bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of impulsive wave transmission through total knee joint prothesis
Authors: Chu M. L. , Yazdani S. , Gradisar I. A.
Published: October 2005

The most significant advancement in orthopaedics in the last 50 years has been the evolution of practical total knee joint replacement. However, in the presence of all these successes, there is a note of “gloom” to a small percentage of patients in which loosening of the prosthesis occur, with the attendant pain and restricted mobility. At present, attempts to reduce the incidence of failure have been directed primarily at redesigning hip and knee implants, and research towards understanding the mechanics of impact force transmission across normal and prosthetic joints is practically nonexistent. The present study is an attempt to evaluate the differences between “normal” and prosthetic joint mode of impact wave transmission. Using cadaveric skeletal remains, an abbreviated (cut at the lower tibia and upper femur ends) lower extremity specimen is suspended vertically by long steel wires. The upper (femur) end is subjected to a 150-lb load (to simulate body weight) and the lower tibia end rests on a 100-lb shaker. The skeletal system is subjected to a 3-g impulsive load at a frequency range of 1–3 Hz to simulate brisk walking and jogging. The procedure is repeated twice; first with the original knee joint intact, and again with the knee joint portion replaced with a prosthesis. Preliminary results reveal that there are significant differences in the mode of impulsive wave transmission across the “normal” and prosthetic knee joints. Prosthetic joints appear to reduce impulsive peaks along both the tibia and femur as compared with “normal” joints. The effects of viscoelastic shoe inserts in the propagation of impact waves across the two types of joints (normal and prosthetic) is also being investigated.
The validity of using phonatory jitter to detect laryngeal pathology
Authors: Ludlow Christy L. , Bassich Celia J. , Lee Young J. , Connor Nadine P. , Coulter David C.
Published: October 2005

A multiple regression model was developed to account for the variance in phonatory jitter among normal speakers and for predicting an expected jitter value and confidence interval for individual subjects. Jitter was measured with a system resolution capable of measuring a minimum perturbation of 2.15 μs. Measures were made from maximum phonation lengths of 95 adults without laryngeal pathology. Seven factors were examined for contributions to the prediction of jitter: sex, age, smoking history, drinking habits, F0, vocal intensity, and length of phonation. A multiple correlation coefficient of determination of 97.6% was obtained for the normal subject pool with a three-factor model including: vocal intensity, F0 and phonation length. For 20 patients with laryngeal pathology, individual predicted jitter values and 90% confidence intervals were computed using the normal regression model, for determining when patients' actual jitter values were outside of their expected confidence intervals. Only 30% of the patients with confirmed laryngeal pathology had jitter values outside of their predicted intervals, indicating that this measure would not be valid for use in screening for laryngeal pathology.
Computer measurements of breathy voice quality
Authors: Ladefoged Peter , Antonanzas Norma
Published: October 2005

Most measures of phonation types analyze samples of steady-state vowels that last several seconds. Such segments do not occur in natural languages. The principle used in the current measure is that within a single period of a voiced speech sound, a waveform with no breathiness should be the same as the waveform produced by the previous glottal pulse. But when a sound is produced with a turbulent glottal flow there will be randomness. Hence an appropriate measure of breathiness is the variance of the difference between the points in a window with a length slightly less than one period and the points in the most similar window of equal length in one of the immediately following periods. The measure can be used on segments of speech lasting only about 150 ms. It is largely unaffected by the changes in glottal pulse frequency that correspond to the intonation, and by period to period jitter. The measure has been tested on two languages that use phonological contrasts dependent on the difference between breathy voice and modal (regular) voice. [Work supported by NINCDS.]
Current developments in heating, ventilating, and air conditioning system noise control
Authors: Kingsbury Howard R.
Published: October 2005

Proper understanding of the sound generating and sound absorbing characteristics of the numerous elements in a typical ducted building air conditioning system has been an elusive goal. In some cases the data base is very thin, in others nonexistent. In addition, the technology of air conditions system design has been advancing faster than our understanding of the acoustical implications of such technology advances. This paper will review our current understanding of the acoustics of system elements and point out some of the areas where additional information is needed.
A speaker-independent isolated word recognition board
Authors: Kabasawa S. , Hsieh M. S. , Chang S. M. , Lin C. H.
Published: October 2005

A one-boarded, out-performance speech recognition system for speaker-independent isolated words has been developed. This board consists mainly of the 4-bit, 1-chip microcomputer and newly developed speech recognition LSI [Ohga et al., IEEE Trans. Consumer Electron. CE-28, 263–270 (1982)]. The board takes multiple templates and the KNN rules to cover various tokens of many persons. A new clustering method CLS (clustering with shared group) is based on the conception of the SNN method and the K-means iteration procedure [Rabiner et al., IEEE Trans. Acoust. Speech Signal Process. ASSP-27, 336–349 (1979)]. The experimental results showed more than 95% recognition accuracy not only for ten Japanese city names but ten Chinese city names. CLS can be easily implemented on the 16-bit microcomputer system and it takes less than 20 min to make seven templates with the microcomputer system.
Stimulus-frequency otoacoustic emissions measured with amplitude-modulated suppressor tones
Authors: Neely Stephen T. , Johnson Tiffany A. , Garner Cassie A. , Gorga Michael P.
Published: October 2005

Stimulus-frequency otoacoustic emissions (SFOAEs) are typically derived as the difference in sound pressure in the ear canal with and without a suppressor tone added to the probe tone. A novel variation of this method applies a sinusoidal amplitude modulation (AM) to the suppressor tone, which causes the SFOAE to also be modulated. The AM-SFOAE can be separated from the probe frequency using spectral methods. AM-SFOAE measurements are described for four normal-hearing subjects using 6-Hz AM. Because the suppressor modulation is at a higher rate, the AM-SFOAE technique avoids the confounding influence of heartbeat, which also modulates the probe tone.
Lamb mode conversion in an absorptive bi-layer with a delamination
Authors: Shkerdin G. , Glorieux C.
Published: October 2005

A theoretical study of Lamb mode propagation through an absorptive composite plate consisting of two parallel layers with a finite-length delamination dividing these layers is presented. In the delamination boundary region, noncontact boundary conditions are assumed. The calculation is based on a modal decomposition method. In thin composite plates containing a few propagating Lamb modes, as a result of diffraction on a delamination, the incident Lamb mode can be efficiently converted into transmitted Lamb modes. Delaminations in absorptive composite plates result in a considerable change of transmitted acoustic energy if the plate is characterized by substantially different absorption coefficients in the layers of the plate. In particular, the delamination can considerably increase the transmission coefficient of the incident Lamb mode if the layer where the incident Lamb mode is mainly concentrated is much less absorptive than the other one.
Consequences of cochlear damage for the detection of interaural phase differences
Authors: Lacher-Fougère Stéphane , Demany Laurent
Published: October 2005

Thresholds for detecting interaural phase differences (IPDs) in sinusoidally amplitude-modulated pure tones were measured in seven normal-hearing listeners and nine listeners with bilaterally symmetric hearing losses of cochlear origin. The IPDs were imposed either on the carrier signal alone—not the amplitude modulation—or vice versa. The carrier frequency was 250, 500, or 1000 Hz, the modulation frequency 20 or 50 Hz, and the sound pressure level was fixed at 75 dB. A three-interval two-alternative forced choice paradigm was used. For each type of IPD (carrier or modulation), thresholds were on average higher for the hearing-impaired than for the normal listeners. However, the impaired listeners’ detection deficit was markedly larger for carrier IPDs than for modulation IPDs. This was not predictable from the effect of hearing loss on the sensation level of the stimuli since, for normal listeners, large reductions of sensation level appeared to be more deleterious to the detection of modulation IPDs than to the detection of carrier IPDs. The results support the idea that one consequence of cochlear damage is a deterioration in the perceptual sensitivity to the temporal fine structure of sounds.
Whistles of small groups of Sotalia fluviatilis during foraging behavior in southeastern Brazil
Authors: Pivari Daniela , Rosso Sergio
Published: October 2005

Whistle emissions were recorded from small groups of marine tucuxi dolphins (Sotalia fluviatilis) in two beaches located in an important biological reserve in the Cananéia estuary (25°03′S, 47°58′W), southeastern Brazil. A total of 17h of acoustic data was collected when dolphins were engaged in a specific feeding foraging activity. The amount of 3235 whistles was recorded and 40% (n=1294) were analyzed. Seven acoustic whistle parameters were determined: duration (ms), number of inflection points, start and end frequency (kHz), minimum and maximum frequency (kHz), and frequency range (kHz). Whistles with up to four inflection points were found. Whistles with no inflection points and rising frequency corresponded to 85% (n=1104) of all analyzed whistles. Whistle duration varied from 38to627ms (mean=229.6±109.9ms), with the start frequency varying between 1 and 16kHz(mean=8.16±3.0kHz) and the end frequency between 2 and 18kHz(mean=14.35±3.0kHz). The importance of this study requires an accurate measurement of the whistles’ emissions in an unusual foraging feeding behavior situation on two beaches where several tucuxis, mostly mother–calf pairs, are frequently present. These two beaches are located in a federal and state environment Environmental Protected Area threatened by the progressive increase of tourism.
Multidimensional analyses of voicing offsets and onsets in female speakers
Authors: Koenig Laura L. , Mencl W. Einar , Lucero Jorge C.
Published: October 2005

This study investigates cross-speaker differences in the factors that predict voicing thresholds during abduction–adduction gestures in six normal women. Measures of baseline airflow, pulse amplitude, subglottal pressure, and fundamental frequency were made at voicing offset and onset during intervocalic /h/, produced in varying vowel environments and at different loudness levels, and subjected to relational analyses to determine which factors were most strongly related to the timing of voicing cessation or initiation. The data indicate that (a) all speakers showed differences between voicing offsets and onsets, but the degree of this effect varied across speakers; (b) loudness and vowel environment have speaker-specific effects on the likelihood of devoicing during /h/; and (c) baseline flow measures significantly predicted times of voicing offset and onset in all participants, but other variables contributing to voice timing differed across speakers. Overall, the results suggest that individual speakers have unique methods of achieving phonatory goals during running speech. These data contribute to the literature on individual differences in laryngeal function, and serve as a means of evaluating how well laryngeal models can reproduce the range of voicing behavior used by speakers during running speech tasks.
Simulation of a traveling-wave thermoacoustic engine using computational fluid dynamics
Authors: Lycklama à Nijeholt J. A. , Tijani M. E. H. , Spoelstra S.
Published: October 2005

A two-dimensional computational fluid dynamics (CFD) simulation study of a traveling-wave thermoacoustic engine is presented. The computations show an increase of the dynamic pressure when a linear temperature difference is applied across the regenerator. An amplification of the acoustic power through the engine is also illustrated. A satisfactory agreement between the calculated and expected gains of the traveling-wave thermoacoustic engine is obtained. The expected gain is defined as the ratio of the absolute temperatures at the ends of the regenerator. Nonlinear phenomena that cannot be captured by existing linear theory, like streaming mass flows and vortices formation, are also visualized. It is concluded that CFD codes could be used in the future to predict and optimize thermoacoustic systems. This is an important step towards the development of nonlinear simulation tools for the high-amplitude thermoacoustic systems that are needed for practical use.
Sonic-boom generated sound field under a wavy air–water interface: Analyses for incident N waves
Authors: Cheng H. K. , Lee C. J. , Edwards J. R.
Published: October 2005

Examples of the sonic-boom generated sound field under a wavy air–water interface based on the theory of Cheng and Lee [J. Fluid Mech. 514, 281–312 (2004)] are studied to determine the surface-wave influence on sound-pressure level, frequency range, and waveform characteristics of disturbances generated by an aerial sonic-boom N wave over water. The study substantiates that, owing to their much lower attenuation rate, the time-dependent disturbances produced by the interaction with a surface-wave train can be comparable to, and overwhelm the flat-ocean (Sawyers) wave field at large as well as moderate depth levels, depending on Mach number, surface-wave length and-height, and the alignment angle of surface waves with respect to the flight track. Computed examples, assuming a 300ft.(91m) signature length and a 2psf(96Pa) peak sea-level overpressure, show that, under a mildly wavy ocean, sonic-boom disturbances at sound-pressure level of 100–126dB (re: 1μPa) can reach a depth of 750–1500ft.(229–457m), where the dominant waveform evolves into an infrasound wave packet of frequency 5–40Hz.
An analysis of the impact of auditory-nerve adaptation on behavioral measures of temporal integration in cochlear implant recipients
Authors: Hay-McCutcheon Marcia J. , Brown Carolyn J. , Abbas Paul J.
Published: October 2005

The objective of this study was to determine the impact that auditory-nerve adaptation has on behavioral measures of temporal integration in Nucleus 24 cochlear implant recipients. It was expected that, because the auditory nerve serves as the input to central temporal integrator, a large degree of auditory-nerve adaptation would reduce the amount of temporal integration. Neural adaptation was measured by tracking amplitude changes of the electrically evoked compound action potential (ECAP) in response to 1000-pps biphasic pulse trains of varying durations. Temporal integration was measured at both suprathreshold and threshold levels by an adaptive procedure. Although varying degrees of neural adaptation and temporal integration were observed across individuals, results of this investigation revealed no correlation between the degree of neural adaptation and psychophysical measures of temporal integration.
Psychophysical tuning curves at very high frequencies
Authors: Yasin Ifat , Plack Christopher J.
Published: October 2005

For most normal-hearing listeners, absolute thresholds increase rapidly above about 16kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966–985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206–13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12–17.5kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.
Silencer design by using array resonators for low-frequency band noise reduction
Authors: Seo Sang-Hyun , Kim Yang-Hann
Published: October 2005

Helmholtz resonators are often used to reduce noise. They are particularly useful when noise has a narrow frequency band. In this study we aim to broaden its narrow band characteristics by combining many resonators. Serial and parallel arrangements of resonators have been tested to obtain broader impedance mismatch characteristics in the broader band. Theoretical and experimental results explain these characteristics in the absence of mean flow. The serial arrangement mainly increases the peak of TL at the resonance frequency. But the parallel arrangement logarithmically increases the peak of TL and expands the bandwidth. The change of acoustic characteristics is explained by introducing an “equivalent impedance analysis.” This shows that the transmission loss has a maximum value when the distance between resonators is λ∕4 of its wavelength. In this study we propose a novel design method that optimizes the arrangement of resonators while keeping the volume minimized. Various transmission loss characteristics are possible when we select different objective functions under constraints.
Phonological neighborhood density and vowel production in older and younger adults
Authors: Watson Peter J. , Munson Benjamin , Belgum Erik H.
Published: October 2005

Recent work has shown that neighborhood density (ND) affects vowel production in young adults (B. Munson and N. Solomon, J. Speech. Lang. Hear. Res. 47, 1048–1058 [2004]). Vowels in words with high ND were produced with larger F1/F2 acoustic vowel space; this effect was independent of word frequency and duration. This may reflect speakers’ modification of vowel production to assist listeners’ vowel perception. However, a post hoc analysis of Munson and Solomon’s data found that the effect is strongest in the low-front vowel /æ/, suggesting that the effect may be due to the ongoing sound change in which /æ/ is progressively becoming lower and more central (Hillenbrand et al., J. Acoust. Soc. Am. 97, 3099–3111 [1995]) occurring more often in high-density words. If so, one should see a larger effect of neighborhood density in younger adults than in older adults. To examine this, vowel production was measured in a group of ten older adults (mean age=76.1 years), and compared to ten younger adults from Munson and Solomon [2004]. The older adults produced vowels with lower-frequency formants than younger adults. Contrary to expectations, age-group differences were not disproportionately larger for /æ /than for other vowels, and both groups showed a robust effect of neighborhood density on vowel production.
Voice quality of children with cochlear implants acquired at early and later ages
Authors: Campbell Melanie M. , Hanstein Stefanie , Ney Christina
Published: October 2005

The speech gains of children with cochlear implants (CIs) are well documented, but the literature on voice quality is sparse. It has reported atypical measures/ratings of voice pitch, pleasantness, timing, and acoustic features [Higgins et al. (2003); Perrin et al. (1998)]. Is voice quality now improving in children implanted very early? This pilot study compared the voice quality of (a) children with early acquired CIs and children with normal hearing and (b) the voice quality of children implanted later and earlier in life. Children aged 6 to 10 years, with early acquired CIs, and participants with normal hearing, age-matched to them, audio recorded sentences, vowels, and conversation. PERCI pressure measures were also performed. PERCI Differential and Oral Pressure values and Computerized Speech Lab (CSL) and Visipitch measures of voice-onset time and fundamental frequency were analyzed comparing the values from the hearing and the early implanted children and values gleaned from the study of Higgins et al. of children with later-acquired implants. CSL and Visipitch measures of intonation contour, intensity, and jitter were analyzed to compare the hearing and the early implanted participants. Ratings on the Wilson Voice Scale were correlated with measures of jitter, fundamental frequency, and intonation contour.
Detection of interaural delay in high-frequency noise
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: October 2005

Subjects’ ability to detect interaural time delays was investigated with four 270-Hz wide bands of noise centered at 4 kHz which differed only in the slope of their low-frequency skirts. Sensitivity to interaural delay increased dramatically with decreases in the slope of the low-frequency skirt. Performance was unaffected by the addition of noise high passed at 3 kHz, but was seriously degraded by the addition of noise low passed at 3 kHz. When only the low-frequency skirt of one of the four noise bands was presented, performance was slightly poorer than that obtained with the entire band. The data strongly suggest that the primary cue was provided by interaural delays of the low-level, low-frequency portions of the nominally high-frequency bands of noise. That is, consistent with Yost et al. [J. Acoust. Soc. Am. 50, 1526–1530 (1971)], who used transients, the subjects were not utilizing differences in the envelopes of the high-frequency noise bands.
Radiation and attenuation of waves in a random medium
Authors: Wenzel Alan R.
Published: October 2005

A theoretical analysis of the wave field radiated by a point source in a weakly inhomogeneous one-dimensional random medium is presented. The analysis is based on a perturbation technique and includes all single- and double-scattering terms, as well as some scattering terms of higher order. Approximate expressions, valid when the absorption of the medium is small, are obtained for the mean intensity (i.e., the mean square of the modulus of the complex wave amplitude) and the mean energy flux of the wave as a function of propagation range. These expressions show that, as a consequence of backscattering by the random inhomogeneities of the medium, the mean intensity and mean energy flux decrease more rapidly with range than would be the case in the absence of randomness. This more rapid rate of decrease with range can be interpreted as an excess attenuation of the wave as a result of the randomness of the medium. It is also found that the mean radiated power is altered slightly by the randomness of the medium. The excess-attenuation results are found to be consistent with observations.
Propagation of long waves in acoustically treated, curved ducts
Authors: Rostafinski W.
Published: October 2005

A two-dimensional, detailed study is presented on the behavior of long waves in lined, curved ducts. The analysis includes a comparison between the propagation in curved and straight lined ducts. A parametric study was conducted over a range of wall admittance and duct wall separation. The complex eigenvalues of the characteristic equation, which in the case of a curved duct are also the angular wavenumbers, have been obtained by successive approximations.
Comparison of stimuli used in sound field audiometric testing
Authors: Dillon Harvey , Walker Gary
Published: October 2005

The problems associated with performing pure-tone threshold measurements in reverberant or diffuse sound fields are illustrated with the use of three-dimensional representations of the sound field within a typical test booth. A microphone mounted on a motorized trolley is used to perform these measurements. A comprehensive comparison is then made of the efficiency with which FM tones, AM tones, damped wave trains, and narrow bands of noise provide a uniform sound field. The conclusion is reached that the bandwidth of the stimulus is the major factor determining the uniformity of the field. A decision about the most appropriate stimulus for sound field work must thus be based on factors other than field uniformity. When the constraints of obtaining suitable spectral distributions, and being able to relate thresholds obtained with complex stimuli to those obtained with pure tones are also considered, FM tones and suitably generated narrow bands of noise appear to be the most suitable stimuli. The selection of suitable parameters is discussed and an Appendix discusses the spectrum and bandwidth of FM signals with different modulation waveforms. The relative accuracy of testing in the direct and reverberant regions in a nonanechoic environment is also discussed.
Voicing-dependent vowel duration in English and French: Monolingual and bilingual production
Authors: Mack Molly
Published: October 2005

It is well established in English phonology that vowels preceding voiceless consonants are approximately two-thirds the duration of vowels preceding voiced consonants when these vowels occur in stressed prepausal environments. It is claimed that such a large voicing-dependent effect does not exist in certain other languages, such as French. However, in previous studies, the syllabic and phonemic structures of the stimuli used for cross-language comparison have not been held constant. Therefore, it was the purpose of this study to compare durational effects in English and French stimulus words having the same syllabic structure and, to the extent possible, the same phonemic structure. An additional issue of the study was the ability of bilinguals to utilize the English durational rule. Computer analysis of 854 stimulus words revealed that (1) there were larger context-dependent differences in preconsonantal vowel duration in English than in French, and (2) the English and French vowel duration ratios of French–English bilinguals were essentially like those of French monolinguals. However, the bilinguals’ English vowels were longer than their French vowels.
Long-term average speech spectra for normal and hearing-impaired adolescents
Authors: Formby C. , Monsen R. B.
Published: October 2005

Acoustical aspects of the speech of hearing-impaired persons have usually been examined over brief periods of time for simple utterances. Of interest in this study was whether abnormal acoustical patterns would be observed when speech was examined over longer periods of time. Spectra were averaged for 20 hearing-impaired adolescents, for whom we had audiometric profiles and an assessment of speaker intelligibility, and also for ten normal-hearing adolescents. An analyzer having constant-frequency bandwidths of 60 Hz, with the center frequencies of the filters spaced at 40-Hz intervals across a 10-kHz range, was used in the measurements (averaging time 27 s). The normal spectra are characterized by a regular pattern of peaks occurring at multiples of the talkers’ fundamental frequencies and by slopes declining at rates of −5 to −6 dB/octave. After correction for lip-radiation impedance, these slopes are similar to that reported for the normal glottal source (−12 dB/octave). The hearing-impaired adolescents produced spectra for which the harmonic structure ranged from the very well defined to the irregular and poorly defined; spectral slopes declined at rates equal to or greater than the normal rate, in some cases declining at twice the normal rate.
Preliminary study of simultaneous-masking and pulsation-threshold patterns of vowels
Authors: Tyler Richard S. , Lindblom Björn
Published: October 2005

We have presented steady-state vowels as maskers and pure tones as signals using simultaneous-masking (SM) and pulsation-threshold (PT) procedures. Extensive data were collected from one subject. The method of adjustment was used to obtain vowel masking patterns: the display of signal thresholds as a function of frequency. For the Swedish vowels /y/, /e/, and /i/, the formant frequencies are usually reflected in both the SM and PT patterns, although the formants appear better preserved in the PT patterns. The masking patterns conform with the corresponding acoustic spectra in that the location of formant peaks depends on the vowel fundamental frequency. Vowel intensity was changed parametrically over a 45-dB range in three steps of 15 dB. For SM, each 15-dB change in vowel level results in about a 10–13-dB change in signal thresholds. For PT, the change in signal thresholds with vowel intensity is dramatically reduced: only a 3–4-dB threshold change in some instances for a 45-dB change in vowel intensity. These results suggest that suppression plays an important role in the coding of speech spectra.
Detection of sinusoidally amplitude modulated noise by the chinchilla
Authors: Salvi Richard J. , Giraudi Diane M. , Henderson Donald , Hamernik Roger P.
Published: October 2005

Amplitude modulation thresholds for sinusoidally amplitude modulated noise were obtained from four monaural chinchillas using shock-avoidance conditioning procedures. The noise was band limited at either 10 or 20 kHz, amplitude modulated at frequencies between 2 and 4096 Hz and presented at levels between 52 and 73 dB SPL. The modulation thresholds of the chinchilla were approximately 9% (−20 dB) at modulation frequencies below 32 Hz. At higher modulation frequencies, thresholds increased at the rate of 1.9 dB/octave. Modulation thresholds were also measured in human listeners using the same experimental apparatus. Amplitude modulation functions for both subject groups exhibited low-pass characteristics; however, the thresholds for humans were better than those of the chinchilla at modulation frequencies below 64 Hz.
Scattering of transient elastic waves by an inhomogeneous obstacle: Contrast in volume density of mass
Authors: Herman Gérard C.
Published: October 2005

A method is described to compute the scattering of transient elastic waves by arbitrarily shaped, three-dimensional, inhomogeneous, penetrable objects of bounded extent that only differ from their surroundings in their volume density of mass. The problem is formulated in terms of a volume-integral equation over the interior of the scatterer. This integral equation is solved numerically by the marching-on-in-time method. Also, another numerical method to solve the integral equation by iteration is discussed. Comparison is made with analytical results for a spherical, homogeneous scatterer, while some numerical results for scatterers of different shapes are presented.
Acoustic propagation in finite length elastic cylinders. Part II: Asymmetric excitation
Authors: El-Raheb Michael
Published: October 2005

The propagation of acoustic waves in a perfect finite length elastic cylinder due to an asymmetric excitation is studied. The frequency response of the coupled system involves sharp resonant peaks lagging the rounded peaks at the empty cylinder resonances and nonresonant maxima often caused by modulated coincidence. The maximum acoustic pressure drops off as an empty cylinder resonance is crossed, then recovers gradually with decaying fluctuations as the frequency nears a higher empty cylinder resonance. Although a definite cutoff frequency exists when the boundaries are rigid, the effect is diffused due to the elasticity of the cylinder wall. Nonresonant peaks become more frequent for modes with a circumferential wavenumber that corresponds to the minimum resonance in the empty cylinder spectrum.
Field patterns of pulsed, focused, ultrasonic radiators in attenuating and nonattenuating media
Authors: Goodsitt Mitchell M. , Madsen Ernest L. , Zagzebski James A.
Published: October 2005

A theoretical method which can be used to calculate the pressure field patterns of pulsed, focused, ultrasonic radiators in attenuating and nonattenuating media is discussed in this paper. The underlying principle involved is the superposition of continuous wave beams to form pressure pulses. The method is adapted to the circumstances associated with using a hydrophone to measure field patterns. Experimentally obtained hydrophone signals are then compared to theoretical predictions. The field patterns of four transducer-pulser combinations are investigated. A medium with tissue-mimicking acoustical properties is used to attenuate the ultrasonic beam in these studies. The theory compares favorably with experiment whether an attenuating medium is present or not. However, the theory fails at positions very close to the transducer face (∠1 cm) and when significant nonlinear effects occur during the transmission of the pulse through the medium. This work may have significant applications in research devoted to designing ultrasonic transducers for particular studies, determining dose profiles of medical ultrasonic machines, and analyzing the ultrasonic signals backscattered from within patients.
Temporal patterns of coarticulation: Lip rounding
Authors: Bell-Berti Fredericka , Harris Katherine S.
Published: October 2005

According to some theories, anticipatory coarticulation occurs when phones for which a feature is unspecified precede one for which the feature is specified, with consequent migration of the feature value to the antecedent phones. Carryover coarticulation, on the other hand, is often attributed to ’’articulatory sluggishness.’’ In this paper, EMG evidence is provided that this formulation is inadequate, since the beginning of EMG activity associated with vowel lip rounding is independent of measures of the acoustic duration of adjacent lingual consonants. We suggest that the vowel-rounding gesture simply co-occurs during predictable intervals with portions of preceding and following lingual consonant articulations.
Ultrasound velocity in muscle
Authors: Mol Chris R. , Breddels Paul A.
Published: October 2005

Measurements are reported on the propagation velocity of ultrasound in muscle tissue. This appears to be dependent on fiber direction for various muscle types (in vitro). Typical results are 1550 m/s perpendicular and 1557 m/s parallel to fiber direction (20° C). A model is drawn up to relate such data to the elastic properties of muscle. It is shown that the assumptions: linear elastic behavior, homogeneity, and anisotropy with cylindrical symmetry, do not harmonize with the experimental results. A more elaborate model is suggested. Contraction dependence of the ultrasound velocity was investigated on human biceps muscle (in vivo) and frog gastrognemius muscle (in vitro). The measured velocity increase in biceps muscle during contraction—up to 3 m/s—is attributed to a varying blood content of the muscle. In (in vitro) frog muscle contraction is not accompanied by a change in ultrasound velocity. This suggests that increased muscle stiffness is not appreciably reflected in ultrasound velocity.
Study of bulk reacting porous sound absorbers and a new boundary condition for thin porous layers
Authors: Bliss Donald B.
Published: October 2005

The effect of bulk reaction on the sound absorption properties of porous materials is studied theoretically and experimentally. Particular attention is focused on the important case of a layer of porous material attached to a rigid wall. In general, it is found that the surface of the porous material can be accurately represented by its normal incidence impedance only if a nondimensional flow resistance parameter is large, i.e., only under this condition is the bulk reaction effect negligible. A new boundary condition is proposed which accounts for the effect of bulk reaction when the thickness of the sound absorbing layer is smaller than the acoustic wavelength. The boundary condition relates the surface pressure and its second derivatives along the surface to the normal velocity. Sample calculations for a theoretical porous material show that the oblique incidence absorption coefficient can be calculated very accurately using this boundary condition. In practice, the boundary condition requires two experimentally determined factors: the normal incidence impedance and a bulk reaction coefficient. An experiment was conducted to demonstrate the importance of bulk reaction effects and to show that a method proposed to measure the bulk reaction coefficient is feasible.
Amplitude attenuation of impulsive waves in random media based on travel time corrected mean wave formalism
Authors: Sato Haruo
Published: October 2005

Waves gradually collapse with propagation through media with random velocity fluctuation; however, impulsive waves propagate without large attenuation when the wavelength is shorter than the correlation distance. The Q−1 value predicted from the usual mean wave formalism monotonously increases with frequency even in the high-frequency limit, due to taking a mean over waves with large travel time fluctuations caused by the long scale velocity fluctuation compared with the wavelength studied. We propose a new statistical averaging method appropriate for the amplitude attenuation measurement of impulsive waves, in which the mean wave is defined after the correction of travel time fluctuations. We investigate impulsive scalar waves propagation in three-dimensional media with homogeneous and isotropic random fractional velocity fluctuation, based on the binary interaction approximation in this improved mean wave formalism. We successfully derive the Q−1 value that has a peak of the order of the mean square fractional velocity fluctuation around the frequency corresponding to the correlation distance and decreases with frequency in the high-frequency limit, when the random media is characterized by the von Karman autocorrelation function. The correction of travel time fluctuation is shown to be equivalent to the neglect of energy scattering around the forward direction.
Acoustic streaming of a sphere near an unsteady source
Authors: Wang C.–Y.
Published: October 2005

A sphere is situated near an oscillatory source. Assuming high-frequency oscillations, the Navier–Stokes equation is solved using matched asymptotic expansions. The nonlinear steady streaming shows multiplicity of recirculating cells. The sphere also experiences a steady force directed towards the source.
Active attenuation of noise—The monopole system
Authors: Eghtesadi Kh. , Leventhall H. G.
Published: October 2005

Proposals have been made to attenuate noise propagating down a duct by adding an antiphase copy of the primary noise. In a number of configurations, two or three sources had been used to produce the secondary noise, but a successful system with one source had not been realized. The conventional monopole system is analyzed and the reason why this type of monopole secondary source is not a practical solution is investigated. A modified system with a new solution of the problem is developed.
Pitch of complex signals according to virtual-pitch theory: Tests, examples, and predictions
Authors: Terhardt Ernst , Stoll Gerhard , Seewann Manfred
Published: October 2005

The pitch-extraction algorithm described by Terhardt et al. [J. Acoust. Soc. Am. 71, 679–688 (1982)] is used to compute a number of examples to test the procedure’s validity, and to illustrate its applicability. The following subjects are considered: (a) pitch of harmonic complex tones (with and without fundamental); (b) existence region of virtual pitch; (c) Shepard pitch phenomenon; (d) virtual pitch of inharmonic complex tones; (e) spectral dominance; (f) effect of amplitude spectrum on pitch; (g) pitch of bell sounds; and (h) tonal evaluation of musical chords. The algorithm’s predictions agree well with psychoacoustic observations and it is concluded that it can be useful in audio-engineering and psychoacoustic research.
Vowel identification: Orthographic, perceptual, and acoustic aspects
Authors: Assmann Peter F. , Nearey Terrance M. , Hogan John T.
Published: October 2005

This study investigates conditions under which vowels are well recognized and relates perceptual identification of individual tokens to acoustic characteristics. Results support recent findings that isolated vowels may be readily identified by listeners. Two experiments provided evidence that certain response tasks result in inflated error rates. Subsequent experiments showed improved identification in a fixed speaker context, compared with randomized speakers, for isolated vowels and gated centers. Performance was worse for gated vowels, suggesting that dynamic properties (such as duration and diphthongization) supplement steady-state cues. However, even-speaker-randomized gated vowels were well identified (14% errors). Measures of ’’steady-state information’’ (formant frequencies and f0), ’’dynamic information’’ (formant slopes and duration), and ’’speaker information’’ (normalization) were adopted. Discriminant analyses of acoustic measurements indicated relatively little overlap between vowel categories. Using a new technique for relating acoustic measurements of individual tokens with identification by listeners, it is shown that (a) identification performance is clearly related to acoustic characteristics; (b) improvement in the fixed speaker context is correlated with improved statistical separation resulting from formant normalization, for the gated vowels; and (c) ’’dynamic information’’ is related to identification differences between full and gated isolated vowels.
Binaural interaction in auditory brainstem responses: Theoretical and methodological considerations
Authors: Dobie Robert A.
Published: October 2005

Binaural interaction (BI) in auditory brainstem responses (ABR’s) has been demonstrated recently in cats [Huang and Buchwald, Electroencephalogr. Clin. Neurophysiol. 44, 179–186 (1978)], guinea pigs [Dobie and Berlin, Arch. Otolaryngol. 105, 391–398 (1979)], and humans [Dobie and Norton, Electroencephalogr. Clin. Neurophysiol. 49, 303–313 (1980)]. Decker and Howe [J. Acoust. Soc. Am. 69, 1084–1090 (1981)] have suggested certain modifications of the usual experimental paradigm and a new interpretation for BI in ABR. The intent of this letter is to discuss both their methods, which I believe are inappropriate, and their theory which, while it is not supported by their data, should be further investigated.
A finite-difference treatment of interface conditions for the parabolic wave equation: The horizontal interface
Authors: McDaniel Suzanne T. , Lee Ding
Published: October 2005

An elegant finite-difference technique applicable to the parabolic wave equation is developed to handle the boundary conditions at the interface between two media with different sound speeds and densities. Continuity of pressure and continuity of the normal component of particle velocity are preserved at the interface. The method is designed to be implicit and is unconditionally stable. A complete mathematical treatment for the case of a horizontal interface is described.
Identification of synthesized /r–w/ continua for adult and child speakers
Authors: Sharf Donald J. , Benson Peter J.
Published: October 2005

A continuing problem in speech research is the comparison of phonetically similar but acoustically distinct sounds such as the comparison between adult speech and child speech. This problem is especially important in the remediation of speech disorders. In this study, we focus on this problem as manifested in the disordered production of /r/ sounds. Stimuli which varied in F2 and F3 onset frequencies were synthesized to span continua from /r/ to /w/ for adult, child, and scaled adult (formants 1.5 times adult values) speakers. These stimuli were presented to 18 naive adults for identification as ’’R’’ or ’’W’’ at three listening sessions to test for stability of category boundaries. Significant shifts in category boundaries were found for all three continua between sessions one and two but not between sessions two and three. Category boundaries in terms of formant frequencies showed significant differences between the adult and childlike continua. Rescaling these values on a psychophysical dimension and adjusting for formant spread brought the category boundaries into close alignment. In free choice testing, synthesized /r/ and /w/ stimuli were identified by most subjects at least as well as natural /r/ and /w/ stimuli but synthesized child /r/ stimuli were identified by most subjects considerably better than natural child /r/ stimuli.
Auditory brainstem response binaural interaction: Stimulus presentation level and auditory tract asymmetry
Authors: Decker T. Newell , Howe Susan W.
Published: October 2005

Dobie’s comments [J. Acoust. Soc. Am. 71, 1031–1033 (1982)] on our recent article on human binaural interaction in the ABR [Decker and Howe, J. Acoust. Soc. Am. 69, 1084–1090 (1981)] are focused principally on two issues: (1) the use of SL rather than constant peSPL for stimulus presentation, and (2) the presence of asymmetry in the right and left ear contributions to the binaural ABR. The intent of this letter is to clarify our position as it pertains to Dobie’s concerns about these methodological and theoretical issues.
Acoustic behavior of echolocating Atlantic Bottlenose Dolphins
Authors: Au Whitlow W. L. , Penner Ralph H. , Kadane James
Published: October 2005

An echolocation click detector was used to monitor the acoustic emission of two dolphins performing a target detection task in the presence of artificially induced white noise. The time of each click emission along with the time of response was measured for every trial of the entire psychophysical experiment, which involved the detection of a 7.62-cm sphere located at a range of 16.5 m from the animals. From the data, the number of clicks, the click interval and its distribution, the response latency, and the total latency as a function of the masking noise level were determined. The average number of clicks emitted per trial increased with the masking noise level, until a particular level was reached after which the number of clicks decreased with further increases in the noise level. The dolphins seemed to have found the task insoluble beyond a 77 dB re 1 μPa2/Hz noise level, and reacted by decreasing the number of clicks emitted per trial. Dolphin E also did not emit any detectable clicks during 20% of the trials at 82 dB and 41% at 87 dB, while dolphin H did not emit any detectable clicks in 14% of the trials at the 87-dB noise level. The response latencies for correct rejections were always greater than for correct detections at all noise levels for both dolphins. The click interval results indicated that the animals seem to have good control of the click intervals used in a click train, and may preprogram a desired click interval even before starting on an echolocation search, based on prior knowledge of the target range. The use of the click detector in conjunction with a microprocessor has provided a convenient technique by which to study the acoustic behavior of echolocating marine mammals.
Comments on ’’Ear dominance and sequential interactions’’[J. Acoust. Soc. Am. 67, 220–228 (1980)]
Authors: Yund E. William
Published: October 2005

The data presented in ’’Ear dominance and sequential interactions’’ by D. Deutsch [J. Acoust. Soc. Am. 67, 220–228 (1980)] do not support the conclusion that sequential interactions are necessary to produce ear dominance. In the case of two of the three experiments in this study, a critical assumption is unsupported, and on the basis of the available evidence, appears to be false. In the case of the other experiment, the method is not valid and the data are inconclusive. If sequential interactions have any effect on ear dominance, that effect remains to be demonstrated.