bluuebunny/crossref_metadata_2025 huggingface dataset:
Pitch perception physiology and psychophysics as a basis for the design of pitch detection algorithms
Authors: Houde Robert A. , Hillenbrand James
Published: October 2005

The generation of high-quality speech with a source-filter vocoder depends to a very great extent on accurate analysis of source parameters. After decades of research, even state-of-the-art pitch detection algorithms tend to make gross errors in the analysis of signals that present no difficulty for the human listener. In this study a review of a broad range of pitch detection algorithms was undertaken, with particular attention to the plausibility of those algorithms in relation to what is currently known about the psychophysics of pitch perception and the neural coding of speech signals. Our principal conclusion from this review is that the most plausible model is a time-domain pitch perception scheme proposed more than 4 decades ago by Licklider [J. C. R. Licklider, Experientia 7, 128–133 (1951)], and extended in more recent studies. The implications of these findings for source-filter vocoders will be discussed, and an implementation of the Licklider model using level-crossing interval histograms will be described.
Dynamic and static properties of imaged speech sounds
Authors: Gagnon Deborah A.
Published: October 2005

The type of information stored in memory for speech sounds was tested using a primed, speeded classification task. The relationship between prime and target was varied in terms of phoneme constituency, phoneme order, or both. Primes were presented either auditorally or visually, allowing for a contrast between perceptual and imaged speech codes. Two other manipulations were made to assess whether the temporal nature of the stimuli, the stimulus quality, or possibly both, play a role in determining imageability: (1) Stimuli either contained stop (dynamically cued) or fricative (relatively statically cued) consonants; and (2) stimuli were either natural or synthetic. Inhibitory effects were found when an auditory prime was presented at a 100-ms ISI, supporting earlier evidence for a positionally specific perceptual speech code (Gagnon and Sawusch, 1992). It was also found that both the manipulation of the type of consonant (stop versus fricative) present in the target and the quality of the stimulus set (natural versus synthetic) had an effect on imageability, supporting both a temporal nature (Surprenant, 1992) and stimulus quality account of imageability. These results will be discussed within the context of current theories of memory, imagery, and speech perception. [Work supported by NIDCD Grant R01 DC00219 to SUNY at Buffalo and Mark Diamond Research Fund grant to Deborah A. Gagnon.]
A comparison of measured and predicted broadband acoustic arrival patterns out to 10-Mm range during the ATOC Acoustic Engineering Test
Authors: Howe Bruce M. , Dushaw Brian D. , Mercer James A. , Odom Robert I. , Spindel Robert C. , Worcester Peter F. , Colosi John , Cornuelle Bruce D. , Dzieciuch Matthew , Baggeroer Arthur B. , Birdsall Ted , Metzger Kurt , Bold Gary , Tan Sze , Tindle Chris , Guthrie Michael
Published: October 2005

A low-frequency acoustic source suspended from R/P FLIP approximately 340 nautical miles WSW of San Diego transmitted to receivers 90 to 10 000 km distant during the Acoustic Engineering Test of the Acoustic Thermometry of Ocean Climate (ATOC) Program. The source was sus-pended for 7 days during November 1994 near the depth of the sound channel axis (about 650 m) in water over 4000 m deep, in order to avoid near-source bottom interactions. The source transmitted a phase-coded m-sequence with a center frequency of 75 Hz and a digit length of 27 ms [Metzger etal., this meeting]. Measured receptions on five bottom-mounted SOSUS receivers at ranges from 300–4000 km, on two vertical line array receivers at ranges of 90 and 3300 km, and on a sonobuoy modified to have the hydrophone on the sound channel axis at about 10 000-km range, are compared with ray theoretic, adiabatic normal mode, and broadband parabolic equation predictions. [Work supported by the Strategic Environmental Research and Development Program through ARPA.]
Time dependence of multiply scattered diffuse ultrasound in polycrystalline media
Authors: Turner Joseph A. , Weaver Richard L.
Published: October 2005

Time domain results are presented for the multiply scattered longitudinal intensity backscattered from a polycrystalline medium. The results are solutions to the ultrasonic radiative transfer equation (URTE), the derivation of which is based upon radiative transfer theory. Unlike steady-state solutions obtained previously, time domain solutions will more closely correspond to experiments that use tone burst sources. This paper is concerned with the time dependence of the backscattered longitudinal intensity from a polycrystalline medium excited by a normally incident longitudinal wave idealized as an impulsive deposition of energy. It is shown that multiple scattering effects become significant at times on the order of a mean free time or less. It is anticipated that this work may be applicable to microstructural characterization of polycrystalline, geophysical and other random media in which multiple scattering effects are important.
Acoustical source characterization by using recursive Wiener filtering
Authors: Bai Mingsian R.
Published: October 2005

This paper discusses a feedback iteration technique that provides the enhancement of backward reconstruction in acoustical imaging. Reconstruction of a vibrating surface motion from acoustic holographic data causes computational difficulties because the problem is ill posed. In order to deal with these difficulties, a method is developed based on a recursive algorithm, where the inverse problem is converted to a well-posed forward propagation problem. An initial guess regarding the source images is required to activate the iterative inversion method. Then, the tentative image is propagated forward to the hologram plane and the residue is determined. Next, a feedback operator is used to process the residue by which the image is updated. Two types of feedback operators were investigated: (1) a Wiener suboptimal operator, and (2) a dynamic, optimal operator (designed subject to minimum mean-square-error optimization criteria). The performance of these iteration methods was investigated by numerical simulations of the holographic reconstruction of a baffled piston field. Both iteration methods provided satisfactory convergence and were found to be relatively insensitive to the choice of initial guess and noise parameters used in the feedback operators.
New full-wave approximation for ocean acoustic travel time predictions
Authors: Tappert Frederick , Spiesberger John L. , Boden Linda
Published: October 2005

A new full-wave parabolic approximation is introduced that is valid for a wide range of grazing angles. By Fourier synthesis it yields travel times of ocean acoustic multipaths that are insensitive to a reference speed of sound. After depths and sound speeds are transformed to new coordinates, the highly efficient ‘‘split-step Fourier’’ algorithm is used to solve the new approximate wave equation for forward propagation. Accuracy of the new approximation has been tested by comparison to a broadband normal mode model in a range-independent environment. At 1000 km range and with a pulse of resolution 20 ms at center frequency 75 Hz, computed travel times of 24 multipaths agreed with maximum difference 3.4 ms, mean difference 0.9 ms, and rms difference 1.5 ms. This approximation may prove to be an efficient method for accurate travel time predictions of multipaths over a wide range of acoustic frequencies and for basin scale distances.
Acoustic classification of the state of artificial heart valves
Authors: Plemons Terry D. , Hovenga Michael
Published: October 2005

Transthoracic acoustic signals from BSCC (Björk–Shiley convexo–concave) mechanical heart valves implanted in human patients were processed to determine if the valves had separated outflow struts. For normal valves with intact outflow struts it is demonstrated that a time-windowed spectral analysis reveals the resonant frequency of the vibrating strut. The strut, which is set into vibration when the valve closes during each cardiac cycle, has a resonant frequency that varies among valves but usually is between 7000 and 8000 Hz. The signal processing technique is based on the hypothesis that the strut’s resonant waveform has a smaller decay rate than interfering signals and noise generated upon closure by other mechanical components of the valve. A time window can be selected that optimizes the outflow strut’s signal-to-interference ratio. It is shown that the absence of the resonant frequency in the 7000- to 8000-Hz interval is an indication that one of the strut’s legs has separated from the valve’s flange. This separation of one leg appears to precede the valve’s failure that occurs if the other leg also separates from the flange, a state referred to as OSF (outlet strut failure). Acoustic data recorded from 18 clinical patients with implanted valves, that were later explanted and examined, formed the database for this study. Of the 18 valves 9 were SLS (single-leg separated) and 9 were intact (both legs of the outflow strut still attached to the valve’s flange). The time-windowed spectral process correctly identified the states of all 18 valves. The success of this classification technique gives promise to the development of a noninvasive screening procedure to determine which of the thousands of BSCC patients worldwide may be at risk of OSF.
Overshoot and the ‘‘severe departure’’ from Weber’s law
Authors: Oxenham Andrew J. , Moore Brian C. J.
Published: October 2005

The link between the two phenomena of overshoot and the ‘‘severe departure’’ from Weber’s law in intensity discrimination was investigated. Masked thresholds for a brief 6.5-kHz signal were measured in the presence of a notched-noise masker over a range of masker levels. The masker was either gated with the signal (overshoot condition) or was of long duration with the signal temporally centered in it. At mid masker levels, thresholds in the gated condition were substantially higher than in the long-masker condition (overshoot). The overall amount of overshoot and the variation in overshoot as a function of masker level support the view that, even at high frequencies, the overshoot effect is dominated by off-frequency masker components. Pure-tone intensity discrimination tasks were then performed in quiet, and in the presence of the same notched noise in both gated and long-duration noise conditions. It was found that the temporal characteristics of the notched noise and not, as previously thought, the pedestal determined whether or not a severe departure from Weber’s law in intensity discrimination was observed. The severe departure from Weber’s law was found only in an overshoot condition and then only when the pedestal was presented near masked threshold. This is not in accordance with a previous explanation of the severe departure in terms of two populations of auditory nerve fibers (high- and low-threshold fibers). A further experiment measured psychometric functions for the detection of the 6.5-kHz signal in both gated and long-duration notched noise. It was found that the psychometric function was markedly shallower in an overshoot condition (mid-level gated masker) than in the other conditions. These findings are consistent with a new theory, explaining the severe departure from Weber’s law in terms of both the variance in the internal representation of stimuli in an overshoot condition, and the loudness of partially masked signals.
Acoustic scattering from an infinite cylinder of small radius coated by a penetrable one
Authors: Roumeliotis John A. , Kakogiannos Nikolaos B.
Published: October 2005

The scattering of a plane acoustic wave normal to the axis of an infinite impenetrable or penetrable cylinder of an acoustically small radius, coated by a penetrable cylinder, is treated in this work. The problem is solved by the method of separation of variables with the use of translational addition theorems for cylindrical wave functions. Analytical expressions are found for the scattered pressure field and the various scattering cross sections, when the radius of the inner cylinder is acoustically small. Numerical results are given for various values of the parameters and for both an impenetrable or penetrable inner cylinder.
Sector-focused processing for stabilized resolution of multiple acoustic sources
Authors: Chandler H. A. , Feuillade C. , Smith G. B.
Published: October 2005

Sector-focusing (SF) is a technique for performing stable high resolution acoustic matched-field processing (MFP) in a waveguide; it has been shown to be highly effective against sensor phase error and acoustic mismatch in an environment dominated by modal noise [Frichter et al., J. Acoust. Soc. Am. 88, 2843–2851 (1990); Smith et al., J. Acoust. Soc. Am. 93, 2617–2626 (1993)]. SF is successfully applied here to a problem of critical importance in MFP: The resolution of multiple, closely spaced acoustic sources under severe model parameter mismatch conditions. The mechanism for mismatch induced instability in Capon’s estimator [Proc. IEEE 57, 1408–1418 (1969)] is described, and the SF procedure for eliminating the resultant sidelobe ambiguities is developed. By judicious sector design and dimensionality selection, these sidelobes are reduced to unambiguously resolve the sources present in a waveguide. Simulations were performed for multiple cw sources in shallow water. It was found that SF can always be made to achieve the stability and performance of the Bartlett processor in the ‘‘small’’ sector limit. In the ‘‘large’’ sector limit, SF is equivalent to the reduced maximum likelihood (RML) processor [Byrne et al., J. Acoust. Soc. Am. 87, 2493–2502 (1990)]. By careful sector selection, the method can be readily tuned to achieve better performance in the intermediate regime.
Discrimination of synthetic full-formant and sinewave /ra–la/ continua by budgerigars (Melopsittacus undulatus) and zebra finches (Taeniopygia guttata)
Authors: Dooling Robert J. , Best Catherine T. , Brown Susan D.
Published: October 2005

Discrimination of three synthetic versions of a /ra–la/ speech continuum was studied in two species of birds. The stimuli used in these experiments were identical to those used in a previous study of speech perception by humans [Best et al., Percept. Psychophys. 45, 237–250 (1989)]. Budgerigars and zebra finches were trained using operant conditioning and tested on three different series of acoustic stimuli: three-formant synthetic speech, sinewave versions of those tokens, and isolated F3 tones from the sinewave speech. Both species showed enhanced discrimination performance near the /l/–/r/ boundary in the full-formant speech continuum, whereas for the F3 continuum, neither species showed a peak near this boundary. These results are similar to human discrimination of the same continua. Budgerigars also showed a peak in discrimination of the sinewave analog continuum paralleling that for full-formant syllables, similar to humans who are induced to perceive sinewave speech as speech. Zebra finches, by contrast, showed a relatively flat function mirroring their performance for F3 sinewaves, similar to humans who are induced to perceive sinewave speech as nonspeech. These data provide new evidence of species similarities and differences in the discrimination of speech and speechlike sounds. These data also strengthen and refine previous findings on the sensitivities of the vertebrate auditory system to the acoustic distinctions between speech sound categories.
Application of probability modeling and Bayesian inversion to passive sonar signal processing. II. Application to ocean acoustic source localization
Authors: Davis Nolan R. , Pitre Richard
Published: October 2005

Part I of this series considers a probabilistic approach to signal processing using Bayesian inversion. This approach allows incorporation of prior knowledge, fusion over multiple data to improve parameter estimates, and interpretation of data in spite of incomplete knowledge. In Part II this inversion technique is applied to the problem of localizing an acoustic source in a shallow water ocean environment. Simulation results are presented that demonstrate the incorporation of additional data to improve the source localization. Further simulation results demonstrate implicit data fusion over frequency and multiple sensors. A third set of simulations examines the case of two sources and demonstrates isolation of a weak source in the presence of a strong interfering source.
Dispersion of elastic waves in random particulate composites
Authors: Kim Jin-Yeon , Ih Jeong-Guon , Lee Byung-Ho
Published: October 2005

Elastic wave propagation in a discrete random medium is studied to predict dynamic effective properties of composite materials containing spherical inclusions. A self-consistent method is proposed which is analogous to the well-known coherent potential approximation in alloy physics. Three conditions are derived that should be satisfied by two effective elastic moduli and effective density. The derived self-consistency conditions have the physical meaning that the scattering of a coherent wave by the constituents in the effective medium vanishes, on the average. The frequency-dependent effective wave speed and coherent attenuation can be obtained by solving the self-consistency conditions numerically. At the lowest resonance frequency, the phase speed increases rapidly and the attenuation reaches the maximum in the composites having a large density mismatch. The lowest resonance is caused mainly by the density mismatch between matrix and particles and higher resonances by the stiffness mismatch. The dispersion and attenuation of longitudinal and shear waves are affected by the lowest resonance much more than by higher ones. The lowest resonance frequency of particles in the effective medium is found to be higher than that of a single particle embedded in the matrix material of composites due to the stiffening effect. The results obtained from the present theory are shown to be in good agreement with previous experimental observations of Kinra et al. [Int. J. Solid Struct. 16, 301–312 (1980)]. Part of the calculated results are compared with those computed by the Waterman and Truell theory. The present theory is in better agreement with the experiments for the examples dealt with.
Underwater sound produced by rainfall: Secondary splashes of aerosols
Authors: Nystuen Jeffrey A. , Medwin Herman
Published: October 2005

Earlier studies have identified three sources of underwater sound production from raindrops: The initial impact, a bubble trapped underwater at the base of the impact crater (type I), and a bubble trapped underwater by a turbulent jet created during the splash canopy formation 50–80 ms after impact (type II). Together these sound sources have been used to predict the underwater sound spectrum produced by rainfall; however, the predictions have underestimated observed sound levels. A new important mechanism of bubble entrapment (sound production) is described—bubbles created during the secondary splashes of drop aerosols thrown up during the initial raindrop impact. These delayed bubbles occur 100–600 ms after the initial impact depending on raindrop size. The average radiated spectral energy incorporating all known sound sources for two large drop sizes (3.2- and 4.7-mm-diam raindrops) are presented. Improved predictions of the underwater sound produced by rainfall are shown. The predictions form the basis for quantitative inversion measurements of rainfall at sea using underwater sound. A roughened water surface does not appear to significantly change the energy radiated by large raindrops.
Active absorption of acoustic waves using state-space model and optimal control theory
Authors: Wu Zhen , Varadan Vijay K. , Varadan Vasundara V. , Lee Kwang Y.
Published: October 2005

The work presented in this paper regards modeling, synthesis, and simulation of an active acoustic field control system under state-space feedback control approach. The active system is supposed to absorb an incident sound energy so that the reflection off an acoustic boundary is diminished. To illustrate the concept, a simple model describing transient sound reflection and transmission in an unbounded, one-dimensional space is derived in a state-space form. The distributed parameter system is approximated with a finite dimensional model using a standard discretization technique with special boundary treatments. Based on the state-space model, a feasible feedback control algorithm is synthesized using optimal control theory (LQG). Numerical simulation of the closed-loop response of an active control system including two sensors and one actuator is presented, which shows a broadband reflection (echo) reduction.
Comparison of auditory filter shapes obtained with notched-noise and noise-tone maskers
Authors: Moore Brian C. J. , Glasberg Brian R. , van der Heijden Marcel , Houtsma Adrian J. M. , Kohlrausch Armin
Published: October 2005

The notched-noise method has been widely used to estimate the shape of the auditory filter. Results obtained using this method may be influenced by combination bands produced by the interaction of components within the upper band of noise in the notched-noise masker. To assess the possible effect of such combination bands, results were compared for two types of masker: A notched noise, as used in previous experiments; and a masker in which the upper band of noise was replaced by a sinusoid with a frequency corresponding to the lower edge frequency of that band. This is referred to as the noise-tone masker. The signal frequency was 2 kHz, and measurements were obtained for two different spectrum levels of the noise masker, 30 and 45 dB. Auditory filter shapes derived using the two maskers were similar on their low-frequency sides, as expected. The low-frequency sides were less steep at the higher masker level. The high-frequency sides of the auditory filters derived using the noise-tone masker were sometimes slightly steeper than those obtained using the notched-noise masker, but the effect was generally small. Changes with level on the high-frequency sides were not consistent across subjects. An analysis of the notched-noise data taking into account the effects of the combination bands suggests that the maximal spectrum level of the combination bands, in the region just below the lower spectral edge of the primary noise band, is about 20 to 30 dB below the spectrum level of the primary band. At this relative level, the combination bands have only a very small influence on the high-frequency sides of the derived auditory filters. The influence on the estimated equivalent rectangular bandwidths (ERBs) of the auditory filters is usually negligible.
Changes in intensity discrimination following monaural long-term use of a hearing aid
Authors: Robinson K. , Gatehouse S.
Published: October 2005

Previous work has shown that a normally aided ear tested without the hearing aid is better able to identify speech-in-noise than the unaided ear at high sound levels, while performance for the unaided ear is superior at lower sound levels [S. Gatehouse, J. Acoust. Soc. Am. 86, 2103–6 (1989); J. Acoust. Soc. Am. 92, 1258–68 (1992)]. This effect was further explored using intensity discrimination for complex stimuli. Stimuli were half-octave bandpass-filtered tone complexes centered at 0.25 and 3 kHz. Four bilateral, symmetric hearing-impaired listeners with mean HL of 24 dB at 0.25 kHz, and 58 dB at 3 kHz were tested. Intensity discrimination was performed across the dynamic range of the listeners. At sound-pressure levels greater than 85 dB, the normally aided ear tested without the aid was more sensitive to changes in intensity than the unaided ear, whereas at lower levels, the converse occurred. This pattern was observed only for the 3-kHz center frequency, and not for the 0.25-kHz center frequency. Insertion gain measurements using the aids at normal volume showed an average of 20 dB gain at 3 kHz, and −2 dB gain at 0.25 kHz. The changes in intensity discrimination in the normally aided ear are consistent with the frequency-gain characteristics of the hearing aid, and suggest that a change in intensity coding occurred.
The iterative time reversal process: Analysis of the convergence
Authors: Prada Claire , Thomas Jean-Louis , Fink Mathias
Published: October 2005

The efficiency of a time reversal acoustic mirror to focus on a reflective target through an inhomogeneous media has been demonstrated. In a multitarget media, the ability of such a mirror to work in an iterative mode in order to focus selectively on the strongest target was shown [C. Prada, F. Wu, and M. Fink, J. Acoust. Soc. Am. 90, 1119 (1991)]. The theory of how the iterative time reversal process is built is based on a matrix formalism and treats the array of L transducers in a given medium as a linear system of L inputs/L outputs. The system is characterized at each frequency by its transfer matrix K and the time reversal iterative process is then described by a time reversal operator K*K. Because of the reciprocity principle, this operator is Hermitian. The following result is shown: If the scattering medium is a set of well resolved targets of different reflectivities then each eigenvector of the operator K*K with nonzero eigenvalue corresponds to one of the targets in the set and provides the optimum phase law to focus on it. Furthermore, the eigenvalue is proportional to the reflectivity of the target. In particular, the ‘‘brightest’’ target is associated to the eigenvector of greatest eigenvalue so that the iterative time reversal process leads to a wave focusing on this target. This analysis is illustrated by numerical and experimental results.
Elastic wave propagation in transversely isotropic media. II. The generalized Rayleigh function and an integral representation for the transducer field. Theory
Authors: Spies M.
Published: October 2005

The basis for the derivation of elastodynamic holography for arbitrarily oriented transversely isotropic materials, given in Part I of this presentation [M. Spies, J. Acoust. Soc. Am. 96, 1144–1157 (1994)], is Huygens’ principle and a resulting relationship which links the spatial spectra of surface traction and displacement distribution. Similar to deriving the plane-wave spectral decomposition of elastic wavefields for given displacement, this relationship yields a corresponding decomposition for the case of given surface traction, which can be applied to model the problem of transducer radiation as significant to nondestructive testing. For a physically reasonable distribution of surface traction within the transducer aperture, an integral representation for the resulting transducer field is obtained. The main problem in this approach is the inversion of the 2-D space-time spectral representation of Green’s triadic function. A specifically interesting result of this inversion is the Rayleigh function for arbitrarily oriented transversely isotropic media, which characterizes the propagation of the respective Rayleigh wavefronts. Since the resulting expressions are explicitly dependent on the orientation of the material’s axis of rotational symmetry, their numerical evaluation will be much more complicated than in the isotropic case.
A second-order theory for piezoelectric materials
Authors: Yang J. S. , Batra R. C.
Published: October 2005

Based on the theory of invariants, from invariant polynomial constitutive relations for piezoelectric materials which are either transversely isotropic or are of class mm2 are derived from the polynomial integrity basis functions. These constitutive relations are assumed to be smooth enough functions of their arguments to be expanded in terms of a Taylor series. These functions are expanded about the values their arguments take in the reference configuration and all terms up to the quadratic terms in the gradients of the mechanical displacement and electric potential are kept. The second-order theory so obtained is then specialized to the case of small deformations and weak electric fields, and the case of small deformations and relatively strong electric fields. The material parameters in the present theory are identified by relating them to those in the more conventional theories.
Leaky waves on weakly curved scatterers. II. Convolution formulation for two-dimensional high-frequency scattering
Authors: Marston Philip L.
Published: October 2005

A simple high-frequency approximation is developed for leaky wave contributions to two-dimensional scattering by curved elastic surfaces. Following Bertoni and Tamir [Appl. Phys. 2, 157–172 (1973)] the method relies on general features of the Laurent expansion of the plane surface reflection coefficient R(kx) about the leaky wave pole of interest at the complex surface wave number kx=kl+iα. The formulation uses the real part kl and radiation damping rate α for leaky waves on the curved elastic surface of interest rather than an analysis of the response of any specific class of structures such as thin shells. The high frequency limit of the complex coupling coefficient Gl [see, e.g., P. L. Marston, J. Acoust. Soc. Am. 83, 25–37 (1988)] is recovered for right circular cylinders and the physical origin of the π/4 phase shift is discussed. An O(kh)−1 phase correction important for empty thin shells of thickness h is obtained in agreement with results from other approaches. The importance of the Fresnel width of the coupling region is illustrated by consideration of a cylinder with an ideal coating having an abrupt edge. The leaky wave contribution becomes proportional to a Fresnel integral having a complex argument. The integral manifests the degree to which launching of a leaky wave can be considered to be a local process. The product of α and the Fresnel width is an important parameter. The detachment of the ray to the far field is taken to be separated from its launching by more than the Fresnel width. Leaky wave contributions to scattering by surfaces of variable curvature are approximated and applications for ultrasonic beams are noted.
Holographic studies of the bubble generated by a seismic airgun
Authors: Langhammer Jan , Graciet Stephane , Vik Irene , Espeland Morten , Lo/kberg Ole J.
Published: October 2005

Using a Nd:YAG laser in single and double pulse mode, the dynamic behavior of bubbles generated by a small airgun, placed in a water tank, has been investigated. Single pulse holograms of the bubble have been obtained with the purpose of investigating the shape and smoothness of the surface. Interferometric holography, or double pulse holography, of the bubble has been performed in order to detect the pressure wave from the gun at the early stages of the bubble expansion. The optical phase delay of the laser beams traversing the test section is caused by a local change in the refractive index of the water in the tank due to the acoustic disturbance. A theory for relating the change of the refractive index to bubble parameters is presented. Modeling of interferometric holograms has been performed with the aim of qualitatively comparing them with the recorded holograms. From the holograms it is observed that the surface of the bubble is relatively smooth during the first expansion. During the contraction, and the following oscillations, the bubble surface becomes highly nonsmooth and chaotic due to the developed turbulence in the surrounding water.
The effect of realistic ground impedance on the accuracy of ray tracing
Authors: Raspet Richard , L’Espérance André , Daigle Gilles A.
Published: October 2005

The heuristic model of sound propagation in the atmosphere has been developed by L’Espérance et al. [Appl. Acoust. 37, 111–139 (1992)] to provide rapid calculation of sound-pressure levels. This model uses an analytic ray trace method to calculate ray paths from the source to the receiver. The effects of finite ground impedance are treated by calculating the spherical wave reflection factor as if the atmosphere was homogeneous. The actual reflection angles and times of flight are used in this formulation. Since the speed of sound varies linearly with height, no focusing factors are calculated. The heuristic model has been compared to full wave calculations and is found to agree well at long ranges. In this paper the agreement between the heuristic model and the fast field program is investigated in detail. Criteria for the accuracy of ray tracing are discussed. It is demonstrated that the heuristic model produces realistic predictions even though certain criteria are violated. The finite ground impedance is shown to remove those rays for which the ray tracing criteria do not hold.
Comodulation masking release (CMR): Effects of gating as a function of number of flanking bands and masker bandwidth
Authors: Hatch Debora R. , Arné Bruce C. , Hall III Joseph W.
Published: October 2005

Normal-hearing subjects participated in two CMR experiments. For experiment 1, two, three, five or nine 20-Hz-wide comodulated flanking bands were presented continuously or gated simultaneously with a 2000-Hz signal. The signal had a duration of 400 ms. Larger CMRs were obtained as the number of flanking bands increased for both the continuous and gated conditions. For fewer number of bands, the average CMR for continuous noise was substantially larger than for gated noise. As the number of bands increased, CMR increased more for gated than for continuous noise, and the difference between CMRs for gated and continuous noise decreased. Experiment 2 involved detecting a 400-ms 1000-Hz pure-tone signal in a seven-band comodulated noise complex. The noise bands, presented continuously or gated with the signal, were either 10, 20, 40, or 80 Hz wide. Larger CMRs were observed for continuous maskers and for smaller masker bandwidths; however, the effect of gating did not change significantly across bandwidth. The results of the first experiment indicate that the effects of gating on CMR are minimized when the number of auditory channels providing information is large. The results of the second experiment indicate that this effect is not simply a function of the large CMR magnitude obtained with a large number of flanking bands.
The discrimination of samples of noise in monotic, diotic, and dichotic conditions
Authors: Heller Laurie M. , Trahiotis Constantine
Published: October 2005

Listeners’ ability to discriminate between independent tokens of 800-Hz-wide bands of noise (centered at 1200 Hz) was measured in monaural, diotic, and several dichotic conditions. In a two-cue, two-alternative, temporal forced-choice task, listeners indicated whether the second or third interval contained a token of noise that was different from the sample of noise that was presented in each of the remaining three intervals. Samples of noise were selected on a trial-by-trial basis from a set of 50 independent noises for each hourly session. Six durations of noise, ranging from 10 to 328 ms, were utilized, and all were presented at an overall level of 79 dB. The baseline condition for comparisons of performance was a monaural presentation of the noises. As expected, discriminability improved when the baseline condition was presented diotically. The next best performance was obtained when the baseline stimuli was presented to both ears with the proviso that the noises were interaurally uncorrelated. Other dichotic conditions, all of which also utilized interaurally uncorrelated noises, produced performance that was worse than that obtained in the monaural condition. Large degradations in performance were observed when the left ear received a different sample of noise in each of the four intervals of a trial while the right ear continued to receive the baseline stimuli. This finding indicates that listeners were effectively unable to ignore the waveforms presented to one ear while performing a task which could be solved with the information presented to the other ear. Data were obtained from several other dichotic conditions, including cases where the stimuli in the left and right ears were spectrally remote.
Effects of level and frequency on the detection of decrements and increments in sinusoids
Authors: Peters Robert W. , Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

Thresholds for the detection of decrements in level of sinusoidal signals were measured as a function of decrement duration, level (25, 40, 55, and 70 dB SPL) and frequency (250, 1000, and 4000 Hz) in eleven normally hearing subjects. Thresholds for detecting a brief increment in level were also measured. The sinusoids were presented in a background noise intended to mask spectral splatter associated with the decrement or increment. Performance tended to worsen with decreasing frequency, for all decrement durations and for increment detection. Performance also worsened with decreasing level. The results were analyzed using a model consisting of a compressive nonlinearity, a sliding temporal integrator, and a decision device. The analysis indicated that the worsening in performance with decreasing frequency and decreasing level can be attributed partly to increases in the equivalent rectangular duration (ERD) of the temporal integrator, but mainly to changes in the efficiency of the detection process following the temporal integrator; at lower frequencies and levels a larger change is required at the output of the integrator for threshold to be reached. At each frequency, the ERD was relatively invariant with level for levels more than about 20 dB above the absolute threshold.
Generalized boundary conditions for scalar fields
Authors: Senior Thomas B. A.
Published: October 2005

Generalized boundary conditions are characterized by the presence of field derivatives higher than the first, and are designed to improve the simulation of the material properties of a surface. A rather general class of conditions is described and the constraints necessary to ensure a unique solution of the boundary-value problem are then derived. In the case of a planar surface, each boundary condition implies a pair of related transition conditions describing membranes. These are complementary in the sense of Babinet’s principle, and the connection between the total fields in the two problems is shown.
Placing small constrained layer damping patches on a plate to attain global or local velocity changes
Authors: Spalding Amy B. , Mann J. Adin
Published: October 2005

Experimental results show how structural intensity can predict where to locate small constrained layer damping patches to attain either local or global velocity changes on a plate. If damping is applied to a region of low shearing reactive structural intensity magnitude, a local velocity change is seen. If damping is applied to a region of high shearing reactive structural intensity magnitude, a global velocity change is seen. In addition, the researchers noted that large damping patches produce global velocity changes. The filtering process needed to calculate the structural intensity was partially automated to reduce computational time.
The relationship between auditory filter bandwidth and temporal resolution
Authors: Strickland Elizabeth A.
Published: October 2005

Temporal resolution was examined in the context of an envelope detector model. This model incorporates two limits to temporal resolution: filtering by the peripheral auditory system, and a central temporal window. It predicts that temporal resolution should increase with the bandwidth of the peripheral filter up to a certain filter width, beyond which it should be determined by the central limitations. To determine whether the predicted relationship between peripheral filtering and temporal resolution could be observed, temporal resolution and auditory filter widths were measured as a function of frequency region and level. Because auditory filters widen with level and with center frequency, the relationship between temporal resolution and filter width could thus be tested both within and across frequency regions. Temporal modulation transfer functions (TMTFs) were measured for frequency regions from 500 to 4000 Hz using narrow-band noise. Auditory filter functions were measured in the same frequency regions, using the notched-noise method with probe level fixed. Both the TMTFs and filter functions were measured at two levels in each frequency region. As predicted, time constants were correlated with filter width for narrow filters, and were constant for wider filters. [Work partially supported by a post-doctoral fellowship from NIH.]
Simulation of ultrasonic propagation through abdominal wall
Authors: Mast T. Douglas , Hinkelman Laura M. , Waag Robert C. , Sparrow Victor W.
Published: October 2005

Ultrasonic pulse propagation through the human abdominal wall is simulated using a model for two-dimensional propagation through anatomically realistic tissue cross sections. The time-domain wave equation for a medium of variable sound speed and density is discretized and solved as a set of coupled finite-difference equations. The finite-difference algorithm used is a two-step MacCormack scheme that is fourth-order accurate in space and second-order accurate in time. The inhomogeneous tissue of the abdominal wall is represented by two-dimensional matrices of sound speed and density values. These values are determined by mapping scanned images of abdominal wall cross sections that have been stained to identify connective tissue, muscle, and fat, each of which is assumed to have a constant sound speed and density. The computational configuration is chosen to simulate the experimental wave-front distortion measurements of Hinkelman etal. [ 530–541 (1994)]. Qualitative agreement is found between those measurements and the results of the present computations. Visualization of calculated sound fields is used to illustrate the salient characteristics of ultrasonic wave-front distortion invivo.
Measurement of upper-sediment geoacoustic properties in the Canadian high Arctic
Authors: Dosso S. E. , Brooke G. H.
Published: October 2005

Geoacoustic properties of the ocean bottom can significantly affect acoustic propagation in shallow water. However, to date, few measurements of geoacoustic properties have been reported for the high Arctic. A seismoacoustic survey was carried out to determine a geoacoustic model for the upper sediments on the continental shelf of the Lincoln Sea, north of Ellesmere Island, Canada. The experiment involved deploying an ocean-bottom seismometer through 5 m of polar pack ice, and recording signals from seafloor sources at ranges of 35–900 m. Subsequently, a layered compressional-speed model of the upper sediments was determined from a travel-time analysis of refracted compressional waves (head waves), and a shear-speed model was determined by matching the observed dispersion characteristics of shear and seismic-interface (Scholte) waves. Frequency-dependent compressional and shear attenuation coefficients were estimated from an analysis of the decay of signal amplitude with range: An approximately linear dependence of attenuation on frequency was observed for both wave types. The sensitivity of acoustic propagation in the ocean to the various geoacoustic parameters was investigated using a numerical propagation model.
Computer model versus reality in a nonshoebox orchestra hall. Part I
Authors: Campbell Richard H.
Published: October 2005

The Portland (Maine) City Hall Auditorium was the venue for acquisition of occupied and unoccupied acoustical data on 4 October 1994, using the MLSSA system. During intermission, an omnidirectional loudspeaker was positioned at center stage in the plane of the proscenium arch and occupied data were collected with nearly a full audience. Three volunteers equipped with eyeglass microphone-pairs and DAT machines occupied six preselected seats in 3.5 min to acquire 18 binaural 64-K impulse responses. The same seat locations were used earlier in the day to obtain the unoccupied data. An ODEON (c) computer model of this hall, created by Kirkegaard and Associates, is used to estimate acoustical parameters from the same source and receiver locations as used in the live audience acquisition. Particular attention is given to response features due to the design of this hall, which is a double-balcony horseshoe-shaped space with curved ceiling. [Work supported by the Concert Hall Research Group.]
A comparison of broadband and narrow-band transmission loss in shallow water
Authors: Frech Karen D.
Published: October 2005

Calibrated acoustic measurements were made at the Hudson Canyon Experiment site [L. Maiocco and W. Carey, J. Acoust. Soc. Am. Suppl. 1 86, S8 (1989)] during area characterization test II(ACT II) conducted in September 1993. This site was chosen because it is a surveyed area with known geophysical and geoacoustic properties. Transmission loss was measured along the previously run radials from bore hole 6010 using calibrated small broadband explosive charge sources and a narrow-band continuous wave (cw) towed acoustic projector. These sources were, for the purposes considered here, co-located in range because of low test ship speed (under 5 kn). The receiving sensor was a 25 element stationary vertical line array spanning the majority of the water column (73 m), with 19 elements extending off the bottom (60 m) and 6 elements along the bottom (30 m). Using the principle of reciprocity, the hydrophone elements at each of the source depths enabled comparisons of the transmission loss measurements for broadband and cw sources to be made over a range interval from 4–22 km at two frequencies (200 and 900 Hz). The comparisons were performed by means of linear regression of the data from the two sources. The results of the comparison will be presented and will include a detailed discussion of the precision of the results and of possible sources of experimental error. Finally, the cw transmission loss from ACT II will be compared with the previous measurements of Maiocco and Carey.
Sediment layer structure and composition effects on pulse propagation at the Atlantic generating station (AGS) site
Authors: Bongiovanni Kevin P. , Badiey Mohsen , Siegmann William L.
Published: October 2005

An investigation of broadband pulse propagation in a shallow water environment is performed using high-order frequency- and time-domain parabolic equation models. High resolution geoacoustical profiles are constructed from cores obtained at the extensively sampled AGS site which lies 5 miles offshore southern New Jersey. These, along with CTD and detailed bathymetric data, are used to model the environment. Acoustic experiments recently conducted at this site [M. Badiey etal., 3593–3604 (1994)] provide broadband acoustic data for comparisons with the modeling predictions. Simulations of transmission loss versus frequency show very good agreement with experimental data over several different propagation tracks. Time-domain simulations are compared with time series of pressure variations generated by the impulsive experimental source along corresponding tracks. Strongly range-dependent mechanisms are observed over short ranges with both models and can be correlated with specific sediment features. A discussion of the modeling results in connection with both environmental and acoustic data sets will be given.
A method of analysis of acoustic emission signals due to leakage by wavelet transform
Authors: Chen Q. M. , Ho Y. S. , Leung T. P.
Published: October 2005

In the test of continual acoustic emission due to leakage, the rms was used to evaluate the energy of AE signals. However, the value of rms strongly relates to measuring conditions, including sensitivity of sensor, mounting pressure, setting amplification, etc. Detecting points of sharp variation of AE signals by wavelet transform to evaluate leakage is explored in this paper. The parameter evaluating leakage is sample zero-crossing counts of wavelet transform at each scale. Based on the sharp variation of AE signals instead of amplitude, this method is robust to measuring conditions. The experimental results obtained under different test conditions demonstrates the applicability of the method.