bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffraction of a Longitudinal Pulse from a Wedge in a Solid
Authors: Grannemann W. W.
Published: September 2005

The diffraction theory developed by Sommerfeld and extended by Pauli is used to approximate the relative amplitude of the diffracted pulses from a wedge in a solid. The geometric terms are neglected and the amplitude of the diffracted wave is obtained from the contour integral. Barium titanate transducers are used for sources and receivers on tar and concrete models to check the predictions of the theory. Several relative amplitude versus distance curves are given for regions where the diffracted pulse is separated from other waves. The experimental and theoretical curves agree to ±4 decibels in the regions tested.
Diffraction Problems in Elastic Wave Propagation in Solids
Authors: Knopoff L.
Published: September 2005

Integral solutions to the differential equations of elastodynamics are given. The solutions for the displacement at any point in an isotropic, homogeneous, elastic medium are obtained in terms of the initial distribution of displacements and stresses within a given volume and over its bounding surface. These initial quantities appear in the solutions as retarded displacements and stresses with two types of retardation depending upon the velocities of longitudinal and transverse waves. Diffraction by rigid obstacles is discussed on the basis of these integral solutions. Examples are given of the diffraction of plane wave pulses of either compression or shear types by infinite rigid slits. Rayleigh scattering by rigid spheres is also discussed
An Automatic Numerically Recording Audiometer
Authors: Brogan F. A.
Published: September 2005

An audiometer will be described which simulates a standard operator type audiometric test. This instrument has an intensity range of plus forty to minus ten decibels for each of the five frequencies tested. The “threshold crossing” is recorded numerically (5-db steps) three times for each frequency for each ear. The test duration for five frequencies (both ears) is currently ten minutes. This time could be shortened to a lower limit of five minutes with modification of the programmer. The design is such that a central frequency source and programmer can be used to control as many as ten test units.
Use of the Psychogalvanic Skin-Resistance Response in Pure-Tone Audiometry
Authors: Hardy William G.
Published: September 2005

There has long been need for audiometric evaluation of infants and young children, as well as certain adults, who cannot or do not cooperate in standard test procedures. Pure-tone evaluation is required so that findings can be related in terms of etiology and pathology to known otologic entities. The galvanic skin-resistance response is considered a useful tool, when employed with a modified conditioned reflex. The nature of the Féré effect (PGSR) is described, and instrumentation and procedures are outlined. Norms of responses of human ears are discussed, and reference is made to some current animal experimentation. Reference is made to certain types of aberrant responses and to absence of responses. The general procedure is related to other clinical findings. Reference is made to several psychophysical details that require further research.
Threshold Recoveries for Continuous and Interrupted Pure Tones Following Auditory Fatigue
Authors: Kopra Lennart L.
Published: September 2005

On four separate occasions each of twenty-four young normal-hearing adults was exposed for three minutes to a 2000-cps tone at 105 db re 0.0002 microbar, and, subsequently, the threshold recovery was traced with a modified Békésy audiometer. The test tones employed for the tracings were a continuous 3000-cps tone and an interrupted tone of the same frequency with an on-off ratio of 1.40 seconds to 1.46 seconds. Each subject underwent an initial practice session in which no fatiguing stimulus was used. Four experimental sessions followed. Major results are summarized as follows: 1. In the practice session, significantly better acuity for the continuous tone was observed after the rest period than prior to it. The threshold level for the interrupted tone remained stable throughout the entire practice session. 2. Two distinct levels of acuity, one for the continuous tone and one for the interrupted tone, occurred in the prefatigue thresholds. 3. The recovery from fatigue for the two test stimuli showed that the interrupted test tone recovered more quickly and maintained a superior level of acuity during the entire recovery period. It is believed that equilibrated adaptation may be responsible for differences in acuity level between the two test stimuli.
Entrained Air Bubbles as Sources of Sound in Liquids
Authors: Strasberg M.
Published: September 2005

Air bubbles, when entrained in water or other liquid, can generate high sound pressures in the liquid. A preliminary theoretical examination of the problem indicates that significant sound pressures are associated only with volume pulsations of the bubble, whereas oscillations in the shape of the bubble do not result in appreciable radiation. Calculations have been made of the sound pressures resulting from excitation of volume pulsations by the following mechanisms: by bubble formation, coalescence, or division; by the motion of a free stream of water containing entrained air bubbles past an obstable; and by the flow of water containing entrained air through a pipe past a constriction. The calculation of the sound pressure generated by bubble formation has been verified by measurements with bubbles formed at a nozzle.
Spectrum of Sound from Cavitation Bubbles
Authors: Fitzpatrick H. M.
Published: September 2005

In many types of cavitating flows, the radiated sound is ascribable to the growth and collapse of individual spherical cavities occurring in random sequence. The equations of hydrodynamics and acoustics allow the bubble growth and collapse paths and the radiated pressure to be computed for representative flow fields. A result derived by Gilmore (Hydrodynamics Laboratory, California Institute of Technology, Report No. 26-4) allows the effects of compressibility of the liquid to be included up to near-sonic wall velocities at collapse. The wave form of the radiated pressure pulses and the associated frequency spectra are given for various values of parameters describing the growth and rebound of the cavity, compressibility of the liquid, and permanent gas content of the cavity. Quantitative expressions for the spectrum of continuous noise radiated in real situations are given, and values derived therefrom are compared with available experimental data.
Conical Horns for Use in Conjunction with Underwater Sound Transducers
Authors: Owens W. R. , McKinney C. M.
Published: September 2005

An experimental investigation has been made using conical horns with barium titanate transducer elements for underwater sound use. The horns were formed from stainless steel and covered with cellular rubber. The dimensions of the horns varied from 28° to 60° flare angles and slant lengths from 7 inches to 22 inches. The frequency range investigated was from 10 kc to 100 kc. The directivity patterns indicate strong suppression of secondary lobes with moderate directivity.
Noise and Jet Transports—A Partial Discussion
Authors: Miller M. M. , Calkins James E.
Published: September 2005

Some aspects of the aircraft noise problem inside high-speed jet-powered transport airplanes are presented. The airplane wing effectively shields a large portion of the airplane fuselage from the intense sounds in the jet stream of pod mounted engines located near or forward of the airplane center of gravity. Measurements of this shielding are presented. Diffraction effects in these measurements verify the distribution of energy and frequency content in the jet mixing region as reported by NACA and British sources. The pressure doubling effect at the fuselage sidewall is also evident in these measurements. Noise data obtained from continuous recordings inside a high speed jet powered airplane during a variety of flight conditions are presented. Noise inside the airplane due to turbulence in the fuselage boundary layer becomes the major noise source at high speeds and the sound levels are very high in the aft fuselage section. There is a great need for research in methods of calculating and reducing this aerodynamic boundary layer noise.
Airborne Noise Levels in Submarines
Authors: Meeker Willard F. , Hawley Mones E.
Published: September 2005

Octave band levels of the airborne noise in most compartments of two submarines were measured for a number of conditions of operation. The majority of the measurements were made both directly, with sound level meter and band analyzer, and from magnetic tape recordings. A two track method was used in which noise was recorded on one channel while the pertinent data were read onto the tape using the other channel. Large differences in noise levels were observed among different compartments and for different operations. Illustrative recordings will be reproduced. Although the data were obtained primarily for use in the design of speech communication systems, they may be of value to others concerned with submarine equipment or operation. This paper reports a portion of the work performed under U. S. Navy contract NObs-56355; a part of the recordings were made in cooperation with the U. S. Navy Electronics Laboratory, San Diego, California.
An Ultrasonic Shutter
Authors: Darner Charles L. , Bobber Robert J.
Published: September 2005

The nearly total transmission of a sound wave through a plate having a thickness of an even number of quarter-wavelengths, and the nearly total reflection from the plate when the thickness is an odd number of quarter-waves, was established mathematically by Rayleigh nearly a century ago. This basic theory becomes complex when applied to some types of piezoelectric plates with their combined electrical and mechanical resonant and antiresonant frequencies. A simplified electromechanical analogy of this type plate is presented to explain how the introduction of a variable electrical load can control the frequency of optimum sound transmission through the plate by varying its effective mechanical impedance. The use of a plate of barium titanate (resonant at 1100 kilocycles) in a water channel demonstrates how the intensity of a sound beam may be controlled over a 40-decibel range by the use of a variable inductance across the plate electrodes. A carbon microphone wired directly to the plate electrodes and affording only passive control permits amplitude modulation of the sound carrier passing through the plate.
Analysis of Ultrasonic Absorption from Double Relaxations
Authors: Beyer Robert T.
Published: September 2005

The appearance of more than one peak in the curves of sound absorption per wavelength vs frequency for several liquids and solutions suggests the need for a more detailed examination of the calculated absorption to be expected from excitation to more than one level. Earlier work on the problem is reviewed and calculations are presented for the relationship between the maximum absorption per wavelength and relaxation frequency on the one hand and the various specific reaction rates and energy levels on the other.
Ultrasonic-Wave Velocity and Attenuation in Liquid Crystal Compounds
Authors: Hoyer W. A. , Nolle A. W.
Published: September 2005

The velocity and absorption of ultrasonic waves in two liquid-crystal compounds, para-azoxyanisole and cholesterol benzoate, were measured at frequencies from 0.5 mc to 6 mc. The absorption coefficient has an inverse second-power frequency dependence for the lower frequencies, but rises less rapidly at the higher frequencies. In the neighborhood of the isotropic-anisotropic liquid transition, the velocity has a sharp minimum as a function of temperature, and the absorption has a large maximum. The velocity in this region shows slight frequency dependence. The absorption in the transition region greatly exceeds that predicted from the shear viscosity. The behaviors of the velocity and absorption are attributed to a structural compressibility with associated relaxation effects. The structural compressibility is connected with the phenomenon of heterophase fluctuations described by Frenkel, and is not describable by a simple two-state model. The temperature dependence of the structural compressibility is explained in terms of Frenkel's theory.
The Velocity and Absorption of Ultrasonic Waves in Liquids under Pressure
Authors: Mifsud J. F. , Nolle A. W.
Published: September 2005

The velocity and attenuation of ultrasonic waves in carbon tetrachloride, carbon disulfide, and benzene are measured as a function of pressure for a range from 1 to 1400 atmospheres. The frequencies used varied from 2 mc to 10 mc and at least two temperatures in the range from 0°C to 70°C were used for each liquid. The velocity and attenuation were obtained by a comparison of the amplitudes and arrival times of two reflected pulsed signals, initiated by the same source, but traversing paths of different length. The absorption per wavelength decreases continuously with increasing pressure for all three liquids. The experimental results will be analyzed in terms of the various mechanisms which have been proposed to explain absorption in excess of that attributed to shear viscosity.
On the Evaluation of Concert Halls and Music Rooms
Authors: Kessler John A.
Published: September 2005

Presently available design criteria relating physical properties to personal judgments are inadequate to permit the use of physical measurements alone to evaluate the merits of a concert hall or music room. It is therefore necessary to review the applicability of survey questionnaires for this purpose, until more appropriate psychophysical techniques can be developed. This paper presents an intercomparison of several questionnaire techniques and discusses the relative advantages and disadvantages of various evaluation methods employed up to the present time.
Comparison of Objective and Subjective Observations on Music Rooms
Authors: Fitzgerald R. Bernard , Blankenship Joseph
Published: September 2005

A comparison of the physical and acoustic measurements of several music rooms at The University of Texas will be made with the subjective reactions of the musicians working in these spaces. Emphasis will be placed on the musicians' viewpoint of desirable room characteristics.
The Field of a Noise Source above an Infinite Plane
Authors: Franken Peter , Oleson Stanley , Ingard Uno
Published: September 2005

The sound field from a random noise source above ground as measured by a receiver with finite band width is studied both theoretically and experimentally. For simplicity, only the far field has been considered. The special case of a perfectly reflecting plane is discussed first, and nondimensional curves are presented of sound pressure level versus distance for two different receiver band widths. The analysis is then extended to a plane of arbitrary normal impedance, and pressure level versus distance curves are given for typical field operating conditions.
The Noise-Cancelling Headset—An Active Ear Defender
Authors: Simshauser Elvin D. , Hawley Mones E.
Published: September 2005

The purpose of this device is to reduce ambient noise at the ear by using a headset to generate a sound pressure equal in magnitude and opposite in phase to the noise. This paper reports the results of pure-tone experiments. A microphone was mounted on each earphone of a conventional military headset. A two-channel system was used in which the signal from each microphone was passed through an amplifier and a phase-shifting network and was then applied to its earphone. The subject wore the headset in a pure-tone field and adjusted the amplifications and phase shifts for minimum loudness. The signal produced by each earphone was then substantially equal in magnitude and opposite in phase to the sound coming through and under its earcap. The proper amplification and phase shift are frequency-dependent and vary among subjects. Eight complete measurements were made on two subjects. The mean values of the two parameters were computed for each frequency. Calculations indicate that a device having these mean characteristics would provide a noise reduction between 100 and 1200 cps that averages 10 db more than is provided by the earcap alone.
Automatic Extraction of Formant Frequencies from Continuous Speech
Authors: Flanagan James L.
Published: September 2005

An electronic apparatus for extracting formant frequencies from continuous speech is described. The short-time speech frequency spectrum or its second derivative with respect to frequency is sampled rapidly and periodically by scanning the outputs of a thirty-six channel filter set. The time function thus produced is analyzed to determine the spectral maxima or formants. The points in time at which maxima occur are separated and converted into voltages by a further sampling and smoothing operation. These voltage outputs correspond to the formant frequencies as functions of time. A vowel segmenting circuit is incorporated in the input to restrict analysis to the vocalic portions of the input speech if desired. Some preliminary results are presented.
The Localization of the Sound from a Single Source
Authors: Sandel T. T.
Published: September 2005

Experiments were conducted to measure the accuracy of localization of sound from single loudspeakers. The results show greater accuracy than heretofore reported. A distinction was made in the present study between bias errors and random errors and it will be shown that the two types of error are different functions of frequency. The results indicate a high accuracy of localization at frequencies below about 1200 cps, and support the conclusion drawn from other studies, that localization of low-frequency sound is largely dependent upon interaural time differences. At frequencies above 2000 cps, where only differences of interaural intensity can provide a basis for localization, errors are larger and the results obscure. Neither the measured pressure-differences at the two ears, nor the subject's audiogram can provide the basis for an accurate prediction of where he will localize the sound, although data from one subject with a large hearing loss in one ear at 3000 cps, shows the expected bias in the direction of the better ear at that frequency.
Some Related Subjective and Objective Measurements on Cornet Tones
Authors: Kent Earle L.
Published: September 2005

In collaboration with a committee from the College Band Directors Association, studies were made to determine if standards could be established regarding acceptable and unacceptable cornet tones. Tests were conducted to determine degree of agreement among musicians as to the classification of tones if possible. Harmonic analyses of the contents of these tones were made to determine the physical characteristic differences between tones in the two major classifications. A variety of tones produced by man-blown and machine-blown cornets were studied to determine the primary essentials of producing acceptable or unacceptable tones. A preliminary report on the results of these studies will be presented using three-dimensional representations of tones, slides, and tape recordings.
Fundamental Acoustics of Electronic Organ Tone Radiation
Authors: Martin Daniel W.
Published: September 2005

The acoustical effects achieved and the techniques used in the radiation of organ tone are quite different from the conventional effects and practices of public-address sound systems. For the latter, point-source radiation with high uniform directivity and a minimum of reverberation are sought, in general, for the creation of the illusion of “presence” of the original sound source. However, in organ music the sound sources are distributed in space. Individually the sources are quite complex in their directional pattern, and collectively their sound distribution is diffuse. This is especially true in those typical cases where the tone sources are enclosed in an organ chamber or box or are installed in a highly reverberant environment. Another distinctive feature of organ tone radiation systems is the relative importance of the octave below 60 cps, a frequency range frequently neglected even in sound systems designed for general musical purposes. In this paper the design principles of organ tone chambers and the types of organ tone cabinets in use are reviewed. Organ installation principles and examples of their application are given. The implication of these principles with regard to optimum reverberation for church auditoriums is discussed.
Calibration of Test Records by Interference Patterns
Authors: Bauer B. B.
Published: September 2005

This investigation stemmed from an attempt to explain the nature of the dispersion occurring when a beam of light is reflected from a test record. Examination through color filters revealed the existence of two distinct patterns of lines which the author has termed the A and B lines. A-lines are identified with the frequency and B lines with the amplitude of the recorded sound. B-line patterns can be readily related to the modulation velocity and lead to an accurate determination of the recorded velocity characteristic of a test record. Characteristics by conventional light patterns are found to be in error owing to diffraction of light at the edges of the pattern. This error is estimated by subtracting the modulation velocity by B-line patterns from that determined by conventional light pattern techniques, and it is found to be approximately equal to the calculated diffraction error from assumed triangular wavelets. Calibrations of representative test records by B-line patterns are in much better agreement than those by conventional light patterns with the calibrations obtained by the variable-speed turn-table technique, especially when the latter are corrected by the estimated amount of error owing to the elastic deformation of the modulated groove by the pickup load.
An Improved Blast Pressure Gauge for Shock Measurements
Authors: Fitzgerald James W. , Marks Spence T.
Published: September 2005

The measurement of transient pressures associated with blast or shock waves propagated in gaseous media imposes stringent requirements on transducer designs that are not usually encountered in most electroacoustic devices. Reasonably accurate reproduction of the shock pressure transient requires a flat response from a fraction of a cps to 100 kcps or better. Pressure peaks encountered may be several hundreds or even thousands of psi. Field testing conditions are rugged and pyroelectric effects due to compressive heating of the shock front must be avoided. Superimposed on these difficulties are perturbations of the local pressure field due to interaction of the gage and its housing with the oncoming shock wave. Most of these difficulties can be overcome through the use of a “streamlined” housing, and through measuring the transverse or “side-on” pressure rather than “face-on” The electroacoustic design and aerodynamic shape of several gages have been studied, both in a shock tube, and in the field, using spherical pentolite charges. A gauge design based on the use of a barium titanate cylinder mounted in, but electrically and mechanically isolated from, a pencil-shaped, streamlined housing can reproduce a theoretical shock within about 2 percent. The sensitive element is sealed and pyroelectric response avoided by means of a bonded Neoprene sheath. Shadow photographs showing the interaction of a shock with several different gauge housings, as well as calibration data, are to be presented.
Differentiation in the Mating Call of Anuran Amphibians
Authors: Blair W. Frank
Published: September 2005

Measurement and comparison of mating calls in anuran amphibians is desirable because differences in call are important mechanisms that help to prevent free interbreeding of closely related species. Calls have been recorded and analyzed on a Sona-Graph for some 27 species representing 10 genera of amphibians. Calls vary individually in natural populations; they vary geographically within species populations; and they differ between species. Closely related species which occur together differ conspicuously from one another in at least one or two variables, such as emphasized frequency or duration.
Normal Zone Sound in Shadow Problems
Authors: Mintzer David
Published: September 2005

Pekeris' integral solutions for the shadow zone problem are used as sound function and Green's function in a Helmholtz-type surface integral. The resulting integral may be approximated to give the solution for the region between source and receiver. Comparison will be made with iso-velocity structures.
Phase Velocities of Waves in a Thin Cylindrical Shell
Authors: Smith P. W.
Published: September 2005

In the course of an investigation of the transmission of sound through a thin cylindrical shell, calculations have yielded the phase velocities and displacement characteristics of progressive waves in the wall of a thin cylindrical shell of an elastic material. The waves considered have a dependence upon the angular coordinate of the type cosnφ, where n is an integer, and a dependence upon the axial coordinate of the type coskz. These standing waves are interpreted, alternatively, as fully progressive waves traveling in a helical direction in the wall of the cylinder with a phase front which is the normal helix.
Sound Pressure Spectra of a Muted Cornet
Authors: Ancell J. E.
Published: September 2005

The acoustic spectra of a cornet have been measured with the instrument equipped with several mutes of the type used in dance orchestra work. Data will be presented showing the sound pressure levels of the first ten to fifteen overtones of the instrument when fitted with each of the mutes. The instrument was blown naturally by a cornetist, with an attempt to obtain a normal characteristic tone for each mute. The sound spectrum of the muted instrument will be compared to that of the open or unmuted instrument. The mutes tend to exhibit the same formant or frequency response for several different notes, indicating resonance phenomena in the acoustic networks. The measurements have been made by playing the instrument in a dead room and recording the sound on tape with a high quality condenser microphone and magnetic tape recorder. The sounds were then analyzed by playback through a heterodyne type wave analyzer.
Influence of Phase Coherence upon the Pitch of Complex, Periodic Sounds
Authors: Licklider J. C. R.
Published: September 2005

The aim of the paper is to resolve a conflict between observations. In the observations, the stimulus is a complex, periodic wave consisting only of high-frequency harmonics of a “missing” fundamental. Schouten found that a low subjective pitch was heard even when a search tone revealed no fundamental. And, recently, low pitch has been heard despite the presence of strong low-frequency masking noise. Yet, using five independently generated harmonics, Hoogland found that the low pitch emerged only when the sound intensity was high and nonlinear distortion produced an audible fundamental. The conflict is resolved by taking into account the phase pattern of the harmonics, which Hoogland did not control. When one adjusts the phases haphazardly, he often duplicates Hoogland's finding. But, when he adjusts them in such a way that all the harmonics come into their maxima at the same time and in sum produce an impulsive wave form, Schouten's low-pitched “residue” is clearly heard. Hoogland's observations thus fall neatly into line with composite place-periodicity theory.
Spectral Properties of Stop and Fricative Consonants
Authors: Hughes George W. , Halle Morris
Published: September 2005

Equipment was assembled and a procedure was developed for the measurement of power spectra of consonants. Detailed power spectra as well as measurements of grosser spectral properties were made on a fairly large sample of English and Russian stops and fricatives. Special criteria were developed for the evaluation of the data obtained. Possibilities of utilizing the data automatic recognition were considered.
On an Ultrasonic Absorption Theory in Liquids
Authors: Beyer Robert T. , Bloch Gene E.
Published: September 2005

In 1950, Gierer and Wirtz advanced a theory of ultrasonic absorption in liquids that attributed virtually all excess absorption to processes involving dislocation migrations in quasi-crystalline liquids. In particular they deduced an expression for the temperature dependence of α involving only one acoustically determined parameter. Use has been made of this theory to calculate the mean temperature coefficient of the absorption coefficient for a number of liquids for which the appropriate physical data were available. In all cases, the agreement with the experimentally determined temperature dependence is very poor, and in general the correct sign for the coefficient is not predicted by the theory. Since the theory was supposed to account for absorption in both associated liquids (negative temperature coefficient) and nonassociated liquids (positive temperature coefficient), the results suggest that the proposed theory is not acceptable. This work was supported in part by the Office of Naval Research.
Effect of Pressure on Ultrasonic Relaxation
Authors: Carnevale E. H. , Kendall P. A. , Litovitz T. A.
Published: September 2005

Measurements of ultrasonic absorption have been made in an associated and a nonassociated liquid as a function of hydrostatic pressure in order to compare the pressure dependence of the relaxation phenomena involved. Absorption data were obtained in carbon bisulfide (non-associated) at frequencies from 15 to 65 mc, up to pressures of 1000 kg/cm2 and at a temperature of −29°C. At this temperature and at atmospheric pressure the data could be fitted by assuming a relaxation frequency of 44.6 mc. As the pressure was raised the absorption coefficient decreased and the relaxation frequency increased. At 1000 kg/cm2 the relaxation frequency was over 65 mc. Absorption measurements in glycerol at 0°C over the same frequency and pressure range showed that the relaxation frequency decreased from about 55 to 43 mc as the pressure is raised. These results are in accord with the concept that different mechanisms of excess sound absorption exist in these two liquids.
Theory of a Nonresonant Single-Crystal Ultrasonic Interferometer for Liquids
Authors: Greenspan Martin
Published: September 2005

The ordinary single-crystal interferometer has been used by many investigators for attenuation measurements in liquids. The accuracy is poor because the peaks and dips have a complicated dependence on attenuation, reflection coefficient at the reflector, and parallelism of crystal and reflector. It will be shown that if the crystal is connected to an appropriate circuit, the voltage on the crystal will have a complex exponential dependence on the crystal-to-reflector distance. That is, the amplitude will fall off exponentially, and the phase will shift linearly, with path length; the reflection coefficient does not affect the results. The advantages of this arrangement are (a) the attenuation is measured directly, and (b) good velocity measurements can be made on liquids even if the attenuation is so high that the dips that are gotten with the conventional arrangement are few and poorly defined.
Ultrasound in Neurology
Authors: Fry William J.
Published: September 2005

The ultrasonic focused beam method of producing selective, precisely localized, quantitatively reproducible lesions in the brains of experimental animals is illustrated. The acoustic calibration procedure, the surgical preparation of the animal, and the technique of irradiation are demonstrated in this motion picture. The complete instrumentation setup is shown in operation. A lesion is produced in the depths of the brain of a monkey. This technique, which is currently being used in studies of brain structure and function, was developed at the Bioacoustics Laboratory of the University of Illinois. A lesion of practically any desired size (as small as one millimeter in diameter) and shape can be produced at any specified location in the brain without disturbance of intervening tissue and without disruption of blood vessels even within the site of the lesion. In addition, it is possible by proper choice of the dosage to irreversibly affect fiber tracts (white matte) without destroying surrounding or neighboring nerve cell bodies (gray matte)r which receive the same dosage of radiation. This means that in producing lesions in white matter it is readily possible to retain the boundary between white matter and neighboring gray matter as the boundary of a lesion produced by ultrasound. Examples of ultrasonically produced lesions in both white and gray matter of a variety of sizes and shapes and at various depths in the brain will be illustrated by stained tissue sections. This procedure represents a significant advance over other methods of producing lesions which have been used up to the present time. The method has considerable potential value for neurosurgery.The support, in this research field, of the Physiology Branch of the Office of Naval Research is acknowledged.
Biological Effects of Sound in Mice
Authors: Anthony Adam
Published: September 2005

Local and systemic changes were studied in hairless mice following irradiation of the integument with high intensity airborne sound. Comparisons were made between effects of subthermogenic (without skin heating) and thermogenic (skin heating) sound levels. Criteria, other than morphological, used in skin analyses included cytochemical examination of skin lipids, glycogen, PAS-reactive substances, and alkaline phosphatase. Failure to induce injury or any change in skin cytochemistry after local skin irradiation daily for three months with subthermogenic sound (18 kc, 150 db) indicated that direct effects of sound are negligible at these levels. The inflammatory response of skins exposed to higher sound levels (20 kc, 160–168 db) was found to result from local absorption of sound energy and its conversion into heat. Analysis of systemic effects included studies of changes in adrenal, hemopoietic, and reproductive organs. Skin treatment with subthermogenic sound produced no appreciable systemic response. A marked systemic reaction, however, always accompanied sound induced skin burns. Additional studies on effects of auditory stimulation on adrenals and eosinophils showed that prolonged exposure of mice to loud noise fields (10–20 kc, 110 db) proved to elicit only a mild systemic response. This work was sponsored in part by the Aero Medical Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio, under contract No. AF 33(616)-2505
Acoustic Absorption of Haired and Hairless Mice
Authors: Farwell Robert W. , Ackerman Eugene
Published: September 2005

The measurements reported here were carried out to check those calculated from the heating of mice in the field of the Penn State siren [Danner, Ackerman, and Frings, J. Acoust. Soc. Am. 26, 731–39 (1954)]. In the present experiments the mice were placed in individual containers in a white noise field within a cylindrical reverberant chamber. Reverberation times were measured using filtered portions of the output of a 633 A microphone placed within the chamber. Care was taken to assure that the absorption coefficients measured were not a function of the number of mice in the chamber. In agreement with the siren measurements these reverberation time measurements showed an increase of the acoustic absorption with increasing frequency for both haired and hairless mice; the numerical values of the absorption coefficient from close to 100% for haired mice at 20 kc down to less than 10% for hairless mice at 6 kc showed agreement within the limits of experimental error. This work was supported in part by USAF contract No. 33(038)-786.
Effect of Short Times of Exposure to Speaker's Voice upon Listener Reception
Authors: Peters Robert W.
Published: September 2005

Listener reception of intelligibility test materials was studied as a function of the amount of prior exposure to the speaker's voice. Separate evaluations were made for listening in quiet and listening in noise. The procedure for each evaluation involved one group of listeners receiving no exposure to the speakers' voices, a second group receiving two-minute exposure, a third group receiving four-minute exposure, and a fourth group receiving eight-minute exposure to the recorded voices of each of the four speakers who read intelligibility test words. Mean reception values for lisening in quiet were significantly higher for the listening groups exposed to the speakers' voices two, four, or eight minutes than was the mean reception value for the listening group which was not exposed to the speakers' voices. For listening in noise, the mean reception value was significantly higher only for the listening group exposed to the speakers' voices for eight minutes as compared to the mean reception values for the listening groups who were not exposed to the speakers' voices or who were exposed to the speakers' voices for two or four minutes. Mean values of listener reception did not follow the same trend for each speaker.
Consonant and Vowel Influences upon Judged Voice Quality of Syllables
Authors: Brubaker R. S. , Dolpheide W. R.
Published: September 2005

Generally quality defects of voice are presented as “independent of phonemes,” i.e., the sounds being articulated, and as the result of the unique wave composition of voice defective speakers. The purpose of this study was to investigate a voice quality disorder while varying specific speech sounds. The subjects with hoarse voice quality were selected to speak syllables in which the phonetic elements were controlled. The utterances were recorded and played to trained judges who rated the degree of hoarseness present in the utterance. Statistical analysis (analysis of variance) of the data collected indicated that significant differences in voice quality do exist as some function of the vowel and consonant content of the syllable. Further analysis (t test) reveals that high vowels result in significantly less judged voice quality defectiveness than the low vowels. Front-back vowel comparisons were generally less indicative of real differences. Of the consonants, it is seen that the voiceless, or whispered, plosives, such as t, p, and k, contribute to a judgment of less defectiveness than the other consonants. Generally, the findings are that voiceless consonants are judged less defective than voiced consonants, fricatives increase the judgment of hoarseness, the manner of articulation of consonants is related to perceived voice quality and place of articulation appears to have only slight correlation. In general the results suggest that the degree of perceived voice quality may be related in part to the secondary acoustic characteristics of syllables, such as duration, frequency, and intensity. Such investigations are now in progress.
Effects of Vocal Effort on Intelligibility
Authors: Pickett J. M.
Published: September 2005

Changes in speech intelligibility which may occur when the talker is forced to lower or raise his voice are of considerable practical and theoretical interest. We consider here the intelligibility of speech produced by eight different amounts of vocal effort ranging from the weakest voiced whisper to the loudest possible shout (a range of speech intensities from 36 to 90 db one meter from the lips). PB-word intelligibility of five male talkers was measured at three signal-to-noise ratios for each level of vocal effort. The noise was random and had an over-all intensity of 70 db. The results show less than 5% deterioration from normal intelligibility over the range from a “low voice” to a “very loud voice” (48 to 78 db at one meter). Beyond these points intelligibility deteriorates abruptly and in a linear relation to the decibel change in vocal intensity. For whispering the rate is about 5% per db and for shouting it is 1.5 to 3%. The deterioration of intelligibility with louder shouting is such that the noise level tolerable for constant intelligibility remains constant above a vocal level of about 78 db at one meter. The extremes of vocal effort are shown to produce changes in vowel confusions and in the distribution of errors over the parts of the syllable.
The Effect of Attenuating One Channel of a Dichotic Circuit upon the Word Reception of Dual Messages
Authors: Tolhurst Gilbert C. , Peters Robert W.
Published: September 2005

Dichotic listener reception of simultaneous messages was studied as a function of attenuation of the signal level of one of the messages. Listeners, serving in panels, received two messages simultaneously through dichotic headset circuits. The signal level of one message was attenuated in five steps of three decibels each relative to the level of the other message. The simultaneous messages were groupings from the multiple-choice intelligibility tests. Listeners heard the messages under conditions of quiet and noise. The noise was simulated aircraft noise. The general effect upon listener reception of attenuating one of two simultaneous messages was to decrease the reception of the attenuated signal and increase the reception of the unattenuated signal. This effect was more pronounced in noise than in quiet, and yielded linear functions under noise conditions but nonlinear functions in quiet.
Research on Word-Spelling Alphabets for Military and Civil Use
Authors: Moser Henry M.
Published: September 2005

Results of continuous and extended testing with trained and naive listeners on several word-spelling alphabets are presented. Methods for analysis of internal structure of limited word sets are applied to arrive at an optimum alphabet for international aviation use. The effects of listener pre- and post-training attitudes are evaluated for effects on intelligibility scores. Effects of confidence and user inhibition for better and poorer alphabets are shown. The above work was carried out under contract with Operational Applications Laboratory, Washington, D. C.
Acoustic Streaming in a Guided Traveling Wave
Authors: Medwin Herman , Fisher Fred
Published: September 2005

A study has been made of the streaming caused when a guided traveling wave is sent through a closed, gas-filled tube. Starting with an approximate expression for the acoustic particle velocity in such a tube, it is shown that the observed streaming can be ascribed to the surface sources of vorticity which are generated in the acoustic boundary layer next to the side walls of the tube. The volume source of vorticity described by C. Eckart [Phys. Rev. 73, 68 (1948)] and H. Medwin and I. Rodnick [J. Acoust. Soc. Am. 25, 538 (1953)] is negligible in this ease. The 2-in. i.d. closed steel tube used for the experiment was approximately 20 ft in length, with the last 10 ft acoustically terminated by a slowly tapering wedge of glass wool. An 8-in. long Lucite section in the tube allowed binocular microscope observation of suspended tobacco smoke or Lycopodium particles, used as tracers to determine the gas motion. Comparison of theoretical predictions and experimental observations will be made. This work was partially supported by the U. S. Office of Naval Research, Contract N6onr 27507.
Acoustic Streaming in the Vicinity of a Sphere
Authors: Lane Carlton
Published: September 2005

Recent studies have led to a satisfactory understanding of the details of acoustic streaming in the vicinity of a cylinder [see Holtsmark, Johnsen, Sikkeland, and Skavlem, J. Acoust. Soc. Am. 26, 26 (1954); Raney, Corelli, and Westervelt, ibid. 26, 1006 (1954); S. Skavlem and S. Tjötta, ibid. 27, 27 (1955)]. Similar studies have now been completed for a sphere. Theory and experiment are in essential agreement and show that the steady flow around a sphere is very like that obtained around a cylinder. Curves of the steady flow boundary layer thickness will be presented. The streamlines of the steady flow around a sphere have a different shape from those obtained for a cylinder and these features will be illustrated with slides. This work was supported by the U. S. Air Force, Wright Air Development Center.
Nonloading Vibration Pickup Utilizing an Ultrasonic Carrier Beam
Authors: Hardy H. C. , Hall H. H. , Callaway D. B. , Schover D. S.
Published: September 2005

A vibration pickup has been developed whose operation depends on Doppler frequency shift in an ultrasonic beam reflected from a vibrating surface. It is a true velocity pickup with no frequency distortion, and since it operates with frequency modulation, its calibration does not depend on the distance between the pickup and the surface being measured. One model has been developed for use in measuring vibration of airborne equipment. The unit is portable and approximately the size of a sound level meter. This paper will discuss the mechanical and electrical components. The source and receiving crystals are barium titanate operating at 110 kc. The beam width is approximately 15 degrees. The unit can be operated at distances between 2 inches and 6 feet. The frequency response is flat between 0 and 700 cps. The sensitivity is approximately 0.01 in. sec−1 Care has to be taken to prevent unmodulated carrier from mixing electrically or mechanically into the frequency-modulated beam, since this causes a minor distortion. The unit can be used for measurement of the vibration of such unusual objects as wires, meter needles, liquid surfaces, loudspeaker cones and other very light mechanical systems. It is very useful in readily determining the positions on a large vibrating object which have the largest amplitudes. For observation of a very small area, the surface may be covered with a mechanical mask consisting of a simple perforation in a sheet of absorbing material.
Study of Limitations on Rapid Signal Analysis
Authors: Corliss Edith L. R.
Published: September 2005

If a frequency analysis of a signal is to be made over a brief time interval with a linear series-resonant system, the maximum Q (figure of merit) can be specified from the requirement that the system output change just perceptibly over the time interval. This limiting value of Q is found by considering the signal-to-noise ratio inherent in the signal as the resolution limit in the discrimination of power level. Corresponding to this “least count” of power and limiting value of Q, there is a limiting difference in frequency that can be discriminated. The relationship between the “least count” in power, limiting discrimination in frequency, and time interval of analysis resembles in form the Heisenberg uncertainty relationship. This work is sponsored by the Office of Basic Instrumentation, National Bureau of Standards.
Measured Amplitude Distribution of Noise Voltages
Authors: Tu L. Y. , Raymond R. C.
Published: September 2005

In this paper a brief theory is given about the amplitude and probability density distribution of a narrow band shot noise. It is found that the probability density distribution follows the normal law and the amplitude distribution is the integral of the normal function. However, if the noise voltage is applied across a nonlinear impedance such as a type 1N34 crystal diode, both the amplitude and probability density distributions are changed. The change depends upon the current-voltage characteristic of the nonlinear impedance. An experimental method is described which can be used to measure the amplitude and the probability density distribution. The noise source was a photomultiplier tube followed by a narrow band amplifier centered at 16 kc. The measured results agree with that obtained by calculations.