it is interesting for mechanical impedance matching to use photosensitive materials such as SU-8 so that patterns may be obtained. Nanocomposite materials based on SU-8 mixed with nanoparticles having adequate impedances were fabricated. These new materials are characterized in terms of their acoustic velocity, impedance and attenuation. For this, the nanocomposite layers are deposited on the substrate by spin coating to obtain a thickness of about 10 μm, in order to separate acoustic echoes from the material (even if λ/4 layer thickness is lower than 1 μm). The insertion losses of the device immersed in water can be simulated as a function of frequency for a given reflection coefficient between the silicon substrate and the photoresist. The characteristics of some nanocomposites made with SU-8 and various concentrations of nanoparticles like Ti02, SrTiO3 or W have been determined.

  8. Evidence for anisotropic dielectric properties of monoclinic hafnia using valence electron energy-loss spectroscopy in high-resolution transmission electron microscopy and ab initio time-dependent density-functional theory

    NASA Astrophysics Data System (ADS)

    Guedj, C.; Hung, L.; Zobelli, A.; Blaise, P.; Sottile, F.; Olevano, V.

    2014-12-01

    The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO2) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO2, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO2 may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.

  9. Nonlinear Acoustics

    DTIC Science & Technology

    1974-02-14

    Wester- velt. [60] Streaming. In 1831, Michael Faraday [61] noted that currents of air were set up in the neighborhood of vibrating plates-the first... ducei in the case of a paramettc amy (from Berktay an Leahy 141). C’ "". k•, SEC 10.1 NONLINEAR ACOUSTICS 345 The principal results of their analysis

  10. Sound transmission through curved aircraft panels with stringer and ring frame attachments

    NASA Astrophysics Data System (ADS)

    Liu, Bilong; Feng, Leping; Nilsson, Anders

    2007-03-01

    A numerical approach based on a receptance method has been developed to evaluate the airborne sound insulation of aircraft panels with stringer and ring frame attachments. Theoretical predictions have been compared with laboratory measurements conducted on both model structures and aircraft panels. Certain parameters were varied in this study to gauge stiffener effects on sound transmission through the panel. For large curved aircraft panels studied here, it was found that the ring frames have little influence on sound transmission loss in the frequency range of interest. However, the stringers may have considerable influence on the sound transmission loss. The stringer improves the sound transmission loss for a curved panel in the vicinity of the ring frequency, but may result in a potential deterioration above this frequency. In addition it was found that the sound transmission loss for the composite skin attached with composite stringers was lower than that of the metallic panel attached with metallic stringers. The results suggest that acoustical optimization design for the stringers is necessary to achieve improved airborne sound insulation for aircraft panels.

  11. Transmission-reflection analysis for localization of temporally successive multipoint perturbations in a distributed fiber-optic loss sensor based on Rayleigh backscattering.

    PubMed

    Spirin, Vasilii V

    2003-03-01

    A novel method is presented for the localization of multipoint loss-inducing perturbations in a distributed fiber-optic sensor. The proposed simple technique is based on measurement of the transmitted and the Rayleigh-backscattered powers of an unmodulated light launched into a sensing fiber. The positions of consecutive perturbations are determined by measuring the slopes of the dependence of normalized Rayleigh-backscattering power versus the square of normalized transmitted power. It is shown that these slopes uniquely depend on the positions of the disturbances along the test fiber. The method allows localization of any number of the perturbations that appear one after another at different positions along the test fiber without ambiguity. Good agreement is obtained between calculated and experimentally measured slopes for a loss that was consecutively induced near the source and remote ends of 2.844-km-long fiber.

  12. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, Butrus T.; Chou, Ching H.

    1990-01-01

    A shear acoustic transducer-lens system in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens.

  13. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, B.T.; Chou, C.H.

    1990-03-20

    A shear acoustic transducer-lens system is described in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens. 9 figs.

  14. Bottom Interaction in Long Range Acoustic Propagation

    DTIC Science & Technology

    2009-09-30

    the implications for seafloor receptions in shallower water. OBJECTIVES On previous NPAL (North Pacific Acoustic Laboratory) tests acoustic...south, east, and west from the DVLA in comparable water depths). Water depth along the 3200km path to the furthest transmission station varied between...been carried out on all of the available OBS hydrophone and geophone data. The geophone (South OBS, East OBS and West OBS) and DVLA (lower most

  15. Graphical Acoustic Liner Design and Analysis Tool

    NASA Technical Reports Server (NTRS)

    Howerton, Brian M. (Inventor); Jones, Michael G. (Inventor)

    2016-01-01

    An interactive liner design and impedance modeling tool comprises software utilized to design acoustic liners for use in constrained spaces, both regularly and irregularly shaped. A graphical user interface allows the acoustic channel geometry to be drawn in a liner volume while the surface impedance calculations are updated and displayed in real-time. A one-dimensional transmission line model may be used as the basis for the impedance calculations.

  16. Acoustic characteristics of circular bends in pipes

    NASA Astrophysics Data System (ADS)

    Firth, D.; Fahy, F. J.

    1984-11-01

    The acoustic properties of circular bends in pipework systems are investigated by calculation of the mode shapes and propagation constants of the acoustic modes of the bend, the torus modes, and by evaluation of the transmission and reflection coefficients at a bend in an otherwise infinite straight pipe. The coefficients for the first three cylinder and torus modes are plotted against frequency for the case of a plane wave incident upon a 90° bend. The pipe walls are assumed to be rigid.

  17. Extreme stiffness hyperbolic elastic metamaterial for total transmission subwavelength imaging

    NASA Astrophysics Data System (ADS)

    Lee, Hyuk; Oh, Joo Hwan; Seung, Hong Min; Cho, Seung Hyun; Kim, Yoon Young

    2016-04-01

    Subwavelength imaging by metamaterials and extended work to pursue total transmission has been successfully demonstrated with electromagnetic and acoustic waves very recently. However, no elastic counterpart has been reported because earlier attempts suffer from considerable loss. Here, for the first time, we realize an elastic hyperbolic metamaterial lens and experimentally show total transmission subwavelength imaging with measured wave field inside the metamaterial lens. The main idea is to compensate for the decreased impedance in the perforated elastic metamaterial by utilizing extreme stiffness, which has not been independently actualized in a continuum elastic medium so far. The fabricated elastic lens is capable of directly transferring subwavelength information from the input to the output boundary. In the experiment, this intriguing phenomenon is confirmed by scanning the elastic structures inside the lens with laser scanning vibrometer. The proposed elastic metamaterial lens will bring forth significant guidelines for ultrasonic imaging techniques.

  18. Extreme stiffness hyperbolic elastic metamaterial for total transmission subwavelength imaging.

    PubMed

    Lee, Hyuk; Oh, Joo Hwan; Seung, Hong Min; Cho, Seung Hyun; Kim, Yoon Young

    2016-04-04

    Subwavelength imaging by metamaterials and extended work to pursue total transmission has been successfully demonstrated with electromagnetic and acoustic waves very recently. However, no elastic counterpart has been reported because earlier attempts suffer from considerable loss. Here, for the first time, we realize an elastic hyperbolic metamaterial lens and experimentally show total transmission subwavelength imaging with measured wave field inside the metamaterial lens. The main idea is to compensate for the decreased impedance in the perforated elastic metamaterial by utilizing extreme stiffness, which has not been independently actualized in a continuum elastic medium so far. The fabricated elastic lens is capable of directly transferring subwavelength information from the input to the output boundary. In the experiment, this intriguing phenomenon is confirmed by scanning the elastic structures inside the lens with laser scanning vibrometer. The proposed elastic metamaterial lens will bring forth significant guidelines for ultrasonic imaging techniques.

  19. Extreme stiffness hyperbolic elastic metamaterial for total transmission subwavelength imaging

    PubMed Central

    Lee, Hyuk; Oh, Joo Hwan; Seung, Hong Min; Cho, Seung Hyun; Kim, Yoon Young

    2016-01-01

    Subwavelength imaging by metamaterials and extended work to pursue total transmission has been successfully demonstrated with electromagnetic and acoustic waves very recently. However, no elastic counterpart has been reported because earlier attempts suffer from considerable loss. Here, for the first time, we realize an elastic hyperbolic metamaterial lens and experimentally show total transmission subwavelength imaging with measured wave field inside the metamaterial lens. The main idea is to compensate for the decreased impedance in the perforated elastic metamaterial by utilizing extreme stiffness, which has not been independently actualized in a continuum elastic medium so far. The fabricated elastic lens is capable of directly transferring subwavelength information from the input to the output boundary. In the experiment, this intriguing phenomenon is confirmed by scanning the elastic structures inside the lens with laser scanning vibrometer. The proposed elastic metamaterial lens will bring forth significant guidelines for ultrasonic imaging techniques. PMID:27040762

  20. Acoustic chaos

    SciTech Connect

    Lauterborn, W.; Parlitz, U.; Holzfuss, J.; Billo, A.; Akhatov, I.

    1996-06-01

    Acoustic cavitation, a complex, spatio-temporal dynamical system, is investigated with respect to its chaotic properties. The sound output, the {open_quote}{open_quote}noise{close_quote}{close_quote}, is subjected to time series analysis. The spatial dynamics of the bubble filaments is captured by high speed holographic cinematography and subsequent digital picture processing from the holograms. Theoretical models are put forward for describing the pattern formation. {copyright} {ital 1996 American Institute of Physics.}

  1. Medical Acoustics

    NASA Astrophysics Data System (ADS)

    Beach, Kirk W.; Dunmire, Barbrina

    Medical acoustics can be subdivided into diagnostics and therapy. Diagnostics are further separated into auditory and ultrasonic methods, and both employ low amplitudes. Therapy (excluding medical advice) uses ultrasound for heating, cooking, permeablizing, activating and fracturing tissues and structures within the body, usually at much higher amplitudes than in diagnostics. Because ultrasound is a wave, linear wave physics are generally applicable, but recently nonlinear effects have become more important, even in low-intensity diagnostic applications.

  2. An acoustic double fishnet using Helmholtz resonators.

    PubMed

    Murray, A R J; Summers, I R; Sambles, J R; Hibbins, A P

    2014-09-01

    The acoustic transmission of a closely spaced pair of patterned and perforated rigid plates is explored in air. The structure resembles an acoustic double fishnet design, with each plate modified such that the gap between them acts as an array of Helmholtz resonators. This allows the center frequency of the stop band to be reduced by a factor greater than 2 from the value obtained for the conventional acoustic double fishnet design. Experimental results accord well with the predictions of a finite element model.

  3. Acoustic dose and acoustic dose-rate.

    PubMed

    Duck, Francis

    2009-10-01

    Acoustic dose is defined as the energy deposited by absorption of an acoustic wave per unit mass of the medium supporting the wave. Expressions for acoustic dose and acoustic dose-rate are given for plane-wave conditions, including temporal and frequency dependencies of energy deposition. The relationship between the acoustic dose-rate and the resulting temperature increase is explored, as is the relationship between acoustic dose-rate and radiation force. Energy transfer from the wave to the medium by means of acoustic cavitation is considered, and an approach is proposed in principle that could allow cavitation to be included within the proposed definitions of acoustic dose and acoustic dose-rate.

  4. Mid-frequency acoustic propagation in shallow water on the New Jersey shelf: mean intensity.

    PubMed

    Tang, Dajun; Henyey, Frank S; Wang, Zhongkang; Williams, Kevin L; Rouseff, Daniel; Dahl, Peter H; Quijano, Jorge; Choi, Jee Woong

    2008-09-01

    Mid-frequency (1-10 kHz) sound propagation was measured at ranges 1-9 km in shallow water in order to investigate intensity statistics. Warm water near the bottom results in a sound speed minimum. Environmental measurements include sediment sound speed and water sound speed and density from a towed conductivity-temperature-depth chain. Ambient internal waves contribute to acoustic fluctuations. A simple model involving modes with random phases predicts the mean transmission loss to within a few dB. Quantitative ray theory fails due to near axial focusing. Fluctuations of the intensity field are dominated by water column variability.

  5. Acoustic Tooth Cleaner

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.

    1984-01-01

    Acoustically-energized water jet aids in plaque breakdown. Acoustic Wand includes acoustic transducer 1/4 wave plate, and tapered cone. Together elements energize solution of water containing mild abrasive injected into mouth to help prevent calculous buildup.

  6. Acoustic plane waves incident on an oblique clamped panel in a rectangular duct

    NASA Technical Reports Server (NTRS)

    Unz, H.; Roskam, J.

    1980-01-01

    The theory of acoustic plane waves incident on an oblique clamped panel in a rectangular duct was developed from basic theoretical concepts. The coupling theory between the elastic vibrations of the panel (plate) and the oblique incident acoustic plane wave in infinite space was considered in detail, and was used for the oblique clamped panel in the rectangular duct. The partial differential equation which governs the vibrations of the clamped panel (plate) was modified by adding to it stiffness (spring) forces and damping forces. The Transmission Loss coefficient and the Noise Reduction coefficient for oblique incidence were defined and derived in detail. The resonance frequencies excited by the free vibrations of the oblique finite clamped panel (plate) were derived and calculated in detail for the present case.

  7. A lightweight low-frequency sound insulation membrane-type acoustic metamaterial

    NASA Astrophysics Data System (ADS)

    Lu, Kuan; Wu, Jiu Hui; Guan, Dong; Gao, Nansha; Jing, Li

    2016-02-01

    A novel membrane-type acoustic metamaterial with a high sound transmission loss (STL) at low frequencies (⩽500Hz) was designed and the mechanisms were investigated by using negative mass density theory. This metamaterial's structure is like a sandwich with a thin (thickness=0.25mm) lightweight flexible rubber material within two layers of honeycomb cell plates. Negative mass density was demonstrated at frequencies below the first natural frequency, which results in the excellent low-frequency sound insulation. The effects of different structural parameters of the membrane on the sound-proofed performance at low frequencies were investigated by using finite element method (FEM). The numerical results show that, the STL can be modulated to higher value by changing the structural parameters, such as the membrane surface density, the unite cell film shape, and the membrane tension. The acoustic metamaterial proposed in this study could provide a potential application in the low-frequency noise insulation.

  8. Acoustic Seaglider: PhilSea10 Data Analysis

    DTIC Science & Technology

    2016-06-13

    understanding that the navigation and the ocean sound speed and currents be jointly determined. LONG-TERM GOALS Within the Ocean Acoustics Deep Water... 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

  9. High Frequency Acoustic Channel Characterization for Propagation and Ambient Noise

    DTIC Science & Technology

    2008-09-30

    has done in close collaboration with Michael Porter and Paul Hursky (HLS Research) also supported by ONR. We have also been collaborating with Steve... Michael Porter , “A passive fathometer technique for imaging seabed layering using ambient noise”, J. Acoust. Soc. Am., 120, 1315-1323, (September...Siderius and Michael Porter , “Modeling broadband ocean acoustic transmissions with time- varying sea surfaces”, J. Acoust. Soc. Am., 124 (1), 137-150

  10. Characterization of anisotropic acoustic metamaterial slabs

    NASA Astrophysics Data System (ADS)

    Park, Jun Hyeong; Lee, Hyung Jin; Kim, Yoon Young

    2016-01-01

    In an anisotropic acoustic metamaterial, the off-diagonal components of its effective mass density tensor should be considered in order to describe the anisotropic behavior produced by arbitrarily shaped inclusions. However, few studies have been carried out to characterize anisotropic acoustic metamaterials. In this paper, we propose a method that uses the non-diagonal effective mass density tensor to determine the behavior of anisotropic acoustic metamaterials. Our method accurately evaluates the effective properties of anisotropic acoustic metamaterials by separately dealing with slabs made of single and multiple unit cells along the thickness direction. To determine the effective properties, the reflection and transmission coefficients of an acoustic metamaterial slab are calculated, and then the wave vectors inside of the slab are determined using these coefficients. The effective material properties are finally determined by utilizing the spatial dispersion relation of the anisotropic acoustic metamaterial. Since the dispersion relation of an anisotropic acoustic metamaterial is explicitly used, its effective properties can be easily determined by only using a limited number of normal and oblique plane wave incidences into a metamaterial slab, unlike existing approaches requiring a large number of wave incidences. The validity of the proposed method is verified by conducting wave simulations for anisotropic acoustic metamaterial slabs with Z-shaped elastic inclusions of tilted principal material axes.

  11. Acoustical properties of drill strings

    SciTech Connect

    Drumheller, D.S.

    1988-08-01

    The recovery of petrochemical and geothermal resources requires extensive drilling of wells to increasingly greater depths. Real-time collection and telemetry of data about the drilling process while it occurs thousands of feet below the surface is an effective way of improving the efficiency of drilling operations. Unfortunately, due to hostile down-hole environments, telemetry of this data is an extremely difficult problem. Currently, commercial systems transmit data to the surface by producing pressure pulses within the portion of the drilling mud enclosed in the hollow steel drill string. Transmission rates are between two and four data bits per second. Any system capable of raising data rates without increasing the complexity of the drilling process will have significant economic impact. One alternative system is based upon acoustical carrier waves generated within the drill string itself. If developed, this method would accommodate data rates up to 100 bits per second. Unfortunately, the drill string is a periodic structure of pipe and threaded tool joints, the transmission characteristics are very complex and exhibit a banded and dispersive structure. Over the past forty years, attempts to field systems based upon this transmission method have resulted in little success. This paper examines this acoustical transmission problem in great detail. The basic principles of acoustic wave propagation in the periodic structure of the drill string are examined through theory, laboratory experiment, and field test. The results indicate the existence of frequency bands which are virtually free of attenuation and suitable for data transmission at high bit rates. 9 refs., 38 figs., 2 tabs.

  12. A study of methods to predict and measure the transmission of sound through the walls of light aircraft. Integration of certain singular boundary element integrals for applications in linear acoustics

    NASA Technical Reports Server (NTRS)

    Zimmerle, D.; Bernhard, R. J.

    1985-01-01

    An alternative method for performing singular boundary element integrals for applications in linear acoustics is discussed. The method separates the integral of the characteristic solution into a singular and nonsingular part. The singular portion is integrated with a combination of analytic and numerical techniques while the nonsingular portion is integrated with standard Gaussian quadrature. The method may be generalized to many types of subparametric elements. The integrals over elements containing the root node are considered, and the characteristic solution for linear acoustic problems are examined. The method may be generalized to most characteristic solutions.

  13. A Very High Bit Rate Broadband Acoustic Modem for Short-to-Medium Range Data Transmission in Ports And Shallow Water Using Spread Spectrum Modulation and Decision Feedback Equalizing

    DTIC Science & Technology

    2008-09-30

    using the high-resolution, low-noise acquisition system developed by EdgeTech in collaboration with FAU . The acquisition system produces complex base...direct transducer coupling; (2) System calibration in the acoustic tank at FAU SeaTech; (3) Field tests in the FAU SeaTech marina. During the later...the FAU SeaTech marina on July 25th, 2008 (Figure 3). During the SeaTech demonstration, the source was operating at 32 W of output acoustic power

  14. Magneto acoustical emission in nanocrystalline Mn–Zn ferrites

    SciTech Connect

    Praveena, K.; Murthty, S.R.

    2013-11-15

    Graphical abstract: Mn{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4} powders were prepared by microwave hydrothermal method. The powders were characterized by X-ray diffraction, transmission electron microscope. The powders were sintered at different temperatures 400, 500, 600, 700, 800 and 900 °C/30 min using microwave sintering method. The grain size was estimated by scanning electron microscope. The room temperature dielectric and magnetic properties were studied in the frequency range (100 kHz–1.8 GHz). The magnetization properties were measured upto 1.5 T. The acoustic emission has been measured along the hysteresis loops from 80 K to Curie temperature. It is found that the magneto-acoustic emission (MAE) activity along hysteresis loop is proportional to the hysteresis losses during the same loop. This law has been verified on series of polycrystalline ferrites and found that the law is valid whatever the composition, the grain size and temperature. It is also found that the domain wall creation/or annihilation processes are the origin of the MAE. - Highlights: • The AE been measured along the hysteresis loops from 80 K to Curie temperature. • The MAE activity along hysteresis loop is proportional to P{sub h} during the same loop. • It is found that the domain wall creation/or annihilation processes are the origin of the MAE. - Abstract: Mn{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4} powders were prepared by microwave hydrothermal method. The powders were characterized by X-ray diffraction, transmission electron microscope. The powders were sintered at different temperatures 400, 500, 600, 700, 800 and 900 °C/30 min using microwave sintering method. The grain size was estimated by scanning electron microscope. The room temperature dielectric and magnetic properties were studied in the frequency range (100 kHz–1.8 GHz). The magnetization properties were measured upto 1.5 T. The acoustic emission has been measured along the hysteresis loops from 80 K to Curie

  15. Acoustic mechanical feedthroughs

    NASA Astrophysics Data System (ADS)

    Sherrit, Stewart; Walkemeyer, Phillip; Bao, Xiaoqi; Bar-Cohen, Yoseph; Badescu, Mircea

    2013-04-01

    Electromagnetic motors can have problems when operating in extreme environments. In addition, if one needs to do mechanical work outside a structure, electrical feedthroughs are required to transport the electric power to drive the motor. In this paper, we present designs for driving rotary and linear motors by pumping stress waves across a structure or barrier. We accomplish this by designing a piezoelectric actuator on one side of the structure and a resonance structure that is matched to the piezoelectric resonance of the actuator on the other side. Typically, piezoelectric motors can be designed with high torques and lower speeds without the need for gears. One can also use other actuation materials such as electrostrictive, or magnetostrictive materials in a benign environment and transmit the power in acoustic form as a stress wave and actuate mechanisms that are external to the benign environment. This technology removes the need to perforate a structure and allows work to be done directly on the other side of a structure without the use of electrical feedthroughs, which can weaken the structure, pipe, or vessel. Acoustic energy is pumped as a stress wave at a set frequency or range of frequencies to produce rotary or linear motion in a structure. This method of transferring useful mechanical work across solid barriers by pumping acoustic energy through a resonant structure features the ability to transfer work (rotary or linear motion) across pressure or thermal barriers, or in a sterile environment, without generating contaminants. Reflectors in the wall of barriers can be designed to enhance the efficiency of the energy/power transmission. The method features the ability to produce a bi-directional driving mechanism using higher-mode resonances. There are a variety of applications where the presence of a motor is complicated by thermal or chemical environments that would be hostile to the motor components and reduce life and, in some instances, not be

  16. Acoustic Mechanical Feedthroughs

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Walkemeyer, Phillip; Bao, Xiaoqi; Bar-Cohen, Yoseph; Badescu, Mircea

    2013-01-01

    Electromagnetic motors can have problems when operating in extreme environments. In addition, if one needs to do mechanical work outside a structure, electrical feedthroughs are required to transport the electric power to drive the motor. In this paper, we present designs for driving rotary and linear motors by pumping stress waves across a structure or barrier. We accomplish this by designing a piezoelectric actuator on one side of the structure and a resonance structure that is matched to the piezoelectric resonance of the actuator on the other side. Typically, piezoelectric motors can be designed with high torques and lower speeds without the need for gears. One can also use other actuation materials such as electrostrictive, or magnetostrictive materials in a benign environment and transmit the power in acoustic form as a stress wave and actuate mechanisms that are external to the benign environment. This technology removes the need to perforate a structure and allows work to be done directly on the other side of a structure without the use of electrical feedthroughs, which can weaken the structure, pipe, or vessel. Acoustic energy is pumped as a stress wave at a set frequency or range of frequencies to produce rotary or linear motion in a structure. This method of transferring useful mechanical work across solid barriers by pumping acoustic energy through a resonant structure features the ability to transfer work (rotary or linear motion) across pressure or thermal barriers, or in a sterile environment, without generating contaminants. Reflectors in the wall of barriers can be designed to enhance the efficiency of the energy/power transmission. The method features the ability to produce a bi-directional driving mechanism using higher-mode resonances. There are a variety of applications where the presence of a motor is complicated by thermal or chemical environments that would be hostile to the motor components and reduce life and, in some instances, not be

  17. [The effects of acoustic overstimulation].

    PubMed

    Häusler, R

    2004-01-01

    Basic aspects of acoustic trauma are presented. Exposure to loud noise leads to an acoustic traumatization with a temporary threshold shift initially and, with increasing exposure, intensity and duration, a permanent hearing loss. Impulse sound such as hammer blows on metal, gun shots and other detonations reaching peak levels of 160 to 180 dB is particularly hazardous to the inner ear. Playing loud musical instruments such as trumpets or percussion may also lead to hearing damage. Less dangerous than often believed is listening to electronically amplified music with walkmen, at discos or rock concerts. The reason is that, while the sound level is quite high, the particularly dangerous sound peaks are absent, as loudspeakers usually have an output limit of 110-120 dB. Traffic noise (cars, trains, air planes) is usually not threatening to the ear, but it may represent a considerable subjective annoyance and a stress factor leading to psychosomatic disturbances (neurovegetative symptoms, sleeping disorders). An effective treatment for the acoustic trauma is still missing. The systematic and consequent prophylaxis either with individual ear protectors (plugs or ear muffs) or by reducing the noise level at the source by means of isolation, encapsulation, or by using motors that are less noisy remains very important. Increasing awareness of acoustic pollution and preventive means have led to a reduction in the incidence of the acoustic trauma in the last decades.

  18. Broadband acoustic cloak for ultrasound waves.

    PubMed

    Zhang, Shu; Xia, Chunguang; Fang, Nicholas

    2011-01-14

    Invisibility devices based on coordinate transformation have opened up a new field of considerable interest. We present here the first practical realization of a low-loss and broadband acoustic cloak for underwater ultrasound. This metamaterial cloak is constructed with a network of acoustic circuit elements, namely, serial inductors and shunt capacitors. Our experiment clearly shows that the acoustic cloak can effectively bend the ultrasound waves around the hidden object, with reduced scattering and shadow. Because of the nonresonant nature of the building elements, this low-loss (∼6  dB/m) cylindrical cloak exhibits invisibility over a broad frequency range from 52 to 64 kHz. Furthermore, our experimental study indicates that this design approach should be scalable to different acoustic frequencies and offers the possibility for a variety of devices based on coordinate transformation.

  19. The North Pacific Acoustic Laboratory deep-water acoustic propagation experiments in the Philippine Sea.

    PubMed

    Worcester, Peter F; Dzieciuch, Matthew A; Mercer, James A; Andrew, Rex K; Dushaw, Brian D; Baggeroer, Arthur B; Heaney, Kevin D; D'Spain, Gerald L; Colosi, John A; Stephen, Ralph A; Kemp, John N; Howe, Bruce M; Van Uffelen, Lora J; Wage, Kathleen E

    2013-10-01

    A series of experiments conducted in the Philippine Sea during 2009-2011 investigated deep-water acoustic propagation and ambient noise in this oceanographically and geologically complex region: (i) the 2009 North Pacific Acoustic Laboratory (NPAL) Pilot Study/Engineering Test, (ii) the 2010-2011 NPAL Philippine Sea Experiment, and (iii) the Ocean Bottom Seismometer Augmentation of the 2010-2011 NPAL Philippine Sea Experiment. The experimental goals included (a) understanding the impacts of fronts, eddies, and internal tides on acoustic propagation, (b) determining whether acoustic methods, together with other measurements and ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions, (c) improving our understanding of the physics of scattering by internal waves and spice, (d) characterizing the depth dependence and temporal variability of ambient noise, and (e) understanding the relationship between the acoustic field in the water column and the seismic field in the seafloor. In these experiments, moored and ship-suspended low-frequency acoustic sources transmitted to a newly developed distributed vertical line array receiver capable of spanning the water column in the deep ocean. The acoustic transmissions and ambient noise were also recorded by a towed hydrophone array, by acoustic Seagliders, and by ocean bottom seismometers.

  20. A laboratory study examining the impact of linen use on low-air-loss support surface heat and water vapor transmission rates.

    PubMed

    Williamson, Rachel; Lachenbruch, Charlie; VanGilder, Catherine

    2013-08-01

    Layers of linens are frequently placed under patients to manage moisture and/or assist with positioning immobile patients, including persons placed on a therapeutic surface because they are at risk for developing pressure ulcers. Because skin microclimate is believed to affect pressure ulcer risk, some therapeutic surfaces are designed to manage skin temperature and humidity (microclimate management). The purpose of this study was to measure the effects of linens and underpads on a low-air-loss (LAL) surface's ability to disperse heat and evaporate moisture. Underpads and transfer sheet combinations (grouped by three common linen functions: immobility, moisture management, and immobility and moisture management) were tested using the sweating guarded hot plate method, which allows for the measurement of the evaporative capacity (g H2O/m2*hour) and the total rate of heat withdrawal (Watts/m2) associated with nine different linen configurations placed on the support surface. Total heat withdrawal and evaporative capacity of the LAL surface with a fitted sheet only was used for comparison (P <0.05) Compared with fitted sheet only, heat withdrawal was significantly reduced by five of eight combinations, and evaporative moisture reduction was significantly reduced by six of eight linen combinations (P <0.05). All combinations that included plastic-containing underpads significantly reduced the surface's ability to dissipate heat and evaporate moisture, and use of the maximum number of layers (nine) reduced heat withdrawal to the level of a static, nonLAL surface. The results of this study suggest that putting additional linens or underpads on LAL surfaces may adversely affect skin temperature and moisture, thereby reducing the pressure ulcer prevention potential of these surfaces. Additional studies to examine the effect of linens and underpads as well as microclimate management strategies on pressure ulcer risk are needed.

  1. Acoustic iridescence.

    PubMed

    Cox, Trevor J

    2011-03-01

    An investigation has been undertaken into acoustic iridescence, exploring how a device can be constructed which alter sound waves, in a similar way to structures in nature that act on light to produce optical iridescence. The main construction had many thin perforated sheets spaced half a wavelength apart for a specified design frequency. The sheets create the necessary impedance discontinuities to create backscattered waves, which then interfere to create strongly reflected sound at certain frequencies. Predictions and measurements show a set of harmonics, evenly spaced in frequency, for which sound is reflected strongly. And the frequency of these harmonics increases as the angle of observation gets larger, mimicking the iridescence seen in natural optical systems. Similar to optical systems, the reflections become weaker for oblique angles of reflection. A second construction was briefly examined which exploited a metamaterial made from elements and inclusions which were much smaller than the wavelength. Boundary element method predictions confirmed the potential for creating acoustic iridescence from layers of such a material.

  2. Acoustic transducer

    DOEpatents

    Drumheller, D.S.

    1997-12-30

    An acoustic transducer is described comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2,000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers. 4 figs.

  3. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    1997-01-01

    An acoustic transducer comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers.

  4. Comparison of Comet Enflow and VA One Acoustic-to-Structure Power Flow Predictions

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.; Schiller, Noah H.; Cabell, Randolph H.

    2010-01-01

    Comet Enflow is a commercially available, high frequency vibroacoustic analysis software based on the Energy Finite Element Analysis (EFEA). In this method the same finite element mesh used for structural and acoustic analysis can be employed for the high frequency solutions. Comet Enflow is being validated for a floor-equipped composite cylinder by comparing the EFEA vibroacoustic response predictions with Statistical Energy Analysis (SEA) results from the commercial software program VA One from ESI Group. Early in this program a number of discrepancies became apparent in the Enflow predicted response for the power flow from an acoustic space to a structural subsystem. The power flow anomalies were studied for a simple cubic, a rectangular and a cylindrical structural model connected to an acoustic cavity. The current investigation focuses on three specific discrepancies between the Comet Enflow and the VA One predictions: the Enflow power transmission coefficient relative to the VA One coupling loss factor; the importance of the accuracy of the acoustic modal density formulation used within Enflow; and the recommended use of fast solvers in Comet Enflow. The frequency region of interest for this study covers the one-third octave bands with center frequencies from 16 Hz to 4000 Hz.

  5. Structural Acoustic Prediction and Interior Noise Control Technology

    NASA Technical Reports Server (NTRS)

    Mathur, G. P.; Chin, C. L.; Simpson, M. A.; Lee, J. T.; Palumbo, Daniel L. (Technical Monitor)

    2001-01-01

    This report documents the results of Task 14, "Structural Acoustic Prediction and Interior Noise Control Technology". The task was to evaluate the performance of tuned foam elements (termed Smart Foam) both analytically and experimentally. Results taken from a three-dimensional finite element model of an active, tuned foam element are presented. Measurements of sound absorption and sound transmission loss were taken using the model. These results agree well with published data. Experimental performance data were taken in Boeing's Interior Noise Test Facility where 12 smart foam elements were applied to a 757 sidewall. Several configurations were tested. Noise reductions of 5-10 dB were achieved over the 200-800 Hz bandwidth of the controller. Accelerometers mounted on the panel provided a good reference for the controller. Configurations with far-field error microphones outperformed near-field cases.

  6. Invariant currents in lossy acoustic waveguides with complete local symmetry

    NASA Astrophysics Data System (ADS)

    Kalozoumis, P. A.; Richoux, O.; Diakonos, F. K.; Theocharis, G.; Schmelcher, P.

    2015-07-01

    We implement the concept of complete local symmetry in lossy acoustic waveguides. Despite the presence of losses, the existence of a spatially invariant current is shown theoretically and observed experimentally. We demonstrate how this invariant current leads to the generalization of the Bloch and parity theorems for lossy systems defining a mapping of the pressure field between symmetry-related spatial domains. Using experimental data, we verify this mapping with remarkable accuracy. For the performed experiment, we employ a construction technique based on local symmetries that allows the design of setups with prescribed perfect transmission resonances in the lossless case. Our results reveal the fundamental role of symmetries in restricted spatial domains, and they clearly indicate that completely locally symmetric devices constitute a promising class of setups with regard to the manipulation of wave propagation.

  7. Long Range Acoustic Communication in Deep Water

    DTIC Science & Technology

    2014-09-30

    Acoustic communication at long range in the ocean is challenging due to the substantial propagation loss, multipath delay spread , and channel...20 Hz in the upward refracting Arctic acoustic channel. However, the seafloor topography in the region of the Chukchi Plateau is very uneven over...which the depth was 600 m and thus the seafloor affected every mode of the ACOUS signal except for mode 1 which was confined to the upper 200 m. In April

  8. A novel broadband waterborne acoustic absorber

    NASA Astrophysics Data System (ADS)

    Wang, Changxian; Wen, Weibin; Huang, Yixing; Chen, Mingji; Lei, Hongshuai; Fang, Daining

    2016-07-01

    In this paper, we extended the ray tracing theory in polar coordinate system, and originally proposed the Snell-Descartes law in polar coordinates. Based on these theories, a novel broadband waterborne acoustic absorber device was proposed. This device is designed with gradient-distributing materials along radius, which makes the incidence acoustic wave ray warps. The echo reduction effects of this device were investigated by finite element analysis, and the numerical results show that the reflectivity of acoustic wave for the new device is lower than that of homogenous and Alberich layers in almost all frequency 0-30 kHz at the same loss factor.

  9. Nonlinear effects in an acoustic metamaterial with simultaneous negative modulus and density

    NASA Astrophysics Data System (ADS)

    Li, Yifeng; Lan, Jun; Li, Baoshun; Liu, Xiaozhou; Zhang, Jiashu

    2016-10-01

    Nonlinear effects in an acoustic metamaterial with simultaneous negative modulus and density based on Helmholtz resonators and membranes periodically distributed along a pipe are studied theoretically. Analyses of the transmission coefficient and dispersion relation of the composite system are realized using the acoustic transmission line method and Bloch theory, respectively. Due to the nonlinearities of the Helmholtz resonators and membranes, the acoustic wave propagation properties vary with the different incident acoustic intensities, and the frequency band gaps of the transmission coefficient are amplitude dependent. The nonlinearities shift the double negative pass band into the adjacent modulus negative forbidden band and transform the metamaterial from an acoustic insulator into an acoustic conductor, leading to some new potential acoustic applications.

  10. Photovoltaic array loss mechanisms

    NASA Astrophysics Data System (ADS)

    Gonzalez, Charles

    1986-10-01

    Loss mechanisms which come into play when solar cell modules are mounted in arrays are identified. Losses can occur either from a reduction in the array electrical performance or with nonoptimal extraction of power from the array. Electrical performance degradation is caused by electrical mismatch, transmission losses from cell surface soiling and steep angle of reflectance, and electrical losses from field wiring resistance and the voltage drop across blocking diodes. The second type of loss, concerned with the operating points of the array, can involve nonoptimal load impedance and limiting the operating envelope of the array to specific ranges of voltage and current. Each of the loss mechanisms are discussed and average energy losses expected from soiling, steep reflectance angles and circuit losses are calculated.

  11. Postnatal Loss of P/Q-type Channels Confined to Rhombic Lip Derived Neurons Alters Synaptic Transmission at the Parallel Fiber to Purkinje Cell Synapse and Replicates Genomic Cacna1a Mutation Phenotype of Ataxia and Seizures in Mice

    PubMed Central

    Maejima, Takashi; Wollenweber, Patric; Teusner, Lena U. C.; Noebels, Jeffrey L.; Herlitze, Stefan; Mark, Melanie D.

    2013-01-01

    Ataxia, episodic dyskinesia and thalamocortical seizures are associated with an inherited loss of P/Q-type voltage-gated Ca2+ channel function. P/Q-type channels are widely expressed throughout the neuraxis, obscuring identification of the critical networks underlying these complex neurological disorders. We recently showed that the conditional postnatal loss of P/Q-type channels in cerebellar Purkinje cells (PCs) in mice (purky) leads to these aberrant phenotypes, suggesting that intrinsic alteration in PC output is a sufficient pathogenic factor for disease initiation. The question arises whether P/Q-type channel deletion confined to a single upstream cerebellar synapse might induce the pathophysiological abnormality of genomically inherited P/Q-type channel disorders. PCs integrate two excitatory inputs, climbing fibers from inferior olive and parallel fibers (PFs) from granule cells (GCs) that receive mossy fiber (MF) input derived from precerebellar nuclei. In this paper, we introduce a new mouse model with a selective knock-out of P/Q-type channels in rhombic lip derived neurons including PF- and MF-pathways (quirky). We found that in quirky mice, PF-PC synaptic transmission is reduced during low-frequency stimulation. Using focal light stimulation of GCs that express optogenetic light-sensitive channels, channelrhodopsin-2, we found that modulation of PC firing via GC input is reduced in quirky mice. Phenotypic analysis revealed that quirky mice display ataxia, dyskinesia and absence epilepsy. These results suggest that developmental alteration of patterned input confined to only one of the main afferent cerebellar excitatory synaptic pathways has a significant role in generating the neurological phenotype associated with the global genomic loss of P/Q-type channel function. PMID:23516282

  12. 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.

  13. An overview of acoustic telemetry

    SciTech Connect

    Drumheller, D.S.

    1992-01-01

    Acoustic telemetry has been a dream of the drilling industry for the past 50 years. It offers the promise of data rates which are one-hundred times greater than existing technology. Such a system would open the door to true logging-while-drilling technology and bring enormous profits to its developers. The basic idea is to produce an encoded sound wave at the bottom of the well, let it propagate up the steel drillpipe, and extract the data from the signal at the surface. Unfortunately, substantial difficulties arise. The first difficult problem is to produce the sound wave. Since the most promising transmission wavelengths are about 20 feet, normal transducer efficiencies are quire low. Compounding this problem is the structural complexity of the bottomhole assembly and drillstring. For example, the acoustic impedance of the drillstring changes every 30 feet and produces an unusual scattering pattern in the acoustic transmission. This scattering pattern causes distortion of the signal and is often confused with signal attenuation. These problems are not intractable. Recent work has demonstrated that broad frequency bands exist which are capable of transmitting data at rates up to 100 bits per second. Our work has also identified the mechanism which is responsible for the observed anomalies in the patterns of signal attenuation. Furthermore in the past few years a body of experience has been developed in designing more efficient transducers for application to metal waveguides. The direction of future work is clear. New transducer designs which are more efficient and compatible with existing downhole power supplies need to be built and tested; existing field test data need to be analyzed for transmission bandwidth and attenuation; and the new and less expensive methods of collecting data on transmission path quality need to be incorporated into this effort. 11 refs.

  14. Acoustic cryocooler

    DOEpatents

    Swift, Gregory W.; Martin, Richard A.; Radenbaugh, Ray

    1990-01-01

    An acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effective to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15-60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintian a cooling load of 5 W at 80 K.

  15. Acoustic transducer

    DOEpatents

    Drumheller, Douglas S.

    2000-01-01

    An active acoustic transducer tool for use down-hole applications. The tool includes a single cylindrical mandrel including a shoulder defining the boundary of a narrowed portion over which is placed a sandwich-style piezoelectric tranducer assembly. The piezoelectric transducer assembly is prestressed by being placed in a thermal interference fit between the shoulder of the mandrel and the base of an anvil which is likewise positioned over the narrower portion of the mandrel. In the preferred embodiment, assembly of the tool is accomplished using a hydraulic jack to stretch the mandrel prior to emplacement of the cylindrical sandwich-style piezoelectric transducer assembly and anvil. After those elements are positioned and secured, the stretched mandrel is allowed to return substantially to its original (pre-stretch) dimensions with the result that the piezoelectric transducer elements are compressed between the anvil and the shoulder of the mandrel.

  16. Acoustics class at Berklee College of Music

    NASA Astrophysics Data System (ADS)

    Hoover, Anthony K.

    2003-04-01

    Berklee College of Music (in Boston) was developing its outstanding Music Technologies Division, and understood the need for a comprehensive class on acoustics. The result was a three-credit-hour class, offered twice per year, covering the fundamentals, architectural acoustics (outdoors, indoors, and transmission), vibration isolation, hearing and psychoacoustics, and more. One outgrowth was the Acoustical Society at Berklee, with presentations by local and visiting ASA members, yearly visits to an anechoic chamber, special studio sessions, tours, and joint meetings with professional societies. Over 2000 students have completed and performed well in the class. The author's favorite measure of success is the growing number of students who have chosen a career in acoustics. This paper will summarize and discuss this class.

  17. Acoustic energy in ducts - Further observations

    NASA Technical Reports Server (NTRS)

    Eversman, W.

    1979-01-01

    The transmission of acoustic energy in uniform ducts carrying uniform flow is investigated with the purpose of clarifying two points of interest. The two commonly used definitions of acoustic 'energy' flux are shown to be related by a Legendre transformation of the Lagrangian density exactly as in deriving the Hamiltonian density in mechanics. In the acoustic case the total energy density and the Hamiltonian density are not the same which accounts for two different 'energy' fluxes. When the duct has acoustically absorptive walls neither of the two flux expressions gives correct results. A reevaluation of the basis of derivation of the energy density and energy flux provides forms which yield consistent results for soft walled ducts.

  18. Localization of acoustic modes in periodic porous silicon structures

    PubMed Central

    2014-01-01

    The propagation of longitudinal acoustic waves in multilayer structures based on porous silicon and the experimental measurement of acoustic transmission for the structures in the gigahertz range are reported and studied theoretically. The considered structures exhibit band gaps in the transmission spectrum and these are localized modes inside the band gap, coming from defect layers introduced in periodic systems. The frequency at which the acoustic resonances appear can be tuned by changing the porosity and/or thickness of the defect layer. PMID:25206317

  19. Acoustic-optical imaging without immersion

    NASA Technical Reports Server (NTRS)

    Liu, H.

    1979-01-01

    System using membraneous end wall of Bragg cell to separate test specimen from acoustic transmission medium, operates in real time and uses readily available optical components. System can be easily set up and maintained by people with little or no training in holography.

  20. Measurement of acoustical characteristics of mosques in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Abdou, Adel A.

    2003-03-01

    The study of mosque acoustics, with regard to acoustical characteristics, sound quality for speech intelligibility, and other applicable acoustic criteria, has been largely neglected. In this study a background as to why mosques are designed as they are and how mosque design is influenced by worship considerations is given. In the study the acoustical characteristics of typically constructed contemporary mosques in Saudi Arabia have been investigated, employing a well-known impulse response. Extensive field measurements were taken in 21 representative mosques of different sizes and architectural features in order to characterize their acoustical quality and to identify the impact of air conditioning, ceiling fans, and sound reinforcement systems on their acoustics. Objective room-acoustic indicators such as reverberation time (RT) and clarity (C50) were measured. Background noise (BN) was assessed with and without the operation of air conditioning and fans. The speech transmission index (STI) was also evaluated with and without the operation of existing sound reinforcement systems. The existence of acoustical deficiencies was confirmed and quantified. The study, in addition to describing mosque acoustics, compares design goals to results obtained in practice and suggests acoustical target values for mosque design. The results show that acoustical quality in the investigated mosques deviates from optimum conditions when unoccupied, but is much better in the occupied condition.

  1. Measurement of acoustical characteristics of mosques in Saudi Arabia.

    PubMed

    Abdou, Adel A

    2003-03-01

    The study of mosque acoustics, with regard to acoustical characteristics, sound quality for speech intelligibility, and other applicable acoustic criteria, has been largely neglected. In this study a background as to why mosques are designed as they are and how mosque design is influenced by worship considerations is given. In the study the acoustical characteristics of typically constructed contemporary mosques in Saudi Arabia have been investigated, employing a well-known impulse response. Extensive field measurements were taken in 21 representative mosques of different sizes and architectural features in order to characterize their acoustical quality and to identify the impact of air conditioning, ceiling fans, and sound reinforcement systems on their acoustics. Objective room-acoustic indicators such as reverberation time (RT) and clarity (C50) were measured. Background noise (BN) was assessed with and without the operation of air conditioning and fans. The speech transmission index (STI) was also evaluated with and without the operation of existing sound reinforcement systems. The existence of acoustical deficiencies was confirmed and quantified. The study, in addition to describing mosque acoustics, compares design goals to results obtained in practice and suggests acoustical target values for mosque design. The results show that acoustical quality in the investigated mosques deviates from optimum conditions when unoccupied, but is much better in the occupied condition.

  2. Effects of Acoustic Impulses on the Middle Ear

    DTIC Science & Technology

    2015-10-01

    impulsive noises (impacts and impulses). Keywords: Noise exposure; hearing loss, noise-induced; impulsive noise; reflex ; conditioned response...stated in the approved SOW are: 1. Determine the prevalence of acoustic reflexes to among young people with H-1 hearing status as per Army...Regulation 40-501, Table 7-1. 2. Determine whether reflexive MEMC are pervasive for multiple acoustic and non-acoustic stimuli. 3. Determine whether

  3. Consideration of some factors affecting low-frequency fuselage noise transmission for propeller aircraft

    NASA Technical Reports Server (NTRS)

    Mixson, J. S.; Roussos, L. A.

    1986-01-01

    Possible reasons for disagreement between measured and predicted trends of sidewall noise transmission at low frequency are investigated using simplified analysis methods. An analytical model combining incident plane acoustic waves with an infinite flat panel is used to study the effects of sound incidence angle, plate structural properties, frequency, absorption, and the difference between noise reduction and transmission loss. Analysis shows that these factors have significant effects on noise transmission but they do not account for the differences between measured and predicted trends at low frequencies. An analytical model combining an infinite flat plate with a normally incident acoustic wave having exponentially decaying magnitude along one coordinate is used to study the effect of a localized source distribution such as is associated with propeller noise. Results show that the localization brings the predicted low-frequency trend of noise transmission into better agreement with measured propeller results. This effect is independent of low-frequency stiffness effects that have been previously reported to be associated with boundary conditions.

  4. 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.

  5. The Impact of Model Uncertainty on Spatial Compensation in Structural Acoustic Control

    NASA Technical Reports Server (NTRS)

    Clark, Robert L.

    2005-01-01

    Turbulent boundary layer (TBL) noise is considered a primary contribution to the interior noise present in commercial airliners. There are numerous investigations of interior noise control devoted to aircraft panels; however, practical realization is a potential challenge since physical boundary conditions are uncertain at best. In most prior studies, pinned or clamped boundary conditions were assumed; however, realistic panels likely display a range of boundary conditions between these two limits. Uncertainty in boundary conditions is a challenge for control system designers, both in terms of the compensator implemented and the location of transducers required to achieve the desired control. The impact of model uncertainties, specifically uncertain boundaries, on the selection of transducer locations for structural acoustic control is considered herein. The final goal of this work is the design of an aircraft panel structure that can reduce TBL noise transmission through the use of a completely adaptive, single-input, single-output control system. The feasibility of this goal is demonstrated through the creation of a detailed analytical solution, followed by the implementation of a test model in a transmission loss apparatus. Successfully realizing a control system robust to variations in boundary conditions can lead to the design and implementation of practical adaptive structures that could be used to control the transmission of sound to the interior of aircraft. Results from this research effort indicate it is possible to optimize the design of actuator and sensor location and aperture, minimizing the impact of boundary conditions on the desired structural acoustic control.

  6. Prediction and Measurement of the Vibration and Acoustic Radiation of Panels Subjected to Acoustic Loading

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Rizzi, Stephen A.

    1995-01-01

    Interior noise and sonic fatigue are important issues in the development and design of advanced subsonic and supersonic aircraft. Conventional aircraft typically employ passive treatments, such as constrained layer damping and acoustic absorption materials, to reduce the structural response and resulting acoustic levels in the aircraft interior. These techniques require significant addition of mass and only attenuate relatively high frequency noise transmitted through the fuselage. Although structural acoustic coupling is in general very important in the study of aircraft fuselage interior noise, analysis of noise transmission through a panel supported in an infinite rigid baffle (separating two semi-infinite acoustic domains) can be useful in evaluating the effects of active/adaptive materials, complex loading, etc. Recent work has been aimed at developing adaptive and/or active methods of controlling the structural acoustic response of panels to reduce the transmitted noise1. A finite element formulation was recently developed to study the dynamic response of shape memory alloy (SMA) hybrid composite panels (conventional composite panel with embedded SMA fibers) subject to combined acoustic and thermal loads2. Further analysis has been performed to predict the far-field acoustic radiation using the finite element dynamic panel response prediction3. The purpose of the present work is to validate the panel vibration and acoustic radiation prediction methods with baseline experimental results obtained from an isotropic panel, without the effect of SMA.

  7. Solid Micro Horn Array (SMIHA) for Acoustic Matching

    NASA Technical Reports Server (NTRS)

    Sherrit, S.; Bao, X.; Bar-Cohen, Y.

    2008-01-01

    Transduction of electrical signals to mechanical signals and vice-versa in piezoelectric materials is controlled by the material coupling coefficient. In general in a loss-less material the ratio of energy conversion per cycle is proportional to the square of the coupling coefficient. In practical transduction however the impedance mismatch between the piezoelectric material and the electrical drive circuitry or the mechanical structure can have a significant impact on the power transfer. This paper looks at novel methods of matching the acoustic impedance of structures to the piezoelectric material in an effort to increase power transmission and efficiency. In typical methods the density and acoustic velocity of the matching layer is adjusted to give good matching between the transducer and the load. The approach discussed in this paper utilizes solid micro horn arrays in the matching layer which channel the stress and increase the strain in the layer. This approach is found to have potential applications in energy harvesting, medical ultrasound and in liquid and gas coupled transducers.

  8. A purely flexible lightweight membrane-type acoustic metamaterial

    NASA Astrophysics Data System (ADS)

    Ma, Fuyin; Wu, Jiu Hui; Huang, Meng; Zhang, Weiquan; Zhang, Siwen

    2015-05-01

    This paper proposes a purely flexible lightweight membrane-type acoustic structure, wherein one kind of flexible lightweight rubber material takes the roles of mass and stiffness and another type of lightweight flexible EVA (ethylene-vinyl acetate copolymer) or plastic material functions as the localized stiffness for each unit. Because both the scatterers and base are constituted by the same material, this type of structure breaks the limitation that the metamaterials and phononic crystals need different materials with relatively large density and elasticity modulus ratios to play the roles of the scatterers and base respectively. Based on the band structures with different units, mass block shapes and size parameters, it is suggested that the shapes of the mass block can significantly affect the band structure. In addition, this type of structure could not only open a full band gap in the low-frequency range below 500 Hz, but also obtain an ultra-low-frequency bending wave band gap in the range below 100 Hz. Finally, we take into account the semi-infinite medium as a component, and calculate the sound transmission loss (STL) to evaluate the interaction between the structure and air. An experimental validation employing the cylindrical mass structure was developed to directly support the simulation results. Since the structures proposed in this study have achieved a purely flexible lightweight design, there exists an important promotion effect to realize the engineering applications of the acoustic metamaterials in practice.

  9. Factors which influence acoustic surveys of marine mammals

    NASA Astrophysics Data System (ADS)

    Rogers, Tracey L.; Ciaglia, Michaela B.; Cato, Douglas H.

    2005-09-01

    Traditionally, many marine mammal populations have been estimated by visual surveys. These count the animals that are available-either seals hauled-out on the ice or whales at the water's surface. Corrections are then made to include the animals that were not seen either because they were in (seals) or under (whales) the water. However when the majority of the animals in a population are not available to a visual survey this approach may be less effective. So we investigated whether acoustic surveys offered promise for estimating the distribution and abundance of Antarctic pack-ice seals. Four acoustic surveys were conducted (October 1996, 1997; December 1997, 1999) between longitudes 600E and 1500E. Surveys were bounded to the south by fast-ice, shelf-ice or the Antarctic continent and to the north by the edge of the pack-ice. No crabeater seals were heard. Leopard and Ross seals were highly vociferous in December coinciding with their breeding season. To predict the area surveyed we modeled transmission loss and measurements of received background levels. To identify the number of seals calling we modeled calling behavior. A preliminary estimate of 0.13 male leopard seals/km2 was calculated which is in the high-density range described from the literature.

  10. Acoustic attenuation design requirements established through EPNL parametric trades

    NASA Technical Reports Server (NTRS)

    Veldman, H. F.

    1972-01-01

    An optimization procedure for the provision of an acoustic lining configuration that is balanced with respect to engine performance losses and lining attenuation characteristics was established using a method which determined acoustic attenuation design requirements through parametric trade studies using the subjective noise unit of effective perceived noise level (EPNL).

  11. Resonant acoustic transducer system for a well drilling string

    DOEpatents

    Kent, William H.; Mitchell, Peter G.

    1981-01-01

    For use in transmitting acoustic waves propagated along a well drilling string, a piezoelectric transducer is provided operating in the relatively low loss acoustic propagation range of the well drilling string. The efficiently coupled transmitting transducer incorporates a mass-spring-piezoelectric transmitter combination permitting resonant operation in the desired low frequency range.

  12. Resonant acoustic transducer system for a well drilling string

    DOEpatents

    Nardi, Anthony P.

    1981-01-01

    For use in transmitting acoustic waves propated along a well drilling string, a piezoelectric transducer is provided operating in the relatively low loss acoustic propagation range of the well drilling string. The efficiently coupled transmitting transducer incorporates a mass-spring-piezoelectric transmitter combination permitting a resonant operation in the desired low frequency range.

  13. Acoustical Barriers To Learning: Children at Risk in Every Classroom.

    ERIC Educational Resources Information Center

    Nelson, Peggy B.; Soli, Sig

    2000-01-01

    This article reviews relevant literature on acoustical barriers to successful learning and provides guidance for school personnel making decisions regarding classroom facilities. Effects of noisy classrooms on young listeners, second language learners, and those with hearing loss are discussed. A rationale for the classroom acoustics standards is…

  14. Canonical Acoustics and Its Application to Surface Acoustic Wave on Acoustic Metamaterials

    NASA Astrophysics Data System (ADS)

    Shen, Jian Qi

    2016-08-01

    In a conventional formalism of acoustics, acoustic pressure p and velocity field u are used for characterizing acoustic waves propagating inside elastic/acoustic materials. We shall treat some fundamental problems relevant to acoustic wave propagation alternatively by using canonical acoustics (a more concise and compact formalism of acoustic dynamics), in which an acoustic scalar potential and an acoustic vector potential (Φ ,V), instead of the conventional acoustic field quantities such as acoustic pressure and velocity field (p,u) for characterizing acoustic waves, have been defined as the fundamental variables. The canonical formalism of the acoustic energy-momentum tensor is derived in terms of the acoustic potentials. Both the acoustic Hamiltonian density and the acoustic Lagrangian density have been defined, and based on this formulation, the acoustic wave quantization in a fluid is also developed. Such a formalism of acoustic potentials is employed to the problem of negative-mass-density assisted surface acoustic wave that is a highly localized surface bound state (an eigenstate of the acoustic wave equations). Since such a surface acoustic wave can be strongly confined to an interface between an acoustic metamaterial (e.g., fluid-solid composite structures with a negative dynamical mass density) and an ordinary material (with a positive mass density), it will give rise to an effect of acoustic field enhancement on the acoustic interface, and would have potential applications in acoustic device design for acoustic wave control.

  15. What Is an Acoustic Neuroma

    MedlinePlus

    ... ANAUSA.org Connect with us! What is an Acoustic Neuroma? Each heading slides to reveal information. Important ... Acoustic Neuroma Important Points To Know About an Acoustic Neuroma An acoustic neuroma, also called a vestibular ...

  16. International Space Station Acoustics - A Status Report

    NASA Technical Reports Server (NTRS)

    Allen, Christopher S.; Denham, Samuel A.

    2011-01-01

    It is important to control acoustic noise aboard the International Space Station (ISS) to provide a satisfactory environment for voice communications, crew productivity, 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 analysis 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 indicate 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 20031. Many new modules, and sleep stations have been added to the ISS since that time. In addition, noise mitigation efforts have reduced noise levels in some areas. As a result, the acoustic levels on the ISS have improved.

  17. 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.

  18. Muscles in a mouse model of spinal muscular atrophy show profound defects in neuromuscular development even in the absence of failure in neuromuscular transmission or loss of motor neurons.

    PubMed

    Lee, Young Il; Mikesh, Michelle; Smith, Ian; Rimer, Mendell; Thompson, Wesley

    2011-08-15

    A mouse model of the devastating human disease "spinal muscular atrophy" (SMA) was used to investigate the severe muscle weakness and spasticity that precede the death of these animals near the end of the 2nd postnatal week. Counts of motor units to the soleus muscle as well as of axons in the soleus muscle nerve showed no loss of motor neurons. Similarly, neither immunostaining of neuromuscular junctions nor the measurement of the tension generated by nerve stimulation gave evidence of any significant impairment in neuromuscular transmission, even when animals were maintained up to 5days longer via a supplementary diet. However, the muscles were clearly weaker, generating less than half their normal tension. Weakness in 3 muscles examined in the study appears due to a severe but uniform reduction in muscle fiber size. The size reduction results from a failure of muscle fibers to grow during early postnatal development and, in soleus, to a reduction in number of fibers generated. Neuromuscular development is severely delayed in these mutant animals: expression of myosin heavy chain isoforms, the elimination of polyneuronal innervation, the maturation in the shape of the AChR plaque, the arrival of SCs at the junctions and their coverage of the nerve terminal, the development of junctional folds. Thus, if SMA in this particular mouse is a disease of motor neurons, it can act in a manner that does not result in their death or disconnection from their targets but nonetheless alters many aspects of neuromuscular development.

  19. Muscles in a mouse model of spinal muscular atrophy show profound defects in neuromuscular development even in the absence of failure in neuromuscular transmission or loss of motor neurons

    PubMed Central

    Lee, Young il; Mikesh, Michelle; Smith, Ian; Rimer, Mendell; Thompson, Wesley

    2011-01-01

    A mouse model of the devastating human disease "spinal muscular atrophy" (SMA) was used to investigate the severe muscle weakness and spasticity that precedes the death of these animals near the end of the 2nd postnatal week. Counts of motor units to the soleus muscle as well as of axons in the soleus muscle nerve showed no loss of motor neurons. Similarly, neither immunostaining of neuromuscular junctions nor the measurement of the tension generated by nerve stimulation gave evidence of any significant impairment in neuromuscular transmission, even when animals were maintained up to 5 days longer via a supplementary diet. However, the muscles were clearly weaker, generating less than half their normal tension. Weakness in 3 muscles examined in the study appears due to a severe but uniform reduction in muscle fiber size. The size reduction results from a failure of muscle fibers to grow during early postnatal development and, in soleus, to a reduction in number of fibers generated. Neuromuscular development is severely delayed in these mutant animals: expression of myosin heavy chain isoforms, the elimination of polyneuronal innervation, the maturation in the shape of the AChR plaque, the arrival of SCs at the junctions and their coverage of the nerve terminal, the development of junctional folds. Thus, if SMA in this particular mouse is a disease of motor neurons, it can act in a manner that does not result in their death or disconnection from their targets but nonetheless alters many aspects of neuromuscular development. PMID:21658376

  20. Advanced Rotorcraft Transmission program summary

    NASA Technical Reports Server (NTRS)

    Bossler, Robert B., Jr.; Heath, Gregory F.

    1992-01-01

    The current status of the Advanced Rotorcraft Transmission (ART) program is reviewed. The discussion includes a general configuration and face gear description, weight analysis, stress analysis, reliability analysis, acoustic analysis, face gear testing, and planned torque split testing. Design descriptions include the face gear webs sized for equal stiffness, a positive engagement clutch, the lubrication system, and a high contact ratio planetary. Test results for five gear materials and three housing materials are presented.

  1. Advanced Rotorcraft Transmission program summary

    NASA Astrophysics Data System (ADS)

    Bossler, Robert B., Jr.; Heath, Gregory F.

    1992-07-01

    The current status of the Advanced Rotorcraft Transmission (ART) program is reviewed. The discussion includes a general configuration and face gear description, weight analysis, stress analysis, reliability analysis, acoustic analysis, face gear testing, and planned torque split testing. Design descriptions include the face gear webs sized for equal stiffness, a positive engagement clutch, the lubrication system, and a high contact ratio planetary. Test results for five gear materials and three housing materials are presented.

  2. Symptoms of Acoustic Neuroma

    MedlinePlus

    ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ...

  3. NPL closes acoustics department

    NASA Astrophysics Data System (ADS)

    Extance, Andy

    2016-11-01

    The UK's National Physical Laboratory (NPL) has withdrawn funding for its acoustics, polymer and thermoelectrics groups, triggering concern among airborne acoustics specialists that the move could undermine the country's noise-management policies.

  4. Identifying the Acoustic Neuroma

    MedlinePlus

    ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ...

  5. Acoustic emission frequency discrimination

    NASA Technical Reports Server (NTRS)

    Sugg, Frank E. (Inventor); Graham, Lloyd J. (Inventor)

    1988-01-01

    In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

  6. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2015-07-17

    under-ice scattering , bathymetric diffraction and the application of the ocean acoustic Parabolic Equation to infrasound. 2. Tasks a. Task 1...QSR-14C0172-Ocean Acoustics -063015 Figure 10. Estimated reflection coefficient as a function of frequency by taking the difference of downgoing and...OASIS, INC. 1 Report No. QSR-14C0172-Ocean Acoustics -063015 Quarterly Progress Report Technical and Financial Deep Water Ocean Acoustics

  7. Deep Water Ocean Acoustics

    DTIC Science & Technology

    2015-10-19

    OASIS, INC. 1 Report No. QSR-14C0172-Ocean Acoustics-093015 Quarterly Progress Report Technical and Financial Deep Water Ocean Acoustics...number. 1. REPORT DATE OCT 2015 2. REPORT TYPE 3. DATES COVERED 01-07-2015 to 30-09-2015 4. TITLE AND SUBTITLE Deep Water Ocean Acoustics...understanding of the impact of the ocean and seafloor environmental variability on deep- water (long-range) ocean acoustic propagation and to develop

  8. Shallow Water Acoustics Studies

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Shallow Water Acoustics Studies James F. Lynch MS #12...N00014-14-1-0040 http://acoustics.whoi.edu/sw06/ LONG TERM GOALS The long term goals of our shallow water acoustics work are to: 1) understand the...nature of low frequency (10-1500 Hz) acoustic propagation, scattering and noise in shallow water when strong oceanic variability is present in the

  9. An acoustic filter based on layered structure.

    PubMed

    Ma, Jianguo; Steer, Michael B; Jiang, Xiaoning

    2015-03-16

    Acoustic filters (AFs) are key components to control wave propagation in multi-frequency systems. We present a design which selectively achieves acoustic filtering with a stop band and passive amplification at the high- and low-frequencies, respectively. Measurement results from the prototypes closely match the design predictions. The AF suppresses the high frequency aliasing echo by 14.5 dB and amplifies the low frequency transmission by 8.0 dB, increasing an axial resolution from 416 to 86 μm in imaging. The AF design approach is proved to be effective in multi-frequency systems.

  10. Assessing the acoustical climate of underground stations.

    PubMed

    Nowicka, Elzbieta

    2007-01-01

    Designing a proper acoustical environment--indispensable to speech recognition--in long enclosures is difficult. Although there is some literature on the acoustical conditions in underground stations, there is still little information about methods that make estimation of correct reverberation conditions possible. This paper discusses the assessment of the reverberation conditions of underground stations. A comparison of the measurements of reverberation time in Warsaw's underground stations with calculated data proves there are divergences between measured and calculated early decay time values, especially for long source-receiver distances. Rapid speech transmission index values for measured stations are also presented.

  11. Beamforming in an acoustic shadow

    NASA Technical Reports Server (NTRS)

    Havelock, David; Stinson, Michael; Daigle, Gilles

    1993-01-01

    The sound field deep within an acoustic shadow region is less well understood than that outside the shadow region. Signal levels are substantially lower within the shadow, but beamforming difficulties arise for other reasons such as loss of spatial coherence. Based on analysis of JAPE-91 data, and other data, three types of characteristic signals within acoustic shadow regions are identified. These signal types may correspond to different, intermittent signal propagation conditions. Detection and classification algorithms might take advantage of the signal characteristics. Frequency coherence is also discussed. The extent of coherence across frequencies is shown to be limited, causing difficulties for source classification based on harmonic amplitude relationships. Discussions emphasize short-term characteristics on the order of one second. A video presentation on frequency coherence shows the similarity, in the presence of atmospheric turbulence, between the received signal from a stable set of harmonics generated by a loudspeaker and that received from a helicopter hovering behind a hill.

  12. Coding Acoustic Metasurfaces.

    PubMed

    Xie, Boyang; Tang, Kun; Cheng, Hua; Liu, Zhengyou; Chen, Shuqi; Tian, Jianguo

    2017-02-01

    Coding acoustic metasurfaces can combine simple logical bits to acquire sophisticated functions in wave control. The acoustic logical bits can achieve a phase difference of exactly π and a perfect match of the amplitudes for the transmitted waves. By programming the coding sequences, acoustic metasurfaces with various functions, including creating peculiar antenna patterns and waves focusing, have been demonstrated.

  13. Tutorial on architectural acoustics

    NASA Astrophysics Data System (ADS)

    Shaw, Neil; Talaske, Rick; Bistafa, Sylvio

    2002-11-01

    This tutorial is intended to provide an overview of current knowledge and practice in architectural acoustics. Topics covered will include basic concepts and history, acoustics of small rooms (small rooms for speech such as classrooms and meeting rooms, music studios, small critical listening spaces such as home theatres) and the acoustics of large rooms (larger assembly halls, auditoria, and performance halls).

  14. Local frequency dependence in transcranial ultrasound transmission

    NASA Astrophysics Data System (ADS)

    White, P. J.; Clement, G. T.; Hynynen, K.

    2006-05-01

    The development of large-aperture multiple-source transducer arrays for ultrasound transmission through the human skull has demonstrated the possibility of controlled and substantial acoustic energy delivery into the brain parenchyma without the necessitation of a craniotomy. The individual control of acoustic parameters from each ultrasound source allows for the correction of distortions arising from transmission through the skull bone and also opens up the possibility for electronic steering of the acoustic focus within the brain. In addition, the capability to adjust the frequency of insonation at different locations on the skull can have an effect on ultrasound transmission. To determine the efficacy and applicability of a multiple-frequency approach with such a device, this study examined the frequency dependence of ultrasound transmission in the range of 0.6-1.4 MHz through a series of 17 points on four ex vivo human skulls. Effects beyond those that are characteristic of frequency-dependent attenuation were examined. Using broadband pulses, it was shown that the reflected spectra from the skull revealed information regarding ultrasound transmission at specific frequencies. A multiple-frequency insonation with optimized frequencies over the entirety of five skull specimens was found to yield on average a temporally brief 230% increase in the transmitted intensity with an 88% decrease in time-averaged intensity transmission within the focal volume. This finding demonstrates a potential applicability of a multiple-frequency approach in transcranial ultrasound transmission.

  15. Nonlinear acoustic fields in acoustic metamaterial based on a cylindrical pipe with periodically arranged side holes.

    PubMed

    Fan, Li; Ge, Huan; Zhang, Shu-yi; Gao, Hai-fei; Liu, Yong-hui; Zhang, Hui

    2013-06-01

    Nonlinear acoustic fields in transmission-line acoustic metamaterials based on a cylindrical pipe with periodically arranged side holes are studied, in which the dispersions and characteristic parameters of the nonlinear acoustic waves are obtained with the Bloch theory, and meanwhile the distributions of the fundamental wave (FW) and second harmonic wave (SHW) in the metamaterial are simulated. Three characteristic frequency bands are defined according to the relations between the frequencies of the FW, SHW, and the low-frequency forbidden band (LFB) in the metamaterial. Especially, when the FW is in the LFB while the SHW is outside the LFB, the SHW can transmit through the metamaterial although the FW is blocked, which exhibits the possibility to extract the information from the SHW instead of the FW. In addition, experiments are carried out to measure the distributions of the acoustic pressures for the FW and SHW along the metamaterial and the experimental results are in agreement with the theory.

  16. Effects of cavity resonances on sound transmission into a thin cylindrical shell. [noise reduction in aircraft fuselage

    NASA Technical Reports Server (NTRS)

    Koval, L. R.

    1978-01-01

    In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the effects of internal cavity resonances on sound transmission into a thin cylindrical shell. The 'noise reduction' of the cylinder is defined and computed, with and without including the effects of internal cavity resonances. As would be expected, the noise reduction in the absence of cavity resonances follows the same qualitative pattern as does transmission loss. Numerical results show that cavity resonances lead to wide fluctuations and a general decrease of noise reduction, especially at cavity resonances. Modest internal absorption is shown to greatly reduce the effect of cavity resonances. The effects of external airflow, internal cabin pressurization, and different acoustical properties inside and outside the cylinder are also included and briefly examined.

  17. Origami acoustics: using principles of folding structural acoustics for simple and large focusing of sound energy

    NASA Astrophysics Data System (ADS)

    Harne, Ryan L.; Lynd, Danielle T.

    2016-08-01

    Fixed in spatial distribution, arrays of planar, electromechanical acoustic transducers cannot adapt their wave energy focusing abilities unless each transducer is externally controlled, creating challenges for the implementation and portability of such beamforming systems. Recently, planar, origami-based structural tessellations are found to facilitate great versatility in system function and properties through kinematic folding. In this research we bridge the physics of acoustics and origami-based design to discover that the simple topological reconfigurations of a Miura-ori-based acoustic array yield many orders of magnitude worth of reversible change in wave energy focusing: a potential for acoustic field morphing easily obtained through deployable, tessellated architectures. Our experimental and theoretical studies directly translate the roles of folding the tessellated array to the adaptations in spectral and spatial wave propagation sensitivities for far field energy transmission. It is shown that kinematic folding rules and flat-foldable tessellated arrays collectively provide novel solutions to the long-standing challenges of conventional, electronically-steered acoustic beamformers. While our examples consider sound radiation from the foldable array in air, linear acoustic reciprocity dictates that the findings may inspire new innovations for acoustic receivers, e.g. adaptive sound absorbers and microphone arrays, as well as concepts that include water-borne waves.

  18. Scattering of Acoustic Waves from Ocean Boundaries

    DTIC Science & Technology

    2015-09-30

    of buried mines and improve SONAR performance in shallow water. OBJECTIVES 1) Determination of the correct physical model of acoustic propagation...Measurements for Range Dependent Geoacoustic Parameters: Bottom loss data from 5 – 30 kHz were collected as part of the Target and Reverberation Experiment...2013 (TREX13). These data were analyzed and range dependent geoacoustic parameters were derived for the TREX reverberation site including bottom loss

  19. Broadband Focusing Acoustic Lens Based on Fractal Metamaterials.

    PubMed

    Song, Gang Yong; Huang, Bei; Dong, Hui Yuan; Cheng, Qiang; Cui, Tie Jun

    2016-10-26

    Acoustic metamaterials are artificial structures which can manipulate sound waves through their unconventional effective properties. Different from the locally resonant elements proposed in earlier studies, we propose an alternate route to realize acoustic metamaterials with both low loss and large refractive indices. We describe a new kind of acoustic metamaterial element with the fractal geometry. Due to the self-similar properties of the proposed structure, broadband acoustic responses may arise within a broad frequency range, making it a good candidate for a number of applications, such as super-resolution imaging and acoustic tunneling. A flat acoustic lens is designed and experimentally verified using this approach, showing excellent focusing abilities from 2 kHz and 5 kHz in the measured results.

  20. Broadband Focusing Acoustic Lens Based on Fractal Metamaterials

    NASA Astrophysics Data System (ADS)

    Song, Gang Yong; Huang, Bei; Dong, Hui Yuan; Cheng, Qiang; Cui, Tie Jun

    2016-10-01

    Acoustic metamaterials are artificial structures which can manipulate sound waves through their unconventional effective properties. Different from the locally resonant elements proposed in earlier studies, we propose an alternate route to realize acoustic metamaterials with both low loss and large refractive indices. We describe a new kind of acoustic metamaterial element with the fractal geometry. Due to the self-similar properties of the proposed structure, broadband acoustic responses may arise within a broad frequency range, making it a good candidate for a number of applications, such as super-resolution imaging and acoustic tunneling. A flat acoustic lens is designed and experimentally verified using this approach, showing excellent focusing abilities from 2 kHz and 5 kHz in the measured results.

  1. Broadband Focusing Acoustic Lens Based on Fractal Metamaterials

    PubMed Central

    Song, Gang Yong; Huang, Bei; Dong, Hui Yuan; Cheng, Qiang; Cui, Tie Jun

    2016-01-01

    Acoustic metamaterials are artificial structures which can manipulate sound waves through their unconventional effective properties. Different from the locally resonant elements proposed in earlier studies, we propose an alternate route to realize acoustic metamaterials with both low loss and large refractive indices. We describe a new kind of acoustic metamaterial element with the fractal geometry. Due to the self-similar properties of the proposed structure, broadband acoustic responses may arise within a broad frequency range, making it a good candidate for a number of applications, such as super-resolution imaging and acoustic tunneling. A flat acoustic lens is designed and experimentally verified using this approach, showing excellent focusing abilities from 2 kHz and 5 kHz in the measured results. PMID:27782216

  2. Vibration measurements on a car transmission housing

    NASA Astrophysics Data System (ADS)

    Weber, Wolfram; Plieske, Marco; Brauchle, Gerhard

    1994-09-01

    In view of stricter future statutory requirements concerning noise emissions by motor vehicles, the acoustic optimization of noise emitting components will become increasingly important. Customers complain about transmission noise when for example gears excite individual resonances (eigenfrequencies) of the transmission housing. Normally the eigenfrequencies and also the excitation frequencies are not moveable out of narrow limits. Therefore, in addition to optimizing gear geometry, the transmission housing must be designed so that dynamic forces acting through the gears onto the shaft bearing points lead to minimum level of radiated sound power from the transmission housing. For this reason, the resonance vibration shapes induced on a car transmission under operating conditions were measured using the laser-transmission test rig. Additionally, a comparison was made between the inspection of an empty transmission housing (using finite element calculation and experimental modal analysis).

  3. Indoor acoustic gain design

    NASA Astrophysics Data System (ADS)

    Concha-Abarca, Justo Andres

    2002-11-01

    The design of sound reinforcement systems includes many variables and usually some of these variables are discussed. There are criteria to optimize the performance of the sound reinforcement systems under indoor conditions. The equivalent acoustic distance, the necessary acoustic gain, and the potential acoustic gain are parameters which must be adjusted with respect to the loudspeaker array, electric power and directionality of loudspeakers, the room acoustics conditions, the distance and distribution of the audience, and the type of the original sources. The design and installation of front of the house and monitoring systems have individual criteria. This article is about this criteria and it proposes general considerations for the indoor acoustic gain design.

  4. Technological, biological, and acoustical constraints to music perception in cochlear implant users.

    PubMed

    Limb, Charles J; Roy, Alexis T

    2014-02-01

    Despite advances in technology, the ability to perceive music remains limited for many cochlear implant users. This paper reviews the technological, biological, and acoustical constraints that make music an especially challenging stimulus for cochlear implant users, while highlighting recent research efforts to overcome these shortcomings. The limitations of cochlear implant devices, which have been optimized for speech comprehension, become evident when applied to music, particularly with regards to inadequate spectral, fine-temporal, and dynamic range representation. Beyond the impoverished information transmitted by the device itself, both peripheral and central auditory nervous system deficits are seen in the presence of sensorineural hearing loss, such as auditory nerve degeneration and abnormal auditory cortex activation. These technological and biological constraints to effective music perception are further compounded by the complexity of the acoustical features of music itself that require the perceptual integration of varying rhythmic, melodic, harmonic, and timbral elements of sound. Cochlear implant users not only have difficulty perceiving spectral components individually (leading to fundamental disruptions in perception of pitch, melody, and harmony) but also display deficits with higher perceptual integration tasks required for music perception, such as auditory stream segregation. Despite these current limitations, focused musical training programs, new assessment methods, and improvements in the representation and transmission of the complex acoustical features of music through technological innovation offer the potential for significant advancements in cochlear implant-mediated music perception.

  5. Vibroacoustic modeling of an acoustic resonator tuned by dielectric elastomer membrane with voltage control

    NASA Astrophysics Data System (ADS)

    Yu, Xiang; Lu, Zhenbo; Cheng, Li; Cui, Fangsen

    2017-01-01

    This paper investigates the acoustic properties of a duct resonator tuned by an electro-active membrane. The resonator takes the form of a side-branch cavity which is attached to a rigid duct and covered by a pre-stretched Dielectric Elastomer (DE) in the neck area. A three-dimensional, analytical model based on the sub-structuring approach is developed to characterize the complex structure-acoustic coupling between the DE membrane and its surrounding acoustic media. We show that such resonator provides sound attenuation in the medium frequency range mainly by means of sound reflection, as a result of the membrane vibration. The prediction accuracy of the proposed model is validated against experimental test. The pre-stretched DE membrane with fixed edges responds to applied voltage change with a varying inner stress and, by the same token, its natural frequency and vibrational response can be tuned to suit particular frequencies of interest. The peaks in the transmission loss (TL) curves can be shifted towards lower frequencies when the voltage applied to the DE membrane is increased. Through simulations on the effect of increasing the voltage level, the TL shifting mechanism and its possible tuning range are analyzed. This paves the way for applying such resonator device for adaptive-passive noise control.

  6. Elastic parabolic equation solutions for underwater acoustic problems using seismic sources.

    PubMed

    Frank, Scott D; Odom, Robert I; Collis, Jon M

    2013-03-01

    Several problems of current interest involve elastic bottom range-dependent ocean environments with buried or earthquake-type sources, specifically oceanic T-wave propagation studies and interface wave related analyses. Additionally, observed deep shadow-zone arrivals are not predicted by ray theoretic methods, and attempts to model them with fluid-bottom parabolic equation solutions suggest that it may be necessary to account for elastic bottom interactions. In order to study energy conversion between elastic and acoustic waves, current elastic parabolic equation solutions must be modified to allow for seismic starting fields for underwater acoustic propagation environments. Two types of elastic self-starter are presented. An explosive-type source is implemented using a compressional self-starter and the resulting acoustic field is consistent with benchmark solutions. A shear wave self-starter is implemented and shown to generate transmission loss levels consistent with the explosive source. Source fields can be combined to generate starting fields for source types such as explosions, earthquakes, or pile driving. Examples demonstrate the use of source fields for shallow sources or deep ocean-bottom earthquake sources, where down slope conversion, a known T-wave generation mechanism, is modeled. Self-starters are interpreted in the context of the seismic moment tensor.

  7. Acoustic Signal Processing

    NASA Astrophysics Data System (ADS)

    Hartmann, William M.; Candy, James V.

    Signal processing refers to the acquisition, storage, display, and generation of signals - also to the extraction of information from signals and the re-encoding of information. As such, signal processing in some form is an essential element in the practice of all aspects of acoustics. Signal processing algorithms enable acousticians to separate signals from noise, to perform automatic speech recognition, or to compress information for more efficient storage or transmission. Signal processing concepts are the building blocks used to construct models of speech and hearing. Now, in the 21st century, all signal processing is effectively digital signal processing. Widespread access to high-speed processing, massive memory, and inexpensive software make signal processing procedures of enormous sophistication and power available to anyone who wants to use them. Because advanced signal processing is now accessible to everybody, there is a need for primers that introduce basic mathematical concepts that underlie the digital algorithms. The present handbook chapter is intended to serve such a purpose.

  8. Automatic transmission

    SciTech Connect

    Miura, M.; Aoki, H.

    1988-02-02

    An automatic transmission is described comprising: an automatic transmission mechanism portion comprising a single planetary gear unit and a dual planetary gear unit; carriers of both of the planetary gear units that are integral with one another; an input means for inputting torque to the automatic transmission mechanism, clutches for operatively connecting predetermined ones of planetary gear elements of both of the planetary gear units to the input means and braking means for restricting the rotation of predetermined ones of planetary gear elements of both of the planetary gear units. The clutches are disposed adjacent one another at an end portion of the transmission for defining a clutch portion of the transmission; a first clutch portion which is attachable to the automatic transmission mechanism portion for comprising the clutch portion when attached thereto; a second clutch portion that is attachable to the automatic transmission mechanism portion in place of the first clutch portion for comprising the clutch portion when so attached. The first clutch portion comprising first clutch for operatively connecting the input means to a ring gear of the single planetary gear unit and a second clutch for operatively connecting the input means to a single gear of the automatic transmission mechanism portion. The second clutch portion comprising a the first clutch, the second clutch, and a third clutch for operatively connecting the input member to a ring gear of the dual planetary gear unit.

  9. AQUIFER TRANSMISSIVITY

    EPA Science Inventory

    Evaluation of groundwater resources requires the knowledge of the capacity of aquifers to store and transmit ground water. This requires estimates of key hydraulic parameters, such as the transmissivity, among others. The transmissivity T (m2/sec) is a hydrauli...

  10. Acoustic tomography. Laboratory technique Implementation.

    NASA Astrophysics Data System (ADS)

    Galvis, Jorge; Carvajal, Jenny

    2010-05-01

    From geomechanical tests carried out on rocks it is possible to determine its physico-mechanical properties, which relate the strain and applied stress; even so, conventional tests do not allow to identify how stress is distributed and how it has affected porous media. Today, techniques like acoustic tomography widely used in medicine, geophysics and others sciences, generates images by sections of the interior of a body. Acoustic tomography allows inferring the stress state within porous media; since wave velocities are closely related to media density, if a stress is applied to a rock, it will generate grains compaction and this will be showed by an increase of wave velocity. Implementation was conducted on rock plugs under diverse stress fields, simultaneously recording P-wave velocities (Compressional) on perpendicular planes to sample vertical axis. Transmission and reception of acoustic waves through porous media were done by piezoelectric crystals (PZT) used as sensors. A transmitting crystal excited by a voltage pulse causes a mechanical vibration, which travels across media; this is known as inverse piezoelectric effect. This vibration is recorded by a receiving crystal in which the direct piezoelectric effect appears; which dictates that if a piezoelectric is disturbed mechanically, an electrical signal between its terminals will appear. This electrical signal is used to obtain the wave velocity. Nevertheless, acoustic tomography corresponds to one of those called inverse Problems that arise when from observed data the model parameters must be obtained; in this way, tomography involves iterative reconstruction techniques (ART or SIRT) which are projections of observed data and its later inversion. Obtained results are cross-sectional images of velocity within the rock. In these images it is possible to identify where stress has a greater concentration observing the color map generated; thus, a greater velocity density area corresponding to a greater

  11. Evaluation of the resolution of a metamaterial acoustic leaky wave antenna.

    PubMed

    Naify, Christina J; Rogers, Jeffery S; Guild, Matthew D; Rohde, Charles A; Orris, Gregory J

    2016-06-01

    Acoustic antennas have long been utilized to directionally steer acoustic waves in both air and water. Typically, these antennas are comprised of arrays of active acoustic elements, which are electronically phased to steer the acoustic profile in the desired direction. A new technology, known as an acoustic leaky wave antenna (LWA), has recently been shown to achieve directional steering of acoustic waves using a single active transducer coupled to a transmission line passive aperture. The LWA steers acoustic energy by preferential coupling to an input frequency and can be designed to steer from backfire to endfire, including broadside. This paper provides an analysis of resolution as a function of both input frequency and antenna length. Additionally, the resolution is compared to that achieved using an array of active acoustic elements.

  12. Decentralized harmonic control of sound radiation and transmission by a plate using a virtual impedance approach.

    PubMed

    Quaegebeur, Nicolas; Micheau, Philippe; Berry, Alain

    2009-05-01

    The problem under study in this article is the active control of sound transmission and radiation of a panel under a periodic excitation. The control strategy investigated uses independent control loops between an individual polyvinylidene fluoride (PVDF) sensor and an individual lead zirconate titanate (PZT) actuator. The specific approach employed here uses the concept of virtual impedance. The aim is to determine for each frequency the optimal impedance between each PVDF sensor and the corresponding PZT actuator in order to reduce the sound power radiated by the plate. Theoretical predictions are compared to measurements of the sound radiated and transmission loss of a panel mounted with eight PZT-PVDF units. Reductions of up to 20 dB of the acoustic power can be achieved around mechanical resonances of the system, while the control strategy has little effect for off-resonance excitations.

  13. Utilizing computer models for optimizing classroom acoustics

    NASA Astrophysics Data System (ADS)

    Hinckley, Jennifer M.; Rosenberg, Carl J.

    2002-05-01

    The acoustical conditions in a classroom play an integral role in establishing an ideal learning environment. Speech intelligibility is dependent on many factors, including speech loudness, room finishes, and background noise levels. The goal of this investigation was to use computer modeling techniques to study the effect of acoustical conditions on speech intelligibility in a classroom. This study focused on a simulated classroom which was generated using the CATT-acoustic computer modeling program. The computer was utilized as an analytical tool in an effort to optimize speech intelligibility in a typical classroom environment. The factors that were focused on were reverberation time, location of absorptive materials, and background noise levels. Speech intelligibility was measured with the Rapid Speech Transmission Index (RASTI) method.

  14. Particle Cloud Flames in Acoustic Fields

    NASA Technical Reports Server (NTRS)

    Berlad, A. L.; Tangirala, V.; Ross, H.; Facca, L.

    1990-01-01

    Results are presented on a study of flames supported by clouds of particles suspended in air, at pressures about 100 times lower than normal. In the experiment, an acoustic driver (4-in speaker) placed at one end of a closed tube, 0.75-m long and 0.05 m in diameter, disperses a cloud of lycopodium particles during a 0.5-sec powerful acoustic burst. Properties of the particle cloud and the flame were recorded by high-speed motion pictures and optical transmission detectors. Novel flame structures were observed, which owe their features to partial confinement, which encourages flame-acoustic interactions, segregation of particle clouds into laminae, and penetration of the flame's radiative flux density into the unburned particle-cloud regimes. Results of these experiments imply that, for particles in confined spaces, uncontrolled fire and explosion may be a threat even if the Phi(0) values are below some apparent lean limit.

  15. Acoustic fluidization - A new geologic process

    NASA Technical Reports Server (NTRS)

    Melosh, H. J.

    1979-01-01

    A number of geologic processes, particularly seismic faulting, impact crater slumping, and long runout landslides, require the failure of geologic materials under differential stresses much smaller than expected on the basis of conventional rock mechanics. This paper proposes that the low strengths apparent in these phenomena are due to a state of 'acoustic fluidization' induced by a transient strong acoustic wave field. The strain rates possible in such a field are evaluated, and it is shown that acoustically fluidized debris behaves as a newtonian fluid with a viscosity in the range 100,000 to 10,000,000 P for plausible conditions. Energy gains and losses in the acoustic field are discussed, and the mechanism is shown to be effective if internal dissipation in the field gives a Q approximately greater than 100. Whether such values for Q are realized is not known at present. However, acoustic fluidization provides a qualitatively correct description of the failure of rock debris under low differential stresses in the processes of faulting, crater slumping, and long runout landslides. Acoustic fluidization thus deserves serious consideration as a possible explanation of these phenomena.

  16. Enhancing sound absorption and transmission through flexible multi-layer micro-perforated structures.

    PubMed

    Bravo, Teresa; Maury, Cédric; Pinhède, Cédric

    2013-11-01

    Theoretical and experimental results are presented into the sound absorption and transmission properties of multi-layer structures made up of thin micro-perforated panels (ML-MPPs). The objective is to improve both the absorption and insulation performances of ML-MPPs through impedance boundary optimization. A fully coupled modal formulation is introduced that predicts the effect of the structural resonances onto the normal incidence absorption coefficient and transmission loss of ML-MPPs. This model is assessed against standing wave tube measurements and simulations based on impedance translation method for two double-layer MPP configurations of relevance in building acoustics and aeronautics. Optimal impedance relationships are proposed that ensure simultaneous maximization of both the absorption and the transmission loss under normal incidence. Exhaustive optimization of the double-layer MPPs is performed to assess the absorption and/or transmission performances with respect to the impedance criterion. It is investigated how the panel volumetric resonances modify the excess dissipation that can be achieved from non-modal optimization of ML-MPPs.

  17. [Neurofibromatosis 2 (bilateral acoustic neurofibromatosis)].

    PubMed

    Yalcinkaya, C; Sarioglu, A; Boltshauser, E

    1989-10-14

    We report a personal series of 28 patients with neurofibromatosis 2 (NF-2), emphasizing the differences from classical NF-1. The hallmark of NF-2 is bilateral acoustic neuromas with initial symptoms usually occurring in the second or third decade. The natural history may lead to bilateral deafness, but hearing loss may also be a complication of surgery. NF-2 is frequently accompanied by additional intracranial tumors (particularly multiple meningiomas). Half of our patients had a spinal space-occupying lesion. NF-2 is inherited as an autosomal dominant trait, and many patients appear to represent new mutations.

  18. Local Frequency Dependence in Transcranial Ultrasound Transmission

    NASA Astrophysics Data System (ADS)

    White, P. J.; Clement, G. T.; Hynynen, K.

    2006-05-01

    The development of large-aperture multiple-source transducer arrays for ultrasound transmission through the human skull has demonstrated the possibility of controlled and substantial acoustic energy delivery into the brain parenchyma without the necessitation of a craniotomy. The individual control of acoustic parameters from each ultrasound source allows for the correction of distortions arising from transmission through the skull bone and also opens up the possibility for electronic steering of the acoustic focus within the brain. In addition, the capability to adjust the frequency of sonication at different locations on the skull can have an effect on ultrasound transmission. To determine the efficacy and applicability of a multiple-frequency approach with such a device, this study examined the frequency dependence of ultrasound transmission in the range of 0.6-1.4 MHz through a series of seventeen points on four ex vivo human skulls. Effects beyond those that are characteristic of frequency-dependent attenuation were examined. Using broadband pulses, it was shown that the reflected spectra from the skull revealed information regarding ultrasound transmission at specific frequencies. This finding demonstrates a potential applicability of a multiple-frequency approach in transcranial ultrasound transmission.

  19. An Overview of Acoustic Telemetry

    SciTech Connect

    Drumheller, D.S.

    1992-03-24

    Acoustic telemetry has been a dream of the drilling industry for the past 50 years. It offers the promise of data rates which are one-hundred times greater than existing technology. Such a system would open the door to true logging-while-drilling technology and bring enormous profits to its developers. The oil and gas industry has led in most of the attempts to develop this type of telemetry system; however, very substantial efforts have also been made through government sponsored work in the geothermal industry. None of these previous attempts have lead to a commercial telemetry system. Conceptually, the problem looks easy. The basic idea is to produce an encoded sound wave at the bottom of the well, let it propagate up the steel drillpipe, and extract the data from the signal at the surface. Unfortunately, substantial difficulties arise. The first difficult problem is to produce the sound wave. Since the most promising transmission wavelengths are about 20 feet, normal transducer efficiencies are quite low. Compounding this problem is the structural complexity of the bottomhole assembly and drillstring. For example, the acoustic impedance of the drillstring changes every 30 feet and produces an unusual scattering pattern in the acoustic transmission. This scattering pattern causes distortion of the signal and is often confused with signal attenuation. These problems are not intractable. Recent work has demonstrated that broad frequency bands exist which are capable of transmitting data at rates up to 100 bits per second. Our work has also identified the mechanism which is responsible for the observed anomalies in the patterns of signal attenuation. Furthermore in the past few years a body of experience has been developed in designing more efficient transducers for application to metal Waveguides. The direction of future work is clear. New transducer designs which are more efficient and compatible with existing downhole power supplies need to be built and tested

  20. Offset Waveguide Transmission Measurements

    NASA Technical Reports Server (NTRS)

    Cravey, Robin

    1997-01-01

    This report describes measurements to determine transmission losses in S-band (2.60-3.95 GHz) waveguide sections due to misalignment of the sections relative to each other. The experiments were performed in support of the Hydrostar program to determine the feasibility of using deployable waveguide sections in a large space radiometer. The waveguide sections would possibly be hinged and folded for launch, then deployed in space to form long sections of waveguide. Since very low losses are required for radiometer applications, the effects of potential misalignment after deployment of the waveguide sections may be significant. These measurements were performed in the Electromagnetic Properties Measurement Laboratory in the Electromagnetics Research Branch.