bluuebunny/crossref_metadata_2025 huggingface dataset:
Soundscape perception of an urban park under flight paths of Naples airport
Authors: Brambilla Giovanni , De Gregorio Leda , Maffei Luigi
Published: October 2013

The Capodimonte historical urban park is the largest green area in Naples, located in the North and under the flight-paths of the city airport. Noise measurements, taken in the morning on two weekdays and one week-end in different sites inside the park, have shown LAeq levels, excluding aircraft noise, lower than 50 dB(A) and up to 55 dB(A) on Sunday morning near the museum. During the noise measurements one aircraft flyover occurred approximately every five minutes, producing an increase of LAeq in the range 5-15 dB(A) and LAmax levels up to 90 dB(A). Interviews have been carried out on a sample of subjects present in the park while the noise measurements were taken. By means of a questionnaire, they were asked to rate different factors describing the environment and influencing their experience to enjoy the park. The analysis of the subjective data collected is in progress and the preliminary outcomes show that the reported annoyance due to aircraft noise is much lower than expected by the noise levels, most likely due to synergetic effects of the other environmental factors.
Application of a diver-operated 4-channel acoustic/video recording device to study wild dolphin echolocation and communication
Authors: Schotten Michiel , Lammers Marc O. , Sexton Ken , Au Whitlow W. L.
Published: October 2013

Despite decades of research on captive dolphins, there still is much to learn about dolphin echolocation and communication in the wild. This is mainly due to the difficulties associated with recording dolphin signals accurately in the wild, such as their broadband (with frequencies over 200 kHz) and directional nature, the difficulty of identifying vocalizing dolphins, and being confined to equipment aboard a vessel. To resolve these difficulties, an underwater portable battery-operated digital recording device was developed that is capable of simultaneously capturing acoustic signals up to 220 kHz on 4 channels as well as video. It consists of a custom-made underwater housing, containing two batteries, a digital camcorder, and an acoustic recording unit with signal conditioning board, 4-channel data acquisition card, PC/104-plus single board computer and power supply, and a notebook hard disk. Attached to the housing is a 4-hydrophone star array. Post-recording, acoustic signals recorded within 15 m are accurately localized in 3-D and attributed to individual dolphins on the video. Thus, acoustic signal features are correlated with different echolocation behaviors and communicative signal exchanges among dolphins are assessed. The system has been successfully field tested with spinner dolphins (Stenella longirostris) along the leeward coast of Oahu, Hawaii.
A computational model of echolocation: Restoration of an acoustic image from a single-emission echo
Authors: Matsuo Ikuo , Yano Masafumi
Published: October 2013

Bats can form a fine acoustic image of an object using frequency-modulated echolocation sound. The acoustic image is an impulse response, known as a reflected-intensity distribution, which is composed of amplitude and phase spectra over a range of frequencies. However, bats detect only the amplitude spectrum due to the low-time resolution of their peripheral auditory system, and the frequency range of emission is restricted. The amplitude spectrum varies with the changes in the configuration of the reflected-intensity distribution, while the phase spectrum varies with the changes in its configuration and location. Here, by introducing some reasonable constraints, we propose a method for restoring an acoustic image from the echo produced by a single emission. The configuration is extrapolated from the amplitude spectrum of the restricted frequency range by using the continuity condition of the amplitude spectrum at the minimum frequency of the emission and the minimum phase condition. The determination of the location requires extracting the temporal changes of amplitude spectra. For this purpose, the Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates was used. The location is estimated from the temporal changes of the amplitude spectra. This method can determine the acoustic images of objects.
Broken line 3-dimensional sperm whale diving trajectory reconstruction using passive acoustics on a single hydrophone
Authors: Laplanche Christophe , Adam Olivier , Lopatka Maciej , Motsch Jean-François
Published: October 2013

Sperm whales make deep dives to hunt. A dive, lasting 45 minutes on average, is composed of a vertical descent to the prey layer depth, the properly so called hunt (at a quasi constant depth) inside the prey layer, and a vertical ascent back to the sea surface. Sperm whales make series of echolocation signals (clicks) during the two first stages. The sea surface/bottom click echo detection and delay measurements then make possible the sperm whale range/depth estimation during these stages, by passively using a single hydrophone. The vertical, rectilinear sperm whale trajectory during the first stage is unambiguously estimated from the echo delays. The sperm whale trajectory can also be reconstructed during the second stage, from the sperm whale range variations only, even when not detecting sea bottom click echoes. These range variations strongly suggest the sperm whale trajectory to be a broken line (e.g., a 2-piece line, 600 m straight ahead, 85 degree bend, 1000 m straight ahead). Assuming a vertical silent reascent, the rough hydrophone-relative 3-dimensional sperm whale trajectory can then be reconstructed for the complete dive, by using a single hydrophone.
Design of an oscillating flow test chamber for modeling the fish ear
Authors: Kotas Charlotte , Rogers Peter , Yoda Minami
Published: October 2013

The acoustically induced oscillating flow fields inside the fish ear, specifically near the otoliths, may provide clues about how fish directionalize underwater sound sources. A new experimental test apparatus has been constructed to study oscillatory and steady streaming flows around model otoliths. The flows are driven by a shaker-piston assembly attached to a 250 mm diameter, 450 mm tall cylindrical test chamber filled with liquid to a depth of 400 mm. This apparatus is capable of generating flow oscillating at frequencies of 1 to 30 Hz with displacements up to a few millimeters within the test chamber. Theoretical predictions of the fluid-borne vibrations in a fluid-filled tube in a vacuum suggest that the flow will have a uniform sinusoidally oscillating velocity field over the central portion of the test section. The flow is visualized in the optically accessible test chamber using small tracer particles; flow velocity fields are measured using particle image velocimetry (PIV). The apparatus is compatible with various working fluids of different viscosities such as water, glycerin and silicon oils to extend the range of attainable Reynolds numbers. Initial results for oscillating flows around basic ‘‘otolith’’ geometries such as spheres and spheroids will be shown. [Work supported by ONR.]
On the measurement of the mechanical properties of acoustic porous materials
Authors: Atalla Noureddine , Sgard Franck , Jaouen Luc
Published: October 2013

This paper discusses the measurements and use of the mechanical properties of porous materials. It starts with a review of the classical methods currently used and concentrates in explaining the assumptions, difficulties and limitations of these methods. Next, it concentrates on two methods: a quasi-static approach accounting for the effect of shape factors on the measured properties and a hybrid inverse method similar to the vibrating beam method used for viscoelastic materials. Through full 3-D numerical simulations, both methods are simulated and their main features, assumptions, and limitations are investigated. In particular, the model uses full poro-elastic modeling and boundary element in order to investigate the effect of acoustic radiation damping and viscous damping. Using various types of materials, comparisons between these two methods and experimental data are also discussed.
Estimation of the accuracy of measured acoustical parameters of porous materials with an acoustical method
Authors: Olny Xavier , Panneton Raymond
Published: October 2013

Acoustical parameters such as tortuosity, viscous and thermal characteristic lengths, or even static thermal permeability are often required to describe the dynamic behavior of porous materials. Using a middle frequency method, based on the use of a standing waves tube, the direct measurements of the resistivity and porosity, and the accurate measurement of the dynamic density and bulk modulus, these intrinsic parameters can be obtained from analytical inversion of Johnsons and Lafarges models. The interests of the method lie in the simplicity of the apparatus and on the clear separation of viscous and thermal dissipative contributions. This last point specially helps to understand the physics of the medium and check the validity of the assumptions made: the material should not have a strong elastic behavior, and it must fit the models used in the inversion process. In this presentation, the robustness of the method is discussed and estimations of the measurement uncertainties are given. The occurrence of systematic errors coming from the use of semi-phenomenological models for determining intrinsic parameters is tackled. The measurement procedure, and the experimental set-up are detailed, and results obtained on materials with very different properties are presented.
Measured characteristic impedance and propagation constant of some common materials using the two cavity method
Authors: Godfrey Richard
Published: October 2013

The acoustics of porous rigid frame materials is characterized by their characteristic impedance and propagation constant. These properties can be measured using the two cavity method. A sample is placed in an impedance tube with an air space behind the sample and ahead of the rigid termination. Measurements are made in accordance with ASTM E 1050. This procedure is repeated with the same sample, but a different air space. These data are analyzed as outlined by Seybert et al. [J. Acoust. Soc. Am. 86, 637 (1989)] to yield the characteristic impedance and propagation constant. This method was used to characterize fiber glass boards with a range of flow resistivities from 2600 to 56000 mks rayls/m. Repeat measurements were made, and these measurements were compared with the Delaney and Bazley model, [Applied Acoustics (3), 1970]. Measurements were also made for cotton shoddy and cellulose, and power law models were developed. The method produced repeatable results comparable to the Delaney and Bazley model with little effort, and it is a useful method of obtaining property data for modeling tools such as Mechels Acoustics Program System (MAPS).
How does ultrasound induce strain related responses in cells?
Authors: Greenleaf James , Bolander Mark
Published: October 2013

The fact that modulated ultrasound at a pulse intensity of 160 mW/cm2 can induce fracture healing implies that cells that are sensitive to strain can feel and respond to this signal. A hypothesis that uses Nyborg inspired methods to investigate this effect will be presented along with data from a wide variety of simulations and experimental data. It appears that the response is mediated through the cytoskeleton and may be associated with interaction of the sound with focal adhesion complexes at one end of the skeletal fibers for high frequency responses and with the nuclear membrane at the other end of the fibers for low frequency responses. Although this hypothesis is nascent it is supported with experimental data from the literature.
Sonochemical synthesis and modification of protein microspheres
Authors: Suslick Kenneth S. , Toublan Farah J.-J. , Dibbern Elizabeth M.
Published: October 2013

The need for organ-targeted delivery of drugs and imaging agents creates an interest in biocompatible, biodegradable vesicles. We make protein microspheres using high-intensity ultrasound; these microspheres have a protein shell and a hydrophobic interior making them ideal for delivering hydrophobic materials. We have previously shown that various proteins, e.g., bovine serum albumin (BSA), form a microsphere shell stabilized by inter-protein cross-linking of cysteine residues. In this study, we explore methods to modify the surface of these microspheres by (1) nanoparticle incorporation and (2) layer by layer electrostatic adhesion of macromolecules. We have explored applications of these microspheres for organ targeted imaging using both MRI and optical coherence tomography (OCT).
Effects of various reverberant conditions on speech intelligibility
Authors: Carr Suzanne P. , Colburn H. Steven
Published: October 2013

Understanding speech in complex environments is a problem for many hearing impaired listeners, yet the specific characteristics of the listening environment which contribute most to listening difficulties are not well understood. Using virtual stimuli, a large range of conditions are tested on a small group of listeners, both normal and hearing impaired, and speech intelligibility thresholds are obtained. Systematic comparisons of the different conditions are made. The conditions that are varied are the amount of reverberation in the virtual room (ranging from pseudo-anechoic to moderately reverberant), the presence or absence of strong, early reflections such as from a wall and/or tabletop, the direction of the target speech relative to the listener, the distance of the target speech from the listener, and the number and location of competing speech maskers. Care is taken to ensure that the conditions are within the bounds of realistic listening. The validity of the use of virtual stimuli is also explored. [Work supported by NIH DC00100.]
Sources of variation in masking by competing speech
Authors: Freyman Richard L. , Helfer Karen S. , Balakrishnan Uma
Published: October 2013

The literature on speech recognition within a competing speech environment shows great variation with respect to the amount of masking produced, as well as variation in the improvement realized from spatial separation of the target and masking speech. Presumably, the sources of variation include differences in methodology and stimuli used by different researchers. In the current study the target speech stimuli were nonsense sentences spoken by a female talker. The competing speech was created from similar nonsense sentences recorded by 10 other female speakers. Five different maskers were created, each a combination of two of the 10 talkers who had similar fundamental frequencies. The results showed that the variation in masking produced by the different two-talker combinations was substantial only when target and masker were presented from the same loudspeaker. As a consequence, the observed benefit from spatial separation varied widely among the different maskers, and was ordered according to fundamental frequency in an unexpected way. The results are interpreted as showing greater variation in informational masking than in energetic masking. Also tested was the influence of different ways of blocking the trials, which effectively manipulated the uncertainty of the masking stimulus from trial to trial. [Work supported by NIH DC01625.]
Distortion product otoacoustic emissions generated by mistuned harmonic stimuli
Authors: Long Glenis R. , Lee Jungmee
Published: October 2013

Psychoacoustic research in humans [Lee and Green, J. Acoust. Soc. Am. 95, 718–725 (1994)] suggests that the detection of the mistuning of an harmonic when the harmonic complex and a mistuned component were presented simultaneously to the same ear stems, at least in part, from the resulting envelope interactions on the basilar membrane. Neurophysiological research in chinchillas [Sinex et al., Hear. Res. 168, 150–162 (2002)], provides evidence that such envelope interactions can be detected at the level of the inferior colliculus. The potential role of cochlear nonlinearites in determining the nature of the signal on the basilar membrane is explored by evaluating the DPOAE generated by multicomponent harmonic and inharmonic complexes. When harmonic complexes are used, the DPOAE all fall at harmonic frequencies. When inharmonic complexes are used, many nonharmonic DPOAE are detected.
Tinnitus neural map; A positron emission tomography study
Authors: Lenhardt Martin L. , Shulman Abraham , Goldstein Barbara
Published: October 2013

The neural map of tinnitus involves more than the classical auditory pathways and the limbic system. PET findings in six patients, with severe problem tinnitus, revealed the involvement of the cerebellum, insula and frontal cortices when these patients were imaged before and after high frequency bone conduction therapy. The frontal cortex and cerebellum demonstrated the highest ratios of metabolic change but changes were also noted in the thalamus and the medial temporal lobe system. The PET data supports the view that the frequency specific map of auditory cortex is dynamic and can change with high frequency therapy, presumably due to neural reorganization. The PET data further reflect alterations in multiple areas of brain in all patients to tinnitus and/or high frequency therapy. Encouraging was the observation that patients with the most dramatic change in their global pre/post PETs were also the ones who exhibited the greatest behavioral improvement in regards to tinnitus relief measured by informal report and standard questionnaires. In those patients, post therapy minimal masking levels dropped indicating less acoustic energy was need to mask their problem tinnitus, interpreted as reflecting central changes. Taken as a whole, these data support the value of frequency specific tinnitus therapy.
Piano soundboards: Experimental and modeling studies
Authors: Giordano Nicholas
Published: October 2013

The piano has attracted the attention of many researchers, and most of that work has focused on piano hammers and string vibrations. The vibrational and radiative properties of the soundboard have drawn much less attention, but are essential for an understanding of the sound produced by the instrument. We review experimental studies of the soundboard’s vibrational modes and their radiative efficiency. We also describe modeling studies of soundboard vibrations and radiation, which aid in understanding the measurements. Prospects for future work and for applications to other instruments are suggested. [Work supported by NSF grant PHY-9988562.]
Vibration study of Indian Gong hung at one point near the edge
Authors: Shravage Paresh , Parmeswaran S. , deSa Keith
Published: October 2013

Indian Gong is made up of brass and circular in nature. It is Percussion Instrument. It is used in some religious processions and music concerts in India. It is hung by a metal wire through a hole near the edge of circumference. It is vibrated by a metal (iron) hammer after repeated intervals to get sound of same pitch. This paper relates to vibrational analysis of Indian Gong. A study has been done to check the vibrational properties and the modes of vibration of the Gong. The study is done by spectrum analysis (FFT) and Time-average holography as a vibration analysis tool. The study will help to analyze certain vibrational features of brass. The tonal quality of brass is also compared to other metals, so that it will be useful in making musical instruments. The analysis of hologram may yield some interesting properties of the plate. In conclusion the paper is going to deal with modes of vibration of Indian Gong. The vibrational properties will depend on the point of actuations. The paper describes the mode of vibration and its mathematical equation.
Does intonation have primitive units?
Authors: Seddoh Amebu K.
Published: October 2013

This study investigated whether listeners can interpret intonation based on partial rather than global fundamental frequency (F0) or pitch information. Matched Statements and echo questions were recorded digitally at 22 kHz sampling rate using a Computerized Speech Lab (CSL). Each production was stored on the CSL and edited by slicing the wave form into two parts that corresponded to terminal (last 150–200 ms span of the F0 contour) and preterminal (section of contour preceding the terminal region) F0 contour regions. A total of 92 stimuli was thus generated and recorded on a DAT tape. The tape was played to 96 young (20–28 years) and old (42–79 years) adults to determine if each stimulus was part of a statement or a question. For preterminal (PTL) stimuli, both groups successfully identified statements 91% and 88% of the time, respectively, compared to 72% each for questions. The respective scores for the terminal (TL) stimuli were 94% and 91% (statements) versus 91% and 87% (questions). Across groups, statements were easier to identify with both TL (p=0.002) and PTL (p=0.001) cues compared to questions. These findings suggest that intonation decoding might involve units smaller than global F0 contour. [Work supported by NIH (NIDCD) grant 5R03DC04955-02.]
Turning speech into music in a two-dimensional space by varying the bandwidth and rate of tone pulses placed along formant tracks
Authors: Darwin C. J.
Published: October 2013

A two-dimensional space is introduced which changes sounds from speech-like to music-like by varying the rate and the bandwidth (decay-time) of individual tones placed along formant contours. At one extreme of a very fast pulse rate and a long decay time, the sounds are equivalent to sine-wave speech. With a more moderate tone rate and a short decay time, the sounds become monotone (at the tone-rate) speech. For tone rates around 10/s with long decay times, individual musical tones are heard at the formant frequencies. Intelligibility is poor for such sounds because of the low sampling rate of the formant contours. Increasing the tone rate and decreasing tone decay time increases intelligibility and makes the sounds less music like. Intelligibility data together with speech-like and music-like ratings of sounds from this space will be presented.
Self-organizing maps for measuring similarity of audio-visual speech percepts
Authors: Bothe Hans-Heinrich
Published: October 2013

The goal of this work is to find a way to measure similarity of audio-visual speech percepts. Phoneme-related self-organizing maps (SOM) with a rectangular basis are trained with data material from a (labeled) video film. For the training, a combination of auditory speech features and corresponding visual lip features is used. Phoneme-related receptive fields result on the SOM basis; they are speaker dependent and show individual locations and strain. Overlapping main slopes indicate a high similarity of respective units; distortion or extra peaks originate from the influence of other units. Dependent on the training data, these other units may also be contextually immediate neighboring units. The poster demonstrates the idea with text material spoken by one individual subject using a set of simple audio-visual features. The data material for the training process consists of 44 labeled sentences in German with a balanced phoneme repertoire. As a result it can be stated that (i) the SOM can be trained to map auditory and visual features in a topology-preserving way and (ii) they show strain due to the influence of other audio-visual units. The SOM can be used to measure similarity amongst audio-visual speech percepts and to measure coarticulatory effects.
Tonal and durational variations as phonetic coding for syllable grouping
Authors: Xu Yi , Wang Maolin
Published: October 2013

While syllables in connected speech are generally believed to be prosodically divided into groups, how such grouping is done phonetically is not fully understood. This study explores the possibility that syllable grouping is partly realized through adjusting articulatory strength and duration. We compared the degrees of tonal undershoot in Mandarin as they are related to syllable position and number of syllables in words or phrases. The sequences consisted of 1–4 syllables with R or F tone and were produced by eight speakers. The all-R and all-F sequences impose great pressure on tone production and hence would best reveal the effects of strength and duration. Results show that as the number of syllables in each sequence increased, both syllable duration and size of F0 excursion decreased. Meanwhile, excursion size varied with syllable location in the sequence. But in each case it was the first and last syllables that had the largest excursions, and the excursion variations cannot be fully accounted for by duration. There thus appear to be both an isochrony effect and an ‘‘edge marking’’ effect. Taking into consideration known prosodic effects on segmental phonemes, syllable grouping as a communicative function seems to involve a rather complex encoding scheme.
The University of South Florida audiovisual phoneme database, v 1.0
Authors: Frisch Stefan A. , Hardin Sarah , Nikjeh Dee Adams , Stearns Adrienne M.
Published: October 2013

An audiovisual database of English speech sounds has been developed for teaching purposes. This database contains a variety of Standard English speech sounds produced in clear speech in isolated words. Phonemes are produced in word initial, word medial, and word final position, unless not allowed by English phonotactics. There is one example of each word spoken by a male talker of Standard American English from the Midwest. The database consists of individual word files that contain simultaneous audio recording, video of the lips, flexible endoscopic image of the pharynx and larynx, and ultrasound video of the tongue in the mid-saggital plane. The files in the database are uncompressed video avi format and are suitable for examination in the Wavesurfer freeware program (Sjolander and Beskow, KTH Stockholm). This database is intended as a multimedia reference for students in phonetics or speech science. Its coverage is relatively complete, though there are some gaps due to technical difficulties with the recording procedure. A demonstration of selected recordings from the database and suggestions for their use will be presented. Plans for further development of the database will also be discussed. [Work supported by a USF Innovative Teaching Grant.]
Derivation of moving-coil loudspeaker parameters using acoustical testing techniques
Authors: Anderson Brian E. , Leishman Timothy W.
Published: October 2013

A novel acoustical method of measuring small-signal moving-coil loudspeaker parameters has recently been developed. This technique involves the use of a plane wave tube to measure acoustical properties (e.g., reflection and transmission coefficients) of a driver under test (DUT). From this data, small-signal parameters are derived using curve-fitting techniques. Current loudspeaker parameter measurement techniques require measurement of the electrical impedance of the DUT. This paper will discuss the acoustical measurement apparatus, system modeling (via equivalent circuits), and a comparison of measured parameters to those derived using electrical techniques.
Secondary microphone calibration: Advantages on the use of the constant envelope sweeps
Authors: Soares Zemar M. D. , Hoffmann Walter E. , Muller Swen
Published: October 2013

With the objective of reducing the costs for the accreditation of secondary laboratories in the electroacoustical area without impairing the quality of the calibration of microphones, the Laboratory of Electroacoustics of INMETRO (Brazil) has investigated the advantages of using sweeps with user-defined spectral distribution and constant temporal envelope to obtain the impulse response between sound source and microphone. In applications in which the sensibility of the microphone in the free field is the objective, the use of anechoic chambers is fundamental. However, they can be substituted by applying a windowing of the impulse response to isolate the direct sound. The same technique can be used to separate reflections in the Jig for calibration of microphones in pressure field, as proposed by IEC61094-5. The calibration process presented here is based on FFT techniques, using a special sweep as excitation signal. The sweep is custom tailored in a way that its energy contents compensates the background noise spectrum. This way, the excitation signals’ signal-to-noise ratio becomes independent of frequency, while the sweep keeps an almost constant temporal envelope which contains the maximum possible energy. (To be presented in Portuguese.)
Gap detection and location in the precedence effect
Authors: Li Liang , Schneider Bruce A.
Published: October 2013

The nature of the precedence effect was investigated by introducing a gap into (1) both the leading and lagging sounds, (2) the lagging but not the leading sound, and (3) the leading but not the lagging sound. When a 50-ms gap was introduced into both sounds with an onset asynchrony equal to the delay between the leading and lagging sounds, the gap was perceived to occur only on the leading side as long as the delay between leading and lagging sounds did not exceed approximately 15 ms, even though the precedence effect itself broke down when the delay between the leading and lagging sounds exceeded approximately 9 ms. Gaps presented only in lagging sounds were always heard as occurring in the source position of the leading sound, but no gaps were perceived when the gap occurred only in the leading sound, rather, the listener heard a noise burst from the position of the lagging (suppressed) sound. The present results indicate that gaps in the lagging sound are perceived as belonging to the leading sound, whereas gaps in the leading sound release the lagging sound from ‘‘echo suppression,’’ indicating that higher-order (top–down) processes are involved in the precedence effect.
Estimating shallow water bottom geoacoustic parameters from ambient noise
Authors: Tang Dajun
Published: October 2013

Knowing bottom geoacoustic parameters is of great importance for using sonar systems effectively in shallow waters. In this paper, ambient noise data recorded on a vertical hydrophone array taken in the frequency range of 1000 to 3000 Hz were used. Forward modeling and model/data comparison show that the energy ratio of down-looking and up-looking beams, after a proper average over time and frequency, is the energy reflection coefficient of the bottom. From the reflection coefficient, critical parameters of the sediments, the sound speed, density, and attenuation coefficient, are obtained. Core data taken at the experimental site support the inversion results.
Geoacoustic inversion of ambient noise
Authors: Harrison Chris H.
Published: October 2013

The vertical directionality of ambient noise is strongly influenced by seabed reflections. Therefore, geoacoustic parameters can be inferred by inversion of the noise. In this approach, using vertical array measurements (16 m aperture), the reflection loss is found directly by comparing the upward with the downward going noise. Theory suggests that this simple ratio is, in fact, the power reflection coefficient (a function of angle and frequency). A layer model and a search is required to find geoacoustic parameters, but no such model or search is required for reflection loss alone. Experimental data have been gathered at 11 sites, 10 in the Mediterranean, and 1 on the New Jersey Shelf during BOUNDARY2001. Site to site variations are discussed, and comparisons are made with simple layer models. Usually the vertical array is bottom-moored, but at two of the Mediterranean sites the array was allowed to drift over a few miles so that bottom properties could be surveyed. Bottom variations could indeed be seen. Simulations using the parabolic equation to mimic spatial variations of bottom properties confirm that the bottom loss inferred from this type of measurement is indeed a local one rather than a regional average.
Midfrequency modeling of coupled-room performance spaces by computation of transmission coefficients of apertures and arrays of apertures
Authors: Summers Jason E. , Torres Rendell R. , Shimizu Yasushi
Published: October 2013

The shapes of the energy decays in a coupled-room system are functions of the energy transmitted by the coupling apertures relative to the irradiation strengths on the boundary surfaces of the rooms. At lower frequencies, the effective coupling areas depart from the geometrical aperture areas as the transmission coefficients of the apertures depart from unity. In order to better predict energy decays in coupled-room systems, transmission coefficients of apertures and arrays of apertures are computed. Power transmission coefficients are calculated for a number of source positions and numerically integrated to yield a random-incidence transmission coefficient. Computed aperture transmission coefficients are compared with analytical frequency-domain solutions for the transmission by circular and rectangular apertures. High-frequency statistical and geometrical models are modified to be applicable at midfrequencies by adjusting the coupling areas in the models according to their computed transmission coefficients. From these models the significance of non-geometrical aperture transmission on the reverberant decays in coupled-room systems is evaluated. Finally, the validity and low-frequency limits of these midfrequency models are evaluated by comparison with measurements of energy decay in actual coupled-room systems. [Research supported by the Bass Foundation.]
Study on ambient noise generated from breaking waves simulated by a wave maker in a tank
Authors: Wei Ruey-Chang , Chan Hsiang-Chih
Published: October 2013

This paper studies ambient noise in the surf zone that was simulated by a piston-type wave maker in a tank. The experiment analyzed the bubbles of a breaking wave by using a hydrophone to receive the acoustic signal, and the images of bubbles were recorded by a digital video camera to observe the distribution of the bubbles. The slope of the simulated seabed is 1:5, and the dimensions of the water tank are 35 m×1 m×1.2 m. The studied parameters of ambient noise generated by breaking wave bubbles were wave height, period, and water depth. Short-time Fourier transform was applied to obtain the acoustic spectrum of bubbles, MATLAB programs were used to calculate mean sound pressure level, and determine the number of bubbles. Bubbles with resonant frequency from 0.5 to 10 kHz were studied, counted from peaks in the spectrum. The number of bubbles generated by breaking waves could be estimated by the bubbles energy distributions. The sound pressure level of ambient noise was highly related to the wave height and period, with correlation coefficient 0.7.
Propagation variability and localization accuracy of infrasonic networks
Authors: Norris David E. , Gibson Robert G.
Published: October 2013

Prediction of propagation variability induced by the environment is used to evaluate the localization performance of infrasonic networks. The dominant source of variability affecting infrasonic propagation is believed to result from gravity waves. A gravity wave spectral model based on scale-independent diffusive filtering is used to generate multiple wind perturbation realizations. A Monte Carlo simulation is executed where rays are traced through the perturbed environmental fields, and uncertainty in ray travel time and azimuthal deviation is calculated. The propagation uncertainties, along with uncertainty in infrasonic measurements, are then used to compute 90 percent confidence bounds of multi-station event localizations. Infrasonic data from the April 2001 Pacific bolide event are used to compute the performance of a five station network, and the network localization is compared to that found from satellites. [Work sponsored by Defense Threat Reduction Agency, Contract No. DTRA01-00-C-0063.]
Results from a series of acoustic variability experiments
Authors: Siderius Martin , Nielsen Peter , Sellschopp Jurgen
Published: October 2013

A series of experiments were conducted in recent years by the SACLANT Undersea Research Centre to measure the effect of the environment on acoustic propagation. These broadband, shallow water experiments used a moored vertical array with both towed and fixed sound sources. During the fixed experiments the sound source was mounted on a steel frame tower that was resting on the seabed. This design was used to isolate the acoustic fluctuations caused by the environment from those due to source motion. During transmissions extensive measurements of the environment were made including range-depth profiling of the ocean sound speed along the propagation track using a vertically towed CTD (conductivity, temperature, and depth) chain. The seabed types at the sites varied from soft clay (sound speed less than in the water) to a highly reflective sand-gravel (sound speed about 1750 m/s). The temporal fluctuations and spatial structure of the received acoustic signals varied greatly between the sites. This had a big impact on propagation modeling for transmission loss; matched-field processing; and model-based, geo-acoustic inversion. In this paper an overview of these acoustic variability experiments will be described along with results showing the effect of the environment on model-based processing.
Reconstruction of transient behavior of a nonuniformly vibrating transducer
Authors: Sapozhnikov Oleg A.
Published: October 2013

An accurate prediction of a transient acoustic field radiated from piezoceramic transducers is important for many applications. The field can be calculated if the normal velocity distribution along the transducer surface is known. However, up to now, there are no reliable direct methods of surface vibration measurement in liquids. The well-developed laser vibrometer method can be employed only when the transducer is in contact with vacuum or gas because of strong acousto-optic interaction in condense media. In this talk, a holographic method is proposed to reconstruct the radiator vibration. The method includes a measurement of the temporal waveform in different points of a plane grid perpendicular to the acoustic axis at some distance from the source, theoretical time reversal of the waveform in each grid-point, and back propagation of the field to the source using the transient form of the Rayleigh integral. The reconstruction procedure is described and accuracy of the method is studied depending on grid-step, distance to the source, and dimensions of the grid. [Work supported by CRDF RP2-2384-MO-02 and RFBR 02-02-17029.]
Transmission of a large unfocused 120-kHz and 1-MHz ultrasound beam through the human skull
Authors: Coussios Constantin-C. , Holland Christy K. , Shaw George J.
Published: October 2013

A three-dimensional characterization of the acoustic beam produced by two 6-cm-diameter unfocused 120-kHz and 1-MHz transducers was performed both in the free field and inside a human skull penetrated through the temporal bone. In the context of transcranial ultrasound-enhanced thrombolysis, intracranial measurements aim at determining the effect of the skull on the beam structure and peak-to-peak pressure amplitude delivered to the middle cerebral artery, which has been identified as a common site for ischemic stroke. Placement of the 120-kHz transducer at least 3.5 cm away from the temporal bone yielded a beam pattern very similar to that in the free field with less than 4.5-dB attenuation in peak-to-peak pressure amplitude. Furthermore, short pulse durations reduced the effect of reflections from the far side of the skull and small rotations of the skull relative to the beam axis hardly affected the intracranial field. By contrast, the presence of the skull was found to strongly disturb the 1-MHz beam for all configurations and to cause as much as 20-dB attenuation in peak-to-peak pressure amplitude. Therefore, 120-kHz ultrasound requires less phase aberration correction and attenuation compensation than 1 MHz for therapeutic transcranial applications.
Health monitoring using Lamb waves. Application to the characterization of low impacts in aerospace structures
Authors: Grondel Sebastien , Assaad Jamal , Delebarre Christophe
Published: October 2013

This work was devoted to the development of a health monitoring system assigned to aerospace applications. The application concerned the detection of low damaging impacts on composite structures due to the extreme sensitivity of this material to this kind of solicitation. The chosen health monitoring was based first on the excitation and reception of Lamb waves along the structure by using thin piezoelectric transducers (active monitoring) and second on a continuous monitoring with the same transducers (passive monitoring). Preliminary tests were performed on a composite plate and the sensitivity of the A0 mode to the damage was demonstrated. Concerning the passive monitoring, the study showed the ability to use the acoustic signature of the impact to detect a possible damage. Further tests were performed on a wingbox composite structure. This wingbox structure consisted of composite skins with variable thickness mounted onto a metallic substructure. Moreover, four stringers were bonded on these skins. The aim was to demonstrate the ability of the system to perform rapid inspections of complex structures. After the application of a serial of impacts at diffent locations of the composite wingbox, the feasibility of the health monitoring was demonstrated.
Wavefront modeling in shallow water acoustics
Authors: Tindle Chris T.
Published: October 2013

Early work in collaboration with David Weston on the relationship between ray and normal mode propagation led to ray theory with beam displacement which showed that ray based solutions were not restricted to high frequencies. In turn this has led to acoustic wavefront modeling which allows the efficient calculation of transient acoustic fields in conditions of rapid range dependence. In wavefront modeling, conventional ray tracing is used to find the wavefronts but the amplitude, phase, and travel time of pulses are found from a depth–time diagram at the receiver range. The method allows for rapidly changing water depth due to surface waves. Reflection of sound beneath surface wave crests leads to focusing and caustics which are handled through approximations to a phase function. There is good agreement with experimental results. [Work supported by ONR.]
Noise sampling issues for impact/impulse noise surveys
Authors: Prince Mary M. , Vipperman Jeffrey S.
Published: October 2013

Noise-induced hearing loss (NIHL) has been recognized as a serious health concern for decades. ISO Standard 1999:1990 provides a means to predict noise-induced hearing loss (NIHL) based on LAeq measurements in the working environments of workers. This standard seems to work well for predicting hearing loss in continuous noise fields. However, it is possible that ISO 1999 does not apply well to impact, impulsive, or other transient noise fields. NIOSH and University of Pittsburgh are currently developing noise-sampling strategies to measure impact and impulse noise in a manufacturing environment with the aim of developing new impulsive noise metrics. As part of the study, broadband impact/impulse pressure measurements will be made. Issues such as instrumentation, data quality, repeatability, spatial sampling, equipment portability, and calibration are addressed. Also, the annotation, digitization, and editing of the waveforms will be discussed. As part of the project, an archival database of manufacturing impulse/impact will be created to support the future algorithmic development. The ultimate goal of the project is to develop new metrics to characterize the hazards of impact/impulse noise that will complement ISO 1999 for predicting NIHL.
Predicting noise-induced hearing loss in human populations. The contribution of the ISO-1999 and ANSI S3.44 standards
Authors: Prince Mary M.
Published: October 2013

This paper reviews the ISO-1999 and ANSI S3.44 standards and the literature related to prediction of noise-induced hearing loss (NIHL) in humans. The dearth of contemporary population-based studies of hearing loss among industrial, low noise-exposed individuals have made the ISO-1999 and ANSI S3.44 standards a key source of comparative data for assessing the risk of NIHL. This paper will highlight how these standards have been used in several published papers to examine the magnitude of NIHL risk, predictions of noise-induced thresholds in hearing conservation data, and to generate hypotheses regarding the biologic plausibility of hearing loss due to chemicals or other ototoxic agents.
Development of a fast method for determining psychophysical tuning curves
Authors: Sek Aleksander , Skrodzka Ewa , Moore Brian C. J.
Published: October 2013

A psychophysical tuning curve (PTC) is usually measured by determining the level of a narrowband noise required to mask a fixed low level tone, for several masker center frequencies. PTCs could be useful clinically for assessing frequency selectivity and for the diagnosis of dead regions in the cochlea. When the signal frequency falls in a dead region, the tip of the PTC is shifted away from the signal frequency. However, PTCs determined in the traditional way are too time consuming for use in clinical practice. A fast method for determining PTCs is being developed and evaluated. This uses a band of noise that sweeps in center frequency. A Bekesy method is used to track the masker level required for threshold. For normally hearing subjects, the new method gives stable results, and PTCs similar in shape to those determined in the traditional way, when the masker sweeps over a 2-octave range in about 4 minutes, and the level changes by 1–2 dB/s. Preliminary results using hearing-impaired subjects also show a good agreement with the traditional method. However, further work is required to determine optimum values for the noise bandwidth and rate of change of frequency and level.
Infants in cocktail parties
Authors: Newman Rochelle S.
Published: October 2013

Most work on listeners’ ability to separate streams of speech has focused on adults. Yet infants also find themselves in noisy environments. In order to learn from their caregivers’ speech in these settings, they must first separate it from background noise such as that from television shows and siblings. Previous work has found that 7.5-month-old infants can separate streams of speech when the target voice is more intense than the distractor voice (Newman and Jusczyk, 1996), when the target voice is known to the infant (Barker and Newman, 2000) or when infants are presented with an audiovisual (rather than auditory-only) signal (Hollich, Jusczyk, and Newman, 2001). Unfortunately, the paradigm in these studies can only be used on infants at least 7.5 months of age, limiting the ability to investigate how stream segregation develops over time. The present work uses a new paradigm to explore younger infants’ ability to separate streams of speech. Infants aged 4.5 months heard a female talker repeat either their own name or another infants’ name, while several other voices spoke fluently in the background. We present data on infants’ ability to recognize their own name in this cocktail party situation. [Work supported by NSF and NICHD.]
Tomographic measurements of sandy sediment sound speed and attenuation
Authors: Tang Dajun
Published: October 2013

During the SAX99, a tomographic system called the Acoustic Imager (AI) was developed to measure sound speed, attenuation and their variability in sandy sediments. It consists of 60 transducers arranged in a ring with a diameter of 29 cm placed in the horizontal plane. When the ring is pressed into the sediment at a certain depth, a set of sound speed and attenuation measurements is made. Taking data at different depths, a 3-D view of the sediment sound speed and attenuation can be obtained. In this paper, two kinds of measurements are reported. The first is measurements of sound speed at different locations over a depth of 10 cm with measurements taken every two cm. The second is a measurement at one location and one depth over a period of 48 hours to examine temporal variation of sediments. [Work supported by ONR.]