bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of digitized waveforms using Shannon entropy
Authors: Hughes Michael S.
Published: October 2005

A novel symbol-oriented, information-theoretic approach to signal analysis is described based on application of Shannon entropy. It is shown that this can be a preferred alternate to conventional digital signal energy analysis by making an experimental comparison of scanned ultrasonic images formed from Shannon entropy, signal energy, and log signal energy measurements. In these images, which were made by c scanning a Plexiglas bar with drill-hole ‘‘defects,’’ the Shannon entropy exhibits approximately two to three times the sensitivity of the two energy measures. However, the Shannon entropy analysis of waveforms suffers from a severe fundamental defect. It depends on the properties of the analog-to-digital converter (ADC) used to acquire the waveform as well as the properties of the waveform itself. As digitizer dynamic range is increased the Shannon entropy ultimately saturates at a level governed by the properties of the digitizer alone. This effect arises from the necessary limited bandwidth of a real ADC; if ADC bandwidth were not limited, the Shannon entropy would grow without bound with increasing dynamic range. To overcome this difficulty, a variant of the Shannon entropy is defined that depends only on the properties of the waveform. It is then shown that this variant is sensitive to the same scattering features as is the Shannon entropy for data acquired from the Plexiglas specimen discussed initially. Furthermore, the variant offers the same sensitivity improvements obtained from the Shannon entropy analysis. Finally, computation of this variant for waveforms having noise is described. Derivation of the variant is given in Appendix A of this work. Several of its more interesting features are also discussed there. Derivation of the procedure required to compute the variant is given in Appendix B.
Miniature microphone probe tube measurements in the external auditory canal
Authors: Hellstrom Per-Anders , Axelsson Alf
Published: October 2005

The use of a miniature microphone probe tube for sound-pressure level measurements in the outer earcanal was studied in four experiments. The main reason was to evaluate this method for clinical applications and for measurements of hearing protector attenuation. All measurements were registered in 1/3-oct bands. The dynamic range, frequency response of the microphone system, the insertion loss of the probe tube walls, and the influence of the probe tube in the ear canal on the sound-pressure level were examined. The first experiment attempted to determine an optimal placement of the probe tube in the earcanal. Sound-pressure levels resulting from a known free-field sound stimulus were measured at 12 different positions in the earcanal of human subjects. The results indicated that the position which is least sensitive for small movements of the probe tube on the measure was within 1 to 3 mm of the tympanic membrane. In a second experiment the changes in sound transfer function to the tympanic membrane caused by the microphone itself, when positioned just outside the ear canal entrance, were studied for 72 angles of sound incidences in ten subjects. A few minor but significant changes were observed with the microphone in this position. In a third experiment, sound transfer functions were measured from free sound field to the tympanic membrane in 19 subjects. The measurements were performed in 1/3-oct frequency bands (0.2 to 20 kHz) with sound incidences from 24 azimuthal positions and for each of these, three different elevations. The inter- and intrasubject-variability are analyzed and discussed. Finally, the reliability of probe tube microphone measurements was evaluated by repeated measurements of the sound transfer function, five times in ten subjects with the sound incidence from one position. The results indicated very small variations between repeated measurements.
Derived band auditory brain-stem response estimates of traveling wave velocity in humans. I: Normal-hearing subjects
Authors: Donaldson Gail S. , Ruth Roger A.
Published: October 2005

Estimates of cochlear traveling wave velocity (TWV) were computed from derived band auditory brain-stem response (ABR) latencies in 24 normal-hearing subjects. Wave V latencies were determined for each of six derived frequency bands (unmasked–8 kHz, 8–4 kHz, 4–2 kHz, 2–1 kHz, 1 kHz–500 Hz, and 500–250 Hz). Representative frequencies were assigned to the derived bands by estimating their energy midpoints, and cochlear positions corresponding to these frequencies were determined using Greenwood’s [J. Acoust. Soc. Am. 33, 1344–1356 (1961)] place-frequency function for humans. Two procedures were used to estimate TWV. In one procedure, an exponential function of the form l=A+BeCd was fitted to each subject’s latency-by-distance data using a least-squares algorithm, and a TWV function was generated by taking the inverse derivative of the latency function with respect to time. In the second procedure, average TWVs between adjacent derived bands were computed directly from subjects’ ipsilateral wave V latencies. Values obtained with the two procedures were similar for middle and apical cochlear loci; however, TWV functions produced lower estimates of TWV at the most basal of five cochlear sites. TWVs based on ipsilateral wave V latencies ranged from 5.6 to 78.0 m/s (geometric mean 11.12 m/s) in the cochlear base (7.53 mm from the stapes) and from 1.2 to 3.4 m/s (geometric mean 1.96 m/s) in the cochlear apex (24.1 mm from the stapes). Intersubject variability was large at the most basal point of TWV estimation but was progressively smaller at more apical sites. Mean TWV estimates were lower than those reported by several previous investigators. The range of values obtained in various studies may stem from differences in the procedures used to estimate TWV.
Effect of low-frequency ‘‘conditioning’’ on hearing loss from high-frequency exposure
Authors: Subramaniam Malini , Henderson Donald , Spongr Vlasta
Published: October 2005

Recent research has revealed that repeated exposures to a low-frequency noise results in a progressive reduction in threshold shifts (TS). This reduction in TS is not restricted to the exposure frequency, but can be observed at frequencies up to 3 or 4 octave higher. Such ‘‘conditioning’’ exposures have also been observed to protect the auditory system against hearing loss from exposures to the same noise at higher levels. The aim of this study was to determine if ‘‘conditioning’’ using low-frequency exposures protects the auditory system against hearing loss from a high-frequency exposure. Monaural chinchillas were exposed to a 0.5-kHz octave band noise (OBN) at 95 dB SPL for 6 h a day. The animals were allowed to recover for 5 days, following which they were exposed to a 4-kHz OBN at 100 dB SPL for 48 h. Hearing thresholds determined using evoked potential recordings, indicated significantly greater permanent threshold shifts in this group of animals when compared to a control group exposed only to the 4-kHz OBN. These results were confirmed by histological examination which revealed greater hair cell loss in the experimental group.
A boundary element formulation for radiation of acoustic waves from axisymmetric bodies with arbitrary boundary conditions
Authors: Soenarko Benjamin
Published: October 2005

This paper presents a computational technique using the boundary element method for the prediction of sound radiated by axisymmetric bodies with arbitrary boundary conditions. By taking advantage of the axisymmetric property of the body, the three-dimensional integral formulation is reduced to a one-dimensional integral along the generator of the body. The arbitrary boundary condition is expanded in a Fourier series with respect to the angle of revolution. The integral equation is solved using a superposition principle involving each term of the series. A numerical procedure is implemented using a curvilinear isoparametric element representation. Examples are given involving an oscillating sphere and a half vibrating sphere. The results are compared with the analytical solutions in which good agreement has been obtained.
Calculation of acoustic parameters by a filter-correlation method
Authors: Courtney Robert C. , Mayer Larry A.
Published: October 2005

This paper presents the filter correlation method, a technique for extracting consistent and accurate estimates of attenuation parameters from acoustic waveform data. The method minimizes problems associated with short time windows and multipath secondary arrivals. The method comprises two stages: a causal passband filter stage followed by a cross-correlation step. The results of the filter-correlation estimator are compared to those of the spectral difference approach for short time series with and without a secondary multipath arrival. Preliminary analyses of acoustic data collected on cored marine silts and clays show the attenuation properties of these materials cannot be described by a constant Q mechanism. The filter correlation method refines estimates of frequency-dependent velocity, revealing a small but systematic anisotropy between measurements made parallel and transverse to the sediments’ bedding plane. The observed velocity anisotropy can be modeled by assuming layered porosity variations in the cored sediments. No systematic anisotropy in attenuation was observed.
A note on onset effects in binaural hearing
Authors: Zurek P. M.
Published: October 2005

Various definitions of interaural ‘‘onset’’ delays in binaural stimuli have led to discrepant conclusions about the relative strength of onset versus ongoing cues. A distinction is offered here between gating (envelope-onset) delays, and early fine-structure (carrier) delays. This distinction, in conjunction with independent experimental results on the relative effectiveness of interaural envelope and carrier delays, leads to a reconciling interpretation.
Sub-Mach-1 sound from a point source near an absorbing half-plane
Authors: Asghar S. , Ahmad Bashir , Ayub M.
Published: October 2005

The scattering of an acoustic wave from a point source near an absorbing half-plane introducing the Kutta–Joukowski condition is studied. The effect of absorption on the diffracted field is shown explicitly. It is found that the field produced by the Kutta–Joukowski condition will be substantially larger than the field produced in its absence when the source is near the edge. It is further observed that the Kutta–Joukowski condition and the absorption do not have much influence on the scattered field away from the diffracting plane.
Modulation detection interference under conditions favoring within- or across-channel processing
Authors: Bacon Sid P. , Konrad Dawn L.
Published: October 2005

A series of experiments was conducted to examine modulation detection interference (MDI) under two general conditions: one where the processing was likely to be across channel (2.0-kHz signal, 4.0-kHz masker), and the other where the possibility of within-channel processing was much more likely (2.0-kHz signal, 1.8-kHz masker). In the first experiment, MDI was measured as the modulation frequency of the signal and masker was increased from 5 to 100 Hz. The amount of MDI decreased as modulation frequency increased from 5 to 20 Hz, beyond which it remained approximately constant. This effect of common modulation frequency was somewhat smaller for the 1.8-kHz masker. The second experiment examined the effects of relative modulator phase between the masker and signal for modulation frequencies of 10 or 100 Hz. In general, there was not a consistent effect of phase. However, when the signal and masker modulators were in-phase, there was a tendency, on average, for the amount of MDI to be at a maximum when the masker frequency was 1.8 kHz and at a minimum when it was 4.0 kHz. In the third experiment, increases in masker modulation depth usually resulted in nearly proportional increases in signal modulation depth at threshold; this was true for both masker carriers, although the increase was slightly greater for the 1.8-kHz masker. The final experiment examined the effects of level for conditions where the signal and masker carriers were either equal or unequal in level. When they were equal in level, the amount of MDI increased somewhat with increases in level for both masker carriers. Comparing the amount of MDI in these conditions with those where the carriers were unequal in level revealed that the amount of MDI was considerably less when the signal was more intense than the masker. This occurred almost exclusively for the 1.8-kHz masker, however, suggesting that it may reflect a within-channel effect. Taken together, the results from the four experiments suggest that the processing underlying MDI was generally the same in the presence of both the 1.8- and 4.0-kHz masker carriers, although within-channel processing via spread of excitation probably influenced some of the results with the 1.8-kHz masker.
Detection of silent temporal gaps between narrow-band noise markers having second-formantlike properties of voiceless stop/vowel combinations
Authors: Formby C. , Barker C. , Abbey H. , Raney J. J.
Published: October 2005

Temporal gap detection thresholds were measured in narrow-band noise-burst markers having acoustic characteristics representative of isolated steady-state second-formant (F2) properties for /p,t,k/ paired separately with /i,1,u,c/. The results revealed that gap detection threshold increased systematically as the difference was increased between the simulated stop and vowel F2 frequencies. A strong positive correlation (r=0.87) between gap detection threshold and linear marker center frequency difference was highly significant (p<0.001). Differences in other stimulus features had little influence on gap detection performance. Implications for speech perception are discussed.
Voice source model for continuous control of pitch period
Authors: Milenkovic Paul H.
Published: October 2005

The voiced speech waveform may be synthesized by exciting an LPC vocal tract filter with a pulse waveform patterned after naturally occurring glottal airflow pulses. Such a pulse waveform may be generated by computing samples of a piecewise polynomial curve at equally spaced time intervals. In this type of synthesis, the pitch period is commonly restricted to an integer multiple of the sample interval. A method is presented for removing this restriction, permitting both pulse duration and pitch period to be varied over continuous time. Aliasing distortion is prevented by computing the sample values of pulses that have been low-pass filtered in continuous time prior to sampling. Applications of this technique include modeling glottal pulses by least-squares fit to inverse filter waveforms, the synthesis of calibration waveforms for evaluating measures of speech waveform jitter, the perceptual evaluation of low levels of waveform jitter, and the synthesis of the singing voice.
Toward the simulation of emotion in synthetic speech: A review of the literature on human vocal emotion
Authors: Murray Iain R. , Arnott John L.
Published: October 2005

There has been considerable research into perceptible correlates of emotional state, but a very limited amount of the literature examines the acoustic correlates and other relevant aspects of emotion effects in human speech; in addition, the vocal emotion literature is almost totally separate from the main body of speech analysis literature. A discussion of the literature describing human vocal emotion, and its principal findings, are presented. The voice parameters affected by emotion are found to be of three main types: voice quality, utterance timing, and utterance pitch contour. These parameters are described both in general and in detail for a range of specific emotions. Current speech synthesizer technology is such that many of the parameters of human speech affected by emotion could be manipulated systematically in synthetic speech to produce a simulation of vocal emotion; application of the literature to construction of a system capable of producing synthetic speech with emotion is discussed.
Spatial versus ensemble averaging for modeling wave propagation in finely layered media
Authors: Stanke Fred E. , Burridge Robert
Published: October 2005

The shapes of plane-wave pulses propagating normally through a discretely layered medium are predicted using three methods. The first uses the method of averaging to predict the pulse traveling through a particular layered medium. This method shows that the pulse spreads solely due to admittance variations from layer to layer. The slowness variations affect only the arrival time of the pulse. The second method applies ensemble averaging. The predicted pulse suffers spreading due to impedance variations, and velocity variations. Ensemble averaging over pulses which have different arrival times (due to velocity variations) causes spreading in excess of that in any realization. The third method applies ensemble averaging after straightening the characteristics (i.e., transforming the spatial variable from distance to travel time). This gives the same result as the first method, although the significance is different in that the first method applies to any realization, but the third only to the ensemble. Thus ensemble averages must be applied with care if there is interest in a single realization, i.e., a particular layered medium; and method one is preferable when it applies.
On the frequency response of antenna array processors
Authors: Godara Lal C.
Published: October 2005

In frequency domain antenna array processing, broadband signals received on elements are Fourier transformed and each bin is processed using narrow-band processors. This paper investigates how these processors perform at different frequency bins for a given array geometry. An analysis is presented to show the effect of isotropic noise on the performance of two array processors. The array processors considered are an element space processor and a beam space processor.
Two-tone suppression of inner hair cell and basilar membrane responses in the guinea pig
Authors: Nuttall A. L. , Dolan D. F.
Published: October 2005

Recordings of receptor potentials from inner hair cells (IHCs) and the basilar membrane (BM) motion were made in pigmented guinea pigs. The acoustic stimuli were single tones near best frequency (BF) and two-tone complexes. Single tone input/output (I/O) functions had a saturating growth for the magnitude and their phase shifts were strongly dependent on the tone frequency relative to BF. For IHCs, a BF tone stimulus produced no phase shift in the ac receptor potential response. Phase lag or lead occurred for tones below or above BF, respectively. BM velocity I/O functions were not as compressively saturating as IHC ac I/O curves. BM phase shifts (in relation to BF) were similar to those of the IHCs. Two-tone suppression was observed in both IHC and BM response measures. Suppressor tones on the low-frequency side of BF produced complex suppression results, which were inconsistent with a simple attenuation model for suppression. The growth of suppression was faster than the attenuation from equivalent level reductions of the probe tone, and phase shifts were phase lead. Depending upon experimental conditions, phase change with suppression may be in the opposite direction from phase change observed from pure attenuation of the probe tone. High-frequency suppressors (relative to BF) are consistent with an attenuation model of suppression for the IHCs of the current study. High side suppression of basilar membrane velocity, however, differed from the IHCs in a systematic way. The phase change caused by suppression of BM velocity was always smaller than that of an equivalent reduction in the probe tone level.
Amplitude modulation detection of narrow-band noise: Effects of absolute bandwidth and frequency region
Authors: Eddins David A.
Published: October 2005

Thresholds and psychometric functions for the detection of amplitude modulation were measured as a function of modulation frequency under several stimulus conditions. The first experiment investigated the relative importance of stimulus bandwidth and frequency region for amplitude-modulation detection. The stimulus bandwidth was either 200, 400, 800, or 1600 Hz. The frequency region was varied by adjusting the high-frequency cutoff of the noise to be either 600, 2200, or 4400 Hz. Temporal modulation transfer functions demonstrated the typical low-pass filter characteristic, with sensitivity to modulation decreasing with increasing modulation frequency. Time constants associated with the transfer functions were derived from low-pass filter functions fitted to the data. The time constants varied inversely with noise bandwidth (≤1600 Hz) and were independent of frequency region. These results are consistent with estimates of temporal acuity based on previous studies of gap detection for narrow-band noise as well as estimates of temporal acuity using deterministic stimuli. In a second experiment, psychometric functions, plotted with modulation depth in dB, demonstrated somewhat steeper slopes as modulation frequency increased. The estimated slope values did not vary greatly with frequency region or noise bandwidth.
Contribution of membrane wave reradiation to scattering from finite cylindrical steel shells in water
Authors: Rumerman M. L.
Published: October 2005

Measured levels of acoustic backscattering from an insonified thin cylindrical steel shell in water (measured in a frequency range corresponding to 5<ka<15) show loci in frequency-angle space along which are discrete areas that represent high levels of backscattering. Using an approximate theoretical model in which shell membrane waves are explicitly represented, it is shown that the high levels of backscattering are due to supersonic membrane waves that are established on the shell. The loci of peaks are associated with combinations of frequency and angle at which a plane wave incident upon a similar infinite shell generates a resonant membrane mode of the infinite shell. The locations of the discrete high level spots along the loci correspond to those axial wave numbers that, together with the corresponding circumferential wave number, define resonant modes of the finite shell. The level of backscattered pressure is high at these locations because, at these frequency-angle combinations, the particular resonant mode is driven by a trace-matched incident wave. The analysis is given for a simply supported shell, but the nature of the approximations make the approach applicable to other homogeneous end conditions.
Membership functions for fuzzy set evaluation of concert hall acoustics
Authors: Wu Shuo-xian , Kittinger E.
Published: October 2005

By summing up the opinions of many experts about concert hall acoustics, this paper suggests a more complete factor set and more detailed membership functions for the fuzzy set evaluation of concert hall acoustics. The mean forte sound-pressure level LpF representative of subjective loudness, is introduced in the factor set in addition to those already considered previously.
A stationary phase approach to the calculation of the correlation of the acoustic field scattered from a two-dimensional random sea surface
Authors: Goalwin Patrick W.
Published: October 2005

The correlation function for the sound field scattered by a random rough surface is computed using a perturbation theory approach and the Born approximation. A point sound source is used. The rough surface is described using a simple ocean wind wave spectrum, including directional effects. A stationary phase treatment is used to evaluate the integrals. This approach significantly reduces the computation time needed for the problem, and makes it possible to compute the correlation function for a two-dimensional rough surface with sufficient accuracy to study the phase. The amplitude of the correlation function for rough surface scattering is shown to increase as either wind speed or acoustic frequency increases. The amplitude of the correlation function is shown to depend on wind direction. The phase of the correlation function for rough surface scattering is shown to differ from the phase of the correlation function for a flat surface.
Nonlinear acoustic phenomena in TeO2
Authors: Troedson Shaun C. , Lindsay Anthony C. , Fuss Ian G.
Published: October 2005

The amplitudes of 1-GHz acoustic waves have been measured in TeO2 at 4 K using acousto-optic diffraction. The amplitude variation is best described by harmonic generation via fourth-order nonlinear phenomena with very low attenuation.
Scattering from boundary protuberances and reverberation imaging
Authors: Yang T. C.
Published: October 2005

Because of multipath propagation, conventional processing of backscattered (reverberation) data cannot separate long-range returns arriving simultaneously from the surface and the bottom, except where there is a dominant feature such as a seamount. Matched-field/mode processing could in principle be used to localize the surface and bottom scatterers separately except that these methods assume pointlike sources whereas in reality the scatterers are extended objects. To develop an appropriate processing method for scattered returns from extended objects, one needs a closed form expression for the scattered field (the replica field). Such an expression in terms of normal mode amplitudes was recently derived by Ingenito [J. Acoust. Soc. Am. 82, 2051–2059 (1987)] for a rigid sphere in an iso-velocity fluid medium. This expression is generalized to more general cases and also to treat scattering from boundary protuberances in this paper. Based on the normal mode expressions of the scattered field, matched-mode processing is extended to localize the boundary scatterers. The effectiveness of this method is evaluated using simulated data. It is indicated how this method could be used to acoustically image/map the surface and bottom features in a basin-wide ocean.
Ultrasonic properties of aqueous solutions of high molecular weight polyethylene oxide
Authors: Bass Henry E. , Tan Jinxing
Published: October 2005

The concentration dependence of shear viscosity, density, and ultrasonic absorption and velocity in aqueous polyethylene oxide in the hydrodynamic screening and coil contact regions is investigated. Six polymer samples were studied covering the molecular weight range of 1.2×105–2.8×107. The ultrasonic measurements cover a frequency range of 130–970 kHz. The experiments indicate that ultrasonic absorption and velocity depend on molecular weight of the polymer. The solutions of high molecular weight polymer exhibit transition phenomenon at the critical overlapping concentration, where absorption reaches a maximum, and the viscosity, density, and velocity reach a plateau. These properties are attributed to polymer–polymer interaction. Experimental results suggest that the screening interaction of macromolecules results in strong viscoelastic coupling between macromolecules and a sharp decrease in compressibility, and that direct contact interaction leads to a temporary network structure having a more rigid but looser conformation. Comparison of the observed results with theoretical calculations indicate that dynamic shear viscosity contributes only a small fraction of the absorption actually observed and the polymer–water interaction is an important source of ultrasonic relaxation processes although this cannot describe the molecular weight dependence. The total absorption can be considered as the sum of contributions from polymer–water and polymer–polymer interactions.
Damping of toroidal shells by a constrained viscoelastic layer
Authors: El-Raheb Michael , Wagner Paul
Published: October 2005

The analysis of shells damped by a constrained viscoelastic layer is extended to toroidal segments. The absorber consists of thin curved strips bonded to the torus with a thin viscoelastic layer. When applied to the torus, the absorber is most effective on response modes with two or more circumferential waves. In this way it resembles the damped cylinder. However, for a given weight of absorber, the torus is damped more than the cylinder. The reason is that the torus induces and couples those circumstantial harmonics that are damped most effectively by this absorber.
Active control of sound radiation from a fluid-loaded rectangular uniform plate
Authors: Gu Yi , Fuller Chris R.
Published: October 2005

Active control of sound radiation from a simply supported rectangular fluid-loaded plate is analytically studied. The plate is assumed to be excited by a point force at subsonic frequencies. The solution to the plate motion is based on the admissible functions for an in vacuo homogeneous plate, which is also the basis for Fourier decomposition of the fluid loading [B. E. Sandman, J. Acoust. Soc. Am. 61, 1502–1510 (1977)]. Feed-forward control is carried out by using point forces applied to the plate. The amplitudes of the control forces are determined by the optimal solution of a quadratic cost function that integrates the far-field radiated acoustic pressure over a hemisphere in the radiation half-space. The results show that for subsonic disturbances, a high global reduction in radiated pressure is possible. For on-resonant excitations, a reasonable sound reduction can be achieved with up to two properly located active control forces, and for off-resonant excitations, up to four control forces may be necessary. The results thus indicate that the active structural acoustic control approach will provide large attenuations in radiated sound when edge mode coupling induced by heavy fluid loading is present. The number and location of the control forces are determined so as to suppress the efficiently radiating modes. The far-field directivity pattern, the plate velocity autospectrum in the two-dimensional wave number domain, and the near-field pressure distribution are studied.
Perceptual separation of simultaneous vowels: Within and across-formant grouping by F
Authors: Culling John F. , Darwin C. J.
Published: October 2005

Six experiments explored why the identification of the two members of a pair of diotic, simultaneous, steady-state vowels improves with a difference in fundamental frequency (ΔF0). Experiment 1 confirmed earlier reports that a ΔF0 improves identification of 200-ms but not 50-ms duration ‘‘double vowels’’; identification improves up to 1 semitone ΔF0 and then asymptotes. In such stimuli, all the formants of a given vowel are excited by the same F0, providing listeners with a potential grouping cue. Subsequent experiments asked whether the improvement in identification with ΔF0 for the longer vowels was due to listeners using the consistent F0 within each vowel of a pair to group formants appropriately. Individual vowels were synthesized with a different F0 in the region of the first formant peak from in the region of the higher formant peaks. Such vowels were then paired so that the first formant of one vowel bore the same F0 as the higher formants of the other vowel. These across-formant inconsistencies in F0 did not substantially reduce the previous improvement in identification rates with increasing ΔF0’s of up to 4 semitones (experiment 2). The subjects’ improvement with increasing ΔF0 in the inconsistent condition was not produced by identifying vowels on the basis of information in the first-formant or higher-formant regions alone, since stimuli which contained either of these regions in isolation were difficult for subjects to identify.

In addition, the inconsistent condition did produce poorer identification for larger ΔF0’s (experiment 3). The improvement in identification with ΔF0 found for the inconsistent stimuli persisted when the ΔF0 between vowel pairs was confined to the first formant region (experiment 4) but not when it was confined to the higher formants (experiment 6). The results replicate at different overall presentation levels (experiment 5). The experiments show that at small ΔF0’s only the first-formant region contributes to improvements in identification accuracy, whereas with larger ΔF0’s the higher formant region may also contribute. This difference may be related to other results that demonstrate the superiority of resolved rather than unresolved harmonics in coding pitch.
A finite-element equivalent bond graph modeling approach with application to the piezoelectric thickness vibrator
Authors: Moon Won-kyu , Busch-Vishniac Ilene J.
Published: October 2005

A bond graph modeling approach that is equivalent to a finite-element method is formulated. This formulation leads to a new definition of the generalized displacements for a continuous system. The newly defined coordinates are easily interpreted physically and easily used in analysis of the system performance. The new bond graph modeling approach is applied to the piezoelectric thickness vibrator. Compared to the Mason equivalent circuit model, the bond graph model offers the primary advantage of physical realizability. Compared to circuit models based on standard discrete electrical elements, the main advantage of the bond graph model is a greater physical accuracy because of the use of multiport energic elements. While results are presented here for the thickness vibrator, the modeling method presented is general in scope and can be applied to arbitrary physical systems.
The Whitaker database of dysarthric (cerebral palsy) speech
Authors: Deller J. R. , Liu M. S. , Ferrier L. J. , Robichaud P.
Published: October 2005

The Whitaker database is a collection of 19 275 isolated-word utterances spoken by six persons whose speech spans a broad spectrum of dysarthria due to cerebral palsy. The database additionally contains utterances by a normal speaker which can be used for reference. The vocabulary is divided into two sets—one of 46 words (the ‘‘TI-46’’ vocabulary consisting of the alphabet, digits, and 10 control words), the other of of 35 words (the ‘‘Grandfather’’ set consisting of phonetically diverse words). The database is available through the electronic mail network for use in studies of recognition, perception, articulation, and other aspects of speech disorders.
Periodicity extraction in the anuran auditory nerve. II: Phase and temporal fine structure
Authors: Simmons Andrea Megela , Reese Gita , Ferragamo Michael
Published: October 2005

Discharge patterns of single eighth nerve fibers in the bullfrog, Rana catesbeiana, were analyzed in response to signals consisting of multiple harmonics of a common, low-amplitude fundamental frequency. The signals were chosen to reflect the frequency and amplitude spectrum of the bullfrog’s species-specific advertisement call. The phase spectrum of the signals was manipulated to produce envelopes that varied in their shapes from impulselike (sharp) to noiselike (flattened). Peripheral responses to these signals were analyzed by computing the autocorrelation functions of the spike trains and their power spectra, as well as by constructing period histograms over the time intervals of the low-frequency harmonics. In response to a phase aligned signal with an impulsive envelope, most fibers, regardless of their characteristic frequencies or place of origin within the inner ear, synchronize to the fundamental frequency of the signal. The temporal patterns of fiber discharge to these stimuli are not typically captured by that stimulus harmonic closest to the fiber characteristic frequency, as would be expected from a spectral coding mechanism for periodicity extraction, but instead directly reflect the periodicity of the stimulus envelope.

Changing the phase relations between the individual harmonics constituting the signal produces changes in temporal discharge patterns of some fibers by shifting predominant synchronization away from the fundamental frequency to the low-frequency spectral peak in the complex stimuli. The proportion of fibers whose firing is captured by the fundamental frequency decreases as the waveform envelope becomes less impulselike. Fiber characteristic frequency is not highly correlated with the harmonic number to which synchronization is strongest. The higher-harmonic spectral fine structure of the signals is not reflected in fiber temporal response, regardless of the shape of the stimulus envelope, even for those harmonics within the range of phase locking to simple sinusoids. Increasing stimulus intensity also shifts the synchronized responses of some fibers away from the fundamental frequency to one of the low-frequency harmonics in the stimuli. These data suggest that the synchronized firing of bullfrog eighth nerve fibers operates to extract the waveform periodicity of complex, multiple-harmonic stimuli, and this periodicity extraction is influenced by the phase spectrum and temporal fine structure of the stimuli. The similarity in response patterns of amphibian papilla and basilar papilla fibers argues that the frog auditory system employs primarily a temporal mechanism for extraction of first harmonic periodicity.
Large-amplitude finite element flexural vibration of plates/stiffened plates
Authors: Rao S. R. , Sheikh A. H. , Mukhopadhyay M.
Published: October 2005

Large-amplitude free flexural vibration of stiffened and unstiffened plates has been studied by using the finite element method. An isoparametric quadratic plate-bending element has been used both for the plate and the stiffener. The dynamic version of von Karman’s field equations has been adopted and the formulation has been done in the total Lagrangian coordinate system. The in-plane deformation and inertia have been taken into account. The resulting nonlinear equations have been solved by the direct iteration technique using a linear mode shape as the starting vector. The stiffener has been elegantly modeled so that it can be placed anywhere within the plate element and it need not follow the nodal lines. This has increased the flexibility of the mesh generation considerably. The arbitrary orientation and eccentricity of the stiffener have been incorporated in the formulation. The shear deformation has been incorporated according to Mindlin’s hypothesis. Stiffened and unstiffened plates that have various boundary conditions have been analyzed and the results have been compared with those available in the literature.
Biophysics of the cochlea: Linear approximation
Authors: Mammano F. , Nobili R.
Published: October 2005

Several deficiencies affecting previous ‘‘box’’ models of the cochlea are overcome in this paper. Both mechanical and hydrodynamical aspects are treated at a level adequate to the complexity of realistic cochlear structures. The dynamics of the cochlea as a passive physical system, in the linear approximation, is described by an integral equation. It is further shown that this equation describes the properties of the working cochlea, provided a force term that accounts for hair cell motility is included. Numerical solutions for different degrees of outer hair cells activity, obtained by matrix methods in the frequency domain, are presented. Amplitudes and phases of the computer-simulated traveling waves are in fair agreement with basilar membrane responses to tones measured in various experimental conditions.
Noninvasive measurement of the cochlear traveling-wave ratio
Authors: Shera Christopher A. , Zweig George
Published: October 2005

The microstructure of threshold hearing curves and the frequency spectra of evoked otoacoustic emissions both often evince a roughly periodic series of maxima and minima. Current models for the generation of otoacoustic emissions explain the observed spectral regularity by supposing that since the cochlea maps frequency into position the spectral periodicity mirrors a spatial oscillation in the mechanics of the organ of Corti. In this view emissions are generated when forward-traveling waves reflect from periodic corrugations in the mechanics, suggesting that the amplitude of the cochlear traveling-wave ratio—defined to be the ratio of the backward- and forward-traveling cochlear waves at the stapes—should manifest pronounced maxima and minima with a corresponding periodicity. This paper describes measurements of stimulus-frequency emissions, establishes their analyticity properties, and uses them to explore the spatial distribution of mechanical inhomogeneities (emission ‘‘generators’’) in the human cochlea. The approximate form and frequency dependence of the cochlear traveling-wave ratio are determined noninvasively. The amplitude of the empirical traveling-wave ratio is a slowly varying, nonperiodic function of frequency, suggesting that the distribution of inhomogeneities is uncorrelated with the periodicity found in the threshold microstructure. The observed periodicities arise predominantly from the cyclic variation in relative phase between the forward- and backward-traveling waves at the stapes.
Application of the Gaussian beam approach to sound propagation in the atmosphere: Theory and experiments
Authors: Gabillet Yannick , Schroeder Hartmut , Daigle Gilles A. , L’Espérance André
Published: October 2005

The Gaussian beam approach solves the wave equation in the neighborhood of the conventional rays using the parabolic approximation. The solution associates with each ray a beam having a Gaussian amplitude profile normal to the ray. The approximate overall solution for a given source is then constructed by a superposition of Gaussian beams along nearby rays. The solution removes ray-tracing artifacts such as perfect shadows and infinite energy at caustics without the computational difficulties of numerical solutions to the wave equation. In this paper, the Gaussian beam approach is applied to atmospheric sound propagation in the presence of refraction above a ground surface. A brief overview of the method is presented. Calculations obtained from Gaussian beam tracing are compared to those obtained from the fast field program (FFP) and to experimental measurements. The experiments were made above a concave surface indoors that simulates propagation under downward refraction (inversion or downwind) in the cases of a hard and finite impedance surface. These experiments include measurements in the presence of a barrier. Measurements were also made in a wind tunnel in the presence of wind and temperature gradients. The results suggest that beam tracing can be applied to complex atmospheric sound propagation problems with advantages over conventional ray tracing and full-wave solutions.
Distortion-product otoacoustic emissions in the bobtail lizard. II: Suppression tuning characteristics
Authors: Köppl Christine , Manley Geoffrey A.
Published: October 2005

The otoacoustic distortion products (DP) 2 f1−f2 and 2 f2−f1 in the ear canal of the bobtail lizard are suppressed by tones in a frequency-selective way. Iso-suppression tuning curves for DP generated by low-level primary tones resemble in detail (e.g., in their threshold and frequency selectivity) excitatory iso-rate tuning curves for single auditory-nerve fibers of this species. The best suppressive frequencies for the DP 2 f1−f2 at low primary-tone levels were near the first primary tone (f1), those for 2 f2−f1 lay near or above f2 . When using high primary-tone levels to generate the DP, the best frequency for suppression of 2 f1−f2 shifted to half an octave below f1 . Facilitation of both DP was also seen, most often over a restricted frequency range above f2 and at levels below those eliciting suppression. The two DP showed a number of differences in their behavior in the presence of a third tone that suggest that they do not originate from the same location or source. These results indicate that in this species, suppression tuning curves of DP generated by low-level primary tones resemble those from mammals in many respects and yield accurate information concerning the integrity of the hearing organ. It is remarkable that, in spite of substantial differences in hearing-organ structure and function, DP patterns in this lizard are so similar to those of mammals. This suggests that the mechanisms generating the DP patterns are based on basic hair-cell properties and not on special structural constellations of hair cells or their accessory structures.
Evaluating a speech-reception threshold model for hearing-impaired listeners
Authors: Lee Lidia W. , Humes Larry E.
Published: October 2005

Plomp’s speech reception threshold (SRT) model [R. Plomp, J. Acoust. Soc. Am. 63, 533–549 (1978)] incorporates a distortion and an attenuation factor that are both expressed in dB and, for hearing-impaired listeners, are greater than 0 dB. The distortion factor is hypothesized to affect the SRT in quiet and in noise and suggests that a hearing-impaired listener will always demonstrate a higher SRT than a normal-hearing listener. The present study examines whether this distortion factor can be explained for many listeners simply by inaudibility of a portion of the speech spectrum. SRTs were obtained from normal-hearing and mild-to-moderately hearing-impaired listeners in quiet and at various noise levels. The results indicate that, at high noise levels, when the noise, rather than the quiet threshold, becomes the dominating factor, the SRT functions of both the normal and the mild-to-moderately hearing-impaired group converge and the distortion factor diminishes to zero. Predictions were also made using an articulation index and similar convergence of the two functions was observed.
The combination of interaural information across frequencies: The effects of number and spacing of components, onset asynchrony, and harmonicitya)
Authors: Stellmack Mark A. , Dye Raymond H.
Published: October 2005

Threshold interaural delays were measured for a single interaurally delayed low-frequency target component presented against a background of two, four, six, or eight diotic ‘‘distractor’’ components. In the first experiment, a 753-Hz target and the flanking distractor components were gated on and off simultaneously. In subsequent experiments, the distractors were gated on 25–200 ms prior to the target. In addition, the target and distractor components were given various harmonic configurations. In general, threshold interaural delays were higher in all conditions in which distractors were present relative to thresholds obtained for the target component in isolation. Subjects reported that the pitch of the target component was more salient when an onset asynchrony between the target and distractors was present, but the components were perceived as occupying a single intracranial position in spite of the various interaural delays across the frequency domain. These results suggest that binaural processing of stimuli consisting of a small number of low-frequency temporally overlapping components occurs in a spectrally synthetic manner in which interaural information is combined across the spectrum, even in situations in which the segregation of pitch information occurs.
A laser-based investigation of higher-order modes in transient Lamb waves
Authors: Schumacher Neal A. , Burger Christian P. , Gien Peter H.
Published: October 2005

This Letter describes the integration of laser and fiber optic methods for generating and detecting broadband, transient Lamb waves in a steel plate. The generated Lamb waves are shown to be a superposition of different Lamb modes including the zeroth-order symmetric together with the zeroth- and first-order antisymmetric modes. Signal processing techniques are used to extract the phase velocities for each of these modes over a continuous, broadband frequency spectrum from the transient time histories of the waves recorded at two locations on a steel plate. The results are found to be in excellent agreement with theoretical phase velocities for each of the three modes evaluated.