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Journal of the Acoustical Society of America

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Jan 1969

Volume 45, Issue 1, pp. 1-347

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Breakage of Tobacco Mosaic Virus by Acoustic Transients: A Hydrodynamical Model

Philip E. Hamrick and Stephen F. Cleary

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 1-6 (1969); (6 pages)

Online Publication Date: 21 Jul 2005

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Tobacco Mosaic Virus (TMV) particles have been exposed to single pulse acoustic transients of 10−7 sec duration produced by the rapid thermal expansion following the absorption of an intense pulse of light from a Q‐switched ruby laser in an optically dense media. A hydrodynamical model is proposed, which relates the observed breakage at the center of the TMV particles, as seen in electron micrographs of exposed particles, to the structure of the TMV particles and to the amplitude and form of the acoustic transient. A velocity gradient of 4 × 107 per sec, which produces a force at the center of the TMV particle of the order of the force necessary to break a carbon‐carbon bond, has been found to be sufficient to break the TMV particle.

Temporal Parameters in Startle Facilitation by Steady Background Signals

Howard S. Hoffman and Barry L. Wible

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 7-12 (1969); (6 pages)

Online Publication Date: 21 Jul 2005

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When an intense acoustic stimulus is presented to the rat in a background of steady random noise, the startle reaction is larger than when the same stimulus is presented against a background of silence. Two experiments examined the temporal parameters of this facilitation effect. The initial experiment sought to determine how long the background signal must be present before facilitation can be detected. The second experiment examined the question of how long facilitation persists following termination of a background signal. Results indicated that 100 msec of exposure to a background signal is adequate for full development of the facilitation effect, and that the effect exhibits a significant decline by no more than 8 msec after the termination of a background signal.

Audience and Chair Absorption in Large Halls. II

Leo L. Beranek

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 13-19 (1969); (7 pages) | Cited 5 times

Online Publication Date: 21 Jul 2005

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Three alternate methods for considering the absorbing power of audience seating areas in the calculation of reverberation time in concert halls are treated. The absorption of audience seating, unoccupied and fully occupied, is expressed in terms of (1) equivalent sound‐absorption coefficient αeq, (2) absorption per unit floor area (with edge corrections), αT, and (3) absorption per person aT. Recent data by Meyer, Kuttruff, and Roy, by Kosten, and by Kath and Kuhl are integrated with the author's data to yield new tables of αeq, αT, αS, αR, aT, and aS, where αR is the absorption coefficient of the nonseated areas of a hall, and αS and aS are the absorptions of unoccupied seating on a per‐unit area and per‐seat basis, respectively. The data show that total audience absorption increases in direct proportion to audience area (uniform distribution of persons and well‐upholstered seats assumed), nearly independently of persons in the area. The halls studied have a range of seating densities from 5 to 8 sq ft of floor space per person and have normally diffuse sound fields.

New Acoustical Test Facilities of the National Gypsum Company

Theodore J. Schultz

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 20-36 (1969); (17 pages)

Online Publication Date: 21 Jul 2005

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This paper describes the new acoustical test facilities of the National Gypsum Company, Tonawanda, New York, comprising one large reverberation chamber, three facilities for measuring the transmission loss of wall structures, one facility for measuring the attenuation over a ceiling‐plenum ceiling path, and one facility for measuring either the transmission loss for airborne sound or the impact isolation of floor‐ceiling structures. The acoustical characteristics of these facilities are compared against the physical requirements stated in existing English‐language measurement test standards.

Distribution Pattern of Cochlear Harmonics

Peter Dallos and Richard H. Sweetman

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 37-46 (1969); (10 pages)

Online Publication Date: 21 Jul 2005

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

Distance Estimation of 0° or Apparent 0°‐Oriented Speech Signals in Anechoic Space

Mark B. Gardner

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 47-53 (1969); (7 pages) | Cited 3 times

Online Publication Date: 21 Jul 2005

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

Intensity Discrimination of Rayleigh Noise

D. A. Ronken

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 54-57 (1969); (4 pages)

Online Publication Date: 21 Jul 2005

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A human observer is less effective at auditory intensity discrimination when the signal is a wide‐band noise than when it is a pure (sinusoidal) tone. An experiment in intensity discrimination of Rayleigh noise shows that amplitude uncertainty seems to govern the discrimination. The empirical psychometric function is found to be only slightly displaced from the performance of an ideal energy detector.

Distribution Pattern of Cochlear Combination Tones

Richard H. Sweetman and Peter Dallos

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 58-71 (1969); (14 pages)

Online Publication Date: 21 Jul 2005

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This study is designed to determine whether or not traveling waves accompany combination tone components generated in the cochlea, and also to describe the amplitude distribution of these nonlinear products. Cochlear microphonics were monitored with the differential electrode technique from the first and third turns of guinea pig cochleas. Cancellation of the distortion components was attempted by introducing bone‐conducted pure tones at the frequency of the combination tone and of controllable amplitude and phase. It was demonstrated that combination tone components can never be canceled simultaneously throughout the cochlea. It was shown that the reason for this inability to cancel is that combination tones are not distributed as their own frequency would indicate, but instead, they seem to have a distribution peculiar to these nonlinear components.

Binaural Masking with Sine‐Wave Maskers

Frederic L. Wightman

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 72-78 (1969); (7 pages)

Online Publication Date: 21 Jul 2005

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The detectability of one binaural tone, masked by another of the same frequency, was measured as a function of the phase difference between them. In one condition, the tone to be detected, the signal, was the same in both ears. In another condition, the signal was inverted at one ear causing a 180° interaural phase difference in the signal. The masking tone was always the same in both ears. It was presented continuously in one experiment, and was gated on and off with the signal in another experiment. In contrast with similar work in which a noise masker was used, binaural signals inverted at one ear are less detectable in some conditions than binaural signals that are the same in both ears: a negative MLD. The negative MLD was largest (about 10 dB) in gated masking conditions and was found to be dependent on signal‐masker duration, growing smaller with longer duration. The detectability of interaurally in‐phase signals as a function of the phase difference between signal and masker can be accounted for by a simple energy‐detection model. However, no existing theory can adequately explain the results obtained with out of‐phase signals, although the results suggest the operation of a system with some of the properties of Durlach's equalization‐cancellation mechanism.

Prevalence of Impaired Hearing and Sound Levels at Work

James H. Botsford

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 79-82 (1969); (4 pages)

Online Publication Date: 21 Jul 2005

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The hearing deficiency of a group may be described in terms of the percentage having impaired hearing in order to focus attention on the abnormalities of medical significance. The prevalence of hearing impairment for speech, as defined by the medical profession, was determined for various populations using published hearing survey data. The incidence of hearing impairment was found to increase with age in all populations and also with A‐weighted sound levels in the groups exposed to harmful noise at work. Curves were drawn for estimating the net increase in incidence of hearing impairment resulting from exposure to various A‐weighted sound levels at work. They show that each decibel of occupational noise above 84 dBA increases the prevalence of impaired hearing by approximately the same amount as would 1 yr of aging. The curves also indicate that noise exposures that do not exceed the limits currently recommended should cause few additional cases of hearing impairment.

Evaluation of the Acoustic Response of an Air‐Water Siren

W. S. Mitchell and D. Muster

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 83-91 (1969); (9 pages)

Online Publication Date: 21 Jul 2005

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The characteristics of air‐operated sirens are described in the literature. Them are also papers devoted to sirens using liquids. This paper is concerned with the characteristics of a siren that can function with either water or air. The siren was built and operated with air at a maximum pressure differential of 4 psig (psi at ground level) and at 7 psig with water over a frequency range of from 50 Hz to 1 kHz. Comparison of the acoustic output of the device for both fluid media showed that, in general, there is little physical change in the siren response; the output pressure fluctuation had a sawtooth waveform. Fluid viscosity produces a damping effect on the response of the liquid‐operated siren so that a more nearly sinusoidal pressure waveform occurs. In addition, it is found that the flow coefficient is dependent on frequency. The experimental results indicate that liquid‐operated sirens should be further developed for use as underwater sound sources.

Investigation of Stress Patterns for Speech Synthesis by Rule

L. R. Rabiner, H. Levitt, and A. E. Rosenberg

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 92-101 (1969); (10 pages) | Cited 1 time

Online Publication Date: 21 Jul 2005

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

Elastic Constants of Composite Materials

Ernst Behrens

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 102-108 (1969); (7 pages) | Cited 3 times

Online Publication Date: 21 Jul 2005

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The elastic constants of a great variety of composites are calculated by evaluating the dispersion relation of sound waves for long wavelengths.

Thermal Relaxation in Nitrogen with Wet Carbon Dioxide as Impurity

M. C. Henderson, K. F. Herzfeld, J. Bry, R. Coakley, and Gaston Carriere

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 109-114 (1969); (6 pages) | Cited 4 times

Online Publication Date: 21 Jul 2005

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

One‐Dimensional Wave Propagation through a Short Discontinuity

Vernal H. Kenner and Werner Goldsmith

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 115-118 (1969); (4 pages) | Cited 1 time

Online Publication Date: 21 Jul 2005

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The one‐dimensional transmission and reflection laws for a change in section have been employed to analyze wave propagation in two elastic circular cylinders with discontinuities resulting from either the insertion of a short wafer of different acoustic impedance between or the eccentric junction of the bars. Appropriate experiments using aluminum cylinders and semiconductor strain gauges have been carried out, and good correlation of the results has been obtained.

Coherence of Acoustic Signals Reradiated from the Time‐Varying Surface of the Ocean

B. E. Parkins

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 119-123 (1969); (5 pages) | Cited 2 times

Online Publication Date: 21 Jul 2005

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The space and time variation of a monochromatic acoustic plane wave reradiated by the moving, rough surface of the ocean is described using coherence theory. The complex degree of coherence of the pressure field is calculated approximately for the extreme cases of slightly rough and very rough surfaces. For both of these cases, the results are specialized to the situation of a wind‐generated sea described by the Neumann‐Pierson directional wave spectrum, and the dependencies of the coherence upon surface roughness and the angles of incidence and observation are shown. For the case of a slightly rough surface, the reradiation is principally a reflection, and the coherence in the direction of specular reflection is the same as that for a smooth surface. Away from this direction, there is scattering, and the coherence depends upon the surface roughness. For very rough surfaces, there is diffuse scattering in all directions with no reflection, and the coherence depends upon the surface roughness for all angles of observation.

Lumped‐Element Transmission‐Line Analog of Sound in a Viscous Medium

Thomas L. Szabo

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 124-130 (1969); (7 pages) | Cited 1 time

Online Publication Date: 21 Jul 2005

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Interest in the transient of a wave in a viscous medium sparks the idea for a transmission‐line analog of the viscous wave equation. For convenience, lumped elements are selected by the application of transmission‐line‐and‐filter theory to simulate the transmission‐line analog. Practical components for the model introduce additional parameters that cause the model to be better described by a higher‐order, more general wave equation. Parameter choices are made to minimize the unwanted differences between the more realistic wave equation for the model and the viscous wave equation. The differential equation describing the actual model seems to have no easily attainable solution. However, a modified form of Blackstock's solution to the viscous wave equation is presented as a solution to a special case of the differential equation describing the actual model. Tone bursts injected into the completed model clearly show the presence of a precursor and a “postcursor.” Comparisons of the waveforms obtained experimentally and those predicted by the modified solution are shown and discussed.

Impacting Oscillatory Devices

G. N. Bycroft

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 131-137 (1969); (7 pages)

Online Publication Date: 21 Jul 2005

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

Vibrations of Circular Cylindrical Shells Due to Gyroscopically Induced Inertia Loads

P. G. Kessel and A. L. Schlack, Jr.

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 138-143 (1969); (6 pages)

Online Publication Date: 21 Jul 2005

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An analytical study is described for both open and closed circular cylindrical shells subjected to gyroscopically induced inertia loads. The shells are considered to be spinning at a constant rate about their longitudinal axis of revolution, which is simultaneously precessing at a constant rate at a fixed angle of nutation. Based on shallow‐shell theory and assuming a dominantly transverse deformation, the equations of motion are formulated for this type of loading. These equations are found to contain distributed harmonic inertia forces whose amplitude and frequency are dependent on the precessional and spin angular velocities, respectively. The solutions of these equations of motion show that the natural frequencies of the shell are reduced by both the spin and precessional angular velocities and that only certain modes of vibration will respond to the gyroscopically induced inertia loading. It is also shown that the reduction in natural frequencies can become important for very shallow shells.

Waves on a Spherical Shell

Michael P. Mortell

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 144-149 (1969); (6 pages)

Online Publication Date: 21 Jul 2005

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

Effect of Rain on Underwater Noise Level

Nicolaas Bom

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 150-156 (1969); (7 pages) | Cited 3 times

Online Publication Date: 21 Jul 2005

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The underwater noise due to precipitation has been measured in a small, shallow lake. The local wind speed, rain rate, atmospheric pressure, and noise level were recorded. If was found that the noise due to wind and the contribution from bottom and boundary reflections over the period during which the data were recorded had a negligible effect. The data in the interval 300–9600 Hz have been analyzed in octave bands, and an estimate of the average noise level versus rain rate has been obtained. In comparison with the laboratory work done by Franz on splashes as a source of sound, our results show significantly higher noise levels and a difference in the shape of the noise level versus frequency curve. However, the average rate of change in noise level with change in rain rate is in agreement.

Theory of the Axial Ray

Melvin A. Pedersen

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 157-176 (1969); (20 pages)

Online Publication Date: 21 Jul 2005

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

Turbulent‐Flow‐Excited Vibration of a Simply Supported, Rectangular Flat Plate

Wayne A. Strawderman and Ronald S. Brand

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 177-192 (1969); (16 pages) | Cited 1 time

Online Publication Date: 21 Jul 2005

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An analytic solution is obtained for the plate‐velocity statistics of a turbulent‐flow excited, simply supported, rectangular flat plate. The radiated acoustic pressure is neglected as contributing to the plate excitation, leaving only the turbulent‐boundary‐layer pressure fluctuations as the exciting force. The mathematical model for the turbulent‐boundary‐layer pressure statistics is based on that of Corcos, which agrees well with experiment. Plate‐velocity statistics are expressed in the forms of dimensionless cross‐power spectral and power spectral densities. Plate‐velocity‐spectral and cross‐spectral densities were obtained with a digital computer for selected flow and plate parameters. From these computed dimensionless spectra, effects of major parameters on the plate‐velocity statistics were determined. A “peak spectrum,” constructed by connecting major spectral peaks of the plate‐velocity‐spectral density, proved to be a useful engineering concept, inasmuch as knowledge of the “peak spectrum” is equivalent to knowledge of the maximum plate velocity spectral density for a given set of input parameters. The computed dimensionless plate‐velocity “peak spectrum” compares well with “peak spectra” constructed from available experimental data.

Intensity Equations in Ray Acoustics. I

Peter Uginčius

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 193-205 (1969); (13 pages)

Online Publication Date: 21 Jul 2005

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A set of differential equations is derived for calculating the intensity loss due to geometrical spreading of planar sound rays in an inhomogeneous medium with a continuous index of refraction varying both in depth and horizontally. Boundary conditions are derived for a reflecting surface and for an interface across which the speed‐of‐sound gradient may vary discontinuously. Exact analytic solutions are given for a two‐layered medium, with either a reflecting surface or an interface, in which the speed of sound is a linear function of depth. The differential equations are also solved numerically for a mathematical model of an ocean with a heat source. Intensity contours are presented for rays in the vicinity of a heat source and a heat sink. The heat sink causes the rays to converge, which results in the formation of a caustic.

Intensity Equations in Ray Acoustics. II

Peter Uginčius

J. Acoust. Soc. Am. Volume 45, Issue 1, pp. 206-209 (1969); (4 pages) | Cited 1 time

Online Publication Date: 21 Jul 2005

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See Also: Erratum

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A new expression for the intensity in ray acoustics is derived, which is valid for a general stationary medium in which the index of refraction may be a continuous function of all three space variables. This expression is derived with the WKB approximation on the wave equation, which results in a line integral along the sound ray. The integrand ∇ ⋅ r′, where r′ = dr/ds is the direction of the ray, is given explicitly in such a way that the integral can be evaluated in closed form for the general case. The result is in terms of functions that can be calculated by integrating simultaneously the vector eikonal equations for the ray paths, together with two other associated vector differential equations.
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