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Journal of the Acoustical Society of America

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Dec 1982

Volume 72, Issue 6, pp. 1673-2059

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Acoustic radiation pressure produced by a beam of sound

Boa‐Teh Chu and Robert E. Apfel

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1673-1687 (1982); (15 pages) | Cited 24 times

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The second‐order force produced by a sound beam directed normally at a plane target is calculated. Previous theories on acoustic radiation pressures associated with plane acoustic waves are examined critically and erroneous results, where they exist, are noted and rectified. A number of general relations are established using a new approach which avoids the necessity of dealing with detailed solutions of the governing nonlinear equations. Some of the concepts inferred from known solutions obtained by previous authors require drastic revision in the light of the present study. Specifically, the notion that Rayleigh radiation pressure depends on the nonlinearity of the medium (while Langevin radiation pressure does not) is not true in the case where the medium is bound by a partially reflecting wall. Again, that the concept that Rayleigh radiation pressure depends on the acoustic field only through the energy density of the field is shown to be false. In one instance it is shown to depend also on how the field is maintained, while in another instance it does not appear to depend on the mean energy density of the field at all.
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43.10.Ln Surveys and tutorial papers relating to acoustics research; tutorial papers on applied acoustics
43.25.Qp Radiation pressure

Gain and efficiency of a traveling wave heat engine

Peter H. Ceperley

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1688-1694 (1982); (7 pages) | Cited 7 times

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Gain and efficiency equations are derived for a traveling wave heat engine, a device in which acoustic traveling waves force gas within a differentially heated regenerator to undergo a Stirling thermodynamic cycle and transform energy between thermal and acoustic forms. This derivation assumes nonturbulent flow conditions, a linear drag coefficient, a constant heat exchange coefficient, and neglects regenerator end effects. The complex characteristic impedance, gain, and efficiency are calculated for a thin slice of the regenerator in terms of dimensionless variables. With a Prandlt number of 0.7, the equations predict an efficiency of 70% that of an ideal Carnot cycle, and gain of 85% of that of theoretical maximum gain when fN ≡ωτ=0.003 and T′N≡ (dT/dx)T−1CIτ=0.4, where ω is the acoustic angular frequency, τ is the thermal time constant for the heat exchange process, dT/dx is the regenerator temperature gradient, and CI is the isothermal velocity of sound. In general, the equations predict that efficient high gain regenerators are quite short, have a large temperature gradient, and operate at low acoustic frequencies. Traveling wave heat pumps are also discussed and are very similar.
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43.38.Ar Transducing principles, materials, and structures: general
43.28.Kt Aerothermoacoustics and combustion acoustics
44.90.+c Other topics in heat transfer (restricted to new topics in section 44)
43.35.Ty Other physical effects of sound

Choice of target and accuracy of measurement in suspended sphere ultrasonic radiometry

R. C. Chivers and L. W. Anson

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1695-1705 (1982); (11 pages) | Cited 2 times

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The results of calculations are presented indicating the ways in which the form of the frequency dependence of the radiation force function Yp for spherical targets is affected by variations in the material parameters of the sphere, in temperature, and of the fluid surrounding the sphere. It is shown that the group II materials have less than 1% variation in Yp over significant frequency ranges for variations of ±5% in the wave velocities in the sphere. The relation of these calculations to experimental arrangements is discussed, with the conclusion that suspended sphere radiometry should be capable of much higher accuracy than has hitherto been achieved.
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43.58.Vb Calibration of acoustical devices and systems
43.30.Sf Acoustical detection of marine life; passive and active
43.20.Fn Scattering of acoustic waves
43.35.Yb Ultrasonic instrumentation and measurement techniques

Physical and acoustical properties of zooplankton

Charles F. Greenlaw and Richard K. Johnson

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1706-1710 (1982); (5 pages) | Cited 4 times

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The target strengths of marine zooplankton are often predicted from fluid sphere scattering models. These models require estimation of certain physical properties of the individual zooplankters: radius of the equivalent sphere, mass density, and either sound speed or compressibility. This report summarizes previously published measurements of these parameters and recent, unpublished data.
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43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems

Ultrasonic absorption and dispersion in biological media: A postulated model

Chandra M. Sehgal and James F. Greenleaf

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1711-1718 (1982); (8 pages) | Cited 1 time

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An integrated approach for the absorption of ultrasound by liquids and tissues is proposed from the solution of a one‐dimensional wave equation of propagation. The proposed model explains the square and linear power dependence of absorption on frequency for liquids and tissues, respectively. The study also provides a new index, specific heat ratio (γ), in terms of which the physical and the chemical state and thus possibly the pathological state of a tissue can be defined quantitatively.
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43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
87.50.Y- Biological effects of acoustic and ultrasonic energy

Quantitative ultrasonic backscatter measurements in the presence of phase distortion

M. O’Donnell

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1719-1725 (1982); (7 pages) | Cited 2 times

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The accuracy of quantitative ultrasonic backscatter measurements has been investigated in the presence of phase distortion. Using both computer simulation and measurements on tissue phantoms, quantitative backscatter estimates have been obtained in the presence of phase distortions capable of producing significant artifacts in conventional B‐scan images. The results of these studies suggest that quantitative measurements of the backscatter can be obtained in highly inhomogeneous tissue using conventional B‐scan equipment.
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43.80.Ev Acoustical measurement methods in biological systems and media
43.80.Qf Medical diagnosis with acoustics
43.58.Ta Computers and computer programs in acoustics

Auditory thresholds of a captive Eastern Pacific bottle‐nosed dolphin, Tursiops spp

Donald K. Ljungblad, Penelope D. Scoggins, and William G. Gilmartin

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1726-1729 (1982); (4 pages) | Cited 8 times

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The hearing threshold of a bottle‐nosed dolphin from the Eastern Pacific was tested using behavioral response techniques. The animal responded to signals ranging from 2 to 135 kHz, but did not respond to higher frequency signals (136–160 kHz) despite repeated trials. The range of greatest sensitivity was between 25 and 70 kHz with peak sensitivities at 25 and 50 kHz. This measured hearing threshold is compared to frequency responses and sensitivities previously reported for other cetaceans.
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43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.66.Cb Loudness, absolute threshold

Quantitative analysis of Weddell seal (Leptonychotes weddelli) underwater vocalizations at McMurdo Sound, Antarctica

Jeanette A. Thomas and Valerian B. Kuechle

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1730-1738 (1982); (9 pages) | Cited 5 times

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The Weddell seal (Leptonychotes weddelli) has a large repertoire of underwater vocalizations. Twelve underwater calls subdivided into 34 call types were classified based on differences in frequency range, duration, repetition rate, number per series, presence or absence of harmonics, auxiliary sound usage, and contour. The repertoire also contains nine dependent auxiliary sounds. In summary, this study standardizes the description and terminology for underwater vocalizations, reports source sound‐pressure levels, and reviews usage differences by male and female seals.
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43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.80.Nd Effects of noise on animals and associated behavior, protective mechanisms

Acoustical spectroscopy of violins

Eric B. Arnold and Gabriel Weinreich

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1739-1746 (1982); (8 pages) | Cited 1 time

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The normal modes of the violin system are investigated by studying its response to external excitation by an incident sinusoidal sound wave of variable frequency. Appropriate transducers are used to sense the vibration of wood, air, and strings. The data are analyzed by computer to yield information on the complex eigenfrequencies and eigenfunctions of the various normal modes. Methods of minimizing errors due to resonances outside the frequency window are discussed. Some representative results are shown.
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43.75.De Bowed stringed instruments
43.60.Qv Signal processing instrumentation, integrated systems, smart transducers, devices and architectures, displays and interfaces for acoustic systems
43.40.At Experimental and theoretical studies of vibrating systems

Input and transfer response of brass wind instruments

Stephen Elliott, John Bowsher, and Peter Watkinson

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1747-1760 (1982); (14 pages) | Cited 4 times

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Relationships among the various acoustical parameters which may be associated with musical wind instruments are explored. By defining appropriate input and output planes and assuming a linear, time‐invariant system, many of the concepts of transmission line theory are applicable. The real and imaginary parts of the propagation constant may be deduced from measurements of the input impedance and transfer function and used to study the effects of wall condition, for example. The influence of the mouthpiece is very different for the trumpet and trombone, and the concept of a unique impedance ‘‘seen’’ by the player is shown to be misleading. The power efficiency of the instruments between input and output planes may be calculated from measured data but more information is needed on the radiation impedance at the bell before detailed estimates of the components due to the regeneration process may be separated from internal losses in the instrument. Finally, it is shown that use of the time domain is very helpful when the influence of particular parts of the instrument is being studied.
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43.75.Fg Brass instruments and other lip-vibrated instruments
43.58.Bh Acoustic impedance measurement
43.20.Ks Standing waves, resonance, normal modes
43.40.At Experimental and theoretical studies of vibrating systems

Perceptual constancy of vowels in rapid speech

T. L. Johnson and W. Strange

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1761-1770 (1982); (10 pages) | Cited 3 times

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In three experiments, we investigated the role of extrasyllabic speech context in the identification of /t/–vowel–/t/ syllables spoken at normal and rapid rates of articulation. Syllables spoken at the normal rate were identified with at least 95% accuracy regardless of the context in which they were presented. However, in experiment I, intrinsically long vowels in rapidly articulated syllables were identified with greater accuracy when the syllables were presented in rapid‐rate sentence context than when they were presented in isolation or in normal‐rate sentence context. Experiment II revealed that part of the performance deficit for excised isolated rapid syllables was attributable to sequential order effects among test items, and to listeners’ assumptions about whether the test syllables were or were not produced in isolation. In experiment III, test syllables were presented in the context of extracted portions of the rapid carrier sentences to determine the locus of the extrasyllabic information for vowel identity. The presence of the stressed syllable which immediately followed the test syllables in the carrier sentence was especially important for accurate identification of intrinsically long vowels in rapidly articulated syllables. Results are discussed in terms of intrinsic timing theories of speech production.
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43.70.Dn Disordered speech
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Perception of short‐term spectral cues for stop consonant place by normal and hearing‐impaired subjects

Dianne J. Van Tasell, Lawrence T. Hagen, Linda L. Koblas, and Sharon G. Penner

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1771-1780 (1982); (10 pages) | Cited 2 times

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The purpose of the experiments described in this paper was to investigate the use by normal and hearing‐impaired subjects of the acoustic information at syllable onset for identification of the place feature of synthetic voiced stop consonants. Two synthetic speech continua served as stimuli. The full‐length continuum comprised 14 syllables that varied from /ba/ to /da/ to /ga/. The 14 stimuli of the short‐stimulus continuum were truncated versions of the full‐length syllables; each contained a burst portion plus two glottal pulses. All normal subjects categorized the full‐length stimuli accurately and consistently, but only two of seven normals performed equally well with the short‐stimulus continuum. The short‐stimulus performance of the remaining five normals improved after training, but remained significantly poorer than their performance with the full‐length stimuli, indicating that the information at stimulus onset did not provide all the necessary place information for those subjects. Hearing‐impaired subjects’ identification of the full‐length stimuli was only slightly less consistent than the normals’, and was highly correlated with their identification of stop consonant place in natural syllables. Their post‐training performance with the short stimuli did not differ from that of the trained normal group. These results indicate that various forms of signal distortion imposed by sensorineural hearing loss may, under certain conditions, have negligible effects on subjects’ use of acoustic place cues when those cues are at suprathreshold levels.
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43.70.Dn Disordered speech
43.66.Sr Deafness, audiometry, aging effects
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Magnitude estimation of degraded speech quality by normal‐ and impaired‐hearing listeners

Gary D. Lawson and Michael R. Chial

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1781-1787 (1982); (7 pages) | Cited 2 times

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Speech quality magnitude estimates (SQME’s) were obtained from 12 normal‐hearing and 12 sensorineurally impaired‐hearing listeners on connected speech samples degraded by changing low‐pass filter cutoff frequency, high‐pass filter cutoff frequency, or percent total harmonic distortion (THD) by linear rectification. Log SQME’s varied linearly with log bandwidth for filtered signals and with log percent undegraded (100−% THD) for linearly rectified signals. Significant variations were found among the slopes of the log–log functions for degradation modes and group‐by‐degradation mode interactions. Slope differences appeared to represent differential sensitivity of the listeners to changes in mode and degree of degradation. The findings are sufficiently encouraging to suggest that direct scaling procedures be employed in future studies of the evaluation of communication systems and the perception of complex signals.
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43.71.Gv Measures of speech perception (intelligibility and quality)
43.66.Sr Deafness, audiometry, aging effects
43.66.Ts Auditory prostheses, hearing aids

The deterioration of hearing with age: Frequency selectivity, the critical ratio, the audiogram, and speech threshold

Roy D. Patterson, Ian Nimmo‐Smith, Daniel L. Weber, and Robert Milroy

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1788-1803 (1982); (16 pages) | Cited 79 times

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The frequency selectivity of the auditory system was measured by masking a sinusoidal signal (0.5, 2.0, or 4.0 kHz) or a filtered‐speech signal with a wideband noise having a notch, or stopband, centered on the signal. As the notch was widened performance improved for both types of signal but the rate of improvement decreased as the age of the 16 listeners increased from 23 to 75 years, indicating a loss in frequency selectivity with age. Auditory filter shapes derived from the tone‐in‐noise data show (a) that the passband of the filter broadens progressively with age, and (b) that the dynamic range of the filter ages like the audiogram. That is, the range changes little with age before 55, but beyond this point there is an accelerating rate of loss. The speech experiment shows comparable but smaller effects. The filter‐width measurements show that the critical ratio is a poor estimator of frequency selectivity because it confounds the tuning of the system with the efficiency of the signal‐detection and speech‐processing mechanisms that follow the filter. An alternative, one‐point measure of frequency selectivity, which is both sensitive and reliable, is developed via the filter‐shape model of masking.
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43.66.Dc Masking
43.66.Ba Models and theories of auditory processes
43.66.Fe Discrimination: intensity and frequency
43.66.Sr Deafness, audiometry, aging effects

Vertical and horizontal sound localization in primates

Charles H. Brown, Teryl Schessler, David Moody, and William Stebbins

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1804-1811 (1982); (8 pages) | Cited 2 times

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Minimum audible angles for localization in the vertical and horizontal planes were psychophysically determined in Old World monkeys (Macaca). In the vertical condition the test stimuli consisted of primate vocalizations and bands of noise. Minimum audible angles ranged from 3° to greater than 20° for signals of various bandwidths. The acuity of vertical localization was dependent upon the high‐frequency content of the signal. Two of the three monkeys were unable to vertically localize sounds if the high‐frequency limit of the signal was below 2000 Hz. The acuity of horizontal localization was tested for pure tones 500, 2000, and 8000 Hz in frequency, positioned at several referent locations in the right frontal quadrant. The acuity of horizontal localization decreased as the test azimuth was displaced from the midline. Minimum audible angles ranged from approximately 4° to greater than 20° and varied as a function of test azimuth.
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43.66.Gf Detection and discrimination of sound by animals
43.66.Qp Localization of sound sources
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing

A signal‐detection‐theory measure of pitch shifts in sinusoids as a function of intensity

Walt Jesteadt and Donna L. Neff

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1812-1820 (1982); (9 pages) | Cited 1 time

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Pitch shifts in sinusoids as a function of intensity result in systematic response biases and differences in performance in forced‐choice frequency‐discrimination tasks. Two approaches are described for converting these effects to a measure of pitch shift in Hz using standard signal‐detection‐theory assumptions. To illustrate these approaches, forced‐choice frequency‐discrimination data were obtained for three listeners at 250 and 4000 Hz, with six intensities from 40 to 90 dB SPL. The resulting pitch‐shift estimates are in good agreement with adjustment data obtained from the same listeners. Collection and analysis of the forced‐choice data can be greatly simplified by using an adaptive procedure. Pitch‐shift estimates obtained in this way for two of the three listeners are in good agreement with the other estimates.
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43.66.Hg Pitch
43.66.Fe Discrimination: intensity and frequency

Masked discrimination of interaural time delays with narrow‐band signal

Yoshiko Ito, H. Steven Colburn, and Carl L. Thompson

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1821-1826 (1982); (6 pages) | Cited 4 times

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Interaural time just‐noticeable‐difference (jnd) of a narrow‐band noise masked by a wideband noise was measured for nine different interaural configurations of the masking noise at a fixed signal‐to‐noise ratio. The narrow‐band noise was 1/3 octave wide centered about 500 Hz, and the wideband masker was bandpass filtered between 250 and 1500 Hz. Our results are in agreement with earlier results with tones [M. F. Cohen, J. Acoust. Soc. Am. Suppl. 1 64, S35 (1978); J. Acoust. Soc. Am. 70, 1289–1293 (1981); J. E. Slocum and R. M. Stern, J. Acoust. Soc. Am. Suppl. 1 68, S60 (1980)] and are the opposite of what may be expected from the results of binaural detection experiments: the jnd is largest for the interaurally phase reversed masker and smallest for the diotic masker. In addition, no consistent relation was observed between the size of the jnd and the perceptual location of the masker. Predicted jnds were calculated from a model based on the interaural phase difference of the stimuli in the two ears and were in rough agreement with the experimental results.
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43.66.Pn Binaural hearing
43.66.Dc Masking
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Clipping degradation in a system used to detect time‐periodic variance fluctuations

H. L. Hurd

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1827-1830 (1982); (4 pages)

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Studies of the effects of nonlinear distortion have typically determined certain properties of the process, y(t)=f[x(t)], where f(⋅) is some nonlinear transfer function under consideration. The property commonly sought is its associated spectral density function or, equivalently, its correlation function. In this paper a particular type of degradation from nonlinear distortion is considered; x(t) is assumed equal to s(t)+n(t), where n(t) is wide‐sense stationary and s(t) is a nonstationary process, independent of n(t), with zero mean and periodically fluctuating variance. It is found that the performance is not degraded when limiting is slight, but severe limiting tends to prevent detection of the variance fluctuations.
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43.60.Cg Statistical properties of signals and noise
43.60.Gk Space-time signal processing, other than matched field processing
43.25.-x Nonlinear acoustics

Time‐delay triangulation ranging using beta density measurement error statistics

E. J. Hilliard, Jr. and Joseph J. Perruzzi

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1831-1837 (1982); (7 pages) | Cited 2 times

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A beta‐type density function is used to model time‐delay measurement errors associated with sensors used in triangulation ranging applications. The range density function together with the mean and standard deviation are derived. Maximum positive and negative time‐delay error limits over which these statistics are valid are also determined. Bounds on the time‐delay standard deviation for the square‐law approximation are established as well as length requirements on the effective baseline to achieve reliable range estimates.
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43.60.Gk Space-time signal processing, other than matched field processing
43.30.Vh Active sonar systems

Curvature of sound decays in partially reverberant rooms

Thomas W. Bartel and Simone L. Yaniv

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1838-1844 (1982); (7 pages) | Cited 2 times

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Measurements were conducted to investigate the departure from linearity of sound decays in partially reverberant rooms—that is, rooms, such as are found in office buildings and residences, that are less reverberant than laboratory reverberation chambers. The extent to which the nonlinearities in the decay curves could be reduced by means of an ensemble‐averaging procedure was determined. Decay curves for five partially reverberant rooms, ranging in size from 45 to 425 m3, were tape recorded and played back at reduced speed into a real‐time analyzer. Decay measurements were also performed in the NBS 425‐m3 reverberation chamber. It was found that ‘‘smooth’’ decay curves, displaying a curvature characterized by a monotonically decreasing decay rate, could be obtained provided that the ensemble averages included decays recorded at several source and receiver locations. Thus, the rate of decay at any point in time for partially reverberant rooms could be precisely and unambiguously determined. The magnitude of the curvature was such that the percentage difference between the early decay rate and the decay rate averaged over a 25‐dB range varied from approximately 2% to 40%, with the greatest differences occurring in rooms containing an absorptive ceiling and floor or an opening connecting them to other rooms.
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43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response
43.55.Mc Room acoustics measuring instruments, computer measurement of room properties

Spectral analysis of impulse noise for hearing conservation purposes

Guy O. Stevin

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1845-1854 (1982); (10 pages)

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Damage‐risk criteria for impulse noise does not presently take the spectrum of the impulse into account; however, it is known that the human auditory system is spectrally tuned. The present paper advocates the extension to impulse noise of the noise dose concept which is widely used for continuous noise. This approach is based upon sound exposure instead of sound pressure. An A‐weighting filter or an octave band analysis can then be used to take the spectral content of the impulses into account. The equipment needed for applying these procedures for impulse noise is an integrating sound level meter or a digital Fourier processor. Generalized spectral methods have been evaluated by means of an impulse simulation applied to a mathematical model of the human hearing mechanism. The results of this simulation agree with the most recent experiments on impulse noise and fully support the proposed rating methods. This conclusion must be emphasized as it leads the derivation of a uniform procedure for predicting loudness and damage risk for hearing which is applicable for continuous noise as well as for impulse noise.
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43.50.Qp Effects of noise on man and society
43.66.Sr Deafness, audiometry, aging effects
43.50.Cb Noise spectra, determination of sound power

Thickness shear, thickness twist, and flexural vibrations of rectangular AT‐cut quartz plates with patch electrodes

P. C. Y. Lee, C. Zee, and C. A. Brebbia

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1855-1862 (1982); (8 pages)

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The influence of the size and the mass of patch (rectangular electrodes on the vibrations and energy trapping in a plate rectangular crystal plate is studied. Mindlin’s two‐dimensional approximate equations of vibrations of crystal plates are employed for which the coupled modes of thickness shear, thickness twist, and flexure are retained. Numerical solutions that satisfy the free‐edge conditions of the plate and the continuity conditions of stresses and displacements at the interface of the plated and unplated regions of plate are obtained by the finite element method using displacement formulation. Numerical computations are made for rectangular AT‐cut quartz plates with symmetrically placd, patch electrodes. Resonance frequencies and their corresponding two‐dimensional modes of vibrations are obtained for various dimensions of plate and electrodes, and for different masses of electrodes. Calculated results are compared with existing analytical results by Mindlin and Lee [Int. J. Solids Structures, 2, 125 (1966)], Lee and Spencer [J. Acoust. Soc. Am. 45, 637 (1969)], and Tiersten [J. Acoust. Soc. Am. 59, 879 (1976)], and experimental data by Curran and Koneval [J. Acoust. Soc. Am. 34, 981 (1967)]. A two‐dimensional Bechmann’s number is obtrained which depends essentially on three parameters; the electrode length‐to‐plate thickness ratio, the electrode wide‐to‐plate thickness ratio, and the ratio of the mass of electrodes to the mass of the plate per unit area.
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43.40.Dx Vibrations of membranes and plates
43.38.Fx Piezoelectric and ferroelectric transducers

Sampling statistics for vibrating rectangular plates

Richard V. Waterhouse, Arthur F. Kilcullen, and James E. Brooks

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1863-1869 (1982); (7 pages)

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A thin, uniform, rectangular, elastic plate is freely supported in air, and driven so that it vibrates flexurally at a resonance frequency. The modal function, which describes the vibrational displacement over the surface of the plate, is approximated as the product of two sine functions. From this modal function the probability density function (pdf), P(s), for random sampling over the plate surface of the rms acceleration, is calculated to be 4π−2 K(1−s2), where K is a complete elliptic integral. Using this expression and experimental values sampled randomly over the plate surface, estimates of known precision can be made of the mean vibrational level of the plate. Experimental results are given for a steel plate measuring 4 ft×3 ft×1/4 in., resonating at a single frequency; they agree quite well with the theoretical cumulative function derived from the pdf given above. Also considered are cases where two overlapping modes are excited at a given frequency. The corresponding pdfs are found, by Monte Carlo calculations, for five different values of phase difference between two modes excited with equal amplitudes. As the pdfs are known for the case where a pure tone excites many overlapping modes (exponential for the mean‐square acceleration, Rayleigh for the rms value), an outline of the sampling statistics is now available for all modal densities.
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43.40.Dx Vibrations of membranes and plates
43.40.At Experimental and theoretical studies of vibrating systems

Sound velocities at hypersonic frequencies in molten alkali chlorides

R. Aronsson, H. E. G. Knape, and L. M. Torell

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1870-1871 (1982); (2 pages)

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Measurements of the hypersonic velocity were made in a number of molten alkali chlorides by using Brillouin spectroscopy. The data indicate that no dispersion appears between the two different hypersonic frequencies studied for any of the molten salts. Furthermore, a comparison with corresponding ultrasonic velocities implies that any relaxation frequency must be higher than the investigated frequencies.
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43.35.Dh Pretersonics (sound of frequency above 10 GHz); Brillouin scattering
43.35.Fj Ultrasonic relaxation processes in gases, liquids, and solids
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions

Surface acoustic wave propagation in a biasing electric field

S. G. Joshi

J. Acoust. Soc. Am. Volume 72, Issue 6, pp. 1872-1878 (1982); (7 pages) | Cited 4 times

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The influence of a biasing electric field on the propagation of surface acoustic waves in LiNbO3, LiTaO3, and PbTiO3 ceramic substrates is experimentally investigated. The 128° rotated Y‐cut, X‐propagating orientation of LiNbO3 shows a linear and fairly large variation of time delay with the biasing field. Fractional time delay changes greater than 0.12% have been obtained, and values up to 0.16% appear possible in SAW devices fabricated on this material. These changes in time delay are adequate to make the technique useful for several applications. Possible applications of this effect for beam steering in phased array antennas, measurement of high voltages, temperature compensation in SAW devices, and improving the efficiency of SAW convolvers are discussed.
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43.35.Pt Surface waves in solids and liquids
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties
43.35.Ty Other physical effects of sound
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