Volume 104, Issue 1, July 1998
- acoustical news—usa
- reports of related meetings
- book reviews
- reviews of acoustical patents
- selected research articles 
- general linear acoustics 
- nonlinear acoustics, macrosonics 
- 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 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- speech processing and communication systems 
- music and musical instruments 
- bioacoustics 
- letters to the editor
Index of content:
- REVIEWS OF ACOUSTICAL PATENTS
104(1998); http://dx.doi.org/10.1121/1.423272View 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.
- SELECTED RESEARCH ARTICLES 
Measurements with reticulated vitreous carbon stacks in thermoacoustic prime movers and refrigerators104(1998); http://dx.doi.org/10.1121/1.424055View Description Hide Description
Reticulated vitreous carbon has been successfully used as a stack material in thermoacoustic prime movers and refrigerators. It is a rigid glassy carbonmaterial, with a porous spongelike structure. Test results indicate peak pressure amplitudes of up to 32% in a prime mover, and refrigeration performance comparable to that of a traditional plastic roll stack.
Application of pulse compression techniques to broadband acoustic scattering by live individual zooplankton104(1998); http://dx.doi.org/10.1121/1.424056View Description Hide Description
Distinct frequency dependencies of the acoustic backscattering by zooplankton of different anatomical groups have been observed in our previous studies [, ICES J. Mar. Sci. 49, 97–106 (1992); Stanton et al., ICES J. Mar. Sci. 51, 505–512 (1994)]. Based mainly on the spectral information, scattering models have been proposed to describe the backscattering mechanisms of different zooplankton groups [, J. Acoust. Soc. Am. 103, 236–253 (1998b)]. In this paper, an in-depth study of pulse compression (PC) techniques is presented to characterize the temporal, spectral, and statistical signatures of the acoustic backscattering by zooplankton of different gross anatomical classes. Data collected from various sources are analyzed and the results are consistent with our acoustic models. From compressed pulse (CP) outputs for all three different zooplankton groups, two major arrivals from different parts of the animal body can be identified: a primary and a secondary arrival. (1) Shrimplike animals (Euphausiids and decapod shrimp; near broadside incidence only): the primary one is from the front interface(interface closest to the transducer) of the animal and the secondary arrival is from the back interface; (2) gas-bearing animals (Siphonophores): the primary arrival is from the gas inclusion and the secondary arrival is from the body tissue (“local acoustic center of mass”); and (3) elastic shelled animals (Gastropods): the primary one is from the front interface and the secondary arrival corresponds to the subsonic Lamb wave that circumnavigates the surface of the shell. Statistical analysis of these arrivals is used to successfully infer the size of the individual animals. In conjunction with different aspects of PC techniques explored in this paper, a concept of partial wave target strength (PWTS) is introduced to describe scattering by the different CP highlights. Furthermore, temporal gating of the CP output allows rejection of unwanted signals, improves the output signal-to-noise ratio (SNR) of the spectra of selected partial waves of interest, and provides a better understanding of the scattering mechanism of the animals. In addition, it is found that the averaged PWTS can be used to obtain a more quantitative scattering characterization for certain animals such as siphonophores.
- GENERAL LINEAR ACOUSTICS 
104(1998); http://dx.doi.org/10.1121/1.423283View Description Hide Description
The propagation of acoustic or ultrasonic pulses and waves in 1-D media with continuous inhomogeneities due to spatial variations in density, Young modulus, and/or cross section of the propagation medium is discussed. A semianalytical approach leads to a general form of the solution, which can be described by a function, whose Taylor expansion is absolutely convergent. The special case of a periodic inhomogeneity is studied in detail and the dispersion law is found. It is also shown that a finite width pulse is generally not broken down by the inhomogeneity, even though its law of motion is perturbed. A numerical treatment based on the Local Interaction Simulation Approach (LISA) is also considered, and the results of the simulations compared with the semianalytical ones.
104(1998); http://dx.doi.org/10.1121/1.423284View Description Hide Description
The propagation of acoustic waves in immersed waveguides has been previously studied with the help of the finite element method, using the ATILA code [A. C. Hladky-Hennion et al., J. Sound Vib. 200, 519–530 (1997)]. But this method, which is a modal analysis, essentially concerns the case of rectilinear, infinite, and uniform waveguides. Thus this paper deals with another way of solving the problem of wave propagation along waveguides, with the help of a time analysis using finite elements. First, the theoretical formulation is presented for immersed structures. Then, Plexiglas and brass wedge guides, of different apex angles, are considered. When immersed in water, these wedges generate either propagating or radiating wedge waves. The finite element results, using a time analysis, are compared to the previous finite element results, using a modal analysis and to the experiments, leading to a good agreement. Thus the approach can be easily extended to other waveguides whatever their cross sections.
104(1998); http://dx.doi.org/10.1121/1.423305View Description Hide Description
The far-field directivity pattern can be computed using the fast Fourier transform (FFT) algorithm. Numerical implementation of the angular spectrum approach (ASA) is generally used to compute the pressure field. The aim of this paper is to demonstrate that the discrete far-field pressure can be only computed by the calculation of the DFT of the normal velocity. In fact, using the asymptotic expression of the Rayleigh’s integral, which is also the solution of Helmholtz equation, it will be shown that the analytical far-field pressure is given by the Fourier transform of the normal velocity. Guidelines for the selection of sampling interval and the size of the baffle in which the source is mounted will be given. Then this paper shows that the size of baffle influences the angular resolution at which the far field is computed and when the source is oversampled the computed discrete pressure becomes better. Numerical results concerning a transducer that exhibits harmonic oscillations will be considered and discussed.
- NONLINEAR ACOUSTICS, MACROSONICS 
Temperature dependence of ultrasonic Grüneisen parameter and ultrasonic attenuation in alkali halides104(1998); http://dx.doi.org/10.1121/1.423240View Description Hide Description
Temperature dependence of ultrasonic attenuation and ultrasonic Gruneisen parameter are investigated in alkali halides in the range 80–300 K. The calculations use a computer program, developed by the authors, for implementing Nava’s modified formulation of Woodruff’s theory. These calculations are done for NaCl, NaF, and LiF for longitudinal and shear waves along the , , and  directions. Compared to calculations based on original Mason formulation, it was found that in most cases the results are in better agreement with the experimental data. The results also help to throw some light on relative merits of different theories of attenuation.
104(1998); http://dx.doi.org/10.1121/1.423241View Description Hide Description
A theory on acoustic streaming generated by Lamb waves propagating in a thin composite membrane was developed. Using this theory, the mass-transport velocity in water, which is loaded on a 4-μm-thick membrane, due to Lamb waves at 4.7 MHz was calculated. The results are in good agreement with the experimental values measured by Moroney et al. [Appl. Phys. Lett. 59, 774 (1991)].
- AEROACOUSTICS, ATMOSPHERIC SOUND 
Measurements of the two-frequency mutual coherence function for sound propagation through a turbulent atmosphere104(1998); http://dx.doi.org/10.1121/1.423242View Description Hide Description
An array of 32 microphones spanning 675 m of range was used to measure the frequency coherence for pulse signals propagating through atmospheric turbulence near the ground. Frequency coherence is the correlation between the fluctuations in received signals of different frequencies as expressed through the two frequency mutual coherence function evaluated at the same point in space and time. The experiments were conducted for frequencies between 200 and 1000 Hz under both downward and upward refracting propagation conditions. Measurements and theory are shown to be in good agreement for line-of-sight propagation. In the acoustic shadow region the frequency coherence bandwidth shows a strong dependence on mean frequency. The effects of refraction and diffraction, which cause wandering in the pulse arrival time and broadening of the pulse width, respectively, are clearly distinguished. The measurements provide experimental characterization of signal fluctuations for sound fields propagating outdoors. They are important for acoustic remote sensing and detection applications and for the validation of theoretical and numerical developments in sound propagation modeling.
104(1998); http://dx.doi.org/10.1121/1.423260View Description Hide Description
The numerical implementation of the Green’s function parabolic equation (GFPE) method for atmospheric sound propagation is discussed. Four types of numerical errors are distinguished: (i) errors in the forward Fourier transform; (ii) errors in the inverse Fourier transform; (iii) errors in the refraction factor; and (iv) errors caused by the split-step approximation. The sizes of the errors depend on the choice of the numerical parameters, in particular the range step and the vertical grid spacing. It is shown that this dependence is related to the stationary phase point of the inverse Fourier integral. The errors of type (i) can be reduced by increasing the range step and/or decreasing the vertical grid spacing, but can be reduced much more efficiently by using an improved approximation for the forward Fourier integral. The errors of type (ii) can be reduced by using a numerical filter in the inverse Fourier integral. The errors of type (iii) can be reduced slightly by using an improved refraction factor. The errors of type (iv) can be reduced only by reducing the range step. The reduction of the four types of errors is illustrated for realistic test cases, by comparison with analytic solutions and results of the Crank–Nicholson PE (CNPE) method. Further, optimized values are presented for the parameters that determine the computational speed of the GFPE method. The computational speed difference between GFPE and CNPE is discussed in terms of numbers of floating point operations required by both methods.
104(1998); http://dx.doi.org/10.1121/1.423261View Description Hide Description
In April 1994, the USAF Armstrong Laboratory, in cooperation with USAF Test Pilot School, conducted an experimental study of controlled focus boom generated by supersonic maneuvers. The objective of this study was to collect focus and postfocus booms and to assess the ability of aircrews to control the placement of the focal region during basic maneuvers. Forty-nine supersonic passes were flown and included level linear acceleration, level turn, accelerating dives, and climbout-pushover maneuvers. These flights were flown under calm and turbulent atmospheric conditions. Turbulent conditions had a defocusing effect which caused distortions in the focus region and resulted in smaller maximum overpressures. Sonic booms were collected by up to 25 boom event analyzer recorders (BEARs) placed in a 13 000-ft linear array. The BEAR units were spaced 500–2000 ft apart with the denser spacing at the expected focal region. This spacing was chosen to evaluate the thickness of both the focal and postfocal regions. The target location varied from 2000–5000 from the uptrack end of the array. Of the 49 flights, a focus boom was placed within the array 37 times and within feet of the target point 27 times, demonstrating the ability to place controlled focus booms.
104(1998); http://dx.doi.org/10.1121/1.423262View Description Hide Description
In this paper the acoustic absorption due to an orifice plate in a duct supporting a mean flow is studied theoretically. Absorption takes place as the acoustic field energizes a vortex field which is generated at the orifice rim. A linearized approximation is made to the absorption mechanism. This work presents an analytical extension of Howe [Proc. R. Soc. London, Ser. A 366, 205–233 (1979)]. The latter deals with unsteady high Reynolds numberflow through a circular aperture in a thin infinite screen. To the author’s knowledge, such an extension has not been previously made. The problem is formulated analytically insofar as it is possible and numerical results are presented. A Green’s function series expansion is used in the formulation. A difficulty arises with the convergence of this expansion. It is solved by a renormalization technique, which has been developed for this problem. The technique appears to be a novel method for dealing with convergence problems associated with term by term differentiation of Green’s function series expansions. To provide a check on the solution, it is shown that when the radius of the duct tends to infinity the present expression for the Rayleigh conductivity of the orifice plate limits to the expression obtained by Howe for an aperture in a thin infinite screen. With respect to the numerical results, it appears that for orifice mean flowMach numbers an orifice to duct open area ratio of 0.3 provides near optimal average absorption, for the band of frequencies limited by the first symmetric mode cutoff frequency.
- UNDERWATER SOUND 
104(1998); http://dx.doi.org/10.1121/1.423263View Description Hide Description
Experimental data (environmental propagation loss and beam response) obtained in the Levantine Basin of the Mediterranean Sea are presented and compared to calculations performed with a multilayer, normal-mode computermodel. The comparisons show good agreement between measured propagation loss and computer calculations. Beam response data show that the primary source of signal gain degradation is the bifurcated and broadened beam response. The degraded response pattern results from the combined effects of acoustic pressure field variations and motional array shape deformation. Calculations performed with the multilayer, normal-mode model show similar degraded response patterns caused by array tilting. These results indicate that system response and performance characteristics can be calculated for a specific sound channel as a function of the array shape and motion.
Dependence of scattered acoustical signal intensity on the form of distribution of plankton concentration104(1998); http://dx.doi.org/10.1121/1.423285View Description Hide Description
Sounding of the plankton aggregation which consists of identical statistically uncorrelated particles by a plane monochromatic wave has been studied. Analytical formulas for scattered signal intensity and interference coefficient have been obtained for an arbitrary plankton spatial distribution form. The role of interference of wavesscattered by individual plankton targets has been under investigation. The influence of the plankton probability density function form on the sounding signal mean intensity has also been considered.