bluuebunny/crossref_metadata_2025 huggingface dataset:
Limitations on the Use of Circumaural Earphones
Authors: Benson Robert W. , Charan Kirti K. , Day James W. , Harris J. Donald , Niemoeller Arthur F. , Rudmose Wayne , Shaw Edgar A. G. , Weissler Pearl G.
Published: October 2005

Published material on the calibration of circumaural earphones is briefly reviewed. The present lack of knowledge about these earphones and about the earphone-to-ear coupling is indicated, and the resultant limitations on the routine use of circumaural earphones in clinical and industrial pure-tone audiometry are presented.
Reply to “Comments on ‘Use of Sensation Level in Measurements of Loudness and of Temporary Threshold Shift’ and on Courtesy in Writing” [J. J. Zwislocki and R. P. Hellman, J. Acoust. Soc. Soc. Am. 41, 714–715 (L) (1967)]
Authors: Ward W. Dixon
Published: October 2005

Rebuttal is given to the arguments of Zwislocki and Hellman. Comments attempt to clarify the discussion involved in the use of sensation-level measurements.
Study of Small-Amplitude Vibrations of Clamped Rectangular Plates Using Polynomial Approximations
Authors: Laura Patricio A. , Saffell Bernard F.
Published: October 2005

By means of the Galerkin method, an analysis is made of the vibration of a rectangular plate whose edges are clamped. Plate deflections are represented by a simple polynomial expression. This requires a minimum amount of labor. A complete table of frequencies is presented. Accurate but very simple frequency equations are derived for the first four modes of vibration.
Interference of Finite-Amplitude Ultrasonic Waves in Solids
Authors: Galster W. B. , Breazeale M. A.
Published: October 2005

A very sensitive means of observing the second harmonic generation of ultrasonic waves of finite amplitude in solids has been developed. The method depends on interference of overlapping pulses, which produces unusual interference effects. The applicability of the method to measurement of the distortion of finite-amplitude waves is discussed.
Structural and Electromechanical Interaction in the Multiple-Exciter Technique for Random Vibration Testing
Authors: Trubert Marc
Published: October 2005

Imposing difficulties arise in the proper generation of the simultaneous driving random forces in the multiple-exciter vibration-testing technique since, owing to structural feedback, each shaker is strongly influenced by any of the others. A general analysis has been made for a p degree-of-freedom structure excited by N electrodynamic exciters (p⩾N) in order to determine the armature voltages e1, e2, …, eN, needed to produce specified accelerations ü1, ü2, …, üN of the structure. The analysis includes the mechanical and electrical properties of the exciters and leads to a system of differential equations representing a multiple input/output interacting electromechanical system. The transfer function matrix H(ω) that transforms the multiple known base accelerations ü1, ü2, …, üN to the multiple desired exciter voltages e1, e2, …, eN is determined. Then the crosspower spectral densities of the voltages are deduced from the crosspower spectral densities of the accelerations. Finally, as an illustration, the analysis is applied to a uniform flexible beam, tied to the armatures of two exciters, but otherwise free. Correlated random base accelerations ü1 and ü2 are considered, and the crosspower spectral densities of the voltages e1 and e2 are determined. These crosspower spectral densities represent the fundamental requirement for the multiple equalization and control system.
Resonance Scattering of Sound by a Small Gaseous Object of Arbitrary Form
Authors: Steinberg M. S.
Published: October 2005

The acoustic scattering amplitude for a dilute gaseous object of arbitrary form in a liquid medium is determined self-consistently for the case of linear dimension small as compared to the wavelength. A scatterer of bulk modulus βo and density ρo in a medium of bulk modulus β and density ρ may exhibit monopole resonance scattering at a frequency ωr = (4πβoC/ρV)12, in which V is the volume and C is the capacitance in electrostatic units of a conducting replica of the scatterer. The criterion for occurrence of the resonance phenomenon is 3Fβo/β≪1, in which the shape factor F = 4πC3/3V⩾ 1 is minimum for a sphere. Dipole scattering is given in terms of the polarizability dyadic of a nonconducting replica of dielectric constant ρ/ρo, and is negligibly small in a neighborhood of the resonance frequency.
Sound Radiation from a Circular Array in an Elastic Baffle
Authors: Feit David
Published: October 2005

The pressure radiated by an ideal circular array located in an infinite baffle is obtained. The solution obtained is compared to that for a circular array in a finite impedance baffle. For frequencies below coincidence, the difference is not important, but for frequencies above coincidence the difference in the far-field directivity pattern is quite significant.
Comments on “Parametric Solution of the Dispersion Relation for Guided Sound Propagation in Shallow Water” [Allan D. Pierce, J. Acoust. Soc. Am. 39, 1139–1141 (1966)]
Authors: Tolstoy Ivan
Published: October 2005

It is pointed out that the solution given by A. D. Pierce for the dispersion equation for Pekeris' shallow water waveguide [J. Acoust. Soc. Am. 39, 1139–1141 (1960)] is not new.
Attenuation Provided by Fingers, Palms, Tragi, and V51R Ear Plugs
Authors: Holland Howard H.
Published: October 2005

Measurements of the attenuation of noise provided by use of the fingers, palms, tragi, and V51R ear plugs are presented for nine test tones. The results of the study show that the tragi provide the best attenuation, the palms and fingers slightly less attenuation, and the ear plugs the least attenuation.
Standard Hydrophone for the Infrasonic and Audio-Frequency Range at Hydrostatic Pressure to 10 000 psig
Authors: Henriquez T. A. , Ivey L. E.
Published: October 2005

A pressure-sensitive reference hydrophone for the frequency range 0.3 Hz to 20 kHz at hydrostatic pressure to 10 000 psig and temperature from 5° to 35°C has been developed at the Naval Research Laboratory, Underwater Sound Reference Division. The nominal open-circuit crystal sensitivity of the hydrophone is −85.5±0.5 dB re 1 V/μbar from 1 Hz to 15 kHz; the output of the lithium sulfate sensitive element is increased by a transistorized 10-dB-gain (nominal) preamplifier. A novel cable gland improves the high-pressure reliability of the hydrophone.
Importance of the Fresnel Correction in Scattering from a Rough Surface. II. Scattering Coefficient
Authors: Horton C. W. , Melton D. R.
Published: October 2005

The scattering coefficient in the specular direction for acoustic pulses of frequency 95.8 kHz was measured for four pressure-release surfaces having a randomly rough relief. The results of these measurements are plotted versus grazing angle for grazing angles from 6° to 80° .Theoretical values were computed on the basis of the Helmholtz formula and the Kirchhoff approximations for the boundary conditions. It is found that the Fresnel approximation is significantly better than the Fraunhofer approximation, but in either case the theoretical formulas predict values for the scattering coefficient that are too small. There is some evidence that the theory fails when the maximum slopes of the scattering surface are too large.
Sound Radiation from Orthotropic Plates
Authors: Feit David
Published: October 2005

By rigorously taking into account fluid loading, the farfield pressure radiated by a point-excited orthotropic plate is obtained. In the case of an orthotropic plate, the coincidence frequencies cover a range bracketed by two coincidence frequencies corresponding to the frequencies at which flexural waves traveling in either of the two principal directions coincide with the sound speed in the ambient fluid. For frequencies below both of the coincidence frequencies, the directivity pattern is nondirective. Above the lowest coincidence frequency, the farfield pattern becomes directive.
Use of a Two-Dimensional Array to Receive an Unknown Signal in a Dispersive Waveguide
Authors: Clay C. S. , Hinich M. J.
Published: October 2005

A relatively simple method is discussed for estimating the phase velocity and direction of an unknown plane-wave signal, propagating across two-dimensional array in a dispersive waveguide. The finite Fourier transform is applied to the output signal of each sensor, and the phases of the smoothed frequency components calculated. The phases of the components are linearly regressed on sensor positions to produce estimates of the wave slowness components. Neither the phase nor group velocity dispersion curves need to be known, except for upper and lower estimates of the range. By smoothing over frequency and transforming, estimates are obtained of the direction and phase velocity of the signal. The precision of estimates depends on the signal-to-noise ratio, the square root of the number of sensors, and the number of wavelengths that fall in the array. Each frequency is treated separately, so that the direction and phase velocity are obtained as a function of frequency. Since the individual frequency components of the signal are separated, the signals observed on a large array can be combined, even though the dispersion is appreciable over the array. For good signal-to-noise power ratios, the dispersion curves are a direct result from the analysis.
Experimental Verification of the Proper Kirchhoff Theory of Wave Scattering from Known Randomly Rough Surfaces
Authors: Fung A. K. , Leovaris A.
Published: October 2005

Backscattered measurements of acoustics waves returned from three known surfaces of different roughnesses were made at four different frequencies. Two surfaces are made of mild steel and one of rubber polymer. The reflection coefficients were measured and found to be approximately constant over the scattering angles ranging from 0° to 30° from the vertical. The correlation functions and the standard deviations of the surface heights were calculated from the surface profiles obtained with a depth gauge. The correlation lengths and the standard deviations were found to be 6.00–27.75 mm and 0.74–1.08 mm, respectively. The range of the working wavelengths is from 1 to 3 mm. Thus, all parameters needed in the Kirchhoff's scattering law are known. Comparison with the usual Kirchhoff's theory [P. Beckman and W. K. Klemperer, “Interpretation of the Angular Dependence of Backscattering from the Moon and Venus,” Nat. Bur. Stand. Radio Sci. 69D, 1669–1676 (Dec. 1965); T. Hagfors, “Relationship of Geometric Optics and Autocorrelation Approaches to the Analysis of Lunar and Planetary Radar.” J. Geol. Res. 71, 379–383 (1966)] shows serious disagreement. It is found that this is due to an overapproximation in evaluating the Kirchhoff's integral. When the integral is properly evaluated, very good agreement between theory and experimental results is obtained. This appears to be the first theory that is capable of explaining both the angular and frequency behaviors of the return signal. We restrict our backscatter angles to be within 30° so that we are sure that the Kirchhoff's theory applies, and no polarization, shadowing, or multiple scattering effects are significant. Thus, the results obtained apply equally well to electromagnetic scattering. The distributions of the surface slopes are also calculated from the surface profiles so that geometric-optics theories of wave scattering (which may be considered to be a special case of the Kirchhoff's theory can also be checked.
Surface-Impedance Nonuniformities as Wave-Vector Convertors
Authors: Maidanik G.
Published: October 2005

Analytical examination is carried out of the interaction of pressure fields with boundaries possessing surface-impedance nonuniformities. The analysis is limited to surface impedances that are point reacting. The analysis is performed in spectral space, and the spectral surface impedances are defined in terms of convolution operators. These operators are shown to generate a spectral component from a spectrum of spectral components in the blocked pressure field on the boundary; the generation is associated with induced changes in the wave vectors of the original components. The nonuniformities that give rise to the convolution operators are thus termed wave-vector convertors. Application of the analysis is limited to boundaries possessing periodic surface-impedance nonuniformities. It is shown that boundaries possessing such surface-impedance nonuniformities act so as to effectively increase the spectral density of the pressure fields on the boundary and consequently increase the radiative efficiency of the boundaries as compared with those of equivalent boundaries possessing uniform surface impedances. The equivalence is expressed in terms of equal effective spectral surface impedances. Calculation of the pressure field on a boundary possessing surface-impedance nonuniformities and subject to the pressure field of a turbulent boundary layer is exemplified.
Reduction of the Longitudinal Vibration of Internally Damped Rods Having Finite Termination Impedance
Authors: Snowdon J. C.
Published: October 2005

Possible methods for reducing the vibration transmitted through internally damped rods to an arbitrary terminating impedance are examined theoretically. The cases considered are a hollow rod comprised of three sections of arbitrary internal diameter and length, and a uniform rod to which either a dynamic absorber or a lumped mass is attached at an arbitrary location. For the purposes of calculation, the dynamic absorber and the lumped mass are placed at the unterminated end of the rod, where they can most effectively counter the driving force applied at that point; the termination is represented by a damped spring. Beside the anticipated resonances of the vibrating rods, an additional resonance is observed at frequencies below the fundamental frequency of each rod; this is the resonance between the rod behaving as a rigid mass and the stiffness of its springlike terminating impedance. The resonance is effectively suppressed only by the dynamic absorber. Conversely, the three-section rod provides superior reduction, of the force transmitted to, and the motion of, the springlike termination at essentially all frequencies higher than that of the fundamental rod resonance.
Turbulence-Induced Plate Vibrations: an Evaluation of Finite- and Infinite-Plate Models
Authors: Strawderman Wayne A.
Published: October 2005

Turbulent-flow-induced plate-vibration statistics are computed for mathematical models of finite and infinite thin plates. The computed statistics for the infinite- and finite-plate models are compared to establish similarities and differences between the vibration statistics for the two plate models. The statistics are also compared with available experimental data to determine which model better approximates reality. These comparisons show little similarity between computed turbulent-flow vibration statistics for the finite- and infinite-plate models. The plate-vibration statistics computed from the finite-plate model are in substantially better agreement with experimental results than those computed from the infinite-plate model.
Use of Probe Microphones to Measure Sound Pressures in the Ear
Authors: Johnstone B. M. , Taylor K. J.
Published: October 2005

The usual techniques employed when probe microphones are used to measure sound pressures at the eardrum are shown to give results with a best accuracy of ±10 dB in the frequency range 10 kHz–30 kHz. Both the size of the ear cavity and the position of the probe within it affect the output from the microphone.
Effect of Acoustic Cues in Fricatives on Perceptual Confusions in Preschool Children
Authors: Abbs Mary Skeel , Minifie Fred D.
Published: October 2005

Seventeen preschool children were tested to determine their ability to discriminate among the fricatives /s, z, f, v, θ, and ð/presented in consonant-vowel (CV) and vowel-consonant (VC) combinations with each of three vowels/ɑ, i, aɪ/. Syllable pairs were presented to the children for each possible fricative comparison, with consonant position and vowel being the same in any one pair. The stimulus tape was analyzed to determine durations of the consonants and vowels, peak amplitude of the fricatives, and center frequency and bandwidth of the resonance curves of each of the fricatives. The contribution of these acoustic cues to discrimination among the fricatives was evaluated. The voiced-unvoiced distinction appears to be facilitated in VC syllables by the ratio of consonant duration to vowel duration. The fricatives /s/ and /z/ are set apart from the other fricatives by their high intensity, high frequency, and shorter spectrums, thus making discriminations between /s/ or /z/ and the other fricatives considerably easier than discriminations among /f/, /v/, /θ/, and /ð/. The highest discrimination error rates are observed in the pairs /f-θ/ and /v-ð/, where there are neither voicing differences nor significant spectral differences between the two fricatives. Considerably lower discrimination error rates are observed when either voicing differences are present between two fricatives or there are significant spectral differences.
A Note on the Range of Estimates of F1 and F2 in German, English, and Chinese
Authors: Sherman D. N.
Published: October 2005

Estimates of the mean (m1) and second moment divided by the mean (m2 m1) of speech-power spectra for 18 bilingual speakers (German and English or Chinese and English) over averaging time of 100 and 140 sec have been obtained. Tabulated results for T = 140 sec support the conjectures of others regarding the utility of m1 and m2 m1 for the extraction of formant frequencies. There is evidence that these statistics, even for averaging times of 140 sec, are similar to those obtained by examining individual phonemes and that they may, in fact, provide information about the average position of the first and second formant frequencies.
Mechanics of the Guinea Pig Cochlea
Authors: Johnstone B. M. , Taylor K. J. , Boyle A. J.
Published: October 2005

The frequency response of a point on the basilar membrane of the guinea pig was measured using Mössbauer techniques. Stapes movement was simultaneously measured, and basilar-membrane motion for a constant stapes amplitude was calculated. A tuning peak of 18 kHz was found for a point about 2 mm from the stapes end. Basilar-membrane movement corresponded to 0.005 Å at 0 dB SPL (18 kHz), and the local frequency gradient was 2.5 kHz for a 0.5-mm length of membrane. With a high-frequency slope of 95 dB/oct, the tuning curve is much sharper than previously thought. Such a slope appears to account for a large part of the primary neural tuning curve.
Postexposure Responsiveness in the Auditory System. I. Immediate Sensitization
Authors: Noffsinger P. Douglas , Tillman Tom W.
Published: October 2005

Human ears were stimulated by 3-min 65–90 dB sound-pressure level continuous tones, and postexposure thresholds for tones of lesser frequency were examined. In most cases, such procedures allowed demonstration of auditory sensitization that was not preceded or succeeded by desensitization and that ran its course in the first postexposure minute. Such sensitization was noted at 200 Hz following certain 500-Hz exposure tones, and at 2000 Hz following certain 3000-Hz exposure tones. The magnitude and duration of the phenomenon seemed dependent on exposure tone intensity.
Horizontal Coherence of Explosive Reverberation
Authors: Urick R. J. , Lund G. R.
Published: October 2005

As a sequel to an earlier paper, measurements have been obtained of the coherence of shallow water reverberation between two hydrophones separated distance apart horizontally. With the same techniques as before, the peak correlation coefficient at a given hydrophone spacing is found to be much lower when the hydrophones are separated horizontally than when separated vertically. The measured coefficients are found to be somewhat higher than theoretical expectations for a uniform distribution of sources in the horizontal plane, probably because the actual reverberation is distributed throughout a small angle in the vertical. The data obtained make possible the rational design of arrays for echo-ranging sonars in shallow water.
Comments on the Comments by Patricio A. Laura on “Frequencies of a Hanging Chain” [P. A. Laura, J. Acoust. Soc. Amer. 46, 1087(L) (1969)]
Authors: Murty T. S.
Published: October 2005

The present letter deals with additional references to those given by Laura for the transcendental equation discussed by Huang and Dareing.
Effects of Electrical Current Applied to Cochlear Partition on Discharges in Individual Auditory-Nerve Fibers. I. Prolonged Direct-Current Polarization
Authors: Konishi Teruzo , Teas Donald C. , Wernick Joel S.
Published: October 2005

This study is designed to reveal the effects of electrical polarization applied to the cochlear partition on discharges in individual auditory-nerve fibers in guinea pigs. Direct current is introduced in the basal turn across the organ of Corti. Its effects on the impulse discharges of the primary auditory fibers are measured during systematic variation of electrical and acoustic parameters. Data, recorded on tape, are analyzed by computing latency and interval histograms. With external current flowing from scala vestibuli to scala tympani, the spontaneous activity and sound-evoked responses increase in most of the auditory-nerve fibers. Current in the opposite direction causes decrease of impulse discharges. These nerve impulses show adaptation during application of the current and an aftereffect following its offset. It appears that electrical polarization modifies the resting current through the hair cells and also the excitability of the initial segment of the afferent auditory fibers.
Integrated Signal on Circular Piston Receiver Centered in a Piston Beam
Authors: Williams A. O.
Published: October 2005

Bass's method for computing the integrated signal at a circular receiver, equal in size to the source, parallel to it, and centered on the same axis, is generalized. Expressions are derived for (1) the velocity potential (and, therefore, the acoustic pressure) at a distance from the axis equal to the source radius; (2) the radial component of particle velocity; and (3) the integrated signal at a circular piston receiver, located as specified above but with radius differing from that of the source. Approximate limits of validity are given. Case 3 is tested against three different sets of experimental data, with good agreement.
Scattering of Linear FM Acoustic Pulses from Aluminum Spheres in Water
Authors: Mikeska E. E.
Published: October 2005

Experimentally recorded farfield echoes from linear frequency-modulated pulses incident on precision aluminum spheres in water are compared with computed echo forms. Good agreement was found using different pulse lengths and swept bandwidths. Spheres having ratios of internal to external radius of 0.95, 0.8, and 0.0 were studied, with either air or water in the hollow interior. Multiple periodic secondary echo components observed under some pulse conditions are interpreted in terms of circumferential waves and internal reflections.
Ambient-Noise-Spectrum Levels as a Function of Water Depth
Authors: Perrone Anthony J.
Published: October 2005

Recent measurements have indicated that the level of ambient sea noise is a function of water depth. The results presented in this paper were obtained from measurements made simultaneously with four hydrophones located in the open ocean, on the slope of a sea mount, in an area of the Northwest Atlantic. The four hydrophones were located in water depths of 400, 1100, 2400, and 2500 fathoms (f). All hydrophones were bottom-mounted except for the hydrophone at 2400 f, which was suspended 400 ft above the bottom. The ambient-noise levels are compared with wind-speed measurements recorded simultaneously from an anemometer system located on a fixed platform in the area of the hydrophones. The data were obtained during the month of January. Broad-band ambient-noise levels from the four hydrophone outputs were sampled simultaneously every 2 h for a 2-min period. An average value of ambient noise in logit filter bands of frequencies ranging from 11 to 1414 Hz was estimated for each 2-min sample. The results show a dependence of ambient-noise levels as a function of water depth, frequency, and wind speed. The spectrum slope as a function of water depth is also observed to be dependent on wind speed. The variations in ambient-noise levels as a function of depth produce a triangularly shaped pattern. This pattern illustrates the changing-spectrum slope as a function of depth. The changing-spectrum slope and the ambient-noise-level depth dependence are probably caused by the two major directional noise sources existing in the open ocean. One noise source is sea surface and is generated by local wind-speed conditions; the second source is generated by long-distance shipping. The surface-generated noise signal is primarily locally generated and arrives at the hydrophones principally via direct paths. Distant shipping contributions arrive at the receiver via refracted, surface reflected (RSR) and wholly refracted (RRR) paths.
Pulses Specularly Reflected by a Soft Cylinder
Authors: Rudgers Anthony J. , Überall H.
Published: October 2005

The formulas resulting from the creeping-wave formulation of acoustic scattering theory are used, and the form of the specularly reflected pulse, resulting from a plane-wave δ-function pressure pulse incident upon an acoustically soft infinite cylinder, is evaluated using a computer. The reflected pulseform is found in the farfield of the cylinder for a number of different angles of observation. The specularly reflected pulseform is also evaluated, taking various numbers of terms in the series that mathematically describes it, in order to examine the convergence properties of this series.
Underwater Sound Propagation Across the Hawaiian Arch
Authors: Northrop John
Published: October 2005

Sound signals from 300 small ( <10 lb) underwater explosions at various depths in the Northeastern Pacific Ocean were monitored on SOFAR depth hydrophones off Midway and Wake Islands. Travel paths to Wake crossed the Hawaiian Arch while those to Midway were unobstructed. The signals received were analyzed, in the 5- to 180-Hz band, for both peak sound pressure level and spectral density. Results indicate that (1) the Hawaiian Arch, as far west as Midway Island, caused complete terrain shadowing of hydrophones at Wake except for small “bathymetric windows” formed by 4-km deep passages through the Arch; (2) peak pressure levels recorded at Wake, for paths through the “windows,” were as much as 35 dB below those at Midway; (3) acoustic shadowing through the “windows” was frequently independent.
SUBJECT POSITIONING AND PHONATION RANGE MEASURES
Authors: Fishman Barbara V. , Shipp Thomas
Published: October 2005

Fifteen young adult male subjects were recorded as they sustained phonation of the extremes of their phonational range in both the supine and standing positions. Results of fundamental frequency analysis of the recorded samples showed a 1.1 semitone range decrease in the supine position owing to an attenuation at both the upper and lower limits.
Effect of Ambient-Noise Level on Threshold-Shift Measures of Ear-Protector Attenuation
Authors: Waugh R.
Published: October 2005

Data showing the effects of ambient noise level on threshold-shift measures of ear-protector attenuation are reported. It is argued that it is possible for errors of up to 10 dB to occur in measurements made according to current USA Standards, and that more stringent ambient-noise-level criteria are therefore required. A possible approach to the formulation of such criteria is suggested.
Flexural Vibrations of a Connected System Consisting of a Bar and a Cantilever Plate of Infinite Length
Authors: Saito Hideo , Sato Kenzo
Published: October 2005

This study considers the free flexural vibration of an elastic bar attached to the free edge of a cantilever plate of infinite length. The frequency equation is obtained for the system, and numerical results are presented for its first two natural frequencies. Experimentally determined frequencies are compared with their theoretical values and the pairs of fundamental frequencies are found to be in remarkably good agreement.
Application of Duct-Lining Technology to Jet Aircraft
Authors: Marsh Alan H.
Published: October 2005

Design studies of various acoustically treated inlet and fan-exhaust ducts were conducted for the JT3D turbofan engine installation on DC-8 airplanes. These design studies resulted in the selection of two configurations of treated engine inlets and one configuration of treated fan-exhaust ducts for full-scale fabrication and testing. On the basis of ground runup test results, one configuration was chosen for subsequent flyover noise and cruise-performance flight testing. This paper discusses some of the design concepts that were studied, presents some of the results of the full-scale ground runup tests, and also presents predictions of the change in flyover perceived noise level owing to installation of treated nacelles on DC-8–50/61 airplanes.
Experiments with the Raes Method for Producing Diffuse Sounds
Authors: Behar Alberto , Menyhart Jorge
Published: October 2005

In a recent paper [J. Acoust. Soc. Amer. 46, 831–834 (1969)], A. C. Raes suggests the producing of diffuse sound fields through the use of two speakers excited alternately. The present paper describes some experiments devoted to research work on the grade of sound diffusion obtained by using this method. To this end, work was carried out in six chambers having different acoustic characteristics. In each case, the chamber was excited by white-noise signals produced by two speakers, first simultaneously and then alternately, in accordance with the suggested method. The sound level was measured at different points in each chamber, and the standard deviation was calculated. The results seem to show that the suggested method does not better diffusion substantially.
Effects of Filtering and Vowel Environment on Consonant Perception
Authors: Gay Thomas
Published: October 2005

The purpose of this experiment was to determine the effects of filtering and vowel environment on consonant perception. Sixteen consonants in consonant-vowel (CV) combination with seven vowels were recorded on tape, low-pass filtered, and played back to a group of listeners. In general, the results indicated that /t, k, b, d, g, s, f, z, w, r, n/ are affected by filter cutoff points, that /k, g, f, v, m/ show multivowel effects, and that /p, b, d, j, n/ show consistently lower scores only when followed by /i/. As expected, error types were predominantly “place” with “manner,” voicing,” and “nasality” errors occurring only at the less favorable cutoff frequencies. The results were discussed in terms of the predictability of the effects as a function of CV-transition characteristics and the suitability of small sample phonetically balanced word lists for assessing speech discrimination of individulas with high-frequency hearing loss.
Asymptotic Solution of the Stochastic Helmholtz Equation for Turbulent Water
Authors: Neubert Jerome A.
Published: October 2005

It is concluded that a two-variable expansion is sufficient for representing sound propagation through a continuous weakly inhomogeneous medium and that the Debye approximation is a proper two-variable expansion. Its application to the stochastic Helmholtz equation yields, to order ασκ(Rt)12/λg2k02, the eikonal equation and the transport equation; α is the rms refractive index variation, σκ is the Prandtl number, Rt is the turbulent Reynolds number, λg is the Taylor microscale, and k0 is the wavenumber. The resultant acoustic frequency limitations for the Stone and Mintzer experiment and for the turbulent upper ocean are developed and compared. The solution of the eikonal and transport equations in a continuous fluid renders a Lagrangian pressure relation. Finally, the Debye and Born approximations are compared for one-dimensional sound propagation.
Ray Theory for Sources and Receivers on an Axis of Minimum Velocity
Authors: Pedersen Melvin A. , White DeWayne
Published: October 2005

This article presents a detailed analysis and numerical investigation of the ray theory of four simple velocity profiles in common use as models of the deep sound channel in underwater acoustics. Comparison with ray-theory results for range and group velocity, obtained after fitting a 19-parameter curve to a realistic ocean profile, indicates that these simple profiles are inadequate. Numerical examples exhibit more completely the significant effect of discontinuities in the second- and third-profile derivatives evaluated at the axis. Some general theoretical results are developed and illustrated by examples. These results include: (1) scaling laws interrelating ray theory results for different sets of profile parameters, (2) the development of range and group velocity in series expansions of the phase velocity, (3) group velocity inequalities, and (4) the role of points of inflection in producing multiple caustics. A method is presented which determines and demonstrates the near-axial ray-theory properties of a velocity profile by comparison with a cosh profile.
Volume-Scattering-Strength Dependence on Depth and Frequency in the Pacific Ocean off San Francisco
Authors: Scrimger J. A. , Turner R. G.
Published: October 2005

A time series of measurements of volume scattering was made in the N.E. Pacific Ocean at a site approximately 55 miles west of Pt. Reyes (near San Francisco). The technique involved the firing of small explosive charges close to a receiving hydrophone and monitoring the broad-band scattered returns originating nearby (approximately 100-ft radius). Lowering the hydrophone-charge combination to various depths enabled the scattering characteristics in the top 2100 ft of the ocean to be examined. The data are presented as spectra of scattering strength versus frequency at 10 evenly spaced depths between 200 and 2000 ft and also as a set of eight profiles of scattering strength versus depth in each of four octave frequency bands between 0.625 and 10 kHz. These profiles are obtained in the course of a 30-min lowering of the equipment—eight of which were carried out between 0600 PST (about 112 h before dawn) and 2000 PST (about 2 h after sunset). Scattering-strength profiles were integrated against depth to give column scattering strength values which are displayed as a function of time. In addition, a comparison was made between integrated scattering strength versus depth profiles obtained both from a scattering strength versus depth profile and from a surface-fired charge.
Analysis of the Frequency Response of Simple Geometric Targets
Authors: Shirley D. J. , Diercks K. J.
Published: October 2005

Measurements of pulse-echo forms and steady-state frequency response of air- and water-filled aluminum spheres and cylinders in water are presented. These compare favorably with theoretical results. The nondimensional frequency (ka) range is 24≦ka≦60. Scattering paths defined by the cross-sectional geometry of the targets are identified, and it is shown that it is constructive and destructive interference between the energy returned along the different scattering paths that generates the frequency response of the target as frequency is changed. Similarities in the backscattered echoes from spheres and cylinders at normal incidence due to similarities in the scattering geometry are described. Measurements of circumferential waves in spherical shells, believed to be the first reported for this target form, are presented.
Two Experiments on Pitch Perception: Diplacusis of Harmonic AM Signals and Pitch of Inharmonic AM Signals
Authors: van den Brink G.
Published: October 2005

In the first experiment, binaural diplacusis for harmonic three-component (amplitude-modulated signals has been measured. There appears to be a good agreement between diplacusis for complex signals and the average of the pure-tone diplacusis for its spectral components. In all cases, the pitch of the stimuli used roughly agreed with the pitch of the common, but nonexistant, fundamental. Apparently, the pitch of the separate components is more important than their frequency. Conclusively, the origin of binaural diplacusis cannot be found in a peripherally located mechanism, but in some higher center. In the second experiment, the pitches of inharmonic amplitude-modulated signals were matched monaurally with those of harmonic signals. The experiment gives direct quantitative information of the pitch deviations which have been found regarding the time-fine-structure theory. These deviations increase progressively with the rate of inharmonicity of the signal and decrease with decreasing intensity and modulation depth. The results suggest that the deviations are due to neural interaction mechanisms and thus can not be described in simple mathematical formulas.
Degrees of Freedom of Cochlear Patterns
Authors: Rink R. E.
Published: October 2005

Although auditory patterns, from the cochlea inwards, are distributed in space and time, they do not have an infinite number of degrees of freedom. Because of mechanical coupling, motions at neighboring points along the cochlea are not statistically independent. Results are given for the number of equivalent degrees of freedom along the spatial axis of auditory patterns when displacement of the basilar membrane is the pattern variable and when envelope of displacement is the pattern variable. These numbers are compared with other estimates of the dimensionality of auditory pattern space.
Validation of the Single-Impulse Correction Factor of the CHABA Impulse-Noise Damage-Risk Criterion
Authors: Hodge David C. , Garinther Georges R.
Published: October 2005

Seventy-six subjects were exposed to single impulse noises produced by two small shoulder-fired rockets, and TTS2 was compared with the CHABA limits. The single impulse, 95% protection, and grazing incidence correction factors of the CHABA damage-risk criterion were validated. Grazing-incidence shock waves produced comparable results when they arrived at the ear from the front and from the rear.
Generalized Maxwell Spherical Structural Systems in Fluid Media
Authors: Bhattacharya B. K. , Carney J. F.
Published: October 2005

The dynamic response and stability of a single-degree-of-freedom structural system composed of a hollow or solid sphere connected by a massless supporting member and submerged in a viscous fluid medium is studied. The constitutive relationship between the connecting member and the base is considered to be of a generalized Maxwell model type. Basset's fluid reaction is included in the integro-differential equation of motion and a closed-form solution is obtained by means of Laplace transforms. Response curves illustrating the effect of each dimensionless parameter on the response of the system are presented, and a dynamic stability criterion based on the character of the solution is employed to develop a stability profile for the system. It is demonstrated that the dynamic response of the system is significantly influenced by the character of the surrounding fluid medium while the stability or instability of the structure is determined by the relative values of the load parameter and the stiffness-coefficient ratio.
Dispersion of Waves in Transversely Isotropic Rods
Authors: McNiven H. D. , Mengi Y.
Published: October 2005

The axisymmetric motions in an infinitely long circular rod made of a transversely isotropic material are studied, and the frequency equation governing such motions is established. The relationship between frequency and wavelength contained in the equation is not explored in detail. Instead, exploration is limited to information that will be useful in a subsequent study in developing an approximate theory that will govern the same motions. By studying the distribution of cutoff frequencies on the frequency wave-propagation constant plane, the conclusion is reached that the three lowest modes of motion strongly influence each other and are in turn influenced to a much lesser degree by the fourth and higher modes. Accordingly, numerical analysis is made of only the three lowest spectral lines.
Comments on “Turbulence-Induced Plate Vibrations: An Evaluation of Finite- and Infinite-Plate Models” [W. A. Strawderman, J. Acoust. Soc. Amer. 46, 1294–1307 (1969)]
Authors: Dowell E. H.
Published: October 2005

Comments are offered on a recent paper by Strawderman along with references to additional relevant literature.
Reliability of Ratings in an Auditory Signal-Detection Experiment
Authors: Bell Donald W. , Nixon James C.
Published: October 2005

Fifty samples of noise waveforms (N) and 50 samples of signal-plus-noise waveforms (SN) were rated on 10 occasions by four listeners. The listeners decided whether the waveform was N or SN, and rated the degree to which the waveform had the N or SN quality. The signal was a 1-kHz tone 500 msec in duration. Both signal and noise were gated. The results indicate greater reliability for ratings of SN waveforms than for ratings of N waveforms. Further, the results suggest that listeners can be quite consistent in rating some waveforms, but still not agree with each other.
The Acoustic Stapedius Reflex in Relation to Critical Bandwidth
Authors: Flottorp Gordon , Djupesland Gisle , Winther Finn
Published: October 2005

The threshold of the acoustic stapedius reflex in man was investigated by means of changes in acoustic impedance of the ear. The contralateral ear was stimulated by using bands of noise and complex tones with various bandwidths. The experiments showed that the reflex threshold, expressed in decibels re 2.10−6 N/m2, is almost constant for bandwidths less than a specific value and designated as “critical bandwidth.” When the bandwidth was further increased, a decrease in the reflex threshold at approximately 3–6 dB/oct was observed. Assuming that the stapedius reflex mechanism is loudness governed in persons with normal hearing, these findings confirm the existence of a critical bandwidth in loudness summation. In addition, the findings indicate that the basis for the critical-band mechanism is located in the peripheral part of the auditory system, probably in the cochlea.
Perception of (Hindi) Vowels in Clipped Speech
Authors: Gupta J. P. , Agrawal S. S. , Ahmed Rais
Published: October 2005

The structure of perceptual confusions among 10 Hindi vowels /i, I, e, ɛ, a, ʌ, ɔ, o, U, u/ was studied in clipped speech. Front vowels were recognized better than back vowels. It has been found in most of the cases that the first and the second probable incorrect vowels have either openness of the vocal tract or place of articulation in common with the corresponding correct vowel. This finding supports the view that vowels can be perceived by these two distinctive features only. The same two distinctive features (dimensions) have been used by Wickelgren [J. Acoust. Soc. Amer. 38, 583–588 (1965)] to explain the coding of vowels in short-term memory.
Air Consumption Values for Oral and Whispered Plosive-Vowel Syllables
Authors: Schwartz Martin F.
Published: October 2005

An examination was made of the magnitude of air consumed for plosive-vowel syllables in oral and whispered speech. The results from 10 adult females revealed consistently greater consumptions for the whispered syllables, generally greater consumptions for the whispered voiceless plosive-vowel syllables as compared with the whispered voiced plosive-vowel syllables, and no consumption differences for place of articulation.
Shadow-Graph and Schlieren Methods in Auditorium Modeling
Authors: Lee James Bernard
Published: October 2005

The shadow-graph method in the classical form used by W. C. Sabine seems better suited to wavefront photography in models of auditoriums than the more complex schlieren method. The former produces photographs in which the optical density is proportional to the density of disturbance within the model; the latter produces photographs that are sensitive to gradients within the model. The return to the techniques of Sabine and others who produced wavefront photographs in the earlier years of auditorium design is recommended as a means of avoiding detrimental effects produced by considerations of geometrical acoustics only.
Farfield of Pulsed Rectangular Acoustic Radiator
Authors: Freedman Albert
Published: October 2005

As an example of a previously described theory for plane and gently curved radiators, the farfield of a rectangular pistonlike radiator is shown to be composed of four components of equal magnitude, each of which behaves as if generated at one of the corners. The magnitude of each component varies monotonically with increasing angle from the acoustic axis and is independent of the dimensions of the radiator. For the steady state, the vectorial superposition of components, taking account of the separations between the four effective sources, yields the familiar CW field, containing lobe structure. In the two normal central planes parallel to the radiator sides, the four components reduce to two, and on the acoustic axis they reduce to one. If instead of a CW signal a pulse is applied to the radiator, the field components arrive sequentially, according to the travel times from each of the corners to the field point. If the applied pulse is sufficiently short, these field pulses may be fully resolved. Successful experimental verification of the theory is described in which resolution was obtained of the two pulses in a central plane of a rectangular transducer.
Speed of Propagation of Acceleration Waves in a Binary Nonreacting Mixture
Authors: Leininger J. R. , Nachlinger R. Ray
Published: October 2005

In this paper, the speeds of propagation of acceleration waves in a two-constituent mixture are developed. The mixture is assumed to behave elastically, and no reaction is assumed to take place. The amplitude of the waves does not have to be small.
Dynamic Green's Function Technique Applied to Shells Loaded by Dynamic Moments
Authors: Bolleter U. , Soedel W.
Published: October 2005

A dynamic moment Green's function for plate and shell structures is defined as the spatial gradient of the normal load dynamic Green's function. With the moment Green's function known for a particular structure, its response to dynamic moments of any type of distribution and time characteristic can be evaluated. The technique is applied to the technically significant problems of a rotating moment acting on a rectangular plate and a circular cylindrical shell segment.
Vibrations of Cylindrical Shells in a Semiinfinite Acoustic Medium
Authors: Chang Kurng Y. , DiMaggio Frank L.
Published: October 2005

An infinite elastic cylindrical shell, submerged in a semiinfinite acoustic medium with a free or rigid surface, is acted upon by a concentrated harmonic line force. By using Flügge's shell equations and the appropriate radiation condition, a boundary-value problem is formulated. In order to make numerical integration feasible, the discontinuities in the solutions of the shell equations due to the concentrated load are removed by subtracting a closed-form static response, and the semiinfinite physical domain is mapped into a finite (rectangular) mathematical one by using a bipolar transformation. Extensive numerical results are presented for the shell displacements and fluid pressure field for steel shells in water.