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Dec 1981

Volume 70, Issue 6, pp. 1561-1819

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Piezoelectricity, its history and applications

Warren P. Mason

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1561-1566 (1981); (6 pages) | Cited 3 times

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This is the 100th anniversary of the discovery of the piezoelectric effect by the brothers Curie. While this was a scientific curiosity for the next third of a century, with the work of Langevin it produced one of the principal electromechanical transducer effects. Quartz, first used as a transducer, also received wide use in controlling oscillators and in selective wave filters. Quartz was soon replaced by Rochelle salt for transducers. This is a rather unstable crystal, which, however, was the first ferroelectric having an intrinsic polarization between its two Curie temperatures. A theory of this effect was given by the writer. Most crystal transducers have been replaced by ferroelectric ceramics. A material somewhat similar to a ferroelectric is an electret. These have become very useful in transmitters and receivers. Finally, thin films of piezoelectric crystals are useful for producing high frequencies in such devices as the acoustic microscope.
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43.38.Fx Piezoelectric and ferroelectric transducers
77.65.-j Piezoelectricity and electromechanical effects
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Electroelastic interactions and the piezoelectric equations

H. F. Tiersten

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1567-1576 (1981); (10 pages) | Cited 4 times

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The relation between the equations of linear piezoelectricity and the more general nonlinear electroelastic equations is discussed. The influence of nonlinear deformation theory and rotational invariance is noted. The linear equations for small dynamic fields superposed on a static bias are presented. An equation for the perturbation of the eigenvalue of the piezoelectric solution due to a bias is exhibited. Some applications of the perturbation equation are given.
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43.38.Fx Piezoelectric and ferroelectric transducers
77.65.-j Piezoelectricity and electromechanical effects
43.40.Ga Nonlinear vibration
43.40.At Experimental and theoretical studies of vibrating systems

Wave propagation and resonance in piezoelectric materials

B. A. Auld

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1577-1585 (1981); (9 pages) | Cited 3 times

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The two basic physical phenomena involved in all piezoelectric devices are wave propagation and resonance. A general review is first presented of the connection between piezoelectricity and crystal symmetry, noting that a recent arrival on the scene (ferroelasticity) is intimately related to crystal symmetry rules for piezoelectricity and promises to be applicable to new devices in the future. Special features peculiar to wave propagation in piezoelectric materials are noted and a brief sketch is given of methods used for solving piezoelectric boundary value problems.
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43.38.Fx Piezoelectric and ferroelectric transducers
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.65.-j Piezoelectricity and electromechanical effects
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

Piezoelectric ceramics: Characteristics and applications

Don Berlincourt

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1586-1595 (1981); (10 pages) | Cited 6 times

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Piezoelectric ceramics have been used for a little over 30 years. The first piezoelectric ceramic was barium titanate and it is still used. The lead titanate zirconate ceramics were introduced about 1955 and quickly became the most widely used piezoelectric material. Compositions were developed for many specific applications, as the strength of ferroelectricity in lead titanate zirconate allowed major chemical modification. The development and characteristics of these materials are described and applications are reviewed. Major emphasis is placed on consumer applications, as it is these that account for the major business in piezoelectric ceramic materials.
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43.38.Fx Piezoelectric and ferroelectric transducers
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.65.-j Piezoelectricity and electromechanical effects

Piezoelectricity in polyvinylidenefluoride

G. M. Sessler

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1596-1608 (1981); (13 pages) | Cited 22 times

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A review of the physical properties of polyvinylidenefluoride (PVDF) with particular emphasis on its piezoelectric activity is given and the applications of this material are discussed. PVDF is a semicrystalline polymer whose crystalline domains appear in four different forms. These forms may be interconverted by the application of heat, electrical fields, and pressure. Thermal poling or corona poling will orient the molecular dipoles in the crystalline parts and thus yield a permanent polarization. This polarization causes, by means of differences in the dielectric and elastic properties of the amorphous and crystalline parts, the piezoelectricity of PVDF. The piezoelectric constant d31 reaches values of about 35 pC/N at room temperature. At decreasing temperatures a drop of d31 and d33 is observed. Compared to other piezoelectric materials, PVDF has such unique properties as flexibility, ruggedness, availability as thin films, and low acoustic impedance, but a somewhat smaller electromechanical coupling factor. Applications of PVDF are in transducers for audiofrequency, ultrasonic, underwater, and electromechanical use and in pyroelectric and optical devices.
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43.38.Fx Piezoelectric and ferroelectric transducers
77.65.-j Piezoelectricity and electromechanical effects

Piezoelectricity in thin film materials

Norman F. Foster

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1609-1614 (1981); (6 pages)

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The need for efficient ultrasonic transducers in the 100 MHz to several GHz frequency range has stimulated the development of a number of transducer structures using piezoelectric thin films. Starting in the early 1960’s with primarily longitudinal bulk mode transduction in CdS films, the piezoelectric thin film transducer technology has progressed over the years to the controlled generation and detection of both longitudinal and shear waves in films of CdS, ZnO, and other materials. While most of the early work was directed towards bulk waves, the more recent strong interest in SAW devices has encouraged the use of piezoelectric thin films, primarily ZnO, in this arena also. A combination of experimental work and theoretical studies has generated a rather comprehensive understanding of the structure and behavior of piezoelectric thin films for both bulk and surface wave applications.
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43.38.Fx Piezoelectric and ferroelectric transducers
77.55.-g Dielectric thin films
77.65.-j Piezoelectricity and electromechanical effects
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Laryngeal adjustments in the production of consonant clusters and geminates in American English

Hirohide Yoshioka, Anders Löfqvist, and Hajime Hirose

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1615-1623 (1981); (9 pages) | Cited 1 time

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The glottal opening gesture and its timing control in various sequences of voiceless obstruents were investigated by the combined techniques of electromyography, photo‐electric glottography, and fiberoptic endoscopy. The results obtained at both electromyographic and movement levels revealed that the glottal opening gesture is characterized by a one‐, two‐, or more‐than‐two‐peaked pattern in a regular fashion according to the phonetic nature of the voiceless segments: each voiceless obstruent or geminate accompanied by aspiration or frication noise tends to require a single separate peak of the opening gesture, while an unaspirated stop embedded in a voiceless environment can be produced within the opening gesture attributed to an adjacent aspirated stop or fricative. Such an independent opening gesture of the glottis for the production of voiceless aspirated stops or voiceless fricatives even in sequentially unvoiced contexts can be interpreted as assuring the aerodynamic requirements for turbulent noise production during the aspirated stop or fricative segment.
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43.70.Bk Models and theories of speech production
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation
43.72.Ar Speech analysis and analysis techniques; parametric representation of speech

Recognition of the Spanish fricatives /s/ and /f/

Jorge A. Gurlekian

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1624-1627 (1981); (4 pages) | Cited 2 times

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The present work examines the role played by the amplitude of a fricative noise relative to the vowel /a/ in the identification of the fricatives /f/ and /s/. Synthetic fricative–vowel syllables were generated in which the fricative portion consisted of bandpass noise with a center frequency of 4500 Hz and a bandwidth of 500 Hz. The amplitude of the noise was varied through a set of ten values relative to a fixed vowel amplitude. Spanish and American speaking listeners identified syllables with low amplitude fricative noise as /fa/ and those with high amplitude as /sa/. In a second experiment, subjects were tested on the same stimuli at three different overall sound pressure levels for the vowels: 40, 60, and 80 dB SPL re 0.0002 dyn/cm2. At the 40‐ and 80‐dB levels, subjects identified more sounds as /f/ than at the 60‐dB level. The responses obtained at 80 dB SPL may be due to a differential masking effect of the vowel at different amplitudes.
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43.70.Dn Disordered speech
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Loudness (or annoyance) summation of combined community noises

Birgitta Berglund, Ulf Berglund, Mikael Goldstein, and Thomas Lindvall

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1628-1634 (1981); (7 pages) | Cited 3 times

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The purpose of the experiment was to study how the loudness (or annoyance) of the constituents in pairs of community noises combines into total loudness (or total annoyance). Three community noises (pile driving, jack hammering, street traffic) were combined pairwise at different sound levels. The observers judged the total loudness of the combined noises as well as the loudness of each component noise when heard alone. Three models of loudness (or annoyance) summation for noise were tested: a vector summation model, a model assuming that the loudnesses of the masked constituent noises add arithmetically, and a simple model stating that the total loudness equals the loudest of the component noises when heard alone. All three models fitted the data satisfactorily from a statistical point of view. The ’’loudest component’’ model was favored because it produced a prediction error of only 14% in the ’’worst case’’ and can, therefore, serve as a ’’rule of thumb’’ for many practical purposes.
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43.66.Cb Loudness, absolute threshold
43.50.Qp Effects of noise on man and society

Re‐examination of the low‐frequency (50–1000 Hz) normal threshold of hearing in free and diffuse sound fields

E. H. Berger

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1635-1645 (1981); (11 pages) | Cited 3 times

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In two experimental replications involving a total of 17 otologically normal subjects, hearing threshold levels were observed that were from 2.6 to 7.1 dB less sensitive in the 125–1000 Hz frequency range, than those specified in ISO R226–1961. The published data from 12 additional threshold experiments conducted since 1933 were reviewed. Variables that could affect the data, such as free versus diffuse sound fields, pure tones versus 1/3‐octave noise band stimuli, psychophysical method, pulsed versus continuous stimuli, binaural versus monaural listening, age, sex, race, and otological rejection criteria, were analyzed. For frequencies from 50–1000 Hz and ages up to 35, the only corrections found to be necessary were for sound field conditions and binaural versus monaural listening. A second‐order polynomial regression line was fitted to the combined, corrected data. The resultant thresholds were 5–6 dB less sensitive than ISO R226 between 50 and 250 Hz, with the divergence dropping to +1.7 and −1.5 dB at 500 and 1000 Hz, respectively.
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43.66.Cb Loudness, absolute threshold
43.66.Yw Instruments and methods related to hearing and its measurement
43.66.Lj Perceptual effects of sound

An excitation‐pattern model for intensity discrimination

Mary Florentine and Søren Buus

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1646-1654 (1981); (9 pages) | Cited 42 times

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This paper evaluates two different versions of Zwicker [Acustica 6, 365–381 (1956)] and Maiwald’s [Acustica 18, 193–207 (1967)] excitation‐pattern model for intensity discrimination. The single‐band version is that originally used by Zwicker and Maiwald. They assumed that performance was determined by the critical band in which the excitation grows most rapidly with increasing level of the stimulus. The multiband version forms an optimum decision based on information in all critical bands. Predictions from the two versions of the model are compared to data for intensity discrimination of tones as a function of level and frequency, for partially masked tones and for white noise. In general, the single‐band version yields predictions in qualitative agreement, but not in quantitative agreement with the intensity‐resolution data for pulsed tones. The multiband version yields predictions in good qualitative as well as quantitative agreement with the data, except at high frequencies.
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43.66.Fe Discrimination: intensity and frequency
43.66.Dc Masking
43.66.Ba Models and theories of auditory processes
43.66.Lj Perceptual effects of sound

Played‐again SAM: Further observations on the pitch of amplitude‐modulated noise

Edward M. Burns and Neal F. Viemeister

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1655-1660 (1981); (6 pages) | Cited 37 times

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The pitchlike sensation elicited by sinusoidally amplitude‐modulated (SAM) noise remains a controversial phenomenon. The controversy centers on two major points: (1) whether this sensation is ’’really’’ pitch rather than, e.g., roughness or intermittency, and (2) the possibility that any pitch sensation is mediated by short‐term spectral information rather than temporal information—thus nullifying an interesting aspect of the phenomenon. Three experiments employing SAM wideband noise, SAM wideband noise bandpass‐filtered after modulation, and a SAM 10 kHz pure tone were performed: (1) open‐set melody identification, (2) melodic dictation, and (3) musical‐interval adjustment. These experiments extend our earlier study [Burns and Viemeister, J. Acoust. Soc. Am. 60, 863 (1976)]. The results provide further evidence that SAM noise can, at suitable modulation frequencies, elicit a sensation of pitch (as defined by the ability to carry melodic information), and that this pitch represents a purely temporal phenomenon.
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43.66.Hg Pitch
43.66.Lj Perceptual effects of sound
43.75.-z Music and musical instruments
43.50.Ed Noise generation

Noise‐induced shifts in the pitch of pure and complex tones

Adrianus J. M. Houtsma

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1661-1668 (1981); (8 pages) | Cited 1 time

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The influence of masking noise on the pitch of dichotic two‐tone complexes and on the pure‐tone pitches of their spectral components is investigated by matching both to the pitch of a binaural periodic pulse comparison signal. It is found that noise‐induced shifts in the pitch of pure tones are considerably larger than induced shifts in complex tone or ’’residue’’ pitch. A pitch matching experiment with pure tones and contralateral noise reveals a general, central effect of noise on pitch. If empirical pitch matching data are corrected for this central effect, complex‐tone pitch is found to be independent of the influence of masking noise, whereas pure‐tone pitch remains subject to significant induced shifts. This finding is inconsistent with some of the modern pitch theories. It is consistent with the notion that pure‐tone pitch is mediated by spatial, and complex‐tone pitch by temporal encoding in peripheral auditory units.
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43.66.Hg Pitch
43.66.Dc Masking
43.66.Ba Models and theories of auditory processes

Monaural phase sensitivity with Ronken’s paradigm

G. Bruce Henning and H. Gaskell

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1669-1673 (1981); (5 pages) | Cited 2 times

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This paper describes an experiment using stimuli (pairs of clicks or pulses) similar to those used by Ronken [J. Acoust. Soc. Am. 47, 1091–1099 (1970)] in one part of his investigation of monaural phase sensitivity. The main difference between the studies is that Ronken’s basic pulses were 250 μs in duration whereas ours were 20 μs in duration; phase discrimination fails in Ronken’s experiments when pulse separation is less than about 2 ms but phase discrimination in our experiment fails only when the pulse separation is made less than 200 μs. We consider three different explanations of the results.
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43.66.Nm Phase effects
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Approximate formula of the averaged sound energy decay curve in a rectangular reverberant room

Mikio Tohyama and Shokichiro Yoshikawa

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1674-1678 (1981); (5 pages) | Cited 2 times

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An approximate formula of the space and ensemble averaged reverberation decay curve in a rectangular reverberant room is derived here theoretically. This approximate decay curve is written by the summation of the decay curve in three (oblique, tangential, and axial) types of diffuse fields. This formula contains not only the averaged sound absorption coefficient of the walls but the number of resonance wave modes excited in a rectangular reverberant room. The sound energy distribution rate of three types of diffuse fields at the steady state is determined by the ratio of the number of resonance wave modes constituting each type of diffuse field.
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43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response

Paper noise in an impact line printer

I. J. Busch–Vishniac and R. H. Lyon

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1679-1689 (1981); (11 pages)

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In many paper handling machines, the sound radiated from impacts on paper is a major noise source. It is shown that in typical impact line printers both nonresonant and resonant paper vibration are significant mechanisms of sound generation. Both can probably be controlled by increasing the backing bar stiffness of the printer while keeping the printing force constant. The paper–hammer impact on the backing bar dominates paper impact noise below 1250 Hz. Above 2500 Hz the hammer impact on the paper is the dominant source. From 1250–2500 Hz the two impacts contribute equally to the sound generation. Finally, consideration of the design of a ’’quiet’’ paper leads to the suggestion of a paper with high density and low bending rigidity. This might be accomplished through microcreping of the paper.
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43.50.Ed Noise generation
43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
43.50.Jh Noise in buildings and general machinery noise

Direct comparison of community response to road traffic noise and to aircraft noise

Fred L. Hall, Susan E. Birnie, S. Martin Taylor, and John E. Palmer

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1690-1698 (1981); (9 pages) | Cited 6 times

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Previous efforts to synthesize information on community responses to various noise sources have been forced to rely on a variety of surveys conducted in different countries over a number of years. Comparability of both the noise measurements and the questions asked has been limited, and has of necessity relied on professional judgment. Data collected recently around Toronto International Airport provide a direct comparison of response to two sources, based on 673 interviews of persons exposed to a variety of levels of both aircraft and road traffic noise. The results of that analysis do not support the assumption that response to these two noise sources is the same. For the same value of Ldn, a greater percentage of the sample is highly annoyed by aircraft noise than by road traffic noise. Possible reasons for this contradiction of the results of a previous synthesis of noise surveys are discussed.
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43.50.Sr Community noise, noise zoning, by-laws, and legislation
43.50.Qp Effects of noise on man and society
43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles

Continuous wave transmission techniques for measuring ultrasonic phase and group velocities in dispersive materials and composites

Lawrence C. Lynnworth, Warren R. Rea, and Emmanuel P. Papadakis

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1699-1703 (1981); (5 pages)

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Phase and group velocities V and U, respectively, were measured in the 100:1 frequency range 50 kHz to 5 MHz using longitudinal and shear ultrasonic continuous waves, in Teflon and in a dispersive three‐dimensional reinforced composite. A transmission approach was developed which utilized broadband transducers and a pair of wedges to obtain V by a differential path, fixed frequency technique, and to obtain U by a fixed path differential frequency technique. The path or frequency was incremented to fit additional whole wavelengths in the path, as indicated by 2π phase shifts in a Lissajous pattern. Cross checks between U and V confirmed the validity of the approach at least for the two materials investigated.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.35.Yb Ultrasonic instrumentation and measurement techniques

Effective density of air in open‐cell polyurethane foam for ultrasonic frequencies

Kiichiro Matsuzawa, Takahi Hasegawa, and Masayuki Ochi

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1704-1706 (1981); (3 pages)

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This article deals with a theoretical analysis of the experimental results reported in a previous paper [K. Matsuzawa and M. Ochi, J. Acoust. Soc. Am. 68, 212–217 (1980)]. An approximate formula for the effective density of air in the foam is proposed as ρ = ρ0 [1+C(1+L)+M(1−j) δ1/(2R)], where ρ0 is the density of free air, C is the material concentration, j = (−1)1/2, δ1 is the viscous boundary layer thickness, R is the volume‐to‐area ratio of pores, and L and M are constants. Then, on the basis of the experimental data, it is found that L = 1.2 and M = 2.6 in common with the foam materials of various pore densities.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.55.Ev Sound absorption properties of materials: theory and measurement of sound absorption coefficients; acoustic impedance and admittance

Ultrasonic attenuation in single crystals of bismuth germanium oxide at low temperatures

Elias A. Omotoso and Kathryn A. McCarthy

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1707-1712 (1981); (6 pages)

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The ultrasonic attenuation of longitudinal acoustic waves in single crystals of bismuth germanium oxide has been measured over a temperature range from 4.2° to 78 °K, using the pulse‐echo technique. The frequency range of the impressed phonons was from 10 to 70 MHz. Measurements have been made for phonons propagated along the [100], [110], and [111] crystallographic axes of the specimens. Analysis of the experimental results indicates that the attenuation can be accounted for entirely by the relaxation interaction of mobile charge carriers with the longitudinal electric fields of piezoelectric origin, which accompany the stress waves in the crystal. Based on this analysis, the electromechanical coupling constants obtained from the attenuation data are an order of magnitude smaller than the previously reported values.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.35.Fj Ultrasonic relaxation processes in gases, liquids, and solids

Ultrasonic attenuation in GaAs

S. S. Shukla and S. S. Yun

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1713-1716 (1981); (4 pages) | Cited 2 times

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The temperature and frequency dependence of the attenuation coefficient, α, of both longitudinal and shear ultrasonic waves, propagating along [100], [110], and [111] directions of GaAs, has been measured by means of the pulse‐echo technique. The temperature range investigated was 110° to 240 °K for shear waves and 110° to 300 °K for longitudinal waves. The frequencies used were in the range of 45 to 170 MHz. In the temperature range investigated, it was found that α∝ωn, with n = 2±0.2 for longitudinal waves and n = 1.7±0.1 for shear waves. By fitting our attenuation data to the theory given by Nava et al. [Phys. Rev. B 14, 800–807 (1976)], the temperature dependence of the effective ultrasonic Gruneissen parameter normalized to 300 °K for longitudinal waves and 240 °K for shear waves has been determined.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants

Characteristics of cw signals propagated under the ice in the Arctic

Peter N. Mikhalevsky

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1717-1722 (1981); (6 pages)

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Envelope statistics and tonal spectra have been measured from 15, 20, and 30‐Hz cw signals propagated via an ice‐covered path over a range of approximately 300 km. These data were taken during the tristen/fram ii experiment on the pack ice over the Pole Abyssal Plain in April/May 1980. Five hours of data are analyzed. The received signals were very stable in time and exhibited only minor fluctuations due entirely to the in‐band noise. The envelope amplitude statistics are Rician. Though the source and receiver were on drifting ice floes, the drift rates were negligible during transmission periods and thus these results apply to transmissions between essentially fixed terminals.
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43.30.Bp Normal mode propagation of sound in water
93.30.Li Arctic Ocean
43.60.Gk Space-time signal processing, other than matched field processing

Inverse problem for a stratified ocean and bottom

D. C. Stickler and P. A. Deift

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1723-1727 (1981); (5 pages) | Cited 2 times

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In this paper it is shown how to use the methods of one‐dimensional inverse scattering theory, in particular the new approach of Deift and Trubowitz [Comm. Pure Appl. Math. XXXII, 121–251 (1979)], to recover the sound speed for the case of a stratified ocean with a pressure release surface driven by a harmonic point source at a finite depth from a measurement of the normal derivative at the pressure release surface. The method is not a perturbation technique. For comparison, this same problem is examined when the sound speed is slightly perturbed from unity using a technique of Cohen and Bleistein [SIAM J. Appl. Math. 32, 784–799 (1977) and Geophysics 44, 1077–1087 (1979)].
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43.30.Bp Normal mode propagation of sound in water
43.30.Cq Ray propagation of sound in water
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries

The acoustic environment of ring BOB

Andrew C. Vastano, Donald B. Olson, and John A. Vastano

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1728-1735 (1981); (8 pages)

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The sound‐speed distribution in ring BOB present during cruise 011 of r/v endeavor (July–August 1977) has been examined on the basis of CTD and XBT observations. Sound‐speed values for the XBTs have been computed utilizing a regression analysis for salinity on the hydrographic data and Wilson’s sound‐speed formula. In addition to the characteristic low sound‐speed lens associated with the ring core, the resolution obtained with the XBT observations has revealed a near‐surface high sound‐speed halo, surrounding the core, in the region of the encircling Gulf Stream remnant. The halo is present between the depths of 50 to 150 m and represents a deviation of approximately 20 m/s relative to ring center at 100 m. The azimuthal deviations of sound speed from circular symmetry are presented in terms of observations taken on cruise 008 of r/v endeavor (May 1977). These perturbations are related to quasi‐geostrophic wave structures within the ring which may be stationary or rotate around the ring. The high sound‐speed halo, low speed lens, shape perturbations, and translation generate a complex acoustic environment within cyclonic rings.
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43.30.Bp Normal mode propagation of sound in water
43.30.Cq Ray propagation of sound in water
43.20.Dk Ray acoustics

Effective range derivative for acoustic propagation loss in a horizontally stratified ocean

H. Weinberg

J. Acoust. Soc. Am. Volume 70, Issue 6, pp. 1736-1742 (1981); (7 pages) | Cited 1 time

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A method for predicting acoustic propagation loss in a horizontally stratified ocean had been developed. We begin by comparing two widely used models, and demonstrate that unresolved discrepancies exist. Then classical ray tracing equations are developed by evaluating a multipath integral by stationary phase. The inaccuracy of ray theory is attributed to deficiencies in the stationary phase approach. In order to correct these shortcomings, we express multipaths in terms of Fresnel integrals and effective range derivatives. The approach is generalized to shadow zone propagation. Finally, we introduce a computer model that is based on the effective range derivative evaluation of the multipath expansion. The main emphasis of this paper, however, is not model comparison, but the effective range derivative technique, itself.
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43.30.Bp Normal mode propagation of sound in water
92.10.Vz Underwater sound
43.20.Dk Ray acoustics
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