Volume 120, Issue 2, August 2006
- jasa express letters
- acoustical news—usa
- acoustical news—international
- book reviews
- reviews of acoustical patents
- letters to the editor
- 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 
- acoustical measurements and instrumentation 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- bioacoustics 
Index of content:
- JASA EXPRESS LETTERS
120(2006); http://dx.doi.org/10.1121/1.2219106View Description Hide Description
Shallow water experiments have been conducted in Nantucket Sound with an autonomous underwater vehicle towed hydrophone array system in an area proximate to that of a previous experiment [Frisk and Lynch, J. Acoust. Soc. Am.86, 1928–1939 (1989)]. Transmission loss was measured, for frequencies between 220 and in an oceanwaveguide, under conditions of an isovelocity water column with an approximate depth of over a sandy-silty bottom. Results obtained at show classic isovelocity waveguide phenomena that include interference effects, mode stripping due to modal attenuation, and transmission loss proportional 15 to .
- REVIEWS OF ACOUSTICAL PATENTS
120(2006); http://dx.doi.org/10.1121/1.2336627View 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
120(2006); http://dx.doi.org/10.1121/1.2214151View Description Hide Description
The loudnessmodel described by Moore et al. [J. Audio Eng. Soc.45, 224–240 (1997)] forms the basis for a recent ANSI standard for the calculation of the loudness of steady sounds. However, the model does not give accurate predictions of the absolute thresholds published in a recent ISO standard. Here it is described how the assumed middle-ear transfer function in the model can be modified to give more accurate absolute threshold predictions. The modified model also gives reasonably accurate predictions of the equal-loudness contours published in a recent ISO standard.
Comment on paper entitled, “An inversion of Freedman’s ‘image pulse’ model in air” [J. Acoust. Soc. Am.119(2), 965–975 (2006)]120(2006); http://dx.doi.org/10.1121/1.2211487View Description Hide Description
Echolocation (i.e., perceiving objects using acoustic echoes) is well-known in underwater detection and to a lesser extent in robot guidance and machine perception. The paper by Tsakiris and McKerrow is concerned with machine perception in air using Freedman’s asymptotic model, which was originally developed to predict the backscattering multiple-echo effect observed in sonar detection. This effect was subsequently shown to be due to the elastic response of underwater targets. Freedman’s model can be used in air because the acoustic target is assumed to be rigid. Also, the model’s prediction of multiple echoes can be used to obtain information about the shape of the target. This is the so-called inversion of the Freedman model by Tsakiris and McKerrow. In their paper, various simple bodies are tested in air using ultrasound and it is shown that the model provides relatively poor information about body shape. Several explanations are given. However, one explanation is not considered, namely that the model itself is not satisfactory. First, there is poor agreement with exact backscatteringtheory. Second, deriving information about target shape from the multiple echoes predicted by the model is a highly questionable procedure. Both these aspects are examined here.
Comment on “Auditory-nerve first-spike latency and auditory absolute threshold: A computer model” [J. Acoust. Soc. Am.119, 406–417 (2006)]120(2006); http://dx.doi.org/10.1121/1.2213569View Description Hide Description
A recent paper by Meddis [J. Acoust. Soc. Am.119, 406–417 (2006)] shows that an existing model of the auditory nerve [Meddis and O’Mard, J. Acoust. Soc. Am.117, 3787–3798 (2005)] is consistent with experimentally-measured first-spike latencies in the auditory nerve [Heil and Neubauer, J. Neurosci.21, 7404–7415 (2001)]. The paper states that this consistency emerges because in the model, the calcium concentration inside the inner hair cell builds up over long periods of time (up to at least ) during tone presentation. It further states that integration over long time-scales happens despite the very short time constants used for the calcium dynamics. This letter demonstrates that these statements are incorrect. It is shown by simulation that calcium concentration inside the hair cell stage of the Meddis model rapidly reaches a steady state within a few milliseconds of a stimulus onset, exactly as expected from the short time-constant in the simple first-order differential equation used to model the calcium concentration. The success of the Meddis model in fitting experimental data actually confirms earlier results [Krishna, J. Comput. Neurosci.13, 71–91 (2002a)] that show that the experimental data are a natural result of stochasticity in the synaptic events leading up to spike-generation in the auditory nerve; integration over long time scales is not necessary to model the experimental data.
120(2006); http://dx.doi.org/10.1121/1.2213570View Description Hide Description
Standing at the foot of the Mayan step pyramid at Chichen Itza in Mexico, one can produce a pitchy “chirp” echo by handclapping. As exposed by Declercq et al. [J. Acoust. Soc. Am.116, 3328–3335 (2004)], an acoustic model based on optical Bragg diffraction at a periodic structure cannot explain satisfactorily the chirp-echo sonogram. Alternatively, considering the echo as a sequence of reflections, and given the dimensions of the pyramid and source-receiver position, the chirp is predicted correctly as a Repetition Pitch glide of which the pitch height is continuously decreasing within from 796 to -equivalent.
- GENERAL LINEAR ACOUSTICS 
Image-source method and truncation of a series expansion of the integral solution—Case of an angular sector in two dimensions120(2006); http://dx.doi.org/10.1121/1.2214133View Description Hide Description
The acoustic ray method rests upon specular reflection, an intuition that gives access only to an approximation of the solution by not taking into account the parts of the field called diffusion and diffraction. In trying to understand rationally the roots of the approximation, it has appeared that the image source could be generalized and also that errors may be partially due to missing generalized sources, already in elementary geometries such as obtuse angles. Indeed, it is shown that the exact integral solution of a two dimensional acoustic problem, expressed as a series of terms, could be seen as the contribution of the different image sources, via a partial use of the Huygens’ principle. With the correspondence between the terms and the image sources shown, the missing sources would appear and the method would thereby be refined.
An orthogonality relation-based technique for post-processing finite element predictions of waves scattering in solid waveguides120(2006); http://dx.doi.org/10.1121/1.2216563View Description Hide Description
In this paper we propose an efficient way to post-process output data predicted by Finite Element(FE) or Boundary Element (BE) codes, when the scattering of Lamb modes by defects in plate-like structures is considered. The use of a general orthogonality relation is compared to classical post-processing made with spatial FFT. To get the amplitudes of incident or scattered modes, this orthogonality relation requires the numerical prediction of the through-thickness displacements, and stress-fields distributions, on each side of the scatterer. The distance between the location where these fields are predicted and the scatterer can be very small, thus allowing huge reductions in the size of the mesh. Through two examples, this orthogonality relation is used to calculate the reflection and transmission coefficients of a pure Lamb mode incident on a notch-like defect, in either an elastic or a viscoelastic plate. Thanks to efficient absorbing regions, the FE meshed domains are reduced to the vicinity of the defects, thus allowing several advantages of the method to be demonstrated in comparison to some weaknesses of the classical post-processing based on spatial FFT.
Effect of ground variability on acoustic-to-seismic transfer function and false alarms in landmine detection120(2006); http://dx.doi.org/10.1121/1.2214159View Description Hide Description
The spatial variability of ground properties leads to fluctuations in the acoustic-to-seismic transfer function (A/S TF), the ratio of the normal particle velocity on the ground to sound pressure. In some cases, these fluctuations may lead to false landmine detection alarms. This work shows that small variations in the ground properties may cause strong variations in the A/S TF. Experimental measurements of the A/S TF performed at a US Army eastern temperate site are presented and a correlation between high magnitudes of the A/S TF (false alarms) and moisture content on the surface is shown. A simple model of the ground explaining this correlation is suggested. This model was used to describe spatial distribution of high magnitudes in the TF and natural spatial variability of the TF. Results of calculations were compared with experimental data. Two frequency modulation scales in the A/S TF are observed at positions on the ground where land mines are not located. It was hypothesized that these are due to influence of wheeled vehicular traffic on the acoustic parameters in the ground layers. A comparison between numerical modeling of the A/S TF and the experimental data was performed. Direct measurements of acoustic parameters confirmed conclusions obtained from analysis of the A/S TF.
120(2006); http://dx.doi.org/10.1121/1.2211447View Description Hide Description
The high-frequency asymptotic theory of acoustic edge waves [P. Ya. Ufimtsev, J. Acoust. Soc. Am.86, 463–74 (1989)] is well suited for investigation of backscattering from perfectly reflecting (soft or hard) three-dimensional objects with edges. However, it needs to be improved for calculation of forward scattering, especially in the directions grazing to the edge faces, where it predicts infinite values. The present paper removes this singularity by the appropriate choice of the so-called uniform component of the surface field. It is defined here as the field induced on the half-plane tangential to the illuminated face of the scattering edge (and to the edge itself). An improved theory of elementary edge waves is proposed, which is valid for all directions of scattering, including the forward grazing directions.
120(2006); http://dx.doi.org/10.1121/1.2217127View Description Hide Description
A phenomenological model that simulates the acoustic attenuation behavior of sonic crystals is developed in this paper. The input of the model is a set of parameters that characterizes each experimental setup, and the output is a simulation of the associated attenuation spectrum. The model consists of a combination of a multiresolution analysis based on wavelet functions and a set of artificial neural networks. An optimized coupling of these tools allows us to drastically reduce the experimental data needed, and to obtain a fast computational model that can be used for technological purposes.
Pore scale numerical modeling of elastic wave dispersion and attenuation in periodic systems of alternating solid and viscous fluid layers120(2006); http://dx.doi.org/10.1121/1.2216687View Description Hide Description
Numerical pore-scale simulation of elastic wave propagation is an emerging tool in the analysis of static and dynamic elastic properties of porous materials. Rotated staggered-grid (RSG) finite difference method has proved to be particularly effective in modeling porous media saturated with ideal fluids. Recently this method has been extended to viscoelastic (Maxwell) media, which allows simulation of wave propagation in porous solids saturated with Newtonian fluids. To evaluate the capability of the viscoelastic RSG algorithm in modeling wave dispersion and attenuation we perform numerical simulations for an idealized porous medium, namely a periodic system of alternating solid and viscous fluid layers. Simulations are performed for a single frequency of (for shear waves) and (for compressional waves) and a large range of fluid viscosities. The simulation results show excellent agreement with the theoretical predictions. Specifically the simulations agree with the prediction of Biot’s theory of poroelasticity at lower viscosities and with the viscoelastic dissipation at higher viscosities. The finite-difference discretization is required to be sufficiently fine for the appropriate sampling of the viscous boundary layer to achieve accurate simulations at the low values of viscosity. This is an additional accuracy condition for finite-difference simulations in viscoelastic media.
120(2006); http://dx.doi.org/10.1121/1.2214153View Description Hide Description
The resonance for the elastic plate with a free edge is studied from the point of view of complex resonance. The variations of the real part and of the imaginary part of the complex resonance frequency as a function of the Poisson ratio are determined numerically. The results confirm the real resonance frequency theoretically predicted in I. Roitberg et al., Q. J. Mech. Appl. Math.51, 1–13 (1998) for a zero Poisson ratio, and a real resonance frequency that corresponds to a Lamé mode is discovered for a Poisson ratio. It is shown that both real resonance frequencies may exist, at these two particular values of , because of the decoupling between the propagating Lamb mode and the set of evanescent Lamb modes.
- NONLINEAR ACOUSTICS 
Measurement of the frequency dependence of the ultrasonic parametric threshold amplitude for a fluid-filled cavity120(2006); http://dx.doi.org/10.1121/1.2214457View Description Hide Description
By driving a transducer at one end of a fluid-filled cavity parallel to a rigid plane reflector at the other end, standing ultrasonic waves can be generated. Variations in the cavity length resulting from transducer motion lead to the generation of resonant frequencies lower than the drive frequency (known as fractional harmonics). This excitation of fractional harmonics in a liquid-filled cavity by ultrasonic waves was described previously as a parametric phenomenon [Laszlo Adler and M. A. Breazeale, J. Acoust. Soc. Am.48, 1077–1083 (1970)]. This system was modeled by using a modified Mathieu’s equation whose solution resulted in the prediction of critical threshold drive amplitude for the excitation of parametric oscillation. The apparatus used by Adler and Breazeale was recently refined for accurate measurements of the threshold amplitude for parametric excitation at frequencies ranging from 2 to . The measurements showed that in this range the threshold amplitude increases with increasing drive frequency in apparent discrepancy with the results of Adler and Breazeale. Analysis of the theory indicates, however, that both past and current results lie in two different stability zones and each is in agreement with the existing theory.
120(2006); http://dx.doi.org/10.1121/1.2215228View Description Hide Description
Coupled equations describing the radial and translational dynamics of an encapsulated gas bubble in an ultrasound field are derived by using the Lagrangian formalism. The equations generalize Church’s theory [J. Acoust. Soc. Am.97, 1510 (1995)] by allowing for the translation motion of the bubble and radiation losses due to the compressibility of the surrounding liquid. The expression given by Church for the inner bubble radius corresponding to the unstrained state of the bubble shell is also refined, assuming that the shell can be of arbitrary thickness and impermeable to gas. Comparative linear analysis of the radial equation is carried out relative to Church’s theory. It is shown that there are substantial departures from predictions of Church’s theory. The proposed model is applied to evaluate radiation forces exerted on encapsulated bubbles and their translational displacements. It is shown that in the range of relatively high frequencies encapsulated bubbles are able to translate more efficiently than free bubbles of the equivalent size.
Translation of bubbles subject to weak acoustic forcing and error in decoupling from volume oscillations120(2006); http://dx.doi.org/10.1121/1.2214132View Description Hide Description
A microbubble in a sound wave oscillates in volume and translates unsteadily. The two motions are coupled. In large-scale simulations of the structure of bubble clouds driven by acoustic fields, it has been of significant convenience to decouple volume oscillations and translation, as an approximation. The errors of this decoupling approximation were considered in an earlier presentation [A. J. Reddy and A. J. Szeri, J. Acoust. Soc. Am.112, 1346–1352 (2002)], in the parameter range of interest in medical ultrasound. In this work, the approximation is reexamined for a much broader range of driving frequencies and bubble sizes. Solving the equation of motion for linearly oscillating bubbles, it is found that even for weak acoustic forcing, the translation speed obtained with the decoupling approximation can be in error as much as 30% relative to the translation speed in the full equations. The error depends on the bubble size, the driving frequency, and the liquid properties. The results are presented in a form convenient for applications. The principal utility of the analysis is for bubbles in microgravity, or in normal gravity driven by a soundfield with a horizontal wave-number vector.
120(2006); http://dx.doi.org/10.1121/1.2214131View Description Hide Description
The acoustic fields of a high intensity focused ultrasound (HIFU) transducer operating either at its fundamental or third harmonic frequency were measured by a fiber optic probe hydrophone (FOPH). At when the electric power applied to the transducer was increased from , the peak positive∕negative pressures at the focus were measured to be and . The corresponding spatial-peak pulse-average and spatial-average pulse-average intensities were and . Nonlinear propagation with harmonics generation was dominant at high intensities, leading to a reduced beam size of the compressional wave but an increased beam size of the rarefactional wave. Enhancement ratio of absorbed power density in water increased from 1.0 to 3.0. In comparison, the HIFU transducer working at produced higher peak pressures and with smaller beam size . Overall, FOPH was found to be a convenient and reliable tool for HIFU exposimetry measurement.