bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Propagation of Elastic Waves in Thin-Walled Cylindrical Shells
Authors: Junger Miguel C. , Rosato Frank J. 
Published: September 2005

This paper presents a study of the propagation of elastic waves in the walls of cylindrical shells. Two modes of propagation in the axial direction are found to exist; at high frequencies, the one corresponds to flexural waves, the other to longitudinal waves. The dispersion curves are in good agreement with published experimental data. Hitherto available analyses are based on the membrane theory of shells, which disregards bending stresses; these analyses lead to partly different conclusions in that they predict a “dead” frequency region where no propagation occurs, and in that they do not account for the high-frequency flexural mode. The discrepancy carries over into the evaluation of the natural frequencies of the tube, and of the dispersion of pressure waves propagating in liquid-filled tubes. Published experimental data on the latter process at ultrasonic frequencies also support the present analysis.
Results of this analysis have been applied to the investigation of the dynamics of barium titanate transducers in the form of cylincrical shells. Some important concepts of sound insulation by lightweight partitions, such as the “coincidence dip,” depend essentially on the ratio of the sound velocity in air to the phase velocity of elastic waves in the partition; the present analysis might therefore also find a practical application in the adaptation of these concepts to cylindrical surfaces, such as the skin of aircraft fuselages or architectural shells.
Pitch Shifts Accompanying Certain Auditory Threshold Shifts
Authors: Webster J. C. , Schubert E. D. 
Published: September 2005

A method was developed for getting a continuous and running record of pitch matches between the two ears, using (1) the sychronized frequency- and paper-drive features of a “Bekesy” type audiometer and (2) the subject's adjustment of the frequency knob of a second oscillator to drive the recording pen. A one-second tone from the motor-driven (standard) oscillator (controlling the paper drive) is presented to one ear and a two-second tone from the subject's (variable) oscillator (controlling the pen writing mechanism) is presented alternately to the other ear. The subject, who controls the frequency of the variable tone, is instructed to keep the two alternating tones matched in pitch.
Ten music students made these pitch matches (90 matches per octave) from 150 to 9600 cps. In the ear in which the standard tone was heard various types and amounts of hearing loss were simulated by masking noises. The pitch tended to shift away from a region of hearing loss to a region of no, or less hearing loss. Downward shifts were observed but were never as marked as the upward shifts.
Propagation of Sound over Single Absorptive Strips in Ducts
Authors: Young James E. 
Published: September 2005

The behavior of single absorptive strips imbedded in one wall of a hard duct is discussed by several approximate methods. The approximations are introduced in the order of increasing complexity. As a result an orderly scheme is obtained by means of which one can predict relevant physical quantities, such as attenuation, reflection coefficient, etc., with an accuracy suitable for practical utilization.
It is assumed throughout that the strips, extending over the width of one wall but of specified length, can be described by their normal impedance ratios. The excitation of the strip-duct structure is that due to a plane wave.
Measurements taken for a range of strip-wavelength ratios such that 0.56⩽kl⩽22.4 indicate that the lumped-parameter approximation is generally inadequate.
A variational principle is derived which together with suitable trial functions yields attenuations agreeing with measurements to within a few percent over the entire range of kl values.
Some attention is given to those limiting strip configurations for which other authors have obtained exact solutions. Comparisons are made between these and the present results.
Cumulative Effects of Repeated Bursts of White Noise on Threshold for 4000-cps Tone Pips
Authors: Lightfoot Charles , Jerger James F. 
Published: September 2005

Cumulative effects of a two-second burst of thermal noise on the threshold shift for 35-millisecond tone pips were examined by tracing the threshold shift over the course of 100 successive noise bursts. When bursts were presented at a rate of 6 per minute, a systematic increase in the threshold shift for the 35-millisecond tone pip was observed over the 100 burst series. Changing the burst-pip interval from 90 to 445 to 1000 milliseconds had little effect on the degree of this accumulation, but changing the SPL of the burst had a marked effect. At a burst level of 110 db (SPL re 0.0002 microbar) the mean threshold shift increased by about 6 db between the 15th and the 100th burst. Decreasing the burst level to 100 db reduced the mean accumulation to about 4 db, and at a burst level of 90 db to about 1 db. Changing the burst presentation rate from 6 per minute to 3 per minute reduced, but did not eliminate, the cumulative effect. The degree of this cumulative phenomenon showed wide individual differences among subjects.
It is concluded that, unless proper allowances are made, the repetitive stimulation required by burst-pip audiometry may be a source of serious error. On the other hand, the reaction of an ear to repeated stimuli may prove to be a useful index of the ear's susceptibility to irreversible acoustic trauma.
Theoretical Investigation on the Diffraction of Light by Superposed Ultrasonic Waves
Authors: Satyanarayana Murty J. 
Published: September 2005

An analytical treatment for the calculation of intensities of diffraction orders in a general case of superposed sound waves of frequencies in the ratio 1 :n and having any phase difference Δ is given proceeding from Raman and Nath's simplified theory for normal incidence. Because of the integral harmonic relationship between the frequencies of the sound waves superposed, a particular order may contain a number of combination lines in addition to the orders due to the individual sound waves. As such, Fues theory, which gives a single expression for the intensity of a combination line, cannot be applied to this case.
Expressions are obtained for the intensities of the diffraction orders in the two specific cases of even and odd values of n. In the case diffraction by two sound waves of frequencies in the ratio 1:2k+1 expressions for the intensities of the orders suggest symmetry in diffraction for all values of Δ. But, when the superposed frequencies are in the ratio 1:2k, the expressions suggest asymmetry in diffraction for all values of λΔ, except π/2. When Δ = π/2, the diffraction is, however, symmetric.
Using the expressions, the intensities of the diffraction orders obtained by two sound waves of frequencies in the ratio 1:3 superposed in three different phases 0, π/2, and π are calculated for the values of v1 = 1 and v3 = 1, 2, and 3.
Gas Bubbles with Organic Skin as Cavitation Nuclei
Authors: Fox Francis E. , Herzfeld Karl F. 
Published: September 2005

The hypothesis discussed that the cavitation nuclei consist in gas bubbles. Due to surface tension, small bubbles would dissolve in a very short time. If the bubbles are larger than 5×10−3 cm, or if the liquid is supersaturated, they may last longer or even be stable, but then no cavitation threshold exists.
The hypothesis expressed that the nuclei are very small bubbles, stabilized by an organic skin, which mechanically prevents loss of gas by diffusion. The cavitation occurs when the skin breaks and the threshold is determined by the breaking strength of the film and the size of the bubble.
An Analog Electronic Correlator for Acoustic Measurements
Authors: Goff Kenneth W. 
Published: September 2005

A study has been made of the applicability of correlation techniques to the field of acoustic measurements. The development of an analog electronic correlator for this study is reported here while the application of the correlation technique to some acoustic measurements is reported in a companion paper.
The analog correlator is divided into the following four main components and each one is discussed in detail: (1) variable time delay; (2) quarter-squaring multiplier; (3) continuous and stepping integrators; (4) system for scanning and plotting the crosscorrelation function on both linear and logarithmic scales.
The correlator operates over an input frequency range of 100 cps to 10 kcps, a range of relative time delay τ from −15 to 190 milliseconds and RC integration times of 0.5 to 16 seconds. A dynamic range in the crosscorrelation function of approximately 50 db is achieved with ±1 db accuracy.
Special attention has been given to the errors in the crosscorrelation function resulting from finite integration time and scanning of the correlation function. A significant increase in permissible scanning speed for a given signal-to-noise ratio has been shown to result from “matching” the equivalent integrator pass band to that of the spectrum common to the two signals applied to the correlator. Relations have been derived between scanning speed, signal-to-noise ratio, and input signal band width for integration performed by either a low-pass filter or a "matched" filter.
Diffraction of Light by Ultrasonic Waves Progressing with Finite but Moderate Amplitudes in Liquids
Authors: Zankel K. L. , Hiedemann E. A. 
Published: September 2005

The study of the asymmetry of the light diffracted by ultrasonic waves progressing with moderate amplitudes in liquids is used to detect and measure the finite amplitude distortion in water and carbon tetrachloride. A theory is developed which relates the distortion present to available isothermal compressibility measurements. This development includes the presence of absorption.
Measurements of the second harmonic were made in water at 2 Mc and 4 Mc, at distances up to 50 cm, and at peak ultrasonic pressures between zero and 1.5 atmos. More detailed measurements were made in carbon tetrachloride at frequencies of 2 and 3 Mc, at distances up to 21 cm, and at pressures up to 0.7 atmos. For both liquids, good agreement is obtained between the experimentally measured values and the theoretically predicted results.
Small amounts of distortion were easily measured. The second harmonic could be measured when the intensity of the harmonic was less than 0.04% of the intensity of the fundamental. Distortion could be measured when the fundamental was much less than 0.2 atmos.
Continuity Effects with Alternately Sounding Tones
Authors: Thurlow Willard R. , Elfner Lloyd F. 
Published: September 2005

The present experiments investigated the conditions under which one of two alternating tones can be made to sound continuous. When one tone, B, of 21-msec duration, was sounded alternately with a tone, A, 11.3 times per sec, tone A appeared to sound continuous if tone B was made 10 to 20 db higher in sensation level than tone A. The intensity required to produce the “continuity” effect was found to be least when tone B was near to tone A in frequency.
The continuity of tone A could be broken, however, by increasing the off-time of tone A (which also increased the on-time of tone B). To measure this more precisely, duration of interruption (off-time) of tone A was varied, and continuity thresholds were obtained for tone A alternating with tone B, when B was set near in frequency to A and at 15 db higher sensation level. It was found that tone A sounded continuous with longer off-times when tone B was present during the interruptions than when it was absent. Certain of these thresholds varied as a function of the rate at which tones A and B were alternated.
Effect of Ultrasonic Waves on Concentration Gradients
Authors: Penn Robert , Yeager Ernest , Hovorka Frank 
Published: September 2005

Schlieren techniques have been used to study the effects of ultrasonic waves on concentration gradients produced by electrochemical methods. With standing waves at intensities below cavitation levels, the zones of depleted electrolyte at the cathode stratify at the displacement nodes of the standing waves while the zones of excess electrolyte at the anode stratify at the displacement loops. These stratification effects provide an explanation for the ripples produced on the surfaces of metals electrodeposited in standing waves.
Microschlieren techniques indicate that ultrasonic waves at cavitation levels reduce the effective thickness of the diffusion layer at an electrode to a value of 10−3 cm or less. The mechanism for the disruption of the gradients is believed to involve the microdisturbances associated with cavitation bubbles at or near the electrode surface.
Surface and Groove Noise in Disk Recording Media. I
Authors: Howling D. H. 
Published: September 2005

A theoretical and experimental investigation into the causes and mechanism of playback surface and groove noise of recorded media has been made. It is shown that such noise can be considered as arising from the random superposition of voltage pulses produced by local changes in the number and size distribution of welded friction junctions or asperities supporting the playback stylus load. A generalized noise equation, involving the physical parameters of the recorded medium and the playback stylus, has been derived and shows reasonable agreement with the measured playback noise spectra for several cold-flowing and rigid plastic surfaces. From the noise equation emerges a concept of modulation noise and prediction of its dependence on modulation velocity. Examination of the playback noise level as a function of recording and playback conditions has also been included. It is also shown that surface noise measurements can be used to give information concerning the n/a ratio associated with the theory of friction.
The measured lower limit of wide band playback noise for most plastic surfaces corresponds to an equivalent rms lateral noise velocity of 10−2 cm/sec or equivalent lateral noise amplitude of 1 μin. peak at a linear velocity of 15 cm/sec. The equivalent roughness is thus half of that associated with an optical flat. Using this information, it is shown that at 1000 lines/in. information density a signal-to-noise ratio of 50 db at a linear velocity of 15 cm/sec should be realized.
On the Influence of the Diffraction of Sound Waves around the Human Head on the Characteristics of Hearing Aids
Authors: Wansdronk C. 
Published: September 2005

A small hearing aid, hanging in an anechoic room is made to drive an AVC circuit, the output signal of which is conducted to a power amplifier and loudspeaker and can be recorded on a tape. During playback of this tape, with the output of the recorder connected to the power amplifier, the same sound field as existed around the hearing aid is reproduced. If the apparatus is placed on a person in the position where it is to be worn and that person is situated so that the hearing aid is at the same point as during the recording, the output of the hearing aid during playback of the tape will indicate the influence of the diffraction around the human head.
Three specimens of hearing aid were measured on different people. The results showed that there exists a large difference between the hearing aids but no fundamental differences between the persons. The curves plotted for males and females showed the same trend, and no correlation was found with the hairdress. We did not succeed in an attempt to replace the human head by a simple model, such as a wooden sphere or a wooden box, the agreement of the diffraction phenomena between model and head being too poor.
Surface and Groove Noise in Disk Recording Media. II
Authors: Howling D. H. 
Published: September 2005

A theoretical and experimental investigation into the causes and mechanism of playback surface and groove noise of recorded media has been made. It is shown that such noise can be considered as arising from the random superposition of voltage pulses produced by local changes in the number and size distribution of welded friction junctions or asperities supporting the playback stylus load. A generalized noise equation, involving the physical parameters of the recorded medium and the playback stylus, has been derived and shows reasonable agreement with the measured playback noise spectra for several cold-flowing and rigid plastic surfaces. From the noise equation emerges a concept of modulation noise and prediction of its dependence on modulation velocity. Examination of the playback noise level as a function of recording and playback conditions has also been included. It is also shown that surface noise measurements can be used to give information concerning the n/a ratio associated with the theory of friction.
The measured lower limit of wide band playback noise for most plastic surfaces corresponds to an equivalent rms lateral noise velocity of 10−2 cm/sec or equivalent lateral noise amplitude of 1 microinch peak at a linear velocity of 15 cm/sec. The equivalent roughness is thus half of that associated with an optical flat. Using this information, it is shown that at 1000 lines/in. information density a signal/noise ratio of 50 db at a linear velocity of 15 cm/sec should be realized.
Transient Behavior of the Dynamic Absorber
Authors: Snowdon J. C. 
Published: September 2005

The ability of a dynamic absorber of optimum design to reduce the transient motion of resiliently mounted equipment is discussed theoretically. The motion of the mounted item is assumed to result from step-like foundation displacements possessing a wide range of rise times. The absorber mass is attached to the mounted item by a viscously damped spring. It is shown that the transient motion of the mounted item is characterized by the rapid manner in which it decays with time.
In general, if the contents of a resiliently mounted item are to receive the greatest possible protection from damage due to shock, the maximum acceleration and the maximum displacement and relative displacement of the mounted item should be simultaneously small. These are conflicting requirements, but they are fulfilled more closely than is possible with a simple mounting when a dynamic absorber of mass comparable to that of the mounted item is utilized.
Siren Design for Producing Controlled Wave Forms at High Intensities
Authors: Allen C. H. , Watters B. G. 
Published: September 2005

On the assumption of the additivity of steady and acoustic flow characteristics, an equation was developed for the time variation of a siren port area required to produce a sinusoidal wave. If low efficiencies can be tolerated the port opening may be kept small and the operating pressure made large compared with the acoustic pressure; then the equation reveals the well-known fact that the proper port area variation is nearly sinusoidal. For high efficiencies the operating pressure must be made to approach the peak acoustic pressure and the port area variation must depart widely from a sinusoid if a sinusoidal pressure wave is to be generated.
A siren was designed and built to verify the assumptions. The output signal was found to be sinusoidal at the design operating pressure and to depart from sinusoidal as expected at operating pressures either higher or lower. Efficiency at the design pressure was between 35 and 45% which is between 70 and 90% of the theoretical maximum efficiency for a sinusoidal sound generator of the siren type using a dissipative valving mechanism.
The derived equation might be used to determine the port area variation of a siren for generating chosen nonsinusoidal wave form by substituting, within limits, the expression for the desired wave in place of the sine function.
Measurement of Ultrasonic Wave Velocities and Elastic Moduli for Small Solid Specimens at High Temperatures
Authors: McSkimin H. J. 
Published: September 2005

An improved buffer rod-specimen unit is described for measuring longitudinal wave velocities in solids at temperatures up to 350°C. The method is particularly useful in determining elastic moduli of single crystals since very small path lengths in any prescribed direction can be employed. The use of molten metals to provide coupling at still higher temperatures is discussed.
Two methods involving mode conversion at an impedance discontinuity are described for measuring shear wave velocities. Application to crystals of cubic symmetry is detailed, with a note on possible extension to less symmetrical crystals of any orientation.
Data for fused silica and single crystal germanium are listed for temperatures up to 300°C in illustration of the methods described.
Acoustic Properties of Hemoglobin Solutions
Authors: Carstensen Edwin L. , Schwan Herman P. 
Published: September 2005

Absorption and velocity of sound in the range 0.5 to 10 Mc have been measured for solutions of hemoglobin under various conditions of temperature, concentration, and chemical environment. The hemoglobins of several species of mammals and different chemical forms of hemoglobin have been studied.
In the absorption per wavelength only minor variations with frequency have been observed. Dispersion in the velocity of sound of these solutions has been measured. It has been possible to relate quantitatively the magnitude of the absorption and dispersion through relaxation theory by assuming broad distribution of relaxation times.
Development of Apparatus for the Analysis of Sound by the Sense of Touch
Authors: Guelke R. W. , Huyssen R. M. J. 
Published: September 2005

An apparatus is described that applies the frequency components of speech, as spoken into a microphone, to the fingers of one hand with the purpose of enabling a deaf person to comprehend speech. Frequency is indicated by position along the fingers. The sense of touch is not called upon to make any direct frequency discrimination by distinguishing vibrational sensations of different frequencies as in previous attempts of this nature [R. H. Gault, J. Franklin Institute 204, 329–358 (1927)]. The frequency analysis is done partly electrically and partly mechanically. Small tuned steel reeds are used for the final frequency analysis. These steel reeds also serve as transducers by operating directly against the fingers.
The results of a short series of experiments on a deaf person are promising but the recognition of individual consonants is difficult.
Listener Reaction to Stereophonic Reproduction by Reflected Sound
Authors: Levy Sidney E. , Sioles George W. , Brociner Victor , Carlisle Richard W. 
Published: September 2005

Comparisons were made by numerous observers of the stereophonic perception of direct versus reflected sound. For conventional direct sound, two loudspeakers having wide frequency response were used at spacings of from six to fifteen feet, directed towards the listeners. For reflected sound, equivalent dual sound sources were used placed back-to-back near the walls of a room in which it was desired to establish a stereophonic sound field. The frequency response of the latter system was equalized to have the same apparent response as the conventional system.
Many of the tests were conducted behind a sound permeable screen. Listeners were mixed in their ability to identify the reflective system and in their preference for one system over the other, although they reacted favorably to both systems.