bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of contrast in limiting vowel-to-vowel coarticulation in different languages
Authors: Manuel Sharon Y.
Published: October 2005

Languages differ in their inventories of distinctive sounds and in their systems of contrast. Here, it is proposed that this observation may have predictive value with respect to how extensively various phones are coarticulated in particular languages. This hypothesis is based on three assumptions: (1) There are ‘‘output constraints’’ on just how a given phone can be articulated; (2) output constraints are, at least in part, affected by language-particular systems of phonetic contrast; and (3) coarticulation is limited in a way that respects those output constraints. Together, these assumptions lead to the expectation that, in general, languages will tend to tolerate less coarticulation just where extensive coarticulation would lead to confusion of contrastive phones. This prediction was tested by comparing acoustic measures of anticipatory vowel-to-vowel coarticulation in languages that differ in how they divide up the vowel space into contrastive units. The acoustic measures were the first and second formant frequencies, measured in the middle and at the end of the target vowels /a/ and /e/, followed by /pV/, where /V/ was /i,e,a,o,u/. Two languages (Ndebele and Shona) with the phonemic vowels /i,e,a,o,u/ were found to have greater anticipatory coarticulation for the target vowel /a/ than does a language (Sotho) that has a more crowded mid- and low-vowel space, with the phonemic vowels /i,e,q,a,co,u/. The data were based on recordings from three speakers of each of the languages.
Acoustic estimations of the front cavity in apical stops
Authors: Sundberg Johan , Lindblom Björn
Published: October 2005

Sweep-tone measurements of front-cavity resonances in apical stops are reported. Volumes inferred from resonance frequency data are presented as a function of place of articulation. The results indicate that, for post-dental points of contact, a cavity located under the tongue tip is formed. It is shown that this sublingual cavity plays a very important role in shaping the spectral structure of apical stops.
Detection of frequency modulation (FM) in the presence of a second FM tone
Authors: Wilson Adam S. , Hall Joseph W. , Grose John H.
Published: October 2005

A series of three experiments was undertaken to investigate detection of sinusoidal frequency modulation (FM) in the presence of FM at a separate frequency. The first experiment measured detection of modulation for an FM tone with a modulation frequency ( f m) of 6 Hz as a function of carrier frequency ( f c) under three conditions: (1) in quiet, (2) in the presence of a 2500-Hz pure tone, and (3) in the presence of a 2500-Hz FM tone with f m=6 Hz, modulating in phase with the signal. Detection of FM in the presence of the second FM tone was worse than for either the signal presented in quiet or in the presence of the unmodulated tone. Threshold varied as an inverse function of frequency separation between the signal and the masker. In the second experiment, FM detection for a signal with f c=1900 Hz and f m=6 Hz was measured as a function of the modulation frequency ( f m=2–18 Hz) of the 2500-Hz masker tone. FM detection improved significantly with increasing difference between the modulation frequencies of the signal and the masker. The final experiment measured detection of FM for a signal ( f c=1900 Hz, f m=6 Hz) in the presence of a second FM tone ( f c=2500 Hz,  f m=6 Hz) as a function of the relative phase of the 6-Hz modulators. Detection of FM improved monotonically as a function of increasing phase difference between the two modulators. The results are discussed in terms of modulation detection interference and perceptual grouping.
Discrimination of modulation depth of sinusoidal amplitude modulation (SAM) noise
Authors: Wakefield Gregory H. , Viemeister Neal F.
Published: October 2005

The detection of sinusoidal amplitude modulation (SAM) provides a lower bound on the degree to which temporal information in the envelope of complex waveforms is encoded by the auditory system. The extent to which changes in the amount of modulation are discriminable provides additional information on the ability of the auditory system to utilize envelope fluctuations. Results from an experiment on the discrimination of modulation depth of broadband noise are presented. Discrimination thresholds, expressed as differences in modulation power, increase monotonically with the modulation depth of the standard, but do not obey Weber’s Law. The effects of carrier level and of modulation frequency are consistent with those observed in modulation detection: Changes in carrier level have little effect on modulation discrimination; changes in modulation frequency also have little effect except for standards near the modulation detection threshold. The discrimination of modulation depth is consistent with the leaky-integrator model of modulation detection for standards below −10 dB (20 log ms); for standards greater than −10 dB, the leaky integrator predicts better performance than that observed behaviorally.
Response timing constraints on the cortical representation of sound time structure
Authors: Phillips D. P. , Hall S. E.
Published: October 2005

The precision of spike response timing of 94 primary auditory cortex neurons was studied using conventional extracellular recording techniques in barbiturate-anesthetized cats to which tone- and/or noise-burst stimuli were presented using sealed sound delivery systems. Precision of spike timing was indexed using the standard deviation of the first-spike latent period in responses evoked by repeated presentation of tonal stimuli systematically varied in frequency, amplitude, and/or repetition rate. Within a neuron, variability of first-spike timing was usually proportional to the mean first-spike latency, in agreement with previous reports. In cases where there was a systematic relation between the precision of response timing and the mean latency, a linear correlation accounted for up to 90% of the data variance. Across the 94 neurons, standard deviations seen in responses of minimum latency were related to minimal mean latencies, and were typically in the range from 0.15–1.5 ms. The data suggest that responses to transients in the cortex show a precision of spike timing which is only slightly worse than that seen in cochlear-nerve fibers. This, however, is in dramatic contrast to previous evidence on the steady-state temporal response of cortical cells, which is at least an order of magnitude poorer than that seen in auditory-nerve fibers and many cochlear nucleus cells. These observations may be directly relevant to the known consequences of auditory cortex pathology in man.
Auditory temporal integration and the power function model
Authors: Gerken George M. , Bhat Vishwa K. H. , Hutchison-Clutter Margaret
Published: October 2005

The auditory temporal integration function was studied with the objective of improving both its quantitative description and the specification of its principle independent variable, stimulus duration. In Sec. I, temporal integration data from 20 studies were subjected to uniform analyses using standardized definitions of duration and two models of temporal integration. Analyses revealed that these data were best described by a power function model used in conjunction with a definition of duration, termed assigned duration, that de-emphasized the rise/fall portions of the stimuli. There was a strong effect of stimulus frequency and, in general, the slope of the temporal integration function was less than 10 dB per decade of duration; i.e., a power function exponent less than 1.0. In Sec. II, an experimental study was performed to further evaluate the models and definitions. Detection thresholds were measured in 11 normal-hearing human subjects using a total of 24 single-burst and multiple-burst acoustic stimuli of 3.125 kHz.

The issues addressed are: the quantitative description of the temporal integration function; the definition of stimulus duration; the similiarity of the integration processes for single-burst and multiple-burst stimuli; and the contribution of rise/fall time to the integration process. A power function in conjunction with the assigned duration definition was again most effective in describing the data. Single- and multiple-burst stimuli both seemed to be integrated by the same central mechanism, with data for each type of stimulus being described by a power function exponent of approximately 0.6 at 3.125 kHz. It was concluded that the contribution of the rise/fall portions of the stimuli can be factored out from the rest of the temporal integration process. In Sec. III, the conclusions that emerged from the review of published work and the present experimental work suggested that auditory temporal integration is best described by a power function in conjunction with the assigned duration definition. The exponent for the power function is typically less than 1.0, and varies with frequency and hearing level. Second, a means of empirically assaying the contribution of the rise/fall portions of the stimuli is presented and evaluated. Finally, properties of a central auditory integrator are hypothesized.
Measurement of acoustic distortion reveals underlying similarities between human and rodent mechanical responses
Authors: Brown Ann M. , Gaskill Sally A.
Published: October 2005

The level of 2f1−f2 acoustic distortion product (ADP) measured in the meatus during two-tone stimulation was compared with N1 thresholds measured at the round window for the guinea pig. A significant inverse relation was found between distortion level and N1 threshold. A similar relationship has also been reported for ADP level and subjective thresholds in half the human ears measured [S. A. Gaskill and A. M. Brown, J. Acoust. Soc. Am. 88, 821–839 (1990)]. Guinea pig and human ADP levels behave similarly in response to varying stimulus parameters. The ADP levels grow to a maximum and decline with increasing stimulus separation. The decline is steeper in the human ear. In both species, ADP growth as a function of stimulus level is approximately 1 with covaried stimuli; more gradual with the level of  f2 (L2) alone increasing and steeper when the level of  f1 (L1) alone is increased. The latter slopes are strongly influenced by the level of the stationary L2 and are less steep in the human ear. A link has been proposed between differences in ADP behavior and differences in auditory filter bandwidth in the two species. Guinea pigs show little intersubject variability in ADP level. They do not show the fine structure in distortion level across frequency or the variation in growth rate seen in human responses. Differences in organ of Corti fine structure may underly these differences.
On the accuracy of models for predicting sound propagation in fitted rooms
Authors: Hodgson Murray
Published: October 2005

The objective of this article is to make a contribution to the evaluation of the accuracy and applicability of models for predicting the sound propagation in fitted rooms such as factories, classrooms, and offices. The models studied are 1:50 scale models; the method-of-image models of Jovicic, Lindqvist, Hodgson, Kurze, and of Lemire and Nicolas; the empirical formula of Friberg; and Ondet and Barbry’s ray-tracing model. Sound propagation predictions by the analytic models are compared with the results of sound propagation measurements in a 1:50 scale model and in a warehouse, both containing various densities of approximately isotropically distributed, rectangular-parallelepipedic fittings. The results indicate that the models of Friberg and of Lemire and Nicolas are fundamentally incorrect. While more generally applicable versions exist, the versions of the models of Jovicic and Kurze studied here are found to be of limited applicability since they ignore vertical-wall reflections. The Hodgson and Lindqvist models appear to be accurate in certain limited cases. This preliminary study found the ray-tracing model of Ondet and Barbry to be the most accurate of all the cases studied. Furthermore, it has the necessary flexibility with respect to room geometry, surface-absorption distribution, and fitting distribution. It appears to be the model with the greatest applicability to fitted-room sound propagation prediction.
Diffraction loss in the [110] direction in cubic crystals
Authors: Papadakis Emmanuel P. , Margetan Frank , Newberry Byron P.
Published: October 2005

A new ultrasonic measurement model using an angular spectrum of plane waves operating upon a Gauss–Hermite expansion of the transducer field has been used to explain the ultrasonic diffraction loss in the [110] direction in cubic crystals. In the [110] direction, the slowness surface exhibits a saddle point. Previous theories for numerical integration could accommodate only parabolas of revolution for the slowness surface in the direction of propagation. The new theory agrees with previously published results in [110] Si, Ge, and NaCl. On the curves of loss versus normalized distance S, the positions along S of characteristics of the curves such as peaks, plateaus, and points of inflection are predicted to within experimental accuracy of 2%–5%. The magnitude of the loss is overestimated by as much as a factor of 2 relative to experiments, but it is thought that part of the discrepancy may lie in the experiments. The operation of the new theory was first checked against previously agreeing experiments and theories in the [100] and [111] directions in cubic crystals and in isotropic media.
Errors resulting from finite beamwidth and sample dimensions in the determination of the ultrasonic absorption coefficient
Authors: Drewniak J. L. , Frizzell L. A. , Dunn F.
Published: October 2005

The error resulting from heat conduction in the measurement of the ultrasonic absorption coefficient using the transient thermoelectric method is studied analytically. An expression for the temperature increase in a tissue specimen of finite dimensions, irradiated by a focused ultrasonic transducer, is given as a function of spatial coordinates, time, radial and axial beam dimensions, and absorption. An error is defined, and results are presented for various values of beamwidth, tissue dimensions, absorption, and time for the purpose of quantifying the experimental error due to heat conduction, and to provide guidance for minimizing this error in experimental procedures. For example, it is shown that the effect of heat conduction on the measured rate of temperature increase is less than 7% when using a transducer with a 5-mm half-power beamwidth at depths greater than 1.5 mm in the tissue.
Patterns of expressive timing in performances of a Beethoven minuet by nineteen famous pianists
Authors: Repp Bruno H.
Published: October 2005

The timing patterns of 19 complete performances of the third movement of Beethoven’s Piano Sonata op. 31, No. 3, were measured from oscillograms and analyzed statistically. One purpose of the study was to search for a timing pattern resembling the ‘‘Beethoven pulse’’ [Clynes, in Studies of Music Performance (Royal Academy of Music, Stockholm, 1983), pp. 76–181]. No constant pulse was found at the surface in any of the performances. Local patterns could be interpreted as evidence for an ‘‘underlying’’ pulse of the kind described by Clynes, but they could also derive from structural musical factors. On the whole, the artists’ timing patterns served to underline the structure of the piece; lengthening at phrase boundaries and at moments of melodic/harmonic tension were the most salient features. A principal components analysis suggested that these timing variations in the Minuet could be described in terms of two orthogonal factors, one capturing mainly phrase-final lengthening, and the other reflecting phrase-internal variation as well as tempo changes. A group of musically experienced listeners evaluated the performances on a number of rating scales. Their judgments showed some significant relations to the measured timing patterns. Principal components analysis of the rating scales yielded four dimensions interpreted as force, individuality, depth, and speed. These preliminary results are encouraging for the development of more precise methods of music performance evaluation.
The role of perceived speaker identity in F0 normalization of vowels
Authors: Johnson Keith
Published: October 2005

In the experiments reported here, perceived speaker identity was controlled by manipulating the fundamental frequency (F0) range of carrier phrases in which speech tokens were embedded. In the first experiment, words from two ‘‘hood’’–‘‘hud’’ continua were synthesized with different F0. The words were then embedded in synthetic carrier phrases with intonation contours which reduced perceived speaker identity differences for test items with different F0. The results indicated that when perceived speaker identity differences were reduced, the effect of F0 on vowel identification was also reduced. Experiment 2 indicated that when items presented in carrier phrases are matched for speaker identity and F0 with items in isolation, there is no effect for presentation in a carrier phrase. Experiment 3 involved the presentation of vowels from the ‘‘hood’’–‘‘hud’’ continuum in two different intonational contexts which were judged to have been produced by different speakers, even though the F0 of the test word was identical in the two contexts. There was a shift in identification as a result of the intonational context which was interpreted as evidence for the role of perceived identity in vowel normalization. Overall, the experiments suggest that perceived speaker identity is a better predictor of vowel normalization effects than is intrinsic F0. This indicates that the role of F0 in vowel normalization is mediated through perceived speaker identity.
Place coding of vowel formants for cochlear implant patients
Authors: Blamey P. J. , Clark G. M.
Published: October 2005

Four multiple-channel cochlear implant patients were tested with synthesized versions of the words ‘‘hid, head, had, hud, hod, hood’’ containing 1, 2, or 3 formants, and with a natural 2-formant version of the same words. The formant frequencies were encoded in terms of the positions of electrical stimulation in the cochlea. Loudness, duration, and fundamental frequency were kept fixed within the synthetic stimulus sets. The average recognition scores were 47%, 61%, 62%, and 79% for the synthesized 1-, 2-, and 3-formant vowels and the natural vowels, respectively. These scores showed that the place coding of the first and second formant frequencies accounted for a large part of the vowel recognition of cochlear implant patients using these coding schemes. The recognition of the natural stimuli was significantly higher than recognition of the synthetic stimuli, indicating that extra cues such as loudness, duration, and fundamental frequency contributed to recognition of the spoken words.
Effect of masker level on overshoot
Authors: Bacon Sid P.
Published: October 2005

Overshoot refers to the phenomenon where signal detectability improves for a short-duration signal as the onset of that signal is delayed relative to the onset of a longer duration masker. A popular explanation for overshoot is that it reflects short-term adaptation in auditory-nerve fibers. In this study, overshoot was measured for a 10-ms, 4-kHz signal masked by a broadband noise. In the first experiment, masker duration was 400 ms and signal onset delay was 1 or 195 ms; masker spectrum level ranged from −10–50 dB SPL. Overshoot was negligible at the lowest masker levels, grew to about 10–15 dB at the moderate masker levels, but declined and approached 0 dB at the highest masker levels. In the second experiment, the masker duration was reduced to 100 ms, and the signal was presented with a delay of 1 or 70 ms; masker spectrum level was 10, 30, or 50 dB SPL. Overshoot was about 10 dB for the two lower masker levels, but about 0 dB at the highest masker level. The results from the second experiment suggest that the decline in overshoot at high masker levels is probably not due to auditory fatigue. It is suggested, instead, that the decline may be attributable to the neural response at high levels being dominated by those auditory-nerve fibers that do not exhibit short-term adaptation (i.e., those with low spontaneous rates and high thresholds).
The relationship of singular value decomposition to wave-vector filtering in sound radiation problems
Authors: Photiadis Douglas M.
Published: October 2005

Singular value decomposition (SVD) has recently been suggested as a filtering tool to analyze acoustic radiation. The relationship between this filtering technique and the more familiar wave vector filtering is examined. For a geometry with a preferred axis, the source ‘‘modes’’ are found to consist approximately of a single wave number, and the accompanying radiation modes are thus beams. Some simple examples are worked out to illustrate the general behavior of the filtering, and some of the properties of the beams are given.
Masking and stimulus intensity effects on duplex perception: A confirmation of the dissociation between speech and nonspeech modes
Authors: Bentin Shlomo , Mann Virginia
Published: October 2005

Using the phenomenon of duplex perception, previous researchers have shown that certain manipulations affect the perception of formant transitions as speech but not their perception as nonspeech ‘‘chirps,’’ a dissociation that is consistent with the hypothesized distinction between speech and nonspeech modes of perception [Liberman et al., Percept. Psychophys. 30, 133–143 (1981); Mann and Liberman, Cognition 14, 211–235 (1983)]. The present study supports this interpretation of duplex perception by showing the existence of a ‘‘double dissociation’’ between the speech and chirp percepts. Five experiments compared the effects of stimulus onset asynchrony, backward masking, and transition intensity on the two sides of duplex percepts. It was found that certain manipulations penalize the chirp side but not the speech side, whereas other manipulations had the opposite effect of penalizing the speech side but not the chirp side. In addition, although effects on the speech side of duplex percepts have appeared to be much the same as in the case of normal (electronically fused) speech stimuli, the present study discovered that manipulations that impaired the chirp side of duplex percepts had considerably less effect on the perception of isolated chirps. Thus it would seem that duplex perception makes chirp perception more vulnerable to the effects of stimulus degradation. Several explanations of the data are discussed, among them, the view that speech perception may take precedence over other forms of auditory perception [Mattingly and Liberman, in Signals and Sense: Local and Global Order in Perceptual Maps, edited by G. M. Edelman, W. E. Gall, and W. M. Cowan (Wiley, New York, in press); Whalen and Liberman, Science 237, 169–171 (1987)].
Acoustic correlates of the front/back vowel distinction: A comparison of transition onset versus ‘‘steady state’’
Authors: Sussman Harvey M.
Published: October 2005

This study investigated whether F2 and F3 transition onsets could encode the vowel place feature as well as F2 and F3 ‘‘steady-state’’ measures [Syrdal and Gopal, J. Acoust. Soc. Am. 79, 1086–1100 (1986)]. Multiple comparisons were made using (a) scatterplots in multidimensional space, (b) critical band differences, and (c) linear discriminant functional analyses. Four adult male speakers produced /b/(v)/t/, /d/(v)/t/, and /g/(v)/t/ tokens with medial vowel contexts /i, i, q, ey, æ, a, v, c, o, u/. Each token was repeated in a random order five times, yielding a total of 150 tokens per subject. Formant measurements were taken at four loci: F2 onset, F2 vowel, F3 onset, and F3 vowel. Onset points coincided with the first glottal pulse following the release burst and steady-state measures were taken approximately 60–70 ms post-onset. Graphic analyses revealed two distinct, minimally overlapping subsets grouped by front versus back. This dichotomous grouping was also seen in two-dimensional displays using only ‘‘onset’’ data as coordinates. Conversion to a critical band (bark) scale confirmed that front vowels were characterized by F3−F2 bark differences within a critical 3-bark distance, while back vowels exceeded the 3-bark critical distance. Using the critical distance metric onset values categorized front vowels as well as steady-state measures, but showed a 20% error rate for back vowels. Front vowels had less variability than back vowels. Statistical separability was quantified with linear discriminant function analysis. Percent correct classification into vowel place groups was 87.5% using F2 and F3 onsets as input variables, and 95.7% using F2 and F3 vowel. Acoustic correlates of the vowel place feature are already present at second and third formant transition onsets.
Analytical expressions for the tonotopic sensory scale
Authors: Traunmüller Hartmut
Published: October 2005

Accuracy and simplicity of analytical expressions for the relations between frequency and critical bandwidth as well as critical-band rate (in Bark) are assessed for the purpose of applications in speech perception research and in speech technology. The equivalent rectangular bandwidth (ERB) is seen as a measure of frequency resolution, while the classical critical-band rate is considered a measure of tonotopic position. For the conversion of frequency to critical-band rate, and vice versa, the inversible formula z=[26.81/(1+1960/f )]−0.53 is proposed. Within the frequency range of the perceptually essential vowel formants (0.2–6.7 kHz), it agrees to within ±0.05 Bark with the Bark scale, originally published in the form of a table.
Rayleigh method for scattering from random and deterministic interfaces
Authors: Berman David H. , Perkins John S.
Published: October 2005

This paper describes Rayleigh methods for computing plane-wave scattering amplitudes for rough interface scattering. For Dirichlet, fluid–fluid, and fluid–solid interfaces, the Rayleigh–Fourier (RF) method is shown to give good results for interfaces with slopes exceeding the limit of the Rayleigh hypothesis. In the case of sinusoidal Dirichlet surfaces, described by z=h cos(2πx/L), the method breaks down for 2πh/L∼2. For gentler surfaces the RF method gives high-quality results more cheaply than boundary integral equation or least-squares methods. In the case of fluid–solid interfaces, results of the RF method, which are apparently presented here for the first time, compare favorably with published results obtained by extinction theorem methods. It is concluded that the RF method is a suitable candidate for studying rough interface scattering by Monte Carlo simulations, even for fluid–solid interfaces.
Collapse and rebound of a gas-filled spherical bubble immersed in a diagnostic ultrasonic field
Authors: Aymé-Bellegarda Eveline J.
Published: October 2005

This work is concerned with the influence of the finite-amplitude distortion of a driving diagnostic ultrasonic field on the collapse and rebound of a gas-filled spherical microbubble, present in the exposed compressible liquid. Such an analysis is especially important since one of the mechanisms for cavitation damage comes from the very large gas pressures generated at bubble collapse and in the subsequent pressure wave formed by bubble rebound. Gilmore’s model [F. R. Gilmore, ‘‘The growth or collapse of a spherical bubble in a viscous compressible liquid,’’ Hydrodynamics Lab. Rep. No. 26-4, California Institute of Technology, Pasadena, CA (1952)] for bubble dynamics is used to obtain the motion of the bubble interface when subjected to a pulsed diagnostic ultrasonic field of large amplitude. Knowledge of the bubble motion allows one to derive the pressure distribution around the bubble. Numerical results over a range of initial bubble sizes, acoustic pressures, and frequencies relevant to medical use show that the strength of the pressure spikes radiated by the rebounding bubble depends upon (i) the acoustic frequency ( f ), (ii) the initial bubble size (R0), and (iii) the magnitude of the pressure amplitude of the fundamental (PF) in a Fourier series description of the distorted pulse. As the pressure spikes propagate outward from the bubble wall, their strength is attenuated as the reciprocal of the distance from the center of collapse.
Measurements of the acoustic backscatter of selected areas of the deep seafloor and some implications for the assessment of manganese nodule resources
Authors: Weydert M. M. P.
Published: October 2005

On the expeditions Echo 1 and Echo 2 the acoustic backscatter from four different seafloor environments was measured at frequencies of 4.5, 9, 15, 28, 60, 112, and 163 kHz and grazing angles from 5–90 deg. Five transducer arrays had been mounted on the stern of the Deep Tow vehicle of the Scripps Institution of Oceanography, similar sidescan sonars, but looking aft. At frequencies above 15 kHz the backscattering strength increases as one goes from deep-sea clay (14 °N, 126 °W) to silty clay (Patton Escarpment), manganese nodules (14 °N,126 °W), and phosphorite nodules and slabs (Thirtymile Bank). This order was found to be preserved at all grazing angles. It is thus possible to distinguish acoustically between the four environments. Detailed studies of the backscattered sound over the nodule field have shown that the returned energy is coherent at normal incidence, while at other grazing angles it is not. At frequencies above 15 kHz it is possible to deduce the percentage of seafloor covered by manganese nodules directly from the measured backscattering strength. At 9 kHz, nodules smaller than 4 cm can be distinguished from nodules larger than 6 cm.
Structure–fluid interaction problems
Authors: Ko Sung H.
Published: October 2005

A synopsis is given of the invited papers presented at the special session entitled ‘‘Structure–fluid interaction problems’’ and held as Session J at the 115th Meeting of the Acoustical Society of America on 16–20 May 1988, Seattle, WA [J. Acoust. Soc. Am. Suppl. 1 83, S23–S26 (1988)]. The session was sponsored jointly by the Technical Committees on Engineering Acoustics and Structural Acoustics and Vibration, and chaired by Sung H. Ko.
Acoustical measurements of bubble production by spilling breakers
Authors: Medwin Herman , Daniel Albert C.
Published: October 2005

The surface bubble spectral density of newly created bubbles has been measured under spilling breakers in a laboratory facility. This has been accomplished acoustically by passively identifying the radius, position, and time of creation of several hundred individual bubbles as their shock-excited pulsations radiate damped spherical waves of sound. The measured bubble spectrum ranges from radius 50 μm to 7.4 mm with a peak of 6 bubbles per square meter in a 1-μs-radius increment at radius 150 μs. The rate of bubble production has an exponential fall-off with time and 97% of the bubbles are produced in the first 500 ms after the breaker passes. The results supplement recent ocean data for low sea states.
Shallow-water matched-field localization off Panama City, Florida
Authors: Feuillade C. , Kinney W. A. , DelBalzo D. R.
Published: October 2005

The results of a shallow-water localization experiment, performed 19 miles south of Panama City, Florida in October 1985, are presented. The experiment involved a 450-Hz source placed 2.2 km from a vertical array of 16 hydrophones in ∼33 m of water. The experimental site was essentially range independent with a flat, hard, sandy bottom. Successful passive localization of the source was obtained using a maximum-likelihood matched-field processor. Studies were undertaken to determine the robustness of the localization to variation of the following parameters: water depth, sediment sound-speed profile, sediment density and attenuation, and array tilt. It was found that, in order to ensure localization accuracy and robustness, the environmental parameters important to know well are the water depth, sediment sound speed, and array tilt. However, the matched-field processor is much more tolerant to inaccuracies in estimates of the sediment density and attenuation. This corresponds clearly with the results of two simulation studies by DelBalzo et al. [J. Acoust. Soc. Am. 83, 2180–2185 (1988)] and Feuillade et al. [J. Acoust. Soc. Am. 85, 2354–2364 (1989)]. A further conclusion drawn from the experiment is that localization in a shallow-water waveguide using maximum-likelihood processing is complicated by the repetitive sidelobe structure of the acoustic field. This suggests that time-domain and other broadband localization techniques may achieve better localization performance because of their additional frequency-averaging capability.
Fourier formalism for describing nonlinear self-demodulation of a primary narrow ultrasonic beam
Authors: Cervenka Pierre , Alais Pierre
Published: October 2005

Presented here is the derivation of nonlinear interactions that occur within a primary narrow beam for which the temporal spectrum is continuous and narrow. This follows the bases of the Fourier formalism. Acoustics levels are presumed weak enough so that second-order equations may be used. In the quasilinear case, the exact theoretical expression of the created parametric farfield, formed from a transient modulated primary signal, is established, by using weakly restrictive assumptions. The case of high primary levels is discussed. Some experimental results are presented.
Resonant acoustic scattering from solid targets
Authors: Norris Andrew N.
Published: October 2005

An asymptotic method of solution is presented for scattering of acoustic waves from solid elastic targets. The asymptotic parameter is the ratio of the fluid density to that of the solid, and the solution is developed using the method of matched asymptotic expansions in this small quantity. The perturbations to the background rigid scattered field are regular for frequencies away from the frequencies of free vibration of the target in vacuo, but, near these frequencies, the perturbation is singular in that an asymptotically small value of the density ratio produces a change in the scattered field of order unity. By combining the regularly and singularly perturbed expansions, a solution is obtained that is uniformly correct at all frequencies. The elements in the uniform solution depend only upon the in vacuo modes and frequencies, and the Green’s function for the equivalent rigid target. At no stage is it necessary to solve the fully coupled system. An analysis of the asymptotic approximation for a spherical target shows that it is equivalent in the high-frequency limit to the approximation predicted by resonance scattering theory.
Experimental verification of a mathematical model for internal ultrasonic inspection of pipes
Authors: Stanke Fred E. , Randall Curt , D’Angelo R.
Published: October 2005

The present paper experimentally verifies the accuracy of a quasi-three-dimensional (3-D) numerical code [C. Randall and F. E. Stanke, ‘‘Mathematical model for ultrasonic, internal inspection of cylindrically layered structures,’’ J. Acoust. Soc. Am. 83, 1295–1305 (1988)] that models a finite-sized, broadband ultrasonic transducer inspecting a cylindrically layered structure from its interior. All verifications employ one of a collection of steel pipes, which have a variety of thicknesses and diameters. In all cases, a fluid fills the pipe and envelops the transducer. This fluid is either water or a dispersive, attenuative, water-based suspension. The exterior surface of the pipe is loaded by a homogeneous layer that is either water, the suspension previously mentioned, or a loaded epoxy. The transducer is operated in pulse/echo mode at a distance of between 10 and 20 wavelengths in water from the pipe. Multiple reflections between the pipe and the transducer itself are excluded by time gating. The transducer has a flat, rectangular active region that is roughly three wavelengths wide (in water) and ten wavelengths high.

Consequently, diffraction significantly affects the received waveforms. The transducer, its excitation, and receiving electronics have a broad bandwidth that encompasses several of the low-order thickness resonances of the pipe that can interfere to produce very complex waveforms and spectra. The transducer is aligned with its length parallel to the axis of the pipe, with a radius of the pipe passing either through the center of its width or to one side. Comparisons are presented as overlayed waveforms (in the time domain) and overlayed spectra (in the frequency domain) of the experimental and calculated results, so that emphasis is placed on the ability of the model to accurately predict even subtle details, as opposed to integrated or other more global measures. Comparisons between the experiments and calculated predictions show that, for all cases examined, the model predicts virtually all visually distinguishable features of waveforms and spectra with at least qualitative accuracy, even when the levels of these features are on the order of 5% of the maximum level of the echo. For many cases, the model is in error by less than 10% on a point-by-point basis even for such fine features. In cases where the model does not perform as well quantitatively, it is a good qualitative guide, and, even for these worst cases, it is still considerably more accurate than a 2-D model would be for any of the cases examined and is computationally nearly as fast.
Analysis of acoustic wave transmission in a piping network
Authors: Craggs A. , Stredulinsky D. C.
Published: October 2005

This paper gives a procedure for analyzing the behavior of sound waves in pipe networks. The method combines the exact solutions for the pipe with those obtained from finite-element models of bends and junctions. These are necessary to allow for the fact that when a plane-wave mode is incident upon a junction, the natural modes of the junction control volume are excited and affect the resulting propagation of the wave. Measurements of the transmission loss across a simple network consisting of straight pipes, ‘‘tee’’ and ‘‘cross’’ junctions, and right-angled bends were made. Although only two-dimensional finite elements were used, the results agreed very well with those predicted with the theory up to the cutoff frequency for the pipes.
Direct estimation of aberrating delays in pulse-echo imaging systems
Authors: Rachlin Daniel
Published: October 2005

Nearfield fluctuations in wave propagation velocity and system timing errors are among the sources of focusing aberrations in pulse-echo imaging systems. For situations in which the source of these errors can be modeled by a stationary phase aberrator placed in front of the transmitter and receiver aperture, appropriate electronic delays might be applied to the signals associated with each array element in order to restore the system to focus. A method is decribed and evaluated for estimating the set of aberrating delays in a linear array utilizing data from a single two-dimensional scan. The underlying principle is analogous to that of phase closure used for one-way passive interferometry and readily generalizes to two-dimensional arrays. Although the following theory is developed in the context of acoustic imaging, the general approach is applicable to other pulse-echo systems, such as radar.
Acoustically generated temperature gradients in short plates
Authors: Atchley Anthony A. , Hofler Thomas J. , Muzzerall Michael L. , Kite M. David , Ao Chianing
Published: October 2005

Thermoacoustic heat transport and its applications, thermoacoustic engines, have been discussed in a number of articles over the past several years. Lacking from these articles is a thorough, quantitative experimental investigation of the basic theory underlying thermoacoustic heat transport. A logical starting point for such a study is to investigate the simplest class of thermoacoustic engine—a stack of short plates referred to as a ThermoAcoustic Couple (TAC). The utility of this choice is that the theory can be reduced to its simplest form for analysis of the results. The results of measurements of thermoacoustically generated temperature gradients in TACs subjected to acoustic standing waves are reported. The value of the temperature gradient, which results from an acoustically generated entropy flow in the gas in thermal contact with the TAC, is a function of the peak acoustic pressure amplitude, the mean gas pressure, the Prandtl number of the gas, the configuration of the TAC, and its position in the standing wave. Measurements were made with a computer-controlled apparatus for drive ratios (the ratio of the acoustic pressure amplitude to the mean pressure of the gas) from approximately 0.1%–2.0%, in argon and helium having mean pressures from approximately 100–368 kPa, for three different TACs as a function of their positions in the standing wave. The results are compared with predictions based on a theory by Wheatley et al. [J. Acoust. Soc. Am. 74, 153–170 (1983)]. The measurements agree well with theory for drive ratios less than approximately 0.4%. However, the agreement diminishes at higher drive ratios, where two regions of behavior are observed. Agreement is, in general, best in the vicinity of acoustic particle velocity nodes at all drive ratios investigated.
Comodulation masking release and auditory grouping
Authors: Hall Joseph W. , Grose John H.
Published: October 2005

The detectability of a pure-tone signal masked by a band of noise centered on the signal can be improved by the addition of flanking noise bands, provided that the temporal envelopes of the flanking bands are correlated with that of the on-signal band. This phenomenon is referred to as comodulation masking release (CMR). The present study examined CMR in conditions in which some flanking noise bands were comodulated with the on-signal band, but other flanking bands (termed ‘‘deviant’’ bands) were not. Past research has indicated that CMR is often substantially reduced when deviant bands are present at spectral locations close to the signal frequency. An investigation was undertaken to determine whether the disruptive effects of such bands could be reduced by factors related to auditory grouping. The signal frequency was 1000 Hz. In one condition, only 20-Hz-wide comodulated bands, centered on 400, 600, 800, 1000, 1200, 1400, and 1600 Hz, were present. The CMR for this condition, referenced to threshold for the on-signal band only, was approximately 15 dB. In a second condition, two deviant bands were added at 900 and 1100 Hz; their presence reduced the CMR to only 3–4 dB.

The number of deviant bands was then increased progressively, from two to eight bands. Deviant bands either shared a common envelope (codeviant), or had unique envelopes (multideviant). The number of bands that were comodulated with the on-signal band was held constant at six. The rationale was that as more deviant bands were added, the auditory system would be more likely to group the deviant bands near the signal frequency with the other deviant bands, rather than with the on-signal band, and therefore the disruptive effects of the proximal deviant bands would be reduced. A second manipulation was to provide an onset/offset asynchrony between the on-signal and comodulated bands, and the deviant bands. The rationale was that the asynchrony would enhance the segregation of the comodulated bands from the deviant bands. Both of the above stimulus manipulations (increasing the number of distally placed deviant bands, and providing onset/offset asynchrony) reduced the disruptive effects of the deviant bands. The results of dichotic conditions showed that the disruptive effects of deviant bands placed at 900 and 1100 Hz could also be reduced by adding codeviant bands (placed at 300, 500, 700, 1300, 1500, and 1700 Hz) in the ear contralateral to the signal. These results indicate that CMR may occur subsequent to stages of auditory grouping or object formation.
Observer efficiency and weights in a multiple observation task
Authors: Berg Bruce G.
Published: October 2005

A sequence of seven tones, sampled from one of two distributions differing in mean frequency, is presented to observers who try to report which distribution was sampled. Estimates are obtained of the weight or importance given to each tone as a function of its temporal position. In five experiments, the reliability of the information is varied by changing the variance of the distributions; tones with high reliability are sampled from distributions with relatively small variance, whereas tones with low reliability are sampled from distributions with relatively large variance. Results show that the observations are weighted more efficiently when the tones have equal rather than unequal reliability, and when the most reliable tones have the greater intensity. Additional results show that the most intense tones often receive the greatest weight, even when those tones have the least reliability.
Role of spectral cues in median plane localization
Authors: Asano Futoshi , Suzuki Yoiti , Sone Toshio
Published: October 2005

The role of spectral cues in the sound source to ear transfer function in median plane sound localization is investigated in this paper. At first, transfer functions were measured and analyzed. Then, these transfer functions were used in experiments where sounds from a source on the median plane were simulated and presented to subjects through headphones. In these simulation experiments, the transfer functions were smoothed by ARMA models with different degrees of simplification to investigate the role of microscopic and macroscopic patterns in the transfer functions for median plane localization. The results of the study are summarized as follows: (1) For front–rear judgment, information derived from microscopic peaks and dips in the low-frequency region (below 2 kHz) and the macroscopic patterns in the high-frequency region seems to be utilized; (2) for judgment of elevation angle, major cues exist in the high-frequency region above 5 kHz. The information in macroscopic patterns is utilized instead of that in small peaks and dips.
On enhancement of spectral contrast in speech for hearing-impaired listeners
Authors: Bunnell H. Timothy
Published: October 2005

A digital processing method is described for altering spectral contrast (the difference in amplitude between spectral peaks and valleys) in natural utterances. Speech processed with programs implementing the contrast alteration procedure was presented to listeners with moderate to severe sensorineural hearing loss. The task was a three alternative (/b/,/d/, or /g/) stop consonant identification task for consonants at a fixed location in short nonsense utterances. Overall, tokens with enhanced contrast showed moderate gains in percentage correct stop consonant identification when compared to unaltered tokens. Conversely, reducing spectral contrast generally reduced percent correct stop consonant identification. Contrast alteration effects were inconsistent for utterances containing /d/. The observed contrast effects also interacted with token intelligibility.