bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Theory of Steady Rotational Flow Generated by a Sound Field
Authors: Westervelt Peter J. 
Published: September 2005

Starting from the Navier-Stokes equations, general equation governing the generation of vorticity R is obtained: ∇2R = μ0−1∇ × ∇ ⋅ 〈ρ0uu〉, wherein R is the time-independent vorticity in the Eulerian frame and 〈ρ0uu〉 is the average value of Reynolds' stress dyadic. The solution to this vorticity equation, when properly transformed to the particle coordinates, is shown to be divergence free.
A specialization of the vorticity equation to the case of solenoidal first-order motion is shown to lead to the generating term employed by Rayleigh and by Schlichting; a specialization to the case of irrotational first-order motion is shown to lead to the generating term employed by Eckart. The sum of the two specialized driving terms does not equal the general term, indicating that the contributions to vorticity from rotational and compression effects are not independent of one another.
The theory is applied to find the streaming generated by a well-defined beam of sound giving results agreeing with Eckart and with Markham. However, when it is applied to a two-dimensional standing wave problem, the configuration of the streaming velocity in the boundary layer is found to differ from the results obtained by Rayleigh.
Finally, the effect on streaming of a time-dependent viscosity coefficient is examined.
Temperature Changes Produced in Tissue during Ultrasonic Irradiation
Authors: Fry William J. , Fry Ruth Baumann 
Published: September 2005

This paper is concerned with the technique of temperature measurement in living tissue during irradiation by high intensity ultrasound. The interpretation of data obtained by the use of thermocouples is presented. The specific biological object used in this study is the spinal cord of rat exposed by laminectomy. This particular preparation serves to illustrate the relative importance of the heat conduction process in contributing to the temperature change as a function of the proximity of the imbedded thermocouple to bone and the time elapsed after initiation of the exposure.
The ultrasonic frequency used in these studies was 980 kc. The sound intensities incident on the cord were between 60 and 80 watts/cm2.
The experimental results presented in the paper are used to obtain values for the acoustic absorption coefficient of the tissue of the spinal cord. The range of values obtained for the intensity absorption coefficient per centimeter from measurements made on six adult rats at various positions in the spinal cord is 0.19 to 0.23 if the heat capacity of the tissue at constant pressure is 1.00 calorie/cm3.
Measurement of the Propagation of Sound in Fiberglas
Authors: Esmail-Begui Z. , Naylor Thomas K. 
Published: September 2005

As an aid to acoustical designers, this paper presents some experimentally determined values of the attenuation coefficient and the speed of propagation of sound in Fiberglas. The propagation parameters α and β in the equation for a plane wave p = p0εjωt−(α+jβ)z are determined by comparing the amplitudes and phases of the sound pressures existing simultaneously at separate points in the Fiberglas. The principle of measurement is similar to that used by Beranek and Scott involving a longitudinal movable probe in a long narrow metal duct filled with rockwool. However, in the redesigned apparatus, edge effects were reduced by using a tube of larger cross section; wall vibrations were damped by laminated rubber and Masonite walls; and the shunting effect of the longitudinal probe hole was eliminated by the use of transversely inserted microphones.
Experimental data were obtained within one db for frequencies between 50 and 1000 cycles for two samples of Fiberglas with nominal weights of 9 lb/cu ft PF (hard) and 414 lb/cu ft TWF (soft). The direction of propagation of the sound was normal to the surface of the blanket. For both samples the attenuation increases almost as the square root of the frequency, but the speed of propagation is found to increase almost as the 14 and 12 root of the frequency for the hard and the soft samples, respectively.
Transducers for Producing Ultrasonic Waves
Authors: Mattiat Oskar 
Published: September 2005

After a short description of mechanical transducers such as the siren in air and the Pohlman Whistle in liquids, some fundamentals of electromechanical transducers using electric and magnetic fields are given, and magnetostrictive and piezoelectric transducers for the irradiation of liquids which are available on the market are mentioned.
In the second part transducers made of barium titanate (“ceramic transducers”) are described. Polycrystalline ceramic material can be shaped and thereafter polarized in such a way as to produce convergent waves, with the possibility of focusing ultrasonic energy and thus creating zones of extremely high ultrasonic intensities. Electrical and acoustic data on spherical ceramic transducers are given. Fair agreement is found between O'Neil's theory of spherical transducers and measurements of the pressure distribution in a sound field along the central axis in front of the transducer. The diagram of motional impedance for a 400 kc spherical bowl and power limitations of ceramic transducers are discussed. Finally, a tubular ceramic transducer is described which seems to offer good possibilities for efficient treatment of large liquid volumes in a continuous flow process.
Magnetic Dispersion of Sound in Electrically Conducting Plates
Authors: Robey Donald H. 
Published: September 2005

It is shown theoretically that plane longitudinal sound waves traveling in an electrically conducting plate will generate complex electric currents provided there is a magnetic induction perpendicular to the particle displacement. The currents react with the induction to produce a complex mechanical force which opposes the particle motion. The impedance associated with this force effectively modifies the impedance of the medium by adding a resistance and a stiffness reactance. The induced resistance attenuates the waves while the induced stiffness increases Young's modulus and therefore increases the sound velocity.
Of all the elements, it appears that this effect is a maximum in lithium, i.e., at a given frequency and induction.
Ultrasonically Induced Cavitation in Water: A Step-by-Step Process
Authors: Willard G. W. 
Published: September 2005

A 2.5-Mc, barium-titanate, spherically focusing radiator was used to produce cavitation in both degassed and aerated water entirely within the restricted, high intensity focal region, remote from the water boundaries. The sonic intensity rises to 1.8 kw/cm2, and the pressure amplitude to ±70 atmos at the focus. High-intensity illumination and an unusual high speed photographic technique permit observation and timing of the step-by-step process of cavitation development.
Feather-shaped cavitation bursts are sporadically produced, being initiated in the insignificant quill portion nearest the radiator, then abruptly expanding to form the catastrophic plume portion. The plume is believed to be formed by myriads of micro-cavities, too small and close for individual observation. These two fundamental steps are identically produced, and with equal ease, both in degassed and aerated water. The whole action is over in several milliseconds, except that in the case of aerated water a third bubble step is produced. In aerated water, non-collapsing gas bubbles are generated by and concurrently with, the catastrophic step. These bubbles remain after collapse of the burst, to be blown off down stream by the sonically induced liquid streaming.
The bubble step is not generated without the presence of the catastrophic step. The latter is generated only if the initiation step reaches a definite degree of development (not always attained). This requires sonic activation for increasing lengths of time for decreasingly smaller sonic intensities. Origination of the initiation step, and hence of the whole cavitation phenomena, is believed to occur whenever a stray nucleus (weak spot) streams into the high intensity sonic field.
The Absorption of Sound in Gas Mixtures
Authors: Angona F. A. 
Published: September 2005

The absorption of sound has been measured in CO2, CS2, C2H4O, and in mixtures of the latter two gases with CO2 for frequencies ranging from 2 to 10 kc and for pressures ranging from 3 to 300 mm of Hg. The tube method was employed. The absorption was determined by observing the decrease in sound pressure as the path length between the speaker and the microphone was increased. A fixed condensor microphone and a movable ribbon-type speaker were used.
The measured absorption coefficient was corrected for the effect of the tube and also for the absorption due to viscosity and heat conduction of the gas. The corrected absorption coefficient was then plotted as the attenuation coefficient per wavelength against the logarithm of the ratio of frequency over pressure. These curves were then compared to those determined from Bourgin's Theory for mixtures of absorbing gases. The agreement between the observed attenuation and that predicted by the theory was within 5 percent.
A Vortex Whistle
Authors: Vonnegut Bernard 
Published: September 2005

Simple whistles have been constructed that produce sound by the escape of a vortex from the open end of a tube. The whistle operates equally well on either air or water.
When the frequency that is produced by the passage of either air or water is plotted against the volume rate of fluid flow, it is found that the frequency depends almost linearly on the rate of flow and that the number of cycles produced by the flow of a unit volume of air is nearly the same as that produced by the flow of a unit volume of water. Measurements have been made relating the frequency of the sound produced to different pressures of air applied to the whistle.
Boundary Layer Flow Near a Cylindrical Obstacle in an Oscillating, Incompressible Fluid
Authors: Holtsmark J. , Johnsen I. , Sikkeland T. , Skavlem S. 
Published: September 2005

1. The flow in two dimensions of an oscillating incompressible fluid near a circular cylinder with its axis normal to the direction of oscillation, is studied theoretically and experimentally. Starting from Navier-Stoke's differential equations the method of successive approximations has been used in order to get approximative solutions, when the appropriate boundary conditions are applied. The zeroth approximation gives the modified field of oscillation near the cylinder as a function of the viscosity. The first approximation also gives a stationary flow, which is found from the solution of an ordinary linear differential equation of 4th order.
2. Experiments have been carried out in air in a Kundt's tube. The velocities in the plane normal to the axis of the cylinder have been found by photographing smoke particles in air. The experimental and theoretical results agree fairly well. Comparison with corresponding data obtained by Schlichting is also made.
Some G functions, derived from Hankel functions which have been used in the theoretical solutions, have been tabulated to 6 digits.
Determination of Absolute Sound Levels and Acoustic Absorption Coefficients by Thermocouple Probes—Theory
Authors: Fry William J. , Fry Ruth Baumann 
Published: September 2005

A detailed theoretical analysis of the operation of thermocouple probes used to determine absolute sound levels or acoustic absorption coefficients is presented.
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 excited 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 theoretical discussion includes an analysis of the relation between the temperature rise at the junction resulting from absorption in the body of the imbedding medium and the sound level. In addition, the effects of (a) viscous forces arising from relative motion between the thermocouple and the imbedding fluid and (b) heat conduction between the thermocouple and the fluid, in contributing to the temperature change at the thermocouple junction are analyzed.
Based on the analysis, a set of design formulas is obtained which are summarized and illustrated for the convenience of other investigators who may wish to design and use such probes.
Acoustic Factors in the Design of Noise-Reducing Telephone Booths
Authors: Bishop D. E. , Hewitt F. G. , Callaway D. B. 
Published: September 2005

Acoustically treated, doorless telephone booths can increase the effectiveness of telephone communication in noisy environments even though practical size and open area requirements limit the amount of noise reduction which can be achieved. The principal factors determining the noise reduction of an acoustically treated booth (where the noise reduction is considered as the decibel difference in octave band noise levels measured outside and inside the booth) have been investigated by use of full size and 13 model booths.
The principal parameters affecting the reduction of an acoustically treated telephone booth were found to be (1) the sound absorption coefficients of the wall surfaces as function of frequency; (2) the ratio of open area to the wall area of the phone booth; (3) the transmission loss of the walls of the phone booth; and (4) the size and shape of the booth.
The investigation resulted in a new triangular design of booth which is fully as effective acoustically as the rectangular booths, yet has added practical advantages.
Subjective Musical Pitch
Authors: Ward W. D. 
Published: September 2005

The subjective relation “octave of” is demonstrated to be a valid interval for determining scales of musical pitch for pure tones presented successively. Octave judgments of trained musicians have a standard deviation averaging about 0.6 percent. Inter-observer variability is 2 to 5 times as great, increasing with frequency. Judgments vary significantly from day to day, but as the direction of shift at different frequencies for a single observer is random, the shifts cannot be attributed to changes in the octave criterion. Instead, this variability, and also (1) differences between right- and left-ear judgments of a given observer, (2) the change in difference between subjective and physical octaves as a function of frequency, and (3) the high inter-observer variability, all confirm the basic instability of pitch-frequency relations implied by the facts of binaural diplacusis.
Individual and group scales of musical pitch are deduced. In these scales, the average rate of change of musical pitch with respect to frequency level is less than unity by a small but significant amount. Although this discrepancy not explained, tests show that it is not an obvious artifact of method. Simultaneous presentation raises variability, but affects means only slightly. The relation betwen the peculiarities of individual scales and binaural diplacusis discussed.
Responding to Both of Two Overlapping Messages
Authors: Webster J. C. , Thompson P. O. 
Published: September 2005

Air control tower operators listened to test transmissions, consisting of speech intelligibility tests couched in airplane-tower phraseology, over four channels. Part of the time the messages of two channels overlapped each other and the degree of overlap was systematically varied. The task was to respond to all messages.
The results showed a decrement in performance related directly to the amount of overlap, the leading message being understood better (unless it was considerably lower in intensity). For those parts of the message which had low informational content, the messages of the overlapping channel increased the total assimilated information per unit time above the total assimilated in the absence of the competing channel messages.
Theory of the Effect of a Thin Air Film on the Vibrations of a Stretched Circular Membrane
Authors: Robey Donald H. 
Published: September 2005

In the design of condenser microphones it is standard practice to insert holes or furrows into the electrode face. This modification helps to prevent radial air flow through the electrode-membrane interstice which can result in large dissipative and reactive effects, provided the separation is small.
The theory governing air reactions from an unmodified electrode is presented. An attempt was made to start with general fundamental equations. Only those simplifications which appeared to have a negligible effect on the accuracy of the results were made; for example, body forces and nonlinear terms have been neglected. Air inertia, rotational and irrotational velocity components, and viscous terms have been retained in the theory. Curves showing the effects of air reactions on the amplitude, phase, and impedance of a stretched titanium membrane are shown. The air stiffness, which continuously increased for increasing frequencies in the range 5 to 20 0000 cps, caused the amplitude of the membrane to diminish by more than 20 db. In general, air which is trapped behind the membrane will cause the response of the microphone to rise as the frequency is lowered.
Some Factors Affecting Multi-Channel Listening
Authors: Egan James P. , Carterette Edward C. , Thwing Edward J. 
Published: September 2005

Certain factors were investigated that affect the intelligibility of a speech message which is presented to a listener simultaneously with an interfering speech message. In two of the four experiments reported, filters were introduced into one of the two channels that carried the messages. Thresholds of perceptibility were not reliably decreased by moderate amounts of filtering of the received message. However, articulation scores were considerably increased by the use of a high-pass filter (500 cps) in either of the two channels.
The great advantage of presenting one message to one ear and the interfering message to the other ear (dichotic presentation) was measured by changes in the thresholds of perceptibility and by articulation tests. Functional relations between thresholds of perceptibility for the message to be received and the intensity of an interfering signal were determined for both monaural and dichotic listening. In separate tests, noise was also used as the interfering signal. Dichotic reception permits a reduction in intensity of the received signal of about 30 db as compared with monaural reception. Articulation-gain functions demonstrated a similar advantage for dichotic over monaural listening.
When the message to be received and the interfering message are monaurally received at equal intensities, the articulation scores for the designated messages are about 50 percent. If the message to be received is somewhat less intense than the interfering one, the cue value of the intensity difference offsets the increased masking of the less intense by the more intense message.
Acoustical Studies of the Tractrix Horn. I
Authors: Lambert Robert F. 
Published: September 2005

When predicting and comparing the acoustical properties of horns it is customary practice to formulate the propagation as a one-parameter plane wave front problem. However, when particular attention is paid to the rapid flare near the mouth of a horn structure such as the tractrix, it also seems plausible to formulate the propagation on the basis of a one-parameter spherical wave front theory. By visualizing the surfaces of constant phase as spheres of constant radii a and the flow lines as tractrixes having a generating arm of length a, a one-parameter wave equation and Ricatti impedance equation may be derived. Solutions to these equations have been obtained by wave perturbation and by analog computer techniques.
Axial response and throat impedance measurements are compared with theoretical calculations postulating first a hemispherical and then a plane piston radiation pattern. It appears that the most satisfactory explanation lies somewhere in between these two limiting cases.
Perstimulatory Fatigue as Measured by Heterophonic Loudness Balances
Authors: Egan James P. 
Published: September 2005

Perstimulatory fatigue is the decrease in loudness of a steady auditory stimulus during its presentation. In the past it has been measured by requiring a simultaneous dichotic loudness balance between two pure tones of the same frequency, one in each ear. Under these conditions the listener hears a single phantom sound whose localization depends upon the relative intensities of the two tones. The present investigation shows that the process of localizing the sound image in making the loudness balance is not critical to the occurrence of perstimulatory fatigue.
Two principal conditions were compared. In the first, the frequency of the comparison stimulus was the same as that of the fatiguing stimulus. In the second, the comparison and fatiguing stimuli differed sufficiently in frequency so that the listener always heard two pure tones which he could correctly localize in the two ears. It is concluded that the amount of perstimulatory fatigue is very nearly the same under these two conditions.
In the early phases of the present research it was suspected that the loudness balances were influenced by absolute judgments of loudness. A procedure is developed which precludes the formation of a single absolute standard of loudness. This method results in greater measured fatigue than the usual procedure.
Steady Rotational Flow of an Incompressible, Viscous Fluid Enclosed between Two Coaxial Cylinders
Authors: Skavlem S. , Tjötta S. 
Published: September 2005

This paper gives a theoretical study of the two-dimensional flow of an incompressible, viscous fluid enclosed between two coaxial cylinders, one of which is oscillating. The Reynolds number is assumed to be small, and the Navier-Stokes differential equations are solved by means of the method of successive proximations. Both for the first and second order solution the proper boundary conditions are applied. We have shown that there exist two stationary circulation systems in every quadrant, and that the direction of circulation is opposite in these two systems. The circulation velocities are calculated in detail, and the results are compared with experimental results referred to in an earlier paper. Some new experimental results, which are not published yet, are briefly mentioned. The agreement between theoretical and experimental results is excellent.
In a discussion at the end of the paper we give the explanation of the remarkable fact that in some experiments the direction of circulation seems to reverse when the oscillation amplitude increases and exceeds a certain critical value.
Simple Derivation of the Boltzmann-Ehrenfest Adiabatic Principle
Authors: Greenspan Martin 
Published: September 2005

The time-average forces exerted by the constraints of a vibrating system (radiation pressure, mean tension in a vibrating string, etc.) are easily computed from the adiabatic principle of Boltzmann and Ehrenfest (BE principle). The usual derivation from the “principle of varying action” is difficult.
Here an equivalent principle (which gives in addition the time dependence of the forces) is derived from Lagrange's equations. It is also shown how similar results can be got from the solution of a linear differential equation with slightly variable coefficients.