bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Intelligibility of Bands of Speech in Noise
Authors: Egan James P. , Wiener Francis M.
Published: September 2005

Articulation tests were conducted with a large number of communication systems having band widths ranging from about one-half octave to a system covering the entire range of speech frequencies. The systems were linear and their responses were approximately uniform over the pass band, with sharp cut-offs at either end. The acoustic gain of the systems was expressed relative to the transmission of speech through one meter of air between talker and listener. Two spectra of masking noise were used, and each system was tested over a wide range of speech-to-noise ratios. In one group of experiments the speech was filtered before mixing with noise and in the other group both the speech and the noise were passed through the same filter. For each of the band-pass systems a relation between syllable articulation and level of received speech was obtained. From these gain functions, families of equal-articulation contours may be derived. These contours show, for example, how the gain must be changed for a given change in the band width of a system in order to maintain a constant articulation score.
Underwater Noise Due to Marine Life
Authors: Loye Donald P. , Proudfoot Don A.
Published: September 2005

The widespread use of underwater acoustical devices during the recent war made it necessary to obtain precise information concerning ambient noise conditions in the sea. Investigations of this subject soon led to the discovery that fish and other marine life, hitherto generally classified with the voiceless giraffe in noisemaking ability, have long been given credit for a virtue they by no means always practice. Certain species, most notably the croaker and the snapping-shrimp, are capable of producing noise which, in air, would compare favorably with that of a moderately busy boiler factory. This paper describes some of the experiments which traced these noises to their source and presents acoustical data on the character and magnitude of the disturbances.
Absorption of Sound by Coated Porous Rubber Wallcovering Layers
Authors: Kosten C. W.
Published: September 2005

In principle, absorption of sound is possible by means of porous compressible materials, either coated or not coated with a non-porous surface layer. As the coated materials can be washed and painted, they offer great advantages in practical applications. The theory of these materials is here entered upon in detail. The theoretical results have been tested by numerous measurements concerning for the greater part layers of sponge-rubber in various modifications. Roughly speaking, these results turned out to be right. A very low density (high porosity), a small rigidity of the compressible skeleton and, besides, a rather low resistance of the air appear to be advantageous. Selective absorption due to resonance frequencies can be counteracted efficiently by providing the layer with inhomogeneities or by fixing it inhomogeneously to the wall. The application at some distance from the wall of a compressible layer with a very low air resistance has led to exceptionally favorable absorption properties.
The Effect of Non-Uniform Wall Distributions of Absorbing Material on the Acoustics of Rooms
Authors: Feshbach Herman , Harris Cyril M.
Published: September 2005

The acoustics of rectangular rooms, whose walls have been covered by the non-uniform application of absorbing materials, is treated theoretically. Using appropriate Green's functions a general integral equation for the pressure distribution on the walls is derived. These equations show immediately that it is necessary to know only the pressure distribution on the treated surfaces to predict completely the acoustical properties of the room, such as the resonant frequencies, the decay constants, and the spatial pressure distribution. The integral equation is solved approximately using (1) perturbation method, and (2) approximate reduction of the integral equation to an equivalent transmission line. Criteria giving the range of validity of these approximations are derived. It was found useful to introduce a new concept, that of “effective admittance,” to express the results for the resonant frequency and absorption for then the amount of computation is reduced and the accuracy of the results is increased. The absorption of a patch of material was found as a function of the position of the absorbing material and was checked experimentally for a convenient case, an absorbing strip mounted on the otherwise hard walls of a rectangular room. Particular attention is given to the case where the acoustic material is applied in the form of strips. The results may then be expressed in series which converge very rapidly and are, therefore, amenable to numerical calculation. Approximate formulas are obtained which permit estimates of the diffusion of sound in a non-uniformly covered room. In agreement with experience, these equations show that diffusion increases with frequency and with the number of nodes on the treated walls. The “interaction effect” of one strip on another is shown to decrease with an increase of the number of nodes. The results are then applied to the case of ducts with non-uniform distribution of absorbing material on its walls. Results are given which permit the calculation of the attenuation per unit length of duct. The methods of this paper hold for any distribution of absorbing material and also if the admittance is a function of angle of incidence.
Absorption of Supersonic Waves in Liquids
Authors: Teeter Charles Edwin
Published: September 2005

There is still no completely adequate theory to explain the discrepancy between the low absorption predicted by the classical theory of sound transmission and the much higher absorption observed in liquids, especially at supersonic frequencies. It seems obvious that as prelude to a better theory, a much larger and more accurate body of data on absorption under widely varying conditions is necessary. It is believed that the method herein presented, which is described in more detail elsewhere, is particularly suitable for measurement of supersonic absorption. This pulse method was developed during the war at the Radiation Laboratory, Massachusetts Institute of Technology, by a group of workers including the present author. Time did not permit full use of its possibilities, but a number of preliminary results were obtained, and in this paper are reported measurements of supersonic absorption at 15 mc for solutions of inorganic salts, organic liquids, and water at various temperatures, and also at 10 mc for water at various temperatures. It is shown that for water, and probably for other substances, the temperature coefficient of absorption may be larger than heretofore supposed, and hence more attention should be paid in the future to thermostatting of absorption apparatus.
Image Interference in the Presence of Refraction
Authors: Young Robert W.
Published: September 2005

Underwater sound transmission has been studied as a function of range at frequencies of 0.2, 0.6, 1.8, 7.5, and 22.5 kc, under a variety of thermal conditions. At the three lower frequencies, marked interference patterns are observed. These result from the combination of surface reflected sound (as from an image source) and directly transmitted sound. Refraction modifies the interference pattern. When the sound velocity increases with increasing depth, the interference pattern is contracted; when the velocity increases with depth, the pattern is extended. An easily used formula is developed to predict this influence of refraction on the propagation of sound emitted from a point source adjacent to a reflecting plane. The theory is in good agreement with the experimental data obtained with the source at a depth of 14 feet from the surface and the receiver as deep as 300 feet.
The Acoustical Concomitants of Cavitation and Boiling, Produced by a Hot Wire. II
Authors: Osborne M. F. M.
Published: September 2005

The properties of an electrically heated wire in various liquids have been investigated in an effort to explain qualitatively the properties of the hot-wire sound generator of the preceding paper. The sound from the hot wire is primarily a cavitation noise—its properties can all be ascribed to the continuous formation and collapse of vapor cavities. Many of the phenomena of cavitation, including corrosion, have a counterpart in boiling. It is shown that under certain conditions the hot wire has two stable forms of operation for the same input power. In one the wire is relatively cold, and the sound emitted has a broad frequency distribution. In the other the wire is red hot, and for some liquids the sound emitted is a single pure tone a whistle of 1000–2000 cycles/sec. Swishing the wire through the liquid increases the intensity of this whistle.
Absorption of Supersonic Waves in Water near One Megacycle
Authors: Labaw L. W. , Williams A. O.
Published: September 2005

Several observers have found that the absorption coefficient for supersonic radiation in water is inversely proportional to the square of the frequency, in the range 3 to 80 megacycles. This agrees with classical theory except in the size of the proportionality constant, but when extrapolated to lower frequencies disagrees sharply with earlier measurements which suggested a strong absorption peak near one megacycle. An experiment is described here which employed a small microphone detector and attempted to measure absorption in a divergent supersonic beam by comparison of the measured and theoretical acoustic pressure curves along the beam axis. The results, between 1.09 and 1.30 mc, are negative in that the computed absorption coefficients fall below the experimental error. However, a fairly reliable upper limit can be set on the coefficient. This limit is consistent with the value predicted by extrapolating the frequency-squared relationship down to one megacycle. There seems little chance of a strong absorption peak in the near neighborhood of one megacycle.
Two Parabolic Reflector Underwater Transducers
Authors: Reitz J. R. , Mueser R. E.
Published: September 2005

A line source underwater transducer may be used in conjunction with a parabolic cylinder reflector to produce a highly directive sound ray similar to that obtained from a shaded plane source. Poor patterns result from the construction of a unit where the element is at the focus of a parabolic cylinder reflector because the finite size of the element is so great as to block a large proportion of the reflected sound rays. To circumvent this difficulty an ideal surface is derived which will allow placing the line source out of the direct path of the reflected rays. This derivation and the construction and acoustic characteristic of the consequent transducer are discussed.
Measurement Conditions Influencing the Front-to-Back Discrimination of an Underwater Hydrophone
Authors: Miller Laymon N.
Published: September 2005

The “front-to-back discrimination” represents the ability of an underwater hydrophone to favor reception of a desired signal originating in front of the hydrophone by discriminating against a usually undesired signal originating behind the hydrophone. Under normal conditions in a confined measurement area, the value of the front-to-back discrimination is influenced to a considerable extent by such measurement factors as conditions of the medium, the directionality characteristics of the projector, and the distance separating the projector and the tested hydrophone. It is reported that reverberation appears to mask the true back-side response of the hydrophone, and that thermal gradients and possibly unusual natural effects oftentimes limit the validity of some underwater measurements. Data are presented to show that a hydrophone measured with highly directional projectors exhibits a higher front-to-back discrimination than if measured with non-directional projectors. It is also shown that the front-to-back discrimination appears to decrease with increasing distance between the projector and the tested hydrophone. These effects are attributed to the absence of a strictly free-field in a bounded volume of water.
On the Diffraction of a Progressive Sound Wave by the Human Head
Authors: Wiener Francis M.
Published: September 2005

An earlier paper described the distribution of sound pressure in the auditory canals of a number of subjects in a plane progressive sound field. At a given frequency, the ratio of the sound pressures at the eardrum and at the entrance to the ear canal was found to be greater than unity and essentially independent of the orientation of the observer with respect to the sound source, as might be expected from theory. With this ratio known, it is possible to determine, with relative ease, the sound pressures at the eardrum as a function of azimuth from pressure measurements near the entrance to the auditory canal. By positioning a probe microphone at the entrance to the ear canal and comparing the sound pressures there with the free-field pressures at the subject's location an estimate of the obstacle effect of head and pinna is arrived at. Adding the known pressure increase in the auditory canal yields a measure of the total obstacle effect of the human head and auditory canal. The subjects were placed in front of a loudspeaker in a room essentially free from acoustic wall reflections. The measurements of the sound pressure at the entrance of the left auditory canal and in the free field in the absence of the subject were carried out by means of a small probe microphone in the frequency range extending from 200–6000 c.p.s. A range of azimuths of 360 degrees was covered in 45-degree steps. If it is assumed that the two auditory canals are alike and that the head is symmetrical about the median plane, the ratio of the sound pressures at the left and right eardrums can be readily computed from these data. This ratio is of importance in the mechanism of binaural localization. The average for six male subjects was compared with the values obtained by Sivian and White from threshold measurements and was found to be in fair agreement.
Improved Theory of the Light Pattern Method for the Modulation Measurement in Groove Recording
Authors: Hornbostel J.
Published: September 2005

A formula is derived that is applicable to the evaluation of light pattern measurements when non-parallel light is used. It is shown that deviation from parallelism encountered in the laboratory may cause Buchmann and Meyer's simplified formula to be in error by several db. Numerical examples are given, and the results are extended to vertical and loop recordings.
Short Duration Auditory Fatigue as a Method of Classifying Hearing Impairment
Authors: Gardner Mark B.
Published: September 2005

Earlier studies have classified deafness cases into two general groups, those having functional disorders of the middle ear and those having impairments resulting from atrophy of the nerve fibers terminating along the basilar membrane (conductive and nerve deafness types, respectively). Such classifications have been made using bone conduction threshold measurements and unilateral loudness balance results as the basis for differentiation. Bone conduction results, however, are often subject to considerable error while the unilateral loudness balance technique can only be applied to individuals having one normal and one impaired ear. These limitations introduce a need for a completely independent monaural method of classifying deafness types. This is particularly true for the selection of candidates suitable for the fenestration operation for the restoration of hearing in otosclerosis (immobilized stapes). The present paper is concerned with an investigation of short time auditory fatigue as a method of obtaining an impairment analysis. In this study, it was found that the fatigue of the conductively deafened observer was similar to the normal observer except the onset of fatigue was shifted by the amount of the threshold loss. For the nerve deafened observer, on the other hand, the onset of fatigue was found to occur at normal intensity levels. The occurrence of excessive fatigue in one of the nerve type impairment cases investigated appears to offer additional information on the nature of the lesion.
Temperature Coefficient of Ultrasonic Velocity in Solutions
Authors: Willard G. W.
Published: September 2005

Extensive measurements have been made, at ten megacycles, of the temperature dependence of ultrasonic velocity in liquids and liquid mixtures. All single liquids tested, except water, were found to have large negative temperature-coefficients in the temperature range of zero to 80°C. Water has a large positive coefficient at room temperature, decreasing to zero at 74°C and then becoming negative (with a peak velocity of 1557 meters/sec.). Solutions in water of various other liquids (and of some solids) give parabolic velocity vs. temperature curves like that for water but with the peak velocity and peak temperature values shifting with the concentration of the solution. In general increasing the concentration raises the peak velocity slightly and lowers the peak temperature markedly from the values for water alone. It has also been found possible by compounding three-component solutions to adjust the values of the peak velocity and peak temperature independently within a narrow range of velocities and a wide range of temperatures.
Measurements of Ultrasonic Absorption and Velocity in Liquid Mixtures
Authors: Willis F. H.
Published: September 2005

The absorption (α) and velocity (V) of sound in liquid mixtures were measured at four frequencies (ν) in the range 3.8 to 19.2 mc, using the Debye-Sears-Lucas-Biquard optical technique improved by the addition of a differential photoelectric cell indicator. This improvement permitted the use of lower sound intensities together with a wider sound beam than in the visual extinction method, thus improving conditions with respect to cavitation and beam distortion. In the mixtures investigated, α/ν2 was found to be independent of frequency within the accuracy of the method, and there was no measurable dispersion of acoustic velocity. An absorption peak at intermediate concentrations not shifting with frequency was found in mixtures of acetone and water, and of ethyl alcohol and water, but was not in evidence in mixtures of acetone and ethyl alcohol, and of glycerol and water. The absorption peaks await theoretical explanation.
A Distortion Reducing Stylus for Disk Reproduction
Authors: McClain E. F.
Published: September 2005

A stylus design is presented which combines the advantages of both large and small tip radii to secure satisfactory tracking on a wide variety of groove dimensions.
Convex Wood Splays for Broadcast and Motion Picture Studios
Authors: Rettinger Michael
Published: September 2005

The purpose of this paper is to present both theoretical and experimental findings in the use of convex wood splays for broadcast and motion picture studios. After a discussion of the term “diffusion,” there follow some calculations intended to circumscribe the term mathematically. An experiment is described in which pillars are used for added diffusion in a sound recording studio, and some criteria are cited for the use of such splays in studios.
The Detection of Internal Leaks in Aircraft Hydraulic Systems
Authors: Nuckolls Richard G. , Trent Horace M.
Published: September 2005

The problem of locating defective valves which cause excessive internal leaks in aircraft hydraulic systems has been successfully solved by the development of an acoustic device called the Hydraulic Leak Detector. In principle, the device monitors the ultrasonic vibrations produced in the system by the leaking valve, which vibrations are most intense at the defective element.
Ultrasonic Measurement of Wall Thickness in Diesel Cylinder Liners
Authors: Struthers Francis W. , Trent Horace M.
Published: September 2005

The modifications that have been developed in order to adapt the Sonigage to the quick inspection of Diesel cylinder liners are described. A method of introducing ultrasonic vibrations from a conventional flat-crystal probe into a curved surface and an adaptor for determining thickness by interpreting the harmonics response have proven to be valuable in expediting this type of work. In the hands of an experienced operator the technique can be made to yield much valuable information concerning the relative homogeneities of the castings.
Analyses of the Tones of Wooden and Metal Clarinets
Authors: Parker Sam E.
Published: September 2005

The harmonic spectra of wooden and metal clarinets were obtained on an harmonic analyzer. The clarinets were blown artificially using a voicing technique similar to that used in certain reed organ pipes. The tests were performed on towers erected for the purpose in the open air. It is concluded that the following factors have no appreciable effect upon the steady-state spectra: the respiratory tract and the-wood or metal of which certain instruments are made. Factors which have important effects include the pressure on the reed and the position at which pressure is exerted; the blowing pressure; and the position of the note in the register. Observation of a vibrating reed under stroboscopic light verifies the conclusion that the reed is a beating reed.
Some Notes on the Measurement of Acoustic Impedance
Authors: Beranek Leo L.
Published: September 2005

A modified form of an earlier design of impedance tube is described here. It is capable of measuring the normal impedance of a sample by the variable length, variable frequency, or traveling microphone methods without disturbing the sample in transferring from one test method to another. The tube also may be used to measure the transmission constant with the aid of a long probe tube. Modern graphical aids to the calculation of the impedance from the quantities measured in the tube are described. Comparison of data obtained by the variable length and traveling microphone methods is made, and good agreement is found over most of the frequency range. It is shown that the clamping effects of the tube walls on the edge of a lightweight, non-rigid sample are serious enough to introduce large gyrations of the impedance curves at frequencies below 500 c.p.s.
Sound Diffraction by Rigid Spheres and Circular Cylinders
Authors: Wiener Francis M.
Published: September 2005

The results of calculations of the pressure distribution on the surface of a stationary rigid sphere and a stationary rigid circular cylinder of infinite length, when exposed to a plane progressive sound wave, are compared with experiment. A small probe microphone was used to measure the sound pressures on the surface of the obstacles in a room essentially free from acoustic wall reflections under a variety of experimental conditions. The sound pressures p on the surface are conveniently expressed relative to the free-field pressure p0 in the undisturbed incident wave.

In the case of the sphere, reasonably good agreement was obtained between theory and experiment in the range of 13 <ka < 10, where k is the wave number of the incident wave and a the radius of the obstacle. In particular, the existence of the “bright” spot diametrically opposite the point nearest the sound source was verified experimentally. This comparison of experiment with theory affords a valuable means of estimating the validity of the experimental procedure.

In the case of the cylinder whose axis was oriented parallel to the wave front of the incident wave and whose length was chosen to equal its diameter, the pressures were measured for the most part in the median plane. There is a marked similarity between the results obtained for this finite cylinder and the results obtained for a sphere. The pressure at the point in the median plane farthest away from the source of sound (θ = 180°) is substantially equal to the free-field pressure only for ka < 5. As the frequency is increased further, the sound pressure near θ = 180° drops rapidly up to and most likely beyond ka = 10 at an approximately constant rate, in decibels per frequency octave. A small microphone located on the surface of such a cylinder at θ = 180° will exhibit a low pass filter action with a cut-off at k ≈ 5.

Tables are furnished of the ratio p/p0 computed for a rigid circular cylinder of infinite length. This ratio is tabulated in magnitude and phase in the range of 12 ⩽ ka 10, for azimuths θ varying from 0 to 180° in 10-degree steps. The results are very similar to the spherical case for θ not exceeding about 150 degrees. There is only an insignificant trace of the bright spot at θ = 180°.
The Variation of Phase Along the Basilar Membrane with Sinusoidal Vibrations
Authors: Békésy Georg V.
Published: September 2005

An optical means of measuring phase relations in the cochlea is described. With the stapes set into sinusoidal vibration, the phase relations, measured along the length of the cochlear partition, show that a traveling wave has been set up. The form of resonance which appears does not correspond at all with that to be found in a simple vibrating system. Measurements are presented for a frequency of 200 c.p.s. of the amplitude and phase of vibration at various places along the cochlear partition. From these is derived a curve showing the longitudinal bending of the partition with the traveling wave at two different points in time.

Very small changes in the form of vibration can easily be demonstrated by the measurements of phase. By this means it is shown that the basilar membrane cannot be released from tension since it is not normally under tension. The elastic properties of the various distinguishable tissues within the cochlear partition were measured. These measurements show that only the elasticity of the basilar membrane changes through the length of the cochlear canal. The other portions of the partition are quite constant throughout the entire distance.

Further, the non-linearity in the vibration of the partition was investigated with results which indicate that the observed lowering of pitch of a tone when the loudness is increased cannot be produced by mechanical means.
On Hearing in Water vs. Hearing in Air
Authors: Sivian L. J.
Published: September 2005

The paper deals with the ability of a submerged listener to hear sounds generated in the air above him, compared with their audibility when his head projects above the water. In a theoretical discussion it is shown that at 1000 c.p.s. a loss of the order of 45–55 db might be expected in the in-water audibility relative to the in-air value. This involves a number of assumptions, e.g., that there is no appreciable noise created by the listener's propulsion, and that the effect of hydrostatic pressure unbalance on the eardrum is negligible. A few measurements made at 1000 c.p.s. and 3000 c.p.s. yielded values which are not at variance with the theoretical analysis.
The Thermophone as a Source of Sound in Liquid Helium and Liquid Hydrogen
Authors: Fairbank Henry A. , Fairbank William M. , Lane C. T.
Published: September 2005

Although the thermophone effect, the generation of sound waves by a varying heat source, has long been known in gases and has proved to be useful in a precision sound source for calibrating microphones, no mention of its use in liquids has come to our attention. In some recent experiments, described in this paper, we have observed this effect in liquid helium I and liquid hydrogen. Suggestions are made for its use as a simple sound source for audiofrequency velocity and absorption measurements in these liquids.
Propagation of Sound Through a Liquid Containing Bubbles
Authors: Carstensen E. L. , Foldy L. L.
Published: September 2005

Experimental data on the transmission, scattering, and reflection of sound by screens of bubbles are presented and shown to agree with theory. A parameter, related to the damping of acoustic energy by bubbles and which cannot be satisfactorily predicted from theory, is evaluated empirically from the data.
An Institute of Musical Science—A Suggestion
Authors: Fletcher Harvey
Published: September 2005

This paper suggests the establishment of an Institute of Musical Science designed to provide a scientific basis and techniques whereby music may contribute more fully to the esthetic life of a larger number of people. The program of research of the Institute extends from the physics of the production of musical sounds to the psychology of their appreciation by listeners. It would measure and study audience reaction under a wide variety of conditions. It would undertake the experimental development of new musical instruments, of new electro-acoustical systems for the production or reproduction of esthetic sounds; and it would study the possibilities of synthetic orchestras and new techniques or orchestration. It would experiment in the application of sound effects to dramatic and operatic performances. Techniques would be worked out for the measurement of musical talent, and scientific apparatus developed for the musical education of individuals and the training of choral or instrumental groups. It would apply to the problems of music the techniques and instrumentalities which have been developed in the fields of acoustics, electrical communications, and electronics. Particular attention would be given to music in the home, and to applications to its needs of devices inherent in recent engineering advances.
Frequency Range Preference for Speech and Music
Authors: Olson Harry F.
Published: September 2005

Frequency range preference tests for reproduced speech and music indicate that listeners prefer a restricted frequency range in monaural reproduced speech and music. In order to obtain a better understanding of the reason for the preference of a restricted frequency range in reproduced sound, a fundamental all-acoustic frequency range preference test has been made. An acoustical filter was placed between the orchestra and the listeners and arranged so that the filter can be turned in and out. A sheer cloth curtain which transmits sound without any appreciable attenuation was placed between the acoustical filter and the listeners. The curtain was illuminated so that the listeners could not see what transpired behind the curtain. The response-frequency characteristic of the acoustical filter was 5000-cycle low pass transmission. The response approximated a good commercial radio or phonograph. The tests made up to the present time have been conducted in a small room which simulates the average living room in dimensions and acoustics. A six-piece orchestra playing popular and semi-classical music was used in these tests. Tests involving one thousand listeners indicated a preponderant preference for the full frequency range. Similar results have been obtained for speech.
Acoustical Impedance of Enclosures
Authors: Daniels Fred B.
Published: September 2005

Formulas are derived for the acoustical impedance of three types of enclosures, a sphere, a cylinder, and a narrow rectangular box. The solutions are valid throughout the entire range from adiabatic to isothermal conditions.
The Diffraction of Sound Due to Right-Angled Joints in Rectangular Tubes
Authors: Miles John W.
Published: September 2005

The diffraction of a plane wave of sound caused by right-angled joints in rectangular tubes is computed by calculating the impedance elements of the equivalent circuit for the discontinuities, the propagation of the principal wave being represented by the voltage and current on a transmission line. A numerical example is given.
The Growth of Auditory Sensation
Authors: Munson W. A.
Published: September 2005

The integration of sensation with respect to time was studied experimentally by means of tones of short duration. Loudness tests were made on sounds persisting from 0.005 to 0.2 second and covering a wide range of levels. The observed increase in magnitude of a sensation as the duration time is increased is attributed to the integration characteristic of the central nervous system, and an equivalent electrical circuit is derived. The circuit analogy is then used in the computation of loudness as a function of the duration of the stimulus.
A Pulse-Tone Technique for Clinical Audiometric Threshold Measurements
Authors: Gardner Mark B.
Published: September 2005

The pulse-tone method of testing hearing, used as a basis for the 1939–40 World's Fair tests in which over one million individuals voluntarily participated, has been adapted for clinical audiometric use. For this purpose, a tri-functional control has been utilized consisting of (1) an electronic method of producing the desired number of tone pulses (normally one, two, three, or four) in a selected sequence under control of the operator, (2) a visual signal which occurs at the beginning of each pulse series to act as a warning to the observer, and (3), a visual signal which flashes in synchronism with the output tone pulses to act as a counter for the operator. In threshold tests in which both the pulse-tone method and the standard audiometric method were used, approximately three out of every four operators and a similar percentage of observers expressed a preference for the pulse-tone procedure. For the very young listener, the pulse-tone test appears to be preferable in the majority of cases. The normal threshold intensity calibrations of the two tests are in good agreement so that either test may be used interchangeably with the other. The time required to make a pulse-tone audiogram is slightly in excess of that required to make a measurement by the standard procedure, but the resulting data are more reproducible.
Auditory Thresholds of Short Tones as a Function of Repetition Rates
Authors: Garner W. R.
Published: September 2005

Auditory thresholds were obtained for repeated short tones (sine-wave) with repetition rates between 14 and 100 per second, and tone durations between 1 and 50 milliseconds. Both noise-masked and quiet thresholds were measured, Although the total energy in a stimulus can be changed by varying either the repetition rate or the duration, the results show that only in the latter case is there an equivalent shift in the threshold. Discussion of the results in terms of spectral distribution of energy of such tones leads to the conclusion that the ear does not perform a Fourier analysis of these tones. Further discussion indicates the conditions necessary for temporal integration of acoustic energy by the ear.
Sensitivity to Changes in the Intensity of White Noise and Its Relation to Masking and Loudness
Authors: Miller George A.
Published: September 2005

Sensitivity to changes in the intensity of a random noise was determined over a wide range of intensities. The just detectable increment in the intensity of the noise is of the same order of magnitude as the just detectable increment in the intensity of pure tones. For intensities more than 30 db above the threshold of hearing for noise the size in decibels of the increment which can be heard 50 percent of the time is approximately constant (0.41 db). When the results of the experiment are regarded as measures of the masking of a noise by the noise itself, it can be shown that functions which describe intensity discrimination also describe the masking by white noise of pure tones and of speech. It is argued, therefore, that the determination of differential sensitivity to intensity is a special case of the more general masking experiment. The loudness of the noise was also determined, and just noticeable differences are shown to be unequal in subjective magnitude. A just noticeable difference at a low intensity produces a much smaller change in the apparent loudness than does a just noticeable difference at a high intensity.
Physiological Noise Generated under Earphone Cushions
Authors: Brogden W. J. , Miller George A.
Published: September 2005

Listeners were required to match the quality and intensity of a low frequency ambient noise to the quality and intensity of the noise which they heard when they held earphones over both ears. A sound-pressure of 55 or 60 db of rumbling, low frequency noise can be generated by the tremor of the tonic contractions of hand and arm muscles.
A Theory as to the Function of the Scala Tympani in Hearing
Authors: de Rosa Louis A.
Published: September 2005

The scala tympani canal is assumed to be coupled to the scab vestibuli of the cochlea through-out its length. If the mathematics are formulated for this premise, with appropriate boundary conditions, it is found that despite the absence of reflections and standing wave patterns, there is, nevertheless, an area of maximum stimulation of the basilar membrane as a function of frequency. Interpretation of various acoustical phenomena is simplified by reference to this analysis.
Reaction of Small Enclosures on the Human Voice
Authors: Morrow Charles T.
Published: September 2005

The paper concerns itself primarily with the acoustical specifications necessary for intelligible speech transmission through radiating enclosures, such as gas masks, placed on the front of the head. The results apply to enclosures whose internal dimensions are small by comparison with the wave-lengths significant for speech. Transmission through larger enclosures is in general poor. A speech transmitting device for a gas mask will ordinarily consist of a diaphragm, a perforated protective cover, and an exhaust valve. The acoustical system, however, must include the cavity between the mask and the face. The enclosures considered here radiate through a circular constriction, a set of perforations, or a diaphragm; specifications for the more complicated case of a diaphragm and cover have not been obtained, but may be inferred from the data presented here. The enclosures all behave as Helmholtz resonators when tested on an artificial voice. They may be specified acoustically by the resonant frequency, and a quantity related to the inertance of the acoustical system. It has been found convenient to express this property of a set of perforations or of a diaphragm in terms of an effective diameter: the diameter of the circular constriction that results in the same resonant frequency for the enclosure, or, in other words, has the same inertance. The intelligibility obtainable through an enclosure increases when either the resonant frequency or the effective diameter is increased. In general, the intelligibility will be satisfactory if the resonant frequency is at least as high as 1500 cycles per second, provided that the effective diameter is at least 1.25 inches.
Effects of Impulsive Interference upon A-M Voice Communication
Authors: Licklider J. C. R. , Goffard S. J.
Published: September 2005

The degree to which noise impairs the intelligibility of speech depends upon the characteristics of the noise. In this paper, which is concerned with electrical interference and radio communication, the questions are: (1) “what characteristics of the noise determine the degree of impairment,” and (2) “what are the functional relations between intelligibility and the important characteristics of the noise?” Answers to these questions were obtained with the aid of articulation tests, conducted with a typical amplitude-modulation system and with a variety of electrical interferences.
Properties of Liquids at High Sound Pressure
Authors: Briggs H. B. , Johnson J. B. , Mason W. P.
Published: September 2005

When sound of high amplitude is transmitted into a liquid by means of a mechanical driving device, the ultimate limitation to the power that can be transferred is cavitation or breakdown of the liquid under high internal stresses. A study of cavitation has resulted in establishing the following results. Under steady-state conditions, light liquids filled with air cavitate when the negative acoustic pressure reaches the atmospheric pressure. When liquids are degassed, their natural cohesive pressure becomes effective and they will withstand a negative acoustic pressure. It is found that the total negative pressure required to cause cavitation is equal to the sum of the cohesive pressure—tensile strength—and the ambient pressure. Viscous liquids have a higher cohesive pressure and a proportionality has been established between the logarithm of the viscosity and the cohesive pressure. The amount of power that a liquid can withstand increases markedly as the pulse length is shortened.

An explanation of these phenomena is attempted on the basis of Eyring's theory of viscosity, plasticity and diffusion. On this theory natural holes exist in the liquid into which molecules can jump, leaving holes behind them. A jump occurs when the molecule has accumulated enough heat energy to surmount an activation potential barrier of energy value E0. Cavitation appears to be the result of coalescing of the natural holes in the negative pressure phase of the cycle. Since a molecule has to jump from a hole in order that this can coalesce with another hole, the cavitation pressure is proportional to the activation energy which in turn is proportional to the logarithm of the viscosity. The increased power-transmitting capacity for short pulse lengths is a result of the finite time taken for the small holes to grow in size to a large enough hole to cause rupture of the liquid.
On the Radiation Problem at High Frequencies
Authors: Lax M. , Feshbach H.
Published: September 2005

The angular distribution of radiation from a vibrating cylinder of arbitrary cross section is considered in the limit of high frequencies. An inhomogeneous integral equation of the first kind is derived for the distribution and is solved by the method of steepest descents. The first approximation yields the “geometric optics” result in which every element of the radiator radiates normally to itself. Higher order terms are obtained for the case in which the boundary conditions on the radiator surface vary smoothly. The case of an abrupt change in boundary condition is also solved and exhibits typical diffraction effects. The techniques used in this paper have a wide range of applicability to problems of radiation and scattering of waves as they occur in field physics.
A Simplified Method for Determining Transducer Directivity Index
Authors: Kendig Paul M. , Mueser Roland E.
Published: September 2005

A system is devised whereby the directivity index of an acoustic transducer may be computed by planimeter measurement of the area under a pattern curve. This is made possible by adjusting the coordinates of a chart so total power may be measured as area.
The Practical Application of the Reciprocity Theorem in the Calibration of Underwater Sound Transducers
Authors: Ebaugh Paul , Mueser Roland E.
Published: September 2005

This article contains an integrated discussion of the underlying theory and practical application of the reciprocity theorem as applied to the calibration of underwater sound transducers. This includes a description of the actual steps involved in performing such a measurement, as well as the inclusion of a typical calibration with sample calculations of sensitivity. The practical examples covered are in the field of underwater sound; however, the theory and technique are equally applicable to air acoustics.
Report by the Music Committee
Authors: Burris-Meyer Harold
Published: September 2005

An effort has been made to determine the desirable scope and nature of the Acoustical Society's official activity in the field of music. This effort involves three steps: (a) the establishment of a conceptual framework within which to develop policy; (b) the development of policy; and (c) a derivation of a plan to implement the policy. The field of acoustics embraces all physical aspects of music from the design of man-made sound generators and the understanding of the structure and operation of the mechanism of the human voice to the physiological mechanisms and facilities by which the auditory stimulus reaches the nervous system, and psycho-acoustics. Largely because of facilities in the field of acoustics, the art of music now has substantially unlimited scope. Music is currently employed in increasing amounts as an element in entertainment, and functionally in the sense of creating a pre-determined emotional atmosphere. However, the terminology of music is indefinite and inconsistent, the criteria by which music and its meaning to and effect upon people are measured, are diverse, and the extensity of the field of music is not generally understood by those concerned with its creation, use, or appreciation. It is proposed that the Acoustical Society, with the assistance of other professional groups concerned, initiate (a) the development of a common terminology for all people concerned with music, (b) the fixing of criteria for the measurement of music and its effect on people, and (c) the establishment of a facility for the exchange of information between individuals and groups engaged in research or development activities in various aspects of music, where no effective liaison exists at present.
Decay Rates of Piano Tones
Authors: Martin Daniel W.
Published: September 2005

Decay curves were recorded for an upright piano, a baby grand, and an electrical spinet. For some tones the partials were recorded separately. Decay rates for the electrical piano were measured at different levels of piano amplification. Analysis of the data reveals the degree of control exerted by the sounding-board upon decay rate, particularly in the initial stage of decay. The significance of this control by the sounding-board is discussed, in relation to the problem of electrical amplification of piano tones.
X-Ray Motion-Picture Studies of the Vocal Organs
Authors: Curry R.
Published: September 2005

The motion-picture demonstration depicts the normal movements of the vocal organs during various types of speech and singing, as viewed on the fluorescent screen of a high-voltage x-ray machine. The views include firstly, the side view of the larynx and mouth, known as the mesial, sagittal view; secondly, the frontal view of the chest, showing the action of the thorax and abdomen in breathing; and finally, the view looking down on the larynx from above, as taken with the ultra high speed “Fastax” camera, by direct photography. The film is presented as a technique and no attempt will be made to draw any special conclusions.
The Performance of Cup Mouthpiece Instruments
Authors: Long T. H.
Published: September 2005

It is shown that the performance of air column cup mouthpiece instruments can be explained quite adequately as a transmission line with one open end and one closed end; the system is driven from the closed end by “buzzing” with the lips and certain ranges of frequency are prohibited and others encouraged by energy feedback, so the system may be properly termed regenerative. The harmonic series obtained coincides quite closely with the complete series associated with open pipe resonance. In order that the odd series associated with closed pipe resonance may match in frequencies the complete series of an open pipe, it is only necessary for the velocity of wave motion within the air column to be an appropriate function of the frequency. It is shown that this actually happens. The influence of frequency on sound velocity is most marked in the mouthpiece and in the flaring bell of the instrument. Both of these influences are in the same direction (velocity increases as frequency is reduced) but since the bell is much the longer of the two, its effect is most pronounced. It is shown that the order of magnitude of the harmonics in a trumpet tone, for instance, can be accounted for by the acoustic overload in the more restricted part of the airz column.