bluuebunny/crossref_metadata_2025 huggingface dataset:
Audibility of Periodic Pulses and a Model for the Threshold
Authors: Flanagan James L.
Published: September 2005

Thresholds of audibility are determined by the Békésy technique for four periodic trains of rectangular pulses. The pulses of a given train are uniform in amplitude and duration, and the trains differ in their periodic patterns of pulse polarity. The parameters considered are pulse rate, pulse duration, and polarity pattern. The stimuli are presented binaurally in quiet over headphones. Data for four subjects are reported. The results show the threshold amplitudes to be little dependent upon polarity pattern. For pulse rates less than about 100 pps the thresholds are also little dependent upon pulse rate. They approach constant values determined by pulse duration. Above 100 pps the thresholds diminish with increasing pulse rate. The experimental technique also provides an estimate of the intensity limen at threshold. An analytical specification of the stimulus is derived which provides an objective correlate of the threshold percept. An electrical circuit model of the threshold is developed which takes account of middle-ear and basilar membrane transmission. The threshold model reflects a constancy of percept over a pulse-rate range of 10 octaves and a pulse-duration range of ten to one. Its application to the metering of subjective loudness is suggested.
Annoyance Threshold Judgments of Bands of Noise
Authors: Spieth Walter
Published: September 2005

Annoyance threshold judgments were obtained by exposing an individual to noise for three minutes and asking him to adjust the intensity to the level which, if any louder, would annoy him if it were present most of the time where he was working.

In one experiment, 21 people made judgments about 13 bands of noise which covered the frequency range of 50 to 13 000 cps, and subsequently made sets of equal loudness matches. No differences were found between annoyance threshold curves and equal loudness curves. In a second experiment, each of 162 people made one annoyance judgment. When these annoyance thresholds were transformed into equivalent loudness terms, the resultant annoyance threshold curve varied reliably with frequency only in that the threshold on the highest band (6600–9000 cps) was reliably lower than those on lower frequency bands.

Office workers who had once worked in noisy situations as well as those working in noisy situations at the time of the experiment gave thresholds about 15 db higher than did people who had only worked in office-type situations.

Within a group who had worked only in quiet situations, those who tried to imagine themselves in an actual working situation gave thresholds that averaged about 15 db higher than the thresholds of those who did not.
Temporary Threshold Shifts from Tones and Noise Bands of Equivalent rms Sound-Pressure Level
Authors: Thompson Paul O. , Gales Robert S.
Published: September 2005

In order to compare the temporary threshold shift (TTS) produced by bands of thermal noise with that produced by pure tones, eight ears (four subjects) were exposed to pure tones of 500 and 3200 cps, and to noise bands 5 cps, one-third octave, and one octave wide, centered at these same frequencies. The exposures were at a sound-pressure level of 110 db. After exposure, the subject tracked his 4000 cps threshold for 3 min and then his 500, 1000, 2000, 4000, and 6000 cps thresholds for the next 12 min on a Békésy type audiometer. The threshold shifts at these frequencies were found to be essentially the same regardless of the exposure stimulus type. The threshold shifts from exposures in the 500 cps region were very small, but the “bounce” phenomenon was particularly prominent.
Use of Delta Function for the Correlations of Pressure Fields
Authors: Maidanik Gideon
Published: September 2005

Using essentially the methods of Lyon and Dyer the response of a one-dimensional, simply supported elastic system (such as a string or a bar) to random convecting force fields is calculated. The spatial as well as the time dependence of the correlation function of the force field are assumed to decay exponentially. The response is analyzed as a function of the force-field parameters in relation to the dynamic characteristics of the system. Special attention is focused on the limiting case where the correlation function approaches the delta-function form in space or time or both. In this way a criterion is established for the validity of the delta function approximation for such problems.
Phonetic Typewriter III
Authors: Olson Harry F. , Belar Herbert
Published: September 2005

Many new improvements over earlier models of the phonetic typewriter have resulted from developments which provide means for reducing the number of different displays obtained for the same syllable without unduly increasing the complexity of the machine. In terms of the ultimate machine which should provide means for handling 1000 to 2000 syllables, model III with a maximum capacity of about 100 syllables is still a rudimentary phonetic typewriter. However, the model III provides a complete system from the sounds of speech input to the typed-page output which is of great value in future research in speech analysis. Specifically, the subjects considered in this paper are as follows: form of the typed presentation, construction, circuits, syllable memory, typing console, spelling memory, choice of vocabulary, procedure for setting up the memory, and codes obtained.
Grain-Size Distribution in Metals and Its Influence on Ultrasonic Attenuation Measurements
Authors: Papadakis Emmanuel P.
Published: September 2005

A transformation has been derived relating the number of spheres of a certain radius R per unit volume (the “volume distribution of spheres”) to the number of circles smaller than a certain radius r per unit area (the “area distribution of circles”) appearing on a plane cutting through the volume. The transformation was applied to several hypothetical grain-size distributions for polycrystalline metals to find the resulting hypothetical area distribution of grain images on photomicrographs. Comparison of the hypothetical area distributions to experimentally found area distributions gave the following conditions that the true volume distribution of grains must meet: (1) It must be finite at R=0, and (2) it must have a nonzero decreasing tail for large values of R. The common assumption of a single grain diameter is insufficient to explain the experimental area distribution of grain images. The functions NV(R) = Rn exp(−kR) and NV(R) = exp[−(lnR/R0)2/2σV2] were judged plausible for the volume distribution function of grains, and a correction was computed for the attenuation formulas for Rayleigh scattering of ultrasonic waves in polycrystalline metals by taking averages of R6 and R3 over these functions.
Ultrasonic Double Refraction in Worked Metals
Authors: Sullivan Paul F. , Papadakis Emmanuel P.
Published: September 2005

In the first part of this work the double refraction observed while measuring the attenuation of ultrasonic transverse waves in heat-treated 4150 steel was investigated. Although the data are not complete, they suggest that this double refraction phenomenon can be utilized to detect the amount of preferred orientation of the crystallites in rolled steel when this orientation is small. Calculated values of fractional velocity differences are given.

In the second part the theory of ultrasonic wave propagation in polycrystalline metal is discussed, and the effect of preferential orientation of crystallites on fractional velocity changes is indicated. The use of ultrasonic double refraction data for determining the extent of preferential orientation is discussed.
Unexpected Waves Observed in Fluid-Filled Bore Holes
Authors: White J. E. , Frost H. H.
Published: September 2005

Measurements of pressure and particle velocity in fluid-filled bore holes have yielded several unexpected results, some of which can be explained by very simple computations. One is an acoustic square wave, a flat-topped pulse which is generated when a slug of water, broken off from the main column by cavitation, rejoins the column. In another instance, the geometry is such that a wave along a steel casing is the first signal to arrive at a pressure detector, and the initial pressure is negative, although the explosive pressure generating the transient is initially positive. The manner in which a steel casing causes reversal of pressure in the “casing break” is described. An expression is also presented which relates the negative pressure observed at the bottom of an uncased well to the elastic constants of the fluid and solid. As a fourth example, initial upward motion of a geophone hanging in a bore hole is shown to be consistent with the circumstances under which the observations were made.
DeForest's “Diffraction Microphone”—Optical Detection of Sound in Air
Authors: Levine Richard C.
Published: September 2005

A theoretical analysis of a microphone which optically detects the changes in air density or index of refraction due to sound waves [Lee DeForest, U. S. Patent 1,726,289 (1924)]. A light ray penetrates a thermal gradient in the air, and predicted deflection of the ray is approximately 3 × 10−5 cm per microbar sound pressure for a 300°K temperature change in a centimeter of path length.
Ultrasonic Attenuation at Low Temperatures for Metals in the Normal and Superconducting States
Authors: Mason W. P. , Bömmel H. E.
Published: September 2005

At very low temperatures the mean free paths of electrons in metals become so large with respect to their values at room temperature that they can acquire momentum from collisions with lattice vibrations which result in ultrasonic attenuation when the electrons are in the normal state. This attenuation drops to zero in the superconducting state. Original measurements in impure lead, tin, and copper showed an attenuation proportional to the square of the frequency which could be directly related to the electron viscosity calculated from the number N, the mass m, the mean free path l and the mean velocity 0 of the electrons.

Recently some very pure tin samples have been obtained and much larger effects have been measured due to the increased conductivity at low temperatures. Six oriented samples have been measured and from the measurements the six elastic constants and six viscosity coefficients have been obtained. These correspond to those for a tetragonal crystal. As the mean free path becomes longer than the acoustic wavelength, the loss is determined by a scattering process and the loss for a given frequency approaches a limiting value in agreement with a theoretical prediction of Pippard. The loss for longitudinal waves is from 2.5 to 7.5 times the predicted value while that for shear waves is about 1.5 times the theoretical value of Pippard's.

Measurements of the elastic constants have been made through the super conducting range and the only discontinuity that occurs is that due to the thermodynamically predicted value. The change for a longitudinal wave is less than that predicted for a volume change in agreement with a theoretical derivation. No relaxation effect occurs for the measured velocity even for very pure tin.
Edge Mode of Thin Rectangular Plate of Barium Titanate
Authors: Onoe Morio , Pao Y. H.
Published: September 2005

The frequency spectrum of a thin rectangular plate of barium titanate ceramics has been measured as a function of length/width ratio with a particular emphasis on a special mode of contour vibration, named edge mode.
Noise in Magnetic Recording Tapes
Authors: Howling D. H.
Published: September 2005

A theoretical and experimental investigation is made into the mechanism of noise in magnetic media as used in magnetic recording. It is shown that the basic noise in a wow and flutter free system arises from the fact that the domain size in metals or the particle size of oxides is finite, and improvement in the lower limit of noise can only be made by reduction of particle or domain size. The effect of impressed ac and dc magnetization on the noise level is also examined.

A theoretical value for the tape noise arising from the particle nature of an oxide medium has been derived by taking into account the modern theories of magnetism of the iron oxides and evaluating exactly the mathematical function f(x) which appears in the noise equation. Good agreement with the observed noise voltage is obtained.

It is also shown that the basic wide-band unmagnetized tape noise level of 0.6 μv for the head employed is extremely low and that for the ideal system the theoretical signal/wide-band unmagnetized tape noise ratio is independent of tape velocity and varies as the square root of the track width.
Performance of Ceramic Ferrite Resonators as Transducers and Filter Elements
Authors: van der Burgt Cornelis M.
Published: September 2005

In recent experiments the compositions and methods of preparation of various ferrites were varied with the aim of achieving optimum mechanical and piezomagnetic performance. Essential improvements were obtained by small cobalt substitutions in the chemical composition and by suitable modifications of the mechanical and thermal treatments.

In CW operation, appropriate ferrites can excite radiation intensities up to at least 10 w/cm2, with an electroacoustic efficiency of more than 75% up to 50 kc/sec. So they are highly promising for underwater transmission and processing, in spite of their brittleness (ultimate tensile strength up to about 6 kg/mm2). Wide-band hydrophones with linear frequency response and high pressure-sensitivity can also be built from such ferrites having magnetomechanical coupling coefficients at remanence up to almost 0.25, like Permendur.

The total variation of the mechanical resonant and antiresonant frequencies of ferrite filter elements in the temperature range from +20 to +50°C, being 0.1–0.25% for existing commercial ferrites, has been lowered to 0.03% and less. Since the mechanical quality factors are usually much better than 2000, such ferrites can be profitably applied to the construction of electrical and electromechanical band filters.
Effect of Vibration Amplitude, Frequency, and Composition of the Abrasive Slurry on the Rate of Ultrasonic Machining in Ketos Tool Steel
Authors: Goetze Dieter
Published: September 2005

Results of experiments conducted to determine the dependence of the ultrasonic machining rate V in Ketos tool steel on the peak-to-peak amplitude 2ξ on the frequency of vibration f on the abrasive particle diameter d and on the ratio of the mass of abrasive to the mass of water used in compounding the slurry are given. It is shown that within the range under investigation the quotient V/2ξfd is a constant for a critical ratio of the mass of abrasive to that of water. It is also shown that events occurring within the volume of a cube having sides equal to d are of fundamental importance in the ultrasonic machining process. A phenomenological equation is derived from which the most probable machining rate can be calculated for the range under investigation.
Direct and Reverberant Field Amplitude Distributions in Nearly Hard Rooms
Authors: Lyon Richard H.
Published: September 2005

The probability distribution of pressure amplitudes in a room is studied theoretically and experimentally. A point source is assumed to emit a Poisson sequence of pulses. The method of cumulant generating functions is used to obtain the distribution of response in the direct field, the reverberant field, and the transition region. In the direct field, the source statistics are reproduced. For sufficiently reverberant spaces, the reverberant field tends to normality independently of the source distribution. For sufficiently short pulses (or short autocorrelation time of the source) the direct and reverberant fields are statistically independent. When these simplifying conditions are not met, we indicate how the results may be generalized. Implications for calculations of random fatigue and component malfunction are discussed briefly.
Form of the Loudness Function in the Presence of Masking Noise
Authors: Lochner J. P. A. , Burger J. F.
Published: September 2005

It was established that the loudness of a 1000-cps pure tone in the presence of random noise is given by ψ = k(In − I0n), where I is the pure tone intensity and I0 the threshold intensity of the pure tone in the presence of masking noise. The exponent n is approximately 0.27, and the value of k depends on the choice of units. This relation also holds when the only masking noise present is the physiological noise generated in the ears, and it thus describes the conventional loudness function.
Experiments with Vibrating Soap Membranes
Authors: Bergmann L.
Published: September 2005

The natural oscillations of membranes can be studied by reflection of light from an acoustically excited soap film. In order to obtain a uniform soap film, it proves advantageous to rotate the film so that its thickness is uniform. The oscillations may be obtained even when the films have become extremely thin after long rotation. In addition, one finds strange streaming phenomena with certain natural oscillations.
Corona-Type Loudspeaker for Animal Studies
Authors: Ackerman Eugene , Anthony Adam , Oda Fujio
Published: September 2005

By use of a high-power, corona type loudspeaker we have been able to demonstrate behavioral and endocrine responses of laboratory rodents to measured high sound-pressure levels at the frequencies at which their hearing is most sensitive, namely, 10 to 40 kc. The corona type loudspeaker behaves in the fashion predicted by the theoretical analysis reviewed in this paper. It is limited by extremely low efficiency (2.5%) and high production of ozone. At high frequencies it is limited by the volume of the corona, and at low frequencies by the failure of the quasi-adiabatic condition within the corona. Despite these limitations its performance has not been equaled by other types of loudspeakers; it is a unique tool for studying the responses of laboratory rodents to sound fields.
Reciprocity Calibration of Electroacoustic Transducers in the Time Domain
Authors: Niemoeller Arthur F.
Published: September 2005

A method of directly evaluating the impulse response of a reciprocal electroacoustic transducer is presented. The method is essentially the time-domain analog of the conventional (frequency-domain) reciprocity method. The transient response of a coupled pair of identical transducers is used to compute the impulse response of either of the pair. A numerical method of obtaining solution is presented and is shown to be equivalent to the numerical solution of a real convolution integral equation. First, an approximate solution for one member of the pair of identical transducers is obtained. Then, a more precise solution is generated by minimizing the squared error between the actual response of the coupled pair and the one obtained by convolving the approximate impulse response with itself.

The method was tried on two pairs of condenser microphones, the microphones within each pair being very nearly identical. A pair of Western Electric 640-AA microphones were tested with the grids both on and off, and a pair of Bruel and Kjaer type 4131 microphones were tested with the grids on an off and with grids equivalent to those on the W.E. 640-AA both on and off.

Two unsatisfactory solutions resulted when W.E. 640-AA grids were used on the transducers. Three solutions were satisfactory, even though each contained slight negative drift for large values of time. One solution contained no appreciable error in its entire time course.
Acoustic Filtering in a Moving Medium
Authors: Lambert Robert F.
Published: September 2005

Formulations of one-dimensional sound propagation in a homogeneous, progressively moving medium are applied to calculations of recurrent filter characteristics of side branch tube attached to the side wall of an air duct. The complex propagation constants and characteristic impedance are functions of the flow Mach number. Therefore, the insertion loss is dependent upon flow but relative changes with flow depend upon the terminating impedance levels as well as geometry. Neglecting dissipation the linear system is found nonreciprocal with respect to phase shift.
Side Branch Insertion Loss in a Moving Medium
Authors: Lambert Robert F.
Published: September 2005

Studies of the insertion loss of a side branch resonant filter in moving air reveal that nonlinear excitation of the resonator and turbulence may influence the measured characteristic. These effects occur at relatively low Mach numbers for particular flow geometry patterns. The insertion loss is found to be destroyed for sufficiently high flow velocities. An interpretation of insertion loss values as averaged over a finite band of frequencies is also given some attention.
Calculation of the Magnetic Noise of Polyphase Induction Motors
Authors: Alger Philip L. , Erdelyi Edward
Published: September 2005

The origin of the magnetic driving forces which are responsible for magnetic noise and a method of calculating the mechanical response of the motor structure are reviewed in this paper. A general method is developed to calculate the sound pressure levels of magnetic noise at a specified point near the motor. The paper gives numerical results of calculations, and the corresponding measured sound pressure levels of the magnetic noise for a particular experimental 4-pole, 30-hp, polyphase induction motor under five different operating conditions; calculations agree with measurements within 3 db.
Reactive Components in Sound Absorber Construction
Authors: Becker Carl
Published: September 2005

Basic criteria are given for the incorporation of many reactive components in sound absorbers. Forms of absorbers, determined by these criteria, are derived. Design parameters are treated in relation to techniques for determining their optimum values. Many reactive components are shown to have the effect of enhancing uniformly high absorption over extended frequency ranges.
Diffraction of Wide and Narrow Light Beams by Distorted Finite-Amplitude Progressive Ultrasonic Waves in Water
Authors: Hargrove L. E. , Hiedemann E. A.
Published: September 2005

Results of an investigation of diffraction of light passing through a distorted finite amplitude ultrasonic wave are given. A method is developed and used to determine the second harmonic component of the distorted wave at various distances from the transducer while maintaining a constant local fundamental component. It is shown that the observed discrete diffraction order intensities (wide light beam) and the observed continuous light distribution (narrow light beam) are in good agreement with theoretically predicted values. Measurements were made at 3.0 Mc in water with approximately 23 atm local fundamental pressure amplitude.
Electronic Binary Selection System for Phoneme Classification
Authors: Wiren Jacob , Stubbs Harold L.
Published: September 2005

A successive-binary-selection system for automatic classification of spoken English into several groups of phonemes is described. The first step separates voiced from unvoiced by measuring the filtered output in the range of the pitch frequency. The next step separates turbulent (noise-like) from nonturbulent by measuring the filtered output in the range of the first formant.

Nonturbulent sounds are classified into 6 groups of 2 or 3 phonemes each in successive selections based on spectrum measurements. For each of the two groups of phonemes being separated in a given step, a frequency band is chosen where phonemes of that group have large amounts of energy compared to those of the other group. The polarity of the weighted difference of the corresponding band-pass-filter outputs determines the classification.

Unvoiced turbulent sounds are separated into stops and fricatives by means of the amplitude information contained the onsets of these sounds. Two of the fricatives, |s| (see) and |∫| (she), are separated by means of their zero-crossing-density levels.
Measurements of Sound Reflection from a Rigid Corrugated Surface
Authors: LaCasce E. O. , McCombe B. D. , Thomas R. L.
Published: September 2005

An examination of the scattering process in the vicinity of cutoff is made using rigid surfaces with sinusoidal corrugations which have a maximum slope near one. Measurements of the specular amplitude for several angles of incidence are presented with small increments in frequency. The ratio of the pressure amplitude at the peaks and troughs of the corrugations as a function of frequency is also observed for several angles of incidence.
Radial Vibrations of a Thin Cylindrical Shell
Authors: Brogan William L.
Published: September 2005

The differential equation for radial vibrations of a thin cylindrical shell is derived by Hamilton's principle for the case of constant internal and transient external pressures. Both pressures are assumed symmetrical about the cylinder's axis of symmetry, and the natural frequencies and mode shapes are obtained. The general solution to the transient forced-vibration problem is presented using integral transform methods. The general solution is then carried out in detail for the specific case where the external pressure is a step function moving over the cylinder in the axial direction. It is pointed out that such a solution may be considered as a crude model of what happens to a thin-skinned missile during launching from a silo. Several other problems are mentioned which have the same type of governing differential equations and for which the solutions presented would be useful.
Learning, a Major Factor Influencing Preferences for High-Fidelity Reproducing Systems
Authors: Kirk Roger E.
Published: September 2005

Frequency range preferences of 210 college students for reproduced music and speech were determined by an A-B-A preference test. Two groups of subjects then listened to music reproduced over a restricted frequency range and a relatively unrestricted frequency range, respectively, for six and one-half weeks. The results of a post-frequency range preference test indicate that: (1) learning plays an important role in determining preferences for sound reproducing systems; (2) continued contact with a particular system produces shifts in preference for this system; (3) the average college student prefers music and speech reproduced over a restricted frequency range rather than an unrestricted frequency range; and (4) the frequency range preferences of college students are in part a function of the type of music to which they are listening.
Lowest Natural Frequencies of Elastic Hinged Arcs
Authors: Volterra E. , Morell J. D.
Published: September 2005

Approximate formulas are derived for the lowest natural frequencies of hinged elastic arcs having the center lines in the form of a circle, of a cycloid, of a catenary, and of a parabola in the case of vibrations occurring either in the plane of the initial curvature or in the plane perpendicular to the plane of the initial curvature of the arcs. Numerical results for the frequencies are presented in tabular and graphical form. The paper supplements previous published papers by the present authors in which the same problems were solved for the case of elastic built-in arcs.
Linguistic Considerations of Porpoise Sounds
Authors: Dreher John J.
Published: September 2005

A brief comparison of intonation and tone languages is given, with criteria of the latter applied to observed whistle contours appearing in underwater recordings of Tursiops truncatus and Langenorhynchus obliquidens.
Resonant Frequencies and High Modes in Layered Wave Guides
Authors: Tolstoy I.
Published: September 2005

When a boundary between two sections of a multilayered wave guide becomes a pressure or particle-velocity node, the sections can be treated independently and the intersections of their characteristic curves define two infinite lattices of points which give the quasi-resonant and antiresonant propagation frequencies of the complete wave guide. The antiresonant lattice points also give the group velocity maxima corresponding to the frequencies for which the modes of the wave guide are strongly coupled to the characteristic modes of an individual layer or section of the guide. The resonant lattice points give the group velocity minima corresponding to a somewhat weaker coupling with the complementary section. In addition to clarifying the physics of guided waves in layered media, these lattices accelerate the numerical procedures and lead, in the case of high modes of propagation, to useful approximations and/or simplifications of the exact solutions.
Viscous Dissipation Caused by a Sphere
Authors: Lane C. A.
Published: September 2005

Recent studies have led to a satisfactory solution to the problem of acoustic streaming in the vicinity of a sphere for s/a≪1, where s is the oscillation amplitude, and a is the radius of the sphere. The results of these studies have now been applied to the calculation of the inherent energy losses. The energies in the dc vortices and in the primary ac vortices have been computed, and it is shown that the energy in the former is negligible in comparison with the energy in the latter. The results are restricted to cases where s/a≪1, and a(ω/2ν)12≫1, where ν is the kinematic viscosity and ω is the frequency of oscillation.
The Upper Limits for the Reverberation Time of Reverberation Chambers for Acoustic and Electromagnetic Waves
Authors: Walther Klaus
Published: September 2005

The upper limits for the reverberation time and Q factor of acoustic reverberation chambers with perfectly rigid walls with a smooth surface are determined. The reflection factor for a rigid wall of arbitrary thermal conductivity is determined from a consideration of the viscosity and heat conductivity-boundary layer. The cases of isothermal and adiabatic boundary conditions are discussed. At very low frequencies the boundary absorption and at very high frequencies the volume absorption are the important factors in determining the losses. The analogous problem of the electric reverberation chamber is compared with the acoustic case. For some conditions the electric and acoustic equations are identical in form, if the electric skin depth is replaced by the thickness of the acoustic viscosity boundary layer. At comparable wavelengths and room sizes the electric Q factors are approximately factor of 50 higher than the acoustic upper limiting values.
Improved Method for Studying Tympanic Reflexes in Man
Authors: Mendelson Emanuel S.
Published: September 2005

This report describes manometric apparatus developed for registering the involuntary displacements of the human tympanic membrane during the reflex contraction of the middle-ear muscles. Recent tests with the new method have been uniformly successful in 14 inexperienced subjects, as contrasted with only 20 out of 57 previously. The reflex reactions have also been recorded from subjects who had been judged nonreactors in previous tests. Extensive repetitions of tests on one subject have yielded a close quantitative relation between stimulus and response-index magnitudes. In this set of experiments the stimulus was a click-free tone of 500 cps, graded in steps of 1 db. The threshold sound pressure level was about 111 db, and response magnitude rose in sigmoid fashion with progressively stronger stimuli.
Theory of the Shadow Zone Diffraction of Underwater Sound
Authors: Noble William J.
Published: September 2005

The problem of the shadow zone diffraction of underwater sound is reduced to that of diffraction by a dark half-plane and an asymptotic expansion of the edge wave used to calculate the transmission anomaly. This theory explains the general shape and the observed break of the transmission anomaly curve. The dependence of the calculated values on range, wavelength, and depth, is shown to agree with observations made during and after the Second World War.
On the Pressure Dependence of Sound Absorption in Liquids
Authors: Liebermann Leonard
Published: September 2005

The theory of the dependence of sound absorption pressure is given for liquids in which absorption significantly depends on the two coefficients of viscosity: bulk viscosity and shear viscosity. The bulk viscosity, and therefore sound absorption, is shown to be related to the equation of state. The equation of state is derived for a liquid model in which the volume is determined by molecular distribution within two states. This equation of state possesses two characteristic constants; these can be numerically evaluated for an actual liquid by comparing the theoretical equation of state with pressure-volume relations available in tables. As an example, the characteristic constants of water are evaluated and used to compute the effect of pressure on sound absorption. The theoretical prediction is in agreement with published observations. As a further example, ethyl alcohol is also treated.
Pitch Synchronous Analysis of Voiced Sounds
Authors: Mathews M. V. , Miller Joan E. , David E. E.
Published: September 2005

A study of vowel sounds by means of a spectral analysis keyed synchronously to the voice pitch has been carried out. Spectra are obtained by Fourier analysis of individual pitch periods which were established by visual inspection of oscillogram. A digital computer served as the analyzer. The spectra are represented by a pattern of zeros and poles obtained by a process of successive approximation, again carried out by computer. The contributions from vocal tract and glottal source can be uniquely separated and examined. These results show that vowel sounds can be represented by a sequence of poles arising from the vocal tract and a sequence of zeros character the izglottal excitation. The frequencies of the vocal tract poles agreed with previous measurements, but the damping factors were not entirely consistent with earlier estimates. The zeros showed approximately uniform frequency spacing, particularly at high frequencies. A theoretical development indicated that this characteristic was to be expected from the known structure of the glottal excitation. The zero pattern was used to estimate the ratio of open-to-closed time for the glottis during voicing.
Determination of the Speech Spectrum through Measurements of Superposed Samples
Authors: Tarnózy T. H.
Published: September 2005

By recording on one magnetic tape the simultaneous utterances of several speakers saying unrelated things, we have obtained noise which is essentially time-invariant, has a continuous spectrum, and displays the average spectral properties of speech much more readily than methods employed heretofore. Spectral analysis of this speech noise has been performed.

The advantages of the method are (1) the integration time needed for determining the long-time spectrum of speech can be reduced to a few seconds; (2) the combination of speech wave forms can be treated as a statistical noise constant in time; (3) this noise does not contain any line spectrum elements; (4) with normal speaking levels, better signal-to-noise ratios are obtained.

The experiments suggest that different languages may be characterized by differences in the long-time average spectra. Spectra obtained by the present method were used to compute the average loudness level of a single speaker. The method is adaptable to measurement of the spectrum of a speech sound or of an individual mode of pronunciation.
Determination of the Elastic Constants of Ice Single Crystals by an Ultrasonic Pulse Method
Authors: Green Robert E. , Mackinnon Lachlan
Published: September 2005

The elastic constants c11, c12, c13, c33, c44 of single crystals of ice have been determined through the measurement of elastic wave velocities by an ultrasonic pulse method.
Comparison of a Familiar Formula for Speed of Sound in Sea Water with the Kuwahara-Mackenzie Formula
Authors: Bellas F. E.
Published: September 2005

A new formula for the speed of sound in sea water was recently published by Mackenzie. This letter compares the new formula with a more familiar formula, since the new one contains more terms and conveys the impression of being a much better approximation.
Acoustic Properties of Stop Consonants
Authors: Halle M. , Hughes G. W. , Radley J.-P. A.
Published: September 2005

The two major cues for stop consonants, the burst of the stop release and the formant transitions in the adjacent vowel, were investigated. Detailed energy density spectra of the bursts were prepared. The transitions were studied by means of sonagrams. Possible criteria for identification were developed and tested. In order to assess the efficacy of the two types of cue, perceptual tests were conducted with isolated segments that contained either stop bursts or vowel transitions alone. Common acoustical properties of bursts and formant transitions are noted; differences as well as similarities are discussed in the light of different varieties of pitch judgments.
Ultrasonic and Visco-Elastic Relaxation in a Lubricating Oil
Authors: Taşköprülü N. Ş. , Barlow A. J. , Lamb J.
Published: September 2005

The velocity of propagation and the absorption of longitudinal waves has been measured in a hydrocarbon oil for which the shear modulus together with the spectrum of shear relaxation times has been determined previously. A volume viscosity is found which is approximately equal to the shear viscosity and the results are surprisingly similar to those found by Litovitz and his co-workers for associated liquids. Structural relaxation appears to play an equally important part in determining the second viscosity of the hydrocarbon oil as it does in associated liquids. The effects of association are found to give slightly higher values for the limiting moduli at high frequencies (the instantaneous moduli) and are also responsible for the marked temperature dependence of these moduli. In the present case the relaxing part K2 of the modulus of compression and the limiting value of the shear modulus are each sensibly independent of temperature. It also appears that for the liquids studied so far K2≅43⋅G∞. The spectrum of compressional relaxation times is determined and good agreement is found between the measured values of the components of the complex compression modulus and the curves recalculated from the spectrum. The absorption at frequencies above the main part of the dispersion region is governed not by an hysteresis type of loss, as found in associated liquids, but by a residual high-frequency contribution to (α/f2) due to the (unrelaxed) contribution of the vibrational specific heat relaxation.
Physiological Evidence for the Masking of Low Frequencies by High
Authors: Deatherage Bruce H. , Davis Hallowell , Eldredge Donald H.
Published: September 2005

Observations were made on guinea pig with intracochlear electrodes. Successive waves of low-frequency stimulation set off well-synchronized volleys of action potentials (AP) as well as the familiar cochlear microphonic (CM). The phenomenon of masking of a 500 cps tone pip is, of course, observed when a low-frequency band of noise, centered on 500 cps, obscures the CM and masks the AP that result from the pip. At comparable levels of stimulation, high-frequency band of noise centered on 6950 cps and having no appreciable energy in the 500 cps region will not mask. But, as the intensity of the high-frequency sound is raised to high levels, masking occurs. A random, low-frequency CM now appears in the apical region in addition to the expected high-frequency CM response in the basal turn. We infer that the ear responds nonlinearly to the high-level noise and “detects” its envelope as random low frequencies of random amplitude. This anomalous masking is produced both by a band of noise and by a high-frequency tone which is amplitude modulated by a low frequency.
Effect of a Reflecting Plane on an Arbitrarily Oriented Multipole
Authors: Bies David Alan
Published: September 2005

Expressions for the power radiated by either a dipole or a quadrupole reflected in an infinite rigid plane are presented. These expressions are perfectly general in that they admit any orientation of the multipole and any kind of a quadrupole. The results include the special cases considered previously by U. Ingard and G. L. Lamb, Jr. [J. Acoust. Soc. Am. 29, 743 (1957)]. The large variations in radiated power observed for a single multipole tend to diminish when averages over a distribution of such multipoles are considered.
Separation of the Vector Wave Equation of Elasticity for Certain Types of Inhomogeneous, Isotropic Media
Authors: Hook Joseph F.
Published: September 2005

The method of separation of both the dependent and independent variables of the vector wave equation of elasticity has heretofore been applied almost exclusively to problems of wave propagation in homogeneous media. In this paper, a generalization of this method that extends its applicability to several types of inhomogeneous media is developed. The mechanical properties of the media considered here depend on one Cartesian coordinate, and Poisson's ratio is taken to be constant. Formulations are given for axially symmetric waves in three dimensions and for waves in two dimensions. Three linearly independent vector solutions of the wave equation are expressed in terms of three scalar potential functions. One of these functions represents generalized SH waves and satisfies an independent second-order wave equation in all the problems considered here. Certain functional forms for the mechanical properties are found for which the remaining two potential functions also satisfy independent second-order wave equations; these potentials may be identified with generalized P and SV waves, respectively. The SH waves are solenoidal, but in general the P and SV waves are not purely irrotational and solenoidal, respectively, for the problems treated.
Theoretical Development of Volume Reverberation as a First-Order Scattering Phenomenon
Authors: Carleton Herbert R.
Published: September 2005

A model for acoustic scattering of an arbitrary pressure wave is developed from the fundamental wave equation. A statistical distribution of scatterers in the medium is assumed and is described by a spatial correlation function. It is shown that the predominant features of volume reverberation can be derived from the model. Furthermore, under certain simplifying conditions, it is shown that the reverberation signal can be represented as a random noise passed through a narrow band filter whose properties are determined by the mode of transmission. The determination of the dependence of reverberation level on operating frequency, and the possibility of optimizing an acoustic system by the choice of transmission is suggested.
Integral Solution of the Shallow Water Sound Field
Authors: Leslie C. B. , Sorensen N. R.
Published: September 2005

A method is developed for the numerical evaluation of the integral solution to the wave equation for a point source in shallow water overlying a “hard” liquid type bottom; i.e., c2>c1. This method is especially useful for intermediate horizontal ranges where satisfactory approximations to the sound field have not been found. In general the integral cannot be evaluated directly because there are singularities in the integrand. Instead it has been transformed into the complex plane in such a way that the resulting integrals and residues can be evaluated on a high speed digital computer. A limited number of calculations were made to illustrate the use of the numerical method.
Electrostatic Analogy to Sound in a Region of Constant Velocity Gradient
Authors: Mittenthal Lothrop
Published: September 2005

Using ray theory a wave front is found for the case of sound from a point source in a medium where sound velocity is proportional to depth. The spreading backwards toward the source is shown to be independent of ray angle. The rays are shown to be harmonic functions similar to lines of flux. The harmonic conjugate to the ray is derived and shown to resemble an electrostatic potential.
Disk-Loaded Torsional Wave Delay Line. II. Theoretical Interpretation of Results and Design Information
Authors: Thurston R. N.
Published: September 2005

In order to account for the magnitude of the delays reported in Part I, the effects of distributed mass and elasticity in the disk must be included in the analysis. Formulas for the torsional impedance at the inner circle of a thin annular elastic disk with a free outer boundary were first derived by H. T. O'Neil. One finds from these formulas that the structure can properly be represented by lumped electrical elements over a relatively wide frequency range. This electrical analog is a tandem arrangement of identical low-pass filter sections for which formulas are conveniently available.

Complicated elastic effects near the sudden change of diameter are not included in the theory, and these effects may account for the discrepancy between theory, and experiment. Relatively simple empirical corrections should be possible after a sufficient number of tests.

The design of disk-loaded delay lines is discussed in the light of the aforementioned analysis.
Nondestructive Testing by Ultrasound: Objectives and Potentialities
Authors: Roth Wilfred
Published: September 2005

Ultrasonic propagation is affected by elastic properties of material distribution of material and stress continuity. Since these are properties that determine structural strength of manufactured parts, ultra sound is useful for nondestructive testing. Variations in internal properties of structure can be detected, but it is often not possible to evaluate the effect that detected structural variations have on the ability of a part to function properly. This paper takes a critical view of the nondestructive testing field in the light of this objective.
On the Edgetone
Authors: Powell Alan
Published: September 2005

The feedback mechanism of classical low-speed edgetones in which the action at the edge is interpreted as an acoustical source is developed in detail. A theoretical development indicating that the acoustic field is primarily due to the dipole associated with the fluctuating fluid force on the edge has been verified. It is the hydrodynamic field of the dipole which disturbs the jet, whose instability characteristics are shown to depend acutely on the Reynolds and Strouhal numbers, and the orifice-edge distance. The gain criterion is developed in detail, it being shown how the eigenfrequencies (which can form no algebraic sequence) arise; the lower limit to the orifice-edge distance is discussed, yielding an estimate of the “linear” instability of the stream. The amplitude of the established edgetone depends on the nonlinear behavior of large-amplitude stream disturbances and the corresponding upper limit to the edge force proves to be in satisfactory agreement with measurements, thus yielding acceptable expressions for the sound pressure. Multiple tones and the circumstances of the hysteretic frequency jumps are discussed. The basic action depends only on Reynolds number for geometrically similar systems, while the sound power depends on the cube of the Mach number also.
Aerodynamic Mixing in a High-Intensity Standing-Wave Sound Field
Authors: Mickelsen William R. , Baldwin Lionel V.
Published: September 2005

Aerodynamic mixing is of fundamental importance in many fluid flow processes, some of which have intense superimposed sound fields. The effect of a transverse sound field on the temperature field downstream from a line source of heat was investigated both analytically and experimentally. In moderately intense sound fields, the temperature field is affected only in the time-mean sense. In intense sound fields, the heat wake is substantially deformed so that both the time-mean and instantaneous temperatures are considerably reduced.