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Dec 1985

Volume 78, Issue 6, pp. 1939-2166

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Viscoelastic modeling of canine vocalis muscle in relaxation

Fariborz Alipour‐Haghighi and Ingo R. Titze

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 1939-1943 (1985); (5 pages) | Cited 5 times

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Analysis of vocal fold vibration requires information on the viscoelastic properties of the vocalis muscle. The force response of two canine vocalis muscles was measured in one‐dimensional, stepwise elongation of the tissue as a function of time with a computer‐controlled ergometer. The viscoelastic behavior of the muscle in its passive state was demonstrated through the relaxation test. A quasilinear viscoelastic model was used to parametrize the relaxation function, and results are reported for various levels of strain. Furthermore, a model was used to obtain theoretical time‐dependent stress–strain curves to compare with experimental data.
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43.70.Aj Anatomy and physiology of the vocal tract, speech aerodynamics, auditory kinetics

Contextual effects on lingual–mandibular coordination

Jan Edwards

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 1944-1948 (1985); (5 pages)

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Coordination between intrinsic and jaw‐related components of tongue blade movement during the articulation of the alveolar consonant /t/ was examined across changes in phonetic context. Tongue–jaw interactions included compensatory responses of one articulatory component to a contextual effect on the position of the other articulatory component. A similar reciprocity has been observed in studies that introduced artificial perturbation of jaw position and studies of patterns of token‐to‐token variability. Thus the lingual–mandibular complex seems to respond in a similar manner to at least some natural and artificial perturbations.
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43.70.Aj Anatomy and physiology of the vocal tract, speech aerodynamics, auditory kinetics
43.70.Bk Models and theories of speech production

Contextual effects on vowel duration, closure duration, and the consonant/vowel ratio in speech production

Paul A. Luce and Jan Charles‐Luce

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 1949-1957 (1985); (9 pages) | Cited 5 times

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Acoustic measurements were conducted to determine the degree to which vowel duration, closure duration, and their ratio distinguish voicing of word‐final stop consonants across variations in sentential and phonetic environments. Subjects read CVC test words containing three different vowels and ending in stops of three different places of articulation. The test words were produced either in nonphrase‐final or phrase‐final position and in several local phonetic environments within each of these sentence positions. Our measurements revealed that vowel duration most consistently distinguished voicing categories for the test words. Closure duration failed to consistently distinguish voicing categories across the contextual variables manipulated, as did the ratio of closure and vowel duration. Our results suggest that vowel duration is the most reliable correlate of voicing for word‐final stops in connected speech.
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43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Release from masking caused by envelope fluctuations

Søren Buus

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 1958-1965 (1985); (8 pages) | Cited 51 times

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This paper examines how short‐term energy fluctuations in a masker affect the thresholds for tones at frequencies above those of the masker. Two equally intense tones at 1060 and 1075 Hz produce up to 25 dB less masking than does a 1075‐Hz tone set to the overall level of the two‐tone complex. At wider frequency separations, two‐tone complexes also produce less masking than the pure tone. These results indicate that envelope fluctuations in a masker, whose spectrum is confined to a single critical band, may result in release from masking. The release from masking probably is related to the comodulation masking release reported by Hall et al. [J. Acoust. Soc. Am. 76, 50–56 (1984b)] for modulated‐noise maskers with bandwidths greater than one critical band. Further measurements with maskers, whose intensity level in the critical band around 1 kHz was 90 dB SPL, show similar masking by a pure tone and a 625‐ to 1075‐Hz bandpass noise, but less masking by narrow‐band noises. These results are inconsistent with a simple frequency selective energy‐detector model and indicate that the auditory system can use periods of low masker energy as brief as a few ms to enhance detection of a tone. The results also imply that the upward spread of excitation is best represented by masking patterns for noises with bandwidths of several critical bands.
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43.66.Dc Masking
43.66.Ba Models and theories of auditory processes

Stimulus parameters governing confusion effects in forward masking

Donna L. Neff

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 1966-1976 (1985); (11 pages) | Cited 24 times

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In forward masking, performance may be affected by confusion, that is, by the difficulty of discriminating a suprathreshold signal from the preceding masker. This study investigated confusion effects for forward maskers composed of repeated bursts of a 1000‐Hz sinusoid followed by sinusoidal signals; such ‘‘pulsing’’ maskers produce confusion when the properties of the signal are identical to those of an individual masker ‘‘pulse.’’ The level, frequency, and duration of the signal relative to an individual masker pulse, as well as offset–onset delay, were varied to determine the minimum change necessary to eliminate confusion. For maskers composed of 20‐ms pulses, confusion was eliminated by changes in signal level of 5 dB or changes in signal frequency of 30 to 40 Hz. For maskers composed of 10‐, 20‐, or 40‐ms pulses, confusion was eliminated by signal delays of 8 to 16 ms or by signal durations less than half or greater than twice the masker‐pulse duration. Results with adaptive procedures designed to measure confusion‐free or confusion‐determined thresholds suggest that confusion effects can be minimized or avoided by extensive listener training with a procedure in which the signal and masker are not presented at similar intensities.
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43.66.Dc Masking
43.66.Fe Discrimination: intensity and frequency
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Frequency and intensity discrimination in humans and monkeys

Joan M. Sinnott, Michael R. Petersen, and Steven L. Hopp

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 1977-1985 (1985); (9 pages) | Cited 4 times

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Frequency and intensity DLs were compared in humans and monkeys using a repeating standard ‘‘yes–no’’ procedure in which subjects reported frequency increments, frequency decrements, intensity increments, or intensity decrements in an ongoing train of 1.0‐kHz tone bursts. There was only one experimental condition (intensity increments) in which monkey DLs (1.5–2.0 dB) overlapped those of humans (1.0 –1.8 dB). For discrimination of both increments and decrements in frequency, monkey DLs (16–33 Hz) were approximately seven times larger than those of humans (2.4–4.8 Hz), and for discrimination of intensity decrements, monkey DLs (4.4–7.0 dB) were very unstable and larger than those of humans (1.0 –1.8 dB). For intensity increment discrimination, humans and monkeys also exhibited similar DLs as SL was varied. However, for frequency increment discrimination, best DLs for humans occurred at a high (50 dB) SL, whereas best DLs for monkeys occurred at a moderate (30 dB) SL. Results are discussed in terms of various neural mechanisms that might be differentially engaged by humans and monkeys in performing these tasks; for example, different amounts of temporal versus rate coding in frequency discrimination, and different mechanisms for monitoring rate decreases in intensity discrimination. The implications of these data for using monkeys as models of human speech sound discrimination are also discussed.
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43.66.Fe Discrimination: intensity and frequency
43.66.Gf Detection and discrimination of sound by animals
43.66.Ba Models and theories of auditory processes

Frequency and intensity discrimination in human infants and adults

Joan M. Sinnott and Richard N. Aslin

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 1986-1992 (1985); (7 pages) | Cited 2 times

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Frequency and intensity DLs were measured in 26 human infants (ages 7–9 months) and six young adults using a repeating standard ‘‘yes–no’’ operant headturning technique and an adaptive staircase (tracking) psychophysical procedure. Subjects were visually reinforced for responding to frequency increments, frequency decrements, intensity increments, or intensity decrements in an ongoing train of 1.0‐kHz tone bursts, and stimulus control was monitored using randomly interleaved probe and catch trials. Infants were easily conditioned to respond to both increments and decrements in frequency, and DLs ranged from 11–29 Hz, while adult DLs ranged from 3–5 Hz. Infants also easily discriminated intensity increments, and DLs ranged from 3–12 dB, while adult DLs ranged from 1–2 dB. No infants successfully discriminated intensity decrements, although adults experienced no difficulty with this task and produced DLs similar to those for increments. The apparent inability of infants to discriminate intensity decrements suggests that the infant CNS may not be well adapted to monitor rate decreases in populations of peripheral auditory neurons.
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43.66.Fe Discrimination: intensity and frequency
43.66.Ba Models and theories of auditory processes

Pitch discrimination of harmonic complex signals: Residue pitch or multiple component discriminations?

Andrew Faulkner

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 1993-2004 (1985); (12 pages) | Cited 6 times

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Two models for pitch discrimination of harmonic complex sounds are discussed, a multiple‐band probability summation model using comparisons among component frequencies, and a model in which residue pitches are compared. The second model is based on Goldstein’s optimum‐processor pitch theory [J. Acoust. Soc. Am. 54, 1496–1516 (1973)], and is distinguished from the multiple‐band model by an internal noise process. Pitch difference limens from 2I2AFC tasks show that when the test signals comprise corresponding harmonics, relative pitch difference limens are less than the smaller relative difference limens for the component frequencies, which is consistent with the multiple‐band model. The absence of corresponding harmonics significantly reduces relative pitch discriminability; this effect supports the model on Goldstein’s theory. It appears that residue pitch comparisons are not used for pitch discrimination between sounds with corresponding components; rather, comparisons based on residue pitch are only employed where there are no common resolved components in the signals to be discriminated.
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43.66.Hg Pitch
43.66.Fe Discrimination: intensity and frequency
43.66.Ba Models and theories of auditory processes

Accuracy, latency, and listener‐search behavior in localization in the horizontal and vertical planes

William Noble and Anne Gates

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2005-2012 (1985); (8 pages)

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Thirty‐six listeners localized continuous filtered noise bursts centered on 2.3 or 8.3 kHz under normal listening conditions or while wearing earmuffs. The noise bursts were from any one of 20 loudspeakers, 18° apart, visible to the listeners, and arranged in the horizontal and vertical planes. Listeners were free to move, while remaining seated, throughout all trials. The noise bursts were terminated by the listeners. Measures of accuracy and latency showed that earmuff listening had a significant effect whereas, overall, signal frequency had no significant effect. There was, however, an apparent downward shift of the 2.3‐kHz signals presented above the midline in the vertical plane. Analysis of video records of listeners’ behavior revealed a strong tendency for initial orientation by head or eye movement to correlate with final response, even when both were inaccurate. The paradigm adopted in this latter aspect of the study illustrates an ‘‘ecological’’ approach to the study of auditory phenomena.
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43.66.Qp Localization of sound sources

Ultrasonic background noise in industrial environments

Henry E. Bass and Lee N. Bolen

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2013-2016 (1985); (4 pages) | Cited 3 times

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Ultrasonic noise associated with various manufacturing operations has been measured in the frequency range 0–1 MHz in order to evaluate typical noise environments for ultrasonically controlled robots. Industrial operations studied include impact, bending, grinding and drilling, laser etching, and high‐velocity fluid or air sprays. The first three operations provide little ultrasonic energy above 100 kHz. For these processes, ultrasonic sensors operating above 100 kHz should have an advantage since signal and noise will both fall off with increasing frequency. Ultrasonic emission from laser etching was found to be quite broadband, making such processes less suitable for ultrasonic control. High‐velocity fluid or air sprays are the most prevalent sources of ultrasonic noise. The noise from these sources rolls off slowly with frequency, and no frequency bands without noise exist for ultrasonic sensing below several hundred kHz. For applications requiring ultrasonic sensing, aerodynamic noise should be reduced.
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43.50.Jh Noise in buildings and general machinery noise
43.50.Nm Aerodynamic and jet noise

Prediction of the effectiveness of noise control treatments in urban rail elevated structures

Paul J. Remington and Larry E. Wittig

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2017-2033 (1985); (17 pages)

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An analytical model is presented for the generation of noise from an open tie deck elevated structure during the passage of a train. Predictions are compared with measurements before and after installation of resilient fasteners. The model is found to be reasonably accurate, predicting an A‐weighted sound level reduction of approximately 2 dB less than actually occurs. The analytical model is then used to estimate the noise reduction achievable through a variety of noise reduction techniques. Resilient rail fasteners seem to be the most promising technique, offering an A‐weighted sound level reduction of nearly 10 dB.
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43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles
43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.

Response of a compliant slab to inviscid incompressible fluid flow

Cahit A. Evrensel and Arturs Kalnins

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2034-2041 (1985); (8 pages) | Cited 1 time

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The dynamics of harmonic wave trains on the interface between a compliant slab and the flow of an inviscid fluid is explored theoretically. The slab is treated as an infinite, elastic or viscoelastic solid of finite thickness, bonded to a rigid half‐space. The viscoelastic behavior is modeled by an isotropic Voigt constitutive model. The two media are coupled through stress and velocity, normal to the surface of the slab. The proposed mathematical model is used to predict the appearance of unstable surface waves of the coating.
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43.40.Dx Vibrations of membranes and plates
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties

A method for solving free vibration problems of three‐layered plates with arbitrary shape

Krzysztof Poltorak and Kosuke Nagaya

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2042-2048 (1985); (7 pages) | Cited 2 times

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This paper deals with a method for solving free vibration problems of three‐layered isotropic plates of arbitrary shape with clamped edges. The direct solution of the Yan and Dowell equation of motion, in terms of Bessel functions, is found. The boundary problem is solved by means of the Fourier expansion collocation method. Nondimensional frequency parameters for circular, elliptical, square, and triangular plates with clamped edges are calculated for a wide range of dimension ratios and two typical material configurations. The validity of the method is also discussed.
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43.40.Dx Vibrations of membranes and plates

The approximation of pressure waveforms of impact sound radiation from clamped circular plates of various thicknesses

Toshio Takahagi and Mikio Nakai

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2049-2057 (1985); (9 pages) | Cited 1 time

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The purpose of this paper is to investigate the mechanism of impact noise generation, in order to reduce noise at its source. A fundamental model, the case of a ball striking a clamped circular plate, was studied. In the experiments, the effects of plate thickness and observation distance on sound pressure were observed. In the theoretical analysis, the rotary inertia of the plate, shear deformation, and the air reaction of the radiated sound were considered. The impact force history was assumed to be a triangular pulse, since it was determined by three parameters: the maximum impact force, the impact duration, and the rise time. The time when the maximum sound pressure occurred, the influence of the rise time on the sound pressure level, and the vibrational modes which contributed to the sound were obtained using this approximation.
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43.40.Dx Vibrations of membranes and plates

Panel vibration damping due to sound‐absorbing liners

A. Trochidis

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2058-2060 (1985); (3 pages)

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A mechanism of panel vibration damping due to the addition of absorbing liners is discussed. An expression for the loss factor associated with the described damping mechanism is derived. It predicts satisfactorily not only the observed damping but also its dependence on the vibration frequency, the acoustical impedance of the sound‐absorptive material, and the separation distance between the panel and absorbing liner surfaces.
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43.40.Dx Vibrations of membranes and plates
43.40.At Experimental and theoretical studies of vibrating systems

A technique for measurement of structure‐borne intensity in plates

Earl G. Williams, Henry D. Dardy, and Richard G. Fink

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2061-2068 (1985); (8 pages) | Cited 5 times

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A measurement technique to determine the structure‐borne intensity (power flow) in a point‐driven, fluid‐loaded, homogeneous thin plate is demonstrated. This intensity is uniquely determined from a knowledge of the normal velocity of the surface of a sinusoidally driven plate. A noncontact method is presented which uses a scanning hydrophone to measure the pressure in a plane very close to the source. It is shown how this pressure measurement is sufficient to compute the two‐dimensional structural intensity vector inside the plate. We call this technique SIMAP for Structural Intensity from the Measurement of Acoustic Pressure. Uses of the structural intensity vectors to compute the power injected into the plate from a point driver are shown. Independent measurement of injected mechanical power is shown to be in close agreement. SIMAP, which is an outgrowth of nearfield acoustical holography (NAH), also provides the normal acoustic intensity radiated into the medium from the same pressure measurement. A comparison of the structure‐borne intensity with this normal acoustic intensity indicates that structural intensity is much more accurate in locating the real source than the acoustic intensity, the latter often failing completely. The examples given in this paper are for an underwater source, but the technique applies without modification to plate sources in air.
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43.40.Dx Vibrations of membranes and plates
43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance

Nonlinear frequency shifts in quasispherical‐cap shells: Pitch glide in Chinese gongs

N. H. Fletcher

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2069-2073 (1985); (5 pages) | Cited 2 times

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The large‐amplitude vibrational behavior of a shallow spherical‐cap shell is investigated theoretically using simple arguments. The results of this approximate analysis are expressed in the form of appealingly simple nondimensional quantities. It is shown that the frequency of the fundamental mode of such a shell falls by as much as 50% as the vibration amplitude is increased to approximately the shell depth. For even larger amplitudes the frequency rises, and it exceeds the small‐amplitude frequency when the amplitude is more than about twice the shell depth. The influence of shell thickness is considered and increasing thickness is shown to decrease the frequency shift. This analysis is shown to account for the pitch glide behavior of certain Chinese opera gongs.
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43.40.Ey Vibrations of shells
43.40.Ga Nonlinear vibration
43.75.Kk Bells, gongs, cymbals, mallet percussion, and similar instruments

Laser‐induced thermoacoustic radiation

Yves H. Berthelot and Ilene J. Busch‐Vishniac

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2074-2082 (1985); (9 pages) | Cited 4 times

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When an intensity‐modulated laser beam illuminates a column of water, it produces, via thermal expansion, a highly directive sound beam. The pressure field radiated by such a thermoacoustic source is analyzed, first by determining the impulse response of the system. The thermoacoustic pressure is then expressed as a convolution between the impulse response and the time derivative of the laser intensity. The analysis is valid in both the nearfield and the farfield of the source and, in principle, for any spatial or temporal distribution of the laser intensity. This approach provides valuable insight into the nearfield of this type of transducer. Resulting theoretical predictions of pressure waveforms and directivity patterns compare well to experimental results, and agree in the farfield limit with existing farfield analyses of thermoacoustic radiation.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration

The ultrasonic field of a Gaussian transducer

Gonghuan Du and M. A. Breazeale

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2083-2086 (1985); (4 pages) | Cited 2 times

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A transducer is described which produces a Gaussian distribution of amplitudes along a radial dimension. The ultrasonic beam produced by this transducer is examined both experimentally and mathematically and is shown to have none of the zeros of amplitude in the Fresnel region, and none of the secondary maxima in the Fraunhofer region characteristic of the piston transducer. Applications both to verification of physical theories and to nondestructive evaluation situations are mentioned.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
43.38.Ar Transducing principles, materials, and structures: general

A simple shallow water propagation model including shear wave effects

Dale D. Ellis and D. M. F. Chapman

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2087-2095 (1985); (9 pages) | Cited 4 times

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The Pekeris model has proved to be very useful in describing some features of acoustic propagation in shallow water, and as a simple test of ideas in normal mode theory. The basic model consists of a homogeneous layer of fluid overlying an infinite homogeneous fluid half‐space of greater sound speed. Here, we extend the Pekeris model to handle the case of a fluid overlying an elastic basement in which the shear speed is less than the (compressional) speed of sound in the fluid. This gives rise to leaky modes in which both the mode eigenfunctions and eigenvalues are complex. The model predictions are compared to some measured propagation losses for a shallow water site overlying a chalk bottom, where compressional to shear wave conversion at the water–chalk interface causes large losses. The predictions of the simple model explain the very high losses measured at frequencies less than 200 Hz. At higher frequencies the sound‐speed profile, absorption of sound by the water, and the effects of a thin sediment layer become important, but then an all‐fluid normal mode model is in agreement with the measured results.
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43.30.Bp Normal mode propagation of sound in water
43.20.Bi Mathematical theory of wave propagation

Investigation of lightning strikes to water surfaces

R. D. Hill

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2096-2099 (1985); (4 pages)

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Recent experiments by Arnold et al. [J. Acoust. Soc. Am. 76, 320–322 (1984)] established that cloud‐to‐water lightning generates acoustic pulses in the ocean. In this paper, the connection of a lightning stroke with an ocean surface is analyzed, and a blow‐off mechanism is proposed for the acoustic pulse generation process.
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43.30.Bp Normal mode propagation of sound in water
43.30.Lz Underwater applications of nonlinear acoustics; explosions
92.10.Vz Underwater sound
92.60.Pw Atmospheric electricity, lightning

On the acoustic response of a deeply corrugated periodic surface— A hybrid T‐matrix approach

Akhlesh Lakhtakia, Vijay K. Varadan, and Vasundara V. Varadan

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2100-2104 (1985); (5 pages)

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The extended boundary condition (EBC) method, as proposed by Waterman [J. Acoust. Soc. Am. 57, 791–802 (1975)], is hybridized with the point‐matching technique in order to derive a T matrix for a periodically corrugated surface on which either the Dirichlet or the Neumann boundary condition is imposed. The limitations imposed by the Rayleigh hypothesis on Waterman’s T matrix are overcome by a correct choice of eigenfunctions for the surface field representation. Highly corrugated surfaces can now be considered. The numerical results are compared with the data computed by Holford [J. Acoust. Soc. Am. 70, 1116–1128 (1981)], using an integral equation method, as well as with the experimental results collected by Lacasce and Tamarkin [J. Appl. Phys. 27, 138–148 (1956)].
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43.30.Dr Hybrid and asymptotic propagation theories, related experiments
43.35.Pt Surface waves in solids and liquids
43.20.Bi Mathematical theory of wave propagation
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties

A fast field model for three‐dimensional wave propagation in stratified environments based on the global matrix method

H. Schmidt and J. Glattetre

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2105-2114 (1985); (10 pages) | Cited 9 times

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A three‐dimensional fast field program (FFP) model based on the global matrix method will be presented. Compared to traditional propagator matrix methods, the global matrix method allows for a more efficient, and, furthermore, numerically stable computation. The three‐dimensional expansion does not restrict sources to be on the center axis, but allows for an arbitrary source geometry—as opposed to earlier two‐dimensional versions. As a consequence, the solution includes simultaneously both vertically and horizontally polarized shear waves. A mathematical description will be given and the numerical aspects will be discussed. Some of the features of the model will be illustrated in two test cases: free‐space and shallow water with strongly reflecting bottom. The free‐space case shows that the three‐dimensional solution gives results identical to those obtained by the two‐dimensional model except for ranges close to the axis r≡0 of a cylindrical coordinate system. For the shallow water case, the well‐known energy transportation in discrete modes above critical wavenumber is first demonstrated. Then the model is used to analyze the field radiated by a long horizontal array, and it is shown that different modes will propagate in slightly different directions.
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43.30.Bp Normal mode propagation of sound in water
43.20.Bi Mathematical theory of wave propagation

Measurements of the acoustic backscatter of manganese nodules

Marco M. P. Weydert

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2115-2121 (1985); (7 pages)

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The acoustic backscatter of eight well‐curated ferromanganese nodules has been measured in 1 °C seawater at frequencies from 45 to 167 kHz. The nodules have diameters from 37 to 121 mm and are thought to be representative of the Cu–Ni–Co‐rich nodules from the area around 14° 40′ N, 125° 25′ W (DOMES site C). They had been collected in box cores on the Echo 1 expedition and were kept refrigerated and water soaked in air‐tight plastic bags. Acoustic backscatter variations of over 10 dB were observed while the nodule was rotated 10° to 30° about one of its principal axes. The complicated fine structure, as well as the target strength, makes it clear that nodules cannot be modeled as simple spheres.
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43.30.Bp Normal mode propagation of sound in water
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries
91.60.Lj Acoustic properties

Rectified heat transfer in vapor bubbles

G. M. Patel, R. E. Nicholas, and R. D. Finch

J. Acoust. Soc. Am. Volume 78, Issue 6, pp. 2122-2131 (1985); (10 pages) | Cited 3 times

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Some experimental findings on the dynamics of vapor bubbles in ultrasonic fields are reviewed. In particular, attention is drawn to a phenomenon which might be described as ultrasonically stimulated boiling. There is also a summary of certain pertinent facts about the threshold of cavitation in liquids with low foreign gas content, such as liquid nitrogen or liquid helium. It is emphasized that threshold pressure amplitudes can be less than the static pressure. It is proposed that an explanation of these observations could lie in a net positive heat transfer into a pulsating bubble. The minimum amplitude required to cause such a ‘‘rectified’’ heat transfer is calculated.
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43.25.Yw Nonlinear acoustics of bubbly liquids
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