bluuebunny/crossref_metadata_2025 huggingface dataset:
Representation of speech by infants
Authors: Jusczyk Peter W. , Mehler Jacques , Bertoncini Josiane , Bijeljac-Babic Ranka
Published: October 2005

Infants are capable of making fine discriminations between speech contrasts. What role do such capacities play in acquiring the sound structure of a native language? One possibility is that when infants learn to recognize spoken words in their native language, they encode all of the acoustic properties they are capable of registering into their representations of words. On this view, the initial representations might be quite detailed and the effect of experience with a specific language would be to eventually eliminate those aspects not relevant to phonemic distinctions in the language. An alternative view is that infants may start with very global representations of words, sufficient to distinguish among a limited number of vocabulary items. Addition of new words would force infants to incorporate into the representations more of the information that they are capable of extracting from their perceptual analyses of speech. Experience with a specific language would serve to select those properties most relevant to making phonemic distinctions in the language. Some support for the latter hypothesis is provided by a series of experiments on newborns' and 2-month-old infants' representation of speech. [Work supported by NIH ♯ 15795 & C. N. R. S.]
Toward an acoustic typology of vocalizations in the first year of life
Authors: Kent Raymond D. , Bauer Harold R.
Published: October 2005

Acoustic methods have been applied sufficiently to the study of infant vocalizations in the first year of life that an acoustic data base has begun to emerge in the literature. This paper considers this data base with respect to (1) its adequacy in describing the pattern of normal phonetic development, and (2) its potential for identification of infants at risk for communication disorder. With respect to (1) above, data will be summarized on several acoustic variables, including vocalic formant frequencies, utterance duration, fundamental frequency, vocal tremor frequency, noise spectra of fricative and trill segments, repetition rate of trills, and voice onset time for syllable-initial stops. With respect to impairment or palatal clefting. A preliminary acoustic typology based on an acoustic coding of infant vocalizations will be presented.
Prosodic contours in English 2-year-olds' words
Authors: Pollock Karen E. , Allen George D. , Goffman Lisa
Published: October 2005

Polysyllabic words produced by six 2-year-old English-speaking children were analyzed for prosodic contours using wideband, narrow-band, and average amplitude spectrograms. The children were tape-recorded as they named pictures and objects during a play situation. Using the procedures previously described for the analysis of similar French children's productions [G. Allen, Acoust. Soc. Am. Suppl. 1 73, S29 (1983)], words were analyzed for fundamental frequency contours over the word, and peak intensity differences and absolute and relative vowel durations between the last two syllables. Data will be presented on each measure alone and in correlation with the other measures. Results will be discussed in relation to universal patterns of early speech production, differences between the English and French children's contours, and differences between individual subjects.
Eigenvalue/eigenvector characterization of slope reflected signals
Authors: Livingston E. , Tolstoy A.
Published: October 2005

Eigenvector/eigenvalue analysis of experimental acoustic propagation data obtained in the region of the East Australian Continental Slope indicates this method is sensitive to changes in multipath structure and can distinguish multiple signal arrivals. A 16-element horizontal array at 300 m was towed in deep water, while a 152-Hz source at 18-m depth was moved from shallow to deep water. Source-receiver separation was about 60 nmi with source bearing near array endfire. Shipboard processing consisted of 1024-Hz time sampling, 4K FFT processing, and production of cross-spectral matrices for selected frequency bins around 152 Hz. The eigenvalues of a spatially whitened cross-spectral matrix may be used to count the number of statistically independent arrivals. These may be from multiple sources or from multipath effects of a single source. The eigenvalues for each sample cross-spectral matrix (five minute averages) were calculated and displayed versus time in order to correlate the number of large eigenvalues with the number of signal arrivals. In addition, conventional, minimum variance (ML), and eigenvector beamforming produced wavenumber-time displays of signal arrivals. For comparison, a GRASS-based ray trace model, using actual bottom reflection coefficients and deep water sound-speed profile, was used to predict expected arrivals. Comparisons of the visible shift in eigenvalues with arrivals in both the beamformed and modeled data show the eigenvalue detection method to be sensitive to changes in the multipath structure and capable of distinguishing multiple signal arrivals that were not detectable with conventional beamforming methods.
Using a multi-dimensional matched filter algorithm to separate multipaths
Authors: Reynolds S. A. , Bell B. A. , Ewart T. E.
Published: October 2005

Acoustic pulse arrivals can often be modeled as a sum of time-shifted, amplitude-scaled replicas. When these arrivals occur at separations of a few wavelengths or less, a multi-dimensional method is required to separate the individual paths. An algorithm that separates the paths by globally optimizating a multi-dimensional matched filter (Bell and Ewart, submitted to IEEE Trans. Acoust., Speech, and Signal Process.) has been used on two data sets. One set, taken during the Mid-ocean Acoustic Transmission experiment (MATE), is heavily contaminated by multipath. The second, taken during the AIWEX Acoustic Transmission Experiment (AATE), is a very large data set that contains segments contaminated by closely spaced paths. The advantages of this algorithm over previous ones are speed and the pulses are solved independently. Because the algorithm is fast, several passes through the data are possible. By varying the dimension of the filter, a better picture of the temporal structure of the multipath arrivals is possible. The effect of errors have been examined.
Effects of intense sound exposure on spontaneous otoacoustic emissions
Authors: Norton Susan J. , Champlin Craig A. , Mott John B.
Published: October 2005

The effects of intense sound exposure on spontaneous otoacoustic emissions (SOAE) were measured in normally hearing human subjects as a function of exposure duration and frequency region. Consistent with the TTS literature, exposures one-half to one-quarter oct below the SOAE frequency have the largest effect. A 30-s, 105-dB SPL exposure shifts the SOAE frequency downward, while having little effect on SOAE amplitude. Recovery is biphasic: In the first minute post-exposure, the SOAE frequency changes rapidly; over the next 20 to 30 min, the SOAE slowly returns to pre-exposure values. Exposures of 15 and 60 s have similar effects. These results suggest that alterations in cochlear mechanics can be produced by stimuli that do not typically produce TTS. [Work supported by NINCDS grants R15 NS23202-01 (SJN & CAC) and T-32-NS07257 (JBM).]
Vapor effects on bubble oscillations
Authors: Prosperetti A.
Published: October 2005

A simplified mathematical model for the description of the therm-fluid dynamical behavior of a bubble containing gas and vapor is described. The pressure in the bubble is taken to be spatially uniform. Diffusion effects and evaporation-condensation processes are properly accounted for in the framework of this approximation. The model is applied to the study of several aspects of forced oscillations which are examined for different temperatures of the hot liquid. The implication of the results for the propagation of pressure waves in bubbly liquids is briefly considered.
Model for a linear viscoelastic medium that has consistent creep and stress-relaxation properties
Authors: Rudgers Anthony J.
Published: October 2005

The stress and strain tensors for a homogeneous isotropic viscoelastic material are related by a general linear transformation, which expresses a complete proportionality of the sum of the stress and the stress-rate fields to the sum of the strain and the strain-rate fields in the medium. This transformation defines the functional forms of all components in the symmetric fourth-rank matter tensors that specify the stiffness and the compliance of the dissipative medium. Corresponding stiffness and compliance moduli (e.g., shear modulus and shear compliance) are found to have the same kind of functional dependence upon the frequency. Thus the stress-relaxation effects exhibited by the any stiffness modulus are consistent with the creep (strain-relaxation) effects exhibited by the corresponding compliance modulus. However, ass consequence of the tensor relation between stress and strain, stiffness (and compliance) moduli of different kinds (e.g., shear modulus and bulk modulus) vary with frequency in different ways. The matrix forms of the stiffness and compliance tensors are discussed in terms of analogous equivalent networks that can be used to represent the mechanical behavior of the viscoelastic medium. Tensor transformations and network-analysis algebra were carried out using computer programs for symbol manipulation.
An experimental study of the polar characteristics of the group and phase velocities of Lamb waves in graphite/epoxy composite plates
Authors: Rose Wade R. , Rokhlin S. I. , Adler Laszlo
Published: October 2005

The anisotropy of graphite/epoxy composite plates was studied using measurements of phase and group velocities of Lamb waves. Three types of composite structures were used: unidirectional, two directional with orthogonal fibers, and quasiisotropic. The phase and group velocities and the angle of deviation between them were measured using angle variable contact ultrasonic transducers which were situated on the surface of the plates. The anisotropy of the plates resulted in the deviation of the ultrasonic beam from the wave normal which was in some cases more than 60°. This beam deviation had to be taken into account to correctly measure phase and group velocities. The experimental data were compared with calculations of the angular dependence of the phase and group velocities of bulk waves in the graphite/epoxy composite material. The advantage of the Lamb-wave technique over bulk waves is the ability to measure the in-plane anisotropic properties of thin composite plates such as those used in actual aircraft applications.
Spurious resonances in adaptation of elastic layer model to simulate liquid layers
Authors: George Jacob
Published: October 2005

When computer programs based on an elastic layer model [e.g., Folds and Loggins, J. Acoust. Soc. Am. 62, 1102 (1977)] are used to simulate liquid layers, spurious resonances appear as a function of frequency. It is shown that they are not caused by numerical precision limitations in the computer, but are inherent in the model. In the computer representation of the elastic layer model, the limit of Lamé constant μ→0 is approximated by assigning a very small value for μ. With such a choice, spurious resonances appear when transmission coefficient is plotted as a function of frequency. This is also proven analytically, and the mechanism of typical resonances with graphs is illustrated. For frequencies away from spurious resonances, the model does yield the correct liquid layer results.
Modeling pitch perception of complex tones
Authors: Houtsma Adrianus J. M.
Published: October 2005

When one listens to a series of harmonic complex tones that have no acoustic energy at their fundamental frequencies, one usually still hears a melody that corresponds to those missing fundamentals. Since it has become evident some two decades ago that neither Helmholtz's difference tone theory nor Schouten's residue theory could adequately account for this phenomenon, several other theories have been proposed that accentuate central neural rather than peripheral mechanical signal processing. Some of these theories will be critically reviewed against empirical evidence from recent psychoacoustic studies. In particular, the relative advantages and disadvantages of the descriptive “virtual pitch” theory of Terhardt and the stochastic “optimum processing” theory of Goldstein are discussed in relation with recent data on pitch perception for simultaneous complex tones. Taped examples of some of the studied phenomena are provided.
Pitch and the perceptual organization of complex spectra
Authors: Hartmann W. M.
Published: October 2005

The psychological attribute of pitch is the most important organizing element by which the human auditory system reduces a steady-state complex signal to one or more perceptual entities. Historically both experimental and theoretical studies of pitch perception have been primarily concerned with the synthetic listening mode and the pitch of a single entity. However, there are experiments which test the analytic mode and the ability to segregate several entities. The mistuned harmonic experiment, in which the task is to hear out a mistuned partial in a complex tone, is a promising approach of this kind, though it demands that the experimenter try to distinguish those effects which are due to beats of mistuned consonances or nonlinear combination tones from those due to perceptual reorganization into segregated entities. The results of mistuned harmonic experiments suggest that the most sensitive segregation operation is mediated by neural processes which are tonotopically local, though they are tuned more broadly than a critical band. Therefore, appropriate models are not based upon pattern matching in a central spectrum but upon cross correlation between the firing patterns in neighboring sharply tuned neural elements or upon autocorrelation of the pattern in a more broadly tuned element. Such models are supported and constrained by physiological observations of the temporal response to complex tones in single cells of the eighth nerve, the cochlear nucleus, the inferior colliculus and the cortex.
Implications of research with nonspeech stimuli for speech processing: A summary of recent studies using world-length tonal patterns
Authors: Watson C. S.
Published: October 2005

A series of discrimination experiments with word-length sequences of brief tones has demonstrated aspects of auditory processing not evident from studies with simpler stimuli (single tones, noise bursts, clicks). The primary new limitations on processing discovered with the nonspeech stimulus patterns are associated with (a) the level of stimulus uncertainty (size of the catalog sampled to generate a sequence of trials) and (b) the information content within the individual patterns (represented by the number of freely varying components per pattern). These jointly determine the level of informational masking within the patterns, a central limit on component detectability that can vary from 0 to 40–50 dB above the expected (peripherally determined) intercomponent temporal masking. These empirical results are interpreted in terms of three properties of auditory memory: long-term memory (LTM), the accessibility of the properties of individual complex waveforms within the LTM, and the informational capacity of short-term auditory memory. Informational masking is reduced or eliminated under conditions that permit LTM-based (top-down) selective attention to meaningful portions of a complex nonspeech waveform. It is proposed that precise discrimination of critical elements of speech waveforms depends on similar central-control mechanisms. [Supported by NINCDS and AFOSR.]
Speech in noise revisited: Evaluation of intelligibility and voice quality of speech in broadband noise
Authors: Smith Caldwell P.
Published: October 2005

Recordings of diagnostic rhyme tests (DRT) for intelligibility and sentence lists for quality assessment spoken by three male speakers were mixed with white noise and low-pass filtered at 4 kHz. Calibration of speech-to-noise energy ratios was accomplished with the Sims algorithm [J. T. Sims, J. Acoust. Soc. Am. 78, 1671–1674 (1985)] to obtain S/N ratios of 6, 12, 18, 24, and 30 dB. The resulting composite signals were recorded with high-quality digital audio equipment (Sony PCM-F1) which was also used to reproduce the signals for presentation to listeners. Voice quality and acceptability were assessed with the diagnostic acceptability measure (DAM) test of Voiers, and the mean opinion score (MOS) rating. Data from analysis of listener responses were used in calculating regression model relating scores for overall intelligibility, feature intelligibility, signal quality, background quality, overall quality, and mean opinion scores, to S/N energy ratios. Models fitted to overall intelligibility scores, as well as some of the intelligibility feature scores, were significantly improved with regard to values of r2 (multiple correlation coefficient squared) by using indicator variables for speakers, i.e., regression models with separate origins for speakers, but a common slope for the regression lines. Regression models also facilitated interpolation of scores to compare descriptive categories that have been used for intelligibility, quality, and MOS scales; e.g., “fair” has been used to categorize intelligibility between 79 and 83, quality scores between 42 and 48, and MOS ratings between 2 and 3. For speech in broadband noise, categories varied widely for the three scales.
A method for automatic phoneme boundary detection
Authors: Selim Hany
Published: October 2005

A three-way classifier is introduced, which reliably differentiates between voiced, unvoiced, and silence segments of a speech utterance. The extreme points of the median smoothed first difference of the output of this classifier are used for the phoneme boundary detection. The classification criterion is calculated by weighting the log of the ratio of high- and low-pass filtered versions of the speech utterance by clipped versions of a normalized root average energy and a normalized zero crossing rate. The high- and low-pass filtering operations were simply performed by calculating the sample difference signal and the sample addition signal. The frequency domain attenuation characteristics corresponding to these simple filters are those of a quarter period of a cosine and sine waves, respectively. These filters were found to be completely sufficient for the purpose of classification. The phoneme boundary detector can be used for the mechanized acquisition of the phoneme inventory of any language and, due to the simple operations involved, in automatic speech recognition.
Inversion techniques for obtaining seabed low-frequency reflection loss at small grazing angle in shallow water
Authors: Zhou Ji-xun
Published: October 2005

Low-frequency bottom reflection loss at small grazing angles is a key parameter for sound field prediction in shallow water, but it is difficult to measure directly. For small grazing angle, the relationship between the bottom reflection loss and the grazing angle is nearly linear, − 20 log|V(θ)| = Bθ, where B ∝ Kp f(n − 1) and sound attenuation in the sediments is expressed by αp = Kp fn (dB/m⋅kHz). The bottom reflection loss parameter B in shallow water can be extracted by inversion techniques from a number of different field characteristics. In this paper, some theoretical inversion methods and extract reflection-loss parameters (B) for different sea areas are presented. The experimental results show that the parameter B apparently increases with increasing frequency. This implies that n > 1, i.e., that the frequency dependence of the sound attenuation in the sediments could be nonlinear. The experimental results of E. C. Lo et al. [J. Acoust. Soc. Am. 74, 1833–1836 (1983)] can be explained very well by using the frequency dependence of bottom attenuation (and sound velocity) obtained by inversion of the normal mode measurements made by J. X. Zhou [J. Acoust. Soc. Am. 78, 1003–1009 (1985)].
Scattering loss of interface waves at a rough seabed: Theoretical calculations
Authors: Zakarauskas Pierre , Chapman David M. F. , Purcell Anthony I.
Published: October 2005

Using the Rayleigh method, a boundary perturbation technique, the propagation of interface waves (i.e., Scholte waves) along a randomly rough fluid/solid boundary is studied. It is assumed that the surface has Gaussian statistics and that the autocorrelation function is exp(− r2/L2), in which L is the correlation length. The method assumes that the rms surface height is small compared to the acoustic wavelength λ, and that the surface slopes are also small. There is no restriction on L/λ. The intensity of the average field decays exponentially with range; the energy lost is scattered into interface waves traveling in other directions and into bulk waves carrying energy away from the boundary. For L/λ<1, the loss varies as (L/λ)5 and energy is lost mostly to bulk waves; for L/λ>1, the loss varies as (L/λ)4 and the energy is lost mostly to interface waves; at intermediate values of L/λ, there is a local maximum of energy loss. This behavior is explained qualitatively using wavenumber-space scattering diagrams. Results for the cases of water over sand, chalk, and granite are presented, respectively.
Rate and frequency effects on brain stem binaural interaction responses
Authors: Parthasarathy T. K. , Moushegian G.
Published: October 2005

Spectrum and presentation rate were parameters utilized to evaluate the binaural interaction component (BIC) of the auditory brain stem response (ABR) at 100 dB SPL in normal hearing adults. Binaural brain stem waveforms were similar in morphology to the sums of the monaurals. For stimulus conditions of this study, amplitudes of the binaural wave V were always smaller with shorter latencies (0.1–0.2 ms) than the summed monaural amplitudes and latencies. Increasing stimulus rate produced small increases in response latencies and decreases in peak amplitudes of the N1-P2 binaural interaction components and concomitantly, an increased latency and decreased amplitude of wave V of ABR. Rate effects at different center frequencies affected the BIC in ways significantly different from known effects of repetition rate on wave V ABR latencies using unfiltered clicks. Both the wave V of ABR and N1-P2 component of BIC from all subjects consistently evoked shorter latencies to the 2000-Hz tone bursts than to either 500- or 1000-Hz tone bursts. At low frequencies, a derived frequency following response (FFR) was obtained having latencies and configurations which suggest that its emanation is central, not peripheral or artifactual.
A relationship between ocean circulation and volume reverberation in the subarctic northeast Pacific Ocean (Gulf of Alaska)
Authors: Browning David G. , Turner R. G. , Powell J. W.
Published: October 2005

Earlier investigations have shown a significant change in integrated scattering [J. A. Scrimger and R. G. Turner, J. Acoust. Soc. Am. 54, 483–493 (1973)] and spectral characteristics [R. P. Chapman et al., J. Acoust. Soc. Am. 56, 1722–1734 (1974)] when transmitting into the subarctic (above 40 north latitude) northeast Pacific Ocean. An analysis of an extensive series of volume reverberation measurements obtained by Turner indicates a strong influence of the counterclockwise circulation around the Alaskan Gyre on the distribution of scattering strengths. At higher frequencies (5–20 kHz) the greater scattering strengths are found in the relatively warm California undercurrent water which flows around the perimeter of the gyre. At lower (1.25–5 kHz) frequencies the greater scattering strengths are found in the relatively cold water such is found in the upwelled subarctic water at the center of the gyre. This implies a significant change in the type of scatterers between these frequency domains. [Work supported by ONT and DREP.]
Neural correlates of tactile roughness perception
Authors: Johnson K. O. , Phillips J. R. , Hsiao S. , Fasman K. H. , Connor C. E.
Published: October 2005

Tactile perception of surface roughness was investigated in a combined psychophysical and neurophysiological study using 18 embossed, tetragonal dot patterns with varying dot spacings (1.3 to 6.2 mm) and sizes (0.4- to 1.2-mm diameter). Psychophysical subjects explored these surfaces with the pad of the index finger and reported their estimates of subjective roughness. The results were inverted U-shaped functions of spatial frequency. In neurophysiological experiments, exactly the same surfaces were scanned across the distal pads of macaque monkeys while recording from peripheral mechanoreceptive afferents (SA, QA, and PC afferents). Neural coding hypotheses were tested by comparing various features of the responses with the psychophysical results. Mean rate codes fared poorly as did codes based on “rate fluctuation” (summed absolute values of differences between rate maxima and minima). However, the second central moment of firing rate (variance) for the SA afferents matched the psychophysical data closely, accounting for effects of both dot size and dot spacing. The same measure proved less effective for QA afferents and much less effective for PC afferents. [Work supported by NIH grants NS 18787 and GM07057.]
Electrocutaneous syllable recognition using quasiarticulatory coding of stimulus patterns
Authors: Piroth Hans Georg
Published: October 2005

Assuming that the rate of variation of articulatory movements is slower than that of acoustic signals, it is hypothesized that tactile speech transmission systems should be based on articulatory rather than acoustical parameters of speech. The “System for Electrocutaneous Stimulation SEHR-2” which produces current-controlled bipolar electrical impulses with freely variable intervals was used to code tactile equivalents of CV and VC syllables. In experiment 1, patterns were delivered to the left forearm in such a way that “place of articulation” was transformed quasiisomorphically to “locus of tactile stimulation.” Without previous training, identification tests showed good recognition rates with an average of 65.83% for six vowels coded in a two-dimensional space (upper-lower, distal-proximal) and fairly good identification (38.33 %) for six (tactile) consonantal places of articulation coded only in the distal-proximal dimension. In experiment 2, differences in “manner of articulation” were transformed to differences in phenomenal “gestalt” of the tactile patterns created by variation of the interpulse intervals. Recognition of (tactile) manner of articulation was poorer (33.75 % for each of four consonants), but clearly above chance level.
The “system for electrocutaneous stimulation SEHR-2”
Authors: Tillmann Hans G. , Piroth Hans Georg
Published: October 2005

SEHR-2 is a 16-channel electrotactile stimulation system producing current-controlled bipolar electrical impulses with freely variable intervals. Its main component is a 16-channel stimulus generation device (expandable to 16 × 16 channels) which produces a periodical series of 16 rectangular pulses with programmable duration and amplitude, as well as a variable pulse repetition rate. Since the impulses are supplied to a capacitive resistance which is depolarized via the skin afterwards, it is ensured that there is no residual dc component. Voltage is adapted to skin resistance so that current intensity is held constant. The device can be connected to a computer by a 16-bit interface mastering the stimulus generation device. A software package has been developed that enables (1) computer-interactive execution of calibration procedures, (2) the editing of stimulus lists for different test procedures, (3) the computer-controlled execution of test sessions, and (4) a preliminary data analysis. The application of the system will be illustrated by the description of typical experiments.
Comparison of tactual and auditory discrimination of speech
Authors: Eilers Rebecca E. , Özdamar Özcan , Kimbrough Oller D. , Miskiel Edward , Moroff Debra
Published: October 2005

The relationship between tactual and auditory perception of speech was investigated by presenting two speech continua to subjects via a 32-channel computer controlled electrocutaneous display and via normal audition. The stimuli were synthetic /a/ to /ə/ and /sta/ to /sa/ with 9 equally spaced intermediate stimuli between each endpoint yielding two 11-step continua. Five well-practiced adults performed three tasks: (1) an adaptive discrimination task using each of the endpoints as target stimuli; (2) a standard identification procedure (all 11 steps categorized as either endpoint 1 or 11); and (3) a same-different task (equal interval stimuli were discriminated across the continuum). For tactual discrimination, channel information was presented in three spectral configurations conforming to (1) logarithmic, (2) linear, and (3) average (arithmetic mean of log and linear) filtering. Results indicate (a) a close correspondence between auditory and tactual perception, (b) subphonemic discrimination in both modalities, (c) categorical perception in both modalities, and (d) a more auditorylike pattern with log and average filter configurations than with linear. Implications in terms of theories of speech perception will be discussed.
Vibrotactile sensitivity of hands occupationally exposed to vibration
Authors: Piercy J. E. , Brammer A. J. , Auger P. L.
Published: October 2005

The threshold of vibrotactile perception at the finger tip has been measured for six forest workers who regularly use a chain saw, and, for comparison, ten laboratory workers with no significant vibration exposure. All subjects were carefully screened for confounding medical variables, such as carpal tunnel syndrome and diabetes. The measurements were performed over the frequency range of 4–400 Hz in the laboratory to permit careful control of physical variables, such as orientation of the vibrating probe with respect to the finger tip, contact force, and hand movement. Preliminary analysis of our results, together with those of others, suggests that the neurological component of the hand-arm vibration syndrome develops first as a change in the threshold of Pacinian corpuscles, which later spreads to the other cutaneous mechanoreceptors.
Methods of articulation in piano performance
Authors: Palmer Caroline
Published: October 2005

Pianists of varying levels of experience performed polyphonic excerpts from the classical repertoire on a computer-monitored (MIDI interface) synthesizer. Preliminary findings showed consistent and reliable temporal patterns of articulation. Both legato and staccato patterns were accurately predicted by a combination of the durations of successive notes in the musical score. Onset times of the individual voices notated as simultaneous differed such that the melody preceded the other voices, similar to Rasch's [J. Acoust. Soc. Am. 43, 121–131 (1979)] finding with ensemble players. Rubato patterns (alterations in tempo from mechanical regularity) were also consistent within an excerpt, demonstrating predictable changes within phrases and at cadences. Patterns of rubato in these polyphonic performances were similar to Bengtsson and Gabrielsson's [Proc. R. Swed. Acad. Music 39, 27–60 (1983)] profiles of monophonic performances by pianists. Each of these patterns of articulation was strongest in experienced pianists, and existed to varying degrees in student musicians. When experts were asked to perform nonmusically, the articulation patterns were still present but dampened in degree. Ongoing research is comparing the influence of amplitude (using a velocity-sensitive weighted keyboard) on pianists' articulation patterns. [Work supported by NSF and NIMH.]
Timbre discrimination of musical instruments in a concert hall
Authors: Goad Pamela J. , Keefe Douglas H.
Published: October 2005

Isolated tones and melodies of six tones were recorded in different locations of a concert hall using five musical instruments played in their upper and lower registers. Each trial consisted of either a pair of tones or a pair of melodies recorded simultaneously at different locations on one instrument. The room transmission path to each location varied. Using a monaural headphone presentation, the task was to determine whether the pair was the “same” or “different” with respect to timbre. To prevent subjects from discriminating based upon room variation in background noise, it was necessary to add pink noise below 2700 Hz; however, the signal-to-noise ratio remained above 30 dB at all frequencies. Our results showed that subjects could discriminate timbre in this context. No significant differences were found between isolated tones and melodies, or between registers. Significant differences appeared between instruments with subjects best able to discriminate flute timbre followed in rank order by clarinet, trumpet, viola, and marimba. Work is in progress to compare results with theories of timbre perception.
Scattering from submerged objects near an interface
Authors: Werby M. F. , Evans R. B.
Published: October 2005

Scattering from bounded objects in a free ocean has been treated extensively in recent years with considerable progress being made to date. Severe complications, however, arise for objects either in a waveguide or in the presence of an interface. It is possible to formulate this problem exactly and we present results for the case of an object near a sound-soft or sound-hard interface. Results are presented for objects as they vary in distance from an interface. Angular distributions are particularly suited for such a study where results are compared with the free ocean case. A comparison of the two cases shows that an object near an interface includes effects not seen in the free ocean example, namely reflections of the refracted wave from the interface and reflections from the object into the bottom and back toward the source of the field. This leads to angular distributions that typically have four peaks as opposed to two peaks from the free ocean case. The exceptions to this case are when the field is either parallel or perpendicular to the interface. The first of these exceptions (as expected) shows little difference with the free ocean case while the latter case is dominated by reflections from the interface itself yielding a large backscattered return.
On conversion of Lamb waves to leaky Lamb waves in a plate partially immersed into the liquid
Authors: Rokhlin S. I.
Published: October 2005

The problem of Lamb waves diffraction on the boundary of separation of the free and immersed (into the liquid) parts of the elastic plate is theoretically analyzed. In the theoretical model, it is assumed that the free part of the plate is separated from the liquid by infinitely thin air barriers. It is shown that in the first approximation the reflection coefficient is proportional to the attenuation factor of the leaky Lamb waves. The diffracted field into the liquid is formed by a cylindrical wave which is generated on the boundary line and by leakage of the energy carried by leaky Lamb waves in the plate. Analysis of the leakage field shows an anomalous behavior of the backward Lamb wave. This backward wave has negative dispersion and therefore the angle of the energy leakage for this wave (angle in Snell's law) must be taken as negative. It is shown that for calculation of the radiation field, the Kirchoff approxirnation can be used.
Application of the integral equation method to the calculation of acoustic scattering by a space launcher
Authors: Malbéqui P. , Candel S. M. , Rignot E.
Published: October 2005

The objective of this paper is to illustrate the possibilities of the integral equation method in the analysis of acoustic scattering by the structure of a space launcher. Such an analysis is important in situations where the sound field reaches critical levels at take-off. In these circumstances an increase in amplitude associated with reflections and scatterings must be estimated with precision. The method is based on integral representations of the wave field and only requires a surface mesh of the solid structure. The number of nodes of such surface meshes is much smaller than the 3-D finite difference or finite element equivalents. Another important advantage of the method is that it automatically incorporates the farfield radiation condition. This condition is only approximated in field methods. The calculations are performed with a code originally developed by Hamdi [M. A. Hamdi, Thèse de doctorat d'Etat, Université de Technologie de Compiègne (1982)] and validated at ONERA for the scattering of a plane wave by a hard sphere. Our presentation concerns more specifically the Ariane 4 fairings (the payload housing). It is found that the geometrical shape of the fairings causes local increases of the sound field. This tendency is confirmed by measurements performed on a 1/20 model of the launcher. [Research supported by Centre National d'Etudes Spatiales.]
Transition from sound-soft to rigid behavior in scattering from submerged elastics shells over a broad frequency range
Authors: Werby M. F. , Gaunaurd G.
Published: October 2005

We have determined previously that at suitably high frequencies elastic shells for a variety of thicknesses behave rigidly in the absence of narrow resonances. This observation was noted for thicknesses ranging from 1% to 2.5% for aluminum, steel, and WC for frequencies out to ka values of 300. Moreover, we have presented results at the low-frequency end (low ka) that showed a distinct sound soft behavior for very thin shells in the absence of a resonance. This behavior persisted out to moderate values of ka. The procedure to determine whether a particular background was manifest to twofold. Firstly, the rigid or sound-soft response is subtracted in appropriate partial wave space from the elastic response to determine the residual response. The residual response shows mainly resonance contributions at the resonance frequencies with little contribution otherwise. One can also examine the relative phase between the expected background and the elastic response and it should vary slowly except at a response where it varies rapidly with changing phase (a change of at least 180 deg). We here choose the case of a steel shell of thickness 0.3% of the radius of the shell and present results for the ka range from 0.0 to 500. Here the background is demonstrated to vary from sound-soft at the lower end of ka to rigid at the upper end with no clear background in between.
The eigenfrequencies of spheroids obtained from an integral phase matching condition
Authors: Merchant Barbara L. , Stoyanov Y. J. , Nagl A. , Überall H. , Brown S. H. , Dickey J. W.
Published: October 2005

The complex acoustic eigenfrequencies of impenetrable spheroids have been found previously by satisfying the boundary conditions with spheroidal wavefunctions [$. M. D'Archangelo et al., J. Acoust. Soc. Am. 77, 6 (1985)]; alternately, they are obtained here by using a T-matrix code. However, a physical explanation of the eigenfrequencies can be given in terms of surface waves circumnavigating the spheroid along a geodesic, and a phase matching condition can be written down which takes the form of an integral, due to the variations of the surface wave propagation constant along the path. A model is used in which the propagation constant is approximated by the known one on a sphere, with the same local radius of curvature along the propagation direction. This condition serves either to obtain the complex eigenfrequencies, or to test the accuracy of eigenfrequencies obtained by other methods. [Supported by NSRDC and ONR.]
Space-time duality for scattered wave inversion by backpropagation
Authors: Porter Robert P.
Published: October 2005

In ultrasonic and acoustic diffraction tomography, objects are scanned over a wide range of illumination angles in contrast with seismic inversion where coverage is limited but wideband data are available. In this presentation it is shown that either wide angle or wide bandwidth illumination is sufficient for determining the structure of a weak scatterer when the scattered field is backpropagated or migrated toward the object. The backpropagation concept is briefly reviewed and generalized to arbitrary recording geometries. After finding the spatial spectra of the backpropagated field, we shall see that the object scattering function can be extracted by scanning an illuminating plane wave over a wide frequency range or over all possible directions. Two recent inversion methods, holographic tomography (monochromatic waves and wide angle coverage) and image filtering (single wide band plane wave) will be discussed as examples of backpropagating methods that exploit space-time duality.
Iterative inverse scattering method employing Gram-Schmidt orthogonalization
Authors: Tobocman W.
Published: October 2005

An inverse scattering method is tested which appears to work very well. It is an iterative procedure based on the distorted wave Born approximation. The resulting Fredholm equation of the first kind is solved by a projection method that requires the construction of an orthonormal set of basis functions from the set of kernel functions. This can be done by the spectral expansion method which entails matrix diagonalization or by Gram-Schmidt orthogonalization. The method is tested on a simple one-dimensional optical wave inverse scattering problem. Both orthonormalization methods lead to a rapidly convergent and stable iteration. The spectral expansion method gives somewhat better results, but the Gram-Schmidt orthogonalization method, which is the novel aspect of our approach, is much less time consuming. We show how the projection method can be generalized to the case of acoustic wave scattering where the target must be characterized by more than a single independent function of position.
Frequency and practice interactions in frequency discrimination
Authors: Olsho Lynne Werner , Koch Elizabeth G.
Published: October 2005

Differences between human infants and adults in frequency discrimination resemble differences between untrained and trained adults: frequency difference limens (FDL's) tend to be relatively worse for infants and untrained adults at low frequencies [L. W. Olsho, Inf. Behav. Dev. 7, 27–35 (1984)]. To demonstrate directly that the effect of training in frequency discrimination depends on frequency, the course of improvement in frequency discrimination was examined in adults at 500, 1000, and 4000 Hz. Stimuli were pure tones presented at a 40-dB sensation level. A two-alternative forced-choice procedure was used, and FDL was tracked using a one-up, two-down adaptive procedure. Four subjects completed 200–250 trials of training at each frequency. For these subjects not only was initial FDL much higher relative to final FDL at the two lower frequencies, but tracking width decreased progressively with increasing frequency. Four additional subjects were tested for a total of 20 h each to make certain that asymptotic performance was reached. The final FDL's obtained by these listeners were similar to those reported by other investigators [e.g., C. C. Weir et al., J. Acoust. Soc. Am. 61, 178–184 (1977)], and the same practice effects were observed as in the first group. [Work supported by NIH.]
Relationship between frequency selectivity and frequency discrimination measured in subjects with unilateral and bilateral cochlear impairments
Authors: Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

These experiments were designed to test a model proposed by Zwicker [E. Zwicker, Acustica 6, 356–381 (1956)] in which the frequency difference limen (DLF) for a pure tone is assumed to be determined by the slope (S) of the excitation pattern at the point where it is steepest (on the low-frequency side), and by the size of the smallest detectable change in excitation at that point (DLI): DLF = DLI/S. S was estimated by measuring the auditory filter shape using a notched-noise maker. The DLF was measured in two tasks: pulsed tones frequency discrimination, and detection of frequency modulation. The DLI was measured in two comparable ways, but a high-pass noise was added to the tone to mask the upper side of the excitation pattern. Subjects had moderate unilateral or bilateral cochlear impairments. Tones were presented at 80 dB SPL. For the modulation-detection task the values of the DLF's predicted by the model were comparable to those actually obtained, although the predicted and obtained values were not highly correlated. For the pulsed-tones task the obtained DLF's were consistently smaller than predicted by the model. Overall the data suggest that Zwicker's model cannot account both for the detection of frequency modulation and for the frequency discrimination of pulsed tones. [Work supported by the Medical Research Council, U.K.]
The perception of preaspirated stops
Authors: Chasaide Ailbhe Ni
Published: October 2005

Production data for preaspirated stops in Scottish-Gaellc, Icelandic, and Irish show a slow breathy-voiced transition (BVT) from the vowel to the truly voiceless aspiration (H). The experiment reported here examined (a) the perceptual relevance of the BVT, and (b) the effect that the amplitude of H has on the percept ofa preaspirated stop. From computer-edited natural speech, stimuli were prepared with and without the BVT, and with differing durations of H at three amplitude levels. Results suggest that: (a) the BVT alone is sufficient to cue the preaspirated stop, even when H is entirely absent; for stimuli which did not contain the BVT, listeners fell into two groups and 40% of subjects did not judge the stops as preaspirated, even when H was long and of high amplitude. (b) For the 60% of subjects who “accepted” stimuli without a BVT as preaspirated stops, there was a strong trading relationship between the amplitude of H and its duration.
Comparison of current source density analysis with multi-unit mapping in the inferior colliculus of the gerbil
Authors: Harris David M. , Lambert David C.
Published: October 2005

In the central nucleus of the inferior colliculus single unit, 2-deoxyglucose studies, and the anatomical structure, define a laminar organization related to frequency coding. The tonotopic axis appears to be along an axis of symmetry, frequency-specific lamina are assumed to be activated synchronously, and the uniform distribution of neurons suggests homogeneous conductivity; conditions necessary for a one-dimensional current source density (CSD) analysis of the distribution of current sources and sinks evoked along the tonotopic axis. We map tone-burst-evoked multi-unit responses (multi-unit PST histograms) at 100-μ intervals as a microelectrode is lowered along the tonotopic axis. From evoked potentials, also collected at the recording sites, we compute the second derivative of the function of voltage with respect to space at a specific latency. This transformation represents the spatial profile of current sources and sinks. These data show that maximum multi-unit evoked activity has the same latency and location as the highest density of current sinks, even as latency and location shift with variations in stimulus parameters. Certain aspects do not coincide. Multi-unit data show a sustained steady-state response not seen consistently in the CSD plots and current sources do not correlate well with suppression of multi-unit activity. [Work supported by NIH.]