Volume 130, Issue 2, August 2011
- jasa express letters
- letters to the editor
- general linear acoustics 
- 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 
- music and musical instruments 
- bioacoustics 
- acoustical news
- reviews of acoustical patents
Index of content:
- JASA EXPRESS LETTERS
130(2011); http://dx.doi.org/10.1121/1.3601925View Description Hide Description
This work investigates the effect of the acoustic feedback of rotary encoders that are common in current human-machine-interfaces. The results are based on subjective trials in which the probands had to complete generic tasks using an encoder with programmable electro acoustic feedback. The tasks had to be performed with individually optimized feedback and two reference conditions. The results of the investigation showed the advantage of well-defined acoustic feedback on both accuracy and speed of task fulfillment.
130(2011); http://dx.doi.org/10.1121/1.3609919View Description Hide Description
Impact sounds synthesized according to a physical model have increasingly become the stimulus of choice in studies of sound source perception. Few studies, however, have incorporated manner of contact in their models because of the complexity of the mechanics involved. Here a simplified model of contact is described suitable for application to perceptual research. The results of the simplified model are shown to be in good agreement with those of more comprehensive numerical methods receiving prior acoustic validation [Chaigne and Lambourg, J. Acoust. Soc. Am.109, 1422–1432 (2001)]. The advantages of the model for applications to perceptual research are discussed.
Ultrasonic anechoic chamber qualification: Accounting for atmospheric absorption and transducer directivity130(2011); http://dx.doi.org/10.1121/1.3606461View Description Hide Description
Qualifying an anechoic chamber for frequencies that extend into the ultrasonic range is necessary for research work involving airborne ultrasonic sound. The ANSI S12.55/ISO 3745 standard which covers anechoic chamber qualification does not extend into the ultrasonic frequency range, nor have issues pertinent to this frequency range been fully discussed in the literature. An increasing number of technologies employ ultrasound; hence the need for an ultrasonicanechoic chamber. This paper will specifically discuss the need to account for atmospheric absorption and issues pertaining to source transducer directivity by presenting some results for qualification of a chamber at Brigham Young University.
130(2011); http://dx.doi.org/10.1121/1.3606571View Description Hide Description
The waveguide invariant summarizes the pattern of constructive and destructive interference between acoustic modes propagating in the oceanwaveguide. For many sonar signal-processing schemes, it is essential to know the correct numerical value for the waveguide invariant. While conventional beamforming can estimate the ratio between the waveguide invariant and the range to the source, it cannot unambiguously separate the two terms. In the present work, striation-based beamforming is developed. It is shown that the striation-based beamformer can be used to produce an estimate for the waveguide invariant that is independent of the range. Simulation results are presented.
130(2011); http://dx.doi.org/10.1121/1.3609125View Description Hide Description
Characterization of laryngealflow velocity fields is important to understanding vocal fold vibration and voice production. One common method for acquiring flow field data is particle imagevelocimetry(PIV). However, because using PIV with models that have curved surfaces is problematic due to optical distortion, experimental investigations of laryngeal airflow are typically performed using models with idealized geometries. In this paper a method for acquiring PIV data using models with realistic geometries is presented. Sample subglottal, intraglottal, and supraglottal PIV data are shown. Capabilities and limitations are discussed, and suggestions for future implementation are provided.
130(2011); http://dx.doi.org/10.1121/1.3609920View Description Hide Description
Lithotripter shock waves (SWs) generated in non-degassed water at 0.5 and 2 Hz pulse repetition frequency (PRF) were characterized using a fiber-optic hydrophone. High-speed imaging captured the inertial growth-collapse-rebound cycle of cavitationbubbles, and continuous recording with a 60 fps camcorder was used to track bubble proliferation over successive SWs. Microbubbles that seeded the generation of bubble clouds formed by the breakup of cavitation jets and by bubble collapse following rebound. Microbubbles that persisted long enough served as cavitation nuclei for subsequent SWs, as such bubble clouds were enhanced at fast PRF. Visual tracking suggests that bubble clouds can originate from single bubbles.
Binaural benefit for speech recognition with spectral mismatch across ears in simulated electric hearing130(2011); http://dx.doi.org/10.1121/1.3606460View Description Hide Description
The present study investigated the effects of binaural spectral mismatch on binaural benefits in the context of bilateral cochlear implants using acoustic simulations.Binaural spectral mismatch was systematically manipulated by simulating changes in the relative insertion depths across ears. Sentence recognition, presented unilaterally and bilaterally, were measured in normal-hearing listeners in quiet and noise at +5 dB signal-to-noise ratio. Significant binaural benefits were observed when the interaural difference in insertion depth was 1 mm or less. This result suggests a dependence of the binaural benefit on redundant speechinformation, rather than on similarity in performance across ears.
130(2011); http://dx.doi.org/10.1121/1.3611395View Description Hide Description
This paper presents a single receiver geoacoustic inversion method adapted for low-frequency impulsive sources. It is applied to light bulb data collected during the Shallow Water 2006 experiment. The inversion is carried out by extracting dispersion curves from the received signal, and comparing them to simulated replicas. To achieve dispersion curve estimation in the time-frequency domain, modal separability is improved using a signal processing method called warping. The inversion scheme allows for a reliable estimation of the New Jersey Shelf sediment properties (compressional sound speed and density). It also provides an accurate estimation of the source/receiver range.
Perception of interrupted speech: Cross-rate variation in the intelligibility of gated and concatenated sentences130(2011); http://dx.doi.org/10.1121/1.3606463View Description Hide Description
Temporal constraints on the perception of variable-size speech fragments produced by interruption rates between 0.5 and 16 Hz were investigated by contrasting the intelligibility of gated sentences with and without silent intervals. Concatenation of consecutive speech fragments produced a significant decrease in intelligibility at 2 and 4 Hz, while having little effect at lower and higher rates. Consistent with previous studies, these findings indicate that (1) syllable-sized intervals associated with intermediate-rate interruptions are more susceptible to temporal distortions than the longer word-size or shorter phoneme-size intervals and (2) suggest qualitative differences in underlying perceptual processes at different rates.
130(2011); http://dx.doi.org/10.1121/1.3602462View Description Hide Description
This study investigated the ability to use temporal-envelope (E) cues in a consonant identification task when presented within one or two frequency bands. Syllables were split into five bands spanning the range 70–7300 Hz with each band processed to preserve E cues and degrade temporal fine-structure cues. Identification scores were measured for normal-hearing listeners in quiet for individual processed bands and for pairs of bands. Consistent patterns of results were obtained in both the single- and dual-band conditions: identification scores increased systematically with band center frequency, showing that E cues in the higher bands (1.8–7.3 kHz) convey greater information.
130(2011); http://dx.doi.org/10.1121/1.3607196View Description Hide Description
Ultrasound propagation in cancellous bone (porous media) under the condition of closed pore boundaries was investigated. A cancellous bone and two plate-like cortical bones obtained from a racehorse were prepared. A water-immersion ultrasound technique in the MHz range and a three-dimensional elastic finite-difference time-domain(FDTD) method were used to investigate the waves. The experiments and simulations showed a clear separation of the incident longitudinal wave into fast and slow waves. The findings advance the evaluation of bones based on the two-wave phenomenon for in vivo assessment.
- LETTERS TO THE EDITOR
Boundary effects on backscattering by a solid aluminum cylinder: Experiment and finite element model comparisons (L)130(2011); http://dx.doi.org/10.1121/1.3613806View Description Hide Description
Backscattering of sound by a solid aluminum cylinder was measured in the free field and with the cylinder near a flat surface. The target was suspended just below the surface of a water tank to simulate some aspects of backscattering when resting on the seabed. Measurements were compared with predictions made by an approximate hybrid approach based on multiple two-dimensional finite element calculations and the use of images. Many of the spectral features present in the tank data were present in the model. Comparing numerical model predictions with experimental data serves to build credibility for the modeling approach and can assist in developing insight into the underlying physical processes.
130(2011); http://dx.doi.org/10.1121/1.3598430View Description Hide Description
The acoustical insertion losses produced by a balcony-like structure in front of a window are examined experimentally. The results suggest that the balcony ceiling is the most appropriate location for the installation of artificial sound absorption for the purpose of improving the broadband insertion loss, while the side walls are found to be the second best. Results also indicate that the acoustic modes of the balcony opening and the balcony cavity resonance in a direction normal to the window could have a great impact on the one-third octave band insertion losses. The maximum broadband road traffic noise insertion loss achieved is about 7 dB.
Hearing thresholds of a harbor porpoise (Phocoena phocoena) for helicopter dipping sonar signals (1.43–1.33 kHz) (L)130(2011); http://dx.doi.org/10.1121/1.3605541View Description Hide Description
Helicopter long range active sonar (HELRAS), a “dipping” sonar system used by lowering transducer and receiver arrays into water from helicopters, produces signals within the functional hearing range of many marine animals, including the harbor porpoise. The distance at which the signals can be heard is unknown, and depends, among other factors, on the hearing sensitivity of the species to these particular signals. Therefore, the hearing thresholds of a harbor porpoise for HELRAS signals were quantified by means of a psychophysical technique. Detection thresholds were obtained for five 1.25 s simulated HELRAS signals, varying in their harmonic content and amplitude envelopes. The 50% hearing thresholds for the different signals were similar: 76 dB re 1 μPa (broadband sound pressure level, averaged over the signal duration). The detection thresholds were similar to those found in the same porpoise for tonal signals in the 1–2 kHz range measured in a previous study. Harmonic distortion, which occurred in three of the five signals, had little influence on their audibility. The results of this study, combined with information on the source level of the signal, the propagation conditions and ambient noise levels, allow the calculation of accurate estimates of the distances at which porpoises can detect HELRAS signals.
- GENERAL LINEAR ACOUSTICS 
130(2011); http://dx.doi.org/10.1121/1.3613707View Description Hide Description
In this paper the virtual source technique is used to compute scattering of a plane wave from a periodic oceansurface. The virtual source technique is a method of imposing boundary conditions using virtual sources, with initially unknown complex amplitudes. These amplitudes are then determined by applying the boundary conditions. The fields due to these virtual sources are given by the environment Green’s function. In principle, satisfying boundary conditions on an infinite surface requires an infinite number of sources. In this paper, the periodic nature of the surface is employed to populate a single period of the surface with virtual sources and msurface periods are added to obtain scattering from the entire surface. The use of an accelerated sum formula makes it possible to obtain a convergent sum with relatively small number of terms (∼40). The accuracy of the technique is verified by comparing its results with those obtained using the integral equation technique.
130(2011); http://dx.doi.org/10.1121/1.3607417View Description Hide Description
The local resonances of a free isotropic elastic plate are investigated using laser ultrasonic techniques. Experimental results are interpreted in terms of zero group velocity Lamb modes and edge mode. At a distance from the edge larger than the plate thickness a sharp resonance is observed at the frequency where the group velocity of the first symmetrical Lamb mode vanishes. Close to the edge of the plate, the resonance due to the edge mode dominates. Both zero group velocity and edge resonances appear at the theoretically predicted frequencies. These frequencies do not vary with the distance from the edge of the plate and the transition between the two modes of vibration, at about the plate thickness, is abrupt. Using a laser excitation on the edge, the amplitude profile of the normal displacement at the edge resonance frequency was determined.
Acoustic attenuation, phase and group velocities in liquid-filled pipes II: Simulation for spallation neutron sources and planetary exploration130(2011); http://dx.doi.org/10.1121/1.3598463View Description Hide Description
This paper uses a Finite Element Method(FEM) to compare predictions of the attenuation and sound speeds of acoustic modes in a fluid-filled pipe with those of the analytical model presented in the first paper in this series. It explains why, when the predictions of the earlier paper were compared with experimental data from a water-filled PMMA pipe, the uncertainties and agreement for attenuation data were worse than those for sound speed data. Having validated the FEM approach in this way, the versatility of FEM is thereafter demonstrated by modeling two practical applications which are beyond the analysis of the earlier paper. These applications model propagation in the mercury-filled steel pipework of the Spallation Neutron Source at the Oak Ridge National Laboratory (Tennessee), and in a long-standing design for acoustic sensors for use on planetary probes. The results show that strong coupling between the fluid and the solid walls means that erroneous interpretations are made of the data if they assume that the sound speed and attenuation in the fluid in the pipe are the same as those that would be measured in an infinite volume of identical fluid, assumptions which are common when such data have previously been interpreted.
- UNDERWATER SOUND 
130(2011); http://dx.doi.org/10.1121/1.3605666View Description Hide Description
It has been hypothesized that at sufficiently high levels of oceanic salinity turbulence it should be possible to observe acoustic backscattering. However, there have been limited in situ measurements to confirm this hypothesis. Using an autonomous underwater vehicle equipped with upward and downward looking 1.2 MHz acoustic Doppler current profilers and with turbulence and fine scale sensors, measurements were performed in a region of intense turbulence and a strong salinity gradient. The approach taken was to correlate variations in the backscattered acoustic intensity, I, with a theoretical acoustic backscattering cross section per volume for salinity turbulence, , to obtain an estimated scattering cross section per volume, . Results indicated that of order 50% of the observed region was characterized by salinity turbulence induced backscattering.
Adaptive projection method applied to three-dimensional ultrasonic focusing and steering through the ribs130(2011); http://dx.doi.org/10.1121/1.3607419View Description Hide Description
An adaptive projection method for ultrasonic focusing through the rib cage, with minimal energy deposition on the ribs, was evaluated experimentally in 3D geometry. Adaptive projection is based on decomposition of the time-reversal operator (DORT method) and projection on the “noise” subspace. It is shown that 3D implementation of this method is straightforward, and not more time-consuming than 2D. Comparisons are made between adaptive projection, spherical focusing, and a previously proposed time-reversal focusing method, by measuring pressure fields in the focal plane and rib region using the three methods. The ratio of the specific absorption rate at the focus over the one at the ribs was found to be increased by a factor of up to eight, versus spherical emission. Beam steering out of geometric focus was also investigated. For all configurations projecting steered emissions were found to deposit less energy on the ribs than steering time-reversed emissions: thus the non-invasive method presented here is more efficient than state-of-the-art invasive techniques. In fact, this method could be used for real-time treatment, because a single acquisition of back-scattered echoes from the ribs is enough to treat a large volume around the focus, thanks to real time projection of the steered beams.