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Feb 1975

Volume 57, Issue 2, pp. 273-523

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Intensity fluctuations of aircraft flyover noise

Robert H. Gonter

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 273-275 (1975); (3 pages)

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Aircraft flyover noise was recorded and played back with a peak detector to detect the intensity fluctuations. The intensity fluctuations were digitized and plotted. Jet noise fluctuations appear more jagged, while prop noise fluctuations are smoother. Spectral analysis of fluctuations shows most of the power is at low frequencies and decreased by 80 dB between 0 and 5 Hz.
Subject Classification: 28.45; 50.50, 50.55.
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43.28.+h Aeroacoustics and atmospheric sound
43.50.+y Noise: its effects and control

Extended modified ray theory field in bounded and unbounded inhomogeneous media

James A. Davis

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 276-286 (1975); (11 pages) | Cited 3 times

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Use of the generalized WKB procedure in place of the WKB procedure to obtain solutions to the separated wave equation leads to modified ray theory. The quantitative consequences of this frequency−dependent theory are investigated and compared with ordinary ray theory and normal−mode theory for both bounded and unbounded media under conditions for the formation of a shadow region in ordinary ray theory. The behavior of the modified ray theory field, which always contains a caustic in the types of problems which are examined, depends on whether the ray theory shadow boundary is a limiting ray or a caustic. In the former case the modified ray theory field, suitably extended to take the caustic into account, approaches the normal−mode field far into the shadow region. In the latter case the modified ray theory field in the shadow region agrees with the ordinary ray theory field, also suitably extended.
Subject Classification: 30.20.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
92.10.Vz Underwater sound
43.20.+g General linear acoustics

Finite−element approach to acoustic scattering from elastic structures

John T. Hunt, Max R. Knittel, Charles S. Nichols, and Don Barach

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 287-299 (1975); (13 pages) | Cited 2 times

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An approximate method is presented for solving the equations of motion that describe the scattering of an acoustic wave by an elastic structure immersed in an infinite fluid medium. The mathematical model that is developed uses the finite−element method to calculate the vibrational response of the elastic body and to calculate the acoustic pressure field of a finite volume of the fluid medium which closely surrounds the elastic body. Analytical methods are used to obtain the boundary conditions for this mathematical model. Results are presented for the total scattering cross section, axial pressure, and scattering patterns for an acoustic plane wave at normal incidence on an aluminum disk.
Subject Classification: 30.30, 30.40.
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92.10.Vz Underwater sound

Predictions of volume scattering strengths from biological trawl data

Richard H. Love

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 300-306 (1975); (7 pages) | Cited 1 time

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A volume reverberation model which utilizes fish distribution data has been developed to permit quantitative predictions of depth−dependent scattering strengths. The model was evaluated by using coincident acoustic volume scattering measurements and biological trawl data collected in the Mediterranean Sea. Biological specimens were collected at discrete depths with an Isaacs−Kidd midwater trawl. Each fish collected was identified and sized, and its acoustic cross section calculated by utilizing regression equations relating fish species, length, and swimbladder volume at frequencies near swimbladder resonance, or equations relating fish length to acoustic cross section at frequencies far above resonance. Scattering strengths for each species were then determined, indicating dominant species at each trawl depth for 1/3−octave frequency bands between 2.5 and 20 kHz. The acoustic data were obtained with surface−vented explosive sources and a shallow onmidirectional hydrophone. These data were processed to yield integrated column strength versus depth profiles, which were then numerically differentiated to produce scattering strength versus depth profiles for each frequency band. Comparison of the model predictions to the scattering strength profiles showed good agreement at the higher frequencies, with the agreement decreasing with frequency below 6.3 kHz.
Subject Classification: 30.30, 30.40.
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92.10.Vz Underwater sound

Propagation of normal mode in the parabolic approximation

Suzanne T. McDaniel

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 307-311 (1975); (5 pages) | Cited 2 times

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The parabolic approximation to the acoustic wave equation is examined within the framework of normal−mode theory. For the case where sOund speed and water de pth are independent of range, three types of errors are found to occur. Discrete modes are shown to propagate with the correct amplitude and mode shape but with errors in phase and group velocities. In addition to these errors, which are inherent in the method, two other sources of error are present. The effect of these other errors may be made negligible in one case by limiting the sound−speed gradients and range considered and, in the other case, by introducing a highly absorptive layer deep in the ocean bottom.
Subject Classification: 30.20,30.50;20.40,20.15.
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92.10.Vz Underwater sound
43.20.+g General linear acoustics

Speed of sound in seawater as a function of temperature and salinity at one atmosphere

Frank J. Millero and Thomas Kubinski

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 312-319 (1975); (8 pages) | Cited 3 times

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The speed of sound in standard seawater (diluted with pure water and evaporated) has been measured relative to pure water with a Nusonics velocimeter as a function of temperature (0 to 40°C, at 5° intervals) and salinity (5 to 40 0/00, at 5 0/00 intervals) at a atm. The results have been fitted to an equation of the form c = c0 + A S (0/00) + B S (0/00)3/2 + C S (0/00)2, where c0 is the speed of sound in pure water, S (0/00) is the salinity in parts per thousand, and A, B, and C are temperature−dependent parameters. The sound speeds fit this equation to a standard deviation of 0.04 m sec−1 over the entire temperature and salinity range. Over the oceanographic range our results, on the average, agree with the work of Wilson to ±0.5 m sec−1 (max 1.08 m sec−1) and with the work of Del Grosso and Mader to ±0.05 m sec−1 (max 0.14 m sec−1). In the low−salinity range, (5−25 0/00 salinity) our results, on the average, agree with the work of Wilson to ±0.3 m sec−1 (max 1.1 m sec−1) and with the work of Del Grosso and Mader to within ±0.1 m sec−1 (max 0.20 m sec−1). From these comparisons it is clear that the 1−atm sound speeds of Del Grosso and Mader are more reliable than those determined by Wilson over the oceanographic range as well as at lower salinities (which is outside of the range of Del Grosso and Mader’s measurements). The adiabatic and isothermal compressibilities of seawater solutions reliable to ±0.003×10−6 bar−1 have been determined from the sound speeds. The isothermal compressibilities are in excellent agreement (avg. dev. ±0.02×10−6 bar) with the direct measurements of Lepple and Millero. The specific heat of seawater solutions at constant volume has also been determined from the sound−derived isothermal compressibilities.
Subject Classification: 30.25.
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92.10.Vz Underwater sound

Sound propagation and attenuation in the deep ocean at very long ranges

V. G. Nomady and H. Überall

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 320-330 (1975); (11 pages)

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Sound propagation in a deep−ocean sound channel is investigated theoretically. A normal−mode series solution which includes effects due to curvature of the earth is obtained as the residues in a pole series arising from the Watson transformation. Analytic expressions are found for the pressure amplitudes due to a continuous wave source using an Epstein sound velocity profile. Attenuation−versus−range curves are given for both phased and random modal sums. The continuous wave solutions are then used for the pulsed source problem. Dispersion curves are obtained. The higher−order modes are shown to arrive earlier, in agreement with experiment. An analytic expression for the pressure of a pulse as a function of time is obtained. The shape of the pulse at a range of several hundred miles is shown and agrees qualitatively with experimentally obtained pulse shapes. Such pulses begin at a low amplitude, increase to a relatively large amplitude peak, then cut off abruptly.
Subject Classification: 30.20.
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92.10.Vz Underwater sound
43.20.+g General linear acoustics

New acoustic resonator for liquids in the 0.2− to 2−MHz range

F. Eggers and Th. Funck

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 331-333 (1975); (3 pages) | Cited 2 times

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A new acoustic resonator with nonplanar quartz transducers for liquids (sample volume about 20 ml) in the 0.2− to 2−MHz range is described. The application of static overpressure onto the liquid cavity causes concave bending of both quartz transducers. This reduces loss contributions from diffraction and ’’side−wall effects’’ considerably, resulting in higher Q values for this resonator; moreover, air inclusions in the cavity are suppressed.
Subject Classification: 35.24, 35.80.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
43.58.+z Acoustical measurements and instrumentation

On a method of superresolution of a limited number of point targets using ultrasonic scanning

Osamu Ikeda and Takuso Sato

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 334-337 (1975); (4 pages)

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To get high−resolution reconstructed images under the conditions of a restricted scanning size and a long wavelength of ultrasonic waves, a method of superresolution imaging is proposed. The basic idea is to multiply computationally the phase of the detected signals and to eliminate the extra deteriorating terms also by means of computational manipulations, and to reconstruct the image using the resulting signals. The principle and some results by computer simulation showing the effectiveness of the method are shown, though the technique is useful only for a limited number of a few point targets at most, and it also requires a priori knowledge of the target.
Subject Classification :35.65.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
43.60.+d Acoustic signal processing

Excitation of surface elastic waves in a piezoelectric layered structure

S. R. Ponamgi and Hang−Sheng Tuan

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 338-346 (1975); (9 pages)

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The excitation of Rayleigh surface waves by an interdigital transducer (IDT) on a piezoelectric layered structure has been studied in this paper. The surface wave velocity, optimum finger width, and number of fingers for maximum bandwidth for the IDT have been calculated for several values of the product (ks) of wavenumber and layer thickness. The frequency response and equivalent circuit of the IDT have been determined. Numerical examples are also presented and discussed.
Subject Classification: 20.15.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
43.20.+g General linear acoustics

Investigation of critical−angle ultrasonic phenomena by Bragg diffraction of laser light

John P. Powers and Robert D. Brown, Jr.

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 347-350 (1975); (4 pages)

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A laser beam probe is used to study ultrasonic phenomena at a liquid−liquid interface. In particular, the technique has been used to detect and quantify evanescent waves generated at such an interface when the critical angle of incidence is exceeded. A mathematical description of the properties of evanescent waves is also given.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound

Velocity−dispersion measurements in liquids between 3.3 MHz and 70.2 MHz

D. Rogez and M. Bader

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 351-355 (1975); (5 pages) | Cited 1 time

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An improved differential phase−comparison method for the measurement of small changes in ultrasonic velocity is described. Velocity dispersion measurements can be carried out in the frequency range from 3.3 to 70.2 MHz; the relative accuracy is one part in 105; only 12 cm3 of liquid are required. Results are presented for aqueous and organic solutions, which are in good agreement with known ultrasonic−absorption data.
Subject Classification: 35.24, 35.35.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound

Radial vibrations of axially polarized piezoelectric ceramic cylinders

Nachman T. Adelman, Yehuda Stavsky, and Emanuel Segal

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 356-360 (1975); (5 pages) | Cited 4 times

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This paper is concerned with the steady−state radial−shear vibrations of an axially polarized piezoelectric ceramic tube of infinite length, whose cylindrical surfaces are either traction−free or subjected to a relative displacement. Open− and short−circuit resonant frequency equations are formulated and the deviation between frequency pairs examined numerically. Fundamental resonant frequency curves are given for traction−free PZT−4 cylinders having arbitrary geometry, which approach the infinite plate solutions for large radius/thickness ratios. The theory is applied to the vibrations of annular accelerometers operating in the radial−shear mode.
Subject Classification: 40.26.
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43.40.+s Structural acoustics and vibration
43.58.+z Acoustical measurements and instrumentation
77.65.-j Piezoelectricity and electromechanical effects

Distribution of natural frequencies in certain structural elements

I. Elishakoff

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 361-369 (1975); (9 pages) | Cited 2 times

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The paper deals with the natural frequency distribution in beams, plates, and shallow spherical shells. Expressions are found for the distribution functions (number of modes not exceeding a given cutoff level), for these integral approximations, and for the frequency derivatives of the latter—the so−called smeared modal densities. Special attention is paid to the singularities in these densities (present in certain elements), which were noted by Bolotin and are referred to in literature as ’’condensation points.’’ It is shown that omission of the concept of lowest natural frequency leads to a physical paradox, and that the findings of most studies of modal densities should be revised. The method of integral approximations is applied to the problem of random vibrations of a shallow spherical viscoelastic panel. It is shown that the integral approximation of the averaged spectral density in the high−frequency range is equivalent to an infinite−system model, and, moreover that the physically inconsistent results reported in literature regarding infinite discontinuities in the spectral densities of damped shells are erroneous and due to application of asymptotic expressions, valid only at high frequencies, to the low−frequency range.
Subject Classification: 40.22, 40.24, 40.26, 40.35.
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43.40.+s Structural acoustics and vibration

Vibration and wave propagation in ribbed plates

M. L. Rumerman

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 370-373 (1975); (4 pages) | Cited 9 times

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A formalism for handling problems of wave propagation and forced vibration in ribbed plates is presented. A general solution is obtained for the forced vibration of an infinite thin plate, periodically stiffened by identical, uniform ribs. The ribs are idealized as parallel line attachments capable of exerting line forces and line moments upon the plate, and the magnitudes of these forces and moments are related to the motion of the plate through the impedances of the ribs and plate. The assumption of an externally applied pressure excitation, which varies harmonically in time and in the plane of the plate, permits an explicit solution, and the principle of superposition is then used to construct the solution to an arbitrary excitation. By setting the amplitude of the harmonic excitation equal to zero, an equation for the free modes of the ribbed plate is derived.
Subject Classification: 20.15.
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43.40.+s Structural acoustics and vibration
43.20.+g General linear acoustics

Comparison of Statistical Energy Analysis power flow predictions with an ’’exact’’ calculation

Paul J. Remington and Jerome E. Manning

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 374-379 (1975); (6 pages) | Cited 1 time

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Statistical Energy Analysis (SEA) predictions of the power flow between two multimodal dynamic systems, i.e., two rods vibrating in compression, are compared with an exact calculation. The exact calculation when averaged in sufficiently broad frequency bands is found to agree closely with the SEA predictions for both strong and weak coupling.
Subject Classification: 45.40.
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43.55.+p Architectural acoustics
43.20.+g General linear acoustics

Chamber for reverberant acoustic power measurements in air and in water

William K. Blake and Lawrence J. Maga

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 380-384 (1975); (5 pages)

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A reverberant chamber for use with both air and water media is described. The chamber is used to investigate the acoustic coupling of simple vibrating structures under conditions of light or of heavy fluid loading. Calibration was effected by measuring 60−dB reverberation times in 1/3−octave bands; decay times on the order of 2 sec in air and the order of 0.2 sec in water were observed. These results were cross checked in water by measuring the spectrum of acoustic pressure in the chamber generated by a calibrated hydrophone source. Sound−pressure levels measured in narrow (50−Hz) bands varied ±3 dB spatially in the air−filled chamber and ±5 dB spatially in the water−filled chamber.
Subject Classification: 55.65; 50.25; 45.10.
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43.55.+p Architectural acoustics
43.50.+y Noise: its effects and control

Time and frequency analyses of auditory signal detection

Al Ahumada, Jr., Richard Marken, and Arthur Sandusky

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 385-390 (1975); (6 pages) | Cited 7 times

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Observers rated 500−msec bursts of wide−band Gaussian noise for presence or absence of a 100−msec, 500−Hz signal tone. The tone was present on half of the 400 trials and was centered in the noise bursts. Bandwidth and integration time estimates were found for each observer by correlating the observer ratings with the output of energy detectors of various bandwidths (20, 40, 100, 250 Hz) and integration times (50, 100, 300, 500 msec) to find the best correlating energy detector. The results, computed separately for signal (SN) and no signal (N) trials, indicate a bandwidth of 40 Hz and an integration time of 100 or 300 msec fit best on both SN and N trials. Energy variations in 25 50−Hz by 100−msec segments of the noise were correlated with the observer ratings and showed negative correlations in frequency and time intervals immediately surrounding the signal region on SN trials, but not on N trials. The results suggest observer monitor detectors sensitive to temporal and spectral changes in the energy of the noise bursts, not just the absolute level of the output of a simple filter−integrator energy detector. The N trial results are accounted for by assuming that the observer is looking for the same pattern of temporal and spectral changes as on SN trials, but is uncertain as to the exact location of the signal tone.
Subject Classification: 65.58, 65.35.
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42.66.-p Physiological optics

Mechanisms of masking

B. C. J. Moore

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 391-399 (1975); (9 pages) | Cited 6 times

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Some of the strategies which an observer might use in detecting a tone presented against a background of noise are discussed. In Experiment I thresholds for tones in noise were measured under a number of different conditions, using flat−spectrum and notch−filtered noises, in a two−interval forced−choice task. Threshold did not correspond to a constant difference in critical−band levels on the two halves of the trial. Performance at the highest frequency used (6.1 kHz) was worse than at lower frequencies (1055 and 4080 Hz), and, in contrast to them, was not independent of overall level. This is contrary to the classical data, and indicates that the critical ratio is not a constant fraction of the critical band. In Experiment II the intensity discrimination of 1/3−octave bands of noise was studied. The noises were presented alone or in a wide−band noise background. For noise bands presented alone, performance is roughly independent of overall level, and improves slightly with increasing center frequency. For noise bands presented against a wide−band noise background, performance is independent of overall level for frequencies up to 4 kHz. A change in level of about 2−3 dB is necessary for 75% correct detection. For frequencies above this, performance worsens with increasing overall level. These results may be explicable in terms of a saturation of neurons at high intensities. The saturation effects are not observed at low frequencies, possibly because the primary cue for detection is a change in the temporal pattern of neural firing, rather than a change in amount of neural firing.
Subject Classification: 65.58, 65,35.
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42.66.-p Physiological optics

Intensity discrimination for noise bursts in the presence of a continuous, bandstop background: effects of level, width of the bandstop, and duration

Brian C. J. Moore and David H. Raab

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 400-405 (1975); (6 pages) | Cited 1 time

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Weber functions for broad−band noise bursts were determined using a 2IFC procedure. Noise bursts were presented either alone or in the presence of a continuous, bandstop−filtered background whose spectrum level in the passband was 10 dB above that of the standard burst. The width of the bandstop was varied from 100 to 3160 Hz in half−log−unit steps. The center frequency of the bandstop was always 1800 Hz. Burst duration was either 10 or 250 msec, and levels ranged from 31 to 81 dB SPL. Weber fractions tended to increase with increasing level for all conditions using a bandstop background, but the effects were small. The form of the Weber function was similar for the long and the short duration bursts. Performance improved with increasing width of the bandstop, but the magnitude of the effect (on average, 2.5 dB per decade of bandwidth) was about half what would be predicted by stimulus−oriented models of discrimination (5 dB per decade).
Subject Classification: 65.35, 65.50.
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42.66.-p Physiological optics

Underwater localization of click and pulsed pure−tone signals by the California sea lion (Zalophus californianus)

Patrick W. B. Moore

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 406-410 (1975); (5 pages) | Cited 3 times

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The objective of this study was to measure the ability of the sea lion (Zalophus californianus) to localize click and pulsed pure−tone signals presented in the horizontal plane. In the first experiment the Minimum Audible Angle (MAA) was determined for a click signal consisting of one cycle of a 1.0−kHz signal presented with a repetition rate of 30 Hz. Thresholds at 63% and 75% correct responses were 6° and 9°, respectively. A second experiment examined the sea lion’s ability to localize pulsed pure tones ranging in frequency from 0.25 to 4.0 kHz at only one angular displacement. The pure tones were presented in the form of a pulse train, each pulse having a duration of 20 msec, rise−fall time of 5 msec, and a repetition rate of 30 Hz. The pulsed pure−tone localization function showed that as signal frequency was increased from 250 Hz to 1.0 kHz, the sea lion’s ability to localize the signal remained relatively constant, while above 1.0 kHz there was a sharp decrement in localization ability.
Subject Classification: 65.62; 80.60.
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42.66.-p Physiological optics
43.80.-n Bioacoustics

Influence of middle−ear muscle contraction on pure−tone suprathreshold loudness judgments

Donald E. Morgan and Donald D. Dirks

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 411-420 (1975); (10 pages) | Cited 1 time

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Some effects of middle−ear muscle (MEM) contraction on TTS and suprathreshold loudness judgments have been assessed in three experiments. Experiment I was designed to demonstrate the effect of MEM contraction on TTS while in Experiments II and III the influence of MEM contraction on the loudness of suprathreshold pure−tone stimuli was measured. In Experiment I, MEM contraction decreased the effective level of a high−intensity TTS−inducing stimulus reaching the cochlea. In Experiments II and III signal paradigms were chosen to reduce or eliminate the effects of binaural loudness summation, and contralateral remote and backward masking effects, and to maximize the influence of MEM contraction. Results of the loudness judgments indicated no effect of binaural interaction, whereas the MEM contraction affected the loudness of pure tones only when the stimuli were low frequencye (250, 500 Hz) and high intensity (≳100 dB SPL). The results further imply that at high intensity levels there was an interaction between the effects of the intensity of the loudness−judgment stimulus and the intensity of the reflex−inducing stimulus. That is, when the reflex was induced the effect on loudness increased as the intensity of the loudness−judgment stimulus was raised; likewise, when the loudness−judgment stimulus was maintained at a constant sound−pressure level but the intensity of the reflex−inducing stimulus was increased, the effect on loudness increased.
Subject Classification: 65.50, 65.22, 65.24.
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42.66.-p Physiological optics

Reaction−time procedure for measurement of hearing. I. Suprathreshold functions

Bryan E. Pfingst, Robert Hienz, Joseph Kimm, and Josef Miller

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 421-430 (1975); (10 pages) | Cited 3 times

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Reaction time (RT), or response latency, to auditory stimuli has been suggested as a measure of loudness in nonverbal animals as well as in man. In this study RT functions were obtained for human and rhesus monkey subjects under normal conditions and under conditions of hearing impairment. In both humans and monkeys RT varied in a similar manner with changes in intensity and frequency of the stimulus, and in response to experimental manipulation of the receptor organ. The study demonstrated that latency functions are similar to functions derived by loudness−matching procedures in humans: in subjects with normal hearing, equal−latency contours corresponded closely with equal−loudness contours. In subjects with impaired hearing, matched−latency and matched−loudness contours also corresponded closely. Rate of decrease in RT with increasing intensity is discussed and related to rate of growth in loudness. The results suggest that RT is a valuable measure of suprathreshold hearing in human and nonhuman primates.
Subject Classification: 65.50, 65.64, 65.66, 65.75; 85.24.
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42.66.-p Physiological optics
43.58.+z Acoustical measurements and instrumentation

Reaction time procedure for measurement of hearing. II. Threshold functions

Bryan E. Pfingst, Robert Hienz, and Josef Miller

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 431-436 (1975); (6 pages) | Cited 2 times

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The reaction−time (RT) procedure applied to the measurement of suprathreshold functions in the preceding paper may also be used to measure threshold. This paper examines threshold contours measured by the RT procedure in human and monkey subjects with normal and impaired hearing. In the human subjects, thresholds obtained using the RT procedure closely paralleled those obtained in the clinic but were an average of 2.7 dB lower; RT thresholds were an average of 5 dB above thresholds obtained in a forced−choice procedure. Thresholds obtained from monkey subjects paralleled the normal human contours within the human frequency range of hearing, but were slightly higher at frequencies below 4 kHz and lower at frequencies above 4 kHz. The monkeys’ hearing extended approximately 11/4 octave above the humans’. Thresholds measured using the RT procedure in human and monkey subjects agreed well with thresholds previously reported in the literature. The effects of sound presentation and calibration procedures on the shape and position of the threshold contours are examined in an appendix.
Subject Classification: 65.50, 65.64, 65.75; 85.24.
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42.66.-p Physiological optics
43.58.+z Acoustical measurements and instrumentation

Audotory intensity discrimination with bursts of reproducible noise

David H. Raab and Israel A. Goldberg

J. Acoust. Soc. Am. Volume 57, Issue 2, pp. 437-447 (1975); (11 pages) | Cited 7 times

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Auditory−intensity discrimination was investigated using gated bursts of reproducible noise. Weber fractions were determined at a number of energy levels with stimuli that differed in intensity, duration, and bandwidth. Weber’s law was approximated in all cases. In addition, discriminability was found to be somewhat dependent on burst duration and relatively independent of noise bandwidth; threshold signal−to−noise ratios improved when duration was increased from 10 to 100 msec, but not when bandwidth was increased from 500 to 5000 Hz. The data were compared with the results of a second experiment in which the stimuli were random—rather than pseudorandom—noises. Finally, the results of both experiments were compared with predictions about intensity discrimination derived from two theoretical models: (1) a Poisson−counting mechanism and (2) an energy detector incorporating additive internal noise.
Subject Classification: 65.35, 65.58.
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42.66.-p Physiological optics
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