bluuebunny/crossref_metadata_2025 huggingface dataset:
Comment on ‘‘Two-tone suppression of inner hair cell and basilar membrane responses in the guinea pig’’ [J. Acoust. Soc. Am. 93, 390–400 (1993)]
Authors: Cheatham M. A. , Dallos P.
Published: October 2005

Recent studies reveal that two-tone suppression is consistent with an attenuation model but only for a restricted set of stimulus parameters. The latter includes magnitude and phase changes produced by high-side suppressors for probe tones at and above CF. For these conditions, results at the mechanical, hair cell, and neural levels are in accord. However, when high-side suppressors are used to decrease responses below CF, data from IHCs in the apical half of the cochlea do not reveal the large phase leads predicted by an attenuation model. Further information from basal-turn IHCs may help to understand this incompatibility.
A solution of the longstanding problem associated with discrete Fourier transform-based, diffractive computation
Authors: Christopher P. Ted
Published: October 2005

The mistake or problem with the established method of Fourier transform (or angular spectrum)-based diffractive computation is identified. Two recent error analysis papers are cited for their misunderstanding of the problem. A recent paper is cited for its analysis of the problem, solution of the problem, and its demonstrated performance including exact agreement with an analytical solution.
A reply to ‘‘A solution to the longstanding problem involving error analysis of Fourier transform-based, diffractive computation’’ [J. Acoust. Soc. Am. 94, 3515 (1993)]
Authors: Williams Earl G.
Published: October 2005

In Christopher’s comments a problem with Fourier transform-based computations is pointed out. This reply addresses some of the points which he has raised, and in particular points to several references that have dealt with this problem.
Dynamics of the two-mass model of the vocal folds: Equilibria, bifurcations, and oscillation region
Authors: Lucero Jorge C.
Published: October 2005

The dynamics of the large-amplitude oscillation of the vocal folds is analyzed using the two-mass model. First, the equilibrium positions are determined in the case of a rectangular prephonatory glottis, and the existence of two equilibrium positions besides the rest position is shown. Their stability is examined and a bifurcation diagram is derived with a normalized subglottal pressure and a coupling coefficient as control parameters. Phase plane plots are shown to illustrate the results. The cases of convergent and divergent prephonatory glottis are then briefly considered. The main results are finally discussed relative to previous analytical works; it is shown that they disprove the previous oscillation theory based on the existence of a glottal negative differential resistance.
Discharge suppression in the silent interval preceding the tone burst in pause-build units of the dorsal cochlear nucleus of the unanesthetized decerebrate cat
Authors: Parham K. , Kim D. O.
Published: October 2005

A recent intracellular study of dorsal cochlear nucleus (DCN) neurons in vitro by Manis [P. B. Manis, J. Neurosci. 10, 2338–2351 (1990)] suggests that the expression of the pause-build discharge pattern is in large part dependent on hyperpolarization of their membrane potentials in a period just preceding a depolarizing stimulus (‘‘hyperpolarization conditioning’’ hypothesis). Our examination of the activity of a sample of pause-build units (n=72) revealed suppression of discharge activity during a time window of the silent interstimulus interval (SII) just preceding the tone burst relative to the spontaneous rate in 74% of all units. The discharge suppression of a subset of DCN pause-build units in the SII satisfies a requirement of the ‘‘hyperpolarization conditioning’’ hypothesis, and thus supports the hypothesis.
Doppler effect for sound emitted by a moving airborne source and received by acoustic sensors located above and below the sea surface
Authors: Ferguson Brian G.
Published: October 2005

The acoustic emissions from a propeller-driven aircraft are received by a microphone mounted just above ground level and then by a hydrophone located below the sea surface. The dominant feature in the output spectrum of each acoustic sensor is the spectral line corresponding to the propeller blade rate. A frequency estimation technique is applied to the acoustic data from each sensor so that the Doppler shift in the blade rate can be observed at short time intervals during the aircraft’s transit overhead. For each acoustic sensor, the observed variation with time of the Doppler-shifted blade rate is compared with the variation predicted by a simple ray-theory model that assumes the atmosphere and the sea are distinct isospeed sound propagation media separated by a plane boundary. The results of the comparison are shown for an aircraft flying with a speed of about 250 kn at altitudes of 500, 700, and 1000 ft.
Spatially localized random forcing of fluid-loaded elastic plates
Authors: McCoy John J. , Dimitriadis Emilios K.
Published: October 2005

The response of a fluid-loaded, linearly elastic plate to a spatially localized, random forcing and the radiation of sound therefrom is formulated in terms of two-point coherence functions. Emphasized is the use of linear-phased arrays, of displacement meters on the surface of the plate and of hydrophones located in planes removed from the plate, in an envisioned model experiment. The formulation shows the total experiment to be described via an ordered sequence of operators, termed propagator/filters. Analytic and numeric investigation of these operators are accomplished for ‘‘typical’’ experimental scenarios. Of particular interest is the complicated manner in which the ‘‘potential for interference’’ of widely separated, in physical or in spectral space, components of an acoustic signal is accommodated in a coherence function formulation. This potential renders a Wigner function, a transformed coherence function, description of a phase space, somewhat inconvenient for discussing the propagation and scattering of deterministic signals. Randomness, which typically eliminates this potential for interference, can make for a convenient Wigner function framework.
Determining suspended sand size and concentration from multifrequency acoustic backscatter
Authors: Crawford A. M. , Hay Alex E.
Published: October 2005

An inversion algorithm for extracting suspended sand size and concentration from simultaneous backscattered acoustic pressure amplitude at three operating frequencies is presented. The algorithm is based on the differences in signal amplitude between different frequency pairs, and is tested using laboratory measurements of multifrequency backscatter from a turbulent sediment-carrying jet. Concentration and size profiles inverted from field and laboratory data are compared with results from a previously developed algorithm based on signal ratios. The difference inversion scheme is less sensitive to errors arising from low signal levels, allowing the size/concentration measurement range to be extended to regions of lower concentration. The concentrations from the field data agree well with independent optically determined estimates. The results demonstrate sensitivity to the backscatter form factor.
Sound scattering from a finite cylinder with ribs
Authors: Moser Philip J. , Überall Herbert , Yuan Jian-Ren
Published: October 2005

The effects of an almost-periodically spaced set of ribs on the scattering of sound from a submerged cylinder of finite length are investigated. The cylinder is either assumed soft (corresponding to a very thin air-filled shell), or rigid (corresponding to a heavy thick shell) and its scattering amplitude is obtained using the geometrical theory of diffraction. The rib scattering amplitude is found from curvature-corrected results of the theory for a flat plate carrying a rib. Numerical results were obtained for the case of soft cylinders (i.e., thin, air-filled shells); they exhibit the onset and emergence of rib effects over the background of scattering from the body of the cylinder.
Vocal affect in three-year-olds: A quantitative acoustic analysis of child laughter
Authors: Nwokah Evangeline E. , Davies Patricia , Islam Asad , Hsu Hui-Chin , Fogel Alan
Published: October 2005

Recordings were obtained of the laughter vocalizations of four 3-year-old children during three sessions of spontaneous free-play between mother and child in a laboratory playroom. Acoustic analysis was used to determine laughter durations, laughter events, F0, and harmonic characteristics, and to suggest a taxonomy of laughter types. Melodic contours were assessed from patterns of F0 change during laughter. Mean duration of laughs ranged from 200 ms to 2.0 s, but events within a laugh were usually about 200-ms duration. Laughs were intuitively classified into four major types, and, following the acoustic analyses, were further defined and classified into types and subtypes of exclamatory and dull comment; chuckle; basic, variable, and classical rhythmical; and squeal. Melodic contours included more rising contours than previously reported for cry, but there was great variability in the types of contours produced especially for rhythmical laughs. The results of the acoustic analyses are discussed in relation to (a) the development of a taxonomy of laughter and (b) different features of the vocal affect characteristics of high-intensity emotion.
Speaker-independent consonant classification in continuous speech with distinctive features and neural networks
Authors: De Mori Renato , Flammia Giovanni
Published: October 2005

This paper provides experimental evidence to the assertion that the design of appropriate neural networks (NN) for speech recognition should be inspired by acoustic and phonetic knowledge, and not only by knowledge in pattern recognition. Rather than investigating the NN learning paradigm, the paper is focused on the influence of the input parameters, of the internal structure, and of the desired output representation on the classification performance of recurrent multilayer perceptrons. As an instructive example, the paper analyzes the problem of classifying ten stop and nasal consonants in continuous speech independently of the speaker. Experiments are reported for the TIMIT database, using 343 speakers in the training set and 77 different speakers in the test set. Comparative experiments show that good performance is obtained when many input acoustic parameters are used, including a time/frequency gradient operator related to transitions of the second formant, and when the desired outputs represent context-dependent articulatory features. Classification is performed by principal component analysis of the NN outputs. Refinement of the design parameters yield increasingly better performance on the test set, ranging from 45% errors for a perceptron without hidden nodes to 23.3% errors for the best NN.
Development of (3,1) drive low-frequency piezofilm hydrophones with improved sensitivity
Authors: Bhat J. Jagannath , Thomson P. Philip , Pillai P. R. Saseendran
Published: October 2005

Piezopolymers are becoming popular as the active material for the design of probes for sensing ultrasonic fields and quantitative determination of acoustic field parameters in water and biological media. A new innovative transducer design proposed here utilizes a poled piezofilm which is made to vibrate in (3,1) drive by a modified structural assembly. The voltage generated in this design is found to be greater compared to that in the conventional design, due to the concentration of acoustic pressure to a very small cross-sectional area. The prototype design consists of a prestretched piezofilm fixed to a phosphor bronze diaphragm through a driver pin. The proposed design yielded sensitivities to the extent of −170 dB re: 1 V/μPa in water at around 1.5 kHz.
Amalgamated body waves, surface waves, and source signature in a half-space under a shear load
Authors: Ziv M.
Published: October 2005

The half-space elastic response to a source of a nonuniformly spatially distributed impulsive shear load is presented in this paper. Specifically, an infinite semicircular canyon of a finite radius is embedded in the surface of the half-space where an impulsive shear load is tangentially distributed over the entire surface of the canyon. In an earlier work, the author gave an analytical-numerical method for transient multicurvilinear dimensional boundary-value problems and its employment to a nonuniformly spatially distributed shear load. Here, the resultant transient deformation of the half-space is described and interpreted. In particular, a detailed discussion is devoted to the appearance of spatially stationary strong discontinuity fronts in the interior of the deformed half-space. These fronts, which disclose the nature of the prescribed source of disturbance, are the source signature. A detailed discussion is then devoted to the appearance of amalgamated wave fronts (not to be confused with head waves), which are neither dilatational nor shear waves, and their surface waves, all revealing themselves explicitly by the solution method.
Third-order elastic constants for an inviscid fluid
Authors: Kostek Sergio , Sinha Bikash K. , Norris Andrew N.
Published: October 2005

In dealing with nonlinear problems involving fluids and solids, whether of a static or dynamic nature, a common description of the fields in terms of Eulerian or Lagrangian variables is desirable. Usually the former is used for fluids and the latter for solids. The choice of primitive variables also differs when dealing with fluids or solids. The material constants describing the constitutive behavior of these media will thus depend on the description adopted. In this paper, explicit relations are provided between third-order elastic constants for an inviscid fluid and the more common coefficients, A and B, appearing in the Taylor expansion of the equation of state. The essential results are c111=−(5A+B), c112=−(A+B), and c123=A−B.
Self-demodulation of amplitude- and frequency-modulated pulses in a thermoviscous fluid
Authors: Averkiou Michalakis A. , Lee Yang-Sub , Hamilton Mark F.
Published: October 2005

The self-demodulation of pulsed sound beams in a thermoviscous fluid is investigated experimentally and theoretically. Experiments were performed in glycerin at megahertz frequencies with amplitude- and frequency-modulated pulses. The theory is based on the Khokhlov–Zabolotskaya–Kuznetsov (KZK) nonlinear parabolic wave equation. Numerical results were obtained from an algorithm that solves the KZK equation in the time domain [Y.-S. Lee and M. F. Hamilton, Ultrasonics International 91 Conference Proceedings (Butterworth–Heinemann, Oxford, 1991), pp. 177–180]. A quasilinear analytic solution, which describes the main features of the waveform at all axial locations, is developed in the limit of strong absorption. Theory and experiment are in good agreement throughout the near- and far fields.
A half-space response to a finite surface groove source of an impulsive shear disturbance
Authors: Ziv M.
Published: October 2005

The response of an ideal elastic half-space to an impulsive shear load is obtained by a computational method based on the theory of characteristics. The impulsive load is distributed unevenly but tangentially over the entire boundary of a semicircular infinite canyon embedded in the surface of the half-space. For this configuration, a wave characteristics formulation is presented where its differential equations are extended to accommodate strong discontinuities that occur in the material motion of the half-space. A step-by-step numerical integration of these extended differential equations is then carried out in a two-dimensional curvilinear wavegrid formed by the bicharacteristic curves of the wave characteristics formulation. The resultant transient deformation of the half-space is shown by plots which give the time history behavior of the dependent variables at a specific spatial location. In these plots, the various wave fronts traversing the half-space explicitly reveal themselves.
Sound transmission through slotted concrete blocks with attached gypsum board
Authors: Warnock A. C. C.
Published: October 2005

Measurements of sound transmission loss through slotted concrete blocks with attached gypsum board showed that the cavity resonance of the blocks has an important beneficial effect. It counteracts the mass-air-mass resonance that occurs when gypsum board is added to the surface of a concrete block wall leaving an air space behind it. This significantly increases the sound transmission class rating relative to the same systems with normal-weight nonslotted blocks. The effects of the two resonances could be seen at different frequencies when there was no sound-absorbing material in the air space behind the gypsum board. When the air space was filled with sound-absorbing material, however, both resonances moved together and could not be separated, but the transmission losses and sound transmission class for the composite wall were still significantly greater than those for wall systems using nonresonant blocks. Sound absorption measurements for the slotted blocks showed the need for one-third octave band data in place of the octave band data often found in trade literature.
Optical detection of transient bubble oscillations associated with the underwater noise of rain
Authors: Stroud John S. , Marston Philip L.
Published: October 2005

A drop of water falling on a water surface entrains a bubble for certain drop diameter–impact velocity combinations. Volume oscillations of the bubble contribute to the underwater noise of rain. A method was developed for optical detection of these volume oscillations in a laboratory environment. The entrained bubble is in the path of a laser beam when the bubble is created. The beam is then directed to a photodetector and the transient signal resulting from oscillations of the optical cross section of the bubble is recorded. This optically obtained record is compared to an acoustic record of each event and the frequencies are in agreement. The general magnitude of the initial radial oscillation is estimated and compared with relevant theoretical results by Og̃uz and Prosperetti [J. Fluid Mech. 228, 417–442 (1991)].
Pitch-synchronous frame-by-frame and segment-based articulatory analysis by synthesis
Authors: Gupta Sunil K. , Schroeter Juergen
Published: October 2005

This paper presents a pitch-synchronous analysis-by-synthesis procedure for estimating model parameters for voiced speech. These model parameters describe the vocal-tract shape and the time derivative of the glottal area function. The excitation waveform is derived from the glottal area function by incorporating source-tract interaction using the current vocal-tract input impedance. The corresponding analysis procedure for estimating the model parameters once every pitch period is outlined. A significant improvement in quality was obtained for the new pitch-synchronous analysis/synthesis procedure relative to the fixed-frame-length-based scheme used previously. It was also found that the new pitch-synchronous articulatory analysis/synthesis scheme achieves lower rms spectral distortion values than the 2.4 kb/s. Federal standard LPC-10E algorithm. A segment-based procedure for estimating the vocal-tract model parameters at a rate much lower than the current pitch is described. In this segment-based analysis-by-synthesis approach, the model parameters are estimated every 50–100 ms. The parameters for the intermediate pitch periods are derived by interpolation. The segments are selected using a maximum likelihood segmentation algorithm that segments an utterance into diphonelike units. A segment-based parameter optimization scheme could lead to a highly economical representation of the speech signal for potential applications in very low bit rate speech coding and speech storage.

The above schemes were optimized for a pilot test sentence and then evaluated using eight test sentences for a log area and the Coker articulatory model representation of the vocal tract. Nine listeners were asked to judge the quality of the synthesis in a paired-comparison test and the results were analyzed using a nonparametric one-tailed sign test. For the log-area representation of the vocal tract, we found a significant degradation in speech quality for the segment-based optimization procedure relative to the frame-based procedure. However, for the Coker model representation, the degradation was found to be insignificant. This shows that unlike cross-sectional areas, the movement of various articulators in the vocal tract during speech production can be described with sufficient accuracy by specifying the position of these articulators and by using an interpolation function at time intervals much longer than a pitch period.
Where the action is: Weber fractions as a function of sound pressure at low frequencies
Authors: Ward Lawrence M. , Davidson Kelly P.
Published: October 2005

Weber fractions for sound intensity were measured for 70-, 100-, 200-, 1000-, and 10 000-Hz tone pulses at sound-pressure levels (SPLs) ranging from just above individual listeners’ absolute thresholds to near their highest tolerable SPLs, using a two-alternative forced-choice adaptive staircase technique governed by a 1-up, 3-down rule. Results for four listeners with normal hearing and varying experience, despite individual differences in absolute values, showed Weber fractions that declined as sound pressure increased above threshold and asymptoted at intermediate SPLs. A power function with a negative exponent describes the data of the individual listeners better than a logarithmic function does. The absolute value of the exponent of the power function, which measures the curvature of the function, was largest at 70 Hz and declined with increasing frequency, similar to how exponents of power functions relating loudness judgments or simple reaction time to stimulus intensity differ with sound frequency.
A quantitative measure of similarity for tursiops truncatus signature whistles
Authors: Buck John R. , Tyack Peter L.
Published: October 2005

Bottlenose dolphins (tursiops truncatus) produce individually distinctive narrow-band ‘‘signature whistles.’’ These whistles may be differentiated by the structure of their frequency contours. An algorithm is presented for extracting frequency contours from whistles and comparing two such contours. This algorithm performs nonuniform time dilation to align the contours and provides a quantitative distance measure between the contours. Two recognition experiments using the algorithm on three dolphin whistles from each of five individuals classified 15 out of 15 single-loop whistles correctly, and 14 out of 15 central loops for multiple-loop whistles correctly.
Processing of spoken CVCs in the auditory periphery. I. Psychophysics
Authors: Ghitza Oded
Published: October 2005

This study provides a quantitative measure of the accuracy of the auditory periphery in representing prespecified time-frequency regions of initial and final diphones of spoken CVCs. The database comprised word pairs that span the speech space along Jakobson et al.’s binary phonemic features [Tech. Rep. No. 13, Acoustic Laboratory, MIT, Cambridge, MA (1952)]. The time-frequency domain was divided into ‘‘tiles’’ by splitting the frequency range into three bands ([0,1000], [1000,2500], [2500,4000] Hz), and by marking the phonemic time landmarks of the CVC utterance. Fourteen modified versions of this database were generated by introducing well-defined distortions into the time-frequency tiles (or combination of tiles). The performance of eight listeners was measured for each of these versions by using a one-interval two-alternative forced-choice paradigm, to minimize the role of cognition. The results demonstrate that in the first and the second frequency bands, the diphone information is far more important than the consonant information or the vowel information alone. As for the third band, most of the information of the diphone is contained in the consonantal time interval. These observations are common to both the initial and the final consonants of spoken CVCs. The study also provides a direct mapping between Jakobson et al.’s features and particular regions in the time-frequency domain. Voicing and nasality are strongly correlated with the diphone information in the first frequency band, graveness and compactness with the diphone information in the second frequency band, and sibilation with the consonantal time interval in the third frequency band. Sustention is equally correlated with the diphone information in the second and the third frequency bands. Since the role of cognition was neutralized to a large extent, the results may also be interpreted as a map of the phonemic distinctive features to some peripheral auditory functions that operate on the corresponding time-frequency regions.
Effect of surface tension on the acoustic radiation pressure-induced motion of the water–air interface
Authors: Cinbis C. , Mansour N. N. , Khuri-Yakub B. T.
Published: October 2005

The displacement of a water–air interface and its relaxation as a function of acoustic energy density and surface tension were analyzed both experimentally and numerically. Experimental systems were devised to observe the time evolution of the surface. A theoretical model to predict the response of the interface to acoustic excitation was also developed. It was found that the Langevin pressure due to a focused acoustic beam will cause the interface to rise to a height that is a function of the energy density of the beam. The rise time, which is the time it takes for the wafer surface to rise to its maximum height, was found to be independent of the incident energy, but was found to be a function of the surface tension. The time of mound formation measurements in clean water at low-energy acoustic excitations were found to be within 20% of the simulation results. These results imply that surface rise time measurements may present a novel way of measuring surface tension of water–surfactant combinations accurately and rapidly by a simple noncontacting technique.
Experimental estimation of the transverse-wave backscatter coefficients for ultrasonic interrogation of weak scattering materials
Authors: Russell Mark D. , Neal Steven P.
Published: October 2005

Estimation of a material’s ultrasonic scattering function is a preliminary step to the inverse problem of inferring the material properties from the scattering function. The necessary theory for backscatter coefficient estimation was recently formulated and then applied to the problem of longitudinal-wave backscatter coefficient estimation for weak scattering polycrystalline materials. The present work extends that approach and demonstrates its applicability to the estimation of transverse-wave backscatter coefficients for weak scattering materials whose backscatter coefficient is independent of depth and angle of interrogation. Backscattered ultrasonic signals were measured from a polycrystalline material using both focused and planar transducers operated broadband. Backscattered signals were measured for several measurement system configurations. The distributed scatterer measurement system response function power was calculated for each configuration based on volume integrals of velocity fields calculated using Gauss–Hermite polynomials. Backscatter coefficients were then estimated by removing the measurement system effects from the measured backscattered signals. Results are presented that show agreement between the frequency dependence of the backscatter coefficient estimates and the frequency dependence of the classically determined attenuation coefficient. The estimated transverse-wave backscatter coefficients are shown to be reasonably independent of water path, depth into the material, angle of incidence of the interrogation, and transducer type.
The relation among fundamental frequency, intensity, and duration varies with accentuation
Authors: Alain Claude
Published: October 2005

The relation among fundamental frequency (F0), sound intensity, and syllable duration was investigated in subjects who articulated unaccentuated and accentuated nonsense syllables. Subjects were instructed to repeat the syllable [pa] with different accentuation patterns (e.g., pa pá pa pá ...). A total of 751 syllables from 16 subjects were analyzed. Positive correlations were found between F0, intensity, and syllable duration across accentuated and unaccentuated syllables and within unaccentuated syllables. However, negative correlations were found between duration and F0 and intensity in accentuated syllables. The results suggest that different motor patterns are involved in the generation of accentuated and unaccentuated syllables.
Response to ‘‘Comments on ‘Cooperative radiation and scattering of acoustic waves by gas bubbles in liquids’ ’’ [J. Acoust. Soc. Am. 94, 2446–2447 (1993)]
Authors: Zabolotskaya E. A.
Published: October 2005

Discussion concerning two approaches to study nonlinear phenomena in bubbly liquids continues. Some aspects associated with a pulsating bubble radiation are elucidated within the volume displacement approach: existence of the additional pressure near the pulsating bubble and the second harmonic generation by hydrodynamic nonlinearity in the near field.
Nonperturbative modal tomography inversion. Part I. Theory
Authors: Jones R. Michael , Shang E. C. , Georges T. M.
Published: October 2005

The mathematical basis for a method to invert modal ocean acoustic tomography measurements without explicitly assuming an initial sound-speed profile is described. The method is based on determining the group and phase travel times for each vertical slice through the tomographic region. The group travel times are determined directly as the measurements of modal pulse travel time. The phase travel times are determined by resolving the cycle ambiguities in the phase measurements with constraints connecting the group and phase travel times. Standard tomographic techniques then determine the modal group and phase speeds within the tomographic region, and Abel transforms can be used to determine the symmetric part (the difference between the upper and lower profiles) of the sound channel. As with ray tomography, modal tomographic measurements supply no information about the antisymmetric part of the sound channel (the average of the upper and lower profiles), but determining the lower part of the sound channel can supply the missing information. The lower part of the sound channel can be estimated from climatology or by using arrays to determine local sound-speed profiles from local modal properties and interpolating into the interior of the tomographic region.
An efficient three-dimensional boundary integral equation method for solving azimuthally symmetric scattering problems in the oceanic waveguide
Authors: Fawcett John A.
Published: October 2005

In this paper an efficient boundary integral equation method (BIEM) is presented for the computation of the pressure field scattered from three-dimensional bathymetry in an oceanic waveguide. The bathymetry is taken to be azimuthally symmetric about an origin and a rigid boundary condition is used. The source, however, can be located off-axis anywhere within the waveguide. The azimuthal symmetry of the bathymetry allows one to solve a sequence of one-dimensional integral equations instead of a very large two-dimensional one. To verify the validity of the method, the results from the three-dimensional BIEM code are compared to the results from a radial coupled-mode program.
Simulation of the effects of loudness recruitment and threshold elevation on the intelligibility of speech in quiet and in a background of speech
Authors: Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

These experiments simulated the threshold elevation and loudness recruitment associated with three different types of cochlear hearing loss: Moderate flat (condition R2), severe flat (condition R3), and moderate-to-severe sloping (condition RX). This was done to allow an examination of the effects of these factors on the intelligibility of speech, in isolation from other factors that are normally associated with cochlear hearing loss, such as reduced frequency selectivity. The simulation was performed by splitting the input signal into 13 frequency bands, and processing the envelope in each band so as to create loudness sensations in a normal ear that would resemble those produced in an impaired ear with recruitment. The bands were then recombined. All tests were performed using subjects with normal hearing. For speech in quiet, simulation of hearing loss produced a reduction in the ability to understand low-level speech. However, speech at sufficiently high levels was highly intelligible in all conditions. Linear amplification according to the National Acoustic Laboratory (NAL) prescription gave high intelligibility for speech at normal conversational levels. For speech presented at a fixed input level of 65 dB SPL, against a background of a single competing talker, simulation of hearing loss produced substantial decrements in performance. The speech-to-background ratios in conditions R2 and RX had to be 11–13 dB higher than in the control condition (unprocessed stimuli) to achieve similar levels of performance. Linear amplification according to the NAL prescription improved performance markedly for the conditions simulating flat losses, but was less effective for the condition simulating a sloping loss. This indicates that threshold elevation combined with recruitment produces a loss of intelligibility for speech in the presence of a single competing talker that is only partly compensated by linear amplification of the type typically used in hearing aids.
Cue trading in the production and perception of vowel stress
Authors: Howell Peter
Published: October 2005

The distinction between stressed and unstressed vowels in noun/verb pairs differentiated by stress (e.g., as in the word ‘‘misprint’’) is known to be cued by the acoustic attributes fundamental frequency, intensity, and duration. The role of these cues and vowel centralization measures in perception is ordered differently from that in production. It is not known what variability there is between speakers, whether the acoustic factors vary with speech clarity that a speaker produces on different occasions, or what the relationship is between the various speech attributes. Importantly, no studies have been performed in which production and perception of materials is compared with respect to these questions. In the current study, noun/verb pairs differentiated by stress were produced by four speakers, and measures of produced and perceived clarity obtained for these subjects. The importance of the acoustic factors to the contrast was modeled in perception and production, and the results compared. Additionally, the variation with produced or perceived clarity was ascertained. Finally, comparison between cue trading in production and perception was made. The results are discussed in connection with models of speech perception and production.
The effect of temporal waveform shape on spectral discrimination by normal-hearing and hearing-impaired listeners
Authors: Leek Marjorie R. , Summers Van
Published: October 2005

A listener’s ability to discriminate differences in amplitude spectra is generally thought to be independent of the temporal waveform shapes of the stimuli. However, there have been reports of enhanced contrast between spectral peaks and valleys of harmonic complexes represented in the temporal firing patterns of auditory-nerve fibers for some combinations of component amplitudes and phases [e.g., Horst et al., J. Acoust. Soc. Am. 88, 2656–2681 (1990)]. The enhancement has been attributed to nonlinear processing of high-amplitude peaked waveforms. To determine whether such enhancements are observed in psychoacoustic responses of human listeners, subjects were asked to discriminate between harmonic complexes that differed in the frequency location of three formantlike increments in harmonic amplitude. The stimuli were constructed to have either a very flat or a very peaked temporal envelope. Over a range of 1- to 10-dB spectral contrast between elevated harmonics and background harmonics, discrimination ability was determined as a function of waveform shape and overall amplitude. Performance was measured for both normal-hearing and hearing-impaired listeners. Normal-hearing listeners showed lower thresholds of spectral contrast for peaked waveforms at high intensities than for any of the other phase-amplitude conditions. Although the effect was small (1 to 2 dB), it is consistent with an hypothesized enhancement due to nonlinear cochlear processing. Hearing-impaired listeners did not demonstrate differential performance across phase or amplitude conditions, perhaps reflecting more linear processing in these damaged ears.
A new stochastic model for auditory-nerve discharge
Authors: Miller Michael I. , Wang Jing
Published: October 2005

This paper investigates the mechanisms for history-dependent probability of eighth-nerve discharge, which is modeled as the probability that the excitatory postsynaptic potential (EPSP) process crosses afferent membrane threshold, with the discharge history dependence due to the dependence of postsynaptic threshold voltage on time since previous action potential. The model parameters are the Poisson intensity αt of vesicle release, the duration ε and probability density pV(v) of single-vesicle EPSP’s, and the threshold voltage curve θ(τ) for spiking. It is proven that the infinitesimal conditional probabilities of discharge exhibit two distinct behaviors. The first is associated with the time τ=TD, exactly the time the neuron releases from absolute refractory where there is no intensity [θ(τ)=∞, for τ<TD]. At this time the neuron has a nonzero probability of discharge Λt(TD) = limΔ→0 Pr{Nt,t+Δ = 1‖t − wNt= TD}. The second regime corresponds to the time since previous spike being greater than dead time, τ≳TD, during which time the intensity exists λt(τ) = limΔ→0(1/Δ)Pr{Nt,t+Δ = 1‖t − wNt= τ≳ TD}. The fact that there is a nonzero probability of discharge following passage from the absolute refractory period predicts the nonmonotonic hazard intensity seen in high spontaneous neurons [R. P. Gaumond, Ph.D. thesis, Washington University, St. Louis (1980)] and high driven rate neurons. It is shown that for the lowest range of vesicle release intensities where the vesicle-release-rate/membrane-integration-time product αtε is small, the nonzero probability of discharge at a point is approximately equal to 0. The discharge intensity is dominated by a term linear in vesicle release intensity: λt(τ)≊αt exp(−∫t−εtασ dσ)∫θ (τ)∞pV(v)dv. This is precisely the Siebert–Gaumond intensity product form with monotonic recovered discharge probability.

At high vesicle release rates, such as for driven rate responses, the nonzero probability of discharging at a point becomes of nonsignificant size, and the intensity of discharge grows nonlinearly with αt, implying the product model does not hold. The model is demonstrated via the analysis of auditory nerve fibers from the cat.
Functional changes in the ventral cochlear nucleus following acute acoustic overstimulation
Authors: Boettcher Flint A. , Salvi Richard J.
Published: October 2005

The effects of acute acoustic overstimulation on the discharge patterns of neurons in the ventral cochlear nucleus (VCN) were evaluated in anesthetized chinchillas. Response measures were obtained from the same neuron before and after presenting a 3- to 5-min intense tone (90–105 dB SPL) located one-half oct above the unit’s characteristic frequency (CF). If a unit had an inhibitory response area at frequencies above CF and if the traumatizing tone reduced the magnitude of the inhibitory response, then the neuron’s discharge rate to suprathreshold tones at CF increased (‘‘enhancement’’) by as much as 25%. However, if a unit lacked an inhibitory response area at frequencies above CF, then the traumatizing tone typically caused either no change or a decrease in the unit’s discharge rate at CF. The traumatizing tone did not alter the shape of the post-stimulus time histograms. Moreover, the width of the excitatory response area was not altered by the exposure even when traumatizing stimulus reduced the magnitude of the inhibitory response above CF. The enhanced firing rate at CF following the exposure could conceivably contribute to the enhanced evoked-potential amplitudes observed in the auditory brain stem following acoustic trauma.
Gender differences in cochlear response time: An explanation for gender amplitude differences in the unmasked auditory brain-stem response
Authors: Don Manuel , Ponton Curtis W. , Eggermont Jos J. , Masuda Ann
Published: October 2005

Derived narrow-band auditory brain-stem responses (ABRs) in young normal-hearing subjects revealed a significant gender difference in response time between frequency regions of the cochlea. Females showed shorter delays than males between derived bands. This differential has not been previously reported. As in many early studies, the unmasked amplitude of the wave V complex was significantly larger (30%) in females than males. However, differences in amplitudes of the narrow-band responses were too small to account for the differential in the unmasked response. It is hypothesized that the larger amplitude of the unmasked wave V complex in females occurs because of a faster response time across the cochlea leading to better neural synchrony and, therefore, larger amplitudes. Furthermore, results can be explained by assuming that the stiffness gradient in the cochlea is 13% larger in females than in males. If males and females have the same cochlear tonotopic mapping, the female cochlea should be 13% shorter. This prediction is highly consistent with recent anatomical studies of cochlear length and gender. The results of the present study indicated possibly important cochlear mechanisms that influence the main parameters of ABRs. An understanding of these cochlear mechanisms may improve the diagnostic capabilities of ABRs in patients with peripheral hearing loss.
On the intonation of sinusoidal sentences: Contour and pitch height
Authors: Remez Robert E. , Rubin Philip E.
Published: October 2005

A sinusoidal replica of a sentence evokes a clear impression of intonation despite the absence of the primary acoustic correlate of intonation, the fundamental frequency. Our previous studies employed a test of differential similarity to determine that the tone analog of the first formant is a probable acoustic correlate of sinusoidal sentence intonation. Though the typical acoustic and perceptual effects of the fundamental frequency and the first formant differ greatly, our finding was anticipated by reports that harmonics of the fundamental within the dominance region provide the basis for impressions of pitch more generally. The frequency extent of the dominance region roughly matches the range of variability typical of the first formant. Here, we report two additional tests with sinusoidal replicas to identify the relevant physical attributes of the first formant analog that figure in the perception of intonation. These experiments determined (1) that listeners represent sinusoidal intonation as a pattern of relative pitch changes correlated with the frequency of the tonal replica of the first formant, and (2) that sinusoidal sentence intonation is probably a close match to the pitch height of the first formant tone. These findings show that some aspects of auditory pitch perception apply to the perception of intonation; and, that impressions of pitch of a multicomponent nonharmonic signal can be derived from the component within the dominance region.
Effect of relative amplitude of frication on perception of place of articulation
Authors: Hedrick Mark S. , Ohde Ralph N.
Published: October 2005

The amplitude of frication relative to vowel onset amplitude in the F3 and F5 formant frequency regions was manipulated for the synthetic fricative contrasts /s/–/∫/ and /s/–/θ/, respectively. The influence of this relative amplitude manipulation on listeners’ perception of place of articulation was tested by (1) varying the duration of frication from 30 to 140 ms, (2) pairing the frication noise with different vowels /i open aye u/, (3) placing formant transitions in conflict with relative amplitude, and (4) holding relative amplitude constant within a continuum while varying formant transitions and the amplitudes of spectral regions where relative amplitude was not manipulated. To determine if listeners were using absolute spectral cues or relative amplitude comparisons between frication and vowel for fricative identification, the frication and vowel were separated by (1) presenting the frication in isolation, and (2) inserting a gap of silence between the frication and vowel. The results showed that relative amplitude was perceived across vowel context and frication duration, and overrode context-dependent formant transition cues. The findings for temporal separations between the frication and vowel suggest that short-term memory processes may dominate the mediation of the relative-amplitude comparison. However, the overall results indicate that relative amplitude is only a component of spectral prominence, which is comprised of a primary frication spectral peak and a secondary frication/vowel peak comparison.
High-frequency sea surface reverberation: An overview
Authors: McDaniel Suzanne T.
Published: October 2005

High-frequency sea surface reverberation is reviewed from an historical perspective starting with the first comprehensive set of measurements made during World War II. Basic theories to predict reverberation due to scattering from resonant subsurface microbubbles and sea surface roughness are also reviewed as well as the environmental inputs to these theories: microbubble distributions and the ocean surface wave-number spectrum. Because resonant microbubbles absorb as well as scatter acoustic energy, a saturation effect is predicted, that is, when the bubble density increases beyond that needed to produce saturation, the backscatter remains constant. The reverberation level in this limit is a unique feature of scattering from resonant microbubbles permitting a clear identification of this scattering mechanism. Comparison of theoretical predictions with representative acoustic data demonstrates that reverberation at high grazing angles is due to rough surface scattering, while at lower grazing angles it is governed by scattering from resonant microbubbles. Large variations in backscattering strength are apparent for measurements performed at the same grazing angle, frequency, and wind speed, with reverberation levels in coastal waters being an order of magnitude higher than those in the open ocean. Although the physical mechanisms responsible for high-frequency reverberation are well understood, the relationship between backscattering variability and environmental factors is not.
Low-frequency acoustic emissions by impacting transient cylindrical water jets in fresh and salt water
Authors: Kolaini Ali R. , Roy Ronald A. , Gardner David L.
Published: October 2005

The impact of a jet of water onto a still water surface results in the entrainment of large amounts of air and the eventual formation of a bubble plume. The densely populated bubble plumes were generated by dropping a fixed volume of water, held in a cylindrical container, onto a still-water surface. The detached bubble plume, which is roughly spherical in shape, undergoes volume pulsations and radiates relatively large-amplitude, low-frequency sound. The results of laboratory study of the noise produced by this process were reported previously by Kolaini etal. [J. Acoust. Soc. Am. 89, 2452–2455 (1991)]. In this presentation, a field study of noise produced by this process in both fresh water (Lake Washington) and salt water (the Puget Sound) will be described. Studies of acoustic emissions from transient bubble plumes as a function of cylinder parameters will be described, with specific attention devoted to a comparison of results obtained in salt and fresh water. The measurements indicate that there is a correlation between the acoustic intensity radiated from bubble plumes and the total potential energy of the water jet. [Work supported by ONR.]