bluuebunny/crossref_metadata_2025 huggingface dataset:
The Radiation Force Acting on a Sphere in a Spherical Sound Field
Authors: Embleton T. F. W.
Published: September 2005

Using a method due to King an analysis has been made of the time average forces acting on a rigid spherical obstacle placed in a progressive spherical sound field. The theoretical results are presented. The theory has been verified using a series of hollow glass spheres (0.22- to 3.03-cm radius) suspended by a fine glass fiber in the sound field in air; the deflection of each sphere was measured at known frequencies (300 to 7000 cps) and amplitudes (0 to 1400 dynes/cm2) of the sound field. Care was taken to protect the sphere from any gas streaming to or from the source and to insure that the field was accurately spherical. It is found that, as the source of the field is approached, the radiation force of repulsion decreases to zero and then becomes a force of attraction. The distance to which this region of attraction extends from the source is determined both by the frequency of the field and by the size of the detecting sphere—lower frequencies and smaller spheres both extend the region. Even when allowance is made for an inverse square law the attractions may by many times greater than the repulsions under similar conditions of frequency and intensity.
Acoustic Fields in Angular Regions
Authors: Kearsley E. A. , Heller G. S.
Published: September 2005

The rigorous solution for the acoustic field due to a line source located between two planes intersecting at an arbitrary angle is presented for both planes rigid, both pressure release, and one rigid and one pressure release. Angularly stratified media cannot be treated by usual methods because the wave equation is not separable in this case. A solution can be effected, however, if the stratification is due only to changes in density. The rigorous solution for this case will also be discussed.
On Progressions of Equal-Appearing Pitch Intervals
Authors: Harris J. Donald
Published: September 2005

The relation between pitch and frequency, as worked out by Stevens in the mel scale, has been of great value as corroborative evidence in critical bandwidth theory, the assignment of frequency to specific regions of the basilar membrane, etc. The utility of the mel scale in these respects removes all doubt as to the finitude of some such relationship, irrespective of however wide individual differences may exist, or of minor changes which may ultimately be made in the final form of the scale. It is, therefore, somewhat surprising that no use of this scale has been systematically exploited in an effort to invite general acceptance of the principle of equal-appearing intervals in progressions of pitch. Using a mel scale developed by Ellis Hartman of this Laboratory, the frequency range 250–500 was divided into equal-appearing intervals. A 12-unit division yielded intervals like no other division ever used or even proposed in any countries including the Scandinavian, but other attempts were more successful. A 19-unit division particularly yielded excellent natural thirds, fifths, sixths, and sevenths together with some good equal temperament quarter-tone intervals. The possibility appears good of increasing our aesthetic resources by subdividing the frequency ratio 2:1 on a purely psychological basis.
Wave Theory of Vortex Scattering
Authors: Dyer Ira , Ingard Uno
Published: September 2005

The scattering of a plane acoustic wave from an ideal cylindrical vortex has been studied theoretically. Because the velocity field of a vortex extends to infinity, special approximation techniques must be employed in the solution for the scattered wave in order to avoid singularities. An approximate solution has been obtained under the assumption that the maximum tangential velocity of the vortex is much smaller than the velocity of sound and that the angular velocity of the vortex is less than the angular frequency of the sound. The connection of vortex scattering with anomalous propagation effects in the atmosphere will be discussed.
Acoustic Wave Propagation Distortion at Several Frequencies
Authors: Campanella Angelo Joseph
Published: September 2005

Distortion in a free field due to propagation of sinusoidal pressure waves in air was measured along the axis of a 4.8-inch essentially plane piston source at the four fundamental frequencies: 14.7, 24.6, 35.0, and 63.6 kilocycles per second. The pressure field was spherically divergent beyond the Fresnel diffraction zone. The data verifies that, at any given distance from the source, the pn's rise as the nth power of the source amplitude, that at large amplitudes the pressure wave form at a distance from the source approaches the stable form of an iterated shock wave, and that wave form distortion increases with frequency at a given distance and source amplitude. At the 14.7- and 24.2-kc frequencies, the variation of pn with x in the initial stages of distortion follows the trend of pn ∝ x(n − 3/2), an expression developed by C. H. Allen for spherically diverging waves. This comparison was not made at 63.6 kc, for the Fresnel diffraction zone extended to about 100 cm.
The Vobanc-Voice Band Compressor
Authors: Bogert B. P.
Published: September 2005

A number of years ago a proposal was made by R. L. Miller of a way to reduce the band width of a speech channel by a factor of two, without an appreciable loss in quality. The proposal was to divide the speech band into three parts by filters at carrier frequency (0–1, 1–2, and 2–3.6 kc bands). Each of these bands usually contains one of the three principal vowel formants. The signal in each band is passed through a regenerative modulator, which halves the frequency of the formant and translates the neighboring frequency components downward correspondingly. The output of the regenerative modulators is filtered to a band width of one-half of the original. This throws out certain frequencies, but ordinarily they are of low amplitude and the loss is not serious. In this way the speech band is halved. At the receiving end the three component bands are separated and each band is frequency doubled and recombined. The recombined signal, having the original band width, is modulated back into the voice frequency range. Experimental verification of the essential principles involved has been made and the results are described.
Syllable Synthesizer for Research on Speech
Authors: Meeks Wilkison W. , Borst John M. , Cooper Franklin S.
Published: September 2005

A highly flexible synthesizer, designed primarily to permit rapid and convenient exploration of certain aspects of speech synthesis will be described. It utilizes three variable tuned filters, whose inputs may be either buzz or hiss signals (or both) and whose resonant frequencies are independently controllable by signal voltages. The device was designed to facilitate the investigations of the effects of such spectrographic variants as the extent and duration of formant transitions. It is especially suited to studies in which the isolation of the significant speech cues requires the generation of long series of comparatively simple syllabic sounds which differ from one to the next only in small changes of a single pattern element.
Autocorrelation Analysis and Correlatograms of Spoken Digits
Authors: Biddulph R.
Published: September 2005

Autocorrelation techniques provide a method of displaying certain characteristics of speech sounds in a three-dimensional form which differs significantly from analogously displayed conventional sound spectrograms. The autocorrelation function ψ11(τ), of a signal I(t) is defined by ψ11(τ) = LimitT→∞ 1T  ∫ T I(t) I (t − τ)dt. Delay τ introduced in the speech signal appears as ordinate in these new displays, time t as abscissa, and magnitude of the resulting correlation function ψ11(τ) is depicted by the density of the pattern. Characteristic features of the displays are discussed and their utility evaluated in terms of the mechanism of the correlation process. Data considered is limited to ten spoken digits: one, two⋯nine, “oh.”
The Linguascope
Authors: Vilbig Friedrich
Published: September 2005

A new device is discussed which photographically transposes speech, originally recorded on 35-mm film sound track, onto a second film, allowing simultaneous visual analysis and selection of arbitrary track segments. The second film is now developed and played back on sound-film apparatus. The instrument serves to investigate special problems of communication and lingusitics, such as transitional phenomena between vowels and consonants, phonemic variation, merging of vowels, frequency band or time compression and expansion, etc. The instrument is particularly valuable in that new procedures may be preinvestigated with the aid of the linguascope before the necessary instrument is even constructed.
The Effect of a DC-Bias on Barium Titanate Near Thickness Resonance
Authors: Kolb J. , Hueter T. F.
Published: September 2005

The application of a dc bias has been found to reduce the dielectric loss factor of prepolarized barium titanate. This finding has lead to the expectation that a dc bias equal to the negative peak of the driving ac field will reduce the heating effects which commonly limit the power output of thickness type barium titanate transducers. To verify this assumption both the temperature rise and ultrasonic power output of barium titanate disks have been measured near thickness resonance as a function of frequency with and without bias. Also, the onset of polarization in a biased disk which is heated by an rf field at the frequency of mechanical resonance has been determined. These measurements indicate that near mechanical resonance, both fundamental or harmonic, the effect of dielectric losses is largely over-shadowed by the electromechanical losses associated with the motion of the transducer. It was found that under certain conditions the application of the bias increases these losses and that rather high dc fields are required to maintain polarization in the presence of the resulting high temperatures. Additional observations have revealed an electromechanical response at the second harmonic under the influence of a reversed bias. This seems to call for the same type of coupling between local mechanical strains and local domain polarization as was evidenced by earlier work.
'Twixt Earth and Sky with Rod and Tube
Authors: Firestone Floyd A.
Published: September 2005

The techniques which comprise the mobility method of vibration computation are introduced into the classical impedance analogy; instead of drawing an analogous classical electrical schematic, a new set of mechanical and acoustical symbols is introduced which permits the drawing of a (classical) hydraulic schematic directly by cautious inspection of the structure to identify the elements and their terminals. In a mobility schematic, a straight line represents an ideal rigid massless rod; in a hydraulic schematic, a line represents a tube of unit cross section filled with ideal massless incompressible liquid which can sustain either tension or compression. Revised mobility schematic symbols are provided for mechanical and acoustical elements, and hydraulic schematic symbols for the same elements have been visualized as tubes filled with mercury or molasses, or chambers filled with methane (or air); all of these symbols resemble their analogous electrical symbols. Rigid and hydraulic junctions are distinguished by different symbols. Correct mobility schematics are obtained by inspection through considering each mass as having one terminal fixed in a frame of reference called the ground, which has zero mobility and infinite mass; correct hydraulic schematics are obtained by inspection through considering each spring as having one terminal fixed in a force of reference (P0 etc.) called the sky, which has zero impedance and infinite compliance (in both cases the analogous electrical element is a conducting sphere in free space, not a condenser). While it is recommended that analogous electrical circuits not be used, they can be copied directly from a mobility schematic by considering mechanical ground analogous to electrical ground, or copied directly from a hydraulic schematic by considering mechanical sky analogous to electrical ground.
Laboratory Evaluation of Field Measurements of the Loudness of Truck Exhaust Noise
Authors: Callaway D. B. , Hall H. H.
Published: September 2005

Simple loudness judgment tests were performed by a jury of 15 observers on the recorded noises of approximately 100 highway trucks. The loudness of the noises calculated by the method proposed by Mintz and Tyzzer ranged from about 20 to 200 sones. Observers were instructed to rank the noises in six loudness classes and were allowed to listen to a sample of class 1 and class 6 after each 25 recordings. The calculated loudnesses were then divided into six classes with class limits set by a 40 percent loudness increase per class. A correlation coefficient of 0.935 was found between the average judgment of the group and the calculated loudness class. The correlation coefficient between average judgment and total sound pressure level was 0.78, while the correlation coefficient between the average judgment and the level on the A network of the sound level meter was 0.826. Experimental techniques and the capabilities and limitations of the loudness calculation methods will be discussed.
Free Field Noise Measurements on Jet Aircraft
Authors: Pietrasanta Adone C.
Published: September 2005

Free field noise measurements have been made on several jet aircraft with and without afterburner at a stationary location on the ground. These data were obtained for several operating conditions. A magnetic tape recorder was used to record the jet engine noise. The microphone was moved continuously around the aircraft on a semi-circular path at various radii, including 50 ft, 100 ft, and 200 ft. The measurement procedure, and the measured spectra, directional patterns, and sound power levels will be discussed.
Acoustic Irritation Threshold of White Pekin Ducks
Authors: Thiessen G. J. , Shaw E. A. G.
Published: September 2005

When exposed to sounds of sufficient intensity to show subjective signs of irritation, Pekin ducks exhibit a characteristic reaction involving a combination of head shaking and tail twitching. This reaction is used to define an irritation threshold. Measurements made at various frequencies on about 30 ducks indicate a minimum average threshold of about 70 db occurring at 500 cps (the individual values ranging from 65 to 85 db in this frequency region). At 15 and 18 kc no consistent responses could be obtained at the highest intensities tried which were 115 and 120 db, respectively. The response number in unit time increases with increasing intensity up to a maximum after which it falls off. When the intensity is kept constant the response number fails off roughly exponentially with time, the half-value period being of the order of 10 minutes. This decay may be interrupted by various disturbances. Warbling the tone causes no appreciable change in the results. Similar experiments performed with chickens and Pilgrim geese showed far fewer responses and hence less accurate results.
High Intensity Sound as a Repellant for Mallard Ducks and Other Water Fowl
Authors: Shaw E. A. G. , Thiessen G. J.
Published: September 2005

Since laboratory experiments on white Pekin ducks indicated a minimum acoustic irritation threshold at about 500 cps, it was considered reasonable that this same frequency might repel Mallard ducks which are responsible for a serious depredation problem in western Canada. A Chrysler air-raid siren (460 cps.) was mounted on a truck and an attempt made to carry out some controlled field tests in Saskatchewan and Alberta. Movement of 99 percent of the population of a slough or lake one mile in extent may be achieved. The repopulation rate may be decreased by irradiation on several successive days, values lower than one percent per day having been obtained. The effect on damage to grain fields is more difficult to assess. Detailed results for different conditions will be reported. Coots, shovelers, Franklin gulls, bitterns, and teals seemed to be unaffected and could not be lifted even at distances as low as 100 yards. An occasional isolated duck proved equally unresponsive. A flock of geese at 2000 feet could not be lifted.
Precision of Centering a Sound as a Function of the Interaural Correlation
Authors: Jeffress Lloyd A. , Blodgett Hugh C. , Deatherage Bruce H. , Musick James E.
Published: September 2005

Using earphone presentation and an electrical lag line for control of interaural time, measurements were made of the subject's variability while attempting to center the sound in his head. This variability is presented as a function of the interaural correlation, which was varied by introducing random noise signals into the two earphone channels. Results show a reduction in precision as the correlation is reduced, but with the subject still doing substantially better than chance with the correlation as low as 0.1.
Destruction Rate of Microorganisms in Measured Sound Fields
Authors: Kinsloe Helen L. , Reid J. J. , Ackerman Eugene
Published: September 2005

The effect of pH and temperature on the rate of destruction of microorganisms in the sound field of a 9-kc Raytheon magnetostriction bar was investigated. The measurements of the sound field were described in the previous paper. Saline suspensions of microorganisms were buffered to maintain pH levels of 4.0, 5.0, and 7.0 and held at 15°, 25°, 35°, and 45°C during exposure to the sound field. The magnetostriction bar was operated with the plate voltage variac at 135 v. No significant difference in killing rate was observed under conditions favorable to the microorganisms studied. Exposures were carried out at pH 7.0 and 15°C at decreasing plate voltages. The breakdown rate decreased with decrease in plate voltage.
Ultrasonics and Progressive Deafness
Authors: Angeluscheff Zhivko D.
Published: September 2005

The solution of the very important and difficult problems presented by progressive deafness due to otosclerosis—its cause, prevention, and cure—is to be found in the biological implications and applications of the newly acquired and as yet incompletely correlated data in the field of ultrasonics. As there are light waves which are beyond the physiological range of human visual perception, there are sound waves that are imperceptible to the human ear—the ultrasonics. The most silent centrifuge has an ultrasonic specter extending to 100 000 cy/sec. The telephone bell produces frequencies to 50 000 cy/sec, powerful, but silent, imperceptible to us. The traffic of everyday life, in the train, bus, car, next to the audible noise, hides a tremendous amount of silent sound which is frightfully dangerous to our hearing organ. A significant fact of modern research is that the intensities of ultrasonics are of not primary importance in influencing the chemical changes in human proteins. Sonics and ultrasonics are equally able to provoke alteration in tissue proteins. Low frequencies of ultrasonics cause liquefaction of thixotropic gels. This occurrence leads to an increase of permeability of the cell membrane and thus advances chemical changes within the protein. The Ph changes are accompanied with a shift within the protein fractions. An increase of the gamma globulins, and a fibrotic trend of defense is in the making. The result of this happening is the structural changes in the living tissue (collagen, bone). The sonorous vibrations are passing from the air into the solid bone of the ossicular chain and into the water medium (liquor) of the labyrinth to arrive at the perceiving apparatus of the cochlea in the inner ear. The sound waves, by reaching new media, are partly reflected and partly transmitted, this according to the exerted resistance. The transferred energy from the air to the tissue is very small. The reflection by the different media can be considerable. The reflected ultrasonics have a damaging effect upon biological structures, because of sublimation of energetic effects (chemical thermic, etc.). Such considerable reflection occurs at the interface of bone medium (stapes) and water medium (the labyrinthin liquor). The body defense which tends to seal the spot of intrusion of ultrasonics develops a fibrotic diathesis. The first stone of this defense barrier is the first step toward the condition of deafness. At this topographic location of defense barrier (the oval window), the aural pathology has been recording for the last half-century the appearance of primary otosclerotic foci, without being able to give any satisfying explanation of their nature. The difficult problem of progressive deafness with its complexity of biological implication could not be understood until sufficient ultrasonic data have been explored and comprehended. The experimentally produced sclerosis by exposing living tissue to ultrasonic has enabled us to penetrate into this enigmatic condition.
Ultrasonic Machining of Tungsten Carbide
Authors: Goetze D.
Published: September 2005

An electronically driven and controlled magnetostrictive transducer is used in conjunction with a suspended abrasive to machine hard, brittle materials such as ceramics and the carbide metals. The transducer has been constructed especially to supply high amplitude vibrations at the surface being machined. Data taken indicate that certain compromises must be made relative to cutting speed and tool wear. The effects of other variables such as vibration amplitude and abrasive size have been optimized for machining tungsten carbide, but no conclusions have yet been reached regarding the mechanism of ultrasonic machining.
Ultrasonics and Medicine
Authors: Herrick J. F. , Krusen Frank H.
Published: September 2005

Many therapeutic procedures have been introduced into the art and science of medical practice empirically by a method of trial and error. Such a method has marked limitations and may produce unfavorable consequences. The facilities available in experimental medicine permit a thorough and extensive investigation of biological effects of many therapeutic agents or procedures before any clinical application is made. Optimal doses of the therapeutic agent can be approximated and a comparative study of various technics designed for clinical application can be made. Unfortunately ultrasound was used clinically by certain enthusiastic therapeutists before a thorough study of its biologic effects was completed. These therapeutists regarded the major biologic effect of ultrasonic energy to be mechanical. They were aware of a heating effect, but considered that it played a minor role. Experimental measurements have shown clearly that the major effect of ultrasound on living tissues is thermal when an intensity suitable for therapy is employed. The heating of bone by ultrasound is spectacular. No other heating agent used in therapy can raise the temperature of bone to such high levels so quickly. The application of ultrasound for diagnostic purposes and also for instrumentation will be described.
Characteristics of Ultrasonic Delay Lines Using Quartz and Barium Titanate Ceramic Transducers
Authors: May John E.
Published: September 2005

Previous analysis of the equivalent circuit for the ultrasonic delay line was applied to quartz crystal transducers and a vitreous silica delay medium. The analysis has been extended to evaluate the use of other material such as magnesium, aluminum, and steel and to include BaTiO3 ceramic transducers. Calculations show the decrease in loss to be expected as the impedance of the delay medium is decreased and, conversely, the increase in band width to be expected as the impedance of the delay medium is increased. The increase in band width resulting from symmetrical loading of the transducers is also evaluated. Modifications to the equivalent circuit for the case of BaTiO3 ceramic transducers are considered. Theoretically, losses can be reduced to 10 db or less using the ceramic transducers with a vitreous silica medium. The band width is slightly less than for quartz transducers. However, by utilizing higher impedance materials, band widths approaching 100 percent should be achieved.
A Noncontact Microdisplacement Meter
Authors: Sharaf Harold
Published: September 2005

A method capable of detecting micro-inch displacements of a transducer surface vibrating in the fractional megacycle range has been developed. The dynamic displacements of a vibrating transducer are detected with the aid of a specialized frequency-modulation system. The vibrating transducer face is incorporated into the system in a manner such that the center frequency of an oscillator is varied in accordance with the transdncer vibrations. The frequency-modulation system transforms the frequency deviations into a corresponding amplitude varying signal. In this way, accurate measurements of transducer vibrations can readily be obtained. The system is inherently capable of detecting transducer displacements with equal facility in either air or a viscous fluid.
The Enhancement of Music by Reverberation
Authors: Martin Daniel W.
Published: September 2005

The tones of traditional musical instruments such as the grand piano and the pipe organ are generally heard through the medium of room acoustics. Some effects of natural room reverberation upon organ and piano tones will be described, and demonstrated by means of magnetic tape recordings. Simple electroacoustic means (described in paper number H-6) for simulation of reverberation in the playing of music in a nonreverberant environment will also be demonstrated.
A Loudspeaker Accessory for the Production of Reverberant Sound
Authors: Martin Daniel W. , Knoblaugh Armand F.
Published: September 2005

Added reverberation has been found to be useful for many purposes in sound recording and broadcasting. In recent years organs, which traditionally have been heard in large, reverberant rooms, have been installed rather frequently in small studios and parlors having very short reverberation time. Modern systems for adding reverberation to sound have generally used a driving transducer, a multiple time-delay means, one or more pickup transducers, and mixing and amplifying circuits. Much of the complication and expense of such a system is avoided in the reverberation devices described in this paper. One type consists of an otherwise conventional direct-radiator loudspeaker, coupled mechanically to multiply resonant helical delay lines mounted in front of the cone. Vibrational energy absorbed by the reverberation coils directly from the loudspeaker voice-coil is transmitted back to the loudspeaker cone and radiated at a later time as reverberant sound. In a second type similar reverberation coils are coupled mechanically to a separate cone which is smaller than the loudspeaker cone and mounted concentrically in front of it. Attenuation of the direct sound radiated through the reverberation cone and around its edge is barely perceptible Yet acoustical coupling between the cones supplies enough energy to the reverberation coils for clearly audible reverberant sound to be radiated from the reverberation cone.
The Construction of an Inexpensive Anechoic Chamber
Authors: Berger Robert , Ackerman Eugene
Published: September 2005

An anechoic chamber built in the subbasement of Osmond Laboratory and costing about seven thousand dollars is described. Details of construction and of transmission characteristics are given for each stage of the acoustical treatment. The finished room has 1212 × 712 × 612 feet of working space with a design cut-off frequency of 110 cps, using 22-inch wedges with a 512-inch air space. The equivalent circuit of the wall section and wedges is given along with the calculated loss at 110 cps. The objective of −10 db per cycle below threshold over the hearing range is shown to have been achieved. A shock tube with P0/Ps equal to 0.6 which was in the room directly over the chamber was used as a loud source of noise. Results of octave-band analyses made at each stage of construction and per 10 cps analyses made before and after construction are given. Anechoic properties, as determined by inverse square law measurements and loudspeaker loading measurements, are given.
Acoustical Design and Measurements of the Communication and Navigation Laboratory Anechoic Chamber
Authors: Duncan Robert K. , Martin Daniel W. , Peters Arthur L. , Lazur Edward
Published: September 2005

A new anechoic chamber has been constructed at the Communication and Navigation Laboratory, Wright Air Development Center, for research on speech communication equipment. The absorbing elements are Fiberglas wedges three to four feet in length and eight inches square at the base. Dimensions of the working space inside the wedge tips are 17 × 1412 × 912 feet. Anechoic properties were checked by inverse-square law measurements along the length and along one diagonal in the horizontal plane. Measurements were made with and without both the removable grille flooring and the padded framework designed to support equipment under test. Particular attention was given to measuring the ambient noise spectrum, as a guide to future experimentors using the chamber. The ambient acoustical noise level was so low that measurement was very difficult, requiring special equipment and care in order to prevent interference from electrical noise. A measurement of the transmission loss of the walls was used to predict the magnitude of adjacent noise fields which can be tolerated without disturbance to acoustical experimentation.
Demonstration Lecture on Polarized Airborne Sound Waves
Authors: Kock Winston E. , Harvey F. K.
Published: September 2005

Sound waves propagating as transverse modes in hollow tubes possess polarization properties similar to electromagnetic waves. A demonstration of these properties will be given which will include the rotation of the plane of polarization by “half-wave plates,” the production of circularly polarized sound waves by “quarter-wave plates,” cut-off effects (as in electromagnetic waveguides), and the radiation pattern of radiators fed by polarized waves. The use of transverse modes in high-Q resonators, filters, concave converging lenses and gyrators will be discussed, also the use of the dispersive properties of transverse wave guides for separating in time pulses of different frequency
Wedge Geometry for Ultrasonic Delay Lines
Authors: McSkimin H. J.
Published: September 2005

Compact ultrasonic delay lines using vitreous silica plates cut in the form of a wedge are described. Shear waves at frequencies in the 10–50 mc/sec range are reflected back and forth between the wedge surfaces, with resulting open beam paths at the sending and receiving transducers, and gradually overlapping paths at the small end of the wedge. By using a plate with two sets of wedge surfaces, delays of 500 microseconds and more can be obtained, with greater than 40-db suppression of undesirable responses.
Determination of Elastic Constants of Crystals from Acoustic Wave Velocity Measurements
Authors: Neigbours John R.
Published: September 2005

A method for determining the elastic constants of a cubic crystal from velocity measurements of acoustic waves traveling in an arbitrary direction in the crystal is well known. Waves traveling in an arbitrary direction are not, in general, either longitudinal or transverse, but show, for example, polarization angles of up to 11° in nickel. The technique for deducing the elastic constants in such cases is here extended to crystals other than cubic.
An Electromagnetic Method for Measuring the Amplitudes and Attenuation of Ultrasonic Waves
Authors: Bömmel H. E.
Published: September 2005

This method is particularly appropriate for measuring large absorption coefficients as for instance in rubber, paraffin, etc. A number of thin wires (r=0.01 mm) are cemented onto, or melted into, a rod of the substance in question, at measured, equidistant intervals, perpendicularly to the rod axis. The rod and the wires are placed in a magnetic field H (H ≐ 1000 gauss) with the direction of H perpendicular to the rod axis, as well as to the wire direction. Longitudinal ultrasonic waves pagging through the rod in the direction of its length vibrate the wires normally to the field. The induced alternating voltage will have a magnitude of V = ω⋅A⋅H⋅d⋅cosωt⋅10−8 volt, where A = amplitude, ω = angular frequency, and d = diameter of the rod (which is the effective length of the vibrating wire). From the voltage ratio of the individual wires, the absorption coefficient α was determined. For the absolute determination of A the apparatus was calibrated with appropriate voltage dividers. Measurements were performed on rods of synthetic rubber, polyvinylchloride, and paraffin at frequencies f=0.83, 2.5, and 3.2 Mc/sec. The measured values of α were between about 0.9 neper/cm and 5 nepers/cm.
Ultrasonic Luminescence of Liquids
Authors: Laufer A. R. , Srinivasan D.
Published: September 2005

Luminescence in various liquids under ultrasonic irradiation has been reported by many observers, but there is little or no agreement among their results. The present preliminary experiments were conducted in ten liquids, using a photomultiplier tube and galvanometer to measure the intensity of luminescence. A vertical ultrasonic beam of frequency 1 mc/sec and intensity up to 10 w/cm2 was employed successively as a progressive wave train and as a standing wave system. Luminescence was observed in the following liquids, listed in order of decreasing intensity: aqueous solution of KCl, aqueous solution of MgSO4, aqueous solution of H2O2, distilled water, fresh tap water, aqueous solution of bromine, aqueous solution of CCl4, glycerin. No luminescence was observed in nitrobenzene or in transformer oil. Almost all of the luminescence originated in the fountain at the free surface of the liquid in the case of progressive waves and just below the reflector in the case of standing waves. The intensity of luminescence increased with increasing ultrasonic intensity.
The Absorption of Finite Amplitude Sound Waves
Authors: Fox F. A. , Wallace W. A.
Published: September 2005

The coefficients of absorption of high-intensity ultrasonic waves in liquids (carbon tetrachloride and water) have been measured as a function of intensity. The absorption coefficient increases by a factor of 2 for water and 5 for carbon tetrachloride for intensities of about 5 watts/cm2 The increase is attributed to wave form distortion of a wave of finite amplitude. A theory is developed in which the medium is treated as the acoustical analog of a transmission line with nonlinear elements. The theory enables one to follow the details of the change of an initially sinusoidal wave of finite amplitude, in a dissipative medium, into an “comparatively” stable distorted wave form that eventually returns to an infinitesimal sinusoidal wave. Quantitative agreement of theory is obtained with experiment for the threshold intensity separating finite and infinitesimal amplitude propagation, the distance needed for comparative stabilization, the growth of harmonic content in the distorted wave, and the details of the absorption process.
The Dispersion of the Velocity of Sound in Water between 500 and 1500 Kilocycles
Authors: McCubbin T. King
Published: September 2005

Dispersion was measured by simultaneously transmitting through water continuous sound waves of the two frequencies. One transducer was used to generate the two sound signals and a second transducer, which could be moved in the direction of the sound beam, was used to receive the signals. Dispersion was determined by measuring the change in the relative phase of the two received signals as the length of the path between the transducers was varied. These measurements were made using the facilities of the State College Ordnance Research Laboratory at Lake Moshannon, Pennsylvania. The conclusion has been reached from these measurements that the dispersion is zero to within one part in 290 000.
An Anechoic Tank for Underwater Sound Measurements under High Hydrostatic Pressures
Authors: Darner Charles L.
Published: September 2005

The new USRL tank for making acoustic measurements under hydrostatic pressures up to 1000 psig and controlled temperatures from near freezing to near boiling is described. The internal treatment of the tank with Insulkrete wedges, a sound-absorbing material composed of pine sawdust and Portland cement, is illustrated with slides. Oscillograms of the pulsed signal show the reduction in reverberation level effected by Insulkrete. The conversion by Insulkrete of high-frequency sound energy into heat is illustrated by schlieren photographs.
The Backscattering of Sound from a Harbor Bottom
Authors: Urick R. J.
Published: September 2005

When underwater sound strikes the bottom of the sea in shallow or deep water, a portion of its intensity is scattered back toward the source of sound. A study of the backscattering from the bottom as a function of pulse length, frequency, and tilt angle at several locations in a harbor along the East Coast was made by using a tiltable transducer mounted on a barge. The results are expressed in terms of quantity called the “scattering strength” of a unit area of bottom. The results suggest that the backscattering of sound from a natural bottom is more the result of its roughness rather than of the fact that it consists of sedimentary particles. Even at normal incidence the bottom of a sea or bay appears sufficiently rough so that little sound is returned by specular reflection. Some evidence in support of these conclusions will be given.
The Scattering of Underwater Plane Ultrasonic Waves by Liquid Cylindrical Obstacles
Authors: Bezuszka Stanley J.
Published: September 2005

An experimental investigation of sound scattering from liquid cylindrical obstacles was performed by Tamarkin following on the work of Bauer and others. A series of scattering patterns, confined to the region about the extended axis of the incident beam and on the opposite side of the obstacle from the source, were determined for ten liquids. The special kia values chosen (ki; = 2π/λi, λi = wavelength of the sound in the medium of the obstacle, a = radius of the cylindrical obstacle) lie in the range 26.0<kia<41.0 and are below and above the corresponding value for the water medium surrounding the obstacle. On the assumption of a plane incident wave, a series solution was found for the total scattered wave and numerical calculations were carried out for conditions approximating those of the actual experiments. The results of this theoretical investigation confirm the experimental findings that scattering of an underwater ultrasonic beam, from the special liquid cylindrical obstacles examined, lies in the zone between the geometrical region and the region of Rayleigh scattering. In this zone, diffraction predominates and the diffraction patterns based on theory agree quantitatively quite well with the positions of the experimental maxima and minima. A rather detailed and extended theoretical study of the resonance curve found experimentally was made and the plotted theoretical resonance curve shows a similar oscillating behavior with amplitude decreasing with increasing kia.
A 9 kc Electrokinetic Hydrophone
Authors: Holak William , Ackerman Eugene
Published: September 2005

An electrokinetic probe hydrophone was constructed with its handle similar to the Spencer-Allen probe microphone developed at The Pennsylvania State College. The sensitive element is similar to the one used by Yeager, a cotton covered platinum wire enclosed by a glass tip filled with distilled water. It was shown that the hydrophone is particle velocity sensitive and readings obtained in the most intense part of the sound field in the test cup of a 9-kc Raytheon Vibrator were approximately 15 db above electromagnetic pickup. The sensitivity of the hydrophone is about −180 db re 1 volt per microbar. The calibration was made at the ORL's testing station at Black Moshannan, Pennsylvania. The Raytheon Vibrator is used to produce intense sound fields to study the breakdown of biological cells. By using a barium titanate hydrophone and and electrokinetic hydrophone, pressure, particle velocity, and phase measurements were made at different points in the test cup of the vibrator. It was found that the acoustic field in the test cup was extremely complex and cannot be simply described.
A New Method for the Calibration of a Plane Hydrophone
Authors: Laufer A. R. , Thomas G. L.
Published: September 2005

The calibration of a plane-disk hydrophone of 112-inch diameter over a wide frequency range by the usual plane-wave reciprocity method would be a very difficult task, requiring a large anechoic tank and precise mechanical alignment gear. A new and absolute method has been developed utilizing the radiation pressure of a standing wave system. The air-backed barium titanate hydrophone was suspended in oil above a quartz crystal projector by means of a sensitive Joly balance spring. The hydrophone thus acted simultaneously as a reflector to set up standing waves, as an electromechanical transducer, and as a device to measure radiation pressure. The weight, buoyant force, spring force, and radiation pressure combined to trap the hydrophone in any one of a number of discrete equilibrium positions, while the radiation pressure tended to align the hydrophone face parallel to the face of the quartz projector. The acoustic pressure was calculated from the spring extension, and the electrical output of the hydrophone was measured with a Ballantine voltmeter. In this manner the sensitivity of the hydrophone was determined over the frequency range 300 kc/sec to 5 Mc/sec. For a hydrophone of 1 Mc/sec resonant frequency, the calibration showed peaks at 1 Mc/sec, 3 Mc/sec, and 5 Mc/sec, and the sensitivity varied from a high of −116 db to a low of −156 db ref 1 volt/(dyne/cm2).
Acoustic Properties of Liquid-Filled Sands
Authors: Nolle A. W.
Published: September 2005

Acoustic properties of liquid-filled sand (particles small compared to wavelength) are computed from physical properties of the medium. Because of small separation of particles, scattering theory cannot be readily adapted to find the propagation constant, but good results are obtained by modifying the well-known analysis of absorbers of airborne sound. The sand behaves as a skeleton of zero elastic modulus, but with coupling to the fluid, as given by Zwikker and Kosten, and with finite compressibility. Transmission and reflection at a plane boundary between fluid and fluid-filled sand are computed from the propagation constant. The reflection loss, approximately 10 db at normal incidence, becomes very small at grazing angles smaller than critical, in agreement with ultrasonic experiment. Incoherent volume scattering by liquid-sand, of sound incident on the boundary from the liquid, is treated by an integration which considers boundary effects, propagation in the liquid-sand medium, and autocorrelation function for scattering centers. Scattering falls sharply as the grazing angle becomes less than critical, in qualitative agreement with ultrasonic data, but is nearly constant at larger angles. The present scattering analysis appears preferable to one previously reported, for a surface distribution of scatterers only, which failed to show the small-angle decrease, but the actual mechanism must be a combination of the two types.
Apparatus for the Study of Cavitation in Liquids
Authors: Galloway William J.
Published: September 2005

An experimental apparatus has been assembled for the study of sonically induced cavitation in liquids in the frequency range of 20 to 40 kilocycles. Radially symmetric standing waves are produced in a spherical resonator driven externally by a magnetostriction transducer. The resonator is a round bottom Pyrex boiling flask suspended by piano wires to provide an extremely low-loss system, permitting acoustic pressures of the order of tens of atmospheres to be established at the center of the sphere. The acoustic pressure within the sphere is measured by a small, probe mounted, barium-titanate transducer positioned at secondary maxima of the standing pressure wave. Equipment is provided for measuring the gas content of the liquid being studied. A description will be given of procedures for measuring cavitation thresholds with hydrostatic pressure, gas content, surface tension, viscosity, and temperature as parameters. Preliminary results will be presented.
Low Temperature Attenuation Measurements in Lead Single Crystals and their Bearing on Acoustic Losses Due to Dislocation Motions
Authors: Mason W. P.
Published: September 2005

An analysis has been made of the attenuation measurements in lead single crystals, carried out by H. Bömmel, down to liquid helium temperatures. Above the superconducting temperature, relaxations have been found which verify the measurements of Bordoni made at lower frequencies. An analysis of the variation of attenuation with temperature and frequency shows that at low temperatures, i.e., up to 50°K, all the attenuation is accounted for by relaxation mechanisms having activation energies from 100 to 1500 calories per mole. Above this temperature, a hysteresis type mechanism enters which produces a loss proportional to the frequency. This has an activation energy similar to the highest energy relaxation mechanism and at room temperature accounts for most of the loss. It is shown that measurements of this type require that dislocations be tied down not only by impurity atoms but also by residual stresses along the dislocation so that there are no freely vibrating dislocations. The dislocation motions are then temperature-induced jumps, biased by the applied stresses, occurring over activation energy barriers from 100 to 1500 calories per mole. The hysteresis component is thought to be a successive step process in which one motion triggers off another at a given part of the cycle. This process causes the plastic component of strain to lag behind the stress, thus producing a hysteresis loop in the stress-strain curve whose area is independent of the frequency up to a frequency limited by the activation energy of the lowest components.
Progress in Noise Control
Authors: Beranek Leo L.
Published: September 2005

The progress of the understanding of the behavior of acoustical materials and structures for noise control is traced over twenty-five years. The present state of the science of acoustical materials and their application to various problems is reviewed. A look into the future, with emphasis on wave acoustics and electronic control, is given.
Propagation of Seismic Wavelets
Authors: Ricker Norman
Published: September 2005

This is a survey paper covering the development of the Wavelet Theory of Seismogram Structure over the past fifteen years. The paper discusses the failure of the classical wave equation in accounting for the nature of seismograms, shows that the absorption of the earth must be taken into consideration, and sketches the development of the theory based on Stokes' wave equation ∇2[Φ + 1ω0 ∂Φ∂t] = 1c2 ∂2Φ∂t2. The results of an extensive series of experimental researches are reviewed, and it is shown that the form and laws of propagation of the seismic disturbance, predicted by the theory, are supported by the experimental evidence. Applications of the theory to practical improvements in seismic prospecting are discussed briefly.
Synthesis of Seismograms from Well Log Data
Authors: Swartz C. A. , Peterson R. A. , Fillippone R. W.
Published: September 2005

Under certain highly simplified but realistic physical assumptions, the basic data from continuous velocity surveys in wells can be made to simulate the variations in acoustic impedance in the ground which give rise to seismic reflections. An electro-optical analog device is described which makes use of the basic well data to produce synthetic seismic records which resemble actual seismograms from shot hole explosions. This provides an interesting insight into the requisite physical conditions as well as the physical processes whereby seismic reflections are set up in the earth.