bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Biological Action of Ultrasound
Authors: El'piner I. Ye.
Published: September 2005

The action of ultrasonics on biological systems (microorganisms) is not limited to mechanical rupture of cells and cell structures. Ultrasound can also cause biochemical and functional changes, without subsequent death of the organism. These changes are mainly due to the action of ultrasonic waves on intracellular molecular complexes. Ultrasound appears to have the ability for “shaking loose” the molecular complexes in tissue and cell structures, which results in liberation or increased activity of cell enzymes. Thus in ultrasonic treated yeast cells (Saccharomyces globosus and Endomyces magnusii) the activity of invertase is considerably increased. Until recently, this enzyme has been thought to be lacking in Saccharomyces globosus. The increase of activity of cholinesterase in cerebral tissue is similarly brought about by ultrasonic irradiation. This enzyme will be inactivated when treated after extraction from brain tissue. The influence of ultrasound upon intracellular molecular complexes is also evidenced by the fact that more ergosterol can be extracted from treated yeast cells than from untreated. The action of ultrasound on protein complexes is accompanied by the rise in sensitivity of corresponding enzymes to the action of venoms. This rise probably accounts for the fact that sublethal doses of H2O2, ammonia, and formalin kill infusoria and trematodes pretreated with ultrasonics not intensive enough to cause the death of these organisms. The report includes a discussion of mechanisms by which the above-mentioned phenomena are brought about.
Ultrasonic Velocity in Supercooled Liquids
Authors: Barone Alfonso , Pisent G. , Sette Daniel
Published: September 2005

Viscosity experiments in some polar liquids which can be easily supercooled have shown that a sudden change of activation energy for viscous flow occurs at a temperature near the melting point. This seems to be due to some structural variation inside the liquid such as a molecular rearrangement. The effects of these structural changes on sound velocity have been investigated by Hunter [A. N. Hunter, Proc. Phys. Soc. (London) B64, 1086 (1951)] in menthol and by Petralia and Cevolani [S. Petralia and M. Cevolani, Ricerca sci. 21, 1623 (1951)] in salol. Hunter reported a slight variation of the temperature coefficient of velocity at the freezing point of menthol; Petralia and Cevolani found no effect in salol within the precision (1/1000) of their method of measurement. In the present research a high precision (about 1/10 000) acoustical interferometer which uses an optical method to detect movements of the reflector by halves of acoustical wavelengths has been employed for studying sound velocity in menthol and salol. For both liquids the temperature coefficient of velocity is higher in the supercooled than in normal region. In salol a transition zone (42–46°C) has been found in which the temperature coefficient of velocity is smaller than either at higher or at lower temperatures. A narrower transition region is probably present also in menthol, masked by a variation of temperature coefficient between normal and supercooled liquids higher than in salol. These results suggest that the changes of structure which take place when these liquids are supercooled are mainly due to formation of molecular associations.
Ultrasonic Absorption in Viscous Liquids
Authors: Mikhailov I. G.
Published: September 2005

(l) The simplest phenomenological relaxation theory taking into account the relaxation of the shear and second viscosity gives the following expression of sound absorption coefficient: d=ω23ρa3 [4/3μ1 + ω2τ12 + η1 + ω2τ22], where μ and η are the shear and second viscosities, ω is cyclic frequency, a is sound velocity, ρ is density, and τ1 and τ2 indicate time of relaxation of the shear and second viscosities. At low frequencies in case when ωτ1≪1 and ωτ2≪1 this expression coincides with the common hydrodynamic expressions for the absorption coefficient, taking into consideration the second viscosity. (2) With the increase of frequency two regions of relaxation must exist: when ωτ1∼1 and ωτ2∼1. The problem whether τ1 > τ2 or τ1 < τ2 may be solved experimentally or by means of theoretical calculations of the time of relaxation. Up to this time such kinds of calculations have been performed for a few liquids only. (3) The experimental data now available make it perhaps possible to assert that in all liquids having a low viscosity τ2 < τ1 i.e., by increasing frequency the second viscosity relaxes first. One experimental data show however that this rule is not always followed. It has been found that, in a series of viscous liquids (castor oil and other oils), the shear viscosity relaxes first, the time of relaxation of τ1 and τ2 being near each other with regard to value. In such a way both relaxing regions follow each other and the absorption in a comparatively small range of frequencies (0.5 mc – 5.0 mc) passes from the higher Stokes values to the lower one. Until now the shear viscosity was supposed to relax in case the absorption in liquid is lower than of Stokes.
Determination of Elastic Constants of Cubic Crystals by Means of Ultrasonic Elastograms
Authors: Bergmann Ludwig
Published: September 2005

As shown by C. L. Schaefer and L. Bergmann in 1934, ultrasonic elastograms may be obtained by diffraction of light transmitted through crystal samples that are excited to high-frequency vibrations. The elastic constants of a number of cubic crystals (KCl, KBr, Kl, NaCl, NaBr, NaF, RbCl, RbBr, LiF, and CaF2) are determined by this method. An attempt is made to interpret the specific form of the resulting elastograms from the lattice structure of the crystals.
Vibratory Drilling of Oil Wells
Authors: Simon Ralph
Published: September 2005

Vibratory drilling refers to the process of drilling into rock by vibrating the drilling tool at audio-frequencies. The basic mechanism of vibratory drilling was ascertained by preliminary laboratory experimentation to consist of a series of impacts on the rock at the frequency of vibration. A fundamental study of this basic mechanism, made by dropping weighted chisels on rock, showed that the primary parameter which determined the rate of penetration was the mechanical power input to the rock per unit cross section of hole; the values of the vibration frequency and of other variables were of minor consequence over wide ranges. A theoretical analysis was made of the vibration of an elongated magnetostriction transducer capable of generating the required power level, taking into account the distributed nature of the generation of vibrations. Intermediate power transducers have been built and tested and a high-power transducer for down-hole operation is under construction. [The material for this presentation is based on work carried out at the Battelle Memorial Institute under the sponsorship of Drilling Research, Inc., an organization formed by a group of major companies engaged in various phases of oil production for the purpose of investigating novel methods of rock drilling.]
Backscattering of Sound from the Sea Surface: Its Measurement, Causes, and Application to the Prediction of Reverberation Levels
Authors: Urick Robert J. , Hoover Robert M.
Published: September 2005

In many applications of underwater sound, the “reverberation,” or backscattered return, from the sea surface is the limiting background in which the desired echo appears. Little has been known about sea-surface backscattering in spite of its importance to the prediction of reverberation levels in practical applications. Using two transducers, one for transmitting and one for receiving, mounted so as to be rotatable in a vertical plane and suspended from a buoy, measurements have been made of the backscattering of sound pulses from the surface of the sea as a function of grazing angle between 5° and 90°, wind speed between 3 and 18 knots, and pulse length. When converted to a scattering coefficient per unit area, the results provide some hints as to the processes by which sound is scattered by the ocean surface, and give the basic data for computing the reverberation to be expected with transducers of arbitrary beam width and orientation.
Attenuation in a Rectangular Slotted Tube of (1,0) Transverse Acoustic Waves
Authors: Hartig H. E. , Lambert R. F.
Published: September 2005

A pick-up device for measuring the standing wave ratio of transverse acoustic waves is described. One of the important features of this device is the elimination of interference from the residual plane wave. An experimental study of the attenuation characteristics of (1,0) transverse acoustic waves propagated in air in a rectangular metal tube employing such a pick-up device is presented in this paper. This study reveals that three losses are important contributors to the attenuation. The results are in good agreement with a tube wall effect predicted by Kirchhoff. In evidence is a gaseous absorption in the medium due to thermal equilibrium adjustments. The remaining attenuation is appreciable and appears to vary with frequency as f2[1−fc2/f2]−1/2. This factor is here attributed to a vibration of the tube walls.
On the Change of Cross Section and Bifurcation of a Cylindrical Tube
Authors: Miles John W.
Published: September 2005

The equivalence between the problems of the change of cross section and the biforcation of a cylindrical tube, previously stated as exact, is only approximate. An exact solution to the latter problem (for a circular tube) has been given by Bailin, and the results are compared with recent calculations for the change of cross section. The approximate equivalence between the two results is found to be sufficiently close for many applications but to be far from exact.
The Speaking Machine of Wolfgang von Kempelen
Authors: Dudley Homer , Tarnoczy T. H.
Published: September 2005

The physiological motions involved in speaking can be indicated to the eye or to the ear. For the eye suitably chosen symbols may be written to indicate the physiological positions assumed informing each sound; for the ear synthetic sounds may be produced by motions in a mechanism built to simulate the speech organs. The degree of phonetic success may be estimated in the case of the visible symbols by listening to sounds formed when the indicated physiological processes are carried out, and in the case of the speech-simulating mechanism by comparing the synthetic speech produced to normally spoken speech. Significant advances along both the visual and the aural lines are described from earliest times down to the present.

Wolfgang von Kempelen produced the first speaking machine worthy of the name around 1780. This paper gives his background, a description of the apparatus he built, and a discussion of the methods used in producing the various sounds, fitting his work into the over-all picture of speech-imitating devices from the speaking of idols of ancient times down to the automatic electrical reconstructing of speech in the vocoder. For portraying to the eye the physiological characteristics of speech there are discussed the more outstanding methods from claimed symbolic alphabets of ancient languages down to the recent spectrographic visible speech.
The Discriminability of Interaural Phase Relations in Two-Component Tones
Authors: Licklider J. C. R. , Webster J. C.
Published: September 2005

In investigations of binaural hearing in which the interaural phase difference has been studied, either (1) the stimuli have been pure tones, in which case there is just one interaural phase difference, or (2) no attempt has been made to vary separately the several or many phase differences that exist, one for each frequency component, when both ears are stimulated by complex waves. In the present observations, we have studied the effect of varying the interaural phase relations in the simplest of complex waves: two superposed sinusoids of equal amplitudes. A two-component tone was presented binaurally, and the interaural phase difference of one of the components was switched alternately from 0 to 180 degrees. The effect of the phase reversal upon the listener's subjective experience and the frequency dependence of the effect are described.
Resonant Acoustic Interferometry with Air-Liquid Reflecting Surface
Authors: Hunter Joseph L. , Fox Francis E.
Published: September 2005

An ultrasonic interferometer has been developed using an air-liquid surface as a reflector. Because of certain simplifications that occur, it is found advisable to recast the mathematical interpretation of the results along different lines than previously. The effect of a loaded piezoelectric crystal at resonance is taken as a variable resistance, and the measured values of this resistance are interpreted to calculate absorption in the liquid.
A New Ultrasonic Interferometer for Liquids
Authors: Hunter Joseph L.
Published: September 2005

An interferometer has been developed which makes use of the free surface of a liquid as a reflector. The emitter is an optically plane quartz crystal which is held perfectly horizontal at the bottom of a vertical liquid column. Changes in the column height produce the effects which are used to measure absorption in the liquid. A sensitive method of adding liquid makes the instrument usable at frequencies well above six megacycles. The leveling is sensitive and positive.
Transient Sounds in Rooms
Authors: Mintzer David
Published: September 2005

The propagation of transient sound waves in bounded one- and three-dimensional regions is studied by means of Laplace transform methods. In the one-dimensional case, a plane wave is considered propagated down a rigid-walled tube from a source at one end toward an acoustic termination at the other end. The velocity potential for an arbitrary particle-displacement input is found as a series, each term of which represents the effect of a reflection from the ends of the tube. In the three-dimensional case spherical wave from an arbitrary input source is considered, first in an unbounded region, and then in regions containing one wall, three perpendicular walls, and two parallel walls; finally, the case of a point source in a rectangular room is solved. An image method is used, the results being found in the form of a series whose terms represent reflections from individual walls, as well as cross reflections between walls. The terms of the series are in the form of plane-wave expansions around the image points; these integrals are approximated by the method of steepest descents. In the last section some sample calculations are made for both the one- and three-dimensional systems.
Rooms with Reverberation Time Adjustable over a Wide Frequency Band
Authors: Arni Paavo
Published: September 2005

A broadcasting studio with variable reverberation characteristics described. Of special interest is the construction of the absorbing units which enable the reverberation time to be varied evenly over a relatively broad frequency range.
Ultrasonic Measurement Techniques Applicable to Small Solid Specimens
Authors: McSkimin H. J.
Published: September 2005

Phase comparison at high ultrasonic frequencies is found to be particularly suited to velocity of propagation measurements (and hence measurement of elastic constants) for small solid specimens such as single crystals. Both longitudinal and transverse waves may be used, with accurate results possible even when the specimen loss becomes high.

A pulse technique is used which allows exact determination of the number of wave-lengths in the acoustic path, and a direct measurement of phase shift at reflecting interfaces. The use of λ/4 plastic coupling seals to minimize errors is explained; necessary theoretical analysis is included.

Illustrative data for fused silica and single crystal germanium are given.
Experiments on Acoustic Absorption in Sand and Soil
Authors: Nyborg W. L. , Rudnick I. , Schilling H. K.
Published: September 2005

The acoustic absorption of sand and soil with varying amounts of water (dry to saturated) has been investigated the 10- to 100-kc range. Two methods were used. In one, the source and a number of equally spaced probe microphones were imbedded in the medium. In the other method the source and receiver were in air and the transmission loss was obtained for samples of varying thickness. The unsaturated media were found to have attenuation coefficients ranging from 2 db/cm for nodulous, loose soils to greater than 25 db/cm for finely divided soils and sand, the value for any particular sample depending in an important way on its flow resistance. In water-saturated media the attenuation was found to depend markedly on the amount of gas present in the mixture. Air-free mixtures prepared in an evacuated chamber had attenuation coefficients which were too small to be measurable—probably less than 2 db/cm. On the other hand, for mixtures prepared in the presence of air the attenuation coefficient immediately after mixing were extremely large. For one sample it ranged from 26 db/cm at 10 kc to 64 db/cm at 30 kc. When a source and microphone, separated by a distance of one centimeter, were immersed in such a freshly stirred mixture and then left undisturbed, the intensity level increased in time—as much as 50 db at 30 kc over a period of 100 hr.
Electroacoustic Phase Shift in Loudspeakers
Authors: Ewaskio Charles A. , Mawardi Osman K.
Published: September 2005

Direct measurements of envelope delay have been obtained for a series of commercial and experimental loudspeakers. The modulation phase shift method of Nyquist and Brand has been adapted for direct indication of envelope delay by utilizing an electronic phase meter. A continuous record of the delay is obtained by an automatic level recorder suitably connected to the phase meter. Pressure-amplitude curves measured under the same conditions provide data for a preliminary attempt to interpret the correlation between delay response and pressure response.
On the Frequency Limits of Binaural Beats
Authors: Licklider J. C. R. , Webster J. C. , Hedlun J. M.
Published: September 2005

The report describes measurements of the frequency limits of binaural beats and outlines a theory of binaural beats, based on synchronous discharges in the two auditory nerves. Two sinusoids of frequencies f1 (fixed) and f2 (variable) were led separately to the two ears; and the difference Δf = |f1−f2| that marked the disappearance of the fluctuating loudness or roughness that is characteristic of binaural beats was determined. Δf was maximal (approximately 35 c.p.s.) for frequencies in the neighborhood of 400 c.p.s. Binaural beats were heard above 1000 c.p.s., but careful attention was required and Δf was small. The shape of the curve relating Δf to f1 provides an explanation for the fact that determinations of the upper frequency limit of binaural beats have not been in agreement; the upper frequency limit depends markedly on Δf. The theory, given to account for the fact that Δf is smaller both at low and at high frequencies than it is near 400 c.p.s., combines elements of the Hill-Rashevsky theory of the excitation of neurons with elements of Wever's volley theory. At low frequencies neurons can discharge in some degree of synchrony with the stimulus wave form, yet fail to coincide within the time interval necessary for synaptic summation. At high frequencies the neurons must take turns discharging, and relatively few can participate in any given volley. At intermediate frequencies, however, each neuron participates in many volleys and the neurons participating in each volley fire almost simultaneously. The result is that at intermediate frequencies synchrony is relatively precise in each afferent pathway and, when the two afferent streams join in a common neural center, beats appear.
A Tentative Criterion for the Short-Term Transient Response of Auditoriums
Authors: Bolt R. H. , Doak P. E.
Published: September 2005

Studies of the response of an auditorium to a short tone burst have indicated that the character of the first 20 or 30 db of sound decay, the “short-term” response, is closely related to the subjective “hearing quality” of the room. Recently Haas has investigated the effect of a single echo on the subjective hearing of speech. On the basis of some of Haas' results and other information on the hearing of speech in rooms, a tentative criterion for the short-term response has been formulated as curves of amplitude vs. time delay of each reflection relative to the direct sound. The criterion correctly rank-orders subjective quality observations reported by others, and agrees quantitatively with some subjective judgments reported here.
A Derivation and Tabulation of the Piezoelectric Equations of State
Authors: Haskins J. F. , Hickman J. S.
Published: September 2005

The linear piezoelectric equations of state with strain, electric displacement, and entropy, as independent variables, are derived from the principle of conservation of energy. These thirteen tensor equations are then specialized to the adiabatic case and used as the starting point for the development of all possible linear piezoelectric equations of state using in turn as independent variables, stress and electric field, strain and polarization, and stress and polarization. This process gives as a by-product the set of relations among the elastic, electric, and piezoelectric coefficients for the various pairs of independent parameters and emphasizes the frequently overlooked fact that the piezoelectric equations of state are mutually convertible. M.k.s. units and the I.R.E. notation are used throughout the discussion and a table is given which compares the I.R.E. notation with the former notations of Cady and Mason.
The Sound Field of a Straubel X-Cut Crystal
Authors: Samuel E. W. , Shankland R. S.
Published: September 2005

The sound beam generated in a liquid by a 7.5 megacycle Straubel X-cut quartz crystal has been investigated by the phenomenon of streaming. The streaming patterns in carbon tetrachloride have been determined by measuring the velocities of sugar particles which have very nearly the same density as the liquid. The velocity distributions produced by a cylindrical sound beam in liquid contained a concentric cylindrical tank are found to be in good agreement with those predicted by Eckart's solution of the hydro-dynamical flow equations. Comparison measurements with square X-cut quartz crystals of the same frequency give poor agreement with theory. Since Eckart's analysis assumes uniform sound intensity across the beam, these experiments indicate that the sound beam radiated by a Straubel cut crystal is very uniform.
Uniform Speech-Peak Clipping in a Uniform Signal-to-Noise Spectrum Ratio
Authors: Martin Daniel W.
Published: September 2005

A graphical function W(r, c) has been determined experimentally, in which W is word articulation, r is the relative level of unclipped speech and the noise, and c is the amount of uniform, symmetrical, speech-peak clipping. Pre-emphasis of the speech signal gave an approximately uniform speech spectrum prior to clipping. Uniform, random noise was mixed with the clipped speech before postequalization, making the final noise spectrum similar in shape to the speech spectrum. The real-ear response of the earphones was compensated electrically to yield a uniform orthotelephonic response for the communication system, in the frequency range contributing significantly to articulation index. For constant clipping cn the function W(r, cn) approaches W(r, 0) as a limit for sufficiently large values of r. For c<r+5, W≒W(r, 0). For the case of no clipping, W(r) when transformed to W(A) (A being articulation index) resembles closely the curve by Pollack.
Toward the Specification of Speech
Authors: Potter R. K. , Steinberg J. C.
Published: September 2005

This is an interim report on studies of the specification of speech sounds from acoustical measurements. Methods based upon analysis, synthesis, and vocal tract models are described. Included are the results of preliminary measurements on the vowel sounds of 25 speakers. Some of the problems in specifying the vowel sounds as indicated by these results are discussed.
Effects of Delayed Speech Feedback
Authors: Lee Bernard S.
Published: September 2005

Delayed speech feedback may act as a governor of the average speed of speech operating on the phoneme unit. Certain aurally monitored manual tasks resemble the speech mechanism. The trigger-like nature of aurally monitored voice on the more rapid articulation element is described. A speech mechanism model is portrayed which satisfies phenomena of natural speech, artificial stutter, and motor aphasias.
The Velocity of Sound through Tissues and the Acoustic Impedance of Tissues
Authors: Ludwig George D.
Published: September 2005

The velocity of sound through various animal organ tissues and through living human tissues is measured, using an ultrasonic pulse method, at 1.25 and 2.5 Mc. The effect of anisotropy (fiber direction) on velocity is determined with beef muscle. Values obtained with the beam traversing the tissue perpendicularly to the long axis of the muscle bundles do not differ significantly from those found with the energy directed parallel with the muscle fibers.

Velocity through living human tissues, consisting mostly of muscle, is measured by transmitting the ultrasound through various thicknesses of the arm, leg, and thigh.

Specific gravities of the tissues are measured. The characteristic acoustic impedances (ρc values), calculated from the density and velocity data, vary between 1.5×105 and 1.7×105 g/cm2/sec. The imaginary component of tissue impedance is calculated and found to be negligible at the frequencies at which these measurements are made.
An Ultrasonic Underwater “Point Source” Probe
Authors: Fein Louis
Published: September 2005

A conically shaped piezoelectric probe of ammonium dihydrogen phosphate is described. Its sensitivity over a frequency range from 1235 to 1280 kc was obtained by means of a reciprocity calibration. The average value is about 0.12 microvolt per dyne per square centimeter. Since the measured pattern of the probe as a receiver was the same at various points in the acoustic field, it may be concluded that the probe is a “point source.”
The Coarse Pattern of the Electrical Resistance in the Cochlea of the Guinea Pig (Electroanatomy of the Cochlea)
Authors: v. Békésy Georg
Published: September 2005

With the knowledge now available concerning the mechanical properties of the cochlea, it is possible to understand how movements of the stapes footplate are transmitted to and along the cochlear partition. But we know little about the electrical constants inside the cochlea (the resistances and capacitances). It is difficult therefore to draw conclusions about how voltages at a given point are transmitted to other parts of the cochlea, for instance, how microphonic voltages are transmitted to the round window. This paper tries to show that for parts of the cochlea near the two windows the cochlear tube (consisting of the two scalae and the cochlear duct) can be considered electrically as a transmission line. The characteristic values of this transmission line are measured for different distances from the windows. In this way, a start has been made toward the development of a type of electroanatomy. The impedance values of the cochlear partition are important for determining the electrical energy losses in the cochlea.
Some Observations on Pitch and Frequency
Authors: Davis H. , Silverman S. R. , McAuliffe D. R.
Published: September 2005

“Tone-pips” were produced by brief rectangular electrical pulses being delivered through two sound-effects filters in cascade with both high and low cut-offs set at 2000 cps. Nearly all of the acoustic energy of the final signal was found to be concentrated in a band about an octave wide and centering at 2000 cps. The pulsing frequency was varied independently between 90 and 150 pips per second.

Listeners describe the resulting sound as a “metallic buzz.” Listeners vary greatly in their ability to identify the two “pitches” present in this sound and in the accuracy with which they match with a pure tone either the pulsing frequency (about 130 per second) or the band-pass frequency (2000 cps in the present series). Errors of exactly one octave are particularly common.

In the theoretical discussion we argue that the “pitch” of a pure tone is a double attribute compounded of “buzz” (correlated with frequency of volleys of nerve impulses) and “body” (correlated with position of maximum stimulation on the basilar membrane).
A Hot-Wire Ultrasonic Interferometer and its Application to Vapors
Authors: Matta K. , Richardson E. G.
Published: September 2005

A fixed path ultrasonic interferometer for use in vapors is described, in which the stationary wave system between the quartz source and the reflector is explored by a traveling hot-wire. The hot-wire is calibrated for its change of resistance in terms of velocity-amplitude in the ultrasonic wave system. A correction is made for diffraction of the ultrasonic beam.

In this apparatus wavelength and absorption measurements are made in ether, ethylene, benzene, carbon disulphide, and acetaldehyde vapors. All show an absorption considerably greater than the theoretical values based on the Stokes-Kirchhoff equations.
Measurements of the Underwater Sound Field Generated by Quartz Transducers
Authors: Keck Winfield , Heller G. S. , Williams A. O.
Published: September 2005

The mean-square pressure distributions in the ultrasonic fields generated in water by quartz transducers of various shapes were presented on an oscilloscope screen and photographed. The beams, pulsed at an audiofrequency, were swept back and forth across a small pressure-sensitive microphone placed at various distances from the source. The pulse envelopes were square-law detected and amplified before presentation. All the transducers were of X-cut quartz, excited near their resonance frequency of about 1 mc. Square pieces with circular and ring-shaped electrodes, as well as circular and ring-shaped pieces, were used; all were about 2 cm in diameter. Comparisons with theory were made for radial and axial mean-square pressure distributions. From study of the axial distributions it was concluded that simple piston theory adequately describes these transducers, provided the baffles and electrodes satisfy certain geometrical conditions. It appears that 18.5° X-cut crystals tend to vibrate over the whole exposed surfaces, even outside the electrode regions.
The Velocity of Sound in Sea Water
Authors: Weissler Alfred , Del Grosso Vincent A.
Published: September 2005

Laboratory measurements of sound velocity in sea water samples from the Caribbean and Middle Atlantic have been made by means of a three-megacycle ultrasonic interferometer. The results at various salinities and temperatures show that the velocity values in current use (Kuwahara's tables) are too low by approximately three meters/second.

In addition, variations in the dissolved air content were found to have negligible effect on sound velocity and absorption. The sulfate/chloride ratio was determined as quite constant in a given region of the sea. Finally, it was established that the velocity and adiabatic compressibility observed for sea water are explainable on the basis of a linear summation of the effects of the individual dissolved salts.
Sound Scattering by Solid Cylinders and Spheres
Authors: Faran James J.
Published: September 2005

The theory of the scattering of plane waves of sound by isotropic circular cylinders and spheres is extended to take into account the shear waves which can exist (in addition to compressional waves) in scatterers of solid material. The results can be expressed in terms of scattering functions already tabulated. Scattering patterns computed on the basis of the theory are shown to be in good agreement with experimental measurements of the distribution-in-angle of sound scattered in water by metal cylinders. Rapid changes with frequency in the distribution-in-angle of the scattered sound and in the total scattered energy are found to occur near frequencies of normal modes of free vibration of the scattering body.
A Study of the Vowel Formants of Well-Known Male Operatic Singers
Authors: McGinnis C. S. , Elnick M. , Kraichman M.
Published: September 2005

The formant regions of vowels sustained by well-known male operatic singers were compared with each other and with those of untrained voices. Since vowel samples from commercial phonograph records were too short for electrical harmonic analysis, these samples were re-recorded on circular grooves. Analysis consisted of measuring the energy content of the individual harmonic partial tones. The result of this method seemed to be more informative in many ways than those obtained by using the sound spectrograph which shows only the general formant regions. Three important formants were found in the male voice, although the third of these was more prominent in trained voices. A fourth of minor importance occurred in trained voices only. The frequency positions of the three important formants are found to be in dose agreement for the various voices analyzed.
Absorption Characteristics of Acoustic Material with Perforated Facings
Authors: Ingård U. , Bolt R. H.
Published: September 2005

This paper extends and unifies the analysis of sound absorptive structures consisting of (1) a layer of porous material separated from (2) a rigid wall by (3) an air cavity, which may or may not contain (4) separating partitions; and the porous material may or may not be covered with (5) a perforated facing. The normal impedance of the porous layer is expressed in a series form in which the first term suffices for a very thin layer. Equations and design charts are given for the impedance and the absorption coefficient, as functions of angle of incidence, for the complete structure with and without partitions. The statistical coefficient, averaged over angle, is plotted for each case over the commonly encountered ranges of all design variables. Calculated coefficients for eight different designs are compared with those measured by the reverberation method and found to be in good agreement.
Some Effects of Interaural Phase Differences on the Perception of Pure Tones
Authors: Garner W. R. , Wertheimer M.
Published: September 2005

Fifty-four naive observers were asked to report whether they could hear a difference between two successive tones which differed only in respect to which ear was leading in phase angle. They were not given specific suggestions to listen for a particular effect, but were later asked what they had heard. Two intensities, eight frequencies, and seven phase leads were used. The major conclusions from the results are: (1) All observers heard differences due to phase and identified the differences as localization, although for most the localization was in terms of which ear was stimulated rather than in terms of apparent localization of a sound source. (2) Pitch and loudness differences also occurred, but cannot be explained on the assumption that only one ear was effectively stimulated. (3) Measures of phase-difference thresholds, upper frequency limits, and time-difference thresholds show approximately the same results as are obtained with other methods.
On the Theory of the Fixed Path Acoustic Interferometer
Authors: Borgnis F. E.
Published: September 2005

A general expression is given for the electric input impedance of the acoustic interferometer. From this expression formulas are derived for determining the velocity of sound by varying the frequency, or for determining changes in velocity due to variations of pressure, temperature, etc. In papers dealing with the fixed path interferometer, one commonly finds the suggestion that the actual path length needs some correction when the path ends at a nonperfect reflector. It will be shown that no such correction is indicated by the theory.
A Loudness Chart for Octave-Band Data on Complex Sounds
Authors: Mintz F. , Tyzzer F. G.
Published: September 2005

The equivalent-tone method of Beranek, Marshall, Cudworth, and Peterson has been used as a basis for developing a loudness chart for octave-band data on noise. The loudness chart consists of contours of equal pressure level in octave bands which are superimposed on a loudness grid. The procedure is based on octave-band data, since octave-band filter sets are readily available commercially and are being widely used in noise measurement. Good agreement is shown with loudness values for various noises determined by Beranek et al., using 300 and 600-mel bands, and there is, therefore, good agreement with existing psychological data. The loudness chart not only facilitates the calculation of loudness but provides graphical loudness curves for comparison of noise and for the evaluation of various noise reduction measures.
Some Statistical Aspects of Half-Loudness Judgments
Authors: Garner W. R.
Published: September 2005

Half-loudness adjustments have been obtained from 18 observers at 10 intensity levels from 10 to 100 db. Adjustments were made with two methods. An analysis of variance of the attenuation scores necessary for half-loudness showed: (1) Intensity accounted for a quarter of the variance. This variance indicates the extent to which the attenuation necessary for half-loudness varies with different intensities. (2) Consistent differences between observers accounted for 35 percent of the variance, indicating that some observers consistently require much greater or less attenuation for half-loudness than others. (3) One-tenth of the variance was a result of the fact that the shape of the half-loudness function with respect to intensity was different for different observers. (4) The error variance, caused by repeated adjustments by the same observer at the same intensity and with the same method, was 22 percent of the total. (5) Other variances were practically insignificant. The average half-loudness function differs markedly from previously reported results. It is suggested that this discrepancy, as well as the large differences between individuals, is largely a result of the fact that observers have difficulty establishing the correct fractional value, and thus are extremely susceptible to indirect suggestion. A means of avoiding this problem of a nonvalid fraction is suggested.
Comfortable Listening Levels for Pure Tones in Quiet and Noise
Authors: Pollack Irwin
Published: September 2005

The most comfortable listening level and the range of comfortable listening levels for pure tones were determined for a group of normal (nonclinical) listeners in the quiet and against various levels of background noise. In general, the most comfortable listening (mcl) level contour has the general shape of the equal-loudness contour at intermediate loudness levels—lowest intensity at the middle frequencies and highest intensity at the lower frequencies. The range of listening levels considered “comfortable” against a quiet background varies from about 20 db at the lowest frequencies to about 35 db at the middle frequencies. The variability of the mcl is larger at high frequencies than at low frequencies, and it is about the same magnitude as the variability of heterophonic equal-loudness matches. The effect of noise is primarily to raise the lower limit of the range of comfortable listening levels and only secondarily to raise the upper limit. As a result, the range of comfortable listening levels is decreased in noise. The possible use of the comfortable listening level test as a gross diagnostic tool in the detection of nerve-type deafness is discussed.
Design Characteristics for Noise Control of Jet Engine Test Cells
Authors: Hardy Howard C.
Published: September 2005

An example is shown of the steps in the design of the structure for noise control of a jet engine test cell from the determination of the design goal to the final acoustic treatment of the cell. An arbitrary design goal was set from a previous survey of city noise. With the expected octave band levels at a distance of 3000 feet, for 10 jet engines with afterburners the quieting necessary is 50 and 55 db, respectively, in the 150–300 and the 300–600 cps bands, these two bands being the most difficult to control. An analysis of the required volume and dependent cost of the structure is given as the function of the amount of quieting needed, the quantity of heated gases exhausted, the temperature of the gases, and the velocity of flow permitted. Two unconventional but economical systems of noise control, (1) a series of acoustically treated plenums and (2) a series of acoustical lined 180-degree turns, are recommended. Design equations and confirming data from model studies are presented.
The Acoustic Properties of Flying Helmets
Authors: Wilkie D. R.
Published: September 2005

A convenient and theoretically satisfactory method for measuring the sound attenuation of flying helmets is described in which a miniature microphone is employed to measure the sound intensity inside the helmet capsule. A theory of sound transmission through helmet capsules is proposed the validity of which is established by a direct comparison of theoretical with experimental results.

It is thus possible to design helmets which are considerably better than standard R. A. F. types. Comparison tests on one such helmet are described.
Phonograph Needle Drag Distortion
Authors: Rabinow J. , Codier E.
Published: September 2005

In the following paper are included: the graphical synthesis which originally led to the belief that the tangential motion of a phonograph playback needle would cause distortion of the output signal; the mathematical analysis of the forces which would tend to cause such motion; and descriptions of equipment, tests, and conclusions reached.

These conclusions are, in brief, as follows: In a common type of crystal pick-up, equipped with the usual steel needle, tangential motion of the stylus tip does occur as postulated, ranging in amplitude up to 0.0012″, the amplitude of the motion being a function of the recorded frequency, the amplitude of recording, the radius of the groove in which the signal is recorded, recording speed, record and needle wear, and needle pressure. In addition to the tangential motion caused by the recorded signal, a vertical resonance occurring in the needle-pick-up arm system causes low frequency tangential motions of the needle tip (24 cps) with amplitudes of up to 0.0015″. Attempts to detect the distortion of the output signal caused by tangential motion were unsuccessful principally because of the presence of other distortions which masked the tangential motion distortion, and which could not be removed from the equipment used. However, since the existence of tangential motions and their amplitudes were established, it became possible to compute the cross-modulation products caused by such motion.
Acoustical Characteristics of Jet-Edge and Jet-Edge-Resonator Systems
Authors: Nyborg W. L. , Burkhard M. D. , Schilling H. K.
Published: September 2005

A jet-edge (JE) system is an arrangement whereby a thin blade of fluid impinges on an edge and thus, under appropriate circumstances, gives rise to tones which are called edge tones. Experimental results are presented for JE systems such as might be employed in jet-edge-resonator type whistles. Operating ranges of parameters are mapped out for various possible stages of self-oscillation. Edge tone fields are described as functions of parameters, particular emphasis being given to magnitudes and distributions-in-space of stage 1 edge tone sound fields. Examination is also made of sound fields generated by a JE system coupled to a resonator; characteristic interaction pattern is described.
Note on Beranek's Theory of the Acoustic Impedance of Porous Materials
Authors: McGrath J. W.
Published: September 2005

Beranek developed in 1942 a relatively simple and easily applicable theory of the acoustic impedance of porous materials. This paper presents a modification of his theory which avoids two approximations used formerly. It is found that the specific dynamic frictional resistance and the effective density of the material are functions of frequency. Their values may be computed from experimental values of the flow resistance, porosity, and certain area ratios which have to do with the structure of the material. A method of determining the area ratios in the isotropic case is presented. Acoustic impedances may then be computed. The modified theory is applied to two common acoustic materials, and it appears to be quite adequate for materials of large porosity and small flow resistance. It is less adequate for other materials. Possible reasons for the latter case are discussed.
On Sound Propagation in MgSO4 Solutions
Authors: Barthel Romard
Published: September 2005

Recent experimental data show that some error in concentration dependence is involved in Liebermann's application of his theory of sound propagation in chemically active media to the case of MgSO4 solutions. Therefore a more careful analysis made of the concentration dependence of some of the factors involved the theory. The proper concentration dependence is shown to be consistent with experimental results. Present experimental data are insufficient for determining whether a unimolecular reaction or a dissociation reaction is causing the observed anomalous absorption in MgSO4 solutions.
Sound Scattering by Thin Elastic Shells
Authors: Junger Miguel C.
Published: September 2005

The theory of scattering of plane waves of sound is extended to scatterers in the form of thin elastic shells of cylindrical and spherical shape. As for all elastic scatterers, the scattering action is the resultant of: (1) “rigid body scattering,” i.e., the scattering which would be present if the scatterer were rigid and immovable; (2) “radiation scattering,” which represents the sound radiation from the shell undergoing forced vibrations under the influence of the incident wave pressure, and which is determined by the dynamic characteristics of the submerged shell. Contrary to solid scatterers, whose dynamic characteristics are little different in vacuum and in the fluid medium, the characteristics of shells are profoundly altered by fluid reaction. When the shell is excited near resonance, the scattering pattern resembles the dynamic response of the shell in that it is highly frequency sensitive.

The mathematical analysis proceeds by correlating the general solution of the wave equation in the fluid medium with the Lagrange equations of the elastic shell; the correlation is obtained by applying one boundary condition and by expressing the energy exchange between the two media in terms of generalized forces. This method should be applicable whenever (1) the solution of the wave equation is known in the appropriate coordinate system; (2) the equations of motion of the elastic scatterer freely vibrating in vacuum can be derived and solved.
Multiple Helmholtz Resonators
Authors: McGinnis C. S. , Albert V. F.
Published: September 2005

The explanation of the acoustical action of multiple Helmholtz resonators, except for one and two cavities, has not been developed. Application of Lagrange's method is made to obtain the equations of motion of the fluid displacements. The equation for the frequencies of resonance is obtained by placing the determinant of the coefficients of the displacements equal to zero. The calculations yield a number of resonances equal to the number of cavities in the system. These are found to be in agreement with the experimental results. This physical method of approach, rather than synthetic electrical circuit theory, affords, among other applications, a more direct and more informative method for explaining the resonances of the vocal tract.