bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation detection as an index of residual auditory function
Authors: Formby C. , Morgan L. , Burton J. , Forrest T. G.
Published: October 2005

Indirect tests of residual auditory function often assume that the temporal envelope is the primary cue in the acoustic signal for profoundly hearing-impaired persons who are without auditory function. In contrast, for hearing-impaired persons who retain residual auditory function, both temporal envelope and spectral cues are available. This hypothesis was evaluated directly by studying simultaneously temporal envelope and spectral resolution in seven profoundly hearing-impaired subjects (ten ears). Amplitude modulation (AM) detection thresholds were measured with a 250-Hz carrier, modulated at rates of 40 and 150 Hz, presented by headphones and by hand vibration. At 40 Hz, where the AM sidebands fell within the same critical band as the carrier and could not be resolved, all subjects yielded similar headphone and vibrator results. At 150 Hz, headphone thresholds for six ears were better than the vibrotactile threshold, while four ears yielded little or no difference in performance between the two transducers. The latter results reflect differences in resolution between ears with and without functional critical band mechanisms and, hence, inherent differences between auditory and vibrotactile processing. [Research supported by NIH.]
Time course of hemispheric differences in spoken word recognition
Authors: Auer Edward T. , Luce Paul A.
Published: October 2005

Previous research has demonstrated differences between hemispheric processing of auditorily and visually presented lexically ambiguous words. The present study further examined the time course of hemispheric processing of lexically ambiguous spoken words. Lexically ambiguous primes (e.g., BANK) were presented binaurally. Fifty or 500 ms later, a target word was then presented monaurally to the left or right ear for a speeded lexical decision response (i.e., WORD-NONWORD). Target words were either (1) related to the dominant meaning of the ambiguous prime (BANK-MONEY), (2) related to the subordinate meaning of the prime (BANK-RIVER), or (3) unrelated to the prime. No significant differential effects of facilitation were found in any condition. In addition, only the fastest subjects in the 50-ms ISI experiment showed a significant right-ear advantage. Implications of these results will be discussed in terms of modality specificity and temporal versus spatial stimulus array.
Speeded comparisons of spoken words
Authors: Luce Paul A.
Published: October 2005

This research evaluated the claim that spoken words are recognized as soon as they diverge from all other words in memory. Pairs of consonant-vowel-consonant (CVC) words were presented for a speeded SAME-DIFFERENT response. Subjects were instructed to respond SAME or DIFFERENT as soon as they could determine if the second word of the pair was the same as or different from the first word. Reaction times were measured from the onset of the second word. The overlap between the two members of the pairs of spoken words was systematically manipulated to determine if reaction times to say DIFFERENT were a simple function of the point at which the two words differed or whether overlapping segments after the divergence point would affect reaction times. The results are consistent with the notion that the temporal window for mapping information onto representations of spoken words in memory spans more than a feature or segment and that spoken words are not necessarily recognized as soon as they diverge from other words in memory.
Context effects in the perception of personal information in the speech signal
Authors: Mullennix John , Johnson Keith , Topcu Meral
Published: October 2005

The speech signal contains linguistic, personal, and social information. Many studies have demonstrated that the perception of linguistic information is subject to context effects. This paper is a report of a study concerning context effects in the perception of personal information. When listeners were asked to identify the speaker of synthetic stimuli (the vowel /i/) in terms of male/female attributes, their responses were most affected by F0 and formant values with only a small effect of glottal waveform shape. The results of a perceptual anchoring study will be reported, in which listeners were asked again to identify the stimuli on the basis of speaker attributes, but with one endpoint of the synthetic continuum presented more often than any of the other stimuli. The results of this experiment will be discussed in terms of the hypothesis that listeners' perceptions of personal information in the speech signal are influenced by context. [Work supported by NIH.]
The release of air bubbles from an underwater nozzle
Authors: Longuet-Higgins Michael , Kerman Bryan R. , Lunde Knud
Published: October 2005

Air bubbles released from an underwater nozzle emit an acoustical pulse that is of interest both for the study of bubble detachment and for elucidating the mechanism of sound generation by a newly formed bubble. In this paper, the sequence of bubble shapes is calculated theoretically from a given nozzle, and it is shown that there is for each nozzle a bubble of maximum volume Vmax. Assuming that the bubble becomes detached at its “neck,” and that the volume of the detached bubble equals the volume V* of the undetached bubble above its “neck,” it is determined for each nozzle diameter D an acoustic frequency f* corresponding to “slow” bubble release. Experiments show that the acoustic frequency, hence the bubble size, depends on the rate of air flow to the bubble, but for slow rates of flow the frequency f is very close to the theoretical frequency f*. High-speed photographs suggest that when the bubble pinches off, the limiting form of the surface is almost a cone. This is accounted for by assuming a line sink along the axis of symmetry. Immediately following pinch off, there is evidence of the formation of an axial jet going upward into the bubble. This may play a part in stimulating the emission of sound.
Numerical simulations of bubble release from underwater needles
Authors: Oguz Hasan N. , Prosperetti Andrea
Published: October 2005

The release of bubbles from a submerged needle is a noisy process that is difficult to stabilize. Longer needles are found to produce a much steadier stream of bubbles than short ones. A possible explanation for this behavior is given by means of a dynamic model that accounts for the pressure drop inside the needle. The flow field created by the injected bubble is assumed to be irrotational and a boundary integral formulation is used to calculate the evolution of the bubble surface. Realistic bubble formation histories are obtained and the numerical results appear to be in good agreement with the available experimental measurements. The behavior of the bubble after detachment and the effect of the previously released bubble are also studied. [Work supported by ONR.]
Statistical description of ray diffusion in random inhomogeneous media
Authors: Saichev Alexander I. , Shchemelev Yevgeny G.
Published: October 2005

The ray approach is often used when coordinates and incoming angles for waves, propagating through smooth inhomogeneities, are analyzed. The probability density for coordinates and angles of rays with fixed ray lengths is determined by a diffusion equation. But if the solution of the diffusion equation is known it is impossible to give an answer about statistical properties of the incoming angle fluctuations at the point of reception. The cause of this is that the length of rays received at the fixed point is not known. This problem is especially important when the small angle approach is violated. The probability density determination for ray length and incoming angles in the fixed point is needed here. The derivation of this probability density is suggested for determination of the statistical properties of the rays in the receiving plane.
Supra-aural and insert earphone occlusion effects
Authors: Wright Diana C. , Angelelli Joseph
Published: October 2005

Monaural and binaural occlusion effects were determined for 30 subjects using mastoid placement of a B-71 bone vibrator using supra-aural earphones (TDH-49/P/N 51) and insert earphones (Eartone-3A/Earlink-3A), which had a shallow or full insertion depth. Statistically significant differences were found for earphone type, frequency, and insert earphone insertion depth. Overall, the mean occlusion effect for all conditions decreased as frequency increased from 250–2000 Hz and was greater for the binaural than the monaural occlusion and for the supra-aural than the insert earphone occlusion. Also, the mean occlusion effect was greater for the shallow compared with the full insertion depth for the insert earphone indicating the occlusion effect increased as the volume of air between the occluder and the ear drum increased. The standard deviations were not consistently higher or lower across frequency for any one occlusion condition. Clinical implications regarding the magnitude of the occlusion effect with supra-aural and insert earphone systems will be discussed.
The detection and classification of objects lying on the seafloor
Authors: de Roos A. , Sinton J. J. , Gough P. T. , Kennedy W. K. , Cusdin M. J.
Published: October 2005

There are many instances when the detection of an object lying on the seafloor is insufficient. In many cases, an idea of what kind of object is lying on the seafloor is also required. The detection and classification sonar described here is based on a wide bandwidth continuous transmission frequency-modulated (CTFM) sonar. The design and operating parameters of CTFM sonars are discussed in some detail with particular reference to their use as classification sonars. One type of CTFM sonar incorporating a technique to eliminate the ‘‘blind time’’ and extend the maximum range is chosen to implement several detection and classification schemes. It is shown that of the various classification schemes used, the one based on a simple rough/smooth discrimination was the most reliable. This reliability was judged by comparison to an alert human operator with access to a variety of visible and audible displays. It was found that the algorithm performed nearly as well as the operator and is of course faster and not subject to fatigue. Many results are illustrated.
The nonlinear pressure field of a plane circular piston: Theory and experiment
Authors: Baker Andrew C. , Anastasiadis Kosmas , Humphrey Victor F.
Published: October 2005

The measured nearfield pressure levels of a plane circular piston are compared with a numerical solution of the parabolic approximation to the nonlinear wave equation under conditions of high nonlinearity (100 kPa at the piston face). The solution allows for nonlinearity, diffraction, and absorption in continuous wave pressure fields. The measurements were made in water, using a transducer (38-mm diameter) driven at 2.25 MHz and a 1-mm-diam membrane hydrophone. Comparisons are made along and across the acoustic axis for the amplitudes of the fundamental, second, and third harmonics and the phases of the second and third harmonics. Good agreement is shown between experiment and theory within the known limitations of both.
Diffraction effects of planar transducers using a numerical expression for edge waves
Authors: Mair H. Douglas , Bresse L. , Hutchins D. A.
Published: October 2005

It is well established that the field from uniformly vibrating piston transducers may be considered as being derived from two components: a plane wave and an edge wave. These have been both predicted and observed in practice, but it would seem that a mathematical expression for the edge-wave component has not yet been developed fully. In this article, expressions are developed for the pressure and particle velocity edge waves that can be used to calculate the field that results when a plane wave is diffracted by an edge. The expressions are used to study a particular example, namely, that of an arbitrarily shaped piston radiator. The results for certain situations are shown to agree with existing solutions for a disk source.
Revisiting stop-consonant perception for two-formant stimuli
Authors: Ohde Ralph N.
Published: October 2005

The purpose of this study was to reexamine the factors leading to stop-consonant perception for consonant–vowel (CV) stimuli with just two formants over a range of vowels, under both an open- and closed-response condition. Five two-formant CV stimulus continua were synthesized, each covering a range of second-formant (F2) starting frequencies, for vowels corresponding roughly to [i,i,1,u,a]. In addition, for the [i] and [a] continua, the duration of the first-formant (F1) transition was systematically varied. Three main findings emerged. First, criterion-level labial and alveolar responses were obtained for those stimuli with substantial F2 transitions. Second, for some stimuli, increases in the duration of the F1 transition increased velar responses to criterion level. Third, the response paradigm had a substantial influence on stop-consonant perception across all vowel continua. The results support a model of stop-consonant perception that includes spectral and time-varying spectral properties as integral components of analysis.
Vibrational–vibrational coupling in air at low humidities
Authors: Zuckerwar Allan J. , Miller Keith W.
Published: October 2005

Calculations of sound absorption in air are traditionally based on the assumption that molecular relaxations in nitrogen and oxygen are independent. In binary mixtures of these two gases, however, they are not independent; rather, molecular relaxation is known to be controlled by a very strong vibrational–vibrational (V–V) coupling, which influences both the relaxation frequencies and the relaxation strengths. This article shows that small concentrations of the air constituents carbon dioxide and water vapor, which themselves possess a strong V–V coupling to N2 and O2, serve to decouple the N2 and O2 relaxations. To characterize the N2–O2 coupling a ‘‘coupling strength’’ is derived, which depends upon the constituent concentrations and the related reaction rate constants. It is found that the molecular relaxations associated with N2 and O2 in air experience a gradual transition from strong to weak coupling as the humidity increases beyond approximately 0.001 mole %.
Thermoacoustic engines
Authors: Swift G. W.
Published: October 2005

Thermoacoustic engines, or acoustic heat engines, are energy-conversion devices that achieve simplicity and concomitant reliability by use of acoustic technology. Their efficiency can be a substantial fraction of Carnot’s efficiency. In thermoacoustic prime movers, heat flow from a high-temperature source to a low-temperature sink generates acoustic power (which may be converted to electric power using a transducer). In thermoacoustic heat pumps and refrigerators, acoustic power is used to pump heat from a low-temperature source to a high-temperature sink. This review teaches the fundamentals of thermoacoustic engines, by analysis, intuition, and example.
Compliances of wood for violin top plates
Authors: Schumacher Robert T.
Published: October 2005

In the orthotropic approximation, nine independent elastic compliance elements are needed to describe the elastic behavior of wood. Many are difficult to determine experimentally, particularly in the audio frequency region, where their dynamic consequences are of interest to violin makers. This study computes the normal mode frequencies of a representative arched shell, using a commercial finite element package, in order to compute a ‘‘dependence matrix,’’ Daij =(sij/f a)(df a/dsij), expressing the relative fractional change of the ath normal mode frequency f a to the fractional change of the sij compliance element. Since the sum of Daij over all nine compliances is − 1/2 for each normal mode a, the relative importance of each compliance element can be read directly from Daij for a given set of compliances and a given plate geometry. This study concludes that only three compliance elements are of critical importance for violin top plates. One of the consequences is that the substitution of manmade composite materials with higher symmetry properties (and, hence, fewer compliance elements) for Norway spruce is feasible.
Evaluation of two voice-separation algorithms using normal-hearing and hearing-impaired listeners
Authors: Stubbs Richard J. , Summerfield Quentin
Published: October 2005

Two signal-processing algorithms, designed to separate the voiced speech of two talkers speaking simultaneously at similar intensities in a single channel, were compared and evaluated. Both algorithms exploit the harmonic structure of voiced speech and require a difference in fundamental frequency (F0) between the voices to operate successfully. One attenuates the interfering voice by filtering the cepstrum of the combined signal. The other uses the method of harmonic selection [T. W. Parsons, J. Acoust. Soc. Am. 60, 911–918 (1976)] to resynthesize the target voice from fragmentary spectral information. Two perceptual evaluations were carried out. One involved the separation of pairs of vowels synthesized on static F0’s; the other involved the recovery of consonant–vowel (CV) words masked by a synthesized vowel. Normal-hearing listeners and four listeners with moderate-to-severe, bilateral, symmetrical, sensorineural hearing impairments were tested. All listeners showed increased accuracy of identification when the target voice was enhanced by processing. The vowel-identification data show that intelligibility enhancement is possible over a range of F0 separations between the target and interfering voice. The recovery of CV words demonstrates that the processing is valid not only for spectrally static vowels but also for less intense time-varying voiced consonants. The results for the impaired listeners suggest that the algorithms may be applicable as components of a noise-reduction system in future digital signal-processing hearing aids. The vowel-separation test, and subjective listening, suggest that harmonic selection, which is the more computationally expensive method, produces the more effective voice separation.
The acoustic signature for intelligibility test words
Authors: Weismer Gary , Kent Ray D. , Hodge Megan , Martin Ruth
Published: October 2005

As part of a research program that aims to develop an explicit acoustic basis for a single-word intelligibility test, an initial attempt to characterize the formant trajectories and segment durations of seven test words produced by 30 normal speakers is described. These characterizations are referred to as ‘‘acoustic signatures.’’ The data indicate that: (1) formant trajectories show two sex effects, namely, that females are more variable as a group than males and tend to have greater slopes for the transitional segment of the second-formant trajectories and that these effects are consistent across words; (2) Bark transformations of the frequency data do not seem to eliminate the interspeaker differences in formant trajectories, nor do they eliminate either of the sex effects described above; and (3) segment durations have different variabilities depending on the syllabic structure of the word; no sex effect was noted here. The discussion focuses on the appropriate form for the acoustic signatures, as well as factors that should be considered in selecting words for signature development. To demonstrate the potential application of these data, formant trajectory and segment duration data from 18 speakers with amyotrophic lateral sclerosis and varying degrees of dysarthria are compared to the acoustic signature for the word wax.
A pitch-synchronous analysis of hoarseness in running speech
Authors: Muta Hiroshi , Baer Thomas , Wagatsuma Kikuju , Muraoka Teruo , Fukuda Hiroyuki
Published: October 2005

A method of pitch-synchronous acoustic analysis of hoarseness requiring a voice sample of only four fundamental periods is presented. This method calculates a noise-to-signal (N/S) ratio, which indicates the depth of valleys between harmonic peaks in the power spectrum. The spectrum is calculated pitch synchronously from a Fourier transform of the signal, windowed through a continuously variable Hanning window spanning exactly four fundamental periods. A two-stage procedure is used to determine the exact duration of the four fundamental periods. An initial estimate is obtained using autocorrelation in the time domain. A more precise estimate is obtained in the frequency domain by minimizing the errors between the preliminary calculated power spectrum and the predicted spectrum spread of a windowed harmonic signal. Analysis of synthesized voices showed that the N/S ratio is sensitive to additive noise, jitter, and shimmer, and is insensitive to slow (8 Hz) modulation in fundamental frequency and amplitude. An analysis of pre- and postoperative voices of six patients with benign laryngeal disease showed that the N/S ratio for vowel /u/ in running speech consistently improved after surgery for all subjects, in agreement with their successful therapeutic results.
Binaural summation and lateralization of transients: A combined analysis
Authors: Algom Daniel , Adam Ronny , Cohen-Raz Lior
Published: October 2005

Subjects judged the loudness and the lateral position of dichotic transient signals, which were presented at equal and unequal levels, synchronously and asynchronously, to the two ears. Binaural loudness summation of clicks does not obey a law of linear addition: It is partial at low level, and superadditive at high level. Supersummation is greater for interaurally delayed clicks than for coincidental ones. The relation between click loudness and sound pressure (over moderate SLs) can be described as a power function with a greater exponent for the binaural function. Lateral positions spread over a greater range for interaural level differences than for interaural time differences. The time-intensity trading ratio was greater than is typically reported for tones. When sound lateralization was induced by interaural time difference, but not by intensity difference, a virtually perfect negative correlation between loudness and extent of off-center displacement existed.
Offset AP masker tuning curve and the FFT of the stimulus
Authors: Henry Kenneth R. , Lewis Edwin R.
Published: October 2005

In previous experiments, it was noted that a cochlear compound action potential (CAP) can be produced by the offset of a tone, provided that the amplitude of the tone is modulated by a trapezoid with slopes that are typically much steeper than required to produce onset responses. Subsequently, such trapezoidal tone bursts with steep slopes were used as probe stimuli in simultaneous and forward masking experiments that were designed to evaluate the tuning characteristics of these offset CAPs. Masker tuning curves (MTCs) were generated by plotting the masker frequency necessary to reduce the amplitude of the offset CAP by 50%. Simultaneous masking of the offset CAP generated a W-shaped MTC, with two sharply tuned tips and one sharply tuned peak. Forward masking generated a sharply tuned V-shaped offset MTC. By contrast, for onset CAPs, both simultaneous and forward masking generated V-shaped MTCs. The very steep stimulus slopes required to produce an offset CAP are likely to generate much more acoustic splatter than the more gradual slopes required to produce an onset CAP, and this may be related to the different shapes of the onset and offset simultaneous MTCs. To explore this possibility, the relationship of the spectral characteristics (determined by fast Fourier transform, or FFT) to the shape of the MTC was studied. The shapes of the FFT were changed by three methods in the described experiments: (1) The probe stimulus duration was varied, thereby changing the power of the splatter, relative to that of the tone; (2) filtered noise was used instead of a pure tone as the probe stimulus; and (3) the rise and decay (r&d) time of the probe stimulus was altered, thereby changing the absolute power of the acoustic splatter. These experiments demonstrate robustness of the shape of the offset MTC under a wide range of changes in the width of the FFT of the probe stimulus. Two crucial determinants of the shape of the offset MTC are the dominant frequency of the probe stimulus and the type of masker (simultaneous versus forward) used to generate the offset MTC. Our observations also suggest that the W shape of the offset simultaneous MTC might be a consequence of a shift of activation along the basilar membrane due to the moderately high level of the probe stimulus.
Theoretical model for circular benders in a rigid baffle and radiating in fluid
Authors: Froelich Benoit G.
Published: October 2005

The bender plate wave equation in vacuum is found to be of a form similar to the usual isotropic plate wave equation. The loading effect of the fluid is then taken into account for a circular bender imbedded in a rigid baffle and acting as a transmitter. This is done using the concept of radiation impedance. The pressure amplitudes generated by two transmitting bender designs are numerically compared. In addition, using the reciprocity relations, the receiving sensitivities of such devices are evaluated.
Threshold recovery functions following impulse noise trauma
Authors: Hamernik Roger P. , Ahroon William A. , Patterson James A.
Published: October 2005

An analysis of the pure-tone threshold recovery functions obtained from 118 chinchillas exposed to high-level impulse noise showed that there are at least three distinctly different types of recovery function: type I—a recovery function for which the initial threshold shift recovers monotonically with increasing postexposure time; type II—a delayed recovery: i.e., for a period as long as 6 h following removal from noise, the pure-tone threshold remains elevated and stable before thresholds begin to follow a monotonic course of recovery; and type III—the growth function, i.e., over a period of at least 6 h following removal from the noise, pure-tone thresholds continue to get worse before they begin to follow a monotonic course of recovery. There is more permanent threshold shift (PTS), more sensory cell loss, and predictions of PTS and cell loss based upon initial measures of threshold shift are less accurate at those frequencies characterized by a type III recovery process than at those frequencies characterized by a type I recovery process.
Distribution of short-term rms levels in conversational speech
Authors: Cox Robyn M. , Matesich Joseph S. , Moore Jeffrey N.
Published: October 2005

For 30 male and 30 female talkers, distributions of short-term rms speech levels, relative to the corresponding long-term rms levels, were determined in each of eight (1)/(3) -oct bands for six short-term measurement intervals. Consecutive, Hanning-windowed, 20-ms time records were combined to produce nominal measurement intervals ranging from 20 to 120 ms. For each measurement interval, mean distributions of short-term rms speech levels relative to long-term levels were very similar for male and female talkers, and intertalker differences were small, especially for short-term amplitudes above the median level. The distribution of short-term rms speech levels relative to long-term rms speech levels varied with measurement interval for the short-term measurements. The effect of measurement interval was least for the highest amplitude speech levels and increased as speech levels decreased. For short-term amplitudes above the median level, the effect of measurement interval was greater in higher frequency regions, whereas for short-term amplitudes below the median level, measurement interval had the greatest effect on the lower frequency bands. These data may facilitate comparisons among investigations using different measurement intervals. In addition, they have implications for amplification strategies.
A note on reflection and transmission of waves at a boundary between two viscoelastic media
Authors: Jones H. W. , Kwan H. W. , Yeatman E. M.
Published: October 2005

This letter notes errors in the previous treatment of the problem of the reflection and transmission of acoustical waves at a boundary between two viscoelastic media. The validity of the corrections that are given is confirmed by the recovery of the solid/solid interface equations of Kolsky and by some experimental evidence.
An invariant imbedding approach to the scattering of sound from a two-phase fluid
Authors: Skelton E. A. , Fitzgerald W. J.
Published: October 2005

Air bubbles are frequently observed near the surface of the ocean, and are of interest to many activities ranging from meteorology to underwater acoustics. The scattering of sound from a liquid containing bubbles can yield important information on the bubble size distribution. It is usually difficult to take into account the effects due to multiple scattering and the present article considers the use of invariant imbedding to calculate the angular dependence of acoustic scattering from a known distribution of bubbles taking multiple scattering into account. The scattering results are compared with Foldy’s effective medium theory. Also, the inverse scattering problem is addressed such that the parameters for a given model of bubble density as a function of position may be derived from the measured angular dependence of the acoustic scattering.
Reflection of elastic waves by a distribution of coplanar cracks
Authors: Sotiropoulos D. A. , Achenbach J. D.
Published: October 2005

A method is presented to evaluate quantitatively the reflection of elastic waves by a distribution of coplanar cracks. The method is based on a novel calculation of crack-opening volumes. To compute the crack-opening volume of a specified crack, the effects of neighboring cracks are approximated by the effects of pairs of vector dipoles at the geometrical centers of those cracks. The strengths of the dipoles are proportional to the crack-opening volumes of the neighboring cracks. Thus a crack-opening volume is expressed as a superposition of solutions of two generic problems. One concerns the interaction of the incident wave with a single crack, while the other is concerned with the interaction of a vector dipole with a single crack. For a plane containing a large number of cracks, closed-form expressions have been derived for the reflection and transmission coefficients in terms of the crack-opening volumes. The results have been generalized to statistical distributions of cracks.
A reexamination of forward masking in the auditory nerve
Authors: Relkin Evan M. , Turner Christopher W.
Published: October 2005

Forward masking, as measured behaviorally, is defined as an increase in a signal’s detection threshold resulting from a preceding masker. Previously, forward masking in the auditory nerve has been measured as a reduction in the neural response to a signal when preceded by a masker. However, detection threshold depends on both the magnitude of the response to the signal and the variance of the response. Thus changes in detectability cannot be inferred from response reduction alone. Relkin and Pelli (1987) have described a two-interval forced-choice procedure that may be used to measure the threshold for the detection of a probe signal in recordings of spike counts in single auditory neurons. These methods have been used to study the forward masking of characteristic frequency probe tones by characteristic frequency maskers as masker intensity was varied. Although the masker does reduce the detectability of the probe tone, it was found that the threshold shifts are much less than those observed behaviorally, particularly for intense maskers. In part, the small threshold shifts can be attributed to the reduction in response variance following the masker, which is the result of the adaptation of spontaneous activity. These results imply that behavioral forward masking must result from suboptimal processing of spike counts from auditory neurons at a location central to the auditory nerve.
Ultrasonic monitoring of texture in cold-rolled steel sheets
Authors: Hirao M. , Hara N. , Fukuoka H. , Fujisawa K.
Published: October 2005

An ultrasonic method is tested for the nondestructive evaluation of rolling recrystallization texture in cold-rolled steel sheets. To determine three orientation distribution coefficients (ODCs) of the fourth order, propagation velocities were measured of the longitudinal and shear waves in the thickness direction and the shear-horizontal (SH0) plate mode within the sheet plane. A simple rule of mixture is used to estimate the volume fractions of the principal components of rolling recrystallization texture. The volume fractions are used to calculate the plastic strain ratio (r value) and the ultrasonic pole figures with the aid of single-crystal values. Both predictions are compared with conventional (destructive) methods. A useful result is the correlation between the in-plane average of r values and the longitudinal/shear wave-velocity ratio, which occurs accompanying the large proportion of crystallites oriented around the {111} component.
Laboratory and i
n s
i
t
u measurements of selected geoacoustic properties of carbonate sediments
Authors: Badiey Mohsen , Yamamoto Tokuo , Turgut Altan , Bennett Richard , Conner Craig S.
Published: October 2005

Selected geoacoustic properties of sediments such as shear modulus (G), frame loss coefficient (δ), porosity (β), and the permeability (ks) are needed as input to predictive geoacoustic models. In situ and laboratory measurements of these properties for carbonate sediments of the Great Bahama Bank are presented here. Shear modulus and frame loss coefficient are measured at very low shear strain amplitude by using a combined torsional, resonant column, and triaxial (CTRCT) apparatus in the laboratory. The in situ shear modulus is measured by a newly developed bottom shear modulus profiler (BSMP). The in situ and laboratory measurements of shear modulus, porosity, and permeability are compared. These comparisons indicate that the laboratory and in situ measurements of shear modulus and porosity are in good agreement; however, in our comparisons, the permeability measurements in the laboratory were always somewhat lower than the in situ values. Particle size analysis indicates that these sediments are mixtures of fine silty sand. The attenuation of compressional waves through shallow water oolitic carbonates is found to be comparable with the data for noncarbonate sediments, indicating that the geoacoustic properties of oolitic carbonates may be estimated by the same methods used for noncarbonate sediments.
Source levels of shallow explosive charges
Authors: Chapman N. R.
Published: October 2005

Experimental measurements are reported in this article for the source levels of 0.82-kg signals underwater sound (SUS) charges detonated at nominal depths of 18.3, 91, and 183 m. The data were recorded in the farfield using a high-resolution digital data acquisition system that provided good reproduction of both the high- and low-frequency components of the signal from the explosion. The results are presented in 1/3 octave bands from 5–630 Hz, and represent the mean values of samples of at least 30 charges for each depth group. The standard deviations were within 1 dB for most frequency bands. Analysis of the distribution of explosion depths indicated that the average detonation depths were consistently deeper than the nominal depths. This result was attributed to the effect of the relatively cold water temperatures at the experimental site. In addition to the measured source levels, estimates for 0.82-kg SUS charges at 244 m were scaled from the experimental data using a method suggested by Hughes [R. Hughes, ‘‘Underwater Explosives:Scaling of Source Spectra,’’ in Underwater Acoustics and Signal Processing, edited by Leif Bjorno (Reidel, Dordrecht, The Netherlands, 1981), pp. 87–91]. Comparisons were made with the values for 0.82-kg SUS source levels provided by Gaspin and Shuler [J.B. Gaspin and V.K. Shuler, ‘‘Source levels of shallow underwater explosives,’’ Naval Ordnance Laboratory NOLTR 67–87 (1971)]. Their predictions are generally higher at high frequencies owing to the relatively high value of the shock wave decay constant that they used to generate their waveforms. At low frequencies, the Gaspin and Shuler predictions were not in good agreement with the scaled values since their analysis did not specifically account for the impulse of the waveform.
Acoustic sounding of rain intensity
Authors: Shamanaeva Lyudmila G.
Published: October 2005

The numerical solution of the scalar wave equation is generalized for the case of a polydispersed medium. The analytical expressions are given for the dependence of sound extinction on the intensity of rain and acoustic frequency. The method of acoustic sounding of rain intensity proposed on the basis of these analytical expressions is theoretically analyzed.
Acoustic transient generation by laser-produced cavitation bubbles near solid boundaries
Authors: Vogel A. , Lauterborn W.
Published: October 2005

The acoustic transients emitted after breakdown and cavitation bubble collapse upon focusing a Q-switch laser pulse into a liquid are investigated with special emphasis on their modifications induced by a solid boundary. For measuring the form p(t)/pmax of the pressure pulses an optical technique with a resolution of 10 ns has been developed. When p(t)/pmax is known, the pressure amplitude can be determined even when a transducer with a rise time much longer than the pulse duration is used. The duration of the transients (20–30 ns) and their pressure are nearly the same after breakdown and spherical bubble collapse. During spherical collapse, a maximum pressure of about 60 kbar is developed inside a bubble with Rmax=3.5 mm, and on average 73% of the bubble energy loss is transformed into acoustic energy. The sound emission near a solid boundary strongly depends on the normalized distance γ between the bubble and the boundary. The highest pressures at the boundary are achieved for γ→0; for γ=0.2 and Rmax =3.5 mm it has been found that p=2.5 kbar. These results are discussed with respect to the mechanisms of cavitation erosion important for hydraulic cavitation, laser lithotripsy, and ocular surgery.
WKBJ seismogram theory in anisotropic media
Authors: Singh S. C. , Chapman C. H.
Published: October 2005

The Wentzel, Kramers, Brillouin, and Jeffreys (WKBJ) seismogram theory has proved useful for computing impulsive waveforms in vertically inhomogeneous media. In this article, the WKBJ seismogram theory is applied to compute the displacement fields in anisotropic media. Several numerical examples of transversely isotropic media are presented with a particular emphasis on the waveforms at and near cusps. Synthetic seismograms are computed for a line as well as for a point source including those regions of space where shear wave triplication occurs. The waveform of the reverse branch is the Hilbert transform of the forward branches. For a line source, the region between the forward branches and the reverse branch carries no energy, and is the region of complete silence known as a lacuna. Diffracted signals due to cusps on the shear wave surface are also observed. The waveform of the diffracted signal depends upon the waveform of the branch with dominant energy at the cusp.
Reference threshold sound-pressure levels for the TDH-50 and ER-3A earphones
Authors: Larson Vernon D. , Cooper William A. , Talbott Richard E. , Schwartz Daniel M. , Ahlstrom Christopher , De Chicchis Albert R.
Published: October 2005

Reference threshold sound-pressure levels were established for a new insert earphone, the ER-3A tubephone, and for the TDH-50 earphone. In test–retest comparisons, the tubephone produced estimates of auditory threshold as reliable as the thresholds produced by the supraaural earphone. Reference thresholds were developed for the two earphones from data contributed by three laboratories. While the TDH-50 data are in good agreement with the provisional ANSI 6-cc coupler reference levels (ASHA, 1982), the ER-3A data are at variance with the manufacturer’s provisional recommendation for 2-cc coupler reference thresholds for frequencies below 1 kHz. The differences are attributed to physiologic noise that masked the lower frequency thresholds.
Identification of vowels in quiet, noise, and reverberation: Relationships with age and hearing loss
Authors: Nábělek Anna K.
Published: October 2005

Vowel identification in quiet, noise, and reverberation was tested with 40 subjects who varied in age and hearing level. Stimuli were 15 English vowels spoken in a /b–t/ context in a carrier sentence, which were degraded by reverberation or noise (a babble of 12 voices). Vowel identification scores were correlated with various measures of hearing loss and with age. The mean of four hearing levels at 0.5, 1, 2, and 4 kHz, termed HTL4, produced the highest correlation coefficients in all three listening conditions. The correlation with age was smaller than with HTL4 and significant only for the degraded vowels. Further analyses were performed for subjects assigned to four groups on the basis of the amount of hearing loss. In noise, performance of all four groups was significantly different, whereas, in both quiet and reverberation, only the group with the greatest hearing loss performed differently from the other groups. The relationship among hearing loss, age, and number and type of errors is discussed in light of acoustic cues available for vowel identification.
Compensation for receiver bandpass effects on ultrasonic backscatter power spectra using a random medium reference
Authors: Peters Kenneth J. , Waag Robert C.
Published: October 2005

A linear model of an ultrasonic pulse-echo system is used to express the measured power spectrum as the product of a scattering medium power spectrum and a transfer function accounting for system effects. Transfer functions are experimentally determined for multiple ranges using a random medium reference. Measured power spectra normalized by these functions are shown to be in close agreement with theoretical power spectra both in shape and absolute magnitude. The results indicate that the model allows scattering media to be distinguished when the media backscatter characteristics differ in the bandwidth of the measurement system.
Absorption of ultrasound by mammalian ovaries
Authors: Carnes K. I. , Dunn F.
Published: October 2005

The transient thermoelectric method was employed to determine the ultrasonic absorption coefficient of excised bovine, canine, feline, murine, ovine, and porcine ovaries at 1 MHz. The dynamics of the organ yields significant variations with physiological stage and structure. Values ranged from 0.017 cm−1 for the follicle to 0.050 cm−1 for the corpus luteum, largely reflecting macromolecular content. Little interspecies variation was observed.
The acquisition of vowel discriminations by nonhuman primates
Authors: Hienz R. D. , Brady J. V.
Published: October 2005

Three adult male baboons were trained on a psychophysical procedure to discriminate five synthetic, steady-state vowel sounds (/a/, /1/, /c/, /U/, and /q/) from one another. A pulsed train of one vowel comprised the reference stimulus during a session. Animals were trained to press a lever and release the lever only when this reference vowel sound changed to one of the comparison vowels. All animals learned the vowel discriminations rapidly and, once learned, performed the discriminations at the 95%–100% correct level. During the initial acquisition of the discriminations, however, percent correct detections were higher for those vowels with greater spectral differences from the reference vowel. For some cases, the detection scores correlated closely with differences between first formant peaks, while for others the detection scores correlated more closely with differences between second formant peaks. Once the discriminations were acquired, no discriminability differences were apparent among the different vowels. Underlying discriminability differences were still present, however, and could be revealed by giving a minor tranquilizer (diazepam) that lowered discrimination performances. These drug-induced decrements in vowel discriminability were also correlated with spectral differences, with lower vowel discriminability scores found for those vowels with smaller spectral differences from the reference vowel.
A technique for simulating the amplifier-to-eardrum transfer function of an i
n s
i
t
u hearing aid
Authors: Egolf David P. , Haley Brett T. , Howell Henry C. , Larson Vernon D.
Published: October 2005

There are numerous articles wherein mathematical models of various parts of an in situ hearing aid have been reported. Such parts include, for example, the microphone, receiver, cylindrical tubes carrying sound to the eardrum and out through the earmold vent, and the external path from the vent back to the microphone. This article extends these earlier works to include the hearing-aid amplifier. In particular, a mathematical technique for characterizing the amplifier in combination with the receiver is reported. Cascade parameters of a two-port model of one particular amplifier/receiver combination are obtained by this method. The cascade-parameter data and the method of obtaining this data are verified by two different experimental procedures. One procedure involves both computing and measuring the input driving-point impedance of the amplifer/receiver combination. In the second procedure, the amplifier-to-eardrum transfer function of a hearing aid incorporating this same amplifier/receiver combination and mounted on an artificial ear is both computed and measured. Experimental and computed values of this transfer function for three different earmold geometries are in reasonably close agreement. The amplifier/receiver model reported herein will be used in future studies of acoustic feedback in hearing aids.
Ear canal acoustic distortion at 2f1−f2 from human ears: Relation to other emissions and perceived combination tones
Authors: Furst M. , Rabinowitz W. M. , Zurek P. M.
Published: October 2005

Two aspects of the intermodulation distortion product at 2f1−f2 generated by normal human ears and measured acoustically in the ear canal were studied: (1) its relation to tone-evoked and spontaneous otoacoustic emissions, and (2) its relation to the perceived combination tone at the same frequency. With regard to (1), substantial differences among ears in the detectability of emissions were observed; ears tended to exhibit all or none of the emission types that were sought. Within ears possessing emissions, the magnitudes of tone-evoked emissions and acoustic distortion showed a similar dependence on frequency. With regard to (2), a three-primary-tone stimulus was employed to ask whether the ear canal acoustic distortion tone is canceled under the same stimulus conditions that produce perceptual cancellation. Simultaneous cancellation of perceptual and acoustic distortion was produced rarely. Results are interpreted qualitatively with a model in which primary tones produce distortion at their interaction region within the cochlea; this distortion propagates to the distortion-frequency place where it mediates perception. This same distortion wave produces emission components at additional locations, including the primary-tone interaction region, which sum vectorially to mediate the emitted acoustic distortion product.