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Journal of the Acoustical Society of America

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Jun 2005

Volume 117, Issue 6, pp. 3335-3971

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Thermodynamic cycles executed in a looped-tube thermoacoustic engine (L)

Yuki Ueda, Tetsushi Biwa, Uichiro Mizutani, and Taichi Yazaki

J. Acoust. Soc. Am. Volume 117, Issue 6, pp. 3369-3372 (2005); (4 pages) | Cited 1 time

Online Publication Date: 31 May 2005

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A looped-tube thermoacoustic engine is composed of only a stack of plates, across which a steep temperature gradient is furnished. In spite of the absence of any mechanical parts like pistons and valves, the energy conversion from heat flow into acoustic power flow is performed in the stack. The thermoacoustically induced acoustic field was observed through the simultaneous measurements of pressure and velocity of the working gas, and the thermodynamic cycle executed in the stack was studied. The experimental results show that the acoustic field is tuned without any external forces so as to realize the efficient thermodynamic cycles as possible. © 2005 Acoustical Society of America.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect

Beamforming with air-coupled surface waves around a sphere and circular cylinder (L)

Gilles A. Daigle, Michael R. Stinson, and James G. Ryan

J. Acoust. Soc. Am. Volume 117, Issue 6, pp. 3373-3376 (2005); (4 pages) | Cited 4 times

Online Publication Date: 31 May 2005

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Beamforming using a microphone array mounted on the surface of a rigid or impedance sphere and cylinder is discussed. The introduction of a structure into the space occupied by or immediately adjacent to the array gives the array an effectively larger aperture and the possibility of enhanced performance. Additional improvements can be obtained through the introduction of a surface that permits air-coupled surface waves to propagate. Since surface waves travel at a speed less than the speed of sound in free space, the aperture of the array can be effectively further increased. © 2005 Acoustical Society of America.
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43.38.Hz Transducer arrays, acoustic interaction effects in arrays
43.20.Fn Scattering of acoustic waves
43.60.Fg Acoustic array systems and processing, beam-forming

Active control of energy density in a one-dimensional waveguide: A cautionary note (L)

Ben S. Cazzolato, Dick Petersen, Carl Q. Howard, and Anthony C. Zander

J. Acoust. Soc. Am. Volume 117, Issue 6, pp. 3377-3380 (2005); (4 pages) | Cited 2 times

Online Publication Date: 31 May 2005

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Acoustic energy density has been shown to be a highly effective cost function for active noise control systems. Many researchers have used the sound field in a one-dimensional waveguide to trial their control strategies before moving onto more realistic three-dimensional sound fields. This letter aims to shed some light on the observations made in the early papers on one-dimensional energy density control and also shows that some of the analysis was incorrect and the conclusions reached may be flawed. © 2005 Acoustical Society of America.
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43.50.Ki Active noise control

Tracking the time to recovery after induced loudness reduction (L)

Yoav Arieh, Karen Kelly, and Lawrence E. Marks

J. Acoust. Soc. Am. Volume 117, Issue 6, pp. 3381-3384 (2005); (4 pages) | Cited 4 times

Online Publication Date: 31 May 2005

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In induced loudness reduction (ILR), a strong tone causes the loudness of a subsequently presented weak tone to decrease. The aim of the experiment was to determine the time required for loudness to return to its initial level after ILR. Twenty-four subjects were exposed to 5, 10, 20, or 40 brief bursts of 2500-Hz pure tones at 80-dB SPL (inducers) and then tested in a series of paired comparison trials. Subjects compared the loudness of a weak target (2500 Hz at 60-dB SPL) to the loudness of a comparison tone at 500 Hz previously judged to match the target. The comparison task was repeated until the two tones were again judged equally loud. The results showed that (a) recovery after ILR is a relatively long process with a time scale of minutes, and (b) recovery time increased approximately 20 s with each doubling of the number of inducers. © 2005 Acoustical Society of America.
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43.66.Cb Loudness, absolute threshold

Effects of vocalic duration and first formant offset on final voicing judgments by children and adults (L)

Caroline Jones

J. Acoust. Soc. Am. Volume 117, Issue 6, pp. 3385-3388 (2005); (4 pages)

Online Publication Date: 31 May 2005

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Developmental research into relative weighting of vocalic duration and spectral properties in final voicing perception has produced different results, depending on whether natural or synthetic speech stimuli have been used and how spectral properties have been manipulated. This paper reports developmental data for final voicing using natural stimuli waveform edited for vocalic duration and resynthesized for first formant offset. Results indicate that in perception of final voicing there are adult-child differences in weighting of vocalic duration and first formant offset, consistent with previous findings for vocalic duration and spectral properties more generally [S. Nittrouer, J. Acoust. Soc. Am. 115, 1777–1790 (2004)]. © 2005 Acoustical Society of America.
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43.71.Ft Development of speech perception
43.71.An Models and theories of speech perception
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