bluuebunny/crossref_metadata_2025 huggingface dataset:
Relations between Speech-Interference Contours and Idealized Articulation-Index Contours
Authors: Webster J. C.
Published: September 2005

A comparison is made between speech-interference (SI) contours [developed from the speech-interfering properties of a representative sample of industrial (Navy) noises] and a set of articulation-index (AI) contours based on theoretical noise spectra encompassing the most-extreme spectra found among real noises. At a level of roughly 70 dB [as based on a speech-interference level (SIL) or decibel average over the octaves centered at 500, 1000, and 2000 cps], the SI and AI contours agree very well. At lesser levels of noise, the SI and AI contours purposely diverge because the SI contours were developed to bridge the gap between noise-criteria (NC) and alternate-noise-criteria (NCA) curves (developed by Beranek to rate both the annoying and speech-interfering aspects of office noises) and the basic SI70 (SI at 70 dB) curve. The complete set of AI contours points up, as do the SI contours, that as the ambient noise increases the importance or pivotal frequency shifts downward from around 2000 to around 1000 cps. The pivotal frequency is the frequency that divides the speech bandwith into two halves, each of which contributes equally to the total intelligibility. Some potential uses of the basic SI contour (SI70) as a filter network in a sound-level meter are discussed.
Coupling to Hypersonic Waves
Authors: Haydl W. H. , Blötekjaer K. , Quate C. F.
Published: September 2005

In this paper, the coupling between electromagnetic sources and acoustic waves with thin piezoelectric disks is discussed for longitudinal waves of hypersound. The experimental results in the range of 500–1000 Mc/sec are in agreement with the calculations. Improved coupling can be obtained by using “double layers” of quarter-wave films. These films act as acoustic transformers, which should produce coupling bandwidths that are proportional to the first power of the electromechanical coupling constant k.
Experimental Determination of the Freefield Sound Speed in Water
Authors: Neubauer Werner G. , Dragonette Louis R.
Published: September 2005

Measurement of freefield sound speed in water was undertaken in a 10×5×5-ft cypress tank. A pulse was transmitted from a fixed source to a receiver at two different distances from the source. The distance difference, of approximately l m, and the travel time over this distance were accurately measured at 41 temperatures between 16.8° and 23.10°C. A 290-deg spherical cap was used as the fixed source. The movable receiver was a disk transducer whose active element radius was 0.16λ at the source resonance frequency. Measurements were also made using 0.63-cm-radius disks as source and receiver with the same results. In the experimental measurements, the maximum uncertainty of +0.20 and −0.23 m/sec is sufficiently small to indicate that the experimentally measured freefield sound speed is significantly lower than that obtained by previous confined-field measurements.
Sound Transmission over Theatre Seats
Authors: Sessler G. M. , West J. E.
Published: September 2005

The propagation of sound waves traveling at grazing incidence over rows of theatre seats was determined both in a concert hall and on a scale model. The measurements in the concert hall show that sound waves are attenuated relative to freefield propagation in the frequency range from 80 to 400 cps. The effect is greatest at frequencies between about 120 and 200 cps. The relative attenuation at these frequencies increases with the number of rows interposed up to about 15 dB for 15 rows or more in the measured hall. Since no low-frequency attenuation was observed with the main-floor seats removed, it is apparent that the seats are responsible for this effect. Investigation into the mechanism of this attenuation was made by means of scale-model experiments in an anechoic chamber. The model measurements show that the frequency of maximal attenuation is determined primarily by the height of the seats; spacing between rows has relatively little influence on either the frequency or magnitude of the attenuation maximum for a given distance between the source and the receiving point. Thus, the attenuation is most likely caused by a vertical resonance in the gaps between the rows. The attenuation maximum is at a frequency where the height of the seats is between one-quarter and one-half wavelength, depending on the opening provided by the underpass beneath the seats. Additional broad-band attenuation at frequencies from 80 to 400 cps results from diffraction of sound waves around the upper edges of the seats.
Procedural Variables Influencing Estimations of Differential Thresholds for Frequency
Authors: Daniloff R. G. , Glattke T. J. , Keith R. W. , Small Arnold M.
Published: September 2005

Using the method of constant stimulus differences, the influence of number and increment size of variable stimuli on the size of differential limen (DL) was measured. Generally, the magnitude of the DL varied directly with the increment size of the variable stimuli and inversely with the number of variable stimuli.
Surface Backscattering Strengths Measured over an Extended Range of Frequencies and Grazing Angles
Authors: Chapman R. P. , Scott H. D.
Published: September 2005

Surface backscattering strengths were measured in octave bands, using explosive sound sources in an experiment similar to that reported by Chapman and Harris [J. Acoust. Soc. Am. 34, 1592–1597 (1962)]. In the earlier experiment, measurements were made in the frequency range from 400–6400 cps and at grazing angles up to 60°. In the present experiment, a wider band of frequencies was covered, 100–6400 cps, and the maximum grazing angle was increased to 80°. Where results could be compared, the scattering strengths in the two experiments were in general agreement, any differences being consistent with the observed differences in ocean swell.
Experiments on the Rijke-Tube Phenomenon
Authors: Friedlander Melvin M. , Smith T. J. B. , Powell Alan
Published: September 2005

A horizontal Rijke tube with movable closed ends (an inversion of the classical open-ended apparatus) was satisfactorily tested over a wide range of experimental parameters, and demonstrated close correlation between observation and existing theory. The horizontal tube isolated operation from the laboratory standing-wave patterns, and allowed precise changes to be made in the various parameters during tube operation.
Electrokinetic, Acoustic Pressure Transducer
Authors: Collins Joseph L. , Ellis G. E.
Published: September 2005

The principles of electrokinetic phenomena are well-documented in classical electrochemistry. This paper discusses a low-frequency, electrokinetic, acoustic pressure transducer, suitable for both airborne- and underwater-sound applications, that uses the principle of electrokinetic transduction. A broad frequency response has been obtained, which extends from 0.001 to 100 cps. A pressure sensitivity of 3.8 μV/dyn/cm2 (266 mV/psi) is illustrated.
Experimental 600-ft Electrosonic Delay Line
Authors: Kaufman M. G.
Published: September 2005

For many types of data-transfer systems, it is desirable that the data be delayed long enough so that the system is ready for the data. In the present Space Surveillance system, it is desirable to delay data until the recorder is up to speed. The requirement for delaying the composite Inter-Range Instrumentation Group (IRIG) FM telemetering signals from a space surveillance site by 12 sec was fulfilled by converting the phone line frequencies into sound, which is then transmitted through a pipe long enough to provide the desired delay and then reconverted into electrical signals. The delayed output is essentially distortionless.
Probe-Tube Microphones
Authors: Leonard R. W.
Published: September 2005

Probe microphones are now in such common use and obtainable in so many different forms that it seems appropriate that a description of the various forms and a comparison of their salient features be set down. This paper discusses (1) the simple probe microphone, which consists of a tube terminating in the diaphragm of a pressure-sensitive transducer; (2) the terminated probe microphone, which consists of a tube terminated in the diaphragm of a pressure-sensitive transducer in parallel with which has been placed the characteristic impedance of the probe tube; and (3) the resistively tipped microphone, in which the damping resistor is placed at the tip of the probe and the probe tube is terminated in a pressure-sensitive diaphragm. In addition to comments on the three types of probes, a suggestion for a figure of merit for probe-tube microphones is also set down. Much of the work done on probe microphones is not original with this author, and proper credit is made to all sources known to the author.
Experiments with the Electrical Analog of a Piezoelectric Transducer
Authors: Redwood M.
Published: September 2005

An electrical analog of a piezoelectric transducer has been built and used to demonstrate the generation and detection of acoustic waves and the electrical characteristics of a piezoelectric resonator. The circuit uses an artificial transmission line to represent the distributed-constant mechanical properties of the transducer, and is therefore capable of reproducing the behavior of a transducer under both transient- and continuous-wave conditions. The theory of the equivalent circuit of a transducer is first extended to facilitate interpretation of the physical processes of generation and detection. This is done by developing an “impulse sequence” that takes into account waves generated at both faces of a transducer, and the delay in time and reflections that they undergo in passing through the transducer. This analysis is used to discuss examples of waveforms obtained with the analog in the following situations (with various simulated combinations of backing and load impedance): (1) as a generator of acoustic waves when excited by an electrical signal in the form of (a) a short impulse, (b) a step, (c) short trains of sinusoidal oscillations of various lengths; (2) as a detector of acoustic waves when excited by an acoustic signal in the form of (a) a step, (b) a train of sinusoidal oscillations. In detection, the effect of terminating the transducer with high and low resistances is also demonstrated. Experiments concerning the continuous-wave response of the analog are also described.
Effect of Wall Material on the Steady-State Tone Quality of Woodwind Instruments
Authors: Backus John
Published: September 2005

A clarinet blown with an artificial embouchure was connected to one end of a large pipe with absorbing material at the other end so that the sound usually radiated was absorbed instead. Under these conditions, the sound radiated from the vibrating body was measured and found to be 48 dB below the sound normally produced by the instrument at the same location. Acceleration levels measured on the body with a vibration meter were correlated with the sound radiated by the body, both for the artificially blown clarinet and for clarinets set into vibration with an attachment energized by a complex signal. The figures obtained were used to check other woodwind instruments. Results showed that the body sound should be at least 37 dB below the normal sound for all instruments measured. The effect of nonrigid walls was checked by comparing tubes of brass and soft TYGON plastic blown on the embouchure, measuring the harmonic structure of the internal standing wave produced and the frequencies and Q's of the resonance modes. The differences were small. It is concluded that the vibrations of the walls of a woodwind instrument do not affect its steady tone either by radiating sound themselves or by affecting the harmonic structure of the internal standing wave.
Ultrahigh-Frequency Ultrasonic Absorption Cell
Authors: Hunter Joseph L. , Dardy Henry D.
Published: September 2005

An ultrasonic absorption cell has been constructed that maintains parallelism sufficient for absorption measurements well above 500 Mc/sec. Constructional details are described and results presented showing absorption in benzene, dioxane, and polysiloxane at 510 Mc/sec. The system as a whole will permit an attenuation of about 35 dB before the signal is lost in the noise. The absorption in benzene divided by the square of the frequency is substantially lower than values obtained at low frequencies, and indicates a relaxation frequency of approximately 600 Mc/sec.
Normal Vibration Modes of Continuous Beams with Distinct Flexural Rigidities for Each Span
Authors: Vet Maarten
Published: September 2005

A derivation is presented in which the normal modes of vibration are found for a continuous beam on simple supports. No conditions of symmetry are imposed and each span may have an arbitrary flexural rigidity that is constant throughout each particular span.
Effect of Transducer Velocity on the Structure of Signals Scattered from the Ocean Bottom
Authors: Hurdle Burton G. , Ferris Raymond H. , Flowers Kenneth D.
Published: September 2005

The fluctuation of acoustic signals scattered from the ocean bottom displays a beat or interference characteristic when the source and/or receivers are in motion. Beat rates obtained statistically from observed data are shown to vary with velocity of source and receiver, as well as with transmitted frequency and acoustic geometry. Data obtained with a conical beam at a frequency of 19.5 kc/sec are compared with a simple physical model. Experimental results of a method for controlling the heat rate by linear frequency modulation of the transmitted signal are illustrated. Implications of the observations relative to reflection and scattering theory are discussed.
Békésy Audiometry at 20 Frequencies from 0.2 to 6 kc/sec
Authors: Harris J. D.
Published: September 2005

Absolute intensive thresholds are presented from 26 men yielding Békésy audiograms at 20 frequencies. Results validate the practice of graphic interpolation between thresholds in octave steps to predict mean thresholds at half octave points. Thresholds are almost indistinguishable from those by conventional audiometry in a very similar population. Data are interpreted to confirm in general the practicability of using the proposed 1964 ISO reference threshold level as the norm for young otoscopically negative adults.
Equivalence of “Vector” and Autocorrelation Pitch Detectors
Authors: Sondhi Man Mohan
Published: September 2005

In this Letter, it is shown that a recently, proposed “vector” pitch detector is equivalent to an autocorrelation pitch detector.
Natural Frequencies of a Uniform Square Plate Bounded by Flexible Beams
Authors: Mahalingam S.
Published: September 2005

Cox and Benfield have used a finite difference method to calculate the natural frequencies of a uniform plate bounded by flexible beams and have given curves showing the variation of the frequency coefficient with the stiffness ratio for six different values of mass ratio. The present Letter, which is an extension of an earlier solution given by the writer [J. Roy. Aeron. Soc. 67, 664–668 (1963)], shows that the curve for the massless stiffener is really the “basic” curve and that the other curves may be obtained from it. A simple approximate expression for the basic frequency curve has also been obtained.
Acoustical Measurements of Static Tests of Clustered and Single-Nozzled Rocket Engines
Authors: Tedrick Richard N.
Published: September 2005

The predictions of the acoustic effects of the static firing of large rocket engines have usually been based upon such engine parameters as specific impulse, nozzle diameter, etc. However, the recent development of large clusters of smaller engines have introduced a new possible variant. Tests were performed using two 1.5-million- pound thrust rocket systems—one with a single engine and one with a cluster of eight smaller rockets. The two systems, NASA's F-1 and Saturn S-1, used the same liquid fuel and were fired on the same test stand. Due to this unusual test configuration, it was possible to equate most of the engine parameters to obtain a comparison of the acoustical effects resulting from static tests of clustered and single-nozzled rockets of similar thrust class. Acoustical data are presented in this paper showing both the over all and octave-band acoustic power levels for both test configurations. In addition, the differences in near- and far-field directivities are presented.
Talker-Recognition Procedure Based on Analysis of Variance
Authors: Pruzansky S. , Mathews M. V.
Published: September 2005

This paper describes a talker-recognition procedure that selects a small subset of features from a much larger body of data and bases recognition on this subset. The subset is chosen as those features having small variation between utterances of a given talker as compared to the variation among utterances of different talkers. This procedure is applied to materials consisting of quantized spectrographic information from a group of 10 talkers uttering 10 different words 7 times each. Features are formed as the average of the speech energy over certain rectangular areas on the spectrograms. Results are computed as a function of the number of features used and as a function of the size of the areas used to form the features. Although this paper treats only talker recognition, the recognition procedure is general and can be applied to other problems where it is desirable to use a simple method to select a few important features from a much larger set that can number several thousands.
Analog and Digital Analysis Methods for Determining Phase Relationships between Complex Acoustical Signals
Authors: Collier Robert D. , Summers Agnes C.
Published: September 2005

The problem is to measure the phase between two physically related, linear vibration signals on an experimental structure subjected to random forces, distributed in space, on which are superimposed known periodic frequencies. The instantaneous phase for a given frequency is obtained with a special-purpose multichannel analog phase and amplitude analyzer. The results are compared with phase measurements as a function of frequency obtained with a digital estimating method from the crosspower spectral estimates. The phase relationships between the two measurement locations define the longitudinal modal behavior under a wide range of random forcing functions. An analog modelwith five masses, connecting springs, and variable damping is used to simulate the experimental structure. The phase response of comparable measurement locations on the analog model is compared with the experimental results and indicates the magnitude of damping in the experimental structure. The digital estimating technique provides the investigator with useful information on phase relationships between complex acoustical signals related to structural damping, mode coupling, modal response under random forcing functions, and sound fields.
Random Vibrations of a Nonlinear Elastic Beam
Authors: Herbert Richard E.
Published: September 2005

The theory of the Markoff process and the associated Fokker Planck equation is used to investigate the large vibrations of a hinged, axially restrained, elastic beam driven by white noise. An expression for the joint probability-density function of the first N modal amplitudes is obtained and used to derive an approximate expression for the mean-squared displacement. Numerical integration of the exact expression for the mean-squared displacement indicates a reduction of this quantity as compared in the linear theory. Calculations also show a range of applicability of the derived approximate expression. Furthermore. computations show that the first node still gives a good estimate of the mean-squared displacement but the coupling effects of the nodes are so strong, for sufficiently large deflections. that the effect of the higher modes must be taken into account when computing the mean-squared value of the first mode.
Random Excitation of a Nonlinear System with Tangent Elasticity Characteristics
Authors: Klein G. Harold
Published: September 2005

The response of a nonlinear, damped, single-degree-of-freedom system subjected to random excitation is studied. The nonlinearity is of the tangent elasticity type, which can be described as a hardening spring whose load-deflection curve is asymptotic to some given maximum displacement. Various response parameters are determined, including the probability density of the displacement, the mean square value of the displacement, the average number of zero crossings per unit tine, and the probability density of peak amplitudes. Fatigue damage is determined for a beam responding in the first mode only for small displacement and assuming a linear stress-displacement relationship. The solution for determining fatigue damage for a non-linear stress-displacement relationship is indicated. It is also proposed that the cosine-power probability density be used in place of the normal probability density for most physical problems. The cosine power distribution has the Gaussian characteristics in the vicinity of the mean, yet limits the random variable to finite values.
Some Deep-Water Sound-Transmission Paths South of Cyprus
Authors: Baxter Lincoln , Brockhurst Robert , Hays Earl E.
Published: September 2005

Deep-water sound-transmission paths extending in range through two convergent zones in the Mediterranean Sea south of Cyprus have been recorded by a new method that permits high-resolution nearly continuous observation of travel-time difference from a rapidly moving sound source as a function of elapsed time. Striking confirmation of some travel-time relations discussed by previous authors are presented. The paths near Cyprus differ from those in the Atlantic because the Mediterranean skip distance is about twenty miles and the axis of the deep-sound channel is only about 1000 ft deep. A number of additional features of the bottom reflected path are clearly indicated. The details of the refracted path indicate scattering that blurs the refracted caustic and permits reception of weak refracted arrivals at lesser ranges and travel times than predicted by simple ray computations.
Wave Scattering and Transmission at Irregular Surfaces
Authors: Kuo E. Y. T.
Published: September 2005

Marsh's theory of surface scattering is applied to the case of imperfect reflectors. The result for backscattering is quite simple for it is only the product of Marsh's result and the absolute value of a modified reflection coefficient squared. Using backscattering data, a method of obtaining the absolute value of the modified reflection coefficient, roughness spectrum, and the physical properties of the surface material is shown for the cases of laboratory sand surfaces, sea bottom, and Arctic-ice cover. Lambert's law is also discussed.
Dynamics of the Acoustic Reflex: Phenomenological Aspects
Authors: Dallos Peter J.
Published: September 2005

The acoustic reflex was studied by measuring the variations in the mechanical-input impedance to the ears of six normal human subjects. The auditory system was stimulated by wide-band noise at various intensity levels. The static magnitude and phase characteristics of the response were obtained at several frequencies. It was shown that reflex activity results in an increase in the magnitude and a decrease in the phase lag of the ear's input impedance. The system dynamics were studied with step stimuli. It was shown that at stimulus onset both the latency and speed of the response are related to stimulus magnitude. With higher intensities, shorter latency and faster response results. At the cessation of the stimulus, in general there was no clear functional relationship between latency and intensity. For some subjects, faster reflex relaxation occurred after low-intensity stimulation than after more-intense activity. For other subjects, there was no such clear trend. It was observed that, during prolonged stimulation with very high intensity noise, stable reflex activity resulted; but if the stimulus was weaker, then response adaptation occurred. In the vicinity of reflex threshold, the adaptation was usually quite rapid.
Binaural Lateralization of Cophasic and Antiphasic Clicks
Authors: Flanagan J. L. , David E. E. , Watson B. J.
Published: September 2005

Results from a computational model for middle ear and basilar-membrane operation suggest several binaural phenomena. The effects are sought experimentally in tests on the binaural lateralization of pulses. The interaural times for producing centered images are measured as functions of pulse polarity and noise masking. To a large extent. the interaural disparities appear explicable in terms of the mechanical response of the basilar membrane together with simple hypotheses about the mechanical-to-neural transduction in the inner ear. The time disparity can be manipulated by symmetrically masking with high-pass or low pass noise. By this means, the coherent neural information is elicited from a restricted place on the membrane and reflects the mechanical properties of that place. Similarly, asymmetrical masking (for example, high pass in one ear and low pass in the other) yields interaural times that reflect the transit times to specific membrane places. Calculations from the mathematical model for the middle ear and basilar membrane are used to interpret the psychoacoustic behavior in terms of physiological response. The results are discussed in the context of related findings, and an effort is made to assess the relative influence of mechanical and neural factors.
Model of Neural Inhibition in the Mammalian Cochlea
Authors: Furman Gershon G. , Frishkopf Lawrence S.
Published: September 2005

There have recently appeared in the literature several independent reports of experimental studies of the responses of primary auditory neurons in a number of different mammals to tonal stimulation. These studies show that a primary neuron that responds to sound at one frequency can be inhibited by a second tone at a slightly higher or lower frequency, and they suggest that this inhibitory interaction occurs within the cochlea. On the basis of this evidence, we have considered the characteristics of a variety of possible inhibitory-connection schemes among elements lying within the cochlea. All of these schemes can lead to a sharpening of the frequency sensitivity of any single neuron. One, based on the principle of shunting generator currents away from the site of neural excitation, and consisting of linear operations except for shunting, yields a nonlinear generator function similar to one that Weiss used to fit the input-output data of single primary units of the cat to click stimuli. Apart from its possible application in the cochlea, shunting inhibition leads to theoretically interesting operations in sensory-information processing.
Adaptation and Fatigue
Authors: Selters Weldon
Published: September 2005

Any audible tone produces measurable changes in the response of the ear to subsequent stimulation. With exposures up to about 70 dB SPL, the response changes can be attributed entirely to neural adaptation. At higher levels, fatigue adds to adaptation. These processes have been separately identified by TTS experiments showing adaptation as primarily a reduction in loudness response and fatigue as primarily a reduction in sensitivity. Adapted ears will show a TTS of 5–10 dB when the threshold is obtained by interpolation between audible and subaudible stimuli, but trained observers tested by a method that minimized the effect of loudness showed only 1 dB TTS.
Backward Masking for Tones in Narrow-Band Noise
Authors: Wright H. N.
Published: September 2005

Appropriate transformations based on the theory of temporal summation were used to determine backward masking as a function of the time interval between the onset of 800-, 1000-, 1200-, and 1750-cps tones and the onset of an 80-dB narrow band noise centered at 1000 cps that partially masked the tones. Backward masking was found to consist of at least two phases separated by a transition region in which threshold did not appear to be determined by the duration of the probe tone. Masking at 800, 1200, and 1750 cps was found similar to that at 1000 cps, but did not extend as far back in time. The results are interpreted to mean that masking first occurs for those tones within a noise band and then spreads to those frequencies outside the band until the pattern commonly observed under simultaneous masking is obtained.
Oscillating Pressures within a Cylindrical Chamber That Has a Circular Piston in One End Wall
Authors: Lansing Donald L. , Watkins Charles E. , Kantarges George T.
Published: September 2005

Equations are derived for calculating the oscillating air pressures within a cylindrical chamber containing a sinusoidally driven circular piston in one end wall. Some numerical results are presented for a flat piston. Experimental data obtained within a cylinder using a loudspeaker source are compared with theory. Good agreement is shown for the frequencies studied that were not close to the structural frequencies of the cylinder.
Longitudinal-Wave Ultrasonic Measurements in Iron up to 400°C
Authors: Lord Arthur Edson
Published: September 2005

The standard pulse-echo ultrasonic technique has been used successfully with longitudinal waves to over 400°C in single-crystal and polycrystalline Armco iron at 7 Mc sec. The method was used to measure both the high temperature damping and the elastic properties of the iron. The details of using the pulse echo method at elevated temperatures are described in considerable detail. Oscilloscope traces of high temperature echo-decay patterns are presented.
Variability in Acoustic Output of Deep Explosive Sources
Authors: Guthrie Albert N. , Shaffer John
Published: September 2005

Several salvos of nine explosive sources were lowered from a drifting ship to a depth of 600 m in water 4420 m deep and the charges were fired seriatim at 1- to 1.5 min intervals by electrical detonation. The signals generated were received by a hydrophone suspended at 300 m below the surface from an anchored ship and were recorded in 8 half-octave frequency bands, between center frequencies of 63 and 715 cps, on photographically recording oscillographs. The variance in peak pressure [1/p][ΣIN(p − p̄)2/N]12 of the signals in each of these frequency bands is calculated for the N arrivals of the same designation in the salvo. This variance in peak pressure is taken as the upper limit to the variance of the acoustic output in the chosen frequency band for the N sources of that salvo. The average values of the variance in peak pressure for all the one-bottom-bounce arrivals of the four best salvos are below 10% for the 63-, 90-, 125-, and 180-cps half-octave bands and are 12%, 13%, and 19%, respectively, for the 250-, 500 , and 715-cps bands. Reflection from the free surface of the ocean does not appear to have a measurable effect on the variance of peak pressure in the frequency bands 63 180 cps, but such an effect does appear to exist in the higher frequency bands. Some characteristics of the bottom reflection process that are revealed in the experiment are noted and discussed.
Correlation of Amplitude and Phase Fluctuations for Wave Propagation in a Medium with Random, Spheroidal Inhomogeneities
Authors: Knollman G. C.
Published: September 2005

A theoretical study is presented of the mutual correlation between amplitude and phase fluctuations when an acoustic (or electromagnetic) wave propagates in a random medium whose correlation function for refractive index is spheroidal-Gaussian. Amplitude-phase correlations are considered for both plane and spherical waves transmitted through a statistically isotropic medium in which the deviations of refractive index about a mean are small. Large-scale inhomogeneities of arbitrary spheroidal shape are treated, and transmitter-to-receiver ranges are taken as large in comparison with the refractive-index correlation length in the transmitter-receiver plane. Comparison is made between the cases of spherical and nonspherical inhomogeneities, for both plane and spherical acoustic waves. The low- and high-frequency extremes of the theory are given special note.
Coupler-Reciprocity System for Hydrophone Calibration at High Pressures
Authors: McMahon G. W.
Published: September 2005

A reciprocity system has been developed for the absolute acoustic calibration of small hydrophones at hydrostatic pressures up to 15 000 psi and frequencies to 400 cps. The method involves electrical measurements on three transducers placed in a closed, stiff-walled “coupler” vessel and a measurement of the static acoustic compliance of the coupler.
Acoustic Radiation from a Finite Cylinder
Authors: Williams W. , Parke N. G. , Moran D. A. , Sherman Charles H.
Published: September 2005

A semianalytic method is presented that can be used to calculate the acoustic radiation in a domain exterior to a source that is vibrating harmonically in time. This method follows the traditional technique of an expansion of the boundary conditions in an infinite series of eigenfunctions and of a least-squares approximation of this expansion by a finite series of the same functions. For simply connected bodies, such as a finite cylinder, that are not constant coordinate surfaces and for which a complete set of geometrically appropriate eigenfunctions is unavailable, the spherical eigenfunctions are employed as the complete set of eigenfunctions. Farfield patterns produced by radially pulsating cylinders of length equal to twice the diameter have been calculated for ka = 1,2, and 5 and are compared to the calculated farfield patterns of the physically similar situations of a finite-length line source and a radially pulsating band of finite length on an otherwise inert, infinite cylinder. In addition, the radiation resistance and directivity index are calculated and compared for the finite and infinite cylinder sources.
Diffraction of Sound by an Array of Rectangular Reflective Panels
Authors: Leonard R. W. , Delsasso L. P. , Knudsen V. O.
Published: September 2005

An investigation in an anechoic room of the diffraction of sound by rectangular panels, similar to panels that have been used for acoustical purposes in concert halls and other auditoriums, confirms certain expectations based on well-known properties of both optical and acoustical diffraction: namely, (1) that, for wavelengths that are large as compared to the dimensions of the panels and the spacing between them, the incident sound on the panels is essentially all transmitted, and therefore for frequencies below a certain critical value, arrays of such panels are essentially nonreflective; (2) that, for wavelengths that are small, the panels reflect most of the sound incident upon them; and (3) that, for wavelengths that are of the same order of magnitude as the dimensions of the panels and spacings, there are complex diffraction effects.
Detection of Markovian Sequences of Signals
Authors: Friedman Morton P. , Carterette Edward C.
Published: September 2005

The influence of constrained stimulus sequences on detection was studied in a two-alternative temporal forced-choice task with feedback. Three observers listened to a weak pure tone embedded in noise whose probabilities of occurrence and repetition in an interval were governed by a first-order Markov process. Each observer listened to examples of each of nine different Markov chains. Results were (a) a single function relating detections to false alarms fitted individual sets of data well, in agreement with the theory of signal detectability, except (b) that detection was higher for more extreme repetition probabilities; (c) responses depended strongly on the previous stimulus with (d) the dependence being peculiar to a given chain; (e) detection probabilities increased during runs of signals in the same interval, yet (f) probability of detection on the first trial of a run in a given interval did not depend on the length of the preceding run in the other interval.
Consistency of Identification of Consonants Heard in Noise
Authors: Pollack Irwin
Published: September 2005

Five measures of response consistency were obtained for three different sets of four consonants over a wide range of speech to noise ratios. The measures are related to uncertainty and variance statistics. Consistency measures were compared for two conditions of presentation: an identical set of utterances in which a given syllable and its noise background were both recorded and played back over the course of 12 replications of the experiment; and an equivalent set of utterances in which 12 separate readings of each utterance were recorded against independent noise backgrounds. Each of the measures demonstrated higher response consistency for identical than for equivalent sets of utterances.
Propagation of Acoustic Transients in Absorbing and Relaxing Liquids
Authors: Carome E. F. , Fleury P. A. , Wagner W. J.
Published: September 2005

A study has been made of the propagation of pressure impulses approximately 0.1 μsec wide in liquids exhibiting viscous absorption, i.e., constant α/ω2, and relaxation effects. Computed variations of impulse shape as a function of path length are obtained by solving numerically the appropriate linearized wave equations. These are compared with experimental data obtained in such liquids as carbon tetrachloride, carbon disulfide, and acetic and propionic acids. Significant differences are noted in the variation of shape and the veocity of propagation of the impulse maximum in the two types of media.
Combined Effect of Shear Viscosity, Thermal Conduction, and Thermal Relaxation on Acoustic Propagation in Linear-Molecule Ideal Gases
Authors: Connolly James H.
Published: September 2005

An acoustic-propagation equation is derived for the case of shear viscosity, thermal conduction, and rotational relaxation in a linear-molecule ideal gas that is fully excited rotationally. By assumption, the rotational relaxation is characterized by a single relaxation time but no assumption is made as to the magnitude of the absorption. The propagation equation is solved approximately, by truncated series, in the general case and in some special cases. Significant interaction appears only when the ratio of the fundamental rotational-relaxation time to the fundamental translational-relaxation time is of the order of unity. The special case of no thermal conduction is treated.
Ultrasonic Absorption and Dispersion in Monatomic Gases
Authors: Enns R. H.
Published: September 2005

The propagation of ultrasound of frequency ω through a classical, dilute, monatomic gas is studied in terms of the Boltzmann collision equation. The collision term is replaced by the relaxation model ∂f∂t]coll = −(f − f̄)τ, where f̄ is the displaced Maxwellian distribution in the presence of the sound wave and the relaxation time τ does not depend on the instantaneous particle velocity. Once the form of f is determined, the homogeneous equations corresponding to number, momentum, and energy conservation are written down. Setting the determinant of the coefficients of the unknowns in these three equations equal to zero yields the general dispersion relation, relating the complex wavenumber k = k1+ik2 ≡ (ω/V)+iα to ωτ. Two special cases are studied: namely, ωτ < < 1 and ωτ > > 1. For the former, our results agree qualitatively with those of Wang-Chang and Uhlenbeck and with experiment. For ωτ > > 1, it is found that the amplitude absorption coefficient α increases linearly with ω while the phase velocity V becomes independent of frequency. Furthermore, a spectrum of such absorption and dispersion curves is found for which there is, at present, no satisfactory physical explanation. At this time, there are no valid experimental data in existence to confirm or disprove our high-frequency results.
Attenuation of Acoustic Waves in Dilute Emulsions and Suspensions
Authors: Chow Joseph C. F.
Published: September 2005

A study is made of the attenuation of acoustic waves by a suspension of fluid droplets in a fluid medium. Special attention is given to the case of small droplets for which the effect of the surface tension is not negligible. Both the droplets and the surrounding fluid medium are considered to be viscous and thermal conducting. The droplets are allowed to execute large translational motion and to undergo a small deformation from a spherical shape. It is shown that the result of Epstein and Carhart on the attenuation of sound waves in air with the suspension of water droplets is applicable even when the displacement of the droplets is large as compared to its radius. The effect of surface tension is to increase sound attenuation in a two-phase medium by increasing the thermal dissipation. This effect is important in the suspension of gaseous bubbles in a liquid for small droplets and is negligible in the case of a gaseous medium containing liquid droplets. The explicit forms for the attenuation, the droplet displacement, the drag force on the droplet, and the heat-transfer rate between phases are given for the case that is applicable to a gas containing the liquid and solid droplets. The expression for the attenuation that is applicable to the suspension of gaseous bubbles in a liquid is also given and is found to be completely dominated by the thermal dissipation.
Acoustic Field of a Circular Plane Piston
Authors: Williams A. O.
Published: September 2005

King's integral for the acoustic field of a circular plane piston in an infinite rigid baffle is recast into a form that has the product of two Bessel-function operators (algebraic-differential) acting upon the wavefunction eikz/(−ikz). Various exact or approximate formulations, previously known, can readily be derived. One of the two operators “displaces” a wavefunction given on the s axis of cylindrical coordinates to its correct value at (r,s). The other acts upon a spherical wave at (r,s), emanating from the origin of cylindrical coordinates, and transforms it to the piston expression.
Conversion between Old and New Octave-Band Levels
Authors: Schultz Theodore J.
Published: September 2005

A simple procedure is suggested for conversion between “old” and “new” octave-band data.
Backscattering Strength of Young Sea Ice
Authors: Chapman R. P. , Scott H. D.
Published: September 2005

The backscattering strength of young sea ice found in the Gulf of St. Lawrence was measured at frequencies from 0.4 to 25.6 kc/sec and at grazing angles from 15° to 70°. The values obtained were a few decibels lower than any previously reported for sea ice. The observed acoustic properties of the ice in this experiment are in substantial agreement with those inferred from propagation measurements made previously in the same area.
Shock-Wave Energy-Spectrum Scaling
Authors: Christian Ermine A.
Published: September 2005

The approximate scaling factors used by Weston may account for the difference between his reported TNT shock-wave energy-spectrum level and that recently measured at 100 yd by Stockhausen. A similar deviation from the measured spectrum at 1 yd occurs when Stockhausen's data are scaled to the shorter range after the manner of Weston. Measured spectra at 1 and 100 yd are in excellent agreement when compared on the basis of Arons' peak-pressure and time-constant functions.
Acoustical Properties of Japanese Temple Bells
Authors: Sato Koji , Kohashi Yutaka
Published: September 2005

A Japanese temple bell is hung in an anechoic room and is forced to vibrate in a single one of its normal modes by means of a vibration pickup fed with a vacuum tube oscillator. The amplitude of vibration over the whole surface of the bell, the distribution of intensity of sound in its neighborhood and its rate of decay have been measured simultaneously. The experiments have been repeated with respect to different modes of vibration and different sizes of bells. As the result of those experiments, the relation between the vibration and the sound of Japanese bells has been found.
Acoustics of the Singing Voice
Authors: Oncley Paul B.
Published: September 2005

This is the third report on the acoustics of the singing voice based on Sonograph measurements carried on at Westminster Choir College and Columbia University. Previous reports discussed certain discontinuities or register changes, and the significance of higher formants in the 2000–4000 cycle region. The present discussion will center around observations on the vibrato pattern. Several types of patterns deviating from the norm as described by Seashore and others are represented in these measurements, including vibratos principally of amplitude, uneven rates and extents, and angular and asymmetrical patterns. The relation of vibrato to rapid scale singing, and its implications for vocal pedagogy are also discussed.
A New Tone Source for Electronic Carillons
Authors: Slaymaker Frank H.
Published: September 2005

All electronic carillons which produce a given musical note by striking a single metal rod have common difficulties. The lower two components in the tone do not fall on the same note as the apparent pitch of the carillon tone, and may differ from the nearest octave of the apparent pitch by as much as a minor or major third. In more familiar types of tones, such as one made up of a fundamental and a series of harmonics, the first and second harmonics do fall on the same note of the musical scale as the apparent pitch. Often there is only one component in an electronic carillon tone that does agree with the apparent pitch. The result is a confusion in pitch that makes most listeners believe the carillon is out of tune. When the tone is generated by striking a bar having a precisely controlled rectangular cross section, however, the two lower components can be made to fall on octaves of the apparent pitch. Demonstrations will be given comparing the tones of real bells, more conventional types of electronic carillons, and the new rectanglar bar electronic carillon.
A Simple Stroboscopic Frequency Indicator
Authors: Krauss Serge L.
Published: September 2005

The stroboscopic principle of frequency measurement has been adapted to a relatively simple device to cover the range from 32 to 4000 cycles per second with a single disk. The stroboscopic disk has seven rings of octavely related patterns. The synchronous motor which drives the disk is powered by a variable frequency oscillator-amplifier combination. The frequency control of the oscillator is made in steps related to the equally tempered musical scale and deviations from the tempered scale are made with a vernier control. The oscillator is designed for simplicity and frequency stability. A microphone amplifier is provided to amplify the signal whose frequency is to be measured and this is used to operate a neon lamp back of the disk.
Acoustic Treatment of Crude Petroleum
Authors: Fleming Ethel R.
Published: September 2005

An experimental program was undertaken to determine the effect of ultrasonic vibrations in connection with the dehydration of crude petroleum. Experiments are described which provide evidence that water is present in crude petroleum both in the free state and as water vapor. Apparatus and techniques are described by which high-frequency ultrasonic vibrations are used to eliminate water in both forms.
Mechanical Impedance Transformers in Relation to Ultrasonic Machining
Authors: Balamuth Lewis
Published: September 2005

Ultrasonic machining of hard materials, such as cemented carbides, steel, sapphire, etc., requires the use of an acoustical transmission line. This line generally consists of a specially shaped solid body designed so as to convey the ultrasonic vibrations of the transducer to the tool which operates on the work piece. This paper deals with a general type of mechanical impedance transformer suitable for the above-stated purposes. The theory has been cast in such form that the design of such lines may be made from universal equations and graphs. Because such equations appear in terms of ratios, one set of curves applies to all materials and to any desired frequency range. Several cases will be treated in detail so as to make the method employed clear. In addition examples will be given of actual transformers with an account of their performance in practical cases. As is the case generally with transformers, the systems described in this paper have applications in many cases where transformation of the ultrasonic vibration amplitude is desired in going from the source generator to the output end of the system.