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Jun 2008

Volume 123, Issue 6, pp. 4023-EL168

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Measurement of the resonance frequency of single bubbles using a laser Doppler vibrometer

Theodore F. Argo, IV, Preston S. Wilson, and Vikrant Palan

J. Acoust. Soc. Am. Volume 123, Issue 6, pp. EL121-EL125 (2008); (5 pages) | Cited 1 time

Online Publication Date: 14 May 2008

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The behavior of bubbles confined in tubes and channels is important in medical and industrial applications. In these small spaces, traditional means of experimentally observing bubble dynamics are often impossible or significantly perturb the system. A laser Doppler vibrometer (LDV) requires a narrow (<1 mm diameter) line-of-sight access for the beam and illumination of the bubble does not perturb its dynamics. LDV measurements of the resonance frequency of a bubble suspended in a small tank are presented to illustrate the utility of this measurement technique. The precision of the technique is similar to the precision of traditional acoustic techniques.
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43.30.Xm Underwater measurement and calibration instrumentation and procedures
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A mechanism stimulating sound production from air bubbles released from a nozzle

Grant B. Deane and Helen Czerski

J. Acoust. Soc. Am. Volume 123, Issue 6, pp. EL126-EL132 (2008); (7 pages) | Cited 2 times

Online Publication Date: 14 May 2008

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Gas bubbles in water act as oscillators with a natural frequency inversely proportional to their radius and a quality factor determined by thermal, radiation, and viscous losses. The linear dynamics of spherical bubbles are well understood, but the excitation mechanism leading to sound production at the moment of bubble creation has been the subject of speculation. Experiments and models presented here show that sound from bubbles released from a nozzle can be excited by the rapid decrease in volume accompanying the collapse of the neck of gas which joins the bubble to its parent.
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43.30.Lz Underwater applications of nonlinear acoustics; explosions
43.30.Nb Noise in water; generation mechanisms and characteristics of the field
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Uncertainties caused by source directivity in room-acoustic investigations

Ricardo San Martín and Miguel Arana

J. Acoust. Soc. Am. Volume 123, Issue 6, pp. EL133-EL138 (2008); (6 pages)

Online Publication Date: 14 May 2008

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Although deviations in the measurement of acoustic parameters should be lower than the subjectively perceivable change in the corresponding parameter measured, this study reflects that directionality of sound sources could cause wide audience areas to break away from this criterion at high frequencies, even when using dodecahedron loudspeakers which meet the requirements of the ISO 3382 standard. The directivity of four different acoustic sources was measured and the influence of its accurate orientation spatially quantified in five enclosures for speech and music. By means of simulation software, the number of receivers affected by uncertainties greater than difference limens was established.
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43.55.Mc Room acoustics measuring instruments, computer measurement of room properties
43.55.Ka Computer simulation of acoustics in enclosures, modeling
43.38.Ja Loudspeakers and horns, practical sound sources
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Determination of acoustic attenuation in the Hudson River Estuary by means of ship noise observations

Heui-Seol Roh, Alexander Sutin, and Barry Bunin

J. Acoust. Soc. Am. Volume 123, Issue 6, pp. EL139-EL143 (2008); (5 pages)

Online Publication Date: 14 May 2008

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Analysis of sound propagation in a complex urban estuary has application to underwater threat detection systems, underwater communication, and acoustic tomography. One of the most important acoustic parameters, sound attenuation, was analyzed in the Hudson River near Manhattan using measurements of acoustic noise generated by passing ships and recorded by a fixed hydrophone. Analysis of the ship noise level for varying distances allowed estimation of the sound attenuation in the frequency band of 10–80 kHz. The effective attenuation coefficient representing the attenuation loss above cylindrical spreading loss had only slight frequency dependence and can be estimated by the frequency independent value of 0.058 dB/m.
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43.30.Nb Noise in water; generation mechanisms and characteristics of the field
43.30.Xm Underwater measurement and calibration instrumentation and procedures
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Infants use prosodically conditioned acoustic-phonetic cues to extract words from speech

Elizabeth K. Johnson

J. Acoust. Soc. Am. Volume 123, Issue 6, pp. EL144-EL148 (2008); (5 pages) | Cited 1 time

Online Publication Date: 14 May 2008

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The Headturn Preference Paradigm was used to examine infants’ use of prosodically conditioned acoustic-phonetic cues to find words in speech. Twelve-month-olds were familiarized to one passage containing an intended target (e.g., toga from toga#lore) and one passage containing an unintended target (e.g., dogma from dog#maligns). Infants were tested on the familiarized intended word (e.g., toga), familiarized unintended word (e.g., dogma), and two unfamiliar words. Infants listened longer to familiar intended words than to familiar unintended or unfamiliar words, demonstrating their use of word-level prosodically conditioned cues to segment words from speech. Implications for models of developmental speech perception are discussed.
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43.71.Ft Development of speech perception
43.71.Sy Spoken language processing by humans
43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech
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Human motion analyses using footstep ultrasound and Doppler ultrasound

Alexander Ekimov and James M. Sabatier

J. Acoust. Soc. Am. Volume 123, Issue 6, pp. EL149-EL154 (2008); (6 pages) | Cited 3 times

Online Publication Date: 14 May 2008

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Human footsteps generate periodic broadband frequency envelopes of sound due to dynamic friction forces. Also, human body motion when walking is a cyclic temporal process. The individual body parts have different acoustic cross sections and velocities that form unique human Doppler signatures. The paper introduces an approach to analyze this motion using passive and active ultrasound. The passive method employs a narrowband microphone that is sensitive to the sound from footsteps. The active method utilizes continuous-wave ultrasound to measure the Doppler shifted signal from the body appendages. These two methods show time synchronization between Doppler and ultrasonic human footstep signatures.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
43.20.Ye Measurement methods and instrumentation
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Bayesian geoacoustic inversion in a dynamic shallow water environment

Yong-Min Jiang and N. Ross Chapman

J. Acoust. Soc. Am. Volume 123, Issue 6, pp. EL155-EL161 (2008); (7 pages) | Cited 5 times

Online Publication Date: 14 May 2008

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This paper presents results for matched field Bayesian geoacoustic inversion of multitonal continuous wave data collected on the New Jersey continental shelf. To account for effects of significant spatial and temporal variation of the water column sound speed, the sound speed profile was represented by empirical orthogonal functions. Data error information for the inversion was estimated from multiple time windows of the data. Inversion results for the sediment sound speeds at three ranges are in excellent agreement with the ground truth.
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43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.60.Pt Signal processing techniques for acoustic inverse problems
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Effect of ocean sound speed uncertainty on matched-field geoacoustic inversion

Chen-Fen Huang, Peter Gerstoft, and William S. Hodgkiss

J. Acoust. Soc. Am. Volume 123, Issue 6, pp. EL162-EL168 (2008); (7 pages) | Cited 5 times

Online Publication Date: 14 May 2008

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The effect of ocean sound speed uncertainty on matched-field geoacoustic inversion is investigated using data from the SW06 experiment along a nearly range-independent bathymetric track. Significant sound speed differences were observed at the source and receiving array and several environmental parameterizations were investigated for the inversion including representing the ocean sound speed at both source and receivers with empirical orthogonal function (EOF) coefficients. A genetic algorithm-based global optimization method was applied to the candidate environmental models. Then, a Bayesian inversion technique was used to quantify uncertainty in the environmental parameters for the best environmental model, which included an EOF description of the ocean sound speed.
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43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.60.Pt Signal processing techniques for acoustic inverse problems
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