bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of an acoustic filter plate using the boundary integral element method
Authors: Mobbs Stephen D.
Published: October 2005

The acoustic filter plate is a device giving a variable aperture, the diameter of which is proportional to the wavelength of the incident sound, thus producing a beamwidth for the transmitted sound that is independent of the wavelength. Previous experimental studies have demonstrated the effectiveness of the filter plate. However, it has been found that the performance of the device is seriously impaired at high frequencies and the purpose of this article is to provide an explanation for this high-frequency failure. The approach is numerical: The Helmholtz equation describing the propagation of sound through and around the filter plate is solved using the boundary integral element (BIE) method. Good qualitative agreement with the experimental results are obtained at moderate frequencies where the filter plate is operating normally and the reason for the high-frequency failure is demonstrated.
Acoustically induced stresses in elastic cylinders and their visualization
Authors: Dardy H. D. , Flax L. , Gaumond C. F. , Subrahmanyam J. V. , Ashrafi S. , Raju P. K. , Überall H.
Published: October 2005

The interior field in elastic cylinders immersed in a fluid and subject to an incident acoustic plane wave has been studied here via an application of the resonance scattering theory (RST), first formulated by Flax et al. [J. Acoust. Soc. Am. 63, 723 (1978)]. The interior field has been shown to consist solely of resonant amplitudes, with a substantial amount of penetration of the incident field into the scatterer occurring only at and near-resonance frequencies. Experimental measurements of stress distributions in a finite glass cylinder isonified by a normally incident acoustic pulse and viewed by axially transmitted light are presented as a function of ka (range of 5–55). The results show that the largest variations in light intensity occur for specific values of ka that correspond to resonance modes of the elastic glass cylinder. A model of the dynamics of the interior motions inside such a cylinder, and corresponding strain equations, are developed and combined with birefringence expressions for the purpose of predicting the light distributions. The elastic body is shown to undergo resonances in the radial and angular directions, except for the merely radial motions of the breathing mode. Calculated light distributions are shown to correspond to measured distributions.
Effects of propagation on the operation of a synthetic aperture sonar
Authors: Tarng J. H. , Yang C. C.
Published: October 2005

Applications of aperture synthesis technique in a radar or sonar system can improve the resolution in the azimuthal direction. However, because of the existence of the vertical sound-speed profile in the ocean, the expressions for some parameters of sonar operation are not as simple as those of radar operation in the atmosphere. Important parameters such as the azimuthal resolution size and bounds of the pulse repetition frequency in the ocean environment are discussed. The method of ray tracing is used to find the formulations of those parameters. A numerical approach is then applied to solve the problem. Results show that the speed of sonar carrier motion must be low enough to find an operational range for the pulse repetition frequency.
Propagation of beluga echolocation signals
Authors: Au Whitlow W. L. , Penner Ralph H. , Turl Charles W.
Published: October 2005

The propagation characteristics of high-frequency echolocation signals (peak energies above 100 kHz) of the beluga (Delphinapterus leucas) were measured while the animal performed a target detection task. The whale was trained to station on a bite plate so that its transmission beam could be measured in the vertical and horizontal planes using hydrophone arrays. The transitional region between the acoustic near- and farfields was also located using an array of hydrophones that extended directly in front of the animal in the horizontal plane. Three distinct modes of signals were observed. Mode 1 signals had click intervals greater than the time required for the signals to travel to the target and back (two-way transit time). Mode 2 signals had click intervals shorter than the two-way transit time, and mode 3 signals had high repetition rates with an average click interval of 1.7 ms, approximately 2% of the two-way transit time. The average click intervals for the modes 1 and 2 signals were 193 and 44 ms, respectively. The vertical and horizontal beam patterns of the mode 1 signals had similar 3-dB beamwidths of approximately 6.5°. The major axis of the vertical beam was directed approximately 5° above the plane defined by the animal’s teeth. The near- to farfield transition region was approximately 0.64–0.75 m from the tip of the animal’s mouth.
Sounds and source levels from bowhead whales off Pt. Barrow, Alaska
Authors: Cummings W. C. , Holliday D. V.
Published: October 2005

Sounds were recorded from bowhead whales migrating past Pt. Barrow, AK, to the Canadian Beaufort Sea. They mainly consisted of various low-frequency (25 to 900-Hz) moans and well-defined sound sequences organized into ‘‘song’’ (20–5000 Hz) recorded with our 2.46-km hydrophone array suspended from the ice. Songs were composed of up to 20 repeated phrases (mean, 10) which lasted up to 146 s (mean, 66.3). Several bowhead whales often were within acoustic range of the array at once, but usually only one sang at a time. Vocalizations exhibited diurnal peaks of occurrence (0600–0800, 1600–1800 h). Sounds which were located in the horizontal plane had peak source spectrum levels as follows—44 moans: 129–178 dB re: 1 μPa, 1 m (median, 159); 3 garglelike utterances: 152, 155, and 169 dB; 33 songs: 158–189 dB (median, 177), all presumably from different whales. Based on ambient noise levels, measured total propagation loss, and whale sound source levels, our detection of whale sounds was theoretically noise-limited beyond 2.5 km (moans) and beyond 10.7 km (songs), a model supported by actual localizations. This study showed that over much of the shallow Arctic and sub-Arctic waters, underwater communications of the bowhead whale would be limited to much shorter ranges than for other large whales in lower latitude, deep-water regions.
An investigation of motor equivalence in the speech of children and adults
Authors: Smith Bruce L. , McLean-Muse Ann
Published: October 2005

Although the concept of motor equivalence (i.e., articulatory intercoordination) is generally accepted as functioning in normal speech production, few studies have experimentally demonstrated its existence. One purpose of the present study was thus to obtain additional data concerning this phenomenon. Because motor equivalence is often assumed to represent a rather sophisticated ability in speakers, another purpose of the study was to determine whether trends could be observed that might demonstrate a developmental progression toward more frequent occurrence of articulatory intercoordination with increasing age. A strain gauge transduction system was used to monitor inferior–superior upper lip, lower lip, and jaw movements produced by a group of adults and three groups of children ranging from 4–11 years of age, as they spoke in a normal condition and in two ‘‘perturbed’’ conditions (bite block and fast rate). Based on the assumption that the presence of a significant negative correlation between two articulators constitutes evidence of articulatory intercoordination, there was little indication of motor equivalence in the speech of the adults or the children.
Effects of stress and final-consonant voicing on vowel production: Articulatory and acoustic analyses
Authors: Van Summers W.
Published: October 2005

Durations of the vocalic portions of speech are influenced by a large number of linguistic and nonlinguistic factors (e.g., stress and speaking rate). However, each factor affecting vowel duration may influence articulation in a unique manner. The present study examined the effects of stress and final-consonant voicing on the detailed structure of articulatory and acoustic patterns in consonant–vowel–consonant (CVC) utterances. Jaw movement trajectories and F1 trajectories were examined for a corpus of utterances differing in stress and final-consonant voicing. Jaw lowering and raising gestures were more rapid, longer in duration, and spatially more extensive for stressed versus unstressed utterances. At the acoustic level, stressed utterances showed more rapid initial F1 transitions and more extreme F1 steady-state frequencies than unstressed utterances. In contrast to the results obtained in the analysis of stress, decreases in vowel duration due to devoicing did not result in a reduction in the velocity or spatial extent of the articulatory gestures. Similarly, at the acoustic level, the reductions in formant transition slopes and steady-state frequencies demonstrated by the shorter, unstressed utterances did not occur for the shorter, voiceless utterances. The results demonstrate that stress-related and voicing-related changes in vowel duration are accomplished by separate and distinct changes in speech production with observable consequences at both the articulatory and acoustic levels.
Tone detection and synthetic speech discrimination in band-reject noise by hearing-impaired listeners
Authors: Thibodeau Linda M. , Van Tasell Dianne J.
Published: October 2005

Frequency resolution was evaluated for two normal-hearing and seven hearing-impaired subjects with moderate, flat sensorineural hearing loss by measuring percent correct detection of a 2000-Hz tone as the width of a notch in band-reject noise increased. The level of the tone was fixed for each subject at a criterion performance level in broadband noise. Discrimination of synthetic speech syllables that differed in spectral content in the 2000-Hz region was evaluated as a function of the notch width in the same band-reject noise. Recognition of natural speech consonant/vowel syllables in quiet was also tested; results were analyzed for percent correct performance and relative information transmitted for voicing and place features. In the hearing-impaired subjects, frequency resolution at 2000 Hz was significantly correlated with the discrimination of synthetic speech information in the 2000-Hz region and was not related to the recognition of natural speech nonsense syllables unless (a) the speech stimuli contained the vowel /i/ rather than /a/, and (b) the score reflected information transmitted for place of articulation rather than percent correct.
Perceptual organization of complex-tone sequences: A tradeoff between pitch and timbre?
Authors: Singh Punita G.
Published: October 2005

Sequences of rapidly occurring sounds that differ from each other are often perceptually segregated into ‘‘streams’’ within which the range of differences is smaller [Bregman and Campbell, J. Exp. Psychol. 89, 244–249 (1971)]. Early research on streaming implied it to be pitch dominated, but Wessel [Comput. Music J. 3, 45–52 (1979)] demonstrated that timbre differences could also bring about segregation. In the present study, pitch and timbre attributes were put in competition in four-tone sequences of the form: T2P1-TmP1-T2Pn-TmPn, with the first pair assigned pitch P1 but different timbres T2 and Tm, and the second pair pitch Pn, and similarly contrasted timbres. Six listeners were asked to indicate whether perceived grouping of 49 such sequences was based on pitch proximity, timbre similarity, or ambiguous percepts not dominated by either cue. Results confirm that timbre can segregate sequences and imply that timbre and pitch compete in perceptually organizing complex sequences. Because timbre differences were provided by varying the locus of four equal-amplitude harmonics, and pitch differences were provided by varying their relative spacing, it is suggested that the tradeoffs observed may actually arise due to differences in perceived salience of ‘‘spectral pitch’’ and ‘‘virtual pitch’’ [Terhardt, J. Acoust. Soc. Am. 55, 1061–1069 (1974)] dependent on relative changes in spectral locus and spectral spacing over time.
Cochlear power flux as an indicator of mechanical activity
Authors: Diependaal Rob J. , de Boer Egbert , Viergever Max A.
Published: October 2005

The question of whether one can conclude just from basilar membrane (BM) vibration data that the cochlea is an active mechanical system is addressed. To this end, a method is developed which computes the power flux through a channel cross section of a short-wave cochlear model from a given BM vibration pattern. The power flux is an important indicator of mechanical activity because a rise in this function corresponds to creation of mechanical energy. The power flux method is applied to BM velocity patterns as measured by Johnstone and Yates [J. Acoust. Soc. Am. 55, 584–587 (1974)] and by Sellick et al. [Hear. Res. 10, 101–108 (1983)] in the guinea pig and by Robles et al. [Peripheral Auditory Mechanisms, edited by J. B. Allen, J. L. Hall, A. E. Hubbard, S. T. Neely, and A. Tubis (Springer, New York, 1986a), pp. 121–128, and J. Acoust. Soc. Am. 80, 1364–1374 (1986b)] in the chinchilla. Before the calculations are performed, the BM data are interpolated and smoothed in order to avoid numerical errors as a result of too few and noisy data points. The choice of the smoothing method influences the computed power flux function considerably. Nevertheless, the calculations appear to make a clear distinction between the ‘‘old’’ data, showing broad BM tuning (Johnstone and Yates, 1974), and the ‘‘new’’ data, in which the response is much more peaked (Sellick et al., 1983; Robles et al., 1986a,b). The former do not give rise to a significant increase of the power flux; the latter do, although less convincingly for the Sellick et al. (1983) data than for the Robles et al. (1986a,b) data. It is thus concluded that the recently obtained, sharply tuned BM responses reflect the presence of mechanical activity in the cochlea.
A fast layer stripping algorithm for reconstructing a lossy layered medium
Authors: Yagle Andrew E.
Published: October 2005

A discrete layered absorbing acoustic medium is probed with an impulsive plane wave at normal incidence, and the reflection response of the medium is measured. The absorbing nature of the medium is specified by a complex wave speed, corresponding to a constant Q. A fast layer stripping algorithm for recovering the profile of the complex wave speed as a function of depth is obtained. The algorithm works by recursively computing the reflection response of that portion of the medium below the current depth, thus stripping away the effects of that portion of the medium at and above the current depth. The algorithm is, in principle, exact, includes the effects of multiple reflections, and admits a clear physical interpretation of its operation. Several computer simulations illustrate the performance of the algorithm on synthetic data.
Vibrations of a hollow circular cylinder of piezoelectric ceramics
Authors: Paul H. S. , Venkatesan M.
Published: October 2005

The wave propagation in a piezoelectric hollow cylinder of class (6-mm) crystals or ceramics (∞ m) with traction-free surfaces is studied. The frequency equations are obtained subject to various types of electrical boundary conditions and are examined numerically for the piezoceramic material PZT-4; the results are presented graphically as well as in tables.
Arctic ambient noise in the Beaufort Sea: Seasonal space and time scales
Authors: Lewis James K. , Denner Warren W.
Published: October 2005

Data from the Beaufort Sea are used to quantify some of the seasonal characteristics of under-ice ambient noise. Noise at 10, 32, and 1000 Hz was studied and seasonal space and time scales were calculated. An interesting result is that summer 10-Hz noise apparently can often be contaminated by cable strum. The summer period is also the only time during which 1000-Hz noise is almost totally a product of ice motion. Within the central Beaufort Sea, lower frequency noise tends to have e-folding space scales of the order of 1000 km. This is true for 1000-Hz noise only during summer, with space scales for the rest of the year being ∼300 km. The time scale analysis also shows this trend. During summer, all frequencies have e-folding time scales of the order of 10–30 h. During fall and winter, the time scales for lower frequencies increase (up to 72 h or longer), but the 1000-Hz time scales drop to as low as 3 h.
Approaches to acoustic fluid–elastic structure interactions
Authors: Junger Miguel C.
Published: October 2005

Major stages are defined in the evolution of analytical, nonnumerical approaches to the vibrations of elastic shells and plates in an acoustic fluid and to the resulting sound field. Concepts are described in roughly chronological order: Emerging from a ‘‘prehistory’’ of interaction solutions based on the Laplace or plane-wave approximations, analyses of structures compatible with rigorous normal mode solutions when radiation loaded; solutions in terms of wavenumber transforms whose asymptotic evaluation permits the explicit formulation of the farfield; substitution of the actual structure by an infinite, analytically tractable structure displaying a similar supersonic wavenumber spectrum, though the subsonic portions of the wavenumber spectra differ.
Frequency-dependent ultrasonic differentiation of normal and diffusely diseased liver
Authors: Lin T. , Ophir J. , Potter G.
Published: October 2005

The attenuation coefficient in 38 pathologically graded in vitro liver specimens was measured over a frequency range from 1.25–8 MHz and fitted to the power law model. The attenuation in the normal group (n=17) exhibited a frequency dependence of the form 0.399f1.139; in the mild disease group (n=13), it exhibited a dependence of the form 0.395f1.212; and in the moderate/severe disease group (n=8), it exhibited a dependence of the form 0.391f1.325. Using a Student’s t test, it is shown that, due to these differences in the frequency dependence, the statistical significance level at which the null hypothesis regarding the difference between the mean attenuation slopes of any two of these categories is rejected, is a strong function of frequency in the range of 1–4 MHz. The significance level relating to the difference between the normal and moderate/severe disease group is more than one order of magnitude better than the other categories. In all cases, no substantial improvement occurs beyond 4 MHz. It is also shown that attenuation slope values at 3 MHz confirm in vivo literature results obtained via different techniques.
Acoustic properties of ice edge noise in the Greenland Sea
Authors: Yang T. C. , Giellis G. R. , Votaw C. W. , Diachok O. I.
Published: October 2005

A towed array experiment was performed by NRL in 1982 in the vicinity of the ice edge in the Greenland Sea. The array was towed normal and parallel to and at ranges between 4–50 km from the ice edge; the received data were beamformed to study the horizontal directionality of the noise. The results indicated that a few localized ‘‘hot spots’’ (with dimensions <5 km) in the vicinity of the ice edge were the dominant noise sources. These sources persisted for nearly 1 day. The nominal separation between the hot spots was about 50 km. The ice edge noise spectrum measured at these ranges decreased 11–12 dB per octave with frequency between 100–500 Hz, as compared with the 6 dB per octave spectrum of ambient sea noise. Possible sources are hypothesized in the context of known eddy, wind, and wave effects in the vicinity of the ice edge.
Second harmonic component of a nonlinearly distorted wave in a focused sound field
Authors: Saito Shigemi , Kim Bong Chae , Muir Thomas G.
Published: October 2005

The second harmonic in a focused nonlinear field is examined with a numerical computation and with experiments done in water. The computation is accomplished by rewriting an expression derived by Lucas and Muir [J. Acoust. Soc. Am. 74, 1522–1528 (1983)] into a form appropriate for numerical computation at any point. The primary velocity distribution at the source is experimentally defined and utilized in the computation. The experiment is conducted with a 2-MHz focusing sound source consisting of a circular transducer coupled to an acoustic lens. The experimental values for amplitude and phase of the second harmonic component are in reasonable agreement with the theory. The second harmonic component focuses more sharply than the fundamental component, and the amplitude ratio of the second harmonic component to the fundamental component attains the maximum value at the focus. The results lead to an interpretation that the component generated in the focal region is the dominant contributor to the propagating second harmonic component.
A time domain formulation of the absorption limited transient parametric array
Authors: Stepanishen Peter R. , Koenigs Paul
Published: October 2005

The impulse response of the absorption limited transient parametric array is developed using a time-dependent Green’s function approach. A simple closed form expression is developed for the farfield spatial and time-dependent impulse response of the parametric array. Farfield pressures are expressed as a time convolution of the impulse response and a source function. Numerical results for the farfield pressures resulting from a Gaussian modulated carrier are presented to illustrate the spatial and time-dependent characteristics of the field. Additional numerical results are presented for the farfield pressures resulting from the pulsed excitation of a simple model of an ultrasonic transducer. These latter results are compared to existing experimental data and noted to be in general agreement.
Sound intensity in the nearfield of a point source over a hard reflecting plane
Authors: Krishnappa G.
Published: October 2005

Theoretical and experimental study of sound intensity in the nearfield of a point source over a hard reflecting boundary was performed. Theoretical analysis was carried out by extending the previously published theoretical work relating to the sound intensity in the nearfield of two interfering monopoles. Based on the method of images, the hard reflecting plane was replaced by an image source at a distance symmetrical to the boundary. Theoretical predictions were verified experimentally inside anechoic and semianechoic rooms using the two-microphone technique for measuring sound intensity. Both theoretical and experimental studies show similar trends, with the experimental results agreeing generally with the theoretical predictions within 1 dB.
Calculation of the surface pressure on a vibrating circular stretched membrane in free space
Authors: Streng J. H.
Published: October 2005

In this article, a method is presented for the calculation of the surface pressure on an edge-clamped vibrating circular stretched membrane in an infinitely extended homogeneous isotropic elastic medium. The coupled differential equations describing the (linear) rotationally symmetric membrane deflection and the (linear) wave propagation in the medium are solved simultaneously by the introduction of a series expansion of the surface pressure. The coefficients in this expansion may be calculated numerically by means of collocation, which is demonstrated for the case of an edge-clamped vibrating circular membrane in air.
On the measurement and interpretation of cavitation thresholds
Authors: Vaughan P. W. , Leeman S.
Published: October 2005

Some comments are made on a technique, proposed in a recent publication by Roy et al. [J. Acoust. Soc. Am. 78, 1799 (1985)], for precisely determining sonoluminescence thresholds in gassy (argonated) water exposed to ultrasound waves. It is suggested that their experimental evidence is not necessarily in accord with their view that sonoluminescence arises from ‘‘transient–violent’’ cavitational events. A mechanism based on shock excitation within the bubble is posited, and this can be operative at moderate ultrasound drive intensities.
Reply to ‘‘On the measurement and interpretation of cavitation thresholds’’ [J. Acoust. Soc. Am. 8
2, 690–691 (1987)]
Authors: Roy R. A. , Atchley A. A. , Crum L. A. , Fowlkes J. B. , Reidy J. J.
Published: October 2005

A reply is given to the comments made by Vaughan and Leeman [J. Acoust. Soc. Am. 82, XXX–XXX (1987)] on a previous article published by the authors [J. Acoust. Soc. Am. 78, 1799–1805 (1985)].
Author’s reply to recent comments on our effective medium theory
Authors: Gaunaurd G. C. , Überall H.
Published: October 2005

In his letter, in this issue [J. Acoust. Soc. Am. 82, XXX–XXX (1987)] Peter Scharnhorst (PS) states concerns in relation to an earlier effective medium theory of the present authors. This theory predicts the effective acoustic behavior of fluid and solid media with microinhomogeneities. Even though the present authors already gave this reply to PS in 1984, it is now provided here for the public record.
Spherical wave scattering by an elastic solid cylinder—A numerical comparison of an approximate theory with the exact theory
Authors: Piquette Jean C.
Published: October 2005

Numerical calculations based on an approximate theory for the problem of the scattering of a spherical wave by an elastic solid cylinder were presented in an earlier article [J. C. Piquette, J. Acoust. Soc. Am. 79, 1248–1259 (1986)]. Shortly after the appearance of this article, an exact theoretical formulation was discovered [H. P. W. Gottlieb, ‘‘On the general solution of the vector Helmholtz equation in cylindrical polar coordinates’’ J. Acoust. Soc. Am. 81, 1628–1629 (1987)]. In this letter, numerical calculations based on the exact theory are presented, and these are compared with both the approximate theory and with plane-wave theory. The calculations each involve a metallic scatterer immersed in a water medium. The approximate theory is found to give good qualitative predictions of the scattered wave in the vicinity of the scatter’s surface. The approximate theory is less reliable for increasing radial observation distances.
Extension of the Helmholtz integral equation method to shorter wavelengths II
Authors: Tobocman W.
Published: October 2005

In an earlier publication [J. Acoust. Soc. Am. 80, 1828 (1986)] the extension to the regime of shorter wavelengths of the Helmholtz integral equation method (HIEM) for calculating the scattering of acoustic waves by arbitrarily shaped targets was studied. That study was limited to values of ka less than 10 due to the limited computing facilities available to us. Having been given access to a more powerful computer, results for ka values up to 21 can now be reported. These calculations confirm the trends noted in the original calculation. The Schenck enhanced version of the HIEM [J. Acoust. Soc. Am. 44, 41 (1968)] gave excellent results at all wavelengths. The breakdown of the simple unenhanced HIEM at the characteristic wavelengths is seen to continue the trend of becoming less significant with decreasing wavelength. Even at the characteristic wavelengths, the unenhanced HIEM remains superior to the Kirchhoff approximation. As in our earlier calculations, it was found that the Schenck enhancement of the HIEM requires an increased expenditure of computing time of about 50%.
Effects of changes in absolute signal level on psychophysical tuning curves in quiet and noise in patas monkeys
Authors: Smith D. W. , Moody D. B. , Stebbins W. C.
Published: October 2005

Forward masking psychophysical tuning curves (PTCs) were measured in patas monkeys (Erythrocebus patas) at 2, 4, and 8 kHz at signal levels of 10, 30, and 60 dB SL in quiet, and at 10 dB above masked threshold in two levels of wideband noise. Absolute signal levels with masking approximated those at 30 and 60 dB SL in quiet. Results in quiet agree with those reported in the literature, demonstrating broadening of the PTC as signal level is increased. The PTCs measured in noise also demonstrated a similar broadening, or loss of selectivity, at higher SPLs. These later findings differ from those of a previous study [D. M. Green, B. R. Shelton, M. C. Picardi, and E. R. Hafter, J. Acoust. Soc. Am. 69, 1758–1762 (1981)] which used maskers to control the broadened excitation pattern in humans at levels of up to 34 dB above threshold. Differences in findings might be attributed to higher SPLs used in the present study. The data taken in noise backgrounds are not consistent with explanations for broadening based on an increase in the width of excitation patterns, but instead support the suggestion that the filter itself is nonlinear. Moreover, comparisons of PTCs in quiet and noise suggest that ‘‘off-frequency’’ listening acts at any given measurement level to artificially sharpen PTCs.
Derivation of primary parameters and procedures for use in speech intelligibility predictions
Authors: Pavlovic Chaslav V.
Published: October 2005

The literature on various parameters that appear in the articulation index-type calculations of speech intelligibility is reexamined. Based on the reported data, the best estimates of these parameters and the most appropriate procedures for their use are suggested. These included: (1) the analysis and specification of the importance of various frequency bands to speech intelligibility; (2) the procedures used for measuring threshold and the calculation of threshold-based parameters used for predicting intelligibility of low-level speech; and (3) the calculation and measurement of relevant speech parameters. All results are given so that the calculations can be performed either in critical bands, 1/3 octaves, or octaves.
On the relation between the growth of loudness and the discrimination of intensity for pure tones
Authors: Hellman R. , Scharf B. , Teghtsoonian M. , Teghtsoonian R.
Published: October 2005

The intensity jnd is often assumed to depend on the slope of the loudness function. One way to test this assumption is to measure the jnd for a sound that falls on distinctly different loudness functions. Two such functions were generated by presenting a 1000-Hz tone in narrow-band noise (925–1080 Hz) set at 70 dB SPL and in wideband noise (75–9600 Hz) set at 80 dB SPL. Over a range from near threshold to about 75 dB SPL, the loudness function for the tone is much steeper in the narrow-band noise than in the wideband noise. At 72 dB SPL, where the two loudness curves cross, the tone’s jnd was measured in each noise by a block up–down two-interval forced-choice procedure. Despite the differences in slope (and in sensation level), the jnd (ΔI/I) is nearly the same in the two noises, 0.22 in narrow-band noise and 0.20 in wideband noise. The mean value of 0.21 is close to the value of 0.25 interpolated from Jesteadt et al. [J. Acoust. Soc. Am. 61, 169–176 (1977)] for a 1000-Hz tone that had the same loudness in quiet as did our 72-dB tone in noise, but lay on a loudness function with a much lower slope. These and other data demonstrate that intensity discrimination for pure tones is unrelated to the slope of the loudness function.
Auditory duration discrimination in Old World monkeys (M
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s) and humans
Authors: Sinnott Joan M. , Owren Michael J. , Petersen Michael R.
Published: October 2005

Auditory duration DLs at 2.0 kHz were measured in Old World monkeys (Macaca, Cercopithecus) and humans using a go, no-go repeating standard AX procedure and positive reinforcement operant conditioning techniques. For a 200-ms standard, monkey DLs were 45–125 ms, compared to 15–27 ms for humans. Weber fractions (ΔT/T) for all species were smallest at standard durations of 200–400 ms and increased as standard duration decreased to 25 ms. Varying intensity from 30–70 dB SPL had only minor effects on DLs, except at the lowest levels tested, where DLs were elevated slightly. Monkeys had difficulty discriminating duration decrements, in contrast to humans. Results are discussed in relation to other comparative psychoacoustic data and primate vocal communication, including human speech.
Unit responses in ventral cochlear nucleus reflect cochlear coding of rapid frequency sweeps
Authors: Shore Susan E. , Clopton Ben M. , Au Yolande N.
Published: October 2005

This study examines the encoding of rapid frequency sweeps in single units of the ventral cochlear nucleus (VCN). Sweeps were designed to explore the role of cochlear mechanics in shaping the temporal responses across cells in the VCN. The time course of frequency change for rapidly rising frequency sweeps theoretically produced simultaneous displacement maxima by canceling travel time along the cochlear partition. Rising sweeps with longer time courses only partially canceled travel time, while falling sweeps had time courses of frequency change equal to or greater than travel time. Falling sweeps thus augmented normal travel time. Latency of unit firing to sweeps across unit characteristic frequency (CF) reflected cochlear delay-line mechanics. The latency-CF functions agreed with predictions from travel-time estimates for rising-frequency sweeps, but responses to falling sweeps were less predictable.
Wave propagation in a plate after impact by a projectile
Authors: El-Raheb M. , Wagner P.
Published: October 2005

The wave propagation in a circular plate after impact by a cylindrical projectile is studied. In the vicinity of impact, the pressure is computed numerically. An intense pressure pulse is generated that peaks 0.2 μs after impact, then drops sharply to a plateau. The response of the plate is determined adopting a modal solution of Mindlin’s equations. Velocity and acceleration histories display both propagating and dispersive features.
Theoretical treatment of acoustic emission sources in microfracturing due to disbonding
Authors: Ohtsu Masayasu , Yuyama Shigenori , Imanaka Takuichi
Published: October 2005

Theoretical treatment of acoustic emission (AE) source is investigated in the disbonding process of stainless steel overlay from base metal. Source representations of AE due to disbonding are studied in the simulation analysis based on a generalized theory. Taking into account a crack size, a point dislocation model for a tensile crack is considered as an AE source. The effects of crack shape and crack expansion on waveforms are clarified. Following Eshelby’s process, penny-shaped tensile cracks are mainly employed as AE sources due to disbonding. An attempt to estimate pressure of hydrogen intrusion suggests that preexisting infinitesimal flaws coalesce as a tensile crack in the disbonding process. The effect of crack orientation is studied by using a moment tensor representation. Since crack orientations can be determined from the eigenvalue analysis of a moment tensor, a technique to determine moment tensor components is applied to simulated waveforms due to inclined cracks. These results confirm that the theoretical treatment of AE waveform is useful for clarifying fundamental mechanisms of microfracturing.
High-frequency coherence functions propagated along ray paths in the inhomogeneous background of a weakly random medium: II—Higher moments
Authors: Mazar R. , Felsen L. B.
Published: October 2005

In a previous article [R. Mazar and L. B. Felsen, J. Acoust. Soc. Am. 81, 925–937 (1987)], it has been shown how the ray trajectories in the refracting background of a weakly fluctuating medium with large scale inhomogeneities can form the basis for propagating and evaluating the high-frequency two-point coherence function. Approximate results there, derived by a multiscale expansion technique, account for multiple isolated ray arrivals at observation points far from caustics, and blend smoothly into the transitional behavior due to closely adjacent rays near caustics. In the absence of fluctuations, this assertion has been verified by recovery of the isolated ordinary and uniform deterministic ray theory intensities, respectively, and it is therefore believed that our spectral construction properly describes the high-frequency two-point coherence function when randomness is included. The ray-based approach is now extended to multifrequency higher-order coherence functions. The new results are shown to recover the predictions from nonuniform and uniform ray theory when the fluctuations are removed, and they are also shown to yield previously obtained results for the special case of the two-frequency fourth moment in a homogeneous background. These checks lend confidence in the validity of the extended theory presented here.
Acoustic scattering in a homogeneous waveguide
Authors: Sammelmann Gary S. , Hackman Roger H.
Published: October 2005

The acoustic scattering from an elastic spherical shell in a homogeneous, range-independent waveguide is studied. New phenomena are observed that have no counterpart in free-field scattering. First, the free-field resonance spectrum exhibits fine structure, that is, the lth resonance splits into (l+1) distinct components. This splitting is most pronounced near the waveguide boundaries. Second, ‘‘superresonances’’ are observed. It is found that at certain water column heights and scatterer depths, significant enhancements of the resonance strength occur. In some cases, more than 100-fold enhancement is observed.
A study of reflection and refraction of waves at the interface of water and porous sea ice
Authors: Yew C. H. , Weng X.
Published: October 2005

Sea ice is modeled as a transversely isotropic brine-saturated porous medium in accordance with the model proposed by Schwarz and Weeks [J. Glaciol. 19, 499–531 (1977)]. The reflection and refraction of waves at the water–ice interface are studied. Numerical results indicate that the porosity of the ice has a noticeable effect on the wave reflectivity. Its effect, however, becomes small when the grazing angle of the incident wave becomes small. The existence of a thin and porous ice skeleton layer on the ice medium further reduces the reflectivity. The reduction of reflectivity becomes more distinct as the frequency of the incident wave increases. Numerical results point out that, in addition to the porosity, the ice layer thickness is the most dominant property influencing the under-ice wave reflectivity. The calculated results show a qualitative agreement with the in situ experimental results by Yang and Votaw [J. Acoust. Soc. Am. 70, 841–851 (1981)].
A Fourier approach to diffraction of pulsed ultrasonic waves in lossless media
Authors: Guyomar Daniel , Powers John
Published: October 2005

A method based on a Fourier domain approach is presented for computing the diffraction of a pulsed ultrasound wave from a rigidly baffled source in lossless media. The propagation from a planar source is dependent on the total impulse response which is just the Green’s function. Computing the spatial transform of the point spread function gives the propagation transfer function which multiplies the spatial spectrum of the spatial excitation to produce the spatial spectrum of the propagated wave. The propagation transfer function can then be considered to be a time-varying spatial filter. The results are valid for separable arbitrary time excitation and planar spatial distributions of the source. The solution is amenable to including the effects of a finite receiver. Results of different simulations using this method are included.
Response to ‘‘Comments on ‘Speed of sound in standard air’ ’’ [J. Acoust. Soc. Am. 8
2, 370–372 (1987)]
Authors: Wong George S. K.
Published: October 2005

This response addresses the comments of Greenspan and discusses the issue of allowance for gas imperfection by means of real gas data. The author agrees with Greenspan that the ‘‘traditional’’ method of calculating sound speed is ‘‘correct’’ as far as the method of calculation is concerned. However, the uncertainties of the above and similar calculations developed by previous air sound-speed investigators had not been reliably presented in the past, and Greenspan’s sound-speed data are practically identical to those obtained over 40 years ago. In light of more recent scientific data, some numerical values and constants have been redetermined during this time. The author reaffirms that the new sound speed c0=331.29 m s−1 is derived from today’s constants and for the standard atmosphere; and it is within the uncertainties associated with previous experimental measurements.
The ability of the California sea lion, Z
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Authors: Turl Charles W.
Published: October 2005

A California sea lion was trained to detect echoes from an underwater target that was ensonified by a sound source. Two cylinder targets located 10 m from the animal station could be ensonified separately. The sea lion was required to report whether the left target or the right target was being ensonified. The signal-to-noise ratio (S/N) was varied by decreasing the output voltage to the projector. A total of 1300 test trials were conducted at six levels. The sea lion’s performance decreased as the S/N decreased. At +3 dB S/N, the sea lion’s correct response threshold was 75%.
Response to Philip Lieberman’s letter [J. Acoust. Soc. Am. 8
, 1521–1522 (1986)]
Authors: Mehler Jacques
Published: October 2005

This letter is a response to a letter by Lieberman [J. Acoust. Soc. Am. 80, 1521–1522 (1986)].
Acoustic parameters measured by a formant-estimating speech processor for a multiple-channel cochlear implant
Authors: Blamey P. J. , Dowell R. C. , Clark G. M. , Seligman P. M.
Published: October 2005

In order to assess the limitations imposed on a cochlear implant system by a wearable speech processor, the parameters extracted from a set of 11 vowels and 24 consonants were examined. An estimate of the fundamental frequency EF0 was derived from the zero crossings of the low-pass filtered envelope of the waveform. Estimates of the first and second formant frequencies EF1 and EF2 were derived from the zero crossings of the waveform, which was filtered in the ranges 300–1000 and 800–4000 Hz. Estimates of the formant amplitudes EA1 and EA2 were derived by peak detectors operating on the outputs of the same filters. For vowels, these parameters corresponded well to the first and second formants and gave sufficient information to identify each vowel. For consonants, the relative levels and onset times of EA1 and EA2 and the EF0 values gave cues to voicing. The variation in time of EA1, EA2, EF1, and EF2 gave cues to the manner of articulation. Cues to the place of articulation were given by EF1 and EF2. When pink noise was added, the parameters were gradually degraded as the signal-to-noise ratio decreased. Consonants were affected more than vowels, and EF2 was affected more than EF1. Results for three good patients using a speech processor that coded EF0 as an electric pulse rate, EF1 and EF2 as electrode positions, and EA1 and EA2 as electric current levels confirmed that the parameters were useful for recognition of vowels and consonants. Average scores were 76% for recognition of 11 vowels and 71% for 12 consonants in the hearing-alone condition. The error rates were 4% for voicing, 12% for manner, and 25% for place.
Transient pressure fields of PVDF transducers
Authors: Hutchins D. A. , Mair H. D. , Taylor R. G.
Published: October 2005

The radiated pressure fields of pulsed polyvinylindene difluoride (PVDF) transducers have been determined experimentally, and compared to theory in three dimensions. The tranducers were in the form of disks, cones, or bowls, excited with a range of known transients in the form of gated sinusoidal voltages. It is demonstrated that good agreement is possible between theory and experiment, and it is shown that more marked interference effects occur as the duration of excitation tone burst is increased. It is also shown that PVDF transducers may be manufactured so as to behave as plane piston radiators.
Mode coupling and the environmental sensitivity of shallow-water propagation loss predictions
Authors: McDaniel Suzanne T. , McCammon Diana F.
Published: October 2005

Variations of seabed parameters, particularly the acoustic compressional velocity relative to that of the water column, have a very strong effect on the predicted magnitude of the propagated acoustic field. In many cases, the sensitivity of the predicted losses to the assumed seabed parameters is sufficiently severe to render the predictions meaningless. In this article, coupled-mode theory is employed to study how the presence of lateral seabed inhomogeneities affects this sensitivity. The dependence of predicted propagation losses on sediment sound speed is first examined for horizontally stratified sediments; then a rough layered structure of clay–silt interbedded with sand is assumed. With the introduction of rough sub-bottom layering, coupling occurs between modes, so that the conversion of energy into progressively higher-order modes, which attenuate rapidly, becomes an important loss mechanism. The extent to which acoustic energy penetrates the seabed and interacts with the sub-bottom inhomogeneities is governed by the sediment sound speed. Hence, the mode coupling that is induced is simply another loss mechanism dependent on sediment sound speed, leading to an increase in sensitivity to this parameter. Studies to determine the effect of inhomogeneous sediment layering on the transverse horizontal spatial coherence of the propagated field reveal that, even in the presence of mode coupling, the coherence remains high over many acoustic wavelengths, in agreement with measured data trends.
A postprocessing method for removing phase errors in the parabolic equation
Authors: Thomson David J. , Wood David H.
Published: October 2005

A method is presented for transforming numerical solutions of the standard parabolic equation of ocean acoustics into solutions of the Helmholtz equation. The method is based on an established integral transform [J. A. DeSanto, J. Acoust. Soc. Am. 62, 295–297 (1977)] that is exact for range-independent media. The Fourier–Bessel transform (with respect to range) of the Helmholtz equation is shown to be related to the Fourier transform of the parabolic equation by means of a nonlinear mapping between horizontal wavenumbers. As a result, fast field program (FFP) techniques can be applied to the Fourier transform of the solution to the standard parabolic equation to obtain an approximate solution to the Helmholtz equation. Several numerical examples are presented to illustrate this postprocessing approach to correcting the phase errors inherent in standard parabolic equation predictions.
Geoacoustic scattering from seafloor features in the ROSE area
Authors: Dougherty Martin E. , Stephen Ralph A.
Published: October 2005

A strong ‘‘refraction branch diffraction,’’ presumably due to scattering from a lateral heterogeneity on or below the seafloor, has been observed on ocean bottom hydrophone data from the Rivera Ocean Seismic Experiment (ROSE). This arrival is unusual because of its coherence and relatively large amplitude. Finite difference modeling of a number of possible seafloor diffractors and associated lateral velocity variations is presented, which demonstrates the occurrence and characteristics of ‘‘refraction branch diffractions.’’ In general, the half-width of the diffractor must be approximately the same as the seismic wavelength in order to produce a strong diffraction. Velocity gradients present in the models, as well as P–S conversion, complicate the wavelength–half-width relationship. Three different models, a hill, a valley, and a subsurface high-velocity block, all produced diffractions of sufficient amplitude to explain the data. There is a hill along the line with approximately the same dimensions as the model hill and it is the proposed source of the diffracted energy in the data. The large models used also clearly demonstrate the existence of phases that are theoretically possible but rarely seen in the marine seismic (geoacoustic) data such as the pseudo-Rayleigh wave and the P and S interference head waves.