bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexural–extensional behavior of composite piezoelectric circular plates
Authors: Adelman N. T. , Stavsky Y.
Published: October 2005

A plate-type theory is developed for the flexural-extensional vibratory response and static voltage deformation of heterogeneous piezoelectric circular transducer elements. Known results for homogeneous disks and bimorphs are shown to be special cases of the theory. Application is made to the design of simply supported metal-piezoceramic unimorph disks, and thin piezoceramic bimorph benders possessing metallic electrodes of non-negligible thickness.
Band-limited power flow into enclosures. II
Authors: Pope L. D. , Wilby J. F.
Published: October 2005

In the parent paper [J. Acoust. Soc. Am. 62, 906–911 (1977)] expressions were presented for band-limited sound power flow into an enclosure in the low-frequency regime where acoustic and structural modes are thinly scattered. Results for transmission by structural modes resonant below and within the frequency band of interest were given. The transmission was assumed to be to resonant acoustic modes of the enclosure. This addendum presents an additional expression for calculating power flow to nonresonant acoustic modes of the enclosure (modes resonant above and below the frequency band of interest) from structural modes resonant below, within, and above the band. If no resonant acoustic modes exist in a band, the new results can be used to predict the power inflow. If resonant acoustic modes do exist, the results can be used to increase the precision of the power inflow calculation. The procedure to be used in the calculation of the sound level in the enclosed space is presented.
Sound source above a rough absorbent plane
Authors: Chien C. F. , Carroll M. M.
Published: October 2005

The scattering of sound from a steady simple source above a rough absorbent plane is treated in the context of the theory of geometrical acoustics. The roughness of the plane is described by a scalar parameter which defines the fraction of the reflected sound energy which is scattered randomly (Lambert’s Law), the remainder being reflected specularly (Snell’s Law). An image principle is derived; the specular image source is nondirectional and the random image source is directional.
Reconstruction of a reflectivity field from line integrals over circular paths
Authors: Norton Stephen J.
Published: October 2005

When a broadband acoustic pulse is emitted from an omnidirectional source into a two-dimensional reflecting medium and the resultant backscattered echoes are recorded as a function of time at a point coinciding with the source, measurements of line integrals of the acoustic reflectivity are obtained over concentric arcs centered at the source point. Sufficient line-integral data can be generated in this fashion, by translating the omnidirectional source–receiver point over a suitable aperture, to reconstruct the unknown reflectivity function. A closed-form solution to this image reconstruction problem is derived, and on the basis of this solution, computer reconstructions of a point reflecting object from simulated echo data are presented. Finally, the closed-form reconstruction formula is shown to be expressible as the sum of two terms, where the first term corresponds to a simple delay-and-sum operation applied to the echo data recorded over the aperture; the second term is new and represents a correction which is shown to provide a noticeable improvement in the temporal–spatial point spread function produced by conventional delay–sum processing alone.
Nonlinearities in auditory-nerve fiber responses to bandlimited noise
Authors: Schalk Thomas B. , Sachs Murray B.
Published: October 2005

Discharge rate was measured as a function of spectral level for noise bursts of one bandwidth and center frequency. Such rate–level functions were measured for a number of bandwidths; either the low- or high-cutoff frequencies were set at fiber characteristic frequency (CF). Rate–level functions were also measured, simultaneously, for single tones at CF. We define dynamic range as the range in decibels over which rate increases from 10% to 80% of the maximum driven rate to CF tones. When pooling data across CF in single cats, dynamic range is an increasing function of fiber threshold for CF tones and noise stimuli. Narrow bands of noise produce rate–level functions that are similar to those for CF tones. For noise bands centered above CF, rate–level functions become less steep as bandwidth is increased, and are always monotonic. For wide bands of noise centered below CF, rate–level functions can be nonmonotonic or appear to plateau at rates less than the saturation rate to CF tones. Thus, wide bands of noise centered above or below CF can produce lower discharge rates than do narrow bands at the same spectral level. This rate reduction has properties similar to those for two-tone suppression. The suppressive effects observed for bandlimited noise are most pronounced on low spontaneous units and least pronounced on high spontaneous units.
Theory of frequency modulation detection for low modulation frequencies
Authors: Hartmann W. M. , Klein M. A.
Published: October 2005

There is general agreement that the frequency difference limen measured in a two-sine-tone frequency discrimination experiment is smaller than that measured in a frequency modulation (FM) experiment. We present a model of frequency modulation detection for low modulation frequencies, within the framework of signal detection theory, which accounts well for the observed difference between frequency discrimination experiments and FM detection experiments. The FM detection model also predicts psychometric functions for detection of FM with different modulation waveforms. FM detection experiments with square, sine, trapezoid, and triangle FM are in reasonable agreement with the model predictions.
Contralateral cueing effects in backward masking
Authors: Puleo Joseph S. , Pastore Richard E.
Published: October 2005

The role of stimulus uncertainty in backward masking was investigated using a Monaural Detection with Contralateral Cueing (MDCC) paradigm. Cues temporally synchronous with and phase locked to the signal (20-ms segment of 500-Hz sinusoid) reduced backward masking, with the amount of reduction being independent of the phase relationship between the cue and the signal. Band-limited noise cues synchronous with the signal also reduced the amount of backward masking, with cue bandwidth having only a small differential effect on the amount of reduction. The important parameter of the cue in reducing backward masking was the temporal synchrony between the cue and the signal; a silent gap in a broadband noise served as an effective cue. These results confirm that, unlike simultaneous masking, backward masking involves a high degree of temporal uncertainty.
The precedence effect and its possible role in the avoidance of interaural ambiguities
Authors: Zurek P. M.
Published: October 2005

The precedence effect, the observation that sound-source localization is determined largely by the interaural cues associated with the earlier-arriving direct sound to the neglect of later-arriving reflections, was investigated in several psychophysical experiments. The first experiment employed a stimulus composed of a continuous noise and its delayed repetition to simulate a direct sound and a single reflection. Comparison of the interaural amplitude and phase differences in this stimulus with its judged lateral position showed that the interaural differences do not predict lateralization judgments as simply as does a knowledge of the temporal pattern of stimulation, given the precedence effect. Most of the experiments were attempts to outline the time course of the precedence effect by measuring just-noticeable differences in interaural time and intensity of brief (less than 5 ms) wide-band noise bursts. The principal finding of these experiments was that interaural sensitivity to changes in both time and intensity follows a nonmonotonic course after the abrupt onset of a sound. Sensitivity is degraded for a period from approximately 0.5 to 10 ms after onset, with the largest jnd’s at delays of 2–3 ms. The precedence effect can be understood as resulting from this temporary lapse of interaural sensitivity. It was speculated that this temporal variation in interaural acuity serves to inhibit: (1) the representation of multiple and ambiguous interaural time delays between corresponding points on the waves of periodic stimuli; and (2) the extraction of interaural phase at frequencies greater than approximately 1400 Hz.
A narrow-band phase shift beamformer suitable for integrated circuit implementation
Authors: Brady J. John
Published: October 2005

The mathematical operations performed in a phase shift beamformer are recorded in a more efficient manner. The result is an implementation that minimizes the hardware needed. The performance of an experimental beamformer using this architecture is assessed; the beam pattern of the phase shift beamformer compares favorably to that of a time delay beamformer. Finally, the implications of integrating the architecture in a single integrated circuit are investigated.
Comments on ’’A sonar target recognition experiment’’ [J. Acoust. Soc. Am. 66, 140–147 (1979)]
Authors: Hampton L. D.
Published: October 2005

Previous work not recognized by the authors of this paper allow a viewpoint different from the conclusions which were drawn.
Reply to ’’Comments on ’A sonar recognition experiment’ ’’ [J. Acoust. Soc. Am. 67, 1067–1068 (1980)]
Authors: Chestnut Paul C.
Published: October 2005

Dr. Hampton’s comments are valid. We do believe, however, that the wider the signal bandwidth, the more information is available for target recognition.
Preservation of vocal tract length in speech: A negative finding
Authors: Tuller Betty , Fitch Hollis L.
Published: October 2005

A primary determinant of vowel quality is vocal tract shape; one aspect of which is vocal tract length. It has been suggested [Perkell, Physiology of Speech Production (MIT, Cambridge, 1969); Riordan, J. Acoust. Soc. Am. 62, 998–1002 (1977)] that vocal tract length is controlled directly, and that one mechanism for its regulation is a coordination between labial and laryngeal gestures. Riordan (1977) observed compensatory changes in the vertical position of the larynx when the characteristic lip protrusion of a rounded vowel was impeded. Although subjects in this study accurately produced the vowels /i/, /-/, /u/, and /-/ with different amounts of lip protrusion, no compensatory larynx height adjustments were observed.
Identification of synthetic /bdg/ by hearing-impaired listeners under monotic and dichotic formant presentation
Authors: Van de Grift Turek Sandra , Dorman M. F. , Franks John R. , Summerfield Quentin
Published: October 2005

Individuals with sensorineural hearing losses of both flat and sloping configuration evidence difficulty in identifying stop consonant place of articulation. To assess whether upward spread of masking is responsible for this difficulty, we presented hearing-impaired listeners with stimuli from a /ba da ga/ continuum in both monotic and dichotic (F1 to one ear; F2/F3 to the other ear) listening conditions. In the monotic conditions, listeners with similar audiograms evidenced great variability in identification performance. In the dichotic conditions performance did not generally improve. For a few listeners, however, the improvement was striking. At moderate levels of signal presentation, upward spread of masking does not appear to be responsible for the poor identification of place by the majority of listeners with moderate hearing losses.
The measurement of transducer efficiency using self-reciprocity techniques
Authors: Widener M. Ward
Published: October 2005

The calibration of transducers by self-reciprocity techniques is simplified by considering the signal source as a Thevenin’s equivalent generator. The absolute electromechanical efficiency is obtained directly using the equivalent generator resistance and the directivity index. Excellent agreement with other more difficult techniques has been obtained.
Comments on coherence estimates in multipath channels
Authors: Smith P. W.
Published: October 2005

A recent analysis [J. Acoust. Soc. Am. 65, 622 (1979)] developed estimates of spatial, temporal, and frequency coherence functions for sound transmitted in a channel. The statistical properties of the governing parameters that were hypothesized appear not to have any basis in physical knowledge. Fortunately, the results of prior studies of these same questions indicate that the estimates may often be largely independent of such unfounded hypotheses. However, physical measurements and computed simulations of the impulse response of oceanic channels reveal complexities that should significantly affect frequency coherence in ways not adequately modeled by simplistic hypotheses.
Reply to ’’Comments on coherence estimates in multipath channels’’ [J. Acoust. Soc. Am. 67, 1061–1062 (1980)]
Authors: Jobst W. , Zabalgogeazcoa X.
Published: October 2005

Explanations of the particular distributions and bounds imposed on the ray parameters are given. Also, a clarification on the term ’’spread’’ is given.
Comment on ’’Some frequencies of underwater noise produced by fishing boats affecting albacore catch’’ [J. Acoust. Soc. Am. 66, 296–299 (1979)]
Authors: Foote Kenneth G.
Published: October 2005

An alternative explanation for the observations analyzed by Erickson is offered. Differences in catch-related success of boats participating in the West Coast Albacore fishery are attributed to the low-frequency content of vessel-radiated noise, which may attract albacore, rather than to the frequency structure above 1500 Hz.
Reply to ’’Comment on ’Some frequencies of underwater noise produced by fishing boats affecting albacore catch’ ’’ [J. Acoust. Soc. Am. 67, 1064 (1980)]
Authors: Erickson Gary J.
Published: October 2005

The author replies to Foote concerning the importance of frequencies below 1000 Hz.
An analysis of Fresnel zone and diffraction fields near the boresight of practical acoustic radar antennas
Authors: Adekola S. Adeniyi
Published: October 2005

Based upon a generalized theory of an analytic model of a practical acoustic radar (echosonde) antenna [S. A. Adekola, J. Acoust. Soc. Am. 60, 230–239 (1976)] whose potential has been exploited to measure atmospheric turbulent velocity fields and temperature fluctuations, we present an analysis of the Fresnel zone and diffraction fields near the boresight of a typical antenna. Invoking the Fresnel zone approximation and employing a tapered parabolic source excitation, the Fresnel zone field at the antenna boresight is evaluated in closed forms in terms of a highly convergent Lommel series function of the form Ω0m (ν,n) that is expedient for practical computations. A generalized diffraction integral equation at the boresight region, which can be used for both circularly symmetric and asymmetric echosonde apertures, is formulated whereby the existing integral, previously derived in the reference above, is split into a sum of zeroth-order Hankel and Lommel transforms that describe the field in the two principal planes of the aperture. The results clearly demonstrate that circular symmetry still leads to zeroth-order Hankel transform, while antisymmetry produces an additional Lommel transform. Analytical examples presented include closed form pattern evaluations for some commonly used source excitations, in terms of tabulated Anger–Weber and Struve functions, while illustrative numerical pattern characteristics discussed comprise beam patterns arising from Hamming—cos2 on a pedestal—and doublet-source distributions. A realization of the echosonde antenna described by the integral equations is discussed. Raw, experimentally measured, beam patterns in the acoustic frequency band 1750–3000 Hz are redrafted, statistically averaged, and presented, using standard error bars. We also discuss a facsimile recording that describes the measurements of turbulence components in the lower marine boundary layer, using an echosonde antenna. An attempt is made towards a rigorous treatment of the echosonde synthesis, based on the synthesis integral equations deduced from the results of the diffraction fields.
Spectrum of intensity fluctuations in the internal wave frequency range
Authors: Unni Santha , Kaufman Charles
Published: October 2005

We show that a simple modification of the theory of Munk and Zachariasen [J. Acoust. Soc. Am. 59, 818 (1976)] somewhat reduces the discrepancy between that and the data of Ewart [J. Acoust. Soc. Am. 60, 46 (1976)].
Simplified calculation of ray-phase perturbations due to ocean-environmental variations
Authors: Hamilton K. G. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

A simplied approach is described for determination of phase perturbations produced by variations in sound speed and current in the ocean. It is shown that corresponding perturbations of the ray geometry may be ignored in determining the phase perturbations, when the former are regular in a specific sense. Principal advantages in the procedure include its efficiency in calculation of phase variations and its indication of situations when ray-geometric perturbations may significantly influence phase. The method is demonstrated for both shallow- and deep-ocean examples, when the phase perturbation arises from weak horizontal deviations from a horizontally uniform sound-speed structure. It is also illustrated for current in the deep ocean, considering cases with and without horizontal variations in current speed. Examples for both types of horizontal variations are shown in which they make significant contributions to ray phase. Finally, the procedure is applied to some single-path acoustic observations in which the time series of travel time is dominated by tidal variations. Ranges of possible environmental changes in sound speed and current, leading to the observed travel-time variations, are indicated.
Consistent environmental acoustics: Application to stochastic internal-wave models
Authors: Watson J. G. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

A consistent environmental-acoustic model for a deep moving ocean is formulated. The acoustic model for regularly perturbed SOFAR rays is approximately solved using a type of WKB  (J) expansion. Interfacing conditions between the hydrodynamics and acoustics are developed which lead to constraints on acoustic frequency and transmission range. As an application, transmissions are considered through stochastic internal-wave fields, which have been modeled in a previously published paper by the authors. Formulas for ray phase variances are derived. These formulas are asymptotically evaluated for rays with relatively significant depth variation, using the stationary phase method. New results are obtained for the dependence of the variances on internal-wave primitives, such as energy spectra. Expected multipath intensity is calculated for transmission through an ocean with static state modeled by a bilinear sound-speed profile. The effects of the internal-wave field and of varying internal-wave parameters on the expected intensity are shown to be significant.
Vibration of a clamped circular plate driven by a noncentral force
Authors: Snowdon J. C.
Published: October 2005

Expressions are stated for the transmissibility and for the driving-point impedance of an internally damped circular plate of radius a with a clamped boundary that is driven by a vibratory point force at an arbitrary distance μa from the plate center. Expressions are also stated for the plate transmissibility and driving-point impedance when the plate is loaded at the arbitrary driving point either by a lumped mass, by a dynamic vibration absorber, or simultaneously by a lumped mass and a dynamic absorber. In all cases, representative calculations of transmissibility and impedance are plotted versus the square root of frequency. These curves clearly show the dependence of transmissibility and impedance on the plate damping factor, the value of the parameter μ, and the extent of the mass loading. They also show the effectiveness of the dynamic absorber, which varies with the value assigned to μ.
Resolving the directions of sources in a correlated field incident on an array
Authors: Cantoni A. , Godara L. C.
Published: October 2005

Adaptive beamforming algorithms are often designed under the assumption that the sources illuminating the array are mutually uncorrelated. When the assumption is not valid, the performance of the adaptive beamforming algorithm in certain applications is severly limited. A simple example is included which illustrates how suppression of a look direction signal occurs when a power minimizing adaptive algorithm is used in the presence of correlated sources. This paper establishes certain properties of the eigenvectors of the correlation matrix of an array illuminated by a field of correlated discrete sources. On the basis of these properties an adaptive algorithm is proposed for resolving the direction of all discrete sources, even if they are mutually correlated. Simulation results are presented showing the performance of the algorithm proposed in this paper.
Degradation of the signal-to-noise ratio of Gaussian signals in Gaussian noise transmitted over a digital channel
Authors: Lyle W. D.
Published: October 2005

This paper presents a mathematical analysis of the signal-to-noise power ratio degradation incurred when Gaussian signals in Gaussian noise are level-quantized, time-sampled, transmitted over a noisy digital channel, and then reconstructed by a low-pass filter. Application of this analysis occurs when very weak acoustic or seismic signals in strong white noise are collected and transmitted over a digital channel to an analysis location remote from the collection point, and where detectability of the information-bearing signals at the analysis location depends on the original signal-to-noise power ratio in small frequency bands. Therefore, it is important to understand the degradation of the original signal-to-noise ratio occurring during transmission. Curves are presented which show bounds on the degradation as a function of the quantizer step size and the channel bit error probability. Also considered is a scheme for transmitting a low-rate digital sequence by periodically interrupting the level-and-time-quantized analog signal. Three schemes are proposed for doing this, and one scheme is mathematically analyzed. It is shown that this scheme increases the degradation of the reconstructed analog signal by about 0.15 dB over that of the uninterrupted case.
Diffraction of Lamb waves by a finite crack in an elastic layer
Authors: Rokhlin S.
Published: October 2005

This paper analyzes the diffraction of Lamb waves by a finite crack situated on the plane of symmetry of an elastic layer. The surface of the crack and of the layer are assumed to be stress-free. The problem is solved by the modified Wiener–Hopf technique. The field of the reflected and transmitted waves, and also the field in the vicinity of the crack, are given as an expansion in natural waves of the elastic layer. The amplitudes of these waves are expressed in terms of certain generalized quantities, which are found from exponentially converging infinite systems of equations. The solution converges at any value of the parameter L/H≳0 (where L is the length of the crack and H is the thickness of the layer) and is particularly effective as this parameter increases. The strongly resonant phenomena in the region of the layer occupied by the crack are identified and discussed.
Nonstationary and nonuniform oceanic background in a high-gain acoustic array
Authors: Anderson V. C.
Published: October 2005

Nonstationary and nonuniform distributions of acoustic background in the ocean are important statistically when detection performance predictions are carried out for high-gain receiving arrays. A high-gain acoustic array, ADA (Acoustic Distribution Array), designed for measurement of high-order temporal and spatial distributions of acoustic backgrounds in the ocean, was used to obtain envelope spectra of directional noise in octave bands centered at 1130 and 2260 Hz. The directional noise was measured through an infinitely clipped DIMUS beamformer and thus, because of the clipped normalization, the envelope spectra represent, solely, variations in the directional structure of the background noise, not its absolute level.
Random and partially random acoustic arrays
Authors: Thorn J. V. , Booth N. O. , Lockwood J. C.
Published: October 2005

Statistical properties of the beampatterns of three-dimensional random arrays of arbitrary geometry are derived. The class of random arrays studied differs from those previously analyzed in that it includes partially random arrays. A partially random array is defined, for purposes of this paper, as a random array in which the various element positions may have different probability density functions and may be interdependent. Results presented include the expected value and variance of the pattern function, expected array power and the associated directivity index, and the variance of the array power. The results are applied to random and partially random disk arrays. The partially random disk array is assumed to have elements arranged in vertical strings. It is found that an array with M-element strings is characterized by a region corresponding in elevation to the main lobe and extending 360° in azimuth in which the side-lobe variance is a factor of M greater than that in the rest of the side-lobe region.
Detection of temporally uncertain signals
Authors: Green David M. , Weber Daniel L.
Published: October 2005

The effects of signal uncertainty on detection performance were measured using a new procedure that allows precise specification of the initial temporal uncertainty. Five different models of the detection process, two assuming a continuous representation of the sensory input and three assuming a discrete representation, were compared with the obtained data. The effects of varying signal uncertainty (the number of potential signal intervals was one, five, or ten) had little effect on detection performance. The one-parameter form of the choice model can be rejected without hesitation. The continuous Gaussian model and the symmetric two-state model are significantly different from the data. The high threshold and sophisticated two-state models provide accurate descriptions of the data that cannot be rejected on statistical grounds.
Pitch of amplitude-modulated low-pass noise and predictions by temporal and spectral theories
Authors: Houtsma A. J. M. , Wicke R. W. , Ordubadi A.
Published: October 2005

Pitch phenomena related to the periodic interruption rate of white noise have traditionally been regarded as evidence for time domain pitch processing in the auditory system since spectra of these signals are flat. Short-term spectra, however, contain information about the interruption rate. Melodic interval identification experiments were performed with sounds comprising low-pass filtered noise modulated by either a sine wave, a square wave, or a periodic narrow pulse wave. Melodic intervals were generated by varying the modulation frequency fm while the low-pass cutoff frequency fco of the noise was an experimental variable. The correct identification score shows a particular dependence on the ratio fco/fm for each type of modulation signal. Shapes and relative positions of performance functions are compared with predictions derived from an energy detector (time domain) model and a short-term power spectrum correlation (frequency domain) model, and are found to support the former more strongly than the latter. There is some evidence, however, for the existence of both types of processing in the auditory system.
Speech-production measures of speech perception: Rapid shadowing of VCV syllables
Authors: Porter Robert J. , Castellanos F. Xavier
Published: October 2005

Five listeners rapidly repeated (’’shadowed’’) a random presentation of the vowel–consonant–vowels (VCV’s) /aba, apa, ama, aka, aga/. Initial vowel duration was varied to eliminate it as a temporal cue to the occurrence of the consonant. These shadowing, choice reaction times (RT’s) were compared to simple RT’s obtained when listeners always produced /aba/ or /ba/ to the same syllables. Both /aba/ and shadowing reactions were extremely fast (170 to 240 ms). Latency differences between the two tasks were attributable to differences in the point at which cues sufficient for responding were present. These results suggest that speech-perception decisions in shadowing are directly available to, and are perhaps made contemporaneously with, the execution of the speech response. The simple /ba/ responses were observed to occur at a point comparable to the consonantal release seen for the simple /aba/ responses. This result suggests that the motor organization required for a /ba/ response includes an implicit time interval appropriate for a consonantal closure.
Acoustical imaging of an object buried in seafloor sediment by using a focused ultrasonic transducer
Authors: Ohgaki Masakatsu , Shimizu Ryoji , Miyazawa Hisashi , Okujima Motoyoshi
Published: October 2005

An experiment to locate objects buried in seafloor sediment by using ultrasonic imaging has been conducted and shows potential for practical application. Attenuation measured in actual seafloor sediment indicated that 15 kHz could be used for detecting objects buried to about 4 m in the seafloor. Tests were conducted using both plane and focused transducers with elements arranged on a concave surface. Imaging of inclined objects by a focused transducer was found to be significantly better than by a plane transducer as long as the object’s gradient was within one-half the transducer aperture angle. Scaled model tests were carried out at a frequency of 150 kHz and full-scale tests were performed at 15 kHz. Two display formats were used—one for the vertical plane and the other for the horizontal plane. In the full-scale test, a cylindrical iron tube and an iron plate were buried in a sand box 4 m long by 3 m wide by 2 m deep. Ultrasonic images were observed on a CRT.
Rare earth iron octagonal transducer
Authors: Butler J. L. , Ciosek S. J.
Published: October 2005

A low-frequency transducer in the form of an ’’octagonal ring’’ 10 in. in diameter and 6 in. high, driven by 16 rare earth Terfenol D (Tb0.3Dy0.7Fe2) rods, has been developed. The transducer resonates in a circumferential expansion mode at 775 Hz with a mechanical Q of 2.4. and an effective electromechanical coupling coefficient of 0.4. Results are presented for the transducer operated with and without a polarizing bias up to acoustic output powers of 80 and 350 W, respectively.
New method of measuring reverberation time by Fourier transforms
Authors: Aoshima Nobuharu
Published: October 2005

Reverberation time can be measured from pulse responses by reversed integration of the squared signal. By this method, however, effects of filters cannot be separated from room characteristics. The author has devised a new method by which reverberation responses of rooms only can be obtained. In this method, integrations on time axis are made, not for squared responses, but for complex numbers derived from impulse responses by Fourier transforms.
The utilization of zero-crossing statistics for signal detection
Authors: Higgins Robert C.
Published: October 2005

The utilization of zero-crossing (ZC) information to detect signals can provide hardware simplifications and cost reductions compared to conventional linear processing techniques. This paper investigates the effectiveness of a ZC processor that uses ZC statistics to detect a sinusoidal signal in the presence of either sinusoidal interference or Gaussian noise. For the sinusoidal interference case, the frequency distribution of ZC intervals for the sum of two sinusoids with different amplitudes, different frequencies, and a uniformly distributed relative phase was calculated. These results, extending the work of Longuet-Higgins, Rice, and Blachman, demonstrated that the use of the mean ZC interval or the mean ZC rate may not be appropriate for processing against sinusoidal interference that is stronger than the desired signal. For the sinusoidal signal plus Gaussian noise case, several ZC statistics, including the mean ZC interval and the standard deviation of ZC intervals, were calculated. It was found that a processor utilizing these statistics can be effective when the input SNR (signal-to-noise ratio) is greater than −14 dB.
Effects of increased vertical dimension on size of constriction port and fricative sound intelligibility
Authors: Warren Donald W. , Nelson Gary R. , Allen George
Published: October 2005

The effect of increased vertical bite dimension on fricative sound productions was studied in five adults who wore dentures. Oral port size and sound intelligibility were evaluated at different degrees of artificially induced open bite. The data demonstrate that rapid compensatory adjustments occurred and oral port size changed minimally at all degrees of opening tested. However, in three of the subjects, sound intelligibility declined at the 6-mm opening, and in all subjects, a four-fold increase in sound distortions occurred in the edentulous state. This finding suggests the possibility that either physiological parameters are controlled more successfully than acoustical parameters or that compensatory efforts to maintain constrictor size may, under certain circumstances, adversely affect sound intelligibility.
Acoustic impedance measurement using constant volume velocity
Authors: Salava Tomas
Published: October 2005

For determining acoustic impedances the direct methods are now often used, based on measuring the sound pressure excited on a measured object by the known volume velocity. With the sine sweep technique it is easily possible to maintain, with sufficient accuracy, the generated volume velocity constant. When using direct methods at higher frequencies gross errors can arise from the sound field inhomogenities in the coupling space among the sound source, the measuring microphone, and the measured object. For some coupling configurations it is, however, possible to find acceptable relations between the measured and the sought values.
A new algorithm for relaxation spectra in ultrasonic spectroscopy
Authors: Ito Naoto , Kitahara Noriyuki , Harada Yoshifumi
Published: October 2005

A new type of algorithm based on a modified least-square method has been developed to analyze ultrasonic absorption for a single relaxation. Compared with the usual heuristic methods, this technique is a more direct one, which enables us to determine with high accuracy the relaxation parameters from a single initial estimated value of the relaxation frequency fc. Computer simulation of the α/f2 vs f curves are presented for various conditions. This method is satisfactorily applied to the ultrasonic absorption of propionic acid over a frequency range from 2.8 to 95 MHz.
Seismic signal processing using an inverse diffraction technique
Authors: Salisbury John I.
Published: October 2005

A seismic processing technique has been developed to remotely determine the effective layer velocity and layer depth of a multilayered ocean floor. The computer algorithm making up the seismic signal processor is based on the Kirchhoff diffraction integral and is referred to as the inverse diffraction processor (IDP). An iterative solution for the effective interval velocity and layer depth is obtained with the use of the Fourier transform. The required input data to the processor are the measured magnitude of the reflected acoustic signal recorded by an array of hydrophones located on the ocean surface. The performance of the seismic processor has been evaluated using synthetic seismic data. This insures that the actual parameters being solved for are known, thus the accuracy and resolution of the processor can be ascertained.
A surface acoustic wave phase shifter with three transducers
Authors: Toda Kohji , Shinoda Yoshiaki
Published: October 2005

The theory and experimental results for a new type of surface acoustic wave phase shifter are described. The device consists of three interdigital transducers, including one with sine-shaped apodization. The phase shifter produces an arbitrary constant phase difference, and has two operation frequency ranges with 180° out of phase, separated at the center frequency of the device.
Symposium on cochlear mechanics: Where do we stand after 50 years of research?
Authors: Zwislocki J. J.
Published: October 2005

The symposium was held at the 1979 Spring Meeting of the Acoustical Society of America on the occasion of the Society’s 50th Anniversary. The subject of cochlear mechanics was chosen because it plays a fundamental and unique role in hearing, because it is experiencing a renewed flurry activity, and because it has always figured prominently in the research of the society’s members, bringing the Nobel Prize to one of them. The following seven articles are the printed versions of the invited oral presentations made at the symposium. With the partial exception of the first, they address themselves to the contemporary state of the art rather than to past achievements. They deal with cochlear experiments as well as with cochlear theory and include most of the disciplines involved in cochlear research, ranging from anatomy and physiology to applied mathematics and biophysics. In part, the papers review the current state of the cochlear science and, in part, they present new experimental findings and theoretical hypotheses; they also reveal some unsolved problems. Together, they show a clear research trend beginning with macromechanics in the early years and focusing increasingly on microprocesses closely tied to the electromechanical transduction in the sensory cells. Hopefully, they present to expert and nonexpert alike a fair picture of where our knowledge of cochlear mechanics stands.
Cochlear anatomy related to cochlear micromechanics. A review
Authors: Lim David J.
Published: October 2005

The sensory cilia of the mammalian cochlea show an orderly gradation in height along the length of the cochlea. The cilia are taller in the apex and shorter in the base. Differences in ciliary gradation also exist between the different rows of outer hair cell cilia along the length of the cochlea. There are gradations in width and thickness in the moveable portion of the tectorial membrane paralleling those in the basilar membrane. There are also gradations in the relationship between the tectorial membrane and the slope of the reticular lamina along the length of the cochlea. This suggests that there may be additional mechanical fine-tuning capability built into the organ of Corti besides the basilar membrane. The tectorial membrane is firmly attached to the outer hair cell cilia along the entire length of the cochlea in all species examined. The inner hair cell cilia do not have the same firm attachment to the tectorial membrane as outer hair cell cilia. This suggests that the modes of mechanical coupling between the tectorial membrane and the inner and outer hair cell cilia are different.
Cochlear models: Two-tone suppression and the second filter
Authors: Hall J. L.
Published: October 2005

With advances in our understanding of the auditory periphery, models of cochlear mechanics have evolved from descriptions of existing data to the point that they can suggest meaningful observations that should be made and predict expected outcomes. As an example, we discuss relationships among mechanical nonlinearities in the inner ear, two-tone suppression, and the auditory ’’second filter.’’ Electrophysiological two-tone suppression data indicate that excitatory tuning curves (stimulus intensity required to elicit a specified amount of activity in a primary fiber as a function of frequency) are more sharply tuned than suppressive tuning curves (stimulus intensity required to suppress the response to a continuous tone at the fiber’s characteristic frequency by a specified amount as a function of frequency). Model simulations which attempt to account for the above difference suggest that there must be a stage of sharpening between the physical variable governing two-tone suppression (tentatively identified as velocity of the basilar membrane) and the physical variable governing neural excitation. An experiment that would unequivocally demonstrate the simultaneous existence of two representations of the stimulus with significantly different tuning properties in the cochlea is described. The future evolution of cochlear modeling, incorporating nonlinear two-dimensional models, is discussed.
Sound-induced resistance changes in the inner ear
Authors: Geisler C. Daniel , Mountain David C. , Hubbard Allyn E.
Published: October 2005

A new technique for measuring sound-induced resistance changes (CR) in scala media in response to pure-tone stimuli by injecting alternating current into guinea-pig cochleas was reported recently [C. D. Geisler et al., J. Acoust. Soc. Am. 61, 1557–1566 (1977)]. Detailed measurements with this technique indicate that while the CR behaves approximately as does the cochlear microphonic (CM) there can be very significant differences between the two variables under certain experimental conditions. Computer analysis of simultaneously recorded CR voltage components and CM indicates that the CR harmonics, in both amplitude and phase, behaved differently with sound intensity and with asphyxia than did the CM harmonics (A. E. Hubbard et al., J. Acoust. Soc. Am 66, 431–445 (1979)]. Direct current injection and stimulation of the crossed olivocochlear bundle (COCB) indicate further differences between CM and CR (D. C. Mountain, Ph.D. thesis, University of Wisconsin—Madison, 1978). Positive dc caused a relative augmentation of CM that grew with sound intensity, and a relative reduction in CR magnitude that decreased with intensity. Negative dc caused effects of similar magnitude but opposite sign. COCB stimulation caused enhancement of both CM and CR. Present models cannot account quantitatively for these results.
Basilar-membrane motion in the alligator lizard: Its relation to tonotopic organization and frequency selectivity
Authors: Peake William T. , Ling Alexander
Published: October 2005

In the alligator lizard the entire basilar membrane is accessible for measurements of its velocity by the Mössbauer method. Tests of the method indicate (1) the Mössbauer source can be placed on the basilar membrane without altering the signal-transmission properties of the cochlea, and (2) the source adheres to the basilar membrane. Isovelocity curves (IVCs) were constructed by plotting (as a function of tone frequency) the sound-pressure level at the tympanic membrane required to produce a specified velocity amplitude. IVCs from 21 lizards for source locations spanning the length of the basilar membrane indicate that basilar-membrane velocity does not vary systematically with longitudinal location as it does in mammalian cochleas. Measurements of velocity waveforms in two lizards do not indicate substantial nonlinearity in the inner-ear mechanical system. The frequency dependence of the basilar-membrane velocity is similar to that of the extrastapes velocity over the range 0.4 to 2 kHz. Thus, the tonotopic organization and frequency selectivity, which have been previously demonstrated in this species in responses of both auditory-nerve fibers and cells of the receptor organ, are apparently not primarily determined by basilar-membrane motion.
Just-noticeable differences of frequency for masked tones
Authors: Dye Raymond H. , Hafter Ervin R.
Published: October 2005

Frequency discrimination was measured as a function of level for tones of 500, 1000, 2000, 3000, and 4000 Hz. The tones were masked by a wide-band noise whose level was set to maintain constant E/No. Frequency discrimination was found to improve with level for tones of 500 and 1000 Hz while it grew worse for tones of 3000 and 4000 Hz. The data for 500 and 1000 Hz are accounted for by the periodicity-type neural timing model of Green and Luce [’’Counting and Timing Mechanisms in Auditory Discrimination and Reaction Time,’’ in Contemporary Developments in Mathematical Psychology, edited by D. H. Krantz, R. C. Atkinson, R. D. Luce, and P. Suppres (Freeman, San Francisco, 1974), Vol. 2]. The data for 3000 and 4000 Hz are explained by the modified energy detection model of Henning [J. Acoust. Soc. Am. 42, 1325–1334 (1967b)].
Evaluation of vowel duration as a cue for the voicing distinction in the following word-final consonant
Authors: Hogan John T. , Rozsypal Anton J.
Published: October 2005

Previous measurements have indicated that vowels before voiced and voiceless consonants exhibit a systematic duration difference, the former being longer approximately by a 3:2 ratio than the latter. Experiments with synthetic speech have shown that vowel duration is an important cue for the voicing distinction of the following consonant in word-final position. In the present paper the role of this cue is evaluated for natural speech, which may also contain secondary cues for maintaining this distinction. The stimuli, spoken by a female speaker, were 24 English monosyllabic words ending with voiced stops, fricatives, and consonant clusters after intrinsically long and intrinsically short vowels. Duration of the vowel nucleus was systematically reduced using a digital gating technique. Recognition rates as a function of vowel duration were obtained. Category change takes place mainly for intrinsically long vowels and for high vowels in combination with final fricatives alone or in consonant clusters. In other cases, category change cannot be established even after the vowel duration is reduced to only 30% of its original duration. In particular, the presence of a long voice bar for a final voiced stop will make shortening of the vowel perceptually less effective. A multiple regression analysis of the experimental data indicates that in natural speech not only vowel duration, but also voice bar duration, duration of silent closure preceding the final release transient, and duration of the release burst or frication noise, depending on the consonant type, vary in weight as cues for voicing under different vowel- and consonant-type conditions.
Dichotic and monotic masking of CV’s by CV second formants with different transition starting values
Authors: Porter Robert J. , Whittaker Ronald G.
Published: October 2005

Listeners were asked to identify ambiguous and unambiguous stop-vowel targets placed in monotic and dichotic competition with second formants (bleats) from voiced consonant–vowel (CV) syllables lying along a place-of-articulation continuum. Target performance varied with bleat-continuum position as well as bleat intensities. In cases where target errors occurred, either dichotically or monotically, they reflected predominantly the place cue of the bleat. This result, like that of previous studies, suggests the dominance of target or bleat reflects the relative ’’salience’’ of the two signals’ cues. Differences were seen between monotic and dichotic conditions in the rate of change in performance with bleat intensity and continuum position. The rate of monotic performance change was a more precipitous (higher slope) function of these variables than was dichotic performance. This difference was interpreted as suggesting that monotic interference includes a peripheral masking component which is sensitive to the relative spectral energies of target and bleat. Dichotic effects, in contrast, seem to primarily reflect the operation of (central) processes which grant different perceptual weights to signals’ cues depending on their intensity-dependent saliences. The observation that ambiguity, per se, of the targets (or the CV’s from which the bleats were extracted) played little role in predicting results, was interpreted as reflecting a primarily prephonetic (i.e., auditory) locus for both monotic and dichotic interactions.