bluuebunny/crossref_metadata_2025 huggingface dataset:
Torsional Vibration of an Elastic Solid Containing a Penny-Shaped Crack
Authors: Sih G. C. , Loeber J. F.
Published: September 2005

The axisymmetric wave equation is solved for the problem of torsional elastic waves impinging on a penny-shaped crack the periphery of which is assumed to be infinitely sharp. Using Hankel transforms, the problem is reduced to the solution of two simultaneous integral equations of the Fredholm type. The proposed method of solution permits an examination of the complete scattered-wave field at points both near to and far from the penny-shaped plane of discontinuity. In elastodynamics, however, it is the nearfield stress solution that is of chief interest. To this end, the singular nature of the local dynamic stress field is determined in elementary closed form, while the magnitude of this stress field, which can be adequately described by a singularity parameter k3, is calculated numerically. The important results are that (1) the stresses are singular of the order r1−12 as r1 → 0 at the diffracting edge of the crack and (2) k3 is found to be proportional to the material constants, the crack radius, and the wavelength or frequency of the incoming waves. A knowledge of this parameter k3 is essential to a clear understanding of the propagation of cracks through structural components undergoing torsional oscillations, since its value has been known to control the stability or instability behavior of cracks.
Scattering of Frequency-Modulated Pulses by Spherical Elastic Shells in Water
Authors: Hickling R. , Means R. W.
Published: September 2005

Previous theoretical work on the scattering of sound pulses by a spherical metallic shell in water is extended to two areas of practical interest; (a) linear frequency-modulated (fm) pulses, and (b) higher frequencies where the wavelength in water is much less than the exterior radius of the shell. Cross-correlation techniques are applied in the analysis of the echo structure. Computations are performed for a water-filled aluminum shell with a ratio of interior to exterior radius of 0.95. It is shown that the frequency dependence of the steady-state farfield echo intensity at high frequencies has the same kind of irregular behavior as that found previously at lower frequencies. Echo pulses are computed for linear fm pulses with different pulse lengths and frequency sweeps. A cross-correlation scan of each fm echo pulse with its incident pulse shows a series of strong correlations within the echo. The first of these indicates that the first part of the echo corresponds to a reflection of the incident pulse from the outer surface of the shell. Another strong correlation appears to arise from a reflection from the back surface of the shell, particularly at high frequencies. It does not seem that the remaining correlations can be readily matched with simple travel paths within or around the shell.
Range Focusing in a Deep-Ocean Sound Channel with Parabolic Profile
Authors: Überall H. , Nicholas N. C.
Published: September 2005

We show, using the case of the parabolic velocity profile c02/c2 = 1 −α2z2 for an underwater acoustic duct, that the normal-mode series of the problem contains a coherent part which dominates, and explicitly exhibits the phenomenon of range focusing, at a range of R − 2π/α and its multiples. Owing to the symmetry of the profile, additional focal points are given by R/2 and its odd multiples, situated as far below the channel axis as the source is above, while the even-multiple focal points lie at the height of the source. The coherent part of the series is given in analytic form, and is shown to approximate a delta function in the depth variable at the focusing ranges.
On Optimum Array Detection of Ocean Acoustic Signals
Authors: Hyde D. W. , Wade W. D.
Published: September 2005

Research into the dispersive characteristics of underwater sound propagation has been approached in several ways. In the macroscopic approach, the medium is characterized as a stochastic time-varying filter. This paper considers the synthesis of an optimum detection system from this approach. The joint moments of the signal processes from an array of K receiving elements are then easily determined, given a knowledge of the joint moments of the impulse responses of the medium. A method for synthesizing the optimum processor containing realizable time varying filters is presented for the case when the transmitted signal is deterministic and the medium noise and channel impulse responses are Gaussian. These filters are obtained by considering a “serial” form of the optimum detector where the signal inputs in (0,T) are grouped serially into a single signal having duration kT sec. This form of the processor is amenable to standard techniques for forming either an analog or digital realizable set of filters. A technique is then employed for partitioning each of these filters into k(k+1)/2 realizable filters whose impulse responses occur in (0,T). This partitioning and the subsequent time translation results in a realizable signal processor.
Underwater Sounds of Migrating Gray Whales, Eschrichtius glaucus (Cope)
Authors: Cummings William C. , Thompson Paul O. , Cook Richard
Published: September 2005

Underwater sounds from migrating gray whales were recorded from a bottom-mounted hydrophone array. Sound-source locations were based upon arrival-time differences and received levels. Visual tracking corroborated sound data. Moans were the most common of more than 231 whale sounds recorded in the presence of at least 218 whales. Moans lasted 1.5 sec; their source level was about 126 dB re 0.0002 dyn/cm2 at 1 yd; and they ranged from 20–200 Hz. Underwater blow sounds from surface exhalations were 1.25 sec long, and they ranged from 15–175 Hz. Infrequent bubble-type signals, lasting 0.7 sec, were about 112 dB re 0.0002 dyn/cm2 at 1 yd, ranging from 15–305 Hz. Knock sounds were as high as 350 Hz at sound-pressure levels up to 116 dB re 0.0002 dyn/cm3 at 1 yd. Gray whales were soniferous during the day and night. The average swimming speed of lone migrators was 5.5 kt, based on sound tracks. No characteristic behavior could be associated with sound production other than blow sounds during exhalations.
Ultrasonic Two-Dimensional Visualization for Medical Diagnosis
Authors: Kossoff George , Robinson David E. , Garrett William J.
Published: September 2005

The spot size of the display unit may be used as the design criterion of the ultrasonic visualization system. Methods to design the transducer to comply with the criterion are presented, and the performance of the scanner and the receiver are discussed. The technique is prone to artifacts caused by axial and nonaxial multiple reflections, velocity changes in tissue, and signal processing. Echograms of the pregnant uterus are used to illustrate the application of the technique.
Simulation of the Secondary Residue Effect by Digital Computer
Authors: Fischler H. , Cern L.
Published: September 2005

A model accounting for the second effect of pitch shift in perception of the tonal residue, is re-examined in the light of a computer simulation. It provides the temporal fine structure of the response of the basilar-membrane motion to stimulation of the ear by AM complex tones. Computation is performed by convolution of the input signal with the impulse response of the ear's mechanical system. The results confirm the earlier claim that the secondary residue effect can be fully accounted for by mechanical filtering, without resorting to neural mechanisms. The function relating the magnitude of the secondary effect to basilar-membrane locations, was certified. The simulation also resolves the ambiguity in the algebraic sign of the secondary residue effect.
Studies of Two-Tone Interaction as Seen in the Guinea Pig Microphonic
Authors: Nieder P. , Nieder I.
Published: September 2005

Responses recorded from the round window of guinea pigs were studied using stimuli consisting of a low frequency fm, usually 250 Hz, and a high frequency fs, usually 8 kHz. Filtered responses were displayed so that amplitude modulation of the fs output component could be observed. The effect was studied as a function of the intensity of each stimulus component. Modulation effects were time locked to the fm output component with amplitude maxima occurring near zero crossings of the fm wave. Interference between the two signals was closely correlated with the modulation effect. Cumulative changes in modulation effects occurred in tests using uninterrupted or burst stimuli reaching only moderately high levels even when duty cycles were below 10%. Monitoring the response during several minutes of two-tone stimulation at fixed moderately high sound-pressure level showed a complex sequence of changes in the modulation envelope and the amplitude of the fm output component. It is concluded that both interference and modulation result from nonlinearity of the microphonic generator. The generator transfer characteristic is labile with stimulation-induced sensitization and depression having different time courses.
Design and Measurement of Infrasonic Gradient Microphones and Windscreens
Authors: Bauer Benjamin B.
Published: September 2005

Until recently, infrasonic phenomena have been explored mainly with pressure microphones. Gradient microphones, especially when arranged in an orthogonal bigradient array, have the capability of providing information about the direction, as well as the intensity and time of sound arrival. A low-frequency bigradient array is described. An equivalent circuit for analyzing infrasonic gradient microphones is developed and applied to the analysis of errors that may be expected when the microphone is measured in a spherical field. A plane-wave calibrator for infrasonic gradient microphones and windscreens, with internal dimensions of 4×4×8 ft, has been built along the principles of the laboratory calibrator for gradient hydrophones described by the present author [J. Acoust. Soc. Amer. 39, 585–586 (1966)] with the added capability for testing the acoustical symmetry of infrasonic microphones. Windscreens affect the low-frequency response of gradient microphones and the new equivalent circuit has been applied to the design of windscreens.
Fluctuations of Sound with Position in a Reverberant Room
Authors: Lubman David
Published: September 2005

Spatial fluctuations of sound in reverberant rooms are examined theoretically for the case of a fixed source and movable receiver. The approach is to describe statistics of the time-averaged squared sound pressure, as a function of frequency. These statistics apply to reverberant rooms at high frequencies, such that the modal overlap (ratio of modal bandwidth to the average spacing between modes) is larger than about 3, and for regions sufficiently removed from the source that the reverberant field prevails. Within these bounds of frequency and space, squared sound pressure may be profitably viewed as a stochastic process over frequency. At each frequency in this range, squared sound pressure is a random variable obeying an exponential probability law over space. The family of random variables obtained by considering all frequencies in this range defines a stochastic process. The process is employed to derive formulas for the spatial variance of squared sound pressure for the cases of single tone, multitone, warbletone, and narrow-band noise excitation. Experimental confirmation and suggested applications are given in many instances. In general, the variance is small when the product of bandwidth and reverberation time is large, as long as reverberation time is not so large as to prevent high modal overlap.
Effect of Masker Spectrum Level on Masking-Level Differences at Low Signal Frequencies
Authors: Dolan Terrence R.
Published: September 2005

Most, if not all, models of binaural hearing predict a dependence of the magnitude of the masking-level difference (MLD) on signal frequency. Specifically, the size of the MLD is expected to increase as the signal frequency is decreased. The results of many experiments in which signal frequency was varied, however, do not support the above prediction. The magnitude of the MLD appears to decrease at frequencies below 300 cps. The present experiment was designed to re-examine the decrease in the size of the MLD at low frequencies and to test a qualitative explanation of this phenomenon based on the concept of internal noise. To do so, the size of the MLD in the N0Sπ masking condition and the N0S0 masking condition was estimated relative to the NMSM masking condition at signal frequencies of 150 and 300 cps at several masker spectrum levels. The results indicated that the magnitude of the MLD at both frequencies is dependent upon spectrum level of the masker. The results further indicate that the dependence of the size of the MLD on spectrum level varies as a function of the signal frequency. The size of the MLD at 150 cps is much more sensitive to changes in masker spectrum level than is the MLD at 300 cps. Both results agree with predictions based on the internal noise hypothesis.
Mechanisms of Frequency Discrimination
Authors: Nordmark Jan O.
Published: September 2005

Difference limens were obtained for the discrimination of pure tones from 62.5 Hz to 12 kHz, and for short pulses from 1 to 4 kHz. In logarithmic coordinates, the data fitted straight lines with different slopes for the high-frequency, the low- and medium-frequency, and, for pulses, the very low-frequency ranges. An analysis was made to show that the discrimination of duration and the discrimination of pitch are both based on time-measuring processes.
Generation and Detection of Acoustic Waves in Pulsed Electrical Discharges
Authors: Nygaard K. J. , Meltz G.
Published: September 2005

Electroacoustic resonances excited in a cylindrical plasma tube are very sensitive to minute changes in electron density and temperature and can therefore be used to detect sound waves. The principle of detection is that in the ordinary acoustic mode, the neutral particles, electrons, and ions move in phase with the same relative density changes. It is demonstrated experimentally that the acoustic transient detected at a certain distance from the negative glow of a pulsed electrical discharge is superposition of a direct pulse and a pulse that has been reflected from the cathode surface. From the perturbations of the electroacoustic resonances, relative density changes of the order of 1% in the acoustic transient are deduced.
Clipstrum Pitch Determination
Authors: Noll A. Michael
Published: September 2005

A new method of pitch determination similar to the cepstrum except that both the time signal and the log power spectrum are infinitely peak clipped before spectrum analysis has been simulated on a digital computer. Although this new method itself, called the “clipstrum,” is inferior to cepstrum pitch determination, the clipstrum of center-clipped speech performs surprisingly well and sometimes is superior to the cepstrum. The clipping in the clipstrum might offer some advantages over cepstrum analysis in certain digital hardware implementations since multiplications could be replaced with additions or subtractions.
Effect of Pitch Averaging on the Quality of Natural Vowels
Authors: Rosenberg A. E.
Published: September 2005

A pitch synchronous analysis was carried out over the vowel portions of the CVC utterances HAYED, HOD, HODE, and the stressed vowel portions of the sentence, “FEW THIEVES ARE NEVER SENT TO THE JUG,” recorded by a male speaker. The analysis provided formant frequencies, excitation parameters, and accurate pitch-period measurements. For each vowel, each measured period was replaced by a period obtained by averaging adjacent periods over a symmetric “window” producing a smoothed pitch contour. The speech samples were reconstituted with the vowels with smoothed pitch contours. Eight window sizes were selected for subjective evaluation, ranging from an imperceptible amount of smoothing to an amount sufficient to produce nearly monotone vowels. Subjective evaluation was carried out by means of paired-comparison tests between utterances with different window sizes, including those with natural-pitch contours. The results indicate that listeners are unable to discriminate between samples with natural-pitch contours and those with an amount of smoothing sufficient to eliminate most of the period-to-period fine structure in the contours. In a addition, it appears that modes of discrimination with respect to pitch smoothing are distinct for the two cases of isolated vowel sounds and sentence-imbedded vowel sounds.
Finite-Amplitude Acoustic Waves in Dielectric Crystals
Authors: Richardson B. A. , Thompson R. B. , Wilkinson C. D. W.
Published: September 2005

Acoustic waves at microwave frequencies show significant nonlinear effects at power densities of 10 W/cm2. These effects have been studied using Bragg diffraction of light from the harmonic components of the acoustic waves. With this technique, direct harmonic analyses of the waves have been obtained without the need for calibrated broad-band transducers. The following effects of finite amplitude waves propagating in quartz have been observed: variation of the attenuation of the fundamental with power level; the presence of the second through fifth acoustic harmonics; the growth and decay of these harmonics as a function of the distance traveled by the acoustic wave; and the behavior of the second harmonic after reflection from a stress-free surface. The growth of the harmonics assures that they were generated in the bulk of the solid. Similar effects have been observed in MgO and MnF2. The experimental observations have been compared with theoretical predictions and estimates of the relevant third-order elastic constants obtained.
Generalized Boundary Condition for Multiple Scatter in Acoustic Reflection
Authors: Biot M. A.
Published: September 2005

A boundary condition is developed that generalizes the author's earlier results and embodies the effect of multiple scatter for acoustic reflection on a rough surface. The size of the roughness is assumed to be sufficiently small in comparison with the wavelength. Both induced radiating dipoles and radiating sources are taken into account. The results are further generalized to take into account roughness of various shapes, nonuniform distribution, and anisotropic properties. The anisotropy represented by a two-dimensional symmetric tensor of Rank 2. Results open the way to the analysis of combined coherent and incoherent reflection including the cooperative resonance due to multiple scatter.
Traveling Load on a Cylindrical Shell
Authors: Mortell Michael P.
Published: September 2005

The response of a semi-infinite circular cylindrical shell that is subject to a constant-pressure wave moving with constant velocity is examined, when the effects of transverse shear and rotatory inertia are included. The time dependence is suppressed by means of a Laplace transform, and the behavior of the motion near the characteristic wavefronts is examined by making an asymptotic expansion for large p, the transform variable, directly on the governing equations. The form of the solution near the load front is given and some resonant velocities are noted. By a simple yet novel technique, it is shown that the dominant long-time disturbance travels with the bar velocity, and the behavior of the solution in this region is shown to be that of an Airy phase.
Geoacoustic Applications of Electroseismic Sources
Authors: Nash D. M. , Barnes T. G.
Published: September 2005

A mobile high-energy source for electrically producing and controlling seismic pulses is described. The source employs an electric discharge across gap in a liquid-filled dome. Applications of this source include the detection and delineation of small anomalies in addition to conventional seismic exploration. A theoretical treatment is given to show that the high-frequency characteristics needed for resolving the small anomalies may be obtained by shaping the pulses and by producing a train of pulses.
Small, Low-Frequency, Omnidirectional, Broad-Band Hydrophone
Authors: Solberg Ruell F. , Kreisle Leonardt F.
Published: September 2005

This article describes some of the design, construction, and rest-performance details of a small, low-frequency, omnidirectional, broad-band hydrophone. The design was of such nature that the hydrophone should withstand high-velocity water impact shock, have a minimum sensitivity of −100 dB relative to 1 V/μbar for the frequency range 10 Hz to 2 kHz, have a minimum capacitance of 10 nF, and be omnidirectional in all planes to 2 kHz. A radially polarized PZT-5H piezoelecrtic ceramic tube with end caps and an internal air cavity was cast in a polyurethane compound. This particular piezoelectric material has a high permittivity, so the minimum capacitance could be obtained within the maximum physical dimensions. The mounting of the ceramic tube is described in which two beryllium copper springs are used to aid in positioning and cushioning the brittle ceramic, and to provide electrical contact to the inside and outside silver-filmed electrodes of the tube. Some of the properties of the hydrophone that are shown are the capacitance-temperature relationship, admittance versus frequency for air and water loading, and directivity patterns. The hydrophone was shown to be omnidirectional in all planes up to 5 kHz.
Sound Focusing and Beaming in the Interference Field Due to Several Shallow-Water Modes
Authors: Weston D. E.
Published: September 2005

The formation of sharp rays or beams in Wood's model shallow-water propagation experiments [V. M. Albers, Ed., Underwater Acoustics (Plenum Press, Inc., New York 1963), pp. 159–192] is due to an angular selection, and the resulting interference between neighboring high-order modes. Details of the interference mechanism are considered. A given beam should vanish and then re-form with a calculable characteristic distance. The distance is about 4 m in Wood's experiments, and the focusing is clearly visible in his results. These ideas are also applied to a moiré fringe analog, to shallow-water propagation, deep-water propagation, and to transmission of images in fiber optics.
Generation of Large Amplitude Periodic Shock-Fronted Pressure Waves in a Resonant Tube
Authors: Goluba R. W. , Weber H. G. , Borman G. L.
Published: September 2005

The construction and performance of an apparatus for generating high frequency shock fronted pressure waves is discussed. Large amplitude shock waves were obtained by periodically interrupting the air flow into a resonant tube with a rotating siren disk. Pressure wave amplitudes as large as 180 psi were obtained at a frequency of 479 Hz.
Reference Signal for Signal Quality Studies
Authors: Schroeder M. R.
Published: September 2005

A family of reference signals for signal quality studies is described that is perceptually similar to speech signals undergoing certain signal-dependent distortions, such as quantizing and predictive coding. This perceptual similarity can yield greater accuracy and reproducibility in subjective comparison tests than do reference signals employing additive, signal-independent noises. Equally important, for nonstationary and the intermittent signals (such as speech) the signal-to-noise (S/N) ratios of the reference signals described here are defined on an instantaneous (sample-by-sample) basis, thus avoiding the troublesome ambiguities in measuring signal and noise powers. The distorted signal whose quality is to be evaluated can be assigned an equivalent S/N ratio independent of the time intervals over which average are extended.
Transmission of Gigahertz Ultrasonic Waves through Optical-Contact Bonds at Room Temperature
Authors: Smith Henry I. , Smith A. B.
Published: September 2005

Measurements of shears and longitudinal wave ultrasonic transmission at 1 to 6 GHz through optical-contact bonds are described. Although most of the data were taken at room temperature, a few longitudinal wave measurements at 77°K are included to show how bond transmission technique can be used to give better than 60% transmission at room temperature up to 6 GHz. Some comments are included on the techniques for making these bonds.
Radiation Impedance of a Rectangular Piston at Very Low Frequencies
Authors: Lindemann Oscar A.
Published: September 2005

In order to demonstrate how the radiation reactance of a piston, at low frequencies, depends on its shape, the solution for a rectangle of varying aspect ratio is obtained by contour integration. The method gives in a few short steps the exact value of the asymptotic accession to inertia, previously available only by means of a much longer computation. The result is graphed as a function of the piston's aspect ratio, and compared with the known value for the circle.
Self-Noise of a Deep Submersible in a Bioacoustic Investigation off Catalina Island, California
Authors: Cummings William C. , Thompson Paul O.
Published: September 2005

An important aspect of bioacoustic studies from submersibles is the possibility of masking biological signals with the vehicle's self-noise. Measurements of self-noise are presented along with biological observations as a result of three 1190-m dives to obtain bioacoustic data with the submersible, DEEPSTAR 4000. Except for discrete frequency components from electromechanical equipments, noise levels in the frequencies from 70–9000 Hz were well below signal levels expected from nearby soniferous organisms. Ambient-noise levels were only slightly below those previously reported for deep water. The only biological signals observed during these dives apparently were from pilot whales, Globicephala scammoni.
Comments on “Focusing Properties of Cylindrical Liquid-Filled Acoustic Lenses with Large Diameter-to-Wave-length Ratios” [D. L. Folds and D. H. Brown, J. Acoust. Soc. Amer. 43, 560–565 (1968)]
Authors: Eby Edward S. , Fein Maier O. , Burt Peter J.
Published: September 2005

It is suggested that the discrepancies noted by Folds and Brown between their theoretical and experimental results may be the result of incorrect theory.
Elastic Constants of Composite Materials
Authors: Behrens Ernst
Published: September 2005

The elastic constants of a great variety of composites are calculated by evaluating the dispersion relation of sound waves for long wavelengths.
Thermal Relaxation in Nitrogen with Wet Carbon Dioxide as Impurity
Authors: Henderson M. C. , Herzfeld K. F. , Bry J. , Coakley R. , Carriere Gaston
Published: September 2005

The pressurized Kundt's tube developed in this laboratory has been used to measure the napier (relaxation) frequency of nitrogen in both binary and ternary mixtures with carbon dioxide and water vapor. Carried out at about 175°C, where the relaxing specific heat of nitrogen becomes readily measurable, the separate contaminants shift the napier frequency upward by amounts proprotional to their respective mole fractions: water vapor by 310 Hz/mole-percent, carbon dioxide by 300 Hz/mole-percent. When both are present, the shift is notably greater and is not linear in the mole fraction. This synergistic effect is explicable on theoretical grounds. Preliminary results with heavy water vapor (D2O) as impurity are also given. Its effect is also nonlinear in the mixed impurities.
Impacting Oscillatory Devices
Authors: Bycroft G. N.
Published: September 2005

An analysis is made of an oscillatory device consisting of two rods, one of which is driven at a certain frequency and one end of which impacts one end of the second rod. This is a particular case of a family of oscillators in which impacts between portions of the system are fundamental to their operation. The conditions under which oscillations can occur is discussed. Subharmonic oscillations may be generated, and consequently such devices may be used as simple mechanical frequency dividers. The qualitative behavior of such a device was checked experimentally and was found to be as predicted by the theory.
Waves on a Spherical Shell
Authors: Mortell Michael P.
Published: September 2005

Within the framework of classical linear elasticity theory, the dynamic equations governing the motion of a spherical shell are given. These include the effects of transverse shear and rotatory inertia, and can be derived on the basis of three assumptions additional to those of linear elasticity. The response of an incomplete spherical shell subject to a suddenly applied, constant moment Mθ is studied. The wavefront behavior of the solution is found by taking the Laplace transform of the equations, and then making an asymptotic expansion for large values of p, the Laplace variable. The solution is given in the form of a traveling wave, which is followed into the focus point and on its reflection from there. The applied discontinuity at the wavefront grows as θ → π; it gives a square-root singularity at θ = π, and a logarithmic singularity on the reflected wavefront. These results are synthesized by an elliptic function.
Theory of the Axial Ray
Authors: Pedersen Melvin A.
Published: September 2005

The theory of the ray that travels along or arbitrarily close to an axis of minimum velocity in the ocean is examined for an extremely wide class of velocity profiles in which the depth is expressed as a generalized power series in the velocity. Although the complete ray theory is intractable for this model, the range and travel-time integrals can be evaluated for the axial ray. Derivatives of these integrals with respect to the ray parameter indicate whether the axial ray is faster or slower than near-axial rays. The results for range, intensity anomaly, and the derivative of the group velocity with respect to the phase velocity are expressed as simple functions of σ1, the smallest exponent in the profile representation. Other ray-theory results are expressed in terms of various order profile derivatives, evaluated at the axis, and the effect of discontinuities in the profile derivatives is examined. Certain range and travel-time derivatives, although finite for symmetric profiles, are found to be infinite for nonsymmetric profiles. Thus, results for several symmetric profiles in common use differ considerably from the results for more-realistic nonsymmetric profiles.
New Acoustical Test Facilities of the National Gypsum Company
Authors: Schultz Theodore J.
Published: September 2005

This paper describes the new acoustical test facilities of the National Gypsum Company, Tonawanda, New York, comprising one large reverberation chamber, three facilities for measuring the transmission loss of wall structures, one facility for measuring the attenuation over a ceiling-plenum ceiling path, and one facility for measuring either the transmission loss for airborne sound or the impact isolation of floor-ceiling structures. The acoustical characteristics of these facilities are compared against the physical requirements stated in existing English-language measurement test standards.
Generation and Propagation of Finite-Amplitude, Rounded, Inverted Sawtooth Waves in Air
Authors: Burns Stephen H.
Published: September 2005

This paper treats a problem of finite-amplitude wave propagation in which a properly distorted wave becomes undistorted during the first stages of propagation and then again becomes distorted during later stages of propagation. A theoretical description of the waveform is given in terms of the amplitudes of the fundamental and of the second, third, and fourth harmonics as functions of propagation distance. Also provided is a theoretical estimate of the distance of propagation that is required for a properly distorted wave to become an undistorted sinusoidal wave. Experimental measurements on waves of frequency 444 Hz in an air-filled traveling-wave tube 2.66 cm in diameter and 18 wavelengths long corroborate the theoretical predictions for peak acoustic pressures from 0.001 to 0.015 bar.
Comparison of Receiver Performance: the ESP Receiver
Authors: Spooner R. L.
Published: September 2005

Treatment of detection problems from a Bayesian viewpoint implies the modeling of uncertain parameters as random variables with known a priori distributions. Attempts to compare performance of the certain parameter case with the uncertain parameter case become difficult because, for the former, performance is usually dependent on the value of the parameter in question, whereas for the latter, this dependence is removed by averaging. A method for a meaningful solution to this problem is proposed here. An auxiliary receiver, the Externally Sensed Parameter (ESP) receiver, is defined, and its performance is used as the standard for comparison purposes. The comparison is meaningful because the ESP receiver performance is independent of the value of any particular parameter in question and is an upper bound in the sense of perfect parameter information. The method appears to be particularly applicable to evaluating learning or adaptive acoustic signal processing systems and to determining the desirability of incorporating additional parameter estimation techniques in these systems.
Periodicity Pitch for Interrupted White Noise—Fact or Artifact?
Authors: Pollack Irwin
Published: September 2005

White noise was interrupted by a “clickless” switch. Accurate pitch matches were obtained for rates of interruption to 2000 interruptions per second.
Recovery from Temporary Threshold Shifts as a Function of Test and Exposure Frequencies
Authors: Smith Richard P. , Loeb Michel
Published: September 2005

Ward [W. D. Ward (1963). “Auditory Fatigue and Masking,” in Modern Developments in Audiology, J. Jerger, Ed. (Academic Press Inc., New York)] has stated that recovery following an exposure sufficient to produce temporary threshold shift (TTS) is a function solely of the amount of TTS and is independent both of the nature of the stimulus producing it and of the frequency of the test tone. In some experiments with impulse noise, the impression was gained (based on very little data) that recovery might be different at very high test frequencies, and since Ward had employed somewhat lower test frequencies in his experiment, it appeared advisable to determine whether his generalizations would hold for higher test frequencies. Apparently they do.
Acoustic Radiation from a Random Line Source
Authors: Gardner S. , Lindemann O.
Published: September 2005

The acoustic radiation from a stationary and spatially homogeneous random line source of infinite extent is studied. Analytical results are obtained for the cross-spectral density of the radiated velocity potential.
Distribution Pattern of Cochlear Harmonics
Authors: Dallos Peter , Sweetman Richard H.
Published: September 2005

This study is designed to determine whether or not traveling waves accompany harmonic distortion products generated in the cochlea, and also to describe the amplitude distribution of these nonlinear components. Cochlear microphonics were monitored with the differential electrode technique from the first and third turns of guinea pig cochleas. Cancellation of the distortion components was attempted by introducing bone-conducted pure tones of the frequency of the harmonic and of controllable magnitude and phase. It was demonstrated that harmonic components can never be canceled simultaneously throughout the cochlea. It was shown that the reason for this inability to cancel is that harmonics are not distributed in the cochlea as their own frequency would indicate, but instead they are prominent in the region where their fundamentals are strong.
Distance Estimation of 0° or Apparent 0°-Oriented Speech Signals in Anechoic Space
Authors: Gardner Mark B.
Published: September 2005

This paper reports the results of tests of the ability of an observer to estimate the distance of speech signals that originate, or appear to originate, at the intersection of the horizontal and median planes in anechoic space. Both live and recorded sources were used over a range of distances from 3 to 30 ft. For such a range (i.e., where differences in the selective effect of air absorption with frequency are relatively small), the results showed a wide difference in observer ability to estimate the distance for these two types of sources. When loudspeaker sources of recorded speech were employed, the judgments reported were essentially independent of the actual distance involved. This was true whether single, multiple symmetrical, or asymmetrical arrays were employed. When a live voice was used as a source, a rather marked degree of ability to estimate relative distance was found depending on the type of vocal output employed and on the degree to which normal level changes with distance were eliminated as a parameter. Use of a shouted voice resulted in overestimating the distance, whereas the apparent distance was foreshortened when a whispered voice was employed.
Intensity Discrimination of Rayleigh Noise
Authors: Ronken D. A.
Published: September 2005

A human observer is less effective at auditory intensity discrimination when the signal is a wide-band noise than when it is a pure (sinusoidal) tone. An experiment in intensity discrimination of Rayleigh noise shows that amplitude uncertainty seems to govern the discrimination. The empirical psychometric function is found to be only slightly displaced from the performance of an ideal energy detector.
Investigation of Stress Patterns for Speech Synthesis by Rule
Authors: Rabiner L. R. , Levitt H. , Rosenberg A. E.
Published: September 2005

In an earlier investigation, a procedure for synthesizing speech by rule was described. Although intelligible, the speech had an unnatural or machinelike quality, owing partly to the lack of suitable rules for controlling prosodic features of the utterance. The factors considered most likely to affect the prosodic features of synthetic speech were investigated experimentally. Several combinations of increments in duration and in fundamental frequency were tested using a paired-comparison technique. The set of conditions producing the most natural sounding (i.e., least machinelike) synthetic speech was obtained using a team of six listeners and three test sentences. The parameter values corresponding to this set of conditions were used to synthesize a new group of five simple declarative sentences. These same five sentences were also synthesized using the earlier synthesis scheme. A second paired-comparison experiment showed that the speech generated by the new scheme was preferred over the old in more than 80% of the comparisons.
Radiation Pressure on a Vibrating Hemispherical Meniscus
Authors: Nyborg Wesley L. , Rooney James A.
Published: September 2005

Measurements have been made on the critical pressure pc required to cause gas flow from a capillary into liquid in the presence of sound. It is found that pc increases as the square of the sonic amplitude. Results are explained in terms of acoustic radiation pressure exerted on the meniscus. Specifically, it is deduced that radial vibration of an emerging hemispherical meniscus with average (peak) displacement amplitude ξ0 causes it to be subjected to the excess time-averaged pressure (ρ0ω2ξ02/4); here, ω is the angular frequency and ρ0 the liquid density.
Rejection of a Coherent Arrival at an Array
Authors: Anderson Victor C. , Rudnick Philip
Published: September 2005

Analysis is presented for the enhancement of a plane-wave signal at an acoustic array relative to noise of which a part is also a plane wave from another direction. The process considered (described in the preceding paper) employs conventional beam forming to estimate the interfering plane-wave form, which is then removed at each element by subtraction. Removal of interference by more than one plane wave, and the relation to optimum beam forming, are briefly considered.
Rôle of Signal Onset in Sound Localization
Authors: Perrott David R.
Published: September 2005

An experiment is reported on the effects of different signal-onset conditions, as a function of signal frequency, on the minimum audible angle obtained with human listeners in a free-field localization situation. Transient binaural differences associated with signal onset were computed on the basis of: (1) the binaural distance difference; (2) the headshadow effect; and (3) the rise time of the signal. The results of the experiment indicate that signal onset may be treated as a short-duration binaural intensity-difference cue. The implications for a theoretical model of localization are discussed.
Differential Asynchrony Thresholds for Auditory Pulse Trains
Authors: Pollack Irwin
Published: September 2005

Absolute and differential thresholds for a single temporal discontinuity, or “gap,” were obtained for auditory pulse trains as a function of: (1) the interpulse interval surrounding the gap region, and, (2) the magnitude of the reference gap. Under conditions implicating a spectral analysis, e.g., a large number of pulses at high pulse frequencies, the differential asynchrony threshold is extremely sensitive to the ratio of the reference gap to its surround. Under such conditions, the differential asynchrony threshold increases sharply as the gap/surround ratio changes by a factor of 2, but is relatively independent of still further changes in the gap/surround ratio. Under conditions implicating a temporal analysis, e.g., at low pulse frequencies, or an incomplete spectral analysis, e.g., a small number of pulses at high pulse frequencies, the differential asynchrony threshold is relatively insensitive to the gap/surround ratio.
Influence of Fundamental Frequency Cues on the Perception of Some Synthetic Intonation Contours
Authors: Majewski Wojciech , Blasdell Richard
Published: September 2005

Synthetic fundamental frequency contours were classified by Polish and American-English listeners as indicating either statements or questions. Graphic analyses were applied to listeners' responses in order to isolate the most prominent F0 cues that served to differentiate statements from questions. Comparisons between the response distributions for the two language groups revealed both common and language-specific cues for F0 contour identification.
Respiratory Volumes in Normal Speech: A Possible Reason for Intraoral Pressure Differences among Voiced and Voiceless Consonants
Authors: Warren Donald W. , Wood Matthew T.
Published: September 2005

Respiratory volumes during phonation of a series of voiced and voiceless fricatives and plosives placed within a carrier phrase were measured in 20 normal adult subjects. The purpose was to (1) determine whether consonant type influences respiratory volume and (2) determine whether intraoral pressure differences among voiced-voiceless consonants could be a reflection of volume differences during speech. The results indicate that voiceless consonants utilize substantially larger volumes of air than their voiced cognates. The data also suggest that consonant intraoral pressures may be influenced more by intraoral respiratory volumes than by energy losses caused by glottal resistance during voicing.
Sound Absorption and Velocity in H2S and CO2/H2S Mixtures
Authors: Shields F. Douglas
Published: September 2005

Sound velocity and absorption measurements have been made in pure H2S at 300°K and in CO2/H2S mixtures at 300° and 500°K. The results of the measurements on pure H2S indicate no observable relaxation taking place at frequency-to-pressure ratios less than 1200 kHz/atm. The measurements on CO2/H2S mixtures showed the CO2 absorption peak to be shifted to higher frequency-to-pressure ratios by the added H2S at rates of 61.8 and 64.8 kHz per percent H2S at 300° and 500°K, respectively. From this, the relaxation times for the bending vibration of a CO2 molecule in 1 atm of H2S are calculated to be 3.16 × 10−8 and 2.97 × 10−8 sec at the two temperatures. These values are in order-of-magnitude agreement with values calculated on the assumption that the CO2 vibrational energy is exchanged with the rotational energy of the H2S molecule in the relaxation process.
Calculation of the Field of a Baffled Array by the Geometrical Theory of Diffraction
Authors: Hutchins D. L. , Kouyoumjian R. G.
Published: September 2005

This paper describes the application of the geometrical theory of diffraction to the calculation of the far-zone radiation pattern of a linear array mounted in a rigid rectangular box. Some theoretical patterns obtained with the method are presented and compared with experimental results.
Free Vibrations of Thin Orthotropic Oblate Spheroidal Shells
Authors: Penzes Leslie E.
Published: September 2005

The problem of the free vibrations of a thin orthotropic, oblate spheroidal shell has been solved by making the assumptions of orthotropic membrane theory and harmonic axisymmetric motion. The theory has reduced the differential equations of motion to a single ordinary second-order differential equation with variable coefficients. The resulting eigenvalue problem is solved by Galerkin's method. The principal directions of the elastic compliances are assumed to be along parallels of latititude and along meridians. Both the oblate spheroidal and spherical shells were studied with various orthotropic constants. The existence of finite bounds for the corresponding mode shapes has been shown. Special consideration is given to the isotropic shell as a limiting case of the orthotropic problem. The present theory in the isotropic case yields the author's previously published results for the isotropic oblate spheroidal shell, as well as the known exact solution of the isotropic spherical shell.
Effects of a Surrounding Fluid on the Free, Axisymmetric Vibrations of Thin Elastic Spherical Shells
Authors: Sonstegard David A.
Published: September 2005

Free, axisymmetric vibrations of thin elastic spherical shells submerged in a fluid are considered in this study. Irrotational motions in compressible and incompressible ideal fluids and motions in vacuum are compared via numerical examples given for steel shells vibrating in water. The results indicate that an incompressible fluid representation is applicable for the determination of natural frequencies for those modal shapes that exhibit both membrane and composite behaviors. Applicability of an incompressible solution for the uniform radial and first-order membrane modes is dependent on the shell radius-to-thickness ratio. Also demonstrated is a change in modal characteristics imposed by a surrounding fluid that provides further insight into the nature of the fluid-shell interaction.
Comments on the Book Review: “The Experimental Psychology of Sensory Behavior” [D. McFadden, J. Acoust. Soc. Amer. 44, 665 (1968)]
Authors: Corso John F.
Published: September 2005

The review in the reference cited above presents such a distorted and inadequate appraisal of the orientation and content of my textbook that I feel professionally obligated to provide a reply. My primary comments are organized into two major categories: (1) those that deal with the reviewer's conception of the general organization and direction of the textbook, and (2) those that concern the reviewer' remarks on specific content. This Letter is not intended to be an exhaustive and point-by-point reply to the reviewer' assertions, but is sufficiently directive to establish that the review grossly misrepresents the textbook.
Vibrational Relaxation of Oxygen by Methane
Authors: Evans L. B. , Winter T. G.
Published: September 2005

Acoustic absorption measurements have been used to determine vibrational relaxation times in pure oxygen and in oxygen with up to 2% methane impurity at 25°C and 126°C. These measurements were undertaken to resolve the disagreement in the measurements reported by two other investigators of the same system. The results presented confirm the results reported by Schnaus [U. E. Schnaus, J. Acoust. Soc. Amer. 37, 1–4 (1965)] and conflict with those reported by Parker and Swope [J. G. Parker and R. H. Swope, J. Chem. Phys. 43, 4427–4434 (1965)].
Comments on “Phase Changes and Pulse Deformation in Acoustics” [I. Tolstoy, J. Acoust. Soc. Amer. 44, 675–683 (1968)]
Authors: Junger Miguel C.
Published: September 2005

The −π/2 phase jump predicted in Tolstoy's analysis for refracted waves passing through a caustic is also predicted, by an entirely different analytical technique, for the related situation of diffracted waves traversing a caustic specifically the caustic at the center of the shadow zone of a spherical scatterer. The phase jump is shown to be related to the cylindrical symmetry of the diffracted field.