Volume 118, Issue 2, August 2005
- acoustical news—usa
- acoustical news—international
- reviews of acoustical patents
- letters to the editor
- applied acoustics paper: transduction
- applied acoustics paper: architectural acoustics
- 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 
- speech perception 
- speech processing and communication systems 
- music and musical instruments 
- bioacoustics 
Index of content:
- REVIEWS OF ACOUSTICAL PATENTS
118(2005); http://dx.doi.org/10.1121/1.2040227View 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.
118(2005); http://dx.doi.org/10.1121/1.1960170View Description Hide Description
- LETTERS TO THE EDITOR
Correcting the use of ensemble averages in the calculation of harmonics to noise ratios in voice signals118(2005); http://dx.doi.org/10.1121/1.1940450View Description Hide Description
A correcting formula for the estimation of harmonics-to-noise ratios (HNR) based on ensemble-averaging techniques is derived. The original method yields a biased approximation which is more accurate as the number of averaged pulses increases. However, the method treats gradual waveform changes incorrectly as noise, which is worsened for large values of . The obtained formula allows the use of as few averaged pulses as desired, while allowing the complete removal of the bias from the estimate of HNR.
118(2005); http://dx.doi.org/10.1121/1.1953187View Description Hide Description
The letter provides alternatively a simple way of computing the Fresnel field integral, a further extension to the Gaussian-beam expansion. The zeroth-order Bessel function of the first kind is expanded into an approximate sum of Gaussian functions. The field integral is then expressible in terms of these simple functions. The approach is useful in treatment of the field radiation problem for a large and important group of piston sources in acoustics. As examples, the calculation results for the uniform and the simply-supported piston sources are presented, in a good agreement with those evaluated by numerical integration.
Application of the phase gradient method to the study of the resonances of a water-loaded anisotropic plate118(2005); http://dx.doi.org/10.1121/1.1942367View Description Hide Description
The phase gradient method is applied to cubic and orthotropic plates. It consists in simply obtaining the positions and the widths of their frequency and angular resonances from the plots of the frequency and angular derivatives of the phase of the reflection coefficient of the immersed plate. There is a good match with the results obtained from the calculation of the modes of the immersed plate in the corresponding complex planes. Moreover, these two derivatives allow us to obtain frequency and angular quality factors.
118(2005); http://dx.doi.org/10.1121/1.1925849View Description Hide Description
A simulation study is conducted to demonstrate in principle that time reversal processing can be used to locate sound sources in an outdoor urban area with many buildings. Acoustic pulse propagation in this environment is simulated using a two-dimensional finite difference time domain(FDTD) computation. Using the simulated time traces from only a few sensors and back propagating them with the FDTDmodel, the sound energy refocuses in the vicinity of the true source location. This time reversal numerical experiment confirms that using information acquired only at non-line-of-sight locations is sufficient to obtain accurate source locations in a complex urban terrain.
Transducer hysteresis contributes to “stimulus artifact” in the measurement of click-evoked otoacoustic emissions118(2005); http://dx.doi.org/10.1121/1.1944547View Description Hide Description
Click-evoked otoacoustic emissions from the human ear are typically several orders of magnitude smaller than the stimuli that elicit them—a measurement technique that attempts to cancel the stimulus signal from the recorded waveform is therefore typically employed. In practice, an imperfect cancellation of the stimulus is achieved, leaving a “stimulus artifact” that obscures the early part of the emission. Input-output nonlinearities of the transducers used in recording emissions are acknowledged as one source of the stimulus artifact. Here an additional source of this artifact, related to hysteresis in the magnetic “receivers” (loudspeakers) used in such recordings, is identified and discussed.
118(2005); http://dx.doi.org/10.1121/1.1937362View Description Hide Description
Simultaneous or near-simultaneous activation of adjacent cochlear implantelectrodes can produce pitch percepts intermediate to those produced by each electrode separately, thereby increasing the number of place-pitch steps available to cochlear implant listeners. To estimate how many distinct pitches could be generated with simultaneous dual-electrode stimulation, the present study measured place-pitch discrimination thresholds for single- versus dual-electrode stimuli in users of the Clarion CII device. Discrimination thresholds were expressed as the proportion of current directed to the secondary electrode of the dual-electrode pair. For 16 of 17 electrode pairs tested in six subjects, thresholds ranged from 0.11 to 0.64, suggesting that dual-electrode stimuli can produce 2–9 discriminable pitches between the pitches of single electrodes. Some subjects demonstrated a level effect, with better place-pitch discrimination at higher stimulus levels. Equal loudness was achieved with dual-electrode stimuli at net current levels that were similar to or slightly higher than those for single-electrode stimuli.
- APPLIED ACOUSTICS PAPER: TRANSDUCTION
The energy method for analyzing the piezoelectric electroacoustic transducers. II. (With the examples of the flexural plate transducer)118(2005); http://dx.doi.org/10.1121/1.1953087View Description Hide Description
The energy method for analyzing piezoelectric electro-acoustic transducers, described in the previous paper [B. S. Aronov, J. Acoust. Soc. Am.117, 210–220 (2005)] is used here in application to transducers operating in the receive mode. Changes to the equivalent circuit of a transducer are introduced, arising from the action of the sound field considered as the external source of energy. The application of the energy method is demonstrated by an example of the circular flexural plate transducer. The validity of the single degree of freedom approximation for calculating the transducer parameters is considered, and estimation is made of inaccuracies arising from the simplifying assumptions regarding the mode of transducer vibration. The acceptable tolerance levels for accuracy in the calculation of the transducer parameters are also discussed.
- APPLIED ACOUSTICS PAPER: ARCHITECTURAL ACOUSTICS
Field impact insulation testing: Inadequacy of existing normalization methods and proposal for new ratings analogous to those for airborne noise reduction118(2005); http://dx.doi.org/10.1121/1.1946267View Description Hide Description
The field test method for determining the Field Impact Isolation Class (FIIC) rating of a floor/ceiling assembly, prescribed in ASTM E 1007, requires an estimation of the receiving room absorption and the normalization of the receiving room sound pressure levels based on a standard quantity of room absorption. Normalization is intended to remove the effects of receiving room acoustical characteristics, but an analysis of field impact testing indicates that this method has a limited engineering value. The normalization correction is strongly dependent on receiving room volume, does not correlate with the normalization used in airborne sound isolation testing, and can be unreasonably large under certain conditions. The current test method leads to potential errors in engineering judgment, as illustrated by example field tests. By contrast, airborne noise reduction ratings (prescribed in ASTM E 336) are either non-normalized or normalized to a standard reverberation time, which provides significant advantages over normalizing to a standard amount of absorption. New impact noise metrics, the non-normalized impact sound rating (ISR) and the normalized impact sound rating (NISR), analogous to the airborne noise reduction metrics NIC and NNIC, are proposed for incorporation into ASTM E 1007. Revised building code requirements using the proposed metrics are suggested.
- GENERAL LINEAR ACOUSTICS 
118(2005); http://dx.doi.org/10.1121/1.1954587View Description Hide Description
Calculation of acoustic axes in triclinic elasticanisotropy is considerably more complicated than for anisotropy of higher symmetry. While one polynomial equation of the 6th order is solved in monoclinic anisotropy, we have to solve two coupled polynomial equations of the 6th order in two variables in triclinic anisotropy. Furthermore, some solutions of the equations are spurious and must be discarded. In this way we obtain 16 isolated acoustic axes, which can run in real or complex directions. The real/complex acoustic axes describe the propagation of homogeneous/inhomogeneous plane waves and are associated with a linear/elliptical polarization of waves in their vicinity. The most frequent number of real acoustic axes is 8 for strong triclinic anisotropy and 4 to 6 for weak triclinic anisotropy. Examples of anisotropy with no or 16 real acoustic axes are presented.
Parametrization of acoustic boundary absorption and dispersion properties in time-domain source/receiver reflection measurement118(2005); http://dx.doi.org/10.1121/1.1954567View Description Hide Description
Closed-form analytic time-domain expressions are obtained for the acoustic pressure associated with the reflection of a monopole point-source excited impulsive acoustic wave by a planar boundary with absorptive and dispersive properties. The acoustic properties of the boundary are modeled as a local admittance transfer function between the normal component of the particle velocity and the acoustic pressure. The transfer function is to meet the conditions for linear, time-invariant, causal, passive behavior. A parametrization of the admittance function is put forward that has the property of showing up explicitly, and in a relatively simple manner, in the expression for the reflected acoustic pressure. The partial fraction representation of the complex frequency domain admittance is shown to have such a property. The result opens the possibility of constructing inversion algorithms that enable the extraction of the relevant parameters from the measured time traces of the acoustic pressure at different offsets, parallel as well as normal to the boundary, between source and receiver. Illustrative theoretical numerical examples are presented.
118(2005); http://dx.doi.org/10.1121/1.1953247View Description Hide Description
This paper concerns a time-domain model of transient wave propagation in double-layered porous materials. An analytical derivation of reflection and transmission scattering operators is given in the time domain. These scattering kernels are the medium’s responses to an incident acoustic pulse. The expressions obtained take into account the multiple reflections occurring at the interfaces of the double-layered material. The double-layered porous media consist of two slabs of homogeneous isotropic porous materials with a rigid frame. Each porous slab is described by a temporal equivalent fluid model, in which the acoustic wave propagates only in the fluid saturating the material. In this model, the inertial effects are described by the tortuosity; the viscous and thermal losses of the medium are described by two susceptibility kernels which depend on the viscous and thermal characteristic lengths. Experimental and numerical results are given for waves transmitted and reflected by double-layered porous media formed by air-saturated plastic foam samples.
118(2005); http://dx.doi.org/10.1121/1.1945470View Description Hide Description
The method of superposition may be applied to reconstruct the field on a partial surface on a radiating structure from measurements made on a nearby limited surface. Unlike conformal near-field holography, where the measurementsurface surrounds the entire structure, in patch holography the measurementsurface need only be approximately as large as the patch on the structuresurface where the reconstruction is required. Using the method of superposition, the field on and near the measurementsurface may be approximated by the field produced by a source distribution placed on a surface inside the structure. The source strengths are evaluated by applying boundary conditions on the measurementsurface. The algorithm requires the inversion of the Green’s function matrix which may be ill-conditioned. Truncated singular value decomposition is used to invert it. The field on the structuresurface is then approximated by the field produced by the source distribution. The algorithm is easier to implement than the boundary elements method because it does not require integrations over singular integrands and may be applied to flat or curved surfaces.