bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Approach to Ultrasonic Cavitation
Authors: Messinò D. , Sette D. , Wanderlingh F.
Published: September 2005

Sound cavitation is due to nuclei existing in the liquid. When they are created in water, they live for a long time, and therefore their equilibrium concentration is much larger than the number of nuclei created in the time unit. Experimental investigation allows measurement of the number of nuclei present in water as a function of the sound pressure needed for their growth to visibility. The statistical approach to cavitation, through the determination of the distribution functions, gives a deeper insight into the processes involved, such as nucleation by penetrating radiation. It is also possible to explain the discrepancies of values of cavitation threshold found under different experimental conditions.
Ultrasonic Absorption in Water Containing Plankton in Suspension
Authors: Watson John D. , Meister Robfrt
Published: September 2005

A study is made to determine the frequency and concentration dependence of the ultrasonic absorption in aqueous suspensions of (1) scenedesmus and diatoms, two forms of algae, and (2) artemia (brine shrimp) eggs. The measurements were made over a frequency range of 125 kc/sec to 55 Mc/sec.

The excess absorption caused by scenedesmus is found to be linearly dependent on concentration and has a value of α/f2=7×10 16 m−1 sec2 for the highest concentration measured, 0.72 g/liter of water. The excess absorption caused by diatoms is also linearly dependent on concentration and has a value of 25×10−15 m−1 sec2 for 290 g/liter of water, the highest concentration measured. For both scenedesmus and diatoms, it is concluded that the normal concentration of these forms of algae found in large bodies of water causes negligible absorption compared to the absorption of the water itself.

The major portion of the excess attenuation due to the shrimp eggs in the kilocycle region is attributed to a scattering mechanism. Application of a theory for elastic scattering in this wavelength region (ka<1) gave good agreement with experimental results. A phase-velocity investigation of a resonance phenomenon at 7 Mc/sec revealed a characteristic velocity dispersion.
Diffraction of Steady Acoustic Waves by Surfaces of Arbitrary Shape
Authors: Banaugh Robert P. , Goldsmith Werner
Published: September 2005

Using integral equations, the scattered field due to an acoustic wave impinging on an arbitrarily shaped cylinder is calculated. The equations are solved by finite difference methods, and the results are compared with those obtained from an eigenfunction expansion for the scattered wave from a right circular cylinder. Both nearfield and farfield results are presented for other cross sections.
Dispersion of Axially Symmetric Waves in Composite, Elastic Rods
Authors: McNiven H. D. , Sackman J. L. , Shah A. H.
Published: September 2005

The dispersive characteristics of axially symmetric waves in infinitely long, composite, elastic rods are explored. The characteristic equation relating frequency to the propagation constant is derived for two-material rods in which a solid, circular core of one material is bounded by and bonded to a circular casing of a second material of different physical properties. The equation is explored numerically using a digital computer for two rods displaying different geometric and physical properties. The lowest few branches of frequency spectra are developed from the roots of the equation, and the dispersive properties of the individual modes shown are discussed. The lowest few cutoff frequencies are established for each of the two rods, and the radial displacement distribution for each frequency is established. Finally, conditions are established for the existence of equivoluminal modes similar to those shown to exist in plates by Lamé and Lamb, in solid rods by Onoe, McNiven, and Mindlin, and in hollow cylinders by Gazis.
Flip-Floating Instrument Platform
Authors: Fisher F. H. , Spiess F. N.
Published: September 2005

A stable platform from which to perform experiments at sea has been a long-sought goal of sea-going scientists. In order to perform fine-scale experiments on fluctuations of acoustic signals in the ocean the manned buoy FLIP has been built to provide the needed stable platform for such work.

The 355-ft-long, 600-ton craft is towed to station in the horizontal position, and operates in the vertical position at a draft of 300 ft with its electronics laboratory about 30 ft above the water line.

A description is given of its development, stability, and operating characteristics, including the unique flipping operation.
Physical Mechanisms for Irradiation Effects of Sound and Ultrasound
Authors: Nyborg W. L. , Brunschwig F. S. , Gould R. , Jackson F. J.
Published: September 2005

Of the many known ways in which high-amplitude sound can produce changes in material processes and systems, there are only a few for which the basic physics is understood. In this paper a report will be made on research directed toward some aspects of the general problem. Since typical sonic irradiation conditions seem forbiddingly complex, an attempt has been made to define “elementary” situations for study, which are nevertheless close enough to practical ones to permit carryover of results. Particular attention is being given to fields in liquids in the neighborhood of (1) a single vibrating bubble resting on a wall and (2) a vibrating tip brought near a wall. In the former case there is interest in the heat produced by the bubble; also, in heat transfer through the wall, as affected by bubble-associated acoustic streaming. In the second case, acoustic streaming motions are seen near the vibrating tip which, e.g., exert steady viscous forces on the neighboring wall, capable of removing surface films. Observations are also made of steady circulation and related events induced in plant cells when a leaf is contacted with a vibrating tip. The present frequency range is mainly from 10 to 100 kc. Important features of the acoustic streaming patterns can be explained on the basis of an approximate theory for boundary layer. [This work is supported by the National Institute of Health (Bio-physics Section) and by the U. S. Air Force, contract AF18(603)-54. W. L. Nyborg is on leave as U.S.P.H. Research Fellow at the School of Advanced Study (Biology), Massachusetts Institute of Technology, Cambridge, Massachusetts. F. S. Brunschwig is now at the University of Illinois, Bio-acoustics Laboratory, Urbana, Illinois.]
Relation of Nuclear Spin Lattice Relaxation to Ultrasonic Relaxation in Liquids
Authors: Litovitz Theodore A.
Published: September 2005

A comparison of the data on nuclear spin relaxation and ultrasonic relaxation is made. It is suggested the correlation time, τc, used in explaining nuclear spin effects is related to the shear and volume relaxational processes occurring in a liquid. The results of comparing the nuclear and ultrasonic processes indicate the following. (1) The average shear relaxation time found for glycerol is close in value to τc (2) The value for τc for water is shown to be very close to the volume relaxation time calculated by Hall. (3) The variation in the nuclear relaxation times in going from water to glycerol are closely related to the variation in the volume relaxation times. (4) Setting τc, proportional to the average shear relaxation time offers an explanation as to why the pressure dependence of the nuclear relaxation time is not a simple function of the viscosity as predicted by present nuclear relaxation theory.
Ultrasonic Velocity, Absorption, and Rotational Dispersion in Methane
Authors: Thomas Kelly Bernard
Published: September 2005

It has been known for some time that the vibrational degrees of freedom in methane are relaxed and no longer contribute to the specific heats at frequency/pressure ratios well below 1 mc/atmos. The rotational degrees, however, should lie much higher. In order to determine the relaxation time for these rotational modes, the velocity and absorption of ultrasound were measured at 3 mc and at pressures from 50 cm down to one cm of mercury. The velocity dispersion curve, when plotted according to Kneser's formula (V2 − V02)/(V∞2 − V02) = (f/fω)2/(1 + (f/fω)2) has a half-rise point at 300 mc/atmos, which corresponds to a relaxation time of 1.06×10−0 sec. This figure was confirmed by simultaneous absorption measurements. The measurements were made with a Hubbard-type, motor-driven, variable-path acoustic interferometer and Brown recorder. The use of the recorder facilitates the measurements immensely, and permits extending them to lower pressures—higher f/p ratios—than has hitherto been feasible.
Equivalent Linearization Techniques
Authors: Caughey Thomas K.
Published: September 2005

The method of equivalent linearization of Kryloff and Bogoliubov is generalized to the case of nonlinear dynamic systems with random excitation. The method is applied to a variety of problems, and the results are compared with exact solutions of the Fokker-Planck equation for those cases where the Fokker-Planck technique may be applied. Alternate approaches to the problem are discussed, including the characteristic function method of Rice.
Sonic Effects on Concentration Gradients
Authors: Yeager Ernest
Published: September 2005

Sound waves at cavitation levels have been found to increase the rates of many physical and chemical processes which are limited by mass transport in a liquid phase, e.g., extraction processes, dialysis, dissolution of solids, cleaning operations, electrodeposition, dyeing of fabrics. Even with extensive mechanical agitation, a boundary layer of 10−3 cm or greater persists in the liquid phase at the interface. Quantitative studies [Penn, Yeager, and Hovorka, J. Acoust. Soc. Am. 22, 471(A) (1954)] with the schlieren microscope indicate that sound waves at ultrasonic frequencies are capable of reducing the effective thickness of the boundary layer at a solid-liquid interface to 10−4 cm. Cavitation bubbles produce agitation effects at the interface as they periodically vary in size, particularly at resonance conditions. Microstreaming phenomena associated with these bubbles are important. Thus, sonically produced cavitation is considerably more effective in expediting mass transfer than conventional forms of forced convection. In general, intense cavitation is not necessary. Hence, only moderate acoustical intensities are required and cavitation erosion of the solid surface is usually negligible, Furthermore, the sound waves are capable of reducing concentration gradients at interfaces which are recessed within solids as in the cleaning and electrodeposition of metal parts of complex geometry. (Based in part on research sponsored by the Office of Naval Research.)
Detection of a Noise Signal of Varying Duration
Authors: Campbell Richard A.
Published: September 2005

The ability of human observers to detect a thermal-noise signal (S) as a function of the duration of S presented in a thermal-noise background has been studied. Subjects were asked to correctly identify, in a two-alternative forced-choice situation, the time interval in which S occurred. Signal-to-noise ratios in dB based on a steady-state voltage (S/N), were varied according to the subject's performance on a block of 12 trials. The S/N was varied in 1-dB steps until a 75% correct-detection level was maintained. This Block Up and Down, Two-Interval, Forced-choice (BUDTIF) procedure is described in detail. Threshold S/N's obtained decreased linearly with increase in log duration from 1.0 to 100 msec, then approached minimum of −9.4 dB at 1000-msec duration. When these same threshold S/N's are converted to increments [(S+N)/N] and expressed in dB a linear decrease with log time from 1.0 to 47 msec is seen with an abrupt discontinuity, then a further nearly linear decrease from 47 to 1000 msec. The question is raised whether S/N or [(S+N)/N] is the effective stimulus to the subject.
Propagation of Audio-Frequency Sound in Free Air
Authors: Delsasso L. P.
Published: September 2005

The attenuation and velocity of sound pulses in the frequency range 500 to 3500 cps have been measured over a 1500-ft path at sea level. Large attenuation fluctuations are observed even for time intervals as short as two seconds. The corresponding changes in velocity were found to be small. Comparison is made with laboratory measurements and with existing theory. (This research was partially supported by Sandia Corporation, U. S. Atomic Energy Commission.)
Formant-Amplitude Measurements
Authors: Fant G. , Fintoft K. , Liljencrants J. , Lindblom B. , Mártony J.
Published: September 2005

Five alternative measures of formant amplitude are defined from circuit-theory analysis of speech production. Each of these is studied analytically as a function of increasing voice fundamental frequency, assuming constant shape and size of voice-source pulses. Some of the formant-amplitude measures display periodic fluctuations with maxima each time a harmonic of the voice fundamental passes through the formant center. This effect, as well as the over-all relations between the various measures, have been verified in human speech within an ensemble of sustained vowels uttered at a large variety of voice fundamental-frequency levels at constant articulation and constant voice effort. The first-formant amplitude is found to increase at a higher over-all rate than predicted from a vocal source of uniform pulses. A systematic departure from the theory of the model found in the second-formant amplitude of one of the subjects suggests a coupling between the vocal-cavity resonances and the vibrations of the vocal cords. Special requirements for formant-amplitude measurements of unvoiced sounds are discussed.
Elastic Wave Propagation in a Semi-Infinite Solid Medium
Authors: Sherwood J. W. C.
Published: September 2005

Plane waves possessing complex angles of propagation play an important role in the theory of elastic wave radiation. A simple physical picture is given of these waves and their utility illustrated by employing them in the study of continuous sinusoidal wave propagation in the neighborhood of an unstressed, plane boundary in a semi-infinite, homogeneous, and isotropic solid medium. The Rayleigh wave and the von Schmidt, or Head wave are particular features of the study. A simpler solution than Sauter's [Z. angew Math. Mech. (1950)] has been found for the displacement field radiated by an impulsive force acting at a line in the surface. By reciprocity this gives the surface displacement due to an internal line force. An equivalent problem is provided by an impulsive force acting at the edge and in the plane of a semi-infinite thin sheet, provided that the bulk dilatation wave velocity is replaced by the thin sheet dilatation wave velocity. This has been simulated experimentally by detonating small explosive charges at the edge of an aluminum sheet, 0.5 mm thick. Displacements detected by a novel condenser microphone technique are in excellent agreement with those determined theoretically.
Nonaxially-Symmetric Motions of Cylindrical Shells
Authors: Mirsky I. , Herrmann G.
Published: September 2005

A Timoshenko-type theory of cylindrical shells, developed by the authors in a previous paper [G. Herrmann and I. Mirsky, J. Appl. Mech. 23, 563-568 (1956)] for the case of axial symmetry, is generalized presently to include nonaxially-symmetric motions. As an application, the propagation of free harmonic waves in the axial direction of a shell of infinite extent is studied and discussed in the light of previous work on this problem. [This investigation was supported by the U. S. Air Force, through the Office of Scientific Research of the Air Research and Development Command, under Contract AF18(600)-1247.]
Reflection of Sound from “Randomly” Rough Surfaces
Authors: Proud J. M. , Beyer R. T.
Published: September 2005

Measurement of the sound reflected from “randomly” rough surfaces can be used to determine the rms amplitude and correlation function of the reflecting surface. The surface is generated by straightline elements perpendicular to the plane of incidence, effectively reducing the problem to two dimensions. A series of step amplitude is arranged spatially to form a stationary surface whose over-all length is several times the length of the surface irradiated. Measurements of the reflection from various portions of the surface can be thought of as equivalent to time-dependent measurements. Each irradiated segment of the surface is composed of approximately the same statistical amplitude distribution as the over-all surface. A Gaussian distribution has been chosen about an average of zero amplitude. The spatial arrangement is such that the correlation function nearly vanishes in a distance which is small compared to the irradiated surface length. Eckart's theory can be successfully applied when the surface slopes are small. The nature of the correlation function can therefore be inferred from the reflection measurements when the acoustic wavelength is much greater than any of the surface amplitudes.
Ultrasonic Visualization of Soft-Tissue Structure, Based on Gradients in Absorption Characteristics
Authors: Fry William J. , Fry Francis J.
Published: September 2005

Experimental support is presented for the feasibility of detecting structural features of soft tissue by a method previously proposed and treated analytically by one of the authors. The method is based on locating regions in which the tissue is characterized by gradients in the value of the ultrasonic absorption coefficient. Two beams of sound are employed—one to induce transient localized nondamaging temperature changes in tissue volumes, thus resulting in gradients of acoustic impedance at sites where ultrasonic absorption-coefficient differences exist, and a second beam to detect and localize the sites of such gradients.
Acoustic Refraction and Scattering with Compliant Tubes in Water
Authors: Toulis W. J.
Published: September 2005

Sound velocity in water may be reduced markedly with compliant structures which effectively increase the compressibility of water. Compliant tubes were derived from round aluminum tubes deformed into flat elliptical sections. Measurements in resonant chambers indicate uniform reduction in sound velocity at frequencies well below the lowest resonant frequency of a compliant tube in water. At higher frequencies, the velocity remains low but varies irregularly for frequencies up to the dipole mode of vibration. Reflection and scattering measurements with plane arrays of compliant tubes indicate high reflectivity over a frequency range that depends inversely on the center-to-center spacing between compliant tubes. The frequency for maximum reflection is also a function of spacing and approaches in the limit the resonant frequency of the compliant tube in vacuum. The characteristic behavior of a compliant tube to underwater sound is predicted with sufficient accuracy by treating it as a clamped-clamped beam and assuming that the distribution of the vibration on the equivalent beam is independent of the interaction with the fluid medium. The reflection coefficient for an array of compliant tubes is readily calculable by using an equivalent circuit, empirical expressions for the radiation load on an array and the mechanical impedance of the compliant tube.
Action Potential, Microphonic and Summating Responses to Tone Bursts
Authors: Davis H. , Deatherage B. H. , Eldredge D. H.
Published: September 2005

Our theory [Physiol. Revs. (January, 1957)] assumes excitation of nerve impulses (AP), by summating potentials (SP) as well as by cochlear microphonics (CM). We have measured CM, SP, and AP in the basal turn in guinea pigs in response to 7000 cps tone bursts with 1 msec rise time. The initial AP (N1) increases over a wide dynamic range approximately as the fourth root of sound pressure level. Low-level AP response, below 80 db SPL, seems to depend chiefly on CM. Increase above 95 db depends chiefly on SP, which continues to increase, although at a decreasing rate, up to destructive sound pressure levels. Except at very high intensities SP requires stronger stimuli than CM for equal voltage. CM goes through a maximum at about 106 db. This may be a protection for a delicate low-level mechanism. SP is a dc response to an ac stimulus and is thus a “detector” mechanism. Fluctuations in intensity of high-frequency signals above 100 db cause on and off effects that are strong enough to travel as mechanical waves on the basilar membrane and evoke AP from more apical regions. This gives a third, very-high-level component in the AP response. [Supported by Office of Naval Research Contract Nonr-272(03).]
Time and Intensity in the Localization of Clicks
Authors: Deatherage Bruce H. , Hirsh Ira J.
Published: September 2005

Interaural differences in time and in intensity constitute determinate conditions for the localization of sounds. The relative importance of time and intensity for the localization of tones has been determined in the so-called centering experiment in which interaural differences in phase (time) were offset by differences in intensity required to put the tone in the center of the head. We have extended the centering experiment to find the intensity-time function for the midline localization of clicks, which can be adjusted with respect to intracranial location, just as tones can be. Our listeners were asked to adjust a time delay, which compensated for preset intensity differences, in such a way that the clicks appeared to be in the center of the head. The results of these judgments show that, for central localization, a linear relation obtains between the logarithm of the time difference and the intensity difference in decibels. [This research was supported by a grant (B-243) from the National Institutes of Health.]
“Doppler” of Boundary Reverberation
Authors: Marsh H. W.
Published: September 2005

Simple formulas are presented for the frequency spectrum of boundary reverberation. The width of these spectra is controlled by the angular beam width of the irradiating source/receiver.
Random Noise Displacement Considerations of an Electrodynamic Shaker System
Authors: Metzgar Kenneth
Published: September 2005

The application of band limited Gaussian noise to wide band Shaker systems has led to the consideration of random displacement peaks of excessive magnitude. Environmental vibration tests often require the use of flat acceleration spectra over a wide frequency band extending to low frequencies. It is a well-known procedure when using a sinusoidal vibration test to limit the low-frequency displacement by providing a constant displacement region at the low-frequency end of the band. The same technique can be used to limit the displacement when random vibration is desired. The selection of a crossover frequency involves the probability of exceeding specified limits. Relations are determined for various test parameters and the expected number per unit time of excessive displacement peaks. Results are presented in convenient graphical form.
Author's Response to Comments by R. S. Woollett
Authors: Toulis W. J.
Published: September 2005

R. S. Woollett expresses the opinion that the traditional theory on electromechanical-coupling factor is adequate for all situations. An examination of his basic arguments indicates that they are self-contradictory.
Apparent Change of Repetitive Noise Bursts
Authors: Elliott Lois L.
Published: September 2005

Noise bursts that are presented at constant, slow-flutter rates (20–160 bursts/sec) through Western Electric 640-AA “earphones” appear to change in rate and loudness. This “illusion” is discussed in terms of neurophysiological evidence and auditory theory.
Theoretical Investigations to Reduce Harmonic Distortions in a Clipping Process
Authors: Vilbig Friedrich , Haase Kurt H.
Published: September 2005

To investigate harmonic distortions of clipped speech, the speech waves are replaced by a sum of two sine waves. Infinite clipping of these two frequencies results in a harmonic distortion of 75%. If the audioband is modulated to a higher frequency range, one of the sidebands clipped, and all distortions beyond the single band width suppressed, the distortion drops to 50%. Distortion is further reduced if the original representative sum of the sine waves is differentiated and transformed to a pulse wave with pulse width modulation, the width corresponding to amplitude maximums and minimums. With pulse width modulation of unit amplitude, the advantages of normal clipped speech transmission are retained. On the receiver side the pulse width modulation is transformed to a pulse amplitude modulation with relatively short pulses. The pulse wave, still highly distorted is applied to a storage device (e.g., a magnetic tape or a ladder network of condensers). The picture of the pulses is smoothed and approximates the picture of the original sum of the two sine waves. Essentially, the approximation is the replacement of the original wave by a triangular one. This process, mathematically seen as a sine modulation of an unit triangular curve, reduced harmonic distortions to 12% instead of 75% as in normal infinite clipping.
Central Factor in Pure-Tone Auditory Fatigue
Authors: Wernick Joel S. , Tobias Jerry V.
Published: September 2005

A long accumulation of psychophysical and physiological evidence indicates that auditory fatigue has its locus of effect in the cochlea; transfer studies with negative or questionable results and studies of cochlear chemistry and potentials with positive results all lead to the same conclusion. However, Galambos's reports of inhibition through efferent stimulation, taken together with his finding of changes in cochlear potentials corresponding to differences in “attentiveness,” provide a basis for testing the existence of a central factor operative in auditory fatigue. The present study was designed to evaluate the possibility that a listener's level of mental activity constitutes an adequate central factor. Subjects were presented with a 4000-cps, 40- or 90-dB SL tone for 3 min under conditions of (a) a mental task or (b) reverie. Pre- and post-fatigue thresholds were measured with a switched (0.2 sec on, 0.2 sec off) tone. For low-level (40 dB) fatigue the frequency of the test tone was 4000 cps and for high-level (90 dB) fatigue, 5656 cps. Subjects consistently showed greater temporary threshold shift and longer recovery time when the fatiguing tone was presented in the mental-task condition. Results thus indicate a central factor in pure-tone auditory fatigue. It is suggested that the degree of effect of a fatiguing tone is a function of the listener's degree of mental activity during stimulation.
Dimensions of Perception for Consonants
Authors: Peters Robert W.
Published: September 2005

Multidimensional analysis of similarity data was applied to the domain of spoken consonants. Listeners responded to productions of their own consonants in terms of the similarity of the consonants to each other. Estimates of psychological distances between consonants were derived from the similarity responses. The distances were used to construct an auditory space, Euclidean in nature, for the consonants. Coordinates of the consonants in the space were of the appropriate dimensionality necessary to account for distances between consonants. Articulatory data were utilized to identify the dimensions. Manner of articulation was the first and most important auditory dimension. Voicing and place of articulation served to identify subsequent dimensions.
Jet Engine Inlet Noise Studies
Authors: Old John D.
Published: September 2005

Studies have been made to determine sound intensities and frequency distribution of axial-flow compressor noise and their relation to compressor stage loading and blade passage rates. Inlet noise measurements of several turbo-jet engines at compressor speeds from idle to maximum power indicate good correlation of peak noise frequencies of the first five stages of the compressor. Measurements on several engines of the lt 000-lb thrust class indicate no significant difference of inlet noise levels. A very intense low-frequency tone, not explicitly related to blade passage frequency, has been measured during part- and full-speed operation of two jet engines. Mechanisms which produce this peculiar noise may include the little understood phenomenon known as “rotating stall.”
Theoretical Treatment of Low-Frequency Sound Attenuation in the Deep Ocean
Authors: Brown C. Bradner , Raff Samuel J.
Published: September 2005

The attenuation of low-frequency sound (20 to 1000 cps) in the deep sound channel is examined theoretically. From a comparison of the theory with experimental data, conclusions are drawn about the magnitude and distribution of velocity inhomogeneities in deep water.
Probability Distribution of Sinusoidal Sound Pressure in a Room
Authors: Diestel H. G.
Published: September 2005

It is shown that the probability distribution of sinusoidal sound pressure in a room depends on the distance from the source to the observation point, the absorption coefficient and the area of the absorbing material in the room, and the directivity factor of the source. An approximate formula is given for the probable sound-pressure deviations in a poor reverberant room from the theoretical values in free space.
Near Field Studies of Jet Noise
Authors: Franklen Peter A. , Dyer Ira
Published: September 2005

It is generally assumed that a jet noise source is composed of noise sources in various frequency ranges distributed along the jet stream axis. Far field measurements on jets are used to locate the distributed sources at various distances from the exhaust nozzle. An attempt is made to use this source information to predict observed levels near the jet stream. Each source is assigned a power level and a directivity determined by the average velocity at the source location. The results are compared with measured levels on a model air jet and on turbojets, and a near field estimation procedure is suggested. (Supported in part by Glenn L. Martin Company, Baltimore, Maryland.)
Instrumentation for the Measurement of Rocket Engine Noise
Authors: Kamperman George W.
Published: September 2005

This paper describes the acoustical instrumentation used for near field sound pressure measurements about a large rocket engine during stationary firing. Pressure and phase in the frequency range from 1 to 5000 cps for 14 different microphone positions were simultaneously recorded on magnetic tape. Miniature barium titanate hydrophones were used as microphones. The signal from these microphones was amplified by special pre-amplifiers and then transmitted to the remote tape-recording station over balanced telephone lines. The over-all system is capable of covering the range from 80 db to 200 db re 0.0002 μbar.
Redefinition of Effective Electromechanical-Coupling Factor
Authors: Toulis W. J.
Published: September 2005

Although some opposition is being voiced to amending the definition of the effective electromechanical-coupling factor, no systematic evidence has been found to contradict the proposed revisions at power-conversion frequencies that are associated with mechanical resonance. On the contrary, earlier evidence has been uncovered that is consistent with the proposed definitive equations. Measurements with an improved piezoceramic specimen show also a much closer agreement between theory and experimental observations.
Preliminary Investigation of Vehicular Noise Associated with Superhighways
Authors: Clark W. E. , Clark Virginia A. , Galloway W. J.
Published: September 2005

Measurements of noise produced by freely moving vehicular traffic have been used to formulate a preliminary description of the superhighway as a noise source. The distribution of individual vehicle positions is assumed to be random at any given instant, while their relative velocities are assumed nearly constant. Under these assumptions the total acoustic power produced at locations adjoining the highway can be directly related to a statistical description of the traffic flow. The effects of flow densities of (a) passenger cars and light trucks, and (b) heavy trucks, are discussed insofar as they affect the time pattern and frequency distribution of the acoustic power produced. A description is given of the use of this characterization of traffic noise in estimating the reaction of a community to noise intrusion by the procedures outlined by Stevens, Rosenblith, and Bolt, Noise Control 1, 63 (1955).
Torsionally Resonant Amplitude Transformers for High Magnification
Authors: Eisner E.
Published: September 2005

The equations governing the propagation of longitudinal and of torsional waves in thin, tapered rods are of similar form. It is, therefore, possible to use the method by which longitudinally resonant amplitude transformers were previously designed [J. Acoust. Soc. Am. 35, 1367–1378, (1963)] to design torsionally resonant transformers. These torsional transformers are capable of extremely high magnifications.
Approximate Transient Solutions for the Coupled Equations of Thermoelasticity
Authors: Achenbach Jan D.
Published: September 2005

The propagation of mechanical and thermal disturbances studied according to the coupled thermoelastic theory. In the formulation of the coupled theory of thermoelasticity, the heat-conduction equation contains the time derivative of the dilatation as a source term. In the procedure introduced here, that term is replaced by one representing the time derivative of the dilatation at the wavefront only. In this way, the equations governing the mechanical and thermal effects are formally uncoupled, and thus are easier to solve; at the same time, it is shown that most of the coupling effect is retained. To check the approximation procedure, two one-dimensional problems are considered. The solutions for these problems show excellent agreement with known exact solutions. The approximation is then applied to the three-dimensional problem of the suddenly applied force in the infinite medium. Curves for the displacement and temperature distributions are provided for this case. The temperature distribution shows a discontinuity that moves with the wavefront of the dilatational wave.
Loudness Calculation and Critical Bands
Authors: Stevens S. S.
Published: September 2005

The formula St = Sm + F(ΣS − Sm) is a linear approximation expressing total loudness St in terms of the loudness of the loudest band Sm and the sum ΣS of the loudnesses of all other bands. It has been shown that this formula holds when steady noises having reasonably continuous spectra are analyzed in terms of octave bands. The value of F is then 0.3. The purpose here is to apply the formula to half-octave and third-octave bands by a procedure slightly different from the one presented earlier. It is found that a single set of equal loudness contours can be used for all widths of bands, provided the values of F are properly chosen. These values are 0.2 for half-octaves and 0.15 for third octaves. A set of equal loudness contours has been so drawn that they can be used as an overlay with standard plotting papers for octave, half-octave, and third-octave bands. This greatly facilitates the procedure of calculating loudness. If further major improvement is to be made in loudness calculation, it will probably prove necessary to analyze sound spectra in terms of critical band widths instead of in terms of the octave systems. The existence of a critical band width in loudness summation [see Zwicker, Flottorp, and Stevens, J. Acoust. Soc. Am. (to be published)] suggests a “natural” division of the sound spectrum that may eventually prove more useful than the octave systems.
Evaluation of Message-Procedures for Communications under Unfavorable Noise Conditions
Authors: Pollack Irwin
Published: September 2005

Several procedures for speech communications under extremely unfavorable speech-to-noise ratios were examined. Communications performance was evaluated in terms of the proportion of items correctly received for a given time utilization of the channel. For message sources of fixed information, a message procedure based on the principle of successive selections among a small number of alternatives, was strikingly superior to a message procedure based upon the principle of repeating an item selected from among a larger number of alternatives. However, the advantage of the former procedure is not entirely the result of restricting the number of alternatives per selection; a message procedure which simply employs different words but which does not restrict the alternatives per selection (e.g., “5, 6, 7” vs “7, 7, 7,” where 7 is the target word) often approaches the effectiveness of the message procedure which restricts the alternatives per selection.
Head Waves from Liquid Layers
Authors: Donato R. J.
Published: September 2005

Experiments are described that confirm that the amplitude of the head wave produced at a liquid layer is modified by reflection from the base of the layer. Knowing the shape of the incident wave (and, hence, of the head wave), it is possible to calculate the decay of the head-wave amplitude with horizontal range. These rates of decay agree well with those determined experimentally.
Geometrical Theory of Elastic Surface-Wave Excitation and Propagation
Authors: Keller Joseph B. , Karal Frank C.
Published: September 2005

A geometrical theory is devised for the description and calculation of surface waves, such as Rayleigh waves, on boundaries or interfaces of elastic solids. It applies to curved surfaces and to inhomogeneous media. The theory, which is an extension of geometrical optics, involves complex rays that travel from the source to the surface, then along the surface, and finally from the surface to points in the solid. It also includes phases and amplitudes associated with each point on each ray. Geometrical formulas are derived for the determination of these phases and amplitudes. They involve certain excitation and radiation coefficients, which are also determined. The total displacement at a point is the sum of the displacements on all the rays through the point, each of which is constructed from the corresponding phase and amplitude. The theory applies to periodic waves of high frequency and short wavelength, as well as to the rapidly varying portions of any waveform. It is a generalization of the authors' earlier geometrical theory of scalar surface waves [J. Appl. Phys. 31, 1039 (1960)].
Confusion Matrices and the Constant-Ratio Rule
Authors: Clarke Frank R.
Published: September 2005

A confusion matrix may be defined as a table of conditional probabilities, p(ak|Ai), showing the proportion of instances in which the listener responded ak when the stimulus item Ai was transmitted. The confusion matrix is termed closed when the total set of messages is known to the listener and all his responses are drawn from this set of messages. If a closed matrix is obtained for some particular set of messages, and, under essentially the same physical conditions, a second closed matrix is obtained for some subset of these items, then the relation between the entries in these two matrices is given by the constant-ratio rule. This rule states that the ratio between any two entries in a row of the submatrix is equal to the ratio between the corresponding entries in the master matrix. This statement of the rule assumes that the only variables which differ in obtaining the two matrices are the different sets of messages and the allowable responses. A series of experiments are reported which support this rule and illustrate its use in predicting the entries in a submatrix when the master matrix is known. Other applications of the rule will be discussed. [This research was supported in part by a National Science Foundation Predoctoral Fellowship and in part by the U. S. Air Force under Contract No. AF 19(604)-1962.]
Spatial Correlation in Acoustic-Structural Coupling
Authors: Bozich Daniel J.
Published: September 2005

The response characteristics of beams and flat rectangular panels excited by specific acoustic fields are analyzed mathematically. Acoustic-structural coupling-coefficient (joint acceptance squared) frequency spectra indicate a marked sensitivity to changes in the spatial-correlation distribution. Panel mode shapes progressively lose their wavelength selectivity as spatial correlation decreases.
Effect of Bending on Vibrations of Spherical Shells
Authors: Kalnins A.
Published: September 2005

This paper is concerned with the vibration analysis of spherical shells, closed at one pole and open at the other, by means of the linear classical bending theory of shells. Frequency equations are derived ha terms of Legendre functions with complex indices, and for axisymmetric vibration the natural frequencies and mode shapes are deduced for opening angles ranging from a shallow to a closed spherical shell. It is found that for all opening angles the frequency spectrum consists of two coupled infinite sets of modes that can be labeled as bending (or flexural) and membrane modes. This distinction is made on the basis of the comparison of the strain energies due to bending and stretching of each mode. It is also found that the membrane modes are practically independent of thickness, whereas the bending modes vary with thickness. Previous analyses with the use of membrane theory have shown that one of two infinite sets of modes is spaced within a finite interval of the frequency spectrum. It is shown in this paper that this set of modes is a degenerate case of bending modes, and, if deduced by means of membrane theory, it is applicable only when the thickness of the shell is zero. When the bending theory is employed, then the frequency interval for this set of modes extends to infinity for every value of thickness that is greater than zero.
Thermoelastic Dissipation in High-Frequency Vibrations of Crystal Plates
Authors: Tasi J. , Herrmann G.
Published: September 2005

A system of approximate, two-dimensional equations is derived for the thermoelastic response of crystal plates. The equations take into account the coupling of thickness-shear, flexural, and extensional motion with symmetric and antisymmetric thermal modes. The thermoelastic dissipation predicted at high frequencies by the approximate theory is compared with a three-dimensional solution, using the free vibrations of an AT-cut quartz plate as a basis of comparison.
Generalized Hamilton's Principle and Variational Equation of Motion in Nonlinear Elasticity Theory, with Application to Plate Theory
Authors: Yu Yi-Yuan
Published: September 2005

A generalized Hamilton's principle and the associated variational equation of motion are presented for finite elastic deformations. By means of the generalized variational equation of motion, it is possible to deduce immediately the usual nonlinear equations of elasticity, such as were discussed by Novozhilov. The inconsistence Novozhilov's work for a simplified nonlinear case of technical importance is pointed out. In its linearized version, the generalized variational equation of motion is next employed in the derivation of plate equations for both flexural and extensional motions, which are finally compared with those given by previous authors.
Digital Compressed-Time Correlators and Matched Filters for Active Sonar
Authors: Allen W. B. , Westerfield E. C.
Published: September 2005

This paper discusses the problems arising in the realization of practical, wide-band signal correlation systems and presents some possible solutions to these difficulties. Function generators and shift-register encoders in particular solve the problem of long, stable delays, by providing wide-band signals that can be reproduced accurately with any desired time delay or Doppler compensation. The use of clipped signals permits operation over a wide range of input-signal amplitudes, while sacrificing absolute amplitude information and some processing gain. High search rates and processing real time are achieved with multichannel correlators, compressed-time correlators, and matched filters. Several ways of instrumenting digital delay-line time compressors, digital-scanned-storage time compressors, and digital matched filters are discussed, including their integration into real-time processing systems. The relative advantages of the different approaches are discussed.
Spreading Loss of Sound in an Inhomogeneous Medium
Authors: Anderson G. , Gocht R. , Sirota D.
Published: September 2005

Geometric spreading of sound in a medium with any given continuous velocity profile is investigated theoretically. The sound velocity is assumed to be dependent on one space coordinate only. The analysis is based on Snell's law. Time and initial angle of the ray are the two independent variables. A set of differential equations describing spreading loss is developed. These equations are solved analytically for the case of constant-velocity gradient yielding well-known results. A short discussion of both analog- and digital-computer solutions for the general case is given. Discontinuous velocity profiles and the interchange of sound source and receiver are also considered.
Mutual-Radiation Impedance and Nearfield Pressure for Pistons on a Cylinder
Authors: Greenspon Joshua E. , Sherman Charles H.
Published: September 2005

Expressions are derived for the sound pressure and mutual-radiation impedance for rectangular pistons on an infinitely long rigid cylinder, and numerical results are presented for typical cases. A comparison of mutual-radiation impedance for pistons on cylinders, spheres, and planes is made.
Acoustic Characteristics of Underwater Bottoms
Authors: Jones J. L. , Leslie C. B. , Barton L. E.
Published: September 2005

Acoustic bottom-reflection coefficients have been measured at five ocean, lake, and river locations. A correlation technique was employed, using octave-band random noise from 200 to 3200 cps as a source. Values obtained ranged from −0.92 to +0.55. Only at Lake Travis, Texas, did the coefficient change substantially with frequency. Angle of incidence made little or no difference up to 45°. Further evidence is presented that pressure-release bottoms are fairly common.
Theoretical Model of Reverberation Noise
Authors: Faure Pierre
Published: September 2005

This paper presents a statistical model of reverberation noise based on the principal assumption that the distribution of the scatterers in the medium is a Poisson process. With approximations, the model is consistent with the known laws of reverberation and permits a study of spectral properties.
Rate of Decay of Auditory Sensation
Authors: Plomp R.
Published: September 2005

The rate of decay of auditory sensation was investigated by measuring the minimum silent interval that must be introduced between two noise pulses to be perceived. The value of this critical time Λt was determined for different intensity levels of both the first and the second pulse. It is shown that in this case the sensation level of the second pulse may be considered as a very good approximation of the level of auditory sensation after Λt, due to the first pulse. From the experiments, we may conclude (1) expressed in dB as a function of log t, the decay of sensation is represented by a straight line; (2) independent of the sensation level of the stimulating sound, the hearing threshold is reached at the same time of about 200–300 msec. These results are compared with other experiments and the differences are discussed.