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Journal of the Acoustical Society of America

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Jul 1978

Volume 64, Issue 1, pp. 1-341

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Elastic waves in rods and clad rods

R. N. Thurston

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 1-37 (1978); (37 pages) | Cited 28 times

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Clad rods have been investigated for use as long delay lines because they offer isolation of the signal from the surface and low dispersion. In addition, single‐mode propagation is achieved with a larger (and hence more conveniently transduced) cross section than is possible with a homogeneous rod at the same frequency. This paper describes the modes that have a steady‐state sin(ωt−βz) dependence on (t,z), with emphasis on the modes and ranges of parameters that are of interest for delay lines. Only rods of circular cross section, and isotropic, linear elastic materials are considered. Attention is drawn to correspondences with homogeneous rods and with the hypothetical case of infinite thickness cladding, which is most useful as a model for understanding the behavior of corresponding modes in an actual clad rod. Written for the nonspecialist, the paper includes a tutorial review of the concepts and results needed to understand wave propagation in rods and clad rods. In addition, the following new results are reported: (1) for homogeneous rods, a representation of the lowest flexural mode dispersion curve that is for practical purposes independent of Poisson’s ratio; (2) for homogeneous rods, displacement distributions of the first three high‐frequency shear modes, i.e., the ’’flexural’’ modes that are asymptotic to the shear velocity (it was found that the distribution previously attributed to the lowest such mode actually belongs to the next); (3) for clad rods, the first demonstration of interface modes of the Stoneley type for nonaxially symmetric waves; (4) classification of clad rods according to the nature and ordering of their asymptotic velocities showing that there are eight types of clad rod, rather than four as stated in the previous literature; (5) for infinitely clad rods having the same shear modulus, proof that the dispersion of torsional waves and their penetration into cladding are universal functions of f/fc∞. The ratio of the shear velocities of the two materials affects the cutoff frequency fc∞, but not the universal penetration and dispersion functions. Subjects on which significant tutorial or descriptive material is given include typical waveguide dispersion, characteristic velocities of an isotropic elastic material, the effect of coupling of dilatational and shear waves at a boundary, waves in homogeneous rods, the connection of isolation to total internal reflection (with Love waves and SH waves in a clad plate as an example), Stoneley waves at a plane interface, and previous results on the clad rod.
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43.10.Ln Surveys and tutorial papers relating to acoustics research; tutorial papers on applied acoustics
43.20.Bi Mathematical theory of wave propagation
43.40.Cw Vibrations of strings, rods, and beams

New approach to a constant beamwidth transducer

Peter H. Rogers and A. L. Van Buren

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 38-43 (1978); (6 pages) | Cited 1 time

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The theory of a broadband constant beamwidth transducer which is to be used primarily as a projector is presented. The transducer is a spherical cap of arbitrary half angle α shaded so that the normal velocity is equal to U0Pν(cos ϑ), where Pν is the Legendre function whose root of smallest angle occurs at ϑ=α. The required value for ν, the order of the Legendre function (which is not, in general, an integer) can be obtained to within 1% for α?1 radian from the approximation ν?0.5[(4.81/α)−1]. The transducer is shown to have uniform acoustic loading, extremely low sidelobes, and an essentially constant beam pattern for all frequencies above a certain cutoff frequency. Under piezoelectric drive the transducer is shown to have a flat transmitting current response over a broad band.
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43.38.Ar Transducing principles, materials, and structures: general
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration

Perceptibility of phonetic features in fluent speech

Ronald A. Cole, Jola Jakimik, and William E. Cooper

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 44-56 (1978); (13 pages) | Cited 1 time

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A series of experiments examined listeners’ ability to detect mispronounced words in a short story. Mispronunciations were produced by changing a single consonant segment in a word to produce a (phonologically permissible) nonsense word. The results of six different experiments showed that prestressed word‐initial stop consonants are more perceptible than other consonants. For example, mispronunciations produced by changing the voicing of a word‐initial stop (e.g., ’’boy’’ to ’’poy’’) were detected about 70% of the time, while changes in voicing of a word‐initial fricative (e.g., ’’voice’’ to ’’foice’’) were detected about 38% of the time. Mispronunciations produced by changing the place of articulation of a prestressed word‐initial stop were most detectable of all (80% to 90% detection) for three different speakers. A change in place of articulation of a word‐initial stop (e.g., ’’baby’’ to ’’daby’’) was detected as often as a change in both place of articulation and voicing (e.g., ’’baby to ’’taby’’). Finally, it was found that a mispronunciation was detected about twice as often in word‐initial than in word‐final position in one syllable words for both stops and nasals. The results suggest that listeners pay special attention to word‐initial stop consonants in natural continuous speech.
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43.70.Dn Disordered speech
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Effects of transition length on the perception of stop consonants

Patricia Keating and Sheila E. Blumstein

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 57-64 (1978); (8 pages) | Cited 2 times

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This study investigated the effects of lengthened transitions on the perception of stop consonants. In experiment I, three continua representing the phonetic categories [da] and [ga] containing transitions of 45, 95, or 145 ms were presented to 20 subjects for both labeling and discrimination. Results indicated that although there was a significant change in identification performance from 95 to 145 ms, the shape of the functions, and the locus and slope of the phonetic boundary did not significantly vary across transition lengths. In addition, discrimination of within‐category stimulus comparisons was significantly better at the 95‐ms transition length than at 45 or 145 ms. In experiment II, the availability of acoustic information was investigated further with the adaptation paradigm. Eight subjects labeled the 45‐ms series before and after adaptation with 45‐, 95‐, and 145‐ms [da] stimuli. No effect of transition length was found. These results suggest that the slope and duration of formant transitions seem to contribute minimally to the perception of place of articulation in stop consonants.
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43.70.Dn Disordered speech
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Indirect assessment of the contribution of subglottal air pressure and vocal‐fold tension to changes of fundamental frequency in English

Randall B. Monsen, A. Maynard Engebretson, and N. Rao Vemula

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 65-80 (1978); (16 pages) | Cited 1 time

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The contributions of vocal‐fold tension and of subglottal air pressure to changing fundamental frequency F0 are indirectly assessed by comparing human glottal‐source data with synthetic glottal waveforms generated by the Ishizaka–Flanagan two‐mass model of vocal‐fold vibration. In this model, synthetic male and female glottal waves may be generated with known values of subglottal air pressure and vocal‐fold tension. Human glottal waves were recorded with a reflectionless tube into which ten male and female adults phonated. The subjects produced interrogative (rising F0) and declarative (falling F0) glides and trisyllabic words with primary stress on the initial, medial, or final syllable. Two types of change in the glottal wave over time are possible, depending on whether F0 is changed primarily by vocal‐fold tension or by subglottal air pressure. Comparison of the natural and synthetic glottal waves indicates that (1) the rise of frequency in interrogative words is due principally to increasing vocal‐fold tension, while (2) the fall of frequency in declarative words is due principally to decreasing subglottal air pressure; (3) in the polysyllabic words, the change of frequency within syllables resembles that of the declarative monosyllables and appears due primarily to changes of subglottal air pressure; and (4) the heightened f0 of the stressed syllable is due to an increase in the vocal‐fold tension, typically accompanied by increased subglottal air pressure.
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43.70.Bk Models and theories of speech production
43.72.Ar Speech analysis and analysis techniques; parametric representation of speech
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation

Multidimensional classification of normal voice qualities

Sadanand Singh and Thomas Murry

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 81-87 (1978); (7 pages) | Cited 1 time

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This study investigates and acoustically defines some of the perceptual parameters used to distinguish among normal male and female voices. Twenty normal speaking subjects, ten male and ten female, produced speech segments which were paired, randomized, and presented to ten listener judges. The judges rated the similarity of all combinations of voices on a seven‐point scale, and these similarities were analyzed by a multidimensional analysis technique, INDSCAL. For each speaker, eight acoustical measures were obtained, and psychophysical ratings of four commonly used descriptive terms were made by ten speech pathologists. These measurements and ratings provided the interpretation of the INDSCAL solution and were also submitted to correlational analyses. The results indicate that, when distinguishing among the voices, the judges gave the greatest weight to the male versus female dimension and its acoustical correlates. The results of both the INDSCAL analysis and the correlational analyses suggest that listeners may use different perceptual strategies to classify male voices than they use to classify female ones.
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43.70.Dn Disordered speech
43.72.Ar Speech analysis and analysis techniques; parametric representation of speech

Occurrence of glottal stops in fluent speech

Noriko Umeda

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 88-94 (1978); (7 pages)

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The use of glottal stops in continuous speech in American English has not been well studied, in spite of the common belief that they may serve as boundary markers. This paper reports the result from measurements of five speakers’ readings of four stories, each arranged in both list and story form. Data were analyzed according to the difference in speakers, materials, versions, phonological situations (phoneme sequence and stress situations), grammatical conditions, and frequency of occurrence of words. Results show that higher‐level factors such as speaker’s reading style and difficulty of material have a stronger influence than phonological and grammatical factors.
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43.70.Bk Models and theories of speech production
43.72.Ar Speech analysis and analysis techniques; parametric representation of speech

Theory of binaural interaction based on auditory‐nerve data. III. Joint dependence on interaural time and amplitude differences in discrimination and detection

H. S. Colburn and J. S. Latimer

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 95-106 (1978); (12 pages) | Cited 1 time

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This paper is primarily concerned with issues of symmetry–asymmetry in the joint dependence of binaural performance on interaural time delay and interaural amplitude ratio. The predictions of our model based on auditory‐nerve data are shown to be inadequate for available data showing asymmetries in interaural time discrimination. Measured detection thresholds for a 500‐Hz tone burst masked by wide‐band noise are reported for nonunity amplitude ratios and both polarities of delays in order to test for asymmetries analogous to those observed in the time discrimination case. The detection results show only small asymmetries and are not inconsistent with the model. A general discussion of our model and the implications of available empirical results leads to a suggested modification of the model. We show by an example that modifications of the type we are suggesting are capable of describing the detection data and at least the gross trends of the discrimination data.
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43.66.Pn Binaural hearing
43.66.Ba Models and theories of auditory processes
43.66.Dc Masking

Binaural summation of the loudness of pure tones

Lawrence E. Marks

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 107-113 (1978); (7 pages) | Cited 9 times

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Subjects made magnitude estimations of the loudness of pure tones (100, 400, and 1000 Hz), which were presented at equal and unequal sound pressure levels to the two ears. The results were consistent with a model of linear binaural loudness summation: The estimates of loudness approximated the linear sum of the loudness estimates of the individual left‐ear and right‐ear components. The relation between loudness and sound pressure, over moderate SPLs, can be described by a power function with an exponent of about 0.6 at 400 and 1000 Hz, 0.75 at 100 Hz.
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43.66.Cb Loudness, absolute threshold
43.66.Pn Binaural hearing

Frequency discrimination in the chinchilla

David A. Nelson and Thomas E. Kiester

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 114-126 (1978); (13 pages) | Cited 2 times

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Chinchillas were trained with shock‐avoidance procedures to discriminate or detect pure‐tone frequency differences. Initial attempts at determining frequency‐difference thresholds utilized a complex discrimination paradigm and a go–no‐go response. Although discriminations of large frequency differences were obtained from chinchillas after considerable training, discriminations of small frequency differences could not be trained. Therefore, determinations of frequency‐difference thresholds could not be made with the complex discrimination paradigm and the go–no‐go response task. A simple detection paradigm, involving the detection of frequency alternation in an ongoing train of tone bursts proved to be a more successful technique. Frequency‐alternation detection was quickly learned by six chinchillas, and frequency‐difference thresholds were obtained with an adaptive sequential procedure. Psychometric functions were reconstructed from the threshold tracking data of chinchillas, and comparisons were made with differential frequency thresholds from cats and humans obtained by previous investigators. Differential frequency thresholds from chinchillas paralleled those from cats and were about twice as large. Differential frequency thresholds from humans were considerably smaller than from chinchillas, especially for low‐frequency tones. When a constant detectability index was used to specify differential frequency sensitivity in chinchillas, chinchilla and human differential sensitivity functions paralleled one another. Human differential sensitivity was about ten times better than that of the chinchilla.
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43.66.Fe Discrimination: intensity and frequency
43.66.Gf Detection and discrimination of sound by animals
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing

Theory of binaural interaction based on auditory‐nerve data. IV. A model for subjective lateral position

Richard M. Stern, Jr. and H. Steven Colburn

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 127-140 (1978); (14 pages) | Cited 22 times

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A model for the subjective lateral position of 500‐Hz tones is presented and compared with experimental lateralization data. Previous papers in this series have explicitly described the auditory‐nerve response to these stimuli and proposed a binaural displayer that interaurally compares the auditory‐nerve firing times. The outputs of the displayer are postulated to represent the only information about detailed firing times that is available to the brain. In the present paper, lateral‐position predictions are obtained by a central nonoptimal weighting of these outputs that depends on the interaural intensity difference of the tone. These predictions describe the results of lateralization‐matching experiments more accurately and over a wider range of stimulus conditions than previous theories, except for those results which suggest that low‐frequency binaural tones can generate multiple perceptual images. The predictions of our model are also consistent with the results of centering and laterality‐comparison experiments. It is argued that the data discussed in this paper are generally incompatible with theories that propose a peripheral interaction of interaural timing and intensity information such as the latency hypothesis.
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43.66.Pn Binaural hearing
43.66.Ba Models and theories of auditory processes

Suppression and critical bands in band‐limiting experiments

Daniel L. Weber

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 141-150 (1978); (10 pages) | Cited 3 times

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Band‐limiting experiments were performed at three noise spectrum levels (N0=25, 40, and 55 dB SPL) for forward, simultaneous, and backward masking. Threshold for a 2‐kHz sinusoid decreased for masker bandwidths greater than a ’’critical bandwidth’’ in nonsimultaneous masking. These results are evidence for a suppression effect not observed in simultaneous masking; however, a qualitative model of suppression can account for the results in all three types of masking. In addition, the data for simultaneous masking support Fletcher’s [Rev. Mod. Phys. 12, 47–61 (1940)] rectangular filter interpretation of the band‐limiting experiment and are well described by a level‐dependent critical band.
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43.66.Dc Masking
43.66.Ba Models and theories of auditory processes
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Behavioral, compound action potential, and single unit thresholds: Relationship in normal and abnormal ears

P. Dallos, D. Harris, Ö. Özdamar, and A. Ryan

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 151-157 (1978); (7 pages) | Cited 4 times

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Comparisons were made for two species (chinchilla and mongolian gerbil) among mean behavioral audiogram, mean just detectable action potential (AP) responses to tone bursts, and single‐fiber response thresholds at the characteristic frequency, averaged in one‐octave bands. In normal animals and in a group of Kanamycin‐treated chinchillas, these mean measures appear to have a well‐ordered relationship. Unit and AP thresholds are within 10 dB from one another throughout the frequency range. Behavioral thresholds are usually 15–20 dB more sensitive, but the three curves are roughly parallel except at the highest frequencies, where the behavioral threshold begins to increase approximately one‐half octave above the physiological ones. Individual examples for four gerbils and four chinchillas having hair cell losses due to Kanamycin intoxication reinforce the notion based on mean data that in most cases AP thresholds can serve to predict the behavioral threshold configuration.
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43.64.Ri Evoked responses to sounds
43.64.Pg Electrophysiology of the auditory nerve
43.64.Nf Cochlear electrophysiology

Some observations on cochlear mechanics

William S. Rhode

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 158-176 (1978); (19 pages) | Cited 6 times

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A set of experiments was conducted using the Mössbauer effect to determine the vibratory characteristics of the basilar membrane, Reissner’s membrane, the malleus, incus, and oval window in squirrel monkey. A few measurements were also made in guinea pig in the basal cochlear region. The nonlinear vibration properties of the basilar membrane are described in detail for the midfrequency region in the squirrel monkey. Only in this region have nonlinear effects been observed. A comparison of mechanical and neural data indicates good qualitative agreement.
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43.64.Kc Cochlear mechanics

Detection of LPM signals with estimation of their velocity and time of arrival

W. S. Hodgkiss

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 177-180 (1978); (4 pages)

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The Bayes optimal detector is derived for a class of linear‐period‐modulated (LPM) signals whose velocities and times of arrival are uncertain. All terms necessary for claculating the a posteriori probability‐density function of the uncertain parameters are shown to be available as a natural by‐product of the optimal detector computations. The processor structure derived is general in that a priori knowledge of velocity and time of arrival other than complete uncertainty can be taken into account.
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43.60.Cg Statistical properties of signals and noise
43.30.Cq Ray propagation of sound in water

Reverberation time, absorption, and impedance

E. H. Dowell

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 181-191 (1978); (11 pages) | Cited 4 times

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A rigorous theoretical model is derived and used to calculate reverberation time of a room in terms of impedance of absorption materials on the wall and geometrical factors associated with such materials and the room. In addition, the reverberation time also depends upon the initial state of the pressure field before decay begins as well as on the single measure of pressure, for example spatial root mean square, used to characterize the decay‐time history. The theoretical model, which consists of a system of harmonic oscillators with damping provided through the wall impedance, is sufficiently general to take into acount all of these factors. Numerical examples are given to illustrate the procedure. A brief review of other methods for calculation of reverberation time is given, including a discussion of random and normal absorption coefficients.
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43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response

Presumed noise‐induced permanent threshold shift resulting from exposure to an A‐weighted Leq of 89 dB

E. H. Berger, L. H. Royster, and W. G. Thomas

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 192-197 (1978); (6 pages) | Cited 2 times

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The noise‐induced permanent threshold shift (NIPTS) resulting form up to ten years of exposure to an average A‐weighted sound level Leq of 89 dB was investigated. Prior occupational noise exposure was controlled for by eliminating subjects with previous high‐noise‐level jobs or uncertain exposure histories. The final population consisted of 42 males and 58 females working in steady‐state broadband noise environments. No attempt was made to screen subjects for any auditory pathology. A 222‐subject control group from the same geographic area as the exposed subjects was selected such that none of its constituents had any effective industrial noise exposure. Presumed NIPTS was calculated by correcting each individual audiogram of the exposed subjects according to the aging curves developed from the control popultion hearing levels. The results indicated a considerable male–female difference in NIPTS, even though both groups were exposed to the same Leq. Averaging the results for all 100 subjects, in order to make comparisons to other available data, yielded results in close agreement to predictions based upon the work of Burns and Robinson, Baughn, NIOSH, and Passchier–Vermeer, indicating that 10 years of exposure to a daily Leq of 89 dB causes measurable hearing loss at 4 kHz.
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43.50.Qp Effects of noise on man and society
43.66.Sr Deafness, audiometry, aging effects
43.66.Cb Loudness, absolute threshold

Nationwide urban noise survey

Sanford Fidell

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 198-206 (1978); (9 pages) | Cited 1 time

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Most current knowledge about community response to noise exposure is derived from studies of high‐level transportation sources. A nationwide urban noise survey was undertaken to study effects associated with more moderate but far more common sorts of noise exposure. Over 2000 respondents at 24 sites in seven cities of varying noise exposure and population density were interviewed by telephone and in person about their reactions to everyday noises. A brief but comprehensive structured questionnaire was based on direct questioning about annoyance and related effects. Among the major findings of the survey were widespread annoyance and speech interference from exposure to urban noise and strong relationships between the extent of annoyance and exposure level, speech interference, and population density.
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43.50.Qp Effects of noise on man and society
43.50.Ba Noisiness: rating methods and criteria
43.50.Sr Community noise, noise zoning, by-laws, and legislation

Analysis of concentric‐tube resonators having unpartitioned cavities

Joseph W. Sullivan and Malcolm J. Crocker

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 207-215 (1978); (9 pages) | Cited 26 times

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In muffler design, concentric‐tube resonators are often used to provide high‐frequency attentuation. These resonators are constructed by shaping a rigid shell around a length of perforated tube, forming an unpartitioned cavity. Often the entire length of tube is perforated. Because of the length of the assembly, it is not possible to use the simple Helmholtz resonator theory to predict the attentuation. Beginning with a one‐dimensional control volume, a mathematical model was derived which accounted for mean flow in the tube and for the wave motion in the cavity and the coupling between cavity and tube via the impedance boundary of the perforate. For impedance in the linear regime, a closed‐form solution for the resonator transmission loss was obtained. With this restriction and for the case of zero mean flow, excellent agreement was obtained with experimental results. Limited parametric studies suggest that the performance of this type resonator is quite sensitive to the porosity of the perforate, and that unusually large bandwidths of attenuation may be obtained for select geometries at zero or near‐zero mean flow conditions. As mean flow is increased, however, the model suggest that such large bandwidths may not be attainable in practice.
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43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
43.20.Ks Standing waves, resonance, normal modes
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators

Disturbance of sleep by noise

G. J. Thiessen

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 216-222 (1978); (7 pages)

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Young, middle‐aged, and old subjects, 35 in all, were tested to determine the probability of disturbance of sleep, as judged by EEG records, by seven noises per night produced by a recording of a passing truck. There is roughly a linear relation with the A‐weighted noise level. Young and old people have nearly the same response while middle‐aged subjects are more sensitive by about 15 dB. This applies also to the probability of awaking. The probability of shifts in sleep to a shallower level does not appear to adapt in 24 successive nights with seven noises per night but the probability of waking drops to half value in about two weeks. Response increases with duration of the stimulus, at least over the limited range from fractions of a second to a minute.
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43.50.Qp Effects of noise on man and society
43.50.Sr Community noise, noise zoning, by-laws, and legislation

Acoustic radiation due to a fluid loading discontinuity on an infinite membrane

Mauro Pierucci

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 223-231 (1978); (9 pages)

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Edge‐mode radiation is determined for an infinite membrane with a discontinuous fluid loading condition. The upper half of the membrane is exposed to a heavy fluid which accounts for a fluid–structure interaction. The lower half of the membrane is exposed to very light fluid which imposes no fluid loading on the structure. A very soft compliant layer is attached to half of the membrane surface. The compliant layer lessens the local coupling between the fluid and the structure, thus creating the fluid loading discontinuity. The effect of this fluid loading discontinuity upon the radiated farfield is evaluated.
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43.40.Dx Vibrations of membranes and plates
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.20.Tb Interaction of vibrating structures with surrounding medium

Subharmonic vibrations of order 1/3 in stretched strings

C. R. Raghunandan and G. V. Anand

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 232-239 (1978); (8 pages)

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Subharmonic vibrations of order 1/3 in stretched strings driven by a single‐mode planar simple harmonic force are investigated. It is shown that both planar and nonplanar subharmonic resonances can occur. Subharmonic vibrations are possible only if the amplitude of the force exceeds a certain critical value which depends upon the magnitude of the damping coefficient. The stability of the solution is analyzed, and it is shown that the region of stable nonplanar vibrations is wider than that of stable planar vibrations. It is also observed in the case of nonplanar vibrations that the amplitude of the subharmonic in the plane normal to the plane of the driving force is larger than that in the plane of the driving force.
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43.40.Cw Vibrations of strings, rods, and beams
43.40.Ga Nonlinear vibration

Generation of ultrasound at metal–electrolyte interfaces

Frank Borsay and Ernest Yeager

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 240-242 (1978); (3 pages)

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When a radiofrequency potential is applied to an electrode such as gold in an electrolyte, ultrasound is generated at the interface. This effect is attributed to changes in the volume of the solution adjacent to the metal and can be used to study the structure of the interface. Preliminary measurements are reported as a function of the dc electrode potential.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
72.50.+b Acoustoelectric effects
73.50.Rb Acoustoelectric and magnetoacoustic effects
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
43.35.Yb Ultrasonic instrumentation and measurement techniques

Phase insensitive acoustoelectric transducer

Joseph S. Heyman

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 243-249 (1978); (7 pages) | Cited 2 times

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Conventional ultrasonic transducers transform acoustic waves into electrical signals preserving phase and amplitude information. When the acoustic wavelength is significantly smaller than the transducer diameter, severe phase modulation of the electrical signal can occur. This results in anomalous attenuation measurements, background noise in Non‐Destructive Evaluation (NDE), and in general complicates data interpretation. In this article, we describe and evaluate a phase insensitive transducer based on the acoustoelectric effect. Theory of operation of the Acousto‐Electric Transducer (AET) is discussed and some optimization procedures outlined for its use. Directivity data for for the AET is contrated with a conventional piezoelectric transducer. In addition, transmission scanning data of phantom flaws in metal plates is presented for both transducers and demonstrates a significant improvement in resolution with the AET.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
72.50.+b Acoustoelectric effects
73.50.Rb Acoustoelectric and magnetoacoustic effects
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
43.38.Gy Semiconductor transducers
43.38.Ar Transducing principles, materials, and structures: general

Effects of diffraction on stress pulse propagation

M. R. Layton, E. F. Carome, H. D. Hardy, and J. A. Bucaro

J. Acoust. Soc. Am. Volume 64, Issue 1, pp. 250-256 (1978); (7 pages) | Cited 1 time

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See Also: Erratum

Show Abstract
Investigations have been made of the effect of diffraction on the propagation of acoustic impulses in water. Gaussian shape pressure pulses were obtained by applying 0.2‐μs‐wide voltage pulses to thick piezoelectric plates that act as piston sources. Acoustic probe techniques were used to examine in detail the resulting pressure profiles. These are strongly affected by diffraction phenomena, and because of the transient nature of the process, special care must be taken in interpreting the observed data. Comparisons between experimental and theoretical time and space pressure profiles are presented.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.20.Fn Scattering of acoustic waves
43.30.Ft Volume scattering
43.38.Fx Piezoelectric and ferroelectric transducers
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