Volume 109, Issue 1, January 2001
- acoustical news—usa
- book reviews
- reviews of acoustical patents
- general linear acoustics 
- nonlinear acoustics 
- aeroacoustics, atmospheric sound 
- underwater sound 
- ultrasonics, quantum acoustics, and physical effects of sound 
- transduction 
- structural acoustics and vibration 
- noise: its effects and control 
- architectural acoustics 
- applied acoustics paper: acoustical measurements and instrumentation 
- physiological acoustics 
- psychological acoustics 
- speech perception 
- speech processing and communication systems 
- bioacoustics 
- letters to the editor
Index of content:
- REVIEWS OF ACOUSTICAL PATENTS
109(2001); http://dx.doi.org/10.1121/1.1333762View Description Hide Description
The purpose of these acoustical patent reviews is to provide enough information for a Journal reader to decide whether to seek more information from the patent itself. Any opinions expressed here are those of the reviewers as individuals and are not legal opinions. Printed copies of United States Patents may be ordered at $3.00 each from the Commissioner of Patents and Trademarks, Washington, DC 20231. Patents are available via the Internet at http://www.uspto.gov.
- GENERAL LINEAR ACOUSTICS 
109(2001); http://dx.doi.org/10.1121/1.1289924View Description Hide Description
The convergence of linear poroelastic elements based on Biot displacement formulation is investigated. The aim is to determine a mesh criterion that provides reliable results under a given frequency limit. The first part deals with 1D applications for which resonance frequencies can be related to Biot wavelengths. Their relative contributions to the motion are given in order to determine if the mesh criteria for monophasic media are suitable for poroelastic media. The imposition of six linear elements per wavelength is found for each Biot wave as a primary condition for convergence. For 3D applications, convergence rules are derived from a generic configuration, i.e., a clamped porous layer. Because of the complex deformation, the previous criterion is shown to be insufficient. Influence of the coupling between the two phases is demonstrated.
109(2001); http://dx.doi.org/10.1121/1.1331110View Description Hide Description
This paper presents an exact three-dimensional analysis of the general nonaxisymmetric free vibration of a piezoceramic hollow sphere by employing a state-space approach. By introducing three displacement functions and two stress functions, the basic equations of a spherically isotropic piezoelectric medium are eventually turned into two separated state equations with variable coefficients. The solutions of these two equations are then obtained by virtue of Taylor’s expansion theorem. Relationships between the state variables at the inner and outer surfaces of a laminated hollow sphere are established. Exact frequency equations corresponding to two independent classes of vibrations are then derived from the free conditions at the spherical boundary surfaces. Numerical results are finally presented.
Spatial analysis of torsional wave propagation in a cylindrical waveguide. Application to magnetostrictive generation109(2001); http://dx.doi.org/10.1121/1.1323717View Description Hide Description
A spatial analysis of the generation and propagation of torsional waves in a cylindrical rod is presented. Starting from the classical linear equation of propagation and assuming a linear medium of propagation, the eigenfunctions of the propagation operator are calculated. Under the hypothesis of separation-of-variables type of solution, two ways of deriving the associated modes are performed. Given the normal mode basis, the behavior of a wavefront generated into the rod is examined. The application to the magnetostrictive generation of torsional waves is studied. Including the influence of eddy currents on the excitation and the geometry waveguideeffects on the wave propagation, an analytical expression of mechanical losses during the first steps of propagation is given. A basic model of the interaction between a defect and the torsional guided waves is also proposed.
Influence of grazing flow and dissipation effects on the acoustic boundary conditions at a lined wall109(2001); http://dx.doi.org/10.1121/1.1331678View Description Hide Description
The problem of sound propagation near a lined wall taking into account mean shear floweffects and viscous and thermal dissipation is investigated. The method of composite expansion is used to separate the inviscid part, in the core of the flow, from the boundary layer part, near the wall. Two diffusionequations for the shear stress and the heat flux are obtained in the boundary layer. The matching of the solutions of these equations with the inviscid part leads to a modified specific acoustic admittance in the core flow. Depending on the ratio of the acoustic and stationary boundary layer thicknesses, the kinematic wall condition changes gradually from continuity of normal acoustic displacement to continuity of normal acoustic mass velocity. This wall condition can be applied in dissipative silencers and in aircraft engine-duct systems.
Structural-acoustic coupling in a partially opened plate-cavity system: Experimental observation by using nearfield acoustic holography109(2001); http://dx.doi.org/10.1121/1.1320476View Description Hide Description
In order to understand the cause and effect relation between a structure and a fluid, many studies on structural-acoustic coupling have been done. However, the studies were restricted to the interaction between only a structure and a fluid located on one or the other side of the structure. It is our aim to understand the coupling mechanism of a generally coupled system that has direct interaction between a finite interior fluid and a semi-infinite exterior one. We believe that this configuration allows the structure to interact with the fluid of the finite volume and that of the infinite one, thus providing a more general structure-fluid coupling (or structural-acoustic coupling) mechanism. For this purpose, we selected a partially opened plate-cavity system which has two different modally reacting boundary conditions: a plate and a hole. In order to understand the physical coupling phenomena of the selected system, visualization of the sound fields was performed experimentally. We used near field acoustic holography to estimate sound field variables, such as pressures and intensities. Examining the acoustic variables, we found that there are two types of coupling mechanisms depending on frequency and associated wavelength. One is where the plate and the cavity are so strongly coupled that the plate can be considered as a source. In this case, the system radiates acoustic energy effectively through the plate. The other is where the coupling interaction behavior decreases the radiation efficiency. The frequencies that determine whether the plate is a good or bad radiator are found to be around the natural frequencies of the plate.
- NONLINEAR ACOUSTICS 
109(2001); http://dx.doi.org/10.1121/1.1328794View Description Hide Description
Godunov-type computation schemes are applied to numerical simulations of wave propagations in time-dependent heterogeneous media (solids and liquids). The parametric phase conjugation of a wide band ultrasound pulse is considered. The supercritical dynamics of the acoustic field is described for one-dimensional systems containing a parametrically active solid. The impulse response function, numerically calculated for a finite active zone in an infinite medium above the threshold of absolute parametric instability, is in a good agreement with the analytical asymptotic theory. The supercritical evolution of the acoustic field spatial distribution is studied in detail for parametric excitations in an active zone of a solid layer, loaded by a semi-infinite liquid on one side and free on the other.
109(2001); http://dx.doi.org/10.1121/1.1332383View Description Hide Description
It is demonstrated that the temperature oscillations near the edge of the thermoacoustic stack are highly anharmonic even in the case of harmonic acoustic oscillations in the thermoacoustic engines. In the optimum regime for the acoustically induced heat transfer, the amplitude of the second harmonic of the temperature oscillations is comparable to that of the fundamental frequency.
- AEROACOUSTICS, ATMOSPHERIC SOUND 
109(2001); http://dx.doi.org/10.1121/1.1328793View Description Hide Description
The amplitude and waveform shape of atmospheric acoustic pulses propagating horizontally over a seasonal snow cover are profoundly changed by the air forced into the snow pores as the pulses move over the surface. This interaction greatly reduces the pulse amplitude and elongates the waveform compared to propagation above other ground surfaces. To investigate variations in snow-cover effects, acoustic pulses were recorded while propagating horizontally over 11 different naturally occurring snow covers during two winters. Two inversion procedures were developed to automatically match the observed waveforms by varying the snow-cover parameters in theoretical calculations. A simple frequency-domain technique to match the dominant frequency of the measured waveform suffered from multiple solutions and poor waveform matching, while a time-domain minimization method gave unique solutions and excellent waveform agreement. Results show that the effective flow resistivity and depth of the snow are the parameters controlling waveform shape, with the pore shape factor ratio of secondary importance. Inversion estimates gave flow resistivities ranging from 11 to 29 kN s m−4, except for two late-season cases where values of 60 and 140 were determined (compared to 345 for the vegetation-covered site in the summer). Acoustically determined snow depths agreed with the measured values in all but one case, when the depth to a snow layer interface instead of the total snow depth was determined. Except for newly fallen snow, the pore shape factor ratio values clustered near two values that appear to correspond to wet (1.0) or dry (0.8) snow.
Perturbation theory applied to sound propagation in flowing media confined by a cylindrical waveguide109(2001); http://dx.doi.org/10.1121/1.1331676View Description Hide Description
First-order perturbation theory is employed to examine sound propagation in flowing media confined by a cylindrical waveguide. The use of perturbation theory allows examination of mode phase-speed changes due to any radially dependent flow as long as the flow magnitude is sufficiently small. The condition to be fulfilled is satisfied in the flow range: m/s for the specific values of cylinder radius, ultrasound frequency, and sound speedanalyzed in the present work [in the general case, however, the condition in Eq. (1) of the present work must be fulfilled]. This freedom of choice, i.e., the possibility to handle any radial flow profile, is used to analyze two flow profile cases: (1) where is a linear combination of a laminar flow profile and a flat profile corresponding to turbulent flow, and (2) where is a linear combination of a laminar flow profile and a more realistic logarithmic-dependent turbulent flow profile. In both cases, it is shown that large errors may result in ultrasoundflow measurements if several modes are excited by the transmitting transducer, and that a logarithmic flow profile in the turbulent regime leads to somewhat larger measurement errors at high flow values as compared to assuming a simple flat profile in the turbulent regime.
Aeroacoustics of diffusers: An experimental study of typical industrial diffusers at Reynolds numbers of109(2001); http://dx.doi.org/10.1121/1.1329618View Description Hide Description
Diffusers as used in gas transport systems have an optimal pressure recovery but are unstable due to marginal flow separation. Coupling of diffuser flow oscillation with acoustic modes in a pipe has been demonstrated in a recent work by Kwong and Dowling [J. Fluids Eng. 116, 842 (1994)] to drive flow unsteadiness. Considered here in addition to the diffuser at a pipe termination is the aeroacoustic response of a diffuser in a long pipe. In both cases reflection coefficientmeasurements show that at moderate and low amplitudes of the acoustical particle velocity compared to the main flowvelocity, diffusers are aeroacoustic sources similar to the whistler nozzle and the horn. This confirms the observations of Kwong and Dowling. At higher acoustical velocity amplitudes diffusers become strong absorbers, which can be explained in terms of a quasistationary flowmodel. Finally, an indication is provided for possible remedial measures when a stable flow is needed.
Numerical modeling of the spectral broadening of sodar echoes by winds perpendicular to the axis of a finite beamwidth antenna109(2001); http://dx.doi.org/10.1121/1.1331677View Description Hide Description
A simple model for determining the amount of spectral broadening in acoustic sounderechoes caused by winds traveling perpendicular to the antenna beam is presented. Key features of the model are that the wind profile is described by an analytic function and the antenna radiation pattern is included in the calculations. The model was restricted to the situation where the antenna was aligned in the vertical direction and the winds were horizontal. The effects of refraction by temperature and wind velocity gradients were neglected. The radiation pattern used in the model was the or function. The wind profiles which were used were a constant windspeed between the antenna and the scattering height, a profile where the windspeed increases linearly with height, and a logarithmic profile. Here, the amount of spectral broadening or spectral width of the echo is calculated by treating the amplitude spectrum of the echo as a probability distribution and determining the standard deviation of this distribution. It was found that the relationship between the standard deviation of the echo, σ, and windspeed, u, was closely described by a linear relationship, with the value of B ranging from 0.05 to 0.08 for the situations modeled here. Observational data are presented. The data were obtained with a sounder whose radiation pattern was approximated with the sinc function. The observed relationship between σ, and u, was essentially linear, agreeing favorably with the model predictions; however, the value of the proportionality constant B was 0.04. A possible explanation for this is that the radiation pattern for the antenna may have been underestimated since the effects of the sound absorbing shielding surrounding the antenna are unknown.
- UNDERWATER SOUND 
109(2001); http://dx.doi.org/10.1121/1.1329622View Description Hide Description
Signals received by low-frequency multibeam echosounders are strongly affected by sound penetration inside the upper sediment layers and by backscattering from buried layers down to depths of a few meters; this may lead to serious ambiguities and misinterpretations of experimental data. These phenomena are modeled here using a concept of equivalent input backscattering strength (EIBS), based on a combination of classical models of local backscattering strength and propagation inside fluid layered media. The local backscattering strength at a buried interface is expressed first to account for the impedance adaptation due to the overlying layers, for the angular refraction effects due to the velocity profile, and for the layered structure of the underlying medium. It is then transferred to the upper water–sediment interface, accounting for propagation inside the layered stack; the transfer coefficient is obtained from the classical theory of plane wave propagation in layered media. The volume backscatteringeffects are processed in the same way and account for the finite thickness of the layers. The various contributions are finally summed to give the backscattering strength, at the upper interface, that features the various effects of propagation and attenuation inside the layered structure.
Bubble clouds and their transport within the surf zone as measured with a distributed array of upward-looking sonars109(2001); http://dx.doi.org/10.1121/1.1331108View Description Hide Description
A collaborative, multi-institute experiment called the Scripps Pier Experiment was conducted in the vicinity of the Scripps pier in La Jolla, California, in March 1997 to study the fate of bubbles in the surf zone and the effects of these bubbles on acoustic propagation. This paper discusses data gathered by the Applied Physics Laboratory, University of Washington, using a set of four upward-looking sonars (frequency 240 kHz), which simultaneously measured vertical profiles of acoustic volume scattering from bubbles at four locations. The transport of bubbles via rip currents emerged as an important, though episodic and localized, feature of the acoustic environment in the surf zone. Images of volumetric backscattering strength vs time and depth reveal the episodic events (of increased scattering level) lasting between 5 and 10 min caused by the passage of bubble clouds over the sonar. Time lags for the onset of increased scattering at the four locations are consistent with a seaward velocity of the bubble clouds of order 10 cm/s, and the length scales of these bubble clouds in the seaward direction are inferred to be in the range 50–100 m. The influence of the incoming surface wave field is also discussed.