bluuebunny/crossref_metadata_2025 huggingface dataset:
A chaos-based wide-angle parabolic equation model for sound propagation in random ocean.
Authors: Ma Li , Xing Hao
Published: October 2013

Recently, the chaos-based methods have attracted much attention in ocean acoustics committee. In this paper, a set of partial differential equations (PDEs), which are based on the wide-angle parabolic equation and Wiener-chaos decomposition, was established to investigate the propagation of sound propagation in the ocean environment with an arbitrary sound speed profile. Simultaneously, a numerical treatment of the PDEs, which employed an implicit difference scheme and a spectral method, was developed. By using this method, three cases with different kinds of randomness under a distinct ocean environment are studied numerically.
Geographic variation in northwest Atlantic fin whale (Balaenoptera physalus) song: Implications for stock structure assessment.
Authors: Delarue Julien , Todd Sean , Van Parijs Sofie , Di Iorio Lucia
Published: October 2013

Passive acoustic data are increasingly being used as a tool for helping to define marine mammal populations and stocks. Fin whale (Balaenoptera physalus) songs present a unique opportunity to determine interpopulation differences. Their highly stereotyped interpulse interval has been shown to vary between geographic areas and to remain stable over time in some areas. In this study, the structure of songs recorded at two geographically close feeding aggregations in the Gulf of St. Lawrence (GSL) and Gulf of Maine (GoM) was compared. Recordings were made from September 2005 to June 2006 in the GSL and intermittently between January 2006 and September 2007 at two locations in the GoM. 6257 pulse intervals corresponding to 19 GSL and 29 GoM songs were measured to characterize songs from the three locations. Classification trees showed that GSL songs differ significantly from those in the GoM. The results are consistent with those derived from the other stock structure assessment methodologies, such as chemical signature and photoidentification analysis, suggesting that fin whales in these areas may form separate management stocks. Song structure analysis could therefore provide a useful and cost-efficient tool for defining conservation units over the temporal and geographical scales relevant to management objectives.
Why has it been so difficult to add acoustics to the criteria of the Leadership in Energy and Environmental Design green building rating system?
Authors: Muehleisen Ralph
Published: October 2013

Leadership in Energy and Environmental Design (LEED) is the most popular green building rating system in use in the United States. There are LEED rating systems for a variety of different building types. The LEED system rates the sustainability and performance in several categories including the indoor environmental quality (IEQ). While LEED incorporates many important IEQ factors including air quality and daylighting in all the rating systems, acoustics has been included only in LEED for schools and the soon to be released LEED for healthcare. The development and subsequent modification of the acoustics portion of LEED for schools highlights some of the problems involved with modifying LEED to include acoustics and some of the issues involved in implementing a LEED rating system that includes acoustics. This paper will discuss why including acoustics within LEED rating systems has been and will continue to be problematic.
Classroom acoustics in green schools.
Authors: Harght Pamela , Coffeen Robert C.
Published: October 2013

Green schools are becoming increasingly common as school districts continue to experience a rapid growth in population. These schools promote academic success and higher retention rates as well as healthier environments with cleaner air and more daylight as compared to their nongreen counterparts. However, green buildings have become synonymous with poor room acoustics because many of these green goals often result in compromising acoustics and noise control with green building implementing natural ventilation, radiant cooling, and green materials, to name a few. This paper will examine the current conditions of room acoustics in classrooms based on field tests for reverberation, background noise levels, speech intelligibility, and noise isolation from adjacent spaces in addition to the overall design of the classroom. In addition to testing, results from an electronic questionnaire issued to those who teach in these green environments on a daily basis will be discussed. This questionnaire addreses common problems in classroom acoustics in additon to seeking feedback on this new teaching environments. Finally, the role of acoustics in Leadership in Energy and Environmental Design for schools, the process for acoustical consultants for certifying a school, will be discussed.
Overall hearing abilities of manatees and ecological acoustical challanges.
Authors: Gerstein Edmund , Gerstein Laura , Blue Joseph , Forsythe Steven
Published: October 2013

A comprehensive series of underwater psychoacoustic tests was conducted to measure the hearing abilities of West Indian manatees. Pure tones, complex and real world sounds were presented to manatees under controlled acoustical conditions. The results from 30 000 threshold trials measured their audiogram, temporal integration, critical ratios, MMAs and directional hearing. Complementing these investigations, underwater acoustical measurements of manatee habitats and vessel noise propagation were conducted to evaluate acoustical factors that render Florida manatees vulnerable to repeated collisions with vessels. Both low-frequency cutoffs in shallow water and near surface boundary effects limit the propagation of the dominant low-frequency spectra from slow moving boats. Slow speed zones implemented to protect manatees do not address this underlying acoustical challenge. Ironically, the strategy can be counter-productive in turbid waters and can exacerbate the problem, making vessels more difficult or impossible for manatees to detect while increasing transect times and the opportunities for collisions. While manatees are not adapted for hearing the dominant low-frequency spectra from a slow watercraft, they are well equipped to detect and locate higher-frequency modulated sounds. This provides a narrow sensory window through which to alert manatees of approaching vessels. A specially designed alarm to alert manatees is being tested. [Work funded by the U.S. Department of Defence Legacy Resource Management Program, Navy, Florida Inland Navigation District, and Florida Fish and Wildlife Conservation Commission.]
Problems and issues in low-frequency aquatic communication.
Authors: Todd Neil
Published: October 2013

A recent study concerning the production, transmission and reception of alligator vocalizations has indicated that there are significant gaps in our knowledge of the physiology and physics of low-frequency sound communication in air and water [Todd, J. Acoust. Soc. Am. 122, 2906–2915 (2007)]. In this paper these issues are discussed, and some possible solutions are considered for aquatic communication by both amphibians and crocodilians in the light of some other recent data on frog vocal behavior in water.
Analitical modeling of piezoelectric ceramic transducers based on coupled vibration analysis.
Authors: Aronov S. Boris
Published: October 2013

The energy method for analyzing piezoelectric ceramic transducers [B. S. Aronov, J. Acoust. Soc. Am. 117, 210–220 (2005)] is applied to the treatment of transducers with mechanical systems that can be considered as two-dimensional. Analysis is made following the general outline of the theory of coupled vibration in two degree-of-freedom systems and its extension to calculating resonance frequencies of elastic bodies, as suggested by Gibbe and Blechshmidt [Ann. Phys. 18, 417–485 (1933)]. The approach to the problem is illustrated with examples of piezoelectric rectangular plates, stripes, and thin-walled cylinders at various orientations relative to crystallographic coordinate system. For all of the examples, the resonance frequencies and effective coupling coefficients are presented as functions of the dimensional aspect ratios. Equivalent electromechanical circuits are introduced, which permit calculation of the transducers performance under different acoustical loading conditions. Practical recommendations for improving the electromechanical properties of the transducers by use of appropriate aspect ratios are discussed.
Acoustic Kramers–Kronig relations in the ultrasonic frequency band.
Authors: Mobley Joel
Published: October 2013

Physical manifestations of the principle of causality, Kramers–Kronig (KK) relations, have proven to be adaptable to a wide array of tasks which include measuring fundamental material parameters, establishing the consistency of laboratory data, and building causally consistent physical models. This talk is concerned with the use of finite bandwidth KK relations between and among the components and derivatives of the complex wavenumber in the low megahertz ultrasound band. Special focus is given to their applicability to data from suspensions of resonant scatterers and media exhibiting attenuation with a power-law dependence on frequency. One recent development is the validation of a KK relation for the direct prediction of the group velocity from the attenuation coefficient, which has demonstrated great utility for suspensions with resonant type dispersion. The roles of KK analysis in other recent issues are also discussed, including the apparent negative dispersion in cancellous bone.
Acoustics of epenthetic vowels in Korean loanwords.
Authors: Kim Hyun-ju
Published: October 2013

Several previous studies reported that epenthetic vowels in other languages were phonetically not the same as lexical vowels: for example, English speakers produce inserted schwas as transitional, which are shorter in duration and lower in F1 than lexical schwas [L. Davidson, J. Phonetics 34, 104–137 (2006)]. This study examines whether Korean epenthetic vowels in the production of non-native phonotactics are real vowels or are transitional elements that appear due to failure to coordinate the two consonant gestures. In the experiment, Korean speakers were asked to produce illegal consonant clusters contained in pseudowords written in English and the same consonants but with an intervening lexical vowel in native words written in Korean. Results showed that epenthetic vowels were not different phonetically (in duration, F1, and F2) from lexical vowels in native words, which is different from what the previous study of epenthetic vowels in English found. Given the fact that complex codas are never possible in Korean phonology, whereas certain types of complex codas are permissible in English, this finding suggests that distinct native phonology may generate language-specific phonetics and force Korean speakers to produce epenthetic vowels as real.
The influence of different tones of Mandarin Chinese on the temporal characteristics of nasalization.
Authors: Zhang Wenlang , Kuehn David
Published: October 2013

This study was designed to investigate whether the four different tones in Mandarin Chinese would influence the temporal characteristics of nasalization. Seven female and seven male subjects were enrolled in this study. Four nasal syllables/ma mi na ni/ in all four tones were embedded in two syllables with initial pressure consonants to form the stimuli. Then the nasal onset intervals, nasal consonant durations, nasal offset intervals, and the whole nasalization durations were segmented in the speech samples. The corresponding durations and ratios for the same syllable were compared pairwisely among the four tones by paired means t-test. Multiple statistically significant differences did exist among the four tones in both the durations and the ratios. The most important differences were as follows: Tone 3 has shorter nasal consonant durations than Tones 1 and 4, and shortest nasal offset intervals and whole nasalization durations among the four tones; it also has a larger nasal onset and nasal consonant duration ratios but least nasal offset ratios among all four tones. Different tones of Mandarin Chinese can influence the temporal characteristics of nasalization, and they may serve as extra cues that can help improve perception.
Palatalization in Romanian: Acoustics, perception, and the role of place of articulation.
Authors: Spinu Laura , Vogel Irene , Bunnell Timothy
Published: October 2013

Departing from the crosslinguistic generalization whereby the contrast between the plain and palatalized consonants is favored at the coronal, as compared to the labial, place of articulation, recent perceptual studies show native speakers of Romanian displaying higher sensitivity to this contrast in labials. To investigate this unexpected behavior, a production study was conducted with 31 subjects. Five plain and palatalized fricatives (/f, v, z, S, h/) were analyzed in terms of average duration and spectral properties (coefficients of the Bark Cepstrum). A linear discriminant analysis was run using duration and the Cepstral coefficients to predict segment type (plain/palatalized). 78.2% of 3674 tokens were classified correctly; however, the contribution of the duration and spectral properties of each segment showed interesting asymmetries. To summarize, /h/ was most successfully distinguished, /S/ was least successfully distinguished, and /f/ and /v/ were distinguished better than /z/. Our acoustic analysis supports the perceptual findings regarding palatalization in Romanian. Perceptually, the distinction between the plain and palatalized consonants was strongest with labials. This is paralleled by the greater acoustic difference between the plain and palatalized /v/, /f/ versus /z/, /S/. Thus, Romanian exhibits palatalization patterns that appear at odds with the claim that the least marked place is coronal.
On the relation between locus equations and subglottal resonances.
Authors: Lulich Steven M.
Published: October 2013

In consonant-vowel transitions, it is well known that the frequency of the second formant at the onset of voicing (F2onset) is linearly correlated with the frequency of the second formant in the middle of the vowel (F2vowel). This correlation, which holds across the vowel contexts for a given consonant place of articulation (POA), is characterized by a regression line (locus equation) with a slope and y-intercept that depend on the consonant POA. Furthermore, for a given POA, slopes and y-intercepts of collections of locus equations are inversely related. The cause of this inverse relation has not yet been explained. In this presentation, we will show that the inverse relation implies that the F2vowel vs. F2onset coordinate system is most naturally described as a mathematical translation away from the origin, and that the size of the translation is a function of the POA and of the second and third subglottal resonances.
Impact of the harbor environment on the performance of a swimmer.
Authors: Stein Peter
Published: October 2013

Over the past several years, Scientific Solutions has been developing the Swimmer Detection Sonar Network (SDSN). It is a novel system that networks individual air-backed parabolic transducers which both transmit and receive in narrow beams. In this paper, system performance issues as related to operating in the port/harbor environment will be discussed. This includes effects due to clutter, noise, multipath propagation, refraction, and tides. Data collected from deployments in two different harbor environments will be used to explore the issues. Both harbors have similar water depths and bottom properties, but one is in a tropical climate, where the sound speed is essentially uniform year-round, and the other is a temperate (midlatitude) climate where the sound speed varies significantly depending on the time of year. The tests in the latter environment were conducted during the summer when the sound speed was strongly downward refracting. The methods by which the SDSN design overcomes the performance issues discussed will also be explored [Work supported by ONR.]
Development of special acoustic materials for the Experimental Media and Performing Arts Center at Rensselaer Polytechnic Institute: Part 1.
Authors: Giegold Carl
Published: October 2013

A series of project-specific interior acoustic elements were developed for the eMPAC project. Most prominent is the fabric ceiling in the concert hall, which was developed in tandem with the canopy of a similar material recently installed in London’s Royal Festival Hall. Other concert hall finishes were also the subject of much mathematical and physical study during the design process. In the two studios, the finishes respond to the client’s acoustic metaphor of a forest clearing, where the acoustic response is relatively alive but highly diffuse at mild and high frequencies. A system of GFRG panels, each of which has several different scales of shaping, was devised and empirically tested in several iterations to achieve the desired result.
Frequency overrepresentation found in the inferior colliculus of Japanese house bats, Pipistrellus abramus.
Authors: Goto Kazuhiro , Hiryu Shizuko
Published: October 2013

In this study, we examined the best frequencies of the inferior collicular neurons of Japanese house bats, Pipistrellus abramus. The bats emit long (>10 ms) and shallow FM pulses (quasi-CF) during their search phase, narrowing the frequency range at around 40 kHz. If the narrowed frequency range is important for detecting a small frequency change or frequency modulation, the bats may need a finer frequency resolution than other frequency ranges. So, the neurons responsive to the frequency range at around 40 kHz must be over-represented somewhere in the auditory system, typically in the inferior colliculus. In order to examine this hypothesis, the tonotopic organization of the inferior colliculus of P. abramus was measured electrophysiologically by metal microelectrodes. Results show that the frequency range corresponding to their quasi-CF frequency, at around 40 kHz, appears to be over-represented in the inferior colliculus. [Research supported by an ONR grant.]
Biosonar features extracted from natural frequencies for natural landmark classification.
Authors: Dai Jinsong , Wang Maosen , Mueller Rolf
Published: October 2013

To navigate in a natural environment, it is practical for an artificial agent to use vegetation as landmark. This is the way bats have done this for its long history. For an outdoor biosonar system based on digital signal processing, it is ideal to extract characteristic features directly from natural landmarks. Any physical structure can be modeled as a number of springs, masses, and dampers. Vegetation with trunks, stems, and foliage in open air always sways in a certain degree; it is possible to extract features from a series of characteristic natural frequencies with electrical biosonar system. In this work, a biosonar system is utilized to study features extracted from several plants for mobile agent navigation. Experimental results indicate that there is always enough air turbulence in the outdoor environment and these biosonar features are efficient in classifying plants. Besides using natural frequency features with the same wind condition, a laboring calibration should be made to improve this method robustness in different wind environments. [Work supported by NSFC.]
Creating a regionally focused online archive for natural sounds: The Western Soundscape Archive.
Authors: Rice Jeff
Published: October 2013

Variations in species distribution and abundance, general topography, as well as regional dialects among species ensure that no two places or environments will sound the same. Regionally focused environmental sound archives can play an important role in documenting these variations. This paper will describe the recent creation of the Western Soundscape Archive (Westernsoundscape.org), an ongoing project led by the J. Willard Marriott Library at the University of Utah that seeks to build a representative and free online resource of animal and environmental sounds of 11 contiguous western United States. The archives primary includes the region’s terrestrial vertebrates, as well as targeted ambient recordings. By gathering existing sound recordings, creating new recordings where appropriate, and employing innovative mapping technology, the archive hopes to document and preserve the soundscape of the West and to create a replicable model for other libraries in other regions. [Work supported by an IMLS National Leadership Grant.]
Developments at the National Institute of Standards and Technology in pressure calibration of laboratory standard microphones.
Authors: Nedzelnitsky Victor , Wagner Randall P. , Fick Steven E.
Published: October 2013

Improvements in apparatus and procedures for determining the pressure sensitivities of IEC Types LS1Pn and LS2aP laboratory standard microphones by the reciprocity method aim at reducing the effects of significant components of uncertainty. One such component involves the uncertainty with which the front cavity depths of the microphones are known. Therefore, various noncontact methods and procedures for measuring these depths using a depth-measuring microscope have been developed and investigated. Other significant uncertainty components involve the voltage measurements performed during the reciprocity method. Careful consideration of the dependence of measurement uncertainty on voltmeter operational mode, voltmeter range, signal voltage variation with frequency, and the voltages at which range switching occurs can significantly reduce the uncertainty components involving voltage measurements. Another component, involving the uncertainty with which the temperature of the gas in an acoustical coupler is known, can contribute significantly to the uncertainty with which the acoustic transfer impedance in the reciprocity method can be determined. Measurement of acoustical coupler temperature during calibration can significantly reduce this component. Examples of how improvements aimed at reducing these uncertainty components are being systematically incorporated in an evolving test bed are described.
Primary sinusoidal calibration of accelerometers.
Authors: Wu Lixue , Hanes Peter
Published: October 2013

Accurate vibration measurements require suitably calibrated transducers. A new system for primary sinusoidal calibration of the voltage sensitivity of accelerometers according to Method 1 (fringe-counting) of ISO 16063-11 has been implemented at the NRC Institute for National Measurement Standards. The system includes a new shaker that is capable of generating sufficient acceleration for calibration of accelerometers at frequencies as low as 2 Hz. The design, construction, and testing of the system will be described. Factors that influence the measurement uncertainty of the calibrations such as transverse motion, rocking motion, acceleration stability, distortion, and repeatability have been evaluated and will be discussed.
Sound field amplification competes with noise control.
Authors: Lubman David
Published: October 2013

Sound field amplifiers continue to be aggressively promoted for mainstream classrooms. Studies showing improved academic achievement with sound field systems mislead by not revealing that the subject classrooms were excessively noisy. Sound field is a band-aid solution for noisy classrooms. Surely, quiet classrooms and natural, unstrained voices improve academic achievement as well as or better than amplifiers. Soundfield is being promoted to school building officials as low cost substitutes for noise control. Marketers mislead school officials by suggesting that classrooms cannot be quieted affordably and that occupied classrooms are so noisy that amplification is indispensable. One might ask how students were classroom educated prior to the invention of electronic amplifiers! In a recent “Trojan horse” strategy, sound field systems are being purchased for classroom multimedia. Sound field reinforcement then becomes a “freebie.” The problem is that all amplified systems work best in quiet rooms. Moreover, though soundfield amplification works well in special education classrooms for hearing impaired students. It is seldom needed in quiet mainstream classrooms. Moreover hearing impaired students in mainstream classrooms are better served by FM systems. Classrooms that depend on amplification are unavailable when the system becomes inoperative due to malfunction, missing parts, or power failures. Quiet classrooms are robust.
Frequency spectra of bilaminar prolate spheroidal shells.
Authors: Hayek Sabih I. , Boisvert Jeffrey E.
Published: October 2013

The kinetic and strain energy densities were derived for the vibration of a bilaminar prolate spheroidal shell of constant thickness. The bilaminar shell is composed of two bonded concentric prolate spheroidal layers of different material properties and thicknesses. The elastic strain energy density has seven independent kinematic variables: three displacements, two thickness shears, and two thickness stretches. Continuity of displacements is enforced at the interfacial reference surface. The shell has constant thickness h=h1+h2, where h1 and h2 denote the thicknesses of the respective layers. The reference surface eccentricity is defined by 1/a, where a is its shape parameter. Using appropriate comparison functions in terms of Legendre polynomials that satisfy the boundary conditions for a closed spheroidal shell, the system is solved using the Galerkin method. Numerical results of the frequency spectra are presented for various ratios of h1/h2 and various material properties for the two layers. Initial results are presented for a=100 (a nearly spherical shape). [Work supported by the ONR/ASEE Summer Faculty Research Program.]
Determining source location from vibration “slowness” vectors.
Authors: Kim Byung-ghun , Chai Jangbom , Lyon Richard H.
Published: October 2013

The time for a wave to transit from one sensor to another is related to its “slowness” and is measured by the phase delay of the cross spectrum of the signals from the sensors. If the sensor separation is much less than a wavelength, this cross spectrum is related to the energy flow in the wave. An “L-shaped” array of three sensors allows one to determine the two vector components of slowness and the direction of the wave. If wave directions are computed at two or more such L-shaped arrays, then it may be possible to ‘‘triangulate’’ and fix a source location. It is possible of course that the directions may be such that there is no solution for a source location. Generally, the wave directions at the arrays are determined for a fixed set of frequencies. Then, at each frequency, a source solution is sought. At some frequencies, there may be no solution so the set of frequencies is diminished. Also, it is possible, even likely, that waves at different frequencies or wavelengths may have taken different paths from the source to the arrays. This paper reviews the results of applying the slowness vector computations to data taken on a model nuclear plant flow loop.
Modulation of middle and long-latency cortical potentials during pitch-shifted auditory feedback perturbation.
Authors: Behroozmand Roozbeh , Liu Hanjun , Karvelis Laura , Larson Charles R.
Published: October 2013

It has been shown that applying perturbation to the real-time voice auditory feedback evokes compensatory responses that minimize the vocal output error. Auditory feedback-based control of the voice fundamental frequency involves the integration of multiple neural substrates that take part in the process of vocal output error detection and correction. Previous studies have shown that the cortical brain potentials are modulated during active vocalization versus passive listening to the self-generated voice in the absence of auditory feedback perturbation. To learn more about these central mechanisms, the present study tested the effect of vocalization condition across different pitch-shifted auditory feedback magnitudes. Twenty English speaking young adults vocalized a vowel sound and received pitch-shifted feedback of +100, 200, or 500 cents while scalp potentials were recorded. Results show that the middle-latency P50 responses were significantly larger during the active vocalization task only at 200 cents frequency shifts. Long-latency N100 and P200 peaks were significantly larger during vocalization for 100 cents and 100 cents/200 cents, respectively. The overall conclusion is that the middle- and long-latency cortical responses are significantly greater during vocalization, but the difference between response peak magnitudes across vocalization and passive listening conditions diminishes with larger pitch frequency shifts in the voice auditory feedback.
Articulatory and acoustic measures of vowel frontness in a study of velar-vowel coarticulation.
Authors: Wodzinski Sylvie M. , Rizzitano Gena , Frisch Stefan A.
Published: October 2013

Previous work has found a strong correlation between the frontness of closure location for velar stops (measured manually from ultrasound images by a trained expert) and the frontness of the following vowel (measured by F2). In this study, semiautomatic measures of tongue frontness for vowels were made from ultrasound images of the vowel articulation. However, it was found that the acoustic measure, F2, correlated more closely with the frontness of the preceding consonant than any of the ultrasound based articulatory measures of the vowel. Explanations for why an acoustic measure of coarticulation would be better than an articulatory measure will be discussed. It may be that the ultrasound based measures do not adequately capture retraction of the tongue root, which would influence F2 and presumably affect coarticulation with the consonant. Surprisingly, it was also found that the frontness measures for the consonant were more highly correlated with F2 than the frontness measures for the vowel, suggesting that the tongue frontness measures may be indirectly affected by tongue height in some way. Overall, the manual measures of an expert appear to be superior to semiautomatically generated measures.
Semiautomatic measures of velar stop closure location using the EdgeTrak software.
Authors: McCormick Sabrina J. , Frisch Stefan A. , Wodzinski Sylvie M.
Published: October 2013

Previous work has found a strong correlation between the frontness of closure location for velar stops (measured manually from ultrasound images) and the frontness of the following vowel (measured by F2). In this study, semi automatic measures of tongue frontness during a velar closure were made. Tongue edge traces were made using the EDGETRAK software (Li et al., 2005, Clinical Linguistics and Phonetics, 545–554). Frontness was then quantified from these traces using three different measures: Bressman’s anteriority index (Bressman et al., 2005, Clinical Linguistics and Phonetics, 573–588), a modified version of the anteriority index created for this study, and a measure of the center of mass of the tongue created for this study. When compared to the original manual measures, the modified anteriority index correlated most highly with both the manual measurement of the consonant closure location and also with F2 of the following vowel. The modified anteriority index uses an angle based weight in the anteriority calculation (as opposed to the arbitrary weights of Bressman’s anteriority index). The center of mass was the worst performing measure, and it appeared to be overly sensitive to the extreme anterior and posterior portions of the tongue edge trace.
Characterization of the near scattered acoustic vector field.
Authors: Barton Robert , Smith Kevin
Published: October 2013

In this study, we investigate the properties of the scattered acoustic vector fields generated by simple geometric objects, including the infinite rigid plate, disk, and sphere. Analytical solutions are derived from acoustic target strength scattering models in the near-field region. Of particular interest is the understanding of the characteristics of energy flow of the scattered acoustic vector field in the near- to far-field transition region. We utilize the time and space separable instantaneous active and reactive acoustic intensities to investigate the relative phase properties of the scattered field. Numerical results are presented for the near region scattered acoustic vector field of simple objects in both two and three dimensions.
Rapid simulation of sonar time series.
Authors: LePage Kevin D.
Published: October 2013

Rapid simulation of element level time series for bistatic sonars requires quality approximations in order to yield accurate results in real time. Here rapid physics-based time series approximations based on closed form expressions for reverberation intensity developed by Harrison [J. Acoust. Soc. Am. 114, 2744 (2003)] are developed for boundary reverberation and target scattering in shallow water waveguides. The simulations include Doppler and waveguide angle and time dispersion effects, and since the simulations are at the element level, they can be processed like real data. Simulations are compared to reverberation predictions obtained with more accurate but slower codes showing good agreement.
Examination of loss mechanisms for a rough bottom Pekeris waveguide using a two-way coupled mode model.
Authors: Stotts Steven , Koch Robert , Knobles David
Published: October 2013

A benchmark scattered-field solution for a two-dimensional rough-bottom Pekeris ocean waveguide has been generated from a two-way coupled-mode model with normal modes evaluated in the complex horizontal wave-number plane. The received level time series coupled-mode solution for a range monostatic source/receiver geometry with a 250 Hz center frequency, 20 Hz band, Gaussian pulse was shown previously to be consistent with a single scatter Born approximation solution [Stotts et al., J. Acoust. Soc. Am. 122, 3075 (2007)]. A new result for a 1 kHz center frequency, 60 Hz band, pulse deviates significantly from the Born approximation solution. Alternative approaches, obtained with the Born approximation but including the additional propagation loss for Kirchhoff scattering [E. I. Thorsos, J. Acoust. Soc. Am. 83, 78–92 (1988)] with and without second order small slope approximation effects are examined. The solutions at 1 kHz with these alternative methods are compared to the coupled-mode solution. The forward scattered fields propagated over finite length roughness segments of varying lengths are analyzed to understand the role of mode-mode interactions in the forward propagation loss mechanisms and for comparison with the Kirchhoff scattering loss description.
Gymnasium room acoustics. Comparisons of different metrics, criteria, measurements, and calculation methods (including acoustical modeling software).
Authors: Bridger Joseph F. , Stulgin Steven S.
Published: October 2013

Gyms are nondiffuse large boxes and have unusual room acoustics challenges related to safety, durability, and volume. Classic room acoustics analysis methods, such as that of Fitzroy and Sabine, measurements, as well as acoustical modeling software results are compared. Speech intelligility results from the room acoustics software are compared against traditional reverberation time criteria. What has been learned about criteria and calculation methods is shared.
Lowering the effect of low-frequency noise generated from boiler exhaust stacks.
Authors: Richardson Kevin , Davis Byron
Published: October 2013

Low-frequency noise from exhaust boiler stacks at a semiconductor plant was measured and the low-frequency noise spectrum was predicted using an analytical impedance model. Nearby residents complained that noise was rattling household items, such as windows and light fixtures. The semiconductor plant speculated that noise from two boiler exhaust stacks was the source of the problem. Sound pressure level measurements conducted at the plant revealed strong tones in the infrasound and low-audible frequency range. The boiler exhaust stack noise source was theoretically characterized by deriving the mechanical impedance of the boiler exhaust stack and the radiation impedance of the top of the boiler exhaust stack as a simple unbaffled source. The analytical model predicted the resonant frequencies of the boiler exhaust stacks and these resonances closely matched the strong low-frequency tones measured. Using this model, possible changes in controlling parameters of common exhaust boiler stack design are described that could decrease the overall noise radiating from the exhaust stacks. As one example, the plant appreciably decreased the sound power contribution from the upper exhaust stack resonances by lowering the overall output of the exhaust boilers. This change lowered the overall noise levels without the use of silencers.
Finite-difference time domain simulations of outdoor sound propagation around manmade structures.
Authors: Collier Sandra L. , Alberts W. C. Kirkpatrick , Parker Leelinda , Noble John M.
Published: October 2013

We develop a finite-difference time domain (FDTD) model of the acoustic propagation around outdoor man-made structures that includes the effects of atmospheric turbulence and porous ground surfaces. The wind flow around the building is determined with a Navier–Stokes approach, whereas, the basic acoustic propagation model is based on the coupled first-order partial differential equations for linear acoustic propagation in a dynamic environment developed in by [Collier et al., Proceedings of the 2005 MSS BAMS]. Special numerical techniques are required to model the sound interaction at the man-made structure, in particular, for buildings with complicated geometries. For two-dimensional propagation, this numerical model can be run on a standard desktop computer. However, for three-dimensional propagation, high performance computers are needed. Here we present results from the numerical simulations and compare them to recently collected data [Alberts and Noble, J. Acoust. Soc. Am. 121, 3064 (2007)].
Predicted and experimental attenuation of obstructed projectile shock waves.
Authors: Perea James , Libbey Brad
Published: October 2013

Acoustic sniper localization algorithms are well established for open field detection; however, these algorithms are less accurate in urban environments due to reverberation and diffraction. Research is being performed to understand the effects of obstructions on shock wave propagation. Barrier attenuation calculations that use Fresnel number to characterize obscurity will be compared to measured attenuation of shock wave frequency components. An artificial building was set up and shock waves from bullets were recorded by microphones with varying degrees of obscurity. The experimental setup allowed for a range of Fresnel numbers between 5 and 11 resulting in attenuation up to 30 dB. Attenuation increased as obscurity and Fresnel number increased up to a threshold. Beyond this point the magnitude of attenuation decreases in both theory and experiment. These data support the relationship between attenuation and microphone obscurity and may provide a means to estimate the amplitude and N-wave slope of the shock wave prior to obstruction.
Numerical simulation of sonic boom propagation through atmospheric turbulence.
Authors: Piacsek Andrew , Locey Lance , Sparrow Victor
Published: October 2013

To better understand the mechanisms by which atmospheric turbulence alters sonic boom rise times and peak overpressures, numerical calculations of sonic boom propagation through atmospheric turbulence have been performed using the NPE time domain model. Turbulence is incorporated into the model as a perturbation of the ambient sound speed that has a random spatial distribution determined by a von Karman energy spectrum. Each simulation employs a new realization of the turbulent field. Output from the finite difference solution includes high resolution movies showing the evolution of a full two dimensional wave field as it propagates from the upper region of the turbulent boundary layer to the ground. The evolution of wave forms corresponding to specific locations along the wave front is also obtained. Results are presented that illustrate how the magnitude, complexity, and spatial and temporal variabilities of the sonic boom wave field depend on turbulence spectrum parameters that represent atmospheric conditions. [V. Sparrow supported by NASA through Wyle Laboratories and by the FAA/NASA/Transport Canada PARTNER Center of Excellence.]
Infrasound studies of hurricanes.
Authors: Hetzer Claus , Talmadge Carrick , Waxler Roger , Gilbert Kenneth
Published: October 2013

Hurricanes, whether in the Gulf of Mexico or the open ocean, are known to produce infrasound in the microbarom band (around 0.2 Hz). Infrasound technology is an excellent choice for monitoring hurricanes because portable, sensitive, and relatively low-cost infrasound arrays can be deployed quickly in areas out of danger from storm winds and waves while still monitoring storm-related signals continuously. The National Center for Physical Acoustics is developing a Gulf Coast hurricane monitoring system involving permanent and portable infrasound arrays. This discussion will focus the results of infrasound studies of the 2008 hurricane season, along with background information on the history and theory of hurricane microbaroms. The latest results of theoretical calculations about the microbarom source and possible effects of storm winds on bearings will also be presented.
Effects of speechreading on understanding mainstream American English by second-language listeners of English.
Authors: Kanekama Yori , Downs David
Published: October 2013

Cross-language speech perception research has shown that, at least across some languages, first-language speakers of English show more of a McGurk effect for English nonsense syllables than second-language speakers of English. This suggests less auditory-visual integration and auditory-visual incompatibility when listening to nonsense syllables of a different language. Researchers, however, have not studied the role of auditory-visual integration and auditory-visual incompatibility on cross-language perception of ongoing everyday speech. The purpose of this study was to measure the effects of speechreading on understanding mainstream American English (MAE) by second-language listeners of English. Specifically, participants were 30 first-language MAE speakers and 30 first-language Indian speakers recruited from the same graduate school engineering program. They participated in two experiments in which they listened to Central Institute for the Deaf Everyday Speech Sentences under auditory-only, visual-only, and auditory-visual conditions at different signal-to noise ratios. Visual enhancement and auditory enhancement scores were computed and compared between language groups. Results have (1) theoretical implications for understanding the role of auditory-visual integration and auditory-visual incompatibility on cross-language perception of connected speech, and (2) have practical implications for understanding whether speechreading helps or hinders listening to a second language in noisy environments.
The English l sound produced by Korean students.
Authors: Yang Byunggon
Published: October 2013

This study examined the lateral l sound produced by 16 Korean students in order to tap a possibility of using acoustical and perceptual criteria to distinguish lateral variants and eventually to assess student’s English pronunciation skills. The subjects read a short story in a quiet office at normal speed. Those words with the lateral sound in onset or coda positions and before a vowel of the following word were analyzed using PRAAT. The following results are shown. First, the majority of the subjects produced the clear l regardless of the contexts. Some students produced the sound as the Korean flap or the English glide /r/. A few missing cases were also seen. Second, the dark l was mostly produced by the subjects of English majors in coda position with a few cases before a vowel in a phrase. Visual displays from the computer analysis were helpful in determining lateral variants but sometimes personal listening to the given sound after temporal manipulation would be necessary in the cases of fast and weak productions of the target words. Further studies would be desirable to compare native productions of the lateral sound with those of non-native speakers.
The influence of signal-to-noise ratio and listener’s native language on vowel intelligibility.
Authors: Bent Tessa , Kewley-Port Diane
Published: October 2013

In a previous study, intelligibility rankings of American English (AE) talkers were different for native and non-native listeners [Bent, et al., J. Acoust. Soc. Am. 122, 3016 (2007)]. To equate overall performance, the native and non-native listeners were tested at two different signal-to-noise ratios (SNRs). Therefore, the differences in intelligibility rankings between the two listener groups may have been affected by the listener’s native language and differences in SNR. The current study explored this issue by testing across-talker differences in AE vowel intelligibility for AE listeners and Korean listeners learning AE as a second language. Listeners heard recordings of ten AE vowels in /bVd/ context produced by ten talkers under three SNRs: −8, −5, and −3 dB. The words were presented for identification in a 10-alternative forced choice task. Results showed that when AE and Korean listeners’ were tested under the same SNR, the across-talker intelligibility scores were highly correlated for the two listener groups. However, Korean listeners were less accurate at vowel identification compared to the AE listeners. Furthermore, Korean listeners’ intelligibility rankings of the talkers were more variable across SNRs whereas the AE listeners were more consistent. (Work supported by NIH DC02229 and T32-DC00012).
Development and analysis of chirplet signal decomposition for detection, estimation, and classification in sonar and nondestructive evaluation (NDE) applications.
Authors: Lu Yufeng , Oruklu Erdal , Saniie Jafar
Published: October 2013

In sonar and ultrasonic nondestructive evaluation applications, backscattered signal contains information pertaining to size, shape, and orientation of reflectors. The echoes from target reflectors are often overlapping and masked in the presence of high clutter. Therefore, it is a challenging problem for target localization and object recognition. In this paper, a chirplet model for an adaptive signal decomposition and parameter estimation algorithm is investigated. The proposed chirplet method is capable of representing a broad range of echo shapes, including narrow-band, broad-band, symmetric, skewed, and nondispersive/dispersive. Chirplet transform is used not only as a means for time-frequency representation but also to estimate the echo parameters, including amplitude, time-of-arrival, center frequency, bandwidth, phase, and chirp rate. These parameters embody the dispersion effect, frequency dependent absorption, and scattering in complex and inhomogeneous environments. Experimental data, including ultrasonic backscattered signal and bat chirp signal, have been analyzed to evaluate the algorithm. It has been shown that the adaptive algorithm performs robustly, yields accurate echo estimations, and results in considerable SNR enhancements. Furthermore, system-on-a-chip implementation based on FPGA has been developed to demonstrate the feasibility of real-time applications. This type of study addresses a broad range of applications, including pattern recognition, deconvolution, target sizing, and characterization.