Volume 118, Issue 5, November 2005
- acoustical news—usa
- acoustical standards news
- 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 
- applied acoustics paper: architectural acoustics
- acoustical measurements and instrumentation 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech perception 
- speech processing and communication systems 
- music and musical instruments 
- bioacoustics 
Index of content:
- ACOUSTICAL STANDARDS NEWS
118(2005); http://dx.doi.org/10.1121/1.2069947View Description Hide Description
118(2005); http://dx.doi.org/10.1121/1.2060712View Description Hide Description
- REVIEWS OF ACOUSTICAL PATENTS
118(2005); http://dx.doi.org/10.1121/1.2060713View 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
118(2005); http://dx.doi.org/10.1121/1.2062650View Description Hide Description
Consonant identification rates were measured for vowel-consonant-vowel tokens gated with -talker babble noise and babble-modulated noise for an extensive range of , at a fixed signal-to-noise ratio. In the natural babble condition, intelligibility was a nonmonotonic function of , with a broad performance minimum from to . Identification rates in babble-modulated noise fell gradually with . The contributions of factors such as energetic masking, linguistic confusion, attentional load, peripheral adaptation, and stationarity to the perception of consonants in -talker babble are discussed.
118(2005); http://dx.doi.org/10.1121/1.2062688View Description Hide Description
The tortuosity of five air-filled stereolithographical cancellous bone replicas has been obtained from measurements using audiofrequency pulses in a rectangular waveguide. The data obtained from the replicas yields information about anisotropy with respect to orthogonal axes of the passages that would be marrow filled in vivo. A strong relationship has been found between the acoustically measured tortuosity and the independently measured porosity. Use of stereolithographical bone replicas has the potential to simulate perforation and thinning of cancellous bone and hence evaluate the dependence of acoustic properties on cancellous bone microstructure. As an “extreme” illustration of such use, “inverses” of the original replicas have been manufactured and acoustic measurements have been made on them. The data reveal significantly greater tortuosity of the passages that are geometrically equivalent to the original solid bone structures.
Retrieving the Green’s function in an open system by cross correlation: A comparison of approaches (L)118(2005); http://dx.doi.org/10.1121/1.2046847View Description Hide Description
We compare two approaches for deriving the fact that the Green’s function in an arbitrary inhomogeneous open system can be obtained by cross correlating recordings of the wave field at two positions. One approach is based on physical arguments, exploiting the principle of time-reversal invariance of the acoustic waveequation. The other approach is based on Rayleigh’s reciprocity theorem. Using a unified notation, we show that the result of the time-reversal approach can be obtained as an approximation of the result of the reciprocity approach.
118(2005); http://dx.doi.org/10.1121/1.2048947View Description Hide Description
Shallow water acoustic reverberation is sometimes exploited to estimate properties of the seabed. In the process of estimating these properties, the scattering kernel (the dependence of the scattering on incident and scattered angle) is often assumed. That is, the scattering kernel is generally not known a priori. The errors associated with assuming an incorrect scattering kernel are explored and quantified for several types of scattering kernels. Choosing an incorrect scattering kernel can lead to significant errors in the frequency dependence of the estimated scattering strength. Finally, it is shown that the sonar equation approach for obtaining scattering strength from reverberation assumes that the scattering strength is independent of both incident and scattered angle. This assumption appears to be contrary to a large body of evidence that indicates the scattering strength decreases at low grazing angles.
118(2005); http://dx.doi.org/10.1121/1.2065847View Description Hide Description
A single-channel algorithm is proposed for noise reduction in cochlear implants. The proposed algorithm is based on subspace principles and projects the noisy speech vector onto “signal” and “noise” subspaces. An estimate of the clean signal is made by retaining only the components in the signal subspace. The performance of the subspace reduction algorithm is evaluated using 14 subjects wearing the Clarion device. Results indicated that the subspace algorithm produced significant improvements in sentence recognition scores compared to the subjects’ daily strategy, at least in stationary noise. Further work is needed to extend the subspace algorithm to nonstationary noise environments.
118(2005); http://dx.doi.org/10.1121/1.2062187View Description Hide Description
Profile-analysis thresholds were measured in the presence and absence of overall level variation at different stimulus levels to determine whether nonlinear changes in the shape of the edges of excitation pattern peaks contribute to poorer spectral-shape sensitivity observed under roving levels. Roving levels decreased sensitivity for stimuli having few components separated widely in frequency to a greater extent than for stimuli having more densely spaced components. The stimulus level did not influence sensitivity when overall level variation was absent, suggesting that listeners rely on peaks in the excitation patterns and not the edges of the peaks (as would have been predicted by the near miss to Weber’s law). Because the edges of the peaks were not used in the absence of roving levels, it follows that the larger rove effects for sparse stimuli were not likely due to excitation pattern inconstancy.
118(2005); http://dx.doi.org/10.1121/1.2074987View Description Hide Description
This letter analyzes the oscillation onset-offset conditions of the vocal folds as a function of laryngeal size. A version of the two-mass model of the vocal folds is used, coupled to a two-tube approximation of the vocal tract in configuration for the vowel. The standard male configurations of the laryngeal and vocal tractmodels are used as reference, and their dimensions are scaled using a single factor. Simulations of the vocal fold oscillation and oral output are produced for varying values of the scaling factor. The results show that the oscillation threshold conditions become more restricted for smaller laryngeal sizes, such as those appropriate for females and children.
- GENERAL LINEAR ACOUSTICS 
118(2005); http://dx.doi.org/10.1121/1.2062269View Description Hide Description
Acoustic field predictions, whether analytical or computational, rely on knowledge of the environmental, boundary, and initial conditions. When knowledge of these conditions is uncertain, acoustic field predictions will also be uncertain, even if the techniques for field prediction are perfect. Quantifying acoustic field uncertainty is important for applications that require accurate field amplitude and phase predictions, like matched-field techniques for sonar, nondestructive evaluation, bio-medical ultrasound, and atmospheric remote sensing. Drawing on prior turbulence research, this paper describes how an evolution equation for the probability density function (PDF) of the predicted acoustic field can be derived and used to quantify predicted-acoustic-field uncertainties arising from uncertain environmental, boundary, or initial conditions. Example calculations are presented in one and two spatial dimensions for the one-point PDF for the real and imaginary parts of a harmonic field, and show that predicted field uncertainty increases with increasing range and frequency. In particular, at in an ideal deep underwater sound channel with a root-mean-square depth uncertainty, the PDF results presented here indicate that at a range of , all phases and a range of amplitudes will have non-negligible probability. Evolution equations for the two-point PDF are also derived.
Doubly focused backscattering from finite targets in an Airy caustic formed by a curved reflecting surface118(2005); http://dx.doi.org/10.1121/1.2046867View Description Hide Description
Caustics can be formed in the water column when sound scatters off a curved-reflecting surface such as the ocean floor or surface. The simplest caustic is an Airy caustic formed by the merging of two rays. Small targets lying in or near Airy caustics have backscattered echoes that can be focused both to the target and upon return. For a point target, the doubly focused backscattering amplitude is proportional to the square of an Airy function whose argument depends on the target location through the changes in relative return times of contributing rays. For a finite sized target, the symmetry is broken and the amplitude unfolds into a hyperbolic umbilic catastrophe. The arguments for the hyperbolic umbilic function are calculated using the relative return times of transient echoes. These doubly focused echoes can lead to amplitudes larger than that of direct or singly focused echoes (echoes which focus once, either to the target or upon return). Experiments using a cylindrical half-pipe as a reflecting surface confirm these predictions.
Acoustic scattering by a metallic tube with a concentric solid polymer cylinder coupled by a thin water layer. Influence of the thickness of the water layer on the two Scholte–Stoneley waves118(2005); http://dx.doi.org/10.1121/1.2065807View Description Hide Description
The problem of a plane acoustic wavescattered by a layered cylinder submerged in water is considered. This cylinder consists of a tube made of aluminum with a solid Lucite cylinder concentrically fitt inside it. These two components are coupled by a thin layer of water. A particular investigation is made on the influence of the thickness of the water layer on the presence of the bending wave A on the tube and the Scholte–Stoneley wave on the cylinder. The presence of these waves is examined in the function of the varying water layer thickness: two special cases are discussed. First, for a layer thickness greater than the tube thickness, it is shown that both the A wave on the aluminum tube and the Scholte–Stoneley wave on the Lucite cylinder are generated. Second, for a thickness much smaller than the tube thickness, a different wave is generated, which is a combination of both waves. These two cases are experimentally verified in a setup that employs a short pulse method.
118(2005); http://dx.doi.org/10.1121/1.2062527View Description Hide Description
One of the stress sources that can be used in dynamic elastographyimaging methods is the acoustic radiation force. However, displacements of the medium induced by this stress field are generally not fully understood in terms of spatial distribution and temporal evolution. A model has been developed based on the elastodynamic Green’s function describing the different acoustic waves generated by focused ultrasound. The function is composed of three terms: two far-field terms, which correspond to a purely longitudinal compression wave and a purely transverse shear wave, and a coupling near-field term which has a longitudinal component and a transverse component. For propagation distances in the shear wavelength range, the predominant term is the near field term. The displacement duration corresponds to the propagation duration of the shear wave between the farthest source point and the observation point. This time therefore depends on the source size and the local shear modulus of the tissue. Evolution of the displacement/time curve profile, which is directly linked to spatial and temporal source profiles, is computed at different radial distances, for different durations of force applications and different shear elastic coefficients. Experimental results performed with an optical interferometric method in a homogeneous tissue-mimicking phantom agreed with the theoretical profiles.
118(2005); http://dx.doi.org/10.1121/1.2062268View Description Hide Description
Experimental results are compared with a theoreticalanalysis concerning wall effects on the symmetric mode resonance frequency of millimeter-sized air bubbles in water. An analytical model based on a linear coupled-oscillator approximation is used to describe the oscillations of the bubbles, while the method of images is used to model the effect of the wall. Three situations are considered: a single bubble, a group of two bubbles, and a group of three bubbles. The results show that bubbles attached to a rigid boundary have lower resonance frequencies compared to when they are in an infinite uniform liquid domain (referred to as free space). Both the experimental data and theoreticalanalysis show that the symmetric mode resonance frequency decreases with the number of bubbles but increases as the bubbles are moved apart. Discrepancies between theory and experiment can be explained by the fact that distortion effects due to buoyancy forces and surface tension were ignored. The data presented here are intended to guide future investigations into the resonances of larger arrays of bubbles on rigid surfaces, which may assist in surface sonochemistry, sonic cleaning, and micro-mixing applications.
118(2005); http://dx.doi.org/10.1121/1.2046807View Description Hide Description
The dispersion spectra of SH guided waves are studied both analytically and numerically for two-layered plates with a plane of propagation being the plane of transverse isotropy. The boundary-value problems are considered for a plate with free, clamped, or clamped/free surfaces. It is noticed that formally the problem is very similar to that for symmetric and antisymmetric Lamb waves in a homogeneous plate. On this basis the Mindlin’s approach of a bound grid is applied for an analysis. It is found that the studied spectra are characterized by the following specific features. They have two asymptotic levels and corresponding to the speeds of SH bulk waves in both layers. In the vicinity of the upper level dispersion curves form a step-like pattern tending to in succession one by one with further going down to the lower asymptote . Over the level there is a zone, where dispersion curves have a wavy form similar to that in spectra of Lamb waves in homogeneous plates. It is shown that the families of dispersion branches related to the boundary conditions of free and clamped surfaces cross each other at the same types of nodes of Mindlin’s grid as those for symmetric and antisymmetric Lamb waves in a free homogeneous plate. The tracing speed level is found where the appropriate families of dispersion curves cross each other beyond the nodes of Mindlin’s grid. It is proved that the spectra of symmetric and antisymmetric SH guided waves in symmetric three-layered plates with free or clamped faces are described by the same four equations as for the studied two-layered plates with free, clamped, free/clamped or clamped/free surfaces.
118(2005); http://dx.doi.org/10.1121/1.2049127View Description Hide Description
A generalized algorithm is developed for studying the sound wave propagation in a system of interconnected rigid walled acoustic filter elements. The algorithm is based on the transfer matrix approach of analysis. Interconnection between various elements is represented by a connectivity matrix. Equations of mass velocity continuity and pressure equilibrium at the interconnections are generated using this connectivity matrix and are solved to get the overall transfer matrix of the system. The algorithm used for generalized labeling of the network and computation of transmission loss is discussed. The algorithm is applied to investigate multiply connected automobile mufflers as a network of acoustic elements. Results for some configurations have been compared with those from the finite element modelanalysis and experiments cited in the literature. A parametric study with respect to some geometric variables is carried out. While the results are illustrated here for a few configurations, the approach holds for all kinds of combinations of acoustic elements with any degree of complexity. The acoustical similarity between apparently different networks is discussed. The approach is flexible to incorporate any other acoustic elements, provided the acoustic variables at the junctions of the element can be related by a transfer matrix a priori.