bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining the effects of low-frequency sound on the fish auditory system
Authors: Hastings Mardi C. , Finneran James J. , Popper Arthur N. , Lanford Pamela J.
Published: October 2005

A 15-m-long flexible waveguide was successfully used to create a traveling wave for frequencies below 300 Hz in water. A cylindrical waveguide that allows only plane-wave propagation was designed and fabricated from Plexiglas. This flexible material reduced the effective stiffness and thus the sonic speed and wavelength of the disturbance generated by a J9 underwater sound projector flanged to one end. In addition, the energy of the wave was dissipated as it traveled along the waveguide; consequently, little if any reflection occurred at its end. The fish were placed inside a PVC mesh cage and positioned in the waveguide approximately 3 m down from the J9. Then they were exposed to either a continuous wave or a pulsed wave similar to manmade sources. Afterwards the fish were held for a specified time period and then sacrificed. The auditory organs were treated with fixative and removed. Then they were shipped overnight to the University of Maryland where the tissue was immediately prepared for scanning electron microscopy to determine if sensory hair cells had been destroyed. This method has yielded dependable data to help assess the effects of low-frequency sound on hearing in fish. [Work supported by ONR.]
Applications of multifrequency acoustics: Spatial patterns in a freshwater lake
Authors: Greenlaw C. F. , Player R. W. , Samilo U. S.
Published: October 2005

Vertical profiles of acoustical scattering at four frequencies were obtained at a mesh of points covering the major regions of a small, manmade freshwater lake. Inversion methods were used to estimate size-abundance profiles of zooplankters using a scattering model validated for oceanic zooplankton such as copepods. These profiles were then used to form estimates of lake-wide 3-D spatial patterns sorted by size classes of the dominant zooplankters. Results illustrate the value of multifrequency acoustical surveys as an adjunct to conventional sampling for rapid assessment of spatial distributional features of zooplankton populations in lakes. Problems with applications of ocean-based assessment techniques to lacustrine environments, such as the lack of validated scattering models for freshwater zooplankton, are discussed.
A publicly accessible database for marine mammal call classification research
Authors: Mellinger David K. , Clark Christopher W.
Published: October 2005

A central problem in bioacoustic transient (animal sound) detection and classification has been the lack of standards against which to compare various methods. A similar problem existed in speech recognition research; it was solved by the creation of databases (e.g., TIMIT) used as common data sources for testing and comparing different methods. A similar database has been initiated for use in marine mammal sound detection and classification. Initially, mysticete sounds have been placed in the database; since their low frequency makes possible a low sampling rate, a large number of sounds may be stored in the space available. The database currently holds sounds of four species of mysticete—1765 blue, 3909 finback, 356 minke, and 589 bowhead whale vocalizations—at sampling rates from 100 Hz to 2 kHz. It was desired to categorize sounds by signal-to-noise ratio, since performance of detection methods will depend on this; since no measure of SNR for transient signals is well known, a simple measure of energy ratio within the sounds’ frequency band was used. The database includes performance data of some detection methods, and it is hoped that other researchers will contribute both sounds and performance data. The database is accessible at ftp.ornith.cornell.edu.
Development of 0–3 piezocomposite transducers for underwater applications
Authors: Geil Fred G. , Matteson Linda L.
Published: October 2005

Piezorubber is a composite material consisting of lead titanate powder dispersed in a neoprene rubber matrix. Piezorubber has certain acoustic properties that sets this transduction material apart from the traditional ceramics. Among these are some good qualities such as a high hydrostatic sensitivity, a relatively low lateral sensitivity, high resistance to shock, and conformability. Some less attractive qualities are the low dielectric constant and high density. Nevertheless, piezorubber has been the material of choice for several US Navy projects. These include a hydrophone flank array for ASW, a high-frequency array of small elements, a 700-element wide bandwidth listening array, a conformal shell-mounted low-frequency hydrophone, a continuous element for towed arrays, and high-frequency elements for side-looking sonars. These six projects will be described briefly, concentrating on the achieved benefits and what has been learned about applying piezorubber to hydrophone applications, also indicating the areas where the application was less than completely successful.
U.S. Navy 0–3 piezocomposite transducers
Authors: Pecoraro Mark L.
Published: October 2005

Interest in 0–3 piezoelectric composite materials for use in hydrophone applications has grown considerably in recent years. Designs which require operation in the hydrostatic mode with a large hydrostatic voltage coefficient gh, are desired to increase free-field voltage sensitivity and meet the ever increasing demands placed on hydrophone performance. U.S. Navy scientists at the Naval Research Laboratory, Underwater Sound Reference Detachment, have investigated the utilization of 0–3 piezocomposite for sonar applications and have developed various hydrophone configurations based on specific program requirements. The requirements of the programs, such as a lightweight, low-profile, and high receive sensitivity, demanded unique designs and the need for utilizing the unique characteristics of 0–3 composite materials. The hydrophones presented in this discussion used a 0–3 composite known at NRL simply as piezorubber or PZR. This material consists of lead titanate particles embedded in a neoprene elastomeric matrix. This discussion will cover the development, including problems and solutions, fabrication, and testing of two unique 0–3 composite hydrophones.
Evaluating speech quality with adaptive psychophysical methods
Authors: Kudumala Muralidhar , Espinoza-Varas Blas
Published: October 2005

This study examines some advantages of adaptive psychophysical tests for obtaining reliable and efficient estimates of speech quality. Specifically, in vowels corrupted by additive noise, noise-detection thresholds were measured adaptively. The 350-ms vowels were obtained by addition of the first 32–35 harmonics of 100–200 fundamental frequencies, with spectral envelopes appropriate for /i/ and /a/. Noise was synthesized by random-phase addition of harmonics of a 10-Hz fundamental; the noise bandwidth and the spectral envelope were equal to those of the vowels. In a 2IFC task, subjects had to determine the observation interval that contained a ‘‘noisy vowel.’’ During a block of trials, the noise level was varied using a ‘‘two-down, one-up’’ rule (Levitt, 1971); the test terminated when the subject completed 6–8 reversals, and thresholds were defined as the average noise level obtained in the last three reversals. The adaptive method yielded threshold estimates in much fewer trials than a constant stimuli procedure used in previous studies. The adaptive method was implemented in labview software, National Instruments DSP boards, and a Macintosh computer. [Work supported by OCAST.]
Development of a microcomputer based system for evaluating hypernasality in vowels of cleft palate patients
Authors: Kataoka Ryuta , Michi Ken-ichi , Okabe Kaoru
Published: October 2005

To evaluate hypernasality quantitatively, frequency analyses were performed on the Japanese isolated vowel /i/ produced by sixteen cleft palate patients with or without speech appliances and four normal subjects. These 26 speech samples were rated by 20 listeners. Analysis of the one-third-octave power spectra revealed an increase in power level between the first and second formant and a reduction in second and third formant regions among hypernasal speech samples. Factor analysis of the five-point listener’s ratings revealed that the consensus perception of hypernasality accounted for 75% of the total variance. Multiple regression analysis revealed a high correlation (0.82) between the perception of hypernasality and the peak levels of two clusters of 1/3-octave bands: the sixth, seventh, and eighth 1/3-octave multiples, and the tenth, eleventh, and twelfth multiples from the band containing the fundamental frequency. Based on these findings, a system for evaluating hypernasality was developed using a computer and 1/3-octave bandpass filter. This approach is presently being used to assess the relationship between velopharyngeal port area obtained from pressure-flow study and hypernasality evaluated by this system.
A noninvasive EM based speech feature estimation method for analysis and recognition of vocal fold cancer
Authors: Gavidia-Ceballos Liliana , Hansen John H. L.
Published: October 2005

The focus of this study is to formulate a speech parameter estimation algorithm for analysis/detection of vocal fold cancer, which does not require direct estimation of the glottal flow waveform. The proposed method separates speech components under healthy and assumed pathology conditions using a mixed excitation speech model. This problem is addressed using an iterative maximum-likelihood (ML) estimation procedure, based on the estimation-maximization (EM) algorithm. Two new features, termed enhancedspectralpathologycomponent (ESPC) and mean area peak value (MAPV) index are estimated and shown to vary consistently between healthy and pathology conditions. For classification, a hidden Markov model recognizer is formulated using MAPV and/or ESPC spectral features. Classifier evaluations using speech recordings from healthy and vocal fold cancer patients for sustained vowels, showed that while MAPV is a useful feature for vocal fold cancer detection (88.7%), superior performance was achieved using a finer spectral representation of ESPC (92.8%). Since direct glottal flow estimation is not necessary, the inability to accurately characterize vocal fold pathology due to incomplete glottal closure is no longer an issue. The results suggest that the ESPC feature can provide a noninvasive approach for analysis, detection, and characterization of speech production under vocal fold pathology.
Bistatic bottom scattering at high frequencies: Experiment and model comparison
Authors: Williams Kevin , Jackson Darrell
Published: October 2005

In 1993 a special research program on Coastal Benthic Boundary Layers (CBBL) was begun. As part of that program an autonomous, spatially scanning, sonar system was deployed in a well characterized regions in the Baltic Sea and off the coast Florida. The goal was to examine high-frequency acoustic scattering from the sediment. This sonar operated at 40 kHz, had a 5° horizontal beamwidth, and acquired backscattering data within a 50-m radius area at least once an hour for several weeks at each site. During part of each deployment it operated in conjunction with a mobile receiving array so as to acquire bistatic data. The bistatic experimental apparatus, procedures, and results are presented. Finally, a recently developed bistatic model (driven, in part, by the environmental parameters measured at the experimental site) is tested against the experimental results. [Work supported by NRL CBBLSRP program.]
Spatial coherence of high-frequency (67-kHz) acoustic fluctuations in fully developed turbulence
Authors: Buckingham Michael J. , Potter John R. , Deane Grant B.
Published: October 2005

As part of ONR’s high-frequency initiative, a field experiment to determine the temporal and spatial coherence of acoustic fluctuations induced by propagation through a fully developed turbulent flow has been planned in collaboration with several other research groups for late September 1994. Narrow-band measurements (67-kHz coded signals) will be taken in Cordova Channel, British Columbia, where strong, semidiurnal tidal flows (up to 1.0 m/s) create fully developed turbulence (Reynolds number ≊107), and strong mixing prevents stratification (bulk Richardson number ≊0.02). Prior experiments have established the turbulent nature of the flow and examined the horizontal arrival angle and intensity fluctuations with time. In the present experiment, a new compact acoustic array, consisting of 128 hydrophones in an elliptical configuration, is being adapted to monitor the acoustic arrivals in the vertical and horizontal, with finer spatial resolution than has previously been obtained. Amplitude and phase data will be recorded from 15 channels. Environmental data from ADCPs, turbulence meters, side-scan sonars, microstructure instruments, CTDs, etc., will be available to help interpret the acoustic results. Preliminary results of the acoustic fluctuation experiment will be presented, with an analysis of the fine-scale phase and intensity coherences, which are intimately related to the microstructure of the transmitting medium.
High-frequency sound variation in a coastal environment
Authors: Jaffe Jules S.
Published: October 2005

Despite the proliferation of high-frequency sonar imaging systems, the variability of high-frequency sound propagation in shallow water has only recently been measured. In a series of experiments adjacent to the Scripps Institution of Oceanography pier, the variability of sound at a frequency of 450 kHz has been measured. The experimental measurement consisted of deploying a multibeam imaging system on a tripod in approximately 20 ft of water. Repeated insonification and subsequent measurement of the backscattered waveforms indicate that a large degree of variability can exist in the backscattered data. In order to define whether the source of the variability in the backscattered data was originating from the bottom or the volume, a corner reflector was deployed. Assuming that the variability in the sound reflected from the bottom consists of the superposition of both volume and the bottom variability, and that the sound from the corner reflector consists of variability only from the volume, assignment of the relative importance between the two forms of variability can be made. The importance of these two sources of variability as a function of environmental conditions such as tide and surface conditions will be presented. [Work supported by ONR.]
Dereverberation of shallow-water, high-frequency signals
Authors: Nam Jean O. , Fricke J. Robert
Published: October 2005

Propagation of high-frequency signals, O(10 kHz), in a shallow-water channel, O(10 m), is complicated by multipath effects associated with the surface and bottom. The goal of this research is to dereverberate the time spread and dispersed received signal into a processed signal with a temporal duration comparable to that of the outgoing pulse. Given the impulse response of the channel and the received signal, an inverse filtering method utilizing minimum-phase components can be effective. However, because of channel dynamics caused by turbulence, internal waves, and thermal stratification, calculation of the exact impulse response is impossible. A more robust signal recovery method, known as cepstral smoothing, has been developed to separate the signal from the channel impulse response in the cepstral domain. Using this method, the recovery is independent of the channel impulse response and is robust in the presence of additive noise. The cepstral smoothing method dereverberates the original signal, but absolute time delay information is lost. A moving rms window applied to the original received signal recovers the lost time delay.
Shallow-water reverberation measurement and prediction
Authors: Miller James H. , Muggleworth Charles E. , Chiu Ching-Sang , Lynch James F.
Published: October 2005

In August 1992, a shallow-water, low-frequency reverberation measurement was made in the Barents Sea utilizing explosive SUS charges as sound sources and a middepth hydrophone as the receiver. The objectives of this work were to analyze the reverberation data from this experiment, compare several theories which have been proposed to model reverberation, develop a technique for estimating the bottom backscattering coefficient in shallow water from single hydrophone acoustic data, and determine the reverberent characteristics of the experimental region. The three-dimensional Hamiltonian Acoustic Ray-tracing Program for the Ocean (harpo) was used as the primary propagation modeling tool. The temporal signal processing consisted of a short-time Fourier-transform spectral estimation method applied to data from the single hydrophone. Chapman’s source spectrum model was used. A bistatic Lambert’s Law with a frequency-dependent constant was found to fit the data from the experiment. A statistical analysis showed that the reverberation from the Barents Sea experiment was Gaussian to a high degree of confidence.
Source localization via received arrival time structure analysis
Authors: Stotts S. A. , Bedford N. R.
Published: October 2005

An efficient and robust method has been developed to locate impulsive sources in an ocean environment. A sonobuoy field was first deployed in a ring-type pattern. GPS receivers were installed on the buoys to obtain their locations within a few meters of accuracy. Charges were then set off at arbitrary locations within the ring. High-resolution plots were used to obtain direct path and first bottom bounce arrivals on each buoy. A model grid of arrival times was constructed, corresponding to the dimensions of the buoy field. A ray model previously developed here at ARL:UT [E. K. Westwood and P. J. Vidmar, J. Acoust. Soc. Am. 81, 912–924 (1987)] was used to obtain model travel times. The minimum value of the least-square error between the real arrival times and the modeled travel times resulted in an unambiguous location of the source, within the limits of the grid spacing chosen. This value was calculated by picking one phone as the reference and then summing the errors of each phone relative to the reference. Successive iterations with finer grid spacings results in source location within the accuracy of the buoy locations. Results obtained at Lake Travis and the Gulf of Mexico will be presented. [This work is supported by Navy Strategic Systems Programs.]
Priming and the enhancement of concurrent vowels
Authors: Paschall D. D.
Published: October 2005

Experiments were conducted to determine whether listeners with normal hearing can exploit information in a prior sample of speech to segregate a target voice from a second, competing voice. There are at least two ways that exposure to a prior sample of speech might aid the perceptual segregation of voices. First, peripheral adaptation processes can reduce the auditory response to preexisting sounds in order to enhance newly arriving energy associated with the onset of a second voice. Second, perceptual grouping based on harmonicity or spectrum envelope cues can reduce the interfering effects of preexisting sounds. To separate the contribution of these factors, concurrent vowel pairs were preceded by a precursor which had either the same F0 and spectrum envelope as one of the vowels (‘‘voiced vowel’’ precursor), the same F0 but a flat spectrum envelope (‘‘buzz’’ precursor), or the same spectrum envelope as one of the vowels, but with noise excitation (‘‘whispered vowel’’ precursor). All three types of precursors resulted in increased accuracy when the precursor was brief (200 ms). When the precursor was 1 s, only the voiced vowel precursor led to an increase in identification accuracy. These results suggest that both adaptation and perceptual grouping may play a role.
Modeling formant frequency discrimination for isolated English vowels using excitation patterns
Authors: Zheng Yijian , Kewley-Port Diane
Published: October 2005

Thresholds for formant discrimination across three sets of female and male vowels with different F0 were significantly different in a recent report [Kewley-Port etal., J. Acoust. Soc. Am. 95, 2978(A) (1994)]. This analysis examined whether excitation patterns could model these and other effects of stimulus parameters on formant thresholds. The goal was to determine if an ‘‘auditory metric’’ would be constant across the three stimulus sets when ΔF thresholds varied by 25 Hz. A separate discrimination study showed that listeners only attend to harmonic components within a restricted region near the formant [Sommers and Kewley-Port, J. Acoust. Soc. Am. 93, 2422(A) (1993)]. Based on those results, four critical bands around the altered formant were selected, and the area between the critical-band spectra for the standard and just discriminable vowel was calculated. This spectral distance across formant frequency and gender was shown to be constant in three analyses: (1) ΔF threshold differences across the three sets of vowels were no longer significant; (2) slopes for ΔF thresholds (approximately 1.0) were flat for spectral distance; (3) variability of spectral distance across F1 and F2 is significantly smaller than that of ΔF thresholds. Results suggest that the auditory system has an inherent nonlinear transformation which changes threshold differences to be almost constant in the internal representation.
Modeling listeners’ categorization of a large F1-F2-F3 continuum
Authors: Nearey Terrance M. , Kiefte Michael
Published: October 2005

A number of alternate spectral representations have been suggested for vowel spectra [see H. Hermansky, J. Acoust. Soc. Am. 87, 1738–1752 (1990)]. To better evaluate the perceptual relevance of some of these, 972 vowels were synthesized. The stimuli were each 115 ms in duration with a falling F0 contour (125–100 Hz). F1 ranged (in 0.5 Bark steps) from 250 to 760, F2 from 750 to 2260, and F3 from 1360 to 3080 Hz. F4 and F5 were fixed at 3500 and 4500 Hz, respectively. (Constraints were placed on formant separations to ensure relatively natural stimuli.) Fifteen speakers of Western Canadian English categorized the stimuli as the vowels /i, i, e, eh, æ, inverted vee, inverted open aye, o, u, u, hooked backward eh/. Preliminary results indicate that while nominal synthesis formant frequencies can provide a relatively good fit to the data, alternate representations such as cepstral coefficients based on Hermansky’s PLP analysis may provide moderate improvements of fit. However, linear transformations of the PLP cepstra show strong correlations with formant frequencies [similar to those noted by D. Broad and F. Clermont, J. Acoust. Soc. Am. 86, 2013–2017 (1985)]. [Work supported by SSHRC.]
The effects of pitch changes on the perception of vowel sequences
Authors: Nordenstrom Benita K. , Chalikia Magdalene H. , Ebsen Elizabeth M.
Published: October 2005

When listeners hear a repeated sequence of steady-state vowels (of the same duration and pitch) phonemic transformations occur, and they report hearing words and phrases absent in the original stimulus. A previous study [M. H. Chalikia, R. Meyer, and R. Lindemann, 34th Psychon. Society Meet. (1993)] investigated the possible effects of variations in vowel duration, pitch, or both. Listeners successfully matched these vowel sequences to the verbal forms heard with vowels of equal duration and pitch (base-line stimuli). In this study a broader variation in pitch was employed, and the vowel sounds were computer-generated rather than naturally produced. Six base-line sequences of six 60-ms vowels (at 100 Hz), followed by a 300-ms silent gap, were used. Four variations of these were created by randomly changing the pitch of individual vowels. Most listeners were able to match the modified vowel sequences to the verbal forms heard with the base-line stimuli, thus confirming the robust, stable nature of the verbal organizations. It is suggested that these organizations are based upon objective acoustic characteristics, and the present stimulus manipulations were probably perceived as prosodic variations.
Perceptual implications of selected aspects of vocal behavior
Authors: Campbell Shari L.
Published: October 2005

The perceptual dimensions derived from acoustical changes associated with vowel quality, voice quality, voice classification, and gender are not clearly defined. This project uses the trained singing voice as a source of controlled variation in parameters important to the timbre of both speech and voice. A database of vowels was collected from 18 singers representing six major voice classifications. Repetitions were made of three vowels at three or four fundamental frequencies and at three dynamic levels in normal register. Six subjects also attempted to match loudness (as indicated by a target of equal phons) for this isoparametric condition. Spectral measures (e.g., FFTs, STFTs, 1/3-octave band levels) were transformed in a manner intended to approximate perceptually relevant aspects of auditory processing (e.g., loudness and sharpness densities and loudness and sharpness over time). By comparing the spectral measures with their transformations, it may be possible to make inferences concerning which acoustical changes are perceptually relevant, and about the nature of their perceptual representation. [Work supported by the Institute for Perception Research, Eindhoven, The Netherlands.]
Five axis programmable positioning system for underwater acoustic measurements at Penn State
Authors: Becker Kyle M.
Published: October 2005

To facilitate underwater acoustic measurements at Penn State, a five axis computer controlled positioning system has been developed by the author and installed in the new water tank facilities at the Applied Research Laboratory. Providing linear motion in three directions and rotations about two axes, the system allows an acoustic transducer to be positioned and oriented at virtually any position and direction within the water tank. Motion is controlled along each axis via programmable controllers (indexers) which are in turned accessed by a computer via RS 232. Resolution in the linear directions is 0.005 in. Angular resolution is 0.18°. Working in conjunction with the appropriate data-acquisition hardware and software, the positioning system allows the entire measurement procedure to be automated. Although designed initially for use in monostatic and bistatic surface scattering experiments, the system is also being used for other interesting underwater experiments, including bottom sediment studies, and the effects of thermal gradients on acoustic signals.
The design, construction, and performance testing of an acoustical agglomeration chamber
Authors: Dudes Laura A. , Prasad M. G. , McAlevy R. F.
Published: October 2005

An acoustical agglomeration system is an apparatus which can be used to enhance the efficiency of current particulate removal devices. This study presents the design and construction of an acoustical agglomeration chamber and associated measurement instrumentation. The system consists of a main chamber 3.05 m long with an inner diameter of 0.075 m. The dimensions are sufficient to develop the particulate gas stream as well as acoustical plane-wave fields up to 2500 Hz. The inlet flow velocities of the gas stream range from 0.5 to 5 m/s with operating pressures ranging from 101 to 1010 KPa. A midrange (e.g., 200–4000 Hz) heavy duty electroacoustic driver is used as the sound source. The particulate size distribution is optically measured with a Malvern 2600 laser particle sizer. A silencer was used to reduce the noise level coming out of the agglomeration chamber. The performance testing of the agglomeration apparatus was carried out using aluminum oxide particulate with frequencies of 1 and 2 kHz in the range of sound-pressure levels between 140 and 160 dB. An increase in particulate size from 16 to 26 μm was achieved in the preliminary measurements. This study will have applications in reducing emission of hazardous, fine particulate into the atmosphere. [Work supported by New Jersey Hazardous Substance Management Research Center.]
Characterizing the performance of piezoelectric ceramic as a function of stress, electric field, and thermal history
Authors: Smith R. Lowell , Bray Alan V.
Published: October 2005

The relatively recent development of large flextensional and other low-frequency, high-power transducers has stimulated renewed interest in the performance of piezoelectric ceramic under conditions of high stress and electric field. This paper addresses the development of special fixturing for the assembly and testing of structures emulating the use of PZT-8 material in high-power projectors. The test fixtures themselves are Tonpilz oscillators. Using a system of four tie rods, axial loads as high as 2.2×105 N (50 000 lbf) can be applied. The tie rods are fitted with strain gauges so that load can be monitored as often as desired during the course of aging and stress and electrical drive sensitivity studies. Initially data were acquired for combined static and dynamic stress in a controlled thermal environment. The performance characteristics of the piezoelectric ceramic are inferred from electrical admittance measurements. Providing for the incorporation of extensometers and closed-loop control of axial stress allows the fixtures to be used for a number of broader applications such as measurement of the viscoelastic properties of ceramic. [Work supported by SPAWAR.]
An experimental investigation of bubble shapes from a nozzle in water
Authors: Choi B. K. , Yoon S. W.
Published: October 2005

The shape oscillations of bubbles from a nozzle in water have been well investigated by Longuet-Higgins [M. S. Longuet-Higgins, J. Fluid Mech. 201, 543–565 (1989)]. In the present paper the elliptical deformation due to a bubble rising in water is introduced in the Longuet-Higgin’s theory. The bubble shape oscillations in water are also experimentally observed using a stroboscope photographic technique. The theory with an elliptical deformation condition well describes the experimental observation of bubble shape oscillations. The dependence of antipole time on bubble radius shows good agreement between the theoretical estimation and the experimental observation. [Work supported by the Korea Science and Engineering Foundation.]
Phase locking of nonlinear monopoles with reactive coupling
Authors: Felman Svetlana , Kobelev Yuri , Ostrovsky Lev , Soustova Irina
Published: October 2005

Recently it was shown that a system of coupled nonlinear acoustic oscillators such as bubbles in a liquid may generate a coherent radiation starting from the initially incoherent state. However, such an active (radiative) coupling is typically weak, especially if the size of the system is smaller than the acoustic wavelength. Here a stronger, reactive coupling, such as an interaction of bubbles via the potential fluid motion around them, is considered. It is shown that an initial incoherent phase distribution is unstable only for the excitation level exceeding a definite threshold. For a nonlinear stage of generation a three-mode analytical model is used, permitting one to perform a phase-plane investigation of a system and to estimate the amplitude and duration of the generated coherent pulse. From the viewpoint of nonlinear dynamics, such an effect is an example of a ‘‘chaos–order’’ transition in a Hamiltonian system (although chaos may be just a lack of coherence). The role of small dissipation is also considered. Some estimates are made for the ensemble of bubbles in a liquid. a)Now at Univ. of Colorado at Boulder, CIRES, ETL/ERL/NOAA, 325 Broadway, R/E/ET, Boulder, CO 80303.
Mass diffusion in spark-induced vapor bubbles
Authors: Allen J. S. , Averkiou M. A. , Crum L. A. , Young C. M. , Hess G. R.
Published: October 2005

The diffusion of gas into a spark-generated vapor bubble is shown to be an important factor when attempting to generate repeated oscillations of the bubble. Predictions for the radius–time curve based on the Trilling equation are matched with experimental measurements and the equilibrium radius is deduced. The effect of the ambient, hydrostatic, and vapor pressures of the liquid on the bubble collapse time is demonstrated. The high-frequency approximation of the first-order solution of the Eller–Flynn formulation for mass diffusion is utilized to estimate the amount of gas diffused into the bubble at the end of a single cycle. An increase in the bubble radius and collapse time is noted and this process is repeated for an extended number of cycles. The frequency signature of the resulting bubble oscillation is analyzed. The increase in the bubble radius and the period of oscillation due to diffusion, and the gas-microbubble residues remaining after collapse, have potentially important effects when generating a repeated sequence of vapor bubbles, as in extracorporeal shock wave lithotripsy. [Work supported in part by the U.S. Navy and the National Institute of Health.]
Forward-masked intensity increment thresholds at two recovery times
Authors: Nizami Lance , Schneider Bruce A.
Published: October 2005

Forward-masked just-noticeable differences were obtained from two listeners using a two-interval forced-choice procedure. In one of the intervals, a 2-kHz, 200-ms masker preceded a 2-kHz Gaussian-shaped tone pip (σ=0.5 ms). The other interval contained the same masker followed by a comparison tone pip. The listener’s task was to identify the interval containing the louder tone pip. Within a block of trails both masker intensity (range =10–80 dB SPL) and masker-target time gap (3 or 80 ms) were kept constant. The intensity of the standard tone pip (before multiplication by the Gaussian envelope) was always set to 20 dB above the level of the masker. When intensity-increment thresholds are plotted as a function of masker level at both time gaps, thresholds rise to a maximum at a masker level of 50 dB SPL before declining again. This pattern may be consistent with the idea of two intensity-processing channels, one for louder sounds and one for softer ones [see F.-G. Zeng, C. W. Turner, and E. M. Relkin, Hear. Res. 55, 223–230 (1991)]. [Work supported by NSERC.]
Effect of the level difference between leading and trailing stimuli on pitch, loudness, and binaural perception
Authors: Aoki Shigeaki , Houtgast Tammo
Published: October 2005

The total perception for pitch and loudness as a function of level difference between the leading and trailing stimuli is investigated using the same stimulus configuration and measuring the paradigm which clearly showed that the dominance of the leading stimulus depends on the level difference [S. Aoki and T. Houtgast, Hear. Res. (1992)]. A brief stimulus of 20 ms is subdivided into two parts with durations T1 and T2. Each part consists of a sinusoidal signal of either 1 or 2 kHz for pitch perception, or each part consists of a 2-kHz sinusoidal signal with either + or −3 dB for loudness perception. The measuring paradigm aims at assessing the critical ratio T1/T2 for which both parts contribute equally to the overall sensation of pitch or loudness for these brief stimuli. In contrast to the earlier study on dichotic cues, the effect of the level difference between the leading and trailing stimuli on pitch perception is found to be smaller and discontinuous. The effect on loudness perception is found to be greater and symmetrical. It is also found that the characteristic curves of these perceptions form a meaningful triangular area.
Efferent adaptation and fatigue: The effect of contralateral noise on spontaneous otoacoustic emissions
Authors: Dykstra Gregory L.
Published: October 2005

Mott etal. [Hear. Res. 38, 229–242 (1989)] have shown that both frequency and amplitude of spontaneous otoacoustic emissions (SOAEs) can be modulated by contralateral acoustic stimulation. They also examined the effects of stimulus durations up to 4 min in search of long-term adaptation, but none was found. Because the driven rate of efferent fibers declines by only about one spike per second per minute [M. C. Liberman and M. C. Brown, Hear. Res. 24, 17–36 (1986)], longer durations might be necessary to observe efferent adaptation/fatigue. In the present study, SOAEs of three subjects were measured in the presence of contralateral narrow-band noises with various frequency characteristics and with durations of up to 60 min. The hypothesized effect—an initial decline in SOAEs amplitude under contralateral stimulation followed by a return to preexposure levels with the onset of efferent adaptation—was not consistently observed. While seen in some sessions for some subjects, it could not be brought under experimental control. Thus these results were in approximate agreement with the findings of Mott etal. Some methodological and functional implications of these findings will be discussed. [Work supported by a NIDCD grant to D. McFadden.]
Processing of nonlinguistic auditory stimuli in Landau–Kleffner Syndrome: A case study
Authors: Kussmaul Clifton , Baynes Kathleen , Kegl Judy
Published: October 2005

‘‘Acquired aphasia with convulsive disorder’’ or Landau–Kleffner Syndrome (LKS) was first described in 1957 [W. M. Landau and F. R. Kleffner, Neurology 7, 523–530 (1957)]. This language disorder typically manifests as a decline in verbal expression and comprehension in children who had been developing normally. EEG is always abnormal, although clinical seizures are not always observed. This report presents a 26-yr-old right-handed female who was diagnosed with LKS at age 4 with an abnormal EEG and seizure activity. Her EEG, MRI, and audiogram are now normal, but PET demonstrates bilateral temporal lobe hypometabolism. A detailed linguistic comparison of her limited spoken English and relatively good signed English is reported elsewhere [K. Baynes etal., Int. Neuropsychol. Soc. (submitted)]. Interestingly, she listens to and enjoys several types of music. This discrepancy motivates our initial investigation of her ability to perform nonlinguistic auditory tasks. Despite easy recognition of environmental sounds, discrimination thresholds of pitch and rhythm are greatly exaggerated. Such data can clarify which brain processes are specific to language, and which correspond to more general auditory or hierarchical processing. [Work supported by NIH.]
Personal sound
Authors: Druyvesteyn W. F. , Aarts R. M.
Published: October 2005

Introducing more audio/video equipment (CD, DCC, TV, CD-I, etc.) into a room creates a new audio problem, one of multiple sound sources with multiple listeners. When different persons, denoted as A, B, C, etc., listen to different programs, denoted as ‘‘a,’’ ‘‘b,’’ ‘‘c,’’ person A experiences program ‘‘a’’ as sound and programs ‘‘b’’ and ‘‘c’’ as noise. Each person would prefer a high sound/noise (S/N) ratio at his listening position. In this contribution the situation of two persons working with their (multimedia) PCs in an office, or watching in a living room two TVs with accompanying sound, is considered. In order to obtain a specification, listening tests were done, which gave a desired S/N ratio of about 20 dB(B). In an anechoic environment such a specification is easily realized using a loudspeaker array to control the directivity. In a real (living) room this is not sufficient and active noise control (to decrease N) and active sound control (to increase S) are used, particularly in the low-frequency region. During the presentation at the conference, recordings will be reproduced of realized S/N ratios of 34 dB(B) in the anechoic room and of more than 20 dB(B) in a living room.
Multisensory interaction: Influence of spatial visual cues on auditory detection
Authors: Parlitz Dietrich
Published: October 2005

Recent physiological and psychological studies suggest spatiotopic maps of auditory space often build up by groups of multisensory neurons. At this neuronal level stimulus representations of different modalities seem to be transformed into a common coordinate system. A multimodal stimulus may produce enhancement, depression, or no interaction effect on the cell activity, depending on its certain spatiotemporal combination. In several experiments the influence of visual cues on auditory perception was examined. The results indicate a dependence on spatial and temporal parameters. [Work supported by DFG.]
Extending the perceptual magnet effect to a CVC word context
Authors: Eyraud Richard , Kuhl Patricia K.
Published: October 2005

Recent research by Kuhl and her colleagues has demonstrated a perceptualmagneteffect in vowels and consonants suggesting that perceptual organization is strongly influenced by category goodness. Equidistant stimuli cluster around the best exemplars of a category, demonstrating poorer discriminability and decreased perceptual distances. Conversely, regions surrounding the worst exemplars of a category are ‘‘stretched,’’ demonstrating relatively better discriminability and increased perceptual distances. The present experiments extend this finding to a word context by investigating the perceptual organization of the American English vowel /i/ in isolation and in a CVC word context, specifically /bid/. In the vowel experiment, eight variants of /i/ were synthesized by independently changing F1 and F2. Similarly, in the CVC word experiment, eight variants of the word /bid/ were synthesized by independently changing the vowel steady states of F1 and F2. Adult monolingual speakers were asked to judge the goodness of each variant and the similarity of paired tokens on a seven-point scale. Multidimensional scaling analyses demonstrated a similar perceptual magnet effect in both the vowel and CVC word experiments. These results suggest that the perceptual magnet effect observed with phonetic units extends to the lexical level, possibly contributing to lexical access. [Work supported by NIH.]
Sensitivity analysis of the Green’s function parabolic equation model for atmospheric sound propagation
Authors: Dobry Michael R. , Hansen Robert P. , Marlin David H.
Published: October 2005

A sensitivity analysis was performed on the Green’s function parabolic equation (GFPE) model to determine parameter bounds which maintain model validity. To determine these bounds, inverse theory was used to determine the ‘‘best’’ combination of input parameters over a two-dimensional domain using a normalized sum of squared residuals. A two-dimensional version of the fast field program (FFP), a widely accepted atmospheric propagation model, was used as comparison. Plots of the error surface were then made to show sensitivity bounds. Upward and downward refracting atmospheres were considered for a range of frequencies. The GFPE model was found to require a height increment parameter of about 0.05 wavelengths while the range increment parameter extended from 10 to 120 wavelengths depending on atmospheric profile and frequency. The thickness of the attenuation layer was found to be frequency dependent and ranged from 50 to over 200 wavelengths. The surface wave integral height was found to be a minimum of 30 and 13 wavelengths for the upward and downward atmospheres, respectively. The CPU time for the GFPE model ranged from 10 to 60 s, depending on frequency, and was approximately 60–1000× faster than the two-dimensional FFP.
Learning to perceive and produce American English vowels: A study of speakers of Brazilian Portuguese
Authors: Szpigel Marialice , Bell-Berti Fredericka
Published: October 2005

Brazilians who are fluent in English have more difficulty perceiving and producing American English vowels than consonants. This study examines vowel perception and production by ten native speakers of Brazilian Portuguese who had begun the sixth year of study of American English (at the Instituto Brasil-Estados Unidos, Rio de Janeiro, Brazil). At this level, all students are able to speak English fluently, but with varying degrees of proficiency; within the program constraints, the subjects were chosen to represent different levels of English proficiency. These bilinguals’ perception of American English vowels (produced by native speakers of American English) will be compared to the reported perception of American English vowels [G. Peterson and H. Barney, J. Acoust. Soc. Am. 39, 151–184 (1952)]. The bilinguals’ productions of 15 American English vowels were identified by six teachers of English (three native Americans and three native Brazilians), with extensive experience teaching English. Ability to perceive the American English vowels will be related to production ability, for the group and for the two best and two poorest students. [Work supported by St. John’s University and by NIH Grant No. DC-00121 to the Haskins Laboratories.]
Baseline acoustic parameters for nasalized vowels in English and French
Authors: Chen Marilyn Y.
Published: October 2005

Acoustic analysis of nasalized vowels in the frequency domain indicates the presence of extra peaks, one between the first two formants with amplitude P1 and one below the first formant with amplitude P0; the first-formant amplitude A1 is also reduced relative to its amplitude for a nonnasal vowel. These acoustic characteristics may be explained by speech production theory. The objective of this study is to determine the base line values for the acoustic parameters in quantifying nasality. A1-P1 and A1-P0 were tested as measures of nasality by comparing vowels adjacent to nasal consonants and those adjacent to stops for English speakers. For high vowels, A1-P1 is a better parameter to distinguish nasal vowels from non-nasal vowels, with an average difference of 10 dB; however, A1-P0 is better for low vowels, with an average difference of 7 dB. French nasal vowels adjacent to stops were also examined. To further test these parameters as measures of nasality, they were systematically manipulated in synthetic speech and presented in perceptual experiments. High correlation was obtained between nasality perception and normalized acoustic parameters. [Work supported by NSF, NIH, and LeBel fellowship.]
Dialect differences in vowel production and perception
Authors: Faber Alice , Best Catherine T. , Di Paolo Marianna
Published: October 2005

Earlier work [Faber etal., J. Acoust. Soc. Am. 94, 1865 (1994)] reported differences among American-English-speaking listeners from Utah and Connecticut/NY in perception of the HEEL–HILL and POOL–PULL contrasts (pairs that are nearly merged in Utah but distinct in the northeast US), measured by three tasks, labeling, AXB discrimination, and keyword identification. On these tasks, a few CT/NY listeners (those with parents from the southern US) performed differently from the other subjects. Their vowel spaces also were qualitatively different from those of the other listeners, based on acoustic analysis of three readings of the keywords. The CT/southern listeners had more high back crowding and did better on Utah POOL/PULL than the other listeners, while the Utah listeners had more high front crowding and did better on Utah HEEL/HILL. These results accord with the literature reviewed by Bradlow [Cross-LinguisticStudyofVowelInventories, Cornell (1993)] relating listeners’ ability to discern small vowel differences to the number of vowels in their language, but were tentative because of the small number of CT/southern subjects. The current study presents perception and production data from additional Connecticut/NY subjects confirming the original finding. [Work supported by NIH.]