bluuebunny/crossref_metadata_2025 huggingface dataset:
Sound Pressure Generated in an External-Ear Replica and Real Human Ears by a Nearby Point Source
Authors: Shaw E. A. G. , Teranishi R.
Published: September 2005

A rubber replica has a pinna, concha, and auditory meatus with dimensions comparable with those of real human ears. At the eardrum position, there is provision for a totally reflecting termination (hard wall) or for various eardrum impedance networks. The replica is mounted in a rigid plane, and a point source at a distance of 8 cm provides sound with various angles of incidence over the frequency range 1–15 kHz. The sound pressure is measured with a probe-tube microphone at selected positions in the open canal and at the center of a plug closing the ear-canal entrance (“meatus-blocked” condition). The response with open canal and the response with blocked meatus have virtually identical angular dependence up to 12 kHz. From 2–7 kHz, there is substantial acoustic gain at the eardrum position associated with a fundamental canal resonance (M1) and a second mode largely controlled by a depth resonance of the concha (M2). Pressure distributions in the canal and concha are given for M1, M2, and three other modes. Limited data for six real ears with open and blocked canal are in good agreement with replica measurements up to 7 kHz. At 8 kHz, however, the on-axis response of real ears passes through a sharp minimum that is either removed to a higher frequency or is largely absent with the sound source above the axis.
Transducer Element Design for an Endfire Array
Authors: Miller Harry B.
Published: September 2005

In the design of resonant transducer elements for a high power array steerable from broadside to endfire, some new design concepts and terminology have arisen such as velocity control, Zoc etc. The new approach tends to avoid explicit use of such design parameters as coupling coefficient, mechanical Q, etc. [H. B. Miller, “High Power Steerable Planar Array,” JUA (USN) 14,401–440 (Apr. 1964)]. The question arises as to whether the new approach alone is sufficient for the designer.
A Plea for Conformity
Authors: Backus John
Published: September 2005

The system of octave notation proposed by Young and incorporated in the American Standard Acoustical Terminology has not yet come into general use by those working in musical acoustics. A survey of books and articles written in the last 26 years shows that, while a creditable hall of these use the approved notation, the remainder use a wide variety of other designations. It is suggested that it would be best if everyone used the standard notation.
Spatial Correlation in Spontaneous Pressure Fluctuations of a Gas Inside an Acoustical Black Box
Authors: van Burik H. C. J. , Alkemade C. Th. J.
Published: September 2005

Cross correlation was measured in the spontaneous fluctuations in pressure on two membranse as a function of their distance. The results of these measurements are in good agreement with predictions from the calculated as well as measured elements of the equivalent four pole, applying the Nyquist formula.
Vanishing of the Surface-Pressure Contribution to the Helmholtz Integral
Authors: Copley Lawrence G. , Schenck Harry A.
Published: September 2005

The classical Helmholtz integral is of current importance in numerical solutions for radiation from arbitrary vibrating surfaces over which the normal velocity is specified. Special conditions on frequency and normal velocity are derived here, under which the Helmholtz integral reduces to an explicit integral representation for the pressure field in the region exterior to an arbitrary vibrating surface. The frequency is required to be a characteristic frequency for the region enclosed by the vibrating surface subject to Neumann boundary conditions. The normal-velocity configuration is required to satisfy either of two equivalent integral relations. It appears that for important geometries such as the finite cylinder and the rectangular parallelepiped these special situations can be identified a priori with minimal effort.
Finite-Amplitude Plane Waves: The Weak-Shock Method
Authors: Morfey C. L.
Published: September 2005

Use is made of the weak-shock approach to give a simplified account of finite-amplitude wave propagation in fluids. Topics covered are waveform distortion, shock formation, and the relative importance of diffusion effects. The analysis is restricted to one-dimensional waves.
Method of Axial Testing for Roller-Bearing Noise Qualities
Authors: Lucht R. F. , Scanlan R. H.
Published: September 2005

A number of investigators have studied the vibration of rolling element bearings by taking samples of bearing-race vibratory velocity, acceleration, or displacement at one point on the race, the bearing being run in a somewhat isolated environment. While such methods have led to considerable progress in the evaluation and amelioration of bearing-generated noise, there has been a constant trend toward improvement of the methods. One promising step in this process is reported here. The present paper discusses the replacement of accelerometer radial testing by accelerometer axial testing, the new connecting link between bearing and accelerameter being a metallic exponential horn. The horn technique avoids problems of accelerometer strain sensitivity and dependence of results upon accelerometer angular orientation with respect to specific bearing anomalies.
Pulse Shape of Totally Reflected Plane Waves as a Limiting Case of the Cagniard Solution for Spherical Waves
Authors: Towne Dudley H.
Published: September 2005

The well-known solution for the pulse shape of a totally reflected plane wave is shown to be identical with the leading term in an asymptotic expansion of the Cagniard solution for spherical waves. This extreme approximation does not yield the correct impulse required by a general theorem. The second-order term in the asymptotic expansion yields an impulse contribution comparable to that of the first term, and the sum has the correct value. A specific illustration of the expansion procedure is given for the case of a triangular pulse at grazing incidence and the results are compared with the exact solution obtainable for this case.
Modified, More Rapidly Converging Modal Series Representation for Mechanical Admittance
Authors: Smith Robert D.
Published: September 2005

The standard modal series representation of mechanical admittance may be slowly convergent, especially at antiresonance, for structures that may exhibit a spatially localized response to a spatially localized excitation, e.g., beams on elastic foundation as well as plates and shells. A William's modal acceleration approach is used to arrive at a modified, faster converging, modal series representation for the displacement admittance of a general, finite, linear elastic structure which contains damping. A freely supported, damped, circular cylindrical shell, driven by a radial point force, is employed as an example for a comparison of the modified and the standard modal representations for driving-point and transfer displacement admittance in various frequency bands. At a shell antiresonance, the convergence of the modified driving-point admittance representation is very rapid in comparison to that of the standard modal representation. This is particularly true for that shell antiresonance that lies between the two most widely separated shell resonances. As one proceeds from the case of very light to intermediate shell damping, the convergence, at antiresonance, of both types of admittance representation improves considerably.
Vibrational Waves in a Thick Infinite Plate of Piezoelectric Crystal
Authors: Paul H. S.
Published: September 2005

Vibrational waves in an infinite piezoelectric plate bounded by two planes of symmetry are investigated. The surfaces of the plate are kept traction free and are completely coated with electrodes, which are shorted. The lowest symmetric and antisymmetric wave modes are discussed. Both types of mode change to surface modes whenever surface modes are possible along the direction of propagation. The waves propagating in the (1,0,0) direction of a cadmium selenide crystal have been analyzed numerically.
Investigation of Impulsive Deep-Sea Noise Resembling Sounds Produced by a Whale
Authors: Corcella Anthony T. , Green Milton
Published: September 2005

Spectral and statistical analyses were performed on sea noise recorded in the Atlantic Ocean a short distance south of Bermuda. The noise is of an impulsive nature with an average duration of approximately 3 msec/impulse and an average time between pulses of approximately 110 msec. The maximum intensity of the impulses occurs in the frequency spectrum around 3000 Hz. The peak source pressure level is estimated to be roughly 35 dB//1 μbar at 1 yd. To a certain extent the characteristics of the noise match those of the sperm whale.
System of Small-Size Transducers as Elemental Unit in Sonar System
Authors: Maidanik G.
Published: September 2005

Can a transducer system consisting of a few small-size transducers replace an extended transducer as an elemental unit in a sonar system? This question is analyzed in some detail, assuming that the external pressure field to which the transducer system of a sonar system is subjected is generated by an incident plane acoustic pressure field and a subsonic turbulent boundary layer. The analysis conducted, by and large, in spectral space, {k,ω} space. The conceptual advantages of utilizing spectral space for the analysis of the response of transducer systems are exemplified and discussed.
Model for the Nonlinear Characteristics of Cochlear Potentials
Authors: Engebretson A. Maynard , Eldredge Donald H.
Published: September 2005

In an effort to clarify certain ideas about the nonlinear behavior of the cochlea, simple nonlinear network was studied. The network was constructed to produce peak-clipping distortion similar to that seen in the cochlear microphonic (CM) of the basal turn of the cochlea. The interference between pairs of tones and the growth of combination tones as well as other manifestations of nonlinearity were similar for the ear and for the network. The degree of similarity between the output of the network and CM from the ear is shown by instantaneous waveforms and by input-output functions. An important finding of this paper is that the linearization effect of two-tone interference in the ear is a property of nonlinear systems, which occurs in the network also. The results also support recent theories that summating potential (SP) is produced by asymmetric nonlinearities in the ear.
Sensory Interaction: Perception of Loudness During Visual Stimulation
Authors: Karlovich Raymond S.
Published: September 2005

Eight subjects engaged in an alternate binaural loudness balance (ABLB) task utilizing the method of adjustment to explore the perception of loudness of a 300-msec-duration 1-kHz auditory stimulus at 20 dB and 50 dB SL's. Conditions utilized were no visual stimulation during ABLB, visual stimulation in synchrony with the standard auditory stimulus during ABLB, and visual stimulation in sychrony with the comparison auditory stimulus during ABLB. The visual stimulus was a short-duration stroboscopic light flash. The data indicated that sensory interaction in terms of visual facilitation of auditory loudness does occur and is more apparent at higher rather than lower SL's. The comparison stimulus was adjusted to a higher SL when the visual stimulus was associated with the standard auditory stimulus than when the visual stimulus was associated with the comparison auditory stimulus. The magnitude of this statistically significant difference was approximately 7 dB and implies that information presented to the visual sensory modality can affect the perception of the magnitude of information presented to the auditory sensory modality.
Identifying Meaningless Tonal Complexes
Authors: Webster J. C. , Carpenter A. , Woodhead M. M.
Published: September 2005

A series of nine tonal complexes was constructed in which varying patterns of harmonics like 2, 4, 6…24; 3, 6, 9…24; 4, 8…24 were emphasized. Six listeners were asked to differentiate the sounds, which they did easily. They were then asked to identify the complexes by number, for example; 4, 8…24 was to be called No. 4; 5, 10…25 called 5. This they did with 33% accuracy. The most easily identified sounds were Nos. 6 (6, 12, 18, 24); 8 (8, 16, 24); 7 (8, 9); and 9 (1, 2, 3, 4…25). Numbers 6 and 8 were judged to be more complex and higher in pitch than the others. Sound 9 was judged to be the least complex and the lowest in pitch. All, in fact, had a fundamental frequency of 75 Hz.
Relation of Threshold Shift to Noise in the Human Ear
Authors: Weissing Heinz
Published: September 2005

Threshold shifts in the average human ear are dependent upon the physical parameters of the noise to which the ear is exposed. The influence of noise level can be described approximately by an exponential function. High-frequency noise components cause much greater threshold shifts than low-frequency components; the point of maximum effectiveness lies near 3000 Hz. In summating the action of different noise components, critical bands of about 1 oct width are effective. Noise components that excite different critical bands produce partial threshold shifts that are, to some extent, independent of one another.
Comments on “The Use of Noise Bands to Establish Noise Pitch” [H. R. Rainbolt and E. D. Schubert, J. Acoust. Soc. Am. 43, 316–323 (1968)]
Authors: Greenwood D. D.
Published: September 2005

In their paper, Rainbolt and Schubert incorrectly attribute at related pilot study to me owing to misrecollection of a letter from me to Schubert in 1963. The personal communication in question and did not represent the study as mine but as a student experiment performed by three graduate students of my acquaintance 3 yr before t heard about it in 1960 and 6 yr prior to my letter to Schubert. It is pointed out here that I did not give permission to cite or publish the data of others. My communication to Schubert indicated that the preliminary experiment, despite its possible importance if confirmable, had certain enumerated limitations, that should now influence the weight attached to it. The 1963 letter also directed attention to the pitch judgments of one subject, which are pertinent to points raised by Rainbolt and Schubert.
Best Inhibitory Frequencies of Complex Units in the Eighth Nerve of the Bullfrog
Authors: Liff Harold , Goldstein Moise H. , Frishkopf Lawrence S. , Geisler C. Daniel
Published: September 2005

Complex units in the bullfrog have Best Excitatory Frequencies (BEF) below 900 Hz, and can be inhibited by tones in a broad frequency range. A unit's Best Inhibitory Frequency (BIF) is always greater than its best excitatory frequency. A scatter diagram of BIF vs BEF for 38 units indicates that mean BIF increases as BEF increases.
On Computer Transcription of Phonemic Symbols
Authors: Reddy D. R.
Published: September 2005

A possible standard for computer transcription of phonemic symbols is proposed.
Ultrasonic Relaxation in Aqueous Mixture of Urea with Enzyme Urease
Authors: Pancholy M. , Saksena T. K.
Published: September 2005

Results are reported of the ultrasonic-absorption coefficient and its variation with frequency in an aqueous mixture of urea with enzyme urease. The probable cause for the observed high absorption are examined.
On the Third-Order Elastic Moduli of Quartz
Authors: Stern R. , Smith R. T.
Published: September 2005

The third-order elastic moduli of quartz have been measured using a pulse-echo interferometer technique. Values for the constants are given and compared with those of previous workers.
Reply to “Comments on ‘Evidence of Phase Shift at Caustics’” [Ivan Tolstoy, J. Acoust. Soc. Am. 43, 380(L) (1968)]
Authors: Barash Robert M.
Published: September 2005

A numerical error by Tolstoy has provided an incorrect basis for his criticism of my interpretations of experimental data on phase shift of explosion pressure pulses in refractive water.
Backscattering from the Deep Sea Bed at Small Grazing Angles
Authors: Buckley J. P. , Urick R. J.
Published: September 2005

The backscattering strength of the deep sea bed has been measured down to grazing angles of 5° by means of a deep hydrophone suspended from a surface ship and a freely sinking deep explosive charge. The necessary horizontal and vertical offsets between charge and hydrophone were found to be a negligible complication of the backscattering geometry. In three deep test locations in the Atlantic Ocean, the measured scattering strengths in the band 2–4 kHz were consistent with earlier measurements at higher angles and showed only slight contamination by backscattering from the volume of the sea or the bottom.
Phase Shift at Caustics and Turning Points
Authors: Silbiger Alexander
Published: September 2005

The phase shift observed in recent underwater pulse propagation tests is shown to originate at the caustic rather than at the turning point.
APPROXIMATE DETERMINATION OF THE SPEED OF SOUND THROUGH LIQUIDS AND SOLIDS
Authors: Bell David S.
Published: September 2005

The speed of sound through liquids and solids can be easily determined using an ultrasonoscope calibrated for a known substance. An expression is derived for calculating the unknown speed. This technique is particularly valuable for understanding the position of echoes reflected from prosthetic devices in the heart.
Absorption and Dispersion of Ultrasonic Waves in Inert, Monatomic Gas Mixtures
Authors: Goldman Edward B.
Published: September 2005

The absorption and dispersion of ultrasonic waves in binary mixtures of inert, monatomic gases is studied using the two-fluid theory of gas mixtures. Expressions are derived for the absorption and dispersion at all ultrasonic frequencies. At low frequencies, these expressions reduce to those verified experimentally by Holmes and Tempest [Proc. Phys. Soc. (London) 75, 898–904 (1960)], while at higher frequencies new viscous effects are shown to be present.
Retarded Potential Approach to the Scattering of Elastic Pulses by Rigid Obstacles of Arbitrary Shape
Authors: Shaw Richard P.
Published: September 2005

The scattering of elastic pulses by rigid obstacles of arbitrary shape is discussed in terms of an integrodifferential equation similar to Kirchhoff's equation. This approach has proved valuable in the treatment of acoustic scattering problems and the extension proposed is relatively straightforward. The advantage of this approach is that the problem can be formulated completely in terms of values of stress and strain on the scattering surface only thereby reducing the order of the problem by one spatial dimension. Field values can be obtained from the surface values by a direct quadrature if required. The simple problem of a P-step wave reflecting from an infinite rigid plane is discussed as an example of the procedure.
Torsional Vibrations of Elastic Prolate Spheroids
Authors: Rand Richard H.
Published: September 2005

Frequency equations and mode shapes are presented in analytic form for the torsional vibrations of solid prolate spheroids and thick prolate spheroidal shells. The solutions are shown to include the previously obtained solid sphere and thin prolate spheroidal shell results as limiting cases. Numerical results are presented for solid prolate spheroids.
Pulse Shapes of Creeping Waves around Soft Cylinders
Authors: McNicholas J. V. , Überall H. , Choate K.
Published: September 2005

The process of diffraction of sound waves by finite obstacles is now commonly analyzed in terms of creeping waves that encircle the scattering object azimuthally. For the example of a soft infinite circular cylinder, we have studied the scattering of pulsed sound waves, both of delta-function and of finite-step-function shape (with or without harmonic modulation). We investigated the changes in pulse shape that occur as the pulse propagates over the cylinder surface. This constitutes an extension of previous work by Friedlander and by the present authors in which only the initial rise of the creeping pulses was obtained numerically, and it has been accomplished by an asymptotic expansion in the Laplace-transform variable s.
Auditory Flutter Fusion and Envelope of Signal
Authors: Harbert F. , Young I. M. , Wenner C. H.
Published: September 2005

Auditory-flutter fusion (AFF) threshold measurements were made for pure tones and white noise by varying the rise and decay time. The tests were conducted with trained, normal-hearing subjects and also those with pathological ears. Off time was the major factor in determining the AFF threshold. The off time required to obtain AFF threshold was dependent upon the rise and decay time and followed a definite pattern referred to in the derived equation. There was no relationship between on time and AFF threshold. Other variables such as testing intensity level, interruption rate, and stimulus components did not provide any statistically significant alteration of AFF threshold. AFF thresholds were similar for both normals and pathologicals with and without abnormal adaptation.
Hearing Hazard from Small-Bore Weapons
Authors: Acton W. I. , Forrest M. R.
Published: September 2005

The potential hearing hazard from 0.22-in. rifles and pistols was investigated by measuring the noise levels from various weapons, and the temporary threshold shifts in a group of firers under controlled conditions. It was concluded that regular use of these weapons on indoor ranges represents a slight auditory hazard to persons of very much greater than average sensitivity to impulse noise.
Usage of Power-Spectral-Density Terminology
Authors: Mangiarotty R. A.
Published: September 2005

In acoustics, turbulence, and similar dynamic phenomena, it has become widespread practice to label the square of practically any spectral quantity as the “power spectral density,” and, in some instances, the turbulence/local velocity ratio as the “intensity.” The confusion of this practice is discussed.
Acoustic Second-Harmonic Generation in Piezoelectric Crystals
Authors: McMahon D. H.
Published: September 2005

The treatment of acoustic second-harmonic generation has been extended to piezoelectric crystals. This extension shows that the third-order elastic constants measured by means of second-harmonic generation are not equal to the field-free third-order elastic constants. It is shown that the size of the effective third-order elastic constants depends on all of the material constants of the crystal free energy that are third order in strain and electric field. Estimates of the relative sizes of the material constants contributing to the effective third-order elastic constants have been made for longitudinal waves propagating along the z axis in LiNbO3. A comparison of these estimates with the measured value of the effective elastic constant C333 in LiNbO3 shows that indirect piezoelectric coupling may produce a large fractional difference between the field-free third-order elastic constant and the effective third-order elastic constant.
Axisymmetric Stress-Wave Propagation across the Common End Face between Two Semi-Infinite Cylinders, Solid to Fluid
Authors: Miller G. Kirby
Published: September 2005

When a harmonic wave train traveling in an elastic rod strikes its interface with a contained fluid column of the same radius, some of the energy is transmitted to the fluid and the rest is reflected back down the rod. In the process, elastic energy is temporarily stored by the deformation of the rod's end face. To study these phenomena in detail analytically, a truncated eigenfunction expansion is used. The equations of motion and the transverse boundary conditions are satisfied exactly in the two media. The resulting eigenfunction expansions for the interface boundary conditions are truncated, and imposed at enough points along a radius on the interface to permit a solution of the resulting system of equations for the amplitude coefficients in the truncated series. The stress and displacement fields at any point in either medium, along with intensity, power, and transmission loss, are then reconstructed, using the appropriate truncated series. The computer results obtained for the case of Nylon and water over a limited frequency range validate the approximation procedure and provide new information about the stress and displacement fields as functions of frequency and location. At the frequency of “end resonance,” it is found that the transmission loss curve has a sharp peak, indicating a possible use for this configuration as an acoustic notch filter.
Normal Vibration Modes of Stiff Strings
Authors: Wolf Dietrich , Müller Helmut
Published: September 2005

This paper compares the theoretical and experimental behavior of a stiff steel string vibrating under clamped boundary conditions. It is shown that the normal vibration modes of the stiff string are governed by one string constant only. The studies have been extended into a range where the standard formulas for the natural frequencies are not valid. Therefore, computations have been performed from more general relations developed here. Precise criteria are stated for the accuracy obtained. Apparatus has been developed that makes it possible to attain clamped boundary conditions and allow a measurement accuracy to about 0.1%. The experimental results observed with this arrangement are in excellent agreement with the calculated data (the mean-square deviations are below 0.15%).
Ray Transmissions in an Underwater Acoustic Duct with a Bottom Having Curvature
Authors: Seifer A. D. , Jacobson M. J.
Published: September 2005

A general spreading-loss equation is developed for specularly reflected rays in a medium whose sound velocity varies with depth and whose bottom has one-dimensional roughness with curvature. When the sound velocity is constant, curvature is found to be most important when the grazing angle is small. The spreading loss is given in terms of a determinant, and the relative importance of bottom depth deviation, slope, and curvature are compared when these parameters are small. Bottom loss is then included, and the amplitudes of ray arrivals at a fixed receiving point are found. The bottom parameters are taken to be random, and the variances of the amplitude in decibels of each arrival and of the total field are determined. In an example, Rayleigh's reflection theory is employed, and the source and receiving points are placed on the bottom. It is found that curvature can cause significant amplitude variation, which might otherwise be negligible if curvature were neglected. Finally, the spreading loss is determined for a layered medium bounded by a bottom with curvature.
Geometrical Acoustic Propagation with Frequency Dependence
Authors: Solomon L. P.
Published: September 2005

One characteristic of geometrical-acoustic solutions is their frequency independence. Geometrical acoustics stems from the solution of the eikonal equation, which is a form of the wave equation in the limit of infinite frequency. Since the effects of the medium and the boundary conditions on the acoustic fields are definitely frequency dependent, it is desirable to obtain approximate solutions that reflect this dependence on frequency. Although data are available on propagation losses for signals of different frequencies, geometrical acoustics does not offer a means of comparison. An asymptotic expansion in terms of inverse powers of the frequency is presented. The first term in the expansion obeys the eikonal equation; all the ray-path solutions obtained from geometrical acoustics are applicable. Here, the first term of the expansion, which is the geometrical-acoustic field, is obtained in closed form using a simplified profile in which the first derivative is continuous everywhere. The calculation of the higher-order terms then involve operators that have known variable coefficients that are functions of the lower-order solutions.
Acoustic Propagation in a Continuously Refracting Medium
Authors: Solomon Louis P. , Ai D. K. Y. , Haven Girard
Published: September 2005

This paper proposes a three-layer model where, in each layer, an analytical expression is used for the speed of sound variation. This results in analytic, easily handled expressions for the ray paths. The speed of sound and its first derivative are matched at each layer interface; the depth of each layer is adjusted, dependent upon the experimental points. The upper layer is either a quadratic or cubic polynomial, the middle layer is a hyperbolic cosine, and the lower layer is linear. The model includes reflections from arbitrary analytic bottoms and flat ocean surfaces. The computer is used purely for computational results, not for integration. This theory may be considered as a “zeroth”-order, analytical solution for more complex propagation models.
Two-State Threshold Theory and the Multiple-Look k-Alternative Forced-Choice Experiment
Authors: Meudell P. R.
Published: September 2005

A prediction from the two state threshold theory is given for the multiple-look k-alternative forced-choice experiment. Experiments so far conducted do not give sufficient information for a direct comparison of the model with the data. Upper and lower limits to the threshold prediction, however, show that it is more likely to be a worse fit to the data than signal-detection theory which, itself, overestimates the data. It is suggested that both these models can encompass the data if one assumes that the observer has an imperfect memory.
Attenuation of Sound in Suspensions and Gels
Authors: Blue J. E. , McLeroy E. G.
Published: September 2005

Measurements were made of sound attenuation in fresh water suspensions of platelet- and needle-shaped particles. The frequency range covered was 150 to 1500 kHz. Concentrations ranged from less than 1% to more than 20% by volume. Platelet-shaped particles produced higher values for attenuation than needle-shaped particles at the same volume concentration. Sound attenuation at concentrations light enough to gel was the same in the gel as in a suspension of the same concentration. This is in agreement with the thixotropic characteristic of some gels. The effect of inorganic salts flocculation and syneresis in gels may lead to higher particle concentrations and resulting different acoustic properties of sea bottoms.
Sound Speed and Attenuation, from 15 to 1500 kHz, Measured in Natural Sea-Floor Sediments
Authors: McLeroy E. G. , DeLoach A.
Published: September 2005

Laboratory measurements of the sound speed and attenuation in natural sea-floor sediments have shown that the speed ranges from 0.997 to 1.19 that in sea water, and that the attenuation is directly proportional to frequency over the range of the measurements (15–1500 kHz. Values of the attenuation coefficient range from 0.7 dB/ft at 15 kHz for silty-clay sediment to 75 dB/ft at 1500 kHz for sand.
Experimental Observation of Three Types of Pulsed Circumferential Waves on Solid Aluminum Cylinders
Authors: Neubauer Werner G.
Published: September 2005

Two types of circumferential waves that travel on solid-aluminum right-circular cylinders are measured by the reception of a pulse using a hydrophone in the diffracted field. Schlieren photographs are presented for both of these types and also of the “Franz type,” which was previously reported.
No Phase Change in a Constant Gradient Medium
Authors: Wood D. H.
Published: September 2005

From a known integral representation of the field due to a point source in an infinite medium with constant sound-velocity gradient, it is shown that no phase shift can occur.
INTERNATIONAL ROUND-ROBIN CALIBRATION IN UNDERWATER SOUND
Authors: Trott W. James
Published: September 2005

A round-robin program of hydrophone calibrations was organized by a committee of the International Electrotechnical Commission to determine the sperad in values obtained by participating international agencies in calibrating the same group of hydrophones. The results were expected to permit specifying a practical figure for accuracy of measurement and to provide information that could be used to design an international standard hydrophone for underwater sound measurements. The average deviation of all data is ±0.6 dB.
Steady-State Flow of a Subsonic Inviscid Stream through Statistically Roughened Wall Ducts
Authors: Ortloff C. R. , Jones J. P.
Published: September 2005

This paper investigates the spatially dependent static pressure field induced by the steady motion of a compressible inviscid fluid in the interior of a two-dimensional duct with small wall roughness. The statistically described wall-roughness height and slope are assumed to be uncorrelated; this is equivalent to considering the wall-roughness height and slope correlation functions as Dirac delta functions. The paper treats the case in which the duct-flow velocity is less than the fluid sound speed. It is found that, for subsonic-flow conditions, a wall possessing a random-roughness distribution induces a static mean-square pressure which is at a maximum at the duct walls. The static pressure field induced in the fluid by the passage through the roughened-wall duct is derived and found to decay with increasing distance from the duct walls. An increase in the free-stream Mach number results in an increase in the mean-square pressure level in the duct; minimum values of mean-square pressure result when the flow is assumed to be incompressible.
Effects of Intense Noncavitating Ultrasound on Selected Enzymes
Authors: Dunn F. , Macleod R. M.
Published: September 2005

The denaturation of enzymes in solution by cavitating ultrasound has been reported previously. This report presents the results of an extensive study of the effects of noncavitating ultrasound on solutions of α-chymotrypsin, trypsin, aldolase, lactate dehydrogenase, and ribonuclease. In one set of experiments, the solutions were irradiated and then analyzed to determine the effects on the physical and chemical properties of the enzyme molecules. Irradiations were carried out at different pH values and temperatures using 1-MHz ultrasound at an intensity of 75 W/cm2, 10-min continuous exposure, and 11-MHz ultrasound at an intensity of 1000 W/cm2, 2000 0.1-sec pulses. Analytical procedures employed included measurements of enzyme activity, specific optical rotation, uv absorption spectrum, and sedimentation coefficient. In a second set of experiments, enzyme-catalyzed reactions were irradiated with ultrasound and simultaneously monitored spectrophotometrically. Ultrasound in the intensity range 0.5–35 W/cm2 at the frequencies 1, 9, and 27 MHz were employed with the temperature and pH held constant. Comparison of the results of this study with those from studies employing cavitation shows that cavitation is a necessary condition for ultrasonic denaturation of the five enzymes of this study.
Can the Binaural System Preserve Temporal Information for Jitter?
Authors: Pollack Irwin
Published: September 2005

Thresholds for temporal irregularity, or jitter, were obtained under three conditions of binaural presentation of auditory pulse trains: (1) periodic pulses delivered to both ears; (2) periodic pulses randomly assigned between the separate ears; and (3) discarding the pulses randomly assigned to one of the ears in Condition 2. A strong test for preservation of temporal information by the binaural system for the analysis of jitter is furnished when thresholds under Condition 1 equal those under Condition 2. A null test for preservation of temporal information by the binaural system for the analysis of jitter is furnished when thresholds under Condition 2. equal those under Condition 3. Over a wide range of conditions, the null test is verified. Additional tests demonstrate that jitter thresholds are related to pitch differences at the separate ears.
Computer Model for Pressure Waves Radiating from Time-Varying Axisymmetric Sources in the Atmosphere
Authors: Remillard Wilfred J.
Published: September 2005

There exists an integral relationship between the time variations of the strength of a line source in a homogeneous atmosphere and the time variations of the resulting pressure disturbances. An analog-computer model is described that uses this relationship to simulate such a source, and that gives a graphical display of the associated pressure waves. Four examples are given.
Analytical and Experimental Studies of the Sound Field in a Propeller Duct
Authors: Fricke Werner , Bissell John R.
Published: September 2005

An analytical approach for predicting the rotational sound due to blade loadings in propeller ducts, based on definable propulsion quantities is presented. It is assumed that the sound field in the propeller plane may be represented by expanding the rotating net blade pressure distribution in a suitable series that satisfies both the wave equation and the boundary conditions associated with the duct and hub. The equations allow for the calculation of the spectral and spatial sound-pressure distribution along the axis and radius. The validity of the analytical approach is investigated by exploring the sound field of a full-scale model duct under measured operational conditions. Calculated and measured sound pressures along the duct wall in front and in the propeller plane are in good agreement. Behind the propeller plane, the deviations increase. This effect may result from an increased turbulence behind this plane as demonstrated by a spectral analysis. The analytical approach did not consider a finite tip clearance. Effects of a variable tip clearance on the sound field were explored experimentally. An increase of tip clearance from 0.38 to 1.5 in. resulted in a reduction of the over-all sound pressure level by 5 dB.
On the Ultrasonic Cleavage of Cyclohexanol
Authors: Currell Douglas L. , Nagy Stanley S.
Published: September 2005

The ultrasonic cleavage of cyclohexanol in aqueous suspension produces acetylene. The rate of the reaction is independent of the concentration of cyclohexanol and is unaffected by the addition of the solid radical scavengers, acrylamide and allylthiourea, but is reduced in the presence of oxygen and nitric oxide. These results are consistent with the idea that the ultrasonic reaction takes place within the cavitation bubbles. Oxygen and acetylene in aqueous solution react to form carbon dioxide when treated with ultrasonic waves.
Diffraction of Sound Waves by a Moving Fluid Cylinder
Authors: Yeh C.
Published: September 2005

The solution of the diffraction of sound waves by an axially moving fluid cylinder is obtained. Results indicate that there is no Doppler frequency shift for the scattered wave and when the angle of incidence is normal to the cylinder axis, the scattered wave is independent of the movement of the medium. Numerical computations for the magnitudes as well as the radiation patterns of the scattered wave as a function of the velocity of the moving medium were also carried out for various incident angles. It is found that the magnitudes and the radiation patterns of the scattered wave are quite sensitive to the variation in the angle of incidence even for slow relative movement of the fluid media.
Acoustic Field Generated by a Vibrating Boundary. II. Planar Array Vibration and Synthesis
Authors: Kuo Edward Y. T.
Published: September 2005

The theory of acoustic radiation, extended from the theory of acoustic scattering, is shown to be applicable to the acoustic-field study of planar transducer or hydrophone arrays. The general nature of the approach is shown to give a new look at the problem of synthesis and the method of studying vibrations acoustically. In the synthesis problem, shading of amplitudes over both space and time is proposed.
High-Frequency Ultrasonic Properties of Freshwater Fish Tissue
Authors: Freese M. , Makow D.
Published: September 2005

Various ultrasonic properties of whitefish (Coregonus dupeaformis) tissues have been determined. The sound velocity, impedance, and absorption were measured at 22°C with pulse echo techniques for the frequencies of 1, 2, 3, 7, and 11 MHz. The average impedance and absorption of fresh whitefish myomere with a fat content of approximately 8% were 1.634 × 105 cgs units and 0.7 dB/cm/MHz, respectively. No significant velocity or absorption anisotropy was observed for the muscle tissues. The effects of freezing on velocity and absorption were investigated. The mean velocity in thawed flesh was only 0.8% higher than in fresh flesh, but increases up to 100% or more were noted in the absorption. This increase depended on the rate at which freezing proceeded; a longer freezing period generally resulted in greater absorption.
Mechanisms for Nonthermal Effects of Sound
Authors: Nyborg Wesley L.
Published: September 2005

Research on cell suspensions, single cells, macromolecular suspensions, and model (nonliving) systems reveal a variety of changes brought about by sound in the absence of gross-heating or transient (“collapse”-type) cavitation. Many of these phenomena are explainable in terms of acoustic streaming, radiation pressure, and other characteristics of ultrasound that arise from nonlinearity. Commonly, the sonic effect depends on nonuniformity in the sound field. Interestig results are obtained with techniques by which one can set up nonuniform vibration in the walls or membranes of individual cells. In ultrasonic beams acting on tissue, it is possible that variations may arise from gradients in the incident field, or from inhomogeneities in the tissue, which scatter sound. Gaseous pockets or bubbles would be especially effective as such inhomogeneities.
Ultrasonic Visualization System Employing New Scanning and Presentation Methods
Authors: Fry William J. , Leichner Gene H. , Okuyama Daitaro , Fry Francis J. , Fry Elizabeth Kelly
Published: September 2005

New methods for the ultrasonic visualization of tissue, achieved by employing a newly developed versatile instrumentation system, are outlined and their application to the examination of brain is illustrated. The complete system, whose operating characteristics are described in detail, incorporates an on-line medium-sized digital computer, implementing omnidirectional scanning, utilizing three translational and two rotational degrees of freedom; relief display, which combines intensity modulation and deflection of the oscillograph beam by the echo signals; and segmental construction of echograms, which incorporates wide dynamic range combined with high resolution via program control of receiver gain as a function of range and echo strength. Omnidirectional scanning permits the more complete viewing of tissue interfaces than is possible with the usual compound-scanning methods. Relief display provides an additional parameter as compared to the common flat format for the presentation of echo information in a two-dimensional picture, and the type of echo signal composition at individual positions on an echogram thus can be represented The relief format also facilitates detection of significant echo signals against the background. Comprehensive presentation eliminates the need for, and problems associated with, time-variable gain in receiver amplification and also provides for much greater flexibility in the choice of an amplifier gain characteristic as a function of signal amplitude. The illustrative results presented demonstrate that new ultrasonic visualization methods can be used to detect and localize (1) internal structural features of the cranial vault, (2) external features of the brain (ventricular, cisternal, and fissural surfaces); and (3) major blood vessels (midsagittal sinuses) in considerable detail, under the condition that acoustic energy does not traverse bone.
Symmetrical Scanning of the Head with Ultrasound Using Water Coupling
Authors: Makow D. M. , McRae D. L.
Published: September 2005

The determination of the absolute position of reflecting structures in the brain is difficult, owing to refraction of the ultrasonic beam and the different velocities of ultrasound in the skull and the brain. Since many brain disorders distort the symmetrical brain structures, emphasis has been placed more on the detection of asymmetries rather than on faithful mapping of the brain. The asymmetry can be displayed with adequate accuracy by symmetrical scanning of the head, simultaneously from both sides with two transducers. An ultrasonic immersion scanner that employs this technique is described, and some results are given.
Transducer Alignment Device for A-Scan Echoencephalography
Authors: Hudson A. C. , Trollope B. J.
Published: September 2005

A transducer alignment device for A-scan echoencephalography is described.
Improvement in the Measurement of Intraocular Distances Using Ultrasound
Authors: Giglio Ernest J. , Ludlam William M. , Wittenberg Sidney
Published: September 2005

The application of currently available technology to the measurement of intraocular distances has improved these determinations a whole order of magnitude. The thickness of the cornea, the depth of the anterior chamber, the thickness of the lens, the length of the vitreous, and the thickness of the tissues at the rear of the eye may be displayed at one time on the face of a 5-in. oscilloscope tube with an over-all magnification of about 25×. This is accomplished through the use of four-channel operation with appropriate variable delays at the beginning of the second and third channels. The fourth channel is used to display time marks that may be used to further increase the accuracy of the measurements in the presence of even small amounts of nonlinearity of beam transit across the face of the tube. The method of application of the probe to the patient continues to be the most difficult link in the system to optimize. An all-water path between crystal and eye produces the best signal quality, but alignment is difficult, requires time, and patient cooperation. The time marks that are derived from a crystal oscillator, which synchronizes the entire system, provide an absolute standard against which all the measurements are made. Measurements of refractive length on any given eye as well as thicknesses and spacings of each of the optical interfaces are well within ±0.03 mm. This provides a precision of measure of intraocular distance better than the clinical optometric measurements routinely made in visual examinations. Ultrasonic measurements of physical length were validated to ±0.016 mm. This validity and reliability data suggest that A-scan can be used for making the most accurate and reliable measurements of in vivo intraocular distances currently available.
Clinical Application of Diagnostic Ultrasound in Obstetrics and Gynecology
Authors: Thompson Horace E.
Published: September 2005

Diagnostic ultrasound offers a new dimension in pregnancy evaluation heretofore unaccomplished by other methods, specifically in the area of fetal and placental develpoment and estimation of fetal size and maturity. Ultrasound offers a new and accurate method of placental localization eliminating exposure of the infant and mother to x-ray irradiation. By the use of serial examinations from 1 to 3 days apart, the diagnosis of fetal death in utero can be made usually within one week. The early diagnosis of hydatidiform mole is now possible before the tumor products are expelled, thereby allowing for early evacuation of the tumor before the develpoment of serious toxic effects.
Sensitization in the Auditory and Tactile Systems Following Exposure to Low and Moderately Intense Stimulation
Authors: Moore Thomas J.
Published: September 2005

A series of investigations into the sensitization of the auditory and tactile systems by prior stimulation is reported. Two apparently different types of sensitization were found: (1) A “sustained” type that was elicited following exposure to low-intensity sitmulation and which may be related to the density of functional receptor elements in the region stimulated; (2) A “transitory” type that required exposure to moderately intense stimulation and which apparently occurred only when two regions of differing sensitivity were stimulated simultaneously. In the auditory system, “sustained” sensitization appeared in both the ipsilateral and contralateral ears, “transitory” sensitization occurred only in the ipsilateral ear.