bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibrations of a Thick-Walled Cylindrical Shell—Comparison of the Exact Theory with Approximate Theories
Authors: Greenspon Joshua E.
Published: September 2005

The results for vibrations of an elastic cylinder as predicted by a number of the approximate shell theories are compared with the results of the exact theory. It is found that the membrane theory of shells is accurate for predicting frequencies and displacement ratios of cylinders with appreciable thickness. Furthermore, the theories which include bending effects as well as membrane effects are good at even the shorter wavelengths; and the theories which include rotatory inertia and shear are accurate over most of the wavelength spectrum of the lowest branch of rather thick shells. However, for the very thick shell (with a ratio of inside radius to outside radius less than 0.5), only the exact theory shows the full characteristics of the displacement distribution.
Rating Scale Method for Comparative Loudness Measurements
Authors: Michels Walter C. , Doser Beatrice Taylor
Published: September 2005

A recently developed method for the use of comparative rating scales in psychophysical measurements has been applied to loudness judgments. It is found that the theoretical predictions are verified to within the experimental accuracy but it is indicated that the method is subject to certain limitations, which prevent complete verification of the theory. The values of the various undetermined parameters which enter into the prediction of judgments have been determined. It is found that the self-adaptation in hearing is large (80%), and that the effects of residual stimuli and of other stimuli than the standard or the stimulus being judged are extremely small.
On the Stability of Random Systems and the Stabilization of Deterministic Systems with Random Noise
Authors: Samuels J. Clifton
Published: September 2005

A general theory of mean square stability of random linear systems is developed when several system parameters vary as white noise stochastic processes. It is found that stability in mean square is determined from the character of the roots of a determinantal equation involving the Fourier transforms of double products of the weighting functions of the “average” system and the spectral densities of the parameter processes.

The general theory is applied to the mean square stability of an RLC circuit in which the resistance and capacitance have purely random fluctuations.

In the course of the study, a new type of dynamic stability is predicted, namely, the possibility of stabilizing unstable deterministic systems with random noise. Preliminary experimental studies appear to confirm this theoretical prediction.
Absolute Pitch
Authors: Bachem A.
Published: September 2005

The author, who possesses absolute pitch since the time of his earliest musical experiences at the age of five years, has spent much time in studying this musical phenomenon. Amused by the fact that the most extensive work on “absolute pitch” was conducted by psychologists who did not possess this faculty and that it was done on large groups of students, none of whom possessed this faculty either [For exception see O. Abraham, Sammelbde d. Internat. Musikges 3, 1 (1901) and G. Révész, Zur Grundlegung der Tonpsychologie (Leipzig)], he was convinced that a study by a possessor of absolute pitch on himself and on a large number of other possessors of absolute pitch might lead to different and better results. An original study [A. Bachem, J. Acoust. Soc. Am. 9, 146 (1937)] was conducted on 96 possessors of absolute pitch and 7 more or less musical persons without this faculty for comparison. The work was extended in the course of time to specific related problems which presented themselves through several discoveries.
Speed of Sound in Sea Water as a Function of Temperature, Pressure, and Salinity
Authors: Wilson Wayne D.
Published: September 2005

Tables for the speed of sound in sea water are presented. These tables have been prepared from an empirical formula which was derived to fit measured sound-speed data obtained over the temperature range −3°C to 30°C, the pressure range 1.033 kg/cm2 to 1000 kg/cm2, and the salinity range 33‰ to 37‰. The discrepancy of −3.0 m/sec found by Del Grosso at 1 atm., as compared to the tables of Kuwahara, is substantiated. In addition, the pressure coefficient of sound speed observed in the present work differs from that predicted by Kuwahara.
Simple Anechoic Tank for Underwater Sound
Authors: Toulis William J.
Published: September 2005

The walls of an underwater sound tank may be made highly absorptive by using thin SOAB wedges to minimize the mismatch at the interface. The performance of an experimental tank has been highly effective at frequencies as low as 10 kc. Design and maintenance problems have been very simple.
Difference Limen for the Intensity of a Vowel Sound
Authors: Flanagan James L.
Published: September 2005

An exploratory experiment to determine just discriminable differences in the intensity of a synthetic vowel sound is described. Results of AB listening tests performed with intra-sample time spacings of 0.5, 1.0, and 1.5 seconds are given. The median value of the DL for vowel intensity obtained from the tests is 1.5 db, and the DL is never less than 1.2 db. Tentative data on the time error for a vowel sound are noted and compared to similar data for pure tones.
Audience and Seat Absorption in Large Halls
Authors: Beranek Leo L.
Published: September 2005

From detailed acoustical studies made in over 40 large concert halls and opera houses in 15 countries, absorption coefficients are derived for audience, chorus, and orchestra areas, unoccupied seating areas, plaster walls and wood walls. It is postulated that the absorbing power of a seated audience, chorus or orchestra in a large hall is proportional to the floor area it occupies. This postulate is validated for audience densities of between 4.5 and 8.5 sq ft per person, including aisles, and for halls with volumes between 200 000 and 1 500 000 cu ft. The “area” concept as opposed to the “per person” concept of audience absorption explains the serious differences reported repeatedly in the literature between reverberation times calculated during design and those measured after completion of the halls. This paper also presents graphical relations between empty and fully occupied hall reverberation times; shows the effect of seat design on empty hall reverberation times; and gives typical reverberation time vs frequency characteristics for fully occupied halls. The results of this study may not be applicable to rooms whose volume, shape, and materials are substantially different from the large concert halls and opera houses included this study.
Value of Ear Defenders for Mental Work during Intermittent Noise
Authors: Woodhead Muriel M.
Published: September 2005

Ear defenders were worn for protection against the distracting effects of bursts of loud, but not unacceptable, noise during a mental task. Two types of noise were used: one characterized by high and the other by low frequencies. Performance was better with defenders than without them. The improvement was particularly marked with the high-frequency burst.
Diffraction of Light by Two Ultrasonic Waves of the Same Frequency
Authors: Zankel K. L.
Published: September 2005

The diffraction of light by two parallel ultrasonic waves of the same frequency is investigated. Measurements which were made with waves 180° out of phase with each other agreed with the predicted results. When the two waves were made nearly identical, the diffraction vanished almost completely. It is suggested that this might be applied as a method for the comparison of ultrasonic pressures, the measurement of absorption, and the investigation of finite amplitude distortion.
Evaluation of Two Formant-Extracting Devices
Authors: Flanagan James L.
Published: September 2005

A procedure for evaluating the operation of two electronic formant extractors is described and results of the evaluation are given. The formant extractors are designed to yield electrical outputs representing the formant frequencies of continuous input speech. These outputs are compared in a prescribed manner to formant data derived from sound spectrograms. The results show that the more reliable extractor of the two follows the first formant of vowel sounds in speech within ±150 cps greater than 93% of the time; it follows the second formant within ±200 cps greater than 91% of the time. The first and second formant outputs of the same extractor are simultaneously within the above tolerances greater than 85% of the time.
Sound Propagation into a Moving Medium
Authors: Franken Peter A. , Ingard Uno
Published: September 2005

If one in the study of transmission of sound into a moving medium allows flow speeds larger than twice that of sound, the analysis indicates at least formally the existence of two critical angles between which total reflection occurs. A discussion of the corresponding behavior of the angle of refraction and the reflection coefficient is presented.
Sound Radiation from the Acoustic Boundary Layer
Authors: Ingard Uno , Pridmore-Brown David
Published: September 2005

The sound radiated from a finite rectangular plate in an infinite wall oscillating in shear motion is calculated. The order of magnitude of the intensity of this sound field is compared with that which is produced when the plane oscillates with the name amplitude in a direction normal to its surface.
Transient Interaction of an Acoustic Wave with a Circular Cylindrical Elastic Shell
Authors: Payton R. G.
Published: September 2005

An infinitely long, circular cylindrical elastic shell is surrounded by an acoustic fluid. A plane pressure pulse, whose front is parallel to the axis of the shell, moves through the fluid, strikes the shell, and subsequently engulfs the shell.

The circular shell is replaced by a fictitious Riemann surface which effectively allows the range of θ (the angular coordinate) to be extended from − ∞ to + ∞. Exact expressions are then found for the subsequent shell and fluid motion in the form of double integrals by the use of integral transform techniques. These integrals are evaluated asymptotically by the method of steepest descent to determine the early time motion of the shell and fluid. In particular, it is found that during this early motion the radial shell velocity and bending moment have a maximum, and the fluid pressure at the interface experiences a minimum.
Ultrasonic Irradiation of the Central Nervous System at High Sound Levels
Authors: Fry William J. , Dunn Floyd
Published: September 2005

High level ultrasound produces, under properly controlled dosage conditions, selective changes in the central nervous system. The physical mechanism of the action of the sound requires elucidation. Some of the problems associated with determining the physical mechanism are discussed and a preparation and procedure are described which are appropriate for accurately determining dosage relations for such a study. The quantitative results obtained with this preparation are presented.
Mechanical Impedance Measurements of Soils
Authors: Runyan Walter R. , Anderson Robert E.
Published: September 2005

A method of measuring the mechanical impedance of the earth is described, and some experimentally measured impedances as functions of water content, soil character, and source diameter are given. A comparison of the measured impedance with some previous theoretical work is also included.
Vibration Sensitivity of Condenser Microphones
Authors: Rule E. , Suellentrop F. J. , Perls T. A.
Published: September 2005

The problem of operating condenser microphones in a vibration environment is considered, and it is pointed out that there is a precise relation between the vibration and pressure response for any given transducer. This relation is shown to be dependent on the mass per unit area of the microphone diaphragm, and graphs are given from which the suitability of a given microphone to perform its function in a vibration environment can be assessed. The results of measurements on a well-known type of condenser microphone are presented to support the theory, and the usefulness and disadvantages of vibration-isolating mounts and of systems using two transducers are discussed. A proposed design of a condenser microphone to be insensitive to vibration is described.
Compressibilities of Aqueous Nitrate Solutions
Authors: Subrahmanyam S. V. , Bhimasenachar J.
Published: September 2005

Ultrasonic velocities in aqueous solutions of NaNO3, KNO3, Ca(NO3)2⋅4H3O, Sr(NO3)2, Pb(NO3)2, and Ba(NO3)2 are determined making use of a variable path interferometer. These solutions have a common nitrate ion. The effects of different cations on the compressibilities are studied and discussed on the basis of coulomb forces.
Ambient Noise in a Deep Inland Lake
Authors: Lomask Morton R. , Saenger R. Alfred
Published: September 2005

Background noise spectra from 11–250 cps have been obtained in a deep inland lake in the absence of wind, waves, shipping, and marine life. An upper estimate of the spectrum level is given. It is 10 db lower than that of the Knudsen zero sea-state curve and its extrapolation to 11 cps. Measurements were also made of the variation in time of the spectrum under moderately rough surface conditions. From 90 to 250 cps the spectrum appears to be generated by the wind, and there is no significant depth effect at these frequencies over the depth range 68–244 ft. This report also discusses special instrumentation problems in the measurement of very low-level, nonstationary ambient noise.
Anomalous Behavior of Rayleigh Disk for High-Frequency Waves
Authors: Awatani Jobu
Published: September 2005

The behavior of the Rayleigh disk whose size cannot be neglected in comparison with the wavelength is investigated. Results obtained are as follows. The sensitivity of the disk set to an angle 45° increases with the frequency of sound and reaches a maximum at the frequency corresponding to k( equals; 2πa/λ)≅1.6, (a is the radius of the disk, λ the wavelength of sound). This maximum value is about 50% larger than that calculated from the König's expression. When k becomes larger than 1.6, however, the sensitivity begins to fall off and its sign, at last, changes to negative when k≅4.5. In the high-frequency region, the negative torque acts on the disk if the angle between its axis and the wave normal is small, but the positive torque if the angle is large. The disk displays the greatest sensitivity at an angle different from the ordinary angle 45°.
High-Frequency Calibration of an ADP Crystal Microphone
Authors: Macpherson P. A. , Thrasher D. B.
Published: September 2005

The free field sensitivity of a microphone over the frequency range 10 000 to 100 000 cps is determined by the reciprocity technique, in which the transducers are oriented perpendicular to each other in order to minimize diffraction effects. This orientation introduces a complication when the wavelength of sound is comparable to or smaller than the diameter of the microphone face. On theoretical grounds it is established that the sensitivity of the microphone should fall to zero at a discrete set of frequencies. Experimental minimum responses were observed that are in reasonable agreement with the theory.
Scattering of Sound by Sound
Authors: Ingard Uno , Pridmore-Brown David C.
Published: September 2005

Calculations and measurements are reported of the summation and difference frequency components which are scattered from the interaction region of two sound beams in air intersecting each other at right angles.
Masking of Tonal Signals
Authors: Jeffress Lloyd A. , Blodgett Hugh C. , Sandel Thomas T. , Wood Charles L.
Published: September 2005

Many of the phenomena of masking can be explained on the basis of two models, one for monaural listening, and the other for binaural. The monaural model is the familiar narrow band-pass filter followed by a detector responsive to changes in output level. The binaural model is a series of coincidence detectors associated with a delay-network capable of matching delay in the stimulus with a delay in the neural path.

The two models have proved helpful in understanding the phenomena of tonal masking, and have led to a number of predictions which have been subsequently verified by experiments reported here. Some of the new findings are related to monaural masking and some to binaural. Among the latter are the fact that masking-level differences can be observed in the masking of one pure tone by another when a short signal is employed, and that a binaural signal can be heard in the presence of uncorrelated noise at the two ears better than a monaural signal can be heard against noise presented monaurally, again provided that a short signal is employed.

Many studies of the masking of tones have appeared during the past few years. They have been characterized by close agreement in results wherever they have had common conditions, and they provide a large body of dependable quantitative information. With this body of fact there also grew, at least in the minds of present writers, a considerable state of bewilderment. Many of the facts appeared to contradict inferences drawn from others. The present paper discusses a number of these facts and attempts to encompass them under a few explanatory principles.
Jet Noise Problem in Aircraft Carrier Islands
Authors: Pietrasanta A. C.
Published: September 2005

Noise during jet aircraft launching operations seriously interferes with communications in important island spaces aboard aircraft carriers. Measurements of sound pressure levels made in these spaces during normal jet operations at sea are reported. It was found that these levels could be estimated from a knowledge of jet engine operating conditions [A. C. Pietrasanta, J. Acoust. Soc. Am. 28, 434 (1956)] and the physical properties of the structures involved. The problem of the selection of criteria for speech communication is discussed. Noise reduction requirements for island spaces, based on estimated noise levels of present and future jet aircraft, are presented.
Sound Pressure Spectra of a Muted Cornet
Authors: Ancell James E.
Published: September 2005

Acoustic spectra of a cornet have been measured with the instrument equipped with several mutes of types used mainly in dance orchestras. Data are presented showing the sound pressure levels of the first 10–15 partials of the instrument when fitted with each of the mutes. The instrument was blown naturally by a cornetist, with an attempt to obtain a normal characteristic tone for each mute. The sound spectrum of the muted instrument is compared to that of the open or unmuted instrument. The mutes tend to exhibit the same formants for several different notes, indicating resonance phenomena in the acoustic networks. The measurements were made by playing the instrument in a dead room, and recording the sound on tape, with a condenser microphone and a magnetic tape recorder of professional quality. The sounds were then analyzed by playback through a heterodyne wave analyzer. Two of the mutes, the Harmon and the Solotone, are equipped with cylindrical aluminum tubes, open at both ends. The formants for these mutes display families of resonance peaks corresponding to the calculated open pipe frequencies. These resonances are also observed when the mutes are driven with an electroacoustic transducer. All of the mutes themselves act as Helmholtz resonators at 200 to 300 cps, which is, however, in the frequency range of considerably reduced output when fitted to the instrument.
Propagation of a Pressure Pulse in a Compressible Flow—Coda
Authors: Powell Alan
Published: September 2005

As explained previously [J. Acoust. Soc. Am. 31, 1527–1535 (1959)] the disturbances due to an initially step-like pressure wave progressing down a channel carrying a compressible flow can be analyzed by a multiple reflection method. For the final “transmitted” and “reflected” pressures, this yields a power series expansion, successive terms representing the effect of higher order reflections. It is now shown that the coefficients of these series are connected to Euler's and Bernoulli's numbers, respectively, and convenient expressions for the coefficients are given. When n is not small, the coefficient cn≃2(2/π)n+1. The infinite power series are shown to have sums simply like sechx and tanhx, respectively. This provides an easy means of numerical evaluation, and gives simple criteria for the accuracy of the approach using the leading term of each of the series. The results when reflections of all orders are taken into account are shown to be analytically identical to those of the “before” and “after” steady flow method.
Ultrasonic Dispersion in a CO2 - H2O Mixture
Authors: Gutowski Frank A.
Published: September 2005

The velocity of ultrasonic waves was measured in CO2 containing a 0.01 mole-fraction of water vapor at the frequencies 1001.8 kc and 540.6 kc in the range from 0.5 Mc/atmos to 6 Mc/atmos at 35.1°C. The mixture was prepared at one fixed CO2 and H2O pressure to give greater assurance of constant composition and was analyzed for water content by gravimetry. Variation of pressure within the interferometer was obtained by varying the rate of flow with a precision needle valve. Complete symmetry of current peak structure and hence a more accurate determination of wavelength was obtained by the technique of continually compensating for frequency shift due to the variation of acoustic impedance of the gas column. The velocity was found to vary from 286.2 m/sec at 6 Mc/atmos to 278.1 m/sec at 0.5 Mc/atmos. The experimental points fit the curve for a single relaxation time of 3.03×10−7 sec corresponding to an inflection frequency of 740 kc/atmos.
Study of MAYDAY and S.O.S. as Radiotelephony Distress Signals
Authors: Neely Keith K.
Published: September 2005

MAYDAY and S.O.S. were compared in the presence of noise and speech to determine their relative detectability values (audibility thresholds). Results of the tests indicated that S.O.S. had the lower audibility threshold and therefore the greater detectability value.
Trapping of Acoustic Energy Near a Source Above a Submerged Elastic Plate
Authors: Biot M. A. , Rosenbaum J. H.
Published: September 2005

The propagation of acoustic waves in a layered medium is considered for the case of an elastic plate submerged at a certain depth below the surface of a liquid-filled half-space. It is shown that there exist unattenuated modes for the plate-liquid layer system which have horizontal phase velocities greater than the sound velocity in the liquid. In spite of such greater phase velocities, radiation into the liquid below does not take place because the lower surface of the plate exhibits no vertical motion. Thus, energy can be trapped in and above the plate by vibrations which leave the underlying liquid undisturbed. It is pointed out that radiation in the horizontal direction may also be very small when the above conditions of total reflection are approximately satisfied, as is indicated by the existence of low group velocities for the modes of a free plate. Attention is called to the three-dimensional nature of such trapping, vertically by an approximate condition of no transmission across the plate, and horizontally by the simultaneous vanishing of the group velocity at nonvanishing angles of incidence. The present modes are in contrast with the usual case of total reflection and “wave guide propagation” in layered elastic media, where the horizontal phase velocity is less than the sound velocity in the liquid (lower half-space), and the signal below the plate decays exponentially with distance from the interface. Conditions under which the present modes can arise have been found and evaluated numerically. Relations between phase velocity, wave number, and ratio of fluid layer to plate thickness are presented for a lucite plate is water. These have been compared with the results of much more elaborate calculations for the point source “singing” problem.
Speech Reception and Temporary Hearing Loss as a Function of Exposure to High-Level Noise
Authors: Tolhurst Gilbert C.
Published: September 2005

Two studies were made to assess the effects of high-level noise (1) upon efficiency in speech reception and (2) in causing temporary hearing losses. Over 1400 observers made responses under various sound-pressure levels for each of 13 different noise spectra. It was found that: (1) Increases in noise level always adversely affected speech reception, while changes in spectra did not always have an effect; time-in-noise did not progressively decrease scores. (2) Hearing threshold shifts of 4 to 5 db were found after a 2-hr noise exposure; certain spectra caused greater threshold shifts than others.
Capacitive Accelerometers with Optimum Frequency-Response Characteristics
Authors: Rule Eric , Suellentrop Fred J. , Perls Thomas A.
Published: September 2005

A series of capacitive accelerometers with frequency-response characteristics governed by the resistive and elastic properties of a thin air film are described. The accelerometers have been designed, in accordance with theory developed previously to have response constant within ±5% at frequencies up to 1.48 times the undamped natural frequency. Experimental data are given to show that the accelerometer response agrees closely with that predicted theoretically.
Random Response of Two Coupled Resonators Without Loading
Authors: Morrow Charles T. , Troesch B. Andreas , Spence Harry R.
Published: September 2005

The root mean square response of a simple mechanical resonator mounted on another, which is excited by vibration of a flat motional power spectrum, is investigated theoretically for the case of no loading effect between resonators. While the solutions are not general for any pair of coupled resonators, the condition of zero loading is of particular interest, as it leads to extreme vulnerability of electronic and electromechanical equipment to shock and vibration when there is a coincidence of resonance frequencies of coupled resonators. Approximate formulas are obtained and computed by hand. The exact equation is solved on a digital computer to yield a series of curves for comparison. The approximate formulas hold surprisingly well, except when the resonators are close in frequency and highly damped. Curves of the derivative of the rms response, as one resonance frequency or the other is varied, are obtained by use of the digital computer. They illustrate the importance of mechanical tolerances in relation to detuning as a factor in design changes for improved reliability.
Some Periodic Variations in Low-Frequency Acoustic Ambient Noise Levels in the Ocean
Authors: Wenz Gordon M.
Published: September 2005

Variations in underwater acoustic ambient noise spectra, from 20 to 1250 cps, were analyzed using a statistical filter technique to examine the spectral density functions in the range from 1 to 80 cycles per week. At frequencies below 100-cps narrow band components at seven cycles per week were observed in the spectral density functions. In several cases harmonics of the seven-cycle-per-week component were also evident. The period of the cyclic variation agreed more closely with the solar day than with tidal period. The maxima occurred at approximately midnight local zone standard time, and at one location additional maxima were observed at approximately noon. The magnitudes of the periodic variation were small, 1.5 to 5.0 db, showing little evidence of seasonal dependence, except that at one location daily changes of 10 to 20 db were observed during the period of the summer solstice while hardly any periodic change was evident during the winter solstitial season. These periodic changes in the ambient noise levels were not correlated with changes in local wind speed.
Computer Identification of Vowel Types
Authors: Foulkes J. D.
Published: September 2005

In a classical study of the vowel sounds of English, G. E. Peterson and H. L. Barney collected a large body of experimental data which related perceived vowel quality to measurements of the first three formant frequencies and the voice pitch. It is difficult for a computer to use this raw data to interpret vowel quality because the vowel types have complicated boundaries in the coordinate system of the physical measurements. This paper describes a coordinate transformation which simplifies these boundaries.
Masked Threshold and Its Relation to the Duration of the Masked Stimulus
Authors: Thwing Edward J.
Published: September 2005

Previous investigations have shown that the masking capacity of a prolonged auditory stimulus remains constant over its duration in spite of its great diminution in loudness. The experiments which follow were designed to determine the relation between the masked threshold and the duration of the masked stimulus. The results show that (1) within limits, as the duration of a pure tone is increased less noise is required to mask the tone, (2) the magnitude of this effect increases as a function of frequency of the masked tone but appears to be independent of its SPL, and (3) in general, these effects diminish somewhat with practice.
Simple Axisymmetric Thickness Vibrations of a Soft Elastic Cylinder with a Hard, Thin, Elastic Skin
Authors: Chu Hu-Nan
Published: September 2005

Frequency equations of simple axisymmetric axial shear and simple axisymmetric radial vibrations were obtained for a soft elastic cylinder with a hard, thin, elastic skin. The soft core is treated on the basis of the three-dimensional exact equations of elasticity while the thin skin is regarded as a membrane. Numerical frequencies for the first several modes for various values of the skin thickness were tabulated and their implications discussed.
Auditory Detection of the Presence and Absence of Signals in Noise
Authors: Fairbanks Grant , House Arthur S. , Melrose Jay
Published: September 2005

An experiment is described in which detection of the absence of signal remained high and relatively constant while detection of intermixed signals varied over the threshold region as a function of signal voltage. Statistical signal detection thresholds of observers with set to detect absence of signal were approximately 2 db lower than those of observers with set to detect signal.
Vibration and Sound Radiation of Damped and Undamped Flat Plates
Authors: Greene David C.
Published: September 2005

Because of the many resonances, plates have an extremely small driving-point impedance, add accurate measurements are difficult to perform. Some of the fundamental difficulties that accompany such measurements are illustrated by experimental results. Measurements performed with thin, rectangular plates show that the asymptotic laws of vibration and sound radiation predict, within the range of experimental error, the characteristic impedance and the sound radiation of plates. The theoretical prediction that damping would have no appreciable effect on either the characteristic impedance or the background level of the radiated sound pressure was found to be accurate.
Sensitivity of the Water-Immersed Ear to High- and Low-Level Tones
Authors: Montague W. E. , Strickland J. F.
Published: September 2005

Two experiments are reported regarding man's sensitivity to waterborne sound. The first study investigated the threshold sensitivity to tones of 250, 500, 1000, 1500, 2000, 3000, 4000, and 6000 cps and the attenuation due to the diver's hood. The second experiment obtained data on the “tolerance” to a high-intensity tone of 1500 cps.

The sound-pressure level needed to reach threshold in water is about 40–70 db higher than the MAP threshold in air. The greatest loss in sensitivity occurs in the regions of greatest air sensitivity. The diver's hood was found to provide about 20 db or more of attenuation of underwater sound at frequencies above 1000 cps.

The “tolerance” limits for hoodless divers is approximately 174 db re 0.0002 dyne/cm2. When wearing the hood divers were able to tolerate at least 180 db, the system's maximum output. Above 165 db all divers reported some distortion of the visual field.
Measurement of the Noise of Ducted Fans
Authors: Van Niekerk C. G.
Published: September 2005

A proposed technique for measuring the noise of a ducted fan by means of a microphone placed inside the fan duct was evaluated by comparing results so obtained with those obtained by measuring the total sound energy radiated from the duct into a reverberation chamber. A suitable microphone windscreen was developed and was used to reduce the aerodynamic self-noise generated by the microphone to a negligible minimum. Good correlation was obtained, and by studying transverse resonance conditions in a duct it was attempted to show how suitable microphone stations could be found to eliminate measuring errors caused by the existence of standing waves.
Auditory Threshold Shifts Produced by Simultaneously Pulsed Contralateral Stimuli
Authors: Sherrick Carl E. , Mangabeira-Albernaz Pedro L.
Published: September 2005

Evidence from studies of tactual sensitivity indicates that transient suprathreshold stimuli presented simultaneously with and contralateral to test signals will mask such signals more effectively than do steady stimuli. The present report presents evidence that when pulsed masking sounds are presented simultaneously with pulsed auditory signals, two major effects are observed: First, a significantly greater amount of contralateral masking is obtained with the pulsed masker than with the steady masker, and, second, the pulsed masker is more effective in the monaural condition also. Furthermore, the masking effect of pulsed maskers increases with the increase of signal frequency, but not with increase of masker intensity. The frequency of the masker must be near that of the signal to be effective, and if pure-tone maskers are used with pure-tone signals, the masking effect shifts continuously to the localization effect as the signal frequency approaches the masker frequency. Some explanations of binaural and contralateral masking are discussed.
Recognition of Speech by a Computer Program that was Written to Simulate a Model for Human Visual Pattern Perception
Authors: Uhr Leonard , Vossler Charles
Published: September 2005

A computer simulation program for visual “pattern recognition” has been tested on an array of extremely degraded spoken digits. The program develops its own set of operators, as a function of its experience with inputs presented to it; so it does not depend upon preanalysis of a specific problem. The program gave (on an array of five different numbers) 100% success on words that had been presented to it for “training” purposes, and 100% success on words spoken by speakers different from those used in training. Results with alphabetic patterns, in which 5-, 10-, and 26-letter arrays were all learned to 100% success, suggest that larger arrays of spoken words may give similar results.
An Approximation to the Remainder of Robey's Reactive Impedance Integral
Authors: Greenspon Joshua E.
Published: September 2005

A procedure is outlined for computing the remainder of Robey's Reactive Impedance Integral for the self and mutual impedance of rings on an infinitely long rigid cylindrical baffle. It is assumed that numerical integration has been carried out to a given point. The remainder of the infinite integral is then computed in terms of the well known sine and cosine integrals which have already been tabulated in the literature.
Comments on a Recent Paper by Hueter et al. on Ultrasonic Lesions in the Central Nervous System
Authors: Fry William J.
Published: September 2005

The recent paper by Hueter et al. on ultrasonic lesions in the central nervous system, which appeared in a recent issue of this Journal (March, 1956), presents a rather limited view of this field and may lead to some misunderstandings.

This note is a critical analysis of the Hueter paper. Some of the more important points discussed are: (1) The unique advantages of producing ultrasonic lesions in the brain by using dosages appropriate for selective action combined with focusing of the beam in contrast to the use of focusing alone. (2) The choice of an irradiation procedure in experiments designed for the elucidation of physical mechanisms of the action of ultrasound on tissue. (3) The specification of the acoustic variables required for a dosage description. (4) The inapplicability of Eyring's theory of viscosity, plasticity, and diffusion to the elucidation of observed dosage relations. (5) The clarification of the usage of the terminology, nontemperature effects. (6) The applicability of the reciprocity method for the calibration of thermo-couple probes.
Ultrasonic Absorption in Alkyl Iodides
Authors: Narasimhan V.
Published: September 2005

Measurements of the absorption coefficients of some alkyl iodides at several temperatures are described. The values differ markedly from those reported by some earlier workers.
Laboratory Measurements of Sound Transmission through Suspended Ceiling Systems
Authors: Hamme Richard N.
Published: September 2005

A laboratory facility is described as evolved for the measurement of sound transmission through suspended acoustical ceilings under field conditions of erection over part high partitions. The results of exploratory measurements are reviewed for a wide range of the dimensional and acoustical parameters of the ceiling-plenum system. Consideration is extended to the ceiling-partition system and to the importance of an accurate simulation of field conditions of erection for the testing of all elements, individually and interacting, in the ceiling-plenum-partition system. The compatibility of this approach with conventional test methods is suggested.
Phasor Analysis of Some Stereophonic Phenomena
Authors: Bauer Benjamin B.
Published: September 2005

An improved understanding of some stereophonic phenomena may be obtained by use of acoustical pressure phasors to portray sound pressure at the ears of the observer. With the help of phasors it is possible to expand and modify certain conclusions of previous observers, and to validate some previously unpublished observations; stereophonic “law of sines” is derived. The existence and location of “out-of-bounds” stereo-phonic image is analyzed and verified. The “allowed maximum out-of-phase ratio” is derived, together with the observation that this maximum is exceeded by certain microphone arrays. The motion and elevation of the center image in stereophonic reproduction is observed and explained.
Just Noticeable Differences in Dichotic Phase
Authors: Zwislocki J. , Feldman R. S.
Published: September 2005

The just noticeable difference in dichotic phase, as a function of sensation level and of frequency, has been determined on a number of listeners with normal hearing. The test tones were transmitted by earphones, and the phase difference between the ears was varied by means of an electronic phase shifter. The psychophysical method used combined paired comparisons and forced choice. The first tone pulse of each pair presented was kept at a constant phase difference at which the subject localized the sound source as equidistant from his ears. The dichotic phase difference of the second pulse was varied irregularly (“randomly”). The results show that the sensitivity to dichotic phase difference is highest (2° of phase) at medium sensation levels, and that the jnd increases with positive acceleration as the sound frequency increases. Around 1300 cps the jnd becomes so great that it cannot be measured. The dichotic time difference calculated from the measured jnd in phase has a minimum near 800 cps.
Contralateral Threshold Shift and Reduction in Temporary Threshold Shift as Indices of Acoustic Reflex Action
Authors: Loeb M. , Fletcher J. L.
Published: September 2005

The purpose of the experiment was twofold: to compare the effectiveness of narrow band noise and a train of clicks in eliciting the middle-ear acoustic reflex, and to correlate two methods of estimating amount of reflex activation. One method involved measurement of increase in threshold in the contralateral ear, the other, measurement of reduction of TTS produced by a series of gun shots. Sixteen subjects were employed. Shifts produced by the clicks and noise were of the same order of magnitude (after correction for the direct masking effect by the clicks), but there was considerable reflex adaptation to the noise and none for the clicks. Correlations between contralateral threshold shift and reduction of TTS were small and not significant.
Hearing Threshold for Periodic Tone Pulses
Authors: Plomp R.
Published: September 2005

In continuation of a previous paper, the relation between threshold, repetition time, and duration for periodically repeated tone pulses is treated. Experimental data at test frequencies of 250, 1000, and 4000 cps appeared to agree very well with a derived relation based on the following assumptions: Switching on a sinusoidal signal of intensity I results in an effect s somewhere in the hearing pathway, that approaches its final value asymptotically according to an exponential function; switching off this signal gives a decay of s also according to an exponential function; perception occurs when s exceeds a critical value s0. For the time constants of the growth and decay of s the same value could be chosen, being in agreement with the corresponding value for single tone pulses (0.2–0.3 sec). For very short repetition times, the data deviate from the predicted curves, which is explained by the assumption that energy integration is restricted to a fixed bandwidth. These critical bandwidths determined for the periodic tone pulses are also in harmony with the results for single pulses.
Neurological Theory of Beat Tones
Authors: Meyer Max F.
Published: September 2005

Tartini pitches and beat tones behave differently and must have different physiological origins. Tartini pitches are heard only if the primary tones remain below 2000 cycles per second, preferably for clear observance below 1000. The cochlea is essential for hearing them. Beat tones are not so limited. Their observation is easiest (least confusing) when the primaries are chosen in the region from 3000 to 5000 cycles per second. But lower tones may be used (although there may then be an overlapping of Tartini pitches and beat tones). The cochlea need not exist for the existence of beat tones.
Masking of Pulsed Tones by Bands of Noise
Authors: Small Arnold M. , Campbell Richard A.
Published: September 2005

If a 2200-cps tone is pulsed 150 times/sec under appropriate conditions, a low pitch (periodicity pitch) will be heard corresponding to that of a 150-cps pure tone. This experiment investigates the effectiveness of different bands of filtered noise in the masking of such pulses and in the masking of two pure tone stimuli, 150 and 2200 cps. Although the pulses and 2200-cps pure tone yield quite different pitches, the present results indicate that the masking of each requires nearly identical frequency components and levels of noise. The 150-cps tone, although yielding a pitch approximating that of the pulses, requires greatly different characteristics of noise to mask. Considering differences in apparatus and technique, reasonable agreement with other studies of pure tone masking by bands of noise is found. If masking is viewed as a neural phenomenon, these data provide additional evidence of the neural nature of periodicity pitch.
Theory of Recognition
Authors: Tanner Wilson P.
Published: September 2005

The theory of statistical decision has previously been applied to the problem of sensory detection of signals. In this paper, the theory is expanded to treat a simple recognition problem. While the data supporting the expansion have been collected in auditory experiments, the theory applies generally to all human sensory behavior.
Vortex-Ring Structure-Transition in a Jet Emitting Discrete Acoustic Frequencies
Authors: Anderson A. B. C.
Published: September 2005

Visualization of the vortex flow pattern in typical jets emitting jet tones was made by means of shadowgraph techniques to show the nature of the ever present process of vortex coalescence in the jet and how this determines the values of the eigenton sound frequencies radiated by the jet. These frequencies are super-imposed on the noise background radiated by the jet. The dependence of (a) vortex shedding frequency from the orifice, (b) jet-tone frequencies, and (c) translational velocity of the vortices on Reynolds number (Re) is shown.

These studies were carried out with carbon dioxide jets discharging into the atmosphere. The flow channel geometry consisted of an orifice plate containing a sharp-edged, circular orifice, 0.250 in. in diameter and 0.093 in. thick attached to a large stilling tank partly filled with sound-absorbing material to eliminate any effects of cavity resonance on the jet. The studies were carried out over the range from Re zero to Re 7000, where Re = vρt/μ and v is mean velocity of discharge of jet; ρ, gas density; t, orifice plate thickness, and μ, gas viscosity.
On Preferred Frequencies for Acoustical Measurement
Authors: Wang Paul
Published: September 2005

A new table of frequencies is suggested to American Standards Association as amendment to S1. 6-1960.
Low-Frequency Sound Propagation in Gases
Authors: Smith F. A. , Tempest W.
Published: September 2005

A resonance-tube method has been developed for the measurement of sound absorption and velocity in gases at frequency to pressure ratios from 36 to 3800 cps atm. Measurements in oxygen at 30°C show velocity dispersion and excess absorption due to relaxation of the vibrational mode of the oxygen molecule with a relaxation time of 3.2±0.3 × 10−3 sec. The results are in agreement with those obtained by Knotzel and Knotzel.
Frequency of Edge Mode of Isotropic Thin Rectangular Plate, Circular Disk and Rod
Authors: Onoe Morio
Published: September 2005

The frequency of the edge mode, which is closely associated with the complex branches of the dispersion equation, has been approximated by taking only the complex branches into account.

The frequencies for a thin rectangular plate, a circular disk and a rod have been evaluated as functions of Poisson's ratio and compared with the observed values by various investigators.
Measurement of Noise Canceling Effectiveness of Microphones
Authors: Levine Leo M. , Hershkowitz Joseph
Published: September 2005

The noise canceling effectiveness of a microphone is determined by measuring the random noise discrimination as a function of frequency under conditions simulating actual usage, and then using this characteristic to compute the articulation index for an ideal system containing the microphone, when operating under specified noise and speech conditions. Results so obtained are shown to correlate with those of articulation tests for three microphones evaluated for three noise types at different noise levels.
Measurement of Diffuseness in Reverberation Chambers with Absorbing Material
Authors: Venzke G. , Dämmig P.
Published: September 2005

Measurements have been carried through about the angular distribution of sound traveling in a reverberation chamber in which a certain amount of absorbing material is installed. It was measured during the decay phase of sound. Two methods were used, the first one with a directional sound source and a nondirectional microphone, the second one using a nondirectional source and a directional microphone developed in the PTB. In the latter case, the differences of angular distribution of sound, impinging on the absorbing sample, could be shown for two different states of diffuseness accomplished in the reververation chamber by installing different numbers of diffusing elements in the room. The angular distributions were investigated at frequencies of 1.2, and 4 kc.