bluuebunny/crossref_metadata_2025 huggingface dataset:
MacCAD, a new Macintosh-based Hypercard program for central auditory diagnostics: Description and preliminary findings
Authors: Lauter Judith L. , Solomon Nancy , Coe Colette
Published: October 2005

Although most components of the classical auditory system lie between the periphery and association cortex, our information about auditory disorders is limited primarily to those extremes. This ignorance is due to the fact that until recently, appropriately sensitive methodologies, both in terms of test design as well as modes for noninvasive brain monitoring, have not been readily available in the clinic. MacCAD is an attempt to address the first of these issues; a companion paper will report on results combining MacCAD with noninvasive physiological testing [repeated evoked potentials (REPs)]. MacCAD brings features of basic-research test design into the clinic, including: ease of use by both tester and client, monaural and dichotic modes for a variety of speech and nonspeech sounds, expansion capability for additional sounds, graduated difficulty for each sound set, client control of test pacing, automatic stimulus/response recording, trial-by-trial feedback, and analysis options including trial-by-trial monitoring, confusion matrices, and percent correct for individual sounds and complete sets. Initial field testing with populations predicted to have damage between periphery and language cortex, including adults with central auditory dysfunction, multiple sclerosis, Parkinson's disease, and presbyacusis, indicates that MacCAD's unique features may render it sensitive to individual characteristics which, when interpreted in the context of results on other tests such as evoked potentials, may be indicative of auditory dysfunctions which are invisible to standard audiological testing. [Work supported in part by Apple Computer, Inc., Community Affairs, with the American Speech-Language-Hearing Foundation.]
On the analysis of fluid-structure interaction from the perspective of instantaneous intensity
Authors: Romano Anthony J. , Williams Earl G. , Schuette Lawrence C. , Russo Kevin L.
Published: October 2005

A new formulation for the structural intensity in thin shells is presented, as well as a method for determining the tangential displacement components within the shell given a knowledge of the normal displacement and surface pressure. These techniques are then applied to real, experimental data taken on a point-driven, fluid-loaded, cylindrical shell. A video will be presented that displays, simultaneously, the instantaneous structural intensity, as well as the instantaneous intensity in the fluid due to a transient pulse delivered by the point driver and the mechanism of fluid-structure interaction in the very near field will be discussed in detail from the point of view of instantaneous energy flow.
Vibrational power flow and energy localization in coupled systems
Authors: Ezanno P. , Dimitriadis E. K. , Burdisso R.
Published: October 2005

A system of two, nearly identical Euler-Bernoulli beams, which are coupled through a torsional spring, is here analyzed in terms of power exchange between and energy localization within this nearly symmetric system. This investigation can be viewed as extending over an ensemble of systems, one member of which consists of two identical beams (the tuned state) and the rest are similar systems except for small perturbations introduced to the tuned system to create mistuned states. Harmonic excitation of members of the ensemble make it clear that vibration localization can occur for small length perturbations. Clearly, the localization degree depends strongly on the coupling strength. Here, the ensemble is examined under wide-band stationary random excitation. Computations are performed of the mean power flow between the two beams over specific frequency bands. It is clearly seen that power flow is strongest in the tuned state, but it is also significant for specific other values of perturbation. The nature of this dependence, along with its possible implications to design methodologies, such as Statistical Energy Analysis, will be discussed.
Eigenmode statistics in large two-dimensional systems
Authors: Weaver Richard L.
Published: October 2005

A finite difference model is used to numerically investigate the higher-acoustic eigenmodes of membranes with random boundaries. Natural frequencies are found to distribute themselves with level repulsion and spectral rigidity like those of the “Gaussian orthogonal ensemble” in accord with the predictions of random matrix theory. These statistics have also been observed in recent experiments determining the higher eigenfrequencies of aluminum blocks. The present work goes further in that it also considers the statistics of the eigenmode shapes. In particular, values for the mean fourth power of modal amplitude (related to the “participation ratio” and to variances of power transfer functions in large systems) are reported, as are results on repulsion between mode shapes. [Work supported by NSF.]
Effects of typicality and interstimulus interval on the discrimination of speech stimuli
Authors: Tsuzaki Minoru , Gurlekian Jorge A.
Published: October 2005

To investigate the effects of processing time and retention interval on the perceptual judgment for speech sounds, Japanese listeners were tested with the AX discrimination task in various interstimulus intervals. Speech stimuli were synthesized to comprise both typical and stypical stimulus sets. In the typical set, the standard stimulus had characteristics of the typical Japanese /aba/ sound. In the atypical set, the standard was not a good exemplar of the Japanese /aba/ sound although it was usually recognized as /aba/. The performance of the subjects was analyzed in terms of both the center and width of discriminal processes. At relatively short intervals, there was a slight tendency for the typical standard to have a smaller width score than the atypical standard. At long intervals, there was no effect of the standard stimulus. Although the center shifted to the direction of more plosive counterparts at longer intervals, there was no effect of the standard on the center of discriminal process. The results suggest that the typical standard is represented with less noise, but this advantage decreases with increases in the interstimulus interval.
The effects of attention on selective adaptation
Authors: Sussman Joan E. , Lane Sandra , Lauckner Valerie
Published: October 2005

Ten young adults participated in four conditions of selective adaptation preceded by baseline labeling: (1) end point-[ba], (2) “focused” (subvocal repetition of the adaptor) end point-[ba], (3) end point-[da], and (4) “distracted” end point-[da] with adaptor and test stimuli presented to the right ear and synthetic [si] and [∫i] syllables presented to the left ear at 40 dB SPL for periodic labeling during presentation of the adaptor. The purpose of the investigation was to determine: (1) if the amount of adaptation could be increased by focusing subjects' attention to the [ba] adaptor and (2) if the amount of adaptation could be decreased by focusing subjects' attention away from the [da] adaptor. Results showed that (1) no significant differences between focused attention and [ba] selective adaptation (5.4% vs 3.7% shift of [ba] labels) and (2) surprisingly, an increased amount of selective adaptation for the “distractor” condition compared to the end point-[da] condition (19.3% vs 10.3% shift of [ba] labels). Results will be related to auditory versus higher-level cognitive determinants during selective adaptation labeling tasks. [Work supported by NSF.]
A two-dimensional model of laryngeal flow
Authors: Alipour Fabriborz , Patel Virendra C.
Published: October 2005

Laryngeal flow was visualized by numerical simulation. Using computational fluid dynamics, a two-dimensional model of laryngeal flow was built and aerodynamic properties were calculated for steady-state laminar regime. Three configurations of vocal folds with convergent, rectangular, and divergent glottis were used to study the effects of glottal shape on the airflow. Navier-Stokes equations were solved with numerical method of Patel et al. A boundary fitted coordinate was used in discretizing the flow domain into exponential grids. The governing equations and coordinates were transformed into computational domain and solved with finite analytic method. Results were reported on the velocity components, pressure distributions, and wall friction coefficient at Reynolds numbers of 100–900 for different configurations. Results were compared with one-dimensional Bernoulli solutions and experimental data. It was found that flow separation exits even at low Reynolds numbers and the separation point moves toward downstream as the Reynolds number increases. [Work supported by NINCDS Grant No. NS 16320-08.]
Acoustic analysis of essential voice tremor
Authors: Colson Karen , Carpenter Mary A. , Ewy Laura , Koller William , Busenbark Karen
Published: October 2005

This study examined differences in selected phonatory characteristics of essential tremor (ET) patients and normal, matched controls. All patients exhibited limb tremor of 4–10 Hz and minimal to severe audible vocal tremor. Tape-recorded speech sample for 14 ET and normal speakers from our subject pool were analyzed acoustically to determine individual and group mean fundamental frequency (f0) measures. Both the female and male ET groups had a significantly lower mean f0 (20–40 Hz) than that of their matched controls during sustained vowel productions. As well, the performance patterns of the ET and control groups were markedly different across repeated trials of vowel production. In connected speech, the male ET speakers' average f0 and phonation range were significantly reduced relative to that of their matched controls. Although there was no statistical difference, female ET speakers also tended to have a reduced mean f0 and phonation range in connected speech compared to their matched controls. These preliminary findings suggest that an abnormally low f0 may be a critical factor contributing to the perception of voice tremor in ET patients. [Work supported by Center on Aging, KUMC.]
Some effects of pharyngealization on tongue shape as seen on ultrasound
Authors: Stone Maureen , Yeni-Komshian Grace H.
Published: October 2005

The present study examined tongue shape during oral and pharyngeal consonants. A female speaker of Lebanese Arabic produced oral and pharyngealized versions of several consonants in the carrier phrase “Kataba CV al yom,” which means “He wrote CV today.” Ultrasound scans of the tongue were made in two planes, midsagittal and anterior coronal, during repetitions of the utterances. The [h] had the most interesting results. Pharyngealized [h] used a higher posterior tongue than oral [h]. In addition, a midsagittal humping was seen in the pharyngeal [h]. The oral [h] had a midsagittal groove as expected. Similar effects seen in other CV combinations will be discussed.
Three-dimensional geometry of the hard palate
Authors: Watkin Kenneth L.
Published: October 2005

The purpose of the present investigation was to determine the three-dimensional geometry of dental casts and in vivo measurements of the hard palate using a pulsed inductive magnetic coil sensing/digitization device connected to an IBM PC/AT. A specially constructed palatal tracing wand, parallel port interface, and software were developed data acquisition along with 3-D database software for real time projection. Comparisons of 3-D palatal morphology will be presented. Results will be discussed in light of current anthropomorphic information on palatal shape and speech production models.
Aging effects on the ability to use temporal context in speech perception
Authors: Tetzeli Marta , Ochs Marleen T.
Published: October 2005

Elderly and young adults listened to a continuum of stimuli varying in closure duration from “rabid” to “rapid” presented at fast and normal speaking rates, with a carrier phrase and in isolation. Rates for the phrase and word were either consistent or conflicting, to determine the relative influence of extrinsic versus intrinsic temporal cues. In addition, the effect of intensity level was examined for all the above conditions. Hearing sensitivity was within normal limits through the low-pass cutoff frequency (3.15 kHz) for the filtered speech. In contrast to previous findings with isolated words [P. J. Price and H. J. Simon, J. Acoust. Soc. Am. 76, 406–509 (1984)], no significant overall age effects were seen for either the word alone conditions at the higher intensity or for any of the phrase + word conditions. These results suggest that, when hearing sensitivity is controlled, age per se may not explain the increased difficulty that many elderly have in processing fast speech. Follow-up research is planned to determine why these data conflict with previous findings.
Experimental measurements of acoustic propagation in the ocean
Authors: Chapman N. R.
Published: October 2005

The comparison of experimental measurements and model calculations is an essential step in developing an understanding of the nature of sound propagation in the sea. In order to carry out such a comparison effectively, the models must be capable of producing accurate results in a range-dependent environment, and the experiment must be designed so that the geometry and environmental conditions can be reconstructed from the measured data for modeling purposes. This paper considers the question of what measurements, in addition to the acoustic field data, should be made to provide a sufficiently well-documented data set. These measurements include nonacoustic data such as navigation and ranging, source and receiver calibration and positions, and environmental data, such as sound-speed profiles, bathymetry, subbottom geoacoustics, and seafloor roughness. For range-dependent conditions, it is essential to sample the environment at a sufficiently fine degree of spatial resolution. Case studies are presented to illustrate model-data comparisons for propagation in a shallow sound channel, propagation over a sloping bottom and propagation over a thin sediment bottom. These examples are used to suggest general guidlines for designing experiments.
Shallow-water transmission measurements taken on the New Jersey Continental Shelf
Authors: Carey William M. , Doutt James , Dillman Lynn Maiocco
Published: October 2005

Calibrated acoustic transmission measurements were made under calm sea conditions on the New Jersey shelf near Amcor 6010, a surveyed area with known geophysical properties. The experiment was conducted in 73-m water with supporting measurements of salinity, temperature, and sound speed. These measurements were obtained with a vertical array of 24 equally spaced hydrophones at 2.5 m; one of which was on the bottom. A source towed at either 12- or 34-water depth transmitted one of two sets of four tones spaced between 50 and 600 Hz for each run to ranges of 4 and 26 km. The data were processed with Hankel transform and Doppler processing techniques to yield horizontal wave-number spectrum at several depths as well as mode shapes. Results were obtained along both a constant and a gradually depth varying radial. Similar modal interference patterns were observed at lower frequencies and critical angle bottom limited propagation at higher frequencies. The constant radial results were compared to calculations using several shallow-water propagation models employing both geoacoustic profiles derived from the geophysical parameters and Yamamoto's (1990) shear wave inversion. Predicted and measured levels generally agreed; however, differences in computed and measured modal interference patterns were observed. [Work sponsored by ONR 1125 OA and NUSC IR.]
An experimental investigation of the horizontal refraction of low-frequency acoustic waves in shallow water
Authors: Shmelerv A. Yu. , Petnikov V. G. , Migulin A. A. , Lynch James F.
Published: October 2005

In shallow water, the measurement of horizontal refraction is a convenient method for the study of ocean mesoscale processes. In this paper, observations of horizontal refraction over a long, fixed acoustic track in shallow water are presented. A tonal signal at 100 Hz was transmitted from a near bottom source to a long, fixed receiving array 70-km distant. The receiving array consisted of 48 hydrophones extending over 450 m horizontally. Continuous measurements of the sound-speed profile showed fluctuations of the thermocline boundary caused by long period (3.5 h) internal waves with 10-m amplitude. Simultaneously, acoustic measurements were made of the deviations from linearity of the phase front along the array. Using spatial Fourier analysis, it was seen that the variability of the phase front showed several scales. Calculations showed that long period phase fluctuations were produced by long period interval waves and short period fluctuations were produced by the interference of direct waves and waves reflected from the shore. It was also possible to account for some of the parameters of the internal waves and the reflected waves.
Laurence Batchelder's contributions to engineering acoustics and underwater acoustics
Authors: Warren Leon R. , Rolt Kenneth D.
Published: October 2005

During Laurence Batchelder's career, while underwater acoustics was still in the early stages of development, he was associated with several of the outstanding pioneers in the field, including Professor G. W. Pierce, Dr. H. C. Hayes, and H. J. W. Fay. During his 40 years as an engineer with Submarine Signal Company and its successor, the Submarine Signal Division of Raytheon Company, his technical contributions were significant and embraced a number of engineering disciplines. The challenging technical environment of the 1930s and 1940s and the small group of Government and industry engineers involved with the development and applications of underwater sound equipment produced a working atmosphere ideally suited to his analytical and creative talents. His contributions included developments in the JL series of listening equipment, the QB and QC series of echo ranging equipment, Fathometers'?? and echo sounding equipment, and participation in the 1937 Guantanamo Bay Expedition, a joint effort involving scientists from the Navy and Woods Hole Oceanographic Institution. This expedition established for the first time the close relationship between underwater acoustics and oceanography. His many published works include the post-war report, “Sonar in the German Navy,” prepared for the U. S. Navy.
Laurence Batchelder's contributions to the Acoustical Society of America
Authors: Ehrlich Stanley L.
Published: October 2005

Laurence Batchelder was a consistent, well-diversified contributor to the Acoustical Society of America from the time he joined the Society in 1946 throughout the remainder of his life. When you ask different members of the Society what he did, you are likely to receive a unique answer, because he shared his expertise with each of them in a different and very personal way. Some of this interaction is being presented by other speakers in this session. A few chronological highlights of his ASA career are that Larry was elected a Fellow of the Society in 1949, served on the Executive Council from 1952–1954, and again as President-Elect, President, and Past President from 1960–1963, received the first Distinguished Service Citation awarded by the Society in 1972, and most recently was awarded the Gold Medal for 1985, the highest award of the Society for contributions to acoustics.
On the origin of the stretched melodic octave
Authors: Hartmann William Morris
Published: October 2005

It is well known that the psychological octave is stretched with respect to the physical octave, i.e., when listeners choose or adjust a melodic octave, the frequency ratio turns out to be greater than 2 to 1. Two explanations have been advanced to explain this effect. Terhardt [J. Acoust. Soc. Am. 55, 1061–1069 (1974)] suggested that the stretched melodic octave is learned from a harmonic octave that is stretched by partial masking of excitation patterns. The origin of the stretched melodic octave is therefore in the central nervous system. However, Ohgushi [J. Acoust. Soc. Am. 73, 1694–1700 (1983)] argued that the stretched melodic octave may be caused by the refractory delay in primary auditory neurons, as observed in electrophysiological single unit recordings. In his model, pitch is determined by the first several peaks in the interspike interval histogram, which are increasingly delayed for higher frequencies. The origin of the stretched melodic octave is therefore in the peripheral nervous system. The present paper shows that one can choose between central and peripheral models by an octave-judgment experiment that does not involve any pitch information in the auditory periphery. This is done by creating central pitch sensations with the Huggins effect. Data obtained from 2AFC constant-stimuli experiments favor the central-origin explanation of the stretched melodic octave. [Work supported by the NIDCD of the National Institutes of Health.]
Measuring similarity of musical timbres
Authors: Iverson Paul , Krumhansi Carol L.
Published: October 2005

Similarity scaling, adjective sealing, and acoustic measurements were used to assess the similarity of 16 digitally recorded tones produced by orchestral instruments playing the same pitch. In similarity scaling experiments, subjects rated the similarity of the tones on a continuous scale. Similarity scaling experiments were run on the complete tones, the first 85 ms of the tones, and on the tones with the first 85 ms removed. In an adjective scaling experiment, subjects rated each complete tone on 21 different adjective scales. Acoustic measurements included correlations between the amplitude spectra of the tones, and correlations between amplitude spectra at regular intervals within each tone. The results of these experiments were analyzed using correlations, multidimensional sealing, factor analyses, and linear regressions. The ratings from the three similarity scaling experiments were highly correlated with each other, and they were each moderately correlated with the results of the adjective scaling experiment. Acoustic attributes were identified that correlated with the results from the other two methods, thus isolating factors common to all three methods. [Work supported by Sigma Xi, The Scientific Research Society.]
Perception of small rhythmic variations
Authors: Marvit Peter
Published: October 2005

A study to determine the mechanisms and parameters of the perception of small timing differences in short rhythmic sequences was performed using 13 subjects (which yielded 10 valid subjects) in a completely within-subjects forced choice factorial design. Manipulated variables included three “base” internote intervals (100, 200, 400 ms—corresponding to different tempos) with respective total durations of the rhythmic figures (1200, 2400, 4800 ms), three categories of two patterns each of varying rhythmic complexity from Povel and Essens [Music Percept. 2, 411–440 (1982)], and six variations in internote note onset timings (0–50 ms). Subjects were played pairs of rhythms, one with the timing variation and one without and then vice versa, and were asked to decide whether the rhythms were the same or different. Scores were based on correct discrimination; reaction time was recorded, but varied too much to be useful. All possible combinations of factors were presented to each subject and order of presentation varied for each subject. Results based on differences between interval variations, plus the strong showing of one of the rhythmic patterns, strongly supported several aspects of a model for an internal clock plus a threshold of 30 ms for detection of timing variation. Except for that one pattern, differences between the patterns did not emerge. This casts doubt on the generality of Povel and Essens' complexity determination of rhythmic figures for pure perception (rather than production). Trends of differences in “base” interval (or tempo) and thus the total duration of the rhythmic sequences, although not statistically significant, suggested possible confirmation of the limits of precategorical acoustic storage or a model of rhythmic regularity. The unintentional factor of presentation order (within a pair of patterns) turned out to be highly significant, further supporting the model of strongly induced internal clocks. Specifically, “regular” rhythms preceding variations produced much stronger discrimination, especially at the 30-ms variation threshold.
A proposed international standard method for calculating the attenuation of sound during propagation outdoors
Authors: Piercy Joseph E. , Sutherland Louis C.
Published: October 2005

This method aims to predict noise levels in the community, with engineering precision, from a variety of sources (ideally any source) of known sound power. It represents an integration by the members of working group ISO/TC43/SC1/WG24 of the national methods, principally from The Netherlands, the Scandinavian countries, Germany, and the USA. This method aims to determine the average sound level LAeq.T under meteorological conditions favorable to propagation (a worst case scenario), and then obtain from that a long-term average sound level LAeq.LT, both as specified in ISO 1996. It consists specifically of octave band algorithms (with center frequencies from 63–8000 Hz) for calculating the attenuation of sound from a point source., or an assembly of point sources.
The use of a one-parameter model to characterize the acoustical properties of asphalt
Authors: Van Wyk K. , Bolton J. S. , Sherman P. J.
Published: October 2005

Following a suggestion by Delany and Bazley [J. Sound Vib. 16, 315–322 (1971)], a single parameter (flow resistivity) fibrous material model has frequently been used to model the acoustical properties of outdoor surfaces. Embleton et al.[J. Acoust. Soc. Am. 74, 1239–1244 (1983)] have shown that an effective flow resistivity for an outdoor surface may be inferred by matching measured and predicted excess attenuations. In this paper, our experience in using such an approach to characterize the acoustical properties of asphalt surfaces will be described. A point source placed directly on the asphalt surface has been used to generate a broadband noise signal. A microphone placed directly on the surface was used to measure 1/3-octave band sound levels aa a function of frequency (1–20 kHz) and distance from the source (0.1–12.8 m). The flow resistivity of the surface was estimated by comparing theoretical and measured level differences between 0.1 m and the other measurement locations. It was found that it is possible to obtain consistent estimates of flow resistivity if the data subset (i.e., the range of frequencies and distances to which the theory is compared) is chosen carefully. It will be demonstrated, for example, that sealed and unsealed asphalt surfaces can be distinguished through estimates of their flow resistivity. However, it has also been found that the best estimate of the flow resistivity of a particular surface tends to vary systematically with the range of frequencies and distances used in the fitting procedure. Thus it appears that a single parameter model is not sufficient to characterize the acoustical properties of an asphalt surface with uniform accuracy over a broad range of frequencies and distances.
Direct observations of edge-diffracted waves from acoustically soft underwater panels
Authors: Piquette Jean C.
Published: October 2005

Sample panels of acoustical materials usually must be fabricated with a sufficiently small size to be accommodated by existing test facilities. However, as test frequency is lowered, the contaminating influence of the diffracted waves originating at the sample's edges becomes increasingly severe. Two techniques for directly observing the edge-diffracted waves when the sample is acoustically soft are described. One method is based on a comparison of measurements obtained from a relatively large sample (having 244 × 244 cm, or 8 × 8 ft, lateral dimensions) to measurements obtained from a relatively small sample (having 76×76 cm, or 2.5×2.5 ft, lateral dimensions). The second method involves direct observation of the edge-diffracted wave from an “airbox” sample. This latter sample is literally a “box of air,” fabricated using thin plastic walls, and having a geometry identical to the 76×76-cm material samples used in the comparison-method tests. The frequency range of interest is 1–10 kHz.
Scattering of Lamb waves at the end section of a plate embedded in water
Authors: Pareige P. , Luppe F. , Ripoche J.
Published: October 2005

The guided nature of a Lamb wave propagating on a water-immersed plate is well known: It is possible to observe its reemission far away from its generation area. Interest is in the phenomena occurring when such a guided wave meets the end of the plate. This study shall not deal with the reflected part of the Lamb wave, but with the forward-scattered wave in water. The experimental study is conducted for different symmetric and antisymmetric incident Lamb waves propagating on an aluminum plate, the end section of which is a right angle. The receiving transducer lies in the plane perpendicular to the diffracting end section. The scattered amplitude is plotted versus the angle between the incidence direction and the diffracted one in that plane. The angular diffraction patterns of the symmetric Lamb waves exhibit a maximum in the incidence direction, while the ones of the antisymmetric Lamb waves exhibit a minimum in that same direction. A simple model, based on the Huygens' principle, and involving the polarization state of the incident wave, provides results similar to the experimental ones. First results are also presented and discussed for end sections of various angles.
Scattering from slender bodies at high frequency
Authors: Van Nhieu Michel Tran
Published: October 2005

A scattered field from rigid slender bodies at high frequency is determined by applying the Kirchhoff and slender-body approximations; this last one is the zeroth-order term of the asymptotic expansion of the solution of the problem in the slenderness ratio ε [M. Tran Van Nhieu, J. Acoust. Soc. Am. 85, 1834–1840 (1989)]. It is shown that the pressure scattered from complex targets can be computed from a simple integral and the geometrical knowledge of the transversal cross sections of the body along its longitudinal axis. An analytical expression for the far-field pressure is obtained explicitly. Some numerical results for the monostatic and bistatic target strengths of bodies of various shapes are presented to illustrate the theory.
Acoustic fields on the surface of a submerged finite cylindrical shell irradiated by plane waves
Authors: Bao Xiaoqi , Varadan Vasundara V. , Varadan Vijay K. , Audoly C.
Published: October 2005

The prediction of acoustic pressure on the surface of baffles is interesting for designers of transducer arrays. A computer simulation program based on a finite/boundary element approach is developed for this purpose. In the simulation, the elastic baffle is modeled by finite elements and the infinite fluid surround the baffle by boundary elements. The two representations are coupled on the surface through eigenmode expansion. The composite program is able to predict the surface acoustic pressure of axisymmetric elastic baffles. The sensitivity and directivity of hydrophone or hydrophone arrays that are mounted on the buffer can then be obtained. A particular example of a baffle that is a cylindrical steel shell with truncated ends is computed. The convergence of the computation is discussed. The results are compared with experimental measurements.
Acoustic scattering from finite elastic cylinders
Authors: Maze Gerard , Ripoche Jean , Bao Xiao-Ling , Überall Herbert
Published: October 2005

Tank experiments on acoustic bistatic and backscattering from elastic cylinders with hemispherical endcaps have been performed at the University of Le Havre and at Catholic University. The resonances apparent in these experiments have been interpreted on the basis of the phase-matching principle [H. Überall et al., J. Acoust. Soc. Am. 61, 771 (1977)] for surface waves that encircle these objects along closed geodesics. Upon axial incidence, the resonances of meridionally propagating surface waves are visible. Upon axial incidence, the resonances of meridionally propagating surface waves are visible. Upon broadside incidence, circumferential wave resonances are visible as well as the meridional ones. The frequencies of both types of resonances are explained very well by the phase-matching principle. [Work supported in part by the David Taylor Res. Ctr.]
Monaural localization, revisited
Authors: Wightman Frederic , Kistler Doris , Arruda Marianne
Published: October 2005

There are numerous reports in the psychoacoustical literature that human listeners can localize sound sources reasonably well with one ear. Since interaural difference cues are presumably eliminated in monaural conditions, the so-called “monaural spectral cues” introduced by pinna filtering are assumed to provide the information necessary for accurate localization in monaural conditions. In these experiments, listeners localize wideband noise bursts presented either in free-field (with one ear occluded) or via headphones (with the signal to one phone either attenuated or disconnected). In the headphone conditions, pinna filtering effects are added digitally, such that the waveforms at a listener's eardrum are nearly the same as those produced by free-field sources. The noise spectrum is scrambled from trial to trial to prevent learning. With the noise bursts presented at about 30 dB SL in free-field, the results are consistent with other recent reports and suggest that some ability to localize, especially in the vertical direction, is retained in monaural conditions. However, when the identical stimuli are presented via headphones, there is no indication that sources can be localized monaurally. In other conditions, listeners localize constant spectrum stimuli, free-field stimuli at 70 dB SL, and binaural headphone stimuli with one ear attenuated. Results from these conditions suggest that monaural localization in free-field is most likely mediated by small head movements, a priori knowledge of the stimulus spectrum, and acoustical leakage through the ear-occluding devices used to monauralize the listeners. [Work supported by NIH and NASA.]
Changing echo thresholds
Authors: Freyman Richard , Clifton Rachel , Litovsky Ruth
Published: October 2005

Echo thresholds for a 4-ms white noise burst were measured in an anechoic chamber with the leading loudspeaker located at 45° left and three lagging loudspeakers at 35°, 45°, and 55° right. The listener judged whether the echo sound came from the loudspeaker at 35° or 55° right by pressing one of two buttons; correct feedback was provided on every trial. This test noise burst was presented in isolation, or preceded by several conditions. Lead only had a train of nine noise bursts from the leading loudspeaker preceding the test noise burst; Lag only had a train from the lagging loudspeaker at 45° right; Precedence effect (PE) had a train from both leading and lagging loudspeaker at 45° left and right. The PE condition had the highest echo threshold (14.9 ms), followed by the isolated burst (11.2 ms), with the lowest threshold for Lead only (6.8 ms). Increased threshold under the PE condition indicated that repetition of the echo during the train was necessary to drive up echo threshold compared to the isolated burst. The single source train appeared to enhance the test burst echo following the train. [Work supported by NSF.]
Thresholds for formant-frequency discrimination of vowels in consonantal context
Authors: Kewley-Port Diane , Watson Charles S.
Published: October 2005

The discrimination thresholds for shifts in formant frequency were shown to be in the range of 1%–2%, in a recent report to this society [Kewley-Port, J. Acoust. Soc. Am. Suppl. 1 87, S159 (1990)]. Thresholds for F1 and F2 obtained from well-trained subjects listening to vowels under minimal stimulus uncertainty were a factor of 3 lower than earlier estimates. The present experiment extends that study to examine the effects of placing a vowel in a consonantal context. The vowel /l/ was synthesized in CVC syllables for the consonants /b/, /d/, /g/, /z/, /m/, and /l/. For F1=450 Hz, the threshold, ΔF, was the same for isolated /l/ as the ΔF averaged over all CVC contexts, about 12 Hz. For F2=2300 Hz, ΔFwas significantly larger (45 Hz) for the vowel in the average CVC context than in isolation (25 Hz). Thresholds for individual CVC's were significantly different from the threshold for isolated /l/, in about one-half of the cases examined. These differences are discussed in terms of the extent of the formant transitions and the durations of the steady-state vowel formants. [Research supported by NIH and AFOSR.]
An approach to the classification of American English diphthongs
Authors: Gottfried Michael
Published: October 2005

Six diphthongs of American English (/au, aɪ, eɪ, oᴜ, ɔɪ, ju/) were produced by four midwestern American speakers (two male, two female) at two tempos (slow, fast) with differing stress (stressed, unstressed) in two contexts ([b_d], [h_d]). Using a plot of the fundamental frequency and the first three formants derived from linear-prediction-coding (LPC) analysis, the onset and offset of each production was determined. The pattern of formants and fundamental frequency at the onset and offset of diphthongs was used to establish a set of parameters that can classify intended productions of the American English diphthongs in varying stress and tempo conditions with an average accuracy of 93%. Results are also presented for diphthong, target-syllable, and sentence durations. The classification results are discussed with respect to hypotheses concerning the perception of diphthongs.
The nonlinear dynamics of categorical perception
Authors: Tuller Betty , Kelso J. A. Scott , Case Pamela , Ding Mingzhou
Published: October 2005

Much research on speech perception over the years has focused on uncovering examples of the nonlinear relationship between acoustics and perception (so-called “categorical perception”). However, little is known concerning the dynamics of this phenomenon. In a variation of the classical categorical perception paradigm, the present experiment explored gradual increases or decreases in a single acoustic parameter. The resulting patterns of perceptual change showed rich dynamics, including hysteresis, “anticipation,” a single boundary, and the progression from hysteresis to anticipation over multiple trials. A dynamical system that could account for these perceptual patterns was investigated by specifying a potential function that corresponds to the layout of phonetic (attractor) states, and how that layout alters as the acoustic parameter changes. The model reproduces the observed features of the experimental data, and makes further predictions about perception, currently being tested. [Work supported by NIDCD and NIMH.]
The duration and perception of English epenthetic and underlying stops
Authors: Lee Sook-hyang
Published: October 2005

In American English, an intrusive stop occurs before the fricative in words such as tense and false, making them very much like words with underlying stops, such as tents and faults. Ohala (1975) treats the inserted stop as an artifact of universal physiological or aerodynamic constraints. But this approach cannot account for the fact that South African English speakers do not insert the stop between sonorant and fricative clusters (Fourakis and Port, 1986). Another approach posits a language- or dialect-specific phonological rule which inserts a phonological segment (Zwicky, 1972). Fourakis and Port (1986) argue against this approach on the grounds that in some pairs the intrusive stop is significantly shorter than the underlying one (although the difference is always very small). This paper presents perception data and duration measurements supporting Zwicky's approach. Phrases with intrusive and underlying stops (intense and in tents, respectively) in citation forms produced by three speakers of midwestern dialects were presented over earphones in random order for subjects to identify. Identification was very poor, just at chance level. Also, duration measurements of the silence gap between the /n/ and /s/ in these words show no significant difference, contrary to Fourakis and Port's findings. Moreover, token judgments in the perception experiment show very poor correlation with the durations except for one speaker, implying that whatever duration differences there are might not be a crucial cue that listeners exploit for labeling the words with epenthetic and underlying stops.
Parallel simulation of broadband ambiguity surfaces
Authors: Mignerey Peter C.
Published: October 2005

A connection machine was used to implement parallel algorithms for the solution of the normal mode equation and for matched-field processing over a large frequency band. The all-acoustic layered model consists of piecewise linear sound-speed and density profiles with a free surface and an acoustic half-space below the bottom. Individual processors are dedicated to one particular mode with the set of processors spanning the frequency band for numerous sound-speed profiles. Ambiguity surfaces as a function of range, depth, and frequency were generated in parallel using a linear estimator. These images show considerable variation in the sidelobes as a function of frequency while the main peak remains at the source location. [Work supported by the Office of Naval Research.]
Joint estimation of range and bearing in the presence of fluctuation
Authors: Bartram James F. , Reese Sudha S.
Published: October 2005

Active sonar joint range-bearing estimation is treated, based on the use of a signal with a large bandwidth-time (WT) product, specifically one with linear frequency modulation (LFM), together with a processing scheme in which range is estimated by means of pulse compression and time-delay measurement, and bearing is estimated using split-array differential phase processing. The degradation in range resolution caused by fluctuation is derived using a simple channel spreading model, whose parameters are B, the Doppler spread, and L, the delay spread, while the degradation in bearing precision is evaluated on the assumption that the physical fluctuation process will cause the returning signal to become normally distributed. It is shown that temporal segmentation of the waveform can have a beneficial effect. The optimum number of segments to use is determined, depending on the WT product of the signal, on the one hand, and the BL product characteristic of the fluctuation process on the other. The effect of using a different type of frequency modulation in the signal design remains for future study.
Modal decomposition of the pressure field on a vertical line array
Authors: Thomson David J. , Ebbeson Gordon R. , Maranda Brian H.
Published: October 2005

For many applications, it is useful to decompose the acoustic field measured in shallow water into its horizontal wave-number components. Recently, a PE-based method was described for effecting the modal decomposition of the depth-dependent field at a given range in a range-dependent waveguide [D. J. Thomson, ]. Acoust. Soc. Am. Suppl. 1 86, S53 (1989)]. This method should be applicable to the analysis of data obtained with a vertical line array (VLA). However, for practical arrays, the measured field is known at only a limited number of hydrophones, whereas the PE-based decomposition method requires the field to be known at each depth on the computational grid. Therefore, to populate the entire PE grid, it is necessary to interpolate the field between hydrophones and to extrapolate it into the bottom. An interpolation and extrapolation scheme suitable for this purpose is proposed. To illustrate the effectiveness of this reconstruction scheme, modal decomposition is carried out using simulated VLA data generated for an environment representative of the continental shelf region of the Canadian Arctic.
Cramer-Rao bound characterization of equivalent horizontal aperture achieved from environmental asymmetry
Authors: Glattetre John , Perkins John S. , Kuperman W. A.
Published: October 2005

The Cramer-Rao bound is a well-accepted lower bound on the mean-square error of estimated values. Applied to estimation of source position parameters as measured by a hydrophone array, it will give the least achievable mean-square errors of source position. As is also well known, estimation accuracy of a source's angular transverse to the line of propagation between source and array. By application of the classical optics limit of the Cramer-Rao bound [A. B. Baggeroer et al., J Acoust. Soc. Am. 83, 571–587 (1988)] it becomes possible to transform a computed lower bound on angular uncertainty into an equivalent array aperture. It has recently been demonstrated [J. S. Perkins and W. A. Kuperman, J. Acoust. Soc. Am. 87, 1553–1556 (1990)] that a vertical array deployed in an azimuthally assymetric environment will achieve angular resolution. Hence, the quantification of this relation between the environment and equivalent horizontal aperture via Cramer-Rao bounds is desired. Numerical modeling results indicating a vertical array's equivalent horizontal aperture will be presented.
Use of bispectral analysis in flow noise measurements
Authors: Leibolt Mary F. , Farabee Theordore M.
Published: October 2005

Characterization of the wall pressure field in a turbulent boundary layer is necessary for accurate models to be developed. Measurements of the wall pressure field of a turbulent boundary layer were made in a quiet wind tunnel with flush-mounted pressure sensors. Bispectral analysis was performed on the resulting digitized data to determine whether frequency phase coupling was present. Bispectral analysis, which is an extension of the commonly used Fourier analysis techniques known as auto- and cross-spectral analysis, identifies three wave phase couplings between frequencies by calculating the expected value of the sum of the phases of three frequencies of interest: B(f1F2) = E{|X(f1)‖X(f2)‖X(f1+2)]| × exp[θ(f1) + θ(f1+2)]}, where |X(f)| and θ(f) are the respective magnitude and phase of the Fourier transform of x(t). Phase coupling can be indicative of nonlinear relationships in a system. [Work supported by DTRC IR/IED Program.]
Ultrasonic focus degradation produced by abdominal wall
Authors: Waag Robert C.
Published: October 2005

Focus degradation produced by human abdominal wall has been studied experimentally using measurements of ultrasonic pulses from a special curved transducer that emits a hemispheric wave and simulates a point source. The pulse waveforms were measured in a two-dimensional aperture after propagation through a water path and after propagation through five different specimens of human abdominal wall. The time history of the virtual point source was reconstructed from the measurements by removing the time delay produced by geometric path differences, finding the complex amplitudes of the temporal harmonics across the aperture, calculating the Fraunhofer diffraction pattern of each harmonic, and summing the patterns. Comparison of the time history in the plane of the virtual source reconstructed from signals that propagated through the abdominal wall specimens and the time history obtained from signals without the abdominal wall specimens present shows that the main features of the reconstructed source waveform are relatively unaffected by the presence of the human abdominal wall but that significant differences in signals greater than 40 dB down from the peak result from propagation through the specimens employed in this study.