bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sound Propagation into the Shadow Zone in a Temperature-Stratified Atmosphere above a Plane Boundary
Authors: Pridmore-Brown David C. , Ingard Uno 
Published: September 2005

The sound field in the “shadow zone” (diffraction region) formed over a plane boundary in an atmosphere with a constant vertical temperature gradient is analyzed both theoretically and experimentally. The boundary condition at the plane is given by a normal acoustic impedance independent of the angle of incidence. As in the corresponding problem of underwater sound where the boundary is a pressure release surface, it is found that the major portion of the sound pressure in the shadow zone decays exponentially with distance at a rate proportional to the one-third power of frequency and two-thirds power of temperature gradient. The effect of boundary impedance enters mainly through its resistive component. The rate of sound decay for a pressure release boundary (zero impedance) is found to be 2.3 times that for a rigid boundary (infinite impedance).
Sound pressure measurements in the shadow zone in a laboratory chamber in which a large temperature gradient was created were made for both hard and absorbing boundaries, and the results were found in essential agreement with theory.
Transducer Design for Ultrasonic Delay Lines
Authors: McSkimin H. J. 
Published: September 2005

The problem of obtaining low loss ultrasonic delay lines for switching, computer, and certain radar applications is discussed. An analysis is made of structures using half-wavelength and quarter-wavelength bonds between the transducer and the acoustic medium to widen the pass-band; results are listed for both quartz crystal and barium titanate transducers.
For barium titanate transducers (80 percent BaTiO3, 12 percent PbTiO3, 8 percent CaTiO3), it is shown that a theoretical flat band width of approximately 30 percent with less than 1 db midband loss can be obtained with a bond of negligible thickness. This band width can be increased to approximately 46 percent without additional loss if a properly designed bond is used, (i.e., 14λ bond for radiating into water, 12λ for use with a fused silica delay medium). A 70 percent band width can be obtained with only 4 db loss per transducer.
Confirming experimental results are described for delay lines using quartz crystals and one-half wavelength plastic seals or one-quarter wavelength solder seals. For the latter, band widths of 85 percent of midband frequency have been obtained. An efficient delay line using BaTiO3 transducers is also described.
Theory of Noise and Vibration Insulation of a System with Many Resonances
Authors: Skudrzyk Eugen 
Published: September 2005

The results obtained in a previous paper, Part I of this study, are summarized and used to derive the theory of vibration and sound insulation of systems with many natural frequencies, such as machines with more than one resonance mounted on resonating springs, a motor spring-mounted on a shell, or plates at higher frequencies. At lower frequencies, the quality of the insulation is a function of the ratio of the square of the lowest fully excited resonant frequency to that of the frequency of the force. Weakly excited natural modes cause spikes in the transmission curve. Resonances in the vibrating masses may annihilate completely the effect of the vibrator mounting, whereas resonances in the springs are harmless as long as the mass is small in comparison to that of the machinery. Spring mounting a vibrator on a shell or plate reduces the noise level considerably. Any measure that increases the fundamental natural frequency to the housing helps to improve vibration insulation. Mounting the vibrator in a rigid cage or onto a rigid girder seems to be expedient; and welding these along a whole circumference or along their whole length onto the housing, to simulate a one-dimensional vibration pattern, is expedient.
The noise radiation of a shell or plate to greater distances can be reduced by increasing the mass of the radiating shell or plate and by decreasing its size sufficiently to reduce the number of modes that radiate sound. Damping diminishes the sound radiation at lower frequencies, but has very little effect on it at higher frequencies.
Analysis of a Logarithmic Solion Acoustic Pressure Detector
Authors: Wittenborn A. F. 
Published: September 2005

An analysis is given of a solion acoustic pressure detector which has a direct current output proportional to the logarithm of the pressure input. An approximate method is used which avoids solving the Navier-Stokes equation describing the fluid flow and the convection diffusion equation for calculating the current.
The calculation consists of (1) solving the zero flow “transient” diffusion equation for the reducible component in the electrochemical redox system, (2) using this transient solution to calculate the output current, with the time spent inside the detector orifice as the independent variable, and (3) relating this time to the pressure by using the known acoustic impedance of the detector orifice.
The calculated results show that the logarithmic response is obtained through a combination of diffusion and hydrodynamic effects. For the ideal case of constant impedance as a function of volume flow, the logarithmic response is degraded.
Beats in Cochlear Models
Authors: Tonndorf Juergen 
Published: September 2005

Beats in cochlear models were studied from two aspects.
(1) Their effect upon cochlear fluid motion which, occurring along elliptical orbits, essentially represents Lissajous figures. The orbits expanded and contracted synchronously with the beat rate. Thereby, a partial rectification (asymmetrical expansion) became apparent which, occurring opposite directions in the two scalae across the partition, constituted the beat. This latter phenomenon was caused by the stiffness gradient of the cochlear partition.
(2) Their effect upon the traveling wave pattern along the partition was originally described by Békésy. Stroboscopic examination revealed that the beat frequency modulates the two primaries thus producing two additional side bands. However, the displacement pattern of the membrane when viewed by high-speed motion photography did not give any evidence of these five frequencies. Only the intertone (and the beat) was present. It then became apparent that the model is really a pattern analyzer of complex sound. In terms of cochlear fluid motion, it is able to resolve complex Lissajous by a spatial filter action along the partition into simple Lissajous. Any deviation from steady Lissajous, which ordinarily result from primaries in relation of integral numbers, produces beats. Thus beats of imperfect unison as well as of mistuned consonances have essentially the same cause: a cyclic phase change between the two primaries.
Ultrasonic Absorption Microscope
Authors: Dunn Floyd , Fry William J. 
Published: September 2005

This paper constitutes a progress report on the development of an ultrasonic instrument for detecting microstructure. The principle of operation of the device (designated by the term “ultrasonic microscope”) is as follows: The specimen is imbedded in a liquid, which closely matches it in acoustic impedance, and is irradiated with short pulses of high-frequency sound. Some of the ultrasonic energy is absorbed in the specimen and the remainder leaves it and excites a small thermoelectric probe placed immediately adjacent to the region being investigated. As the specimen, which is between the sound source and the probe, is moved in a direction normal to the direction of sound propagation, a varying acoustic signal will be detected by the probe. This is a consequence of the fact that the amount of acoustic energy absorbed by the specimen in the portion immediately adjacent to the probe is determined by the structure of that part of the specimen.
Preliminary experimental results obtained with such a “microscope” operating at a frequency of 12 mc/sec are presented.
Acoustics of the Fredric R. Mann Concert Hall, Tel Aviv, Israel
Authors: Beranek Leo L. 
Published: September 2005

The Fredric R. Mann concert auditorium for an audience of about 2900 and a volume of 750 000 cu ft opened on October 2, 1957. This article covers general design objectives, factors influencing reverberation time (the final value of reverberation time at 500–1000 cps with full occupancy is 1.55 sec), shaping, means for controlling reverberation, echo studies, orchestra enclosure, control of exterior noise, and subjective assessments and recommendations for subsequent changes.
The auditorium was designed in accordance with specifications laid down by the Building Committee in September 1951. The design achieved the original objectives. Some changes in the orchestra enclosure and ceiling are desired by the musicians. Acceptance of the hall by audiences has been excellent.
Measurements of the Backscattering of Underwater Sound from the Sea Surface
Authors: Garrison G. R. , Murphy S. R. , Potter D. S. 
Published: September 2005

Measurements of the backscattering of 60-kc sound from the surface of the sea have been made in Puget Sound in an effort to relate the strength of the scattered sound to the character of the surface. In addition to providing a means of predicting reverberation levels, an attempt has been made to obtain a better understanding of the fundamental mechanism of scattering at the air-water boundary.
The reverberation measurements are presented, along with observations of several oceanographic and meteorological parameters. An examination of the data allows the following conclusions: (1) reverberation pulses from an area of several square yards follow a Rayleigh distribution; (2) reverberation cannot be directly related to the wave height, but is closely correlated with wind speed; (3) reverberation increases with wind speed to a speed of 14 knots, and remains constant for higher wind speeds; and (4) reverberation is independent of the angle with the surface for angles from 20 to 60 degrees, but drops off rapidly as the angle is decreased below 20 degrees.
Noise Production in a Turbulent Boundary Layer by Smooth and Rough Surfaces
Authors: Skudrzyk E. J. , Haddle G. P. 
Published: September 2005

In a turbulent boundary layer, the effective velocity fluctuations amount to about 4% of the free-stream velocity, independent of the curvature of the body and within wide limits independent of the velocity of the flow. The fluctuations in pressure can then be computed from those of the velocity by an equation similar to the standard Bernoulli equation, except that the numerical constant is different. Vortices pass along the receiving hydrophone; they represent pressure pulses that generate a constant power spectrum at low frequencies that decreases approximately inversely proportional to the cube of the frequency at higher frequencies. This information, in conjunction with the pressure equation, makes it possible to compute the power spectrum of the flow noise as a function of the frequency, the boundary layer thickness and the speed of the flow. The flow noise at greater speeds and at higher frequencies turns out to be predominantly generated by the surface roughnesses.
A small hydrophone records the local fluctuations at the pressure in the boundary layer; on the other hand, a large hydrophone is very insensitive to the small-scale turbulence. It indicates the true sound pressure that is produced by the generation and the decay of the turbulence and by the vibrations of the walls of the vessel. A large hydrophone therefore reads the same pressure, whether it is placed inside the boundary layer or outside the near field region, not too far away from the turbulent layer. The theoretical conclusions are borne out, qualitatively and quantitatively, by the experimental results obtained with the aid of a rotating cylinder and through measurements in the test section of the Garfield Thomas Water Tunnel.
Spoken Digit Recognition Using Time-Frequency Pattern Matching
Authors: Denes P. , Mathews M. V. 
Published: September 2005

A study of the machine recognition of the spoken digits zero through nine has been carried out by a digital computer simulation. The spoken utterances were converted to time-frequency patterns of spectral energy. Recognition was done by cross correlating the pattern of an unknown utterance with a test pattern for each digit and selecting the digit having the highest correlation. Time normalization could be applied to all patterns, thus reducing utterances to a standard duration. Six male and one female speakers provided 38 samples of each of the 10 digits. Pauses were made between successive words for segmentation.
No errors were observed recognizing a single speaker using test patterns from his own speech with time normalization. A group of five male speakers and test patterns averaged over the group produced 6% errors with time normalization and 12% without. A 25% rate occurred for the woman matched against male patterns.
The study indicates both the effectiveness and limitations of this simple recognition procedure for limited vocabulary and limited number of speakers. Time normalization improves performance in all cases.
Ultrasonic Waves and Electrochemistry. V. The Frequency Characteristics the Electrokinetic and the AC Polarized Gas Electrode Effects
Authors: Saunders Frank , Yeager Ernest , Hovorka Frank 
Published: September 2005

The frequency characteristics of the acousto-electrokinetic effect and the ac polarized gas electrode effect have been determined with pulse-modulated ultrasonic waves in the range 200 to 1000 kc/sec as a function of solution and electrode parameters. The electrokinetic effect involves the alternating potentials produced by acoustical waves on an electrode surrounded by a porous coveting in a dilute electrolyte while the ac polarized gas electrode effect involves the production of alternating components in the potential of a polarized electrode in an electrolytic solution with a gas such as hydrogen being liberated by a polarizing current. In the case of the electrokinetic effect, the open-circuit response relative to the pressure amplitude is inversely proportional to the frequency in very dilute solutions. The frequency dependence becomes considerably less with increasing conductance of the solution. The pressure response for the polarized hydrogen electrode also decreases with increasing frequency although the extent of the decrease is a function of current density and specific conductance. Both the response and stability of the polarized gas electrode have been greatly improved by the use of a directed flow of solution past the electrode to remove the cloud of gas bubbles in the bulk of the solution surrounding the electrode.
The mechanisms proposed for these effects in earlier publications have been further substantiated by the present work.
Shearing Motion in Scala Media of Cochlear Models
Authors: Tonndorf Juergen 
Published: September 2005

In 1953, Bekesy first reported the occurrence of shearing motion within the cochlear duct and furthermore the notion that it is this mode of motion which constitutes the adequate stimulus for the hair cells. There were two modes of shear motion: radially directed in the region proximal to the place of maximal amplitude of the traveling-wave pattern, and longitudinally directed distal to that point.
This phenomenon was studied in cochlear models. The envelopes over both modes of shear motion were found to be much smaller than that over the traveling-wave pattern. A simple explanation presented itself. The direction of the shearing motion in each domain coincides with the dominant curvature produced by the traveling waves in that section of the cochlear duct.
Earlier, it had been shown that under the effect of Bekesy's eddies, i.e., at higher driving amplitudes, the displacement pattern of the cochlear partition becomes asymmetrical. This asymmetry produces a dc-shift in both domains of shear motion: in an outward direction within the domain of radial shear and in an apical direction within the domain of longitudinal shear. However, when the round window was driven, both directions of the dc-components were reversed. The latter finding aided in establishing the causal relationship mentioned in the foregoing.
Patterns of Injury Produced by Overstimulation of the Ear
Authors: Wever Ernest Glen , Lawrence Merle 
Published: September 2005

Measurements of the cochlear potentials as recorded from the round window were carried out on a series of guinea pig ears to ascertain the effects of injury by overstimulation with various tones. The results showed general impairments of the responses after such injury. With rare exceptions, the maximum responses to any tone are much less impaired than the sensitivity, and the maximums are more seriously affected for the low tones. In general, these changes are independent of the frequency of the tone producing the injury.
These observations confirm those of earlier studies on the patterns of action of tones in the cochlea, and indicate that all tones when raised to extreme levels cause widespread damage to the hair cells. It is suggested that certain hair cells, which are normally involved in the peak actions of all tones, are particularly susceptible to damage by overstimulation.
Listening to Differentially Filtered Competing Voice Messages
Authors: Spieth W. , Webster J. C. 
Published: September 2005

An attempt was made to improve listeners' ability to respond to one of two or more simultaneous or overlapping voice messages by differentially filtering the competing message channels.
The limits of satisfactory intelligibility of two digits and two International Civil Aeronautics Organization (ICAO) phonetic alphabet words in a message also containing an address were determined under various conditions of high- and low-pass filtering and speech-to-noise ratios (S/N). Within these limits, several amounts of filtering were tried in various combinations.
When performance on differentially filtered competing messages was compared with performance on unfiltered competing messages, it was found that differential filtering almost always improved performance. This was true regardless of whether it was the desired message that was filtered or whether it was one or more of the competing messages that was filtered, and the degree of filtering was relatively uncritical. High-pass cutoffs of 565, 800, or 1130 cps were about equally effective and were considerably better than high-pass cutoffs at or below 280 cps. Low-pass cutoffs of 1600, 1130, and 800 cps also improved performance substantially.
Side Scattering of Sound in Shallow Water
Authors: Urick R. J. 
Published: September 2005

When a sound beam travels through the sea, it is scattered in all directions by inhomegeneities of various sorts in the sea and on its boundaries. In the backward direction, the aggregate of all the scattered contributions is called “reverberation.” In other directions, the “side scattering” can be studied by using two directional transducers, trained so that the beams cross each other, to measure the sound scattered out of one beam and received on the other. This method was employed in an off-shore area in the Gulf of Mexico having a particularly uniform bottom. Using two bottomed transducers a mile and a half apart, the intensity of scattering was measured at 22 kc for different angular orientations of the two beams. The measurements were reduced to the coefficient, scattering strength, without requiring either transducer calibrations or direct measurements of transmission loss.
The results indicate a bottom scattering strength between −30 and −40 db having no appreciable dependence on angle between the two beams. Within the angular range from the backward direction around to 150° in the forward direction, the scattering appears isotropic. This indicates that isotropic bottom scattering may be safely assumed in applications utilizing separated transmitting and receiving transducers at kilocycle frequencies.
Effect of Damping and Vibration Detector Position in Resonance Measurements
Authors: Ryan John A. 
Published: September 2005

Vibrations in a finite-length, thin rod at low frequencies are considered. Two cases are discussed. In the first, the pressure amplitude at the driven end is assumed constant and, in the other, the particle-velocity amplitude is taken as being constant.
An oscillatory character to the amplitudes of the resonance peaks is found which is a function of detector position and attenuation.
This phenomenon may explain the observed differences in the heights of the resonance peaks, and the recurrence of groups of large and smaller peaks in rods, plates, shells, and other vibrating systems. It may also have a considerable effect on the apparent Q (or bandwidth) of the resonance curves.
Phonon Viscosity and Its Effect on Acoustic Wave Attenuation and Dislocation Motion
Authors: Mason Warren P. 
Published: September 2005

When dislocations move through a crystal, they are damped by some thermal mechanism. It is shown in this paper that good agreement with available measurements is obtained if the dislocations are damped by phonon viscosity. Phonons are quantized sound waves, which carry the thermal energy in an insulator. The interchange of energy between the longitudinal branch and the two shear branches occurs through the nonlinear elastic constants of the solid and requires a finite time τ. The effect of a shear wave, which is equivalent to a compression in one direction and an equal extension at right angles, is to raise the instantaneous temperatures for those phonons having components along the compressed direction and to lower the temperature for those having components along the extended direction. The flow of heat between the hot and cold phonons produces a damping of the sound wave corresponding to a viscosity η = E0K/CvV̄2 as long as the time of application of the shear wave is long compared to τ. When the product ωτ≫1 this source of loss disappears. Phonon viscosity contributes directly to the acoustic attenuation and indirectly produces a damping for dislocation motion.
By using thermal and sound velocity measurements to evaluate the viscosity, it is shown that available data on the attenuation of sound in metals and nonconducting crystals are in agreement with the calculated values of dislocation damping by phonon viscosity. A direct check for both edge and screw dislocations is obtained from recent work on the velocity of dislocations in lithium fluoride. The variation of internal friction in quartz as a function of temperature is in agreement with the temperature variation of phonon viscosity, but is not in agreement with calculations by Eshelby and Leibfried on dislocation damping by thermoelastic effects and by phonon scattering.
Structure and Velocity of the Periodic Vortex-Ring Flow Pattern of a Primary Pfeifenton (Pipe Tone) Jet
Authors: Anderson A. B. C. 
Published: September 2005

Visualization of the vortex flow pattern in typical primary Pfeifenton jets was made by means of shadow-graph techniques to show the transition in form of the vortex pattern as it moves downstream in the jet, as well as, the dependence of the downstream translational vortex velocity and the geometry of the vortex pattern on the Reynolds number of the jet.
Results of experiment are compared with available theory. These studies were carried out with carbon dioxide jets discharging into the atmosphere. The flow channel geometry consisted of a pipe 78 in. in diameter, 12.013 in. long effectively, open at one end which was inserted into a large stilling tank and terminated at the other end by an orifice plate containing a sharp-edged circular orifice, 0.250 in. in diameter and 0.093 in. thick.