bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigations Concerning Polarization in Barium Titanate Ceramics
Authors: Waidelich D. L. , Marks G. W. , Monson L. A.
Published: September 2005

Considerable information can be obtained concerning polarization in barium titanate ceramics by a careful analysis of hysteresis loops. Mathematically it was shown that both symmetrical and unsymmetrical loops, the latter being characteristic of polarized specimens, can be represented best by a Fourier series. It was found that direct voltage and even harmonic components are present in the unsymmetrical loops. The percent second harmonic and the electromechanical coupling coefficient both rise with increasing dc polarizing voltage and reach a maximum value at approximately 15000 volts per centimeter. The measurement of the second harmonic is possible even when the activity is so small that measurement of the coupling coefficient becomes very inaccurate or impossible. The addition of calcium titanate in small percentages markedly raises the coercive force but lowers the spontaneous and remanent polarization in the range from 0 to 80°C but does not have marked effect between the latter temperature and the Curie point. It was found from studies of the discharge currents on depolarizing specimens by sudden immersion in hot oil that depolarization apparently occurs in two steps: rapid removal of the induced polarization and more gradual disorientation of the domain structure.
Experimental Study of the Effect of Bond Thickness and Position on Q in Butt-joined ADP Crystal Plates
Authors: Faraday B. J. , Gregan D. J. G.
Published: September 2005

In the design of resonant piezoelectric transducers of conventional type which utilize zxt 45 ammonium dihydrogen phosphate (ADP) plates vibrating longitudinally, the low-frequency limit is determined by the transverse dimensions of the mother block from which individual plates are cut. The growth habit of ADP, however, precludes significant accretion in the lateral direction. By cementing single crystal plates end to end, i.e., butt-joining, greater crystal lengths are produced and proportionately lower frequencies are attained. Severe limitations brought about by the properties of ADP eliminate practically all adhesive types except the epoxide resins. Two principal factors considered for butt-joined bonds were the thickness of the bond and its relative position along the over-all length of crystal. The dissipation factor, the reciprocal of the mechanical Q, was measured for variable thickness of bond, keeping the position constant, and for variable position, keeping the thickness constant. These tests indicated that the thickness should be kept at a minimum and that the bond should be located away from the position of the antinode of stress and strain.
On the Vibrations of a Thick Split Ring
Authors: Bernstein Bernard
Published: September 2005

The thin ring theory of Ikebe is extended to a thick split ring by bringing in shear. This theory uses the Rayleigh-Ritz method of approximation. The value of λ, which is a function of frequency, is determined for the first and second approximations. The theory is compared with experimental results. The theory deviates from the experiment by 0.31% for a silicon steel ring and by 0.48% for a 47–50 ring. The Ikebe theory for the thin ring deviates from the experiment by 6.2% and 8.3%, respectively. The error in the theory can probably be attributed to the error in the determination of the modulus of elasticity.
Sound Transmission Through Thin Cylindrical Shells
Authors: Smith P. W.
Published: September 2005

Results will be given of an analysis of the impedance presented by a thin cylindrical shell as a function of the axial wavelength and the angular dependence of the forcing pressure. This information has been used to compute the “transmission loss” of the shell for various particular cases. The results and their implications will be discussed. (This work was supported in part by the Office of Naval Research.)
Comparison of Predicted and Obtained Thresholds for Speech
Authors: Royer Fred L. , Corso John F.
Published: September 2005

A basic problem in the field of contemporary audiology concerns the need for a better understanding of the hearing processes involved in speech reception. The present study was designed to determine the relation between the threshold of spondaic speech intelligibility (CID Auditory Test W-2) and the threshold for speech as predicted from pure-tone ADC audiograms using the Fletcher technique [H. Fletcher, J. Acoust. Soc. Am. 22, 1–5 (1950)]. The results obtained on 103 subjects tested in an anechoic chamber (monaural listening with earphones) show that the Fletcher technique [re AMA sound pressure levels; see Council on Physical Medicine and Rehabilitation of the American Medical Association, J. Am. Med. Assoc. 146, 255–257 (1951)] produces an underestimate of the mean Hearing Loss for Speech of approximately 10.0 db when compared with the obtained mean Hearing Loss for Speech (re 20 db SPL). A new technique for speech threshold prediction was, therefore, devised using the 3000 cps pure-tone threshold value obtained from the “peak curve” of a Békésy-type audiogram. With this procedure, the underestimate of mean Hearing Loss for Speech was reduced to approximately 1.0 db. Further studies must be conducted on other groups of subjects before the validity of the new speech threshold prediction technique can be determined. This work was supported by the U. S. Air Force.
A Survey of Organ-Pipe Oscillations in Combustion Systems
Authors: Putnam Abbott A. , Dennis William R.
Published: September 2005

The open literature on organ-pipe type oscillations generated in various types of combustion systems by the flame, or the combusion process, is reviewed. The driving mechanisms proposed in various instances are outlined. Some general remarks are made, based on the survey, concerning the mathematical formulation of mechanisms to explain the oscillations in particular cases.
Proposed New City Zoning Performance Standard for Noise in Chicago
Authors: Hardy H. C. , Bonvallet G. L.
Published: September 2005

The older concept of industrial zoning was based on limiting use of city space to industries and specified the type of industry according to the manufacturing process involved. The modern concept of establishing zoning and prevention of neighborhood nuisances is on the basis of a performance standard rather than arbitrary use classification. In the new proposed zoning ordinance in Chicago, maximum allowable performance criteria are set in regard to various nuisances such as noise, smoke, air pollution, odors, traffic, sewerage, potential explosion, and vibration. This paper will discuss the limiting noise spectrum which has been set up for the City of Chicago. It was decided that the limiting levels should apply to the residential boundary nearest the plant. This implies that if a plant finds itself surrounded by other industrial property, it can make more noise than if it borders on a residential district. From the experience of many years of study of urban noise conditions, the following limiting spectrum was reached for the City of Chicago:

Below 75 150 300 600 1200 2400 Above

75 150 300 600 1200 2400 4800 4800

72 67 59 55 46 40 34 32

For the boundary between industrial and commercial areas (for instance, shopping centers), the same relative spectrum was chosen, but all the levels were raised by 7 db. It should be emphasized that this standard was determined empirically for Chicago and would not apply necessarily to other communities. For instance, in many suburban communities much lower levels might be specified. After specification of the above spectrum, the principle has been tested by observations of zoning experts and building inspection officials and has been approved by these agencies. Since the drawing up of the standard, one Chicago plant has been silenced to the above specification and the neighborhood noise complaints eliminated.
Just Noticeable Dichotic Phase Difference
Authors: Zwislocki J. , Feldman R. S.
Published: September 2005

The just noticeable dichotic phase difference, as a function of sensation level and of sound frequency, has been determined on a number of listeners with normal hearing. The test tones were transmitted by earphones and the phase difference between the ears was varied by means of an electronic phase shifter. The psychophysical method used combined paired comparisons with forced choice. The first tone pulse of each pair presented was kept at a constant phase difference at which the subject localized the sound source as equidistant from his ears. The dichotic phase difference of the second pulse was varied irregularly (“randomly”). The results show that the sensitivity to dichotic phase difference is highest (2° of phase) at medium sensation levels and that the jnd increases with positive acceleration as the sound frequency increases. Around 1300 cps the jnd becomes so great that it cannot be measured. The dichotic time difference calculated from the measured jnd of phase has a minimum around 800 cps.
Representation of Some Periodic Stimuli in the Bifrequency Plane
Authors: Goldstein Moise H.
Published: September 2005

Recently attention has been focused on psychophysical experiments with nonsinusoidal stimuli of a periodic nature. These studies were concerned with the “residue,” the “missing fundamental,” and more generally with amplitude modulated signals, bursts of noise, and repeated clicks. The results were often in contradiction with Ohm's acoustic law according to which a complex stimulus is analyzed during the listening process into its sinusoidal (Fourier) components. It therefore appeared desirable to develop a mathematical transformation that would bring to light certain aspects of these stimuli that are of importance in determining psychophysical judgments. A bifrequency transform will be presented which is a function of two variables, both of which have the dimension of frequency. One variable relates closely to Fourier frequency, the other to the time-varying envelope of the signal. The shape of the bifrequency plot of a number of auditory stimuli will be illustrated, and the method of analyzing psychophysical experiments employing these stimuli will be described. In several instances the bifrequency method makes plausible psychophysical judgments that are not predicted from Ohm's law. [This work was supported in part by the Signal Corps, the Office of Scientific Research (Air Research and Development Command), and the Office of Naval Research.]
Intelligibility Increase Accompanying Time Interval between Ears
Authors: Schubert Earl D.
Published: September 2005

Comparisons were made of the intelligibility of continuous speech in noise under three listening conditions: Speech arriving simultaneously and in phase at the two ears; speech arriving at one ear later than the other; and speech arriving simultaneously, but in opposite phase in one ear. Time intervals between ears ranged from 200 microseconds to 7 milliseconds. Delaying speech to one ear under these conditions does increase intelligibility but is little, if any, better than the simple expedient of phasing the phones. With the materials and method used, the maximum increase occurs with a delay between ears somewhere between 0.5 and 1 msec, though there is some indication that delays 1 msec and longer may be slightly better under the most difficult listening conditions tried.
On Acoustic Momentum Flux and Radiation Pressure
Authors: Pyett J. S.
Published: September 2005

The explanation of acoustic radiation pressure in terms of momentum flux, often given for problems in one dimension, also may be used for some problems in three dimension. The case of a small spherical obstacle in a plane progressive wave is treated specifically, the force resulting from radiation pressure on the sphere being obtained by considering the momentum flux in the primary field and the secondary (scattered) field. The force is, in general, not proportional to the scattering cross section.
Modifications to Improve the Efficiency of a Diaphone-Type Fog Horn
Authors: Thiessen G. J.
Published: September 2005

The use of a high impedance acoustical load for the type B diaphone is capable of raising the efficiency of the fog horn system from an often encountered 0.2% to values of 10 to 16% for normal operating pressures. The high impedance is provided by a resonant exponential or catenoidal horn. To provide the high degree of frequency stability required by the high Q resonant load the mechanical impedance of the diaphone piston is reduced to permit it to lock in with the horn frequency. The piston impedance is reduced by reducing its mass through the use of an aluminum alloy and by supporting it on a central shaft thus reducing (and stabilizing) the frictional forces. The stability thus achieved is such that the frequency varies only 3% for an air supply pressure change from 5 to 35 psi.
Turbulence and Intense Sound Fields
Authors: Kraichnan Robert H.
Published: September 2005

A brief review is given of present experimental and theoretical knowledge of phenomena involving interaction of strong sound fields and turbulence. Consideration is given to the scattering of sound and shock waves by turbulence, the generation of noise by turbulence, and the effect of intense noise fields or strong resonances on the evolution of a turbulent flow. Differences are pointed out in the nature of the interactions for the cases of weak and strong sound and turbulence fields. When the particle velocities associated with the sound field and turbulence are quite small compared to the velocity of sound, the interaction is essentially nonenergetic, the dominant phenomenon being the “elastic“ scattering of sound by turbulence. For higher excitations, however, theoretical considerations indicate that inertial transfer forces tend to bring about an equipartition of acoustic and turbulent energy. This implies that, in addition to the phenomenon of the generation of noise by strong turbulence, there should exist situations in which some of the energy of a localized intense sound field is transformed into kinetic energy of turbulent motion and situations in which substantial energy transfer accompanies the scattering of sound and turbulence. A discussion is given of the physical interaction mechanisms involved in these phenomena, and the question considered of their realization in physical systems. [Support of the U. S. Air Force, Wright Air Development Center, is acknowledged.]
Evaluation of Two Automatic Formant Extractors
Authors: Flanagan James L.
Published: September 2005

An evaluation of two electronic devices designed to automatically extract the formant frequencies from continuous speech is described. Both formant extractors yield three continuous dc output voltages whose magnitudes, as functions of time, represent the frequencies of the first three maxima in the short-time spectrum of the input speech. The two devices operate, however, upon different principles. One extractor periodically scans the speech spectrum to determine the frequencies of the maxima, while the other periodically examines appropriately restricted segments of the spectrum to determine the frequency of the maximum within each spectral segment. Evaluation tests are described for determining quantitatively the accuracy and reliability of both formant extractors. Specially constructed speech material is fed into the extractors, and their outputs are compared in a prescribed manner to spectrographic analyses of the input speech. The results of the evaluation show that the best formant extractor (the second) follows the first formant of the vowels in speech within ± 150 cps greater than 93% of the time; it follows the second formant within ± 200 cps greater than 91% of the time. The first and second formant outputs of the same extractor are simultaneously within the above tolerances greater than 85% of the time. An analysis of the test results according to the constituent sounds in the speech material shows that the nasal consonants and the extreme front and extreme back vowels cause the most formant errors. Examples of the typical operation of both formant extractors are presented.
Acoustic Absorption in Suspensions: Dependence on Particle Concentration
Authors: Morse R. W.
Published: September 2005

Two methods are customarily used to describe acoustic absorption in suspensions: a wave scattering analysis, which includes viscous scattering; or a macroscopic formulation in terms of Stoke's law. Both of these are valid, however, only for low-particle concentration (really not more than a few percent by volume). In these cases the relation between absorption and particle concentration is linear. In this paper a macroscopic formulation along the lines of Ament is set up in which a general viscous coefficient between particles and fluid is used. The expected behavior of this coefficient with particle concentration is discussed. Because of increasing interaction between particles as the concentration is increased it predicts that the attenuation should be a maximum at around 20% volume concentration of particles; above this the attenuation should actually fall with increasing particle concentration. Comparison with previous reported data will be made.
Delays Associated with Certain Sidetone Pathways
Authors: Stromsta Courtney
Published: September 2005

An investigation of the temporal delays associated with internal-sidetone pathways was undertaken. The results showed delay to be a function of frequency for impulsive signals transmitted from the incisors to the mastoid process by bone and from the thyroid cartilage to the mastoid process by tissue. A similar finding was obtained for phonated signals transmitted from the vocal cords to the mastoid process by the internal sidetone pathways of minimum delay irrespective of media.
Sound Propagation in a Temperature- and Wind-Stratified Medium
Authors: Pridmore-Brown David C.
Published: September 2005

The general linearized equations governing the propagation of sound in a dissipationless temperature- and wind-stratified medium are derived. A formal integral expression is given for the field of a point source located in such a medium, when it is bounded by an absorbing plane under conditions which lead to the formation of a shadow zone. This integral yields the following approximate (high-frequency) expression for the decay rate within the shadow |p|2 = (B/r) exp[−(n/c)f13(−c′−U′ cosφ)23r]. Here p is the acoustic pressure, r is radial distance from the source, B is independent of r, f is frequency in cps, c is sound speed, c′ and U′ are sound- and wind-speed gradients at the ground surface, φ is the angle between the wind direction and the direction of sound propagation, and n is equal to 5.93 for a pressure release boundary and to 2.58 for a hard boundary.
Selective Attenuation of Elastic Wave Motions in Strips of Polycrystalline Metals
Authors: Meitzler Allen H.
Published: September 2005

Longitudinal and flexural waves in an infinite plate of an isotropic elastic material can be analytically synthesized from a single dilatational potential function and a single rotational potential function. If A is the amplitude of the former and B is the amplitude of the latter, it is possible to calculate the ratio A/B for a particular mode as a function of frequency once the values of the roots of the appropriate frequency equation are at hand. Calculations of this kind have been carried out for the lowest three longitudinal and lowest three flexural modes and show that, in general, these modes are composite wave motions involving varying combinations of dilatational and rotational components such that A/B varies in amplitude and phase in a given mode as a function of frequency. The primary purpose of this paper is to introduce the “character” of the various modes, defined as [(A/B)(A/B)*], as a concept useful in understanding the selective attenuation of high-frequency elastic modes in polycrystalline metal strips. In this type of medium, rotational waves are attenuated appreciably more than dilatational waves; hence a given mode might be expected to exist more strongly over the frequency range in which the total wave motion is predominantly dilatational in character. Measurements of the attenuation of elastic pulses having 5 to 35 Mc carrier frequencies and traveling in thin strips of polycrystalline aluminum have been made. In the results, a good correlation is observed between the frequency range over which a given mode is observed and the frequency range over which, theoretically, the character of the mode is large; i.e., [(A/B)(A/B)*]>1.
Sound-Induced Vibrations of Cylindrical Vehicles
Authors: Franken Peter A.
Published: September 2005

Relations between the external sound field and the resulting radial vibration and strain of cylindrical vehicles are proposed and compared with measured data.
Damping of Shaker-Excited Beams Calculated Solely from Displacement-Amplitude Measurements
Authors: Rodden William P. , Whittier James S.
Published: September 2005

For some experimental setups involving a cantilever beam in steady-state vibration there exist simple relations between the tip-to-root displacement-amplitude ratio and the damping of the beam. Derivations of these relations are presented along with a statement of conditions for their legitimate application.
Simple Laboratory Setup for Obtaining Sound Spectrograms
Authors: Ramaswamy T. K. , Ramakrishna B. S.
Published: September 2005

A technique for obtaining sound spectrograms using common laboratory equipment is described. The procedure is to record the signal on a tape loop and reproduce it repeatedly. The tape output is fed successively through different bandpass filters to the intensity electrode of an oscilloscope. The oscilloscope beam is triggered by a 2-kc pulse inserted ahead of the signal. After each repetition of the signal, the filter selector and the vertical position of the trace on the scope are advanced by one step. An oscilloscope recording camera registers the spectrogram under time exposure. The Performance of this setup is improved by using an AVC circuit to accommodate the wide range of intensities encountered in speech within the recording range of the oscilloscope and film.
Rate Functions for Auditory Nerve Responses to Bursts of Noise: Effect of Changes in Stimulus Parameters
Authors: Peake W. T. , Kiang N. Y.-S. , Goldstein M. H.
Published: September 2005

Rate functions for the amplitude of neural responses are presented as a function of stimulus parameters, such as burst length, intensity, and stimulus power level. The data show that the rate functions depend on all of these parameters in a manner that does not allow for a simple description. Rate functions are also reported for noise bursts in the presence of various levels of steady masking noise. Near visual detection level these rate functions exhibit characteristics that are well accounted for by a model that deals with the overlapping of successive neural responses.
Resonant Side-Branch Acoustic Filters for Liquid Piping Systems
Authors: Hixson E. L. , Kahlbau J. V. , Mikeska E. E.
Published: September 2005

Nondissipative side-branch acoustic filters for liquid piping systems are discussed in this report. Simple spring-mass resonators are used as branch elements. The filters are analyzed as lumped-parameter systems for short pipe lengths and as distributed-parameter system for long lengths. One-, two-, and three-section filters are treated and results of tests under both flow and no-flow conditions are given. Band rejection characteristics are obtained with attenuations up to 40 db for no liquid flow. Under turbulent flow conditions effective attenuation is found to be reduced by noise regeneration.
Dilatational-Wave Transmission through a Viscoelastic Layer at Normal Incidence
Authors: Thurston George B. , Wu Shi-Yu
Published: September 2005

The theory of transmission of a plane dilatational wave through an infinite plane layer is considered where the three media involved are assumed to be linearly viscoelastic, their properties being specified by four elastic constants. Relations for the complex transmission and reflection factors are obtained as well as for the intensity relations and specific acoustic impedance in the incident medium. The equations of state for a viscoelastic fluid and viscoelastic solid are used to relate the basic elastic constants to the basic propagation constants for the media. The transmission relations are then given in terms of these propagation constants. Computed transmission characteristics for water through steel into air and for water through rubber into air are presented and the dependence of these characteristics on the dissipative properties of the media are shown. These numerical examples illustrate the transition of transmission properties in going from low-frequency, thin plate conditions to high frequency, thick plate conditions. Special relations for these limiting conditions are also given.
Preliminary Investigation of the Equivalence of Acoustically and Mechanically Induced Vibrations
Authors: Marin L. , Kroeger R. C.
Published: September 2005

Tests were run on small cantilever beams in a standing-wave tube and on a mechanical shaker. Measurements were made of tip amplitude and root strain at resonance for a given sound pressure level and input acceleration. Comparison of these measurements indicates that the acoustic pressure required to produce the same root strain (or tip amplitude) that would be caused by a given input acceleration varies inversely as the cube of the specimen's natural frequency.
Sound Absorption in Sea Water
Authors: Schulkin M. , Marsh H. W.
Published: September 2005

An expression is presented for sound absorption in sea water as a function of frequency, temperature, salinity, and pressure. It is based on available data reported in the literature and new data taken in the North Atlantic Ocean in the frequency range 2–25 kcps.
Effects of Ambient Noise and Nearby Talkers on a Face-to-Face Communication Task
Authors: Webster John C. , Klumpp Roy G.
Published: September 2005

From 1 to 5 talker-listener pairs, talkers seated shoulder-to shoulder on one side of a table with listeners on the other, communicated word lists in conditions of quiet and ambient thermal noise levels of 65, 75, and 85 dB. Each talker read one word at a time to his listener-partner, who repeated back each word for verification by the talker. Talker—listener pairs were instructed to maintain an accuracy of 90% or better.

For the lower ambient levels the speech level of a central pair increased about 5 dB for an additional 10 dB of noise or for each doubling of the number of pairs around them. The rate of utterance decreased with noise but showed no clear cut pattern of change as the number of additional talkers was varied. Accuracy of communication was, on the average, 94% and was never below 84%. Communication errors defy simple description but in general (1) for a constant noise level, increasing the number of talkers results in increasing errors; and (2 for 3 or fewer talker-listener pairs, percent error does not increase until the ambient-noise level reaches 85 dB.
Hydrophone Calibration in a Vibrating Column of Liquid
Authors: Schloss F. , Strasberg M.
Published: September 2005

Absolute pressure calibrations of hydrophones have been performed in the laboratory by immersing the hydrophone in a column of liquid set into vibration. Sound pressures of over 1000 dyn/cm2 can easily be obtained. Various limitations on the procedure, such as those due to fluid motion around the hydrophone and wave effects in the liquid column are discussed.
Note on the Critical Bandwidth
Authors: de Boer E.
Published: September 2005

Exceptionally small values of the critical bandwidth are found from masking thresholds of a tone in narrow bands of noise, when the test tone's frequency remains at the center of the band of noise components. Numerous other experiments—by no means limited to masking—have led to the conception of a markedly wider critical band. In this communication the evidence on this ambivalence. especially as regards masking at the central frequency of a noise band, is critically examined. It appears that the critical band cannot be expected to be accurately determined from central-masking experiments. The most important reason is that the effective power of masking noise is not the sole determinant of masking. The inherent fluctuations of random noise, becoming less rapid and more noticeable at small bandwidths, exert a considerable influence on the detection of tones. The extent of this effect can be evaluated from the intensity difference limen of narrow-band noise. It is to be concluded from the discussion that the larger values of the critical bandwidth are to be preferred, and that the smaller values should be rejected.
Fourier Coefficients of Speech Power Spectra as Measured by Autocorrelation Analysis
Authors: Manley Harold J.
Published: September 2005

Time-domain speech processors, that analyze the short-time autocorrelation function in terms of a set of orthogonal functions, are shown to yield parameters that are the coefficients of a generalized Fourier cosine series representation of the speech power spectrum. Two examples are described, one using a Laguerre filter and one using a tapped delay line as in the autocorrelation Vocoder. In the case of the autocorrelation Vocoder, the derived power spectrum representation reduces to a simple Fourier cosine series in the frequency domain.
Application of Linear Response Techniques to Stress and Fatigue Analyses in Acoustical Loading Problems
Authors: Wang Paul
Published: September 2005

A new method is presented for the analysis and utilization of linear and nonlinear response data obtained from structural elements under conditions of acoustical loading. It is found that due to phase angle differences, the significance of resonance response lies in the amplification of bending stresses, regardless of secondary tension forces induced at the constraints. Comparisons are presented with values so calculated. Correlation of an equivalent linear system possessing the theoretical amplification factor with a nonlinear system of known behavior (determined by tests) is demonstrated. This correlation is also useful in transforming sinusoidal test data to random response, thereby rendering a better application of the cumulative damage rule in sonic-fatigue expectancy calculations for aerospace-vehicle structures.
A Distributed Loudspeaker
Authors: Boersma Sipko L.
Published: September 2005

In ordinary loudspeakers for the audible range, the paper cone forms the matching device between driving mechanism and air load. It is well known that the cone cannot be designed without much trial and error, as movement at the higher frequencies is very complicated. The system described here behaves simply and is alternative to horn matching: traveling waves are set up in a structure. This structure presents to the driving mechanism a mechanical impedance that is designable, real, and constant over a wide frequency range.
Cavity-Loaded Piston Resonators
Authors: Sims Claude C. , Henriquez T. A.
Published: September 2005

A piston-type resonant element for use in underwater sound-transducer arrays is described. The acoustic loading on the piston is varied by the use of a shallow cavity. The element is stable under high hydrostatic pressure, and its efficiency is higher than 90% over a broad bandwidth. An equivalent circuit that successfully reproduces the measured characteristics of the transducer is developed.
Effects of Background Noise on Auditory Detection of Noise Bursts
Authors: Green David M. , Sewall Susan T.
Published: September 2005

The ability of human observers to detect signals that are bursts of white noise is measured by two experimental procedures. In both procedures, the observer's task is to select the interval containing the signal from the two temporal intervals, marked by lights, which constitute a trial. In the first, the signal is added to a continuous background of white noise; in the second, the signal is added to one or the other of two equal noise bursts, that are added to the continuous background noise during the observation intervals.

The psychometric functions obtained in the two experimental conditions are different. In the first experimental condition the psychometric functions are consistent with the assumption that the observer is uncertain about either the exact time when the signal occurs or its exact duration, or about both. In the second procedure, in which two noise bursts mark the observation intervals, the psychometric functions are consistent with the prediction of a statistical-decision model that assumes exact knowledge of the temporal occurrence of the signal. In this second procedure the signal to noise ratio for some constant level of detectability is considerably affected by the relation between the continuous background noise and the level of the two noise bursts. The minimum value of signal-to-noise ratio occurs when the continuous noise is ∼5–10 dB more intense than the equal noise bursts; the signal to noise ratio increases from this minimum as the background level is changed in either direction.
Hydrodynamic Theory of Shock Waves in Solids
Authors: Duvall George E.
Published: September 2005

The impact of two solids traveling with relative velocity of 3 km/sec or more, or the detonation of high explosive in contact with a solid, generates compression waves in which the magnitude of the stress can easily exceed 100 000 atmospheres while its duration may be but slightly, more than a microsecond. In this situation, which lies outside the realm of classical elastic behavior, all the classical criteria for plastic flow are greatly exceeded; it appears, however, that the strain rate is so high that the usual mechanisms of plastic flow cannot act, so nonplastic behavior is to be expected. There is a considerable body of evidence which indicates that metals, at least, behave very much like ideal fluids under these conditions. This evidence includes the hydrodynamic behavior of metal liners in hollow explosive charges, the anomalously low measured shock velocity in iron, and agreement between dynamic compressions measured by Walsh and the extrapolation of static data obtained by Bridgman. These data are reviewed and the plausibility of the hydrodynamic theory is discussed.
Transmission of Pulses through Plates
Authors: Ginzbarg A. S.
Published: September 2005

A rigorous solution based on the method of L. Cagniard has been obtained for the transmission of a pulse from a point source of pressure in a fluid through a solid plate imbedded in the fluid. On the normal from the source to the plate the pressure response is given by a closed form expression requiring no integration. Numerical results on the normal agree in essential features with experiment. The formal solution on the normal can be expressed in terms of reflection and transmission coefficients for compressional and shear waves at the two boundaries. In this form the solution is easily generalized to a many layer problem. [A preliminary report was given at the American Physical Society meeting held on Febraury 26 and 27, 1954, at Austin, Texas. See Phys. Rev. 94, 3, 812 (1954).]
Effect of Switching Earphone Channels upon the Precision of Centering
Authors: Jeffress Lloyd A. , Blodgett Hugh C.
Published: September 2005

The precision of centering a noise signal in the head is improved by switching the earphone channels; either by communicating them, or by switching from a single channel for both ears to one channel for one ear and one for the other. Switching reduces both random errors and bias errors.
Disk-Loaded Torsional Wave Delay Line. I (Construction and Test)
Authors: Andreatch P. , Thurston Robert N.
Published: September 2005

Torsional waves are propagated in a uniform diameter rod with the shear velocity (μ/ρ)12. On the other hand, the effective velocity is slower in a disk-loaded rod with alternate large-diameter and small-diameter sections. Because of the slower velocity, a disk-loaded rod will delay a signal longer than conventional ultrasonic delay lines of the same path length. This paper describes the construction of these disk-loaded torsional wave delay lines, and of electromechanical transducers for generating and detecting the torsional waves. The method of testing and the results of tests on the lines are presented. For example, a brass line having a disk diameter four times the diameter of the sections between the disks provided a delay of 43 μsec/cm at 32 kc, with an insertion loss of about 0.25 db/cm. For contrast, the delay of a uniform diameter brass rod is only 4.7 μsec/cm.
Elastic Constants of Staurolite
Authors: Bhimasenachar J. , Vankata Rao G.
Published: September 2005

The elastic constants of staurolite have been determined using the ultrasonic wedge method. The values of the constants are c11=34.3; c22=18.5; c33=14.7; c44=4.6; c55=7.0; c66=9.2; c23=12.8; c31=6.1; c12=6.7 in units of l011 dynes/cm2. The value of compressibility is 7.58 × 10−13 cm2/dyne.
Development of Traveling-Wave Theories
Authors: Wever Ernest Glen
Published: September 2005

The traveling-wave theories are traced historically from their earliest formulation to modern times. Special consideration is given to the weighty influence on the later developments of these theories exerted by Békésy's direct visual observations of the movements of cochlear structures in response to sounds. Finally, a résumé is given of the characteristics of the tonal patterns and their dependence upon the physical variables operating within the cochlea, according to Békésy's experiments on mechanical models and specimens of human and animal ears. Hereby are brought into focus the many conditions that a final theory of hearing must meet.
Time/Frequency Analysis along the Partition of Cochlear Models: A Modified Place Concept
Authors: Tonndorf Juergen
Published: September 2005

With respect to the present inquiry, cochlear analysis of an applied signal is considered to be given by the distribution of amplitudes along the partition. Since Ohm and Helmholtz, this form of resolution has been thought to correspond to the result of a straightforward Fourier analysis. The present paper intends to show that cochlear models of the Békésy-type perform a time/frequency analysis in the sense of Gabor. Along the existing time/frequency continuum, the response to sinusoidal signals represents one extreme, approaching a pure Fourier (frequency) analysis, and the response to transients the other extreme, approaching a pure time (waveform) analysis. Responses to all other signals arrange themselves between those two extremes; i.e., the resolution depends upon spectral as well as temporal features of the applied signal.

With modulated signals, a process of demodulation occurs. Its origin was finally traced to hydrodynamic events which take place in the region of rapid phase changes of the traveling waves. Since it occurs only along partitions in which stiffness varies with distance, this demodulation appears to be a characteristic property of Békésy models. From the analytic standpoint, demodulation is the detection of a temporal property of the signal.
Radiation Pressure of Second Sound in Liquid Helium
Authors: Herrey Erna M. J.
Published: September 2005

It is a well-known fact that the low-temperature modification of helium, liquid helium II, can propagate two different types of waves with two distinct velocities: “first sound” or waves of pressure variation and “second sound” or waves of temperature variation. The second sound waves may be visualized as internal vibrations between two interpenetrating fluid components, such that the net momentum density remains zero at all times. The momentum current however is not zero. Therefore second sound must exert a radiation pressure and should be detectable with the same radiation pressure methods as used in ultrasonics. An apparatus built for this purpose will be described. It allows detection and measurement of the momentum current in a high-frequency second sound beam as a function of temperature and of input power. The momentum current in the beam reflected from a plate and hence the reflection coefficient of the plate for second sound can also be determined. A solid plate imposes the same boundary condition on both fluid components, but a plate with very small holes is impermeable for one and permeable for the other. Measurements on a thin solid copper vane and on a porous copper membrane will be described. [Supported by a fellowship of the American Association of University Women and a grant from the American Philosophical Society.]
Morphological Basis of Directional Sensitivity of the Outer Hair Cells in the Organ of Corti
Authors: Flock Åke , Kimura Robert , Lundquist Per-Gotthard , Wersäll Jan
Published: September 2005

Electron-microscope studies of cross sections of hair bundles on the outer hair cells in the organ of Corti show a consistent orientation of the sensory hairs. In the cuticle, a basal body is regularly found on the side of the cell toward the Hensen's cells. The sensory hairs are organized in the shape of w pointing towards the basal body. The morphological polarization of the hair cells in the organ of Corti is discussed in the light of similar polarization of the hair cells in the vestibular sensory epithelia and the lateral-line canal organs. A close relation is to be found between the morphological and electrophysiological polarization of the mechanoreceptors in the sense organs of hearing and equilibrium.
Possible Uses of Cavitation in Chemical Processing
Authors: Lindström Olle
Published: September 2005

Cavitation promotes a number of processes, such as extraction, emulsification, dispersion, degassing, diffusion, depolymerization, etc. Its true chemical effects (reactions involving oxidation, reduction and polymerization) are the result of free radicals formed in the cavitating liquid. These effects have been studied for some time but have so far been of no industrial importance because of high costs in comparison with already established procedures. Sonic extraction procedures have aroused special interest in the past. The polymerization and/or depolymerization processes are studied at present in some industrial laboratories. A few specific features of the cavitation process are unique and cannot easily be produced by other means. Cavitation is preceded by a homogenous or heterogenous nucleation process. The homogenous nucleation is an easily controlled process. One obvious application is to eliminate bumping in distillation and evaporation operations. The heterogenous cavitation is utilized in sonic industrial cleaning and degreasing operations. The same technique would be most useful in increasing the activity of solid catalysts in liquid systems, where the reaction products or by-products are blocking the surface of the catalyst. The use of cavitation to improve and accelerate electroplating constitutes one successful, already established application in the foregoing sense.
Cochlear Potentials in the Rhesus and Squirrel Monkey
Authors: Fernández C. , Butler R. , Konishi T. , Honrubia V. , Tasaki I.
Published: September 2005

The cochlear potentials were studied in rhesus and squirrel monkeys. Contrary to previous reports, the data revealed no important differences between the results obtained in these animals and those reported for the cat and guinea pig. Round-window recording of responses to sound stimuli exhibited cochlear microphonics of nearly 2 mV at maximum. The input-output curves showed that CM of these primates behaved not differently from those reported for the cat and guinea pig. When a micropipette was advanced from scala tympani into the organ of Corti, an increase in magnitude of CM was recorded, as well as a negative dc potential of about 75 mV. Perforation of the reticular lamina was associated with a change in polarity of CM and the appearance of an endocochlear potential (about +75 mV). Oxygen deprivation depressed CM and changed the polarity of the endocochlear potential from +75 to −20 mV. A comparative anatomical study showed that the cochleas of primates, cat, and guinea pig are similar.
On the Effects of Ultrasound on the Electrolytic Separation of Metals
Authors: Roll Albert
Published: September 2005

In the electrolytic deposition of metals, electrochemical quantities are affected by ultrasound. The action is similar to that caused by intensive stirring of the electrolyte in front of the cathode. This ultrasonic stirring can be explained by an increased motion caused by sound radiation pressure of the hydrogen bubbles deposited together with the metal at the electrode surface. Consequently, the deposition potential and the current yield are primarily affected. Furthermore, such properties of the metal deposit as brilliance, porosity, structure, texture, adhesiveness, hardness, and tensile strength are affected by the ultrasound. In the case of alloy baths, the composition of the deposited layer is changed. The effects of ultrasound that have been discovered up to now can have technological value only if new methods for intense and uniform sound irradiation of large baths become available.
Isotopic Techniques in the Study of the Sonochemical Formation of Hydrogen Peroxide
Authors: Del Duca Michael , Yeager Ernest , Davies M. O. , Hovorka Frank
Published: September 2005

When hydrogen peroxide is produced sonochemically in water containing dissolved oxygen gas, the rate of production of the hydrogen peroxide is appreciably greater than with just an inert gas such as argon to support cavitation. This gives rise to the question as to whether the oxygen gas in the cavitation bubbles actually participates in the chemical reaction or just modifies the thermal or possibly electrical conditions within the cavitation bubble so as to favor the peroxide formation. Isotopic techniques involving oxygen-18 enriched gas have been used to prove that approximately 30% of the oxygen in the peroxide originates with gaseous oxygen in water saturated at 1 atmos. Through the use of nonequilibrated isotopically enriched gas, the following further information has been obtained. In hydrogen peroxide molecules for which the gas is the source of oxygen, both of the oxygen atoms come from a single gas molecule without the formal breakage of the O-O bond. The significance of these results will be discussed in terms of proposed mechanisms for sonochemical reactions. [Research partially supported by the Office of Naval Research.]
Centrifugal Inhibition of Afferent Secondary Neurons in the Cochlear Nucleus by Sound
Authors: Pfalz Reinhard K. J.
Published: September 2005

In 40 anesthetized guinea pigs and one cat, the left middle-ear apparatus and cochlea were destroyed in order to de-afferent this side of the auditory pathway. Via the left internal meatus, glass electrodes were placed inside the cochlear nucleus. The de-afferented secondary neurons in the cochlear nucleus were never found to be excited by sound, but their excitability could be checked by recording their spontaneous activity. In 34 out of 260 spontaneously discharging secondary neurons, the repetition rate was clearly depressed by sound given exclusively to the opposite intact ear. This sound-produced inhibition must have been transmitted by centrifugal fibers. The degree of inhibition depended on the intensity and frequency of the sound. With pure tones, inhibition showed either a maximum or a minimum in a certain frequency range which was typical for the particular neuron. “Worst frequency” of centrifugal inhibition might be a correlate of “listening” to a certain frequency range; “best frequency” of inhibition might be a correlate of the reverse process, perhaps to be called “hearing-off.” The view is offered for discussion that worst frequency and best frequency of centrifugal inhibition are possibly important for the function of focusing or defocusing the auditory system upon or away from a particular frequency range.