bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in mechanoreceptor-specific vibrotactile thresholds with ongoing occupational exposure to hand-transmitted vibration
Authors: Brammer A. J. , Piercy J. E. , Nohara S. , Nakamura H.
Published: October 2005

The purpose of this paper is to explore the influence of occupational exposure to hand-transmitted vibration on mechanoreceptor acuity, for possible future use as a screening test for early symptoms of the hand–arm vibration syndrome (HAVS). Mechanoreceptor-specific vibrotactile thresholds were determined using the tactometer at frequencies mediated by the SAI receptors (4 Hz), FAI receptors (32 Hz), and FAII receptors (100 Hz) [A. J. Brammer and J. E. Piercy, ‘‘Measuring vibrotactile perception thresholds at the fingertips of power-tool operators,’’ Proc. U.K. Informal Group Meeting on Human Response to Vibration, Buxton (1991)]. Thresholds were obtained from 33 seasonal operators of chain saws and brush cutters, who had so worked for up to 39 years. Twenty-three of the workers were judged clinically to suffer from mild to moderate symptoms of HAVS. A progressive reduction in acuity with increasing years of exposure was observed, on average, in this group, for each mechanoreceptor population. A reduction in acuity remained even after correcting for changes in threshold with age.
Comments on ‘‘The variation of the specific heat ratio and the speed of sound in air with temperature, pressure, humidity, and CO2 concentration’’ [J. Acoust. Soc. Am. 93, 2510–2516 (1993)]
Authors: Wong George S. K.
Published: October 2005

In the subject paper, Cramer calculated the sound speed in air at 273.15 K and 101.325 kPa based on parameters such as the ideal gas specific heat at constant pressure and the second virial coefficients of the constituents of air. Cramer underestimated the uncertainties of the above parameters and arrived at several misleading conclusions. The uncertainties in Cramer’s calculation are re-assessed and confirm that the sound speed c0=331.29 m s−1 is within the range of estimated uncertainties.
On general properties of ray arrival sequences in oceanic acoustic waveguides
Authors: Virovlyansky Anatoly L.
Published: October 2005

Some properties of ray arrival sequences valid in a waveguide with an arbitrary sound-speed profile are ascertained using the simple approximate formula connecting differences in ray travel times and adiabatic invariants of their trajectories. It is noted that the following conservation law takes place: The mean difference in travel times of rays having their launch angles inside the fixed narrow angular interval does not depend upon the distance between the source and the receiver. This law holds true not only in the range-independent waveguide but in the adiabatically varying waveguide as well. Some general conclusions concerning the relationship between travel times and launch angles of rays reaching the receiver are made.
Comments on ‘‘The hydroacoustics of a raindrop impact’’ [J. Acoust. Soc. Am. 92, 1017–1021 (1992)]
Authors: Pumphrey Hugh C.
Published: October 2005

A recent paper [J. A. Nystuen, L. H. Ostwald, and H. Medwin, ‘‘The Hydroacoustics of a raindrop impact,’’ J. Acoust. Soc. Am. 92, 1017–1021 (1992)] describes the pressure pulse measured by placing a hydrophone in the water below an impacting raindrop. The form of the pulse as measured at a range of about 0.1 m is undoubtedly correct, consisting of a spike of about 60 μs in width followed by a ‘‘plateau,’’ which remains approximately constant over a time scale of about half a millisecond. Nystuen et al. interpret the spike as the near-field acoustic pressure, i.e., the term that reduces to a solution of Laplace’s equation as the sound speed tends to infinity. They infer that the far-field pressure will be its time derivative, a single-cycle pulse. The plateau they describe as being quite unconnected with the acoustic field. The purpose of this Letter is to point out that this is not the only possible interpretation. The alternative is that the plateau is the near-field pulse and that the spike is the far-field pulse, being proportional to the time derivative of the plateau.
An alternative approach for solving attenuated leaky Rayleigh waves
Authors: Wu Junru , Zhu Zhemin
Published: October 2005

The dispersion equation for leaky Rayleigh waves including viscosity and neglecting thermal conduction has been derived using the viscous boundary-layer concept. It has been shown that the effect due to thermal conduction is usually negligible compared with that from viscosity.
Floquet waves and classical plane waves in an anisotropic periodically multilayered medium: Application to the validity domain of homogenization
Authors: Potel Catherine , de Belleval Jean-François , Gargouri Yacine
Published: October 2005

The aim of this paper is to better understand the correspondence between classical plane waves propagating in each layer of an anisotropic periodically multilayered medium and Floquet waves. The last are linear combinations of the classical plane waves. Their wave number is obtained from the eigenvalues of the transfer matrix of one cell of the medium. A Floquet polarization which varies with its position in the periodically multilayered medium has been defined. This allows one to define a Floquet wave displacement by analogy with the displacement of classical plane waves, and to check the equality of the two displacements at any interface separating two layers. The periodically multilayered medium is then an equivalent material, considered as homogeneous, and one can draw dispersion curves and slowness surfaces which are dispersive. In the low-frequency range, when the relation between the Floquet wave numbers and the frequency is linear, the multilayered medium can be homogenized; the Floquet polarization at different interfaces tends to a limit which is the polarization of the classical plane wave in the homogenized medium.
Ultrasonic probe modeling and nondestructive crack detection
Authors: Boström A. , Wirdelius H.
Published: October 2005

The mathematical modeling of a typical situation in ultrasonic nondestructive testing for defects is considered. The first objective is the modeling of a reasonably general type of ultrasonic probe. This is performed by prescribing the traction vector on the surface of an elastic half-space. The effective probe area may be rectangular or elliptic and the traction may or may not include the tangential part (glued or fluid-coupled probe, respectively). The probe can be of P, SV, or SH type and of any angle. The traction is either constant across the probe (piston-type source) or it may taper off toward the edges. Numerical results for some representative cases are given showing snapshots of the field beneath the probe. The second objective of the paper is to include the presented probe model into a complete model of the ultrasonic testing situation. To this end the probe field is, via a series of transformations, expressed in spherical vector waves centered at the defect. The influence of the defect is given by its transition matrix. To model the electric signal obtained from the receiving probe, a reciprocity argument is used, giving this signal essentially as a product of the spherical expansion coefficients of the transmitting probe, the transition matrix of the defect, and the spherical expansion coefficients of the receiving probe. For a defect that is a penny-shaped crack or a spherical cavity some numerical examples are given showing the received signal as a function of position on the scanning surface.
Modeling of induced strain actuation of shell structures
Authors: Chaudhry Zaffir , Lalande Frederic , Rogers Craig A.
Published: October 2005

Based on the thin-shell Donnell theory, a model to represent the action of discrete induced strain actuator patches symmetrically bonded to the surface of a circular cylindrical shell has been developed. The model provides estimates of the bending curvatures due to the out-of-phase actuation and the in-plane strains due to the in-phase actuation of the bonded actuator patches. The magnitudes of the induced curvature and the in-plane strain are found to be identical to those of plates; however, due to the strain-displacement relations in cylindrical coordinates, the in-plane and out-of-plane displacements are coupled. Expressions for the equivalent forces and moments that represent the action of the actuator patches have been developed. Due to the curvature of the shell, the representation of the in-phase actuation with an equivalent in-plane line force applied along the edge of the actuator results in the application of erroneous rigid-body transverse forces. To avoid these rigid body forces, a method to represent the in-phase actuation with a system of self-equilibrating forces is proposed. The action of the actuator is then represented by an equivalent in-plane force and a transverse distributed pressure applied in the region of the actuator patch. Finite element verification of the proposed model is presented. The displacements due to the actual actuator actuation are compared with the proposed model, and very good agreement is found.
Feedforward control using the higher-harmonic, time-averaged gradient descent algorithm
Authors: Kewley Dorene L. , Clark Robert L. , Southward Stephen C.
Published: October 2005

A unique approach to adaptive feedforward control, namely the higher-harmonic time-averaged gradient descent algorithm (H-TAG), is presented. As opposed to the more common adaptive feedforward control method based on the filtered-x LMS algorithm, H-TAG does not require a measure of the control to error sensor transfer function for the system. Thus if the system dynamics change during the control process, H-TAG will simply adapt to the new optimal control configuration, rendering the approach model insensitive. Until now, work presented on the H-TAG algorithm has been limited to a single-input, single-output theoretical simulation. This paper describes the additional considerations involved in implementing the algorithm on an actual complex laboratory model (a de Havilland Dash 7 turbo-prop fuselage) that has multiple inputs and multiple outputs. Results from this preliminary experimental study suggest that the H-TAG algorithm is a viable alternative for adaptive feedforward control of systems with slowly time-varying parameters.
A regression approach for simulating feedforward active noise control
Authors: Ruckman Christopher E. , Fuller Chris R.
Published: October 2005

Regression analysis is used to examine feedforward active noise control from a statistical point of view. Since numerical techniques for simulating feedforward active noise control in the frequency domain are mathematically similar to linear least-squares regression, two regression-based numerical methods can be applied to control problems. The first uses regression diagnostics such as the F-test, the t-test, and confidence intervals to model the effects of error sensor measurement noise. The second uses collinearity diagnostics to address a form of numerical ill conditioning that can corrupt the results. The regression diagnostics allow realistic modeling of random measurement error; the collinearity diagnostics help avoid numerical difficulties that might otherwise go undetected. Numerical results are given for a structural-acoustic control problem involving a fluid-loaded cylindrical shell.
Statistical errors in the estimation of the magnitude and direction of the complex acoustic intensity vector
Authors: Loyau Thierry , Pascal Jean-Claude
Published: October 2005

The statistical error in the estimation of one of the directional components in the complex acoustic intensity vector has already been studied. However, in order to completely determine the intensity vector using a six-microphone sound intensity probe, the statistical error in both its magnitude and angle of orientation must be known. The expressions found for these errors require that the covariance between the different orthogonal components be evaluated. Formulations are obtained for both the active and reactive intensity, and these are valid for spectral densities or for a frequency band. The behavior of the statistical error is studied here in two dimensions in different types of analytically defined fields. In addition to the difference in pressure and intensity levels, it is also shown that uncertainties in the modulus are related to the coherence between the pressure in the direction of the resultant vector and that the errors in the angle of orientation are a function of the coherence of the pressure in the perpendicular direction. Furthermore, the low-frequency influence of random electronic noise in the circuits of the microphone apparatus is demonstrated. The use of the different formulations for the prediction of statistical errors is discussed.
High-resolution sonar volume scattering measurements in marine sediments
Authors: LeBlanc Lester R. , Schock Steven G. , DeBruin Darryl L. , Jenkins Michael , Munro Lachlan
Published: October 2005

This paper develops a simple volume scattering model for use with high-resolution sonar measurements. A model of volume scattering for sediments is used to analyze data from the Canadian Hy-Gro experiment. Measurements made at four sites are used in a comparison of acoustic volume scattering coefficient with core data. The volume scattering coefficient is a relative measure of the scattering strength of a cubic meter of sediment. Scattering measurements in a sediment depth interval of 0–2 m revealed two separate scattering probability density functions. Volume scattering is characterized by an exponential density function and was found to originate from incoherent scatterers in a 0.5- to 2-m depth interval. In the 0- to 0.5-m depth interval, signals were reflected from the seafloor boundary and the density function corresponded to a Rayleigh density function. In comparing the estimated sediment scattering coefficient to sediment properties, in general, sediments with large grain components produced larger volume scattering coefficients. Sediment volume scattering measurements, when combined with other clues such as sediment attenuation and impedance profiles, are potentially very useful in classifying seafloor sediments. Moreover, sub-bottom volume scattering measurements, when combined with sidescan surface scattering measurements, will be very useful in extrapolating seafloor sediments predictions over very large areas.
Optimum two-dimensional beamforming employing sum-and-difference technique
Authors: Lee Ta-Sung , Lin Tsui-Tsai
Published: October 2005

A 2-D adaptive beamforming scheme using a quadruplet array is presented. The scheme is developed based on the sum-and-difference technique employed in conventional monopulse trackers. The construction of the proposed beamformer involves a joint linearly constrained minimum variance procedure on the sum-and-difference processors. With the difference beam used as an auxiliary to suppress the desired signal, the resulting sum beam exhibits robustness to pointing errors in acquiring the desired signal. To maintain an accurate look direction, a simple method for desired source localization is developed using beamspace MUSIC. The proposed beamformer working in conjunction with the angle estimator provides a much better solution to 2-D beamforming than the MVDR beamformer, as confirmed by analysis results and numerical examples.
Direction of arrival estimation in the presence of distributed noise sources: Cumulant based approach
Authors: Naidu Prabhakar S. , Subramaniyan Raghavan
Published: October 2005

In the past few years there have been attempts to develop subspace methods for DoA (direction of arrival) estimation using a fourth-order cumulant which is known to de-emphasize Gaussian background noise. To gauge the relative performance of the cumulant MUSIC (MUltiple SIgnal Classification) (c-MUSIC) and the standard MUSIC, based on the covariance function, an extensive numerical study has been carried out, where a narrow-band signal source has been considered and Gaussian noise sources, which produce a spatially correlated background noise, have been distributed. These simulations indicate that, even though the cumulant approach is capable of de-emphasizing the Gaussian noise, both bias and variance of the DoA estimates are higher than those for MUSIC. To achieve comparable results the cumulant approach requires much larger data, three to ten times that for MUSIC, depending upon the number of sources and how close they are. This is attributed to the fact that in the estimation of the cumulant, an average of a product of four random variables is needed to make an evaluation. Therefore, compared to those in the evaluation of the covariance function, there are more cross terms which do not go to zero unless the data length is very large. It is felt that these cross terms contribute to the large bias and variance observed in c-MUSIC. However, the ability to de-emphasize Gaussian noise, white or colored, is of great significance since the standard MUSIC fails when there is colored background noise. Through simulation it is shown that c-MUSIC does yield good results, but only at the cost of more data.
A linear reconstructive approach to super-resolution array processing
Authors: Willis A. J. , De Mello Koch R.
Published: October 2005

The problem of target characterization by phased array sonar is approached as one of spectral estimation of a bandlimited function from a finite number of arbitrarily located samples. A unique solution is extracted from the resultant underdetermined system by application of singular value decomposition (SVD) techniques to derive a minimum norm, or best least-squares estimator of the spatial spectrum. The process of a single matrix decomposition is employed to derive a general basis set spanning the signal space, dependent only on the sensor locations. This can be used to reconstruct arbitrary target profiles two orders of magnitude faster than standard high-resolution methods but with significantly better resolution than a beamformer. Since only a single snapshot is used, coherency in the source is not problematic. Through a suitable regularization scheme the algorithm works well under conditions of unknown correlated noise, and produces super-resolution of features through flexible introduction of a priori knowledge in the localization and/or shape of the target.
Long-term effect of acoustic trauma on distortion product otoacoustic emissions in chickens
Authors: Froymovich Oleg , Rebala Vikram , Salvi Richard J. , Rassael Hadi
Published: October 2005

Distortion product otoacoustic emissions (DPOAE), 2F1−F2, were measured in chickens before and after exposure to a 1.5-kHz pure tone presented at 120-dB sound-pressure level for 48 h. The low-level component of the DPOAE input/output function was shifted to the right at all frequencies immediately after the exposure with the greatest effect occurring at and above the exposure frequency. The slope of the high-level component of the input/output also increased significantly for test frequencies close to and above the exposure frequency so that the amplitude of the DPOAE was equal to or greater than normal at high stimulus levels. DPOAE obtained at the highest and lowest frequencies were almost normal after 8 weeks of recovery; however, the input/output functions near the exposure frequency showed almost no improvement over the 8-week recovery period. The lack of recovery could conceivably be due to residual damage to hair cells that survived the exposure or to incomplete regeneration of the tectorial membrane.
Phonation threshold pressure in a physical model of the vocal fold mucosa
Authors: Titze Ingo R. , Schmidt Sheila S. , Titze Michael R.
Published: October 2005

The vocal fold mucosa, which consists of the epithelium and the superficial layer of the lamina propria, has been modeled by a fluid encapsulated in a silicone membrane. The artificial mucosa was attached to a rigid (metal) vocal fold body and introduced into an airflow channel, creating a rectangular glottis. Flow-induced oscillation of the mucosa was achieved at various subglottal pressures and glottal diameters. Phonation threshold pressure, the parameter of interest, was lowest (on the order of 0.4 kPa) for glottal diameters between 0.0 and 0.1 mm and for fluids with the lowest viscosity. There was a consistent hysteresis effect; that is, phonation threshold pressure was always lower for oscillation offset than onset.
Physiological modeling of speech production: Methods for modeling soft-tissue articulators
Authors: Wilhelms-Tricarico Reiner
Published: October 2005

As the initial components of a comprehensive physiological model of speech production, methods have been developed for modeling soft tissue structures, such as the tongue and lips, as continua. This approach provides a foundation for applying finite element methods to simulate these structures in a biomechanical model of speech production. Movements and deformations of the structures can then be computed as the solutions of a nonlinear second-order constraint system of ordinary differential equations, which is obtained from a finite element approximation of an energy rate equation. The muscle fibers in the soft tissue structures are represented as fields that specify the directions in which active and passive tensile stress is produced. The elastic behavior of the passive components is modeled using an isotropic exponential constitutive strain energy function, and the viscous stress components, by using linear viscosity. Incompressibility is maintained elementwise in the simulation using a simultaneously solved system for the computation of Lagrange multipliers. As first step towards modeling a vocal tract, a preliminary model of a tongue with eight muscles has been completed. Simulation results demonstrate the validity of the method and they support the feasibility of a physiologically based model of speech production.
Acoustic characteristics of American English vowels
Authors: Hillenbrand James , Getty Laura A. , Clark Michael J. , Wheeler Kimberlee
Published: October 2005

The purpose of this study was to replicate and extend the classic study of vowel acoustics by Peterson and Barney (PB) [J. Acoust. Soc. Am. 24, 175–184 (1952)]. Recordings were made of 45 men, 48 women, and 46 children producing the vowels /i,i,e,ε,æ,a,open‘‘oh’’,o,u,u,Λ,hook backward‘‘eh’’/ in h–V–d syllables. Formant contours for F1–F4 were measured from LPC spectra using a custom interactive editing tool. For comparison with the PB data, formant patterns were sampled at a time that was judged by visual inspection to be maximally steady. Analysis of the formant data shows numerous differences between the present data and those of PB, both in terms of average frequencies of F1 and F2, and the degree of overlap among adjacent vowels. As with the original study, listening tests showed that the signals were nearly always identified as the vowel intended by the talker. Discriminant analysis showed that the vowels were more poorly separated than the PB data based on a static sample of the formant pattern. However, the vowels can be separated with a high degree of accuracy if duration and spectral change information is included.
Absence of effect of coherent frequency modulation on grouping a mistuned harmonic with a vowel
Authors: Darwin C. J. , Sandell Gregory J.
Published: October 2005

When a single harmonic close to the first formant frequency is mistuned by about 8%, that harmonic makes a reduced contribution to the vowel’s first formant frequency as measured by a shift in the phoneme boundary along an F1 continuum between /i/ and /ε/ [C. J. Darwin and R. B Gardner, J. Acoust. Soc. Am. 79, 838–45 (1986)]. In the present experiments, phoneme boundaries along an /eh/–/ε/ continuum were measured for vowels differing in F1 whose fourth harmonic (500 Hz) was mistuned by 0, ±3, ±6, or ±9%. All the harmonics of a vowel (including the mistuned one) were given either no FM or coherent FM at a rate of 6 Hz and modulation depth of ±5%. The results replicated the previous findings, but found no evidence for coherent FM preventing the segregation of the mistuned harmonic from the vowel.
Active noise cancellation by using the linear quadratic Gaussian independent modal space control
Authors: Bai Mingsian R. , Shieh Chifong
Published: October 2005

The objective of this study is to develop an active noise controller based on optimal control approaches for enclosed Gaussian noise fields. By independent modal space control, the individual mode in the acoustic field is suppressed by the corresponding modal control exerted by loudspeakers. The formulation of the modal controller is considerably simplified because modal coupling is neglected. For the Gaussian noises considered in this study, the linear quadratic Gaussian algorithm in conjunction with the Kalman–Bucy filter is employed to perform state feedback and estimation. The developed controller is validated by simulations for a duct and a rectangular room. The results indicate that the technique will yield significant noise reduction if one uses the same number of controlled modes, microphones, and loudspeakers. Satisfactory performance is possible if one carefully avoids placing microphones and loudspeakers at the nodal points.
Measurement and interpretation of the impulse response for backscattering by a thin spherical shell using a broad-bandwidth source that is nearly acoustically transparent
Authors: Kaduchak Gregory , Kwiatkowski Christopher S. , Marston Philip L.
Published: October 2005

A novel source was developed to produce a plane-wave unipolar pressure impulse with a wide range of frequency components. The source consisted of a PVDF sheet with water in contact with both sides. The PVDF was driven by a step voltage. This source is nearly acoustically transparent and was used for backscattering from an empty stainless-steel spherical shell. The shell was placed in the near field of the source where it experienced a plane-wave pressure impulse followed much later by edge contributions resulting from the finite source size. A hydrophone was placed in the far field of the scatterer on the opposite side of the source. Prominent features in the shell’s calculated impulse response are observed over a wide frequency interval. Time records reveal an approximately Gaussian wave packet from the excitation of the subsonic a0− wave associated with the backscattering enhancement near the coincidence frequency (≊309 kHz). Superposed on the same records are large contributions from the low-frequency excitation of the a0− wave and from the s0 wave. A bipolar feature of the initial response was found to be associated with the finite inertia of the shell and the null frequency. An approximate theory predicts that the associated relaxation time depends on the mass per area of the shell and the density and sound speed of the surrounding water. The shell used in the experiment has a thickness to radius ratio of 2.3% and the scattering phenomena of interest occur between 8 and 450 kHz corresponding to ka from approximately 1 to 70. The 10-kHz ringing of the target associated with the a0− wave is quite pronounced.
Sound radiation from two semi-infinite dissimilar plates subject to a harmonic line force excitation in mean flow. II. Asymptotics and numerical results
Authors: Zhu Jinshuo , Wu Sean F.
Published: October 2005

Asymptotic formulations are derived for describing far-field acoustic radiation from two semi-infinite dissimilar plates subject to an harmonic line force excitation at the joint in the presence of mean flow. Analysis shows that mean flow affects the acoustic pressure in three ways: (1) It enhances the wave number and amplitude of an acoustic wave propagating in the upstream direction, while it suppresses those of an acoustic wave propagating in the downstream direction; (2) it reduces the decay rate of the upstream propagating wave, while it increases that of the downstream propagating wave as they propagate in the plate normal direction; and (3) it rotates the radiation beam angles toward the downstream direction. The effects of mean flow are obvious when the excitation frequency is above the plate coincidence frequency, but decays significantly at low frequencies. The condition at the joint of two plates does not change the characteristics of the radiation pattern, but merely the amplitude of the radiated acoustic pressure. The looser the joint, for example, two plates being mechanically unconnected, the higher the amplitude of the resulting acoustic pressure.
Improved method for the measurement of acoustic properties of a sound absorbent sample in the standing wave tube
Authors: Cheung Wan-Sup , Jho Moon-Jae , Kim Yang-Hann
Published: October 2005

This paper introduces a novel way of reconstructing the one-dimensional acoustic field in the tube from multiple pressure measurements. It presents a detailed derivation for estimating the best fitted, in a least-squares sense, incident and reflected wave components at the sample surface. This attempt reveals that their estimation is no longer independent of the number of pressure data and their measurement positions. The best condition for selecting these two experimental factors is proposed for a finite number of microphone positions. The singular condition and spatial aliasing are shown to arise from their inadequate choice in space and their protection schemes are also presented. These results lead to the logical ways of improving the accuracy of experimentally assessed acoustic properties. Furthermore, the proposed estimation method of the wave components allows the experimental reconstruction of the pressure pattern existing in the tube from measurement. It also presents the clear understanding of acoustic field itself existing in the tube. Experimental results are illustrated to make these points clear.
Acoustic streaming induced in focused Gaussian beams
Authors: Kamakura Tomoo , Matsuda Kazuhisa , Kumamoto Yoshiro , Breazeale Mack A.
Published: October 2005

Axisymmetric flow equations for a viscous incompressible fluid are transformed into the vorticity transport and Poisson’s equations. They are numerically solved via a finite difference method imposing appropriate initial and boundary conditions. A model source of 1-cm radius and 5-cm focal length with Gaussian amplitude distribution radiates 5-MHz ultrasound beams in water. Numerical examples are shown for buildup of acoustic streaming along and across the acoustic axis. Evidently, hydrodynamic nonlinearity has an essential effect on the streaming generation in comparison with a linear flow case; the nonlinearity reduces the streaming velocity in the focal and prefocal region, whereas it tends to accelerate the flow in the postfocal region.
On resonant features of supersonic jets at off-design flow regimes
Authors: Pimshtein Valerii G.
Published: October 2005

Acoustic excitation of supersonic jets emitting a discrete tone at off-design flow regimes is considered. It has been shown that in the case of action by sufficiently high-intensity sound on the jet, Powell’s mechanism of discrete tone emission is broken down and there arises some other mechanism of discrete tone emission. This mechanism is related to sound radiation by disturbances moving with supersonic convection velocity along the irradiated jet boundary. At a definite value of the external sound-pressure level that depends on the total pressure in the jet, both these mechanisms of sound radiation can exist simultaneously. Supersonic jets at off-design flow regimes have no resonant features due to external acoustic excitation.
Use of temporal envelope cues in speech recognition by normal and hearing-impaired listeners
Authors: Turner C. W. , Souza P. E. , Forget L. N.
Published: October 2005

The temporal acuity of listeners with sensorineural hearing loss is currently a matter of some controversy. In this study, the ability of normal-hearing and hearing-impaired listeners to utilize temporal cues of speech was measured directly. In addition to natural (unprocessed) nonsense syllables, several processed-speech conditions were employed. Nonsense syllables were digitally processed to remove the original spectral information, resulting in a time-varying speech envelope amplitude modulating a noise carrier. The processed-speech conditions were the envelope of a broadband speech signal modulating a broadband noise, a low-pass speech signal modulating a low-pass noise, a high-pass speech signal modulating a high-pass noise, and a two-channel signal comprised of the low- and high-pass modulated signals combined. Recognition of the envelope stimuli in quiet and also in modulated and steady noise backgrounds was tested. Listeners were tested at presentation levels yielding their maximum performance on a syllable recognition task. The hearing-impaired listeners performed more poorly on a recognition task than the normal-hearing listeners for unprocessed speech signals. However, for listeners with hearing losses of either flat or sloping configuration, there was no significant deficit in their ability to use temporal cues in speech, even in frequency regions of hearing loss up to 70 dB HL. These results demonstrate that moderate to severe sensorineural hearing loss does not impair the temporal (nonspectral) acuity of listeners in terms of speech recognition, when audibility of the stimuli is compensated for.
Temporal resolution in the dolphin’s auditory system revealed by double-click evoked potential study
Authors: Supin Alexander Ya. , Popov Vladimir V.
Published: October 2005

Temporal resolution of hearing in two bottlenosed dolphins was estimated by measuring auditory brain-stem response (ABR) recovery in conditions of double-click stimuli. From these data, temporal transfer function of the supposed integrator was derived assuming nonlinear transform of the integrator output to ABR amplitude. The obtained temporal transfer function showed a nearly constant level up to 200 μs, then decay to approximately −3 dB at 300 μs (as presented in the sound intensity domain), and subsequent decay of 10–11 dB per time doubling (about 35 dB/decade).
Comments on ‘‘Acoustic streaming near a rigid sphere’’ [J. Acoust. Soc. Am. 95, 556 (1994)]
Authors: Williams Harry E.
Published: October 2005

It is noted that the expression used by Nyborg [J. Acoust. Soc. Am. 95, 556 (1994)] is valid only for incompressible flow. The general identity is given.
Second-order constitutive relations for transversely isotropic piezoelectric porous materials
Authors: Batra R. C. , Yang J. S.
Published: October 2005

Based on the theory of invariants, polynomial constitutive relations for transversely isotropic piezoelectric porous materials are derived from the polynomial integrity bases for an energy density function depending on a symmetric second-order tensor and two vectors. They are assumed to be smooth functions of their arguments, are expanded about the values their arguments take in the reference configuration and all terms up to the quadratic terms in the gradients of the mechanical displacement, the electric potential, and the gradients of the volume fraction are kept. The second-order constitutive relations so obtained are then specialized to the case of infinitesimal deformations and weak electric fields, and also to the case of infinitesimal deformations and strong electric fields.
Inversion of acoustic data using a combination of genetic algorithms and the Gauss–Newton approach
Authors: Gerstoft Peter
Published: October 2005

An inversion procedure for obtaining speeds, attenuation, densities, and thicknesses for a layered medium is described. The inversion is carried out using the least-squares technique and the forward modeling is based on SAFARI. The optimization is a hybrid method combining the global genetic algorithms and the local Gauss–Newton method. This is done by taking several gradient steps between each update of the object function for each ‘‘individual’’ in the population. The gradients for the Gauss–Newton method are computed analytically; this makes the computation faster and more stable than computing the gradients by numerical differentiation. The combination of a global and a local method makes the hybrid method faster and it gets closer to the global minimum than a pure global method. Examples based on both real and synthetic data in wave-number-frequency and range-frequency domains show that the method works well.
Sound generation by ice floe rubbing
Authors: Ye Zhen
Published: October 2005

The acoustic signatures of ice breaking and ice floe interaction have been observed previously by in situ experiments [e.g., Xie and Farmer, J. Acoust. Soc. Am. 91, 1423–1428 (1992)]. It was conjectured that the rubbing of adjacent ice floes in the later phase of an ice breaking event can excite SH waves in the ice that may dominate the response, resulting in the pure tone that is observed in the water. Motivated by these experimental observations, in this paper it is shown that the SH waves are in fact excited by the interaction of rough ice surfaces. In a simple model the characteristics of the sound field in response to the ice floe rubbing are derived. How the roughness of the interacting surfaces affects the observed sound field is discussed. It is also shown that the tonal nature may be due to the resonance of the SH waves within the ice floe. The effects of the rubbing speed are also discussed.
A simple neutrally buoyant sensor for direct measurement of particle velocity and intensity in water
Authors: Gabrielson Thomas B. , Gardner David L. , Garrett Steven L.
Published: October 2005

Acoustic particle velocity is commonly inferred from measurement of pressure or pressure gradient; however, in water, direct measurement is simple. A moving-coil sensor embedded in a neutrally buoyant package produces a voltage directly proportional to the particle velocity in the surrounding fluid for frequencies above the mass-spring resonance. Leslie et al. [J. Acoust. Soc. Am. 28, 711–715 (1956)] built such a sensor by mounting a moving-coil element inside a hollow brass sphere. The sensor described in this paper is identical in principle but is considerably easier to fabricate. Useful from tens of hertz to several kilohertz, this sensor consists of a glass- microballoon-and-epoxy composite cast around a small, commercial geophone. The sensor is inexpensive, rugged, and has good immunity to interference. In conjunction with a pressure hydrophone, acoustic intensity can be measured without the errors associated with subtraction of nearly equal signals (as in the two-hydrophone method).
Measurement of sound propagation in glass wool
Authors: Tarnow Viggo
Published: October 2005

A new acoustic method for directly measuring the flow resistance, and the compressibility of fibrous materials such as glass wool, is given. Measured results for monochromatic sound in glass wool are presented and compared with theoretically calculated results. The agreement between experimental results and theory is good. Results of measurements of characteristic impedance, attenuation, and phase shift for plane monochromatic traveling waves are presented and compared with theoretically calculated ones. Good agreement between experimental and theoretical results was found.
Using maximum length sequence coherence for broadband distortion measurements on hearing aids
Authors: Schneider Todd , Jamieson Donald G.
Published: October 2005

Measurement procedures using broadband noise stimuli for testing hearing aids have recently been standardized in an attempt to ensure that test results more closely reflect the ‘‘real-world’’ performance of hearing aids. Although a number of researchers have employed coherence measures made with broadband noise stimuli to characterize the broadband distortion of hearing aids, broadband distortion measurement methods have not yet been standardized. In this paper, it is demonstrated through simulations and measurements on hearing aids that similar results are obtained when coherence is measured using maximum length sequence (MLS) and conventional unbiased statistical-based methods. The calculation of single- and dual-channel MLS coherence are also formalized. Signal-to-distortion ratio (SDR) measurements for two automatic signal processing hearing aids are presented.
Dependence of distortion-product otoacoustic emissions on primary levels in normal and impaired ears. I. Effects of decreasing L2 below L1
Authors: Whitehead M. L. , McCoy M. J. , Lonsbury-Martin B. L. , Martin G. K.
Published: October 2005

The 2f1−f2 distortion-product otoacoustic emission (DPOAE) is evoked by two primary tones of frequencies f1<f2, and levels L1 and L2. Previous reports indicate that decreasing L2 below L1=L2 can; (1) increase DPOAE amplitude in normal ears, and (2) increase the degree to which DPOAE amplitudes are reduced by cochlear trauma. Although both of these factors could be advantageous for clinical applications of DPOAEs, neither has been explored in detail. In the present study, 2f1−f2 DPOAE-amplitude frequency functions were collected from normal and impaired ears of rabbits and humans, with L1=L2, and with L2<L1, at each of three values of L1. In rabbits, controlled tonal or noise overexposures were used to produce permanent reductions of DPOAE amplitudes. Comparison of pre- and postexposure DPOAE-amplitude frequency functions demonstrated that the frequency-specific reductions of DPOAEs were enhanced by decreasing L2 below L1. In humans, DPOAE-amplitude frequency functions obtained with the various L1 and L2 combinations were collected from 16 normal ears to provide preliminary normative data for each stimulus-level condition.

The L1−L2 that produced the maximum DPOAE amplitude in normal ears was systematically dependent on L1. Thus at most frequencies, decreasing L2 below L1=L2 substantially reduced mean DPOAE amplitude when L1≥75 dB SPL, but increased mean DPOAE amplitudes at L1=65 dB SPL. However, the increase of mean DPOAE amplitude obtained by decreasing L2 below L1=65 dB SPL was small, being less than 3.5 dB at most frequencies. More importantly, at L1=65 dB SPL, L2 could be decreased considerably below L1=L2 without reducing mean DPOAE amplitude relative to that at L1=L2. Inspection of DPOAE-amplitude frequency functions obtained from subjects with mild or moderate sensorineural hearing losses indicated that, in frequency regions of hearing impairment, decreasing L2 below L1 can enhance the degree of reduction of DPOAEs below the corresponding normative amplitudes, without reducing the normative amplitudes. It is concluded that decreasing L2 below L1=L2 has the potential to enhance the performance of DPOAEs in clinical applications.
Dependence of distortion-product otoacoustic emissions on primary levels in normal and impaired ears. II. Asymmetry in L1,L2 space
Authors: Whitehead M. L. , Stagner B. B. , McCoy M. J. , Lonsbury-Martin B. L. , Martin G. K.
Published: October 2005

Previous studies indicate that the amplitude of 2f1−f2 distortion-product otoacoustic emissions (DPOAEs), evoked by two tones of frequencies f1<f2, demonstrates a complex dependence on the levels (L1 and L2) of the primary tones. In the present study, 2f1−f2 DPOAE amplitudes were measured over a wide range of L1 and L2 in normal human ears, allowing a systematic, level-dependent asymmetry of DPOAE amplitude in L1,L2 space to be characterized. The L1,L2 at which DPOAEs were largest was close to L1=L2 at high stimulus levels, but moved monotonically toward L1≳L2 as stimulus levels decreased. A related observation was that DPOAE amplitude had a greater dependence on L1 than on L2. These asymmetries were quantified in normal human ears, and compared to the corresponding asymmetries apparent in data from animal models. Recent studies have demonstrated that the reduction of DPOAE amplitude by cochlear trauma is greater when L1≳L2 than when L1=L2, suggesting that the reduction of DPOAEs by trauma demonstrates an asymmetry in L1,L2 space that is qualitatively similar to that of normative DPOAE amplitude. To investigate this issue, 2f1−f2 DPOAE amplitudes were measured over a wide range of L1 and L2 in rabbit ears pre- and postinjection of the ototoxic loop-diuretic ethacrynic acid. The results indicate that the asymmetry in L1,L2 space of the reduction of DPOAEs by trauma is both qualitatively and quantitatively similar to the asymmetry in L1,L2 space of normative DPOAE amplitude. Specifically, the L1 values that maximized normative DPOAE amplitudes for any specified L2 (or, equivalently, the L1 values that allowed L2 to be minimized for any specified normative DPOAE amplitude) also yielded the greatest reduction of DPOAEs by the diuretic. In humans, the L1 values that maximize normative DPOAE amplitudes for any specified L2 are well approximated by a simple equation, with parameters that vary with frequency and f2/f1. It is suggested that the L1,L2 values defined by this equation may be optimum for use in clinical applications.
Frequency contribution to the click-evoked auditory brain-stem response in human adults and infants
Authors: Abdala Carolina , Folsom Richard C.
Published: October 2005

The results of previous research reports have led some investigators to hypothesize that frequency contribution to the infant click-evoked auditory brain-stem response (ABR) is low-frequency dominated and derived primarily from the apical cochlea. This is in contrast to latency and morphology of the adult click-evoked ABR which reflects contributions from the basal cochlea. Recent research, however, has suggested that a simple low-frequency first model of development does not adequately describe the infant auditory brain-stem response. This experiment was conducted as a carefully controlled comparison of infant and adult click-evoked ABRs restricted to narrow frequency ranges with notched-noise masking. The primary objective of this experiment was to define frequency contribution to wave I and V click-evoked ABR latency and morphology in adults and 3-month-old infants. Results indicate that 3-month-old infants have adultlike latency shifts (re: unmasked latency) when the ABR is recorded in the presence of notched-noise masking with center frequencies ranging from 500–8000 Hz. With high-frequency centered notches, latency, and morphology change are similar to the unmasked response, while low-frequency centered notches induce an average latency shift of approximately 3.5 ms for wave I and V of both infant and adult subjects. These data suggest that by 3 months of age, in normal hearing infants, ABR latency and appearance are determined by high-frequency spectral components in the broadband click which activate the basal cochlea. The adultlike pattern of latency shift observed in the ABR of these infants suggests that relatively mature tonotopic organization is established by 3 months of age.
A computer model of dorsal cochlear nucleus pyramidal cells: Intrinsic membrane properties
Authors: Hewitt Michael J. , Meddis Ray
Published: October 2005

Manis [P. B. Manis, J. Neurosci. 10, 2338–2351 (1990)] studied ‘‘simple spiking,’’ pyramidal cells of the dorsal cochlear nucleus (DCN) maintained in vitro. Response profiles to hyperpolarizing and depolarizing current pulses were generated. Hyperpolarization of the cell membrane followed by depolarization produced markedly different response profiles from those generated when no prehyperpolarization was imposed. By manipulating the magnitude of the hyperpolarizing and depolarizing pulses, ‘‘chopper,’’ ‘‘pauser’’ and ‘‘build-up’’ response patterns, similar to those in vivo, could be generated by individual cells. Manis concluded that the different response profiles resulted from the modulation of intrinsic membrane conductances by the prehyperpolarizing pulses. Here a computer model is used to show that (a) steady-state hyperpolarization can influence cell responding to subsequent depolarization in a manner consistent with the data reported by Manis; and (b) the effects reported can be generated by the addition of a modeled transient potassium conductance to the standard Hodgkin–Huxley model of spike generation [A. L. Hodgkin and A. F. Huxley, J. Physiol. 117, 500–544 (1952)]. The model will be of use to those who wish to consider the role of various excitatory and inhibitory inputs to pyramidal cells and to establish their functional role within the DCN.