bluuebunny/crossref_metadata_2025 huggingface dataset:
Auditory Memory in a Pitch-Discrimination Task
Authors: Thomas Ian B. , Dinicola Paul D. , Ella Michael P. , Pasierbiak Carl S.
Published: October 2005

Discrimination of pure tones after a variable time delay was investigated using an ABX procedure. Three experiments were performed. In the first, scores for subjects were near perfect (>90%) for systematically increasing delays between B and X of up to 120 sec when A and B were equal-amplitude pure tones of 1000 and 1100 Hz, respectively. In the second and third experiments, three tone pairs were employed having frequency spacings of 10% and 2%, respectively. The pair used, the order within pairs, and the order in which variable delays were presented were all randomized. In these experiments, scores fell abruptly after a delay of 20 sec for the 10% spacing and after 5 sec for the 2% spacing. The superior discrimination of Expt. 1 is attributed to learning.
Elimination of Biases in Loudness Judgments for Tones
Authors: Warren Richard M.
Published: October 2005

Loudness judgments are especially sensitive to experimentally induced biases. By using a method derived from studies of visual intensity, it was found possible to obtain loudness estimates free from known biasing factors. Judgments of 50% loudness corresponded to 25% stimulus intensity (6-dB attenuation) for 1000-Hz tones from 42 through 92 dB, and for tones from 250 through 8000 Hz presented at moderate intensity. These results agree with other data supporting the physical correlate theory of sensory intensity. It is suggested that the sone scale of loudness reflects the influence of known experimental biases and hence does not represent a fundamental relation between stimulus and sensation.
Threshold Ultrasonic Dosages for Structural Changes in the Mammalian Brain
Authors: Fry F. J. , Kossoff G. , Eggleton R. C. , Dunn F.
Published: October 2005

The relationship between the acoustic intensity and the time duration of exposure, for a single pulse, necessary to produce a threshold lesion in the cat brain was studied. Focused ultrasound of 1, 3, and 4 MHz was employed with intensities ranging from 102 to 2×104 W/cm2 with the corresponding pulse durations from 7 to 2×10−4 sec, respectively. Three types of lesions were observed attending three regions. At the lower intensities and long time durations of exposure, the lesion is produced by a thermal mechanism. At the highest intensities and shortest time durations, cavitation is believed to be the mechanism responsible for the sometimes randomly appearing lesions. At intermediate dosages, the lesions are formed by a mechanical mechanism which is thus far not well understood. These results exhibit good agreement with that of other investigators on both the cat and the rat brain.
Propagation of Axially Symmetric Waves in Hollow Elastic Circular Cylinders Subjected to a Step-Function Loading
Authors: Chong K. P. , Lee P. C. Y. , Cakmak A. S.
Published: October 2005

Axially symmetric waves in semi-infinite hollow elastic circular cylinders, with traction-free lateral surfaces and subjected to a pressure-step loading, are considered on the basis of the equations of motion derived by McNiven, Shah, and Sackman [J. Acoust. Soc. Amer. 40, 784–792; 1073–1076 (1966)]. By using double integral transforms, asymptotic solutions are obtained for the strains as functions of time and material and geometric parameters. Strains are presented for times near the head of the pulse of the extensional mode at the same distance from the finite end for various radii ratios a* and for different distances but for the same radius ratio. It is of interest to note that, for thin cylinders (a* less than approximately 1.7, owing to its slight dependence on Poisson's ratio), the maximum group velocity of the radial mode is slightly higher than that of the extensional mode although less than the dilatational wave velocity.
Approximate Theory of Torsional Wave Propagation in Elastic Circular Composite Cylinders
Authors: Haines D. W. , Lee P. C. Y.
Published: October 2005

An approximate one-dimensional theory is developed for axially symmetric torsional deformation of elastic circular composite cylinders. The cylinders are composed of a core perfectly bonded to an outer casing. The equations of motion accommodate the first two frequency branches of the dispersion relation for symmetric torsional waves propagating along the axis of the cylinder. Important parameters are the ratios of densities, shear moduli, and radii of the core and casing. Dispersion relations obtained from this approximate theory are studied for ranges of values of these parameters, and a comparison made with the results of the “exact” theory, i.e., three-dimensional elasticity. In order to match closely the results from the exact analysis, two correction factors are introduced, and values are tabulated for typical material and geometric properties. Sufficient conditions at the ends of finite cylinders are obtained to provide a unique solution.
Propagation of Harmonic Waves in a Composite Elastic Cylinder
Authors: Lai Jai-Lue , Dowell Earl H. , Tauchert Theodore R.
Published: October 2005

In this paper, the propagation of harmonic waves with an arbitrary number of circumferential nodes in an infinitely long two-layered composite circular elastic rod is investigated. The composite rod is made of a circular solid rod encased by a circular shell having different material properties. The frequency equation derived on the basis of the three-dimensional linear isotropic elastic theory is presented. The reduction of this equation to the frequency equations for some special problems, such as longitudinal wave propagations, torsional wave propagations, flexural wave propagations, axial-shear vibrations, and plane-strain vibrations is discussed. Simplified equations for phase velocities of longitudinal and torsional waves at very long wavelength are obtained. Numerical results, in terms of frequency and real wavenumber, are given for a composite rod made of a soft core with a stiff casing.
Errata: “Line Admittance of Infinite Isotropic Fluid-Loaded Plates” [P. R. Nayak, J. Acoust. Soc. Amer. 47, 191–201 (1970)]
Authors: Nayak P. Ranganath
Published: October 2005

Corrections to the paper “Line Admittance of Infinite Isotropic Fluid-Loaded Plates” [J. Acoust. Soc. Amer. 47, 191–201 (1970)] are presented.
Continuity in Alternately Sounded Tonal Signals in a Free Field
Authors: Elfner Lloyd F.
Published: October 2005

An experiment is reported that employed 20 normally hearing listeners who demonstrated an ability to concentrate on an interrupted signal that alternated with a shorter, more intense signal. The purpose of the study was to investigate the effects of the frequency relationship between the two components, to determine the effect of angular separation of the two components, and to demonstrate continuity effects in a free field. The results indicated a definite frequency effect and a significant though small effect due to angular separation on the continiuty threshold.
Study of Motion of a Bowed Violin String
Authors: Kohut J. , Mathews M. V.
Published: October 2005

The velocity of a bowed violin string was measured at various points along its length and with various bow positions by placing a magnetic field perpendicular to the string and observing the voltage induced in the string. The string was found to oscillate in a simple triangular pattern described by Helmholtz. At all points on the string, the ratio of flyback time to period of the oscillation equaled the distance from bridge to observation point divided by string length. This equality implies that larger-amplitude vibrations for a given bow speed can be achieved by bowing closer to the bridge. It also implies that the waveform at the bridge has an exceedingly rapid flyback time and hence is rich in high-frequency components which are transmitted to the body of the instrument. Deviations from a triangular waveform were observed. These consist of slight rounding of the corners of the triangle and a superimposed sinusoidal oscillation of small amplitude.
Perception of Coarticulated Nasality
Authors: Ali Latif , Gallagher Tanya , Goldstein Jeffrey , Daniloff Raymond
Published: October 2005

CVC and CVVC syllables were prepared in which the final consonants were either nasal consonants (/m/, /n/) or non-nasal consonants. The entire final consonant along with its vowel-consonant transition was spliced away. The resulting CV and CVV syllables along with carrier phrases were spliced at random onto a tape for presentation to listeners who were asked to predict whether the missing consonant was nasal or nonnasal. Results indicate that the presence of nasal consonants can be predicted very well. It is hypothesized that listeners utilize this information to lighten the phoneme-processing load. Such perceptually significant coarticulation of velar opening across the vowels in CVVN-type sequences probably has counterparts in the coarticulation of other articulatory gestures. In this way, perception uses or follows production.
Effect of Glottal Pulse Shape on the Quality of Natural Vowels
Authors: Rosenberg A. E.
Published: October 2005

A pitch-synchronous analysis was carried out over the vowel portions of the CVC utterances HAYED, HOD, HODE and the sentence FEW THIEVES ARE NEVER SENT TO THE JUG recorded by a male speaker. For every pitch period, the analysis provides formant frequencies and the waveform of the vocal-cord excitation. The excitation waveform was replaced by a simulated excitation waveform, with which the utterances were resynthesized. In Expt. I, six simulated waveforms with pulse shapes differing in the number and location of slope discontinuities were investigated. Listening tests indicated that simulated excitations with pulse shapes with a single slope discontinuity at closure are preferred. In Expt. II, simulated excitations with 16 combinations of opening and closing times of a preferred pulse shape were investigated. Listening tests indicated that very small opening or closing times, or opening times approximately equal to or less than closing times, are not preferred. In general, it was demonstrated that good-quality synthetic speech can be generated by using simple excitation waveforms specified uniformly over an utterance. The use of tournament testing strategies for perceptual evaluation of speech samples is also described.
Acoustico-Lateralis System of Fishes: Cross-Modal Coupling of Signal and Noise in the Grunt, Haemulon parrai
Authors: Cahn Phyllis H. , Siler William , Auwarter Alan
Published: October 2005

Behavioral studies on sailor's choice (bony shallow-water fish) determined that, at 200 Hz, sonic particle velocity noise received by the lateral line did not mask a sonic pressure signal received by the ear; but sonic pressure noise received by the ear can mask the sonic particle velocity signal received by the lateral line. At 50 Hz, the fish failed to respond to the pressure signal, but pressure noise was still coupled into the velocity-sensitive lateral-line system.
A New Class of Adaptive Array Processors
Authors: Chang J. H. , Tuteur F. B.
Published: October 2005

This study deals with the design and analysis of an adaptive array processor in which the individual filters consist of tapped delay lines and adjustable gains. The gains are adjusted automatically by an iterative procedure which is a modified form of the stochastic approximation method of Robbins and Monro. The criterion for optimality is that the mean-square error between filter output and an ideal signal be a minimum. However, it is shown that the ideal signal need not be available to the processor; it suffices that the signal autocorrelation function and spatial direction be available. General expressions are obtained for convergence of the iterative algorithm, and an explicit expression for an upper bound on the rate of convergence is derived. System performance is analyzed by considering a noise field consisting of a spatially isotropic component and a single directional component. It is shown that the adaptive system eventually acts to eliminate the effect of the directional component. The theoretical behavior of the system has been verified experimentally using actual sonar data and a six-element array.
Ultrasonic Waveguide Effects in Inhomogeneous Rods of Radial Symmetry
Authors: Papadakis Emmanuel P.
Published: October 2005

When sound waves are generated in a homogeneous rod many wavelengths in diameter by a transducer of smaller diameter affixed coaxially to its end, the pressure received by the same transducer in a pulse-echo mode or by a similar transducer on the other end of the rod is not a monotonic function of the length of the rod. There are strong fluctuations in sound level with length. The fluctuations are caused by waveguide effects. These effects have been made inoperative in the past by techniques such as cutting screw threads on the surface of the rod. In this experiment the material of the rod itself was made inhomogeneous in a radially symmetric manner by heat treatment. It was found that the waveguide fluctuations were extinguished and the wave died out exponentially in the inhomogeneous rods. Much background noise, however, was generated through the spatial diffusion of the wave.
Low-Frequency Acoustic Attenuation in the South Pacific Ocean
Authors: Kibblewhite A. C. , Denham R. N.
Published: October 2005

The first known measurement of the attenuation of sound in deep water at frequencies below 1 kHz in the South Pacific Ocean is described. The receiver was situated off the east coast of the North Island of New Zealand. It was found that the attenuations are in most cases comparable with the values of attenuation measured in the North Pacific Ocean and the Atlantic Ocean between Bermuda and South America. However, on one of the paths over which the attenuation was measured, there was an abrupt change in the quality of sound transmission, which is thought to be a result of the path crossing the Subtropical Convergence; south of this discontinuity the attenuations were found to be comparable with those obtained previously in the Southern Ocean.
A Portable Hydrophone Calibrator
Authors: Trott W. James
Published: October 2005

A portable hydrophone calibrator with associated electronic circuitry is described for calibration of a wide variety of hydrophones. The calibrator covers the frequency range from 1 Hz to 3.5 kHz and simulates operating depth by means of hydrostatic pressure to 1000 psi and temperature variation from 4°C to room temperature. The calibrator is a closed chamber in which a sinusoidal pressure is produced by a piezoceramic tube that forms half of the cylindrical wall. A second piezoceramic tube forms the other half and measures the pressure in the region of the hydrophone. A step pressure establishes the absolute calibration of the system.
Wave Propagation in a Liquid Layer Bounded between a Rigid Plane and a Semiinfinite Fluid Space
Authors: Wang W. M.
Published: October 2005

The acoustic field induced by a point source in a liquid layer, bounded between a rigid plane and a semiinfinite fluid space, is analyzed. The total field is decomposed into the field of normal modes and a lateral wave, and they are studied separately. The farfield solution is obtained for the sound field within the liquid layer. The solution is applicable to the case of mutual coupling between the array elements in an underwater transducer with a ρc-rubber window, and some discussions are presented.
Sound from Turbulent-Boundary-Layer-Excited Panels
Authors: Davies Huw G.
Published: October 2005

The acoustic power radiated by thin flexible panels excited by turbulent-boundary-layer wall-pressure fluctuations is estimated using a modal analysis, light fluid loading effects being included. Previous estimates of the modal radiation coefficients are improved. Radiated power is estimated in two ways: the first estimate is made by directly summing over resonant modes and the second is based on a statistical energy analysis (SEA). The estimates are compared with experimental results. It would seem that the additional computation required to sum directly does not lead to a prediction significantly better than that obtained by SEA.
Statistical Theory of Atmospheric Turbulence Effects on Sonic-Boom Rise Times
Authors: Pierce Allan D.
Published: October 2005

The measured sonic-boom rise times at ground level are typically of the order of 1–10 msec, which is two to three orders of magnitude larger than what would be predicted on the basis of a planar shock propagating in a homogeneous atmosphere. A tentative explanation of how such anomalous rise times are caused by atmospheric turbulence is given in terms of the Keller-Friedlander geometrical acoustics theory of weak shock propagation in an inhomogeneous medium. It is suggested that the shockfront initially develops ripples that subsequently are transformed into folds in the front when the shock passes vertices of caustics. This wavefront-folding mechanism may produce sonic-boom signatures that have a fine structure consisting of many small pressure jumps (microshocks), each jump corresponding to a segment of the folded wavefront. This fine structure may, however, be smeared out by viscosity. To assess the mechanism's effectiveness quantitatively, a stochastic model of an initially sharp shock propagating through the earth's turbulent boundary layer is derived by use of an adiabatic perturbation to the Green's-function solution for waves in a homogeneous medium subject to specified normal fluid velocity at a boundary. The model depends on turbulence statistics through three parameters, one of which is the characteristic time tc estimated previously by Crow as 0.7 msec. An analysis based on the model substantiates the supposition that typical waveforms are composed of many very small discrete microshocks. An approximate derivation gives an expression for the ensemble average of the early portion of ground-level signatures. The corresponding rise time is found to be of the order of (2 to 3)tc, which is in reasonable agreement with the data. Nonlinear effects, while not necessarily negligible, would appear to be insufficient to nullify the mechanism. However, because of the many approximations employed in the analysis, the conclusion that wavefront folding is the primary cause of anomalous rise times remains tentative.
Sound Speed in Water-Ethylene Glycol Mixtures as a Function of Temperature and Pressure
Authors: Hebert Harris J.
Published: October 2005

Sound speed measured as a function of temperature and pressure in mixtures of de-ionized water and ethylene glycol is presented graphically. Temperature and pressure coefficients calculated from these data are tabulated.
Low-Field Acoustoelectric Interaction and Thermal Brillouin Scattering
Authors: Smith R. W.
Published: October 2005

Brillouin scattering is used to study very small changes produced in the distribution of thermal phonons by the acoustoelectric interaction. Perturbation in the thermal acoustic flux has been observed with carrier drift velocity less than the sound velocity.
Astigmatic Imaging Properties of Bragg Diffraction
Authors: Korpel A.
Published: October 2005

This paper shows, by means of a ray-tracing method, the existence of two orthogonal line foci in the scattered light arising from the interaction of a Huyghens' sound source and a converging fan of light. It extends to a higher degree of approximation the ray theory of Bragg diffraction imaging in three dimensions.
Studies of Resolution in a Bragg Imaging System
Authors: Smith Roy A. , Wade Glen , Powers John , Landry John
Published: October 2005

This paper presents the results of experiment and theory concerning the resolution capabilities of a Bragg diffracting system which uses a cylindrically convergent laser beam for imaging objects which scatter sound. The derived theory predicts that thin wires, oriented parallel to the convergence line of the light beam and separated by one wire diameter, will just be resolved if the wire diameter is equal to (Λ/2)/sinαm, where Λ is the sound wavelength and αm is the semiangle of the light convergence. For wire orientation at right angles to this direction, the resolution is of quite a different character. The predicted wire diameter is then (Λ/2)/sinθm, where θm is half the angle subtending the light beam in the direction perpendicular to the wire axes. Copper wires as small as 10 sound wavelengths in diameter could be experimentally resolved in our system when the wires were oriented parallel to the convergence line of the light beam. When oriented at right angles, wires as small as 23 of a sound wavelength could be resolved. These figures demonstrate good experimental verification of the theory.
Rayleigh Scattering in Dilute Gases
Authors: Yip Sidney
Published: October 2005

Large-angle Rayleigh scattering of light provides a tool for studying fluctuations in dilute gases where the wavelength is comparable to the mean free path. Interpretation of such an experiment requires a molecular calculation of the spectrum of the density fluctuation. The initial value problem can be formulated using the linearized Boltzmann equation. Solutions are obtained for two types of repulsive intermolecular potential, Maxwell molecule and rigid sphere, and the results are used in a quantitative analysis of high-resolution measurement. The problem of studying molecular gases in a similar way is also discussed.
Light Scattered from Thermal Fluctuations in Gases
Authors: Broz A. , Harrigan M. , Kasten R. , Monkewicz A.
Published: October 2005

A high-sensitivity high-resolution system for the study of light scattered from thermal fluctuations in gases has been constructed. A Bendix Channeltron photomultiplier tube with a dark noise of three-tenths of a photoelectron/second is the basis of an experimental setup which includes a Fabry-Perot interferometer having a bandwidth of 10 MHz with a piezoelectric scan and a frequency stabilized single-mode He-Ne laser. Resolution of 10 MHz is, therefore, attainable, and signal levels as low as six-tenths of a photoelectron/second yield reliable data. With this apparatus the density-density correlation function, G(r,t), of several gases has been investigated for a range of pressures. Whether the form of G(r,t) is derived from a kinetic or hydrodynamic view depends on the value of the Knudsen number, i.e., the ratio of λs, the wavelength of the scattering fluctuation, to the mean free path. Previous studies have concentrated on varying the angle of scattering (changing λs) while this study varies the gas pressure itself (changing the mean free path), allowing a more detailed investigation of the transition from the kinetic to the hydrodynamic view.
Interaction of Light and Sound in Process of Thermal and Stimulated Molecular Scattering of Light
Authors: Fabelinskii I. L. , Starunov V. S.
Published: October 2005

A summary of important results obtained by the authors on stimulated Brillouin scattering is presented. The paper deals with three topics: (1) fine structure of light scattering by the Rayleigh line wing, (2) stimulated Mandel'stam-Brillouin scattering and temperature light scattering, and (3) stimulated Mandel'stam-Brillouin scattering and glass fracture.
Effects of Temporal and Spectral Combinations on the Judged Noisiness of Aircraft Sounds
Authors: Pearsons Karl S. , Bennett Ricarda L.
Published: October 2005

The effects on perceived noisiness of spectral and temporal combinations of stimuli at varying durations were determined by 20 college students in an anechoic chamber. Several recordings of turboprop, turbofan, turbojet, and helicopter flyovers were also included in the list of stimuli. The results indicated that the most accurate predictor of the judged noisiness was perceived noise level with tone and duration corrections as outlined by the Federal Aviation Administrations (1968) aircraft certification procedure. To illustrate the responsiveness of effective perceived noise level (EPNL) over perceived noise level (PNL) in predicting the noisiness of stimuli, the results of the duration test revealed that, at judged equal noisiness, 75% of the data were within 4 dB of the standard signal for EPNL with the FAA tone and integrated duration measure as compared to 11 dB for PNL.
Optimum and Conventional Detection Using a Linear Array
Authors: Lewis J. B. , Schultheiss P. M.
Published: October 2005

The method described by Bryn [J. Acoust. Soc. Amer. 34, 289–297 (1962)] and Vanderkulk [J. Brit. IRE 26, 285–292 (1965)] for analyzing optimum passive detection of weak stationary Gaussian plane waves in additive stationary Gaussian noise is applied to a linear array of hydrophones which may be closely spaced. The advantage in optimum over conventional delay-sum-square-integrate processing is assessed in various situations. At a particular temporal frequency, the noise is characterized by a spatially derived spectrum. If this noise spectrum is reasonably flat over the principal response band of the steered array and if there are no effects from outside this band, then conventional processing will produce almost as high an array gain as the optimum detector. This situation is expected in reasonably isotropic noise fields at steerings near broadside. For long arrays of closely spaced hydrophones, a quantity termed the BL product roughly expresses the flatness of the spatial noise spectrum in the response band. When the BL product is high, the maximum nonsuperdirective array gain is simply the inverse of the spatial spectrum properly scaled. This gain is achieved by conventional processing the absence of strong interference; otherwise it is achieved by a weighting of the spatial spectrum, e.g., by a partial nulling.
Temporal Position of Discharges in Single Auditory Nerve Fibers within the Cycle of a Sine-Wave Stimulus: Frequency and Intensity Effects
Authors: Anderson David J. , Rose Jerzy E. , Hind Joseph E. , Brugge John F.
Published: October 2005

Period histograms, which display the distribution of spikes throughout the period of a periodic stimulus, were computed for discharges recorded from single auditory nerve fibers of the squirrel monkey when low-frequency tones were employed. For frequencies up to about 4 kHz, where phase locking is observed, the average phase angle of the discharges was tracked as frequency was varied in small steps from low to high. To a first approximation, the cumulative shift in average phase angle is a linear function of frequency as would be observed for an ideal delay line. The slopes of these phase-versus-frequency lines were found to be related through a power law to the best frequencies of the fibers. Thus, it seems possible to estimate the travel time of a mechanical disturbance between the oval window and any point on the cochlear partition. A more detailed examination revealed that average phase angle is also sensitive to intensity, depending upon the relation of the stimulating frequency to the best frequency. For stimulating frequencies below best frequency, discharges tend to occur progressively later in the cycle as intensity increases. Above best frequency, an opposite tendency often prevails if a change in phase angle occurs. At or near best frequency, little change in average phase angle is noted as intensity varies.
On-Frequency Masking with Continuous Sinusoids
Authors: Leshowitz Barry , Wightman Frederic L.
Published: October 2005

The detectability of brief, 1000-Hz sinusoids added in phase or in quadrature to a continuous tonal masker (pedestal) of the same frequency as the signal was examined in the presence of a continuous wide-band noise. The effects of signal duration, shape of the signal's energy-density spectrum, sound-pressure level (SPL) of the pedestal, and noise spectrum level were investigated. For conditions in which the background noise level was low, two unusual phenomena were noted: (1) a complete absence of the customary trading relation between signal power and duration; and (2) an extremely shallow masking function relating signal SPL and pedestal level. These departures from the law of temporal integration and Weber's law are consistent with a simple filter model of the ear in which it is assumed that the location of the auditory filter is altered in response to changes in the parameters of the signal and masker. A basic assumption of the model is that the location of the filter is changed in order to maximize the ratio of signal energy to masker energy at the output of the filter. For detection of a tonal signal in the presence of another sinusoid, it appears that observers can listen at frequencies far removed from that of the signal, where signal energy is as much as 40 dB down from the peak.
Relation of Temporary Loudness Shift to Temporary Threshold Shift
Authors: McPherson D. Frank , Anderson Charles V.
Published: October 2005

This investigation was designed to explore the relationships between postexposure temporary threshold shift (TTS) and postexposure temporary loudness shift (TLS) when both measures were obtained under similar experimental conditions. A special paradigm was designed which could be adapted to measure either TTS or TLS. Three different measures of sensitivity (TTS, TLS with loudness balances made at the exposure level, and TLS with loudness balances made at a constant 30 dB SPL) were obtained on one ear of each of five normal-hearing trained observers. The measures were obtained at 1000 and 1400 Hz by means of a Békésy-type tracking procedure both before and following a 5-min exposure to three different levels (50, 80, and 110 dB SPL) of a 1000-Hz pure tone. Analysis of the results of the investigation indicated that when TLS is measured at a constant level (30 dB SPL), both its growth pattern and its recovery pattern are similar to those of TTS, but when TLS is measured at the same level to which the ear is exposed, its growth pattern and its recovery pattern are different from those of TTS.
Some Effects of Bandwith-Duration Constraints on Frequency Discrimination
Authors: Ronken Don A.
Published: October 2005

It has been suggested that at very short durations, frequency spread of the signal is what determines the frequency resolving power of the auditory system. The validity of this notion is examined by applying a version of the “uncertainty principle,” which says that the product of “effective bandwidth” and “effective duration” is a constant that depends on the signal envelope. This bandwidth-duration constraint permits several different envelopes to be used for the carrier signal in a frequency-discrimination experiment, while at the same time restricting all the signals to the same nominal bandwidth. Rectangular, exponential, Gaussian, and gamma functions were used as envelope functions for a 1000-Hz carrier. Parameter values were selected to equate the signal bandwidths to the bandwidth of a rectangular envelope signal, which had a duration ranging from 2 to 32 msec. The frequency-discrimination data indicate that equating signal bandwidth in this way does not serve to make the signals equally discriminable. A more accurate way to estimate the discriminability for the different envelope sinusoids is to measure how long each signal envelope provides an acceptable signal-to-noise ratio.
ANSI-1969 Standard Reference Threshold Sound-Pressure Levels for Audiometers: Some Comments
Authors: Weissler Pearl G.
Published: October 2005

New standard reference threshold sound-pressure levels for four audiometric earphones are given in Appendix F of ANS “Specification for Audiometers” S3.6 (1969) effective 1 September 1970. The change in reference level from ASA (1951) to ANSI (1969) is shown to be different for each earphone type. The sources of data for these new reference levels and the relationship of these new levels to ISO standards is discussed.
Acoustical Variables in Open Planning
Authors: Pirn Rein
Published: October 2005

The articulation index (AI) has been widely accepted as an objective measure of environments for speech communication and/or privacy. It quantifies speech intelligibility in terms of the signal-to-noise ratio on a scale extending from 0 to 1. While more experimentation is required to verify the subjective equivalent of any given AI, the AI itself can be calculated and hence predicted. It has been found that in buildings without complete floor-to-ceiling partitions the AI changes drastically with the following variables: speech effort, speaker orientation, background noise, speaker-to-listener distance, and barrier attenuation (if present and unflanked). This paper discusses the relative effect of these variables on the AI, and thus demonstrates the importance of each parameter in the design of open-plan facilities.
Effect of Boundary Layer on the Transmission and Attenuation of Sound in an Acoustically Treated Circular Duct
Authors: Eversman Walter
Published: October 2005

The transmission of sound in an acoustically treated circular duct containing sheared flow is treated by reduction of the governing equations to a two-point boundary-value problem. The pressure modes and transmission wavenumbers are obtained by an iterative procedure for a wide range of driving frequencies, duct-flow Mach numbers, and boundary-layer thicknesses with a given lining impedance model. Computations are made for both inlet and exhaust flows. For inlet flows, the direction of sound propagation is opposite to the flow direction, while in the exhaust flow the sound is propagated in the same direction as the flow. The numerical results show a major reduction of achievable attenuation of the least attenuated mode in the inlet flow, owing to the presence of the boundary layer, particularly at the higher Mach numbers. The attenuation in the exhaust flow shows only minor effects due to the presence of a boundary layer. The reduction in attenuation in the inlet flow indicates that the design of acoustic linings for inlet applications must include careful consideration of boundary-layer effects.
Microwave Acoustic Properties of Fluids by Bragg Scattering
Authors: Rheault Fernand , Adler Eric L.
Published: October 2005

A thin-film resonance technique is described for measuring the dispersion and absorption of acoustic waves in lossy liquids from 0.5 to 2.2 GHz. The method uses Bragg scattering of laser light to measure the incident and reflected acoustic power from a 4.2-μ liquid film formed between two sapphire rods. It is shown how the velocity and absorption are calculated from the measured acoustic reflection coefficient. The technique is used to study the two Dow Corning resins 276-V2 and 276-V9, both of which are found dispersionless within experimental error. The absorption per wavelength initially decreases with frequency for both resins; for resin V9, however, the absorption shows an increase at the higher frequencies. The results obtained are interpreted in terms of relaxational processes.
Character of Surface and Pseudosurface Waves in a Discrete Lattice
Authors: Alldredge G. P. , Allen R. E. , de Wette F. W.
Published: October 2005

The character of surface and pseudosurface waves in a discrete lattice is discussed. Results are given for the particular example of a model fcc crystal with (100) surfaces and anisotropy ratio η>1. The lattice results extend and complement the elastic continuum results of Lim and Farnell. General arguments allow qualitative extension of the present results to encompass the cases of cubic crystals having different surfaces [viz., (110) or (111)] or having anisotropy ratio η<1.
Similitude Approximations for Vibrating Thin Shells
Authors: Soedel Werner
Published: October 2005

True dynamic similitude in the Newtonian sense proves often to be too restrictive in experimental investigations of dynamic characteristics of large shell structures by use of smaller models. Also, design information yielded by true similitude considerations is limited because of the usual requirement of total geometrical scaling. Thus, approximate similitude relationships were derived starting with Love's equations of motion for thin shells. Depending on the relative dominance of bending and membrane stress influences, selection is made between two similitude expressions. This allows the introduction of shell thickness as a parameter independent of the scaled surface geometry. Free as well as forced vibrations are examined. Some of the implications of approximate similitude are illustrated using as an example a simply supported circular cylindrical shell.
Some Properties of Acoustic Surface Waves on X-Cut Quartz
Authors: Lewis M. F. , Patterson E.
Published: October 2005

The angular dependence of the surface acoustic wave velocity and piezoelectric coupling coefficient have been measured for X-cut quartz. The results in satisfactory agreement with the calculations of Coquin and Tiersten. Also reported is the first observation of pseudosurface waves on X-cut quartz.
On the Vibrations of a Thin Cylindrical Shell
Authors: Eriksson L. J.
Published: October 2005

The extensional vibrations of a thin cylindrical shell as described by Love and Haskins and Walsh [J. Acoust. Soc. Amer. 29, 729–734 (1957)] are discussed, using concepts recently presented by Drumheller and Kalnins [J. Acoust. Soc. Amer. 47, 1343–1353 (1970)]. Additional numerical results are presented and used to discuss the coupling of the longitudinal and radial motions. Calculations are presented to illustrate the “in phase” and “out of phase” modes described by Drumheller and Kalnins.
Spatial and Temporal Correlation of the Sea Surface
Authors: Fortuin L. , de Boer J. G.
Published: October 2005

The spatial and temporal correlation function of the sea surface, quantities required in underwater acoustic studies, can be formulated via the surface-wave energy spectrum. For two spectral functions, proposed by Neumann-Pierson and by Pierson-Moskowitz for a fully developed sea, time and space correlation functions are calculated numerically. The latter ones, although functions of two variables, can be constructed from two auxiliary functions, dependent only on correlation distance, when a cosine-squared law for the directionality of the wave spectrum is assumed. These auxiliary functions are tabulated and plotted. The two spectra produce results that differ only slightly.
Comments on “A New Approach to the Determination of Acquiring Rays in Singly and Doubly Layered Oceans” [D. T. RAPHAEL, J. Acoust. Soc. Amer. 48, 1249–1256 (1970)]
Authors: Jacobson Melvin J.
Published: October 2005

The approach presented by the author of the subject paper is not new, having appeared in numerous papers in recent years. Further, in his application of the method to an ocean with linear sound-speed profile, few novel results are presented since this problem has been investigated previously.
Measurements of the Attenuation of Muzzle Shock Waves in Air
Authors: Gjaevenes Kjell , Homstöl Arnfinn
Published: October 2005

The attenuation of the impulsive sound from a pistol is measured in an anechoic chamber by means of miniature condenser microphones. The shock waves were measured 1.3–4.7 m from the source and exhibited peak levels from 147 to 159 dB re 2 × 10−5 N/m2. The duration of the positive phase was about 200 μsec. The peak pressure P as a function of the distance s is described by the relation P/P0 = (s0/s)1.17±0.03. Limited variations in relative humidity, temperature, and atmospheric pressure did not significantly influence the exponent of this relation.
Tone Radiation from an Isolated Subsonic Rotor
Authors: Morfey C. L.
Published: October 2005

A solution has been found for the acoustic power extracted from the near potential field of a subsonic rotor, by interaction with a nonuniform inlet flow. The analysis is based on Lighthill's aerodynamic sound equation, modified to allow for a uniform mean flow, and is restricted to low-solidity rotors (lifting line approximation). Within this approximation, the power at blade-passing frequency is compared with that radiated from unsteady blade forces arising from the same nonuniform inlet flow. The comparison shows that more power may be radiated by the potential field interaction at high subsonic Math numbers, if the rotor disk loading is high.
Energy Flow Criteria for Acoustic Propagation in Ducts with Flow
Authors: Eversman Walter
Published: October 2005

The propagation of sound in a rigid-wall rectangular duct is investigated for the purpose of determining the energy-transmission properties of the higher pressure modes. It is known in the case of ducts with no flow that for low frequencies these higher modes are cut off and transmit no energy. This phenomenon is easily recognizable in the wave-propagation solution by the appearance of purely imaginary wavenumbers. In ducts with a steady mean flow, the form of the solution for sound propagation is more complicated and the question of the direction of acoustic transmission is not clearly indicated. A complete investigation of this problem requires the use of the energy equation. This study uses forms of the energy density and energy flow vector in a uniform moving medium which are applicable for a linear theory of acoustic propagation. These relations are used in combination with the solution for sound propagation to identify the types of transmission which occur throughout the frequency range in a given mode of propagation.
Real-Ear Attenuation Characteristics of Selected Noise-Excluding Audiometric Receiver Enclosures
Authors: Copeland Alfred B. , Mowry Harris J.
Published: October 2005

The attenuation characteristics of each of three commercial audiometric headsets of the noise-barrier type—(1) Aural Research (AR-100) “Auraldomes,” (2) Madsen (type ME-70) “Noise-Excluding Headset,” and (3) Rudmose (RA-125) “Otocups”—were measured, as were the attenuation characteristics of a standard audiometric headset (Telephonics TDH-39 earphone with an MX-41/AR cushion). The threshold-shift method was used, employing a pure-tone sound field in an anechoic room. The resulting attenuation data for each of the three noise-barrier headsets were compared statistically to those for each of the others and to the data for the standard headset. The data were contrasted with those supplied by the manufacturers. In terms of their attenuation capabilities for the octave bands pertinent to audiometry, the Rudmose Otocup (RA-125) is ranked first, the Auraldome (AR-100) second, and the Madsen (ME-70) headset third. It is suggested that attenuation data alone should not determine the acceptability of any such device. The potential user should, in view of the attenuation data yielded by this study, consider such use only after measurement of octave-band noise levels in the environment in question.
Spatial Patterns of Cochlear Difference Tones
Authors: Worthington Don W. , Dallos Peter
Published: October 2005

First-order intermodulation components in cochlear-microphonic potentials were measured with the differential electrode technique from all four turns of the guinea pig cochlea. Measurements were made with six pairs of primary frequencies and a wide range of primary signal intensities. The spatial patterns of the first-order difference tones were compared with those of the primaries, and with pure tones whose frequency was the same as that of the difference tone. The results indicated that at low and moderate primary intensity levels the distortion component was localized in the cochlea somewhat apical from the region of maximum excitation by the higher-frequency primary. With increasing stimulus intensity, a general shift of the distribution pattern was observed, accompanied by the development of a second region of maximal difference-tone activity. This second region, where the difference tone became more prominent as the intensity was increased, corresponded to the location of maximal microphonic elicited by a pure tone whose frequency was the same as that of the difference tone. These results further confirm that distortion of the cochlear microphonic is a two-stage process.
Determination of Vocal-Tract Shape from Impulse Response at the Lips
Authors: Sondhi M. M. , Gopinath B.
Published: October 2005

A method is described for determining the shape of the vocal tract from a measurement of the acoustic impulse response at the lips. Under the assumptions that the wave motion is planar and that the losses are negligible, the method gives the area function uniquely. It is further shown that a one-point measurement cannot provide any information about losses. A preliminary experiment is described which verifies the feasibility of the method.
Discrimination of Filtered/Clipped Speech by Hearing-Impaired Subjects
Authors: Thomas Ian B. , Sparks David W.
Published: October 2005

A form of preprocessed speech known to be highly intelligible to normal listeners was heard by a group of hearing-impaired subjects. The preprocessing technique involves high-pass filtering (cutoff 1100 Hz, slope 12 dB/oct) and infinite amplitude clipping. The subjects heard both unmodified and filtered/clipped word lists at 40-, 30-, and 20-dB sensation levels. Discrimination scores for 13 out of 17 cases were significantly higher at 20- and 30-dB sensation levels for filtered/clipped speech than for unmodified speech.
Effects of Auditory Masking on Vocal Intensity and Intraoral Air Pressure during Sentence Production
Authors: Brown W. S. , Brandt John F.
Published: October 2005

Previous research has demonstrated that a speaker has a high degree of control over his articulatory behavior when asked to repeat sentences several times in exactly the same way. The present research was designed to investigate the use of auditory cues during phonation. Normal-hearing speakers were instructed to read each of five sentences 25 times in exactly the same manner. While the speakers were talking, a masking noise was presented binaurally through earphones at several sound-pressure levels (SPLs) (up to 107 dB SPL), which the speakers were instructed to ignore. Measures of peak and integrated intraoral air pressure, SPL, and total phonation time were made to determine the stability of the utterances. Slight increases in SPL, intraoral air pressure, and phonation time accompanied increases in the masker SPL. However, these increases were minimal in comparison to published data suggesting sensory-motor information other than auditory was utilized by the speakers to control and maintain constant articulatory behavior.
Underwater 20-Hz Signals Recorded near Midway Island
Authors: Northrop John , Cummings William C. , Morrison Michael F.
Published: October 2005

From time to time, strong underwater acoustic signals with frequencies near 20 Hz have been recorded from hydrophones in nearly all oceans. Further details, such as source level, waveform, and movement, are not so well known. These signals may be divided into two main classes: short (∼1 sec) and long (up to 35 sec) emissions of sound at or near 20 Hz. We describe some low-frequency long signals that were recorded on hydrophones near Midway Island, thus providing a further example of these interesting phenomena. The slow (∼1 knot) meandering of the source, its relatively high signal level (∼70 dB re 1 dyn/cm2 at 1 yd) and low frequency (23–25 Hz) suggest a large biological source.
Speech Communication in Diving Masks. II. Psychoacoustic and Supplementary Tests
Authors: Morrow Charles T. , Brouns Austin J.
Published: October 2005

As work progressed from the physical measurements reported in Part I [J. Acoust. Soc. Amer. 50, 1–9 (1971)] to psychoacoustic testing, the gradient microphone proved not merely to perform somewhat better than the pressure microphone in diving-mask cavities, but to be essentially insensitive to cavity acoustics. With the gradient microphone, no optimum cavity dimensions were found, and standing-wave absorption within the cavity became unnecessary. These results were confirmed by sonograms and by response measurements with an artificial vocal tract.
Speech Communication in Diving Masks. I. Acoustics of Microphones and Mask Cavities
Authors: Morrow Charles T. , Brouns Austin J.
Published: October 2005

The acoustic properties of representative diving-mask cavities were measured, using a high-impedance sound source. Curves of impedance presented to the lips and of microphone transmission, relative to those of free space, were obtained. Both nonabsorbent cavities and cavities with standing-wave absorption adaptable to a marine environment were investigated.