Volume 125, Issue 4, April 2009
- jasa express letters
- letters to the editor
- general linear acoustics 
- nonlinear acoustics 
- aeroacoustics, atmospheric sound 
- underwater sound 
- transduction 
- structural acoustics and vibration 
- architectural acoustics 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- speech processing and communication systems 
- music and musical instruments 
- bioacoustics 
- acoustical news—usa
- acoustical news—international
- reviews of acoustical patents
- program abstracts of the 157th meeting of the acoustical society of america
- award encomiums
- program abstracts of the 157th meeting of the acoustical society of america
Index of content:
- JASA EXPRESS LETTERS
125(2009); http://dx.doi.org/10.1121/1.3081975View Description Hide Description
The virtual reflector method simulates new seismic signals by processing traces recorded by a plurality of sources and receivers. The approach is based on the crossconvolution of the recorded signals and makes it possible to obtain the Green’s function of virtual reflected signals as if in the position of the receivers (or sources) there were a reflector, even if said reflector is not present. This letter presents the virtual reflector theory based on the Kirchhoff integral representation theorem for wave propagation in an acoustic medium with and without boundary and a generalization to variable reflection coefficients for scattered wavefields.
125(2009); http://dx.doi.org/10.1121/1.3082003View Description Hide Description
Energy streamlines provide insights into mechanisms of wave propagation and scattering and are often utilized to visualize wave fields. In contrast to rays, which are essentially an asymptotic, short-wave concept, energy streamlines adequately represent arbitrary wave fields. However, the usefulness of energy streamlines in studies of wave fields is limited by the fact that, unlike rays, no general laws governing energy streamline refraction are known. Here, a simple refraction law is derived for energy streamlines of acoustic and linearly polarized electromagnetic waves. It is shown that analysis of energy streamlines provides a helpful supplementary perspective on wave transmission through interfaces.
125(2009); http://dx.doi.org/10.1121/1.3081983View Description Hide Description
Permeability of a porous material with a fluid interface is shown to be related to the propagation of the slow longitudinal wave. The propagation threshold of the slow longitudinal wave occurs when the wave number is higher than the critical wave number, . Measuring can provide the intrinsic permeability of a porous interface. The ability to detect a change in due to differences in pore size and fluid viscosity is demonstrated. This measurement is demonstrated in a model material with two pore sizes and two fluid viscosities. The results suggest opportunities to extend the method to a range of materials of scientific and technical importance.
125(2009); http://dx.doi.org/10.1121/1.3082002View Description Hide Description
The dispersion curves of four lowest plate acoustic waves (PAWs) in the cut of a periodically poled lithium niobate (PPLN) wafer are computed numerically and investigated experimentally. Experiment is in agreement with simulated dispersion curves. Calculations and measurements reveal the stop-bands in the dispersion curves of the PAW modes in PPLN despite a wafer that has uniform mechanical properties. At a specific wave number, within the frequencies of the stop-bands, the acoustic modes do not propagate.
125(2009); http://dx.doi.org/10.1121/1.3082261View Description Hide Description
Echo threshold variability has previously been examined using stimuli that are carefully controlled and artificial (e.g., clicks and noise bursts), while studies using speech stimuli have only reported average thresholds. To begin to understand how echo thresholds might vary among speechsounds, four syllables were selected in pairs that contrasted abruptness vs gradualness of onset envelopes. Fusion and discrimination suppression thresholds, two echo thresholds commonly used to study the precedence effect, differed among syllables. Results were used to evaluate two predictive heuristics adapted from perceptual center (p-center)models.
125(2009); http://dx.doi.org/10.1121/1.3082263View Description Hide Description
The purpose of this study was to derive vocal tract modes from a wider range of vowel area functions for a specific speaker than has been previously reported. Area functions from Story et al. [(1996). J. Acoust. Soc. Am.100, 537–554] and Story [(2008). J. Acoust. Soc. Am.123, 327–335] were combined in a composite set from which modes were derived with principal component analysis. Along with scaling coefficients, these modes were used to generate a [F1, F2] formant space. In comparison to formant spaces similarly generated based on the two area function sets alone, the combined version provides a wider range of both F1 and F2 values. This new set of modes may be useful for inverse mapping of formant frequencies to area functions or for modeling of vocal tract shape changes.
125(2009); http://dx.doi.org/10.1121/1.3093797View Description Hide Description
The rotary subwoofer is a novel low frequency transducer capable of efficiently generating infrasound from a compact source. A field-deployable version of this device may find application as a calibration source for infrasound arrays of the International Monitoring System (IMS) [(2001). The Global Verification Regime and the International Monitoring System (CTBTO Preparatory Commission Vienna International Centre, Vienna, Austria)]. A prototype tested at the IMSinfrasound array I59US demonstrated the ability to insonify all elements of the array from a standoff distance of . Signal-to-noise ratios of continuous wave signals ranged from , indicating the utility of this source to transmit controllableinfrasound signals over distances of .
125(2009); http://dx.doi.org/10.1121/1.3089733View Description Hide Description
When a brass instrument is played loudly, the energy level of the higher harmonics increases dramatically. The generally accepted explanation for this is non-linear steepening of the wavefront and generation of shock waves within the instrument bore. However, it has also been suggested that changes in the player’s lip vibration could play a role in generating this “brassy” sound. To test this hypothesis, the dependence of lip opening-area on time has been measured for different dynamic levels in trombones and horns. Results suggest that the behavior of the open area does not change dramatically when the instrument enters the brassy regime.
125(2009); http://dx.doi.org/10.1121/1.3097680View Description Hide Description
This paper presents a method of determining the compressional wave attenuation in marine sediment from a short range measurement. The data were collected on a vertical line array at a range of 230 m during the Shallow Water 2006 experiments. The sediment attenuation is extracted from the signal strength ratio of the sea bottom reflection to a sub-bottom reflection at different frequencies from 1.75 to 3.15 kHz. Linear frequency dependence of the attenuation is found from the estimation. The sediment attenuation estimate is lower than the values estimated from the inversions of acoustic field data previously done in the vicinity.
Sand acoustics: The effective density fluid model, Pierce/Carey expressions, and inferences for porous media modeling125(2009); http://dx.doi.org/10.1121/1.3097681View Description Hide Description
Recently, Pierce and Carey [J. Acoust. Soc. Am.124, EL308–EL312 (Year: 2008)] presented a low frequency analysis of sound propagation in sand/silty sediments. Here, equivalent expressions are presented using a low frequency expansion of an unconsolidated version of Biot porous medium theory. The resulting expression for attenuation allows identification of the non-dimensional parameter in the Pierce/Carey result in terms of physical parameters. The agreement of these two derivations motivates further analyses. The results imply that porous media propagation models that treat the medium’s inertia via a single component approximation disregard a fundamental physical effect resulting from the relative inertia of the grains and fluid and are thus incomplete.
125(2009); http://dx.doi.org/10.1121/1.3097690View Description Hide Description
A statistical estimation of source location incorporating uncertainty in ocean environmental model parameters is derived using a Bayesian approach. From a previous geoacoustic inversion, a posterior probability distribution of the environmental parameters that reflects uncertainty in the ocean environment is obtained. This geoacoustic uncertainty then is mapped into uncertainty in the acoustic pressure field and is propagated through the Bartlett matched-field processor for source localization. Using data from the ASIAEX 2001 East China Sea experiment, the estimated source location and variability over time are compared with the known source positions.
- LETTERS TO THE EDITOR
Monitoring stress related velocity variation in concrete with a relative resolution using diffuse ultrasound125(2009); http://dx.doi.org/10.1121/1.3079771View Description Hide Description
Ultrasonicwaves propagating in solids have stress-dependent velocities. The relation between stress (or strain) and velocity forms the basis of non-linear acoustics. In homogeneous solids, conventional time-of-flight techniques have measured this dependence with spectacular precision. In heterogeneous media such as concrete, the direct (ballistic)wave around 500 kHz is strongly attenuated and conventional techniques are less efficient. In this manuscript, the effect of weak stress changes on the late arrivals constituting the acoustic diffuse coda is tracked. A resolution of in relative velocity change is attained which corresponds to a sensitivity to stress change of better than 50 kPa. Therefore, the technique described here provides an original way to measure the non-linear parameter with stress variations on the order of tens of kPa.
Comment on “Measurement of the frequency dependence of the ultrasonic parametric threshold amplitude for a fluid-filled cavity”125(2009); http://dx.doi.org/10.1121/1.3089223View Description Hide Description
Measurements of the threshold amplitude of the pump signal for parametric excitation of ultrasonic standing waves in a water-filled container are described in the paper of Teklu et al. [(2006). J. Acoust. Soc. Am.120, 657–660]. The threshold is reported to increase with increasing pump frequency from 2 to 7 MHz, in apparent disagreement with earlier measurements made in 1970 over the same frequency range in similar apparatus showing a decrease in parametric threshold with increasing frequency. It is shown that the very theory presented in both papers may explain the frequency dependence observed with the new 2006 data rather than the old 1970 data if proper account is taken of the variation in the acoustic absorption coefficient of water with frequency. However, other questions raised by data in both papers indicate the possibility that the phenomenon they describe was not parametric excitation.
125(2009); http://dx.doi.org/10.1121/1.3082123View Description Hide Description
A set of equations has been derived which corresponds to the time domain formulation of the equivalent fluid model. It models the propagation of an acoustic pulse in rigid frame porous material accounting for both viscous and thermal effects. It has been shown analytically and confirmed numerically that the equations can be reduced to those published previously in the limit of long and short duration pulses. Numerical solutions have been found for different pulse durations and the results have been compared with other time domain models.
125(2009); http://dx.doi.org/10.1121/1.3081500View Description Hide Description
Comparisons are performed between the results of a simple classic formulation for the acoustic field created by a point source above a porous layer and an exact description. A semi-infinite layer and layers of finite thickness are considered. It is shown that for layers of finite thickness and small flow resistivity the use of the classic formulation can lead to large errors close to grazing incidence.
- GENERAL LINEAR ACOUSTICS 
A filtered convolution method for the computation of acoustic wave fields in very large spatiotemporal domains125(2009); http://dx.doi.org/10.1121/1.3077220View Description Hide Description
The full-wave computation of transient acoustic fields with sizes in the order of wavelengths by 100 periods requires a numerical method that is extremely efficient in terms of storage and computation. Iterative integral equation methods offer a good performance on these points, provided that the recurring spatiotemporal convolutions are computed with a coarse sampling and relatively few computational operations. This paper describes a method for the numerical evaluation of very large-scale, four-dimensional convolutions that employs a fast Fourier transformation and that uses a sampling rate close to or at the limit of two points per wavelength and per period. To achieve this, the functions involved are systematically filtered, windowed, and zero-padded with respect to all relevant coordinates prior to sampling. The method is developed in the context of the Neumann iterative solution of the acoustic contrast source problem for an inhomogeneous medium. The implementation of the method on a parallel computer is discussed. The obtained numerical results have a relative root mean square error of a few percent when sampling at two points per wavelength and per period. Further, the results prove that the method enables the computation of transient fields in the order of the indicated size.
- NONLINEAR ACOUSTICS 
125(2009); http://dx.doi.org/10.1121/1.3081385View Description Hide Description
Parametric array applications in air, such as highly directional parametric loudspeaker systems, usually rely on large radiators to generate the high-intensity primary beams required for nonlinear interactions. However, a conventional transducer, as a primary wave projector, requires a great deal of electrical power because its electroacoustic efficiency is very low due to the large characteristic mechanical impedance in air. The feasibility of a micro-machined ultrasonic transducer as an efficient finite-amplitude wave projector was studied. A piezoelectric micro-machined ultrasonic transducer array consisting of lead zirconate titanate uni-morph elements was designed and fabricated for this purpose. Theoretical and experimental evaluations showed that a micro-machined ultrasonic transducer array can be used as an efficient source transducer for a parametric array in air. The beam patterns and propagation curves of the difference frequency wave and the primary wave generated by the micro-machined ultrasonic transducer array were measured. Although the theoretical results were based on ideal parametric array models, the theoretical data explained the experimental results reasonably well. These experiments demonstrated the potential of micro-machined primary wave projector.
125(2009); http://dx.doi.org/10.1121/1.3081530View Description Hide Description
At sufficient gain an ultrasonic feedback circuit rings with a “Larsen” tone that depends on the acoustic properties of the solid body to which it is attached. Because the frequency of this tone may be measured virtually continuously and with high precision, it is potentially capable of responding to fast small changes in materials. Here a tentative theory for Larsen dynamics is introduced and compared with laboratory measurements. Larsen monitoring is then applied to observation of the curing process of a cement paste sample and to studies of “slow dynamics” in which mesoscale nonlinear materials subjected to modest loads experience a drop in modulus but then recover in a characteristic manner like . The present technique, using as it does higher frequencies and the Larsen effect and brief transient loads, extends investigations of slow dynamics to earlier times. For the materials and loads investigated, it is found that behavior fails at the shortest times, recovery being faster over the first several milliseconds.
125(2009); http://dx.doi.org/10.1121/1.3083223View Description Hide Description
Acoustic and seismic waves provide a method to localize compliant mines by vibrating the top plate and a thin soil layer above the mine. This vibration is mostly linear, but also includes a small nonlinear deviation. The main goal of this paper is to introduce a method of processing that uses phase-inversion to observe nonlinear effects in a wide frequency band. The method extracts a nonlinear part of surface velocity from two similar broadcast signals of opposite sign by summing and canceling the linear components and leaving the nonlinear components. This phase-inversion method is combined with time reversal focusing to provide increased seismic vibration and enhance the nonlinear effect. The experiments used six loudspeakers in a wood box placed over sand in which inert landmines were buried. The nonlinear surface velocity of the sand with a mine compared to the sand without a mine was greater as compared to a linear technique.
- AEROACOUSTICS, ATMOSPHERIC SOUND 
Finite difference time domain electroacoustic model for synthetic jet actuators including nonlinear flow resistance125(2009); http://dx.doi.org/10.1121/1.3081514View Description Hide Description
A lumped element electroacoustic model for a synthetic jet actuator is presented. The model includes the nonlinear flowresistance associated with flow separation and employs a finite difference scheme in the time domain. As opposed to more common analytical frequency domain electroacoustic models, in which the nonlinear resistance can only be considered as a constant, it allows the calculation of higher harmonics, i.e., distortion components, generated as a result of this nonlinear resistance.Model calculations for the time-averaged momentum flux of the synthetic jet as well as the radiated sound power spectrum are compared to experimental results for various configurations. It is shown that a significantly improved prediction of the momentum flux—and thus flow velocity—of the jet is obtained when including the nonlinear resistance. Here, the current model performs slightly better than an analytical model. For the power spectrum of radiated sound, a reasonable agreement is obtained when assuming a plausible slight asymmetry in the nonlinear resistance. However, results suggest that loudspeaker nonlinearities play a significant role as well in the generation of the first few higher harmonics.