bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulus dependencies of the gerbil brain-stem auditory-evoked response (BAER). I: Effects of click level, rate, and polarity
Authors: Burkard Robert , Voigt Herbert F.
Published: October 2005

Three experiments evaluating the effects of various stimulus manipulations on the click-evoked gerbil brain-stem auditory-evoked response (BAER) are reported. In experiment 1, click polarity and level were covaried. With increasing click level, there is a parallel decrease in the latency of the first five BAER peaks (i–v) and an increase in BAER peak amplitudes. Mean wave i amplitude was greater for rarefaction than condensation clicks at high click levels; mean wave v amplitude was greater for condensation clicks at higher click levels. Experiment 2 covaried click rate and polarity. The latency of the BAER peaks increased with increasing click repetition rate. This rate-dependent latency increase was greater for the later BAER peaks, resulting in an increase in the i–v interval with increasing click rate. As rate increased, the amplitudes of waves i and v decreased monotonically, whereas the amplitudes of waves ii–iv were largely uninfluenced by click rate. As in experiment 1, mean wave i amplitude was greater for rarefaction clicks, whereas mean wave v amplitude was greater for condensation clicks. The magnitude of these polarity dependencies on waves i and v amplitude decreased with increasing click rate. Experiment 3 evaluated the effects of click polarity on BAERs to high-intensity (100 dB pSPL) clicks presented at a rate of 10 Hz. In eight of ten gerbils evaluated, wave i amplitude was greater to rarefaction clicks, and, in all ten animals, wave v amplitude was greater to condensation clicks. The effects of click level and rate on BAER peak amplitudes, latencies, and interwave intervals are reminiscent of stimulus dependencies reported for the human BAER. The effects of click polarity on the amplitudes of waves i and v of the gerbil BAER have also been reported for the human BAER.
Repetition rate and signal level effects on neuronal responses to brief tone pulses in cat auditory cortex
Authors: Phillips D. P. , Hall S. E. , Hollett J. L.
Published: October 2005

This study describes the effects on the spike count, spike timing, and entrainment of cat auditory cortex neurons of parametric variations in the repetition rate and amplitude of a brief, characteristic frequency tone pulse. Data were obtained from single neurons in barbiturate-anesthetized cats to which signals were presented monaurally to the ear contralateral to the recording electrode. All neurons showed low-pass sensitivity to tone repetition rate. In cells with a monotonic rate response, the effect of an increasing stimulus level was to elevate the response rate and to extend performance to higher repetition rates. In nonmonotonic cells, cutoff frequencies (for repetition rate) varied with overall spike count. Latent periods increased with increases in repetition rate. This effect developed over the first few stimulus trials at any given repetition rate. Spike entrainment to the tone pulses varied with both repetition rate and signal level. Increases in signal level improved entrainment for responses to stimuli presented at low repetition rates, but entrainment at high repetition rates always saturated at significantly imperfect levels.
Range estimation by echolocation in the bat E
p
t
e
s
i
c
u
s f
u
s
c
u
s: Trading of phase versus time cues
Authors: Menne Dieter , Kaipf Ingrid , Wagner Inge , Ostwald Joachim , Schnitzler Hans-Ulrich
Published: October 2005

Bats of the species Eptesicus fuscus have been trained to discriminate a stationary simulated target from a target with a virtual distance that jitters from sound to sound. Similar to Simmons [Science 207, 1336–1338 (1979)], a jitter-detection threshold below 1 μs was found. However, Simmons’ decreased performance at a time delay jitter of 30 μs could not be replicated , a critical feature used to postulate the idea that bats employ a coherent cross-correlation receiver for ranging. Such a receiver uses all phase information in the signal for delay estimation and therefore will be biased by phase manipulations. To test for such a bias, a phase jitter of ±45° and a time jitter in the echo were overlaid. It was not found that there was a combination of both where their effects canceled. Full phase information is thus not used in delay estimation. However, bats were able to detect a pure phase jitter, e.g., polarity inversion of the signal. Bats could also detect phase jitter in the presence of randomized time jitter and vice versa. Phase jitter and time jitter, therefore, are separable features for a bat. The underlying physiological mechanism is not clear.
Minimum audible angle thresholds for broadband noise as a function of the delay between the onset of the lead and lag signals
Authors: Perrott David R. , Pacheco Sandy
Published: October 2005

Minimum audible angle (MAA) thresholds were determined for six experienced subjects using a two-alternative, forced-choice adaptive paradigm. Broadband pink noise from a single generator was led to two identical speakers. The two sources were activated sequentially, each for a period of 10 ms. The subject’s task was to indicate whether the second (lag) sound came from a source to the right or left of the first (lead) sound. The delay between the onset of the lead and the onset of the lag signal [interstimulus onset interval (ISOI)] was systematically varied from 1 ms (both 10-ms signals were concurrently active for 9 ms) to 200 ms. For a given ISOI, the spatial separation was varied adaptively to determine the MAA. A 450% improvement in auditory spatial resolution was evident as the ISOI increased from 1 to 150 ms. A further increase in the ISOI had no systematic effect on spatial resolution. These results indicate that there is a minimum integration period between 100–150 ms for the resolution of spatial information in the auditory modality.
Leaky Lamb waves in an anisotropic plate. I: An exact solution and experiments
Authors: Dayal Vinay , Kinra Vikram K.
Published: October 2005

The propagation of leaky Lamb waves in a plate consisting of a general balanced symmetric composite material is considered. The problem has been examined both analytically as well as experimentally. An exact solution for the dispersion equation was obtained. Numerical results for complex-valued wavenumber were obtained for an isotropic material (aluminum) and a (0/903)s graphite/epoxy laminate. Excellent agreement for the isotropic case and a satisfactory agreement for the anisotropic case between the theory and experiment were observed.
A paraxial theory for the propagation of ultrasonic beams in anisotropic solids
Authors: Newberry Byron P. , Thompson R. Bruce
Published: October 2005

The necessity of nondestructively inspecting cast steels, weldments, composites, and other inherently anisotropic materials has stimulated considerable interest in wave propagation in anisotropic media. Here, the problem of an ultrasonic beam traveling in an anisotropic medium is formulated in terms of an angular spectrum of plane waves. Through the use of small angle approximations, the integral representation is reduced to a summation of Gauss–Hermite eigensolutions. The anisotropic effects of beam skew and excess beam divergence enter into the solution through parameters that are simply interpreted in terms of the slowness surface. Both time harmonic and pulsed solutions are discussed. Formulas are also presented for transmission of a beam through a curved interface between two media. Examples are given illustrating how this method may be applied to predicting beam patterns during ultrasonic inspections.
Environmental mismatch in shallow-water matched-field processing: Geoacoustic parameter variability
Authors: Feuillade C. , Del Balzo D. R. , Rowe Mary M.
Published: October 2005

The effects of variations in geoacoustic environmental parameters on the performance of a matched-field localization processor in shallow water were investigated. The SUPERSNAP propagation model was used to generate a reference acoustic pressure field and to simulate an ‘‘experimentally detected’’ field due to an acoustic ‘‘source.’’ These were then correlated using a maximum-likelihood estimator for selected degrees of mismatch of environmental parameters. It was found that small perturbations in a downward-refracting summer water sound-speed profile of ±1σ (i.e., ±1 standard deviation) from average measured values caused severe degradation in localization performance, with predictions of source range and depth becoming highly unstable. However, similar perturbations of an almost isospeed winter profile caused comparatively little degradation. Similarly, perturbations in the sediment sound-speed profile of up to ±1σ from average measured values were possible while still giving stable and reliable estimates of source location. The processor also appeared to be relatively insensitive to mismatch of sediment density and attenuation. The source was correctly localized even when the density and attenuation deviated by significantly more than ±1σ from average measured values.
Impedance profile and overall attenuation estimation of layered sea bottoms from their normal incidence acoustic reflection response
Authors: Cobo-Parra P. , Ranz-Guerra C.
Published: October 2005

Inversion of high-frequency acoustic reflection data in low-noise layered sea bottoms is presented. The assumed geoacoustic model includes attenuation effects. An overall attenuation coefficient of the whole sedimentary column is estimated by logarithmic regression on the spectral ratio of nonoverlapped replicas. The attenuation response is filtered out of the impulse response by the minimum square inversion of the sea bottom lossy transfer function, previously computed by deconvolving the input pulse from the reflection response. Applying this inversion scheme to a known artificial bottom, experimental values lying within a 7.4% range below the actual data are obtained.
Sensitivity of matched field processing to sound-speed profile mismatch for vertical arrays in a deep water Pacific environment
Authors: Tolstoy A.
Published: October 2005

In this paper, the sensitivity of matched field processing to sound-speed profile mismatch will be examined (based upon archival profiles resulting in various degrees of mismatch). A 10-Hz source is considered whose field is generated by a normal mode model and only the water-borne energy is used, thereby eliminating issues relating to the estimation of bottom parameters. This paper will examine how array parameters, i.e., number of phones and array depth, affect range and depth localization for various degrees of mismatch. In particular, it will be seen where an array is most and least sensitive to sound-speed mismatch as a function of depth from the surface and range from the source, and the degree to which range and depth resolution are possible under ideal, as well as under likely, mismatch conditions.
Accurate depth-independent determination of acoustic backscatter coefficients with focused transducers
Authors: Hall Timothy J. , Madsen Ernest L. , Zagzebski James A. , Boote Evan J.
Published: October 2005

The accuracy of a method of data reduction for determining acoustic backscatter coefficients was tested using focused transducers and narrow-band pulses. Two phantoms with well-defined scattering properties were the bases of the tests, one having low attenuation and one with tissue-mimicking attenuation. The experimentally determined backscatter coefficients were found to be independent of transducer-to-scattering-volume distance and to agree very well with theoretical values, typically within 10%.
Measurements with a thick conical piezoelectric transducer
Authors: Hutchins D. A. , Bresse L. F. , Palmer S. B.
Published: October 2005

Transducers have been designed and tested based on a piezoelectric element that is 25 mm thick and conical in cross section. These devices do not require any backing, have low levels of radial mode vibration, and present a small area of contact to the surface of a solid. Theory and experiment are compared, and reasonable results are obtained.
Reply to ‘‘Comments on ‘Two-mass models of the vocal cords for natural sounding voice synthesis’ ’’ [J. Acoust. Soc. Am. 8
5, 2220–2221 (1989)]
Authors: Koizumi Takuya , Taniguchi Shuji , Hiromitsu Seijiro
Published: October 2005

The authors respond to the comments of Nudelman and Hoyt [J. Acoust. Soc. Am. 85, 2220–2221 (1989)] and give corrected versions of equations and figures found in the original article.
Viscous attenuation of acoustic waves in suspensions
Authors: Gibson Richard L. , Toksöz M. Nafi
Published: October 2005

A model for attenuation of acoustic waves in suspensions is proposed that includes an energy loss due to viscous fluid flow around spherical particles. The expression for the complex wavenumber is developed by considering the partial pressures acting on the solid and fluid phases of the suspension. This is shown to be equivalent to the results of the Biot theory for porous media in the limiting case where the frame moduli vanish. Unlike earlier applications of the limiting case Biot theory, however, a value for the attenuation coefficient is developed from the Stokes flow drag force on a sphere instead of attempting to apply a permeability value to a suspension. Accurate modeling of observed phase velocities from suspensions of spherical polystyrene particles in water and oil and successful inversion for kaolinite properties using attenuation and velocity data from kaolinite suspensions at 100 kHz show that this viscous dissipation model is a good representation of the effects controlling the propagation of acoustic waves in these suspensions. The viscous effects are shown to be significant for only a limited range of solid concentration and frequency by the reduced accuracy of the model for attenuation in a kaolinite suspension at 1 MHz.
Thermodiffusive surface waves in semiconductors
Authors: Maruszewski Bogdan
Published: October 2005

This article deals with the considerations of the propagation of the coupled surface waves along the surface that bounds the semiconducting half-space with relaxation of heat and charge carrier fields. Based on the general equations, two particular cases are investigated: the elastodiffusive surface waves of the electron field and the thermodiffusive surface waves of the electron fields.
Neuronal responses to amplitude-modulated and pure-tone stimuli in the guinea pig inferior colliculus, and their modification by broadband noise
Authors: Rees Adrian , Palmer Alan R.
Published: October 2005

Neuronal responses were recorded to pure and to sinusoidally amplitude-modulated (AM) tones at the characteristic frequency (CF) in the central nucleus of the inferior colliculus of anesthetized guinea pigs. Temporal (synchronized) and mean-rate measures were derived from period histograms locked to the stimulus modulation waveform to characterize the modulation response. For stimuli presented in quiet, the modulation gain at low frequencies of modulation (approx <50 Hz) was inversely proportional to the neuron’s mean firing rate in response to both the modulated stimulus and to a pure tone at an equivalent level. In 43% of units the mean discharge rates in response to the AM stimuli were greatest for those modulation frequencies that generated the largest temporal responses. These discharge-rate maxima occurred at signal intensities corresponding to the steeply sloping part of the neuron’s pure-tone rate-intensity function (RIF). The change in mean-rate response to modulated stimuli, as a function of intensity, was qualitatively similar to the pure-tone RIF. Adding broadband noise to the modulated stimulus increased the neuron’s temporal response to low modulation frequencies. This increase in modulation gain was correlated with mean firing rate in response to the modulation but did not bear a simple relationship to the noise-induced shift in the RIF measured for a pure tone.
Reductions in overshoot following intense sound exposures
Authors: Champlin Craig A. , McFadden Dennis
Published: October 2005

Overshoot refers to the poorer detectability of brief signals presented soon after the onset of a masking noise compared to those presented after longer delays. In the present experiment, brief tonal signals were presented 2 or 190 ms following the onset of a broadband masker that was 200 ms in duration. These two conditions of signal delay were tested before and after a series of exposures to a tone intense enough to induce temporary threshold shift (TTS). The magnitude of the overshoot was reduced after the exposure when a TTS of at least 10 dB was induced, but not when smaller amounts of TTS were induced. The reduction in overshoot was due to a decrease in the masked thresholds with the 2-ms delay; masked thresholds with the 190-ms delay were not different pre- and post-exposure. The implication is that the mechanisms responsible for the normal overshoot effect are temporarily inactivated by the same stimulus manipulations that produce a mild exposure-induced hearing loss. Thus the result is the paradox that exposure to intense sounds can produce a loss of signal detectability in certain stimulus conditions and a simultaneous improvement in detectability in other stimulus conditions.
On the minimum audible angle—A decision theory approach
Authors: Hartmann William Morris , Rakerd Brad
Published: October 2005

The minimum audible angle (MAA) technique is a well-known psychoacoustical paradigm often used in the study of localization of sound. A difficulty with this paradigm, however, is that, in terms of decision theory, it is subject to two quite different interpretations. Although it is normally regarded as involving a discrimination task, this work suggests that it is more likely to be an absolute identification task. Because of this difference in interpretation, it is found that previous work has overestimated the ability of listeners to localize sources of sound.
Evolving theories of vowel perception
Authors: Strange Winifred
Published: October 2005

Research on the perception of vowels in the last several years has given rise to new conceptions of vowels as articulatory, acoustic, and perceptual events. Starting from a ‘‘simple’’ target model in which vowels were characterized articulatorily as static vocal tract shapes and acoustically as points in a first and second formant (F1/F2) vowel space, this paper briefly traces the evolution of vowel theory in the 1970s and 1980s in two directions. (1) Elaborated target models represent vowels as target zones in perceptual spaces whose dimensions are specified as formant ratios. These models have been developed primarily to account for perceivers’ solution of the ‘‘speaker normalization’’ problem. (2) Dynamic specification models emphasize the importance of formant trajectory patterns in specifying vowel identity. These models deal primarily with the problem of ‘‘target undershoot’’ associated with the coarticulation of vowels with consonants in natural speech and with the issue of ‘‘vowel-inherent spectral change’’ or diphthongization of English vowels. Perceptual studies are summarized that motivate these theoretical developments.
Static, dynamic, and relational properties in vowel perception
Authors: Nearey Terrance M.
Published: October 2005

The present work reviews theories and empirical findings, including results from two new experiments, that bear on the perception of English vowels, with an emphasis on the comparison of data analytic ‘‘machine recognition’’ approaches with results from speech perception experiments. Two major sources of variability (viz., speaker differences and consonantal context effects) are addressed from the classical perspective of overlap between vowel categories in F1×F2 space. Various approaches to the reduction of this overlap are evaluated. Two types of speaker normalization are considered. ‘‘Intrinsic’’ methods based on relationships among the steady-state properties (F0, F1, F2, and F3) within individual vowel tokens are contrasted with ‘‘extrinsic’’ methods, involving the relationships among the formant frequencies of the entire vowel system of a single speaker. Evidence from a new experiment supports Ainsworth’s (1975) conclusion [W. Ainsworth, Auditory Analysis and Perception of Speech (Academic, London, 1975)] that both types of information have a role to play in perception. The effects of consonantal context on formant overlap are also considered. A new experiment is presented that extends Lindblom and Studdert-Kennedy’s (1967) finding [B. Lindblom and M. Studdert-Kennedy, J. Acoust. Soc. Am. 43, 840–843)] of perceptual effects of consonantal context on vowel perception to /dVd/ and /bVb/ contexts. Finally, the role of vowel-inherent dynamic properties, including duration and diphthongization, is briefly reviewed. All of the above factors are shown to have reliable influences on vowel perception, although the relative weight of such effects and the circumstances that alter these weights remain far from clear. It is suggested that the design of more complex perceptual experiments, together with the development of quantitative pattern recognition models of human vowel perception, will be necessary to resolve these issues.
Data labeling and sampling effects in harmonics-to-noise ratios
Authors: Cox Neil B. , Ito Mabo R. , Morrison Murray D.
Published: October 2005

The harmonics-to-noise ratio (HNR) was proposed for measurement of noise in sustained vowels. A generalized algorithm is described here for removing the dependence on the data offset and for reducing the influence of jitter and shimmer. In addition, a new algorithm is proposed that accommodates periodic perturbations. Formulations are presented that can be computed in a single pass through the data under certain assumptions, thus simplifying the implementation of an efficient analysis program. A mathematical analysis of the effect of small errors in pitch-period demarcation is presented. The analysis indicates that the sensitivity to demarcation errors depends on the preponderance of high-frequency components, and significant underestimation is predicted for /a/ and /i/ data. A method for correcting quantization and demarcation errors in pitch-period markers is described. The method is shown to be effective at reducing demarcation errors for all but the most severely perturbed waveforms. Examples of the use of this method for HNR estimation are provided. Finally, a comparison with recent work by Milenkovic [J. Speech Hear. Res. 30, 529–538 (1987)] is presented.
Transducer characterization using the angular spectrum method
Authors: Schafer Mark E. , Lewin Peter A.
Published: October 2005

A measurement technique for analyzing the surface velocity patterns of ultrasonic transmitters is presented. The technique is based on the angular spectrum method of wave field analysis. In this approach, acoustic propagation between parallel planar surfaces is modeled using the two-dimensional (2-D) Fourier transform of the wave field, with each element in the spatial frequency domain multiplied by the appropriate phase factor. The technique was extended from the basic monochromatic model to the wideband pulsed case. An experimental system was built to measure the acoustic fields from various transducers, including single-element and multielement phased arrays. Backpropagation results are shown for circular planar, circular focused, and rectangular phase steered transducers. The results demonstrate the ability of the extended angular spectrum method to reconstruct the surface velocity distribution of complex acoustic radiators.
Phase aberration correction in medical ultrasound using speckle brightness as a quality factor
Authors: Nock Levin , Trahey Gregg E. , Smith Stephen W.
Published: October 2005

Medical ultrasonic images are degraded by tissues with inhomogeneous acoustic velocities. The resulting phase aberration raises the off-peak response of the imaging system’s point spread function (PSF), decreasing dynamic range. In extreme cases, multiple images of a single target are displayed. Phase aberration may become a limiting factor to image quality as ultrasonic frequency and aperture size are increased in order to improve spatial resolution. A method is proposed to correct for unknown phase aberration, which uses speckle brightness as a quality factor. The phase delays of a phasd array transducer are modified, element by element, to maximize mean speckle brightness in a region of interest. The technique proposed is analogous to the Muller–Buffington correction technique, [R. A. Muller and A. Buffington, J. Opt. Soc. Am. 64 (9), 1200–1209 (1974)] used to adaptively focus incoherent optical telescopes. The method is demonstrated using a computer model with several different simulated aberration profiles. With this model, mean speckle brightness is calculated using the two-dimensional PSF. Experiments have also been conducted in which speckle brightness is shown to increase as the phase delays of an ultrasonic scanner are modified in order to compensate for a rippled aberrating layer made of silicone rubber. The characteristics of the proposed method, and the possibility of employing it clinically to correct for unknown inhomogeneities in acoustic velocity, are discussed.
A parabolic equation model for scattering in the ocean
Authors: Collins Michael D. , Werby Michael F.
Published: October 2005

The small-angle-of-propagation limit and the method of matched asymptotics are applied to derive an efficient model for solving realistic underwater acoustics problems involving both propagation and scattering from a submerged object. The propagation and scattering aspects of the waveguide scattering problem are decoupled by approximating the waveguide Green’s function on the surface of the scatterer. For low frequencies, the small-angle limit also allows one to approximate the incident field with a horizontally propagating plane wave and the scattered field with an azimuthally specular point-source field. With these approximations, scattering calculations can be performed efficiently in the time domain. Calculations involving the three-dimensional parabolic equation and the time-domain parabolic equation are presented.
Independence in sonar observations
Authors: Weston David E.
Published: October 2005

The effect of correlations on the cumulation of detection probability resulting from several looks is considered. Simple formulas are derived for two pulses and for several pulses, including the case of several pulses obeying a Markov chain process. This allows a consistent account to be given of the detection process, with various critical values for the correlation coefficient. Using the relations between the correlations before and after asymmetrical clipping, the observations are found to be more nearly independent than might initially be thought.
Effects of acoustic overstimulation on spectral and temporal processing in the amphibian auditory nerve
Authors: Penna Mario , Narins Peter M.
Published: October 2005

Activity of isolated auditory-nerve fibers in tree frogs (Eleutherodactyl us coqui) exposed to continuous 3-min tones of different intensities at their characteristic frequencies (CFs) was recorded. Period histograms show a retardation in the preferred phase of discharge during and after the cessation of the exposure. Postexposure phase shift is concomitant with an elevation in CF thresholds and related to the level of tone exposure above threshold. Vector strength does not show comparable trends of change; postexposure shifts are related to preexposure CF thresholds. Recovery of phase retardation is rapid; units exposed to successive 3-min tones of the same intensities with intervals of 10–14 min between exposures experienced similar changes in their patterns of temporal discharge. Micromechanical changes affecting stereocilia stiffness or structural alterations in the tectorial membrane of the amphibian papilla may underly the transitory phase shifts observed in traumatized anuran auditory fibers.
Temporal resolution in frog auditory-nerve fibers
Authors: Dunia Richard , Narins Peter M.
Published: October 2005

Sinusoidally amplitude-modulated (SAM) noise was monaurally presented to the neotropical frog, Eleutherodactyl us coqui, while recording intracellularly from auditory-nerve fibers. Neuronal phase locking was measured to the SAM noise envelope in the form of a period histogram. The modulation depth was changed (in 10% steps) until the threshold modulation depth was determined. This was repeated for various modulation frequencies (20–1200 Hz) and different levels of SAM noise (34–64 dB/Hz). From these data, temporal modulation transfer functions (TMTFs) were produced and minimum integration time (MIT) for each auditory fiber was calculated. The median MIT was 0.42 ms (lower quartile 0.32, upper quartile 0.68 ms). A noise level-dependent effect was noted on the shape of the TMTF as well as the minimum integration time. The latter results may be explained as a loss in spectral resolution with increasing noise level, which is consistent with the correlation that was found between minimum integration time and bandwidth.
A reexamination of the frequency discrimination of random-amplitude tones, and a test of Henning’s modified energy-detector model
Authors: Emmerich David S. , Ellermeier Wolfgang , Butensky Brenda
Published: October 2005

A surprising result is reported by Henning [G. B. Henning, J. Acoust. Soc. Am. 39, 336–339 (1966)]: For frequencies lower than 4000 Hz, frequency discrimination was not impaired by the introduction of random differences in level between the two tones to be discriminated in a two-interval forced-choice (2IFC) task. This result is inconsistent with a model of detection and discrimination proposed by Henning [G. B. Henning, J. Acoust. Soc. Am. 42, 1325–1334 (1967)], one of a class of models in which the observer monitors the output of a single auditory filter, as well as with excitation-pattern models of frequency discrimination. In the first experiment reported here, however, an impairment of frequency discrimination with random differences in level is found when a within-subjects experimental design is used. In a second experiment, the role of pitch-intensity relationships in an experimental situation similar to that of Henning (1966) is explored. Finally, in a third experiment, an independent test of this model, which does not involve level differences, is carried out. The results are not consistent with the single-filter model, but can be accounted for by a version of the model that incorporates two filters.
Temporal overshoot in simultaneous-masked psychophysical tuning curves from normal and hearing-impaired listeners
Authors: Kimberley Barry P. , Nelson David A. , Bacon Sid P.
Published: October 2005

Simultaneous-masked psychophysical tuning curves (PTCs) were obtained from normal-hearing and sensorineural hearing-impaired listeners. The 20-ms signal was presented at the onset or at the temporal center of the 400-ms masker. For the normal-hearing listeners, as shown previously [S. P. Bacon and B. C. J. Moore, J. Acoust. Soc. Am. 80, 1638–1645 (1986)], the PTCs were sharper on the high-frequency side for a signal in the temporal center of the masker. For the hearing-impaired listeners, however, the shape of the PTC was virtually independent of the temporal position of the signal. These data suggest that the mechanisms responsible for sharpening the PTC with time in normal-hearing listeners are ineffective in listeners with moderate-to-severe sensorineural hearing loss
Frequency selectivity in amplitude-modulation detection
Authors: Houtgast T.
Published: October 2005

For a broadband noise carrier, the modulation detection threshold for sinusoidal amplitude modulation (the test modulation) is measured in the presence of an additional modulation (the masker modulation). Two traditional approaches for revealing effects of frequency selectivity in the audiofrequency domain are shown to give comparable results in the modulation-frequency domain: (1) a typically peaked modulation-detection threshold pattern when the masker modulation is a fixed narrow band of noise, and (2) an effect of leveling off of the increase of the modulation-detection threshold when, for a fixed test-modulation frequency, the masker-modulation bandwidth is widened beyond a certain ‘‘critical’’ bandwidth. It is argued that the present results on frequency selectivity in modulation detection underline the perceptual relevance of a spectral decomposition of a signal’s temporal envelope and provide a rationale for the application of modern concepts like the speech-envelope spectrum or the modulation-transfer function in relation to speech intelligibility.
Physiologic and acoustic differences between male and female voices
Authors: Titze Ingo R.
Published: October 2005

Comparison is drawn between male and female larynges on the basis of overall size, vocal fold membranous length, elastic properties of tissue, and prephonatory glottal shape. Two scale factors are proposed that are useful for explaining differences in fundamental frequency, sound power, mean airflow, and glottal efficiency. Fundamental frequency is scaled primarily according to the membranous length of the vocal folds (scale factor of 1.6), whereas mean airflow, sound power, glottal efficiency, and amplitude of vibration include another scale factor (1.2) that relates to overall larynx size. Some explanations are given for observed sex differences in glottographic waveforms. In particular, the simulated (computer-modeled) vocal fold contact area is used to infer male–female differences in the shape of the glottis. The female glottis appears to converge more linearly (from bottom to top) than the male glottis, primarily because of medial surface bulging of the male vocal folds.
Vocal fundamental frequency characteristics during the first two years of life
Authors: Robb Michael P. , Saxman John H. , Grant Andrew A.
Published: October 2005

Vocal fundamental frequency (F0) characteristics were sampled for a group of seven young children. The children were followed longitudinally for a 12-month period, spanning preword, single-word, and multiword vocalizations. The F0 characteristics were analyzed with reference to chronological age, vocalization length, and lexicon size. Measures of average F0 and F0 variability changed little during the 12-month period for each child. A rising–falling intonation contour was the most prevalent F0 contour among the children. In general, the influence of vocalization length and language acquisition on measures of F0 was negligible. It is suggested that relative uniformity in vocal F0 exists in early vocalizations across preword and meaningful speech periods.
Perceptual differences between vowels located in a limited phonetic space
Authors: Kewley-Port Diane , Atal Bishnu S.
Published: October 2005

The perception of subphonemic differences between vowels was investigated using multidimensional scaling techniques. Three experiments were conducted with natural-sounding synthetic stimuli generated by linear predictive coding (LPC) formant synthesizers. In the first experiment, vowel sets near the pairs /i–i/, /q–æ/, or /u–u/ were synthesized containing 11 vowels each. Listeners judged the dissimilarities between all pairs of vowels within a set several times. These perceptual differences were mapped into distances between the vowels in an n-dimensional space using two-way multidimensional scaling. Results for each vowel set showed that the physical stimulus space, which was specified by the two parameters F1 and F2, was always mapped into a two-dimensional perceptual space. The best metric for modeling the perceptual distances was the Euclidean distance between F1 and F2 in barks. The second experiment investigated the perception of the same vowels from the first experiment, but embedded in a consonantal context. Following the same procedures as experiment 1, listeners’ perception of the /bv/ dissimilarities was not different from their perception of the isolated vowel dissimilarities. The third experiment investigated dissimilarity judgments for the three vowels /æ–a–v/ located symmetrically in the F1×F2 vowel space. While the perceptual space was again two dimensional, the influence of phonetic identity on vowel difference judgments was observed. Implications for determining metrics for subphonemic vowel differences using multidimensional scaling are discussed.
Bond graph models of sound and vibration systems
Authors: Busch-Vishniac I. J. , Paynter H. M.
Published: October 2005

Traditional models of physical systems consist of discrete (lumped) elements connected using circuit conventions. Such circuit models are of great use because they provide physical insight and suggest a formal analysis procedure. However, conventional circuit models of systems have serious deficiencies that limit their usefulness. Most notable of these deficiencies are the inability to directly model multiport cross-domain energic elements and the neglect of causal relations. As will be shown in this article, bond graph models of physical systems, which are not beset by the same problems, offer an alternative to circuit models that provides enhanced physical insight and computational ease. The scope of application of bond graphs will be demonstrated by showing their use in modeling transducers, and their relation to statistical energy analysis.
Length error analysis for impedance tube measurements
Authors: Banks-Lee P. , Peng H.
Published: October 2005

Length error analysis of the transfer function method and improved standing wave ratio (SWR) method for impedance tube measurements is presented in this letter. The error of measuring the complex reflection coefficients R is caused by errors in measuring the positions of the two microphones (or the two pressure points for the improved SWR method). Results agree with Abom and Boden’s [J. Acoust. Soc. Am. 83, 2429–2438 (1988)] conclusions, i.e., errors will be large if s, the separation distance of the two microphones, is about one-half wavelength and will be small if s is about one-quarter wavelength. Results also show that in order to reduce the amplitude error of R, it is better to locate one microphone near a minimum pressure point and the other near the adjacent maximum pressure point. To reduce the phase error of R for the transfer function method, preference of the two microphone locations depends on the combination of length errors Δl1 and Δl2. Phase error reduction for the improved SWR method requires an accurate measurement of the minimum pressure point.
Minimum audible movement angle: Marking the end points of the path traveled by a moving sound source
Authors: Perrott David R. , Marlborough Kent
Published: October 2005

Four experienced subjects were tested on their ability to discriminate the direction of motion or the order of events in a single-interval, two-alternative, forced-choice adaptive paradigm. Two conditions, employing a broadband ‘‘pink’’ noise (500–8000 Hz), were examined: (1) A continuous noise was available from the moving sound source during the entire period of travel; and (2) 10-ms noise pulses were presented from the moving source at the beginning and end of the arc traveled (during the interpulse interval the source was inactive). Minimum audible movement angle (MAMA) thresholds were significantly lower when the moving source was active throughout the period of travel (0.914°) than when only the end points of the arc of travel were ‘‘marked’’ (1.604°). These results do not support the notion that the discrimination of motion can be reduced to a simple comparison of the location of the source at signal onset and the position of the source at signal offset. The MAMA thresholds obtained with broadband noise in the current experiment are considerably lower than the thresholds previously observed with tonal targets.
Pitch identification of simultaneous diotic and dichotic two-tone complexes
Authors: Beerends John G. , Houtsma Adrianus J. M.
Published: October 2005

This study examines subjects’ ability to recognize the pitches of two missing fundamentals in two simultaneous two-tone complexes whose partials are distributed in various ways between subjects’ ears. The data show that identification performance is affected on different levels. Limited frequency resolution in the peripheral auditory system can degrade performance, but only if none of the four stimulus partials is aurally resolved. Identification performance is only weakly dependent on the manner of distributing partials between the ears. In some cases it was found that, probably at a very central level (e.g., attention), the identification processes of both simultaneous pitches interfere with one another. Some subjects are more likely to identify the pitch of one two-tone complex when the harmonic order of the other complex is higher than when this harmonic order is lower. Finally, some subjects tend to hear the complex tones analytically, i.e., perceive pitches of single partials instead of the missing fundamentals for some distribution of partials between the ears.
Differentiation between acutely ischemic myocardium and zones of completed infarction in dogs on the basis of frequency-dependent backscatter
Authors: Wear Keith A. , Milunski Mark R. , Wickline Samuel A. , Perez Julio E. , Sobel Burton E. , Miller James G.
Published: October 2005

The goal of this work was to determine whether the frequency dependence of apparent backscatter coefficient (not corrected for attenuation within the myocardium) could differentiate completed, remote infarction from acute myocardial injury in vivo. Myocardial infarcts were produced in six dogs by coronary artery occlusion. One to 12 months later, acute ischemic injury was induced in each dog by ligation of a coronary artery that supplied a region of myocardium adjacent to the established infarct. Infarct, ischemic, and normal regions were interrogated with a 5-MHz, circular, 0.5-in. diam, broadband, focused, piezoelectric transducer mounted in a water-filled stand-off device placed against the exposed, beating heart. Apparent backscatter coefficients were measured over the range of frequencies from 3–7 MHz. The frequency dependence was obtained from the slope of log apparent backscatter coefficient versus log frequency. No significant difference in frequency dependence was found between normal and acutely ischemic myocardium for periods of up to 2 h of ischemia. In contrast, frequency dependence in regions of remote infarct (1.8±0.1, mean±standard error) was significantly lower than that in acutely ischemic or nonischemic regions (2.3±0.1) (p<0.01). These results suggest that remote myocardial infarction can be differentiated from acutely injured but still potentially salvageable myocardium in vivo on the basis of the frequency dependence of backscatter.
Speech perception in children with histories of recurrent otitis media
Authors: Clarkson Richard L. , Eimas Peter D. , Marean G. Cameron
Published: October 2005

The present study investigated the ability of 5-year-old children to perceive differences in voice onset time (VOT) in naturally produced speech. Three groups of children whose hearing was within normal limits at the time of the experiment were tested on identification and discrimination tasks: (1) group C, in which the children had normal language abilities and no history of severe, recurrent otitis media (OM), (2) group OM, in which the children had histories of severe, recurrent OM but normal language abilities, and (3) group OM/DL, in which the children had histories of severe OM and delays in the acquisition of linguistic competence. Compared to group C, group OM/DL showed marked differences in their ability to identify and discriminate speech patterns. Their perception was less categorical, as well, in that there was less of a peak in the discrimination function at the region of the phoneme boundary. The performance of group OM fell between the other two groups, with deficits being more pronounced in the discrimination task than in the identification task. The results supported the idea that episodes of OM can produce periods of sensory deprivation that alter perceptual abilities. The relation of a history of OM to later language and academic difficulties was also considered.
Intracellular recordings from supporting cells in the guinea-pig cochlea: AC potentials
Authors: Oesterle Elizabeth C. , Dallos Peter
Published: October 2005

Supporting cells and hair cells from the low-frequency region of the guinea-pig cochlea were studied in vivo using intracellular recording and horseradish peroxidase marking techniques. Response characteristics of the support cells to tone bursts at various sound levels, frequencies, and durations were compared to hair-cell responses and potentials recorded in the organ of Corti fluid spaces. Findings suggest that the fundamental component of the support-cell response accrues from hair-cell-generated currents. This component of the support-cell response probably results from the flow of receptor currents across support-cell membranes through nonspecialized membrane patches, or across nonspecialized membranes and through gap junctions that couple adjacent support cells. Findings suggest a lack of electrotonic coupling between hair cells and neighboring support cells.
A method for active noise control using a source-point model
Authors: Dohner J. L. , Shoureshi R.
Published: October 2005

In this paper, an active noise-control method is derived from a source-point model and discrete optimal control theory. A discrete state-space formulation of the model is found via a free-space Green’s function. The states of the model are pressures at past and present times on the boundary of an acoustic domain. The state-space model is used to produce a discrete single-input, single-output feedback filter that minimizes sound at selected points in the one-dimensional acoustic domain. Theoretical results are given for a single detector microphone in the acoustic domain and for full-state feedback. Both the single measurement and full-state feedback responses give satisfactory results in simulation and theory.
Insertion loss of absorbent barriers on ground
Authors: L’Espérance André , Nicolas Jean , Daigle G. A.
Published: October 2005

This paper presents a method for calculating the insertion loss (IL) of a thin barrier covered with absorbent material, either on the source side, on the receiver side, or on both sides. The method used combines a classical theory for the propagation of sound over ground with an approximate solution for diffraction around an absorbent barrier, which can take into account the specific impedance of each side of the barrier. The validity of the method was confirmed by comparing theoretical results with experimental measurements for various geometrical configurations and screen boundary conditions. The results show that, when the angles of diffraction are significant, the insertion loss (IL) of a hard barrier can be substantially increased by covering one of its surfaces with an absorbent material. This absorbent layer must be placed on the surface of the barrier associated with the greatest angle of the diffracted rays paths (source top-edge or receiver top-edge). When these angles are about the same on each side of the barrier, the increase will be the same if the absorbent material is placed on the source or on the receiver side. In this case, by covering both sides of the barrier, the increase of the IL due to the absorbent will double compared to a single covering.