bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic Radiation Pressure
Authors: Westervelt Peter J.
Published: September 2005

An expression obtained (1951) by the author for the radiation force on a scattering obstacle with arbitrary normal impedance is now shown to be valid for any scattering obstacle. The derivation of the final expression for the force in terms of the asymptotic scattering function for the obstacle in the field of an incident plane wave is accomplished by taking into account the interaction of the incident wave with the scattered wave. Thus the former assumption of a perfectly collimated beam (1951) is avoided by considering the incident plane wave to be of infinite extent. The result for the force in the direction of the incident wave is F∥ = c0−1{power scattered+power absorbed−∫Γs cosθdA} where c0 is the velocity of sound, Γs is the magnitude of the mean scattered intensity, θ is the angle formed between the incident and scattered waves. This is the same result as that obtained in 1951.

The expression given in 1951 for the force perpendicular to the incident wave is correct only for an object which scatters in a restricted way. The correct general expression for the perpendicular component of the force is F⊥ = − c0−1∫Γs cosβdA in which β is the angle formed between F⊥ and Γs.
Noise Transmission from Boundary Layer Pressure Fluctuations
Authors: Kraichnan Robert H.
Published: September 2005

A theoretical study is made of noise spectra radiated by the vibration of thin, stiff, flat plates under the action of turbulent boundary layer pressure fluctuations. The transmitted radiation investigated arises from the streamwise convection of quasi-static pressure fluctuations by the steady flow and is critically influenced by the dispersive character of transverse wave propagation in the plates. At moderate subsonic Mach numbers and typical parameter values the total transmitted power varies approximately as the fifth power of Mach number, for sufficiently thin boundary layers. At lower Mach numbers the dependence may be flatter and near certain transonic velocities should be steeper. The dominant transmitted frequencies increase with Mach number, varying, under certain conditions, as Mach number squared. Plate parameters which importantly influence sound transmission included mass/unit area, size of independent plate sections, stiffness, and damping factors for the various vibrational modes. For sufficiently thin boundary layers, the transmitted spectrum shape is essentially independent of boundary layer thickness, but the total transmitted power varies approximately as the fourth power of the thickness. For thicker boundary layers, the dependence is flatter and the Much number dependence is also flattened. Several possible procedures for reducing the noise transmission are mentioned briefly.
Cylindrical Wave Reciprocity Parameter
Authors: Bobber Robert J. , Sabin Gerald A.
Published: September 2005

A cylindrical wave reciprocity parameter Jc = (2/ρc) (Rλ)12L for use in a standard reciprocity calibration when the waves between the source and receiving transducers are cylindrical is derived from both four-terminal network theory and wave propagation theory. Experimental data from calibration measurements on underwater sound line transducers are presented to prove the validity of the parameter.
Measurements of Traffic Noise in West Germany
Authors: Meister F. J.
Published: September 2005

Methods used in the measurement and evaluation of traffic noise in cities in West Germany are summarized. Particularly useful are the values of (1) the background level, (2) the mean peak levels, and (3) the average level (as obtained by a planimeter), evaluated for one-minute periods. For spectral considerations, the “summation spectrum” is used; this is the sum of the spectra of a variety of vehicles which therefore averages out the variations between individual sources. Typical measurements are presented. Steps taken to reduce the disturbance from traffic noise by redesign of public vehicles and by town planning are described.
Acoustics of the Rochester (New York) War Memorial Auditorium
Authors: Olney Benjamin , Anderson Roy S.
Published: September 2005

This arena-type auditorium with a stage at one end has a volume of 3.24 million cubic feet, seats 5774 persons in stationary chairs and a total of nearly 10 000 with additional, portable chairs. Both the stationary and the portable chairs have upholstered seats. The acoustical hazard of concave rear wall and opposite wall containing the proscenium opening was ameliorated by special treatment. A combination structural-acoustical ceiling was used. The design objective of a reverberation time of about 2.5 seconds in the unoccupied room at 500 cps was attained without adjustment. The results of reverberation-time measurements are shown and discussed. The public-address system is described and the subjective assessment of the auditorium is mentioned.
Lateralization vs Localization
Authors: Jeffress Lloyd A. , Taylor Robert W.
Published: September 2005

The accuracy with which subjects could assign an azimuth position to a sound coming to them over earphones was studied. The subjects did about as well initially as Stevens and Newman's subjects did with an external source, and they showed a small amount of improvement with practice.
Neural Volleys and the Similarity between Some Sensations Produced by Tones and by Skin Vibrations
Authors: v. Békésy G.
Published: September 2005

Some similarities and differences between skin sensations and hearing have been investigated. The sensation of pitch on the skin has little similarity to the pitch sensation in hearing. The pitch sensation on the skin changes very much with changes in loudness, and there is a strong diplacusis between different parts of the skin. But the rotating skin sensations and rotating tones (Drehton) have many aspects in common. It was further found that the apparent size of the sensation on the skin and in the ear vary similarly as the stimulus changes. From a neurophysiological point of view, it seems to be important that it is possible to find a situation on the skin where two stimuli of different frequencies cancel each other completely. In this case, one sensation is inhibited by another, but the inhibiting sensation is felt no more. In order to be able to extrapolate from the skin to the cochlea, for several phenomena on the skin, the changes are plotted which occur when the vibrator is moved from an insensitive spot on the skin to a more sensitive one.
Auditory Masking and the Critical Band
Authors: Greenwood Donald D.
Published: September 2005

Masked audiograms were studied as a function of the bandwidth, level, and frequency of a masking noise. In a reverse procedure, audiograms were determined when a movable, narrow, and approximately rectangular band of noise was used as signal in the presence of one or more masking tones. In both cases changes in the masked audiograms as a function of bandwidth made it possible to measure critical bandwidth. When masked audiograms were studied as a function of level, discontinuous changes in their height and shape occurred when the masking stimulus reached a certain “transition” level. If masking noises of subcritical or critical width were used, the growth of masking with level contained a discontinuity at a level of the masking stimulus equal to about 50 db SL. An abrupt change in the shape of the masked audiograms occurred at the same level. The change of shape when a pure tone was the masking stimulus consisted in the appearance of a “notch” one critical bandwidth above the frequency of the masking tone. Findings associated with the bandwidth parameter suggest interpretations of the critical band and of masking. The changes occurring at the transition level may indicate the threshold of the inner haircells.
Ultrasonic Velocity and Thermal Relaxation in Dry CO2 at Moderate Pressures
Authors: Henderson M. C. , Peselnick L.
Published: September 2005

The velocity and absorption of ultrasound in dry CO2 have been measured along the 50.8° isotherm with a Hubbard-type, variable path, recording acoustic interferometer at six frequencies from 300 kc to 7 mc and from 0.3 to 250 atmos, i.e., up to liquid densities. Velocity dispersion is clearly shown in addition to the change in velocity attributable to the nonideality of the gas. The values of the frequency/density ratio f/ρ, at which the transition from V02 to V∞2 is half-completed as the pressure is lowered, and at which the maximum absorption per wavelength occurs, were measured wherever possible. From these determinations the relaxation time of the gas has been determined as a function of the density. It proves to be inversely proportional to the density up to the highest density reached (0.8 g/ml), indicating that ternary collisions have not become important and that the number of binary collisions required to excite the internal vibrations does not vary with density. At 50.8° and one atmosphere the relaxation frequency 1/2πτ is about 26 kc and the number of collisions required to excite the molecule is 48 500. The extra absorption (in excess of the classical) remains a consequence of thermal relaxation up to liquid densities, and no new mechanism need be postulated to explain it. Further work at higher densities and other temperatures is in progress.
Transient Performance of a Piezoelectric Transducer
Authors: Redwood M.
Published: September 2005

The methods of transform calculus are used to solve several problems in which the transient response of a piezoelectric transducer is of interest. The electrical signal produced by a step function of force is derived, both for open-circuit and resistive loading at the electrical terminals, and the mechanical signal produced by a voltage step is also discussed. The analyses are performed for both the plate transducer in compressional thickness vibration and the bar in compressional length vibration, and the important differences between the two transducers are discussed. The analyses commence with the fundamental piezoelectric equations, and solutions are found which represent successive time-delayed reflections of the mechanical transient between the end faces of the transducer. The results are also discussed with reference to the exact transmission-line electrical equivalent circuits of the transducers, whose development is outlined briefly. Simple equivalent circuits which do not involve lines are described; these make it possible to determine many features of the transient without recourse to the full theoretical analysis.
Acoustical Radiation from a Point Source in the Presence of Two Media
Authors: Paul David I.
Published: September 2005

Two semi-infinite isotropic media (porous or nonporous) are separated by a plane interface. A simple point source of sound is imbedded in either of the media. Expressions for the resultant wave function are obtained by the method of steepest descents as modified by Banos and Wesley. In particular, two different asymptotic solutions are presented. The first solution is valid in the vicinity of the interface. The expansions, calculated out to three terms, yield the wave solution as a continuous function of the parameters of the two media and the space coordinates for horizontal ranges beginning at small distances from the source and extending to infinity. It is shown that a surface wave exists and that this wave gradually disappears when the horizontal range becomes sufficiently large. The second solution consists of a simple three term asymptotic expansion valid in the vicinity of the vertical axis. The mathematical treatment uses a new path of integration not found in the literature on this problem.
Observations on Models of the Basilar Papilla of the Frog's Ear
Authors: van Bergeijk Willem A.
Published: September 2005

Observations on models of the tectorial membrane in the basilar papilla of the frog are described. The model membranes constitute a series of increasing complexity, and are studied with sinusoidal stimulation and stroboscopic illumination. It is found that traveling waves occur on these models, and that frequency-dependent maxima are formed. By arrangements of fibers and small masses on the membranes the direction of wave travel and location of maxima can be altered. Measurements of the elastic gradients on the membranes show that waves tend to follow a path defined by the smallest change in elastic properties per unit distance. It is concluded that the frog's basilar papilla is capable of performing frequency analysis according to the place principle.
Performance on a Simple Vigilance Task in Noise and Quiet
Authors: Jerison Harry J.
Published: September 2005

Twenty subjects, working individually, monitored a simple vigilance task, a modified “Mackworth Clock Test,” for 134 hr in noise (112.5 db SPL) and for 134 hr in quiet (79 db SPL). No difference in efficiency attributable to noise level was found. This result is in conflict with previous reports from this and other laboratories which ascribed decrement in performance on vigilance tasks to noise levels. Vigilance tasks in which performance decrements due to noise were found, differed from the present task in that they required subjects to scan a series of displays in addition to maintaining vigil over each display. It is, therefore, suggested that flexibility of attention may be affected by noise, whereas vigilance without the requirement for flexibility may be unaffected.
Notes and References for the Measurement of Elastic Moduli by Means of Ultrasonic Waves
Authors: McSkimin H. J.
Published: September 2005

Aspects of wave propagation of particular importance for the measurement of elastic moduli of solids are first reviewed. Experimental techniques are then discussed, with notes on the suitability for a given application and on factors affecting the accuracy of results. Literature references to the more detailed descriptions are listed.
Representation of the Field of an Acoustic Source as a Series of Multipole Fields
Authors: Oestreicher Hans L.
Published: September 2005

A representation of the field of a sound source of arbitrary shape and size as a series of multipole fields of increasing order is derived. This series is convergent for sources of any size if the surface is sufficiently regular, but its main advantage is for sources small compared to the wavelength. In this case the source has, in general, the directivity pattern of a multipole, the order and strength of which can be determined from the formula.

Although the representation is not unique, certain coefficients have physical significance. The presently used definition of “strength of a sound source” is discussed and a modified definition suggested.
Motion of the Surface of a Uniform Elastic Half-Space Produced by a Buried Pulse
Authors: Pekeris Chaim L. , Lifson Hanna
Published: September 2005

An exact solution is obtained for the motion of the surface of a uniform elastic half-space due to the application at a depth H below the surface of a concentrated vertical force. The time-variation of the applied force is assumed to be represented by the Heaviside unit function. The solution for the horizontal and vertical components of displacement cast in the form of single integrals over a fixed range, and these have been evaluated on the electronic computer of the Weizmann Institute (WEIZAC). The assumed source emits both S waves and P waves. Beyond a distance r1 from the epicenter, which is equal to H/√ in the case λ = μ, the original S wave is converted on reaching the surface into a diffracted SP wave traveling along the surface. At large ranges, the SP phase is more pronounced than the P phase. The S phase is marked by a finite jump for rr1. The coefficient of the logarithmic term is zero both at r=r1 and at large ranges, having a sharp maximum at r=1.004r1. There is no Rayleigh wave at r<r1. At large ranges (r/H≫1) the solution, as a function of the reduced time τ = ct/R, approaches the form of the solution for the surface pulse.
Comparison of the Auditory Threshold as Measured by Individual Pure Tone and by Békésy Audiometry
Authors: Burns W. , Hinchcliffe R.
Published: September 2005

Twenty subjects, age 20 to 58 years, were clinically screened to exclude gross otological pathology. Their auditory thresholds were then determined both by Békésy audiometry and by conventional individual pure-tone audiometry by the method of limits, in 2 db steps. Measurement of the threshold of hearing by either method gave essentially similar results, and the reliabilities of the methods were of the same order for all frequencies tested. When both tests were repeated after an interval of one week, mean improvements of 1 to 2 db were found at all frequencies by the Békésy method, and in all but one by the individual pure tone method. In both methods, however, improvements were significant only at 1000 and 3000 cps.
Hearing Loss among Air Force Flight-Line Personnel
Authors: Kopra Lennart L.
Published: September 2005

As a part of an investigation on the hearing acuity of Air Force personnel, pure-tone audiometric tests and job, noise, and medical history questionnaires were administered to 996 Bergstrom AFB flight-line personnel. For 16 Air Force Specialty groups mean hearing losses (better and worse ear) at 4000 cps ranged from 1.8 db to 20.7 db re audiometer zero. Worse-ear hearing losses at 3000 cps and at 4000 cps in nine Air Force Specialty groups (N=854) did not differ significantly from one group to another. Significant positive correlation was found when 4000-cps hearing loss was correlated with age and when 4000-cps hearing loss was correlated with length of noise exposure. However, when the positive hearing loss vs exposure correlation was adjusted for the positive relationship between age and exposure, no remaining statistically significant relationship existed between 4000-cps hearing loss and length of noise exposure. Infrequent use of ear protection is interpreted as evidence indicating a real need for effective noise and ear-protection indoctrination of personnel exposed to high-level on the job noise.
Threshold of Hearing and Equal-Loudness Relations for Pure Tones, and the Loudness Function
Authors: Robinson D. W. , Dadson R. S.
Published: September 2005

During recent years a program of work has been in progress at the National Physical Laboratory with the objective of providing improved data on several aspects of subjective acoustics. In connection with standards for audiometry, measurements have been made of the threshold of hearing for pure tones by earphone listening, and these have since been extended to the case of listening in free field. Latterly a redetermination of the equal-loudness relations for pure tones has been completed aimed at resolving discrepancies between former determinations and providing an improved basis for the establishment of a standard set of contours. These results apply to a large team of otologically normal observers, and cover the range from 25–15 000 cps and up to 130 db in sound pressure level. The results of this investigation enable the equivalent loudness of any pure tone to be expressed by simple formulas with coefficients varying smoothly with frequency. Considerable attention has also been devoted to the determination of the loudness scale, i.e., the function relating loudness level in phons to the magnitude of the loudness sensation expressed on the sone scale. An assessment of the experimental evidence has led to the formulation of a simple relation which appears adequate for practical purposes in noise measurement. Investigations are continuing on the determination of loudness levels of complex sounds from their objective spectra.
Hearing of Naval Aircraft Maintenance Personnel
Authors: Ward W. Dixon
Published: September 2005

Audiograms were obtained on 1200 naval enlisted men at NAS Cecil Field, Florida. Although hearing losses were slightly greater among men who were or had been exposed to noise from reciprocating engines and jets without afterburner, this is probably due to the fact that these men have also been exposed to more gunfire. Follow-up audiograms taken on 220 of these men (all men in three squadrons whose planes had afterburners) revealed no additional hearing loss after seven months of moderate exposure. A similar negative result was found in a study of flight-deck personnel during a three-month cruise aboard an aircraft carrier.
Further Test of the Constant-Ratio Rule in Speech Communication
Authors: Clarke Frank R. , Anderson Clint D.
Published: September 2005

The use of the constant-ratio rule to predict the confusion matrices for each of two five-item subsets given the confusion matrix for a ten-item master set is tested with naive subjects. Ninty percent of the predicted cell entries (expressed as proportions) deviated by less than 0.05 from the obtained cell entries. The predicted articulation score for the first subset was 67.9%, and the obtained articulation score was 68.9%. For the second subset the predicted and the obtained articulation scores were 78.4% and 82.6%, respectively.
Vibrations of the Reed and the Air Column in the Clarinet
Authors: Backus John
Published: September 2005

The vibrations of an artificially blown clarinet were studied by a photoelectric method in which light from a source placed at the bell of the instrument passed through the aperture between the reed and the mouthpiece and into a photomultiplier tube whose output was observed on an oscilloscope. It was found that for loud tones the aperture is practically completely closed for about one-half cycle and completely open for the other half. For softer tones the aperture does not close completely and the reed motion becomes nearly sinusoidal. A small condenser microphone inserted in the clarinet mouthpiece allowed simultaneous observations of the reed vibrations and air column vibrations to be made. It was found that during that part of its motion that the reed is not in contact with the mouthpiece it follows quitef aithfully the variations in mouthpiece air pressure. The sound pressure level in the mouthpiece reaches 166 db for loud tones; this value checks well with the pressure required for blowing the instrument. The increased loudness of the clarinet on harder blowing is due primarily to the increased production of harmonics.
Smoothly and Step Tapered Structures
Authors: Young Frederick J. , Young Beverly H.
Published: September 2005

It is shown that a manifold of uniform tubes becomes a smoothly tapered horn as the number of members in the manifold increases to infinity.
On Scattering and Reflection of Sound by Rough Surfaces
Authors: Twersky Victor
Published: September 2005

We consider random distributions of arbitrary identical protuberances on free or rigid base planes, and derive the approximate reflection coefficients R = |1 + Z1 − Z|2 and differential scattering cross sections per unit area σ(s,ki) = ρk2|f(s,ki)1 − Z|2. Here Z = πρf(k0,ki)k2n ⋅ k0, where f(s,ki) is the scattering amplitude of an isolated protuberance. ki, k0, and s are the directions of incidence, specular reflection (with respect to the base plane), and observation; n is the normal of the base; ρ is the average number of scatterers in unit area, and k = 2π/λ. (For a two-dimensional “striated” surface we divide Z by π/k, and σ by π/2k.) We find for example, that if the horizon angle β approaches zero (i.e., near grazing incidence), then the reflection coefficients approach unity minus terms of the order β, while the back scattering vanishes like β1, β2 for a free, rigid base. Explicit forms are given for arbitrary hemispheres and circular semicylinders, and for the limiting cases of free and rigid surfaces with scatterer radius very small and very large compared to wavelength. The analysis is based on a Green's function formulation of the problem of a single configuration; R and σ follow from an approximation of the ensemble averaged energy flux which takes account of multiple coherent scattering. (The transmission problem of a “random screen” is treated simultaneously.) An elementary derivation is also given, and extensions to distributions of nonidentical scatterers are made.
Piezoresistive Semiconductor Microphone
Authors: Burns Fred P.
Published: September 2005

A microphone using the piezoresistive effect of n-type germanium has been designed and constructed with a cantilever beam arrangement. Frequency response curves were taken in a sound field of 10 microbars with the microphone in a bridge type circuit and biased with 9 and 18 milliamperes.

The microphone produces 10−11 watt in the flat low frequency range and peaks to 10−9 watt at a resonance at 2570 cps with a total bias of 18 ma in a bridge type circuit. Other designs of transducers and different types of semiconductor material are discussed. The performance of a germanium rod microphone is compared with a standard carbon button transmitter.
Mechanical Pressure-Gradient-to-Pressure Sound Transducer
Authors: Embleton T. F. W. , Thiessen G. J.
Published: September 2005

In places of high ambient-noise level, the use of electrical devices as an aid to speech communication is sometimes precluded by safety requirements. A mechanical device may then be used provided that the individuals concerned are close to each other. Such a device can be made to incorporate all the acoustical benefits of a dose-talking microphone. Sentence intelligibility tests showed that when the articulation index was zero for a nearby speech source the median subject obtained a score of 28% using ear covers alone and 84% with the sound transducer; the subjects with extreme scores improved from 0 to 14% and from 88 to 100% respectively. No subject using the device suffered a decrease in intelligibility.
Normalized Representation of Noise-Band Masking and Its Application to the Prediction of Speech Intelligibility
Authors: Saito Shuzo , Watanabe Shingo
Published: September 2005

Measurements are made of the masking of pure tones by various bands of noise. Curious masking spreads beyond upper frequency limits of noise are observed and these are expressed uniquely by means of the relative masking and the incremental bandwidth. Then the normalized representation of noise-band masking in some restricted ranges is achieved and applied for the prediction of speech intelligibility. Predicted articulation scores agree fairly well with measured ones.
Some Measurements of the Impedance at the Eardrum
Authors: Zwislocki J.
Published: September 2005

Three methods are described for measuring the impedance at the eardrum. Two methods are psycho-physical and one is purely physical. Although the physical method seems to be more appropriate for this kind of measurement, all three methods yield comparable results. The final results agree with some of the measurements made in the past on the reactance at the eardrum up to 1000 cps. They disagree on reactance above 1000 cps and on resistance. The new data seem to fit the general picture of sound conduction in the ear better than did values obtained earlier. They could lead to corrections in the coupler cavities used for miniature earphones and in calculations the sound attenuation afforded by some ear protectors.
Optimum Envelope Resolution in an Array Correlator
Authors: Jacobson Melvin J.
Published: September 2005

A correlator detector is considered which processes the outputs of two identical collinear arrays of uniformly spaced elements. When the input signal is sinusoidal, the mean system output is bounded by the product of the space factors of the arrays. Complex amplitude factors are introduced following each element, and it is shown how to choose them in order to optimize the main lobe-width-side-lobe-level relationship of the space-factor product or envelope. In addition, it is proved that the use of amplitude factors for improving envelope resolution gives rise to a signal-noise degradation relative to the corresponding uniform amplitude system. Various numerical results are given, including the fact that the optimum system provides an envelope main-lobe-width reduction of approximately thirty percent when twenty or fewer elements appear in each array.
Some Possible Uses of Single Sideband Signals in Formant-Tracking Systems
Authors: Cherry E. Colin , Phillips V. J.
Published: September 2005

An amplitude-modulated single-sideband waveform can be separated into two parts, viz., an amplitude or “envelope” term, and a frequency-modulation term. Some existing proposals for the use of the frequency-modulation part in speech compression schemes have been investigated, and although these schemes were found to be fallacious, some results having possible application to speech formant tracking were obtained.
Reflection of Plane Sound Waves from a Sinusoidal Surface
Authors: Parker John G.
Published: September 2005

The problem of calculating the specular component of the sound field reflected from a sinusoidal pressure release surface is discussed. The incident field is assumed to be plane and directed normally to the surface. Basically, the problem consists of obtaining the solution to a nonlinear differential equation derived in an earlier paper. This was done numerically and the results compared with existing experimental data on sound reflection from two differently formed surfaces. In one case agreement between calculated and measured values is quite good while in the second case there is considerable discrepancy. A possible explanation of this discrepancy is given.
Reflection from a Thin Infinite Plate Using the Epstein Method
Authors: Goodman R. R.
Published: September 2005

In the calculations concerning the vibrations of thin elastic shells, several approximations called “shell-theories” have been introduced in an attempt to simplify the mathematical formalism. In this paper one of these approximation methods, known as the Epstein method, is used to obtain the reflected field produced by a plane wave impinging on an infinite plate. The results are given to first order in kh, where k is the wave number and 2h is the thickness of the plate. A comparison with the exact results shows exact agreement to first order.
On the Role of Microbubbles in the Nonlinear Transmission of Sound in Liquids
Authors: Adams Carl E. , Jackson Francis J.
Published: September 2005

The harmonic content of 25-kc sound transmitted through water was measured as a function of ambient pressure (0–12 atm) and an inverse relationship was found to hold; the nonlinearity disappeared completely at the higher pressures. It is suggested that gaseous cavitation, a pressure-dependent phenomenon, may be involved as a mechanism in the sound transmission.
Measurement of the Attenuation of Low-Frequency Underwater Sound
Authors: Sheehy M. J. , Halley R.
Published: September 2005

Underwater sound signals from the deep atomic explosion of Operation Wigwam in May, 1955, were recorded on bottom-mounted hydrophones at Point Sur and Point Arena, California, and Kaneohe Bay, Oahu. Reflected signals were recorded for two hours at Kaneohe and nearly four hours at Point Sur, and many reflectors were tentatively identified. Values for the attenuation of 20–200 cps sound in the sea were obtained from an analysis of the change in spectra of the reflected signals with travel distance. These values, plus earlier work at higher frequencies, indicate that the attenuation in db per kiloyard (kyd) over the frequency range 20 cps to 60 kc is equal to 0.033f32, f being in kc per sec.
Sensations on the Skin Similar to Directional Hearing, Beats, and Harmonics of the Ear
Authors: v. Békésy G.
Published: September 2005

A mechanical model of the cochlea in which the skin of the arm is used as a sense organ was compared with the organ of Corti. Three phenomena were investigated: (1) directional hearing, (2) heats, and (3) harmonics. For directional hearing almost no differences were found between hearing and the sensation produced by the model. In the case of beats it was possible to confirm the earlier observations of Helmholtz by improving the frequency resolution of the model ear. Concerning the harmonics it was found that the method of best beats does not permit the measurement of overtones of the ear.
Downward Spread of Masking
Authors: Spieth Walter
Published: September 2005

Pulsed pure-tone audiograms were obtained in quiet and in the presence of narrow bands of noise centered at 500, 1000, 2000, and 4000 cps and at several levels. The masking produced at lower frequencies was of particular interest: The bands of noise at about 75 db/cy SPL produced from 12 to 24 db of masking at 100 cps and from 25 to 40 db of masking at frequencies between about 200 cps and the lower effective limit of the band of noise. This phenomenon contrasts with the fact (briefly reaffirmed in this paper) that a single pure tone of comparable frequency and intensity does not produce appreciable masking at these lower frequencies.

It is hypothesized that a band of noise is functionally somewhat equivalent to a bunch of pure tones which when passed through a nonlinear transducer (the ear), produce aural difference tones which elevate the threshold for signals of lower frequency, while a single tone masker would not have this effect. It was found that two pure tones at a spectrum level and at frequencies comparable to the bands of noise do produce aural difference tones (as measured by best beats) of a level which correspond well with the level of lower frequency masking effects in question.
Noise Masked Thresholds as a Function of Tonal Duration and Masking Noise Band Width
Authors: Hamilton P. M.
Published: September 2005

Noise masked thresholds for 800 cps tonal pulses 25 to 400 msec long were measured in masking noise bands from 19 to 1100 cps wide. It was found that the threshold remained constant for equal values of band width, pulse-length product. The threshold varied according to a formula proposed on the basis of limited data in an earlier report (T. H. Schafer and C. A. Shewmaker, U. S. Navy Electronics Laboratory Report 372, 1953): S/N = m/BT0.8, where S is the signal power, N is the noise power in the pass band of the filter, B is the band width, T is the pulse length, and m is a constant.
Generation of Sound in Cavities by Flow Rate Changes
Authors: Franken Peter A.
Published: September 2005

Sound generated by mass or heat flow changes in a cylindrical cavity is considered. The special case of a high-pressure-ratio orifice is studied. Experimental results show good agreement with values predicted from a scaling equation.
Frequency Difference Limens for Narrow Bands of Noise
Authors: Michaels Richard M.
Published: September 2005

Frequency difference limens (DL) were measured for Gaussian noise having band widths of 12 to 64 cps centered at 800 cps and for a pure tone, also at 800 cps. Six listeners were used, and the DL's were defined as the probable errors of the fitted transition curves. For band widths wider than 8 cps, the DL rises regularly. Between 12 to 8 cps the threshold changes are small, having a minimum at about 8 cps. None of the DL's for noise approach that of the pure tone, all being at least twice as large. It is suggested that the failure of ΔF for narrow bands of noise to converge on ΔF for a pure tone is due to the dependence of frequency discrimination on intensity discrimination. In narrow bands of noise, the auditory system follows the amplitude fluctuations, which increases the uncertainty of judgments of intensitive differences. For the bands of noise wider than 8 cps, ΔF increases directly with band width. A linear increase in ΔF with band width is predicted for a limited range of band width and was found to fit the data.
Estimates of the Maximum Precision Necessary in Quantizing Certain “Dimensions” of Vowel Sounds
Authors: Flanagan James L.
Published: September 2005

Results of psychoacoustic experiments are used to estimate the greatest precision necessary in quantizing narrow band-width data specifying the vowel sounds of speech.
On Standard Methods of Measurement in Architectural Acoustics
Authors: Waterhouse Richard V.
Published: September 2005

Suggestions are made pertaining to standard methods of measuring the sound absorption of acoustical materials and the sound transmission loss (STL) of partitions. (1) Concerning the reverberation chamber method of measuring the sound absorption of materials, it is shown that the absorption varies with the position of the sample in the chamber, owing to interference patterns. An estimate is made of the difference in absorption of a sample on the floor (a) centrally and (b) touching one side wall. It is suggested that sample position should be specified as distant at least half a wavelength (λ/2) from walls and reflecting surfaces other than the one backing the sample. (2) Regarding the measurement of STL it is suggested that microphone position be specified as at least λ/2 from walls and the corresponding distances from edges and corners of reverberation chambers. The technique in which the microphone is placed near a wall is not recommended. (3) As a single figure for the over-all sound insulation value of a partition, the arithmetic mean of the decibel STL figures at various frequencies is often used. It is suggested that a better average figure is obtained if the linear ratios corresponding to these decibel figures are averaged instead of the decibel figures themselves. This removes the logarithmic weighting of the latter average, for which there is no physical justification.
Compressibility vs Ionic Size of the Cation in the Aqueous Solutions of Electrolytes
Authors: Suryanarayana M.
Published: September 2005

The compressibility of aqueous solutions of electrolytes with a common onion is found in the literature to decrease in some cases and increase in some others with the increase of the radius of the cation. It is suggested that the compressibility depends both on the hydration and the charge density of the ions, the effect on the compressibility of one being opposite to that of the other. The net trend of the compresibility depends on which factor is predominant.
Effects of Acoustical Waves on the Annealing of Steels
Authors: Fairbanks H. V. , Dewez F. J.
Published: September 2005

The object of this investigation was to determine the effect of ultrasonic energy on 0.07 and 1.05% carbon steels during transformation from austenite to ferrite under controlled cooling. The ultrasonic energy was produced by means of a bowl-shaped crystal of barium titanate and was coupled to the steel samples through distilled water. Ultrasonic frequencies of 400 and 1000 kc were used.

It was found that the ultrasonic treated samples of 0.07% carbon hypo-eutectoid steel had finer grain size and greater hardness than the reference samples which had undergone the same heat-treating cycle but with no ultrasonic treatment. When either the intensity or the frequency of the ultrasonic energy was increased, the grain size was further decreased.

For the 1.05% carbon hyper-eutectoid, it was found that the lamellar layers of ferrite and iron carbide making up the pearlite crystals were definitely thicker in the ultrasonic treated samples than in the untreated ones. Hardness tests made on the pearlite crystals substantiated the above results.
On the Air Resistance and the Bernoulli Effect of the Human Larynx
Authors: van den Berg Jw. , Zantema J. T. , Doornenbal P.
Published: September 2005

A model of the larynx has been constructed, and measurements of air resistance for this model have been made. The dc resistance R was measured for diameter d of the glottis from 0.1 to 3.2 mm, for subglottic pressures Ps up to 64 cm water and/or volume velocities v up to 2 liters/sec. To a good approximation, the resistance was equal to the sum of a frictional term, proportional to d−3, and a turbulence term, proportional to vd−2. The frictional term dominates at small diameters and/or small volume velocities, with v proportional to Psd3 and the differential resistance Rd=R. The turbulence term dominates at large diameters and/or large volume velocities, with v proportional to Ps12d and Rd= 2R. Over the major region the pressure at the outlet of the glottis was about −12PB, where PB is the kinetic pressure in the glottis, and the pressure over the entry of the glottis was about 1.37PB. The applicability and the implications of the results to various problems of normal voice production are discussed.
On the Propagation of Ultrasonic Waves of Finite Amplitude in Liquids
Authors: Krassilnikov V. A. , Shklovskaya-Kordy V. V. , Zarembo L. K.
Published: September 2005

The dependence of the ultrasonic absorption coefficient on the intensity was measured indifferent liquids (water, ethyl and methyl ethers, toluene, transformer oil, and glycerine) by means of the thermal method (thermocouples). The measurements were made at 1.5 Mc/sec with intensities of 0.3–9 w/cm2. There was found a considerable increase of nearly two orders of magnitude in the absorption. Measurement at higher static pressures, up to 15 kg/cm2, gives results which coincide, within the range of error, with the results of the measurements at atmospheric pressure, suggesting that the influence of cavitation is small.

Direct experimental observation of the harmonics in a traveling wave of finite amplitude was accomplished. The receivers were quartz plates with their fundamental frequencies equal to the frequencies of the harmonics; to remove standing waves between the receiver and the transducer, an acoustic filter was used, consisting of a thin plate “transparent” for the appropriate harmonic and opaque for the fundamental at a certain angle. Absolute measurement of the harmonic intensity was obtained by a radiometer which was placed behind the acoustic filter.
Ultrasonic Dispersion in Dissociating Dinitrogen Tetroxide
Authors: Blend Harvey
Published: September 2005

The velocity of sound was measured in dissociating dinitrogen tetroxide. These measurements were made over a frequency range of 20 to 800 kc and pressure range of 1 to 70 cm Hg giving a frequency/pressure range of 0.0217 to 60.8 Mc/atm. The temperature range covered was from 0° to 50°C. At 20°C and 10 cm Hg the velocity change was 4% over the frequency range stated and the relaxation time was 1.72 μsec.
Variations of Cavitation Intensity in an Ultrasonic Generator
Authors: Weissler Alfred , Hine Elizabeth J.
Published: September 2005

The amount of cavitation produced in an ultrasonic generator depends on factors such as tank geometry, water height, and continuous-operation time. Some typical results are presented, which may help to explain the quantitative variability found in, for example, industrial cleaning and biochemical applications.
Temperature and Amplitude Dependence of Acoustic Absorption in Tissue
Authors: Dunn Floyd
Published: September 2005

The acoustic intensity absorption coefficient of tissue of the central nervous system has been determined at the sound frequency of 1 Mc/sec in the temperature range from 2° to 28°C at incident sound intensities ranging from 5 to 200 W/cm2. The absorption coefficient exhibits an increase with increasing temperature and no variation with the acoustic intensity.
Response of an Electrical Model of the Cochlear Partition with Different Positions of Excitation
Authors: Bogert B. P.
Published: September 2005

This note describes some measurements on the network representing the basilar membrane, which were made to determine the effect of the position of excitation on the response of the cochlear partition. It was found that the response of the electrical model is insensitive to the position of excitation if the excitation is applied on the stapes side of the point of maximum response. If the excitation is applied on the helicotrema side, the response is highly localized around the point of excitation and has an over-damped character.
Analysis of Echoes from a Solid Elastic Sphere in Water
Authors: Hickling Robert
Published: September 2005

It is well known in sonar work that the pulse form of a direct echo from a target bears little relation to the form of the original signal. This is true even for regularly shaped bodies, such as a sphere. In this paper, the case of a homogeneous elastic sphere in water is examined theoretically and it is shown in comparison with experimental results, that the observed effects originate from vibrations induced in the sphere by the incident sound. Calculated results are presented for a variety of solid materials and it seems that echo forms could possibly provide information about the size and constitution of a sonar target.
Sound and Ultrasound Absorption Resulting from Heat Radiation
Authors: Bhatia A. B.
Published: September 2005

Following a suggestion by Markham, Beyer, and Lindsay, the Stefan-Boltzmann radiation law is applied to estimate the attenuation of approximately plane compression waves resulting from heat radiation. The attenuation is found to be independent of the frequency of the compression waves in the entire relevant frequency range and inversely proportional to a linear dimension of the wave fronts. At ordinary temperatures, this attenuation is negligible compared to that due to thermal conduction and viscosity, verifying the results of Rocard and Rayleigh. In gases at temperatures of 1000°K or more, however, the attenuation due to heat radiation is not entirely negligible under certain conditions.
Nonlinear Response of Aircraft Panels in Acoustic Noise
Authors: Kirchman E. J. , Greenspon J. E.
Published: September 2005

This paper considers the response of thin elastic plates to sinusoidal acoustic excitation. A theoretical method for obtaining the dynamic deflection and stress in the nonlinear region is given. The theory is compared with test results showing rather good agreement. The application of the theory to the design of panels to withstand acoustic fatigue is discussed in the latter part of the paper.
Ray Theory Solution for the Sound Intensity in Water Due to a Point Source above It
Authors: Hudimac A. A.
Published: September 2005

The sound intensity in the water due to a point source above it has been determined by the ray theory. For a given height of source and depth of point of observation, the intensity and lateral range are given by a pair of parametric equations in terms of the angle of incidence. An example is given for which iso-intensity lines are plotted. A striking feature is the way in which intensity increases appreciably with depth (except directly below the source).
Cylindrical Wave in a Viscoelastic Solid
Authors: Lubliner Jacob
Published: September 2005

The propagation of a cylindrical wave in an infinite viscoelastic (standard linear) solid is studied by means of the Laplace transformation. Numerical results are obtained over a time interval encompassing the most significant characteristics of wave propagation, namely, attenuation of the initial peak, formation of the delayed peak, and asymptotic decline to the steady state. It is found that no marked change in the wave shape occurs until the distance from the axis exceeds a certain characteristic length (which is infinite in a perfectly elastic solid) and that the change becomes more marked at greater distances.
Ultrasonic Shear and Compressional Relaxation in Liquid Glycerol
Authors: Piccirelli Robert , Litovitz T. A.
Published: September 2005

Relaxation of the real parts of the shear and compressional moduli of liquid glycerol was investigated using ultrasonic pulse techniques. Measurements of the decibel loss/echo for a glycerol-quartz interface were made at frequencies from 15 to 85 megacycles per second over the temperature range from +70°C to −40°C. Measurements of the velocity of longitudinal waves in glycerol were made at frequencies from 1 to 55 Mc per sec over the temperature range from +50° to −80°C. The limiting values of the real parts of the shear and compressional moduli are studied and compared over the temperature range. The behavior of the relaxational parts of the real parts of the shear and compressional moduli cannot be quantitatively explained by either classical or single relaxation time theory. A distribution of relaxation times is shown to be adequate to explain both the shear and compressional relaxations. The average compressional relaxation time is found to be equal to 0.81 times the average shear relaxation time.