bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of partial coherence and singular value partial field decomposition in the context of near-field acoustical holography
Authors: Kwon Hyu-Sang , Bolton J. Stuart , Hammond J. K.
Published: July 2002

Sound fields radiated by complex noise sources, e.g., automotive engines, generally comprise superposed individual fields generated by incoherent subsources. When applying near-field acoustical holography (NAH) to such fields it is first necessary to decompose the total sound field measured on the hologram plane into coherent partial fields, each of which is then projected to a reconstruction plane where they are summed on an energy basis. The partial field decomposition is performed after first calculating the cross spectra between a number of reference microphone signals that have been conditioned by using either partial coherence or singular value decomposition procedures, and the spatially sampled sound pressures on the hologram plane. That cross-spectral information then allows the partial fields to be created. In this presentation, the performance of the two reference signal decomposition procedures will be compared theoretically and experimentally. In particular, it will be shown that partial coherence decomposition allows the partial fields to be associated with the fields radiated by individual subsources if the latter are sufficiently separated spatially. In contrast, the singular value decomposition procedure usually results in partial fields that combine the properties of the subsources, and are thus not directly related to the fields radiated by individual subsources.
Direction and speed of internal waves in SESAME II, and their effect on acoustic transmission
Authors: George Jacob , Field Robert L. , Hallock Zachariah R.
Published: July 2002

Analysis of thermal data from SESAME II has revealed variations of both long and short durations. Variations of long durations have been clearly identified with tidal cycles, and are nearly identical at two thermal arrays 433 m apart in range, with no significant relative time lag between the two. Though a zero relative time lag would imply a southeastern direction for the wave vector, the long wavelengths involved and the short range between the arrays make such a prediction inconclusive. Variations of shorter durations arrive at the two arrays with a relative time lag that ranges between 5 and 26 min. Wavelet analysis has confirmed this time lag, and shows that it holds for a range of wavelengths. This puts constraints on the direction and speed of the short-duration components. The implications of these results on acoustic propagation will be discussed. [Work supported by ONR and NRL.]
Forward propagation analysis for the summer Shelfbreak PRIMER Experiment
Authors: Sperry Brian J. , Lynch Jim , Chiu Ching-Sang , Gawarkiewicz Glen G. , Pickart Robert S. , Miller James H. , Robinson Allan R.
Published: July 2002

One of the primary objectives of the 1996 Shelfbreak Primer Experiment, located in the Mid-Atlantic Bight south of Nanucket Shoals, was to investigate the effects of the shelfbreak front on the propagation of acoustic signals. The acoustic component of the experiment consisted of two 16-element vertical hydrophone arrays (VLAs) along the northern edge of the region (inshore of the shelfbreak), and three sources (one 224 Hz and two 400 Hz) along the southern edge (seaward of the shelfbreak). Source-to-receiver path lengths ranged from 40–60 km. The high-quality oceanographic data collected, including SeaSoar sections and numerous thermistor records, are critical to modeling and interpreting the acoustics. From a modal perspective, there is strong coupling from not only the front, but also from the sloping bathymetry and from scattering by solitons. The receptions at the northeast VLA coinciding with a 6-day period of SeaSoar deployment are considered here. Fluctuations in the signal arrivals are consistent with the picture provided by the measured oceanography. Results from coupled-mode propagation modeling are also discussed. [Work supported by ONR.]
Influence of phonotactic rules on perception of ambiguous segments
Authors: Moreton Elliott
Published: July 2002

In every language, some sequences of sounds are illegal. English, for instance, bans stressed lax vowels word-finally—[bI] cannot be an English word. Linguists traditionally attribute this to language-particular phonotactic rules. More recently, some psychologists have suggested instead that phonotactics is the emergent statistical property of the lexicon, caused by the frequency of some sequences and the rarity of others. The issue is tested here by comparing the effects of absolute phonotactic rules versus nonphonotactic lexical frequency differences on phonetic category boundaries. Stimuli are disyllabic English pseudowords ending in a stressed syllable whose vowel is ambiguous. One continuum is [gri] (very common in that position) to [grI] (illegal); another is [kri] (legal but very rare) to [krI] (illegal). Controls, with both end points legal, are [grich]-[grIch] and [krich-krIch]. The [I] end point’s illegality should move the i–I boundary towards [I] compared with the controls. The rule theory predicts equal shifts for the [gr] and [kr] continuua; the statistical theory says it will be much larger for the frequent [gr]. [Work supported by NIH.]
The effect of presentation level on the perception of voicing
Authors: Kirk Cecilia J.
Published: July 2002

Kluender et al. [J. Acoust. Soc. Am. 97, 2552–2567 (1995)] propose that voicelessness in a continuum from short to long lag VOTs is signaled by abrupt synchrony capture of F2–F3 tuned fibers by F1 when voicing begins. Their hypothesis also predicts more capture at higher presentation levels, producing crossover to voiceless judgments at shorter VOTs, an effect observed in their experiments. In an attempt to replicate Kluender et al.’s findings, listeners were presented with a /ba/−/pa/ continuum at 48, 60, and 72-dB SPL: VOT crossovers did not differ significantly between the two highest levels, but were significantly longer for the lowest compared to the two highest levels. A second experiment tested manipulations of relative aspiration level by combining aspiration levels of 42, 48, 54, 60, and 66 dB with a 72-dB vowel; VOT crossovers increased with decreasing aspiration level. The results of these two experiments are compatible with the alternative hypothesis that reducing aspiration level below a critical level makes aspiration effectively inaudible. In any case, the synchrony capture hypothesis fails on two counts: Sinex and MacDonald [J. Acoust. Soc. Am. 85, 1995−2004 (1989)] observe that capture of mid- and high-CF neurons by F1 does not vary with VOT for VOTs less than 50−60 ms. In addition, Lotto and Kluender [J. Acoust. Soc. Am. 99, 2591(A) (1996)] demonstrate that the level effect still obtains when F1 is presented to a different ear than the higher formants.
Acoustic and intelligibility characteristics of sentence production in neurogenic speech disorders
Authors: Jeng Jing-Yi , Laures Jacqueline S. , Weismer Gary
Published: July 2002

Although sentence production is more common than single-word production in daily life, acoustic and intelligibility data from persons with neurogenic speech disorders is largely limited to single-word and target-word utterances. The purpose of the current study is to examine sentence productions of individuals with Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS), and to compare them to data obtained from neurologically normal individuals. Each speaker produced multiple repetitions of a small set of sentences. Acoustic measures included overall sentence durations, segment durations, and vowel formant frequencies. Speech intelligibility of the sentences was measured using scaling techniques. For some subjects, previously obtained acoustic and intelligibility data for single words will be related to the findings for sentences. Results will be discussed descriptively as deviations from patterns observed in normal individuals, and in terms of associations between the acoustic and intelligibility data. [Work supported by NIDCD Award DC00319.]
Cross-validation study of vowel perception in Finnish and English
Authors: Nearey Terrance M. , Kiefte Michael
Published: July 2002

A large stimulus continuum (972 stimuli in an F1–F2−F3 space) was categorized by both Finnish and English listeners. Further results of logistic regression modeling of listeners′ responses using formant frequencies and/or a spectral shape representation (warped−frequency LPC cepstral coefficients) are reported. Cross-validation model selection methods [J. Shao, J. Am. Stat. Assoc. 88, 486−494 (1993)] indicate that a combination of the two parameter sets (formant and cepstral) is superior to either alone. However, for both languages the best prediction scores were obtained from a purely formant-based analysis that included squares and cross products of frequency values, thereby allowing for quadratic category boundaries in the formant space. Analysis to date provides no evidence that spectral-shape information (versus formant frequencies alone) plays a role in listeners’ perception of these stimuli in either Finnish or English. Results of additional analyses will be presented at the meeting. [Work supported by SSHRC.]
Subjective evaluation of space discretized ray tracing
Authors: Olesen Soeren K.
Published: July 2002

The growing interest in multimedia raises questions like how to present 3-D sound to the user of a multimedia system. Such presentations should not necessarily be exact replicas of the real-life experiences; however, they should still provide a quality that convinces the user of being present in the acoustical environment intended. This paper briefly introduces an alternative method of ray tracing that indeed is simplified compared to that of the conventional ray-tracing/mirror-image approach. The method may be considered as a space discretized version of ray tracing and it is considerably faster than the latter. In order to reveal subjective differences between the two methods, a psychoacoustical listening experiment was carried out using binaural synthesis. Twenty subjects participated and in two sessions they were asked to rate coloration and reverberation, respectively, by clicking a mouse—each time listening to a music or speech sound frame. In a third session a sketch of a room and the position of the subject were shown, and the subjects were asked to indicate from what position the sound appeared. The sounds were produced using the new method and traditional ray tracing. The results from the listening experiment are presented in the paper.
Passive target tracking for future littoral test and evaluation ranges
Authors: Lazauski Colin J. , Vuono Jeffery P.
Published: July 2002

Currently, the U.S. Navy uses active acoustic pingers for tracking vessels on its test and evaluation ranges. Although tracking accuracy for these ranges is excellent, this performance comes with some penalties. For instance, test realism can be lost due to loud pinger emissions, small or prototype vehicles might require modification for pinger installation, and ship time is often lost during fitting and removal of pingers. Drawing upon the U.S. Navy’s experience in passive tracking, advances in matched mode localization, and increases in computational capacity, passive acoustic tracking on T&E ranges can now be implemented. The use of pingers is not required and realism is restored to the testing scenario. Test target hardware is no longer required and the cost of the traditional shallow-water hydrophone grid can be reduced. One design for a passive tracking range utilizes acoustic arrays with vertical and horizontal apertures, in situ environmental monitoring, fast and accurate propagation models, and real-time tracking algorithms. Results from several recent field tests demonstrate the potentials and challenges of passive acoustic signature tracking on T&E ranges. The results are compared with ground truth data as well as range simulations and error analysis.
Further advances in the development of a novel acoustic range-bearing tracking node
Authors: Stein Peter J. , Euerle Steven E. , Menoche Richard K. , Janiesch Robert E.
Published: July 2002

During the next several years the U.S. Navy will be installing large area O(1500 km2) shallow-water training ranges off the U.S. mainland. These ranges require underwater acoustic tracking of targets to an accuracy of 100 m. Tracking will be performed via high-frequency pingers (10–50 kHz) located on the targets and bottom-mounted hydrophones (nodes). Development progress on a novel acoustic range-bearing node was presented by the authors at the December 1996 ASA Conference (Hawaii). The node consists of a compact concrete structure containing a minimum number of sensors (4) and implements an axisymetric acoustic horn. Further advances in the development of the device are presented here. Additional results of data processing from testing of the prototype device and results of in-air acoustic tests will be shown. A second prototype, which is currently being constructed, will be described. The design incorporates a modified horn shape, an acoustic window and support structure, and integral ‘‘tone-pilz’’ type stacked crystal transmitters located in the horn.
Telemetry and tracking methods for noisy multipath environments
Authors: Kraszewski Raymond J.
Published: July 2002

Abstract underwater tracking of submerged vehicles in a noisy acoustic environment presents significant performance challenges caused by the presence of countermeasures, multipath interference, and propagation loss. The challenge is exacerbated in shallow water. The Naval Undersea Warfare Center (NUWC), Keyport, has assessed several techniques for improving underwater tracking system performance. The study showed that implementation of a ‘‘telemetric’’ system based upon signal modulation techniques could afford considerable benefits in performance. This has been confirmed through experiments conducted at a shallow-water tracking range site on the continental shelf area of the Washington State coast. The quality of ‘‘raw’’ tracking data rivaled that of traditional data which had undergone postprocess ‘‘smoothing.’’ To perform these experiments, a software-controlled, processor-based tracking system known as Counter Measure Tolerant Telemetry and Tracking, or CMTTT, was developed employing phase and frequency shift keyed modulation and adaptive normalization techniques to afford improved localization accuracy under conditions, which include the presence of countermeasures in shallow water. A description of the hardware configuration of CMTTT as well as the theoretical foundations for the core signal processing algorithms are presented. Test results and accuracy issues are discussed together with suggestions for further improvement of performance.
Evidence of hearing loss in an Atlantic bottlenose dolphin (Tursiops
truncatus)
Authors: Brill Randall L. , Moore Patrick W. B. , Dankiewicz Lois A. , Ketten Darlene R.
Published: July 2002

Auditory thresholds were behaviorally measured for two Atlantic bottlenose dolphins (Tursiops truncatus); a 14-year-old female, and a 33-year-old male. Stimuli were delivered directly to the lateral sides of the lower jaw via jawphones as opposed to free-field broadcasts. The female’s audiogram clearly reflects the standard for this species [C. S. Johnson, in Marine Bio-Acoustics, edited by W. N. Tavolga, pp. 247–260 (1967)]. Previous thresholds for the male measured at age 26 indicated a hearing loss in the left ear of approximately 2 to 3 dB [re: 1μPa] between 4 to 10 kHz, which were considered unremarkable. At age 33, the same male demonstrates distinctive losses. The right ear shows a 16–33-dB loss over 10–40 kHz, the range of best sensitivity. Above 55 kHz, the right ear is 2–3 dB more sensitive than the left. Both ears then decline to an upper frequency cutoff of approximately 70 kHz below the standard 120 kHz. Hearing losses due to age have been reported for this species [S. H. Ridgway and D. A. Carder, J. Acoust. Soc. Am. 101, 590–594 (1997)]. The data reported in this paper suggest both uni- and bilateral hearing losses in the male which may be the result of age, impairment of the auditory system, or both.
Auditory frequency selectivity and masked hearing capabilities in an Atlantic bottlenose dolphin
Authors: Lemonds David W. , Au Whitlow W. L. , Nachtigall Paul E. , Vlachos Stephanie , Roitblat Herbert L.
Published: July 2002

Frequency selectivity capabilities of an Atlantic bottlenose dolphin were examined by calculating critical ratios from masked hearing data. Absolute sensitivity to pure tones from 40–140 kHz was measured as a base line, and masked sensitivity was determined for the same signals masked by three levels of white noise (52, 42, and 32 dB re:1 μ Pa2/Hz). Absolute and masked sensitivity were essentially constant between 40 and 120 kHz at each of the masking conditions. Sensitivity decreased approximately 100 dB per octave between 120 and 140 kHz. Critical ratios averaged across noise levels were constant between 40 and 120 kHz, averaging 26 dB. The critical ratio at 140 kHz was 42 dB. This flat trend in critical ratios between 40–120 kHz does not agree with the constant-Q filter-bank models used to account for earlier critical ratio and bandwidth measurements for the species [W. W. L. Au and P. W. B. Moore, J. Acoust. Soc. Am. 88, 1635–1638 (1990)], but comparison to other cetacean masked hearing work [Johnson et al., J. Acoust. Soc. Am. 85, 2651–2654 (1989)] indicates that the trend has been recorded before, but not explicitly reported.
Zones of masking around icebreakers affecting beluga whales
Authors: Erbe Christine
Published: July 2002

Masked hearing thresholds of a beluga vocalization in four types of noise were measured during behavioral experiments with one beluga whale. In particular, propeller cavitation noise and bubbler system noise created by an icebreaker were studied and compared to naturally occurring icecracking noise and artificially created Gaussian white noise. Critical signal-to-noise ratios, at which each noise just masked the beluga vocalization, were used for ocean sound propagation analysis. A three-point scenario was established involving the relative distances between a noise-creating icebreaker, a vocalizing beluga whale, and a listening conspecific. Maskograms are color plots visualizing the two overlapping sound fields and indicating zones of masking around the noise source. Results are that propeller cavitation noise (source level 200 dB re:1 μPa at 1 m) has a maximum radius of masking of 23 km. Bubbler system noise (source level 190 dB re:1 μPa at 1 m) masks over 15 km. The masking zone around natural icecracking noise (source level 150 dB re:1 μPa at 1 m) has a radius of only 10 m. This is the same for broadband Gaussian white noise with a source level of 160 dB re:1 μPa at 1 m.
Ambient noise maps of the near shore region
Authors: Olivieri Marc P. , Glegg Stewart A. L. , Coulson Robert K.
Published: July 2002

A broadband sparse volume array has been developed to study ambient noise in the near shore region [J. Acoust. Soc. Am. 100, 2732(A) (1996)]. The array has been deployed along the coast of Boca Raton, FL, and it was found that, in the absence of boat traffic, biological noise sources were dominant and were concentrated in clusters around man-made structures or distributed over natural reefs. The sonar was deployed at different sites to triangulate on the location of these sources. Ambient noise maps of the coastal region were generated by combining the contribution from each source with a propagation model. These maps show the expected average sound pressure level from these biological sources as a function of depth and range in the along-shore and off-shore direction. Single hydrophone measurements have been made at different locations in the region to verify the maps. [Work supported by ONR.]
Fabrication of low-sound-speed particulate composites for acoustic applications
Authors: Frohlich Molly , Kaduchak Gregory , Loeffler Charles M.
Published: July 2002

Low-sound-speed elastic materials are of great interest in a wide range of applications. The present research addresses the fabrication of a low-sound-speed elastic material in the form of a particulate composite. A polymeric matrix material is combined with highly compressible particu-lates (40-μm diameter). At frequencies well below the monopole resonance of the particles, dilatational sound speeds as low as 400 m/s have been measured in experiments. The attenuation characteristics of the material are highly dependent upon frequency and may display transmissive or absorptive properties. The measured sound speeds and attenuations compare well with theoretical predictions for composites with relatively low volume fractions of particulates. Applications of these materials will also be discussed. [Work sponsored by the ARL:UT Independent Research and Development Program.]
Long-term operation tests of giant magnetostrictive driving units for low-frequency sources
Authors: Nakamura Toshiaki , Nakano Iwao , Tsuboi Tomohiro
Published: July 2002

A sound source with the frequency below 70 Hz and transmitting level over 195 dB is needed to investigate global ocean climate change by acoustic monitoring like the ATOC project for long-range sound propagation of 5–10 Mm of gyre scale. Long-term operation of the source over 10 years is also required for this purpose. A low-frequency sound source of 70 Hz is planned using the same driving units of giant magnetostrictive type as the units used in the 200-Hz source for our tomography system [Nakamura et al., J. Acoust. Soc. Am. 96, 3256(A) (1994)]. Acceleration tests of long-term operation of the driving units were conducted to realize the equivalent operation to 10 years of the 70-Hz source in a shorter period. As the resonance frequency of the driving unit is about 1 kHz, the acceleration rate is 1000/70. The driving unit was operated 40 000 times for 1 min, which corresponds to a 30-min operation for the 70-Hz source every 4 h for 10 years. Variation of strain, impedance, and displacement-current sensitivity of five driving units were measured every 10 000 times operations. It was found there was no significant variation for these parameters during the experiment.
Acoustics of piano tone
Authors: Martin Daniel W.
Published: July 2002

A tutorial review of research into acoustics of piano tone emphasizes and includes tape demonstrations of the importance of tonal attack, envelope slope, optimum tuning, voicing technique, and directivity. Recent research articles about structural and dynamic piano properties and their effects upon piano tone are surveyed.
Large grand versus small upright pianos: Factors of timbral difference
Authors: Galembo Alexander , Cuddy Lola L.
Published: July 2002

The difference in timbre, especially in the bass range, is one of the important reasons why pianists prefer large grand pianos to small uprights. The work discussed in this presentation addresses acoustical and design factors responsible for this difference. [Work supported by NATO and NSERC.]
Piano bridge and soundboard motion
Authors: Giordano N.
Published: July 2002

The bridge of a piano is the place where two important components, the strings and the soundboard, meet and interact. The motion of the bridge is important for understanding soundboard vibrations and sound production. This motion is also central to the interaction between strings, and to coupling of the different modes of a single string. Recent experimental and theoretical studies of bridge and soundboard motion are described. While the dominant motion is, as one would expect, perpendicular to the plane of the soundboard, the experiments show that motion parallel to this plane is also quite significant. Quantitative results for the in-plane motion are presented, and its role in sound production is discussed. We also consider the implications for modeling of soundboard and string motion. [Work supported by the National Science Foundation through Grant PHY-9722031.]
Measuring speech intelligibility in K–5 classrooms in a Seattle public school
Authors: Heerwagen Dean , Anderson Karen , Lang Dale , Towne Robin
Published: July 2002

A speech intelligibility pilot study is being conducted in primary school classrooms in Seattle. The properties of a number of unoccupied, conventional classrooms have been determined [e.g., EDT, RT60, and background noise levels without and with operating mechanical (HVAC) systems]. Intelligibility tests have been conducted in one room using four groups of children, two from grades 1–3 and the others from grades 3–5. The tests employed prerecorded AUDITEC words lists and Test of Auditory Comprehension short paragraphs and picture images. The test conditions used prerecorded tapes played through a loudspeaker placed at the front of the class. These tapes were played back at levels 15 dB(A) above background noise levels. Four playback conditions served as the major variable for these tests: with the HVAC system ‘‘off;’’ with HVAC system ‘‘on;’’ through an FM system; and a repeat of the first condition. Other test variables are student grade levels and student’s location versus the loudspeaker. An additional variable arises from the ethnic diversity of the school population: 46 distinct ethnic groups are present in the student body. Data analysis is presently underway. [Work supported by University of Washington Royalty Research Fund.]
Wave propagation in a unique class of inhomogeneous porous materials
Authors: Hickey Craig J. , Sabatier James M. , Spanos Tim J. T. , de la Cruz Vicente
Published: July 2002

A system of equations describing wave propagation in a unique class of inhomogeneous porous media is presented. The specific porous medium considered consists of an elastic matrix whose pores are filled with a viscous compressible fluid. The two components, solid and fluid, are microscopically homogeneous but the porous medium is inhomogeneous because the unperturbed porosity varies with position. Volume-averaging theorems are used to construct the general equations which form the basis for the analysis. It is shown that, in general, the presence of a porosity gradient introduces new coupling terms between the fluid and solid phases in the equations of motion. Since inhomogeneity usually implies anisotropy the problem is further specialized for the case of transverse anisotropy. It is further assumed that the wave propagates in the direction of the porosity gradient, which is a principal direction of the anisotropy. The equations are compared to recent work describing rigid framed grounds with exponential porosity profiles. [Work supported by ONR and USDA ARS National Sedimentation Laboratory.]
Nonsmooth impedance profile identification using reflection data
Authors: Magalhaes Marcelo , Tenenbaum Roberto
Published: July 2002

Many works published about identification of acoustic properties of inhomogeneous media present methods based on the assumption that these properties vary smoothly along the propagation direction. This work presents a comparison between two time-domain sequential inverse methods for evaluation of either smooth or nonsmooth impedance profiles of transversely infinite media excited by plane waves at normal incidence. Sequential methods, also known as layer stripping methods, despite having the disadvantage of being quite sensitive to noise in the measured signal, are faster than other approaches, such as those that use global optimization techniques. The first method in the comparison [R. A. Tenenbaum and M. Zindeluk, J. Acoust. Soc. Am. 92, 3364–3369 (1992)] assumes a smooth profile by using a transformation of variables, which neglects the refraction effects between two consecutive layers. The second one, more general, performs some more calculations since it takes these effects into account, paying the price of a higher CPU time, being suitable for non- smooth profiles. Numerical experiments are carried out in order to establish applicability limits for both algorithms as discontinuities are included in the impedance profile, and also to evaluate their sensitivities when the identification is performed using noisy data.
Individual differences in speech production
Authors: Johnson Keith
Published: July 2002

Common experience suggests that, to a certain extent, people can be recognized by their speech, even over the limited bandwidth of a telephone line. Such talker individuality is at least partly determined by anatomical features such as vocal-fold and vocal-tract geometry. Additionally, linguistic factors such as dialectal and speech community membership give rise to noticeable variation across talkers. In this paper two acoustic/phonetic studies which sought to hold these sources of variation constant will be presented. The first is a study of the relative strengths of (perceptually trading) acoustic cues for the /s/–/sh/ distinction in English. The talkers in this study were a dialectally homogeneous group of female college undergraduates. Substantial individual differences in the relative strengths (in a discriminant analysis) of acoustic cues such as F2 transition onset, frequency of the first fricative pole, and duration of the fricative noise were found. The second study explores the patterns of pronunciation exhibited by identical twins. Previous research suggests that identical twins have virtually identical long term average spectra, and that their voices are difficult to discriminate. The present study is designed to look in closer detail at twins’ patterns of pronunciation in diphthongs, voice onset time, and cue trading.
Individual differences and the link between speech perception and speech production
Authors: Newman Rochelle
Published: July 2002

Prior research has suggested that speakers vary in the precise muscle movements used to make phonemic distinctions [K. Johnson, P. Ladefoged, and M. Lindau, J. Acoust. Soc. Am. 94, 701–714 (1993)]. There has also been evidence that individuals differ slightly in their perception of speech [V. Hazan and S. Rosen, Percept. Psychophys. 49, 187–200 (1991)]. One possibility is that these sources of variability are due to the same underlying cause. In support of such a notion, data will be presented briefly demonstrating the range of acoustic-phonetic variability across individuals in both production and perception independently. Following this, evidence will be provided suggesting that these sources of variability are related. More specifically, individuals’ perceptual prototypes in both a VOT series and a stop place series were correlated with acoustic-phonetic measurements on their own productions. This suggests that differences between individuals’ perception are related to the idiosyncrasies of their production. These results fit well with theories of language acquisition emphasizing the role of individual experience. Since the voice that one has the most experience with and which one hears most often is one’s own, an individual’s own productions are likely to have an especially important role in the formation of perceptual expectations.
Variability in normal speech intelligibility: Separate and combined effects of talker-, listener-, and item-related characteristics
Authors: Bradlow Ann R. , Torretta Gina M. , Pisoni David B.
Published: July 2002

Various acoustic–phonetic and listener–transcription analyses were conducted using materials from two large databases of recorded speech. The first database consisted of sentence-length materials spoken by 20 talkers, along with intelligibility data in the form of transcriptions by ten native English listeners per talker. Acoustic–phonetic analyses of the digitized speech samples showed that talkers who exhibited a high degree of ‘‘articulatory precision’’ had higher intelligibility scores than talkers who produced more ‘‘reduced’’ speech. The second database consisted of a set of words spoken by ten talkers at three speaking rates, along with transcriptions by native English listeners. Analyses of the transcription accuracy scores showed a strong effect of inherent lexical characteristics, and a strong effect of speaking rate. Furthermore, the difficulties imposed by one factor, such as a fast speaking rate or an inherently difficult lexical item, could be overcome by the advantage gained through the listener’s experience with the speech of a particular talker. Taken together, these data provide important information regarding the separate and combined effects of talker-, listener-, and item-related factors on normal speech intelligibility.
Localization with individual and nonindividual binaural recordings
Authors: Moeller Henrik , Hammershoei Dorte , Jensen Clemen B. , Soerensen Michael F.
Published: July 2002

The localization performance was studied when subjects listened (1) to a real sound field and (2) to binaural recordings of the same sound field, made (a) in their own ears, and (b) in the ears of other subjects. The sounds to be localized were loudspeaker reproductions of female speech at natural level, from 19 different positions in a standard listening room. The binaural recordings were reproduced by carefully equalized headphones. With individual recordings the performance was preserved compared to real life, whereas nonindividual recordings resulted in significantly more errors for sound sources in the median plane. Errors were seen in terms of confusion not only between nearby directions, but also between directions further away, such as between sound sources in front and behind the subject. However, nonindividual recordings made in the ears of a carefully selected ‘‘typical’’ subject resulted in a performance much closer to the real-life performance, although still inferior.
Multimicrophone arrangement as a substitute for dummy-head recording technique
Authors: Mellert Volker , Tohtuyeva Natalyia
Published: July 2002

Natural sound is usually recorded in head-related stereophony by ear microphones of a dummy head in order to ensure a virtual reality, e.g., for subjective sound-evaluation procedures. However, in many applications the use of a dummy head is disturbing. Additionally, it is difficult to change the geometry or shape of a dummy head in order to adjust a recording individually. The spatial information of the sound field, which is perceived in appropriate stereophonic reproduction, is encoded in the two signals of the ear microphones by recording the modifications of the wave field from the near-field diffraction of the obstacle ‘‘dummy head.’’ A diffraction pattern can be approximated by a sufficient number of monopole sources at appropriate locations, and adjusted in amplitudes and phases. This method of source substitution is used for an arrangement of pressure microphones. Each microphone signal is processed twice and added in the stereophonic channels. If locations and transfer functions are optimized, the two channels represent an approximation of the ear-microphone signals of the dummy-head’s (or real head’s) diffraction information. The preliminary results of the optimization and listening experiments are reported. [Work supported by the German Graduate School on Psychoacoustics.]
Acoustic and visual studies of blue whales near the California Channel Islands
Authors: Teranishi Arthur M. , Hildebrand John A. , McDonald Mark A. , Moore Sue E. , Stafford Kate
Published: July 2002

Preliminary results are presented from a combined acoustic and visual study of blue whales in the Channel Islands National Marine Sanctuary off the California coast, conducted during four 3-day expeditions in July 1996. Acoustic recordings were collected using GPS positioned sonobouys arrays, with up to five sonobuoys deployed at approximately 1-km spacing. Visual observations were made to estimate the number of blue whales in the vicinity of the arrays, and to record whale behaviors. Significant numbers of blue whales (5–15) were sighted each day, and as many as 100 blue whale calls per hour were recorded. About one-third of the time, large ships transited through this area, providing loud low-frequency sound sources to examine blue whale sensitivity to noise. Low-frequency blue whale calls, similar to those previously designated ‘‘A’’ and ‘‘B’’ in the literature, were recorded. Additional blue whale calls include an approximately 4-s duration frequency downswept tone between 30 and 80 Hz, often heard at about the same intensity as the more typical ‘‘A’’ and ‘‘B’’ calls. Cross correlation of signals received by sonobuoys provides information to localize calling whales. The location accuracy relative to the different call types will be discussed.
Low-frequency whale calls recorded on hydrophones moored in the eastern tropical Pacific
Authors: Stafford Kathleen M. , Fox Christopher G.
Published: July 2002

Six moored hydrophones have been recording low-frequency sound in the eastern tropical Pacific (ETP) since May, 1996 (sample rate 100 Hz, low-passed at 40 Hz). These hydrophones are spaced widely: they are moored at latitudes 8 N, 0 and 8 S along longitudes 95 W and 110 W. These distances make it very unlikely that two or more hydrophones will simultaneously record sound from one animal. Continuous spectrograms of data from every third day for each hydrophone were examined for whale calls. Calls attributed to eastern north Pacific blue whales (Balaenoptera musculus spp.) were the most commonly recorded recognizable calls. Additionally, western north Pacific blue whale calls were detected as were calls that resemble those recorded in the presence of blue whales off Chile. Pulse series similar to those which have been attributed to minke whales (B. acutorostrata) were also recorded. A number of unidentified ‘‘biologicals’’ were recorded. Among these are groups of 1–6 low-frequency pulses with regular interpulse spacing. The data from the eastern hydrophones show more call variability and abundance than do those to the west. This array of hydrophones is semipermanent and should provide years of acoustic data from the ETP.
Biosonar dynamics of the bottlenose dolphin in VSW search and detection tasks
Authors: Sigurdson John E.
Published: July 2002

The components of the dolphin’s biosonar are well studied, but their combination and dynamic adjustment during echolocation in open waters are poorly understood. A lack of adequate measurement and research techniques has delayed progress, but new technology and methods now allow for the continuous recording of the animal’s interpulse-interval, head-attitude, azimuth, and pulse waveform during search and detection in very shallow open water. Such measurements were made in controlled tests with bottom objects in random positions on random sand backgrounds. The data provided a 3-D description of the variation in biosonar search behavior as a function of object position and practice effects. Basic findings included the adaptation of the search pattern to the spatial distribution of previously detected objects, correlations between the animal’s orientation, pulse rate, and object location, as well as an inverse relation between the number of pulses on object and the object’s distance. Steady pulse rates on nearby objects were also observed with only half of the ‘‘over-two-way’’ interval previously reported. Coincident with these dynamic adjustments, the pulse spectra displayed considerable variation with detected objects, changing distance and grazing angles. The spectral data also indicate a dual-frequency source.
Allocation of hearing loss in civil litigation
Authors: Krutz Fred
Published: July 2002

The defense of product liability cases filed by plaintiffs alleging that their hearing loss was caused by defendants’ noise-making products always involves the analysis of all relevant evidence to determine the relative contributions of different causes (occupational noise, recreational noise, aging, etc.). That is because in most jurisdictions the plaintiff will be required to prove that exposure to the defendant’s product was a ‘‘substantial factor’’ in causing his or her hearing loss, and because the size of any verdict may depend on the magnitude of that contribution. Moreover, for that same reason and also in order to determine whether a statute of limitations defense is available in the case, it is often important to estimate the progression of a plaintiff’s hearing loss over time. All relevant evidence, including quantitative methods based on epidemiological standards supported by expert testimony, should be used to assist the jury in determining whether the plaintiff has proven his or her case by a preponderance of the evidence (50.1% vs 49.9%).
Apportionment of hearing impairment causation—Are we there yet?
Authors: Lipscomb David M.
Published: July 2002

The ability to discern between etiological factors in hearing impairment depends upon using an accurate and fair method for apportionment. The popular method for division of causation assumes: (1) that pure tone audiometric information reflects the condition of the hearing mechanism (validity); and (2) that the AMA handicap percentage calculations accurately represent the degree of handicap experienced by a given individual (validity, again). Neither of these assumptions can be substantiated. Histological evidence contradicts the notion that pure tone hearing testing gives adequate information on the true status and condition of inner ear sensory neuroepithelium for purposes of apportionment. To ‘‘break apart’’ (allocate) complex causation in audiometric data, the effects of etiologies must be ‘‘additive’’ or they must combine in some measurable fashion. There is no convincing evidence regarding the additive nature of two or more etiologies with respect to pure tone audiometric data. In fact, hair cell injury and destruction is due to complex interaction between etiological factors.
Using ANSI S3.44-1996 to assess the hearing losses of individuals
Authors: Doswell Royster Julia
Published: July 2002

ANSI S3.44-1996 is a valuable tool for the audiologist to use when reviewing individuals’ audiometric records within occupational hearing conservation programs, as well as when evaluating claimants for Worker’s Compensation or hearing-related legal actions. By comparing the amount of hearing loss for an individual to the predictions of the model in the standard, the professional can more objectively assess the probable contribution of workplace noise to the individual’s total hearing impairment. Likewise, by comparing the time course of the development of loss as shown in hearing conservation program audiograms to model predictions, one can better judge the probability that occupational noise may have caused a recent hearing change (such as an OSHA STS). Examples of actual cases will be shown to illustrate the steps involved in these applications of the standard.
Incorporation of subjective measures in active noise control
Authors: Samuels Timothy O. , Sommerfeldt Scott D.
Published: July 2002

An attempt is made to refine a standard active noise-control algorithm in order to take into account the unique response of the human auditory system. It has been shown that decreasing the sound-pressure level at a location does not guarantee a similar decrease in the perceived loudness at that location [W. R. Saunders and M. A. Vaudry, Proc. of Noise-Con 96, 385–390 (1996)]. Typically, noise cancellation is based on the ‘‘error signal’’ from a mechanical device such as a microphone, whose response is nominally flat in the frequency range of the human ear. However, if the response of the ear can be approximated by digitally filtering the error signal before it reaches the adaptive controller, one can, in effect, minimize the more subjective loudness level, as opposed to the sound-pressure level. The work reported here entails simulating noise control based uponminimizing perceived loudness for a varied collection of input noise signals. A comparison of the loudness of the resulting error signal is made to the loudness of the error signal resulting from standard sound-pressure-level minimization. This comparison helps assess the worthiness, for a given noise signal, of utilizing the extra processing time this technique requires.
The active control of payload fairing interior acoustics using active blankets
Authors: Houston B. H. , Marcus M. H. , Bucaro J. A.
Published: July 2002

The results of numerical experiments associated with examining the potential performance of active blankets attached to the interior of a payload fairing to reduce the interior acoustic levels are presented. These studies are carried out using a finite-element–infinite-element model of the full fluid-structure system. In this model, the main rocket body is modeled as a finite cylinder with an attached rib-stiffened fairing. The interior fluid is modeled with finite acoustic elements while the entire exterior fluid is modeled with finite and infinite acoustic elements. Examined first is the broadband nature of the interior acoustic response due to a high-order acoustic field developed as a result of a point acoustic source located at the base of the rocket and laterally separated by approximately one rocket length. Next, control simulations are performed that impose a specific acoustic impedance at the interface between the structure and the fluid, thus simulating the acoustic boundary control (ABC) approach. Finally, the performance of an acoustic boundary control implementation is examined for several specific acoustic impedances together with some simple antisound configurations. [Work supported by the Office of Naval Research.]
Use of genetic algorithms for the vibroacoustic optimization of plates
Authors: Ratle Alain , Berry Alain
Published: July 2002

Genetic algorithms have proven to be helpful for solving complex optimization problems where more traditional gradient-based methods have failed. The optimal design of vibroacoustic systems often leads to complex optimization problems requiring a method able to find a globally optimal solution through a large number of locally optimal solutions. The vibroacoustic behavior of a simply supported plate carrying one or more point masses has been investigated through a genetic algorithm optimization method, in order to determine optimal placement of the masses for maximal sound or vibration attenuation. It has been shown that the use of an optimization method able to search through the whole optimization domain can give unexpected solutions resulting in a higher level of reduction in radiated noise or vibration response, when compared to intuitive solutions like placing the point masses on excitation points. In particular, when a well-defined frequency range is targeted, genetic algorithms can be used for tailoring a special design giving highest reduction in the specified range. [Work supported by the IRSST.]
Waves in an acoustic medium with microstructure
Authors: Barbone Paul E. , Shuman Rebecca B.
Published: July 2002

Acoustic wave propagation in a medium with microstructure is considered. By microstructure, it is meant that the medium properties change on a length scale that is short compared to an acoustic wavelength. An effective wave equation is derived for the ‘‘long’’ scale acoustic field using the method of multiple scales (i.e., homogenization). It is shown that the standard approximation breaks down in a few wavelengths. The effective equation is renormalized in an attempt to obtain a theory, which is valid for long propagation distances. The resulting equation is related to that derived by McDevitt et al. (McDevitt et al., ‘‘Dispersive Elastodynamic Models of Periodic Structures Using a High-Order Homogenization Approach,’’ Proceedings of Fourth U.S. National Congress on Computational Mechanics, San Francisco, August 6–8, 1997). Asymptotic validity of the equation for finite propagation distances is demonstrated. Over larger distances, solutions of this effective equation exhibits dispersion and attenuation. Strong scattering terms are shown to dominate these effects, however, when the medium is not statistically homogeneous. This asymptotic theory is validated by comparison to reference numerical calculations. [Work supported by NSF.]