bluuebunny/crossref_metadata_2025 huggingface dataset:
The value of utilizing binaural dummy head recordings in evaluating physical acoustic changes in concert halls
Authors: Jaffe Christopher , Cooper Russell , Rivera Carlos
Published: October 2013

In some instances, after a concert hall is built there may be a need to modify the physical environment of the space through the application of diffusion or absorptive surfaces, the addition of reflector systems or the repositioning of the orchestra in the space. Prior to moving forward with suggested changes to the physical environment, it has been customary to conduct evaluation rehearsals with physical mock-ups installed to confirm the acousticians recommendations. Questionnaires are given to the musicians, the conductor and the administration staff to document the effect of the changes, and physical measurements are taken before and after the installation of the mock-ups. The questionnaires can be difficult to correlate and the differences in data resulting from the physical measurements may be too small to properly evaluate. More recently, Jaffe Holden Acoustics has added dummy head recordings to the mix. These recordings are extremely representative of what a human hears and one can place these devices in various locations on stage and in the audience chamber. The recordings create a permanent record of the event and the results of subsequent A/B evaluation can be more closely correlated to render judgments.
Use of a 600-kHz ADCP to characterize submerged aquatic vegetation in a very shallow estuary
Authors: Warren Joseph D. , Peterson Bradley J.
Published: October 2013

Submerged aquatic vegetation (SAV) serves as a key habitat for the larval forms of many commercially important marine organisms. In coastal waters, anthropogenic factors can cause severe damage and loss to this habitat. In order to measure changes in the spatial coverage of SAV, aerial photography or diver surveys are required. We investigated an alternative approach using a high-frequency (600 kHz) acoustic Doppler current profiler to make high-resolution (in the vertical) measurements of the scattering in several very shallow bays in Long Island, NY. These data were used to determine the presence and amount of SAV in an area. Diver surveys provided ground-truthing of these data. Field measurements are also compared with an acoustic scattering model for eel grass (a common SAV type in the northeast United States). The purpose of this project was to determine whether acoustic sampling of benthic vegetation could accurately determine species type and coverage. If this is possible, then acoustic sampling could provide maps of spatial and temporal changes in SAV distribution and abundance. [Work was supported by an award from UNH CICEET.]
Modeling low-frequency acoustic scattering from densely populated fish schools
Authors: Hahn Thomas R.
Published: October 2013

Scattering of sound from a school of swimbladder-bearing fish is clearly related to the scattering from a cloud of air bubbles. From an ‘‘effective’’ medium perspective, such bubble clouds can be viewed as a single object with acoustic bulk properties determined from the physical properties of the individual bubbles and the effect of multiple scattering between them. The acoustic modeling at low frequencies of bubble clouds based on the effective medium approach has been successfully applied to bubbles in the ocean and laboratory bubble plumes by a variety of authors. Applicability and limitations of an effective medium approach to scattering of sound waves from fish schools are investigated and compared to other acoustic models. It is argued that, particularly in the regime of highly populated fish schools, where other approaches (e.g., born or random-phase approximation, etc.) fail due to strong multiple scattering effects, the effective medium model can be applied for a wide range of frequencies, fish numbers, and densities.
Diurnal trends in the mid-water biomass community of the Northwestern Hawaiian Islands observed acoustically
Authors: Lammers Marc O. , Brainard Russell E. , Au Whitlow W. L.
Published: October 2013

The nighttime mid-water biomass occurring near six banks in the Northwestern Hawaiian Islands was investigated using 38- and 120-kHz EK60 echosounders. Locations investigated included: French Frigate Shoals, Maro Reef, Lisianksi Island/Neva Shoals, Pearl and Hermes Atoll, Kure Atoll and Midway Atoll. Surveys were designed to sample transect lines parallel and normal to shore between 10 p.m. and 7 a.m. and once during daylight hours. A diurnal trend was found in the occurrence of mid-water sound scattering organisms at all six locations. Communities of organisms accumulate at night on the edges of each island between the 20- and 100-fathom isobaths. The highest densities of organisms restrict their horizontal movements to depths of 20 fathoms or deeper, but increases in biomass were also observed at shallower depths. The northern islands of Kure, Midway, and Pearl and Hermes Atolls exhibited patchier distributions than the southern islands. The composition of the biomass is presently unclear but resembles the mesopelagic boundary community found near the Main Hawaiian Islands. Simultaneous observations with the TOAD camera system revealed clouds of zooplankton mixed with small fish and other micronekton. The nightly influx of these organisms is likely a significant, though poorly understood, component of these islands ecosystems.
Identifying stable frequencies for performing animal abundance estimation with a multifrequency system
Authors: Roberts Paul L. , Jaffe Jules S.
Published: October 2013

The practice of using acoustic backscatter at multiple frequencies for estimating animal abundance has become commonplace. However, the choice of frequencies to use, in order to optimize the data analysis and resulting estimates, is often not considered. The usual procedure is to use an inversion that is based on a forward model. One is generally free to choose the model used, and in some cases the frequencies used for data collection. Unfortunately, the frequencies are often chosen without regard for the stability of the inversion. The stability of a model-based multifrequency inversion depends on the condition number of the associated reflectivity matrix. This condition number in turn depends on the assumed size classes of the animals, the scattering model used, and the frequencies used to collect the data. Results indicate that the choice of frequencies has a significant effect on the condition number with greater than 3 orders of magnitude variation over a practical frequency range for the size classes considered. The analysis highlights the use of the condition number in evaluating the stability of the inversions. In addition, it provides a way to interpret estimates from existing systems, and a tool for designing future systems.
The use of ultrasound to probe structural and material properties of bone: State-of-the art
Authors: Laugier Pascal
Published: October 2013

The knowledge of the elastic properties of bone can be used to investigate the effects of aging, disease, and treatments. Elastic properties are also required as input for both computational and analytic models. An alternative approach to direct bone mechanical testing is to use ultrasonic testing. Furthermore, ultrasound is appropriate for multiscale analysis. In vitro, ultrasound has been widely used to derive nondestructively the stiffness coefficients or the elastic moduli at the whole specimen level at low frequency (structural elasticity) or at the tissue level at higher frequency (material stiffness). Quantitative ultrasound (QUS) techniques have also been developed for in vivo skeletal status assessment based on the assumption that ultrasonic properties reflect skeletal factors of bone fragility. In vivo QUS is then used to predict fracture risk. Several different techniques are currently available or under development involving different type of waves (bulk compressional waves, surface waves, guided modes). Measured ultrasonic properties in transmission or in reflection depend on a variety of material properties and macro- or micro structural characteristics. However, the complexity of the interaction mechanisms between the incident ultrasonic field and bone is still not fully elucidated and requires a better understanding.
Theoretical analysis of a directional source for four dimensional seismic monitoring
Authors: Berraki Madjid , Dubus Bertrand , Baroni Axelle
Published: October 2013

The aim of four dimensional seismic monitoring is to monitor the changes in the subsurface in time; to achieve this, measurements are continuously repeated with the same space configuration. Reliability and repeatability of the acquisition footprint are thus key requirements for four dimensional surveys. The weathered zone (WZ) is the main cause of source signal fluctuations, polluting the signal coming from reservoir variations. This zone is directly located beneath the surface and its mechanical properties vary with weather. To eliminate this perturbation, a directional source, buried under the WZ and radiating downwards, is analyzed here. Assuming that the source size to wavelength ratio is small, a model is developed for the directional source buried in a layered half space: the Green’s tensor in a layer is calculated using the discrete wavenumber method [M. Bouchon, Bull. Seismol. Soc. Am. 71(4), 959-971 (1981)] and the solution is then propagated using the reflectivity method [J. Muller, Geophysics 58, 153–174 (1985)]. Using a typical seismic signal called Ricker, synthetic seismograms are computed for the directional source buried in a half space covered by a layer (the WZ). The obtained results validate the directional source concept. [Work supported by an I.F.P. grant.]
The role of hysteresis in propagating acoustic wave in porous materials
Authors: Lu Zhiqu , Sabatier James
Published: October 2013

Hysteresis and end-point memory are universal behaviors of porous materials including rock, sandstone, soil, sediment, ceramic, and some cracked materials. Recently, there have been growing interests in studying hysteresis and linking this static property to dynamic behaviors, particularly in modeling nonlinear acoustic phenomena in porous materials. This study aims at exploring the role of hysteresis in propagation of an acoustic wave in soils. A modified triaxial cell was used to measure stress/strain and sound speed/strain relationships in a triaxial test. Soil samples were subjected to a load stress path that was designed to undergo a series of meso-scopic unload-reload stress cycles with axial strain in the range of 10Exp(−5)–10Exp(−4). It is found that the slope of the hysteresis loop is linearly correlated with the dynamic elastic modulus, which implies that the fluctuation of acoustic pressure may create micro-hysteresis loops that make the dynamic elastic modulus higher than static elastic modulus. This discovery may lead to a correction in the classical equation of state by adding a hysteresis term. [Work supported by the U.S. Department of Agriculture.]
Fifty years of progress in speech synthesis
Authors: Schroeter Juergen
Published: October 2013

A common opinion is that progress in speech synthesis should be easier to discern than in other areas of speech communication: you just have to listen to the speech! Unfortunately, things are more complicated. It can be said, however, that early speech synthesis efforts were primarily concerned with providing intelligible speech, while, more recently, ‘‘naturalness’’ has been the focus. The field had its ‘‘electronic’’ roots in Homer Dudley’s 1939 ‘‘Voder,’’ and it advanced in the 1950s and 1960s through progress in a number of labs including JSRU in England, Haskins Labs in the U.S., and Fant’s Lab in Sweden. In the 1970s and 1980s significant progress came from efforts at Bell Labs (under Jim Flanagan’s leadership) and at MIT (where Dennis Klatt created one of the first commercially viable systems). Finally, over the past 15 years, the methods of unit-selection synthesis were devised, primarily at ATR in Japan, and were advanced by work at AT&T Labs, Univ. of Edinburgh, and ATR. Today, TTS systems are able to ‘‘convince some of the listeners some of the time’’ that synthetic speech is as natural as live recordings. Ongoing efforts aim at replacing ‘‘some’’ with ‘‘most’’ for a wide range of real-world applications.
Fifty years of progress in speech and speaker recognition
Authors: Furui Sadaoki
Published: October 2013

Speech and speaker recognition technology has made very significant progress in the past 50 years. The progress can be summarized by the following changes: (1) from template matching to corpus-base statistical modeling, e.g., HMM and n-grams, (2) from filter bank/spectral resonance to Cepstral features (Cepstrum + DCepstrum + DDCepstrum), (3) from heuristic time-normalization to DTW/DP matching, (4) from gdistanceh-based to likelihood-based methods, (5) from maximum likelihood to discriminative approach, e.g., MCE/GPD and MMI, (6) from isolated word to continuous speech recognition, (7) from small vocabulary to large vocabulary recognition, (8) from context-independent units to context-dependent units for recognition, (9) from clean speech to noisy/telephone speech recognition, (10) from single speaker to speaker-independent/adaptive recognition, (11) from monologue to dialogue/conversation recognition, (12) from read speech to spontaneous speech recognition, (13) from recognition to understanding, (14) from single-modality (audio signal only) to multi-modal (audio/visual) speech recognition, (15) from hardware recognizer to software recognizer, and (16) from no commercial application to many practical commercial applications. Most of these advances have taken place in both the fields of speech recognition and speaker recognition. The majority of technological changes have been directed toward the purpose of increasing robustness of recognition, including many other additional important techniques not noted above.
Microphones for speech and speech recognition
Authors: West James E.
Published: October 2013

Automatic speech recognition (ASR) requires about a 15- to 20-dB signal-to-noise ratio (S/N) for high accuracy even for small vocabulary systems. This S/N is generally achievable using a telephone handset in normal office or home environments. In the early 1990s ATT and the regional telephone companies began using speaker-independent ASR to replace several operator services. The variable distortion in the carbon microphone was not transparent and resulted in reduced ASR accuracy. The linear electret condenser microphone, common in most modern telephones, improved handset performance both in sound quality and ASR accuracy. Hands-free ASR in quiet conditions is a bit more complex because of the increased distance between the microphone and the speech source. Cardioid directional microphones offer some improvement in noisy locations when the noise and desired signals are spatially separated, but this is not the general case and the resulting S/N is not adequate for seamless machine translation. Higher-order directional microphones, when properly oriented with respect to the talker and noise, have shown good improvement over omni-directional microphones. Some ASR results measured in simulated car noise will be presented.
Ocean noise and marine mammals: A tutorial lecture
Authors: D’Spain Gerald , Wartzok Douglas
Published: October 2013

The effect of man-made sound on marine mammals has been surrounded by controversy over the past decade. Much of this controversy stems from our lack of knowledge of the effects of noise on marine life. Ocean sound is produced during activities of great benefit to humans: commerce, exploration for energy reserves, national defense, and the study of the ocean environment itself. However, some recent strandings of marine mammals have been associated with the occurrence of human-generated sound. The documented increase of man-made sound in the ocean suggests the potential for more extensive though subtler effects than those observed in the mass strandings. The purpose of this tutorial is to present the scientific issues pertaining to ocean noise and marine mammals. Basic physics of sound in the ocean and long term trends of ocean sound will be presented. The biology of marine mammals, particularly their production, reception and use of sound in monitoring their environment, social interactions, and echolocation, will be reviewed. This background information sets the stage for understanding the effects of man-made sound on marine mammals. The extensive gaps in current knowledge with respect to marine mammal distribution and behavioral and physiological responses to sound will highlight research needs.
Measurement of transmission loss trends for orthotropic sandwich panels at a subscale facility
Authors: Rajaram Shankar , Wang Tongan , Nutt Steve
Published: October 2013

Interior noise studies in airplanes have identified floors as one of the primary noise paths. The acoustic barrier properties of floor panels are typically quantified by sound transmission loss (STL) measurements. A subscale transmission loss suite consisting of a reverberant room and an anechoic room was constructed and qualified to study the relative transmission loss trends of orthotropic sandwich panels used in airplane floors. A host of material combinations accounting for a variety of mechanical properties were tested for their acoustic performance. The transmission loss measurements were based on a sound intensity technique (ASTM E 2249-02) and a sound pressure technique (SAE J 1400-90). The results from these two techniques were compared to results from a full-scale accredited facility using the two-reverberation room method (ASTM E 90-02). The STL trends for orthotropic sandwich panels from the sub-scale facility were comparable to trends from the full-scale facility between 315 and 5000 Hz. The measurements permitted a ranking of several standard floor panels with respect to acoustic performance. [Support for this research from Mervyn C. Gill Foundation is gratefully acknowledged.]
Auditory brainstem response hearing measurements in free-ranging bottlenose dolphins (Tursiops truncatus)
Authors: Cook Mandy L. H. , Wells Randall S. , Mann David A.
Published: October 2013

Bottlenose dolphins (Tursiops truncatus) rely on sound for communication, navigation, and foraging. Both natural and anthropogenic noise in the marine environment could mask the ability of wild dolphins to detect sounds, and chronic noise exposure could cause permanent hearing loss. The hearing abilities of a wild population of bottlenose dolphins in Sarasota Bay, FL are being investigated to determine whether they suffer hearing losses in comparison to animals living in quieter environments. This study is the first to measure the hearing sensitivity of a large population of wild dolphins that are exposed to significant levels of noise. Data on hearing sensitivities at frequencies used for acoustic communication (5–20 kHz) and echolocation (20–100 kHz) are reported. Hearing sensitivity was measured in the field using the non-invasive auditory brainstem response (ABR) procedure. ABR responses were evoked by the presentation of amplitude-modulated (AM) tones (carrier frequencies of 5, 10, 20, 30, 60, and 80 kHz) through a jawphone. The tones were modulated at 600 Hz, which elicited a robust envelope following response. A rapid ABR procedure was employed so that an entire audiogram could be obtained in approximately 30 min. This study also provides baseline data for longitudinal hearing studies in known individuals.
Focusing effects due to solitons: 3D Gaussian beam modeling
Authors: Hursky Paul , Porter Michael B. , Sperry Brian J.
Published: October 2013

As is well known, the SOFAR channel in deep water reduces spherical spreading, to cylindrical spreading, allowing sound to propagate to enormous distances. Similarly, soliton packets can produce channels in shallow water, forming acoustic corridors, their walls consecutive solitons. As the solitons pass over a propagation path they can generate dramatic focusing and defocusing effects. Acoustic modeling of such phenomena is challenging in that 3D (horizontal refraction) effects are clearly important (Nx2D approaches fail here). The geotime evolution is equally important—we must model a series of frozen oceans as the soliton packet passes by. Gaussian beam tracing models are ideally suited for such 4D modeling. We have developed a MATLAB Gaussian beam-tracing model to address these problems. It includes capabilities for a variety of useful beam options, from ‘‘geometric beams’’ to the most formal beam theory based on paraxial approximations. The latter is implemented using a novel ‘‘reduced delta-matrix formulation’’ that greatly simplifies the algorithms. The new model also allows for broadband calculations, 3D bathymetry, and 3D oceanography. We will discuss a variety of applications, with particular emphasis on the effects of solitons.
Uncertainty due to chaotic effects of internal waves in shallow water
Authors: Luter Robert R. , La Cour Brian
Published: October 2013

Acoustic ray propagation is investigated in shallow water environments that include internal waves. Internal waves cause perturbations to the sound speed profile which results in ray chaos and causes uncertainty in the expected dynamics. In shallow water, the deep-water resonance structure exhibited in surfaces of section is largely missing due to the interaction of the rays with the ocean bottom. Instead, resonances caused by reflections create bands of chaos within large regions of regular dynamics. Lyapunov exponents are used to determine the extent of chaotic regions and to distinguish between regular and chaotic acoustic ray properties. Floquet theory is used to analyze range-periodic Hamiltonians that result from inclusion of the internal waves.
A contrast source inversion method for imaging acoustic contrasts
Authors: van Dongen Koen W. A. , Wright William M. D.
Published: October 2013

The propagation and scattering of acoustic wavefields is described by an integral equation of the second kind. In the forward problem, the kernel contains known Green’s tensors and contrast functions and is applied on the unknown total wavefields. Since the contrast functions, given by changes in density and compressibility, and the incident wavefields are known, the total wavefields can be obtained by solving the integral equation iteratively via a conjugate gradient (CG) method. In the inverse problem, the complete incident wavefields and the total wavefields at a limited number of positions are known, while the contrast function is unknown. To solve the inverse problem, the contrast function can be obtained from the integral equation by using the same CG scheme. However, for each update of the contrast function the forward problem must be solved. To avoid this problem, contrast sources are introduced, defined by the product of contrast functions and corresponding total wavefields. Hence, the integral equation will be solved by reconstructing contrast sources, from which the true amplitude contrast function is obtained via a single step minimization procedure. Results obtained with standard imaging methods like back propagation will be compared with images obtained via the contrast source formulation.
Micromachined microphones with integrated optical nanoscale displacement sensors
Authors: Hall Neal A. , Lee Wook , Jeelani Mohammad K. , Degertekin F. Levent , Okandan Murat
Published: October 2013

Micromachined microphones with diffraction-based optical displacement detection are presented. A compliant membrane is made part of a phase-sensitive diffraction grating, and the deflection resulting from external acoustic pressure alters the intensities of the diffracted orders which are monitored with integrated photodiodes. The scheme provides the displacement sensitivity of a Michelson interferometer and can be integrated without beam splitters or critical alignment problems into volumes on the order of 1 mm3. Preliminary characterization with ultrasonic sensors shows a displacement resolution of 1×10−4 Å/Hz1/2 near 100 kHz with 60 μW of laser power incident on the photodetector. Current research is aimed at achieving similar displacement resolution in the audio frequency range while demonstrating the potential for high-fidelity miniature microphone arrays for hearing and measurement applications. The approach is implemented and characterized using microphone membranes with integrated diffraction grating bottom electrodes fabricated on silicon using Sandia National Laboratories’ dedicated processing platform. Preliminary results on nonoptimized implementations show a flat frequency response to 15 kHz with internal noise levels below 40 dBA. [The authors would like to thank NIH and DARPA for supporting this research.]
Sources of excess noise in silicon piezoresistive microphones
Authors: Dieme Robert , Sheplak Mark , Nishida Toshikazu
Published: October 2013

The reduction of acoustic microphone size using microelectromechanical systems (MEMS) technology enables increased spatial and temporal resolution. Whether the small size can be effectively utilized depends on the signal-to-noise ratio and minimum detectable signal (MDS) that are a function of the structural geometry, material properties, and transduction method. The optimal MDS depends on both electronic and thermomechanical noise sources. Fundamental noise sources may be divided into frequency independent thermal noise and frequency dependent excess noise dominating at low frequencies. There have been some questions regarding the dominance of electrical or mechanical sources of the excess noise in piezoresistive microphones [A. Zuckerwar et al., J. Acoust. Soc. Am. 113, p. 3179–3187 (2003)]. Noise power spectra have been measured for various piezoresistive microphones. We present results on the bias dependence of the excess noise that indicate that the primary source of excess noise is electrical. The relative contributions of mechanical and electrical noise sources will be discussed.
Propulsion airframe aeroacoustics practices at Honeywell
Authors: Weir Donald S.
Published: October 2013

Honeywell has been developing and applying acoustic models of propulsion airframe aeroacoustic phenomena for over 20 years. The initial application of a wing-shielding model was developed for the NASA General Aviation Synthesis Program in 1982. Since that time, more sophisticated models of wing shielding and reflection have been developed with internal and NASA funding. Recent work has involved models of wing shielding for aft mounted engines and wing reflection for wing mounted engines. These methods are described in the presentation. Comparisons with the Raynoise Code by LMS and measured aircraft fly over noise data are made to show the effectiveness of the model. The attenuation of the inlet noise by the wing of an aft mounted engine and the amplification of the noise by wing mounted engines are evaluated.
Contributions of a thin attenuating layer in forest sound propagation
Authors: Swearingen Michelle , White Michael
Published: October 2013

The GFPE has been modified to incorporate a forest by replacing the local wavenumber with the bulk wavenumber of Twersky’s multiple scattering theory. For modeling the effect of the forest canopy, this corresponds to an attenuating layer at some height above the ground surface. Because of propagation paths above and beneath the canopy, the attenuation per unit distance is generally less than that of the canopy. In this presentation, the attenuation contribution of this layer will be examined by comparing propagation predictions with and without the attenuation layer, with refracting and non-refracting sound speed profiles, and with rigid and realistic ground surfaces. It is interesting that some propagating modes in the forest are suppressed by the attenuation, removing a source of interference and leading to an apparent decrease in attenuation. An analysis of the sensitivity of the GFPE to attenuation layers of different strengths will be performed for receivers near the ground, taking both frequency and distance into account.
Nonlinearity in outdoor propagation of periodic signals: Measurement results
Authors: Downing J. Micah , James Michael M. , Hobbs Christopher M. , Gee Kent L. , Sparrow Victor W. , McInerny Sally A.
Published: October 2013

As a continuation of a joint program among Wyle Laboratories, Penn State, and The University of Alabama to develop better noise models for military aircraft, field measurements of high-amplitude periodic and broadband waveforms were conducted at Blossom Point Range, MD. The source of the acoustic signals was the Army Research Laboratory’s Mobile Acoustic Source (MOAS) pneumatic speaker, which was designed to produce high-amplitude, low-frequency sounds. The results of the measurements demonstrate nonlinear effects in the higher harmonics when compared to linear models and provide a relative comparison of nonlinear effects with other propagation effects such as atmospheric and ground. The results also provide a simple data set for evaluation of proposed propagations models without introducing some of the complexities produced by real jet noise sources. One such comparison is provided in a companion paper (Kent L. Gee et al. [J. Acoust. Soc. Am 116, 2517 (2004)]). [Work is supported by the Strategic Environmental Research and Develop Program.]
Nonlinearity in outdoor propagation of periodic signals: Prediction model development
Authors: Gee Kent L. , Sparrow Victor W. , James Michael M. , Downing J. Micah
Published: October 2013

Propagation measurements made of high-amplitude periodic signals generated by the Army Research Laboratory’s Mobile Acoustic Source (MOAS) demonstrate greater energy at high harmonics relative to linear predictions, suggesting the possible influence of nonlinear effects (see Downing et al. [J. Acoust. Soc. Am. 116, 2517 (2004)]). An arbitrary-waveform version of an Anderson-type algorithm has been developed in order to compare numerical predictions with the measured MOAS spectra. In general, results demonstrate good agreement between predicted and measured spectra out to 375 m. However, comparisons at greater distances (approximately 1 km) and also for measurements made later in the afternoon exhibit less agreement. For these cases, the Anderson calculations generally overpredict the amount of high-frequency energy present in the measurements. Probable causes for these discrepancies include the effects of propagation at grazing incidence over a finite-impedance ground as well as increased atmospheric turbulence. [Work supported by the Strategic Environmental Research and Development Program.]
Comparison of computer codes for propagation of high-frequency energy from blast waves
Authors: Loubeau Alexandra , Sparrow Victor W.
Published: October 2013

Current environmental regulation requires that the Department of Defense assess the potential impact of noise from military training on endangered wildlife. One concern is the effect of noise from Army weapons on the hearing of bats. High frequencies are generated from nonlinear propagation of finite-amplitude shock waves created by explosions. These frequencies may be harmful to bats because their auditory systems are sensitive to high-frequency information that they use for flight navigation, communication, and hunting. Determining the spatial extent of high-frequency propagation requires an understanding of the short rise times associated with blast waves. A comparison of computer codes is performed for the most sensitive frequency range of bat hearing, 10–100 kHz. Earlier published results by the authors [A. Loubeau and V. W. Sparrow, Proc. NOISE-CON 2004, 193–201 (2004)] are compared to numerical solutions of the generalized Burgers equation with molecular relaxation included. The approaches considered are a time-domain method by Cleveland and a hybrid time–frequency-domain algorithm by Anderson. The results are also compared to recent experimental explosion data obtained by the US Army. [Work supported by US Army Engineer Research and Development Center CERL.]
Propagation of spark generated N waves through turbulent media
Authors: Blanc-Benon Philippe , Ollivier Sébastien
Published: October 2013

It is generally accepted that turbulence plays a role in the propagation and the distortion of sonic booms generated by supersonic flights. This paper describes laboratory experiments in which acoustic shocks from electric sparks have been used to model the propagation of sonic booms [Ollivier et al., 10th AIAA/CEAS Conference, AIAA 2004-2921]. In order to study separately the influence of random fluctuations of temperature and velocity, the N-waves are propagated through a turbulent plane jet or over a heated grid. The recording of 1000 snapshots allows statistical analysis of the variation of the parameters used to describe N-waves, including the maximum and the minimum peak pressures, the rise time, the arrival times and the duration of the wave. In particular, the data show that the increase of the average rise time and the decrease of the average peak pressure with the increase of the rms value of the fluctuations or the increase of the propagation distance could be linked to the probability of occurence of random caustics as observed in numerical simulations [Blanc-Benon et al., J. Acoust. Soc. Am. 111, 487–498 (2002)]. [This work is partly supported by the European Community SOBER project, Contract No. G4RD-CT-2000-00398 and by the French Ministère de la Recherche et des Nouvelles Technologies.]
Exploitability of fluctuations to enhance signal processor performance
Authors: Gilbert Kenneth E. , Wagstaff Ronald A.
Published: October 2013

Acoustic literature abounds with experimental and theoretical studies of fluctuations. Fluctuations are often the cause of a signal processors failure to satisfy its objectives, e.g., not achieving enough signal-to-noise ratio (SNR) gain to detect a signal of interest. Fortunately, the spectral time-histories of fluctuating parameters, such as amplitude, are encoded with signal present or signal absent information. Overcoming and exploiting the fluctuations to achieve various forms of gain requires understanding the changes in the fluctuations that are caused by the signal being present and then choosing the appropriate fluctuation-based signal processing algorithm to exploit those differences. First, detrimental influences of fluctuations on the general performance of signal processors will be discussed. Next, differences in the fluctuations for signal present and for signal absent will be addressed, with their corresponding implications for degrading signal processor performance. It will be illustrated that when knowledge of the differences in the fluctuations is applied to signal processing algorithms, higher levels of signal processor performance can be achieved. Improvements include increases in SNR, spatial and spectral resolution, temporal coherence, and unalerted auto-detection of signals of interest. [Work was sponsored by the U.S. Army under Contract No. DASG60-00-C-0061.]
An intonational analysis of disfluency patterns in chronically stuttered speech
Authors: Arbisi-Kelm Timothy R.
Published: October 2013

While previous stuttering research has successfully revealed areas vulnerable to disfluency at the word level in stuttering, identifying the specific factors responsible for this instability has proved difficult; moreover, inconsistent results are complicated by a failure to control for the effects of phrasal prosody, which govern such word-level factors as lexical stress. The present experiment tested the hypothesis that disfluencies in stuttering are directly proportional to the prominence-level of a given production. Three stuttering subjects participated in an oral sentence-reading task testing a variety of sentence types while manipulating intonational factors such as pitch accent type and location. It was anticipated that pitch-accented syllables, representing a higher degree of stress in an intonation phrase than stressed but non-pitch-accented syllables, would be most prone to triggering disfluency, since they bear a greater level of prominence in the utterance. The results of the study confirmed the major hypothesis: in all of the comparisons between pitch-accented and non-pitch-accented positions of stress, the former attracted the highest rate of disfluent speech productions. This supports the principal hypothesis that intonationally prominent domains, not simply lexically stressed syllables, are a better indicator of unstable positions in stuttered speech.
Two-dimensional wave field decomposition using circular microphone arrays and its application to acoustic source localization
Authors: Teutsch Heinz , Kellermann Walter
Published: October 2013

Two-dimensional wave fields can be used as reasonable models for propagating acoustic sound fields in closed rooms where ceiling and floor reflections are sufficiently attenuated. A natural way of analyzing a 2D wave field is to decompose it into an orthogonal set of eigensolutions to the acoustic wave equation in cylindrical coordinates, i.e., the cylindrical harmonics. These harmonics can be shown to be the coefficients of a Fourier series expansion applied along a circular aperture that is located within the 2D wave field under observation. Circular microphone arrays and, in particular, microphones mounted in a rigid cylindrical baffle that perform the cylindrical harmonics decomposition will be presented and its advantages and limitations will be discussed. As a specific example for utilizing the wave field decomposition approach, its application to acoustic source localization will be considered. By exploiting structural similarities between the response of linear microphone arrays and the decomposed response of circular microphone arrays, most well-known subspace tracking algorithms can be applied to this problem with only minor modifications. It will be shown that acoustic source localization based on wave field decomposition has the potential to track multiple simultaneously active sources in the array’s full 360° field of view.
Objective measures of steady-state auditory evoked potentials in cetaceans
Authors: Finneran James J. , Houser Dorian S.
Published: October 2013

Although behavioral methods provide the most direct means of assessing hearing capability, the time, access, and cost required to train individual marine mammal subjects has limited large-scale application of this technique. As an alternative to behavioral testing, auditory evoked potentials (AEPs) have been measured in a number of marine mammal species. AEP measurements using steady-state amplitude modulated tones allow rapid estimates of hearing threshold without extensive subject training. These stimuli result in sinusoidal AEPs, allowing frequency domain measures of AEP amplitude. Unfortunately, AEPs from near-threshold stimuli possess very low signal-to-noise ratios, making discrimination of AEPs from noise difficult. The most common procedures used for AEP threshold estimates in marine mammals have featured a subjective component, requiring an experienced observer to assess the presence or absence of the AEP. In this talk, the use of objective techniques to determine the presence of an AEP will be discussed. The focus of the talk will be on parametric and nonparametric methods within the frequency domain and the importance of AEP phase information. Steady-state AEPs measured in bottlenose dolphins will be used to evaluate the different techniques and compare to behavioral response measures. [Work supported by ONR and SSC San Diego ILIR.]
Hearing thresholds of a stranded infant Rissos dolphin
Authors: Nachtigall Paul E. , Yuen Michelle M. , Mooney T. Aran , Taylor Kristen A.
Published: October 2013

The underwater hearing of an infant male Rissos dolphin that stranded off the coast of southern Portugal was measured using evoked auditory potentials (AEPs). Hearing thresholds were measured from envelope following responses to amplitude modulated pure tones ranging from 4 to 150 kHz. Acoustic signals were presented within the calibrated rehabilitation pool. Evoked responses were passively gathered from human EEG electrode sensors imbedded within rubber suction cups that were gently attached to the animal with slight suction and conductor gel. One sensor was placed behind the blowhole and the other reference sensor on the back. Tones were presented 1 m directly in front of the animal under water while the animal was held in a neutrally buoyant position. Unlike the previously published audiogram for an older Rissos dolphin, the audiogram, obtained by presenting 18 different frequencies, showed that this very young animal heard tones up to 150 kHz in a manner similar to other odontocetes. These data, collected within 4 days, are the first measure of the hearing of a neonate marine mammal, verify that very young dolphins likely hear better than older animals, and show the value of using AEPs to obtain hearing thresholds of stranded animals undergoing rehabilitation.
In vivo imaging correlated with otoacoustic emissions as a metric for ear disease in seals
Authors: Ketten D. R. , Dolphin W. F. , William R. , Arruda J. , O’Malley J.
Published: October 2013

Otoacoustic emissions (OAEs) coupled with auditory brainstem responses (ABR) can help differentiate central, sensorineural, and conductive hearing losses. Pinnipeds with moderate bore canals are good OAE candidates, but OAE utility for assessing marine mammal inner ear health is not known. We examined three juvenile harbour seals (Phoca vitulina) with ear disease with computerized tomography (CT), OAE, and ABR. Combining CT, OAE, and ABR allowed simultaneous ear pathology documentation, quantification, and intracanal probe microphone position determination. Hearing was tested bilaterally from 500 Hz to 15 kHz. CT/OAE/ABR results were assessed independently. In two animals, CT showed middle ears occluded with fluid but normal auditory nerve anatomy, suggesting short-term circumscribed infection with no retrograde neuronal loss. OAE found moderately elevated response levels consistent with conductive hearing loss. ABR confirmed normal brainstem functioning. In the third animal, no OAEs or ABRs were obtainable up to 70 dB re 1 μPa, suggesting retrograde loss through brainstem level. CT for this animal showed inner, middle, and external ear occlusions consistent with aggressive, long-term disease. These data show volume and site of auditory pathologies are strongly correlated with OAE results in pinnipeds. [Work supported by Seaver Institute and ONR N00014-93-1-0940; N00014-94-1-1081.]
Ocean bioacoustics, human generated noise and ocean policy
Authors: Stocker Michael
Published: October 2013

The recent release of the U.S. Commission on Ocean Policy (USCOP) report, just a year on the heels of the Pew Oceans Commission report, has alerted policymakers and the public about the precarious biological health of our seas. While the reports discuss ecosystem based management, ocean bioacoustics is given short treatment in both reports. The ocean is not a visual-dominant environment, rather it is an acoustic environment. Most animals in the sea depend on sound, but we know next to nothing about how living organisms use it. We do know from recent studies that ocean habitats are being seriously compromised by human generated noise in evidence through stranded whales and, more recently, high fish mortality and low productivity in fishing areas due to seismic exploration and civil engineering. Due to the ubiquity of sounds and noises in all of our ocean enterprises, legislating anthropogenic sound promises to be a Byzantine endeavor. This paper examines some of the known challenges to crafting ocean noise policy.
High frequency components in cetacean echlocation signals
Authors: Muir Thomas G. , Toland Ronald W. , Baker Steven R. , Blackwood Diane J. , Thompson Lew A. , Wilson Preston S.
Published: October 2013

The rich literature of high-resolution biosonar capability is sometimes baffling as to attainable sonar resolution. This has led us to measurements in San Diego Bay, on captive research dolphins, utilizing an extremely wide band piezo-composite hydrophone, with a frequency response extending to 2 MHz. The results indicate that cetacean echolocation signals contain frequency components, above ambient noise, that can extend to the neighborhood of 500 kHz. The study was conducted on two bottlenosed dolphins and one beluga whale. Attempts were made to determine if these animals were actually using these high frequency components in echolcation, but they were not completely successful. However, measurements with rho-c matched, acoustic, low pass filter panels, placed between the blindfolded subjects (on a bite bar) and their test targets, showed that as the detection tasks became more difficult, the animals increased the intensity of the high frequency content of their transmissions (to ∼500 kHz) and their pulse repetition frequencies also increased. [Work supported by the U.S. Navy ONR.]
Vertical line array beamforming of signal and noise in shallow-water regions
Authors: Duda Tim , Lynch James , Abbot Phil , Wei Ruey-Chang
Published: October 2013

The familiar mode-stripping and coupling processes are prevalent in shallow water, shaping the vertical directional content of noise from distributed sources and of signals from discrete sources. Directional patterns can help in the determination of the physical processes, including internal waves, controlling acoustic behavior in a given region. VLA beamformer output from the New England PRIMER and the South China Sea ASIAEX studies are shown. Beamformed output from moored source signals and of noise vary rapidly for ASIAEX, less so for PRIMER. Fluctuations of signal and noise directional content have limited coherence. Correlated fluctuations of these will not alter the signal/noise ratio for a given beam, whereas uncorrelated fluctuations will. Such correlation depends upon the distance between the mode-coupling structure and the receiver. Predictions of pattern variability are complex because many environmental degrees of freedom are involved. For example, mode coupling of distant sources will spread the pattern from near horizontal (low mode), but not always for nearby sources; mode coupling of noise will energize low angle beams, although most effectively near noise sources. Implications of waveguide characterization based on beam energy variability will be discussed and compared with direct environmental waveguide measurements and with other signal properties. [Work supported by ONR.]
Installed jet noise prediction with Jet3D
Authors: Hunter Craig
Published: October 2013

Much of the aircraft noise reduction research in recent decades has been concentrated at the component level in understanding the physics of noise generation, formulating noise prediction methods, and developing noise reduction strategies. A new strategy in NASA’s noise reduction program is a focus on the noise effects specifically attributable to installation. This focus will also extend to developing noise reduction strategies that take advantage of installation effects. An essential requirement for an installed jet noise prediction method is that it must be able to predict noise from complex three-dimensional flows. Having this physics based capability is also desirable in order to develop a flexible noise prediction method applicable to the investigation of advanced concepts and revolutionary configurations. A jet noise prediction tool satisfying these objectives is currently under development at NASA Langley Research Center. The Jet3D methodology is based on Lighthills Acoustic Analogy and uses Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) simulations from the PAB3D flow solver, with temperature-corrected two-equation turbulence closure and anisotropic Reynolds stress modeling. This talk describes development of the Jet3D noise prediction method and its application to installed jet configurations.