Volume 5, Issue 2, April 2004
Index of content:
5(2004); http://dx.doi.org/10.1121/1.1637051View Description Hide Description
The optoacoustic effect has been used to study the concentration of gaseous carbon disulfide in a binary mixture with air. A 1.25-MW nitrogen laser having a wavelength of 337 nm and pulse duration of 800 ps was used as the optoacoustic source. Microphones and a laser Doppler vibrometer were used to detect the optoacoustic signal. Several test cells were used to investigate optoacoustic signals in order to detect the presence and concentration of a gas in binary mixture with air in open and closed cell environments.
5(2004); http://dx.doi.org/10.1121/1.1636502View Description Hide Description
An existing collective oscillation model for low-frequency sound generation from an open-ocean wave is extended to the surf zone. The hemispherical geometry of the open-ocean breaking wave entrained bubble cloud is replaced by a prolate hemispheroidal cloud. A Green’s function is obtained for a point source within this cloud. The far-field acoustic intensity is then computed for a distribution of point sources within a cloud. It is hypothesized that cloud resonances, assuming a “long” orientation is applicable, are determined by the minor-axis length for cloud sizes observed in the surf zone at frequencies of interest here.
5(2004); http://dx.doi.org/10.1121/1.1635751View Description Hide Description
One of the main motivations for publishing this paper is to make available a matrix of phone-distance measures which may be useful in dealing with large corpora of conversational speech. The paper reports how this matrix of phone-distances was created from transcriber labeling disagreements, and how it can be used in a dynamic time warping algorithm to align phonetic transcriptions of conversational speech with their citation forms. The weighted string edit distance produced by the phone-distance DTW algorithm may also be useful in calculating neighborhood densities for studies of auditory word recognition.
5(2004); http://dx.doi.org/10.1121/1.1638811View Description Hide Description
A masking problem in time dependent three dimensional acoustic obstacle scattering is considered. The masking problem consists in making masked a bounded scatterer characterized by an acoustic boundary impedance and immersed in a homogeneous isotropic medium that, when hit by an incident acoustic field, generates a scattered acoustic field. The precise definition of the masking problem is given later. This problem has been formulated as an optimal control problem for the wave equation. The corresponding first order optimality condition is derived and solved with a highly parallelizable numerical method. Some numerical experience on a test problem is shown.
5(2004); http://dx.doi.org/10.1121/1.1635431View Description Hide Description
The present study investigated whether a new tool for nearly natural speech synthesis, STRAIGHT [Kawahara et al., Speech Commun. 27, 187–207 (1999)], could be used for fine manipulation of vowelformants, using a psychophysical test of formant discrimination. Thresholds for formant discrimination of F1 and F2 for an /ɛ/ vowel, originally synthesized by the KLTSYN [Klatt, J. Acoust. Soc. Am. 67, 971–995 (1980)] and then resynthesized by STRAIGHT, were estimated. Thresholds for vowels generated by KLTSYN and by STRAIGHT were not significantly different. This result validates that STRAIGHT resynthesis can finely manipulate formant frequencies from natural speech for use in speech perception experiments.
Effect of the diameter and the sound speed of a kidney stone on the acoustic field induced by shock waves5(2004); http://dx.doi.org/10.1121/1.1635432View Description Hide Description
A time-domain finite-difference solution to the acoustic waveequation was used to model the propagation of lithotripsy shock waves in kidney stones. Varying the sound-speed of the stone had minimal effect on the pressure within the stone. Reducing stone diameter dramatically reduced negative, but not positive, pressures. For composite stones the pressures amplitude changed little, but specific configurations resulted in the peak negative pressure occurring at an internal interface—a likely weak point in the stone. These results indicate that the pressure field in a kidney stone is very sensitive to the size and internal composition of the stone.
5(2004); http://dx.doi.org/10.1121/1.1688405View Description Hide Description
A method is presented for determining the amount of information transferred through an oceanic channel caused by a variation of source position. The method generalizes to parameters other than source position. The amount of information transferred is shown to depend on the modulation by propagation and also the signal to noise ratio of the data. A simple numerical example is presented for a single, fixed receiver and a broadband source at a variable position in a two-mode channel.
5(2004); http://dx.doi.org/10.1121/1.1687471View Description Hide Description
A loudness matching procedure was used to construct an excitation scale for cochlear implant patients relating neural excitation to electric charge per pulse. Statistical analysis shows the relationship to be linear for sufficiently low charge levels, with a constant slope across electrodes within individual patients. The excitation scale enables an “incremental” encoding procedure from acoustic level to electric stimulus that is independent of the pulse rate used. The statistical properties of the scale parameters can be used to simplify the fitting procedure for the implant processor. Perception of vowels and consonants using conventional and “incremental” encoding produced similar scores for four patients.
Using hearing aid directional microphones and noise reduction algorithms to enhance cochlear implant performance5(2004); http://dx.doi.org/10.1121/1.1666869View Description Hide Description
Hearing aids and cochlear implants are two major hearing enhancement technologies but yet share little in research and development. The purpose of this study was to determine whether hearing aid directional microphones and noise reduction technologies could enhance cochlear implant users’ speech understanding and ease of listening. Digital hearing aids serving as preprocessors were programmed to omni-directional microphone, directional microphone, and directional microphone plus noise reduction conditions. Three groups of subjects were tested with the hearing aid processed speech stimuli. Results indicated that hearing aids with directional microphones and noise reduction algorithms significantly enhanced speech understanding and listening comfort.
5(2004); http://dx.doi.org/10.1121/1.1652111View Description Hide Description
An experimental study has been performed for cell suspensions to compare efficiency of cell transfection. It was demonstrated that electroporation was superior to sonoporation in terms of viability (65.8±2.3% vs 50.8±4.15%) and transfection efficiency (15.83±3.5% vs 7.53±0.4%) for Jurkat lymphocytes (nonprimary cells), and sonoporation was better in terms of viability (64.8±1.51% vs 53.7±1.53%) and transfection efficiency (2.73±0.21% vs 0.43±0.06%) for human peripheral blood mononuclear cells (primary cells). The electroporation was performed using a Gene Pulser® II Apparatus with voltage of 250 V, and the sonoporation was achieved using 2-MHz pulsed ultrasound exposure assisted with encapsulated bubbles (Optison®).
5(2004); http://dx.doi.org/10.1121/1.1650411View Description Hide Description
In this paper the performance of generalized sidelobe canceller (GSC) in room with reverberation is analyzed. GSC is inefficient in interference suppression when there is any correlation between interference and desired signal. The reason for this is unwanted cancellation of desired signal. It was shown that cancellation of the desired signal is proportional to the correlation between the direct wave of desired signal and its reflections. There is no cancellation if the GSC weightings are estimated in pauses of desired signal. Using these facts, a new algorithm based on pause detection was proposed. Simulations prove the advantage of proposed algorithm.
5(2004); http://dx.doi.org/10.1121/1.1651193View Description Hide Description
Using model reduction, an efficient low order modeling process for speech is presented. In this approach, the modeling process starts with a relatively high order model obtained by some classical methods. The model is then reduced using the -based method. The model reduction yields a reduced order model which interestingly preserves the key properties of the original full order model such as stability. Line spectral frequencies and signal-to-noise ratio behavior are also investigated. To illustrate the performance and the effectiveness of the proposed approach, some simulations are conducted on some practical speech segments, such as phonemes and sentences.