Volume 117, Issue 6, June 2005
- acoustical news—usa
- acoustical news—international
- book reviews
- reviews of acoustical patents
- letters to the editor
- general linear 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 
- acoustical measurements and instrumentation 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- speech processing and communication systems 
- bioacoustics 
Index of content:
- BOOK REVIEWS
117(2005); http://dx.doi.org/10.1121/1.1928891View Description Hide Description
- REVIEWS OF ACOUSTICAL PATENTS
117(2005); http://dx.doi.org/10.1121/1.1904638View 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.
- LETTERS TO THE EDITOR
117(2005); http://dx.doi.org/10.1121/1.1904503View Description Hide Description
A looped-tube thermoacoustic engine is composed of only a stack of plates, across which a steep temperature gradient is furnished. In spite of the absence of any mechanical parts like pistons and valves, the energy conversion from heat flow into acoustic power flow is performed in the stack. The thermoacoustically induced acoustic field was observed through the simultaneous measurements of pressure and velocity of the working gas, and the thermodynamic cycle executed in the stack was studied. The experimental results show that the acoustic field is tuned without any external forces so as to realize the efficient thermodynamic cycles as possible.
117(2005); http://dx.doi.org/10.1121/1.1898598View Description Hide Description
Beamforming using a microphone array mounted on the surface of a rigid or impedance sphere and cylinder is discussed. The introduction of a structure into the space occupied by or immediately adjacent to the array gives the array an effectively larger aperture and the possibility of enhanced performance. Additional improvements can be obtained through the introduction of a surface that permits air-coupled surface waves to propagate. Since surface waves travel at a speed less than the speed of sound in free space, the aperture of the array can be effectively further increased.
117(2005); http://dx.doi.org/10.1121/1.1920213View Description Hide Description
Acoustic energy density has been shown to be a highly effective cost function for active noise controlsystems. Many researchers have used the sound field in a one-dimensional waveguide to trial their control strategies before moving onto more realistic three-dimensional sound fields. This letter aims to shed some light on the observations made in the early papers on one-dimensional energy density control and also shows that some of the analysis was incorrect and the conclusions reached may be flawed.
117(2005); http://dx.doi.org/10.1121/1.1898103View Description Hide Description
In induced loudness reduction (ILR), a strong tone causes the loudness of a subsequently presented weak tone to decrease. The aim of the experiment was to determine the time required for loudness to return to its initial level after ILR. Twenty-four subjects were exposed to 5, 10, 20, or 40 brief bursts of 2500-Hz pure tones at 80-dB SPL (inducers) and then tested in a series of paired comparison trials. Subjects compared the loudness of a weak target (2500 Hz at 60-dB SPL) to the loudness of a comparison tone at 500 Hz previously judged to match the target. The comparison task was repeated until the two tones were again judged equally loud. The results showed that (a) recovery after ILR is a relatively long process with a time scale of minutes, and (b) recovery time increased approximately 20 s with each doubling of the number of inducers.
Effects of vocalic duration and first formant offset on final voicing judgments by children and adults (L)117(2005); http://dx.doi.org/10.1121/1.1906058View Description Hide Description
Developmental research into relative weighting of vocalic duration and spectral properties in final voicing perception has produced different results, depending on whether natural or synthetic speech stimuli have been used and how spectral properties have been manipulated. This paper reports developmental data for final voicing using natural stimuli waveform edited for vocalic duration and resynthesized for first formant offset. Results indicate that in perception of final voicing there are adult-child differences in weighting of vocalic duration and first formant offset, consistent with previous findings for vocalic duration and spectral properties more generally [S. Nittrouer, J. Acoust. Soc. Am. 115, 1777–1790 (2004)].
- GENERAL LINEAR ACOUSTICS 
117(2005); http://dx.doi.org/10.1121/1.1904303View Description Hide Description
In 1909 Sommerfeld gave an exact solution for the reflection of a spherical wave from a plane surface in terms of an oscillatory integral and also presented an asymptotic solution for the case where both source and receiver are at the boundary. Weyl (1919) presented an alternative solution and also an asymptotic solution for the case where the source is at the boundary. It is known that the general case is solved if a general solution for the case where the source is at the boundary is known. Here it is demonstrated that it is sufficient to have the general solution for the case where both source and receiver are at the boundary. This is mainly of theoretical interest, but may have practical applications. As an example it is demonstrated that Sommerfeld’s approximate solution gives Ingard’s (1951) approximate solution which is valid for arbitrary source and receiver heights.
117(2005); http://dx.doi.org/10.1121/1.1914080View Description Hide Description
There are two critical issues when deriving a macro-scale prediction model starting from a more complete, underlying model. The first is the precise relationship of the fields predicted by the more complete model and the fields predicted by the macro-scale model. The second is the manner of solving a closure problem that is invariably encountered in all such derivations. The understanding that moving averages of the fields predicted by the more complete model are the fields predicted by the macro-scale model is challenged on the grounds that accomplishing a moving average does not eliminate micro-scale variation, it only appears to do so in one representation of the moving average field. The solution of a closure problem by assumption is challenged on the grounds that the most common assumptions are demonstrably invalid, even while leading to prediction models that can provide reasonable estimates of the macro-scale response in some scenarios. In presenting the challenges, it is further shown how a multiresolution analysis by an orthogonal wavelet system provides a framework for both precisely defining macro-scale response fields, i.e., fields from which all micro-scale variation has been eliminated, and presenting a formally exact solution for a precisely described closure problem.
117(2005); http://dx.doi.org/10.1121/1.1893428View Description Hide Description
Analytical solutions describing propagation of monochromatic acoustic waves inside long pores of simple geometries and narrow flat slits are obtained with accounting for gas rarefaction effects. It is assumed that molecular nature of gas is important in Knudsen layers near solid boundaries. Outside the Knudsen layers, the continuum approach is used. This model allows for extension of acoustic analysis to regions of low pressures and microscopic cross-sectional sizes of channels. The problem is solved using linearized Navier-Stokes equations with the boundary conditions that resulted from the first-order approximation with respect to small Knudsen number Kn. For slits and pores of circular and square cross sections, the theoretical dependencies of the dynamic density in the low-frequency range are compared with those that resulted from known experimental data on steady-state flows of rarefied gases in uniform channels. Despite the formal restriction Kn≪1 of asymptotic analysis, the theoreticalmodel agrees well with experiments up to Kn∼5. It is shown that the molecular phenomena affect acoustic characteristics of micro-channels and pores starting from relatively small Knudsen numbers Kn>0.01, especially at low frequencies. The obtained results may be used for analyses of acoustic properties of waveguides, perforated panels, micro-channels and pores in wide range of gas pressures as well as for stationary flows of rarefied gases through long uniform pipes etc.
Multiple scattering by random configurations of circular cylinders: Second-order corrections for the effective wavenumber117(2005); http://dx.doi.org/10.1121/1.1904270View Description Hide Description
A formula for the effective wavenumber in a dilute random array of identical scatterers in two dimensions is derived, based on Lax’s quasicrystalline approximation. This formula replaces a widely-used expression due to Twersky, which is shown to be based on an inappropriate choice of pair-correlation function.
117(2005); http://dx.doi.org/10.1121/1.1920147View Description Hide Description
This article studies the influence of the head wave in the lateral and longitudinal components of the displacements generated by the radiation of low-frequency elastic waves in an isotropic and homogeneous soft solid. Low-frequency shear waves are used to characterize elastic properties of soft tissues. In this context, it is useful to have a detailed study of the low-frequency wave field in this kind of material. A soft medium is characterized by the fact that the head wave is found in the source’s axis. Even though its amplitude is small compared with the shear wave, it is possible to be observed experimentally by recording consecutive ultrasonic A-lines while the low-frequency wave propagates inside the medium. A standard one-dimensional speckle tracking technique is employed to measure the displacements. Experimental results were interpreted through the exact Green’s functionsolution to the half-space problem. According to the theoretical and experimental analysis, the head wave and surface related terms in general contribute to the displacements in the low-frequency range. This article thoroughly analyzes and experimentally shows the contribution of the head wave for the lateral component, which is not fully addressed by the literature.
Fluctuations in diffuse field–field correlations and the emergence of the Green’s function in open systems117(2005); http://dx.doi.org/10.1121/1.1898683View Description Hide Description
Recent intense interest in diffuse field correlation functions, with applications to passive imaging in underwater acoustics and seismology, has raised questions about the degree with which a retrieved waveform can be expected to conform to the Green’s function, and in particular the degree with which a ray arrival may be discerned. On considering a simple scalar wave model consisting of fields with distributed random sources, the difffuse field-field correlation function R is defined as a sum of correlation integrals, one for each of the many distinct distributed sources. It is then shown that this ensemble of fields has a correlation function with expectation equal to the Green’s function. This model also lends itself to calculations of the variance of R, and thus to estimates of the degree to which an R calculated using finite amounts of data will conform to the Green’s function. The model predicts that such conformation is strongest at low frequencies. Ray arrivals are detectable if sufficient data have been collected, but the amount of data needed scales in three dimensions with the square of the source–receiver separation, and the square of the frequency. Applications to seismology are discussed.
117(2005); http://dx.doi.org/10.1121/1.1904405View Description Hide Description
Acoustic particle manipulation has many potential uses in flow cytometry and microfluidic array applications. Currently, most ultrasonic particle positioning devices utilize a quasi-one-dimensional geometry to set up the positioning field. A transducer fit with a quarter-wave matching layer, locally drives a cavity of width one-half wavelength. Particles within the cavity experience a time-averaged drift force that transports them to a nodal position. Present research investigates an acoustic particle-positioning device where the acoustic excitation is generated by the entire structure, as opposed to a localized transducer. The lowest-order structural modes of a long cylindrical glass tube driven by a piezoceramic with a line contact are tuned, via material properties and aspect ratio, to match resonant modes of the fluid-filled cavity. The cylindrical geometry eliminates the need for accurate alignment of a transducer/reflector system, in contrast to the case of planar or confocal fields. Experiments show that the lower energy density in the cavity, brought about through excitation of the whole cylindrical tube, results in reduced cavitation, convection, and thermal gradients. The effects of excitation and material parameters on concentration quality are theoretically evaluated, using two-dimensional elastodynamic equations describing the fluid-filled cylindrical shell with a line excitation.
117(2005); http://dx.doi.org/10.1121/1.1905639View Description Hide Description
This paper considers the oscillatory motion of gases inside a long porous tube of the closed-open type. In particular, the focus is placed on describing an analytical solution for the internal acoustico-vortical coupling that arises in the presence of appreciable wall suction. This unsteady field is driven by longitudinal oscillatory waves that are triggered by small unavoidable fluctuations in the wall suction speed. Under the assumption of small amplitude oscillations, the time-dependent governing equations are linearized through a regular perturbation of the dependent variables. Further application of the Helmholtz vector decomposition theorem enables us to discriminate between acoustical and vortical equations. After solving the wave equation for the acoustical contribution, the boundary-driven vortical field is considered. The method of matched-asymptotic expansions is then used to obtain a closed-form solution for the unsteady momentum equation developing from flow decomposition. An exact series expansion is also derived and shown to coincide with the numerical solution for the problem. The numerically verified end results suggest that the asymptotic scheme is capable of providing a sufficiently accurate solution. This is due to the error associated with the matched-asymptotic expansion being smaller than the error introduced in the Navier-Stokes linearization. A basis for comparison is established by examining the evolution of the oscillatory field in both space and time. The corresponding boundary-layer behavior is also characterized over a range of oscillation frequencies and wall suction velocities. In general, the current solution is found to exhibit features that are consistent with the laminar theory of periodic flows. By comparison to the Sexl profile in nonporous tubes, the critically damped solution obtained here exhibits a slightly smaller overshoot and depth of penetration. These features may be attributed to the suction effect that tends to attract the shear layers closer the wall.