bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive phase transform processors for time delay estimation
Authors: Youn Dae Hee , Chiou Shen-Neng , Mathews V. John
Published: October 2005

This paper introduces two recursive realizations of the phase transform (PHAT) processor for time-delay estimation (TDE), using a simple one-pole low-pass filter and the least-mean-square (LMS) adaptive filter, respectively. It is shown that these adaptive methods are capable of tracking time-varying delay functions which correspond to moving sources or receivers, and are very effective in reducing the effect of interfering tonals which must be generated by the target as jamming signals to mask its movement. The performances of these methods are compared with those of other existing adaptive TDE algorithms via computer simulations.
Harmonic distortion of a finite amplitude Gaussian beam in a fluid
Authors: Du Gonghuan , Breazeale M. A.
Published: October 2005

The diffraction of a Gaussian ultrasonic beam in absorbing fluids produces a Gaussian field distribution in the fundamental component. An analytical expression for the second harmonic is derived and it is also a Gaussian function in the quasilinear approximation. Our expressions for the second harmonic are free of the nearfield oscillations characteristic of the radiation from a piston transducer. Calculated results are compared with measurements taken with a Gaussian transducer. Reasonable agreement between theory and experiment is found for both the fundamental and the second harmonic of an initially sinusoidal Gaussian ultrasonic beam in water at 2 MHz. An Appendix is given in which expressions are derived for the first four harmonics of a Gaussian beam. All harmonics are found to obey a Gaussian function. Moreover, the Gaussian coefficient of the nth harmonic is exactly n times that of the fundamental component. This means that the width at half maximum changes in proportion to 1/(n)1/2. The phase shift across the beam behaves in a similar manner.
Frequency-dependent angular scattering of ultrasound by tissue-mimicking materials and excised tissue
Authors: Davros W. J. , Zagzebski J. A. , Madsen E. L.
Published: October 2005

An apparatus and method of experimentation for measuring frequency-dependent angle scattering from in vitro tissue samples and tissue-like scattering media have been developed. Distinguishing features of this method are that data collection is rapid, data reduction is simple, and results, given in the form of the differential scattering cross section per unit volume, are accurate and absolute. Reported are the results of tests to determine the overall accuracy of the method. Also, results of the differential scattering cross section per unit volume from female human breast tissue are presented.
Effects of forward and simultaneous masking on intensity discrimination
Authors: Widin Gregory P. , Viemeister Neal F. , Bacon Sid P.
Published: October 2005

Experiments on intensity discrimination determine the size of the smallest detectable increment added to a fixed pedestal. This paper examines the effects of a masker which either precedes the pedestal (forward masking) or is simultaneous with the pedestal. The increment and pedestal were 1-kHz tones masked in forward masking by pure tones and in simultaneous masking by a broadband noise. Simultaneous masking by the broadband noise eliminates the ‘‘near miss’’ to Weber’s law, and thus degrades intensity discrimination at high pedestal levels. Forward masking by the pure tone also degrades intensity discrimination, which may, in part, be explained by the elimination of the near miss. However, the effect on intensity discrimination in some cases is greater in forward than in simultaneous masking, suggesting that some additional process (e.g., adaptation) is involved.
Masking-level differences for trains of clicks
Authors: Dye Raymond H. , Yost William A.
Published: October 2005

Masking-level differences (MLDs) were measured for trains of 2000-Hz bandpass clicks as a function of the interclick interval (ICI) and the number of clicks in the train. The magnitude of the MLD grew as the number of clicks in the train was increased from 1 to 32. While the MLDs tended to be larger at longer ICIs, the effect was mediated by changes in detectability in the homophasic conditions. For click trains consisting of 4–32 clicks, the improvement in detectability in the antiphasic conditions with increases in the number of clicks appears to be the result of integration of acoustic power, as is the case for the homophasic conditions. The absence of MLDs for short trains of high-frequency transients remains quite puzzling, since large MLDs are found with single, low-frequency transients.
A biophysical model of cochlear processing: Intensity dependence of pure tone responses
Authors: Shamma Shihab A. , Chadwick Richard S. , Wilbur W. John , Morrish Kathleen A. , Rinzel John
Published: October 2005

A mathematical model of cochlear processing is developed to account for the nonlinear dependence of frequency selectivity on intensity in inner hair cell and auditory nerve fiber responses. The model describes the transformation from acoustic stimulus to intracellular hair cell potentials in the cochlea. It incorporates a linear formulation of basilar membrane mechanics and subtectorial fluid–cilia displacement coupling, and a simplified description of the inner hair cell nonlinear transduction process. The analysis at this stage is restricted to low-frequency single tones. The computed responses to single tone inputs exhibit the experimentally observed nonlinear effects of increasing intensity such as the increase in the bandwidth of frequency selectivity and the downward shift of the best frequency. In the model, the first effect is primarily due to the saturating effect of the hair cell nonlinearity. The second results from the combined effects of both the nonlinearity and of the inner hair cell low-pass transfer function. In contrast to these shifts along the frequency axis, the model does not exhibit intensity dependent shifts of the spatial location along the cochlea of the peak response for a given single tone. The observed shifts therefore do not contradict an intensity invariant tonotopic code.
Mathematical model for a free-flooded piezoelectric cylinder transducer
Authors: Rogers Peter H.
Published: October 2005

A mathematical model for the transmitting response and electrical impedance of a free-flooded, thickness-polarized piezoelectric cylinder transducer has been developed. The elasticity of the cylinder is described using membrane equations which have been modified to account for piezoelectric effects. An additional consequence of the piezoelectricity of the shell is a significant alteration in the boundary conditions for the ends of the cylinder. A particular solution to the membrane equations which satisfies these modified boundary conditions is obtained. The complete solution for the vibration of the cylinder is then found in the form of a sum of the particular solution and the normal modes appropriate to a nonpiezoelectric cylinder with free ends. The acoustic field loads the solution, couples the normal modes, further couples the particular solution and the normal modes, and changes the boundary conditions. The acoustic influence coefficients needed to incorporate these effects are calculated using the ship computer program. The water-loaded normal surface velocities are determined and the surface pressures and farfield radiation characteristics are calculated using ship. The model fully accounts for such effects as the cavity resonance, the velocity of the ends of the cylinder, distribution of velocity along the length of the cylinder, and the difference between the velocity on the inner and outer surfaces of the cylinder. Comparisons between theoretical and experimental results are presented.
Suppression and (2 f1−f2)-difference tones in a nonlinear cochlear preprocessing model with active feedback
Authors: Zwicker Eberhard
Published: October 2005

The two nonlinear effects of two-tone suppression and of (2 f1−f2)-difference tone creation are measured in a hardware model which consists of 90 sections containing nonlinear feedback loops. The basic data are the level and phase distributions along the 90 sections produced by single tones in the linear passive system which are almost identical to those produced in the nonlinear active system at high levels. Enhancement is created at medium and low input levels resulting in more strongly peaked level-place patterns. Two-tone suppression is, therefore, described as a ‘‘de-enhancement’’ which is produced by the gain reduction in the saturating nonlinearity of the feedback loop in consequence of increasing input levels (that of the suppressor as well!). Characteristics of suppression are given in normalized form. The creation of (2 f1−f2)-difference tones is based on the same nonlinear effects. In each section, difference-tone wavelets are created which travel—changing level and phase thereby—to their characteristic place, where they add up to a vector sum corresponding to the audible difference tone. In case of cancellation, the vector sum has to be compensated by an additional tone of the same frequency and amount but opposite phase. Based on this strategy of (2 f1−f2)-difference tone development, the relevant relations are measured on the model and averaged either in normalized graphs or in equations in order to offer the possibility to simulate the hardware model on the computer. Psychoacoustically measured cancellation data are compared with data measured using the model. The two data sets agree not only in general but also in many details indicating that the model describes cochlear nonlinear preprocessing to a useful approximation.
Normal-mode sound propagation in an ocean with sinusoidal surface waves
Authors: Anand G. V. , George Mathews K.
Published: October 2005

The normal-mode solution to the problem of acoustic wave propagation in an isovelocity ocean with a wavy surface is considered. The surface wave amplitude is assumed to be small compared to the acoustic wavelength, and the method of multiple scales is employed to study the interaction between normal-mode acoustic waves and the surface waves. A nonresonant interaction causes small fluctuations of the amplitude and phase of the acoustic wave at a rate dependent on the frequency of the surface wave. Backscatter occurs if the wavenumber of the surface wave is larger than that of the acoustic wave. The interaction becomes resonant if appropriate phase-matching conditions are satisfied. In this case, two acoustic normal modes get coupled, resulting in a large-scale periodic exchange of energy from one mode to another.
Shallow-water propagation effects over a complex, high-velocity bottom
Authors: Beebe J. H. , Holland C. W.
Published: October 2005

Shallow-water propagation experiments conducted on the Scotian Shelf in 1978 produced very high transmission losses at low frequency for a range of only 4 km. The bottom along the propagation track consisted of a thin layer of coarse sand over granite bedrock which protruded through the sediment in certain regions. The sources of the high losses at low frequency are investigated by varying the acoustic properties of the geoacoustic model. It is shown that neither scattering nor shear effects in the granite basement accounts for this loss, but that a third mechanism, excitation of shear waves in the sediment, can cause such high losses.
Causality, caustics, and the structure of transient wave fields
Authors: Brown Michael G. , Tappert Frederick D.
Published: October 2005

Transient acoustic wave fields in the vicinity of caustics in both two and three space dimensions are considered. In the vicinity of some possible caustics, the time history of the wave field due to an impulsive source includes a precursor. This noncausal behavior is reconciled with the physical principle of causality by requiring that such caustics be a part of certain higher dimensional caustics. With this constraint all noncausal arrivals are preceded by a causal arrival and the total time history is causal. This constraint is used to derive some simple general properties of transient wave fields in the short wave limit, e.g., the number of arrivals must be an odd number.
Theory of acoustic propagation around a conical seamount
Authors: Buckingham Michael J.
Published: October 2005

A theoretical model of acoustic propagation in the ocean around a conical seamount is presented. The sea surface and the surface of the seamount are assumed to be perfect reflectors, with the apex of the seamount just touching the surface of the ocean. This geometry is such that the boundary surfaces of the channel can be represented by the surfaces of a separable (spherical polar, origin at the apex) coordinate system. The solution of the Helmholtz equation for a point source in the channel is shown to consist of a sum of normal modes in which the variable is angular depth, and in which the mode amplitude functions contain the entire range/azimuth dependence of the field. These mode amplitude functions show that, in each mode, there is a sharply defined shadow zone lying behind the seamount, and surrounding the shadow is an ensonified region where the field shows very rapid spatial oscillations. This oscillatory behavior indicates that strong interference occurs within a single mode. An important feature of the model is that it specifies completely the three-dimensional field around the seamount, giving both amplitude and phase. The theory is therefore relevant to studies of the performance of acoustic arrays in this type of environment.
Ultrasonic reflection mode imaging of the nonlinear parameter B/A: I. A theoretical basis
Authors: Cain Charles A.
Published: October 2005

The theoretical basis of a new method for obtaining both reflection and transmission mode images of the nonlinear parameter B/A is given. An expression for the instantaneous (not cumulative) phase shift in a sinusoidal probe waveform due to nonlinear interaction with an arbitrary pump waveform propagating in the opposite direction is derived. This instantaneous phase shift is proportional to the convolution of the pump waveform with the spatial distribution of the nonlinear parameter B/A along the propagation path of the pump and interacting probe. The instantaneous phase of the probe can be obtained in real time giving a measure of the variation of B/A along an image line.
Interaural magnification
Authors: Durlach N. I. , Pang X. D.
Published: October 2005

In principle, magnification of interaural differences, as could be achieved by the use of an enlarged head, will improve auditory spatial perception. This note presents some preliminary thoughts and observations on a signal-processing scheme for interaural magnification.
The relation between the human frequency-following response and the low pitch of complex tones
Authors: Chambers Ron D. , Feth Lawrence L. , Burns Edward M.
Published: October 2005

The relation between the auditory brain stem potential called the frequency-following response (FFR) and the low pitch of complex tones was investigated. Eleven complex stimuli were synthesized such that frequency content varied but waveform envelope periodicity was constant. This was accomplished by repeatedly shifting the components of a harmonic complex tone upward in frequency by Δf of 20 Hz, producing a series of six-component inharmonic complex tones with constant intercomponent spacing of 200 Hz. Pitch-shift functions were derived from pitch matches for these stimuli to a comparison pure tone for each of four normal hearing adults with extensive musical training. The FFRs were recorded for the complex stimuli that were judged most divergent in pitch by each subject and for pure-tone signals that were judged equal in pitch to these complex stimuli. Spectral analyses suggested that the spectral content of the FFRs elicited by the complex stimuli did not vary consistently with component frequency or the first effect of pitch shift. Furthermore, complex and pure-tone signals judged equal in pitch did not elicit FFRs of similar spectral content.
Central adaptation of complex pitch
Authors: Hall Joseph W.
Published: October 2005

The adaptation of a complex and pure-tone pitch was examined, using an adaptation stimulus composed of components of low harmonic number and test stimuli composed of components of high harmonic number, in order to examine separately the effects of pure-tone and complex pitch adaptation. The test stimulus either had the same fundamental as that of the adaptation stimulus, or it had a fundamental lower than that of the adaptation stimulus. Adaptation was measured using a pitch matching method. The adaptation and test stimuli were presented to one ear, and a pure-tone matching stimulus was presented to the opposite ear. Adaptation generally shifted the complex pitch of the test stimulus to a lower pitch. The component pitches, on the other hand, did not change, or shifted upwards slightly. The downward complex pitch changes were consistent with the adaptation of a central complex pitch channel.
Temporal discrimination for single components of nonspeech auditory patterns
Authors: Espinoza-Varas Blas , Watson Charles S.
Published: October 2005

This paper extends previous research on listeners’ abilities to discriminate the details of brief tonal components occurring within sequential auditory patterns (Watson et al., 1975, 1976). Specifically, the ability to discriminate increments in the duration Δt of tonal components was examined. Stimuli consisted of sequences of ten sinusoidal tones: a 40-ms test tone to which Δt was added, plus nine context tones with individual durations fixed at 40 ms or varying between 20 and 140 ms. The level of stimulus uncertainty was varied from high (any of 20 test tones occurring in any of nine factorial contexts), through medium (any of 20 test tones occurring in ten contexts), to minimal levels (one test tone occurring in a single context). The ability to discriminate Δt depended strongly on the level of stimulus uncertainty, and on the listener’s experience with the tonal context. Asymptotic thresholds under minimal uncertainty approached 4–6 ms, or 15% of the duration of the test tones; under high uncertainty, they approached 40 ms, or 10% of the total duration of the tonal sequence. Initial thresholds exhibited by inexperienced listeners are two-to-four times greater than the asymptotic thresholds achieved after considerable training (20 000–30 000 trials). Isochronous sequences, with context tones of uniform, 40-ms duration, yield lower thresholds than those with components of varying duration. The frequency and temporal position of the test tones had only minor effects on temporal discrimination. It is proposed that a major determinant of the ability to discriminate the duration of components of sequential patterns is the listener’s knowledge about ‘‘what to listen for and where.’’ Reduced stimulus uncertainty and extensive practice increase the precision of this knowledge, and result in high-resolution discrimination performance. Increased uncertainty, limited practice, or both, would allow only discrimination of gross changes in the temporal or spectral structure of the sequential patterns.
Localization of sound in rooms, III: Onset and duration effects
Authors: Rakerd Brad , Hartmann W. M.
Published: October 2005

The steady-state sound field of a sine tone does not provide useful localization information in a room. Nevertheless, listeners can localize a sine tone in a room if it has an onset transient which allows the precedence effect to operate. In the present study, we made a quantitative assessment of onsets and the precedence effect by systematically varying onset duration from 0 s (impulsive), where the precedence effect is maximal, to 5 s, where there is no precedence effect at all. We also assessed listeners’ sensitivity to the steady-state sound field under impulsive conditions by varying the total duration of tone pulses. Our experiments were conducted in a room with a single acoustical reflection having various directions and delays, and in an anechoic room. The results for tones of various frequencies (500 and 2000 Hz) and sound-pressure levels (65 and 40 dBA) indicate the following: (1) Localization in rooms is facilitated by onsets even if the onsets are as long as 100 ms. (2) The facilitation depends upon the peak intensity of the tone, as well as the onset duration, suggesting that onset rate is critical for the precedence effect; our results are most consistent with rate expressed as an increase in sound pressure per unit time. (3) The facilitation also depends upon the reflection delay time for a room; gradual onsets take on much more importance for the precedence effect in rooms with long delays. (4) As onsets begin to lose their effectiveness listeners become increasingly ‘‘misdirected’’ by invalid cues in the steady-state sound field. The pattern of misdirection suggests a perceptual averaging of cues over an interval more than an order of magnitude longer than previous estimates of the summation window for the precedence effect. (5) The pattern of misdirection varies with the frequency of a tone, due to frequency-dependent interference effects in a room, but it is independent of signal level. (6) Localization of an impulsive sine tone in rooms is very insensitive to the pulse duration; this suggests that binaural inhibition models of the precedence effect must be supplemented by an evaluative component that we term the ‘‘plausibility hypothesis.’’
A fibrous dynamic continuum model of the tympanic membrane
Authors: Rabbitt Richard D. , Holmes Mark H.
Published: October 2005

The geometry and anisotropic ultrastructure of the tympanic membrane are used in combination with curvilinear shell equations to formulate a general continuum model describing its dynamic behavior. Primary terms appearing in the model are associated with shell membrane restoring forces, bending-type structural damping, and transverse inertia. Since the model is based extensively on the physical characteristics of the membrane, it is relatively easy to account for differences between species as well as pathological conditions. The fibrous structure and cone-shaped geometry, readily apparent in mammalian eardrums, introduce several small parameters into the model that are exploited in order to construct a closed-form asymptotic solution. The solution includes the coupling to the three-dimensional motion of the ossicular chain and it includes the frequency-dependent pressure distribution in the auditory canal. When applied to the cat eardrum, this asymptotic solution is shown to reproduce a large manifold of experimentally observed frequency and excitation-dependent vibrational shapes. In addition to the shapes, transient amplitude and phase data for the cat are reproduced.
Monte Carlo simulation of sound propagation through leafy foliage using experimentally obtained leaf resonance parameters
Authors: Tang S. H. , Ong P. P. , Woon H. S.
Published: October 2005

A computer-generated simulation of sound propagation through six different types of leafy foliage has been carried out. To reduce the number of adjustable input variables, the simulation makes use of experimentally obtained leaf resonance parameters. In general, the resonance exhibits two groups of normal modes of vibrations in the audio frequency range. These modes have been attributed to the longitudinal and transverse vibrations of the leaf. Typical results of the simulation obtained are comparable to those determined experimentally in an anechoic chamber by Martens [J. Acoust. Soc. Am. 67, 66–72 (1980)].
On higher-order elastodynamic rod theories
Authors: Vasudeva R. Y. , Bhaskara R. K. , Govinda Rao P. , Avadhani B. V. S.
Published: October 2005

A hierarchy of approximate elastodynamic theories for the (axisymmetric) vibrations of rods is derived from the three-dimensional equations of elasticity. The derivation is based upon the method of asymptotic expansions in a characteristic parameter as adopted by Bache and Hegemier [‘‘On higher order elastodynamic plate theories,’’ J. Appl. Mech. 41, 423–428 (1974)], in obtaining a similar hierarchy of approximate elastodynamic plate theories. Approximate theories of any desired order of accuracy are contained in a single compact set of partial differential equations, with the order of approximation determined by the truncation of the differential operators appearing in the equation. An example introducing compensation coefficients has been worked out for the first-order theory in the case of harmonic wave propagation and the results are compared with an approximate theory of Mindlin and McNiven [‘‘Axially symmetric waves in elastic rods,’’ J. Appl. Mech. 27, 145–151 (1960)], as well as with the exact theory.
Acoustic diffraction by a variable thickness fluid layer
Authors: Reese J. Mark , Thompson William
Published: October 2005

The effect of a variable thickness, cylindrical, fluid layer on the directional response patterns of a particular acoustic source distribution is investigated. The source consists of an array of parallel line sources on a rigid cylindrical baffle surrounded by a constant thickness cylindrical fluid layer. Located off center of these two cylinders is a third cylinder of a second fluid, which has a variable thickness because it is nonconcentric with the other two. The outer cylinder is surrounded by an infinite medium of the same fluid as the inner cylindrical layer. An analytical solution for the acoustic field is obtained by writing appropriate expressions for the pressure in each region, and applying the boundary conditions between the regions to solve for the unknown modal coefficients in these expressions. The translational addition theorem for cylindrical wavefunctions is used to simplify the matching of boundary conditions on the nonconcentric cylinders. The expression for the farfield pressure is used to produce numerical results for variations of some of the many parameters of the problem.
Quantitative grain size evaluation using ultrasonic backscattered echoes
Authors: Saniie Jafar , Bilgutay Nihat M.
Published: October 2005

Grain size characterization using ultrasonic backscattered signals is an important problem in nondestructive testing of materials. In this paper, a heuristic model which relates the statistical characteristics of the measured signal to the mean ultrasonic wavelet and attenuation coefficient in different regions of the sample is investigated. The losses in the backscattered signal are examined using temporal averaging, correlation, and probability distribution functions of the segmented data. Furthermore, homomorphic processing is used in a novel application to estimate the mean ultrasonic wavelet (as it propagates through the sample) and the frequency-dependent attenuation. In the work presented, heat-treated stainless steel samples with various grain sizes are examined. The processed experimental results support the feasibility of the grain size evaluation techniques presented here using the backscattered grain signal.
Note on the use of correlations in speech timing
Authors: Benoit Christian
Published: October 2005

A large number of investigators use Pearson’s product–moment correlation in analyzing the temporal organization of speech. Some of their papers present results obtained by correlation between overlapping intervals. The purpose of this letter is to show that a high correlation could be a ‘‘statistical artifact’’ in such a method. Second, it mathematically points out incorrect reasoning by Tuller and Kelso in their reply to such an argument [J. Acoust. Soc. Am. 76, 1030–1036 (1984)].
Vibration and sound radiation of a piano soundboard
Authors: Suzuki Hideo
Published: October 2005

Vibration and radiation characteristics of a piano soundboard for a 6-ft grand piano are investigated by use of modal analysis and surface-intensity methods. The mode shapes and frequencies of six resonances below 200 Hz are shown, and their relations to intensity patterns are discussed. The intensity pattern changes in a very complex manner as the frequency varies. The radiation efficiency below 80 Hz is very low. Sound is radiated fairly efficiently in the frequency range of 100 Hz–1 kHz, and very efficiently above 1.4 kHz. The results indicate that it is very important to make the input power to the soundboard as constant as possible with respect to the driving point as well as the driving frequency, in order to achieve a smooth change of sound power output from note to note.
Extension of a binaural cross-correlation model by contralateral inhibition. I. Simulation of lateralization for stationary signals
Authors: Lindemann W.
Published: October 2005

Running interaural cross correlation is a basic assumption to model the performance of the binaural auditory system. Although this concept is particularly suited to simulate psychoacoustic localization phenomena, there exist some localization effects which cannot be explained by pure cross correlation. In this paper a model of interaural cross correlation is extended by a ‘‘contralateral-inhibition mechanism’’ and by ‘‘monaural detectors’’ in order to simulate a wide range of psychoacoustic lateralization data. The extended model explains lateralization of pure tones with interaural time differences as well as with interaural level differences. Multiple images are predicted for tones with characteristic combinations of interaural signal parameters and for noise signals with different degrees of interaural cross correlation. The model is also capable of simulating dynamic lateralization phenomena, such as the ‘‘law of the first wave front’’ which is dealt with in a companion paper [Lindemann, J. Acoust. Soc. Am. 80, xxx–xxx (1986)]. The present paper is restricted to a comparison of the model predictions for stationary signals with the results of dichotic listening experiments.
Extension of a binaural cross-correlation model by contralateral inhibition. II. The law of the first wave front
Authors: Lindemann W.
Published: October 2005

This paper explains the ‘‘law of the first wave front’’ and related binaural phenomena on the basis of the model presented in the previous paper [Lindemann, J. Acoust. Soc. Am. 80, xxx–xxx (1986)] in which a contralateral inhibition mechanism was added to the well-known model of binaural cross correlation. In order to verify the predictions of the extended model, psychoacoustic experiments were performed with pairs of narrow-band impulses which were presented through headphones. The test signals consisted of a diotic primary sound and an ‘‘echo’’ with an interaural arrival-time difference. Lateralization was measured as a function of the time delay between primary sound and echo. For delays below the echo threshold, summing localization and the law of the first wave front were simulated; for delays above the echo threshold, the model predicts an influence of the primary sound on the lateralization of the echo.
Comments on ‘‘Sound generation by flow over relatively deep cylindrical cavities’’ [J. Acoust. Soc. Am. 7
8, 1785–1795 (1985)]
Authors: Elder S. A.
Published: October 2005

A solution for the Strouhal numbers of flow-excited deep cavity tones, given by Parthasarathy et al., is incorrect in that it overpredicts the number of self-sustained modes. The correct formula, taken from an earlier paper by Elder, predicts only those modes capable of supporting self-sustained oscillation.
A model for vocal fold vibratory motion, contact area, and the electroglottogram
Authors: Childers D. G. , Hicks D. M. , Moore G. P. , Alsaka Y. A.
Published: October 2005

The electroglottogram (EGG) has been conjectured to be related to the area of contact between the vocal folds. This hypothesis has been substantiated only partially via direct and indirect observations. In this paper, a simple model of vocal fold vibratory motion is used to estimate the vocal fold contact area as a function of time. This model employs a limited number of vocal fold vibratory features extracted from ultra high-speed laryngeal films. These characteristics include the opening and closing vocal fold angles and the lag (phase difference) between the upper and lower vocal fold margins. The electroglottogram is simulated using the contact area, and the EGG waveforms are compared to measured EGGs for normal male voices producing both modal and pulse register tones. The model also predicts EGG waveforms for vocal fold vibration associated with a nodule or polyp.
Articulatory movement characteristics of labial consonant productions by children and adults
Authors: Smith Bruce L. , McLean-Muse Ann
Published: October 2005

One purpose of the present investigation was to attempt to better understand articulatory movement characteristics of children’s speech, particularly as they might relate to the question of why acoustic measures of children’s segment durations are often longer than those of adults. In order to address this issue and to consider other general characteristics of children’s speech production development, a variety of data were obtained from three groups of children and from a group of adults using strain gauge instrumentation to monitor superior–inferior lip and jaw displacement and peak velocity. Results indicate that the children’s peak velocity and articulatory displacement measures were in many respects quite similar to those of the adults, although certain differences were observed. For a number of measures, there were also few peak velocity or displacement differences observed among the three age groups of children, despite the fact that they spanned about a six-year age range. In general, it appears that even when children and adults produce consonant sounds that are perceptually ‘‘correct,’’ articulatory differences can be observed among their productions.
Limitations of first-order approximations for calculations using intensity jnd’s
Authors: Hellman Rhona P. , Hellman William S.
Published: October 2005

The way in which the noninfinitesimal size of the intensity jnd affects calculations using power functions for pure-tone loudness and neural count is examined. The results of the commonly used first-order differential for representing the change in the power functions due to a jnd in intensity are compared with the second-order approximation and the exact formula. Examples are taken from a variety of psychophysical studies dealing with loudness and intensity discrimination. The second-order and exact formulas are shown to be more consistent with experimental data than the first-order differential.
Basilar membrane mechanics at the base of the chinchilla cochlea. II. Responses to low-frequency tones and relationship to microphonics and spike initiation in the VIII Nerve
Authors: Ruggero Mario A. , Robles Luis , Rich Nola C.
Published: October 2005

Low-frequency stimuli (40- to 1000-Hz tones) have been used to correlate the motion of the 8- to 9-kHz place of the chinchilla basilar membrane with the cochlear microphonics recorded at the round window and with the responses of auditory nerve fibers with appropriate characteristic frequency. At the lowest stimulus frequencies, maximum displacement of the basilar membrane toward scala tympani occurs in near synchrony with maximum rarefaction at the eardrum and maximum negativity at the round window; at higher frequencies, the mechanical and microphonic response phases progressively lag rarefaction, reaching −240 deg at 1000 Hz. At most frequencies (40–1000 Hz) near-threshold neural responses, once corrected for neural travel-time and synaptic delays, somewhat lead (by some 40 deg) maximal scala tympani displacement and maximal negativity of the round window microphonics. The variation of sensitivity with frequency is similar for basilar membrane displacement and microphonic responses: Under open-bulla conditions, sensitivity is constant for frequencies between 100 and 1000 Hz; below 100 Hz, sensitivity decreases at rates close to 12 dB/oct toward lower frequencies. Neural response sensitivity matches BM displacement more closely than BM velocity.
Acoustic surface waves on an impenetrable cylinder with periodically varying circular cross section
Authors: Lundqvist Lennart
Published: October 2005

The exterior acoustic problem is considered for a periodically corrugated cylinder, with an impedance boundary condition. The existence of surface waves along the cylinder is investigated by using the null field approach. The axial wavenumber of the surface wave is determined numerically as the frequency, the boundary condition, or the period of the corrugations varies. The modes on the surface have some features which are essentially identical to the modes inside the cylindrical duct; i.e., two modes that propagate in opposite directions interact destructively leading to a stop band, when the real parts of their axial wavenumbers coincide. But in contrast to the interior problem, there are intervals of the impedance condition in which only leaky waves exist and, also in contrast to guided modes, there seems to exist an upper cutoff frequency. No indication of the existence of surface waves on a sound-hard cylinder has been found.
Acoustic scattering in an inhomogeneous waveguide: Theory
Authors: Hackman Roger H. , Sammelmann Gary S.
Published: October 2005

A transition matrix formalism is developed for the acoustic scattering from a target in a layered, inhomogeneous waveguide. The connection is made with the normal mode model of propagation and the total acoustic wave is expressed as a sum over waveguide modes. For a target in a deep ocean environment, the scattering solution may be expressed in terms of the free-field T matrix and the normal mode wavefunctions for the empty waveguide. Both homogeneous and inhomogeneous layers are considered.
Spatial autocorrelation functions for calculations of effective propagation constants in polycrystalline materials
Authors: Stanke Fred E.
Published: October 2005

Spatial autocorrelation functions effect the scattering processes and the effective propagation constants of elastodynamic waves in single-phase, polycrystalline media. The spatial autocorrelation function W(r1,r2) is the probability that the two points r1 and r2 are in the same grain. A ‘‘grain’’ is a discrete, homogeneous domain within an inhomogeneous medium which is composed completely of such domains. One way to calculate W(r1,r2) is empirically. It employs cord lengths measured on a micrograph, and thus provides a means of determining the autocorrelation function for real materials. A second way to calculate W(r1,r2) is analytically, and employs expressions for the probability density of the cord lengths. Analytical calculation allows the use of assumptions about the geometrical nature of the grains in a material to be incorporated into theoretical expressions for effective propagation constants, and gives measures of effective ‘‘grain size.’’ Two specific assumptions have been important for such calculations, and so serve as examples in the present paper: that the cord lengths have Poisson statistics, and that the grains are spherical. Analytical calculation is also useful for the prediction of errors caused by empirically calculating W(r1,r2) from a finite data set of measured cord lengths.
Acoustical reflection and scattering from the underside of laboratory grown sea ice: Measurements and predictions
Authors: Stanton T. K. , Jezek K. C. , Gow A. J.
Published: October 2005

Acoustical reflection and scattering properties of the underside of undeformed sea ice which was grown in an outdoor pond were studied. Echo amplitude fluctuations of normal incidence sonar pings (100–800 kHz) were measured as the sonars moved horizontally under the ice and accumulated into echo amplitude histograms. The Rice probability density function (PDF) was fit to the data and the resultant statistical parameter was combined with the Eckart acoustical scattering theory to estimate an rms roughness of the water/ice interface to be 0.3 mm. Because the ice thin sections showed the ice to be porous and permeable at the interface with dendrites 0.5 mm thick, it appeared that the dendrites controlled the scattering. The average reflection coefficient was of the order 0.05. The low reflection coefficient (low compared to the 0.35 value which is predicted from the bulk properties of sea ice) was attributed to the dendritic structure which was porous and permeable at the water/ice interface. From the data and modeling done, scattering, and, hence, echo fluctuations, for normal incidence sonars of various frequencies and beamwidths were also predicted.
Farfield radiation patterns of a circular piston in a soft baffle with noninfinite extent
Authors: Tanaka Shokichi
Published: October 2005

This paper presents some numerical results of farfield radiation patterns of a circular piston flush mounted in the end of a semi-infinite soft (pressure release) circular cylinder. The method of equivalent edge acoustic sources is applied to the calculation of the diffracted field due to the finite extent of the end. The results obtained by this method for various radii of the cylinder and locations of the piston demonstrate the effect of a soft baffle with finite extent on farfield radiation patterns of the piston. Experimental results, which agree well with numerical ones even in the shadow region, are also presented.
Modeling the role of inherent spectral change in vowel identification
Authors: Nearey Terrance M. , Assmann Peter F.
Published: October 2005

Statistical analysis of F1 and F2 measurements from nucleus and offglide sections of isolated Canadian English vowels shows significant formant frequency change not only for the ‘‘phonetic diphthongs’’ /e/ and /o/, but also for the ‘‘monophthongs’’ /ι/, /q/, and /1/. In a perceptual experiment, brief sections were extracted from ‘‘nucleus’’ and ‘‘offglide’’ portions of naturally produced vowels. Two sections from each vowel were presented to listeners in each of three conditions: (1) natural order (nucleus followed by offglide); (2) repeated nucleus (nucleus followed by itself); and (3) reverse (offglide followed by nucleus). Listeners’ error rates for the natural order condition were comparable to those for unmodified full vowels (averaging 14% and 13%, respectively). Significantly higher error rates were found for the repeated nucleus (32%) and reverse (38%) conditions. Observed confusion matrices were strongly correlated with predictions from a pattern recognition model incorporating the formant measurements. This study provides evidence for the importance of inherent spectral change in listeners’ perception of isolated vowels. In addition, the problem of the parametric representation of formant trajectories is discussed and preliminary evidence for the persistence of vowel-inherent spectral change in consonantal context is presented.
Are active elements necessary in the basilar membrane impedance?
Authors: Diependaal Rob J. , Viergever Max A. , de Boer Egbert
Published: October 2005

This article is motivated by the current hypothesis [Kim et al., Psychological, Physiological and Behavioural Studies in Hearing (Delft U. P., The Netherlands, 1980); Neely, Doctoral dissertation, Washington University, St. Louis, MO (1981); de Boer, J. Acoust. Soc. Am. 73, 567–573 (1983a) and 73, 574–576 (1983b)] that it is necessary to include active elements in the basilar membrane (BM) impedance in order to explain recent data on the vibration of the BM [Khanna and Leonard, Science 215, 305–306 (1982); Sellick et al., J. Acoust. Soc. Am. 72, 131–141 (1982); Robles et al., Peripheral Auditory Mechanisms (Springer, New York, 1986)]. In order to test this hypothesis, first, a method which is an inversion of the customary description of cochlear mechanics is described. Instead of computing the BM velocity for a given point impedance of the membrane, we show how to compute the impedance function from a given BM velocity pattern in response to a sinusoidal input at the stapes. This method is then used to study the sensitivity of the recovered impedance to perturbations in the velocity pattern. The simulations used show that the real part of the impedance is extremely sensitive to such perturbations. Therefore, measured velocity patterns are unlikely to resolve the issue of whether active elements should be included. Frequency responses measured at a few points on the membrane are even less likely to do so.
Low-frequency noise observations in the deep ocean
Authors: Adair Richard G. , Orcutt John A. , Jordan Thomas H.
Published: October 2005

Simultaneous measurements of ocean-bottom infrasonic and ocean-bottom and sub-bottom seismic noise in the frequency band 0.1–20 Hz are presented. The data were obtained in 5.5-km-deep water in the South Central Pacific with a triaxial borehole seismograph and six triaxial ocean-bottom seismographs having externally mounted hydrophones. The borehole sensors were emplaced 54 m within basement rock overlain by 70 m of pelagic clay. In the band 0.1–1 Hz, noise propagation as seismic modes trapped in the seafloor is supported by observed spectral coherences, cross phases, and ratios between ocean-bottom pressure and vertical ground motion, and by the relatively lower noise levels in the borehole. Noise variations in this band are clearly correlated with changes in local wind direction and speed, presumably through ocean-bottom pressure fluctuations caused by nonlinear wind wave–wind wave and wind wave–swell interaction.
Level discrimination as a function of level for tones from 0.25 to 16 kHz
Authors: Florentine Mary , Buus So/ren , Mason Christine R.
Published: October 2005

Difference limens for level {ΔL in dB=20 log [(p+Δp)/p], where p is pressure} were measured as a function of level for tones at 0.25, 0.5, 1, 2, 4, 8, 10, 12, 14, and 16 kHz. At each frequency, test levels encompassed the range from near threshold to 95 dB SPL in steps of 10 dB or smaller. The stimulus duration was 500 ms and the interstimulus interval was 250 ms. An adaptive two-alternative forced-choice procedure with feedback was used. Results for six normal listeners show individual differences among listeners, but the general trends seen in the average data clearly are present in the individual data and show the following. First, the ΔLs at all but the highest frequencies are generally smaller at high levels than at low levels. Second, the ΔLs at equal SPLs are largely independent of frequency up to about 4 kHz, but increase with frequency above 4 kHz. Third, at 8 and 10 kHz, the ΔLs are clearly nonmonotonic functions of level, showing consistent deterioration in the mid-level ΔLs relative to the low- and high-level ΔLs. The present data are discussed qualitatively in terms of current models of level discrimination.
Resonance reciprocity calibration of an ultracompliant transducer
Authors: Swift Gregory W. , Garrett Steven L.
Published: October 2005

A resonant reciprocity calibration technique for an ultracompliant acoustic transducer is developed. The technique is applied to a magnetohydrodynamic (MHD) transducer with both salt water and mercury as wave-propagating media. The waves in question are not ordinary acoustic waves, but rather are low-frequency gravity waves in an open trough. Agreement between the reciprocity calibration and a calibration based on a primary standard is excellent. This result demonstrates that the sensitivity of the MHD transducer is just that given by the simple application of Faraday’s law, in contrast to recent measurements indicating otherwise. This reciprocity technique should be applicable to calibration of a wide range of transducers, including hydrophones and accelerometers.
On the general solution of the vector Helmholtz equation in cylindrical polar coordinates
Authors: Gottlieb H. P. W.
Published: October 2005

The general solution to the vector Helmholtz equation in cylindrical polar coordinates is derived by choosing combinations of components for which the equations do separate. A recent approximate solution form for the azimuthal component assumed by J. C. Piquette, ‘‘Spherical wave scattering by an elastic solid cylinder of infinite length’’ [J. Acoust. Soc. Am. 79, 1248–1259 (1986)], may with slight modification accordingly be rendered exact. The radial component need not be assumed to be approximated by zero; the corresponding actual exact solution is displayed.