bluuebunny/crossref_metadata_2025 huggingface dataset:
Incurrence and alterations in contralateral tinnitus following monaural exposure to a pure tone
Authors: Young I. M. , Lowry L. D.
Published: October 2005

A subject who had a tinnitus with 10 000-Hz pitch equivalent in the left ear and no tinnitus in the right ear was exposed in the left ear to a steady tone of 2000 Hz, 107 dB SPL, for 10 min. This exposure resulted in a permanent tinnitus in both ears with similar pitch of approximately 10 000 Hz and loudness of 50–55 SPL (5–10 dB SL). When the left ear of this subject was exposed to a steady 500-Hz pure tone at 121 dB SPL for 21 min, tinnitus disappeared temporarily from the stimulated ear but was heard in the nonstimulated ear. In the left ear: 3 h after stimulation, tinnitus reappeared as a mixture of multiple pitches superimposed upon broadband noise and/or low-pass filtered noise; 24 h after stimulation, tinnitus pitch changed to 3260 Hz, two days later to 5100 Hz, three days later to 8310 Hz and one week later to the original 10 000 Hz and has remained there since. In the nonstimulated right ear: Immediately after cessation of stimulation, tinnitus pitch was 6700–8000 Hz for 48 h; thereafter, tinnitus has been fluctuating between 8000–9000-Hz tone and a narrow-band noise centered around 7986 Hz with a bandwidth of 2710 Hz; the tinnitus did not return to the previous pre-exposure pitch of 10 000 Hz until about four weeks after exposure. We suggest that these contralateral effects of tinnitus are mediated by the central auditory system.
On the acoustoelastic effect
Authors: Tverdokhlebov A.
Published: October 2005

A simple method is presented for obtaining the stress tensor for small displacements in nonlinearly strained material. The physics of sonic wave propagation in deformed materials and acoustoelastic effects are discussed, and a feasable experiment is suggested for early diagnosis of plastic deformation. The calculational results for surface wave velocity as a function of applied static stress are presented in tabular form convenient for the experiments.
Nonlinear extensional vibrations of quartz rods
Authors: Tiersten H. F. , Ballato A.
Published: October 2005

The one-dimensional scalar differential equation describing the extensional motion of thin piezoelectric rods is obtained from the general nonlinear three-dimensional description. Only the elastic nonlinearities are considered. The relations between the quadratic and cubic coefficients of the rod and the fundamental anisotropic elastic constants of various orders are derived. The quadratic rod coefficients are calculated for various orientations of quartz rods, but not the cubic rod coefficients because the fundamental elastic constants of fourth order, which are required for the calculation, are not presently known. The nonlinear equation and boundary conditions are applied in the analyses of both intermodulation and nonlinear resonance of quartz rods. In each instance a lumped parameter representation of the solution, which is valid in the vicinity of a resonance, is obtained and the influence of the external circuitry is included in the treatment.
Free vibration of circular-segment-shaped membranes and plates of rectangular orthotropy
Authors: Irie Toshihiro , Yamada Gen , Kobayashi Yukinori
Published: October 2005

An analysis is presented for the free vibration of circular-segment-shaped membranes and plates of rectangular orthotropy. A circular-segment-shaped membrane is formed on an orthotropic rectangular membrane by fixing several segments. With the reaction forces acting on the edges of an actual membrane regarded as unknown harmonic loads, the stationary response of the membrane to these loads is expressed by the use of the Green’s function. The force distribution along the edges is expanded into Fourier series with unknown coefficients, and the homogeneous equations for the coefficients are derived by restraint conditions on the edges. For a circular-segment-shaped plate clamped at the edges, it is formed on a rectangular plate simply supported at the edges, in which the bending moments act on the edges in addition to the reaction forces. In this case, the moments regarded as unknown harmonic loads are also expanded into Fourier series with unknown coefficients, and are included in the equations for the coefficients. The natural frequencies and the mode shapes of the actual membrane or plate are determined by calculating the eigenvalues and the eigenvectors of the equations. The method is applied to circular-segment-shaped membranes and plates of rectangular orthotropy, the natural frequencies and the mode shapes of the membranes and plates are calculated numerically, and the effect of the shape and orthotropy is discussed.
A simple, accurate method for predicting sonar performance without the need for computer simulations
Authors: Richter W. J. , Šmits T. I.
Published: October 2005

This paper presents a new analytical technique for computing sonar performance which can be run on a programmable hand calculator. It is simple and rigorous, and does not require complex computer simulations which obscure the critical parameters. It allows the individual terms in the sonar equation to have two or more different relaxation times, and allows the Recognition differential (RD) term to be presented as a curve of probability of detection versus signal-to-noise ratio (SNR) rather than a jump in probability of detection versus SNR from 0 to 1. This method treats the sonar equation as a random process with a mean and standard deviation as in standard simplified techniques, but treats successive observations of received signals as a multivariate Gaussian distribution with observations correlated in accordance with the decorrelation times of the individual terms in the sonar equation. Restrictions of this method are twofold: the terms of the sonar equation are normally distributed (in dB) and the RD term is derived from a probability of detection versus SNR relationship which is represented by a straight line on normal probability paper.
Rise–fall time effects on the brainstem auditory evoked response: Mechanisms
Authors: Hecox Kurt , Deegan Don
Published: October 2005

Experiments were conducted to assess the contribution of place mechanisms to the effect of rise–fall time on wave V of the human brainstem auditory evoked response (BAER). Noise bursts of 4- and 10-ms duration were presented at various rise–fall times (0, 1, 2, and 5 ms). Subtractive high-pass masking techniques were used to determine the effect of rise time as a function of derived-band frequency. In general, increasing rise time prolonged wave V latency but did not affect amplitude. Rise-time effects did not depend on derived-band frequency and similar effects were seen in the unmasked conditions. In addition, narrowing the derived band did not alter the observed effects on latency and amplitude. Signal envelope showed no effects on traveling wave velocity. These results suggest that place mechanisms contribute little to changes in the BAER associated with rise–fall time.
A general equation describing frequency discrimination as a function of frequency and sensation level
Authors: Nelson David A. , Stanton Mary E. , Freyman Richard L.
Published: October 2005

Frequency-discrimination thresholds, for a wide range of stimulus frequencies and stimulus levels, were obtained from three normal-hearing listeners. Linear regression analyses of the present data, and of data from two previous studies, indicate that an SL−1 transformation of stimulus level and a (F)1/2 transformation of stimulus frequency yield linear dimensions that allow accurate predictions of frequency-discrimination thresholds from normal-hearing listeners over a wide range of stimulus frequencies (125–8000 Hz) and stimulus levels (5–80 dB SL) with a single prediction equation.
A new higher order dynamic theory for thermoelastic bars. II: Application to thermoelastic circular and rectangular bars
Authors: Akkaş Nuri , Mengi Yalçin
Published: October 2005

In order to show and illustrate the power of the theory proposed in Part I [J. Acoust. Soc. Am. 73, 1918–1922 (1983)] for the dynamic behavior of thermoelastic bars, the theory is applied to bars with circular and rectangular cross sections. In these applications, the order of the theory m is chosen to be 3. The general equations of the approximate theory governing all of the deformation modes (such as longitudinal, flexural, torsional, etc.) of circular and rectangular bars, and accomodating the thermal effects are presented. With the object of assessing the approximate theory, approximate and exact dispersion curves are compared for the flexural and longitudinal waves propagating in circular bars. A good match between these two is obtained without using any correction factors in the approximate theory. Further, experimental wave profiles are compared for longitudinal waves in rectangular bars. It is observed that the two agree quite well.
Linearity of fisheries acoustics, with addition theorems
Authors: Foote Kenneth G.
Published: October 2005

An experiment to verify the basic linearity of fisheries acoustics is described. Herring (Clupea harengus L.) was the subject fish. Acoustic measurements consisted of the echo energy from aggregations of encaged but otherwise free-swimming fish, and the target strength functions of similar, anesthetized specimens. Periodic photographic observation of the encaged fish allowed characterization of their behavior through associated spatial and orientation distributions. The fish biology and hydrography were also measured. Computations of the echo energy from encaged aggregations, derived by exercising the linear theory with the target strength functions of anesthetized fish and gross behavioral characteristics of encaged fish, agreed well with observation. This success was obtained for each of four independent echo sounders operating at frequencies from 38 to 120 kHz and at power levels from 35 W to nearly 1 kW. In addition to demonstrating the basic linearity of fisheries acoustics, the experiment verified both conventional acoustic measurements on anesthetized fish, at least for averaging purposes, and the echo integration method. Two simple theorems summarizing the meaning of linearity for use with the echo integration method are stated.
Influence of physiological noise and the occlusion effect on the measurement of real-ear attenuation at threshold
Authors: Berger E. H. , Kerivan J. E.
Published: October 2005

The most commonly alleged experimental artifact associated with real-ear attenuation at threshold (REAT) measurements of hearing protection devices (HPDs) was examined: Masking of the protected thresholds due to physiological noise amplified by the occlusion effect. An ear canal mounted subminiature microphone was used to obtain objective measures of physiological noise in occluded and unoccluded test conditions and of the insertion loss (IL) of insert, semi-aural, supra-aural, and circumaural HPDs when exposed to broadband noise with a sound pressure level of 93 dB. Measurements spanned 1/3 octave bands from 125 Hz to 2 kHz. Attenuation was also measured via a subjective REAT procedure and the magnitude of the occlusion effect was examined via bone conduction audiometry. The IL data confirmed the accuracy of the REAT results except at the lowest frequencies tested, where the degree to which the REAT values were spuriously inflated was quantified and found to be device related. Furthermore, the magnitude of the error (which never exceeded 5 dB) could be predicted by measuring the physiological noise in the occluded ear and calculating how much this would mask the occluded threshold. It was noted that no evidence was found in the data to suggest a dependency of HPD attenuation on sound level.
Antiplane strain harmonic waves in infinite, elastic, periodically triple-layered media
Authors: Karim-Panahi K.
Published: October 2005

Propagation of horizontally polarized shear waves in periodically triple-layered, elastic medium is studied by using Floquet’s theorem. The dispersion relation is characterized. The propagation and attenuation of harmonic waves inside and outside the Brillouin zones are identified. Variation of the spectrum following the modification of the comparative mechanical properties of the three layers is also examined.
Wave propagation in strongly curved ducts
Authors: Keefe Douglas H. , Benade Arthur H.
Published: October 2005

A theoretical and experimental investigation has been made of wave propagation in the long-wavelength limit in curved ducts of both rectangular and circular cross section. The two-dimensional solution of the wave equation for propagation in curved rectangular bends is adapted for the case of a circular cross section. The wave admittance and phase velocity are computed in terms of integrals over the cross section of the duct, in which there is a radial variation in flow. Experiments to measure the wave admittance and phase velocity are carried out with semicircular segments from a baritone horn musical instrument tuning slide. Three air column arrangements are used; the curved duct assembly is placed in the center of the air column between segments of straight tubing, or antisymmetrically placed near the open or closed ends of the air column. The first-mode resonance frequencies of the air column are measured, and the frequency shifts relative to a straight duct are used to compute the wave-admittance and phase-velocity shifts in the curved duct assembly. For a toroidal duct with a radius of curvature of 12.7 mm and whose circular cross section has a radius of 9.25 mm, the measured increase in the wave admittance is 6.3% and in the phase velocity is 4.7% relative to their straight duct values. Dissipationless theory predicts equal shifts of 8.9%. The viscous energy losses within the interior of the curved duct due to shear are computed, and these losses are not negligible relative to the wall loss. The presence of the additional shearing losses lessen the admittance and phase velocity shifts by equal amounts. The observed inequality between the wave-admittance and phase-velocity shifts thus remains unaccounted for.
A coupled mode solution for acoustic propagation in a waveguide with stepwise depth variations of a penetrable bottom
Authors: Evans R. B.
Published: October 2005

A coupled mode solution is formulated for the problem of acoustic propagation in a cylindrically symmetric ocean divided, in range, into a finite number of adjoining Pekeris waveguides of differing water depths. Attenuation is included in the bottom and the problem is discretized by assigning a pressure release boundary condition at a depth which is sufficiently far removed to prevent significant energy from returning to the water. This formulation includes backscatter from the depth variations of the water column and full coupling between a finite number of modes propagating in the water column and in the bottom. Numerical results based on an implementation of this solution are presented.
Stimulus characteristics and relative ear advantages: A new look at old data
Authors: Lauter Judith L.
Published: October 2005

A recent report of a series of dichotic listening experiments [Lauter, J. Acoust. Soc. Am. 71, 701–707 (1982)] showed that although individual listeners differ in the ‘‘absolute ear advantage’’ shown for a given sound, there are patterns of ‘‘relative ear advantages’’ that are consistent across listeners. It was suggested that these patterns might provide a means of studying which features of test sounds are important in determining ear advantages. A survey of 12 earlier experiments, including a brief synopsis of procedures, results, and conclusions, followed by reanalysis of individual scores, shows that patterns of relative ear advantages were also present in earlier results, though obscured by an analysis that focused on the average listener. Examination of these patterns and the characteristics of sounds tested reveals a few acoustical features of sounds (e.g., event timing, bandwidth, number of dimensions changing with time) that seem to affect ear differences in a consistent way, from listener to listener and under a variety of experimental procedures. It is suggested that with attention to systematic manipulation of characteristics of test sounds, patterns of relative ear advantages may prove helpful in telling us more about the perception of complex sounds.
Effect of finite ground impedance on the propagation of acoustic pulses
Authors: Raspet Richard , Bass Henry E. , Ezell Jean
Published: October 2005

The propagation of an acoustic transient in the vicinity of a finite impedance ground plane has been numerically simulated. A waveform characteristic of a small explosive charge was selected for analysis. Pulse waveforms and amplitudes were computed for propagation distances from 3 to 3000 m, for microphone heights from 0 to 30 m, and for flow resistances from 10 to 1000 g cm−3 s−1. Typical values of atmospheric variables were assumed. Nonlinear propagation effects, atmospheric refraction, and turbulence were excluded from the analysis. This study indicates that finite ground impedance can significantly affect acoustic pulses from explosives. The need to consider ground effects when relating the results of small-scale explosive tests to larger scale explosions is demonstrated. Finite impedance effects are small (<2 dB) for the pulse shape studied if the numerical distance of the fundamental frequency is less than 0.1. The surface wave term as formulated by Donato [J. Acoust. Soc. Am. 60, 34–39 (1976)] produces significant differences in peak level and sound exposure level for explosive pulses at moderate ranges (up to a 10-dB difference for the waveforms modeled in this study). An experimental design is suggested to determine whether this surface wave exists over natural ground surfaces.
Acoustic high-frequency scattering by elastic cylindrical shells
Authors: Dickey J. W. , Nixon D. A. , D’Archangelo J. M.
Published: October 2005

Acoustical scattering resulting from a high-frequency plane-wave incident upon an infinite aluminum circular cylindrical shell immersed in and filled with water is determined by applying the Sommerfeld–Watson transformation to the classical Rayleigh normal-mode series solution. The resulting contour integrals are computed by both the saddle point method and by summing residues over poles which correspond to the zeros of a 6 ×6 determinant resulting from satisfying the necessary boundary conditions. The Bessel functions and their derivatives which appear in the 6 × 6 determinant are evaluated using asymptotic representations of both the Airy and Debye type depending upon the region of the complex plane. Emphasis is placed on the transitions in the scattering characteristics as the shell goes from a solid cylinder to a thin-walled shell. This dual behavior will be discussed in terms of the number and trajectories of allowed modes of the scatterer, the dispersion curves of various modes, and the contributions of the various modes to the scattered pressure field.
Resonance effects and the ultrasonic effective properties of particulate composites
Authors: Gaunaurd G. C. , Überall H.
Published: October 2005

We present a basic frequency-dependent theory for the effective material properties (moduli, wave speeds, attenuations, ...) of particulate composites. The composite is modeled as an aggregate of solid elastic spheres of many sizes, randomly dispersed throughout an elastic matrix. The method constructs an ‘‘effective medium’’ via a scattering approach valid only at low (i.e., <25%) concentrations of the inclusions, since multiple rescattering effects are neglected. This work generalizes earlier work of ours for fluid inclusions in an elastic matrix. Many earlier results, available in the prior literature, are recovered as particular cases of this approach. We display our predictions in many graphs, and compare them to recent experimental observations for glass spheres in epoxy, with very satisfactory results. This good theoretical/experimental agreement is along the acoustical branches of the dispersion curves, which demonstrates the monopole nature of the resonance scattering process along these branches. The dispersion behavior along the optical branches is dominated by dipole resonances, not accounted for by the present model. The names of acoustical/optical branches, strictly accurate for crystals and other periodic structures, are used here for these random particulate composites, only as the result of a commonly accepted (but misleading) analogy.
Dependence of noise-induced hearing loss upon perilymph magnesium concentration
Authors: Joachims Z. , Babisch W. , Ising H. , Günther T. , Handrock M.
Published: October 2005

Noise-induced hearing loss (NIHL) is significantly greater in rats fed a magnesium-deficient diet than in rats on a magnesium-rich diet. The hearing loss was found to be negatively correlated with the magnesium concentration of the perilymph. It is suggested that also in man, the magnesium concentration in the perilymph may be of importance in determining susceptibility to NIHL.
A method for treating statistically dependent inputs to an OR-ing device
Authors: Struzinski William A.
Published: October 2005

A technique is presented to compute the OR-ing loss for statistically dependent inputs to an OR-ing device. An example is given, and it is concluded that the OR-ing loss decreases with an increase in the correlation coefficient.
Convergence zone positions via ray-mode theory
Authors: Beilis A.
Published: October 2005

Ray-mode theory is used to predict the location of convergence zones. The WKB formulation of ray-mode theory is extended to account for sound speed depth variations that are more rapid than allowed by the WKB approximation. The location of the zones based on these two formulations are compared to numerically calculated values. The agreement between the numerically calculated locations and the locations based on ray-mode theory is good. A range variation of the environment is included into the ray-mode formulation. The range variation is taken slow enough that mode identity is preserved (adiabatic mode theory). This analytical calculation shows how the positions of convergence zones change in a range-dependent environment.
Pressure radiated by an infinite plate driven by distributed loads
Authors: Junger Miguel C.
Published: October 2005

The pressure radiated by an effectively infinite elastic plate is formulated for rectangular and axisymmetric load distributions and for straight and circular line forces. The farfield pressure on the normal to the plate is shown to depend only on the resultant load applied, irrespective of its distribution. For extensive loads, the directivity pattern may display nulls which reduce the mainbeam width below that of the point-excited plate. The location of these nulls is not altered by plate orthotropicity as they are exclusively a function of the load distribution. The load distribution may be adjusted to have a null cancel the coincidence peak at a selected frequency. Power radiated by a point force is greater than for distributed loads or line forces. Finally, the plate acceleration in response to an incident spherical wave is related by the reciprocity principle to the plate’s volume acceleration in response to an arbitrary distributed load.
Gap detection as a function of frequency, bandwidth, and level
Authors: Shailer Michael J. , Moore Brian C. J.
Published: October 2005

The threshold for detection of a temporal gap in a noiseband was measured. A notched noise masker was used to restrict listening to a limited spectral region. Threshold was measured as a function of center frequency, bandwidth, and level. For a signal bandwidth of one-half the center frequency, the gap threshold decreased from 22.5 ms for a center frequency of 0.2 kHz to 3.2 ms at 8.0 kHz: a wideband condition provided an estimate of 2.3 ms, a value in agreement with previously published estimates. Bandwidth manipulation showed that the variation with frequency was not due to changes in absolute bandwidth alone. The effect of changes in level was determined at three frequencies, 0.4, 1.0, and 6.5 kHz, using a signal bandwidth of half the center frequency. At all frequencies gap threshold decreased as the signal spectrum level was raised from 10 to 25 dB, but a further increase to 40 dB showed no additional improvement. At frequencies up to about 1.0 kHz, the variation of gap threshold with frequency matches well the reciprocal of the bandwidth of the auditory filter, as determined from masking experiments using a notched-noise masker. This suggests that the temporal response of the auditory filter may limit gap detection at low frequencies.
Vibrotactile forward masking: Evidence for channel independence
Authors: Gescheider George A. , O’Malley Martin J. , Verrillo Ronald T.
Published: October 2005

Threshold shifts for the detection of vibrotactile test stimuli were determined as a function of the intensity of a masker. A 50-ms sinusoidal test stimulus was applied to the thenar eminence of the hand 25 ms after the termination of a 700-ms sinusoidal masker applied to the same site. The intensity of the masker was varied over a range of 0–44 dB SL. The frequency of the masker was either 15 or 250 Hz and the frequency of the test stimulus was either 15, 25, 100, or 250 Hz. The results support the hypothesis that the detection of vibrotactile stimuli is mediated by at least two receptor systems which do not mask each other.
The transmission of signals by auditory-nerve fiber discharge patterns
Authors: Johnson Don H. , Swami Ananthram
Published: October 2005

Recent developments in the theory of point processes are used to analyze the accuracy by which signals are conveyed by the discharges of single auditory-nerve fibers. It is shown that the only spike trains which can convey a signal without distortion are those well-described by a Poisson process model. Theoretical predictions are made of the distortion present in the transmission of signals by auditory-nerve fiber discharge patterns. Absolute refractory effects are shown to result in more distortion than relative refractory ones. Procedures are developed to compensate for these distortions. The procedures designed to compensate for absolute refractory effects operate on the PST histogram. Computer simulations are used to confirm the theoretical predictions and to assess the accuracy of the compensation techniques.
Representation of stop consonants in the discharge patterns of auditory-nerve fibers
Authors: Miller M. I. , Sachs M. B.
Published: October 2005

The representation of the speech syllables /da/ and /ba/ in populations of auditory-nerve fibers was studied. Post-stimulus-time histograms were computed from 20-ms segments of fiber spike trains occurring in response to the stimulus. Discrete Fourier transforms with a resolution of 50 Hz were computed from each histogram. As a measure of the response of the population of fibers to each harmonic of the 50-Hz resolution frequency of the transform, the magnitude of the response to that frequency was averaged across all fibers whose characteristic frequencies were within one-fourth octave of that harmonic. We have previously called this measure the average localized synchronized rate (ALSR). Response profiles for the 20-ms segments of the stimulus were generated by plotting the ALSR versus frequency. Time-varying spectral features of the /da/ and /ba/ stimuli are well preserved by such profiles. For example, the onset spectrum and formant transitions of the consonant–vowel syllable are well represented. Furthermore, the fine structure in the speech spectrum related to the pitch of the excitation source is maintained in these ALSR plots. Average discharge rate profiles were generated in a manner similar to that for the ALSR; in this case average rate replaces Fourier transform components as response measure. Such average rate profiles can represent the transitions of at least formants two and three. However, such average rate profiles do not represent the steady-state formants or the voice pitch.
An experimental evaluation of the Neyman–Pearson detector
Authors: Woods Joseph , Estes Arthur J.
Published: October 2005

Several aspects of the discrete time Neyman–Pearson detector are investigated using experimental acoustic data. The problem considered is the detection of a known signal in a surface reverberant environment. The Neyman–Pearson detector is formulated with a given noise ensemble, and then employed to detect a known signal in that noise field. The noise background consists of sonar returns obtained by directing the transmitter and receiver array toward the wind driven surface of a freshwater lake. The noise process is assumed Gaussian with a known covariance matrix, which is estimated with an ensemble average over the reverberation events. Data for the known signal consist of a single echo from a Styrofoam sphere recorded with no measurable reverberation present. Signal plus noise returns are created by adding samples of the target return to samples of the reverberation returns at specified signal-to-noise ratios (S/N). The performance of the detector is obtained experimentally and compared to the performance predicted from theoretical considerations based on the Gaussian assumption and the empirical covariance matrix. The performance is investigated as a function of S/N, number of channels, and transmission type. Two types of transmission are employed, a 1.0-ms pulsed continuous wave (cw) signal at a carrier frequency of 80 kHz, and a 1.0-ms pulsed linear frequency modulated (LFM) signal with a 10-kHz sweep centered at 80 kHz. The degradation of the detector’s performance due to simplifying assumptions that have been placed on the noise process is investigated. The Neyman–Pearson detector using the experimental data displays the following improvements in performance over the simple matched filter: 12 dB for the cw data and 9 dB for the LFM data.
Robust detector for narrow-band signals in non-Gaussian noise
Authors: Shin Jung Gil , Kassam Saleem A.
Published: October 2005

For the detection of a bandpass signal with Rayleigh amplitude and uniform phase we first show the degradation in performance of the square-law detector when the in-phase and quadrature noise components have small degrees of non-Gaussian contamination. A robust detector using limiter-squarers instead of square-law characteristics to limit the influence of occasional, large observations is proposed. Specific numerical results illustrate the considerable advantage of the robust structure when small degrees of deviation occur from the nominal Gaussian assumption.
Sound transmission through windows II. Double and triple glazing
Authors: Quirt J. D.
Published: October 2005

Experimental sound transmission loss data for double-glazed windows have been compared with the predictions of several theoretical models. Simple equations that provide a satisfactory empirical fit to the data were found. The transmission loss of double glazing was compared with that of triple glazing; the results are very similar when the combined interpane spacings of the triple window match the spacing of the double glazing. The triple glazing did, however, exhibit consistently higher transmission loss both at frequencies below the mass-air-mass resonance and in the vicinity of the coincidence dip.
Concurrent underwater acoustic wave-front fluctuations at two frequencies
Authors: Broek H. W.
Published: October 2005

An experiment was performed to determine whether or not a relative phase fluctuation between two receivers of a signal transmitted over a long ocean path can be expressed as the angular frequency times a frequency-independent delay fluctuation. Short pulses were transmitted alternately at 400 and 114 Hz every 15 s from a ship-suspended source at 1000-ft depth to a set of seven bottomed receivers at about 4400-ft depth in a slope northwest of Bermuda. Measurements were made at two ranges: 75 and 145 nmi. Relative delays in arrival at each receiver were measured and the data analyzed. It was concluded that delay fluctuation in units of time is independent of frequency.
Green’s function continuation for acoustic propagation in range-dependent environments
Authors: Weinberg Henry
Published: October 2005

The acoustic field in a range-dependent ocean environment is expressed as a surface integral of Green’s functions. Then, if one can find Green’s functions for small domains, the solution can be continued to large domains. Several simplifying approximations are introduced. If we express the known pressure and Green’s functions in raylike expansions, and apply stationary phase, the transverse integration can be eliminated. It is suggested that certain forward derivatives are negligible at typical ranges and frequencies of interest. The principal result of this article considers propagation in a vertical plane through the source. Finally, it is shown that the Green’s function continuation agrees with ray theory in the high-frequency limit. In general, the approach developed here should be accurate and readily evaluated for many problems of practical interest.
Broadband interference patterns in shallow water
Authors: Bachman Richard T. , Kaye G. Thomas
Published: October 2005

Variations in received sound pressure level resulting from the multipath interference of broadband noise in shallow water were reconstructed using a simple ray model which ignores sound propagation through the sea floor. The frequency range was from 200–1200 Hz, and source-to-receiver distance varied between 50 and 1000 m. Qualitative agreement between the reconstructed and measured interference patterns was achieved using 12 ray paths at ranges beyond 200 m and at frequencies above 600 Hz. Evidently, a more comprehensive treatment of subbottom sound propagation, not justified by the environmental data currently available, is required for frequencies below 600 Hz.
On the disturbance produced by an impulsive shearing stress on the surface of a semi-infinite poro-elastic medium
Authors: Pal P. C.
Published: October 2005

The disturbance produced by an impulsive shearing stress in a semi-infinite poro-elastic medium is studied here. Using the Laplace–Fourier transforms the expressions for the solid displacements in the interior as well as on the surface of the semi-infinite medium are obtained. The inversion of the Laplace and Fourier transforms is carried out following Cagniard’s technique modified by Gakenheimer. In the limiting case the results for the classical elastic case are also obtained. Last, the variation with time of the solid displacements after the arrival of shear wave are exhibited graphically and the results for classical case are included for the sake of comparison.
On the Green’s function for acoustical diffraction by a strip
Authors: Gautesen A. K.
Published: October 2005

We assume that the solution to the problem of diffraction by a strip with an impedance boundary condition of a plane-wave incident under a fixed angle φ is known. We show how to construct the Green’s function and the solution for a plane-wave incident under any angle from this known solution; and we also give a simple equation which relates the farfield coefficient for plane-wave incidence under any angle to the known farfield coefficient corresponding to the angle of incidence φ.
Observation of the acoustic glory: High-frequency backscattering from an elastic sphere
Authors: Marston Philip L. , Williams Kevin L. , Hanson Timothy J. B.
Published: October 2005

Measurements of the scattering of 2.10-MHz ultrasonic bursts gave direct evidence of the acoustic glory. Echo amplitudes were measured as a function of the transverse displacement x from the backward axis; they were maximized on the axis and they manifested side lobes. Except near minima, the amplitudes were proportional to J0(kbx/zn), where b and zn are the radius of, and axial distance to, the virtual focal circles from which the echoes appeared to emanate. This dependence on x is direct evidence of axial focusing. (The principal feature of optical glories of drops and bubbles is also axial focusing.) The experiment was performed in water with a fused silica sphere having a radius a≂51.6 mm for which 2πa/λ=ka≂457. A theory is developed for certain of the echo amplitudes and focal parameters. The theory typically overestimates the amplitudes of the stronger of the echoes by 5%. Appendices describe aspects of the theory not amenable to the experiment, including: (i) a shift of focal parameters which should be significant when ka≲100, and (ii) a distortion of transients described in part by the half-order derivative operator.
Acoustic wave scattering by elastic cylindrical shells in water
Authors: Pillai T. A. K. , Varadan V. K. , Varadan V. V. , Radlinski Ronald P.
Published: October 2005

Frequency dependence of acoustic wave scattering by an infinite cylindrical shell of arbitrary cross section is analyzed using the T-matrix approach. Explicit expression for the T matrix of a two-layered cylinder is presented. Numerical results are obtained for plane wave incidence normal to the axis of the shell but arbitrary with respect to the noncircular cross section for a range of frequencies. Backscattering cross sections for various angles of incidence are presented for aluminum, steel, and plastic compliant tubes. The results obtained for circular and elliptical cross sections are compared with other available theoretical and experimental results.
Normalization of ultrasonic scattering measurements to obtain average differential scattering cross sections for tissues
Authors: Campbell James A. , Waag Robert C.
Published: October 2005

An integral expression is derived for the normalization of ultrasonic scattering data to obtain an average differential scattering cross section per unit volume for tissue which is modeled as a random, fluidlike medium. The expression assumes narrowband signals and involves the incident beam, receiver beam pattern, and time gates. The beams and gates combine to form a window which limits the scattering volume. The derivation of the expression requires that the dimensions of the window be large compared to the correlation length of the scattering medium. Numerical values of the normalizing integral are given for cylindrical and beamlimited scattering volumes as a function of incident frequency and scattering angle under the assumptions of Gaussian beams and rectangular time gates. A set of curves is presented to relate the percent difference between the result for backscatter from a cylindrical scattering volume and from a beamlimited scattering volume which does not include the truncation effect of the cylinder boundary. Although similar in form to normalizations used by others, the integral in this paper is obtained from a derivation which treats physical parameters rigorously and provides a precise statement of conditions which are sufficient to obtain system-independent scattering data.
Acoustic admittance of organ pipe jets
Authors: Thwaites S. , Fletcher N. H.
Published: October 2005

The admittance of a turbulent jet as the generator in organ flue pipes was investigated experimentally with respect to the relevant parameters, that is, the frequency, the jet efflux velocity, the mouth end-correction, and the jet tip deflection at the edge. First, an experiment was performed using a jet with a pulsating velocity to drive a pipe to isolate and identify the various drive mechanisms occurring in the jet-pipe interaction. The two established drive mechanisms, momentum drive and volume drive, were found to be operating, but the relative proportion of momentum drive was greater than expected. Turning then to a typical flue pipe arrangement, as a preliminary experiment, the jet admittance in the pipe was shown to be independent of the jet tip deflection so long as the deflection was less than about 0.7 jet widths. This constant admittance regime was then used to facilitate measurement of the pipe excitation as a function of the three remaining parameters. The admittance magnitude and phase were used, in conjunction with a knowledge of the jet behavior, to quantify the relative importance of the two drive mechanisms here, revealing once again a greater proportion of momentum drive than expected. To a good approximation, the admittance magnitude multiplied by the efflux velocity, and the admittance phase were each found to lie on a universal curve when plotted against a parameter consisting of the frequency divided by the efflux velocity, provided the cutup was constant. A deviation from expected behavior, as yet to be explained, was found in the jet admittance and phase for very low frequencies and high blowing pressures.
The relationship between the rms level and the average absolute magnitude of long-time continuous speech
Authors: Niederjohn Russell J. , Haworth Daniel G.
Published: October 2005

The relationship between the average absolute magnitude and the rms level of long-time continuous speech is reported in this paper. The ratio of these two measurements (called β) and the standard deviation of this ratio have been experimentally determined as a function of speech utterance lengths from 2.5 s to 10 min. For utterance lengths greater than about 20 s, the average value of β is approximately 0.55 and 0.60 for male and female speakers, respectively.
Vibration isolation from irregularity in a nearly periodic structure: Theory and measurements
Authors: Hodges C. H. , Woodhouse J.
Published: October 2005

This article describes the theory and a simple experiment carried out to demonstrate the phenomenon of Anderson localization in an acoustical context. This is an effect whereby the propagation of vibration in a structure which is not entirely regular is impeded by the irregularities, giving rise on the average to an exponential decay of vibration level away from the driving point, even in the absence of any dissipation. The structure used in the experiment was a stretched string with masses attached to it. This string was studied with regular spacings of the masses and after the masses had been moved in a controlled way to provide a small degree of irregularity. In both cases, the transmission of energy from end to end of the string was measured as a function of frequency, and also the mode shapes in the second and fourth passbands were measured so as to demonstrate the underlying physics of the localization phenomenon, in which the individual modes making up each passband change from being extended throughout the structure in the regular case to being localized in specific areas of the structure in the presence of irregularity. All measurements yielded satisfactory agreement with the theoretical predictions.
Dynamic specification of coarticulated vowels
Authors: Strange Winifred , Jenkins James J. , Johnson Thomas L.
Published: October 2005

An adequate theory of vowel perception must account for perceptual constancy over variations in the acoustic structure of coarticulated vowels contributed by speakers, speaking rate, and consonantal context. We modified recorded consonant–vowel–consonant syllables electronically to investigate the perceptual efficacy of three types of acoustic information for vowel identification: (1) static spectral ‘‘targets,’’ (2) duration of syllabic nuclei, and (3) formant transitions into and out of the vowel nucleus. Vowels in /b/–vowel–/b/ syllables spoken by one adult male (experiment 1) and by two females and two males (experiment 2) served as the corpus, and seven modified syllable conditions were generated in which different parts of the digitized waveforms of the syllables were deleted and the temporal relationships of the remaining parts were manipulated. Results of identification tests by untrained listeners indicated that dynamic spectral information, contained in initial and final transitions taken together, was sufficient for accurate identification of vowels even when vowel nuclei were attenuated to silence. Furthermore, the dynamic spectral information appeared to be efficacious even when durational parameters specifying intrinsic vowel length were eliminated.
Effect of a single interfering noise or speech source upon the binaural sentence intelligibility of aged persons
Authors: Duquesnoy A. J.
Published: October 2005

The free-field speech-reception threshold (SRT) for sentences was investigated in quiet and under nine conditions involving noise or competing speech for a group of 20 elderly subjects (ten male, age 75–85; ten female, age 76–88) and a reference group of ten young normal-hearing subjects. The noise source had the same long-term average spectrum as the competing speech. The interfering signals were presented at a constant level of 55 dBA. All elderly subjects had moderate, nearly symmetrical pure-tone hearing losses with an average loss at 500, 1000, and 2000 Hz of between 9 and 40 dB re: ISO-389. The main results are (1) the SRT values in noise and competing speech are about equal, whereas the normal-hearing subjects showed a lower SRT (7 dB lower for the condition that both sound sources are in front) in competing speech than in noise; apparently, the elderly subjects do not benefit from the relatively silent periods in competing speech; (2) the gain obtained by moving the interfering noise source from the front to the lateral position is only 2.5 dB, in contrast to a gain of 9.6 dB for the young subjects; apparently, the elderly are unable to make full use of the spatial divergence between primary speaker and noise source.
Suggested formulae for calculating auditory-filter bandwidths and excitation patterns
Authors: Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

Recent estimates of auditory-filter shape are used to derive a simple formula relating the equivalent rectangular bandwidth (ERB) of the auditory filter to center frequency. The value of the auditory-filter bandwidth continues to decrease as center frequency decreases below 500 Hz. A formula is also given relating ERB-rate to frequency. Finally, a method is described for calculating excitation patterns from filter shapes.
Broadband masking noise and behavioral pure tone thresholds in cats
Authors: Costalupes John A.
Published: October 2005

The threshold for detection of pure tones in broadband noise was determined for three cats using an auditory reaction time procedure. Critical ratio is defined as the ratio of the signal power at the masked threshold for detection to the spectrum level of the noise. Critical ratios were obtained for 250-, 500-Hz, and 1-, 2-, 4-, 8-, and 16-kHz tones over a wide range of noise intensities. Results indicate that critical ratios increase with the frequency of the tone stimulus. At frequencies below 4 kHz, critical ratios remain constant at moderate and high noise intensities. For frequencies above 4 kHz, critical ratios increase as the level of the masking noise is raised from moderate to high levels. The difference between low- and high-frequency behavior of the level dependence of critical ratios is considered in terms of two possible mechanisms: (1) different mechanisms may be involved in the encoding of low- and high-frequency information by the nervous system or (2) the difference in level dependence may be due to attenuation by the action of the middle ear muscles at high sound levels.