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Journal of the Acoustical Society of America

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Jun 2012

Volume 131, Issue 6 (Express)

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Vowel enhancement effects in cochlear-implant users

Ningyuan Wang, Heather Kreft, and Andrew J. Oxenham

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL421-EL426 (2012); (6 pages)

Online Publication Date: 04 May 2012

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Auditory enhancement of certain frequencies can occur through prior stimulation of surrounding frequency regions. The underlying neural mechanisms are unknown, but may involve stimulus-driven changes in cochlear gain via the medial olivocochlear complex (MOC) efferents. Cochlear implants (CIs) bypass the cochlea and stimulate the auditory nerve directly. If the MOC plays a critical role in enhancement then CI users should not exhibit this effect. Results using vowel stimuli, with and without preceding sounds designed to enhance formants, provided evidence of auditory enhancement in both normal-hearing listeners and CI users, suggesting that vowel enhancement is not mediated solely by cochlear effects.
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43.64.Me Effects of electrical stimulation, cochlear implant
43.66.Ba Models and theories of auditory processes
43.71.Es Vowel and consonant perception; perception of words, sentences, and fluent speech
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Categorical perception of intonation contrasts: Effects of listeners’ language background

Chang Liu and Amanda Rodriguez

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL427-EL433 (2012); (7 pages)

Online Publication Date: 04 May 2012

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Intonation perception of English speech was examined for English- and Chinese-native listeners. F0 contour was manipulated from falling to rising patterns for the final words of three sentences. Listener’s task was to identify and discriminate the intonation of each sentence (question versus statement). English and Chinese listeners had significant differences in the identification functions such as the categorical boundary and the slope. In the discrimination functions, Chinese listeners showed greater peakedness than English peers. The cross-linguistic differences in intonation perception were similar to the previous findings in perception of lexical tones, likely due to listeners’ language background differences.
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43.71.Hw Cross-language perception of speech
43.71.Sy Spoken language processing by humans
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Sound propagation in saturated gas-vapor-droplet suspensions with droplet evaporation and nonlinear relaxation

Max Kandula

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL434-EL440 (2012); (7 pages)

Online Publication Date: 04 May 2012

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The Sound attenuation and dispersion in saturated gas-vapor-droplet mixture in the presence of evaporation has been investigated theoretically. The theory is based on an extension of the work of Davidson [J. Atmos. Sci. 32(11), 2201–2205 (1975)] to accommodate the effects of nonlinear particle relaxation processes of mass, momentum and energy transfer on sound attenuation and dispersion. The results indicate the existence of a spectral broadening effect in the attenuation coefficient (scaled with respect to the peak value) with a decrease in droplet mass concentration. It is further shown that for large values of the droplet concentration the scaled attenuation coefficient is characterized by a universal spectrum independent of droplet mass concentration.
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43.20.Hq Velocity and attenuation of acoustic waves
43.25.Ed Effect of nonlinearity on velocity and attenuation
43.50.Nm Aerodynamic and jet noise
43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
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Field transformational approach to three-dimensional scattering from two-dimensional rough surfaces

Kevin B. Smith

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL441-EL447 (2012); (7 pages)

Online Publication Date: 04 May 2012

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In 1985, Tappert and Nghiem-Phu introduced a field-transformation technique for computing rough surface scattering from a parabolic equation model utilizing a split-step Fourier marching algorithm. The approach was based on a two-dimensional parabolic equation with a standard operator approximation that was capable of computing scattering from a one-dimensional rough surface. Although this approach has been used extensively and effectively, extensions of this approach to higher order approximations or three-dimensional propagation have only recently been investigated. In this work, the expressions that incorporate higher-order approximations and three-dimensional scattering from two-dimensional rough surfaces are presented. The implications of some computationally necessary approximations are also provided.
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43.30.Hw Rough interface scattering
43.20.Fn Scattering of acoustic waves
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Echolocation behavior of franciscana dolphins (Pontoporia blainvillei) in the wild

Mariana L. Melcón, , Mauricio Failla, , and Miguel A. Iñíguez

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL448-EL453 (2012); (6 pages)

Online Publication Date: 08 May 2012

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Franciscana dolphins are small odontocetes hard to study in the field. In particular, little is known on their echolocation behavior in the wild. In this study we recorded 357 min and analyzed 1019 echolocation signals in the Rio Negro Estuary, Argentina. The clicks had a peak frequency at 139 kHz, and a bandwidth of 19 kHz, ranging from 130 to 149 kHz. This is the first study describing echolocation signals of franciscana dolphins in the wild, showing the presence of narrow-band high frequency signals in these dolphins. Whether they use other vocalizations to communicate or not remains uncertain.
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43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
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About the transition frequency in Biot’s theory

Patrick S. Kurzeja and Holger Steeb

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL454-EL460 (2012); (7 pages)

Online Publication Date: 09 May 2012

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Biot’s theory of wave propagation in porous media includes a characteristic frequency which is used to distinguish the low-frequency from the high-frequency range. Its determination is based on an investigation of fluid flow through different pore geometries on a smaller scale and a subsequent upscaling process. This idea is limited due to the assumptions made on the smaller scale. It can be enhanced for a general two-phase system by three properties: Inertia of the solid, elasticity of the solid, and frequency dependent corrections of the momentum exchange. They become important for highly porous media with liquids.
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43.20.Bi Mathematical theory of wave propagation
43.20.Jr Velocity and attenuation of elastic and poroelastic waves
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“Ladder” structure in tonal noise generated by laminar flow around an airfoil

Tze Pei Chong and Phillip Joseph

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL461-EL467 (2012); (7 pages)

Online Publication Date: 14 May 2012

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The presence of a “ladder” structure in the airfoil tonal noise was discovered in the 1970s, but its mechanism hitherto remains a subject of continual investigation in the research community. Based on the measured noise results and some numerical analysis presented in this letter, the variations of four types of airfoil tonal noise frequencies with the flow velocity were analyzed individually. The ladder structure is proposed to be caused by the acoustic/hydrodynamic frequency lag between the scattering of the boundary layer instability noise and the discrete noise produced by an aeroacoustic feedback loop.
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43.28.Ra Generation of sound by fluid flow, aerodynamic sound and turbulence
43.28.Bj Mechanisms affecting sound propagation in air, sound speed in the air
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Discriminating resonant targets from clutter using Lanczos iterated single-channel time reversal

Zachary J. Waters and Paul E. Barbone

J. Acoust. Soc. Am. Volume 131, Issue 6, pp. EL468-EL474 (2012); (7 pages)

Online Publication Date: 16 May 2012

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Power iterated single-channel time-reversal is extended to employ Lanczos iterations. The properties of these algorithms are studied in the presence of varying levels of noise and broadband clutter. It is shown the Lanczos iterated method possesses superior convergence properties in comparison to the standard power iterated technique. Results demonstrate that such algorithms provide an efficient means through which to isolate and extract the properties of resonant scatterers in the presence of noise and coherent interference.
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43.60.Tj Wave front reconstruction, acoustic time-reversal, and phase conjugation
43.30.Zk Experimental modeling
43.20.Fn Scattering of acoustic waves
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