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Top 20 Most Read Articles
October 2011
The 20 articles with the most full-text downloads during the month, in descending order.
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J. Acoust. Soc. Am. Volume 75, Issue 1, pp. 299-299 (1984); (1 page)
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Simulations of vocal fold movement and aerodynamics using the Uintah Computational Framework J. Acoust. Soc. Am. Volume 121, Issue 5, pp. 3201-3202 (2007); (2 pages) Online Publication Date: 04 May 2007
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This study applies a tightly coupled fluid‐structure interaction algorithm to the modeling of phonation. The Uintah Computational Framework models vocal fold material using the Material Point Method (MPM), which permits arbitrarily large material displacements and multiple materials characterizing the vocal fold properties. The air is modeled using a compressible Navier‐Stokes solver, the Implicit Continuous‐fluid Eulerian (ICE) method developed at Los Alamos National Laboratory by B. A. Kashiwa. The MPM and ICE methods are coupled together to generate a unique simulation tool. Preliminary simulations are shown of 2‐D model vocal folds interacting with prescribed transglottal pressures between 100 Pa and 800 Pa illustrating the intrinsic coupling between the vocal folds and the air. Results are presented showing how the new simulation scheme characterizes the materials and how the aerodynamics that results displays the essential characteristics of glottal flow. The next steps of incorporating three‐dimensionality and acoustics will be discussed. The present simulations set the stage for a realistic computational glottis and for eventual modeling of the effects of vocal fold pathologies on the acoustical output. [Work supported at Bowling Green State University in part by the National Institutes of Health and at the University of Utah by the Department of Energy.] |
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Beamforming using compressive sensing J. Acoust. Soc. Am. Volume 130, Issue 4, pp. EL232-EL237 (2011); (6 pages) Online Publication Date: 09 Sep 2011
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Compressive sensing (CS) is compared with conventional beamforming using horizontal beamforming of at-sea, towed-array data. They are compared qualitatively using bearing time records and quantitatively using signal-to-interference ratio. Qualitatively, CS exhibits lower levels of background interference than conventional beamforming. Furthermore, bearing time records show increasing, but tolerable, levels of background interference when the number of elements is decreased. For the full array, CS generates signal-to-interference ratio of 12 dB, but conventional beamforming only 8 dB. The superiority of CS over conventional beamforming is much more pronounced with undersampling.
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Scattering of a spherical wave by a small sphere: An elementary solution J. Acoust. Soc. Am. Volume 130, Issue 4, pp. EL135-EL141 (2011); (7 pages) Online Publication Date: 08 Sep 2011
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Wave scattering by objects that are small compared to the wavelength (Rayleigh scattering) is usually studied for plane incident waves. However, knowledge of the full Green’s function of the problem becomes necessary when the separation of scatterers from either an interface or each other is comparable to the scatterers’ dimensions. Here, an elementary analytic solution is derived for diffraction of a spherical sound wave by a small, soft sphere. The approximate solution is obtained from asymptotic expansions of an exact solution, holds everywhere outside the sphere, and reduces to classical results due to Kelvin and Rayleigh in appropriate special cases.
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A note about insensitivity to pitch-change direction J. Acoust. Soc. Am. Volume 130, Issue 4, pp. EL129-EL134 (2011); (6 pages) Online Publication Date: 08 Sep 2011
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Some listeners are insensitive to the direction of pure-tone frequency changes when the standard frequency is roved widely over trials, but less so when the standard frequency is fixed and trial-by-trial feedback is provided. The present experiment tested the hypothesis that fixing the standard frequency and providing feedback is advantageous for direction-impaired listeners because under these conditions the listeners can learn to respond correctly without genuinely perceiving frequency-change direction. This hypothesis was ruled out by the experiment. It appears instead that direction-impaired listeners find it difficult to ignore the irrelevant frequency changes introduced by roving.
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A cautionary note on the use of the adaptive up–down method J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2098-2107 (2011); (10 pages)
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Up–down staircases with equal sizes for the steps up and down are widely used to estimate detection and discrimination thresholds in psychoacoustics, but the conventional average-of-reversals estimator does not converge on its presumed percent point in Yes–No tasks or in two-alternative forced-choice detection tasks. The particular percent point of convergence is partly determined by the relative size of the steps with respect to the spread (inverse of slope) of the underlying psychometric function. In particular, threshold is increasingly underestimated as the spread of the psychometric function decreases. This characteristic may have serious consequences when thresholds estimated via up–down staircases are compared across conditions in which the spread of the psychometric function varies, because then these thresholds do not represent comparable measures of performance. This paper documents the misbehavior of the average-of-reversals estimator under up–down rules and types of forced-choice task that are in common use in psychoacoustics but which have not been studied before in simulations. It is also shown that a relatively simple modification of the up–down design (namely, using steps up and down of different size and in a certain ratio depending only on the task and the up–down rule being used) stabilizes the performance of these staircases.
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Nonlinear Biot waves in porous media with application to unconsolidated granular media J. Acoust. Soc. Am. Volume 127, Issue 2, pp. 692-702 (2010); (11 pages) Online Publication Date: 05 Feb 2010
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The nonlinear propagation through porous media is investigated in the framework of Biot theory. For illustration, and considering the current interest for the determination of the elastic properties of granular media, the case of nonlinear propagation in “model” granular media (disordered packings of noncohesive elastic beads of the same size embedded in a visco-thermal fluid) is considered. The solutions of linear Biot waves are first obtained, considering the appropriate geometrical and physical parameters of the medium. Then, making use of the method of successive approximations of nonlinear acoustics, the solutions for the second harmonic Biot waves are derived by considering a quadratic nonlinearity in the solid frame constitutive law (which takes its origin from the high nonlinearity of contacts between grains). The propagation in a semi-infinite medium with velocity dispersion, frequency dependent dissipation, and nonlinearity is first analyzed. The case of a granular medium slab with rigid boundaries, often considered in experiments, is then presented. Finally, the importance of mode coupling between solid and fluid waves is evaluated, depending on the actual fluid, the bead diameter, or the applied static stress on the beads. The application of these results to other media supporting Biot waves (porous ceramics, polymer foams, etc.) is straightforward.
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An iterative method to solve acoustic scattering problems using a boundary integral equation J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 1792-1798 (2011); (7 pages)
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In this work, a simple iterative method to solve the acoustic scattering/radiation problems using the boundary integral equation (BIE) formulation is presented. The operator equation obtained in the BIE formulation is converted into a matrix equation using the well-known method of moments solution procedure. The present method requires much fewer mathematical operations per iteration when compared to other available iterative methods. Further, the present iterative method can easily handle multiple incident fields, a highly desirable feature not available in any other iterative method, much the same way as direct solution techniques. Several numerical examples are presented to illustrate the efficiency and accuracy of the method.
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Harvesting mechanical energy via structural vibrations J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 1783-1786 (2011); (4 pages)
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Influence of pitch, loudness, and timbre on the perception of instrument dynamics J. Acoust. Soc. Am. Volume 130, Issue 4, pp. EL193-EL199 (2011); (7 pages) Online Publication Date: 08 Sep 2011
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The effect of variations in pitch, loudness, and timbre on the perception of the dynamics of isolated instrumental tones is investigated. A full factorial design was used in a listening experiment. The subjects were asked to indicate the perceived dynamics of each stimulus on a scale from pianissimo to fortissimo. Statistical analysis showed that for the instruments included (i.e., clarinet, flute, piano, trumpet, and violin) timbre and loudness had equally large effects, while pitch was relevant mostly for the first three. The results confirmed our hypothesis that loudness alone is not a reliable estimate of the dynamics of musical tones.
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Lateral reflections are favorable in concert halls due to binaural loudness J. Acoust. Soc. Am. Volume 130, Issue 5, pp. EL345-EL351 (2011); (7 pages)
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A recent study on perceptual difference in simulated concert halls showed that a concert hall renders stronger sound with more bass when the temporal envelope of a signal is preserved in the reflections [Lokki et al., J. Acoust. Soc. Am. 129, EL223–EL228 (2011)]. In the same study the lateral reflections were shown to contribute to the perceived envelopment and openness. Moreover, the listening test results suggest that lateral reflections contribute to perception of sound source distance. Here, it is shown that lateral reflections are beneficial due to their increasing effect on binaural loudness—the phenomenon known well in psychoacoustics, but not in architectural acoustics. The reflections from the side are amplified more than median plane reflections, in particular at high frequencies, due to the shape of the human head.
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New Fellows of the Acoustical Society of America J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2302-2302 (2011); (1 page)
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Ambient noise in large rivers (L) J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 1787-1791 (2011); (5 pages)
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This paper presents the results of hydroacoustic noise research in three large European rivers: the Danube, the Sava, and the Tisa. Noise in these rivers was observed during a period of ten years, which includes all annual variation in hydrological and meteorological conditions (flow rate, speed of flow, wind speed, etc.). Noise spectra are characterized by wide maximums at frequencies between 20 and 30 Hz, and relatively constant slope toward higher frequencies. Spectral level of noise changes in time in relatively wide limits. At low frequencies, below 100 Hz, the dynamics of noise level is correlated with the dynamics of water flow and speed. At higher frequencies, noise spectra are mostly influenced by human activities on river and on riverbanks. The influence of wind on noise in rivers is complex due to the annual variation of river surface. The influence of wind is less pronounced than in oceans, seas, and lakes.
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Time reversal reconstruction of finite sized sources in elastic media J. Acoust. Soc. Am. Volume 130, Issue 4, pp. EL219-EL225 (2011); (7 pages) Online Publication Date: 09 Sep 2011
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The ability of the time reversal process to reconstruct sources of finite size relative to a wavelength is investigated. Specifically the quality of the spatial reconstruction of a finite sized source will be presented through the use of time reversal experiments conducted on an aluminum plate. The data presented in the paper show that time reversal can reconstruct a source equally well regarding less of its size, when the source is a half wavelength or less in size. The quality of spatial reconstruction when the source is larger than a half wavelength progressively decreases with the size of the source.
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Evidence for simultaneous sound production in the bowhead whale (Balaena mysticetus) J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2257-2262 (2011); (6 pages)
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Simultaneous production of two harmonically independent sounds, the two-voice phenomenon, is a well-known feature in bird song. Some toothed whales can click and whistle simultaneously, and a few studies have also reported simultaneous sound production by baleen whales. The mechanism for sound production in toothed whales has been largely uncovered within the last three decades, whereas mechanism for sound production in baleen whales remains poorly understood. This study provides three lines of evidence from recordings made in 2008 and 2009 in Disko Bay, Western Greenland, strongly indicating that bowhead whales are capable of simultaneous dual frequency sound production. This capability may function to enable more complex singing in an acoustically mediated reproductive advertisement display, as has been suggested for songbirds, and/or have significance in individual recognition.
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Calibration of otoacoustic emission probe microphones J. Acoust. Soc. Am. Volume 130, Issue 4, pp. EL238-EL243 (2011); (6 pages) Online Publication Date: 13 Sep 2011
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Recently, investigators of otoacoustic emissions (OAEs) have shown interest in measuring OAEs to frequencies higher than 10 kHz. Most commercial instruments used to measure OAEs do not specify the microphone frequency response at higher frequencies, nor does their typically integrated design make it convenient to measure it. OAE probes manufactured by Etymotic Research have reasonably constant microphone sensitivity up to about 10 kHz and allow direct access to both the sound sources and microphone preamplifier output. A detailed procedure for calibrating the Etymotic Research OAE probe microphone to extend its usable frequency range to frequencies up to 20 kHz is described.
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J. Acoust. Soc. Am. Volume 130, Issue 4, pp. 2054-2062 (2011); (9 pages) Online Publication Date: 03 Oct 2011
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Cochlear implant (CI) users have been shown to benefit from residual low-frequency hearing, specifically in pitch related tasks. It remains unclear whether this benefit is dependent on fundamental frequency (F0) or other acoustic cues. Three experiments were conducted to determine the role of F0, as well as its frequency modulated (FM) and amplitude modulated (AM) components, in speech recognition with a competing voice. In simulated CI listeners, the signal-to-noise ratio was varied to estimate the 50% correct response. Simulation results showed that the F0 cue contributes to a significant proportion of the benefit seen with combined acoustic and electric hearing, and additionally that this benefit is due to the FM rather than the AM component. In actual CI users, sentence recognition scores were collected with either the full F0 cue containing both the FM and AM components or the 500-Hz low-pass speech cue containing the F0 and additional harmonics. The F0 cue provided a benefit similar to the low-pass cue for speech in noise, but not in quiet. Poorer CI users benefited more from the F0 cue than better users. These findings suggest that F0 is critical to improving speech perception in noise in combined acoustic and electric hearing.
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The role of the external ear in vertical sound localization in the free flying bat, Eptesicus fuscus J. Acoust. Soc. Am. Volume 121, Issue 4, pp. 2227-2235 (2007); (9 pages)
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The role of the external ear in sonar target localization for prey capture was studied by deflecting the tragus of six big brown bats, Eptesicus fuscus. The prey capture performance of the bat dropped significantly in the tragus-deflection condition, compared with baseline, control, and recovery conditions. Target localization error occurred in the tragus-deflected bat, and mainly in elevation. The deflection of the tragus did not abolish the prey capture ability of the bat, which suggests that other cues are available used for prey localization. Adaptive vocal and motor behaviors were also investigated in this study. The bat did not show significant changes in vocal behaviors but modified its flight trajectories in response to the tragus manipulation. The tragus-deflected bat tended to attack the prey item from above and had lower tangential velocity and larger bearing from the side, compared with baseline and recovery conditions. These findings highlight the contribution of the tragus to vertical sound localization in the free-flying big brown bat and demonstrate flight adaptations the bat makes to compensate altered acoustic cues.
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Sound transmission through finite lightweight multilayered structures with thin air layers J. Acoust. Soc. Am. Volume 128, Issue 6, pp. 3513-3524 (2010); (12 pages)
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The sound transmission loss (STL) of finite lightweight multilayered structures with thin air layers is studied in this paper. Two types of models are used to describe the vibro-acoustic behavior of these structures. Standard transfer matrix method assumes infinite layers and represents the plane wave propagation in the layers. A wave based model describes the direct sound transmission through a rectangular structure placed between two reverberant rooms. Full vibro-acoustic coupling between rooms, plates, and air cavities is taken into account. Comparison with double glazing measurements shows that this effect of vibro-acoustic coupling is important in lightweight double walls. For infinite structures, structural damping has no significant influence on STL below the coincidence frequency. In this frequency region, the non-resonant transmission or so-called mass-law behavior dominates sound transmission. Modal simulations suggest a large influence of structural damping on STL. This is confirmed by experiments with double fiberboard partitions and sandwich structures. The results show that for thin air layers, the damping induced by friction and viscous effects at the air gap surfaces can largely influence and improve the sound transmission characteristics.
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Modification of digital music files for use in human temporary threshold shift studies J. Acoust. Soc. Am. Volume 130, Issue 4, pp. EL142-EL146 (2011); (5 pages) Online Publication Date: 08 Sep 2011
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An exposure that is reproducible across clinical/laboratory environments, and appealing to subjects, is described here. Digital music files are level-equated within and across songs such that playlists deliver an exposure that is consistent across time. Modified music is more pleasant to listen to than pure tones or shaped noise, and closely follows music exposures subjects may normally experience. Multiple therapeutics reduce noise-induced hearing loss in animals but human trial design is complicated by limited access to noise-exposed subject populations. The development of standard music exposure parameters for temporary threshold shift studies would allow comparison of protection across agents with real-world relevant stimuli in human subjects.
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