bluuebunny/crossref_metadata_2025 huggingface dataset:
Coherent Reflection by the Rough Sea Surface of the Acoustic Field from a Source of Arbitrary Directivity
Authors: Clarke Richard H.
Published: October 2005

The angular plane-wave spectrum representation of the acoustic field due to a source of arbitrary directivity is used to formulate the problem of scattering by a rough sea surface. An approximate solution is obtained by applying Kirchhoff-type boundary condition at the surface. The solution suggests a straightforward modification of current ray-tracing techniques in order to estimate the coherent part of the reflected field.
Velocity of Transient Cavities in an Acoustic Stationary Wave
Authors: Crum Lawrence A. , Nordling David A.
Published: October 2005

This paper concerns the high-speed motion of transient cavities generated in an acoustic stationary wave in a cylinder filled with water. Time-exposure photographs are presented of the cavities illuminated by a high-speed stroboscope showing multiple exposures of an individual cavity as it was propelled outward from a region of large acoustic pressure amplitude. The photographs show several interesting details of the cavitation event. Velocities obtained by the cavities were on the order of 1 m/sec, pressure amplitudes on the order of 5 bars, and cavity lifetimes on the order of 10 msec. A theoretical analysis of the cavity motion is obtained by considering the cavity as a spherical inhomogeneity in an acoustic stationary wave. Comparison of theory and experiment show good agreement provided that a velocity-squared drag law is used with a drag coefficient of 0.77.
Ray Propagation in a Channel with Depth-Variable Sound Speed and Current
Authors: Franchi E. R. , Jacobson M. J.
Published: October 2005

Ray geometry, travel time, and spreading loss are examined for a moving medium. The sound speed and current are both depth-variable, and the current direction is fixed in space. For a linear sound speed and current, ray geometry is investigated and an approximate solution is obtained which leads to helical paths. For a bottom-mounted source and receiver in the vertical plane of the current, the linear model is used to investigate ray geometry, travel time, spreading loss, and the acoustic field associated with refracted/bottom-reflected (RBR) transmissions. It is shown that the effects of current gradients and bottom currents on the phase and amplitude of the acoustic field are important and cannot be ignored. Further, long-term time variations in the current gradient are shown to cause much shorter-term variations in phase and amplitude.
Acoustic Propagation in a Uniformly Moving Ocean Channel with Depth-Dependent Sound Speed
Authors: Stallworth L. A. , Jacobson M. J.
Published: October 2005

The effects of uniform channel motion on the ray geometry, spreading loss, and travel time of individual arrivals are examined in a channel with horizontal boundaries and a linear depth-dependent sound speed. The properties of corresponding arrivals are compared for the case of the above channel, the case of a uniformly moving channel with a constant sound speed, the case of a channel with a linear depth-dependent current and a constant sound speed, and the case of a stationary channel with a linear depth-dependent sound speed. The total field at a fixed receiving point is considered, and it is shown that the intensity and phase are not independent of a small uniform current. The total field in the BIFI range, a 33-km×40-m channel, is calculated under summer and winter conditions. It is found that small changes in the current can produce significant variations in the amplitude and phase of the total field.
Acoustic Volume-Scattering Measurements at 3.5, 5.0, and 12.0 kHz in the Eastern Pacific Ocean: Diurnal and Seasonal Variations
Authors: Vent R. J.
Published: October 2005

Diurnal and seasonal acoustic volume-scattering data obtained with directional transducers at 3.5, 5.0, and 12.0 kHz from a deep-water area in the Eastern Pacific are presented. Results are shown graphically as volume-scattering strength versus depth and also as column-scattering strength. Comparisons from day to day, night to night, day to night, and from season to season indicate that: (1) Scattering-strength profiles do not change appreciably from one day to the next or from one night to the next. (2) Day-to-night changes in scattering profiles occur mainly within the upper 350 yd of ocean. Large day-to-night changes in scattering strength at a particular depth may not be evident in changes of column strength. (3) Seasonal changes affect 5.0-kHz sound scattering more than 3.5 or 12.0 kHz. Nighttime profiles at 5.0 kHz during March show a strong near-surface scattering layer having a maximum scattering strength of −58 dB and a column strength of −42 dB. Change of season affects the magnitude of the daytime scattering profiles at 3.5 kHz and the thickness of the deep scattering layer at 5.0 kHz. Seasonal observations at 12.0 kHz indicate negligible dependence upon season.
Refracted/Reflected Ray Propagation in a Channel with Horizontal and Vertical Sound-Speed Gradients
Authors: Warfield J. T. , Jacobson M. J.
Published: October 2005

The sound-speed gradient is assumed to be a vector of constant magnitude and direction that has both horizontal and vertical components. Ray geometry, travel time, and spreading loss are derived for refracted/bottom-reflected rays having an arbitrary initial direction at a bottom-mounted point source and experiencing multiple bottom reflections in a horizontal channel. Rays intercepting a bottom-mounted receiving point after traversing a given number of lobes are isolated and studied. It is found that the changes in travel time and spreading loss caused by the presence of the horizontal gradient are approximately proportional to the component of the horizontal gradient in the direction of the receiving point. With the receiving point placed in the direction of the horizontal gradient, a calculation is made of the total field due to a CW source as a function of the magnitude of the horizontal gradient. Substantial changes from the values when the gradient is purely vertical are found in both intensity and phase. An approximate formula shows that the change in phase is also proportional to the component of the horizontal gradient in the receiving-point direction.
Simple Pressure Source Model of Jet Noise
Authors: Scharton T. D. , White P. H.
Published: October 2005

The simple pressure source model of the sound radiated by a sonic jet is investigated analytically and experimentally. From the simple source model, the ratio of the frequency spectra of the radiated sound power and the jet pressure is derived for an assumed form of the jet-pressure cross correlation. The spatial variation of the overall jet pressures, the frequency spectra of the jet pressures, the axial and radial cross correlations of the jet pressures, and the cross correlation between jet pressure and farfield sound pressure are measured for a cold jet. Some implications of the simple source model with regard to noise suppression are also discussed.
Comments on “Generation of Fractional Harmonics in a Resonant Ultrasonic Wave System” [L. Adler and M. A. Breazeale, J. Acoust. Soc. Amer. 48, 1077–1083 (1970)]
Authors: Rogers Peter H.
Published: October 2005

By considering the boundary value problem in Lagrangian coordinates it is shown that there should be no generation of fractional harmonics in a fluid-filled resonant cavity when the parameter of nonlinearity of the fluid (1+B/2A) is zero. It is proposed that the mathematical model of Adler and Breazeale, which is independent of 1+B/2A, be made consistent with this result by taking into account the variation in the mean density of the fluid which accompanies the periodic change in the length of the cavity.
Comments on “Farfield of Pulsed Rectangular Acoustic Radiator” [A. Freedman, J. Acoust. Soc. Amer. 49, 738–748 (1971)]
Authors: Stepanishen P. R.
Published: October 2005

In a recent paper, Freedman investigated the farfield time-dependent pressures radiated from a rectangular piston with a pulsed velocity. Subject to specified bandwidth assumptions on the velocity, the resulting pressures in the farfield were shown to consist of replica pulses of the velocity. A comparison of Freedman's results with the results obtained from an alternate approach which requires no bandwidth assumptions is presented here. Although the pressure results from both approaches are in agreement in the principal planes of the piston, the exact approach shows the pressures at other points in the field are related to the piston displacement rather than the velocity. Since the farfield pressures resulting from a pulsed velocity can be expressed as a sum of pulses which are proportional to the piston displacement, significant differences in the numerical results obtained using Freedman's approach and the exact approach are noted.
Effect of Fringe on Masking-Level Difference When Gating from Uncorrelated to Correlated Noise
Authors: Bell Donald W.
Published: October 2005

Binaural detection of a signal having 180° interaural phase difference (Sπ, 500 Hz, 125 msec) in broad-band correlated noise having no interaural phase difference (N0, 46.1 dB/Hz) was investigated when broad-band uncorrelated noise (NU, also 46.1 dB/Hz) temporally surrounded the 125-msec observation interval. The N0 was switched from the NU either simultaneously with the onset of the observation interval, or 100, 300, or 500 msec before the onset of the observation interval. The N0 was switched back to NU at the end of the observation interval. Detection was also examined when the N0 was switched from NU at the start of the observation interval, but switched back to NU 100 or 300 msec following the end of the observation interval. When the temporal limits of the correlated noise coincided with the observation interval, the masking-level difference (MLD) was less than that found when detecting in continuous correlated noise, even though the correlated noise had been switched from uncorrelated noise of the same level. Switching from uncorrelated noise to correlated noise before the observation interval, or delaying the switch back to uncorrelated noise after the observation interval tended to restore the MLD.
Display of Three-Dimensional Ultrasonic Data for Medical Diagnosis
Authors: Robinson D. E.
Published: October 2005

In most ultrasonic diagnostic methods so far suggested, the output is in the form of a two-dimensional image, and a serial set of cross sections is used to give three-dimensional information about the part examined. The paper demonstrates the practicability of forming a section at any arbitrary angle through the three-dimensional information using a digital computer. In addition, information from two mutually perpendicular sets of planes can be consolidated into a single series of echograms, thus overcoming to some extent the loss of information due to specular reflection. While this technique does not appear to be practical for routine diagnosis with the present generation of pulse-echo machines, it would be simply incorporated in a computer-based device using acoustical holography, Bragg imagery, or a transducer array technique for data acquisition.
Disorganization and Disruption of Mammalian and Amoeboid Cells by Acoustic Microstreaming
Authors: Williams Alun R.
Published: October 2005

Mouse Ehrlich ascites carcinoma cells and the amoeba Hartmanella castellanii were subjected to an acoustic microstreaming field generated around a partially submerged transversely oscillating wire. The various forces responsible for the intracellular “consistency” (i.e., the viscoelastic tendency to resist mechanical deformation) of ascites cells are so strong that the organelles remain attached to each other after the plasma membrane has been torn off, whereas the cell contents of the amoebae are easily dispersed once the plasma membrane is ruptured. Present evidence suggests that the high internal consistency of ascites cells prevents any form of intracellular streaming, whereas the low internal consistency of amoebae might allow artifically induced streaming within the intact cell.
Effects of Stimulus Bandwidth on Listener Judgments of Vocal Loudness and Effort
Authors: Brandt John F.
Published: October 2005

The direct magnitude-estimation scaling technique was used to investigate listener perception of vocal loudness and vocal effort of a continuous speech sample. Three experimental conditions were developed that represented (1) normal changes in loudness and effort; (2) intensity held constant and effort varied; and (3) intensity varied and effort held constant. The experiment was conducted twice, once with all stimuli low-pass filtered below 2000 Hz and once unfiltered. The speech samples were judged by five normal-hearing listeners on the magnitudes of loudness and of the amount of effort used by the speaker during phonation. Exponents of the loudness and effort functions suggested that vocal loudness and effort were different percepts of the listener. A likely cue that listeners use in perceiving vocal effort was suggested to be the change in the speaker's fundamental frequency concomitant with increases vocal effort.
Capacitance-Microphone Static Membrane Deflections
Authors: Warren J. E. , Brzezinski A. M. , Hamilton J. F.
Published: October 2005

The nonlinear equations for the static deflections of the moving electrode due to the electrical fields between the electrodes in capacitance microphones are presented. These equations are valid for the historic method of constant bias voltage and the more recently developed polymer electret biasing. The equations were solved numerically for boundary conditions of circular and annular membranes. Because of the nonlinearity of the electrical attraction forces, certain values of the microphone parameters exist for which the deflections can become unstable. The results compare closely with past solutions and experimental deflection data obtained on constant bias voltage microphones using a laser interferometer.
Single-Number Noise Rating for One-Third Octave Band Sound Power Levels
Authors: Maling G. C. , Lang W. W.
Published: October 2005

Few methods are available for converting 13-oct sound power levels to a single rating number. In this study, the relationships between sound level A, the Air-Conditioning and Refrigeration Institute (ARI), sound rating number (SRN), and perceived noise level (PNL) are explored. If the ARI rating method is modified slightly, a direct correspondence can be established between the sound rating number of a band power spectrum and the perceived noise level of a band-pressure spectrum whose band levels are 20 dB lower in value. To differentiate between a rating based on sound power and a rating based on sound pressure, a single number called the power level rating (LPR) expressed in units of PRdB is proposed.
Noise Radiation by Plane Arrays of Incoherent Sources
Authors: Tatge R. Bruce
Published: October 2005

Generalized curves and a simple equation are developed by which it is possible to relate the sound-power level of a plane array of equal, incoherent, simple sources to the sound-pressure level at any distance. The array may have the form of a circular disk or a rectangle.
Shallow Water Ray Tracing with Nonlinear Velocity Profiles
Authors: Weinberg N. L. , Dunderdale T.
Published: October 2005

By specifying the ray paths and deriving the corresponding profiles, nonlinear ray-tracing techniques have been developed for stratified shallow water areas above the minimum sound velocity axis using elliptical and hyperbolic ray paths. The method results in closed-form expressions for the ray path equation, travel time, range, initial angle, and relative intensity which can be easily evaluated by manual computations. Experimental profiles from the Straits of Florida are approximated by functions which yield elliptical and hyperbolic ray paths, and numerical comparisons of the nonlinear method with a linear and a piecewise-linear approximation are presented for range and travel time which indicate that the nonlinear method yields a more realistic model of the sound propagation paths.
Supersonic Turns without Superbooms
Authors: Ribner H. S.
Published: October 2005

It is shown that focused booms that arise in turning flight can be suppressed by the simple (although not always practicable) expedient of slowing down the aircraft. The correct deceleration will eliminate the local curvature of the wave front responsible for the focusing. Specifically, the tangential deceleration resolved along the normal to the wavefront is adjusted to cancel out the centripetal acceleration similarly resolved. Horizontal turns of a prescribed limiting sharpness are not of concern for this suppression technique: their focused booms will be cut off from reaching the ground by atmospheric refraction. The minimum turn radius for focus cutoff is related herein in a simple fashion to the tabulated width of the sonic boom carpet for rectilinear flight, as a function of Mach number and altitude.
A Useful Analytical Model for the Parametric Acoustic Array
Authors: Bartram James F.
Published: October 2005

In 1963, Westervelt presented a simple analytical model for the parametric acoustic array. Making a number of simplifying assumptions, among them that nonlinear attenuation is negligible, Westervelt arrives at the following: (1) quadratic dependence of secondary level on primary level and (2) Rutherford scattering angle dependence, independent of primary level. Now, experiments show that: (1) the quadratic level dependence goes over to a linear dependence at high levels and (2) the difference frequency beamwidth broadens with increasing level. These effects are not predicted by Westervelt's model. In this letter, it is shown that it is easy to substitute the attenuation of a shocked sound wave in place of the simple linear attenuation used by Westervelt. The resulting Green's function integral is no longer elementary, but has a simply expressed hypergeometric series solution. On axis, the series sums to a simple closed form solution, correctly predicting the transfer from the quadratic to linear level dependence. Off axis, the series apparently does not sum to closed form, but is readily evaluated with a digital computer. The results agree rather well with experiment.
Effect of Distributed Quadratic and Equivalent Viscous Damping on Longitudinal Vibrations of Prismatic Bars
Authors: Michalopoulos C. D.
Published: October 2005

Forced longitudinal vibrations of a prismatic, slender bar with distributed quadratic damping and equivalent viscous damping are considered. The bar is free at one end and subjected to harmonic excitation at the other. The nonlinear differential equation with the velocity-squared term is solved numerically by the method of characteristics. The linearized equation is solved by Laplace transforms and the solution is compared to that of the nonlinear system. The damping is linearized by equating the energies dissipated per cycle by the two types of damping. Frequency-response curves, through the second natural mode, are given for several sets of the nonlinear and equivalent viscous damping coefficients.
On the Intensity of Aeolian Sound under Water
Authors: Castelliz H.
Published: October 2005

The study aims at prediction of the intensity of Aeolian sound created under water by an ocean current passing a wire or cable. Particular application is a mooring line of a deep-sea taut-moored buoy. The work is based on a paper by Phillips [J. Fluid Mech. 1, 607–624 (1956)] but the difference in scale between sound waves in air and in water necessitates the extension of Phillips' equations into the acoustical nearfield. A brief outline of the theory and numerical values are given.
Acoustic Wave Interaction with a Coherent Light Beam
Authors: Gruber S. , Marhic M.
Published: October 2005

We develop a theoretical treatment of the effect of pressure fluctuations on the phase of an electromagnetic wave propagating through them. The pressure variations may be either acoustic or turbulent in nature. We then describe an experiment in which acoustic noise excitation of a weakly resonant system is measured by laser interferometry. Wide-band acoustic noise energy is generated by a “free jet” emptying into a long pyrex pipe which is continuously pumped on by a large-capacity mechanical vacuum pump. The acoustic noise propagates down the pipe into a region traversed axially by a laser beam in which acoustic resonances occur. The phase of the coherent light is measured relative to a stable path and is related to the density variations produced by the random acoustic field. The spectrum of the phase fluctuations in the path gives explicit information about the acoustic noise. Theory and experiment are compared.
Absolute Accuracy of the Pulse-Echo Overlap Method and the Pulse-Superposition Method for Ultrasonic Velocity
Authors: Papadakis Emmanuel P.
Published: October 2005

It is shown that the errors in the absolute values of the measured delay times (after correction for diffraction phase and bond thickness) in the pulse-echo overlap and the pulse-superposition methods can be less than 0.015τ and 0.027τ, respectively, where τ is the period of the fundamental radio frequency of the transducer used. If broad-band pulses are used with the pulse-echo overlap method, then the error is larger but still less than 0.10τc at the center frequency. Translated into fractional errors in the single round-trip delay time, the errors may be as small as a few parts per million. It is emphasized that the diffraction phase can introduce an error up to 0.25τ if the diffraction phase correction is not applied. Empirical methods for finding some contributions to the total error are given.
Forced Harmonic and Random Vibrations of Concentric Cylindrical Shells Immersed in Acoustic Fluids
Authors: Magrab Edward B. , Burroughs Courtney
Published: October 2005

The forced harmonic and random vibrations of an elastic cylindrical shell surrounded by an inviscid fluid and concentrically contained by another thin elastic shell which itself is immersed in another inviscid fluid of infinite extent is considered. The motion of the shells and fluids is assumed independent of the axial coordinate. The motion of the shells is described by a theory which accounts for transverse shear and rotatory inertia. The motion of the fluids is described by the classical wave equation. Expressions for the acoustic pressure at the outer surface of the inner shell and the inner and outer surfaces of the outer shell are obtained along with the displacements (velocity) at these surfaces. Numerical results for the near- and farfield acoustic pressure are given for the case wherein the interior of the cylinder is subjected to diametrically opposed point forces which vary either harmonically or randomly with time. The random excitation is assumed to be spatially uncorrelated, broad-band white noise.
Reflection of Pulses at the Interface between an Elastic Rod and an Elastic Half-Space
Authors: Boucher S. , Kolsky H.
Published: October 2005

The problem of the reflection of elastic stress pulses at the interface between a rod and a half-space is treated theoretically and experimentally. The axis of the rod is taken to be perpendicular to the free surface of the half-space and its flat end to be in frictionless contact with this surface. It is shown that for the reflection of an infinite train of sinusoidal waves at such a boundary the conditions are analogous to those that apply for the reflection of such a train at the boundary between an elastic and a linear viscoelastic rod, and that a “cross-over effect” may be observed. This effect is that a critical frequency ωc may exist such that if the frequency of the incident wave is ω the phase of the reflected wave shows a sudden jump of π as ω passes through ωc. Thus if a dc pulse is reflected at the interface and if its relevant Fourier spectrum extends over this critical frequency, an s shaped pulse is found to be reflected. It is also shown in this paper that the accuracy with which the dynamic properties of the material of the haft-space can be determined is limited by the precision with which the values of the Fourier components of the incident and reflected pulses are known.
Vibrations of Beams with Hysteresis Damping
Authors: Lo C. C.
Published: October 2005

The transient vibration problem of beams with hysteresis damping is studied. The hysteresis damping is characterized by being strain dependent, frequency independent, and having a stress-strain loop with sharp corners. The mathematical solution employing the asymptotic method is given first, followed by the equivalent linear solution. Finally, the usefulness of the equivalent linear solution is discussed.
Thermomechanical Coupling Effects in the Longitudinal Oscillations of a Viscoelastic Cylinder
Authors: Ting Edward C.
Published: October 2005

The heat generation in a viscoelastic cylinder which results from thermomechanical coupling behaviors is investigated. Material behaviors and the dissipation function are temperature dependent. The inner surface of the hollow cylinder is subjected to cyclic shear loadings at high frequencies. This assumption leads to a nonlinear differential equation for stress distributions and the dissipation. A closed-form approximate solution is obtained by using the familiar WKB technique. The temperature distributions resulting from dissipation are solved by means of a finite-difference method. Numerical examples for a solid propellant are given. It is found that a large temperature rise will occur at the inner surface.
Speed of Sound in Castor Oil
Authors: Timme R. W.
Published: October 2005

The speed of sound in Baker DB-grade castor oil has been measured at temperatures between 0° and 40°C and pressures between atmospheric and 110 MPa (megapascals). The data have been fitted with an empirically determined equation.
Noise Signature of an Aircraft in Level Flight over a Hydrophone in the Sea
Authors: Urick R. J.
Published: October 2005

An aircraft flying over a hydrophone in the sea produces a noise signature whose magnitude and duration depend on such parameters as hydrophone depth, water depth, and flight altitude. This signature represents sound reaching the hydrophone in four different ways: via a direct refracted path, via one or more bottom reflections, via the so-called lateral wave, and via sea scattering. Of these, the refracted path is the most important and easiest to evaluate. Generalized contours for the nearfield of this component are given; in the farfield it is shown that the source in air can be replaced by an equivalent in-water source having a cosine-squared directivity pattern and a source level 7 dB less than that of the real source. In a field experiment, a Navy P3 Orion turboprop aircraft flew over hydrophones at two depths in deep water. The brief noise signature, lasting but a few seconds, was found to be accounted for statisfactorily by the refracted sound field. However, under conditions not existing in the field experiment, such as in shallow water, in rough seas, or at very shallow depths, it is conceivable that the other contributors to the total underwater sound field may become important.
An Algorithm for Analysis of Phase Effects: Application to Monaural Distortion Product Estimation
Authors: Erdreich John , Clack T. Dean
Published: October 2005

Estimation of aural harmonic magnitudes with the tone-on-tone masking paradigm requires calculation of the monaural phase amplitude effect from measurements of threshold level tones. Such amplitudes have been approximated with a sinusoid but may be more precisely determined by fitting the data with the circle, Ar2 = Ae2+A12−2AeA1 cos(ψ). An algorithm for this procedure is detailed.
Combination Bands of Even Order: Masking Effects and Estimations of Level of the Difference Bands (fh − fl) and 2(fh − fl)
Authors: Greenwood Donald D.
Published: October 2005

The levels of the difference bands, fh − fl and 2(fh − fl), generated by a pure tone and a narrow band of noise, have been estimated in a manner reported in previous papers (Greenwood, 1971a, 1972a, 1972b). Results and conclusions follow: (a) Combination bands of the form fh − fl and 2(fh − fl) vary in level as functions of stimulus parameters in ways very similar to the variation in level of the difference tone, fh − fl, produced by tonal primaries, as measured by cancellation techniques. Difference band levels are rather insensitive to increases of primary frequency ratio in the ranges explored (about 1.35–1.85). Difference band level obeys different functions of primary intensity depending on whether one or two, and whether the upper or the lower, primaries are varied. When the lower primary level is varied alone, square-law behavior is observed, in agreement with Goldstein (1967) and with Zwicker (1955); when the upper primary or both primaries vary, curves depart from square-law behavior in near agreement with Goldstein. Békésy's 1934 observations (1960) and Wenner's (1968) results suggest a conceivable explanation that might resolve some apparent discrepancies among results of Goldstein, Zwicker, and this paper when both primaries vary. (b) At primary levels exceeding about 60 dB SPL, combination tones of the form n(fh − fl) and combination tones of the form (n + 1)fl − fh will exist simultaneously, and since they lie in the same frequency region they will interchange places, with varying interactions, as primary ratios are varied—producing perceptual effects relevant to higher-level phenomena of consonance generally and to the beats of mistuned consonance specifically.
Effects of Intense Auditory Stimulation: Hearing Losses and Inner Ear Changes in the Squirrel Monkey
Authors: Hunter-Duvar Ivan M. , Elliott Donald N.
Published: October 2005

Twelve squirrel monkeys were exposed to pure-tone stimuli at intensities and durations sufficient to produce, in six, repeated temporary threshold shifts (TTSs) from 15 to 25 dB and, in the remaining six, permanent threshold shifts (PTSs) from 10 to 20 dB. Thresholds were determined by means of an avoidance conditioning procedure similar to that of Clack and Herman (1963), in which observation intervals were signaled by the houselight and the animals required to press a bar if an auditory signal was presented, and to withold response if not. Following final behavioral testing, animals were sacrificed and the effect of the exposures upon hair cells was determined. This was accomplished with surface preparation techniques and phase microscopy. The organ of Corti was examined along its length and the number of missing and visibly damaged hair cells was determined for each of the inner and outer rows from a point 1 mm from the apex to a point 17 mm from the apex. There was no clear evidence of hair cell damage due to the exposure. It is concluded that pure-tone stimulation sufficient to produce PTSs of 10–20 dB may not produce anatomical injuries to the organ of Corti that are detectable by phase microscopy.
Note on Psychometric Invariance of Detection Functions
Authors: Mulligan B. E. , Cornelius P. T.
Published: October 2005

The invariance that may be found to exist among monaural and antiphasic binaural psychometric functions is briefly reexamined and evidence is presented that is consistent with earlier findings—monaural and antiphasic psychometric functions differ by only a multiplicative factor.
Survey of Motor Vehicle Noise
Authors: Olson N.
Published: October 2005

Transportation noise, and motor-vehicle noise in particular, account for the steady or slowly varying ambient noise level, particularly in urban areas. Being so numerous, motor vehicles can be treated statistically, and this establishes consistent noise emission characteristics. Vehicles are categorized as: passenger cars [including light delivery trucks up to 6000 lb gross vehicle weight (GVW)], light, medium, and heavy trucks with GVW ranges of 6000–15 000, 15 000–30 000, and over 30 000 lb, respectively, tractor trailers, buses, cement-mixer trucks, and motorcycles. Speed ranges are 20–29, 30–39, 40–49, 50–59, and 60–69 mph. The sound level of the average vehicle of a given category increases consistently with speed and weight. The average vehicle is defined as the hypothetical vehicle having a sound level (A, B, or C weighting) and band-pressure levels equal to the weighted-mean decibels in the statistical distributions. The rate of increase with speed is such that in going from 30–39 mph to 60–69 mph, the sound level (A weighting) increases 8.5 dB for passenger cars, 9 dB for trucks and buses, 7 dB for tractor trailers, and 12 dB for motorcycles. For an estimated doubling of weight (motorcycles not included), sound levels increase 3.5 dB. For motorcycles, maximum noise occurs for full throttle setting, independent of road speed, gear, or engine loading. The octave-band spectrum of the average vehicle has a shape which is characteristic of each category and shows progressive change in level and shape with increasing speed. The octave-band spectra of four motorcycles, as examples, indicate dependence of level and shape on such parameters as type and size of engine, muffler configuration, and throttle setting. The sound level for acceleration is equivalent to about 40–49 mph cruising speed for tractor trailers and heavy trucks, and 30–39 mph for cement-mixers, but the octave band spectra for the two modes of operation exhibit consistent differences. Sound levels recorded continuously for 24-h periods at five locations, and analyzed for percentile distributions in each 1-h interval, have a diurnal cycle that follows a consistent pattern in response to motor-vehicle traffic.
On Propagation of Long Waves in Curved Ducts
Authors: Rostafinski W.
Published: October 2005

A two-dimensional detailed study of the behavior of long waves in curved ducts and in junctions between straight and curved ducts will be given. The mathematical treatment of the problem utilizes the method of separation of variables. Solutions and expressions for principal mode of the wave are obtained by using the linearized equation of motion solved for its characteristic values. The unavoidable approximations in the numerical solutions of the cylindrical functions are due to use of series expansion of Bessel functions and from restrictions necessary to solve infinite matrices.
An Extended-Range Hydrophone for Measuring Ocean Noise
Authors: Henriquez T. A.
Published: October 2005

A pressure-sensitive hydrophone that is capable of making acoustical measurements in ambient noise of sea state zero in the frequency range 10 Hz to 60 kHz and at depths to 700 m has been developed. The nominal open-circuit crystal voltage is −185 dB re 1 V/μPa. This hydrophone is completely isolated from seawater by a butyl rubber covering to ensure a long service life without corrosion and water migration.
Parametric Acoustic Transmitting Arrays
Authors: Muir T. G. , Willette J. G.
Published: October 2005

A numerical solution of Westervelt's inhomogeneous wave equation is obtained to describe the pressure field of sum and difference frequency radiations created by the nonlinear interaction of two monochromatic carriers in the farfield of a circular piston source. Experimental results are presented on the propagation and beam patterns of sum and difference frequency radiations resulting from the interaction of 418- and 482-kHz carriers emitted by a 3-in.-diam piston located in a fresh water lake. These results support the numerical methods. Several approximations commonly made to obtain dosed-form solutions are then evaluated with the numerical solution.
Underwater Acoustic Scattering from Lake Surfaces. I. Theory, Experiment, and Validation of the Data
Authors: Plemons Terry D. , Shooter Jack A. , Middleton David
Published: October 2005

A statistical analysis, based directly on ensemble averages, is made of reverberation data obtained from the wind-driven surface of a fresh water lake. To produce the reverberation, two types of signals consisting of gated (linear “chirp”) FM or CW pulses, are transmitted with a carrier frequency of 110 kHz. In the CW cases the pulse durations are 0.1 and 1.0 msec. The bandwidth of the FM signals (pulse durations 1.25 msec) is 9.6 kHz, and operation in all instances is monostatic (R@T). In the CW experiment the grazing angle is 22°, and in the FM experiment the grazing angle is 0°. Particular care is taken to insure that a valid sample ensemble is obtained by testing each sample ensemble for independence (from a one-sample runs test) and homogeneity (by a suitable Kolmogorov-Smirnov test). A recently developed point scattering model is introduced and adapted to the present experimental geometry to provide a theoretical description of the reverberation and a basis for later comparisons with the data. From this model covariance functions and intensities of the scattered signal are determined and quantitative insight obtained regarding the nonstationarity of the reverberation process.
Fixed-System Studies of Underwater Acoustic Propagation
Authors: Steinberg J. C. , Clark J. G. , DeFerrari H. A. , Kronengold M. , Yacoub K.
Published: October 2005

Sound waves of 420 Hz continuously transmitted across the Florida Current from a fixed source to fixed hydrophones are used to investigate relationships between temporal fluctuations of the waves and changes of Florida Current transport and water-column temperatures. The amplitude and phase of the received waves show variations with periods in the range from seconds to weeks and longer-term trends. Characteristically, variations of acoustic phase correspond to changes of transport and temperature, but fluctuations of acoustic amplitude are noiselike and not readily identifiable. Long period changes of transport and temperature result in slowly changing phases of the multipath arrivals and varying patterns of interference and amplitude fading. Spectra of the amplitude fluctuations show components over a wide frequency range which mask components corresponding to transport and temperature changes. The above characteristics also appear in calculations with ray-propagation models in which sound speed versus depth was varied with time in accordance with measured variations. Since the models have plane parallel boundaries, characteristic features of the variations appear to be independent of surface and bottom irregularities. This raises questions of modeling amplitude fluctuations from transport and temperature changes obtained from acoustic phase measurements. The paper summarizes relevant observations and analyses.
Turbulence-Induced Plate Vibrations: Some Effects of Fluid Loading on Finite and Infinite Plates
Authors: Strawderman W. A. , Christman R. A.
Published: October 2005

The effects of a fluid environment on the flow-induced vibration of finite and infinite plates are theoretically examined. Qualitative effects of fluid loading are deduced from the mathematical models. Examples of computed flow-induced vibration statistics for identical plates, with and without water loading, illustrate the quantitative effects of fluid loading. The fluid environment exerts forces on the plate in temporal phase with the plate inertial and resistive forces. For heavy fluids (i.e., water), the inertial component of the fluid loading is several orders of magnitude greater than the resistive component. Comparison of fluid-loaded finite and infinite plate statistics reveals that the infinite plate velocity spectral density provides a good approximation to the level and general shape of the finite plate velocity spectral density. However, the cross-spectral characteristics of the infinite and finite plate vibrations are substantially different.
The Zoning of Radiation Mode of Finite Plate on a Wavenumber Diagram
Authors: Tseo Gus G.
Published: October 2005

It is convenient to show various radiation modes of a resonant panel on a wavenumber diagram to clarify the dependence of radiation on frequency and vibration mode pattern. A correct zoning of the radiation mode on wavenumber diagram and some deductions concerning the critical frequency of a finite plate are presented.
Visualization of the Time-Average Pressure Distribution in a Rectangular Resonant Cavity
Authors: Galaitsis Anthony G.
Published: October 2005

A rectangular resonant cavity is partially filled with liquid and excited by sound. Actual and predicted mean pressure variations caused by the sound wave are studied by comparing pictures showing the shape of the liquid surface with pictures showing its predicted shape.
Estimating the Noise Reduction of Wall Structures of Enclosures
Authors: Tseo Gus G.
Published: October 2005

A simple method based on plane-wave normal incidence is used to calculate the transmission coefficient, reflection coefficient, and absorption coefficient of a wall structure. The performance of the wall structure for enclosing the noise source is estimated by a term called “noise reduction,” which is the ratio of the sound intensity at the exterior side of the wall to the sound intensity at the same point with no enclosure present. Several structures with combinations of impervious layers, air space, and sound-absorbing material are evaluated and used as examples to demonstrate the effect of mass, acoustical impedance, propagation constant, and arrangement of materials (impervious layer, absorbing material, and air) on the acoustical performance of the wall.
Cooperation of Listener and Computer in a Recognition Task. II. Effects of Computer Reliability and “Dependent” versus “Independent” Conditions
Authors: Corcoran D. W. J. , Dennett J. L. , Carpenter A.
Published: October 2005

Two experiments are reported upon the influence of a computer aid on the recognition of complex sounds. Twelve 112-h training and test sessions were conducted over a period of two weeks. Measures of unaided listener performance (L), computer performance (C), and combined performance (C & L) were obtained. In Expt. 1 the reliability of the computer was varied, while audio signal-to-noise (S/N) ratio was kept constant. The results showed (1) that as C increases so (C & L) increase; (2) that excessively high C performance reduces the listeners performance; and (3) that the strategy involved in using the computer and audio displays tends to evolve with training. Initially, attempts to compromise between computer and audio information often lead to (C & L) performance lower than it need be if the poorer display had been ignored. Later, the more valid display tends to be relied upon and finally in certain instances an optimal strategy tends to emerge in which (C & L) performance is above both C and L. Experiment 2 compared “dependent” and “independent” systems. In the former condition audio and computer displays are fed to the same observer; in the independent condition one observer receives the audio imputs and a partner views the computer display and makes the final (C & L) decision. No major differences in overall preferences were observed, except that the independent condition yields poor L performance.
Network Representation of the External Ear
Authors: Gardner Mark B. , Hawley Melville S.
Published: October 2005

Two of the basic requirements of an ear-model design is that the transfer characteristic of the ear canal and the impedance as measured at the eardrum closely agree with results obtained on real ears. In the case of the electrical analog model, this requires that the number of sections that are used to represent the ear canal provide an upper cutoff well beyond the highest frequency under study. This is particularly true where the effect of ear-canal taper is of interest. For these purposes, 10-section analog networks of uniform and of tapered design were employed. For network representation of the eardrum and the adjacent connecting structures, the effectiveness of one-, two-, three-, and four-branch terminations were explored. Of these, the two- and the four-branch analog networks were found to provide the best overall representations.
A Response-Contingent Measure of Proportion Correct
Authors: Gummerman Kent
Published: October 2005

Current methods of calculating proportion correct from the raw data of forced-choice experiments involve obtaining the proportion of times that a given response was made, contingent upon the occurrence of the corresponding stimulus. Here, another method is introduced: obtaining the proportion of times that a given stimulus occurred, conditional upon the occurrence of the corresponding response. Both of these computational methods are examined with respect to their stability over variations of sensitivity, response bias, and stimulus bias.
Response Patterns of Single Cochlear Nerve Fibers to Click Stimuli: Descriptions for Cat
Authors: Pfeiffer Russell R. , Kim Duck On
Published: October 2005

Response patterns to click stimulation of 907 single cochlear nerve fibers, having characteristic frequencies below 2000 Hz, can be separated into two populations on the basis of salient features. Population I consists of approximately 93% of the fibers, and Population II consists of approximately 7% of the fibers. A statistical description of the correlation between properties of response patterns of Population I fibers and stimulus level and characteristic frequency is given. For the Population I fibers, with characteristic frequencies below 500 Hz, deviations from the precise interlacing of preferred times of spike discharges in response to rarefaction and condensation clicks, as well as some instances of biased response to condensation clicks are described. The features that set Population II fibers apart from those of Population I are given, and a correlation of these populations with anatomical details of innervation is suggested.
Automatic Speaker Recognition Based on Pitch Contours
Authors: Atal B. S.
Published: October 2005

An automatic speaker-recognition method, using temporal variations of pitch in speech as a speaker-identifying characteristic, is described. The pitch data was obtained from 60 utterances, consisting of six repetitions of the same sentence, spoken by 10 speakers. The pitch data for each utterance was represented by a 20-dimensional vector in the Karhunen-Loève coordinate system. The 20-dimensional vectors representing the pitch contours were linearly transformed so that the ratio of interspeaker to intraspeaker variance in the transformed space was maximized. A reference vector was formed for each speaker by averaging the transformed vectors of that speaker. The recognition procedure was based on measuring the Euclidean distance between the test vector and the reference vectors in the transformed space; the speaker corresponding to the reference vector with the smallest distance was selected as the speaker of the test utterance. The percentage of correct identifications was found to be 97%. The results suggest that temporal variations of pitch could be used effectively for automatic speaker recognition.
Pure-Tone Auditory Thresholds for the Carp, Cyprinis carpio
Authors: Popper Arthur N.
Published: October 2005

Auditory capabilities of the Japanese carp, Cyprinis carpio, were determined using an avoidance conditioning procedure. Cyprinis could hear sounds from 50 to 3000 Hz with maximum sensitivity from 300 to 1000 Hz where the thresholds were below −34 dB (re 1 μbar). The thresholds for this species from 50 to 1500 Hz are very similar to thresholds determined for a number of other species in the same superorder of the teleosts (Ostariophysi). It is suggested that the similar hearing capabilities in these animals may be typical of all of the species of fish in this group.