bluuebunny/crossref_metadata_2025 huggingface dataset:
The Mean Pressure and Velocity in a Plane Acoustic Wave in a Gas
Authors: Westervelt Peter J.
Published: September 2005

The one-dimensional wave equation is discussed to the second order of approximation by means of a transformation that carries the equation from the Eulerian to the Lagrangean form. Airy's solution to this equation in Lagrangean form has been shown by Fubini to be an excellent approximation to an exact solution of Earnshaw's equation of motion; therefore, Airy's solution is chosen as the basis for much of this discussion. An expression for the local mean hydrostatic pressure in a plane progressive wave is obtained by transforming Airy's solution from particle to local coordinates. In a similar way, the particle velocity in fixed coordinates is shown to possess a time-independent component proportional to, and in a direction opposite to, the intensity vector This d.c. counter-velocity is predicted without recourse to viscous forces and is compatible with zero average mass velocity. For a sound pressure level of 151 decibels in air there should exist a steady particle velocity of 1 cm/sec. Small particles suspended in the field can, under certain circumstances, acquire this velocity. An approximate treatment is suggested for handling second-effects arising from stationary field configurations. The influence of viscosity is discussed qualitatively.

One purpose of this paper is to correlate work in the field which has not so far been published in this country.
Sound Scattering from a Fluid Sphere
Authors: Anderson Victor C.
Published: September 2005

The scattering of sound from a spherical fluid obstacle of size comparable to a wave-length is considered, neglecting dissipation. Calculations of the acoustic pressure and the total energy in the scattered wave are presented graphically; sound velocities and densities of the sphere lie between 0.5 and 2.0 times that of the external medium. The limiting cases of Rayleigh scattering and scattering from a fixed rigid sphere are also shown for comparison. In the region where the diameter of the sphere is comparable to a wave-length, the scattering is a complicated function of frequency, showing in some cases large maxima and minima. The amplitude of the scattered wave in the backward direction from a fluid sphere a few wave-lengths in diameter exceeds twice that from a rigid sphere of the same size for the case of the sound velocity 0.8 and density equal to that of the surrounding medium.
An Experimental Study of Vowel Intensities
Authors: Fairbanks Grant , House Arthur S. , Stevens Eugene L.
Published: September 2005

One hundred and ten monosyllabic words, 10 for each of the 11 common American vowels, were spoken in isolation by each of 10 subjects. Most of the differences between the mean relative intensities of the vowels were found to be statistically significant. Among the words for a given vowel the intensity of that vowel was found to differ significantly in most instances, variation tentatively attributed to consonantal environment.
The Acoustic Pathways to the Cochlea
Authors: Wever Ernest Glen , Lawrence Merle
Published: September 2005

Measurements are made of the relative effectiveness of the round window as a route of entrance of sounds to the cochlea. When the ear is normal this route is of no importance, but when the middle ear apparatus is absent and its advantage is lost to the oval window route a sound will have nearly equal access by both windows. When the inner ear is reached by both pathways at once the cochlear potentials represent the vector sum of what would result from the two separate waves. As phase and intensity relations between the two pathways are altered the potentials pass through maximum and minimum values, which for equal intensities of the two waves vary from a 6 db gain to a complete loss.

Evidence is produced to show that each pathway of stimulation excites the same sensory cells and in the same intensity pattern.

Over the major portion of the frequency range a minimum of response results when the waves are in phase as they enter the oval and round windows. Departures from this relation, which are most prominent at the highest frequencies, are explained as the result of reactance differences between the two windows.

These results apply to the explanation of forms of deafness caused by interruption of the ossicular chain, and also to the explanation of the treatment of otosclerosis by means of the fenestration operation.
San Diego County Fair Hearing Survey
Authors: Webster J. C. , Himes Harold W. , Lichtenstein Malcolm
Published: September 2005

A phonographically recorded test of the ability to hear pure tones was given to 3666 people at the San Diego County Fair in the summer of 1948. Absolute thresholds were determined at five frequencies and masked thresholds at two frequencies. The results were analyzed according to the age, sex, musical training, and past noise environment of the listeners, and according to their statements as to whether or not they had difficulty in hearing. As expected, auditory sensitivity was found to decline with age; women were found to be more sensitive than men for the higher frequencies; and men who worked in noise showed greater than normal losses at high frequencies. The data indicated, in addition, that musically trained men and women possess greater hearing sensitivity than do men and women without musical training, and that the 20–29 year old males tested at San Diego in 1948 appeared to have a greater loss at the high frequencies than did most males of the same age group who were tested in surveys before the war.
Resonance Characteristics of a Finite Catenoidal Horn
Authors: Thiessen G. J.
Published: September 2005

Expressions for the impedance components of a finite catenoidal horn are derived and a comparison with similar exponential and conical horns made. The impedance of a section of a catenoidal horn is also calculated and it is shown how, for the finite as well as the infinite horn, this approaches that of the exponential as more length is trimmed from the throat end.

The assumption that the resonance characteristics of a horn are the same as that of a uniform tube, provided the higher velocity of sound for the horn is used, seems to be borne out for the catenoidal horn but for the exponential horn the agreement is not very good except at higher frequencies.
The Trill Threshold
Authors: Miller George A. , Heise George A.
Published: September 2005

Two tones of different frequencies alternated successively five times per second. When the difference in frequency was small, the alternation sounded like a continuous up-and-down movement of the pitch. When the difference in frequency was large, the alternation sounded like two unrelated, interrupted tones. The transition point between these two perceptual organizations is called the trill threshold. The trill threshold was measured as a function of frequency for 14 subjects; the results are summarized in Fig. 1.
Theory of Operation of the Cochlea: A Contribution to the Hydrodynamics of the Cochlea
Authors: Ranke O. F.
Published: September 2005

This paper presents a short summary of calculations on the vibrations of the cochlear partition (basilar membrane). It is possible to determine the shape, velocity, and amplitude distribution of the traveling waves running from the stapes to the inner ear. Furthermore, it is shown that the calculated vibration pattern is in agreement with observations made on the human cochlea and on models of human inner ears. In particular, analogies between the waves in the inner ear and on the seashore are pointed out. These analogies show the importance of the velocities of propagation for the excitation of the hearing nerve cells.
Effects of Humidity on Ultrasonic Absorption in Air at 1.46 Megacycles
Authors: Sharan Verma Gurdeva
Published: September 2005

The absorption coefficient for moist air has been measured at 1.46 Mc for relative humidities varying from zero to 84 percent. Maximum absorption at this frequency (α = 0.52 cm−1) is found to occur at 46 percent relative humidity.
Physical Factors Involved in Ultrasonically Induced Changes in Living Systems: I. Identification of Non-Temperature Effects
Authors: Fry W. J. , Wulff V. J. , Tucker D. , Fry F. J.
Published: September 2005

The results of the first step in a systematic investigation of the mechanism of the action of ultrasound on tissue are reported. The temperature changes resulting from absorption of acoustic energy were determined while irradiation was in progress.

Experimental evidence is presented which demonstrates the existence of non-temperature effects in various nerve tissue preparations.
Microphonics Produced by Touching the Cochlear Partition with a Vibrating Electrode
Authors: v. Békésy Georg
Published: September 2005

A vibrating electrode has been developed, with which the microphonics produced at a single point on the cochlear partition can be measured. With this electrode, which can be made to vibrate in any of three orthogonal directions, different places on the cochlear partition were investigated. The basilar membrane is more sensitive to displacement in the radial direction than in the direction perpendicular to its plane. The important question is whether microphonics are produced by a constant stationary displacement or whether they are produced only during the movement of the cochlear partition. With the aid of trapezoidal waves it was possible to show that in a fresh cochlear preparation only the static displacement produces the microphonic voltage. A single displacement of the basilar membrane produces astatic voltage lasting for several seconds. This fact has an important bearing on the energetics of the microphonics.

Preliminary experiments suggest that the same technique may be used to investigate the inner parts of the cochlear partition.
Ultrasonic Absorption of Glycerin in the Liquid and Vitreous State
Authors: Litovitz Theodore A.
Published: September 2005

The ultrasonic absorption of an associated liquid, glycerin, has been measured, in the liquid and vitreous state, at 31 Mc. The value of absorption found exceeds the theoretical value at high temperatures by a factor of 2.1. This indicates that both compressional and shear viscosity contribute to the absorption process. When the liquid was cooled, a peak in the absorption was found at −6.5°C; and at still lower temperatures the absorption fell to considerably lower than classical values. The appearance of a peak in the absorption experimentally verifies the fact that both compressive and shear viscosity are associated with a relaxation phenomenon. The relaxation times for the two processes are of the same order of magnitude, and the same is true of the activation energies.
Calculation and Measurement of the Loudness of Sounds
Authors: Beranek L. L. , Marshall J. L. , Cudworth A. L. , Peterson A. P. G.
Published: September 2005

An equivalent-tone method for calculating the loudness of sounds is described. With this method the spectrum of the sound is divided into frequency bands which are treated as pure tones in determining their loudness. The individual values of loudness are added to obtain the total loudness of the sound. Calculations for bands of white noise and for complex tones are compared with subjectively obtained data of Pollack and Fletcher and Munson. The agreement between calculated and experimental values is good. It is felt that improvement of the method must await further psychoacoustic data.
Place Mechanisms of Auditory Frequency Analysis
Authors: Huggins W. H. , Licklider J. C. R.
Published: September 2005

One of the central problems in auditory theory is to reconcile (a) the acute perception of slight changes in pitch displayed by the human listener with (b) the broad tuning of his cochlear analyzing mechanism. This paper attempts to describe and to relate a number of theoretical solutions to that problem. The hypotheses involve mechanisms, both mechanical and neural, for sharpening the analysis inherent in the cochlear transformation from frequency of stimulation to locus of vibration. These mechanisms operate in the domain of place—they are place theories that supplement the classical place theory. In a future paper, we plan to describe and discuss other sharpening mechanisms that operate in the domain of time.
Effect of Delay Distortion upon the Intelligibility and Quality of Speech
Authors: Flanagan J. L.
Published: September 2005

Speech articulation and quality tests were made on an all-pass system capable of advancing or delaying one frequency band relative to the rest of the spectrum. Parameters in the investigation were (a) width of the advanced or delayed band, (b) amount of advance or delay, and (c) position in the frequency spectrum of the advanced or delayed band. Data were taken at signal-to-noise ratios of 30 db and 0 db. The results indicate that maximum impairment of speech intelligibility and quality occurs when the delays and advances are of the order of 14 second, and when the band that is advanced or delayed is near the center of the speech spectrum and has an articulation index equal to 0.5. These findings are related to data from statistical studies of the timing of speech energy bursts.
Measurements of Ultrasonic Absorption in Various Mixtures of Nitrobenzene
Authors: Sette Daniele
Published: September 2005

To obtain information the characteristics of relaxation phenomena in liquids, measurements of ultrasonic absorption were performed in seven binary mixtures having nitrobenzene as one component.

The absorption coefficients in some systems (benzene, chloroform) confirm the results obtained previously in mixtures formed by an unassociated, very absorbing liquid and another component with much smaller absorption coefficient. In this case, the absorption coefficient decreases quickly when small quantities of the second liquid are added to the first one. The explanation of this behavior seems to be found in the fact that an increase of the efficiency of collisions between the molecules occurs. When different molecules are added to the high absorbing liquid, they decrease the time necessary to establish equilibrium among the internal degrees of freedom of the high absorbing molecules.

In other mixtures the two components have similar absorption coefficients. These systems are of great interest, because the characteristic behavior of the ultrasonic absorption in the mixture then depends on the nature of both pure liquids. If the two liquids are unassociated and their molecules do not interact strongly between themselves, the curve of the absorption coefficient versus concentration presents a very clear minimum. If, instead, there are strong interactions, the shape of the curve is altered. This would indicate the presence of an additional type of energy loss.

In the systems of nitrobenzene and an alcohol, the absorption coefficient, as a function of the mole fraction, has a maximum at an intermediate concentration, just as happens in some mixtures of water and alcohols.
Information and the Human Ear
Authors: Jacobson Homer
Published: September 2005

Calculations of the informational capacity of the human ear are made by computing the number of discriminable sound patterns per second, and applying the Shannon information theory. A maximum of 104 bits/sec transmission found. This is compared with the capacity of existing auditory channels and recording media, and with the rate of actual information perception from speech and music. It is shown that a capacity of upwards from 5 × 104 bits/sec, depending on the informational match to the ear, is necessary for high fidelity transmission or recording. It is also shown that the brain can utilize less than 1 percent of the information transmitted by the ear. Finally, an average capacity of about 0.3 bit/sec, or of 40 tones/sec, is calculated for an individual cochlear fiber.
A Free Field Method of Measuring the Absorption Coefficient of Acoustic Materials
Authors: Ingård U. , Bolt R. H.
Published: September 2005

A free field method is reported for the measurement of the normal impedance and the absorption coefficient of a material. The pressure and phase of an incident “plane” wave in steady state are measured at a point in the absorptive surface and compared with the pressure and phase measured at the same point in space at the surface of a perfectly reflecting material, or at the same point in free space without any panel. From these data are determined the phase and magnitude of both the incident and reflected waves, and this information in turn yields both the normal impedance and the free wave absorption coefficient for the particular angle of incidence involved. Tests have been made with an 8-ft square sample of material mounted in an anechoic chamber and rotated about a vertical axis in the presence of a fixed horizontal beam of an approximately plane wave. As a check of the validity of the method, measurements have been made using two types of material with known properties, one with the normal impedance essentially independent of the angle of incidence and the other with a considerable angular dependence. The experimental values are shown to be in good agreement with calculations.
Acoustic Wave Propagation Along a Constant Normal Impedance Boundary
Authors: Lawhead R. B. , Rudnick I.
Published: September 2005

An expression is obtained for the amplitude and phase of an acoustic wave above a boundary due to a point source on or near a boundary which exhibits a constant normal specific acoustic impedance. This is shown to be a special case of the solution for an isotropic medium with constant characteristic acoustic impedance; specifically, the case is one in which the ratio of the propagation constant in the upper medium to that in the lower approaches 0.

A material which obeyed a constant normal impedance boundary condition was constructed from ordinary drinking straws. Measurements of amplitude and phase as a function of receiver position along and above the boundary showed good agreement with theory.

The nature of the approximations involved in the solution are discussed and it is shown to be an adequate representation of the sound field for distances greater than one wavelength from the source.
Propagation of Sound in a Duct with Constrictions
Authors: Ingård U. , Pridmore-Brown D.
Published: September 2005

The transmission of sound through a duct periodically loaded with constrictions (iris partitions) is studied. The attenuation as a function of frequency in such ducts both with hard and absorptive side walls is given. In the case of a hard-walled duct the results of the analysis are presented in chart form. It is shown that by proper choice of side wall absorption and iris partitions a broad attenuation band can be obtained. Measured values of the attenuation are found to be in good agreement with the theory.
A Recording Ultrasonic Interferometer and its Alignment
Authors: Stewart James L. , Stewart Ellen S.
Published: September 2005

The first part is the description of a circuit employing rf amplification which converts an ultrasonic interferometer into a sensitive self-recording instrument whose records can be simply analyzed to yield a rapid determination of the attenuation and reflection coefficients of gases at low pressures. The second part is a summary of the sources of error in ultrasonic interferometry, their detection and their correction. In the third part, some data on the velocity, attenuation, and reflection in helium in the region two to sixty Mc/atmos are presented to illustrate the range, precision, and absolute errors of the instrument.
Acoustical Energy Generated by the Ocean Waves
Authors: Daniels Fred B.
Published: September 2005

An estimate of the order of magnitude of the acoustical energy generated by ocean waves indicates that this energy, is large enough to cause an appreciable heating effect at ionospheric levels, where most of it is absorbed. Using data obtained from surface measurements of the pressure amplitude, it is found that relative density changes of the order of 1 percent occur at ionospheric levels. and the suggestion is made that the “twinkling” of cosmic sources of radio waves is a result of this phenomenon.
Recovery of the Auditory Threshold after Strong Acoustic Stimulation
Authors: Hirsh I. J. , Ward W. D.
Published: September 2005

After an ear is exposed to an intense sound, the absolute threshold for many sounds is raised, usually temporarily. The manner in which the absolute threshold recovers to its normal value after such stimulation is the subject of these experiments. It is found that recovery from such auditory fatigue is not a simple monotonic process. Rather these experiments show that under certain conditions the threshold first recovers to an approximately normal value about 1 minute after the cessation of the exposure but then rises again to a higher value that reaches a maximum at about 2 minutes after the exposure. This diphasic recovery curve, with its characteristic “bounce,” is found when the exposure involves sound pressure levels between 100 and 120 db and durations of the order of several minutes.

Recovery curves are shown for the auditory thresholds of clicks, bands of noise, and pure tones. Fatiguing stimuli include bands of noise and pure tones.

Two subsidiary observations are also reported. First, in many recovery curves there is evidence for a second “bounce” or rise in the threshold after stimulation. Second, after stimulation by moderate intensities the initial recovery (about 1 minute after stimulation) may demonstrate facilitation, i.e., a temporary reduction in the absolute threshold below the normal value. Qualitative observations concerning the pitch and timbre of the test stimuli and of tinnitus following stimulation are related to some of the data.
Rotational Dispersion in the Velocity, Attenuation, and Reflection of Ultrasonic Waves in Hydrogen and Deuterium
Authors: Stewart Ellen S. , Stewart James L.
Published: September 2005

Data are presented on the dispersion of the velocity of sound and on the effect of impurities upon the rotational relaxation times determined therefrom. The attenuation due to the relaxation is shown to agree with the theory, with some evidence of multiple relaxation. Anomalous dispersions of the classical attenuation and of the Herzfeld reflection coefficient are predicted. The latter is confirmed experimentally and also yields a determination of the accommodation coefficient.
Radiation Loading of Cylindrical and Spherical Surfaces
Authors: Junger Miguel C.
Published: September 2005

This paper presents a series of curves of acoustic reactance and resistance ratios for partial waves emitted by cylindrical and spherical sound radiating sources whose dynamic configuration is expressible by infinite series. This information permits the calculation of sound pressure at the radiating surface, power of sound emitted, and accession to inertia for wavelengths and sound radiators in the range 0⩽ka⩽10.
On the Measurement of the Loudness of Speech
Authors: Pollack Irwin
Published: September 2005

A previous paper discussed several experimental procedures for setting up scales of loudness for white noise and for pure tones. In general the results obtained by various procedures were reasonably similar. However, when a speech signal was used, large discrepancies were obtained. The present paper describes these results and presents a loudness scale for speech based upon the data available.
Gross Localization of the Place of Origin of the Cochlear Microphonics
Authors: v. Békésy G.
Published: September 2005

An apparatus was developed that made it possible to push an electrode automatically with an absolutely even and smooth velocity through the cochlear partition of an anesthetized guinea pig. The ac and dc potentials of this perforating electrode were recorded during the perforation when sound was applied to the eardrum, or when an electrical generator was connected to the vestibular and tympanic channels of the cochlea. These measurements enable us to show that the endolymph is surrounded by an electrically insulating layer, and that the inner part of the organ of Corti is protected from external electrical potential fields. Further, it was shown that the microphonics produced by a vibration of the eardrum have larger values inside the endolymph than in the perilymph or near the round window. The microphonics seem to reach a maximum near the organ of Corti.

The perforation measurements also made it possible to discriminate three types of tissues in the cochlea: (1) highly sensitive cells with large microphonics and dc potentials; (2) cells that do not produce large microphonics but still have in them large dc potentials; and (3) tissues that are electrically indifferent and can be represented by an electrical resistance. These distinctions and the measurement of the electrical conductivity of the endolymph permit a coarse description of the electro-anatomy of the cochlear partition.
The Thermal-Noise Limit in the Detection of Underwater Acoustic Signals
Authors: Mellen Robert H.
Published: September 2005

The criteria for an “optimum” hydrophone receiving system for underwater acoustic signals are considered, and the equilibrium thermal-noise pressure spectrum expression is shown.

Experimental ambient sea-noise spectrum levels are in excess of the thermal noise at all frequencies below 25 kc. Extrapolation of experimental curves (−5 db/octave) shows intersection with thermal-noise spectrum (+6 db/octave) between 50 and 200 kc, depending on sea state. (For a definition of “sea state,” see Instructions to Marine Meteorological Observers (U. S. Department of Commerce Weather Bureau, U. S. Government Printing Office, Washington, D. C., June, 1941), seventh edition, circular M.) The ambient-noise level is expressed as a function of the equivalent temperature.

Formulas are then derived for the required plane-wave signal level for which electrical signal-to-noise ratio is unity. The operating noise factor is defined in terms of the electroacoustical efficiency of the linear reversible hydrophone, the amplifier noise figure, and the equivalent ambient-noise temperature for the sea condition and frequency under consideration.
The Space-Time Pattern of the Cochlear Microphonics (Guinea Pig), as Recorded by Differential Electrodes
Authors: Tasaki I. , Davis H. , Legouix J.-P.
Published: September 2005

Pairs of very small electrodes were placed in two or more turns of the cochlea of the guinea pig. The cochlear microphonic from a short segment (about 1 mm) of the cochlear partition can thus be recorded, and without contamination by action potentials. The outputs of the second, third, and fourth turns were compared with that of the first turn with respect to both amplitude and phase as a function of frequency. The space-time pattern thus revealed is a traveling wave which passes up the cochlea to a distance that depends on the frequency. The pattern agrees well with that of mechanical movement (Békésy) except that the cochlear microphonic shows relatively greater amplitude (voltage) in the basal turn. Low frequencies travel farther up the cochlea than do high. The velocity (for a 750 cps tone) is about 100 m/sec in the basal turn and about 2 m/sec in the fourth turn. Phase differences of as much as 5π were observed, by means of Lissajous patterns, between the responses of the first and the third turn. Certain discontinuities in the input-output relationships and in phase relationships were found to be a function of frequency and of position along the cochlear partition. These discontinuities occurred at or near the frequencies that showed a phase difference of 2π from the basal end of the cochlea. The relation of these critical frequencies to position along the cochlea constitutes a new “frequency-map” of the cochlea.

The space-time pattern of the cochlear microphonic proved to be very little affected by removal of portions of the bony wall of the cochlea or delivering acoustic energy through a hole near the apex. It is concluded that, in addition to “direct driving” of the cochlear partition by pressure differences between the two scalae and to “surface waves” arising from such drying, the transmission of transverse waves along the solid structures of the cochlear partition must also be included for a satisfactory interpretation of all of the available data.
Brownian Motion and the Transmission of Energy in the Cochlea
Authors: de Vries H. L.
Published: September 2005

It is shown that Brownian motion at the eardrum is only partly due to noise of the air. (This part has been calculated by Sivian and White.) The main part is due to Brownian motion of the eardrum itself. The apparent flow of energy is close to the absolute threshold of the ear; it is reduced to one half when the ear is provided with an exponential horn.

The discussion of the Brownian noise in the inner ear reveals a serious discrepancy; considering one individual cell it proves to be very difficult to reconcile the low threshold with the thermal agitation. A mechanism is suggested for the excitation of the sense cells by which the disturbances by Brownian motion are appreciably suppressed; in this model the microphonic activity plays an important part. The model is based on some recent measurements of the microphonic activity of the lateral line organs of fishes, which are shortly summarized. It follows from these measurements that the microphonic potentials are related with the tension of the hairs on the sense cells.
On the Process of Speech Perception
Authors: Licklider J. C. R.
Published: September 2005

The process of speech perception is analyzed into three main operations: (1) translation of the speech signal into form suitable for the nervous system, (2) identification of discrete speech elements, and (3) comprehension of meaning. The first operation appears to correspond roughly to the transformation made by the sound spectrograph. The second may be carried out by the neural equivalent of a set of matched filters. The third appears to involve a neural form of cross-correlation that exhibits some of the properties of the analogous electronic process.
The Phonetic Basis for Identification of Phonemic Elements
Authors: Fischer-Jørgensen Eli
Published: September 2005

Phonemic analysis must be based to a large extent on considerations of phonetic similarity and difference. For this purpose various stages of the speech event may be chosen, in particular the articulatory, the acoustic, and the auditory stage. It does not seem irrelevant which stage is chosen, for the analysis may give different results in each of the three stages. However, it is usually not possible to state general reasons for preferring one stage over another. In a given language functional reasons may in some cases decide the choice.
Electromechanical Properties of BaTiO3 Compositions Showing Substantial Shifts in Phase Transition Points
Authors: Berlincourt Don A. , Kulcsar Frank
Published: September 2005

Incorporation of CaTiO3 or Y2O3 into BaTiO3 ceramics causes a downward shift of the second transition point, resulting substantial improvement of temperature stability in the normal operating range.

Dielectric and electromechanical properties of BaTiO3 ceramics containing CaTiO3, Y2O3, and PbTiO3 are shown from −40° to +120°C. The composition containing 5 weight percent CaTiO3 combines high piezoelectric response with low temperature dependence of operating characteristics.
Translational Dispersion in Monatomic Gases
Authors: Boyer Robert A.
Published: September 2005

A comparison made between the results of experiment and theoretical predictions of translational dispersion in the monatomic gases argon and helium. Second-order approximations to the dispersion are presented for the continuum theory, treating the Stokes-Navier equations as exact, and for deductions from kinetic theory, assuming that the molecules behave as (1) elastic spheres, (2) Maxwellian molecules, and (3) molecules obeying a Lennard-Jones type potential. Agreement between experiment and kinetic theory predictions is rather favorable in the range compared, which is at 0°C, approximately 970 kc, and down to about 2 mm Hg pressure. The increases velocity of propagation (at the lowest pressures) over that at standard conditions are 27 percent for argon and 0.6 percent for helium.
Nonlinear Dissipative Distortion of Progressive Sound Waves at Moderate Amplitudes
Authors: Mendousse J. S.
Published: September 2005

The first part of this investigation deals with the case of a simple-harmonic wave which becomes eventually distorted into a relatively stable shape resembling the shape of a saw-tooth wave with rounded-off corners. A simplified-picture theory is developed in which the wave is idealized as consisting of a non-dissipative linear portion of length λ1 and a dissipative simple-harmonic portion of length λ2. The amplitude A of the distorted wave and its rate of absorption αA are computed (1) from the dissipative wavelength 2λ2 and (2) from the “build-up distance” L = Nλ at which stability of shape is achieved, both λ2 and N being regarded as experimental data. Tests of the theory are made by using shadowgrams of waves generated in air by a piezoelectric quartz at the frequency of 0.405 megacycle (see reference 2). The second part of the paper presents an approximation treatment of the classical wave equation in which either of two different transformations of variables lead to a quasi-linear differential equation of the type ∂2z/∂y2 = ∂z/∂x+∂(z2)/∂y. In the first transformation, more suitable for periodic waves, x is used for the distance from the source and y for the time, while the reverse is done in the second transformation, more suitable for shock waves. An exact solution is given for the case of the simple-harmonic source already discussed in the first part.
Effect of Different Types of Electrodes in Electrophonic Hearing
Authors: Flottorp Gordon
Published: September 2005

Depending upon the kind of electrode system employed, a sinusoidal electric current gives rise to at least five phenomena. (1) With a moving electrode on the skin or on the roof of the mouth (fricative effect), the subject receives the strongest sensation of hearing. He may hear either the first harmonic or the first and second harmonics, or the second harmonic alone, depending upon the applied voltage and upon the placement and properties of the electrode. (2) With a large-area electrode any place on the skin of the head, if the skin is dry the subject hears the second harmonic; if it is wet, he hears nothing. (3) When the electrode is immersed in salt solution in the ear (the most common method), the subject hears a complex tone containing mostly second harmonic, suggesting the action of a square-law transducer. (4) When the electrode is on the mucous tissue inside the middle ear (with eardrum removed), the subject hears the first harmonic and/or a noise. (5) When the electrode is in contact with the epidermis of the meatus, the subject hears the first harmonic, and at low frequencies he may also hear a noise. The experimental results seem to indicate that the hearing of a tone under any of these five conditions is probably due to vibrations set up outside the cochlea, although there appear to be at least four different transducing mechanisms. Contrary to earlier hypotheses, the tympanic membrane is apparently not involved in the conversion of the electrical energy into mechanical vibration.
The Acoustics of the Royal Festival Hall, London
Authors: Parkin P. H. , Allen W. A. , Purkis H. J. , Scholes W. E.
Published: September 2005

The Royal Festival Hall was opened in London in May, 1951. This paper describes in some detail its acoustical design, the test concerts held in it before the opening, the objective measurements made in it, and the comments about its acoustics that have been made during the first eighteen months since its opening. These comments show that the “definition” is excellent, but that for some types of music more “fullness of tone” would be desirable. It is concluded that the reverberation time is the only objective measurement which, at the present stage of development, is of practical use. Its value in the Royal Festival Hall when full is 1.5 seconds (at 500 cps), which is 0.2 second shorter than the optimum value given by Knudsen and Harris for a hall of this size. It seems probable that the “fullness” would be adequate if the reverberation time could be lengthened to 1.7 seconds or somewhat longer.
The Effects of Biological Tissues on 15-mc Pulsed Ultrasound
Authors: Wild J. J. , Reid John M.
Published: September 2005

The subject of this paper, which is mainly descriptive, grew out of the desire of a biologist to measure the thickness of the human bowel wall in the living intact subject. [J. J. Wild, Surgery 27, 183 (1950)]. The object was to justify certain methods of treatment for the suspected underlying mechanisms at work, the results of which are lumped together by surgeons under the title of bowel distension.

The approach to the subject has been almost entirely biological, not ignoring, however, the theory of sound where applicable. It will be seen that biological methods of control are used as a first approximation in order to justify more detailed examination of the system. Some of the difficulties of the exact approach from theory will be discussed after presentation of the experimental facts. It may be of interest to the more exact-thinking members of the audience to note that a system having a nightmare of complexity to the physicist may be considered simple by the biologist in his blissful ignorance. This situation is perhaps fortunate because otherwise the biologist might be tempted to give up too easily. It is the duty of the biologist to try to simplify complex phenomena so that his more able colleagues in more exact branches of science will be stimulated to “pitch in” and help. We hope that today we shall be able to bring about this desirable end and succeed in stimulating more workers to investigate this field. It should, however, be realized at the outset that the increasing exploitation of the observed phenomena does not necessarily need to wait upon whatever fundamental explanations may be forthcoming. The experimental results will not necessarily be presented in chronological sequence but an attempt will be made to present some of our collected experimental data in as logical a manner as possible.
The Analogous Acoustical Impedance for Discontinuities and Constrictions of Circular Cross Section
Authors: Karal F. C.
Published: September 2005

The impedance introduced by an abrupt change of circular cross section of a tube has been examined. It is shown that in the case of an ideal viscousless fluid the effect of the discontinuity is to introduce an inductance in series with the acoustical transmission system. The discontinuity inductance has been determined as a function of the ratio of the tube radii and has been plotted for different values of this ratio. The problem of a small tube or constriction inserted between two larger tubes has also been treated. It is shown that the constriction inductance is equal to the sum of the discontinuity inductances of each end taken separately to a very good approximation. The constriction inductance can be considered as a correction term to be added to the analogous acoustical inductance of the tube and can be interpreted physically as an increase in the equivalent length of the tube.
The Noise of Choked Jets
Authors: Powell Alan
Published: September 2005

The noise of a jet changes character after the pressure ratio exceeds the critical value appropriate to sonic exit velocity, the general roar being dominated by a loud “whistling” or “screeching.” Schlieren photographs show that sound waves of ultrasonic frequency are caused by the transition of the initially laminar boundary layer to turbulence and also by this turbulence interacting with the shock waves of the flow. Larger disturbances have also been noted, involving both the jet stream and some of the air external to the jet, and these also give rise to sound waves which have been photographed: it is these which are held responsible for the audible effects. A two-dimensional study has shown the latter phenomenon to be enhanced, and it is shown how the system of disturbances is self-maintained by virtue of sound waves creating initially small disturbances at the jet exit. The directionality of the sound field has been predicted and found in agreement with experiment, and the dimensions of the motion are compatible with the suggested mechanism. The relation to edge tones is pointed out and the mechanism indicated, a photograph of this phenomenon also being shown. Finally mention is made of how the characteristic noise of jets working above the critical pressure might be reduced, the suggested methods having been found successful in practice.
On Noise of Aerodynamic Origin
Authors: Mawardi Osman K. , Dyer Ira
Published: September 2005

An attempt is made in this paper to classify noises of various aerodynamic origin by means of an efficiency of conversion from mechanical to acoustical energy, and also by means of representative spectra associated with corresponding characteristic frequencies. The classification has been tried successfully on measurements of wind tunnel noises, turbojet noises, and air jet noises.
Ultrasonic Waves and Electrochemistry. I. A Survey of the Electrochemical Applications of Ultrasonic Waves
Authors: Yeager Ernest , Hovorka Frank
Published: September 2005

The applications of ultrasonic waves in electrochemistry are discussed in terms of (1) the effects of ultrasonic waves on electrode processes, (2) electrokinetic phenomena involving ultrasonic waves, and (3) the use of ultrasonic waves as a tool in the study of the structure of electrolytic solutions.
Ultrasonic Waves and Electrochemistry. II. Colloidal and Ionic Vibration Potentials
Authors: Yeager Ernest , Dietrick Harry , Hovorka Frank
Published: September 2005

When ultrasonic waves are introduced into an ionic solution or a suspension of charged colloidal particles, alternating potential differences are generated between points separated by a finite distance in the direction of propagation (other than an integral multiple of the wavelength). Pulse-modulated ultrasonic waves have been used to study these effects at a carrier frequency of 200 kc/sec. The colloidal vibration potentials have been measured in a number of colloidal silica suspensions of various concentrations, particle sizes, and conductivities. The experimental results are in general agreement with the mathematical treatment of Enderby. Measurements of ionic vibration potentials in potassium chloride solutions indicate a value of 6μv per cm/sec for a 10−3-molar solution. This value corresponds to a difference of 80 in the apparent gram-ionic-masses of the hydrated potassium and chloride ions.
Ultrasonic Dispersion in Water Solutions of Magnesium Sulfate
Authors: Fox Francis E. , Marion Thomas M.
Published: September 2005

In a dispersive medium the relative phases of the components of a complex sound wave change with path length. The present article describes a method of measuring dispersion in which the change in relative phases of a complex wave consisting of a fundamental and a selected harmonic are measured as a function of the path length. Sensitivities, in measuring difference in velocity, of one part in 105 with a probable error of 3 parts in 105 were obtained experimentally. Dispersion measurements made in water solutions ofMgSO4 below one megacycle show linear dependence upon concentration up to 0.5 mole per liter and agree with those calculated from absorption data. The data indicate total dispersion of 13.6×10−4 per mole per liter, with a relaxation frequency of 160 kc at 24°C.
Graphical Aids in Interpreting the Performance of Crystal Transducers
Authors: Cady Walter G.
Published: September 2005

When the mechanical damping of a transducer is large, as by acoustic radiation from one or both faces into a liquid or solid, the circular diagram that represents its characteristics requires special treatment. As a background for this treatment, the uses and limitations of the conventional circle for a resonator with small losses is first reviewed. The problem of the transducer with large losses is then considered with special reference to the equations and graphs for a thickness-type transducer with unsymmetrical loading. For plane-wave transducers the expressions are exact for all loads and at all frequencies, including harmonics. Either the voltage or the current may be constant. From the admittance or impedance diagrams the magnitude and phase of current, voltage, particle velocity, and vibrational amplitude at any frequency can be obtained immediately. Similar results would be found with plates in lengthwise vibration. A new type of diagram is developed for representing vibrational amplitudes. As an illustration, the case of a quartz plate radiating into three liquids of widely different acoustic properties is treated.

When the load is unsymmetrical, there is no true node anywhere in the crystal except when the load is zero or infinity. There is, however, a plane of minimal vibration, the amplitude and location of which are derived. The equations indicate certain peculiar effects when the specific acoustic resistance of the medium is just twice that of the crystal.
An Electrical Analog of the Vocal Tract
Authors: Stevens K. N. , Kasowski S. , Fant C. Gunnar M.
Published: September 2005

The design and construction of an electrical analog of the human vocal tract is described. The vocal tract is viewed as an acoustic tube of varying cross-sectional area, terminated by the vocal cords at one end and by the lip opening at the other. The analog is a lumped-constant electrical transmission line consisting of thirty-five pi-sections. Each section represents a 12-cm length of the vocal tract and is adjustable to simulate a range of cross-sectional areas from 0.17 to 17 cm2. The electrical line can be excited by a periodic current source representing the vocal cord output or by a random voltage representing the noise from turbulent air flow at a constriction. The electrical analog can synthesize with good quality all English vowels and some consonants. The physical characteristics of the output of the analog for each sound are shown in terms of measured formant frequencies or by conventional spectrograms. For each sound, the vocal tract dimensions that the electrical network simulates are shown in graphical form. Applications of the speech synthesizer to linguistic and engineering research are discussed briefly.
Shearing Microphonics Produced by Vibrations near the Inner and Outer Hair Cells
Authors: v. Békésy G.
Published: September 2005

It is possible to show that a laterally vibrating needle placed on the tectorial membrane produces microphonics. The size of these microphonics changes according to the direction of the lateral movements and the place on the tectorial membrane. On the outer edge of the tectorial membrane the microphonics went through a maximum when the direction of the vibrations lay in the direction of the fibers of the tectorial membrane. Perpendicular to this direction the microphonics went through a minimum. On the inner edge of the tectorial membrane the whole direction pattern is turned around counterclockwise somewhat less than 90 degrees. There are two sets of microphonic generators very close to the inner and outer hair cells. The inner set is more sensitive to lack of oxygen. These two sets may be able to discriminate between the radial and longitudinal vibrations of the organ of Corti, a change that occurs near the place of maximal stimulation in the cochlea exposed to a tone.