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Top 20 Most Read Articles
August 2010
The 20 articles with the most full-text downloads during the month, in descending order.
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Near-field vector intensity measurements of a small solid rocket motor J. Acoust. Soc. Am. Volume 128, Issue 2, pp. EL69-EL74 (2010); (6 pages) Online Publication Date: 29 Jul 2010
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Near-field vector intensity measurements have been made of a 12.7-cm diameter nozzle solid rocket motor. The measurements utilized a test rig comprised of four probes each with four low-sensitivity 6.35-mm pressure microphones in a tetrahedral arrangement. Measurements were made with the rig at nine positions (36 probe locations) within six nozzle diameters of the plume shear layer. Overall levels at these locations range from 135 to 157 dB re 20 μPa. Vector intensity maps reveal that, as frequency increases, the dominant source region contracts and moves upstream with peak directivity at greater angles from the plume axis.
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MP3 player listening habits of 17 to 23 year old university students J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 646-653 (2010); (8 pages) Online Publication Date: 09 Aug 2010
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This study evaluated the potential risk to hearing associated with the use of portable digital audio players. Twenty-eight university students (12 males, 16 females; aged 17–23) completed a 49-item questionnaire assessing user listening habits and subjective measures of hearing health. Sound level measurements of participants’ self-identified typical and ‘worst case’ volume levels were taken in different classrooms with background sound levels between 43 and 52 dBA. The median frequency and duration of use was 2 h per day, 6.5 days a week. The median sound levels and interquartile ranges (IQR) at typical and ‘worst case’ volume settings were 71 dBA (IQR = 12) and 79 dBA (IQR = 9), respectively. When typical sound levels were considered with self-reported duration of daily use, none of the participants surpassed Leq(8) 85 dBA. On the questionnaire, 19 students reported experiencing at least one symptom of possible noise-induced hearing loss. Significant differences in MP3 user listening patterns were found between respondents who had experienced tinnitus and those who had not. The findings add to a growing body of literature that collectively supports a need for further research investigating MP3 player user listening habits in order to assess their potential risk to hearing health.
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Interrupted speech perception: The effects of hearing sensitivity and frequency resolution J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 881-889 (2010); (9 pages) Online Publication Date: 09 Aug 2010
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Jin & Nelson (2006) found that although amplified speech recognition performance of hearing-impaired (HI) listeners was equal to that of normal-hearing (NH) listeners in quiet and in steady noise, nevertheless HI listeners' performance was significantly poorer in modulated noise. As a follow-up, the current study investigated whether three factors, auditory integration, low-mid frequency audibility and auditory filter bandwidths, might contribute to reduced sentence recognition of HI listeners in the presence of modulated interference. Three findings emerged. First, sentence recognition in modulated noise found in Jin & Nelson (2006) was highly correlated with perception of sentences interrupted by silent gaps. This suggests that understanding speech interrupted by either noise or silent gaps require similar perceptual integration of speech fragments available either in the dips of a gated noise or across silent gaps of an interrupted speech signal. Second, those listeners with greatest hearing losses in the low frequencies were poorest at understanding interrupted sentences. Third, low-to mid-frequency hearing thresholds accounted for most of the variability in Masking Release (MR) for HI listeners. As suggested by Oxenham and his colleagues (2003 and 2009), low-frequency information within speech plays an important role in the perceptual segregation of speech from competing background noise.
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J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 578-589 (2010); (12 pages) Online Publication Date: 09 Aug 2010
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A joint China-U.S. underwater acoustics experiment was conducted in the Yellow Sea with a very flat bottom and a strong and sharp thermocline. Broadband explosive sources were deployed both above and below the thermocline along two radial lines up to 57.2 km and a quarter circle with a radius of 34 km. Two inversion schemes are used to obtain the seabottom sound speed. One is based on extracting normal mode depth functions from the cross-spectral density matrix. The other is based on the best match between the calculated and measured modal arrival times for different frequencies. The inverted seabottom sound speed is used as a constraint condition to extract the seabottom sound attenuation by three methods. The first method involves measuring the attenuation coefficients of normal modes. In the second method, the seabottom sound attenuation is estimated by minimizing the difference between the theoretical and measured modal amplitude ratios. The third method is based on finding the best match between the measured and modeled transmission losses (TLs). The resultant seabottom attenuation, averaged over three independent methods, can be expressed as α = (0.33±0.02)f1.86±0.04(dB/m kHz) over a frequency range of 80–1000 Hz.
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An electromechanical low frequency panel sound absorber J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 639-645 (2010); (7 pages) Online Publication Date: 09 Aug 2010
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The sound absorbing properties of a thin micro-perforated plate (MPP) coated with piezoelectric material with shunt damping technology is investigated. First a theoretical model is presented to predict the sound absorption coefficients of a thin plate attached with a piezoelectric patch and electrical circuits. Then the model is extended to analyze the sound absorption for a thin plate with micro perforations and piezoelectric material. Measurements are also carried out in an impedance tube and found to be in good agreements with the theoretical model. The sound absorption of the constructions can be much improved by tuning the electrical circuits.
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Cross-correlation function of acoustic fields generated by random high-frequency sources J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 600-610 (2010); (11 pages) Online Publication Date: 09 Aug 2010
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Long-range correlations of noise fields in arbitrary inhomogeneous, moving or motionless fluids are studied in the ray approximation. Using the stationary phase method, two-point cross-correlation function of noise is shown to approximate the sum of the deterministic Green’s functions describing sound propagation in opposite directions between the two points. Explicit relations between amplitudes of respective ray arrivals in the noise cross-correlation function and the Green’s functions are obtained and verified against specific problems allowing an exact solution. Earlier results are extended by simultaneously accounting for sound absorption, arbitrary distribution of noise sources in a volume and on surfaces, and fluid inhomogeneity and motion. The information content of the noise cross-correlation function is discussed from the viewpoint of passive acoustic characterization of inhomogeneous flows.
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J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 664-671 (2010); (8 pages) Online Publication Date: 09 Aug 2010
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The objective of this paper is to propose a simple tool to estimate the absorption vs. transmission loss contributions of a multilayered blanket unbounded in a double panel structure and thus guide its optimization. The normal incidence airborne sound transmission loss of the double panel structure, without structure-borne connections, is written in terms of three main contributions; (i) sound transmission loss of the panels, (ii) sound transmission loss of the blanket and (iii) sound absorption due to multiple reflections inside the cavity. The method is applied to four different blankets frequently used in automotive and aeronautic applications: a non-symmetric multilayer made of a screen in sandwich between two porous layers and three symmetric porous layers having different pore geometries. It is shown that the absorption behavior of the blanket controls the acoustic behavior of the treatment at low and medium frequencies and its transmission loss at high frequencies. Acoustic treatment having poor sound absorption behavior can affect the performance of the double panel structure.
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Between-speaker and within-speaker variation in speech tempo of American English J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 839-850 (2010); (12 pages) Online Publication Date: 09 Aug 2010
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This study characterizes the speech tempo (articulation rate, excluding pauses) of two distinct varieties of American English taking into account both between-speaker and within-speaker variation. Each of 192 speakers from Wisconsin (the northern variety) and from North Carolina (the southern variety), men and women, ranging in age from children to old adults, read a set of sentences and produced a spontaneous unconstrained talk. Articulation rate in spontaneous speech was modeled using fixed-mixed effects analyses. The models explored the effects of the between-speaker factors dialect, age and gender and included each phrase and its length as a source of both between- and within-speaker variation. The major findings are: (1) Wisconsin speakers speak significantly faster and produce shorter phrases than North Carolina speakers; (2) speech tempo changes across the lifespan, being fastest for individuals in their 40s; (3) men speak faster than women and this effect is not related to the length of phrases they produce. Articulation rate in reading was slower than in speaking and the effects of gender and age also differed in reading and spontaneous speech. The effects of dialect in reading remained the same, showing again that Wisconsin speakers had faster articulation rates than did North Carolina speakers.
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The synthesis of robust broadband beamformers for equally-spaced linear arrays J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 691-701 (2010); (11 pages) Online Publication Date: 09 Aug 2010
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Broadband beamforming applied to superdirective arrays is known to be highly sensitive to transducers characteristics errors. Recently, an effective method to synthesize a robust, broadband, data-independent, filter-and-sum beamformer, which considers the probability distributions of errors, has been proposed. It considers an array with arbitrary lay-out and provides a spatial directivity pattern close to the desired one. Unfortunately, the evaluation of the cost function requires a computational load and an amount of memory that increases very quickly with the transducers and the filter coefficients. As the synthesis process requires an iterative minimization, it may become unacceptably long. In this paper, an alternative procedure for evaluating the same cost function is presented, drastically reducing such problems and without introducing any approximation. The only additional constraint is on the antenna which must be an equally-spaced linear array. This procedure makes it much easier to apply the above-mentioned synthesis method to a wide panorama of practical situations.
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Proof of principle for inversion of vector sensor array data J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 590-599 (2010); (10 pages) Online Publication Date: 09 Aug 2010
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Acoustic data collected from a 22 m long horizontal line array with elements comprised of omni-directional hydrophone sensors co-located with acceleration vector sensor triplets are analyzed for seabed geo-acoustic information. Broadband and continuous wave tone data were recorded from the passage of a surface vessel source, the R/V Montague, in an August 2006 experiment conducted in Monterey Bay. The water depth at the array and along the source track was approximately 85 m. Simultaneous inversions for source track and geo-acoustic parameters were performed with 18 tones from the 62–415 Hz tone data for source ranges 0.5–2.0 km. The efficacy of inversions with vector sensor data is demonstrated by the fact that data from vector sensor acceleration components parallel to the array line of bearing produced inversion solutions approximately identical to the solutions obtained from the inversion of data for the same tones from the hydrophone array components. In addition the source spectra derived from these inversions are in nominal agreement with the source spectra obtained from an independent measurement.
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Simulations of cochlear-implant speech perception in modulated and unmodulated noise J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 870-880 (2010); (11 pages) Online Publication Date: 09 Aug 2010
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Experiment 1 replicated the finding that normal-hearing listeners identify speech better in modulated than in unmodulated noise. This modulated-unmodulated difference (“MUD”) has been previously shown to be reduced or absent for cochlear-implant listeners and for normal-hearing listeners presented with noise-vocoded speech. Experiments 2–3 presented normal-hearing listeners with noise-vocoded speech in unmodulated or 16-Hz-square-wave modulated noise, and investigated whether the introduction of simple binaural differences between target and masker could restore the masking release. Stimuli were presented over headphones. When the target and masker were presented to one ear, adding a copy of the masker to the other ear (“diotic configuration”) aided performance but did so to a similar degree for modulated and unmodulated maskers, thereby failing to improve the modulation masking release. Presenting an uncorrelated noise to the opposite ear (“dichotic configuration”) had no effect, either for modulated or unmodulated maskers, consistent with the improved performance in the diotic configuration being due to interaural decorrelation processing. For noise-vocoded speech, the provision of simple spatial differences did not allow listeners to take greater advantage of the dips present in a modulated masker.
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Auditory frequency focusing is very rapid J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 795-803 (2010); (9 pages) Online Publication Date: 09 Aug 2010
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The present experiments examine the effect of a weak 40-ms tone burst (cue) on the detection of a closely following 40-ms signal at the same frequency. Detection becomes more difficult as the temporal separation (onset to onset) between them shortens from around 300 ms to under 52 ms. The threshold increase or proximal interference is similar whether signal frequency is constant from trial to trial—frequency certainty—or changing—frequency uncertainty. The increase is also similar whether the cue goes to the same ear as the signal or to the opposite ear. This contralateral interference by such weak cues, only 4 dB SL against a continuous broadband noise, appears to exclude a role for forward masking by the cues. When the preceding tone burst differs in frequency from the signal, threshold increases little at any temporal separation. Combined with earlier results on frequency uncertainty (
Scharf, B., et al., 2007, J. Acoust. Soc. Am. 121, 2149–2157
), the present results show that a listener can shift focusing to an unexpected signal frequency in less than 52 ms. However, the rapidity of focusing is usually obscured by proximal interference, which possibly occurs whenever cue and signal share the same period ( ∼ 200 ms) of temporal integration.
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Impact of source depth on coherent underwater acoustic communications J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 555-558 (2010); (4 pages)
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A recent paper [
Song et al., J. Acoust. Soc. Am. 123, 856–865 (2008)
] investigated ocean variability impact on coherent underwater acoustic communications (8–16 kHz) for a single near-seafloor transmitter in shallow water during an extended period (27 h). This letter extends that investigation to various source depths and receiver subarrays. Specifically, the middle water column source, which is either in or out of the thermocline, experiences performance variability of 6–7 dB in terms of output signal-to-noise ratio. Further, the source below the thermocline consistently outperforms the source above the thermocline when the receiver subarray is located below the thermocline.
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The perceptual organization of sine-wave speech under competitive conditions J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 804-817 (2010); (14 pages) Online Publication Date: 09 Aug 2010
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Speech comprises dynamic and heterogeneous acoustic elements, yet it is heard as a single perceptual stream even when accompanied by other sounds. The relative contributions of grouping “primitives” and of speech-specific grouping factors to the perceptual coherence of speech are unclear, and the acoustical correlates of the latter remain unspecified. The parametric manipulations possible with simplified speech signals, such as sine-wave analogues, make them attractive stimuli to explore these issues. Given that the factors governing perceptual organization are generally revealed only where competition operates, the second-formant competitor (F2C) paradigm was used, in which the listener must resist competition to optimize recognition [
Remez, R. E., et al. (1994). Psychol. Rev. 101, 129–156
]. Three-formant (F1+F2+F3) sine-wave analogues were derived from natural sentences and presented dichotically (one ear = F1+F2C+F3; opposite ear = F2). Different versions of F2C were derived from F2 using separate manipulations of its amplitude and frequency contours. F2Cs with time-varying frequency contours were highly effective competitors, regardless of their amplitude characteristics. In contrast, F2Cs with constant frequency contours were completely ineffective. Competitor efficacy was not due to energetic masking of F3 by F2C. These findings indicate that modulation of the frequency, but not the amplitude, contour is critical for across-formant grouping.
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Perceptual assimilation of American English vowels by inexperienced Russian listeners J. Acoust. Soc. Am. Volume 128, Issue 2, pp. EL80-EL85 (2010); (6 pages) Online Publication Date: 29 Jul 2010
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In a perceptual assimilation task, 16 Russian speakers categorized American English (AE) vowels [iː, ɪ, ɛ, aeː, ɑː, ʌ, ʊ, uː] in /Vpə/ disyllables into Russian (RU) response categories and rated their perceived goodness on a 9-point Likert scale. Cross-language discriminant analysis established acoustic similarities to Russian vowels. For all but AE [ε], acoustic similarity predicted modal assimilation responses. Russian listeners consistently assimilated AE point vowels to their Russian counterparts, whereas assimilation of the remaining vowels was less consistent. These acoustic and perceptual similarity patterns provide a baseline for future studies of AE vowel discrimination by Russian learners of English.
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Speech-on-speech masking with variable access to the linguistic content of the masker speech J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 860-869 (2010); (10 pages) Online Publication Date: 09 Aug 2010
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It has been reported that listeners can benefit from a release in masking when the masker speech is spoken in a language that differs from the target speech compared to when the target and masker speech are spoken in the same language [
Freyman, R. L. et al. (1999). J. Acoust. Soc. Am. 106, 3578–3588
;
Van Engen, K., and Bradlow, A. (2007), J. Acoust. Soc. Am. 121, 519–526
]. It is unclear whether listeners benefit from this release in masking due to the lack of linguistic interference of the masker speech, from acoustic and phonetic differences between the target and masker languages, or a combination of these differences. In the following series of experiments, listeners’ sentence recognition was evaluated using speech and noise maskers that varied in the amount of linguistic content, including native-English, Mandarin-accented English, and Mandarin speech. Results from three experiments indicated that the majority of differences observed between the linguistic maskers could be explained by spectral differences between the masker conditions. However, when the recognition task increased in difficulty, i.e., at a more challenging signal-to-noise ratio, a greater decrease in performance was observed for the maskers with more linguistically relevant information than what could be explained by spectral differences alone.
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J. Acoust. Soc. Am. Volume 128, Issue 2, pp. EL86-EL92 (2010); (7 pages) Online Publication Date: 29 Jul 2010
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A preview of the results of applying a categorization method to twenty towns with populations between 2200 and 700 000 inhabitants and areas between 0.57 km2 and 59 km2 is presented. This represents a significant expansion of the population size and area of urban sites studied by this method, with variations of two to three orders of magnitude, including the fourth most populous town in Spain. It is found that there is a relationship between urban noise and inhabitants, and also between urban noise and inhabited area, reflecting the urban structure defined in the strata of the categorization method.
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Ultrasonic output from the excised rat larynx J. Acoust. Soc. Am. Volume 128, Issue 2, pp. EL75-EL79 (2010); (5 pages) Online Publication Date: 29 Jul 2010
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The source of ultrasonic vocalizations (USVs) produced by rats is thought to be within the larynx. The purpose of this investigation was to determine if the rat larynx is capable of producing ultrasounds with the full range of frequencies reported in vivo. Acoustic output of excised rat larynges with and without vocal fold constriction was measured. At biologically-reasonable airflow rates and pressures, only larynges with a constriction produced the full range of ultrasounds reported in vivo, providing support for the hypothesis that a constriction within the larynx is likely the source of rat USVs.
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The just noticeable difference of center time and clarity index in large reverberant spaces J. Acoust. Soc. Am. Volume 128, Issue 2, pp. 654-663 (2010); (10 pages) Online Publication Date: 09 Aug 2010
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Just noticeable difference (JND) values are available for most acoustical parameters currently used in practice. However, they have been determined with reference to conditions typically encountered in concert halls and in rooms for speech, covering a range of reverberation times (T) spanning from 0.5 s to 2 s. When reverberation gets longer, the relationship between measured parameters describing acoustic clarity may change significantly and subjective perception might also be different. The proposed research investigates the influence of reverberation time on JND for clarity measures taking into account three reference cases having T values varying from 2 s to 6 s. Measured B-format impulse responses were properly modified to introduce the desired changes and then auralized with two music motifs for presentation on a 4-channel playback system. Listening tests based on paired comparisons were carried out to determine subjective limens. The results proved to be independent of music motifs and showed that JND in the clarity index is almost independent of T, while JND in the center time is significantly related to T and can be assumed as the 8.5% of the reference TS value.
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Automatic identification of individual killer whales J. Acoust. Soc. Am. Volume 128, Issue 3, pp. EL93-EL98 (2010); (6 pages) Online Publication Date: 13 Aug 2010
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Following the successful use of HMM and GMM models for classification of a set of 75 calls of northern resident killer whales into call types [
Brown, J. C., and Smaragdis, P., J. Acoust. Soc. Am. 125, 221–224 (2009)
], the use of these same methods has been explored for the identification of vocalizations from the same call type N2 of four individual killer whales. With an average of 20 vocalizations from each of the individuals the pairwise comparisons have an extremely high success rate of 80 to 100% and the identifications within the entire group yield around 78%.
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