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Top 20 Most Read Articles
March 2007
The 20 articles with the most full-text downloads during the month, in descending order.
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J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1604-1612 (2007); (9 pages)
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A survey of data on the perception of binaurally presented sounds indicates that loudness summation across ears is less than perfect; a diotic sound is less than twice as loud as the same sound presented monaurally. The loudness model proposed by
Moore et al. [J. Audio Eng. Soc. 45, 224–240 (1997)]
determines the loudness of binaural stimuli by a simple summation of loudness across ears. It is described here how the model can be modified so as to give more accurate predictions of the loudness of binaurally presented sounds, including cases where the sounds at the two ears differ in level, frequency or both. The modification is based on the idea that there are inhibitory interactions between the internal representations of the signals at the two ears, such that a signal at the left ear inhibits (reduces) the loudness evoked by a signal at the right ear, and vice versa. The inhibition is assumed to spread across frequency channels. The modified model gives reasonably accurate predictions of a variety of data on the loudness of binaural stimuli, including data obtained using loudness scaling and loudness matching procedures.
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Multipath pulse shapes in shallow water: Theory and simulation J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1362-1373 (2007); (12 pages)
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In shallow water propagation the steeper ray angles are weakened most by boundary losses. Regarding the sound intensity as a continuous function of angle it can be converted into a function of travel time to reveal the multipath pulse shape received from a remote source (one-way path) or a target (two-way path). The closed-form isovelocity pulse shape is extended here to the case of upward or downward refraction. The envelope of the earliest arrivals is roughly trapezoidal with a delayed peak corresponding to the slowest, near horizontal refracted paths. The tail of the pulse falls off exponentially (linearly in decibels) with a decay constant that depends only on the bottom reflection properties and water depth, irrespective of travel time, a useful property for geoacoustic inversion and for sonar design. The nontrivial analytical problem of inverting explicit functions of angle into explicit functions of time is solved by numerical interpolation. Thus exact solutions can be calculated numerically. Explicit closed-form approximations are given for one-way paths. Two-way paths are calculated by numerical convolution. Using the wave model C-SNAP in several broadband cases of interest it is demonstrated that these solutions correspond roughly to a depth average of multipath arrivals.
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Interaural time difference processing of broadband and narrow-band noise by inexperienced listeners J. Acoust. Soc. Am. Volume 121, Issue 3, pp. EL103-EL109 (2007); (7 pages) Online Publication Date: 02 Feb 2007
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Recent functional magnetic resonance imaging (fMRI) data might be interpreted as being in disagreement with existing psychophysical data regarding the laterality of broadband noise stimuli presented with large interaural time differences (ITDs). This study investigated the possibility that lateral judgments made by inexperienced listeners who did not receive feedback might be different than those reported for experienced listeners, especially when the ITD is longer than that occurring in nature, and therefore data from inexperienced listeners presented unnaturally long ITDs for the first time might be more consistent with the possible interpretation of the fMRI results. The results from this study using inexperienced listeners were not basically different from those reported in the literature based on experienced listeners, suggesting a possible difference does exist between inferences drawn from fMRI data and human psychophysical results.
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Gray whale target strength measurements and the analysis of the backscattered response J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1383-1391 (2007); (9 pages)
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One of the current Integrated Marine Mammal Monitoring and Protection System (IMPAS) directions is concentrated on the design and development of the active sonar modality representing just one component of the global system. The active sonar was designed, built, and tested during the Marine Mammal Active Sonar Test (MAST 04), producing whale detections and whale tracks. The experiment was conducted in January 2004 off the coast of California. One of the objectives of the current work is to distinguish whale backscattered responses from the ones generated by the environmental clutter in a waveguide. Furthermore, the work aims to identify and analyze the target signature features that are necessary for enhanced active sonar detection and classification of marine mammals. Over the years there have been very few documented attempts to capture and analyze the backscattering response of whales using an active sonar system. Nevertheless, whales, mostly owing to their size, their motion, and the aspect dependence of their backscattered field, possess desirable properties that help distinguish their scattered response from clutter and other environment related false alarms. As an initial step, data collected during the MAST 04 experiment are presented, and gray whale target strength measurements are obtained. Results are compared to the previously published whale target strengths. Additionally, an investigation is conducted in an effort to provide whale feature identification points suitable for automated detection and classification, as means of relating gray whale active acoustic signatures to their inherent characteristics and their motion.
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Ultrasonic wave generation due to human footsteps on the ground J. Acoust. Soc. Am. Volume 121, Issue 3, pp. EL114-EL119 (2007); (6 pages) Online Publication Date: 02 Feb 2007
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Human footsteps generate broadband frequency vibrations in the ground/floor and sound in the air from a few Hertz up to ultrasonic frequencies due to striking and sliding contacts between a foot and the ground/floor. The high-frequency (above 1 kHz) vibrations from footsteps were detected on a building floor, but were not detected on the outdoor ground, even at 1 m from a walker. This paper presents results of ultrasound registration from footsteps on the ground at greater distances. Results are based on sound measurements in air, since the sound absorption in air is less than vibration absorption in the ground.
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Quantifying the effects of fast-acting compression on the envelope of speech J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1654-1664 (2007); (11 pages)
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Fast-acting compression has several effects on the envelope of speech signals, especially when a target and a background are mixed together. Three measures of the envelope are described, which can be used to quantify these changes: (1) Within-signal modulation correlation or coherence, the degree of correlation (or coherence) of the envelope (on a dB scale) of a single source across different frequency regions, which is reduced by fast-acting compression; (2) fidelity of envelope shape, the degree to which the envelope shape of the target speech in different frequency channels is preserved following compression; and (3) across-signal modulation correlation or coherence (ASMC), the extent to which the target and background acquire a common component of modulation when they are compressed together, which becomes greater in absolute value (more negative) when the target and background are compressed together. Values of these measures are presented and compared with intelligibility scores obtained using stimuli processed (with a noise-vocoder) so as to preserve mainly envelope cues in a limited number of frequency channels. The results suggest that the dominant factor affecting intelligibility is ASMC.
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Finite element analysis of guided waves in fluid-filled corrugated pipes J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1313-1323 (2007); (11 pages)
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Free wave propagation in fluid-filled corrugated pipes is analyzed using finite element methods in combination with a wave-based approach. By combining discretized models with a wave-based approach, complex mechanism of wave motion in the three-dimensional waveguide is fully included. The pipes are treated as waveguides having periodic properties in the direction of wave propagation. The analysis of these guided waves leads to dispersion curves which show the strong frequency-dependency of the different wave modes. The method also allows the inclusion of coupling between fluid-borne and structure-borne wave modes which occur at the acoustic–structure interface. Phase and group velocities of the wave modes are derived in postprocessing steps. Additionally, the energy ratio of the fluid-domain and solid-domain vibrational energies is computed. Finally, linear damping models are included in order to explore wave mode attenuation.
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J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1255-1255 (2007); (1 page) Online Publication Date: 05 Mar 2007
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J. Acoust. Soc. Am. Volume 121, Issue 4, pp. EL125-EL130 (2007); (6 pages) Online Publication Date: 13 Mar 2007
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Nonlinear resonant ultrasound spectroscopy (NRUS) consists of evaluating one or more resonant frequency peak shifts while increasing excitation amplitude. NRUS exhibits high sensitivity to global damage in a large group of materials. Most studies conducted to date are aimed at interrogating the mechanical damage influence on the nonlinear response, applying bending, or longitudinal modes. The sensitivity of NRUS using longitudinal modes and the comparison of the results with a classical linear method to monitor progressive thermal damage (isotropic) of concrete are studied in this paper. In addition, feasibility and sensitivity of applying shear modes for the NRUS method are explored.
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Radiation force and shear motions in inhomogeneous media J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1324-1331 (2007); (8 pages)
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An action of radiation force induced by ultrasonic beam in waterlike media such as biological tissues (where the shear modulus is small as compared to the bulk compressibility) is considered. A new, nondissipative mechanism of generation of shear displacement due to a smooth (nonreflecting) medium inhomogeneity is suggested, and the corresponding medium displacement is evaluated. It is shown that a linear primary acoustic field in nondissipative, isotropic elastic medium cannot excite a nonpotential radiation force and, hence, a shear motion, whereas even smooth inhomogeneity makes this effect possible. An example is considered showing that the generated displacement pulse can be significantly longer than the primary ultrasound pulse. It is noted that, unlike the dissipative effect, the nondissipative action on a localized inhomogeneity (such as a lesion in a tissue) changes its sign along the beam axis, thus stretching or compressing the focus area.
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Silent research vessels are not quiet J. Acoust. Soc. Am. Volume 121, Issue 4, pp. EL145-EL150 (2007); (6 pages) Online Publication Date: 15 Mar 2007
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Behavior of herring (Clupea harengus) is stimulated by two ocean-going research vessels; respectively designed with and without regard to radiated-noise-standards. Both vessels generate a reaction pattern, but, contrary to expectations, the reaction initiated by the silent vessel is stronger and more prolonged than the one initiated by the conventional vessel. The recommendations from the scientific community on noise-reduced designs were motivated by the expectation of minimizing bias on survey results caused by vessel-induced fish behavior. In conclusion, the candidate stimuli for vessel avoidance remain obscure. Noise reduction might be necessary but is insufficient to obtain stealth vessel assets during surveys.
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Illusory percepts from auditory adaptation J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1632-1641 (2007); (10 pages)
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Phenomena resembling tinnitus and Zwicker phantom tone are seen to result from an auditory gain adaptation mechanism that attempts to make full use of a fixed-capacity channel. In the case of tinnitus, the gain adaptation enhances internal noise of a frequency band otherwise silent due to damage. This generates a percept of a phantom sound as a consequence of hearing loss. In the case of Zwicker tone, a frequency band is temporarily silent during the presentation of a notched broadband sound, resulting in a percept of a tone at the notched frequency. The model suggests a link between tinnitus and the Zwicker tone percept, in that it predicts different results for normal and tinnitus subjects due to a loss of instantaneous nonlinear compression. Listening experiments on 44 subjects show that tinnitus subjects (11 of 44) are significantly more likely to hear the Zwicker tone. This psychoacoustic experiment establishes the first empirical link between the Zwicker tone percept and tinnitus. Together with the modeling results, this supports the hypothesis that the phantom percept is a consequence of a central adaptation mechanism confronted with a degraded sensory apparatus.
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Elastic waves excited by a plane source on the surface of a multilayered medium J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1440-1448 (2007); (9 pages)
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Elastic waves excited by a plane piezoelectric source with an arbitrary shape on the surface of a multilayered medium have been studied for the first time in this paper. On the basis of Abzo-zena [
Geophys. J. R. Astron. Soc. 58, 91–105 (1979)
] and Menke [
Geophys. J. R. Astron. Soc. 59, 315–323 (1979)
], the propagator matrix for the elastic wave field in multilayered medium is extended from two- to three-dimensional (3D) space. 3D elastic wave field is investigated and the displacement-stress response for the boundary conditions is obtained. The propagation of elastic wave in multilayered media is analyzed in 3D space in the frequency domain. The P-SV and SH modes corresponding to the poles are studied. The excitation and propagation of the modes are analyzed further. It is found that the propagation velocities of the P-SV and SH modes do not depend on the propagation azimuth θ in the plane parallel to the free surface of the multilayered medium while the displacement amplitudes are strongly dependent on the azimuth θ. The directional distribution functions of the modes are independent of the medium parameters and the modes and dependent on the shape and excitation fashion of the source. Finally, as an example, the displacement fields of the P-SV and SH modes excited by a rectangle source are analyzed. The displacement representation and numerical results of the directivity distribution functions for the P-SV and SH modes are obtained.
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J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1564-1575 (2007); (12 pages)
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Originally proposed as a method for measuring the power gain of the cochlear amplifier, Allen–Fahey experiments compare intracochlear distortion products and ear-canal otoacoustic emissions (OAEs) under tightly controlled conditions. In this paper Allen–Fahey experiments are shown to place significant constraints on the dominant mode of reverse energy propagation within the cochlea. Existing Allen–Fahey experiments are reviewed and shown to contradict the predictions of compression-wave OAE models recently proposed in the literature. In compression-wave models, distortion products propagate from their site of generation to the stapes via longitudinal compression waves in the cochlear fluids (fast waves); in transverse traveling-wave models, by contrast, distortion products propagate primarily via pressure-difference waves whose velocity and other characteristics depend on the mechanical properties of the cochlear partition (slow waves). Compression-wave models predict that the distortion-product OAEs (DPOAEs) measured in the Allen–Fahey paradigm increase at close primary-frequency ratios (or remain constant in the hypothetical absence of tuned suppression). The behavior observed experimentally is just the opposite—a pronounced decrease in DPOAE amplitude at close ratios. Since neither compression-wave nor simple conceptual “hybrid-wave” models can account for the experimental results—whereas slow-wave models can, via systematic changes in distortion-source directionality arising from wave-interference effects—Allen–Fahey and related experiments provide compelling evidence against the predominance of compression-wave OAEs in mammalian cochlear mechanics.
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Separation of components from impulses in reassigned spectrograms J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1510-1518 (2007); (9 pages)
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Two computational methods for pruning a reassigned spectrogram to show only quasisinusoidal components, or only impulses, or both, are presented mathematically and provided with step-by-step algorithms. Both methods compute the second-order mixed partial derivative of the short-time Fourier transform phase, and rely on the conditions that components and impulses are each well-represented by reassigned spectrographic points possessing particular values of this derivative. This use of the mixed second-order derivative was introduced by Nelson [
J. Acoust. Soc. Am. 110, 2575–2592 (2001)
] but here our goals are to completely describe the computation of this derivative in a way that highlights the relations to the two most influential methods of computing a reassigned spectrogram, and also to demonstrate the utility of this technique for plotting spectrograms showing line components or impulses while excluding most other points. When applied to speech signals, vocal tract resonances (formants) or glottal pulsations can be effectively isolated in expanded views of the phonation process.
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Noncontact transportation in water using ultrasonic traveling waves J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1332-1336 (2007); (5 pages)
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A noncontact transport experiment in water using ultrasonic traveling waves was investigated. Acrylic, aluminum, and brass discs were used as test objects. Traveling waves were generated using two ultrasonic transducers attached at the ends of a vibrating plate. One side was used as the wave-source side and the other side was used as the wave-receiving side. Acrylic plates cemented to the sides of the vibrating plate formed a tank to hold water. Object transportation was accomplished by adding a small amount of water to the vibrating structure. The transport velocity of floating objects in water is faster than for floating transport in air because of buoyancy. The transport velocity of an object depends on water height. The minimum value of the velocity occurs when the disc thickness is equal to the water height. The transport velocity increases as the height of water increases. For very shallow depths, the largest velocity is obtained when cavitation-induced streaming occurs.
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Word-internal versus word-peripheral consonantal duration patterns in three languages J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1665-1678 (2007); (14 pages)
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Segmental duration patterns have long been used to support the proposal that syllables are basic speech planning units, but production experiments almost always confound syllable and word boundaries. The current study tried to remedy this problem by comparing word-internal and word-peripheral consonantal duration patterns. Stress and sequencing were used to vary the nominal location of word-internal boundaries in American English productions of disyllabic nonsense words with medial consonant sequences. The word-internal patterns were compared to those that occurred at the edges of words, where boundary location was held constant and only stress and sequence order were varied. The English patterns were then compared to patterns from Russian and Finnish. All three languages showed similar effects of stress and sequencing on consonantal duration, but an independent effect of syllable position was observed only in English and only at a word boundary. English also showed stronger effects of stress and sequencing across a word boundary than within a word. Finnish showed the opposite pattern, whereas Russian showed little difference between word-internal and word-peripheral patterns. Overall, the results suggest that the suprasegmental units of motor planning are language-specific and that the word may be more a relevant planning unit in English.
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Evaluation of companding-based spectral enhancement using simulated cochlear-implant processing J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1709-1716 (2007); (8 pages)
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This study tested a time-domain spectral enhancement algorithm that was recently proposed by
Turicchia and Sarpeshkar [IEEE Trans. Speech Audio Proc. 13, 243–253 (2005)]
. The algorithm uses a filter bank, with each filter channel comprising broadly tuned amplitude compression, followed by more narrowly tuned expansion (companding). Normal-hearing listeners were tested in their ability to recognize sentences processed through a noise-excited envelope vocoder that simulates aspects of cochlear-implant processing. The sentences were presented in a steady background noise at signal-to-noise ratios of 0, 3, and 6 dB and were either passed directly through an envelope vocoder, or were first processed by the companding algorithm. Using an eight-channel envelope vocoder, companding produced small but significant improvements in speech reception. Parametric variations of the companding algorithm showed that the improvement in intelligibility was robust to changes in filter tuning, whereas decreases in the time constants resulted in a decrease in intelligibility. Companding continued to provide a benefit when the number of vocoder frequency channels was increased to sixteen. When integrated within a sixteen-channel cochlear-implant simulator, companding also led to significant improvements in sentence recognition. Thus, companding may represent a readily implementable way to provide some speech recognition benefits to current cochlear-implant users.
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Acoustic measures of low-frequency noise in extended high-frequency audiometry J. Acoust. Soc. Am. Volume 121, Issue 3, pp. EL120-EL124 (2007); (5 pages) Online Publication Date: 08 Feb 2007
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A very high signal-to-noise ratio is required for equipment designed for extended high-frequency audiometry because listeners with almost no hearing ability in the extended high-frequency range may have normal hearing sensitivity in the lower frequencies. Two commercially available systems designed for pure-tone audiometry were evaluated both in the conventional and extended high-frequency range. Unwanted lower frequency signals greater than the noise floor occurred predominantly at presentation levels of approximately 110 dB SPL or higher. Test tones in the extended high-frequency range should be restricted to levels that are not associated with lower frequency noise.
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Experiments on sound generation in corrugated pipes with flow J. Acoust. Soc. Am. Volume 121, Issue 3, pp. 1337-1344 (2007); (8 pages)
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The article reports acoustic measurements on short corrugated pipes with flow. Such pipes might generate high sound levels associated with length resonances. One of the main objectives of the study was to estimate the location of the effective sources by studying the energy flow through the pipes. It was found that a short section of corrugations will only produce sound effectively when placed at the inflow end, while for fully corrugated pipes, the sound-producing regions are located around the pressure maxima of the observed standing waves. It was further found that the net energy flow is in the upstream direction for nearly the complete length of pipe.
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