bluuebunny/crossref_metadata_2025 huggingface dataset:
Techniques for Speech Bandwidth Compression, Using Combinations of Channel Vocoders and Formant Vocoders
Authors: Gold Bernard
Published: September 2005

Both channel vocoders and formant vocoders have often been used as bandwidth-compression devices. This paper explores several configurations wherein elements of both are combined into a single system. Frameworks are proposed within which the element forms can be systematically changed. Experimental results from several specific cases are discussed. Most significant of these is the comparison between an 11-parameter system presented in this paper and a 16-channel laboratory vocoder. The quality obtained from the two systems was comparable, indicating that data-rate savings are possible with the new configurations.
Transient Scattering of a Monochromatic Acoustical Wave by a Scatterer Fixed in Space
Authors: Lauvstad V. R.
Published: September 2005

Formal solutions for the transient scattering of a monochromatic wave by a scatterer fixed in space are given in the cases where the corresponding steady-state solutions are known. The characteristic space and time parameters are L, the linear dimension of the scatterer, and L/c, where c is the speed of sound. The transient waves are found to trail off behind the wavefront, their time of persistence at a given point of observation being of an order of magnitude L/c. The solutions are applied to yield the transient scattering by a sphere and by a circular cylinder. The quantities governing the convergence of the solutions are found to be the same as in the corresponding steady-state problems. If the scatterers are perfectly hard, the transient waves extract more energy from an incident wave of very long wavelength than does the accompanying steady-state wave. The opposite holds for perfectly soft scatterers. For both kinds of boundary conditions, however, the transient waves are of very short wavelength. In the case of the incident waves with short wavelength, the poor convergence of the solutions prevents any explicit evaluation of the scattering. However, an order-of-magnitude analysis shows that the amplitude of the transient waves does not exceed that of the steady-state waves. Moreover, parts of the power radiated as transient waves will be in the long-wave domain of the spectrum.
Family of Cylindrical Velocity Transformers; Study by Analog Computer Techniques
Authors: Russell L. T. , Heaps H. S.
Published: September 2005

Determination is made of the longitudinal-vibration characteristics of a family of tapered cylindrical bars. It is shown that the required solutions may be obtained very conveniently by use of an analog computer.
Near-Surface Measurements of Deep Explosions I. Pressure Pulses from Small Charges
Authors: Blaik Maurice , Christian Ermine A.
Published: September 2005

The characteristics of pressure pulses recorded near the surface directly above small explosions at great depths are summarized. Charge weights ranged from 0.04 to 10 lb and burst depths varied from 3000 to 22 000 ft. Significant pressure and time parameters of the initial shock wave, the subsequent negative-pressure phase, and the first bubble pulse are shown in graphs and Tables. The vertical measurements of shock-wave peak pressure can be represented by the same power function that Arons previously determined from horizontal measurements of shallow explosions. These data extend the range of measurement for this parameter over an additional logarithmic cycle of the similitude curve to a distance R (ft) of 4×104 W12, where W is charge weight in pounds. The first period of the bubble oscillation also continues to show the same weight and depth dependence previously reported for depths ⩽500 ft down to depths of 22 000 ft.
Near-Surface Measurements of Deep Explosions II. Energy Spectra of Small Charges
Authors: Christian Ermine A. , Blaik Maurice
Published: September 2005

Energy flux spectra have been digitally computed for near-surface pressure-time curves obtained from small (0.067 10 lb) charges detonated at depths ranging from 3000 to 22 000 ft. As charge detonation depth (which is also the range in these experiments) increases, the spectrum reflects changes in relative, as well as absolute, distribution of energy between the initial shock wave and subsequent bubble-pulse phases of the pressure wave. The peak spectrum level occurs at the bubble-pulse fundamental frequency , which varies with charge weight and depth. The slope of the high-frequency end of the spectrum increases from an f−2 to an f−3 dependency as depth (range) increases. Apparent propagation losses” for deep 1-lb charges were also estimated from an octave-band analysis between 250 cps and 16 kc/sec. For midband frequencies near the bubble fundamental, the estimated “losses” as depth (range) increases from 6000 to 22 000 ft are only about half those predicted by spherical spreading.
Experiment on Propagation in Surface Sound Channels
Authors: Kibblewhite A. C. , Denham R. N.
Published: September 2005

An experiment was carried out to investigate the influence of a surface sound channel on propagation when the receiving site is in relatively deep water and the hydrophone below the duct. To examine this, a two- hydrophone vertical array was employed, with one hydrophone in the duct and the other on the sea bed. For frequencies below 200 cps, the propagation was controlled by the nature of the bottom. For frequencies high enough for the first mode to be trapped, propagation to both receivers was controlled by the duct. However, at the higher frequencies higher attenuation and lower energy levels were obtained at the bottomed hydrophone. This behavior can be explained in terms of normal mode theory.
Sound-Wave Fluctuations in an Environment of Simulated Random Inhomogeneity
Authors: Knollman G. C. , Hartog J. J.
Published: September 2005

A research program has been conducted under controlled laboratory conditions of acoustic amplitude fluctuations arising during sound transmission through an underwater medium containing a spatially random distribution of inhomogeneities that are temporally stationary. Spherical, thin-walled, liquid-filled balloons of a diameter large in comparison with the acoustic wavelength were situated at random in a large underwater facility. Refractive indices of the fluid spheres were varied up to 1% from the index for water. Thus, numerous weak, large-scale refractive index variations were introduced in an experimental acoustic chamber under controlled temperature conditions. Signal fluctuations were measured in plane-wave sound transmission through the simulated random environment for four different ultrasonic frequencies and four transmitter-to receiver ranges. Multitudinous ensembles were realized at each frequency and range by rotation of transmitter receiver line of sight about its midpoint. The experimental arrangement and measurement procedures are detailed herein. and mean-square amplitude fluctuations that were determined are presented as a function of both acoustic frequency and transmitter-to-receiver range. Theoretical results for plane wave propagation in a statistically isotropic medium are included as a formulation for the laboratory findings.
Time-Intensity Relations in Binaural Unmasking
Authors: Colburn H. S. , Durlach N. I.
Published: September 2005

Variations in the threshold of a 500-cps tone masked by random noise are studied as a function of simultaneous shifts in the interaural amplitude ratio and interaural time delay of the tone. The experimental results are found to coincide with the results of computations based on the equalization and cancellation model and are used to define a time-intensity trade for binaural unmasking.
Semantic Approach to the Perception of Complex Sounds
Authors: Solomon Lawrence N.
Published: September 2005

In an attempt to derive a limited number of descriptive adjectives with which to characterize passive sonar sounds, 50 U.S. Navy sonarmen (median sonar experience of one year) rated 20 different passive sonar sounds on 50 seven-point scales defined by polar-opposite adjectives (e.g., heavy-light). The intercorrelations between scales (calculated over both subjects and sounds) were factor analyzed by the Thurstone complete centroid method. Seven interpretable orthogonal factors (accounting for approximately 40% of the variance of judgments) were extracted from the data.

The generality of the methodology for psychological research on auditory perception is considered and suggestions for research along these lines are presented.
Information Transmission with Elementary Auditory Displays
Authors: Sumby William H. , Chambliss Davis , Pollack Irwin
Published: September 2005

A procedure for transmitting the letters of the alphabet by tone-coded signals was examined in quiet and against a noise background. The procedure employed successive selections, each from among a small number of alternatives, in order to transmit a target vocabulary of 25 letters. Four stimulus variables: tonal frequency, sound level, location, and duration were examined, one at a time. Successive selections were made among two, three, and five alternatives per variable. The highest reception rate was obtained with a three-alternative frequency-coded display. Reception of tone-coded signals in noise was nearly equivalent to that in the quiet, when the tonal signals were about 3 db above masked threshold.
Uncertain Signal Detection with Simultaneous Contralateral Cues
Authors: Sorkin Robert D.
Published: September 2005

A series of auditory signal-detection experiments was run under conditions of signal-parameter uncertainty. This uncertainty was effected by allowing one signal parameter, either signal frequency or starting time, to vary randomly across the sequence of experimental trials. These experiments, run monaurally, employed a simple yes-no detection procedure, signal plus noise occurring on half of the trials and noise alone occurring on the other half. A series of comparison experiments using the same observers was run under identical conditions, with the addition of a simultaneous cue signal in the contralateral ear. This cue was present on both signal and no-signal trials and was identical, in all parameters except amplitude, to the signal that might have been presented to the detecting ear. The results demonstrated (a) the previously noted result—that a simultaneous contralateral cue degrades performance at relatively high signal-to-noise levels—and (b) a new result—that at low signal levels such a cue facilitates performance of the detection task. The degrading effect is a function of the cue signal energy. The resulting psychometric functions suggest an interpretation in terms of a crossmasking and uncertainty-reduction hypothesis.
Effect of the Transmission Characteristic of the Ear on the Threshold of Audibility
Authors: Zwislocki J.
Published: September 2005

The threshold of audibility as a function of frequency is determined by the transmission characteristic of the ear and by the sensitivity of the nervous system. In order to separate the two factors, the sound transmission characteristic calculated on the basis of known experimental data and compared to the threshold of audibility. As a final result a simple curve is obtained which describes the sensitivity of the nervous system as a function of frequency.
Application of Adaptive Threshold Elements to the Recognition of Acoustic-Phonetic States
Authors: Dammann James E.
Published: September 2005

The relation of acoustic phonetic states to the problem of speech recognition is discussed. It is suggested that a first step toward understanding the dynamics of the speech signal could be made by recognizing small number of acoustic-phonetic classes. Adaptive threshold elements are proposed as a means of recognizing these classes and a method of utilizing the adaptive threshold elements in a decision procedure is presented. The means employed to gather the data representing the classes consists essentially of taking amplitude samples from a bank of 15 filters at 10-msec intervals. Samples obtained this manner are used as input for the adaptive-decision procedure, which is simulated in a general-purpose computer. Samples representative of each class are used to train the adaptive-decision procedure, and the capability to generalize to new samples is observed. For one speaker, generalization results of 92%-correct sample classification were achieved, and generalization from one speaker to another was demonstrated. It further was shown that the selection of an output code can significantly affect the generalization and that sequences of recognized samples can represent dynamic changes through words.
Examination of Two Different Formant-Estimation Techniques
Authors: Peterson Gordon E. , Hanne John R.
Published: September 2005

The errors associated with two formant-frequency estimators are compared theoretically for the simple case of a single steady-state isolated formant. The estimators considered are (a) the zero-crossing frequency, and (b) the frequency of the highest-energy harmonic. The results of the analyses show that for a given harmonic the zero-crossing counter gives the smallest magnitude error while the highest-energy, harmonic tracker gives the smallest percentage error.
Experimental Study of Fraunhofer Light Diffraction by Ultrasonic Beams of Moderately High Frequency at Oblique Incidence
Authors: Klein W. R. , Tipnis C. B. , Hiedemann E. A.
Published: September 2005

A systematic investigation of Fraunhofer light diffraction by a progressive ultrasonic wave is described. Measured light-intensity distributions are compared with theoretical values obtained from numerical solution of the difference equations describing light diffraction and with the solutions of Phariseau for high ultrasonic frequencies. A criterion for Bragg-type diffraction is established.
Mechanical-Impedance Characteristics at Ends of a Rockdrill Rod
Authors: Becker E. Carl H.
Published: September 2005

Although lacking the mechanical precision refinements hitherto reported, a conventional rockdrill hammer and drill rod comprise the experimental elements in derivation of mechanical impedance from transient waveforms. With allowance for nonlinearities and other limitations, it is demonstrated that new information is provided on hammer vibration and rock fracture at impact. Also, a single cylinder replaces the two cylinders previously required for this method of impedance determination.
Mean-Square Approximate Systems and Their Application in Estimating Response in Complex Disordered Linear Systems
Authors: Bogdanoff J. L.
Published: September 2005

A new method is presented for predicting approximately the response in complex, lightly damped, disordered linear systems to transient or steady-state disturbances when the frequency content of the disturbance is in a band involving high natural frequencies of the undamped system. The method consists of constructing sequences of coupled oscillators that derive from the system description by minimizing a mean-frequency weighted function of the coordinates subject to suitable constraints.
Axisymmetric Vibrations of Prolate Spheroidal Shells
Authors: Nemergut P. J. , Brand R. S.
Published: September 2005

The determination of the mode shapes and frequencies of the axisymmetric vibrations of a spheroidal shell is reduced to the solution of an ordinary second-order differential equation, in which the eccentricity of the ellipse and Poisson's ratio are parameters. The first four mode shapes and frequencies are found for each of five eccentricities, by means of numerical integration of the equation. It is found that the frequencies associated with the higher modes are strongly dependent on the eccentricity.
Arrays for the Investigation of Ambient Noise in the Ocean
Authors: Anderson Victor C.
Published: September 2005

A discussion of the important parameters to be considered in the use of directional arrays for the study of noise fields in the ocean leads to specialized array designs. Some properties of circular and spherical arrays composed of omnidirectional elements are presented. Consideration of these properties leads to an optimum selection of geometry and element spacing for each of two cases: a distributed noise source, and a set of point noise sources.

The calculation of directivity index for a spherical array is carried out by the use of the space-correlation functions of an isotropic noise field.

The measured, broad-band directivity pattern of a model circular plane array as a function of frequency is also shown.
Propagation of Short-Wavelength Acoustic Waves through an Inhomogeneous Medium
Authors: Barnard G. R. , McCormack K.
Published: September 2005

Pressure-amplitude losses for a plane wave impinging on a reference depth are calculated for different depth positions in a medium with a variable index of refraction. These losses, calculated for several grazing angles, are compared with transmission coefficients calculated using a simple Rayleigh analysis considering only two semiinfinite extents of different velocity fluids. The method of determining an expression for the velocity profile is discussed, along with the details of the transmission coefficient calculation.
Attenuation of Sound in Lined Air Ducts
Authors: King A. J.
Published: September 2005

Theoretical predictions of the performance of silencers are apt to be difficult and unreliable, so experimental results are often very valuable.

A previous paper contained curves giving the attenuation of sound with frequency in lined ducts of various widths and thicknesses of lining of rock wool. Subsequent experience has shown the need for an extension of these curves to cover thicker linings and splitters, and advantage has been taken of an opportunity to obtain further data on 16-in. splitters and air channels. New curves including these data are given for a 50% space factor, together with an extrapolation to 32-in. splitters. Thicknesses greater than 16 in. are unlikely to be used unless frequencies lower than 100 cps are important. For covering very wide frequency bands two-stage filters are recommended.
Covariance of Surface-Generated Noise in a Deep Ocean
Authors: Liggett W. S. , Jacobson M. J.
Published: September 2005

The space-time covariance of surface-generated noise is investigated using a model that assumes that the covariance of the pressure is specified for all pairs of points on a plane and that the acoustic pressure satisfies a wave equation with constant coefficients in the semiinfinite region below this plane. It is shown that one may imagine the noise to be generated by a plane distribution of statistically dependent dipole sources. Alternatively, one may imagine dependent omnidirectional sources if the surface covariance of the normal derivative of the pressure is specified. A second noise model employs ray theory and supposes that the noise is generated by a plane distribution of statistically independent directional point sources. The covariance functions predicted by the two models at points in deep water are compared and are shown to be equal when the covariance on the plane of the first model is properly related to the source directionality in the second model. This relationship allows us to specify a surface covariance function for a given source directionality and conversely. Surface covariance functions corresponding to the common source directionalities (cos)m are investigated, and directionality is examined for Gaussian surface covariance.
Temporary Threshold Shift and Masking for Noise of Uniform Spectrum Level
Authors: Miller James D.
Published: September 2005

This experiment was designed to test the hypothesis that differences in the effective noise level from one critical band to the next can account for the typical audiogram showing the temporary threshold shift which results from an exposure to noise of uniform spectrum level.

For equal masking, or (B+K−β0), the greatest losses were found at the highest frequencies and the smallest losses at the lowest frequencies. However, the hypothesis implied that for equal masking all frequencies would show equal losses.

Further analysis revealed that when the data for temporary threshold shift were plotted against the quantity (B+2.7K−β0), the points for all test-tone frequencies fell on a common curve.
Anomalous Absorption of Pressure Waves from Explosions in Sea Water
Authors: Marsh H. W. , Mellen R. H. , Konrad W. L.
Published: September 2005

Measurements of the rise time of pulses from explosive sources in sea water show persistent anomalies owing to finite amplitude. This leads to apparent absorption values that are too small at high frequencies and, consequently, too large at low frequencies. The nonacoustic behavior is consistent with the empirical peak pressure and rise-time scaling laws of Arons. The status of development of a comprehensive finite-amplitude theory is reported.
Ray Acoustical Model of the Ocean Using a Depth/Sound-Speed Profile with a Continuous First Derivative
Authors: Stewart Kenneth R.
Published: September 2005

A layered method of calculating the ray parameters of range, intensity, and travel time has been developed in which the sound speed c in a layer is the following function of depth z: c2 = (a1z2+a2z+a3)−1 where a1, a2, and a3 are constants. These constants are chosen so that (dc/dz)'s match at layer boundaries, thus creating a depth/sound-speed profile that has a continuous first derivative. Some ray characteristics using this type of model have also been studied. The major difficulty with this method is the creation of an excess number of maxima, minima, and points of inflection in the profile if the layer boundaries are not chosen properly. This difficulty can be demonstrated through the use of a sample calculation.
Distributed Transducer
Authors: Greenspan Martin , Wilmotte Raymond M.
Published: September 2005

The distributed transducer is an array of transducers separated by inactive material having their common characteristic impedance, Z0, and terminated in Z0 at one (the absorber) end. The other end radiates into a load. The input voltages at the successive inputs are delayed so that the speed of the electrical wave, traveling in the direction absorber to load, equals the speed of sound in the transducer material. The elements may or may not be identical and they may or may not be operated near resonance; the acoustic waves arrive at the load in phase in any case. A great variety of frequency-response characteristics is readily synthesized; particular attention is paid to a flat response over a very broad range. At the same time, the response at the absorber is subject to some control so that the power there dissipated can be minimized.
Masking of English Words by Prolonged Vowel Sounds
Authors: O'Neill John J. , Dreher John J.
Published: September 2005

One-hundred and ten monosyllabic words selected from the Thorndike list of 1000 most frequently occurring words in English to represent equally each of 10 vowels were presented to 300 American listeners in an articulation test. Also tested were 72 spondee words, half selected from those in use in audiological tests and half from those in frequent use in air traffic control, further to represent the same vowel sounds. Masking of the stimuli was accomplished by recording separately each of nine prolonged vowels intoned by a trio of male voices. Results indicate that vowels of equal sound pressure levels differ considerably in masking effectiveness, that words containing specific vowel are not masked optimally by the same vowel, and that spondees are masked by prolonged vowels in the same rank as are the monosyllables. Prolonged vowel sounds with relatively high concentrations of energy between 700 and 1000 cps are most effective as masking agents. Rank order correlation of observed masking effectiveness with masking effectiveness predicted by the Strasberg method is 0.52, the Beranek method is 0.59, and by the Pickett-Kryter method, 0.69. Some observations on resistance of words to masking are made in relation to phonemic transition areas within words.
Ultrasonic Reflectoscope with an Indicator of the Degree of Coupling between Transducer and Object
Authors: Lutsch A.
Published: September 2005

A further development of Firestone's Reflectoscope is described, indicating the degree of coupling between transducer and the test object. It is shown that the distortion of a radio-frequency pulse—produced by the transducer—is a function of its coupling to the test object. Therefore, the distortion can be used to measure the coupling. The trailing edge of the radio-frequency pulse is amplified by a time-selective amplifier, rectified and connected to a galvanometer. Different conditions of coupling are analyzed. Figures are given for a barium titanate transducer working at 500 kcps. References such as back boundaries are no longer necessary in the field of nondestructive testing.
Technique for Objective Measurement of Speech Levels
Authors: Bricker Peter D.
Published: September 2005

This Letter describes a technique for making digital measurements of the average speech level during speech spurts. Results are free of variability owing to the subjectivity and unreliability of the human reader. Data relating these measurements to VU-meter readings and to loudness judgments are presented.
Averaging Time and Data-Reduction Time for Random Vibration Spectra. II.
Authors: Morrow Charles T.
Published: September 2005

In Part I, formulas were given for uncertainty when a power-spectral-density plot is estimated from a short sample of random vibration. The relation between this problem and the time required to obtain the spectrum was investigated for the sweeping of a simple analyzer through the frequency band. Other methods of obtaining the spectrum are now discussed.
Theory of Focusing Plane Waves by Spherical, Liquid Lenses
Authors: Boyles C. A.
Published: September 2005

This paper presents a numerical evaluation of the rigorous solution to the wave equation for the internal field of an underwater, spherical, liquid lens that is being irradiated by plane waves. The numerical computations, which were performed for three refracting liquids with indices of refraction 1.8, 2.25, 2.82, and for the range 1⩽d/λ0⩽15 (d, the diameter of the lens; λ0 the wavelength in water), are presented graphically. The relative pressure and the relative intensity were computed along the axis of the lens. It was found that the intensity is not proportional to the square of the pressure and, furthermore, that the focal point for the intensity field did not always coincide with the focal point for the pressure field. Since hydrophones commonly used for measurements in underwater acoustics are pressure-sensitive, only the focal point for the pressure field was considered. Pressure polar patterns were then calculated at the focal point for the pressure field. Also, the beamwidth and gain were determined as a function of d/λ0. In general, the theoretical results were found to be in good agreement with the experimental observations of W. J. Toulis [J. Acoust. Soc. Am. 35, 286–292 (1963)].
Underwater Sound Transducer with a Conical-Shell Radiation Pattern
Authors: Sanders D. R.
Published: September 2005

This paper describes the design and construction of a line transducer with a conical-shell directivity pattern. The desired beam orientation is obtained through a combination of physical spacing of the elements of the line, connection of elements, and phasing of the driving voltage. Minor-lobe reduction is achieved through the use of elements cut to size to provide a shaded distribution. Measurements show the minor lobe to be about 20 dB below the main-lobe level. This particular transducer was designed to obtain bottom and surface backscattering data at 40 kc/sec for a grazing angle of 30° through all azimuthal angles.
Modulated Combustion (Dragon) Loudspeaker
Authors: Arnold James S.
Published: September 2005

The burning of a combustible-gas mixture after passage through an electrically controlled flow modulator can increase the acoustic output by 10–20 dB over the no-combustion condition. The pyroacoustic amplification appears to result from a thermal interaction of the flameholder with the flame, to achieve a high degree of positional stability for the combustion reactions. This forces the gas-burning rate to fluctuate with the modulation, and results in enhanced acoustic output. A conceptual model of the phenomenon has been developed that agrees with the experimental facts. The largest device of this kind constructed to date produced a sound-pressure level on the horn axis that would be the same as that from a piston source of 9.1 acoustic watts in an infinite baffle. The electrical power was 5.2 W, the pneumatic power less than 7 W, and the thermochemical input approximately 400 W.
Test of Phonemic Differentiation: The Rhyme Test
Authors: Fairbanks Grant
Published: September 2005

Materials are presented for a test of word identification in which the cues for response are confined to the initial consonants and consonant-vowel transitions. Some preliminary results are discussed.
Ultrasonic Determination of Crystalline Resonances and Sound Velocities, Using NMR Techniques
Authors: Mahler R. J. , Tanttila W. H.
Published: September 2005

In this paper, we describe a technique using nuclear-spin saturation that will accurately determine crystal sonic resonances and measure sound velocities at any temperature, and, in particular, when the crystal is immersed in a liquid coolant such as liquid nitrogen. The results of the experiment show that the internal energy density increases by a factor of 10 as one changes the frequency from a crystal nonresonance to a crystal resonance. We derive an expression relating the voltage on a driving transducer bonded on one end of the crystal to the internal energy density of the added phonons and compare this with out experimental results.
Ultrasonic Dispersion and Absorption in n-Hexane Vapor
Authors: Klose Jules Z.
Published: September 2005

The velocity of high-frequency sound waves in n-hexane vapor at 35.15°C has been measured at frequencies of 998.5 kc and 687.0 kc, and at pressures ranging from 1.10 to 12.28 cm Hg, using an ultrasonic interferometer. The dispersion which was detected in the velocity is attributed to the slow rate of energy exchange between the translational and vibrational states of the molecule. Although the upper limiting sound velocity could not be reached experimentally owing to weak response at low pressures and strong absorption at high frequencies, it was established that the inflection point in the velocity vs frequency/pressure curve lay at 137 Mc sec−1 atmos−1. This corresponds to a relaxation time of 6.46×10−9 sec at one atmosphere if it is assumed that there is only a single dispersion region involving the relaxation of the vibrational modes as a unit. Finally, a value of 127 was found for the average number of collisions necessary to deactivate the n-hexane molecule. Measurements of the amplitude absorption coefficient were also carried out and the relaxation time derived from these measurements.
Torsional Waves in Composite Rods
Authors: Armenàkas Anthony E.
Published: September 2005

The propagation of torsional waves in composite, infinitely long, tractionfree, circular, cylindrical rods is investigated on the basis of the three-dimensional linear theory of elasticity. The composite rods consist of an internal circular rod made of one material, bounded by and bonded to a circular casing made of another material. The effect of the variation of the geometric and physical parameters on the frequency of the torsional motion is discussed. It is shown that, in general, for composite rods, the first torsional mode (no nodes along the radius) may not exist uncoupled.
Small Scale Acoustic Streaming near a Locally Excited Membrane
Authors: Jackson Francis J. , Nyborg Wesley L.
Published: September 2005

Experiments are described involving a membrane set into oscillatory motion (40 kc) by contact with a vibrating tip of small area. Small scale acoustic streaming is observed in a liquid above the membrane, especially near the area of contact; its character depends on the membrane tension. Loosely adhering films are removed from certain areas of the membrane. The cleared areas form a pattern, indicative of the surface stress distribution set up by the eddying liquid. The main features of the reported results are accounted for, at least, qualitatively, by application of acoustic streaming theory to idealized cases. Referring to the above results, the possibility is discussed of motion induced in biological cells by external vibrating bubbles.
Torques Due to Acoustical Radiation Pressure
Authors: Maidanik G.
Published: September 2005

A general expression for the torque on an object due to acoustical radiation pressure is derived by an approach similar to that used by P. J. Westervelt to derive the general expression for the force.

The general expression is then specialized to plane waves incident in an arbitrary direction. The simplification which is obtainable in the case of disks is also discussed.
Nonlinear Character of Resonance in Stretched Strings
Authors: Murthy G. S. Srinivasa , Ramakrishna B. S.
Published: September 2005

The forced vibrations of stretched strings near their resonance frequencies exhibit several features that cannot be explained on the basis of the classical theory. As the driving frequency approaches resonance frequency, the increase in the amplitude of vibration of the string causes a change in its tension and the restoring force becomes nonlinear. Experiment shows that the amplitude response exhibits a downward jump while the driving frequency is being increased and an upward jump at a different frequency while the frequency is being decreased. Moreover, when the amplitude of vibration in the plane of the driving force reaches a certain critical value, which depends upon the magnitude of the driving force, the string acquires a component of motion in a direction normal to the plane of the string and the force. These phenomena are always observed in a more or less conspicuous manner, depending upon the magnitude of the force. When the restriction to infinitesimally small amplitudes of vibration (which is untenable near resonance) is removed, the motion of the string is governed by a pair of nonlinear, partial differential equations. Appropriate solutions of these equations show that the jump phenomena and the nonplanar vibration are the normal pattern of resonance behavior of stretched strings, however small the driving force may be. Response patterns and other results deduced from theory agree closely with those obtained from experiment.
Experiments on cm Waves in Analogy with Acoustic Techniques Made in Göttingen
Authors: Meyer Erwin
Published: September 2005

In the past four years a series of experiments has been carried out which serve to demonstrate the success of analogies between acoustical systems and electromagnetic wave systems in the microwave frequency region. Measuring techniques in the two disciplines are compared, with particular emphasis on the use of reverberation chambers. Analogous directive microphones and electromagnetic devices have been constructed. The design and performance of absorbing structures of both nonresonant and resonant types is discussed at length.
Some Acoustic Cues for Synthesis of the /n-d/ Distinction
Authors: Pickett J. M.
Published: September 2005

Listening tests, using confidence ratings, were carried out on acoustic cues for synthesis of the /n-d/ distinction. The cues occurred in 30 different phrases produced by a series-resonance. formant-coded synthesizer with separate oral- and nasal-tract analogs. The cue variations associated with the test sounds were (1) rate of offset of nasal-tract excitation and complementary onset of oral-tract excitation; (2) oral-tract formant transition patterns during oral onset; and (3) presence or absence of nasal-tract excitation during the consonant interval. The best n responses in listening were produced by presence of nasal-tract excitation with slow offset and /n/-modelled formant transitions. The best d responses required rapid oral onset, absence of nasal tract excitation, and /d/-modelled formant transitions.
Comments on “Propagation of Forced Sound Waves in Rarefied Gasdynamics” [L. Sirovich and J. K. Thurber, J. Acoust. Soc. Am. 37, 329–339 (1965)]
Authors: Maidanik Gideon , Fox H. L.
Published: September 2005

A recent paper of Sirovich and Thurber [J. Acoust. Soc. Am. 37, 329–339(1965)] presents comparisons of their theory with experiments. The comparison is inappropriate since the theory does not describe the experimental situation. Their theory is appropriate to free waves, propagating a distance that is large as compared with the mean free path between intermolecular collisions. The experimental data at low pressures have been determined by apparatus dimensions that are small as compared with that mean free path.
Intelligibility of Selected Message-Sets
Authors: Pollack Irwin , Decker Louis R. , Rubenstein Herbert
Published: September 2005

Four message-sets were constructed on the basis of phonemic confusion patterns with the aim of modifying the role of frequency-of-occurrence in the determination of speech intelligibility in noise. Deliberate selection of words may reinforce, nullify, or negate word-frequency effects for known message-sets.
Nonlinear Interaction of Two Sound Beams
Authors: Berktay H. O.
Published: September 2005

Extension of previous contributions by Westervelt [J. Acoust. Soc. Am. 32, 934(A) (1960); 35, 535–537 (1963)] and by Bellin and Beyer [J. Acoust. Soc. Am. 34, 1051–1053(1962)] concerning the nonlinear interaction of two coincident sound beams to allow for cylindrical and spherical spreading is discussed; conclusions of Naze and Tjøtta [J. Acoust. Soc. Am. 37, 174–175(L) (1965)] are reviewed and commented upon.
Noise from Impinging, Two-Dimensional, Underexpanded Jet Flows
Authors: Sheeran William J. , Dosanjh Darshan S.
Published: September 2005

Under a certain range of jet reservoir pressures, optical studies of two transversely impinging, narrow, two-dimensional, underexpanded jet flows have revealed a discrete, high-frequency, intense acoustic emission that was not observed for a single underexpanded jet operated in the same pressure range.
Reaction-Time Distributions in the Detection of Weak Signals in Noise
Authors: Carterette Edward C. , Friedman Morton P. , Cosmides Robert
Published: September 2005

Reaction times were collected for three observers in a YES-NO signal detection experiment, for two different signal strengths, and three a priori probabilities of a signal occurrence—P (S): 0.2, 0.5, and 0.8. Each server gave 1800 responds under each of the six conditions. A trial ended only when the observer terminated it. Some of the major findings are (1) latencies have Pearson distributions, mainly Beta of the first and second kind; (2) there is an apparent genetic character to the distributions—that is, they resemble each other according to the response (YES or NO) rather than the stimulus (signal or noise alone); (3) at P (S) = 0.2, the mean latency of a false rejection of a signal is least, that of a correct detection greatest, but for P (S) = 0.5, and 0.8, mean latency is least for correct detection, and greatest for correct NO'S, and (4) generally, reaction times are inversely related to the a priori probability of their associated stimulus classes.
Tonal Consonance and Critical Bandwidth
Authors: Plomp R. , Levelt W. J. M.
Published: September 2005

Firstly, theories are reviewed on the explanation of tonal consonance as the singular nature of tone intervals with frequency ratios corresponding with small integer numbers. An evaluation of these explanations in the light of some experimental studies supports the hypothesis, as promoted by von Helmholtz, that the difference between consonant and dissonant intervals is related to beats of adjacent partials. This relation was studied more fully by experiments in which subjects had to judge simple-tone intervals as a function of test frequency and interval width. The results may be considered as a modification of von Helmholtz's conception and indicate that, as a function of frequency, the transition range between consonant and dissonant intervals is related to critical bandwidth. Simple-tone intervals are evaluated as consonant for frequency differences exceeding this bandwidth. whereas the most dissonant intervals correspond with frequency differences of about a quarter of this bandwidth. On the base of these results, some properties of consonant intervals consisting of complex tones are explained. To answer the question whether critical bandwidth also plays a rôle in music, the chords of two compositions (parts of a trio sonata of J. S. Bach and of a string quartet of A. Dvořák) were analyzed by computing interval distributions as a function of frequency and number of harmonics taken into account. The results strongly suggest that, indeed, critical bandwidth plays an important rôle in music: for a number of harmonics representative for musical instruments, the “density” of simultaneous partials alters as a function of frequency in the same way as critical bandwidth does.
Acoustic Water Tunnel
Authors: Fand R. M.
Published: September 2005

An acoustic water tunnel has been constructed that can be used to study various solid-liquid interface processes, such as heat transfer and scale formation, in the presence of intense sound. The tunnel, in modified form, can also be used to measure the acoustical impedance of various structures, such as porous metal plates, both in the presence and absence of convective flow.
Effect of Divalent Ion Substitutions on the Magnetomechanical Properties of Nickel Ferrite
Authors: Ferebee S. F. , Davis C. M.
Published: September 2005

Magnetostrictive properties of cobalt-substituted nickel ferrous-ferrite were investigated to determine its suitability for use in electromechanical transducers. Toroidal samples were sintered at 1400°C and cooled by quenching in air. The following parameters were measured and compared with the corresponding parameters of previously investigated magnetostrictive materials: electromechanical coupling coefficient, reversible permeability, dynamic magnetostrictive constant, maximum stress, and the product of characteristic frequency times the thickness squared.

The results of the investigation indicate that a ferrite having the formula (NiO)1−x−y(CoO)x(FeO)y(Fe2O3) with 0.015 ⩽ x ⩽ 0.04 and 0.02 ⩽ y 0.065 moles per mole of ferrite meets the requirements for transducer applications. The electromechanical coupling coefficient for this range of compositions varies from 0.28 to 0.37. The value of the characteristic frequency times the thickness squared (4200) is approximately 1700 times that of nickel. The maximum stress increases with ferrous iron, reaching a value of 68×106 dynes/cm2 for 0.06 mole of FeO per mole of ferrite as compared with 32×106 dynes/cm2 for no ferrous iron.
Investigation of Progressive Ultrasonic Waves by Light Refraction
Authors: Breazeale M. A. , Hiedemann E. A.
Published: September 2005

The optical method used by Loeber and Hiedemann for the study of stationary ultrasonic waves has been adapted to the study of progressive waves. Three methods are described by which one may determine the presence of distorted wave forms in liquids. Distorted wave forms caused by finite amplitude effects are shown to be present in liquids and the increase of wave form distortion with distance is shown for water and carbon tetrachloride.
Elementary Results for Scattering by Large Ellipsoids
Authors: Burke James E. , Twersky Victor
Published: September 2005

Elementary high-frequency approximations for scattering by an arbitrary body are specialized to ellipsoids and applied in detail for source and observation points at distances large compared to the scatterer's size. It is shown, for example, that, if the direction of observation is varied in a fixed plane containing the direction of incidence, then except for the near-forward direction (“shadow region”) the first approximation for the far-distant field for a given ellipsoid is specified by a “universal curve.” In particular, if the fixed plane contains an axis of the ellipsoid, then there is a unique curve for the intensity versus the angle measured from the reflection of the direction of incidence in the contained axis. For the special case of the spheroid, the field on the “axially specular” cone (the cone defined by the angle of incidence with the axis of rotation) remains constant until one gets near the shadow region, and the fields on adjacent cones (i.e., with generators at other than the specular angle with the axis) vary slowly with the azimuthal angle; for many practical purposes, we may neglect the slowly varying effects and approximate the reflected intensity pattern in the vicinity of the axially specular cone by a conical lobe of revolution. Numerical examples are given for a family of spheroids; e.g., we determine contours of constant intensity on a plane containing the source as functions of the spheroid's distance from the plane, etc.
Exact Analysis of the Plane-Strain Vibrations of Thick-Walled Hollow Cylinders
Authors: Gazis Denos C.
Published: September 2005

The plane-strain vibrations of a thick-walled hollow cylinder are investigated in the framework of the linear theory of elasticity. Approximate expressions for the frequencies of free modes are derived for moderately thick shells. The transition from the shell vibrations to the Pochhammer vibrations of a solid cylinder is investigated by means of a numerical solution of the frequency equation using an IBM 704 digital computer.
Harmonic Distortion of Spherical Sound Waves in Water
Authors: McDaniel Oliver H.
Published: September 2005

The problems arising from the generation of harmonic distortion by underwater sound devices are discussed. Expressions are derived for the harmonic distortion of spherically propagating finite-amplitude sound waves, and distortion is calculated for a typical high-intensity sound source. The calculation illustrates that finite-amplitude effects can produce a significant amount of second-harmonic distortion in a practical situation.
Everyday-Speech Intelligibility
Authors: Webster J. C. , Davis Hallowell , Ward W. Dixon
Published: September 2005

We are happy to see J. D. Harris [J. Acoust. Soc. Am. 37, 824–830 (1965)] introduce the phrase “everyday speech” into the speech-intelligibility controversy. The controversy in this case is whether the pure-tone sensitivity at 500, 1000, and 2000 cps or at 1000, 2000, and 3000 cps should be used to predict the intelligibility of “everyday speech.”
Temperature Coefficients of Relaxed and Unrelaxed Bulk Moduli for Pressure-Induced Relaxation Processes
Authors: Bhatia A. B.
Published: September 2005

Using Hall's two-state model, a relation between the temperature coefficients of relaxed (B) and unrelaxed (B∞) bulk moduli is derived. The relation predicts that, in general,d ln B2/dT, [B2 = B∞ − B], may be expected to be of the same sign as d ln B/dT, and numerically a few times larger than d in B/dT. This conclusion is in qualitative agreement with the observations on liquids of high viscosity, made by Litovitz and his collaborators although. strictly speaking, a two-state model is not adequate for these liquids.
Intensive Determinants of Remote Masking
Authors: Bilger Robert C.
Published: September 2005

Five experiments were conducted to determine those aspects of a masking noise for which remote masking is invariant. The relative contributions of spectrum level and band width to remote masking can be described by the general equation LR = 2Ls+Lf+C, where LR is remote masking in db; Ls is spectrum level in db, the SPL of a 1-cps band width; and Lf is band-width level in db re a 1-cps band width. The constant is specific to each group of subjects. For remote masking less than 30 db, the formula does not predict remote masking, but does enable us to equate different conditions of spectrum level and band width. This equation does not hold as well when frequencies above 4000 cps are included in the masking noise. The possible causes of this inconsistency are discussed.