bluuebunny/crossref_metadata_2025 huggingface dataset:
On the characteristics of English speech timing control by Japanese learners
Authors: Tsubaki Hajime , Nakamura Shizuka , Sagisaka Yoshinori
Published: October 2013

This paper introduces analysis results of temporal characteristics of English language uttered by Japanese subjects aiming at automatic evaluation of L2 prosody control. As a preliminary study, 11 sentences uttered by about 200 Japanese children were compared with native’s speech. The correlation between subjective scores on temporal naturalness and differences in segmental durations were measured in different speech units at every position for sentence by sentence. A wide range of correlation differences were observed such as from −0.70 to 0.23 at unstressed syllables, from −0.33 to 0.19 at stressed syllables, and from −0.70 to −0.04 at function words. The strongest negative correlation −0.70 at unstressed syllables and at function words reflects L1 characteristics of mora-timing characteristics of Japanese. Further analysis results will be given at the conference with additional huge L2 speech database currently under construction. [Work supported in part by Waseda Univ. RISE research project of ‘‘Analysis and modeling of human mechanism in speech and language processing’’ and Grant-in-Aid for and Scientific Research A-2, No. 16200016 of JSPS.]
Native speakers and Korean-speaking advanced learners of English show similar discrimination of English prosodic contours
Authors: Hwang Hyekyung , Schafer Amy J.
Published: October 2013

Previous studies of native versus non-native perceivers argue that phonology can shape perception (e.g., Huang, 2001; Hume et al., 1999). The phonological inventory of prosodic phrasing contours differs between Korean and English. Phonologically, Korean accentual phrases have final rises (within intonation phrases), although this varies at the phonetic level, while English intermediate phrases (ips) can end in falling, rising, or level contours. Previous work has suggested that advanced learners (L2ers) use ips markedly less effectively than native speakers (L1ers) to recover English syntactic structure (Hwang and Schafer, 2005). This study investigated whether that is due to perceptual differences. L1ers and L2ers listened to pairs of phrases in an AX task that crossed boundary strength (same versus different size) with contour: rising (L*L*H-) versus level (L*L*L- or L*L*) or falling (H*H*L-) versus level (H*H*H- or H*H*). Little variation was found between L1ers’ and L2ers’ discrimination, and L2ers’ discrimination patterns correlated highly with L1ers’ (r=0.966). For both groups a falling-level contrast was more salient than a rising-level contrast (in the context tested) and boundary strength contrasts were more difficult than contour contrasts. The results suggest that the L2ers’ poor use of ips in comprehension is likely due to difficulty with prosody-syntax mappings.
The effect of phonological knowledge on word learning in second language acquisition
Authors: Maekawa Junko
Published: October 2013

Past research in first language (L1) acquisition suggests that phonological knowledge (individual sounds and sound sequences) influences word learning. In second language (L2) word learning, phonological knowledge is dependent on the mapping of L2 sounds to L1. This study explores how the L2-L1 phonological mapping affects L2 word learning for native speakers of Japanese learning English. The learners phonological knowledge was explored through a perceptual discrimination task (same-different task) and a production probe containing English real words and nonwords. L2 word learning was explored through exposure to novel words and comprehension and production testing. The results of the same-different task showed that r-l and θ-s contrasts were the most difficult to perceive, supporting findings from past research. For the production probe, w, t, and s were produced more accurately than r, l, and θ in both real words and nonwords. For L2 word learning, nonwords with w, t, and s were learned more rapidly than nonwords with r, l, and θ in production, but not comprehension. Taken together, phonological knowledge appears to constrain L2 word learning for language expression, but not comprehension. This mirrors the findings for L1 acquisition.
Context effects in recognition of English disyllabic word and nonwords by native and non-native listeners
Authors: Felty Robert , Benkí José
Published: October 2013

30 native (L1=English) and 30 non-native (L1=German) speakers listened to English CVCCVC words and nonwords mixed with noise. Of the words, half were monomorphemic and half bimorphemic. The j-factor model [Boothroyd and Nittrouer, J. Acoust. Soc. Am. 84, 101–114 (1988)] was used as a measure of lexical context effects. For both native and non-native speakers, words showed greater context effects than nonwords, though the difference was not as large for non-native speakers. Monomorphemic words also exhibited greater context effects than bimorphemic words, though only for native speakers. In an items analysis, a negative correlation with j was found for lexical frequency and a positive correlation for neighborhood density, for both native and non-native speakers, though more pronounced in native speakers. Misperceptions between native and non-native speakers were also compared, with non-native speakers showing patterns predictable by phonological differences between the two languages. The j-factor results extend previous research using CVC stimuli, providing additional support for its efficacy as a measure of context effects. The differences (and lack there of for non-native speakers) between mono- and bimorphemic words are interpreted as evidence in support of a combinatorial model of lexical access. [Work supported by NIH/NIDCD.]
Application of a microphone array to the automatic structuring of meeting recordings
Authors: Asano Futoshi , Ogata Jun , Matsusaka Yosuke
Published: October 2013

A microphone array system applied to the automatic structuring of meeting recordings is introduced. First, speakers in a meeting are identified at every time block (0.25 s) by sound localization using a microphone array, and then the speech events are extracted (structuring). Next, overlaps and insertions of speech events such as ‘‘Uh-huh,’’ which greatly reduce the performance of the automatic speech recognition, are separated out. The difficulty in eliminating overlaps and insertions is that the overlapping sections are sometimes very short, and data sufficiently long for conventional separation techniques, such as independent component analysis, cannot be obtained. In this system, a maximum-likelihood beamformer is modified so that all the information necessary for constructing the separation filter, such as speaker location and spatial characteristics of noise, are estimated from the recorded data based he structuring information. Evaluation of the performance of the speech event separation by automatic speech recognition is also presented.
Eigenbeam beamforming for microphone arrays
Authors: Meyer Jens , Elko Gary W.
Published: October 2013

In this talk, we describe a beamforming spherical microphone array consisting of many acoustic pressure sensors mounted appropriately on the surface of a rigid sphere. The associated beamformer is implemented in a two-stage process: a first stage that decomposes of the sound-field into spatially orthonormal spherical harmonics, which are called eigenbeams, and a second stage that combines the eigenbeams to form the overall output beampattern. It is shown that this approach allows for a computationally efficient, flexible, and scalable beamformer structure. As an example of beamforming flexibility, an acoustic zoom feature will be described. This application enables continuous variability of the beamwidth in a simple and elegant manner. Simultaneously, the array beampattern can be steered without affecting the beampattern shape. There are many applications for such a feature, one being the coordination of the acoustic and image scenes of microphone and a video camera.
Effect of low independency on independent component analysis and countermeasures against it
Authors: Kobatake Hidefumi , Hu Xuebin
Published: October 2013

Independent component analysis (ICA) is extensively adopted in blind signal separation (BSS). It works well in general. However, processing must be made at every short-time interval and, as a consequence, the assumption of independency cannot always hold due to insufficient data length. This local low-independency can be the cause of degradation in the overall separation performance. In this paper, two approaches to solve that problem caused by local low-independency between source signals are presented. The first one is the combination of ICA-based BSS with beamformer (BF). The BF does not depend on the independence assumption. In the proposed method, ICA and BF are applied in parallel. The frequency components separated by those methods are evaluated by each other and the frequency bin with higher segmental similarity measure is adopted. The second one is a kind of TDD method with a recursive algorithm. A criterion on the performance of separation is introduced. The proposed method has a function to improve the separation filter characteristics recursively. Experiments to evaluate the performance of those methods and demonstrations are given.
Bayesian space-time processing for acoustic array source estimation using a towed array
Authors: Candy James V , Godsill Simon J.
Published: October 2013

The development of a model-based Bayesian processor for a horizontally towed array using synthesized narrow-band, spatio-temporal data is discussed. The basic processor is developed from the Bayesian perspective, capturing the bearing estimation problem of acoustic sources moving in a surveillance volume. Far-field sources characterized by simplified random motion as well as nonlinear measurement models representing the array motion and propagation of the source signatures contaminated by noise are incorporated into the processor. The entire dynamical system is cast within a Bayesian framework aimed at estimating the underlying posterior filtering distribution of the bearing in a pseudo real-time environment. It is shown that the resulting sequential Bayesian processor is capable of dynamically estimating the instantaneous posterior distribution enabling the extraction of the bearing estimates. The problem solution involves the estimation of the posterior using sequential importance sampling/resampling leading to the development of a particle filter for this problem. The particle filter is simply an empirical representation of the posterior characterized by the weights (probability) and location variables (particles). It is shown how the particle filter successfully extracts the desired signals comparing the results to classical nonlinear processors (e.g., extended/unscented Kalman filters) for this problem.
Pressure-sensitive paint as a distributed optical microphone array
Authors: Gregory James W. , Sullivan John P. , Wanis Sameh S. , Komerath Narayanan M.
Published: October 2013

Pressure-sensitive paint is presented and evaluated in this paper as a quantitative technique for measurement of acoustic pressure fluctuations. This work is the culmination of advances in paint technology, which enable unsteady measurements of fluctuations over 10 kHz at pressure levels as low as 125 dB. Pressure-sensitive paint may be thought of as a nanoscale array of optical microphones with a spatial resolution limited primarily by the resolution of the imaging device. Thus, pressure-sensitive paint is a powerful tool for making high-amplitude sound pressure measurements. In this work, the paint was used to record ensemble-averaged, time-resolved, quantitative measurements of two-dimensional mode shapes in an acoustic resonance cavity. A wall-mounted speaker generated nonlinear, standing acoustic waves in a rigid enclosure measuring 216 mm wide, 169 mm high, and 102 mm deep. The paint recorded the acoustic surface pressures of the (1,1,0) mode shape at 1.3 kHz and a sound pressure level of 145.4 dB. Results from the paint are compared with data from a Kulite pressure transducer and with linear acoustic theory. The paint may be used as a diagnostic technique for ultrasonic tests where high spatial resolution is essential, or in nonlinear acoustic applications such as shock tubes. a)Currently at the Dept. of Aeronautics, U.S. Air Force Academy.
A simple model for time-dependent scattering by changing seafloor roughness
Authors: Jackson Darrell R. , Williams Kevin L. , Jones Christopher D. , Richardson Michael D. , Briggs Kevin B. , Lyons Anthony P.
Published: October 2013

The roughness of sandy seafloors is constantly changing due to biological and hydrodynamic activity. Even when these processes are in equilibrium so that the average acoustic backscattering intensity does not change, the character of successive backscatter echoes changes on time scales from minutes to days, with strong frequency dependence. This change can be characterized by the temporal correlation of the backscattered signal between consecutive pings, expressed as a lag-dependent correlation coefficient. A simple model for roughness change has been developed based upon the diffusion equation. This model assumes that newly created roughness is uncorrelated with existing roughness. It predicts exponential decay of the correlation with e-folding time 1/(DK2B), where KB is the Bragg wave number, and D is the horizontal diffusivity. During SAX99 and SAX04, photographic and acoustic observations were made of changing natural and artificially generated roughness. The acoustic observations were made at 40 and 300 kHz, with the higher frequency exhibiting much more rapid decorrelation as predicted by the model. The diffusivities obtained by fitting the model to photographic and acoustic data ranged from roughly 10−9 to 10−10 m2s−1 with the highest diffusivities found at locations where bottom-feeding fish were active. [Work funded by ONR.]
Using forward scattering from a rippled sand/water interface to determine its flat surface reflection coefficient: Validation via simulation and use in testing sediment models
Authors: Williams Kevin
Published: October 2013

Real-world sediments are inherently rough. At high frequencies (greater than 10 kHz) the roughness is typically sufficient to eliminate any coherent reflection at all but very shallow grazing angles. However, simulation results will be shown that demonstrate that an ensemble average of a large number [O(50)] of forward-scattered signals from different regions of a rippled sand/water interface can be used to estimate the flat surface reflection coefficient for the interface. With this validation in hand, a forward scattering experiment carried out during a sediment acoustics experiment in 2004 (SAX04) will be described. The flat surface reflection coefficients derived from this experiment will be compared with predictions using a fluid and a Biot model for the sand sediment. This comparison indicates that a Biot sediment model is a more accurate predictor for the reflection coefficient. [Work supported by ONR.]
High-resolution mapping and backscatter studies in support of the Ripples Program
Authors: Kraft Barbara , de Moustier Christian , Calder Brian , Mayer Larry
Published: October 2013

The long-term goal of the Office of Naval Research’s RIPPLES DRI is to develop the ability to predict the geometry and evolution of seabed morphology, particularly the presence or absence of ripples which have been shown to affect the sub-seabed penetration of acoustic energy. In support of the RIPPLES and SAX04 programs, high-resolution, multifrequency, multibeam mapping surveys were completed during September and October 2004 within three small areas off Destin, FL. The first survey was completed prior to Hurricane Ivan and followed the burial of minelike targets in the SAX04 field area. The second survey occurred during the SAX04 experiments approximately 6 weeks after Hurricane Ivan made landfall. Ripples were not observed in the bathymetric data from the first survey. Some small-scale features are present in the bathymetry from the second survey; however, most of the ripples generated by Hurricane Ivan had degraded by the time the survey was completed. Large-scale ripple features are present in the bathymetric data that extend off-shore from the SAX04 area. Difference maps of the pre- and post-Hurricane Ivan bathymetry and the acoustic backscatter data show remarkable evidence of sediment deposition and erosion. [Work supported by ONR Grant N00014-04-1-0624.]
Adaptive predictive-error optimal gridding
Authors: DelBalzo Donald R. , Pflug Lisa A.
Published: October 2013

Transmission loss computations in littoral areas often require a dense spatial and azimuthal grid to achieve acceptable accuracy and detail. The computational cost of accurate predictions in complex areas can be unacceptable for some Naval applications. EAGLE (Efficient Adaptive Gridder for Littoral Environments) was developed to reduce the computational requirements by adapting the fundamental calculation grid to the natural environmental structure. EAGLE produces a nonuniform grid structure within which the underlying data have approximately constant spatial uncertainty, or iso-deviance. The EAGLE point-selection approach is based on a predictive-error metric and least-squares polynomial curve fitting with arbitrary order. This research indicates the degree to which EAGLE grids are related to the underlying coherence properties of the natural environment. The results show significant efficiency enhancements compared to uniform grids of the same accuracy, when the environmental coherence properties are used to control the polynomial order. [Work sponsored by NAVAIR.]
The effect of an ocean front on sound propagation in shallow water
Authors: Lin Ying-Tsong , Newhall Arthur E. , Lynch James F.
Published: October 2013

From a perspective of sound propagation, a sloping bottom found in typical shallow-water environments can cause propagating sound to horizontally refract offshore. Additionally, an offshore ocean front can cause horizontal reflection/refraction shoreward. Combining these two effects, sound tends to propagate along the front, and ‘‘whispering gallery’’ modes can be observed. To model this effect, we first derived an analytic solution for the sound field using a point source in a rigid wedge environment that has a front placed offshore. The analytic solution gives us clear physical insight into this problem. For a more complicated environment, we exploited a 3-D acoustic propagation program in the Acoustics Toolbox, which uses a vertical mode and horizontal Gaussian beam method. This model shows sound energy trapped ahead of the front with observable frequency and modal dependence. Also, when including the foot of the front, which is commonly seen on the continental shelf and extends inshore along the bottom, the model shows less modal attenuation, which raises the level of the trapped energy.
Polynomial chaos expansions as extended Markov approximations in the propagation of uncertainty
Authors: Creamer Dennis
Published: October 2013

The use of polynomial chaos for incorporating environmental variability into propagation models has been previously investigated where it was found that low-order expansions work quite well when the medium correlation length in the direction of propagation was small, i.e., the Markov approximation is roughly valid. It was suggested that an iterative scheme incorporating extensions of the Markov approximation might be useful. Using the method of successive approximations introduced by Klyatskin and Tatarskii (who used the method for investigating the validity of the Markov approximation), we show how the polynomial chaos equations can be written as a (smaller) set of equations that are basically nested expansions in the correlation function. This allows the use of a closure scheme, which does not involve truncating the expansion and which seems to be simpler to use. Comparisons are made between the approximation schemes in a geometrical optics limit.
Acoustical qualities of three Leadership in Energy and Environmental Design (LEED) certified buildings and why some disappoint
Authors: Pettyjohn Steven D.
Published: October 2013

Obtaining points for acoustical qualities in office building or schools is difficult under the current LEED system. For this reason, the selection of partitions to provide speech privacy or prevent speech interference, the design of HVAC systems to meet background sound or vibration goals, or the inclusion of acoustical materials to provide the desired reverberation time is often either left out from the beginning or the first to be cut when budgets are tight. The results of sound tests done as a part of the commissioning of two office complexes and a new combination school, learning center, and administration building are shared. NIC tests were done on fixed and operable wall assemblies, background sound levels were measured in various spaces when due to mechanical and electrical systems and exterior sources, and reverberation time tests were done in conference rooms, classrooms, offices, and auditoria. The reason design goals were not met in two of the three complexes is related to budget cuts and a misunderstanding of the requirements and their importance to the successful use of the facilities. The commissioning process failed to correct the deficiencies.
Acoustical evaluation of six ‘‘green’’ office buildings
Authors: Hodgson Murray , Hyde Rosamund , Fulton Blair , Richter Max
Published: October 2013

As part of a project evaluating the performance of six ‘‘green’’ office buildings, detailed acoustical measurements were made to explain the positive and negative comments of building occupants obtained from a questionnaire survey. The objective was to determine how to design better green buildings. This paper presents an overview of the measurement protocal used, the measurements made, the results, and the lessons learned regarding optimal design.
Acoustical evaluation of a ‘‘green’’ office building
Authors: Hodgson Murray , Hyde Rosamund , Fulton Blair , Richter Max
Published: October 2013

As part of a project evaluating the performance of six ‘‘green’’ office buildings, detailed acoustical measurements were made on three floors of an office building in order to explain the positive and negative comments of building occupants obtained by a questionnaire survey. The objective was to determine how to design better green buildings. The building contained public spaces, private/closed offices, and open-plan-office areas. This paper presents details of the measurements performed, the results, and the design lessons learned.
Achieving acoustical satisfaction in a green building
Authors: Salter Ethan , Salter Charles M. , Davis Chuck , Shell Scott
Published: October 2013

The Carnegie Institution’s Global Ecology Research Center at Stanford University has garnered many accolades, including the AIA’s Excellence in Sustainability Award. This building incorporates many ‘‘green’’ and energy-saving design features, mechanical systems, and materials. The occupants of this facility have given it high marks in U.C. Berkeley’s Center for the Built Environment’s (CBE) survey of buildings. Staff at the Global Ecology Research Center are shown to be more satisfied with their acoustical environment than occupants of other green buildings surveyed by CBE. Measured acoustical data for speech privacy in open plan and enclosed conference rooms will be presented along with descriptions of acoustical design attributes for the building.
Indoor occupant productivity perception and environmental sound measurement correlation
Authors: Landsbeger Brian J. , Tan Liangcai , Hu Xin
Published: October 2013

Occupant comfort and productivity have gained increasing attention by building owners and managers in comparison with traditional concerns about costs associated with building function and operating efficiency. To properly assess building performance, a comprehensive method for measurement and verification of integrated building performance was developed. Indoor sound, temperature, air movement, humidity, lighting, and air quality were measured for 3 days each in ten office buildings and ten schools. Concurrently, a perception questionnaire was completed by a subset of the occupants in the buildings and schools. The resulting questionnaire data were correlated with the physical measurements to determine what measures or combination of measures most accurately indicate worker perception of productivity variation when working under various environmental conditions. This presentation concentrates on correlation of acoustic measures, including dBA, NC, NCB, RC, and RC Mark II to worker perception of noise effects on productivity variation. Also, worker perception of productivity variation due to all measured indoor environmental factors was examined to determine additive effects and interaction between noise and other environmental factors. An ultimate goal of the study is to produce a method to quantitatively determine expected worker productivity variation based on measurable environmental factors.
Spatial coverage of reflector panels predicted with and without edge diffraction
Authors: Rathsam Jonathan , Wang Lily M. , Torres Rendell R.
Published: October 2013

This investigation concerns the spatial coverage of reflector panels. The specular reflection zone (SRZ) is the spatial coverage predicted by geometrical acoustics, which is commonly used when designing reflector panels. A more accurate prediction of spatial coverage accounting for edge diffraction from the panels is called the effective scattered zone (ESZ). At higher frequencies, the SRZ and the ESZ are typically similar, but notable differences emerge at lower frequencies. In this study a variety of reflector panel arrays will be examined using a boundary element method (BEM) model based on the Kirchhoff-Helmholtz integral equation. The effective scattered zone is studied as a function of incidence angle, distance from array to source and receiver, and ka, the ratio of panel dimension to wavelength. The authors seek rules of thumb to predict configurations in which the SRZ and ESZ differ most notably. [Work supported by National Science Foundation.]
Helmholtz resonator array for low-frequency sound absorption
Authors: Kim SangRyul , Kim Yang-Hann
Published: October 2013

An array of Helmholtz resonators is often used for reducing low-frequency noise because of the high performance at its resonance frequency. One of the very attractive characteristics of the resonator array is that its effective frequency band is much wider than what can be obtained by a single resonator. This paper discusses a method of designing a Helmholtz resonator array panel for low-frequency sound absorption. First, various experimental results are introduced and studied. Second, based on the experimental results, a theoretical method is presented that can predict reasonably well the panel’s absorption characteristics. Any configuration of resonator arrangement can be treated in the method, while all the resonators may or may not be identical. Comparisons between the predicted and experimental results reveal the accuracy of the proposed method. Finally, a numerical optimization is performed to design the Helmholtz resonator array panel. Some examples of optimal designs under some restrictions are also introduced.
Concept of active reverberation box
Authors: Suzuki Hisaharu , Omoto Akira , Fujiwara Kyoji
Published: October 2013

A concept of a small reverberation box is proposed. This box has an active controller that can control the energy flow direction: it is a controller for the sound intensity. Consequently, the box is useful to measure the absorption characteristics of materials, even in a low-frequency range. The controller can create an arbitrary incident condition towards the materials. The measurement procedure with this ‘‘active reverberation box’’ is assumed as follows: (1) The incident angle of the sound is changed by the controller. (2) Impulse responses are measured in some points. (3) Steps 1 and 2 are repeated many times and impulse responses are averaged in an energy domain. (4) The reverberation time is calculated using the averaged impulse response. (5) Absorption characteristics are calculated by comparing the reverberation time of the empty room. The controller is formulized using a pseudo-Hermitian quadratic form of the sound intensity in the box. Numerical examination is performed using the finite difference time domain (FDTD) method. Experimental results demonstrate the effectiveness of the controller’s performance. Availability of the active reverberation box is examined using some conventional measurement methods. Numerical results correspond approximately to the absorption coefficients that were taken in a reverberation chamber.
Nonlinear phenomena in vertebrate vocal production
Authors: Herzel Hans-Peter , Zaccarelli Riccardo , Riede Tobias , Neubauer Juergen , Fitch W. Tecumseh
Published: October 2013

Nonlinear phenomena such as subharmonics, biphonation (two independent frequencies), and deterministic chaos are widespread in animal communication. Examples from primate vocalizations, African wild dogs, hyena whoops, and bird songs are presented. Despite the variability of size and morphology, vocal production in vertebrates is governed by the same underlying mechanism: vibrating tissues such as vocal folds, membranes, or labia are driven by overcritical airflow. Consequently, sophisticated biomechanical-aerodynamic models of human voice production can serve as a starting point for modeling nonhuman vocal production. However, there is a variety of additional anatomical features in diverse species: pronounced air sacs, extensions of the vocal folds termed ‘‘vocal membranes’’ or ‘‘vocal lips,’’ or the coordinated action of left and right syrinx in song birds. It is shown that such specific features can induce voice instabilities. For instance, source-tract interactions lead to subharmonics and chaos, and vocal membranes allow multiple ‘‘registers.’’ Finally bifurcations in biomechanical models of the syrinx are discussed. [Work supported by the Deutsche Forschungsgemeinschaft (Grant He 2168/7).]
The creative walrus: Novel sound production via contingency learning
Authors: Schusterman Ronald J. , Reichmuth Kastak Colleen , Quihuis Debbie , Holt Marla M.
Published: October 2013

Walruses (Odobenus rosmarus) have a range of anatomical specializations that can provide plasticity to their vocal emissions. These include respiratory adaptations related to breath-holding and buoyancy and soft tissue adaptations of the mouth, lips, and tongue related to suction feeding. The aim of this study was to examine the extent to which contingency learning using food reinforcement could modify the sound production of walruses. One male and three female captive walruses participated in the current study. Animals were first trained in air in a series of four experimental steps: (1) induce and reinforce natural sound production, (2) establish stimulus control over sound production and inhibition, (3) establish stimulus control over different sound types by mapping them to different discriminative stimuli, and (4) encourage the production of novel sounds by withholding reinforcement for previously emitted sounds and reinforcing only novel variants. Subsequently, two of the walruses were transferred from airborne to underwater testing. In the absence of additional training, both individuals, when prompted to vocalize, emitted a range of underwater sounds, many of which were qualitatively different from those produced in air and those recorded in baseline conditions under water. Thus, walruses, like cetaceans, can learn to modify their sound production.
Modern acoustic microscopy and applications
Authors: Kessler Lawrence
Published: October 2013

The concept of acoustic microscopy was first suggested in the late 1930s by S. A. Sokolov and first demonstrated in a one-dimensional scan by Floyd Dunn and W. J. Fry in 1959. The notion of producing images of materials and biological tissues with UHF ultrasound to characterize their microelastic properties has broad appeal, however, most of the modern day (commercial) systems have been used instead for defect detection in manufactured products such as semiconductor devices. This paper will review a spectrum of applications from both the materials and biological worlds.
Floyd’s contribution to B/A measurement of biological materials
Authors: Frizzell Leon A.
Published: October 2013

Ultrasound as used for medical diagnosis and high-intensity therapy is of sufficient amplitude that the effects of nonlinear propagation are important. Critical to modeling and understanding these nonlinear effects is knowledge of the nonlinearity parameter, B/A, for the biological tissues involved. In a series of papers Floyd Dunn and colleagues determined the value of B/A for several biological materials and soft tissues using the thermodynamic and finite amplitude methods. They showed that the B/A value depended directly upon the solute concentration in protein solutions. The value of B/A was around 7 for many soft tissues, including liver, muscle, and brain, but was around 11 for fat. Homogenized liver had a value that was less than that for whole liver, demonstrating an effect of structure. These results provided information regarding the range of B/A for biological materials and its dependence on concentration and structure and suggested the possible use of B/A in tissue characterization.
Antioxidant use in the prevention of noise-induced hearing loss and ototoxic chemicals in the workplace
Authors: MacLean Uberuaga Sandra C.
Published: October 2013

There have been discoveries in auditory research as to how the cochlea is injured during noise exposure and how it may sometimes be possible to reverse or prevent acute noise damage with medications. There are two primary mechanisms of damage; mechanical, as delicate tissue structures are torn apart when loud blasts occur above 125–130 dB SPL, and metabolic exhaustion, which commonly results from habitual noise exposure. During metabolic exhaustion toxic waste products (free radicals) form as cells in the cochlea are stressed. Our bodies can react to noise trauma by presenting a defense of antioxidant enzymes. However, when these defenses are overwhelmed, the hair cell is subject to serious damage to its nuclear DNA, mitochondria, and membranes. This research has been promising in animal studies. We will discuss pharmacological agents that can be used by the ear to synthesize the toxic products. The next step is well-designed human clinical trials in occupational settings where extreme noise levels cause hearing loss despite the seemingly appropriate use of hearing protection devices (e.g., aircraft carrier decks, mining and petroleum industries). Chemicals and agents that can cause hearing loss in the workplace will also be reviewed.
Near-field mapping of pressure fields during active noise control of small axial cooling fans
Authors: Shafer Benjamin M. , Gee Kent L. , Sommerfeldt Scott D. , Duke Cole V.
Published: October 2013

In the past, tonal noise from small axial fans has been globally reduced using active noise control (ANC) with near-field error sensors placed according to a theoretical condition of minimized radiated power [K. L. Gee and S. D. Sommerfeldt, J. Acoust. Soc. Am. 115, 228–236 (2004)]. The theoretical model, based on mutual coupling of point sources, showed that pressure nulls exist in the near field when the radiated power is minimized. Error sensor placement at these locations should then optimize global ANC. This study comprises an experimental investigation in which the actual locations of these near-field pressure nulls have been measured over a two-dimensional grid with a linear array of microphones. The array consists of 25 quarter-inch microphones with half-inch spacing. This array has been used to map the pressure field from a 60-mm cooling fan during ANC, in addition to a benchmark case, where a small loudspeaker has been mounted in place of the fan. The experimental results are compared to the theoretical pressure null locations in order to determine the efficacy of the point source theoretical model.
Case study: Predict acoustical quality of renovated classroom
Authors: Lam Coriolanus , Leung Chun Wah , Li Kai Ming
Published: October 2013

The study on prediction of acoustical quality of two standard and identical classrooms, one of which has been renovated, was presented. Acoustical back-wall panels and sound-reflecting panels were installed in the renovated classroom. The study was carried out by raynoise under the same conditions and acoustical characteristics of field measurements in the classrooms. Several acoustical quantities such as signal-to-noise ratios, reverberation time, and speech transmission index have been studied. Comparison was focused on the qualities of speech communication between the classrooms with and without renovation. Additional comparison was conducted with the results of field measurements. The results of the present study found that the quality of speech communication varied depending on changes in absorption. The results further implied the limitations and the precautions on application of raynoise for different studies. [Work supported by Research Grants Council of The Hong Kong SAR Government, Research Committee of The Hong Kong Polytechnic University, and Architectural Services Department of The Hong Kong SAR Government.]
Experimental determination of end reflection loss (ERL) over a range of common types and configurations of duct terminations
Authors: Michaud Alexander P. , Cunefare Kenneth A.
Published: October 2013

The two-microphone impedance tube method ASTM E1050 was applied to directly measure the termination impedance of rectangular duct configurations of different aspect ratios and end conditions over a 25- to 500-Hz frequency band. Measured values of the acoustic impedance, and hence the reflection coefficient, of the duct termination permits computation of end reflection loss. ERL is essentially the insertion loss of duct termination. The measurement program is challenging, as the precision required for accurate ERL computation is much higher than that for accurate determination of the reflection coefficient. The measurement program is part of a project to assess the available published data on duct ERL. The ASHRAE Handbook contains a tabulation of ERL data derived from predictions of the radiation impedance of a circular plane piston, and there have been some validation measurements made on a limited set of circular duct configurations and orifice plate terminations. Results to date closely conform to published ERL values. [Work supported by ASHRAE.]
Shock-wave–inertial-bubble interaction near an elastic boundary
Authors: Sankin Georgy , Zhong Pei
Published: October 2013

The interaction of laser-generated single cavitation bubbles (maximum diameter Dmax=1.34 mm) near a silicon rubber membrane with a shock wave (39–75 MPa in peak pressure and 1.7 μs in compressive pulse duration) is investigated. The interaction leads to directional, forced collapse of the bubble with microjet formation along shock wave propagation direction. Maximum jet penetration into the membrane is produced during the bubble collapse phase with optimal shock wave arrival time and stand-off distance s, a condition that ensures that the forced collapse time of the bubble matches with the compressive duration of the shock wave to generate presumably the maximum axial jet velocity toward the boundary. A maximum penetration depth of 0.5 mm is observed at dimensionless proximity γ (=2s/Dmax)=0.7 when the bubble establishes contact with the boundary during expansion. At larger γ (≥1.2), jet impact is significantly attenuated by the interposing water layer separating the collapsing bubble and the membrane surface. Such interaction may provide a novel acoustic means for in vivo microinjection, applicable to targeted delivery of macromolecules and gene vectors to biological tissues.
Measurements of 3-D propagation effects at a shelfbreak front
Authors: Moore Kristy A. , Miller James H. , Potty Gopu R. , Dossot Georges A. , Glenn Scott M. , Lynch James F.
Published: October 2013

Acoustic data collected on two Webb Slocum gliders deployed by Rutgers University during the Shallow Water Experiment (SW06) on the continental shelf off New Jersey are presented. Acoustic recording systems were attached to the two gliders, which also collected oceanographic data. These gliders periodically surfaced for GPS fixes and data transfer via satellite phone. A major goal of these measurements was to quantify 3-D propagation effects including the horizontal analog to the classical Lloyd’s mirror. The Lloyd’s mirror effect is produced by the fact that fronts can totally internally reflect sound incident upon them at low grazing angles. The direct and reflected arrivals can add up to produce an interference pattern in range, potentially increasing the received intensity level by 6 dB [Lynch et al., IEEE J. Ocean. Eng., in press]. The gliders crossed the shelfbreak front at ranges of approximately 20 km from the sources and in water depths of approximately 80 m. Measurements of the acoustic arrivals from 224 and 400 Hz tomography sources are compared to 3D modeling results. The increase in the intensity level predicted by the horizontal ray-vertical mode model is discussed. [Work supported by Office of Naval Research.]
The perception of apparent source width and its dependence on frequency and loudness
Authors: Witew Ingo B. , Buechler Johannes A.
Published: October 2013

While it is widely accepted that apparent source width (ASW) is an important factor in characterizing the acoustics of a concert hall, there is still a lively discussion on how to refine the physical measures for ASW. A lot of experience has been gathered with interaural-cross-correlation and lateral-sound-incidence measures during the last years. As a result it was learned that different frequencies contribute differently to the perception of ASW and that the level of a sound also influences the perception of the apparent width of a source. With many technical measures having an influence on the perceptual aspect of ASW, the design of psychometric experiments becomes challenging as it is desirable to avoid the interaction of different objective parameters. In the experiments for the study presented, the perception of ASW is investigated for frequencies ranging from 100 Hz to 12.5 kHz at different levels of loudness. It is shown how the frequency and the loudness of a sound influence the perception of ASW.
Spherical and hemispherical microphone arrays for capture and analysis of sound fields
Authors: Duraiswami Ramani , Li Zhiyun , Zotkin Dmitry N. , Grassi Elena
Published: October 2013

The capture of the spatial structure of a sound field and analysis is important in many fields including creating virtual environments, source localization and detection, noise suppression, and beamforming. Spherical microphone arrays are a promising development to help achieve such capture and analysis, and have been studied by several groups. We develop a practical spherical microphone array and demonstrate its utility in applications for sound capture, room measurement and for beamforming and tracking. To accommodate equipment failure and manufacturing imprecision we extend their theory to handle arbitrary microphone placement. To handle speech capture and surveillance we describe the development of a new sensor, the hemispherical microphone array. For each array the practical performance follows that predicted by theory. Future applications and improvements are also discussed. [Work supported by NSF.]
Impulse response measurement system and its recent applications
Authors: Takashima Kazuhiro , Nakagawa Hiroshi , Tanaka Natsu , Sekito Daiki
Published: October 2013

Our impulse response measurement system has been developed for ten years. During this decade, the environment related to this measurement has changed significantly. In this article, the features and notes on the measurement system using the sound card, and our brand new system, which is expanded for multichannel inputs, will be presented. Finally, a new technique, which combines multichannel impulse response measurement and signal processing with microphone array, will be presented. The microphone array was designed for noise analysis for automobile interiors. The array consists of 31 microphones on the surface of an acoustically hard sphere. Moreover, 12 cameras are arranged on the surface of the sphere to take photos. Some applications and future development will be presented.
Development of evoked-potential audiometry in odontocetes
Authors: Supin Alexander
Published: October 2013

Evoked-potential methods are widely used for investigation of hearing in whales, dolphins, and porpoises. For this purpose, mostly the auditory brainstem response (ABR) or rhythmic trains of ABRs, the envelope-following response (EFR), are used. Although very productive, these methods require further elaboration. (i) Traditionally the EFR is provoked by sinusoidally amplitude-modulated tones (SAM). SAM stimuli have narrow frequency band, which makes them little effective to produce the EFR, because response amplitude depends on the stimulus bandwidth. A solution of the problem is the use of trains of short tone pips instead of SAM tones. Such stimuli produce several times higher EFR than SAM tones. This makes the threshold determination much more confident and precise. The effect is achievable at stimulus bandwidths, which still do not influence negatively the precision of attribution of the threshold to a certain frequency. (ii) To extract low-amplitude evoked potentials from noise, the average technique is traditionally used. This operation returns a mean value of averaged traces. Effectively diminishing stationary noise, this method poorly eliminates big artifacts, which may spoil the record even it if appeared once or twice during acquisition. With this respect, computation of the median instead of mean is much more effective.
Electrophysiological investigation of temporal resolution in three pinniped species: Adaptive implications
Authors: Mulsow Jason , Reichmuth Kastak Colleen
Published: October 2013

Electrophysiological studies of auditory temporal processing in marine mammals have traditionally focused on the role of highly refined temporal resolution in dolphin echolocation. Studies in manatees, however, have found their temporal resolution to be better than expected, leading to speculation that such capabilities are an adaptation for underwater sound localization. This study measured the ability of auditory brainstem responses to follow rhythmic click stimuli in California sea lions (Zalophus californianus), harbor seals (Phoca vitulina), and northern elephant seals (Mirounga angustirostris). Trains of 640-s clicks were presented in air at repetition rates of 125–1500 per second and averaged rate-following responses were recorded. Rate-following responses were detected in both the harbor seal and the sea lion at rates up to 1000 clicks per second, indicating that pinnipeds, like manatees, possess temporal resolution greater than humans but inferior to dolphins. While this finding might support an underwater sound localization hypothesis, comparable results were obtained in preliminary testing of a dog (Canis familiaris), suggesting that increased temporal resolution in pinnipeds may not be the result of the evolutionary pressure of an aquatic environment, but rather a result of increased high-frequency hearing essential to mammalian sound localization. [Work supported by NOPP, ONR, and NMFS.]