bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Absolute Sound Levels and Acoustic Absorption Coefficients by Thermocouple Probes—Experiment
Authors: Fry William J. , Fry Ruth Baumann
Published: September 2005

A stable, readily constructable thermocouple probe has been developed for determining absolute sound levels in ultrasonic fields in liquid media. This paper includes criteria for design of such probes and a discussion of experimental measurements made with such a device.

It is a consequence of the method that if the sound intensity at an appropriate size thermocouple junction imbedded in an absorbing medium is known the acoustic absorption coefficient of the material can be determined. The method thus makes possible the determination of absorption coefficients of minute quantities of material.

The probe consists of a thermocouple imbedded in a sound absorbing medium which closely matches in density and sound velocity the medium in which the sound level is to be determined. In use the transducer which generates the acoustic field is exctied to generate sound pulses with a rectangular envelope. The initial time rate of change of the temperature at the thermocouple junction is determined. In addition to the measurement of the temperature change, the calculation of the absolute sound intensity requires only a knowledge of the absorption coefficient of the imbedding material and its heat capacity per unit volume at the temperature at which the measurements are made.

The experimental results include a comparison of the sound level determined by a thermocouple probe and a determination by radiation pressure methods. The values obtained by the two methods agree within the uncertainty of the experimental measurements.
Wave Propagation in a Viscous Liquid Contained in a Flexible Tube
Authors: Morgan G. W. , Kiely J. P.
Published: September 2005

A theoretical analysis of the propagation of pressure waves through liquid filled flexible tubes is presented. Expressions are derived which show the dependence of phase velocity and damping factor on the viscosity of the liquid, and on internal damping in the tube wall. The analysis is restricted to tubes with thin walls and to waves whose amplitude is infinitesimal and whose wavelength is large compared to the radius of the tube.
An Acoustic Streaming Experiment in Gases
Authors: Medwin Herman
Published: September 2005

A radially symmetric progressive acoustic beam has been set up in a closed, gas-filled tube to cause streams driven by the Eckart, volume, source of verticity. A careful determination of the acoustic pressure at all points of a cross section of the beam has been used successfully to predict the stream velocities at this cross section, for argon. The work with argon and the results of further experiments with dry nitrogen and moist air indicate that: (1) the Navier-Stokes equation, the equation of continuity, and the acoustic “equation of state” p1 = ρ1c02+Rρ̇1, provide a valid basis for second-order studies of streaming; (2) thermal conduction effects may be introduced into the Eckart streaming equations in the same manner as they appear in the attenuation formulas; (3) the macroscopic quantity, bulk viscosity, is made up of contributions from the intramolecular processes of vibrational and rotational relaxation.
Axially Symmetric Vibrations of a Finite Isotropic Disk. IV
Authors: Aggarwal R. R. , Shaw E. A. G.
Published: September 2005

The method described in Part III has been applied to another normal mode of a particular disk by combining the motions corresponding to the one imaginary and two real values of α. The residual stresses at the cylindrical surface of the disk are small, and the displacement distribution of the plane surfaces agrees reasonably well with that obtained experimentally.
On the Identification of Speakers by Voice
Authors: Pollack I. , Pickett J. M. , Sumby W. H.
Published: September 2005

The effect of several factors upon voice identification was examined. These factors were: the size of the class of possible voices, the duration of the speech signal, the frequency range of the speech signal, voicing vs nonvoicing speech characteristics, and the simultaneous presentation of several voices. One of the most effective factors for speaker identification was the duration of the speech signal. Duration, as such, appears to be important, however, only insofar as it admits a smaller or larger statistical sampling of the speaker's speech repertoire.
Transmission of Sound through Thin Elastic Plates
Authors: Young James E.
Published: September 2005

The transmission of sound through thin elastic plates set in a plane infinite baffle or an infinite duct is discussed in some detail. A two-dimensional configuration is considered in both instances. The problems then are the transmission through a strip set in an infinite baffle and transmission through a plate set in a duct supporting lowest mode propagation.

These systems make it possible to indicate in a formal manner how the boundary conditions affect transmission. The notion of bending impedance is used as a means of categorizing the mounting conditions.

Experimental investigations of the transmission through circular plates in ducts of the same cross section were carried ont. It is shown that the transmission loss varies with the manner in which the plates are mounted. The conditions under which this behavior is predictable are discussed.
Oscillations of the Jet in a Jet-Edge System. II
Authors: Bouyoucos John V. , Nyborg Wesley L.
Published: September 2005

The use of low velocity dyed-liquid jets to obtain a motion picture history of the jet oscillation in a jet-edge system is discussed. A group of photographs selected from such a history is presented, illustrating the jet configuration between orifice and edge at various intervals in the cycle of the jet motion. These photographs are then compared with the profiles predicted by a theory of one of the authors. It is found that when the actual divergence of the jet stream is accounted for, good agreement exists between the theoretical profiles and those observed.
Measurements of the Tonal Characteristics of Carillon Bells
Authors: Slaymaker Frank H. , Meeker Willard F.
Published: September 2005

High quality magnetic tape recordings were made of individual bells at the carillon location, including bells cast by Meneely and Company, Watervliet, New York; Van Aerschodt, Louvain, Belgium; John Taylor and Company, Loughborough, England; Franz Schilling Söhne, Apolda, Germany. Measurements made on the tapes with a sound analyzer, Stroboconn and an automatic level recorder give the relative tuning, the relative amplitudes at the microphone position, and the decay rates of the various components in the bell tone.
The Measurement of Human Channel Transmission Characteristics
Authors: Munson W. A. , Karlin J. E.
Published: September 2005

The full benefits of modern communication engineering will be realized only when we have enough quantitative knowledge of the transmission properties of the human communication channel to guide technological development. This deficiency is a limiting factor in the effort to achieve economy of transmission through more efficient use of the time and frequency dimensions in peace time telephony and television; it has also become of serious concern in our inability to extract adequate information from marginal signals in military applications.

This paper uses concepts in information theory and psychophysics to provide a basis for the quantitative measurement of certain communication properties of the human being. Part 1 of the paper discusses testing techniques in which binary signals were used for measuring information transmitted over a human communication channel. Part 2 proposes a model of this channel for investigating the factors which influence this information rate. The model involves three parameters: the signal level, the noise level of the human circuits, and the discriminant level of the human circuits. Some illustrative experimental measurements of these parameters are included.
Observation of the Tartini Pitch Produced by “sin 9x+sin 13x”
Authors: Meyer Max F.
Published: September 2005

The combination of the physical tones of the frequency ratio 9:13 makes the secondary pitch 5 clearly audible; but neither the difference tone pitch nor the summation tone pitch, nor any so-called aural harmonic is audible. The theoretical discussion is based on the hydraulic (nonvibratory) mathematics of cochlear mechanics.
Ultrasonic Hysteresis in Viscous Liquids
Authors: Litovitz T. A. , Lyon T.
Published: September 2005

The ultrasonic absorption coefficients for longitudinal waves in glycerol and pentachlorobiphenyl are measured over the frequency range from 7.5 to 70 Mc. The measurements are made in the range of viscosities from 105 to 107 poise so that the ultrasonic frequencies used are well above the main relaxation frequencies associated with viscous flow processes in these liquids. The results indicate that the absorption coefficient per cm can be represented by the expression α = B plus; Hf, where B and H are constants and f is the ultrasonic frequency. The constants B and H in both liquids are found to decrease with increasing temperature, exhibiting an “apparent” activation energy of about 24 kcal/mole and 12 kcal/mole for the pentachlorobiphenyl and glycerol respectively.

It is concluded that the results found here indicate that both terms B and Hf found in a could best be explained by assuming that one or more distributions of relaxation times exist.

It is suggested that ultrasonic hysteresis in both liquids and solids have a common origin indicating that the hysteresis effect in liquids is not related to the viscous flow mechanism causing the absorption maximum at lower frequencies and viscosities. A possible mechanism offered for the hysteresis loss is the coupling of the acoustic energy into heat energy due to the anharmonicities in the lattice structure.
A Note on the Audibility of Intense Ultrasonic Sound
Authors: Deatherage Bruce H. , Jeffress Lloyd A. , Blodgett Hugh C.
Published: September 2005

This note is concerned with some observations on the audibility of ultrasound by bone conduction.
A Remark on the Transmission of Sound Pulses in a 2-Layered Liquid Half-Space
Authors: Uretsky Jack L.
Published: September 2005

Pekeris obtained a solution for the transmission of sound in a 2-layered liquid half-space by dealing with the Hankel transform of the potential function. It is shown that in satisfying the boundary conditions at the interface his method involves an unjustified interchange of a differentiation and an integration.
Loudspeakers and Microphones
Authors: Beranek Leo L.
Published: September 2005

This paper covers the development of loudspeakers and microphones and gives many illustrations of commercially available units dating from 1915 to the present time.
Sound Systems for Large Auditoriums
Authors: Beranek L. L.
Published: September 2005

This paper gives a comprehensive review of the design of sound systems for large auditoriums. It covers the following subjects: (a) When is a sound system necessary?; (b) Ambient noise effects; (c) Reverberation effects; (d) Classification of sound systems; (e) Behavior of direct-radiator, multi-cellular, acoustic lens and “column” types of loudspeakers; (f) Psycho-acoustic considerations; (g) Naturalness; (h) Loudspeaker arrangements; (i) Sound system in the large hall of the University City in Caracas, Venezuela; (j) Sound system in Plenary Hall of the United Nations Headquarters, New York City; (k) Stereophonic sound system in a municipal theatre; (1) Distributed “column” sound system in the Holy Cross Cathedral; and (m) Tests for evaluating sound systems.
Unidirectional Microphone Utilizing a Variable Distance between the Front and Back of the Diaphragm
Authors: Wiggins A. M.
Published: September 2005

A unidirectional pressure-gradient microphone is described which utilizes a front-to-back distance which varies approximately inversely as the frequency. The varying front-to-back relationship is achieved by utilizing two sound entrances with frequency discriminating parameters. One entrance is situated at a large distance from the front surface of the generating element while the other entrance is placed directly behind the sound responsive element. With this microphone desirable characteristics can be obtained which would not be possible in the conventional cardioid type having a fixed front to back distance. The principle of its operation is described and compared with that of the conventional fixed distance cardioid microphone.
Pressure Calibration of Condenser Microphones above 10 000 cps
Authors: Simmons Bernard D. , Biagi Fernando
Published: September 2005

A “plane wave” acoustic coupler and an electrical admittance method are described for the pressure calibration of condenser microphones in the ultrasonic frequency range. Calibration results are given for frequencies to 40 kc.
Diffraction of an Acoustical Wave Obliquely Incident upon a Circular Disk
Authors: Heaps H. S.
Published: September 2005

The calculated diffraction pattern behind a circular disk irradiated by an obliquely incident plane wave of sound is compared with that resulting from a normally incident wave. The total sound pressure received by a line receiver is tabulated in terms of its length and position along a certain line.
Radial Vibrations of Thick-Walled Hollow Cylinders
Authors: McFadden J. A.
Published: September 2005

Approximate formulas are given for the natural wavelengths associated with the free radial vibration of a thick-walled, infinitely long, hollow cylinder. For the radial extensional mode, the wavelength is nearly proportional to the nth-order mean radius, where n depends on Poisson's ratio. For the thickness modes, a correction factor is derived which may be applied to the plane-wave solution. The extensional solution is also applied to the case of a thin, flat washer.
On Acoustic Boundary Layer Heating
Authors: Mawardi Osman K.
Published: September 2005

The conventional investigations of the propagation of sound waves in conduits, when taking into account the effect of dissipation through friction and conduction of heat through the walls, assume the fluctuating part of the temperature of the gas to vanish at the boundaries. This is in essence a first-order approximation. Very different effects, however, are expected when second-order terms are considered. The purpose of the present paper is to discuss in detail the nature of the solution obtained from a second-order approximation.
Heating of Haired and Hairless Mice in High Intensity Sound Fields from 6 to 22 kc
Authors: Danner P. A. , Ackerman E. , Frings H. W.
Published: September 2005

Experiments have been conducted to provide a comparison of sound absorption by haired and hairless mice in high intensity air-borne sound fields. At 18–20 kc, threshold intensities for heating of the mice are 144±2 db for haired animals and 155±2 db for hairless animals. From 6–22 kc, effectiveness of the sound in heating the mice increased with frequency. Absorption coefficients computed from the data are higher at higher frequencies for both types of animals. Death time is dependent upon intensity and frequency of the sound, external covering of the animals, and portion of the animal exposed to the most intense part of the sound field. At frequencies of 18 and 22 kc, localized burns were found on hairless animals, and these were studied. The configuration of the sound field and its relation to the results is discussed. Measurements of the field made with and without a hairless mouse showed increased distortion at higher frequencies of the sound field by the body of the mouse.
Effect of Psychological Feedback on Conversational Noise Reduction in Rooms
Authors: Korn T. S.
Published: September 2005

In many cases when sound absorptive treatment has been applied to rooms, the effective noise reduction has been found larger than that predicted by the conventional formula. It is shown that this discrepancy appears in cases where conversational noise is predominant, and that it is the result of a phenomenon which may be termed “psychological feedback,” which increases the conversational noise reduction (expressed in decibels) by a factor of about 1.6.
Resonance Reverberation Method for Sound Absorption Measurements
Authors: Karpovich John
Published: September 2005

A resonance-reverberation method for measuring sound absorption in liquids from about 20 kc to above 600 kc has been developed. A single spherical glass container holds the liquid under test. The spherical system is excited with an intermittent train of continuous sound waves generated by a piezoelectric element. A second piezoelectric element detects the manner in which the sound energy dies away after the excitation stops. The time constant of this decay is inversely proportional to the sound absorption of the system. The liquid container was calibrated with liquids of known absorption to enable the separation of the wall losses from the liquid absorption. The sound absorption coefficients of 44 liquids are tabulated. Acoustic relaxations which were observed in some of the compounds studied are attributed to the perturbation by the sound wave of equilibria between rotational isomers. The application of the resonance-reverberation technique to sound absorption measurements in solids is presented.
Ultrasonic Temperature Measurement in Internal Combustion Engine Chamber
Authors: Livengood J. C. , Rona T. P. , Baruch J. J.
Published: September 2005

A method and apparatus for measuring the velocity of propagation of sound in the gases within the combustion chamber of an operating internal combustion engine are described. Two barium titanate crystals are used to generate and receive transient acoustical signals of approximately 2 Mcps. A calibrated commercial oscilloscope is the time base of the system.

From the value of the velocity of sound it is possible to compute the temperature of the portion of the engine gas which lies in the measuring path, provided it is permissible to assume that the gas mixture behaves like a perfect gas, that it is of known composition, and that thermal relaxation effects are negligible. The maximum error is estimated at 4.7 percent and experiments indicate a dispersion of results less than 1 percent.
An Experimental Study of Acoustically Induced Cavitation in Liquids
Authors: Galloway William J.
Published: September 2005

An apparatus has been assembled for the study of sonically induced cavitation in the frequency range of 20 to 40 kilocycles. Radially symmetric standing waves are produced in a spherical resonator driven externally by a magnetostriction transducer. The acoustic pressure within the sphere is measured by a small barium-titanate transducer positioned at secondary maxima of the standing pressure wave. Equipment is provided for measuring the gas content of the liquid being studied.

Measurements of cavitation thresholds as functions of air content, hydrostatic pressure, temperature, and surface tension have been made using different liquids. The highest thresholds measured were 200 bars for water and 140 bars for benzine (petroleum ether).

The air content of the liquid appears to be the dominant factor limiting the maximal negative pressure which the liquid can withstand as long as the air content is greater than five percent of saturation. At lower percentages of air saturation the threshold becomes essentially independent of air content, becoming limited by as yet undetermined factors.
Relaxation Processes in Aqueous Solutions of MnSO4 and CoSO4
Authors: Carstensen Edwin L.
Published: September 2005

Absorption and velocity dispersion in the electrolytes MnSO4 and CoSO4 have been measured using difference techniques. Good agreement is found between measured velocity dispersion and that which is predicted by simple relaxation theory from the measured values of absorption.
An Approximation Method for the Determination of the Elastic Constants of Single Crystals
Authors: Neighbours John R.
Published: September 2005

Plane elastic waves traveling in an arbitrary direction in a crystal are, in general, neither transverse nor longitudinal and in fact show polarization angles up to 11° in nickel. A method for deducing the elastic constants of a cubic crystal is well known. The method is here extended to other crystal classes where the method may be used in order to deduce all the elastic constants of a crystal.
Dispersive Reflection at the Interface between Ideal and Viscous Media
Authors: Miles John W.
Published: September 2005

The effects of viscosity and heat conduction (in the reflecting medium) in producing dispersive reflection of a plane wave at the plane interface separating two media are investigated. If the reflecting medium is treated as a condensed fluid, heat conduction is found to have no effect, while, in first approximation, viscosity is found to produce no change in amplitude but a phase shift proportional to frequency (and therefore no phase distortion) at angles of incidence above critical and to produce no phase shift but amplitude distortion at angles below critical. This amplitude distortion is found to be important only in the neighborhood of a sharp wave front.
Intensity Discrimination Thresholds under Several Psychophysical Procedures
Authors: Pollack Irwin
Published: September 2005

Discrimination thresholds for the detection of a change in the sound level of a tone were obtained under five experimental procedures. These procedures differed primarily in terms of the presence or absence of an objective comparison signal and in terms of the stability of the test conditions under examination. Under comparable conditions, discrimination in the absence of an objective comparison signal is only slightly less acute than in the presence of such a signal. On the other hand, relatively large increments in the detection thresholds are associated with increases in the instability of the testing conditions, especially over long discrimination intervals. The results are examined in terms of molar concepts more pertinent to the listener than to the ear.
Method of Reproduction and the Identification of Elementary Auditory Displays
Authors: Pollack Irwin
Published: September 2005

A psychophysical procedure which combines the salient features of the classical discrimination and identification experiments is described. Improvement in the identification of aspects of elementary auditory displays is associated with the procedure. However, the improvement is only a fraction of that reasonably expected on the basis of a classical differential threshold analysis.
Anesthesia and Hearing
Authors: Rosner Burton S. , Heise George A.
Published: September 2005

Evoked potentials to pure tone bursts were recorded from auditory cortex in cats. Thresholds for various frequencies as measured by this technique increased in a complicated fashion as depth of anesthesia increased.
Electronic Hydrophone for Calibrations at Very Low Frequencies
Authors: Bobber Robert J.
Published: September 2005

The anode of a vacuum tube has been used as the vibrating element of an electronic hydrophone, which is described. The free-field voltage response of this hydrophone is constant from static pressures to 150 cps.
Twenty-Five Years of Musical Acoustics
Authors: Young Robert W.
Published: September 2005

Two highlights of musical acoustics of the past twenty-five years are the advent of practical electrical musical instruments and research on deviations from the regular in music. Included in the latter are studies of the vibrato, transient modifications of tone quality, departures of intonation from rigid scales. The “steady-state” concepts of the past now need refurbishing in the light of “deviation” evidence. An analysis of papers directly related to music and published in the first twenty-five volumes of the Journal of the Acoustical Society of America reveals a steadily increasing interest in musical acoustics until World War II. In common with other subjects the publication rate dropped sharply during the war. Publication in acoustics as a whole increased rapidly after the war, but interest in musical acoustics (at least as evidenced by papers in the Journal) did not revive. Patents on musical devices, however, now constitute a significantly larger percentage of the annual output of the U.S. Patent Office than was the case in 1941. Technology is outstripping research in musical acoustics; interest in research must be revived immediately for the benefit of those who will listen to music in the next twenty-five years.
Electronic Pulse Method for Measuring the Velocity of Sound in Liquids and Solids
Authors: Cedrone N. P. , Curran D. R.
Published: September 2005

A pulse method is described employing a “sing around circuit” wherein each new pulse is triggered by the preceding pulse after it has traversed the acoustic sample. The resulting pulse repetition rate is measured with an electronic stop watch, thus giving a measure of the combined acoustic and electronic delay times. This in turn, upon the elimination of the electronic delay time, gives the velocity of sound in the sample. Velocity data are presented and sources of error discussed.
Measurement of High-Frequency Sound Velocity in Mammalian Soft Tissues
Authors: Goldman D. E. , Richards J. R.
Published: September 2005

A two crystal interferometer for rapid measurement of sound velocity in liquids and soft animal tissues is described. Velocities can be determined to within three parts per thousand with a path length of a few millimeters. The frequencies used are 1, 2, 4, 12, and 36 mc. Temperature is controlled to 0.1°C. A phase comparison method is used for wavelength incorporating dual heterodyne reduction to audio-frequency with presentation as a Lissajous figure on an oscilloscope. Results are given for a few mammalian tissues showing the precision and reproducibility of measurements.
Absorption of Finite Amplitude Sound Waves
Authors: Fox F. E. , Wallace W. A.
Published: September 2005

The coefficients of absorption of high intensity ultrasonic waves in liquids (carbon tetrachloride and water) have been measured as a function of intensity. The absorption coefficient increases by a factor of 5 for water and 2 for carbon tetrachloride for intensities of about 5 watts/cm2. The increase is attributed to wave form distortion of a wave of finite amplitude. A theory is developed in which the medium is treated as the acoustical analog of a transmission line with nonlinear elements. The theory enables one to follow the details of the change of an initially sinusoidal wave of finite amplitude, in a dissipative medium, in to a “comparatively” stable distorted wave form that eventually returns to an infinitesimal sinusoidal wave. Quantitative agreement of theory is obtained with experiment for the distance needed for comparative stabilization, the growth of harmonic content in the distorted wave, and the details of the absorption process.
Channels of Reception in Pitch Discrimination
Authors: Pikler Andrew G. , Harris J. Donald
Published: September 2005

Pitch discrimination was studied in 4 normal hearing subjects monaurally, binaurally, and in a variety of other channels of reception. No difference exists in sensitivity between the two normal earn of a subject, nor is there a difference between the sensitivity of the monaural channels and the binaural channel if all are matched for loudness. Also bone conduction was found to yield essentially equal pitch DL's after loudness was matched. All channels, except successive interaural, are equivalent under matched conditions. Successive interaural channels (standard in the right, variable in the left, and vice versa) show some deterioration of sensitivity and some increase in variance which can be attributed to the monetary fluctuations of diplacusis. Similar fluctuations were found also with respect to a channel utilizing a monaural standard and a binaural variable stimulus, the two ears matched in loudness. Under these conditions, furthermore, a third pitch is sensed, a phenomenon we term “triplacusis.” The authors suggest an interpretation of diplacusis and triplacusis as interaural interactions.

In cases of perceptive hearing loss, however, the channels are not usually equivalent in pitch discrimination even if matched for loudness. Evidently other principles must be sought for the pathological case.
Metastable Jet-Tone States of Jets from Sharp-Edged, Circular, Pipe-Like Orifices
Authors: Anderson A. B. C.
Published: September 2005

Characteristics of spectra from relatively thick orifices differ from those from relatively thin. In a given range of Reynolds number, in many cases the jet may exist in any one of several reproducible jet-tone states (metastable states) characteristic of the orifice. The dependence of the component frequencies of the jet-tone spectra (expressed in terms of the orifice-number fd/(Δp/ρ)12) on Reynolds number [ρd(Δp/ρ)12]/μ is shown, where d is diameter of orifice; f, frequency; Δp, pressure difference across orifice; ρ, density; and μ, viscosity of gas. The orifice numbers of the components of the jet-tone spectra generally tend to fall on a single array of equally spaced orifice-number levels. Jet-tones from the same orifice plate, characteristic of both thin as well as thick orifice plates, are found to coexist over a small transition range of orifice thickness-diameter ratio. If the orifice number of the head of the most probable spectral mode for a given orifice thickness-diameter ratio is noted, the same will be found again for the head of the most probable mode at approximate orifice thicknesses t±nd, where n is a small integer.
Ultrasonic Absorption in Toluene
Authors: Beyer Robert T.
Published: September 2005

The ultrasonic absorption coefficient has been measured in toluene by means of the spherical resonator method of Leonard and Wilson. Measurements were made in the temperature range 6°–40°C and in the frequency range 50–400 kc. The existence of a relaxation peak in this region, previously reported by Moen, has been confirmed, and a second peak has been identified at a lower frequency. The temperature dependence of the first peak indicates heat of reaction of 5.2 kcal/mole and an activation energy of 8.5 kcal/mole. This result is inconsistent with the hypothesis of a stretching vibration of the C–H bond, and suggests some sort of structural source for the absorption.
Model Study of Air-Coupled Surface Waves
Authors: Press Frank , Oliver Jack
Published: September 2005

Flexural waves generated in a thin plate by a spark source are used to investigate properties of air-coupled surface waves. Both ground shots and air shots are simulated in the model. Effects of source elevation, fetch of air pulse, and cancellation by destructive interference are studied.
An Instantaneous Pitch-Period Indicator
Authors: Dolanský Ladislav O.
Published: September 2005

Instantaneous indication of the beginnings of individual pitch periods of a voice-sound speech wave is often desirable in speech analysis. With conventional means, such as linear filtering and subsequent waveform shaping, this instantaneous indication is very hard to achieve because of the considerable time delay involved.

In the “instantaneous” pitch-period indicator the problem is solved by using nonlinear techniques and a variable time-gating circuit; a pitch-period beginning is indicated by a marker pulse having a maximum delay of the order of five percent of the pitch-period duration. The application of the device to certain problems of speech analysis is indicated.
Noise Control for NACA Supersonic Wind Tunnel
Authors: Beranek L. L. , Labate S. , Ingard U.
Published: September 2005

To reduce an intense noise with frequency components extending from 5 to 10 000 cps due to the burning of a jet engine in the test section of a supersonic wind tunnel, a special muffler was built having an open cross-sectional area of 600 square feet. For frequencies below 11 cps, large Helmholtz type resonators were used. Between 11 and 20-cps intermediate-sized Helmholtz resonators were employed. Between 20 and 800 cps a tuned set of six Fiberglas lined square ducts, were constructed. At higher frequencies two lined bends were employed to reduce the noise. Performance data measured in models and in the full scale wind-tunnel are presented. The result is a wind tunnel that is so quiet that nearby listeners are unaware of its operation.
Effect of Ultrasonic Energy Applied During the After-Ripening Stage of Photographic Emulsion Preparation
Authors: Herold Richard C. , Jones J. Byron , Knighton Charlotte D.
Published: September 2005

When a photographic emulsion of the boiled type is treated with 800 kc ultrasonic energy at an energy level of 5 w/sq cm during the after-ripening or digestion period, an increase the photographic sensitivity of that emulsion occurs. No significant change in the gamma or the grain size distribution of the emulsion results from this treatment. The mechanism appears to be a transport phenomenon which disrupts grain-sensitizing-agent concentration gradients in the intergrain gelatin matrix.
An Explosive Noise Source
Authors: Galloway William J. , Watters Bill G. , Baruch Jordan J.
Published: September 2005

A 10-gauge blank shotgun shell, exploded in a small cannon, has been used as an impulse source in performing a variety of acoustical measurements. The source has a peak power of the order of 10 000 watts with good reproducibility. The frequency spectrum simulates that of a typical turbojet engine. Instrumentation has been developed to permit simple and rapid analyses of measurements made with this source. Typical applications are described, and results obtained with the impulse source are compared to results obtained with continuous sources.
The Application of Correlation Techniques to Some Acoustic Measurements
Authors: Goff Kenneth W.
Published: September 2005

This paper discusses the application of an analog correlator which computes the crosscorrelation function between two sound pressures to such measurement problems as the localization of noise sources, the determination of transmission loss, and the reduction of microphone wind noise.

The crosscorrelation function φ21 (r) between two nonperiodic signals will have a peak in amplitude if a component of each signal originates from a common source. The value of time delay τ for which this peak occurs equals the difference in time required for the individual components to propagate from the common source to the two points under study. An analog electronic correlator described in a companion paper has been constructed which, by employing this property of the crosscorrelation function, can separate the acoustic signal at a given point into components according to: (1) their points of origin (assuming independent sources), (2) the transit time from source to the point in question, and (3) frequency.

Preliminary experimental results show that correlation provides a practical method for determining the amount of sound contributed to the field at a given point by each of several sources. The correlator, by separating the signal transmitted directly through the structure from the flanking signal on the basis of arrival time, is also a useful tool for measuring the transmission loss of walls.
An Acoustic Intensity Meter
Authors: Baker Stuart
Published: September 2005

A device is described for measuring the intensity of an acoustic wave at a point. The instrument employs a crystal microphone as a pressure transducer, directional hot-wire anemometer as a velocity transducer and an electronic multiplier and integrator. We can directly measure the intensity for any pressure or velocity wave form without having to assume any relationship between pressure and velocity. Several types of measurements have been made to indicate the present capabilities of the instrument.
Note on the Propagation of Normal Modes in Inhomogeneous Media
Authors: Tolstoy Ivan
Published: September 2005

Given a wave duct with continuously variable parameters extending from y=0 to y=H, the reflection coefficients for originally plane downgoing and upgoing waves are written in the form R↓ = −exp(2iχ↓) and R↑ = minus;exp(2iχ↑), respectively. It is then shown that the characteristic equation governing the dispersion of undamped normal modes in the medium is χ↓+χ↑=mπ, m being an integer defining the mode number. χ↓ and χ↑ are solutions of nonlinear first-order differential equations. If the medium consists of n homogeneous layers of finite thickness, the differential equation is replaced by a recursion relation, and the characteristic equation shown above includes one additional term.
Studies on Acoustic Radiation Pressure. I. (General Considerations)
Authors: Awatani Jobu
Published: September 2005

The equation derived by Kotani and King relating to the excess pressure valid to the second order in the acoustic field is examined. It is shown that the solution of the usual wave equation can be used in the case when the radiation pressure in the Langevin's sense is derived from this equation. The reason as to why not only the normal force but also the tangential force on the nonstiff surface result due to the radiation pressure defined from the viewpoint of the pressure in hydrodynamics, is clarified by considering the motion of the surface. The general expression for the radiation pressure on the rigid object which is in motion due to inertia effect, is led by introducing moving coordinates.
Ultrasonic Attenuation Studies in Biased BaTiO3 Ceramics
Authors: Hueter T. F. , Neuhaus D. P.
Published: September 2005

The attenuation of pulsed 10-megacycle ultrasound in barium titanate ceramics is studied as a function of temperature and applied field. In the region of the coercive field strength attenuation maxima are observed which correlate with a rapid change of the electromechanical response. Both phenomena can be traced to domain wall movements of two different kinds. A model is proposed which identifies one kind of attenuation maximum with a stress equalization in the polarized crystal grains of a ceramic, and the other kind with the nucleation of antiparallel domains. In both cases the losses appear to be caused by an elastic hysteresis due to dislocation movement.
A Method of Transducing an Ultrasonic Shadowgraph or Image for Display on an Oscilloscope
Authors: Suckling E. E. , MacLean W. R.
Published: September 2005

It is found that the pattern of piezoelectric voltage on the surface of a resonant crystal corresponds to the pattern of the exciting ultrasonic field. A capacity scanning system is described whereby ultrasonic shadow-graphs and images are reproduced for observation in a manner similar to that used in television.
Elastic Wave Velocities in Laminated Media
Authors: White J. E. , Angona F. A.
Published: September 2005

The velocities of elastic waves in a laminated medium have been determined by calculating the effective elastic parameters and the effective density. The procedure is to assume the medium to be in static equilibrium and exposed to certain stresses. The stresses are of such a nature as to generate strains similar to those which would exist during the passage of an elastic wave through the medium. From the application of Hooke's law, an effective stiffness constant for the medium is obtained. The ratio of this effective stiffness to the effective density is the square of the velocity of the elastic wave. For a medium consisting of layers of two materials with the same density but with a velocity contrast of two (2), the velocity of compressional waves traveling parallel to the layering is 20 percent higher than the velocity of the same wave traveling perpendicular to the layers. The SH shear wave has a velocity which is 25 percent higher than the SV shear wave for the same laminated medium.
Calculations on a Model of the Vocal Tract for Vowel /i/ (Meat) and on the Larynx
Authors: van den Berg Jw.
Published: September 2005

As a sequel to experiments on the transmission of the vocal cavities, calculations on a model of the vocal tract for the vowel /i/ (meat) are performed to determine the magnitude of the impedances along the vocal tract and the relative contribution of radiation, friction, and coupled vibrations of the cavity walls to the total damping. Calculations also are made to estimate the impedances of the different parts of the larynx. From these calculations the effects of the coupling of the vocal cavities upon the larynx can be understood. Finally an old singing-pedagogical problem concerning the resonances in the head is discussed.
An Analysis of Perceptual Confusions Among Some English Consonants
Authors: Miller George A. , Nicely Patricia E.
Published: September 2005

Sixteen English consonants were spoken over voice communication systems with frequency distortion and with random masking noise. The listeners were forced to guess at every sound and a count was made of all the different errors that resulted when one sound was confused with another. With noise or low-pass filtering the confusions fall into consistent patterns, but with high-pass filtering the errors are scattered quite randomly. An articulatory analysis of these 16 consonants provides a system of five articulatory features or “dimensions” that serve to characterize and distinguish the different phonemes: voicing, nasality, affrication, duration, and place of articulation. The data indicate that voicing and nasality are little affected and that place is severely affected by low-pass and noisy systems. The indications are that the perception of any one of these five features is relatively independent of the perception of the others, so that it is as if five separate, simple channels were involved rather than a single complex channel.
Contribution to the Study of Auditory Fatigue
Authors: Lightfoot Charles
Published: September 2005

Fatigue and other effects of 3 minutes of strong (105 db) acoustic stimulation were studied. Four combinations of fatiguing sound (white noise or 2-kc tone) and test frequency (3 or 4 kc) were each used twice for each of 24 Ss. Mean threshold recovery, functions closely resembled many of the individual functions reported by Hirsh and Ward and confirmed the phenomenon they called “bounce” however, many individual functions, like Hood's, were monotonic. Largest inter-subject and smallest intra-subject variability were associated with the noise/4000 combination. Ss differed considerably with respect to general fatiguability and recovery rate, and they tended to remain in the same rank order throughout the post-stimulatory period. There was a positive but low relationship between the fatigue a S displayed under one condition and what he displayed after the same recovery time under another condition; the relationship was generally highest after the first 3 minutes following stimulation. Many individual recovery charts displayed roughness indicative of a recurring disturbance of considerably shorter duration than the bounce effect. There was no obvious relationship between threshold shift and display of either roughness or bounce; nor could these latter two phenomena be entirely accounted for by tinnitus.
Auditory Perception of Submerged Objects by Porpoises
Authors: Kellogg W. N.
Published: September 2005

Two captive porpoises (or bottle-nosed dolphins) were given a variety of tests for their ability to perceive and avoid objects in water by reflected sound signals. The tests were made in a specially constructed anechoic pool in which visual perception was eliminated by the turbidity of the water. The results showed that trains of underwater sound pulses were emitted periodically by the animals in this situation whether they were swimming or at rest. The signals became more numerous when reflecting targets were lowered into the water. Sound pulses could also be triggered by surface splashes, but they were not sustained after a splash if no target was present. These porpoise sonar noises are similar in some ways to man-made sonar, although they differ from it in several important characteristics.

The porpoises would locate and approach food fish by this method but would avoid nonedible objects. They were also able to swim accurately through a field of obstructions without colliding with them—even in darkness. The ability to avoid obstacles by sound did not appear to be affected by artificial jamming noises.
Optical Methods for the Measurement of the Sound Pressure in Liquids
Authors: Breazeale M. A. , Hiedemann E. A.
Published: September 2005

In order to evaluate the method for measurement of the ultrasonic pressure amplitude in progressive waves which was developed by Loeber and Hiedemann for stationary waves, a comparison between it and two other optical methods was made. Pressure measurements under identical conditions by the three methods are given. Experimental considerations for the use of optical methods for measurement of sound pressure amplitudes are discussed.
Propagation of Sound in Plate-Shaped Solid Delay Lines
Authors: Sutton Paul M.
Published: September 2005

Acoustic propagation in plate-shaped solid delay lines is analyzed using diffraction theory. The analysis yields the dependence of group velocity (time delay), phase velocity, pulse shape, pulse rise time, output amplitude ripple spacing, and ripple amplitude on the parameters of frequency, delay line length, free-medium sound velocity, and plate thickness. Data are presented corroborating the theory quantitatively for time delay dependence on frequency and plate thickness, ripple spacing dependence on frequency and mode, and pulse rise-time dependence on frequency. The diffraction theory is compared to the wave equation plane-wave solutions for infinite plates. The results of the diffraction analysis are more appropriate for the description of sound propagation in plate-shaped delay lines.
Tables of the Speed of Sound in Water
Authors: Greenspan Martin , Tschiegg Carroll E.
Published: September 2005

An equation and tables for the speed of sound in water are reprinted from a recent paper published in The Journal of Research of the National Bureau of Standards.
American Standard Recommended Practice for Laboratory Measurement of Air-Borne Sound Transmission Loss of Building Floors and Walls
Authors: Ingard K. U. , Huntley R. , Jack W. A. , Summerfield M. B. , Tyzzer F. , Waterhouse R. V.
Published: September 2005

The American Standards Association recently issued the standard which is reproduced below, complete and unabridged, with their permission.

This new standard can be regarded as an up-to-date revision of the ASTM Tentative Recommended Practice for the same measurement (ASTM E 90-50T, later ASTM E 90-55), which was printed in this Journal [23, 686, (1951)]; in 1955 the “Tentative” was deleted from the title, the text remaining unchanged.

Some other countries, including Britain and Germany, have standards on this topic (British Standard 2750:1956, and German Standard DIN 52210, both obtainable from the American Standards Association), and a draft exists for an international standard; the latter includes provisions for field measurements as well as laboratory measurements, and for measurements of impact as well as air-borne sounds. At present ASTM Committee E-6 is working to prepare a new Recommended Practice for the measurement of the sound transmission loss of building structures, and will consider the inclusion of field and impact measurements.
Pulse Technique Applied to Acoustical Testing
Authors: Cho Alfred C. F. , Watson Robert B.
Published: September 2005

The lack of validity of the diffusion assumption makes it desirable to search for further means of assessing the acoustical properties of a room rather than a criterion based solely upon reverberation time. A pulse technique is devised to study transient sound in a room. An electroacoustic system was constructed for generating sound pulses in a room and for receiving and recording the pulses after transmission to various points in the room. Acoustical testing also included the determination of the absorption coefficient of a wall and the tracing of a sound path in a room. A pulse statistical analysis was made to give the root-mean-square deviations of the pulse transient response from the exponential steady state decay based on the known reverberation time. It is concluded that for the lecture room tested arms deviation less than 0.50 represents good acoustical conditions for speech.