bluuebunny/crossref_metadata_2025 huggingface dataset:
Inverse scattering using backpropagated eigenfunctions.
Authors: Mast T. Douglas , Nachman Adrian I. , Waag Robert C.
Published: October 2005

A new approach to inverse scattering using the eigenfunctions of scattering operators is presented. This approach provides a unified framework that encompasses eigenfunction methods of focussing, diffraction tomography, and inverse scattering in arbitrary media. The eigenfunctions of scattering operators are used to specify source distributions that focus incident energy in the vicinity of inhomogeneities. The present inverse scattering approach represents unknown scattering media using products of numerically backpropagated fields of eigenfunctions. Recent progress in the mathematical theory of inverse scattering has suggested that these products are an appropriate basis for the reconstruction of unknown inhomogeneities. Because of the focussing property of scattering operators, these products also form an efficient basis for computational implementations of inverse scattering. The currently suggested approach has the further advantage of applicability to any medium for which a background Green’s function can be determined. Computational results illustrate focussing of eigenfunctions on discrete and distributed scattering media, quantitative imaging analogous to diffraction tomography, and high-resolution inverse scattering in media with strongly scattering inhomogeneous backgrounds.

All posters will be on display from 8:30 to 11:30 a.m. To allow contributors an opportunity to see other posters, contributors of odd-numbered papers will be at their posters from 8:30 to 10:00 a.m. and contributors of even-numbered papers will be at their posters from 10:00 to 11:30 a.m.
Acoustic correlates of fricatives and affricates.
Authors: Castleman Wendy A. , Diehl Randy L.
Published: October 2005

Six adult speakers of American English produced voiceless fricatives and affricates in word initial position in a carrier phrase, varying vowel context, and stress patterns. From each of the productions, the following acoustic measurements were made: silence duration, frication duration, amplitude rise time, amplitude rise slope, frication onset centroid frequency, and following vowel duration. A discriminant function analysis revealed that silence duration was the best at discriminating between the fricatives and affricates, followed by frication duration, onset frequency, and rise slope. No additional discrimination was found due to either rise time or vowel duration. The traditional acoustic measure of rise time, which includes the duration and the slope of the rise, may be due entirely to the contribution of the slope rather than the duration itself. Although rise time has long been considered an important perceptual cue in the distinction between fricatives and affricates, recent research has brought this into question [K. R. Kluender and M. A. Walsh, Percept. Psychophys. 51, 328–333 (1992)]. The results of this study suggest that duration measurements (preceding silence interval and frication duration) are more salient acoustic correlates than amplitude rise-time measures. [Work supported by NIDCD.]
Fundamental frequency in minimal pair sentences.
Authors: Trout J. D.
Published: October 2005

The declination of fundamental frequency was investigated in minimal pair sentences which sound alike but which have word boundaries in different positions (e.g., The monkey races it/The monk erases it). Early results suggest that fundamental frequency declines over these minimal pair sentences in accordance with the results reported on global declination effects [t’Hart et al., A Perceptual Study of Intonation (Cambridge U. P., New York, 1990)]. Baseline fundamental frequency over sentences will be compared to that for word boundaries in two-word sequences (e.g., monkey races/monk erases) excised from those minimal pair sentences. Further analysis will determine whether local properties of fundamental frequency movement and acceleration differ significantly in word boundary versus intraword position, and so whether such properties may act as a local cue to word boundary. [Work supported by NIDCD Program Project Grant.]
Effects of ‘‘clear speech’’ on duration-dependent vowel contrasts.
Authors: DeMerit Jean L.
Published: October 2005

Acoustic and perceptual effects of ‘‘clear speech’’ were investigated by focusing on two duration-dependent vowel contrasts in American English, /ε, æ/ and /■, ■/. Minimal pairs of words were recorded in carrier sentences by four native female speakers under two speech style conditions, conversational and clear. Measurements of vowel duration and formant frequency were made. The acoustic analyses revealed patterns of durational behavior that differed by speaker but were generally uniform across both vowel contrasts. F1 and F2 frequencies from the grouped data were displaced toward more peripheral regions of the vowel space in clear speech. However, no consistent patterning was evident across individual speakers. A perceptual test using gated speech stimuli from two of the speakers was used to assess the relative amount of acoustic signal required to identify each vowel per speech style. Also, vowel identification rates were examined for initial gated segments (which included the first 25 ms of the vowel) as well as for full word presentation. Statistical analyses showed significant effects of speech style on vowel identification. Interactions among several factors, however, indicate that the perceptual improvements from speaking clearly depend on the speaker, vowel category and subsequent consonantal context.
Effects of speech style on the perceptual assimilation of American English vowels by Japanese speakers.
Authors: Yamada Reiko A. , Strange Winifred , Fitzgerald Brett H. , Kubo Rieko
Published: October 2005

Of specific interest in this study was the extent to which speech style (citation form versus sentence form) affected perceptual assimilation of AE vowels by Japanese listeners. Four adult male speakers produced 11 AE vowels in /hVba/ bisyllables in both citation form (lists) and in the sentence ‘‘I hear the /hVb/ on the tape.’’ Response categories, designated in Katakana symbols, included five short vowels, five long vowels, and eight vowel combinations (e.g., ou, ei, ja:). Twenty-four Japanese listeners selected the response category which was most similar to the /hV/ syllable they heard and rated its ‘‘goodness of fit.’’ Results indicated that, in general, AE vowels were assimilated to the Japanese vowel category closest in articulatory vowel space. However, intrinsic duration information was utilized much more consistently when the syllables were embedded in a carrier sentence. That is, intrinsically long (or diphthongized) AE vowels were assimilated to long-vowel or two-vowel response categories more often in the sentence condition. Acoustical analysis indicated that some, but not all, of the variation in assimilation patterns could be explained by F1/F2 variation. Implications for Japanese L2 learners of English are discussed. [Work supported by NIDCD.]
Response complexity effects on vocal reaction time in normal aged speakers.
Authors: Fozo Michael S. , Watson Ben C.
Published: October 2005

Reaction time (RT) studies reveal that vocal responses present an exception to the pervasive finding of slowed performance in aged adults. Previous vocal RT studies that compared young and aged speakers elicited a single-word response. Inconsistent findings may be attributed to their use of a limited range of response complexity. Young speakers show a significant increase in vocal RT from vowel to sentence responses [Watson et al., J. Voice 5, 18–28 (1991)]. This study tested the hypothesis that aged speakers in good physiologic condition show significantly longer vocal RT values relative to young speakers as responses increase in complexity. Vocal RT was recorded for isolated vowel, word, and sentence responses. The simple RT paradigm included variable foreperiods and intertrial intervals. Young subjects ranged from 24–31 yr. Aged subjects ranged from 68–85 yr. Group, response, and group x response effects were significant. Post hoc comparisons revealed significant between-group vocal RT differences for the word and sentence responses. Consideration of peripheral and central factors that may underlie the response complexity effect on vocal RT in aged speakers supports the conclusion that the origin of the complexity effect resides in central linguistic and/or motor planning for the response.
The effects of the attenuation of second and third formant frequencies on the recognition of stop consonant vowel syllables in aphasic and nonaphasic subjects.
Authors: Goldberg Lyn
Published: October 2005

The effects of the attenuation of second and third formant frequencies on the recognition of stop consonant vowel syllables (/p,b,t,d,k,g/ paired with the vowel /a/) in fluent and nonfluent aphasic and nonaphasic normal subjects were examined. Statistical analyses revealed significant differences between groups, between formant conditions, and between stop consonants. All groups responded similarly under the formant conditions, but the attenuation of F2 appeared to account for the most striking disparity between consonant recognition scores irrespective of group. A series of confusion matrices showed that confusions made by aphasic subjects involved both place of articulation and voicing errors, particularly for nonfluent aphasics, and involved the substitution of more anterior consonants. Important cues for the voicing of anterior consonants appeared to be carried by F2. The finding that more intact speech production abilities appeared to facilitate more accurate speech recognition was interpreted as support for the motor theory of speech perception.
Optimization for source waveform synthesis of pathological voices.
Authors: Gabelman Brian C. , Kreiman Jody , Gerratt Bruce , Alwan Abeer
Published: October 2005

This paper describes an algorithm that fits analytical source models of the glottal volume velocity to glottal source waveforms from inverse-filtered vowels. The analytical models include the KGLOTT88, LF, and simplified LF [Qi and Bi, J. Acoust. Soc. Am. 96, 1182–1185 (1994)]. In the first stage of the algorithm, curve features (peak values, zero crossing, period, etc.) are automatically extracted from samples of pathological voices and least-squares fitting is performed. The parameters are then fine-tuned based on the perceptual quality of the synthesized voices. Goodness of approximation of the resultant source function is determined by perceptually comparing the final synthesized vowel sounds to the original sound. Limitations of current source models with respect to modeling pathological voice will be discussed. [Work supported by NIDCD.]
Acoustic characteristics of voice source for pathological voices: Some case studies.
Authors: Ananthapadmanabha T. V. , Mallikarjun B. , Mallikarjun Dipti
Published: October 2005

The aim of this study is to examine the voice source signal of pathological voices. Pathological cases of vocal nodules, polyps, paralysis, malignancy, and laryngitis have been investigated. Some pre- and postoperative cases have also been studied. The sustained vowel /a/ of the subject has been recorded. The acoustic signal has been analyzed using an inverse filtering technique to obtain the voice source signal (derivative of glottal air flow). The voice source signal is displayed and marked for detailed examination. Acoustic recording, analysis, and marking is done using a VAGHMI system. For each type of pathology, certain consistent features deviating significantly from the normal cases have been noted in the voice source signal. For example, occurrence of double peak during the open phase, prolongation of the interval near glottal air flow peak, absence of clearly defined negative peak near epoch, etc. Interpretation of the voice source signal in terms of the vocal fold vibratory pattern and pathology has been attempted. Such an interpretation is validated against direct laryngoscopic observation where ever available. This on-going study suggests the possibility of differential diagnosis of the vocal fold pathology by acoustic analysis of vowel sound.
Analysis of ‘‘cold-affected’’ speech for inclusion in speaker recognition systems.
Authors: Tull Renetta G. , Rutledge Janet C.
Published: October 2005

Parameters of speech produced during winter weather are analyzed to determine the potential influence of distorted voices due to common cold on automatic speaker recognition systems. This research examines speech recorded before, during, and after bouts with the common cold. ‘‘Cold-affected’’ speech shows noticeable acoustic and phonetic differences between test sessions. Examining the different states of one male speaker’s voice allows an opportunity to address the speaker intersession problem that exists in speaker recognition technology. Specific emphasis is placed on the contrasts in various sessions of TIMIT inspired sentence ‘‘She had your dark suit in greasy wash water all year.’’ It also analyzes phonetic contrasts and looks at differences in formant patterns. Phonetic transcriptions of ‘‘cold’’ and ‘‘normal’’ sessions reflect changes in place of articulation. Perceptual and acoustic analyses reveal pauses and epenthetic syllables that are not constant throughout all sessions. ‘‘Cold-speech’’ also produces noise caused by hoarseness and coughing. Research presented here shows evidence of variability beyond ‘‘normal’’ speech patterns. Contributing to the information on intraspeaker variability, this work provides a preliminary analysis of ‘‘cold-affected’’ speech in an effort to include ‘‘abnormal’’ speech and speech affected by communications disorders into the framework of automatic speaker recognition.
Analysis of the glottal excitation of intoxicated versus sober speech: A first report.
Authors: Cummings Kathleen E. , Chin Steven B. , Pisoni David B.
Published: October 2005

The objective of the research reported here was to perform an analysis of the voicing characteristics of sober and intoxicated speech in order to assess the possibility of detecting intoxication from the speech signal. Because the glottal excitation is the result of complicated and intricate motions by the vocal folds, it should be significantly affected by alcohol use. In this study, excitation parameters were extracted from non-nasalized vowels in eight utterances spoken in both sober and intoxicated conditions by four speakers. Fifteen parameters, including pitch, pitch contour, rms intensity measures, and measures of shimmer and jitter, were extracted directly from the speech waveform. As expected, the most significant differences between sober and intoxicated speech were in parameters measuring perturbations in adjacent pitch periods. Also as expected, there were no significant differences in more global parameters such as average pitch. Additionally, glottal waveforms were extracted from two of the speakers in both conditions using an adaptation of Wong’s closed-phase glottal inverse-filtering method. Again, the most significant differences between sober and intoxicated glottal excitation were found in pitch-period-to-pitch-period variability. [Supported by a grant from the Alcoholic Beverage Medical Research Foundation to Indiana University.]
A numerical measure of alcohol depression.
Authors: Hayre Harb. S.
Published: October 2005

Consumption of alcoholic beverage is said to cause depression which is then followed by a high. A literature review shows that this depression had not been measured numerically. Chemical impairment measure (CMI) based on speech was used by the author to detect and measure the physiological/neurological depression. CMI ranges from zero to three on a special scale. Twenty subjects were given a double drink of whiskey each, and their CMI were measured at 2-min intervals starting 2 min prior to alcohol ingestion and continued for 60 min thereafter. CMI, in all cases was observed to initially decrease to a minimum, then monotonically increase to a maximum, and eventually decrease thereafter until it reaches a value near the predrink value. The time to reach the minimum as well as the depth thereof varied from one person to the next verifying the fact that each person has their own tolerance level.
Effects of syllable duration on stop-glide perception by humans and monkeys.
Authors: Sinnott Joan M. , Brown Charles H. , Mosteller Kelly W.
Published: October 2005

Humans and monkeys were compared in their perception of phoneme boundary shifts along two synthetic stop-glide /bα-wα/ continua differing in overall syllable duration (150 vs 320 ms). Humans were first tested with a written identification procedure and showed a boundary shift to longer transition durations with increased syllable duration, as previously reported in the literature. Humans and monkeys were then tested with a low-uncertainty discrimination procedure but showed little evidence of a sensory-level discontinuity underlying the identified boundaries: Instead sensitivity tended to follow Weber’s law. Finally, both humans and monkeys were tested with a go/no-go identification procedure specifically designed for monkeys. Similar stop-glide boundaries emerged and shifted with increased syllable duration for both species, indicating that monkeys make good models of human stop-glide sensitivity in identification procedures that involve higher level attentional and memorial processes. [Work supported by NIDCD.]
A study of lecture and computer-based teaching of articulatory and acoustic aspects of American English vowels.
Authors: Clarke William D.
Published: October 2005

Students in introductory courses on speech science have considerable difficulty in understanding the articulatory and acoustic phonetics involved in the production of vowels. A computer-based course of instruction has been developed that is intended to increase students’ understanding of the interrelationships of the important concepts in this difficult area [Jackson et al., J. Acoust. Soc. Am. 95, 3014(A) (1994)]. The present experiment evaluated the computer-based exercises along with the traditional lecture method. Students were assigned to two groups, and each group received both the lecture and computer instruction but in a different order. Cognitive structures tests using similarity ratings were administered to assess students’ understanding of the material before and after each type of instruction. Twenty concepts from the disciplines of articulatory and acoustic phonetics of vowels were paired for similarity ratings. Students’ mental models were compared to those of experts using ‘‘Pathfinder’’ network, multidimensional scaling, and profile correlations. The students’ shift toward expert-like patterns was small after lecture-only or computer-only presentations. The shift was moderate when the computer was first and lecture was second. The shift was large when the lecture was followed by the computer.
Perceptions of music and speech based on the autocorrelation and interaural cross-correlation functions.
Authors: Ando Yoichi
Published: October 2005

Based upon a model of auditory pathways which consists of the autocorrelation and the interaural cross-correlation mechanisms [Ando, Concert Hall Acoustics (Springer-Verlag, New York, 1985)], perceptions of music and speech as well as subjective responses of sound field in rooms are well described. This paper reviews some subjective attributes from recent investigations. The factors extracted from the autocorrelation function (ACF) of source signals include: (1) the energy of sound signal; (2) the effective duration of the normalized ACF; and (3) peaks as a function of its delay. These factors are deeply related to (1) loudness, (2) subjective attributes of the temporal structure of sound field, (3) the missing fundamental of complex sounds, respectively. Factors which may be extracted from the interaural cross-correlation function are included: (1) the IACC, the maximum value in the range of the interaural delay time; (2) τIACC, the delay of the IACC; (3) WIACC, the width of IACC. The first factor well describes the clarity of speech as well as subjective preference of sound field. The second factor may be related to the apparent source width (ASW), and the last one is related to the image shift of sound source.
Infant preference for harmonic closure in musical sequences.
Authors: Tucker Michael L. , Smith J. David , Jusczyk Peter W.
Published: October 2005

Previous investigations of Western tonal sensitivity suggest that young infants may have rudimentary tonal knowledge, for they notice altered notes and chords in a variety of change/no-change discrimination tasks. In contrast, infants’ preference for different tonal structures was evaluated here using the head-turn preference procedure. A group of infant subjects (age 6 months) was presented diatonic melodic sequences, identical in duration, tempo, and intervallic distance, that either reached harmonic closure (closed) or did not (open). Six closed–open pairs were constructed by matching sequences for pitch contour. The sequences were presented in a random order, and orientation times to each sequence were recorded. Surprisingly, 6-month-olds revealed a significant preference for the harmonically open melodic sequences. An additional study examines whether 9-month-olds exhibit a reversal of this preference, or whether harmonic incompleteness continues to recruit attentional processes. These findings are considered in light of the child’s growing experience with Western tonal music, and auditory-perceptual reorganizations that may occur during the latter half of the first year in music and speech. [Work supported by NIDCD.]
Bottom interactions of pulse propagation and corresponding real-time reverberation.
Authors: Smith Kevin B.
Published: October 2005

A simple, memory-intensive algorithm using a split-step Fourier cw PE model to compute the time-domain animation of a pulse has been developed. By examining such an animation in the presence of a rough, deep ocean bottom, the significance of secondary multipaths on predicted reverberation returns was found to be non-trivial. The existence and relative magnitude of these secondary arrivals has been confirmed in measured data. An additional algorithm has recently been developed to compute the exact two-way travel times associated with bottom interface reverberation by convolving the one-way travel times from the source and the receiver. Presented here is a simultaneous visualization of the one-way pulse propagation and the corresponding two-way reverberation. To determine the influence of the secondary multipaths on reverberation, the bottom has been altered in the near field to remove the multipath influence. This also shows the errors encountered in predicting reverberation when only the incident field is computed. [Work supported by ONR.]
Modeling target strength of reflective objects using computer ray tracing technique.
Authors: Gay Gerard P. , Raichel Daniel R.
Published: October 2005

Monostatic target strength of perfectly reflective geometric objects may be predicted through the use of a non-recursive ray tracing technique. This solution is based on the analytical infinite series solution of the wave equation. The ray tracing theory embodies the premise that the properties of sound, with wavelengths small compared to the size of the target objects, are analogous to those entailed in the propagation of electromagnetic waves. Simple geometric objects including spheres, disks, and cylinders are generated as object-oriented three-dimensional models; objects are ray traced so the model may be viewed and results may be calculated. The data produced by the use of this technique agree with theoretical results, thereby suggesting the validity of this method.
Modal time series structure in range and depth of a shallow-water area.
Authors: Knobles David P.
Published: October 2005

A theoretical analysis of pressure time series generated by small explosive sources and recorded on both an HLA and a VLA deployed in the Hudson canyon region off the New Jersey coast near the AMCOR 6010 borehole is presented. The SVP in the water column has an isovelocity layer down to a depth of about 20 m followed by a strong negative gradient to about 45 m where the profile becomes approximately isovelocity to theseafloor at 73 m. This sound-speed structure creates a unique time series structure on the VLA as a function of source range. The data are simulated with a broadband normal mode- approach recently discussed in the literature [J. Acoust. Soc. Am. 98, 1682–1698 (1995); IEEE J. Ocean. Eng. 21 (1) (1996)]. The representation of the spatial and temporal structure of the time series in terms of a modal structure reveals several unique aspects of the structure of the SVP in the water column and the geoacoustic structure of the bottom. The details of the modal structure of the sound field clearly define the propagation mechanisms in the water column and the interaction with the seafloor and sub-bottom sediment layers. [Work supported by Advanced Research Projects Agency.]
Mode coupling and mode stripping in propagation across the range-dependent Atlantic Generating Station (AGS) site.
Authors: Jaya Indra , Badiey Mohsen , Siegmann William L.
Published: October 2005

The complicated patterns of modal structure and attenuation observed in sound propagation through a range-dependent shallow-water environment are used to investigate and visualize the mechanisms of mode coupling and stripping. Broadband experiments have been carried out at the geologically known AGS site in the past few years. This presentation reports on a recent experiment which provides significantly more acoustic data along different propagation tracks and, consequently, permits high resolution of physical processes in range. A mode-filtering technique is used to construct modal structure from the data, while modal attenuation is obtained from spectral ratios. The evolution of modal structure is determined as a function of frequency and range. This is examined in view of environmental parameters along a selected propagation track. Numericalsimulations are carried out using interpolations of the known geoacoustic environment and employing the KRAKEN normal mode and RAM parabolic equation models. Results from these simulations are compared with the experimental data.
Mapping acoustic echosounder data to human color vision.
Authors: Boyle Frank A.
Published: October 2005

A colormapping algorithm was developed and applied to echosounder data from the seafloor. The technique offers a simple method of conveying subtle information about the seabed that might be useful in sediment classification. Features with different spectral content appear in a processed image with different shades of color. Broadband scatterers, such as rigid objects or interface roughness emerge as white or gray features, while narrow-band scatterers, such as trapped gas bubbles appear with a hue corresponding to their resonance frequency. The method has the potential to resolve the ambiguity between rigid and gassy sediments, which are indistinguishable in a grayscale display. A description of the colormapping algorithm, followed by a presentation of the results of its application to echosounder data and a discussion of their interpretation is given. [Work supported by NRL.]
New developments in noise control for HVAC systems.
Authors: Foulkes Timothy J.
Published: October 2005

The HVAC equipment industry is not known for rapid change. Although control systems have improved rapidly over the past few years, fans are still much the same as they were 20 years ago. Accessories such as air diffusers and vibration isolators have gone through small, incremental changes in the same time period. In the past 12 months, several new products have caught the author’s attention. These represent significant improvements in noise control and/or design flexibility and installation quality. This presentation will include product information on these new products along with a discussion of their pertinent advantages. Industry trends such as wider availability of sound data and custom engineered air handling units will also be discussed.
Duct breakout sound associated with ducts constructed of fiberglass duct board.
Authors: Reynolds Douglas D. , Degner Keith M.
Published: October 2005

Sound breakout from rectangular HVAC ducts constructed of fiberglass duct board has been investigated. Duct sizes that were tested were 12×12, 12×24, 12×36, 24×36, and 36×36. All dimensions are in inches. Four duct lengths for each duct size were tested: 4, 8, 12, and 16 ft. The sound breakout values for the fiberglass duct board were compared to corresponding values obtained from similar sized rectangular sheet metal ducts. Major objectives of the study were to obtain duct transmission loss values for rectangular ducts constructed of fiberglass duct board, to compare these values with corresponding values obtained from similar sized rectangular sheet metal ducts, and to specify conditions in which rectangular ducts constructed of fiberglass duct board can be used in situations where the control of duct breakout noise is important.
Dialects in South Pacific humpback whale song.
Authors: Helweg D. A. , Cato D. H. , Jenkins P. F. , Garrigue C.
Published: October 2005

Humpback whales (Megaptera novaeangliae) migrate annually between high-latitude summer feeding waters and low-latitude winter mating waters with a high degree of site fidelity. During migration and in winter waters, adult (male) humpbacks produce long complex songs. Song content is dynamic, but singers incorporate changes as they occur. Song sharing across regions is cultural, thus similarity of songs from different regions may be an index of reproductive isolation. Songs recorded in Tonga, New Caledonia, Eastern Australia, and Kaikoura, New Zealand, in the winter of 1994 are compared. The song from Kaikoura is the most southerly recording of song, over 2000 km south of winter migration termini. Seven themes were shared by all regions plus two themes not observed in Tonga. Differences in regional variants were most pronounced between Tongan and Eastern Australian song. New Caledonian and Kaikouran song were proportionately more like Eastern Australia. Kaikoura song was more similar to Eastern Australian song than Tongan song. These regional differences can be considered to be dialects that are maintained through cultural transmission of regional variants. The results suggest some migratory exchange among widely separate wintering regions of area V and speculation that song sharing occurs throughout migration and breeding seasons.
A nonparametric statistical approach to representation of variations within a class of marine mammal vocalizations.
Authors: Hayward Thomas J.
Published: October 2005

A nonparametric statistical approach has been developed for representing variation within a class of vocalizations. This statistical representation permits computationally efficient a posteriori estimation, based on training in a supervised learning context, of the probability density associated with the class. This approach avoids the assumption of parametric forms for the probability density; parametric forms may not be suitable in cases where the probability density has a complex, multimodal character. Two applications of the statistical representation are described. First, the a posteriori densities associated with several classes of transients can be computationally ‘‘evaluated’’ on a new sample to provide a basis for classification of marine mammal vocalizations as well as a measure of confidence in that classification [J. Acoust. Soc. Am. 96, 3312 (1994); 98, 2969 (1995)]. Second, the statistical representation provides for quantitative characterization of variability using information-theoretic measures. Examples of both applications are presented. [Work supported by ONR and NRL.]
Intraspecific variations in finback (B. physalus) 20-Hz doublets: An acoustic multipath interpretation.
Authors: Premus V. , Spiesberger J. L.
Published: October 2005

Biologists have pointed to differences in received calls as evidence for some separation in finback populations in different locations [Watkins et al., J. Acoust. Soc. Am. 82, 1901–1912 (1987)]. More specifically, it has been concluded by Thompson et al. that the unique finback doublet interpulse intervals recorded in the Gulf of California constitute corroborating evidence for the hypothesis that ‘‘Gulf of California fin whales may be a separate population, distinct from fin whales in nearby Pacific regions’’ [Thompson et al., J. Acoust. Soc. Am. 92, 3051–3057 (1992)]. An alternative explanation is offered—that regional differences in finback doublet interpulse intervals may be accounted for by differences in acoustic propagation conditions. In this work, a broadband acoustic propagation code is combined with an empirically derived geoacoustic seafloor model for the purpose of interpreting finback doublet sequences recorded in the northern Gulf of California by Thompson et al. in 1987 [ibid.]. The result is that for ranges less than 30 km, it is possible to explain the appearance of the finback doublet in terms of multipath propagation through the water column and the seafloor. Further, the interpulse delay is demonstrated to be strongly range dependent. Scientists might consider the possibility that finbacks make use of multipath intervals to estimate distances to other finbacks, perhaps for reasons related to social behavior.
Experiments on the directional startle reflex in goldfish.
Authors: Lewis Thomas N. , Woods Theresa J. , Rogers Peter H.
Published: October 2005

The acoustic startle reflex in goldfish (Carassius auratus) was studied experimentally in the large acoustic tank at Georgia Tech. Individual free swimming fish were placed in an acoustically transparent cage and positioned in the center of the tank. Their behavior was graded for a response to acoustic signals and the direction of response with respect to the sound source. A preliminary study indicated two interesting features. First, the fish was much more likely to respond in the ‘‘correct’’ direction (away from the source) when responding to subthreshold stimuli. Second, there was strong dependence of signal amplitude at threshold on fish size. For the two weight groups tested (1.6 g, n=3 and 23.6 g, n=4), the sound-pressure level at threshold was 15 dB lower for the smaller subjects. The initial study has recently been augmented with tests on a range of subjects weighing between these two extremes. Also, since only the first half-cycle of the acoustic stimulus is thought necessary to elicit the response, the concept of frequency to characterize the sound stimulus is inappropriate. Therefore, thresholds were measured as a function of signal rise time. A parallel effort has involved modeling a biologically relevant stimulus: the acoustic field generated by an attacking predator. [Work supported by ONR.]
Variation in whistle-type and rate produced by captive dolphins relative to in-water interactions with humans.
Authors: Frohoff T. G. , Packard J. M. , Benson R. H.
Published: October 2005

The relative importance of expression and symbolic content in acoustic communication of cetaceans has been debated. These topics may be examined by observing how general rates of vocalizations change with excitatory state and how specific vocalizations vary independently of state and depend upon content. In this study, whistles (0.32 to 22 kHz) of two captive bottlenose dolphins (Tursiops truncatus) were recorded underwater before, during, and after six swim sessions in which the behavior of the dolphins and four human swimmers was controlled by a trainer on the dock. Sonograms of 205 min of recorded whistles were analyzed. Variation of whistle-type and rate was observed relative to the three contexts. The contours of distinguishable whistles (n=591) revealed 32 types. Ten types were observed during one context only; during the swim sessions. Almost half of the whistle types (15 to 32) were more likely to occur prior to swim sessions and the others were more likely during swim sessions. None were more frequent after swims. Rate of whistles was significantly higher than expected during the swim sessions (z=7.21) and lower than expected after the swim sessions (z=−0.03).
The attenuation and dispersion of sound in water containing multiply interacting air bubbles
Authors: Feuillade C.
Published: October 2005

The classic theory of linear acoustic propagation in bubbly water inaccurately represents the physical behavior of dense populations of resonating bubbles. It assumes the bubbles always oscillate independently, while they may actually be strongly coupled by acoustic radiation, especially when uniformly sized. Sound propagation can be properly understood only in terms of the collective action of the medium, which is dominated by the ‘‘symmetric’’ normal mode. In this work, the propagational characteristics of bubbly water are determined by averaging the ensemble behavior of the symmetric mode over distributions of bubble radii and locations. The method includes all orders of multiple scattering, and incorporates ‘‘shielding’’ effects in the medium. New theoretical expressions for the phase speed and attenuation are obtained, and compared to experimental data by integrating multiple scattering effects over a ‘‘region of collective interaction’’ around each bubble. For uniform bubbles and volume fractions β ≥ 0.22%, multiple scattering strongly influences propagation. When β < 0.22%, the effects apparently diminish sharply. For nonuniform bubbles and β ≊ 0.02%, multiple scattering effects are not indicated. These results imply that the classic theory should provide an adequate description of the acoustic properties of bubble plumes and clouds typically encountered in the ocean.
Measurement and prediction of the reflection coefficient of porous layers at oblique incidence and for inhomogeneous waves
Authors: Brouard Bruno , Lafarge Denis , Allard Jean-François , Tamura Masayuki
Published: October 2005

Near-field acoustical holography (NAH) is used in the present work to measure the reflection coefficient of porous layers from normal to grazing incidence and for inhomogeneous waves. Measurements are compared with predictions obtained from a recent model. A lateral propagating mode inside the porous layer is evident.
Sound localization in noise: The effect of signal-to-noise ratio
Authors: Good Michael D. , Gilkey Robert H.
Published: October 2005

The sound localization ability of human observers has been frequently examined in quiet environments, but there have been relatively few studies that have considered the effect of noise on sound localization. In this study, three subjects judged the perceived direction of a broadband click-train signal in the quiet and in the presence of a broadband noise at nine signal-to-noise ratios, which varied over a 23-dB range. The signal could originate from any of 239 spatial locations that completely surrounded the subjects in azimuth (360°) and ranged from −45° to +90° in elevation; the masker (when present) was always located directly in front of the subjects at 0° azimuth and 0° elevation. The subjects indicated the perceived direction of the signal by pointing at a 20-cm-diam spherical model of auditory space. As the signal-to-noise ratio was lowered, the accuracy of localization judgments decreased nearly monotonically. However, the accuracy of judgments relative to the median plane (i.e., the left/right dimension) was less strongly influenced by the presence of noise than was the accuracy of judgments relative to the horizontal plane (i.e., the up/down dimension). The accuracy of judgments relative to the frontal plane (i.e., the front/back dimension) was most strongly influenced by noise.
The effect of talker rate and amplitude variation on memory representation of spoken words.
Authors: Bradlow Ann R. , Nygaard Lynne C.
Published: October 2005

This study investigated the encoding of spoken word attributes in a task of continuous recognition memory. In experiment 1, subjects were presented with a list of spoken words, and for each word they judged whether the word was ‘‘old’’ (had occurred previously in the list) or ‘‘new.’’ Results showed that subjects were more accurate at recognizing a word as ‘‘old’’ if it was repeated in the same voice (condition 1), and at the same rate of speech (condition 2); however, no recognition advantage was found for words repeated at the same amplitude (condition 3). In experiment 2, subjects gave an additional explicit judgment as to whether ‘‘old’’ words were repeated in the same voice (condition 1), rate (condition 2), or amplitude (condition 3). Subjects again showed a recognition advantage for words repeated in the same voice and rate, but no advantage occurred in the amplitude condition. However, subjects in all three conditions were significantly above chance accuracy in recognizing whether an ‘‘old’’ word was repeated in the same voice, rate or amplitude. These data suggest that, even though voice, rate, and amplitude information may be encoded differently, information along all three dimensions is retained in memory. [Work supported by NIH.]
Implicit memory for silent-center syllables: Effects of talker, token, and delay.
Authors: Hura Susan L. , Chasey Lauren E. , Kopf Joshua S. , Muelhausen Emily C.
Published: October 2005

Listeners’ ability to reconstruct missing vowel information in silent-center (SC) syllables has been viewed as evidence that vowels are dynamically specified by the information in syllable transitions. In this study implicit memory techniques are used to explore the representations formed when listeners perceive SC syllables. A set of CVC words spoken by several talkers was used to create SC and full syllable stimuli. A subset of SC stimuli was presented to listeners for identification. After a variable delay listeners were tested on the complete set of full syllables, some of whose SC versions were presented in the initial phase. Other full syllables overlap with the SC set in terms of talker or token. Performance on full syllables with differing degrees of overlap between SC and full stimuli is compared across a range of delays. Facilitation on full syllable stimuli is viewed as evidence that representations of individual SC stimuli are stored in memory and accessed in later perception of full syllables.
Identification of vowels based on visual cues within raw complex speech waveforms.
Authors: Stokes Michael A.
Published: October 2005

Testing was performed to demonstrate that subjects can identify vowels using visual displays of raw complex waveforms. Two Midwestern males produced nine vowels [Peterson and Barney, J. Acoust. Soc. Am. 24, 175–184 (1952)] for two identification trials. In both trials, nine vowels were presented in random order by an experimenter. Subject MS correctly identified five out of nine vowels in both trials. Identification was accomplished by recognizing temporal interactions between F0 and F1 that provide categorical boundaries across the vowel space. The presence or absence of F2 in the range of 2000 Hz also provides a distinguishing characteristic between categorical pairs. When formant values and articulatory data are organized by categories seen within speech waveforms, the vowel space resembles the pairings of the stop consonants /b/–/p/, /d/–/t/, and /g/–/k/. Tongue position (reflected in F1 values) categorizes a vowel as place of articulation categorizes stop consonants. Lip position (reflected in F2 frequency) distinguishes vowels within a category as voicing distinguishes these consonant pairs. The details and potential success of a new model of vowel perception based on these findings will be discussed.
Temporal and acoustic parameters mediating perceptual overshoot in vowel perception.
Authors: Hawks John W.
Published: October 2005

The experiments reported here represent the preliminary findings of an investigation designed to provide a better understanding of the parameters underlying perceptual overshoot in vowel perception. Continua of dynamic vocalic tokens were synthesized which spanned multiple vowel categories and varied in (1) F1, F2 location of starting and ending points, (2) rate of frequency change, (3) direction of dynamic transition, and (4) total duration. Subjects determined (1) whether each token was heard as containing one or more than one vowel quality, and (2) the identity of the vowel quality(s). The results suggest the values of the varied parameters sufficient for eliciting the overshoot phenomenon and will be discussed in terms of evidence for a purely auditory mechanism for overshoot or whether an articulatory (biomechanical) basis can be considered.
The perceptual magnet effect as an emergent feature of neural map formation.
Authors: Guenther Frank H. , Gjaja Marin N.
Published: October 2005

The well-known perceptual magnet effect [e.g., P. K. Kuhl, Percept. Psychophys. 50, 93–107 (1991)] is characterized by a warping of perceptual space near phonemic category centers. Whereas previous explanations of this effect have been formulated within the theoretical framework of cognitive psychology, the model proposed here builds on research from both psychology and neuroscience to account for the effect. This model embodies two principal hypotheses supported by considerable experimental and theoretical research from the neuroscience literature: (1) Sensory experience guides development of an auditory neural map, and (2) a population vector analysis can predict psychological phenomena from map cell activities. These hypotheses are realized in a simple, self-organizing neural network model. The magnet effect arises in the model from language-specific nonuniformities in the distribution of map cell firing preferences. These nonuniformities result from exposure to language-specific distributions of attended sounds experienced by the network during training, in keeping with neurophysiological results from auditory cortex [G. H. Recanzone, C. E. Schreiner, and M. M. Merzenich, J. Neurosci. 13, 87–103 (1993)] and other sensory areas. Numerical simulations verify that the model captures the known general characteristics of the magnet effect and provides very accurate fits to specific psychophysical data.
Modeling processing dependences in speech perception.
Authors: Crowther Court S.
Published: October 2005

The goal of this work was to determine whether acoustic cues to the phonetic features of a segment are processed independently. For stop–vowel (CV) syllables, one point of controversy concerns whether place information (as conveyed by formant transitions) and voicing information (as conveyed by VOT) are processed mutually independently. In this experiment, a replication of Massaro and Oden [J. Acoust. Soc. Am. 67, 996–1013 (1980)], F2 and F3 transitions and VOT were manipulated as place and voicing cues in CVs. Members of a family of multinomial models, including FLMP, were fitted to each subject’s data. FLMP, which assumes that processing is independent at both the perceptual and decisional levels, failed to account for the data. Two other models retained the perceptual independence assumption, but one assumed the voicing decision was contingent on the outcome of the place decision, and the other assumed the opposite contingency. Both fitted better than FLMP, but nevertheless were rejected on statistical grounds. A model assuming decisional independence, but perceptual dependence, fitted each subject’s data well. It was concluded that the formant transitions and VOT were not perceived independently, but that the voicing and place decisions were made independently. [Work supported by NIDCD (2-T32-DC-00013-16).]