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Top 20 Most Read Articles
January 2008
The 20 articles with the most full-text downloads during the month, in descending order.
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New Fellows of the Acoustical Society of America J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 1-1 (2008); (1 page)
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J. Acoust. Soc. Am. Volume 123, Issue 1, pp. EL1-EL7 (2007); (7 pages) Online Publication Date: 13 Dec 2007
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Just-noticeable interaural time differences were measured for low-frequency pure tones, high-frequency sinusoidally amplitude-modulated (SAM) tones, and high-frequency transposed stimuli, at multiple levels with or without a spectrally notched diotic noise to prevent spread of excitation. Performance with transposed stimuli and pure tones was similar in quiet; however, in noise, performance was poorer for transposed stimuli than for pure tones. Performance with SAM tones was always poorest. In all conditions, performance improved slightly with increasing level. The results suggest that the equivalence postulated between transposed stimuli and pure tones is not valid in the presence of a spectrally notched background noise.
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Structural health monitoring by extraction of coherent guided waves from diffuse fields J. Acoust. Soc. Am. Volume 123, Issue 1, pp. EL8-EL13 (2007); (6 pages) Online Publication Date: 13 Dec 2007
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Recent theoretical and experimental studies in a wide range of applications have demonstrated that Green’s functions (impulse responses) can be extracted from cross-correlation of diffuse fields using only passive sensors. This letter demonstrates the passive-only reconstruction of coherent Lamb waves (dc–500 kHz) in an aluminum plate of thickness comparable to aircraft fuselage and wing panels. It is further shown that the passively reconstructed waves are sensitive to the presence of damage in the plate as it would be expected in a typical “active” guided wave test. This proof-of-principle study suggests the potential for a structural health monitoring method for aircraft panels based on passive ultrasound imaging reconstructed from diffuse fields.
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J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 145-153 (2008); (9 pages)
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This paper proposes a modified boundary condition to improve the room-acoustic prediction accuracy of a diffusion equation model. Previous boundary conditions for the diffusion equation model have certain limitations which restrict its application to a certain number of room types. The boundary condition employing the Sabine absorption coefficient [
V. Valeau et al., J. Acoust. Soc. Am. 119, 1504–1513 (2006)
] cannot predict the sound field well when the absorption coefficient is high, while the boundary condition employing the Eyring absorption coefficient [
Y. Jing and N. Xiang, J. Acoust. Soc. Am. 121, 3284–3287 (2007)
;
A. Billon et al., Appl. Acoust. 69, (2008)
] has a singularity whenever any surface material has an absorption coefficient of 1.0. The modified boundary condition is derived based on an analogy between sound propagation and light propagation. Simulated and experimental data are compared to verify the modified boundary condition in terms of room-acoustic parameter prediction. The results of this comparison suggest that the modified boundary condition is valid for a range of absorption coefficient values and successfully eliminates the singularity problem.
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Auditory-visual speech perception in normal-hearing and cochlear-implant listeners J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 428-440 (2008); (13 pages)
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The present study evaluated auditory-visual speech perception in cochlear-implant users as well as normal-hearing and simulated-implant controls to delineate relative contributions of sensory experience and cues. Auditory-only, visual-only, or auditory-visual speech perception was examined in the context of categorical perception, in which an animated face mouthing /ba/, /da/, or /ga/ was paired with synthesized phonemes from an 11-token auditory continuum. A three-alternative, forced-choice method was used to yield percent identification scores. Normal-hearing listeners showed sharp phoneme boundaries and strong reliance on the auditory cue, whereas actual and simulated implant listeners showed much weaker categorical perception but stronger dependence on the visual cue. The implant users were able to integrate both congruent and incongruent acoustic and optical cues to derive relatively weak but significant auditory-visual integration. This auditory-visual integration was correlated with the duration of the implant experience but not the duration of deafness. Compared with the actual implant performance, acoustic simulations of the cochlear implant could predict the auditory-only performance but not the auditory-visual integration. These results suggest that both altered sensory experience and improvised acoustic cues contribute to the auditory-visual speech perception in cochlear-implant users.
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Mechanical response measurements of real and artificial brass players lips J. Acoust. Soc. Am. Volume 123, Issue 1, pp. EL14-EL20 (2007); (7 pages) Online Publication Date: 13 Dec 2007
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Mechanical frequency responses of human and artificial lips in brass instrument playing have been measured using a high-speed digital video technique, in an attempt to classify the true nature of the “lip-reed.” Four semiprofessional human players were used, and three notes played on a trombone were studied. All measurements revealed a strong mechanical resonance with “outward striking” behavior; the played note always sounded above this frequency. Several measurements also showed a weaker second resonance, above the played frequency, with “inward striking” behavior. The Q values of the dominant resonances in human lips were lower than those typical of artificial lips.
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Spectral envelope sensitivity of musical instrument sounds J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 500-506 (2008); (7 pages)
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It is well known that the spectral envelope is a perceptually salient attribute in musical instrument timbre perception. While a number of studies have explored discrimination thresholds for changes to the spectral envelope, the question of how sensitivity varies as a function of center frequency and bandwidth for musical instruments has yet to be addressed. In this paper a two-alternative forced-choice experiment was conducted to observe perceptual sensitivity to modifications made on trumpet, clarinet and viola sounds. The experiment involved attenuating 14 frequency bands for each instrument in order to determine discrimination thresholds as a function of center frequency and bandwidth. The results indicate that perceptual sensitivity is governed by the first few harmonics and sensitivity does not improve when extending the bandwidth any higher. However, sensitivity was found to decrease if changes were made only to the higher frequencies and continued to decrease as the distorted bandwidth was widened. The results are analyzed and discussed with respect to two other spectral envelope discrimination studies in the literature as well as what is predicted from a psychoacoustic model.
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Nonlinear distortion of short pulses radiated by plane and focused circular pistons J. Acoust. Soc. Am. Volume 102, Issue 5, pp. 2539-2548 (1997); (10 pages)
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Detailed measurements of finite-amplitude pulses radiated by plane and focused circular pistons in water are presented. Comparisons of time waveforms and frequency spectra, both on and off axis, are made with numerical calculations based on the nonlinear parabolic wave equation. Emphasis is on nonlinear distortion of amplitude- and frequency-modulated tone bursts. Use of short pulses enabled resolution of the direct and diffracted waves prior to their coalescence and subsequent shock formation along the axis of the source. Because of its relevance to investigations of cavitation inception, attention is devoted to variation of the peak positive (p+) and negative (p−) pressures along the axis of a focused source. It is shown that with increasing source amplitude, the maximum of each shifts away from the focal plane, toward the source. This effect is more pronounced for p−than for p+. © 1997 Acoustical Society of America. |
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Supporting evidence for reverse cochlear traveling waves J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 222-240 (2008); (19 pages)
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As a result of the cochlea’s nonlinear mechanics, stimulation by two tones results in the generation of distortion products (DPs) at frequencies flanking the primary tones. DPs are measurable in the ear canal as oto-acoustic emissions, and are used to noninvasively explore cochlear mechanics and diagnose hearing loss. Theories of DP emissions generally include both forward and reverse cochlear traveling waves. However, a recent experiment failed to detect the reverse-traveling wave and concluded that the dominant emission path was directly through the fluid as a compression pressure [
Ren, 2004, Nat. Neurosc.7, 333–334
]. To explore this further, we measured intracochlear DPs simultaneously with emissions over a wide frequency range, both close to and remote from the basilar membrane. Our results support the existence of the reverse-traveling wave: (1) They show spatial variation in DPs that is at odds with a compression pressure. (2) Although they confirm a forward-traveling character of intraocochlear DPs in a broad frequency region of the best frequency, this behavior does not refute the existence of reverse-traveling waves. (3) Finally, the results show that, in cases in which it can be expected, the DP emission is delayed relative to the DP in a way that supports reverse-traveling-wave theory.
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J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 450-461 (2008); (12 pages)
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Cochlear-implant users perform far below normal-hearing subjects in background noise. Speech recognition with varying numbers of competing female, male, and child talkers was evaluated in normal-hearing subjects, cochlear-implant users, and normal-hearing subjects utilizing an eight-channel sine-carrier cochlear-implant simulation. Target sentences were spoken by a male. Normal-hearing subjects obtained considerably better speech reception thresholds than cochlear-implant subjects; the largest discrepancy was 24 dB with a female masker. Evaluation of one implant subject with normal hearing in the contralateral ear suggested that this difference is not caused by age-related disparities between the subject groups. Normal-hearing subjects showed a significant advantage with fewer competing talkers, obtaining release from masking with up to three talker maskers. Cochlear-implant and simulation subjects showed little such effect, although there was a substantial difference between the implant and simulation results with talker maskers. All three groups benefited from a voice pitch difference between target and masker, with the female talker providing significantly less masking than the male. Child talkers produced more masking than expected, given their fundamental frequency, syllabic rate, and temporal modulation characteristics. Neither a simulation nor testing in steady-state noise predicts the difficulties cochlear-implant users experience in real-life noisy situations.
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J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 414-427 (2008); (14 pages)
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Studies comparing native and non-native listener performance on speech perception tasks can distinguish the roles of general auditory and language-independent processes from those involving prior knowledge of a given language. Previous experiments have demonstrated a performance disparity between native and non-native listeners on tasks involving sentence processing in noise. However, the effects of energetic and informational masking have not been explicitly distinguished. Here, English and Spanish listener groups identified keywords in English sentences in quiet and masked by either stationary noise or a competing utterance, conditions known to produce predominantly energetic and informational masking, respectively. In the stationary noise conditions, non-native talkers suffered more from increasing levels of noise for two of the three keywords scored. In the competing talker condition, the performance differential also increased with masker level. A computer model of energetic masking in the competing talker condition ruled out the possibility that the native advantage could be explained wholly by energetic masking. Both groups drew equal benefit from differences in mean F0 between target and masker, suggesting that processes which make use of this cue do not engage language-specific knowledge.
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J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 163-173 (2008); (11 pages)
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A subjective survey on perceived environmental quality has been carried out on 51 secondary-school classrooms, some of which have been acoustically renovated, and acoustical measurements were carried out in eight of the 51 classrooms, these eight being representative of the different types of classrooms that are the subject of the survey. A questionnaire, which included items on overall quality and its single aspects such as acoustical, thermal, indoor air and visual quality, has been administered to 1006 students. The students perceived that acoustical and visual quality had the most influence on their school performance and, with the same dissatisfaction for acoustical, thermal and indoor air quality, they attributed more relevance, in the overall quality judgment, to the acoustical condition. Acoustical quality was correlated to speech comprehension, which was correlated to the speech transmission index, even though the index does not reflect all the aspects by which speech comprehension can be influenced. Acoustical satisfaction was lower in nonrenovated classrooms, and one of the most important consequences of poor acoustics was a decrease in concentration. The stronger correlation between average noise disturbance scores and LA max levels, more than LAeq and LA90, showed that students were more disturbed by intermittent than constant noise.
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The role of spectral modulation cues in virtual sound localization J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 302-314 (2008); (13 pages)
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Sound localization cues generally include interaural time difference, interaural intensity difference, and spectral cues. The purpose of this study is to investigate the important spectral cues involved in so-called head related transfer functions (HRTFs) using a combination of HRTF analyses and a virtual sound localization (VSL) experiment. Previous psychoacoustical and physiological studies have both suggested the existence of spectral modulation frequency (SMF) channels for analyzing spectral information (e.g., the spectral cues coded in HRTFs). SMFs are in a domain related to the Fourier transform of HRTFs. The relationship between various SMF regions and sound localization was tested here by filtering or enhancing HRTFs in the SMF domain under a series of conditions using a VSL experiment. Present results revealed that azimuth localization was not significantly affected by HRTF manipulation. Applying notch filters between 0.1 and 0.4 cycles/octave or between 0.35 and 0.65 cycles/octave resulted in significantly less accurate elevation responses at low elevations, while spectral enhancement in these two SMF regions did not produce a significant change in sound localization. Likewise, low-pass filtering at 2 cycles/octave did not significantly influence localization accuracy, suggesting that the major cues for sound localization are in the SMF region below 2 cycles/octave.
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J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 133-144 (2008); (12 pages)
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While at school children are exposed to various types of noise including external, environmental noise and noise generated within the classroom. Previous research has shown that noise has detrimental effects upon children’s performance at school, including reduced memory, motivation, and reading ability. In England and Wales, children’s academic performance is assessed using standardized tests of literacy, mathematics, and science. A study has been conducted to examine the impact, if any, of chronic exposure to external and internal noise on the test results of children aged 7 and 11 in London (UK) primary schools. External noise was found to have a significant negative impact upon performance, the effect being greater for the older children. The analysis suggested that children are particularly affected by the noise of individual external events. Test scores were also affected by internal classroom noise, background levels being significantly related to test results. Negative relationships between performance and noise levels were maintained when the data were corrected for socio-economic factors relating to social deprivation, language, and special educational needs. Linear regression analysis has been used to estimate the maximum levels of external and internal noise which allow the schools surveyed to achieve required standards of literacy and numeracy.
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A comparison of filter design structures for multi-channel acoustic communication systems J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 174-185 (2008); (12 pages)
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The application of inverse filter designs as a means of providing improved communication performance in acoustic environments is investigated. Tikhonov regularized inverse filters of channel transfer functions calculated in the frequency domain are used as a means of obtaining multi-channel filters. Three classifications of inverse filter structures have been considered using time-domain simulations. The performance of Tikhonov regularized inverse filters designed according to each of these classifications is compared with each other and against a filter design developed by Stojanovic [
Stojanovic, M. (2005). “Retrofocusing techniques for high rate acoustic communications,” J. Acoust. Soc. Am. 117, 1173–1185
]. It is shown that the filter design developed by Stojanovic requires less regularization and outperforms the Tikhonov regularized inverse filter designs when communicating over a single channel. While the filter developed by Stojanovic is designed to use multiple transmitters to transmit to a single receiver, the filter was implemented in a multi-channel system and proposed to have a focusing similar to that obtained using time-reversal. It was found that for the scenario used in the simulation, the Tikhonov regularized inverse design for full multi-channel inversion achieved better focusing than the design by Stojanovic, where simulation results show 20 dB less cross-talk at the expense of around 2 dB loss in signal strength.
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Algorithm for determining the endpoints of isolated utterances J. Acoust. Soc. Am. Volume 56, Issue S1, pp. S31-S31 (1974); (1 page) Online Publication Date: 11 Aug 2005
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An important problem in speech processing is to detect the presence of speech in a background of noise. This problem is often referred to as the endpoint location problem. By accurately detecting the beginning and end of an utterance, the amount of processing of the speech data can be kept to a minimum. The algorithm proposed for locating the endpoints of an utterance is based on two measures of the signal, namely, zero crossing rate and energy. The algorithm is inherently capable of performing correctly in any reasonable acoustic environment where the signal‐to‐noise ratio is on the order of 30 Db or better. The algorithm has been tested over a variety of recording conditions and for a large number of speakers and has been found to perform reasonably well across all tested conditions. |
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Reconciling the origin of the transient evoked ototacoustic emission in humans J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 212-221 (2008); (10 pages)
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A pervasive theme in the literature for the transient evoked otoacoustic emission (TEOAE) measured from the human ear canal has been one of the emission arising solely (or largely) from a single, place-fixed mechanism. Here TEOAEs are reported measured in the absence of significant stimulus contamination at stimulus onset, providing for the identification of a TEOAE response beginning within the time window that is typically removed by windowing. Contrary to previous studies, it was found that in humans, as has previously been found in guinea pig, the TEOAE appears to arise from two generation mechanisms, the relative contributions of these two mechanisms being time and stimulus-level dependent. The method of windowing the earliest part of the ear canal measurement to remove stimulus artifact removes part of the TEOAE i.e., much of the component arising from a nonlinear generation mechanism. This reconciliation of TEOAE origin is consistent with all OAEs in mammals arising in a stimulus-level dependent manner from two mechanisms of generation, one linear, one nonlinear, as suggested by
Shera and Guinan [J. Acoust. Soc. Am. 105, 782–798 (1999)]
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On the reflection of coupled Rayleigh-like waves at surface defects in plates J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 88-98 (2008); (11 pages)
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The reflection of coupled Rayleigh-like waves from surface defects in elastic plates is investigated experimentally and analyzed on the basis of an analytical model and finite difference simulations. The propagation of Rayleigh-like waves in plates is characterized by an energy transfer to the opposite plate side and back over a distance called the beat length. Experimental results clearly show this beating effect and its dependency on the frequency-thickness product, and excellent agreement is obtained with existing analytical predictions. The propagation and scattering are modeled separately for the fundamental A0 and S0 Lamb modes that constitute the incident Rayleigh-like wave. The reflection coefficients from surface slots are investigated using finite difference simulations and the reflected Rayleigh-like wave is obtained by superposition. The theoretical model reveals strong dependencies of the reflected field on the ratio between excitation distance and beat length and on the cutoff frequencies of specific higher Lamb modes. Standard pulse-echo measurements allow for the detection of small defects from a remote transducer location. Good agreement is obtained between the predicted and measured amplitude spectra of the reflected Rayleigh-like wave. The developed model allows for the evaluation of defect location and damaged plate side using a combination of time-of-flight and frequency measurements.
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Control Methods Used in a Study of the Vowels J. Acoust. Soc. Am. Volume 24, Issue 2, pp. 175-184 (1952); (10 pages) Online Publication Date: 29 Jun 2005
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Relationships between a listener's identification of a spoken vowel and its properties as revealed from acoustic measurement of its sound wave have been a subject of study by many investigators. Both the utterance and the identification of a vowel depend upon the language and dialectal backgrounds and the vocal and auditory characteristics of the individuals concerned. The purpose of this paper is to discuss some of the control methods that have been used in the evaluation of these effects in a vowel study program at Bell Telephone Laboratories. The plan of the study, calibration of recording and measuring equipment, and methods for checking the performance of both speakers and listeners are described. The methods are illustrated from results of tests involving some 76 speakers and 70 listeners. |
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Approximations of inverse boundary element methods with partial measurements of the pressure field J. Acoust. Soc. Am. Volume 123, Issue 1, pp. 109-120 (2008); (12 pages)
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Boundary element methods (BEMs) based near-field acoustic holography (NAH) requires the measurement of the pressure field over a closed surface in order to recover the normal velocity on a nearby conformal surface. There are practical cases when measurements are available over a patch from the measurement surface in which conventional inverse BEM based NAH (IBEM) cannot be applied directly, but instead as an approximation. In this work two main approximations based on the indirect-implicit methods are considered: Patch IBEM and IBEM with Cauchy data. Patch IBEM can be applied with a continuation procedure, which as its predecessor patch NAH (a well known technique that can be used on separable geometries of the wave equation) continues the pressure field using an iterative procedure, or it can be applied by a direct procedure. On the other hand, IBEM with Cauchy data requires measurements over two conformal patches and it will be shown that this technique will be reliable regardless of the position of the source. The theory behind each method will be justified and validated using a cylindrical surface with numerical data generated by point sources, and using experimental data from a cylindrical fuselage excited by a point force.
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