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Jul 2000

Volume 1, Issue 1, pp. 1-30

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Wavelet processing for wideband scattering function estimation

Lora G. Weiss

ARLO Volume 1, Issue 1, pp. 1-6 (August 2000); (6 pages)

Online Publication Date: 25 Aug 2000

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Signal processing of acoustic signals scattered from distributed objects and in time-varying environments has become an increasing challenge. A major difficulty is to estimate or characterize the distributed scattering phenomena. Often, a spreading function or a scattering function are used to characterize the spreading that results when the signal is scattered. This article shows how wavelet processing can be used to more accurately characterize signal spreading when the transmit waveform has a large bandwidth. This wavelet processing is then used to estimate the wideband scattering function associated with scattering from distributed objects or within complex time-varying channels. © 2000 Acoustical Society of America.
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43.60.Gk Space-time signal processing, other than matched field processing
43.30.Vh Active sonar systems
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Wall pressure fluctuations and radiated sound from turbulent boundary layer on an axisymmetric body

Seungbae Lee, Hooi-Joong Kim, O-Sup Kwon, and Sang-Kwon Lee

ARLO Volume 1, Issue 1, pp. 7-12 (August 2000); (6 pages) | Cited 1 time

Online Publication Date: 25 Aug 2000

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An experimental investigation of the near-field pressure fluctuations on a hemisphere-nose of an axisymmetric body was conducted in three regions—laminar separation, turbulent shear layer, and developing turbulent boundary layer—at a Reynolds number (ReD) of 2.43×105 in an anechoic wind tunnel facility. A significant increase of energy level, especially at low frequencies, was noticed downstream of the laminar separation on the nose, and the positive events were observed in the turbulent shear layer region. © 2000 Acoustical Society of America.
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43.28.Ra Generation of sound by fluid flow, aerodynamic sound and turbulence
43.50.Ed Noise generation
43.30.Zk Experimental modeling
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The effects of buoyancy on sonoluminescing bubbles

Thomas J. Matula, Vassilious J. Bezzerides, Paul R. Hilmo, Lisa N. Couret, Trevor W. Olson, Lawrence A. Crum, Jarred E. Swalwell, David W. Kuhns, and Ronald A. Roy

ARLO Volume 1, Issue 1, pp. 13-18 (August 2000); (6 pages) | Cited 3 times

Online Publication Date: 25 Aug 2000

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Sonoluminescence from a single bubble was studied under microgravity and hypergravity environments to determine how buoyancy affects the light emission. The long-term objective of these experiments is to determine if buoyancy-related instabilities play a role in limiting the parameter space of single-bubble sonoluminescence. Understanding the parameter space limitations may ultimately lead to novel approaches for enhancing the extreme conditions within the bubble. Our results reveal several buoyancy-related effects, which should be further investigated in an extended microgravity environment. © 2000 Acoustical Society of America.
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43.35.Hl Sonoluminescence
43.25.Yw Nonlinear acoustics of bubbly liquids
47.20.Bp Buoyancy-driven instabilities (e.g., Rayleigh-Benard)
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Application of wavelets to scattering for wavepacket synthesis

Charles F. Gaumond

ARLO Volume 1, Issue 1, pp. 19-24 (August 2000); (6 pages)

Online Publication Date: 25 Aug 2000

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A novel nonlinear, continuous wavelet transform filter is developed to separate short-time and narrow-frequency components from a set of broadband echoes from a finite cylindrical shell. The components are caused by specific physical phenomena and are called wavepackets. Two wavepackets sometimes overlap in time and frequency, which makes wavepacket synthesis more difficult. © 2000 Acoustical Society of America.
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43.60.Cg Statistical properties of signals and noise
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.30.Vh Active sonar systems
43.40.Fz Acoustic scattering by elastic structures
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Place and temporal cues in pitch perception: are they truly independent?

Colette M. McKay, Hugh J. McDermott, and Robert P. Carlyon

ARLO Volume 1, Issue 1, pp. 25-30 (September 2000); (6 pages) | Cited 28 times

Online Publication Date: 01 Sep 2000

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Four adult users of the Mini System 22 cochlear implant participated in an experiment to investigate the perceptual independence of place-of-stimulation and temporal cues for pulsatile electrical stimulation. The motivation was the relatively poor rate discrimination ability of cochlear implantees compared to the higher accuracy of temporal coding revealed by electrophysiological measurements and the performance of normal hearing listeners. The hypothesis tested was that the central auditory system can combine consistent rate and place cues in a way that is more effective than using each cue independently. Difference limens for rate change, place change, and combined rate and place change (with consistent and inconsistent cues) were compared for stimulation at low and high rates. The results were compatible with place and rate cues being used independently in the combined rate- and place-change conditions, with no advantage found for the consistent-cue conditions. © 2000 Acoustical Society of America.
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43.66.Fe Discrimination: intensity and frequency
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
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