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Top 20 Most Read Articles
August 2009
The 20 articles with the most full-text downloads during the month, in descending order.
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Active noise control technique for diesel train locomotor exhaust noise abatement J. Acoust. Soc. Am. Volume 112, Issue 5, pp. 2427-2428 (2002); (2 pages) Online Publication Date: 25 Oct 2002
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An original prototype for train locomotor exhaust gas pipe noise reduction (electronic muffler) is proposed: the system is based on an active noise control technique. An acoustical measurement campaign has shown that locomotor exhaust noise is characterized by very low frequency components (less than 80 Hz) and very high acoustic power (up to 110 dB). A peculiar electronic muffler characterized by high acoustical efficiency at very low frequencies has been designed and realized at Perugia University Acoustic Laboratory; it has been installed on an Italian D.245 train locomotor, equipped with a 500‐kW diesel engine. The electronic muffler has been added to the traditional passive muffler. Very low transmission losses are introduced by the electronic muffler because of its particular shape; thus, engine efficiency does not further decrease. Canceling noise is generated by means of DSP‐based numerical algorithm. Disturbing noise and canceling noise destructively interfere at the exhaust duct outlet section; outgoing noise is thus reduced. The control system reduces exhaust noise both in the steady and unsteady engine regime. Measurement results have shown that electronic muffler introduces up to 15 dB noise abatement in the low‐frequency components. |
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Pyschoacoustical comparison of active versus passive noise control techniques J. Acoust. Soc. Am. Volume 117, Issue 4, pp. 2528-2528 (2005); (1 page)
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Comparisons of active versus passive noise control techniques can be found in various papers. However, this comparison mainly concerns economic, operational, or technical considerations. The present contribution aims at describing the psychoacoustical effects produced by some of the classical solutions used in passive and active noise control. The models introduced by Zwicker and his coworkers, and by Moore and Glasberg are used to evaluate the auditory efficiency of passive and active noise control techniques. Several types of signals were examined: (i) test signals obtained with a band of noise embedded in a white noise or a pink noise; (ii) actual environmental noises: noise produced by the turbine of an aircraft or by a car engine, and several interior noises (locomotive, helicopter and car). It is shown that the modifications in the spectrum of a signal that can be produced by active control are sometimes disappointing, because they induce a subjective enhancement of the high‐frequency portion of the spectrum. What the listener then commonly reports is that overall the signal has become slightly softer, but also more unpleasant. The use of a hybrid noise control technique, combining active and passive control, can greatly reduce this effect. |
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Analysis of the part-pedaling effect in the piano J. Acoust. Soc. Am. Volume 126, Issue 2, pp. EL49-EL54 (2009); (6 pages) Online Publication Date: 15 Jul 2009
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This letter reports basic acoustic phenomena related to part-pedaling in the piano. With part-pedaling, the piano tone can be divided into three distinct time intervals: initial free vibration, damper-string interaction, and final free vibration. Varying the distance of the damper from the string, the acoustic signal and the damper acceleration were measured for several piano tones. During the damper-string interaction, the piano tone decay is rapid and the timbre of the tone is affected by the nonlinear amplitude limitation of the string motion. During the final free decay, the string continues to vibrate freely with a lower decay rate. |
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Improvement of acoustic theory of ultrasonic waves in dilute bubbly liquids J. Acoust. Soc. Am. Volume 126, Issue 3, pp. EL69-EL74 (2009); (6 pages) Online Publication Date: 27 Jul 2009
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The theory of the acoustics of dilute bubbly liquids is reviewed, and the dispersion relation is modified by including the effect of liquid compressibility on the natural frequency of the bubbles. The modified theory is shown to more accurately predict the trend in measured attenuation of ultrasonic waves. The model limitations associated with such high-frequency waves are discussed.
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Sound absorption of porous metals at high sound pressure levels J. Acoust. Soc. Am. Volume 126, Issue 2, pp. EL55-EL61 (2009); (7 pages) Online Publication Date: 15 Jul 2009
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This paper is a study about sound absorption properties of porous metals at high sound pressure levels. A method of deriving the nonlinear static flow resistance for highly porous fibrous metals is proposed by solving Oseen’s equation to take account of the inertia effect, validated by experiments of airflow measurement. In order to predict nonlinear sound absorbing performance of a finite thickness porous metal layer, a numerical method is employed, verified by sound absorption measurement in an impedance tube. Accordingly, the effects of the nonlinear coefficient on the porous metal sound absorption are investigated.
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Perceptually relevant parameters for virtual listening simulation of small room acoustics J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 776-791 (2009); (16 pages)
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Various physical aspects of room-acoustic simulation techniques have been extensively studied and refined, yet the perceptual attributes of the simulations have received relatively little attention. Here a method of evaluating the perceptual similarity between rooms is described and tested using 15 small-room simulations based on binaural room impulse responses (BRIRs) either measured from a real room or estimated using simple geometrical acoustic modeling techniques. Room size and surface absorption properties were varied, along with aspects of the virtual simulation including the use of individualized head-related transfer function (HRTF) measurements for spatial rendering. Although differences between BRIRs were evident in a variety of physical parameters, a multidimensional scaling analysis revealed that when at-the-ear signal levels were held constant, the rooms differed along just two perceptual dimensions: one related to reverberation time (T60) and one related to interaural coherence (IACC). Modeled rooms were found to differ from measured rooms in this perceptual space, but the differences were relatively small and should be easily correctable through adjustment of T60 and IACC in the model outputs. Results further suggest that spatial rendering using individualized HRTFs offers little benefit over nonindividualized HRTF rendering for room simulation applications where source direction is fixed.
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J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 728-738 (2009); (11 pages)
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Distortion-product otoacoustic emission (DPOAE) input/output (I/O) functions were measured in 322 ears of 176 subjects at as many as 8 f2 frequencies per ear for a total of 1779 I/O functions. The f2 frequencies ranged from 0.7 to 8 kHz in half-octave steps. Behavioral thresholds (BTs) at the f2 frequencies ranged from −5 to 60 dB hearing loss (HL). Both linear-pressure and nonlinear, two-slope functions were fitted to the data. The two-slope function describes I/O compression as output-controlled self-suppression. Most I/O functions (96%) were better fitted by the two-slope method. DPOAE thresholds based on each method were used to predict BTs. Compared to estimates based on linear-pressure functions, individual BTs predicted from DPOAE thresholds based on the two-slope model had lower residual error and accounted for more variance. Another advantage of the two-slope method is that it provides an estimate of response growth rate (RGR) that is not tied to threshold. At all frequencies, the median low-level RGR (across I/O functions of the same f2 and BT) usually increased as BT increased, while high-level compression decreased. The observed characteristics of DPOAE I/O functions are consistent with the loss of cochlear compression that is typically associated with mild-to-moderate HL.
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Vowel and consonant contributions to vocal tract shape J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 825-836 (2009); (12 pages)
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The purpose of this study was to develop a method by which a vowel-consonant-vowel (VCV) utterance based on x-ray microbeam articulatory data could be separated into a vowel-to-vowel transition and a consonant superposition function. The result is a model that represents a vowel sequence as a time-dependent perturbation of the neutral vocal tract shape governed by coefficients of canonical deformation patterns. Consonants were modeled as superposition functions that can force specific portions of the vocal tract shape to be constricted or expanded, over a specific time course. The three VCVs [əpɑ], [ətɑ], and [əkɑ], produced by one female speaker, were analyzed and reconstructed with the developed model. They were shown to be reasonable approximations of the original VCVs, as assessed qualitatively by visual inspection and quantitatively by calculating rms error and correlation coefficients. This establishes a method for future modeling of other speech material.
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Effects of envelope bandwidth on the intelligibility of sine- and noise-vocoded speech J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 792-805 (2009); (14 pages)
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The choice of processing parameters for vocoded signals may have an important effect on the availability of various auditory features. Experiment 1 varied envelope cutoff frequency (30 and 300 Hz), carrier type (sine and noise), and number of bands (2–5) for vocoded speech presented to normal-hearing listeners. Performance was better with a high cutoff for sine-vocoding, with no effect of cutoff for noise-vocoding. With a low cutoff, performance was better for noise-vocoding than for sine-vocoding. With a high cutoff, performance was better for sine-vocoding. Experiment 2 measured perceptibility of cues to voice pitch variations. A noise carrier combined with a high cutoff allowed intonation to be perceived to some degree but performance was best in high-cutoff sine conditions. A low cutoff led to poorest performance, regardless of carrier. Experiment 3 tested the relative contributions of comodulation across bands and spectral density to improved performance with a sine carrier and high cutoff. Comodulation across bands had no effect so it appears that sidebands providing a denser spectrum improved performance. These results indicate that carrier type in combination with envelope cutoff can alter the available cues in vocoded speech, factors which must be considered in interpreting results with vocoded signals.
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J. Acoust. Soc. Am. Volume 126, Issue 2, pp. EL62-EL67 (2009); (6 pages) Online Publication Date: 21 Jul 2009
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When a random rove is used in a perceptual task to control the influence of an unwanted cue that may confound the decision strategy of primary interest, the effectiveness of the rove is determined by its range.
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Response to noise from modern wind farms in The Netherlands J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 634-643 (2009); (10 pages)
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The increasing number and size of wind farms call for more data on human response to wind turbine noise, so that a generalized dose-response relationship can be modeled and possible adverse health effects avoided. This paper reports the results of a 2007 field study in The Netherlands with 725 respondents. A dose-response relationship between calculated A-weighted sound pressure levels and reported perception and annoyance was found. Wind turbine noise was more annoying than transportation noise or industrial noise at comparable levels, possibly due to specific sound properties such as a “swishing” quality, temporal variability, and lack of nighttime abatement. High turbine visibility enhances negative response, and having wind turbines visible from the dwelling significantly increased the risk of annoyance. Annoyance was strongly correlated with a negative attitude toward the visual impact of wind turbines on the landscape. The study further demonstrates that people who benefit economically from wind turbines have a significantly decreased risk of annoyance, despite exposure to similar sound levels. Response to wind turbine noise was similar to that found in Sweden so the dose-response relationship should be generalizable.
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Practical aspects of implementing car interior active noise control systems J. Acoust. Soc. Am. Volume 123, Issue 5, pp. 3532-3532 (2008); (1 page)
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When implementing real‐world, close‐to‐production active noise control (ANC) systems for car interiors, many aspects far beyond textbook theory have to be taken into consideration ‐‐ many of which might also be left out for first demonstrator systems. Due to the predominant role of robustness and reliability, any kind of uncertainty in the system has to be considered carefully. Among others, the uncertainties and changes of the acoustical environment, e.g. due to temperature changes, number of passengers, open windows and also of system components, e.g. loudspeakers and microphones have to be measured and̸or modeled. This also gives some new insight into the acoustical environment inside cars at low frequencies. In addition, the quality of input data (e.g., the update rate for rpm information) is of major importance for the acoustical performance in terms of noise reduction. Finally, stability analyses and robustness calculations must be extended to incorporate uncertainties as well as time domain effects even for more or less freqency domain problems like engine noise. This requires to re‐formulate feed‐forward systems as feed‐back systems and calculate system responses. Measurement results on the interior acoustics (and its uncertainty) as well as additional developments on ANC system robustness will be presented. |
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Perceptual contributions of the consonant-vowel boundary to sentence intelligibility J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 847-857 (2009); (11 pages)
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Although research has focused on the perceptual contribution of consonants to spoken syllable or word intelligibility, in sentences vowels have a distinct perceptual advantage over consonants in determining intelligibility [
Kewley-Port et al., J. Acoust. Soc. Am. 122, 2365–2375 (2007)
]. The current study used a noise replacement paradigm to investigate how perceptual contributions of consonants and vowels are mediated by transitional information at segmental boundaries. The speech signal preserved between replacements is defined as a glimpse window. In the first experiment, glimpse windows contained proportional amounts of transitional boundary information that was either added to consonants or deleted from vowels. Results replicated a two-to-one vowel advantage for intelligibility at the traditional consonant-vowel boundary and suggest that vowel contributions remain robust against proportional deletions of the signal. The second experiment examined the combined effect of random glimpse windows not locked to segments and the distributions of durations measured from the consonant versus vowel glimpses observed in Experiment 1. Results demonstrated that, for random glimpses, the cumulative sentence duration glimpsed was an excellent predictor of performance. Comparisons across experiments confirmed that higher proportions of vowel information within glimpses yielded the highest sentence intelligibility.
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J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 806-815 (2009); (10 pages)
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Sensitivity to interaural time difference (ITD) in constant-amplitude pulse trains was measured in four sequentially implanted bilateral cochlear implant (CI) subjects. The sensitivity measurements were made as a function of time beginning directly after the second ear was implanted, continued for periods of months before subjects began wearing bilateral sound processors, and extended for months while the subjects used bilateral sound processors in day-to-day listening. Measurements were also made as a function of the relative position of the left/right electrodes. The two subjects with the shortest duration of binaural deprivation before implantation demonstrated ITD sensitivity soon after second-ear implantation (before receiving the second sound processor), while the other two did not demonstrate sensitivity until after months of daily experience using bilateral processors. The interaural mismatch in electrode position required to decrease ITD sensitivity by a factor of 2 (half-width) for CI subjects was five times greater than the half-width for interaural carrier-frequency disparity in normal-hearing subjects listening to sinusoidally amplitude-modulated high-frequency tones. This large half-width is likely to contribute to poor binaural performance in CI users, especially in environments with multiple broadband sound sources.
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Deep seafloor arrivals: An unexplained set of arrivals in long-range ocean acoustic propagation J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 599-606 (2009); (8 pages)
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Receptions, from a ship-suspended source (in the band 50–100 Hz) to an ocean bottom seismometer (about 5000 m depth) and the deepest element on a vertical hydrophone array (about 750 m above the seafloor) that were acquired on the 2004 Long-Range Ocean Acoustic Propagation Experiment in the North Pacific Ocean, are described. The ranges varied from 50 to 3200 km. In addition to predicted ocean acoustic arrivals and deep shadow zone arrivals (leaking below turning points), “deep seafloor arrivals,” that are dominant on the seafloor geophone but are absent or very weak on the hydrophone array, are observed. These deep seafloor arrivals are an unexplained set of arrivals in ocean acoustics possibly associated with seafloor interface waves.
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Long-term road traffic noise exposure is associated with an increase in morning tiredness J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 626-633 (2009); (8 pages)
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This study investigates the association between night time road traffic noise exposure (Lnight) and self-reported sleep problems. Logistic regression was performed in a large population based cohort study (GLOBE), including over 18 000 subjects, to study the association between exposure at the dwelling façade and sleep problems. Measures of sleep problems were collected by questionnaire with two questions: “Do you in general get up tired and not well rested in the morning?” and “Do you often use sleep medication or tranquilizers?” After adjustment for potential confounders, a significant association was found between noise exposure and the risk of getting up tired and not rested in the morning. Although prevalence of medication use was higher at higher noise levels compared to the reference category (Lnight<35 dB), after adjustment for covariates this association was not significant. Long-term road traffic noise exposure is associated with increased risk of getting up tired and not rested in the morning in the general population. This result extends the earlier established relationship between long-term noise exposure and self-reported sleep disturbance assessed with questions that explicitly referred to noise and indicates that road traffic noise exposure during the night may have day-after effects.
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J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 866-877 (2009); (12 pages)
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This study investigated whether individuals with small and large native-language (L1) vowel inventories learn second-language (L2) vowel systems differently, in order to better understand how L1 categories interfere with new vowel learning. Listener groups whose L1 was Spanish (5 vowels) or German (18 vowels) were given five sessions of high-variability auditory training for English vowels, after having been matched to assess their pre-test English vowel identification accuracy. Listeners were tested before and after training in terms of their identification accuracy for English vowels, the assimilation of these vowels into their L1 vowel categories, and their best exemplars for English (i.e., perceptual vowel space map). The results demonstrated that Germans improved more than Spanish speakers, despite the Germans’ more crowded L1 vowel space. A subsequent experiment demonstrated that Spanish listeners were able to improve as much as the German group after an additional ten sessions of training, and that both groups were able to retain this learning. The findings suggest that a larger vowel category inventory may facilitate new learning, and support a hypothesis that auditory training improves identification by making the application of existing categories to L2 phonemes more automatic and efficient.
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High-frequency acoustic communications achieving high bandwidth efficiency J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 561-563 (2009); (3 pages)
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A recent communications experiment was conducted in a shallow water environment at high-frequency permitting the use of a large bandwidth (11–19 kHz). This paper investigates the communication performance versus various symbol rates (or bandwidths) in terms of output signal-to-noise ratio with an assortment of constellations, illustrating a trade-off between performance and data rate. A high bandwidth efficiency of 4 bits/s Hz is demonstrated using 32 quadrature amplitude modulation with a data rate of 31.25 kbits/s over a 2.2-km range.
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Voice gender perception by cochlear implantees J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 762-775 (2009); (14 pages)
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Gender identification of human voices was studied in a juvenile population of cochlear implant (CI) users exposed to naturalistic speech stimuli from 20 male and 20 female speakers using two different voice gender perception tasks. Stimulus output patterns were recorded from each individual CI for each stimulus, and features related to voice fundamental frequency and spectral envelope were extracted from these electrical output signals to evaluate the relationship between implant output and behavioral performance. In spite of the fact that temporal and place cues of similar quality were produced by all CI devices, only about half of the subjects were able to label male and female voices correctly. Participants showed evidence of using available temporal cues, but showed no evidence of using place cues. The implants produced a consistent and novel cue to voice gender that participants did not appear to utilize. A subgroup of participants could discriminate male and female voices when two contrasting voices were presented in succession, but were unable to identify gender when voices were singly presented. It is suggested that the nature of long-term auditory categorical memories needs to be studied in more detail in these individuals.
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Nonlinear parabolic equation model for finite-amplitude sound propagation over porous ground layers J. Acoust. Soc. Am. Volume 126, Issue 2, pp. 572-581 (2009); (10 pages)
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The nonlinear parabolic equation (NPE) is a time-domain method widely used in underwater sound propagation applications. It allows simulation of weakly nonlinear sound propagation within an inhomogeneous medium. So that this method can be used for outdoor sound propagation applications it must account for the effects of an absorbing ground surface. The NPE being formulated in the time domain, complex impedances cannot be used and, hence, the ground layer is included in the computational system with the help of a second NPE based on the Zwikker–Kosten model. A two-way coupling between these two layers (air and ground) is required for the whole system to behave correctly. Coupling equations are derived from linearized Euler’s equations. In the frame of a parabolic model, this two-way coupling only involves spatial derivatives, making its numerical implementation straightforward. Several propagation examples, both linear or nonlinear, are then presented. The method is shown to give satisfactory results for a wide range of ground characteristics. Finally, the problem of including Forchheimer’s nonlinearities in the two-way coupling is addressed and an approximate solution is proposed.
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