bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption of Sound in Air in the Audio-Frequency Range
Authors: Harris Cyril M.
Published: September 2005

This paper concerning the absorption of sound in air as a function of humidity presents new data in the frequency range between 2000 and 12 500 cps. These data are for air at normal atmospheric pressure and at a temperature of 20°C. First the measurement system is described. Then the data are compared with theory and with other published results in the same frequency range. The data also are presented in a graphical form that is particularly convenient for use in computing the contribution of air absorption to the total absorption of sound in a room. In this form the data are plotted directly in terms of the quantity 4mV as a function of frequency and humidity, where m is the attenuation coefficient and V is the volume of the room.
Circumferential Waves in Thin-Walled Air-Filled Cylinders in Water
Authors: Diercks K. J. , Goldsberry T. G. , Horton C. W.
Published: September 2005

Experimental measurements of the velocity and the rate of decay of circumferential waves traveling within the shells of thin-walled air-filled metallic cylinders in water have been made. Outside diameters of 3.5, 5.5, 8.5, and 12 in. were studied. Ratios of d (shell thickness) to λ (wavelength) of 0.01 to 0.97 were obtained over a frequency range of 80 to 300 kc. The measured velocities are compared with the theoretical velocities for the longitudinal and flexural modes in infinite plates. The agreement obtained defines the nature of the waves measured and supports the analogy of an infinite plate applied to the cylindrical surfaces. Empirical relations describing the decay measurements are given.
Correlation of Signals Having a Linear Delay
Authors: Remley Winslow R.
Published: September 2005

The output signal of a cross-correlation detector is calculated for a general signal spectrum and integration time under the assumption of a constant delay rate but otherwise ideal conditions. The delay-rate degradation of the output signal is shown to be equivalent to passing the ideal cross-correlation function through a low-pass filter. The output signal-to-noise ratio is evaluated for the threshold case by introducing straight-forward noise statistics. Subsequently, low-pass rectangular signal spectra are assumed, and the output signal-to-noise ratios for various delay rates and time-bandwidth products are numerically evaluated. For zero delay rates, the output signal-to-noise ratio is a linear function of the time-bandwidth product, but for nonzero delay rates, optimum points exist.
Logarithmic-Periodic Underwater Sound Projector
Authors: Walther Klaus
Published: September 2005

In this paper the performance of a logarithmic-periodic projector for underwater sound is described. The projector consists of a barium titanate cylinder driving a logarithmic-periodic mechanical waveguide structure of approximately 12-in. length (material: brass). The mechanical waveguide has the form of a disk-loaded cylindrical rod of variable cross section in which the disk diameters expand with a linear taper along the axis. The acoustic-power output from the projector stays constant within ±1.5 dB over a frequency range from 38.2 to 130 kc. Electroacoustic efficiencies ηea larger than 60% are obtained over nearly this entire frequency range; ηea≧70% is realized in the frequency range between 41 and 72 kc. Details of the acoustical logarithmic-periodic operation are discussed. Analogies and differences in comparison with the well-known logarithmic-periodic antennas for electromagnetic waves are pointed out.
Statistical Detection of Errors in Microphone Calibrations
Authors: Embleton T. F. W. , Dagg I. R.
Published: September 2005

Microphone sensitivities obtained by reciprocity calibration depend on the measurements of several quantities, e.g., volume of a coupler, electrical capacitance, etc. Errors in the best values of these parameters are systematic and undetectable unless an alternative method of calibration is used. A number of microphones of various types have been measured by both reciprocity and pistonphone methods, and the individual pairs of sensitivities are studied statistically to determine the probable existence and amount of the following classes of errors: (a) those related to constants of the pistonphone or reciprocity apparatus, which affect all microphones, (b) those in any coupler used for the reciprocity calibrations, which affect only the microphones used with this coupler, and (c) those associated with individual microphones.
Masking of Tones by Noise for the Cat
Authors: Watson Charles S.
Published: September 2005

Masked thresholds were obtained by the method of behavioral audiometry fur each of four cats at eleven frequencies over the range from 125 to 16 000 cps. Bands of noise, which were approximately one to two octaves wide, as well as two broad bands of noise, were used as masking stimuli. Experiment I shows that the function relating masking to noise level has exactly the same form for cat as for man; the signal to-noise ratios, however, are greater for cat than for man. The critical ratio (K) is defined as the ratio of signal power to spectrum level at the masked threshold. The function relating K to frequency was determined for cat in experiment II; tiffs function parallels that for man, but lies 4 to 5 dB above it at most frequencies. The masking data for the cat are shown to be consistent with measurements of frequency discrimination for this animal.
Acoustic Siren for Generating Wide-Band Noise
Authors: Cole J. N. , Powell R. G. , Oestreicher H. L. , von Gierke H. E.
Published: September 2005

Principle, theory, and an experimental development program for a new type of siren, capable of generating wide-band noise, are discussed with special emphasis on its application to the economic and realistic simulation of high-intensity jet and rocket-noise environments. In contrast to conventional sirens with a single rotor, this wide-band noise siren uses a series of overlapping, slotted rotors rotating at different speeds to produce the modulation of an air flow through a nozzle. The sound field generated by this siren can, mathematically, best be approximated by an “almost periodic” function; that is, a function whose spectrum is a line spectrum but with infinitely many lines in each interval of frequency. A series for the power spectrum can be derived and used to guide the design. For most practical purposes, the resulting acoustic field radiated by the siren represents random noise. Data on acoustic power, spectrum, efficiency of noise generation, and fine structure of the noise for various experimental siren types are presented. The potential value of this principle for large-scale installations (sonic fatigue and missile-component testing and bio-acoustic applications) is evaluated.
Resolution of Pressure in Turbulence
Authors: Corcos G. M.
Published: September 2005

The finite size of a transducer-sensing element limits its space resolution of a pressure field associated with a local turbulent flow. Such pressure fields are translated at a speed comparable to the characteristic velocity of the flow. Consequently, a lack of resolution in space causes an apparent inability to resolve in time. This problem—an example of the mapping of a random function of several variables by a linear operator—is examined here. With the help of a formalism which has been previously discussed and of some recent experimental information about the spatial structure of turbulent pressure fields in boundary layers, the mapping or distortion of statistical quantities associated with the second-order moments of the pressure field is given. The attenuation of the frequency spectral density and of the cross-spectral density is given explicitly in table form and in asymptotic form. The numerical results indicate that the attenuation caused by the finite size of transducers is generally more severe than previous computations had suggested, mainly because the lateral correlation of pressure is highly frequency-dependent, a typical turbulent pressure-wave component being inclined to the stream direction at roughly 45 degrees.

The results are applied to an evaluation of contemporary measurements of turbulent pressure fields in shear flows. It is shown that the transducer size used introduces undesirable large errors in these measurements, which lead to doubts even about the magnitude of the intensity of turbulent pressure fluctuations.

Asymptotic formulas for the attenuation of large transducers are given which yield estimates of the degree to which a flush-mounted sonar receiver immersed in a boundary layer is able to reject the background noise provided by turbulent pressure fluctuations.
Word-Frequency Effect and Errors in the Perception of Speech
Authors: Savin Harris B.
Published: September 2005

The following interpretation of the word frequency effect—the tendency for common words to be perceived correctly at much lower speech to-noise ratios than uncommon words—was proposed and verified experimentally. When a stimulus word is only a few decibels below its intelligibility threshold, many of its features—the number of syllables, for example—are still perceived correctly. If enough such features are heard, then only a small number of English words will be consistent with them. Subjects' incorrect responses will be taken from that small set of words, and furthermore they will usually be the relatively common words in the set. If the stimulus is an uncommon word and there are common English words that are phonetically quite similar to it, then these common words will usually be given as (incorrect) responses except at quite high speech-to noise ratios. This interpretation is confirmed by an analysis of errors in an articulation test. The results show that all subjects tend to give the same incorrect responses, that these incorrect responses are usually more common than the stimuli to which they were given, and that, when a word is not confused with another in this way, its threshold is relatively low regardless of its frequency of occurrence in English usage.
Computer Technique for High-Speed Extraction of Speech Parameters
Authors: Weiss Mark R. , Harris Cyril M.
Published: September 2005

An automatic system is described for high-speed extraction of speech parameters. Data obtained from a high-resolution, real-time spectrum analyzer of the correlation type are converted to digital format and processed by a large-scale computer. An effective program has been written in FORTRAN and FAP languages for the extraction of spectrum power, amplitudes and frequencies of the first three formants, and other functions of these parameters. Typical output data are presented.
Elastic Constants of Compound Semiconductors—ZnS, PbTe, GaSb
Authors: Einspruch Norman G. , Manning Robert J.
Published: September 2005

The elastic constants of three compound semiconductors, ZnS, PbTe, and GaSb, were measured at 29°C using the ultrasonic pulse-echo technique. The constants are found to be

c 11 c12 c44

(in units of 1011 dyn cm−2)

ZnS 9.76 5.90 4.51

PbTe 10.72 0.768 1.300

GaSb 8.97 4.12 4.48.

These results are compared with previously reported measurements made by other techniques.
Some Acoustical Characteristics of Underwater Explosions of Hydrogen-Oxygen Mixtures
Authors: Leroy C. C. , Parkes D. J. , Sirovich E. M.
Published: September 2005

The acoustic characteristics of a hydrogen-oxygen explosive mixture are investigated in an attempt to find a substitute for solid explosives (e.g., TNT) which will achieve a simple underwater acoustic pulse uncomplicated by bubble oscillations. Data are shown relating the intensity and form of the acoustic signal to the proportions and amounts of gas mixture, point of ignition, hydrostatic pressure, length to-diameter ratios of chambers, and various chamber appendages and terminations. It is shown that for certain conditions the bubble pulse can be almost suppressed or dissipated. Some experimental techniques and difficulties associated with practical application are included.
Note on Interesting Physics Students in the Study of Acoustics
Authors: Stumpf F. B.
Published: September 2005

The need to attract physics students to the study of acoustics and ways of attracting them are presented.
Effects of Ocean Waves on Acoustic Signals to Very Deep Hydrophones
Authors: Beckerle John C.
Published: September 2005

Amplitude fluctuations of surface-reflected signals from a source at 50-ft depth were recorded by two receivers at 2600 fathoms. Some features of the observations are attributed to ocean-wave focusing effects. It is shown that the signal-amplitude distribution may be described by using a Rayleigh distribution modified by adding a single, focused contribution of random phase. An observed delay in the envelope of the signals recorded by the two receivers that is greater than the wavefront delay is explained as resulting from the sweeping action of an acoustic caustic produced by the ocean waves. Auto- and cross-correlation functions were computed from the data.
On Structural Fatigue under Random Loading
Authors: Miles John W.
Published: September 2005

The stress spectrum and equivalent fatigue stress of a structure subjected to a random loading are determined on the approximation of a single degree of freedom and the hypothesis of cumulative damage. The results are applied to the development of a similarity expression for the probable value of the equivalent fatigue stress for a panel subjected to jet noise.
Nonlinear Response of Aircraft Panels to Acoustic Noise
Authors: Kirchman E. J. , Greenspon J. E.
Published: September 2005

This paper considers the response of thin elastic plates to sinusoidal acoustic excitation. A theoretical method for obtaining the dynamic deflection and stress in the nonlinear region is given. The theory is compared with test results and shows rather good agreement with these tests. The application of the theory to the design of panels to withstand acoustic fatigue is discussed in the latter part of the paper. The basic assumption involved in the theory is that the panel behaves like a nonlinear spring with a restoring force of F = C1w+C2w3, where F is the restoring force, C1, and C2 are constants which depend upon the physical characteristics of the panel, and w is the deflection of the center of the panel. The constants C1, and C2 are found from the static large deflection curves obtained either theoretically (S. Way, Proceedings Fifth International Congress of Applied Mechanics, Cambridge, Massachusetts, 1938) or experimentally. The amplification factors for the resonant response of the plate are obtained by combining these static large deflection curves with the nonlinear vibration analysis as given in “Nonlinear Vibrations,” by J. J. Stoker, Interscience Publishers, Inc., 1950. Experiments were conducted on aluminum panels, some containing Z stiffeners. The panels were excited by a horn and strains were picked up by use of SR-4 strain gages. Square panels up to length of side/thickness = 120 exhibited nonlinear behavior under sound pressure of 150 db. The magnification factors calculated by use of linear theory were approximately five times those actually experienced, while those calculated by use of the nonlinear theory presented in this paper were of the same order of magnitude as those obtained in the experiments.
Some Effects on Listener Accuracy of Competing Messages Varied Systematically in Number, Rate, and Level
Authors: Hogan D. D. , Hanley T. D.
Published: September 2005

A criterion speaker read intelligibility-test sentences against a background of competing voices in fixed combinations with respect to number, level, and rate as controlled by a time compression-expansion device. The essential finding was that all main factors when raised in number or amount were associated with decrements in intelligibility scores. Statistical analysis yielded a significant three-way interaction; hence trends in individual main effects must be interpreted conservatively.
Principles of Very Low Power Electrochemical Control Devices
Authors: Lane R. N.
Published: September 2005

A new technology utilizing electrochemical phenomena has been developed, from which it is possible to design acoustic indicating and control devices requiring extremely low-power consumption, in the order of 100 to 1000 times smaller than that of transistors. As an example, a mercury cell, one-volt, battery-powered, electrochemical detector for acoustic energy operates on 10 microwatts in the quiescent state, delivering 300 to 500 microwatts when fully excited. Besides the low power consumption, other advantages of these devices are inherent stability, long life, ease of manufacture, and simplicity of operation. Their principal disadvantage is the limited frequency range over which they are presently operable, 0 to 200 cps. The component parts of these new systems vary widely in the type of function performed. There are, for example, elements for detecting and metering both dc and ac fluid flows, or dc and ac electrical signals; units for taking logarithms, derivatives, and products of electrical and/or fluid flow inputs; units for integrating pressures, flows, or electrical signals over short intervals of time; etc.
Small-Vibration Theory of the Clarinet
Authors: Backus John
Published: September 2005

A theory of the clarinet is developed based on the experimental observation that for weak tones the reed and air-column vibrations are nearly sinusoidal. The clarinet is assumed to be a cylindrical air column open at one end and closed at the other by a diaphragm containing a slit of variable width, corresponding to the aperture between reed and mouthpiece. A velocity potential appropriate to a tube with wall friction is assumed. The impedance of the slit as a function of opening and pressure across it is evaluated experimentally and checked against theory. The volume flow through the slit is calculated from the velocity potential and equated to the flow calculated from the slit impedance. The flow and impedance both depend on the pressure, which in turn is again calculated from the velocity potential. Expressions for the operating frequency and threshold blowing pressure are obtained by assuming the flow to consist of a small alternating component superimposed on a steady component. The frequency is found to be below the resonance of the system considered as a tube closed at the reed end, the shift varying nearly linearly with the slit opening and depending on the reed damping. The threshold blowing pressure is found to be proportional to the opening and to the reed stiffness. Operating frequencies and pressures for the artificially blown clarinet were measured experimentally and found to be in very good agreement with values calculated from the theory.
Spectrum of Sound from Cavitating Water Jets
Authors: Jorgensen D. W. , Fitzpatrick H. M.
Published: September 2005

Measurements have been made of spectra of sound radiated by submerged cavitating jets of water. Circular nozzles of diameter 38 in., 34 in., and 112 in. were employed. Sound pressures were measured in half-octave bands over the frequency range 125 cps to 11 000 cps. Ambient pressure was varied from 12 atmos to 2 atmos, and the dissoved-air content of the water was controlled. The sound spectra can be correlated when presented wholly in terms of dimensionless parameters. The spectral distribution of the radiated sound power conforms with the theory of the sound from single bubble cavitation, presented previously [H. M. Fitzpatrick, J. Acoust. Soc. Am. 27, 202(A) (1955), paper D4].
Pitch Extraction by Computer Processing of High-Resolution Fourier Analysis Data
Authors: Harris Cyril M. , Weiss Mark R.
Published: September 2005

A method of automatic pitch extraction is describe, and examples are shown of results obtained. The speech signals are processed by a real-time Fourier analyzer whose output is converted to digital form and recorded on tape for processing by an IBM 700 computer. The logic of the computer program, written in FORTRAN language, is described together with a discussion of the accuracy of the over all pitch extraction system.
Some Measurements of the Threshold for Growth of Air Bubbles by Rectified Diffusion
Authors: Strasberg M.
Published: September 2005

It is known that a gas bubble pulsating in a sound field in a liquid containing dissolved gas can grow by a process called “rectified diffusion.” If the liquid is undersaturated with the gas at the existing static pressure, growth of the bubble will occur only if the sound pressure exceeds a threshold value. The threshold sound pressure for growth by rectified diffusion has been measured for individual air bubbles trapped at the center of a water-filled sphere resonating at a sound frequency of about 25 kc/sec. The data cover a range of bubble sizes, static pressures, and air contents of the water. The measured thresholds are several times larger than Blake's theoretical values (Acoust. Research Lab. Harvard Univ. Tech. Memo. 12, September, 1949) or values calculated from several refinements of the theory.
Precise Measurement of the Speed of Sound in Water
Authors: Greenspan Martin , Tschiegg Carroll E.
Published: September 2005

An X-cut quartz crystal is optically wrung on each end of a stainless-steel tube of which the length as a function of temperature is known. Electrical pulses are applied to one crystal at such a rate (PRF) that the pulses, received on the other crystal and viewed on an oscilloscope, coincide. The coincidence is among the first received pulse corresponding to a particular electrical pulse, the first echo corresponding to the electrical pulse next preceding, and so on. The speed of sound is twice the path length times the PRF, which is set by a stable sine-wave oscillator having fine control and then measured with a counter. The result is meaningful for nondispersive liquids only. The results, which are easily reproduced to within 1 part in 35 000, will be presented for water over the temperature range 0 to 100°C.
Pattern-Matching Procedure for Automatic Talker Recognition
Authors: Pruzansky Sandra
Published: September 2005

A pattern-matching procedure for automatic recognition of talkers was used to study the effects of variations in patterns upon recognition performance. Several utterances of common words, excerpted from context, were spoken by ten talkers and converted to time-frequency-energy patterns. Some of each talker's utterances were used to form reference patterns and the remaining utterances served as test patterns. The recognition procedure consisted of cross-correlating the test patterns with the reference patterns and selecting the talker corresponding to the reference pattern with the highest correlation as the talker of the test utterance. The same recognition procedure was used with patterns reduced to two dimensions. The recognition score for three-dimensional patterns was 89%. Reducing the original patterns to time-energy patterns resulted in a lower recognition score; however, when only spectral information was retained, recognition results were the same as those for three-dimensional patterns. No errors were made in recognition based on a small sample of patterns consisting of pooled spectra of several different voiced sounds.
Experimental Determination of the Eigenvalues of Fluid Spheroids with Free Surfaces
Authors: Lax E. , Leonard R. W.
Published: September 2005

The theoretical determination by perturbation methods of the eigenvalues of spheroidal free surfaces by S. A. Moszkowski, in connection with his recent developments in nuclear shell theory [Phys. Rev. 99, 803 (1955)], stimulated interest in solving the problem experimentally. Accordingly, spheroidal bodies of water with free surfaces were constructed, and 20 to 30 consecutive acoustic eigenmodes were identified and measured in each body. The experimental eigenvalues agreed with theory to ±0.2%. These results suggest that the method can be used to solve the Helmholtz equation Δ2ψ+k2ψ = 0 with the boundary condition ψ = 0 on the surface of other smooth but irregular figures of revolution. (This work was supported by the Office of Naval Research.)
Transient Response of Nonlinear Isolation Mountings to Pulselike Displacements
Authors: Snowdon J. C.
Published: September 2005

The transient response of damped nonlinear isolation mountings to pulselike foundation displacements has been determined theoretically. The response of both “stiffening” and “softening” springs has been examined, and large departures of spring stiffness from linearity have been considered. The effective duration τ of the displacement pulses has been varied through a broad range of values. Shock spectra for three displacement pulses of widely different duration have been determined in the case of a linear spring. It is found that only when τ is small can both the displacement and acceleration of the mounted item be reduced significantly, in which case the displacement of the item relative to its foundation has attained a large constant value. The shock spectra obtained when the item is resiliently mounted and unmounted are shown to differ in level by a factor that is given—in two well-defined regions—by the ratio of the maximum displacements or the maximum accelerations above and below the isolation mounting. In such cases it is possible to predict the difference in level of the shock spectra by a single figure of merit.
Measurement of Sound Absorption Coefficients with Acoustic Pulses
Authors: Anderson R. E. , Watson R. B.
Published: September 2005

Sound absorption coefficients of acoustical materials are commonly measured by the reverberation chamber technique, thereby requiring knowledge of the characteristics of the chamber. Use of acoustic pulses allows determination of reflection coefficients and absorption coefficients without the use of a special chamber, since the pulse reflected from the sample of material may be isolated from other pulses arising from reflections from other surfaces if the pulses be short enough. An essentially plane wave front is obtained by use of a parabolic reflector behind the source of pulses. To compare results from the pulse measurements with data from reverberation chamber measurements, variation of angle of incidence must be carried out in the pulse measurements, and frequency must be varied in the chamber measurements. A preliminary measurement at one-pulse frequency shows satisfactory agreement between the two methods.
Sound Power Measurement in Nonstandard Environments
Authors: Smith Charles H.
Published: September 2005

The measurement of the sound power produced by many types of apparatus is often desirable and sometimes necessary when neither an anechoic chamber nor a reverberation room is available. When measurements are made in an enclosure where the absorption of the walls may be arbitrary, some means of determining the effect of the enclosure upon the observed sound pressure level measurements is necessary. One possible means of attack has been suggested [R. J. Wells, “Power apparatus and systems,” Trans. Am. Inst. Elec. Engrs., No. 21, 1170 (December, 1955)]. An alternative method is presented here, having the significant advantage that no measurements need be made until after the apparatus whose sound power is to be measured has been installed in an enclosure having reasonably arbitrary absorption characteristics. The procedure requires the taking of two sets of sound pressure measurements—one set with the apparatus operating in the enclosure as normally constructed, and a second set after the sound absorbing properties of the enclosure have been modified by the introduction of acoustic material of appropriate area and absorption coefficient. From these data, the sound power output of the apparatus may be determined.
On the Use of Pressure Quadrupole in Place of Velocity Quadrupole for Aerodynamic Noise
Authors: Meecham William C.
Published: September 2005

An objection that one cannot use the Laplacian of the pressure as the source term for aerodynamic noise is examined. It is shown that no conclusion can be drawn from the development.
Direct Method of Accelerometer Calibration
Authors: Brennan J. N. , Nisbet J. S.
Published: September 2005

Present methods for accelerometer calibration include small-amplitude sinusoidal drive, large-amplitude sinusoidal drive, and pulse-integration (ballistic pendulum) methods. The first of these is of limited use because it fails to reveal nonlinear effects and pulse saturation. The second is difficult to accomplish except at a limited number of frequencies, while the third gives very little high-frequency information. A method of direct calibration, using bonded wire strain gages as a standard, is described. The method is valid over a very wide frequency range, up to 40 kc with present instrumentation. Several examples of the use of the method are discussed. Results show that the method is an easy one to use and that it quickly reveals any deficiencies of accelerometers and their amplifiers, if present, e.g., “droop” resulting from insufficient low-frequency response, overloading of cathode follower, loss of high-frequency detail caused by too low cutoff of accelerometer filter, hash caused by accelerometer resonance, etc. Limitations of the method and evaluation of accuracy also are discussed. This method has been found to give a complete picture of the actual operation of the accelerometer and associated circuits quickly and accurately, and the results are easily interpreted. (This research is sponsored by Quartermaster Corps, U. S. Army.)
The Sonar Equation
Authors: Bennett G. S.
Published: September 2005

The sonar equation, in terms of energy content of the pulse, is discussed. In this form, account must be taken of the discrete paths and reflections so that the total incident energy is included. An appropriate formulation of the sonar equation for these conditions is given.
Gaussian-Filter Spectrum Analyzer
Authors: Harris Cyril M. , Waite William M.
Published: September 2005

A real-time audio-frequency spectrum analyzer is described which consists of a bank of 54 contiguous bandpass filters of the Gaussian type. Up to 1000 cps, the filters have a constant bandwidth of 70 cps; above this frequency the bandwidths increase at a constant percentage of about 6.5%. The output of each filter is rectified and the resulting dc signals are scanned by a solid-state multiplexer. Thus, a single output, which is a function of the power spectrum, is made available for visual display and/or computer processing. Practical advantages of Gaussian filters are described for the analysis of transients of noise, music, or speech, and examples of the analyzer output are presented.
Generation of High-Intensity Sound Using Loudspeakers for Environmental Testing of Electronic Components
Authors: Hilliard J. K. , Seeley E. S.
Published: September 2005

This paper describes loudspeakers and enclosures capable of generating sound pressure levels of sufficient intensity to observe the malfunction of aircraft and missile components. The reverberant box enclosure, pistonphone, and plane wave tube methods are discussed. The various types of loudspeakers used to cover the audible range and their total radiated power ratings are surveyed.
Loudness, Sound Pressure, and Subglottal Pressure in Speech
Authors: Ladefoged Peter , McKinney Norris P.
Published: September 2005

Three experiments using one speaker and 30 listeners provided correlated data on subglottal pressure, average volume velocity through the glottis, fundamental frequency, effective sound pressure in front of the speaker, and judgments of loudness. Experiment 1: In 12 repetitions each of bee, bay, bar, bore, and boo spoken at various loudnesses, it was found that in the middle range (subglottal pressure) ∝ (effective sound pressure)0.6; and the level of the vowel in bar was about 5 dB greater than in bee or boo produced with the same subglottal pressure. Experiment 2: In 32 repetitions of the vowel /ɑ/ uttered at various loudnesses with the pitch uncontrolled, it was found that an increase of subglottal pressure of about 6.5 cm aq accompanied an increase in frequency of half an octave; and to a first approximation (rate of flow) ∝ (subglottal pressure). It follows that (rate of work done on the air) ∝ (subglottal pressure)2 ∝ (effective sound pressure)1.2. The exponent 1.2 compares well with the exponent 1.1 found by Lane, Catania, and Stevens for the autophonic response. Experiment 3: Thirty subjects judged the loudness of each word taken from Experiment 1 relative to the reference token in the frame Compare the words: bar and …. It was found that for any one vowel in the middle range, (loudness) ∝ (effective sound pressure)1.2, suggesting that subjects assessed the work done and not the auditory sensation in the usual way as found by Lane, Catania, and Stevens.
Ultrasonic Relaxation in Linear Polysiloxanes
Authors: Hunter J. L. , Lewis T. B. , Montrose C. J.
Published: September 2005

Ultrasonic measurements of relaxation phenomena in the 30- to 270-Mc/sec range have been obtained in 10 homogeneous linear polysiloxane liquids (commonly called silicones) and in a number of heterogeneous mixtures of them. Absorption and velocity data for both instances are presented. In the former case, an analysis is presented on the basis of single-relaxation theory. Special emphasis here is placed on the 6- and 10-atom fluids. The discussion of the results in the heterogeneous liquids is given in terms of a “dynamic viscosity.”
Ultrasonic Velocity and Absorption in Dry CO2 at Moderate Pressures
Authors: Henderson M. C. , Peselnick L.
Published: September 2005

The velocity and absorption of ultrasound in dry CO2 have been measured at 51°C with a Hubbard-type, recording, ultrasonic interferometer at six frequencies from 300 kc to 7 Mc and from 0.3 to 250 atmos, i.e., up to liquid densities. Velocity dispersion is clearly shown in addition to the change in velocity with pressure attributable to nonideality of the gas. The values of f/p at which the transition from V02 to V∞2 is half completed as the pressure is lowered, and f/p at which the maximum absorption per wavelength—(αλ)max—occurs, were both measured whenever possible. At low frequencies, absorption, and at high ones, velocity becomes difficult. Experimentally f/p calculated from the velocity is constant at 38 kc/atmos up to 3 Mc and 70 atmos, while f/p is constant at 28 kc/amagat from 2 to 6 Mc. Up to 75 atmos, the value of (αλ)max can be explained by assuming total excitation of the bending vibrations. The relaxation times at 51° decrease from 0.76 μsec at 7.4 atmos to 0.031 μsec at 96 atmos.
Vibrations of Longitudinally Polarized Ferroelectric Cylindrical Tubes
Authors: Martin Gordon E.
Published: September 2005

The theory of vibrations of longitudinally polarized, thin-wall ferroelectric ceramic tubes is derived including the lateral influence on the longitudinal vibrations. Tenors are utilized throughout the derivation, but a summary of the results is presented in the commonly used matrix forms.

The equations of motion and the equations of state for materials possessing transverse isotropy are transformed to cylindrical coordinates. A new electromechanical equivalent circuit is obtained which is similar to that of Mason, except that the latter ignores lateral effects. The new theory explains experimental results which would be considered anomolous in the older one-dimensional theory.
Elastic Moduli of Pyrolytic Graphite
Authors: Papadakis Emmanuel P. , Bernstein Harold
Published: September 2005

The elastic moduli of pyrolytic graphite, a polycrystalline material exhibiting large elastic anisotropy, have been measured by the ultrasonic pulse-echo method. In units of 1011 dyn/cm2, they are c11 = 5.21, c12 = 1.88, c13 = 1.80, c33 = 2.58, and c44 = 0.15.
Recent Developments in Solid State Acoustics
Authors: Mason W. P.
Published: September 2005

Dislocations in metals are the source of internal friction and elastic dispersion. Depending on the strain amplitude, they can act by several different mechanisms. At the highest strain amplitudes, the Frank-Read source is the predominant mechanism and leads to an anelastic region and a fatigue plastic region. In the fatigue region dislocations can cut through other dislocations, producing jogs and vacancies. These vacancies deposited on incipient cracks can cause them to grow and produce the fatigue cracks observed in metals. At lower strains, breakaway from pinning atoms can cause an amplitude-dependent internal friction. This type of loss can be closely correlated to the density of dislocations, concentrations of impurity atoms, etc. For strains so small that breakaway cannot occur, an internal friction occurs which is amplitude independent. For zigzag dislocations not lying along minimum energy positions, the internal friction mechanism proposed by Koehler appears to account for this loss in the megacycle range but not in the kilocycle range. For moderately strained materials, dislocations can lie along minimum energy positions and give rise to Bordoni relaxations whose internal friction values peak at definite temperatures for definite frequencies. These appear to be connected with Peierls forces.
Experimental Techniques in Solid State and Low-Temperature Acoustics
Authors: Bömmel H. E.
Published: September 2005

At the present time, solid state acoustics extends over the frequency range from about 1 cy/sec up to ultrasonic frequencies of several hundred Mc/sec. A brief survey of the problems and techniques related with different frequency intervals will be presented. A detailed discussion will be presented of special techniques in low-temperature acoustics in relation to recently discovered effects on ultrasonic attenuation in normal and superconducting metals.
Absolute Threshold Differences Resulting from Two Different Group-Testing Methods
Authors: Thompson P. O. , Webster J. C.
Published: September 2005

Absolute thresholds at 4000 cps were determined on nearly 2000 persons attending the Southern California Exhibition. Eight people were tested simultaneously by two different pulsed-tone group testing procedures. The U. S. Navy Medical Research Laboratory (MRL) technique of presenting all pulses within a group at the same level and programming groups at the following levels: 40, 30, 20, 10, 0, −5, 5, 15, 25, 35 db hearing loss (HL) was used as one basic test. The U. S. Navy Electronics Laboratory (NEL) technique of varying the pulses both within and among groups of pulses to cover a 48-db HL range in 2-db steps was the second basic test. Four series of tests, recorded on magnetic tape, were constructed so that, although only four tests were given to any one person (on the right ear), the following comparisons were possible: Test-retest scores on the NEL test using warble tones; test-retest scores on the MRL test using pure tones; NEL test scores vs MRL test scores; and MRL test scores using pure tones vs MRL test scores using warble tones. Data will be presented showing differences in threshold resulting from psychophysical method, warble tone vs pure tone stimuli, and test-retest scores.
Intelligibility as a Function of Internal Time Delay
Authors: Goodnow R. K. , Jeffress L. A.
Published: September 2005

Lists of PB monosyllables were presented to listeners binaurally by means of headphones, both with and without a time delay in the channel to one ear. A wide-band masking noise was presented at the same time and was in phase at the two ears. Its level was sufficient to reduce intelligibility to about 60%. With the time-delays employed, 80 and 160 msec, the delayed speech was somewhat more intelligible than the undelayed. The differences obtained were statistically reliable and were of about the same magnitude as those reported by Schubert at the fiftieth meeting of the Society. Schubert used a much shorter time delay which he compared in its effect with that of an interaural phase reversal.
Onset Discrimination for White Noise
Authors: Pollack Irwin
Published: September 2005

The discrimination of the rate of onset of a white noise was examined for sigmoidal onsets. The average ratio of the longer to the shorter onset for 75% correct discrimination was determined for each of five listeners. The average ratio varied from about 4.0 to about 1.5 as the shorter onset time varied from 1 to 500 msec. Over the range of onsets from 5–100 msec the ratio was about 2.0. That is, an increment of 100% in the onset of a white noise is required over a wide range of onsets for 75% correct discrimination. The discrimination of rise time was also examined as a function of the level of the onset burst above a steady noise background, the noise frequency range, the burst level, and the method of presentation.
Pitch Judgments for Repeated Bursts of Tone and Noise
Authors: Goldstein Moise H.
Published: September 2005

Recently much interest has been shown in the study of pitch judgments for complex auditory stimuli. In the present investigation five subjects were instructed to judge which of a pair of stimuli sounded higher in pitch. One stimulus, the standard, of every pair had a repetition rate of 200/sec; the variable stimulus had a repetition rate that ranged from 175/sec to 225/sec. Within a given pair the stimuli differed thus with respect to modulation rate; the signal to be modulated remained the same. The results of three experiments are reported: in two experiments the stimuli were bursts of 2000 cps tones having different rise times while the third experiment involved bursts of wide-band noise. For repetition rates in the vicinity of 200/sec the difference limen for burst rate is smaller for bursts containing tonal stimuli than for bursts of wide-band noise. These data are discussed in relation to the findings of Miller and Taylor, Small, DeBoer, and Mowbray et al. [This work was supported in part by the U. S. Army (Signal Corps), the U. S. Air Force (Office of Scientific Research, Air Research and Development Command), and the U. S. Navy (Office of Naval Research)].
Loudness of Interrupted White Noise
Authors: Pollack Irwin
Published: September 2005

The loudness of an interrupted white noise was studied over a wide range of burst durations and of intervals between successive bursts. A previous finding is confirmed: the loudness of an interrupted noise may be greater than the loudness of a continuous noninterrupted noise of the same peak amplitude. For interrupted noise presented above a silent background, the loudness of an interrupted noise is determined approximately by the time integral of noise bursts in a specified sampling period. For interrupted noises presented above a background noise level, the background may either reinforce or inhibit the loudness of the noise bursts, depending upon relative levels of the noise bursts and the background.
The Basis of Psychophysical Judgments
Authors: Stevens S. S.
Published: September 2005

The notion that we learn to judge the intensities of our sensations only by noting their relation to one or another stimulus property is becoming less plausible as new discoveries are made in psychophysics. (1) By direct cross-modality comparisons, great variety has been demonstrated in the operating characteristics of the various sensory channels. (2) Loudness grows as a power function of sound pressure with an exponent different from that which the learning theory predicts. (3) In the visual system, the operating characteristic can be drastically altered by changing the state of adaptation of the sense organ and by setting up inhibitory processes under simultaneous contrast.
Propagation of Explosive Sound beneath the Sea Floor
Authors: Raitt Russell W.
Published: September 2005

Sound waves propagated through the sea floor from explosions near the sea's surface have yielded much knowledge of the velocity structure of the oceanic crust. The interpretation of the observations is customarily based on the relation between the wave travel time and the distance between shot and receiver. The records of received sound are usually used merely for identification and measurement of the time of the first arrivals of significant waves. It is also of interest to consider the problem in terms of the intensity and spectrum of the entire train of waves propagated through the sea floor. The sea observations have the advantage of a uniformity and elastic simplicity of the medium at the source and receiver not possessed by similar observations on land. (This paper represents results of research carried out by the University of California under contract with the U. S. Navy Department.)
Short-Range Propagation of Sound in Shallow Water
Authors: Weinstein Marvin S.
Published: September 2005

The short-range propagation of sound in shallow water has been studied experimentally, using model techniques, and compared to theoretical predictions. Measurements for a sand bottom were made at frequencies between 20 and 30 kc in water depths of 1/2 to 2 ft. It has been found that the image form of the Pekeris solution is in excellent agreement with the experimental results for ranges which are short enough for the incident angle associated with the first bottom image to be less than the critical angle for the plane wave reflection coefficient. The simpler ray theory yields results which are considerably more accurate than previously believed. For the case of an elastic solid bottom, similar measurements were made at 20 kc in 2 ft of water. The results indicate that the shear waves excited in the bottom must be included in the theoretical computations. The ray theory then yields results in excellent agreement with experimental data except in the vicinity of the range for which the incident angle for the first bottom reflection is equal to the critical angle for longitudinal waves in the plane wave reflection coefficient.
Visualization of Traveling Ultrasonic Wave Packets
Authors: Rollins Fred R.
Published: September 2005

A strobe-type optical system has been used to observe visually traveling ultrasonic wave packets. Typical photographs are shown, and advantages of the technique are discussed.
Underwater Acoustic Transmission Variations Caused by Thermal Layers—Experimental
Authors: Garrison G. R. , Murphy S. R. , Potter D. S.
Published: September 2005

Acoustic transmission experiments have been conducted in Dabob Bay, located in northern Puget Sound. At depths between 100 and 600 ft the water is normally considered to be of uniform temperature and salinity; thus, no deviations from the inverse square law would be expected in the directly transmitted sound intensity. However, transmission of short pulses of acoustic energy at frequencies of approximately 100 kc over a distance of several hundred yards results in intensity variations with time or depth as high as 20 db. Recent measurements of the temperature as a function of depth with a probe sensitive to 0.01°C have revealed the presence of thermal layers of considerable horizontal extent at very nearly the same depths at which acoustic anomalies have been observed. (This work was supported by the Bureau of Ordnance, U. S. Navy, under Contract NOrd 12937.)
Signal and Context Components of Word-Recognition Behavior
Authors: Stowe Arthur N. , Harris William P. , Hampton Donald B.
Published: September 2005

Data are presented on the effect of speech-to-noise ratio and context on intelligibility of monosyllabic words. The context for words in noise was provided by parts of noisefree sentences. A formula called the discriminant rule is derived from a multidimensional theory of discrimination. It accounts for the speech-to-noise and context effects both for these data and for word-list effects found in experiments reported elsewhere. Fit of the discriminant rule to both experimental situations shows in what sense context limits the number of alternatives afforded the listener.