bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Focusing Effect of Reflection and Refraction in a Velocity Gradient
Authors: Noble William J.
Published: September 2005

The divergence factor, which is of importance in the reflection of waves from a convex spherical surface, is shown to have its counterpart in plane reflection and refraction in the presence of a velocity gradient. Within a small angle approximation, linear velocity gradient gives the ordinary spherical spreading of a pencil of rays; any discontinuity of gradient causes divergence or convergence of the pencil. Analytical expressions and tables of typical values are calculated for four different cases.
Reverberation Time Characteristics of Severence Hall
Authors: Ormestad Helmut J. , Shankland Robert S. , Benade Arthur H.
Published: September 2005

Following the changes in the acoustical conditions made in Severance Hall during the summer of 1958 [see R. S. Shankland and E. A. Flynn, J. Acoust. Soc. Am. 31, 866 (1959)] a series of reverberation time measurements were made during the 1958–1959 concert season of the Cleveland Orchestra. Measurements were made in the empty hall, in the hall with orchestra during rehearsals, which is also the condition for recordings, and with a full audience during the regular symphony season. Measurements were made of 38-caliber revolver shots, of fully orchestrated chords played at rehearsals by Dr. George Szell especially for our measurements, and of the endings of movements in a symphony (Mendelssohn No. 4 in A major) and a concerto (Dvořák B minor, Op. 104) during concerts. The results show a considerable increase in the reverberation time at all frequencies as compared to the conditions existing prior to 1958. The present reverberation time with a full audience is about 1.7 sec in the mid-frequencies and rises steadily to well above 2 sec at lower frequencies. Due to the heavily upholstered seats in Severance Hall the sound absorption increment on account of a full audience is unusually low. Measurements made during rehearsals have permitted a determination of sound absorption by the orchestra. Reverberation times measured with microphone pickup on the main floor, in box seats, and in the balcony, are essentially the same. The measurements will be continued during the 1959–1960 concert season, especially to determine the effects of a new humidity control system which was installed during the summer of 1959.
Masking by Octave Bands of Noise in Normal and Impaired Ears
Authors: Jerger James F. , Tillman Tom W. , Peterson John L.
Published: September 2005

The masking of sinusoids by three octave lands of thermal noise was measured in normal and hearing-impaired ears at each of two effective noise levels. For frequencies within the noise band results were essentially equivalent for all groups studied at either effective level. At frequencies both above and below the noise band no differences among groups were noted at the 10-db effective level. At the 30-db effective level, however, both presbycusics and sensori-neural losses of presumably cochlear origin showed more masking than either normals, plugged normals, or conductives.
Temporal Irregularity of Excitations: How Much Is Accepted by the Brain for Reporting Pitch?
Authors: Meyer Max F.
Published: September 2005

For many years the only obstacle standing in the way of crediting the theory of the hydraulic-cochlea model [M. F. Meyer, Am. J. Psychol. 72, 293–296 (1959)] as a hypothetical “theory of hearing” has been the notion that the brain reports a pitch to consciousness only when it receives excitations from the auditory sense organ in strictest temporal regularity. The test of this notion has now been accomplished by experimenting with a siren—and the obstacle has been removed.
Elastic Constants of Zircon
Authors: Bhimasenachar J. , Venkataratnam G.
Published: September 2005

The elastic constants of a single crystal of zircon have been determined using the ultrasonic wedge method. The values of the constants are (units of 1011 dynes/cm2) c11 = 7.35, c33 = 4.60, c44 = 1.38, c66 = 1.60, c12 = 0.90 and c13 = −0.54. The value of compressibility β=47.6×10−13 cm2/dyne.
Instrument to Study Relaxation Rates behind Shock Waves
Authors: Resler E. L. , Scheibe M.
Published: September 2005

An instrument is described which combines the schlieren technique, a photomultiplier tube and an oscilloscope in a manner that enables one to measure the density distribution behind shock waves (in gases) produced in a shock tube. From these measured distributions one can determine the way in which the gas or gases relax to equilibrium and the time it takes to reach equilibrium after the gas's enthalpy is increased suddenly a calculable amount in passing through the shock wave.

The theory of the instrument is discussed and its predicted performance verified experimentally by measuring vibrational heat capacity relaxation times behind shock waves in CO2 containing water vapor. The instrument in the reported tests demonstrated a sensitivity sufficient to record a change in atmospheric density of 12% over 1-mm distance and a space resolution of the density in the shock tube of 1/10 mm corresponding to times of the order of 1/10 μsec.
Compressional Relaxation with a Tuning Fork
Authors: Andreae J. H. , Jupp C. , Vincent D. G.
Published: September 2005

A new resonator comprising a fused quartz tuning fork with a hollow, liquid-filled arch has been used to measure compressional loss in the liquid. Initial measurements on an aqueous solution of BeSO4 near 100 cps confirm the existence of relaxational behavior in this solution.
On the Effects of Sound Waves on Heat Transfer
Authors: Holman Jack P.
Published: September 2005

A discussion is presented of the physical mechanism as proposed by Westervelt whereby heat transfer rates may be increased in the presence of intense sound fields.
Some Acoustic Correlates of Word Stress in American English
Authors: Lieberman Philip
Published: September 2005

Twenty-five English noun-verb pairs, differing principally in their stress patterns, were recorded by 16 native speakers of American English. The fundamental frequency, relative amplitude, duration, and integral of the amplitude with respect to time of the stressed and unstressed syllables were measured and related to the aurally perceptible stress patterns. The relative value of these factors as cues to such patterns varied with different speakers, but it was found that certain “trading effects” offset a lack of differentiation in one acoustic dimension by changes, coherent with the perceptual stress pattern, in another dimension. A simple binary automatic stress recognition program, based on the redundancies inherent in the acoustic correlates and trading effects, was then devised. The stress judgments made with this program agreed with the perceived patterns 99.2%
Input Impedances of Simple Cylindrical Structures
Authors: Franken Peter A.
Published: September 2005

A thin cylindrical shell driven in vacuum below its radial resonance by a point force may be described by membrane theory. Each nonaxisymmetric modal impedance contains a resistance and a mass of equal magnitude, as in the case of an infinite bar. The impedance decreases with increasing mode number up to a “cutoff” mode, and stiffness effects become important for modes above the cutoff mode. The analysis includes finite shells and rings.
Bistatic Scattering from Totally Reflecting Flat Plates
Authors: Ankerman P. W. , Rubega R. A.
Published: September 2005

This paper deals with an investigation of the characteristics of the scattering of sound from a flat plate, five wavelengths long. The scatter patterns were calculated based on the simplifying assumption of total reflection and experimentally checked by echo ranging in air. Agreement was found to be reasonably good although some interesting deviations in the side-lobe structure were observed. Patterns calculated and experimentally, obtained include bistatic backscatter patterns as well as the scatter patterns for a given incident wave.
Relation between Loudness and Duration of Tonal Pulses. II. Response of Normal Ears to Sounds with Noise Sensation
Authors: Miskolczy-Fodor F.
Published: September 2005

Investigations of threshold change as a function of various durations of a tonal pulse indicate a reduced rate of threshold change and a shortened time threshold for noise as compared with normal values for a 1000-cps pure tone. This result is explained by the increased loudness level of low noise intensities, and supports the concept of a direct relationship between loudness and time threshold. However, this relationship is modified as the frequency distribution of the test tone changes noticeably with shortening of pulse duration. For tonal pulses shorter than click pitch, the threshold change shows an increased rate in a frequency dependent range of duration. This may be due to an increased energy spread along the frequency axis. However, a further decrease of tonal pulse duration produces a smaller rate of threshold change than has been found for any other duration ranges of pure tones between 250 and 4000 cps; this rate of threshold change is similar to that found for noise. The perceived changes, caused by the energy spread, may limit the direct relationship between time threshold and loudness in the case of very short signal durations.
Notes on the Exact Equations Governing the Propagation of Sound in Fluids
Authors: Hunt Frederick V.
Published: September 2005

The assumptions underlying the exact equations of motion for a thermoviscous fluid are reviewed and the complete equations are given, for reference convenience, in both tensor and vector form. The first- and second-order acoustic equations are then exhibited and used to obtain the source terms that account for the generation of vorticity and streaming. In order to preserve a broad base from which to make the approximations appropriate under various circumstances, all terms are retained explicitly including those arising from any functional dependence of the viscosity and thermal coefficients on the state variables.

The distinction between spatial and material coordinate systems is carefully drawn and conversion transforms are derived rigorously and their use illustrated. The general properties of finite-amplitude waves are demonstrated by including the second-order terms in a plane-wave solution of the exact wave equation in material coordinates, with special concern for the effects of large amplitude on speed of propagation and on wave-form distortion.

Sound absorption and dispersion measures for a viscous conducting fluid are analyzed in terms of Truesdell's recent exact solution of the first-order secular equation. These differ characteristically from the corresponding measures predicted for pure relaxation in a two-fluid mixture. It is concluded that a complete and adequate theory of sound absorption and dispersion will need to take into account both relaxation and viscothermal phenomena as well as their interaction, and that until such a general theory is available, the exact theory of viscothermal effects—rather than the crude linear approximation commonly, but inappropriately, called “classical”—should be used in computing the “excess” absorption and dispersion to be accounted for by relaxation processes.

The exact solutions of the secular equation permit a new evaluation, in series form, of the characteristic acoustic impedance for a thermoviscous medium. The notes conclude with a revised account of the spectral character of thermal noise in the acoustic medium based on the quantum hypothesis and a merger of the concepts of architectural acoustics and specific-heat theory.
Heat Conduction Losses in the Acoustic Boundary Layer
Authors: Young James E.
Published: September 2005

The attenuation resulting from heat conduction of the quasi-plane mode in a cylindrical conduit is discussed in the high-frequency (narrow boundary layer) limit. The heat conduction part of the Kirchhoff losses is derived by means of a volume integral whose physical interpretation can be given.

Preliminary to considering the Kirchhoff case, the heat conduction attenuation of a plane wave is computed to illustrate the use of the integral form.

Finite thermal conductivity of the walls, as it gives rise to attenuation in guided propagation, is also discussed.
Recovery from High Values of Temporary Threshold Shift
Authors: Ward W. Dixon
Published: September 2005

Twelve normal observers were exposed to noise that produced at least 50 db of temporary threshold shift (TTS) measured 2 min after cessation of the noise. The TTS was measured at regular intervals until recovery was complete. Results indicate that while the recovery from these high values of TTS proceeds as a function of the logarithm of time during the first few hours, later recovery is instead linear in time.
Microphone Diaphragm Null Method for Sound Pressure Measurement
Authors: Koidan Walter
Published: September 2005

A null technique is described for accurately measuring sound pressure with a condenser microphone while its diaphragm is held stationary. The method is particularly useful when it is desirable that the microphone present an infinite impedance to the medium and absorb no energy from the sound field. Sound pressure is determined by means of the electromechanical coupling constant, defined as φ = (p/e)u=0, where p is the sound pressure, e is the alternating voltage applied to the microphone terminals, and u is the volume velocity of the diaphragm. By using this definition, a concise derivation of an expression for φ in terms of measurable quantities is described. The value of φ for two Western Electric Company type 640AA condenser microphones was measured as constant with frequency to within ±0.25 db from 500 cps to 20 kc.

The effect of the finite acoustic impedance of a microphone on the magnitude of the incident sound pressure is calculated in terms of quantities obtained by driving the microphone electrically. The measurement of high sound pressure levels in resonant tubes is also discussed.
Phase Velocities and Displacement Characteristics of Free Waves in a Thin Cylindrical Shell
Authors: Smith P. W.
Published: September 2005

Results are presented giving values of the phase velocities and the relative magnitudes of the components of displacement for all possible free waves in the wall of a thin, elastic, cylindrical shell. Three classes of waves are identified and their natures are discussed as frequency is varied continuously. The vibrations are interpreted not only as standing waves and waves progressing the axial direction, but also as fully free waves traveling in a helical direction in the wall of the cylinder.
Ultrasonic Absorption in Ethyl Acetate
Authors: Carome E. F. , Burlage S. R.
Published: September 2005

Measurements of ultrasonic absorption in ethyl acetate in the range 2 to 20 Mc indicate that the relaxation frequency below 10 Mc reported by various investigators is spurious and probably due to diffraction effects.
Propagation of Band Limited Noise
Authors: Smith M. W. , Lambert R. F.
Published: September 2005

Theoretical and experimental work on the propagation of band limited noise in a plane wave tube are here reported. Characteristics of the spatial crosscorrelation curve are controlled by the arithmetic mean frequency of the band and the bandwidth of the noise. The amplitude of the correlation function for zero spatial separation is directly proportional to the total power Akb where A is the density of the cross power spectra and kb is the bandwidth in wave number. Agreement between theory and experiment is quite good for relatively small spatial separations.
Fundamental Acoustics of Electronic Organ Tone Radiation
Authors: Martin Daniel W.
Published: September 2005

The acoustical effects achieved and the techniques used in the radiation of organ tone are quite different from the conventional effects and practices of public-address sound systems. For the latter, point-source radiation with high uniform directivity and a minimum of reverberation are sought, in general, for the creation of the illusion of “presence” of the original sound source. However in organ music the sound sources and their images are widely distributed in space. This is especially true in those typical cases where the tone sources are enclosed in an organ chamber, or are installed in a highly reverberant environment. Another distinctive feature of organ tone radiation systems is the relative importance of the octave below 60 cps. This paper contains design principles for electronic organ tone chambers and describes several types of organ tone cabinets now in use. Examples of the application of organ installation principles are given.
Hand-Held Calibrator for Pressure-Measuring Systems
Authors: Rule Eric , Perls Thomas A.
Published: September 2005

The problems involved in laboratory and field calibrations of high-amplitude dynamic-pressure measuring systems are discussed. A novel method is described which utilizes the vibration sensitivity of the transducer for the generation of high amplitude dynamic pressures at a frequency suitable for calibration. The design, construction, and evaluation are described for a simple hand-held calibrator based on this principle and providing over all system calibrations ±12.5 psi and ±5 psi, at 60 cps.
Method for Measuring Bulk Modulus of a Liquid Using a Helmholtz Resonator
Authors: Ehlers F. Edward
Published: September 2005

An analysis is given for a method of measuring the bulk modulus of a liquid by means of a Helmholtz resonator driven by an oscillating diaphragm in the cavity wall. The influence of the pressure transducer on the resonant frequencies is considered. In addition to the bulk modulus, the viscosity can be estimated by measuring the “Q” of the cavity.

One resonator was built, tested, and calibrated. Some difficulty was encountered in measuring resonant frequencies of the fluid-filled cavity at atmospheric pressure because of the formation of vapor bubbles. The results obtained for five common liquids compared favorably with earlier measurements of bulk modulus found in the literature.

This method is especially suitable for measuring the bulk modulus of corrosive liquids since the liquid may be completely sealed in the cavity under pressure and no measuring probes are moved through the liquid.
Probe Microphone Analysis and Testing at High Temperatures and High Intensities
Authors: Goff Kenneth W. , Mercer Derwent M. A.
Published: September 2005

A probe microphone has been developed suitable for measuring sound fields within such structures as altitude wind tunnels and jet engine test cells. This paper describes the methods of testing and analyzing the instrument. The microphone consists of a 38-in. inside diameter probe tube with a porous metal tip, a condenser microphone, and a spiral resistive termination. It operates at sound-pressure levels up to 170 db with 2% distortion, at ambient pressures down to 0.2 atmosphere, and with probe tip temperatures up to 900°F. The normal incidence response is flat within ±3 db from 10 to 10 000 cps.

An electrical analog of the acoustical system is given as a basis for explaining and predicting the performance of the microphone under varying ambient conditions. It appears that the microphone can be used satisfactorily as a cavity terminated probe microphone for frequencies below the frequency at which the spiral termination ceases to be “anechoic.” The required length of the spiral termination is then determined by the probe-tube length rather than the lowest frequency of interest.

Testing methods and apparatus are discussed, including a high-temperature flow resistance apparatus, a low-pressure test chamber, and a resonant tube device for developing sound pressures up to 175 db with low distortion.
Ultrasonic Absorption and Velocity in Water Containing Algae in Suspension
Authors: Meister Robert , St. Laurent Rodrique
Published: September 2005

A study is made of the ultrasonic absorption and velocity of longitudinal waves in water containing suspended algae in order to determine the effect of biological suspensions on sound propagation. The ratio α/f2 is found to be independent of frequency and is linearly dependent on algae concentration. These results indicate that scattering is not a mechanism for absorption and also shows that there is negligible interaction between particles. It was also found that the excess loss due to algae had the same temperature dependence as the shear viscosity. However the magnitude of the excess absorption calculated from the shear viscosity is insufficient to account for the total loss. Assuming that the structural viscosity of the liquid is increased by either the presence of the suspended material modifying the structural viscosity of the pure liquid, or by a structural viscosity associated directly with the cell, it is found that the increase in structural viscosity is 44 times the increase in shear viscosity for a given increase in concentration.
Mechanical Mechanism of Destructive Effects of Sound on Tissue
Authors: Welkowitz Walter
Published: September 2005

A mechanical mechanism is presented to explain some of the nonthermal, noncavitation effects of high-intensity sound on tissue. The theory proposes that the observed effects result from unidirectional forces produced by the acoustic wave, and that these forces cause elastic failure in the system. Some experimental verification is presented from measurements on irradiated frog muscle tissue and on irradiated frog spinal cord.
Sonic Absorption in Carbon Disulfide Vapor as a Function of Temperature
Authors: Gravitt James C.
Published: September 2005

The thermal relaxation absorption in carbon disulfide vapor at temperatures between 0° and 160°C has been obtained for frequencies between 50 kc and 4 Mc per sec per atm. The data were obtained by the tube method. The relaxation time, the transition probability, and the collision efficiency were determined as a function of temperature from the measured data. The collision efficiency as a function of temperature is adequately predicted by the Landau and Teller theory.
Acoustic Electronic Pulse Equipment
Authors: Skudrzyk Eugen
Published: September 2005

Detailed information is given for the construction of relatively simple, efficient pulse equipment. The repetition rate of the pulse generator varies between once in 10 sec and 25 000 times a sec with a pulse duration from 13 μsec to 100 msec. Pulses of sinsuoidal oscillations may be generated in the frequency range from 50 cps to 100 Mc. The circuits are free from ringing at frequencies below 5 Mc. The power output for pulses of less than 2-msec duration is between 50 to 250 w at frequencies below 10 Mc. A thyratron stage produces a triggering pulse to activate a monostable multivibrator. The adjustable-width multivibrator pulse passes through a cathode follower and furnishes the screen voltage for the output tube. If the frequency is below a few Mc, the output tube may be used to gate a sinusoidal voltage supplied by a standard signal generator. But for high power or at high frequencies, the output tube is preferably driven as a gated, self-excited oscillator.

The receiving amplifier may be connected in parallel with the output of the pulse generator so that the same transducer can be used as both sound projector and microphone. This amplifier limits the large voltage of the driving pulse and is capable of full sensitivity immediately after this pulse has decayed. Some valuable experiences with acoustic transducers are discussed.
Design and Testing of Earmuffs
Authors: Zwislocki J.
Published: September 2005

Factors controlling the sound attenuation provided by earmuffs are analyzed and an upper limit is estimated of the attenuation that can be expected from simple earmuffs without sacrificing comfort. Further discussion concerns the best dimensions of the earmuff and what can be achieved by adding one or more Helmholtz resonators.

The sound attenuation provided by two different earmuffs was determined on eight subjects in three sessions with a Békésy audiometer. The experimental procedure is described in detail and the results are analyzed statistically. Special attention has been paid to the changes in the listener's threshold of audibility with increasing experience.
Acoustic Streaming near a Heated Cylinder
Authors: Fand R. M. , Kaye J.
Published: September 2005

A photographic study employing smoke as the indicating medium has shown the existence of a new type of streaming near a heated horizontal cylinder in the presence of a horizontal transverse sound field. This phenomenon, called “thermoacoustic streaming,” is characterized by the development of two vortices above the cylinder; the fluid pattern resembles vortex shedding behind a cylinder in forced flow normal to its axis. In the presence of sound waves whose half-wavelength is six or more times greater than the diameter of the heated cylinder, the formation of the vortex flow is a function of the sound intensity only; for such wavelengths the vortices begin to appear at 140 db (re 0.0002 μbar) and become fully developed at 146 db. This type of streaming is a flow phenomenon which is much stronger than isothermal streaming for the same geometry and sound intensity. It appears that thermoacoustic streaming will have important practical applications, particularly in the field of heat transfer.
Influence of Loud Contralateral Stimulation on the Threshold and Perceived Loudness of Low-Frequency Tones
Authors: Loeb M. , Riopelle A. J.
Published: September 2005

Two experiments, employing different psychophysical procedures, were performed to measure the attenuation at intensities near the threshold due to the acoustic reflex. In both, a contralateral tone was introduced to activate a reflex and the resultant threshold shift for a test tone noted. Shifts observed were small and apparently inconsistent with findings of past experiments. Possible significance of the results was discussed.

The hypothesis was advanced that the reflex, once activated, attenuated loud sounds more than faint ones. Two additional experiments employing a loudness-matching technique were devised as a test of this hypothesis. In both of these the apparent loudness of different test tones was noted in the presence and absence of a contralateral activating tone. Results were in accord with the prediction. Applications and further tests of the hypothesis are discussed.
Improvements in Message Reception Resulting from “Sequencing” Competing Messages
Authors: Webster J. C. , Sharpe L.
Published: September 2005

Ten naval personnel heard tape-recorded messages in control tower phraseologies over four channels. Any of four stations could be called over any channel. On three of the channels the operator controlled the playback of the messages by means of controls that allowed him to start and/or mute messages. The operator had no control over when the messages came in over the fourth channel although he had provisions for muting it. The muting was used to silence messages that the subject was not required to respond to and was employed for one half of the test conditions. Each message contained twenty bits of information and was approximately five seconds long. In each half hour test session 378 messages were presented. Listening conditions ranged from having the operator respond to only one station with muting to answering three stations without muting. The results indicated slight but statistically significant increases in errors and in the times necessary to complete the jobs as the response task increased from one to three stations. Most errors occurred on the channel over which the operator had no sequencing control. For the message rates and density used in these experiments the operator could handle three stations with sequencing almost as accurately as he could handle one station without sequencing.
Effects of Response Complexity upon Listening to Competing Messages
Authors: Webster J. C. , Solomon L. N.
Published: September 2005

Three groups of twelve men listened to sequences of two, three, or four competing messages. They listened under four different conditions, two conditions of filtering (filters in—filters out) and two conditions of spatial separation (channels split—channels together). They responded on certain occasions to one message of the set and at other times to two messages. The first group wrote down, in simple symbols, the content of the message (s) whose address(es) they were to guard. The second group spoke the content of the assigned messages to a partner who wrote it down. The third group transposed (decoded) the message content before writing it down.

The results show that (1) more than twice as many errors occurred when responding to two instead of one message, (2) whether responding to one or two messages, transposing or talking produced an increase frequency of errors of 10% over writing, and (3) errors increased as the listening condition changed from Filtered-Split to Unfiltered-Split to Filtered-Together to Unfiltered-Together.
Relative Intelligibility of Speech Recorded Simultaneously at the Ear and Mouth
Authors: Oyer Herbert J.
Published: September 2005

Monosyllabic words recorded at the lips and left ears of six speakers were fed to the headsets of 24 trained listeners at −12, −15, and −18 S/N ratios. Although the trend for intelligibility scores throughout the test is in the same direction for signals of both origins, decreasing S/N ratio is more destructive to the speech picked up at the lips.
Sound Level Identification and Intertrial Stimulus Variations
Authors: Pollack Irwin
Published: September 2005

Sound level identification was examined for two restricted ranges of sound levels concurrently. The principal variable was the rate of shifting between the two restricted ranges. In general, identification performance decreases as the rate of shifting between the two ranges increases. However, because of the loss of stimulus information, the arbitrary restriction of the stimulus range results in a lower over-all information transmission than without the procedural restriction. An implication for the scaling of elementary aspects of auditory displays is discussed.
Further Studies on Perstimulatory Fatigue
Authors: Egan James P. , Thwing Edward J.
Published: September 2005

Perstimulatory fatigue, or auditory adaptation, was measured by various procedures which were designed to determine (1) the effects of brief re-stimulation of the adapted ear, and (2) the role of sound localization.
Auditory Facilitation following Stimulation at Low Intensities
Authors: Rubin Herbert
Published: September 2005

Auditory thresholds may become lower (improve) following stimulation by sound of low intensity. This shift in threshold was determined by comparing the reference threshold of a test pulse, presented alone, to the threshold for the test pulse preceded by a stimulating pulse. Duration, intensity, and frequency of the stimulating pulse were controlled, as were duration and frequency of the test pulse and duration of the interval between pulses. For pulses of 1000 cps, facilitation, or a lowering of the threshold, consistently follows stimulation by sound of 25 db SL or less; the lower the stimulating intensity, the more widespread the facilitation, over the various poststimulatory intervals tested. Facilitation reaches a maximum of 5 to 7 db 160 msec after the termination of the stimulating pulse, although some negative shift in threshold occurs after the longest interval (2 sec). Stimulation by white noise may depress the threshold for a pure tone, although a pure tone seems to have no effect upon the threshold for a white noise. When the stimulating pulse is a 1000-cps tone, facilitation occurs for test tones between 500 and 2000 cps. The maximal shift is at 160 msec for all test tones except 2000 cps. The nature of the facilitatory process, auditory or attentional, and its locus, whether peripheral or central, are discussed.
Binaural Interactions of Impulsive Stimuli and Pure Tones
Authors: Harris Gerard G.
Published: September 2005

The time-vs-intensity trade (ΔT/ΔI) in binaural lateralization was measured for pure tones and impulsive stimuli by the null method for high-pass and low-pass clicks at a repetition rate of 20 pps and pure tones of 200, 500, and 700 cps. Mean sensation levels (SL) of 20, 30, and 40 db and interaural intensity differences of 0, 4, and 6 db were used. The data on four subjects indicate a difference between high-pass and low-pass clicks: for instance, ΔT/ΔI≈0.025 msec/db for low-pass clicks below 1000 cps and I = 30 db SL, whereas at the same intensity ΔT/ΔI≈0.060 msec/db for high-pass clicks above 4000 cps.

It is concluded that the time vs-intensity trade is important for the localization of high-frequency impulsive stimuli. The interaural intensity difference also affects the ability to liberalize since the error of lateralization is least when both the interaural intensity difference and interaural time difference are zero. From the foregoing and from experiments with two liberalized images, it is concluded that the timing information used in binaural lateralization travels along frequency-dependent neural pathways. Any physiological timing signal must be able to explain this phenomenon.
Ultrasonic Studies in Melts and Solutions
Authors: Subrahmanyam S. V. , Bhimasenachar J.
Published: September 2005

The variation of ultrasonic velocity with concentration of phenyl salicylate, o-chloronitrobenzene, stearic acid, naphthalene, o-nitrophenol, m-nitrophenol, and palmitic acid in suitable solvents has been studied using an ultrasonic interferometer. The linear plots of velocity vs percentage weight of the solute are extrapolated to evaluate the velocities corresponding to 100% of the solute in each case. The agreement between the values obtained from solutions using different solvents is good. Sound velocities in the melts of the above substances have also been determined. It is found that the characteristic velocity obtained from data on solutions corresponds to the velocity at melting point in all cases except in that of naphthalene.
Effect of Pressure on the Structure of and Sound Velocity in Water
Authors: Yasunaga Tatsuya
Published: September 2005

A simple model was used to describe the propagation of sound in water. This model assumed that sound waves travel at infinite velocity within the molecules and at gas kinetic velocities through the spaces between the molecules. Resulting calculations showed that the latter velocity increases with pressure. From the change of sound velocity and acoustical properties for normal water and from those for nonassociated water, which were obtained from acoustical data for mixtures of alcohol and water, the change of the water structure with pressure was calculated and compared with the results of Gierer and Wirtz.
On the Vibration Statistics of a Randomly Excited Hard-Spring Oscillator
Authors: Lyon Richard H.
Published: September 2005

The system considered is a harmonic oscillator with a hard spring excited by random noise of the “infinitesimal impulse” type. An expression for the joint density of displacement and velocity is obtained and from this; the distributions of displacements and extrema and the average number of zero crossings are found. In addition, by solving a fundamental integral equation, we are able to find the shape of the distorted sine wave “carrier” for finite amplitude vibrations.
Random Vibration
Authors: Morrow Charles T.
Published: September 2005

There is, at present, a great interest in random vibration as a special aspect of shock and vibration, especially in relation to effects on equipment. An attempt will be made to explain what is meant by random vibration as opposed to other excitations that might be confused with it, what is involved in random vibration testing, what the corresponding objectives are, why there is controversy about these general subjects, and how some of the controversies may be resolved.
Low Sound Velocities in High-Porosity Sediments
Authors: Hamilton Edwiwn L.
Published: September 2005

Recent in situ and laboratory determinations of density and velocity of sound in fine-grained, high-porosity sediments of the sea floor off San Diego, California, reveal several stations at which the velocity of sound in the sediment was 2% to 3% less than the velocity of sound in the water just above the bottom. Comparison of the compressibility of the sediment computed in two ways and of the ratio: velocity in sediment/velocity in water computed and actually measured indicates that these high porosity sediments are approximately described acoustically by the velocity formula which applies to a suspension. The theoretical explanation for this phenomena was apparently made by R. J. Urick, [J. Appl. Phys. 18, 983 (1947); J. Acoust. Soc. Am. 20, 283 (1948)] and R. J. Urick and W. S. Ament [J. Acoust. Soc. Am. 21, 115 (1949)].
Dependence of Sound Absorption Coefficients Upon Area of Acoustical Material
Authors: Gifford George , Muehlhausen Almon
Published: September 2005

The theoretical basis for area correction curves in reverberation chambers was presented by T. D. Northwood [J. Acoust. Soc. Am. 31, 595 (1959)]. Data are presented which agree with T. D. Northwood's article, but disagree with many area correction curves measured in the past.
Acoustic and Other Physical Properties of Shallow-Water Sediments off San Diego
Authors: Hamilton E. L. , Shumway George , Menard H. W. , Shipek C. J.
Published: September 2005

This paper reports on a continuing study of the mass physical properties of surficial, shallow-water marine sediments off San Diego, California. Sound velocity measurements in situ at 100 kc were made by pulsing between small transducers inserted into the bottom by diver. Density, porosity, and size analyses were determined on relatively undisturbed samples taken by diver. The following averaged representative values have been obtained:

Velocity in

sediment at Impedance

Density Porosity Med. diam 60°F (105 g/

Sediment type (g/cc) (%) (mm) (ft/sec) cm2 sec)

Fine sand 1.93 46.2 0.19 5520 3.25

Very fine sand 1.92 47.7 0.12 5435 3.18

Silty very fine sand 1.68 61.3 0.05 5075 2.60

Medium silt 1.69 60.9 0.03 4825 2.49

Clayey fine silt 1.60 65.6 0.02 4800 2.34

Laboratory measurements of velocity and attenuation 25 to 35 kc were made by a resonant-chamber method using diver-taken samples; average attenuation values of about 0.5 db/ft (silt) to about 5 db/ft (fine sand) were obtained. At three stations the sediment sound velocity was less than the velocity in the bottom water.
On the Resonant Vibrations of Thick Barium Titanate Disks
Authors: Shaw E. A. G.
Published: September 2005

An optical interference technique employing illuminated multiple beam Fizeau fringes has been used to study the surface motion of barium titanate disks. In a properly polarized, accurately shaped cylindrical disk only normal modes having symmetry with respect to the axis and to the central plane are observed. A particular disk having radius/semithickness ratio (a/l) of 3.86 has been studied in some detail, and the displacement patterns for three important modes in the thickness resonance region have been accurately measured. Stress distributions for these three modes have been calculated from theory and these show that the wave motion is of a complex character in all three cases; this question is discussed in the light of elementary conceptions of thickness resonance. A more comprehensive experimental survey covering 25 different values of a/l within the range 1.14 to 6.63 has now been completed, and vibration patterns of 12 modes are given together with graphs of resonance frequency and values of electromechanical coupling coefficient. At relatively low frequencies the observed modes are obviously of the radial type but as the frequency approaches a value such that 2.5l = Λs where Λs is the wavelength of Rayleigh waves, take the form of a surface wave resonance with maximum motion occurring at the edge of the disk. There is no single mode which can be uniquely identified as the fundamental dilatational thickness resonance Rather, as a/l changes, each mode in turn passes through a maximum or minimum of electromechanical coupling the thickness resonance region. In general, for any given value of a/l two or three modes have high coupling this region, and the vibration patterns have certain well-defined forms but none approaches uniform piston-like motion. Nevertheless, there is some evidence suggesting an optimum value of a/l in transducer design.
Temporal Sampling Parameters of Interaural Noise Correlations
Authors: Pollack Irwin
Published: September 2005

The minimal interaural noise correlation discriminable by trained listeners was examined as a function temporal sampling parameters of the noise. The prime determinant of the listeners' performance is the total integrated duration of the noise samples, irrespective of the other temporal parameters. Within the restriction of a constant integrated duration, superior performance is attained with an interval of about 2 msec between successive brief noise samples.
Propagation of Elastic Waves in Cylindrical Shells, Including the Effects of Transverse Shear and Rotatory Inertia
Authors: Naghdi P. M. , Cooper R. M.
Published: September 2005

Two systems of equations of motion, designated as (I) and (II), for thin elastic cylindrical shells are derived which include the effects of both transverse shear deformation and rotatory inertia. The character of the two systems of equations is such that, upon the neglect of transverse shear deformation and rotatory inertia, Eqs. (I) will reduce to those known as Love's first approximation, while (II), which enjoys a considerable mathematical simplicity as compared to (I), will correspond to those given by Donnell. Both systems of Eqs. (I) and (II) are employed in a study for propagation of axisymmetric waves in an infinite cylindrical shell. The agreement between the predictions of the two systems of equations, in all modes of motion, for phase velocities of propagated waves in the complete range of wavelengths is found to be excellent. The results, with reference to the nature of the modes of motion according to both (I) and (II), are further examined and the relative merit of the present paper to the work of other authors is discussed.
Pressure Field within Homogeneous Anisotropic Turbulence
Authors: Kraichnan Robert H.
Published: September 2005

Integral expressions are derived for the mean-square fluctuation pressure, pressure correlation, and certain moments of the pressure correlation within general anisotropic, homogeneous turbulence. Application is made to idealized flow models exhibiting certain anisotropy characteristics similar to those observed in boundary layer turbulence. Pressure fluctuations arising from the turbulence itself and from interaction of the turbulence with a mean flow exhibiting constant shear are compared with the isotropic case. It is found that, in contrast to the completely isotropic case, the anisotropic pressure correlation is negative for some difference coordinate values and exhibits a “tail” which falls off with distance x as x−3 at separations for which the velocity correlations have fallen essentially to zero. It is concluded that in general the principal normalized moments of the pressure correlation will tend to be less than the corresponding velocity correlation moments. For isotropic turbulence this implies that the pressure correlation must fall off with distance faster than the velocity correlation. For the models of anisotropic turbulence treated it is found that departure from isotropy results in lower mean-square pressure fluctuations for a given mean kinetic energy of turbulence.
Detection of Signals of Uncertain Frequency
Authors: Creelman C. Douglas
Published: September 2005

Theoretical models for frequency sensitivity in human observers are discussed. One decision procedure for a multiple-filter model is considered in some detail as a general model for decision situations in which each available response is tied to more than one of the possible signal alternatives. Two experiments were conducted in an attempt to choose between a sweeping-filter model and a multiple-filter model. Detection in a two-alternative forced-choice experiment in which the signal could be one of two possible signals was measured over a range of frequency separations. The data yield further support for a multiple-filter model.
Angular Deviation in Directional Receiver Correlation
Authors: Jacobson Melvin J. , Talham Robert J.
Published: September 2005

When the axes of two directional pressure gradient receivers providing inputs to a steerable correlator receiving system deviate from the desired broadside direction, the system output is altered. An analysis of the improvement in output signal-noise ratio shows that, in general, the maximum improvement decreases, the direction of maximum improvement shifts from broadside, and the range on source direction over which there is improvement decreases. Simplified expressions are given for these changes in the important case of small deviation angles. The system output is then studied under the condition that the deviation angles are random variables and probability expressions are derived for the maximum improvement, the direction of maximum improvement, and the improvement at a given source direction. An example is included for the case of independent deviation angles having identical, even, uniform distributions.
Propagation of Correlation Functions in Continuous Media
Authors: Lyon Richard H.
Published: September 2005

The correlation properties of noise fields when considered as a random superposition of elementary sources are derived as an extension of Rice's work on the shot effect [S. O. Rice, Bell System Tech. J. 34, 282 (1944); 24, 46 (1945)]. Next a formalism is derived which calculates the correlation properties of the response of a continuous, linear system when subject to an applied noise field. The requirements for solution are a knowledge of the impulse response of the system and the correlation function of the source. The latter may be obtained experimentally or from calculation.
Propagation of Sound Pulses in a Dispersive Medium
Authors: Proud J. M. , Tamarkin P. , Kornhauser E. T.
Published: September 2005

The dispersion of a rectangular pulse with many cycles of carrier frequency propagated along an acoustic wave guide of rectangular cross section has been observed experimentally. The main signal is propagated with the group velocity and is observed to separate from the initial and final transient portions which travel with the greater, free medium velocity. In the dispersion process, the beating of the initial transient with the main signal causes fluctuations in the envelope of the carrier which compare favorably with the mathematical formulation given. This experiment serves, essentially, as a calibration of the wave guide so that it can be used qualitatively as a type of analog computer to predict the effects of similar dispersion on the transmission of pulses of other shapes that are not amenable to actual computation.