bluuebunny/crossref_metadata_2025 huggingface dataset:
Further Data on Low-Frequency Sound Attenuation in the Deep Ocean
Authors: Urick R. J.
Published: September 2005

In April 1964, an aircraft flew southeastward from Bermuda into the South Atlantic Ocean and around South Africa to Australia. Explosive charges were dropped en route, and the shots were recorded at various MILS (missile impact location system) stations in the Atlantic, as well as off New Zealand by the (New Zealand) Naval Research Laboratory. The signals recorded at Bermuda when analyzed in the conventional way yield values for the attenuation of sound over a track 2600 miles long between Bermuda and Brazil. The measured coefficients between 20 and 320 cps are found to be lower than those measured on another flight between Bermuda and Great Britain [J. Acoust. Soc. Am. 35, 1413 (1963)]. The disparity of present data on low-frequency attenuation would indicate that different attenuation processes must operate in different deep-water regions. The nature of these processes, however, it still open to conjecture. Among those that come to mind are sea-surface scattering, eddy-viscosity absorption (as suggested by Schulkin), diffraction into the bottom (as suggested by Brown and Raff), and scattering by large-scale volume inhomogeneities.
Stability of CW Acoustic Signals, Straits of Florida
Authors: Clark J. G. , Dann R. , Yarnall R.
Published: September 2005

A 43-mile underwater transmission range that transects the Florida Current was recently utilized for a study of acoustic phase stability in the ocean medium. Measurements were made relative to the transmitted signal phase using a method based on phase-coherent demodulation. Phase variations in the received 420-Hz signal were less than 90° during many half-hour periods and remained within 360° for periods of up to 3 h. Certain time variations that did occur seem likely to be associated with tides, weather, and surface waves. A prominent diurnal periodicity in signal phase may be significantly related to the local dynamics of the Gulf Stream. [Work conducted with The University of Michigan, and was supported by the U. S. Office of Naval Research Acoustics Programs.]
Autocovariance Spectrum of Sound-Velocity Microstructure in Deep Caribbean Water
Authors: Lord Norman W.
Published: September 2005

Aiming at a complete representation, two large sets of data taken with horizontally towed velocimeters were analyzed for the range of reciprocal path length, 10−2→2−2 M−1. The first set of data was taken at four latitudes, 13°N→16°N on the longitude 68°W, towing a simply weighted velocimeter at depths between 500 and 1000 m. Using an effective depth and orientation-stabilizng device, a similar set of data was taken at 14°30″N, 62°W for depths between 350 and 1200 m. The sampling interval was 0.25 M and fluctuations were measured from an average calculated over a moving interval of 250 M, then corrected for the depth discrepancy. Total variance ranged between 0.016 and 0.84 M2 sec 2. The spectra are exponential decays that drop into the random level of 0.001 M 2 sec−2 near 1 M−1. Of these total variances a proportion between 0.1 and 0.8 falls without the initial 0.02 M−1. Superposed on the decay are moderate peaks common to all the spectra, some of which can be attributed to short-term undetected depth fluctuation. The spectra of the second set have a smaller proportion of total variance in the initial range. [Hudson Laboratories of Columbia University Informal Documentation No. 85. Work supported by the U. S. Office of Naval Research.]
Underwater-Acoustic-Propagation Measurements to 5000-foot Depths
Authors: Whitmarsh David C. , Leiss William J.
Published: September 2005

Underwater-acoustic-propagation measurements were made along a vertical plane in the ocean in the Key West, Florida, area during the winter of 1964–1965. Two deep submergence vehicles were allowed to sink freely and slowly through the water to depths as great as 5000 ft while transponding acoustically with each other. Pulses at frequencies of 10, 20, and 40 kc/sec were used in the experiment. All received acoustic signals were recorded continuously in digital form in each vehicle. Also recorded were water temperature and pressure as well as the vehicle action in rotation and wobble. The direct acoustic signals showed amplitude fluctuations of the order of 20 dB over depth changes of 20–30 ft in the upper 2000 ft of ocean at ranges of 2000–4000 yd. These fluctuations decreased at greater depths. These fluctuations are discussed in terms of transmission loss and are compared to the loss predicted by ray theory on the basis of the measured temperature structure of the water. Absorption coefficients appear as part of the data reduction and agree rather well on the average with published coefficients. [This research was supported by the U. S. Navy, Bureau of Weapons.]
Importance of Noise-Spectrum Measurements for Noise Control in Railway Vehicles
Authors: Urbanek Günther E. , Hirschwehr Edmund
Published: September 2005

The authors have been working on noise control in railroad cars and engines. The key problem is the loudness evaluation of the typical broad-band railway noise with sufficient accuracy. However, it was found that the absolute value of the loudness level is of less importance than the difference between two noises—e.g., any improvement caused by some sort of acoustical adaptation, the increase of loudness level owing to higher moving speeds, the separation of the noise into single components, etc. For this purpose, direct measurements with the sound-level meter are simple, but so crude that sometimes they even contradict the subjective impression of loudness. Loudness calculations based on spectrum data give much better results. Results of loudness measurements and calculations for typical railroad noises are given. The differences between some of the usual loudness measures are outlined, and some conclusions with regard to noise control are discussed.
Infrasonic-Noise Power Level and Wind-Velocity Correlation Study
Authors: Bowman Howard S.
Published: September 2005

Measurements of infrasonic-noise power and analyses of wind-velocity data were made. Correlation was found between infrasonic-noise power levels at a particular location and wind-velocity measurements taken at a distance of approximately 11 miles away. This information is useful for studying infrasonic-signal data, improving the signal-to-noise ratio in physical measurements of infrasonic signals, and for the selection of sites for infrasonic stations.
Model Freon Compressor for Acoustic Investigations
Authors: Wells R. J. , McGrew J. M.
Published: September 2005

Studies have been made of the feasibility of simulating acoustical and aerodynamic characteristics of a full-scale axial-flow air compressor with a scale model operating in freon in a closed-loop system. Correlation was attained between model and prototype for both acoustical and aerodynamic performance. Agreement was obtained with a previously published generalized acoustic-prediction curve; and an acoustic scaling law was developed that permits rapid prediction of full-scale sound power levels from measurements of the sound power levels produced by a model. [Work supported by the Aircraft Development Service, Federal Aviation Agency.]
Utilization of the Saturn S-1C Booster as an Acoustic Source
Authors: Dendrinos Steve , Peskar Robert E.
Published: September 2005

George C. Marshall's Saturn S-1C booster has a power output of 200 million acoustic watts for a period of 128 sec. A large number of static firings of this unique acoustic source are planned between 1966 and 1967. It is the purpose of this paper to show one method of utilizing, for acoustical investigation, the intense noise field generated during static firings of the Saturn vehicle. A testing facility, designated the Mobile Acoustic Research Laboratory (MARL), has been designed for positioning large test specimens in the field. The acoustical field around the Saturn booster is presently being defined by measurement and analytical techniques. It will be possible to obtain limited control of the intensity level and spectrum shape by choosing suitable locations in the region of the Saturn. Some of the projects planned for testing in the MARL are described.
Acoustic Losses from Model Rocket Chambers
Authors: Slates R. , Buffum F. , Dehority G. , Price E.
Published: September 2005

An experimental investigation was made of the behavior of various model rocket chambers driven acoustically by cold air flowing through a porous plate at the head end. Analysis showed that bulk losses and viscous losses were negligible as compared to losses through the sonic nozzle. Nozzle losses were found to vary linearly with J (nozzle-throat/grain-port-area ratio) in the range tested (O<J<0.4). Results are compared with zero-length “linear-entrance-area” sonic-nozzle theory and also with linear acoustic theory for a piston-driven chamber having zero net flow. Three separate experimental methods were used to determine the nozzle attenuation constants. The steady-state technique was the only method that was satisfactory through the entire range of practical interest. The steady-state “decay-rate method” was limited to J's of less than 0.14. The pulse technique was not satisfactory. The tests show conclusively that the change in nozzle radiation losses during burning (caused by the variation of “J”) drastically alters the acoustic response of rocket chambers to a given excitation.
Effects of Combustion Instability on Rocket-Engine-Noise Sources and Levels
Authors: Tedrick Richard N.
Published: September 2005

Instabilities in the combustion of liquid-fueled rocket engines cause wide variations in both over-all sound-pressure level and frequency content. This paper considers the types and modes of such instabilities and their possible effects upon noise-source locations and oscillation. Data from a model test program using 500- and 4000-lb-thrust liquid-fueled engines are presented. It was found that, while the over-all sound-pressure level varied only a few decibels, individual narrow bands might vary by as much as 22.5 dB. Specific direction is indicated for future analyses and research projects. [Work performed for the National Aeronautics and Space Administration.]
Vortex Noise of Helicopter Rotors
Authors: Schlegel Ronald G. , Mull Harold R.
Published: September 2005

An improved procedure for the prediction of helicopter main-rotor vortex noise under conditions of uniform inflow has been developed. The method permits the calculation of the over-all vortex-noise levels and gives a generalized spectrum shape in octave bands. The procedure is given a theoretical basis by analysis of the theory developed for the vortex noise from rotating rods and propellers. Two main rotor systems were measured for three rotor speeds each and over a range of disk loading. The measured results are compared with the theoretical predictions and empirical constants determined that permit accurate calculation of the vortex noise. Onset of tip stall was found to effect the spectral distribution of the unpitched noise. Under tip-stall conditions, the upper frequency bands increase relative to the usual vortex-noise peak. The results can be generalized into two spectra: one for the rotor system operating out of stall and the other where tip stall is present. This spectral change is shown to correspond with the onset of drag divergence. [Study partially supported under U. S. Aviation Material Laboratories Contract.]
Boundary-Layer-Noise Measurements on a Large Turbofan Aircraft
Authors: Gibson J. S.
Published: September 2005

An extensive set of boundary-layer-noise measurements has recently been made on the Lockheed C-141A, a large turbofan aircraft. Data were taken at three external locations on the fuselage and at several altitudes and airspeeds ranging from Mach 0.24 at 2000 ft to Mach 0.80 at 40 000 ft. Due to the lack of standardized methods of boundary-layer-noise prediction, it is felt that analysis of the data would be of interest, since previous similar data have been obtained primarily on much smaller jet aircraft, missiles, and from wind-tunnel studies. The frequency spectra obtained have been generalized and compared with similar data from other aircraft and tests. Generally, good agreement was found with a tendency for somewhat higher levels in the low-frequency range. The ratio of over-all sound pressure to dynamic pressure agrees closely with previous results, averaging approximately 0.006.
Reverberation-Chamber Measurements of the Acoustic Power of “Frequency-Varying” Sources
Authors: Maling George C. , Nordby Knut S.
Published: September 2005

In a reverberation chamber, the sound-pressure pattern produced by a source that emits a pure tone or line spectra in a narrow band consists of many maxima and minima. In order to determine the acoustic power radiated by such a source, an effective rms sound-pressure level (SPL) must be determined by an analysis of this pattern. The statistical distribution of the peaks of the SPL pattern has been analyzed and found to be nearly Gaussian. The mean value of the distribution is related to the effective rms pressure in the reverberation chamber. Results obtained by using an ideal pure-tone source were presented at the 5th International Congress on Acoustics, September 1965, Liège, Belgium (paper J65). In this paper, the method is used for the analysis of the patterns produced by sources that emit line spectra in a narrow band (frequency-varying sources). Emphasis is placed on the reverberation-chamber determination of the sound power radiated by axial fans and centrifugal blowers that exhibit spectra with discrete components at the blade-passage frequencies.
Listener Judgments of Motor-Perceptual Characteristics of Bisyllable Nonsense Words
Authors: Baker Donald J.
Published: September 2005

The purpose of this study was to investigate the ability of subjects to judge the relative difficulty of articulating bisyllable nonsense words. Twenty-five trained listeners were instructed to listen to each of 240 nonsense words produced by one speaker and rate their ability to articulate the sequence. The 240 bisyllable words represented the combination of three vowels [i, ɑ, u] with each of 20 consonant sounds in each of four VCV stress-position configurations; the stress was on either the first or second syllable and the consonant served as either the final sound of the first syllable (VC) or as the initial sound of the second syllable (CV). A rating scale of 1 to 5 was used, 1 representing very easy, 5 representing very difficult. The median scale value for each of the 240 words by the 25 listeners was used as the criterion measure in most analyses; however, in certain instances, the method of graded dichotomies was used to obtain scale values. Relationships between the perceived difficulty of articulation and features such as place, manner, and voicing are discussed.
Temporal Effects in Talker Identification
Authors: Bricker Peter D. , Pruzansky S.
Published: September 2005

Sixteen listeners identified the voices represented by various samples of the utterances of 10 talkers. Types of samples and their percentages correct were sentences (98%), disyllables (87%), monosyllables (81%), excerpted C-V sequences (62%), and excerpted vowels (55%). Another group of naive listeners performed ABX discriminations among all pairs of six of these talkers using sentences with the X sentence in reverse. Some of the more significant findings were (1) when identification was based on a single excerpted vowel, both the order of identifiability and the pattern of confusions were affected by the particular vowel chosen; (2) reinstating the consonant before the vowel raised performance in general and altered the response pattern for some talkers; (3) confusion matrices were asymmetrical for both naive and sophisticated listeners. In general, talker identification depends strongly on what was said. These findings offer little encouragement for the notion that the recognition process is based on vocal attributes that are characteristic of talkers and independent of what they say.
Negative Group Velocities in Semiinfinite Plates
Authors: Torvik Peter J. , Plunkett Robert
Published: September 2005

Tolstoy and Usdin [J. Acoust. Soc. Am. 29, 37–42 (1957)] have remarked on the phenomenon of opposite phase and group velocities for the second symmetric mode of elastic strips. For harmonic forced excitation of semiinfinite strips in this mode, energy radiates away from the origin as the wave troughs and crests travel toward it. In the case of single-frequency steady-state excitation, it is difficult to assign any rôle to group velocity as defined in terms of a frequency band. However, a numerical calculation of the integral of the tensor product of stress and displacement shows that the direction of energy propagation is, in fact, opposite to the direction of wave propagation for precisely those frequencies for which the group and phase velocities have opposite sign. [Work supported in part by a NASA fellowship (PJT) and in part by the U. S. Navy Bureau of Ships.]
Fourier-Transform Technique for Measuring Terminating Impedances
Authors: Plunkett Robert , Wittig L. E.
Published: September 2005

The mechanical impedance at the termination of an elastic bar is found from the Fourier transforms of pulse shapes incident upon and reflected from this termination. The transform integrals were evaluated by a digital computer. The termination impedance so obtained is compared with impedance measurements made at the actual termination with an impedance head and driver. Experimental advantages and disadvantages of this technique are discussed, along with the limitations inherent in making measurements by this method. Direct engineering application is demonstrated by the use of an 1 beam as a waveguide terminated with a structural configuration. Good results are highly dependent upon obtaining accurate waveforms. [Work supported by U. S. Navy, Bureau of Ships (Code 345).]
Investigation of a Method for Attenuating Plane Waves in Bars
Authors: Plunkett Robert , Hanson C. E.
Published: September 2005

This investigation is the experimental verification of the mathematical analysis developed for “Attenuation of Plane Waves in Semiinfinite Composite Bar” [R. Plunkett and C. H. Wu, J. Acoust. Soc. Am. 37, 28–30 (1965)]. Traveling compressive waves in bars can be attenuated effectively by a composite configuration consisting of serrated septa bonded to the bar by layers of viscoelastic, dissipative adhesive. Attenuation depends on the ratio of sonic velocities of the septa and the bar, frequency, relative dimensions, and the complex shear modulus of the adhesive. Configurations of septa with low effective sonic velocitiy and zero sonic velocity were tested on square bars and 1 beams. Agreement between calculated and experimental attenuation factors is shown. Factors necessary for optimum attenuation are also discussed. [Work supported by U. S. Navy, Bureau of Ships (Code 345).]
Model Study of Panel Response to Boundary-Layer Pressure Fluctuations
Authors: Bies David Alan
Published: September 2005

The response of two well-damped panels to boundary-layer pressure fluctuations has been investigated at Mach 1.4 and Mach 3.5 in a 1×1-ft blowdown wind tunnel. Both fully developed turbulent boundary layers and mildly perturbed flow fields have been considered. The scale of one of the panels is designed with suitable corrections to the measured response, to simulate a panel near the aft end of a supersonic transport at Mach 3.5 for the frequency range of high modal density. The responses of the panels to reverberant acoustic noise have also been investigated, and the results have been found to be consistent with those obtained in the wind-tunnel investigation. The results of these investigations are briefly outlined.
Behavior of Finite-Amplitude Sound Waves in Nonlinear Solids
Authors: Ford Joseph , Paré Victor K.
Published: September 2005

This paper reviews nonlinear elasticity theory, with special emphasis on waves whose amplitude is just large enough that nonlinearity must be taken into account. Methods for obtaining traveling-plane-wave solutions and the mathematical and physical properties of these solutions are discussed. Particular attention is given to that part of the theory that relates experimental measures of distortion to the third-order elastic constants. Finally, the relevance of these constants to other areas of physics is mentioned. [Research sponsored by the U. S. Atomic Energy Commission under contract with Union Carbide Corporation and by a National Science Foundation grant to the Georgia Institute of Technology.]
Determination of Nonlinear Properties from the Velocity of Small-Amplitude Waves in Statically Stressed Crystals
Authors: Thurston R. N.
Published: September 2005

One of the most accurate methods for determining the nonlinear elastic properties of crystals is by observing the changes in the propagation velocity of small-amplitude waves as a function of static stress. By this method, from measurements made under hydrostatic pressure and uniaxial stress, the third-order elastic coefficients (coefficients of the cubic terms in the strain energy) have now been determined for a number of materials. This paper indicates the definition of third-order elastic coefficients and explains their relation to the better-known pressure derivatives of elastic coefficients. The derivation of equations for determining the third-order coefficients from the transit time of small-amplitude waves is reviewed. Finally, some of the uses of the available information on nonlinear elastic properties are discussed.
Optical Studies of Nonlinear Interactions
Authors: Cook Bill D.
Published: September 2005

Nonlinear effects of ultrasonic waves propagating in liquids are easily observed by optical methods. Techniques have been developed to use the light-diffraction patterns to yield detailed information concerning the deformation of the waves. These techniques can be characterized by the following: optical observation of an isolated harmonic of the wave; prediction of the intensities of the individual diffraction orders or the envelope of the diffraction pattern; and direct methods of calculating the waveform from the measured diffraction orders. A review of these techniques is presented, showing the success and limitations of the optical methods.
Absolute-Amplitude Measurements of Distorted Ultrasonic Waves in Solids
Authors: Gauster W. B. , Breazeale M. A.
Published: September 2005

Measurements of the amplitude of pulsed ultrasonic waves at megacycle-per-second frequencies in solids are discussed. A capacitive detector described previously [D. O. Thompson, M. A. Breazeale, and W. B. Gauster, Proc. Conf. Acoust. Solid Media, Warsaw, Poland (5–10 Oct. 1964)] has been developed further so that amplitude measurements can be made not only of the fundamental component of a distorted wave, but also of the second harmonic of the driving frequency. Results are given for some single-crystal samples. [Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation.]
Calculation of B/A for Water from Velocity vs. Pressure and Temperature Measurements
Authors: Hagelberg M. Paul , Kao Samuel , Holton Gerald
Published: September 2005

Recently-measured values of the velocity of sound in water in the temperature range from 0° to 80°C and at pressures of 8000 kg/cm2 [Bull. Am. Phys. Soc. 10, 129(A) (1965)] are used to calculate values of B/A, the nonlinearity parameter, by the method described by R. T. Beyer [J. Acoust. Soc. Am. 32, 719–721 (1960)]. Additional data are taken from P. W. Bridgman [Proc. Am. Acad. Arts Sci. 48, 309–362 (1912)]. These values agree, within experimental error, with those calculated by Beyer for atmospheric pressure from data reported by W. Wilson [J. Acoust. Soc. Am. 31, 1067–1072 1959)]. The value of B/A for a given temperature increases as the pressure is increased, reaching a maximum at a pressure in the neighborhood of 3000 kg/cm2. [This work is supported by the National Science Foundation.]
Correlation between Multiple Observers in Correlated and Independent Noise
Authors: Bilger Robert C.
Published: September 2005

In theory, when multiple-listeners experiments are performed in noise, the responses of the observers will be correlated if the same noise is presented to each listener. To determine the extent of this correlation, six pairs of listeners were tested under conditions of perfectly correlated and independent noise. A YES-NO procedure was used. In addition, to hit and false-alarm rates, the congruence of observers' responses was tabulated as a function of whether or not signal was presented. When two noise generators were used (rn=0), the two listener responses were always independent. When the one noise generator was used for both observers (rn=1), their responses were always highly correlated for “noise-alone” presentation. For “signal-plus-noise” presentation, no correlation was found between the responses of unsophisticated observers, but was generally present for sophisticated pairs of listeners. [Research supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
ROC Curves from an Ear Model
Authors: Jeffress Lloyd A. , Gaston Audley D.
Published: September 2005

Many investigations have likened the ear in its ability to detect a tonal signal in noise to a narrow filter followed by a detector mechanism. The present paper describes the performance of such a device, consisting of a 50-cps filter centered at 500 cps followed by an envelope filter. The latter is a half-wave rectifier, an RC integrator, and a low-pass filter. Gated noise or noise plus signal is presented to the device and its output is sampled at each presentation. For a stimulus duration equal to the reciprocal of the bandwidth of the filter, the efficiency measure η is near to unity. At longer and shorter durations, the efficiency decreases. The ROC curves yielded by the device resemble those obtained with human subjects, and are shaped like those for the ideal detector of a signal of unknown phase. [Work supported through a contract with the U. S. Navy Bureau of Ships and a grant from the National Aeronautics and Space Administration.]
Masking-Level Differences as a Function of Masker Level
Authors: Canahl Julius A. , Small Arnold M.
Published: September 2005

The size of the masking-level difference (MLD) was investigated as a function of the spectrum level of a wide-band noise (100–4800 cps). The masking noise was presented at seven spectrum levels: −10, 0, 15, 30, 45, 60, and 70 dB re 0.0002 dyn/cm2. Four signals were used: 167, 250, 500 cps and a wide-band noise (100–4700 cps). The signals were presented either homophasic or antiphasic (N0S0, N0Sπ). Thresholds were obtained using the method of adjustment. The present study confirms the data of Hirsh [J. Acoust. Soc. Am. 20, 536–544 (1948)] that the size of the MLD is dependent upon the level of the masking noise. However, for the pure tones used in the present study, a maximum value of the MLD occurred such that further increases in the level of the masking noise did not produce a larger MLD. A definite maximum of the MLD for the noise signal did not occur.
Interaural Noise Correlation and Detection of Low-Frequency Monaural Signals
Authors: Whitmore John K. , Wilbanks W. A.
Published: September 2005

This study is an extension of research reported by the authors at the 69th meeting of the Society [J. Acoust. Soc. Am. 37, 1179(A) (1965)]. In the present study, 200-msec tonal signals of 150, 200, 225, and 250 cps were masked by narrow-band noise. The interaural correlation of the masker was varied between +1.00 and zero by mixing correlated and uncorrelated noise. Data were also obtained for purely monaural detection (NmSm). The results show that the magnitude of the binaural advantage for detection depends upon the frequency of the signal and the interaural correlation of the masking noise. At 250, 225, and 200 cps, N0Sm is superior to NuSm by about 10, 7, and 4 dB, respectively. These MLD's diminished rapidly as the noise correlation was decreased from unity. No appreciable binaural advantage was obtained with the 150-cps signal. As in our previous study, the data suggest that for some observers NmSm is slightly superior to NuSm at low frequencies.
Detection of a Narrow-Band Noise as a Function of Its Interaural Correlation
Authors: Wilbanks W. A. , Whitmore John K.
Published: September 2005

This paper presents the results of a study on the detection of a narrow-band noise signal as a function of its interaural correlation, as well as of the correlation of the masker. The signal was a 100-cps noise centered at 250 cps. The masker was a continuous wide-band noise. The interaural correlation of the signal was varied between +1.00 and zero. The correlation of the masker was either +1.00 or zero. The phase relation between the signal and the masker was random for all values of signal and noise correlation; i.e., the signal and the noise were obtained from independent sources. With a correlated masking noise (N0), detection is about 8 dB better with an uncorrelated signal (SU) than with a correlated signal (S0). With an uncorrelated masking noise (NU), the difference between SU and S0 is negligible. Detection of S0 is about 2 dB better with N0 than with NU. The implications of these findings for binaural-masking theory are discussed.
Statistics of Interaural Time Differences under Antiphasic Stimulus Conditions
Authors: Jeffress Lloyd A. , Gaston Audley D.
Published: September 2005

At the Austin meeting of the Society, Watson, Rilling, and Bourbon [J. Acoust. Soc. Am. 36, 1991(A) (1964)] presented ROC curves obtained from subjects' responses under one antiphasic condition N0Sπ. An attempt was made to fit their data from theoretically derived probability densities for noise and signal. The signal distribution was obtained by a rather tedious numerical computation. The present paper shows examples of the interaural time differences arising under various antiphasic stimulus conditions. The distribution for dichotically presented noise Nπ is distinctly platykurtic. The distribution obtained by adding a signal NπS0 is bimodal with greater separation of the modes as the signal is increased. The distribution for N0Sπ has a density function that resembles the Rayleigh distribution, and has zero frequency of occurrence of zero interaural time differences. [Work supported through a contract with the U. S. Navy Bureau of Ships and a grant from the National Aeronautics and Space Administration.]
Diffraction Corrections for Ultrasonic Attenuation and Velocity Measurements in Crystals
Authors: Papadakis Emmanuel P.
Published: September 2005

The echo train in a pulse-echo ultrasonic measurement does not decay exponentially but displays irregular variations in the Fresnel region. Similarly, the apparent travel time of the wave will be slightly nonlinear as a function of distance. These variations are caused by diffraction from the finite transducer, and cause errors in attenuation and velocity measurements. The incremental diffraction loss and delay can be computed from the radiation pattern of the transducer by considering both amplitude and phase in finding the integrated pressure at a receiver, and corrections can be applied to the measurements. The loss goes through several peaks and troughs versus S=zλ/a2, the distance normalized by the Fresnel length, while the phase climbs toward π/2 through the same number of slopes and plateaus. A phase plateau is located at a loss peak. The loss finally becomes monotonic, increasing with a monotonic decreasing slope. The location of a loss peak along S is a strong function of the anisotropy of the crystal under study. Computed curves of the diffraction-loss/distance and phase/distance characteristics are presented, and data from pulse-echo measurements on several crystals are shown to verify the theory. The method of making diffraction corrections for attenuation and velocity is outlined, and the effect of these corrections on experimental data is shown.
Measurements of Shear-Wave Attenuation in Polycrystalline Metals by Means of Guided Waves in Long Strips
Authors: Meitzler Allen H.
Published: September 2005

The common method of measuring acoustic loss, the pulse-echo method, becomes difficult to apply at low megacycle-per-second frequencies because of uncertainties in evaluating the contributions by diffraction effects and bond losses to the total measured loss, and these uncertainties are particularly troublesome for the case of shear-wave measurements. This paper describes a technique of using guided modes of shear-wave propagation in long thin strips to evaluate the shear-wave attenuation coefficient. The method is best suited to measuring materials such as polycrystalline metals because these materials are readily formed by commercial rolling and slitting techniques into the required shape. Measurements of a commercial aluminum alloy, 5052, in the form of strips 10 mils thick, 1 in. wide, and over 100 ft long, have resulted in observed Q's of about 1.5×105 in the range of 2–3 Mc/sec. This value of Q is comparable to values obtained by Fraser [Paper N2. This meeting.] using the recently developed sphere technique.
Ultrasonic Internal Conical Refraction
Authors: Artman Robert A.
Published: September 2005

Conflicting evidence of ultrasonic. internal conical refraction casts a certain doubt on the existence of the effect. Data have been taken on ultrasonic shear waves propagating in the [111] direction in a KCl single crystal. Measurements of amplitude and polarization direction around the perimeter of the base of the cone for several directions of the input polarization have been made. The refraction angle has been measured by determining the attenuation caused by cylindrical absorbers placed on the base of the cone coaxially with it. These data are in agreement with plane-wave theory. It is proposed that this theory is incomplete and, as in the optical case, the possibility of observing the effect depends upon the diffraction suffered by the input radiation that fills a cone whose semiangle is larger than the error in orientation of the sample. If the optical analogy is correct, one should observe two partially filled concentric rings with the position of minimum energy between them corresponding to that predicted by plane-wave theory. The absorption data indicate a need for a more refined experiment to establish the existence of the minimum with certainty. [Research sponsored by the National Science Foundation.]
Transient Solution for Sound in a Viscous Fluid
Authors: Blackstock David T.
Published: September 2005

The transient behavior of a small-signal, plane, progressive sound wave in a viscous fluid is considered. In terms of the particle velocity u, the boundary condition is u(0,t)=u0H(t) sin ωt, where H(t) is the unit step function. By making an approximation, we transform the viscous wave equation into the heat equation and thereby obtain the solution u/u0=e−αx siny+12e−y2/AαxIm[w(A+jy/2A)], where y−ωt−kx, A=(αx)12, α is the viscous attenuation coefficient, and w(z) is the error function of complex argument [Natl. Bur. Std. Handbook of Mathematical Functions, AMS 55, p. 297 (1964)]. The first term is the steady-state solution. The second term “annihilates” the steady-state solution in the region x>ct (i.e.. ahead of the wavefront) and also contains the transient solution. The latter is important in the neighborhood of the wavefront and in particular gives the wave a precursor. The possibility of observing this precursor experimentally is discussed. [Work supported by the U. S. Air Force Office of Scientific Research, Office of Aerospace Research.]
New Modifications and Solutions of D. J. Korteweg's Equations to Determine Accurately the Sound Speed in Circular Elastic-Walled Liquid Columns
Authors: Rivera Charles J.
Published: September 2005

The purpose of this paper is to present modifications and new solutions of the three “Korteweg equations.” The equations define the velocity reduction of acoustic pressure waves propagating at low frequency through circular elastic-walled liquid columns. This theory uses a new mathematical model defining the sound speed in the liquid column as dependent on the time-varying boundaries that are affected by acoustic standing waves in the liquid. The theory replaces G. Wertheim's “Ratio of Strains,” used by D. J. Korteweg, with S. D. Poisson's theory as known today, and extends the solution to include “thin” or “thick-walled” circular tubes and incorporates an approximation for “extremely thick-walled” tubes. The tubes evaluated were four sizes of acrylic resin, four sizes of MC 901 Nylon, one size hard-drawn copper, and one size stainless steel. All tubes contained distilled water, and the entrapped air content and temperature were controlled. The average probable error of the measurement technique used was 2.40%. The average approximate error of the computer-calculated sound speed with the experimental determined value, for the frequency range investigated, was 1.4%. [Work supported by in-house independent research program at laboratory.]
Monostatic Scattering from the Ocean Volume
Authors: Flowers Kenneth D. , Hurdle Burton G.
Published: September 2005

Monostatic volume-scattering experiments were conducted in the Atlantic with a piston transducer operated at 19.5 kc/sec and having a beam width of approximately 8° at the half-power points. This investigation was made to determine the correspondence between measured returns and a model based on the theory of isotropic scattering from a volume. Intensities from measured values were averaged and the volume-scattering strength computed as a function of depth for several depression angles and for a range of pulse lengths. Scattering strength was found to be independent of the ensonified volume in regions of uniform scattering strength. In regions of varying scattering strength, increasing pulse length or volume tended to smooth the variations in scattering strength.
Operational Relation between the Phonetic Forms of Elementary Words
Authors: Bhimani B. V. , Mitchell R.
Published: September 2005

Phonetic representations of elementary words, as recorded for various dialects of English by five authoritative sources, were compiled by two sets of highly accurate computer programs [B. V. Bhimani, J. L. Dolby, and H. Resnikoff, J. Acoust. Soc. Am. 36, 1988(A) (1964)], resulting in about 40 000 phonetic forms for approximately 5700 graphic forms. The data so compiled were analyzed [B. V. Bhimani, L. Earl, and R. Mitchell, ibid. 37, 1210(A), (1965); B. V. Bhimani, ibid. 37, 1210(A) (1965)] and a program written to relate the orthographic form of each of these words to the five sets of phonetic representations. The relations and exception words incorporated in this program were analyzed with the aim of evaluating (1) the precision of (a) sound change representing the various dialects and (b) the interpretation of orthographic forms musing dialects; and (2) their impact on the theories of speech perception and on techniques of evaluating speech processing equipment. [Work supported by Lockheed Independent Research.]
Bionics Approach to Speech Segmentation and Synthesis
Authors: Mundie J. Ryland , Fahle William A.
Published: September 2005

With the real-time digital data-processing system for biological research speech is divided into fundamental auditory fractions. These subunits form a library from which speech is synthesized. The library is formed in the following manner. Data from a single utterance enter the computer in two forms. The analog signal from a microphone enters through an analog-to-digital converter and is held in digital format. The same signal simultaneously passes through an electronic model of the inner ear and nervous system, which transforms the signal into neural like pulse patterns. A visual display of these pulse patterns is presented by the computer. From this display, a single segment, such as a glottal pulse of a voiced sound, is selected as typical. The computer identifies the corresponding portion of the digitized analog signal that produced the chosen pulse pattern, and it is entered into the library. To produce synthetic speech, these basic analog segments are compiled by the computer to give a continuous signal from the digital-to-analog converter.
Model of Larynx Activity during Phonation
Authors: Crystal Thomas H.
Published: September 2005

With the steady-state measurements made by van den Berg, et al. [J. van den Berg, J. T. Zantema, and P. Doornebal, Jr., “On the Air Resistance and Bernoulli Effect of the Human Larynx,” J. Acoust. Soc. Am. 29, 626–631 (1957)] as a basis, a quasistatic model of larynx activity during phonation has been developed. A computer simulation of this larynx model in conjunction with models of the vocal and subglottal tracts permits calculation of the various air-flow and pressure waveforms associated with the vocal-cord operation. Results of the simulation as they pertain to (1) correspondence with actual experiments, (2) physiological control of pitch, and (3) vocal source-vocal tract interaction are presented. The air-flow per cycle corresponds with average pressure and flow measurements made on singers and the waveforms and spectra are of the same forms as those obtained by inverse filtering. Source-tract interaction appears to be minimal. [Work supported in part by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare, by the U. S. Air Force Cambridge Research Laboratories, OAR, by Project MAC, an MIT research program sponsored by the U. S. Department of Defense.]
Distributions of Silent Periods in Speech: Stutterers versus Nonstutterers
Authors: Watson Charles S. , Love Laura R.
Published: September 2005

The distribution of silent periods in speech (frequency of occurrence of silent periods as a function of their duration) has been shown by other investigators to be a stable characteristic of the individual speaker, but these distributions differ considerably among speakers. Data are presented that extend this finding, previously established for silent periods ranging from 0.5 to 10.0 sec, to intervals as brief as 0.1 sec. Silent periods between 0.1 and 0.5 sec in the present data are found to be even more effective than the longer periods in distinguishing between speakers. Comparison between average distributions for normal speakers and stutterers shows unusually high numbers of brief silent periods for the stutterers, which could not be attributed to overt stuttering. [Work supported in part under a grant from the National Aeronautics and Space Administration through the U. S. Office of Naval Research.]
Impact-Noise Rating of Various Floors
Authors: Mariner T. , Hehmann H. W.
Published: September 2005

The impact-noise characteristics of approximately 50 floors have been examined using both the standard (ISO) hammer machine and real footfall as sources of excitation. The floors include concrete and wood-base constructions; isolation layers; furred construction; simple and composite surfacings of various degrees of compliance; suspended ceilings. The recently introduced impact-noise rating (INR), derived from machine data, is compared with the objective loudness computed from footfall spectra. The scatter of data confirms the authors' earlier conclusion that a rating method based on the standard hammer machine does not rank-order floors with adequate precision [T. Mariner, J. Acoust. Soc. Am. 35, 1453 (1963); T. Mariner et al., Building Res. 1, No. 1, 52–60 (1964); T. Mariner, J. Acoust. Soc. Am. 36, 1024(A) (1964); H. W. Hehmann, ibid. 36, 1024(A) (1964)].
Test Procedure for Evaluating Impact Transmission through Structures
Authors: Huggins Donald N.
Published: September 2005

As part of the development of facilities at this laboratory to assess the over-all acoustical performance of floor-ceiling structures, a generalized impact sound-transmission test procedure has evolved for evaluating floor response to direct-impact excitation on the upper surface. The use of footsteps as an impacting source, the measurement of the downstairs sound-pressure response, and the relationship between this objective measurement and the level of random noise subjectively judged to just mask the transmitted footfalls are discussed. Test results on floors evaluated by the ISO tapping-machine procedure and by this alternate impact method are presented and the implications of the two methods are reviewed. [Work supported in part by the Insulation Board Institute.]
Multimode Response of Panels to Sonic Boom
Authors: Crocker Malcolm J.
Published: September 2005

The response of panels with simply supported and fully fixed boundary conditions to normal or traveling shock waves from sonic boom and explosions has been studied both theoretically and experimentally. The theory gives, by means of a Duhamel integral method, a closed-form solution for the displacement and strain time histories for panels subjected to the above loads. It is found that the contribution to the panel displacement of the higher modes is relatively small. However, the panel strain time history is highly dependent upon the contributions of higher modes and the panel strain computed merely from the first mode response can seriously under-estimate the magnitude of the maximum strain. Good agreement is obtained between the experimental and theoretical strain maxima; also the initial part of the strain time history is predicted by the theory with fair accuracy. Since the maximum strain rather than maximum displacement is a better criterion for determining panel failure, the theory developed to predict the strain time history has applications in the design of windows or walls to resist sonic boom or explosive blast.
Probability Density of a Frequency-Modulated Sound Signal in a Reverberant Enclosure
Authors: Gammell Paul M. , Waterhouse Richard V.
Published: September 2005

One of the statistics of a random sound field of the type used for transducer calibration in a reverberant enclosure is the distribution in time of the instantaneous sound pressure at a fixed point in space. Theoretical results are presented showing that the probability density of the instantaneous sound pressure in an enclosure excited by an FM source tends toward Gaussian if the source contains a large number of sidebands at which the frequency response of the enclosure is uncorrelated. The smallest frequency interval required for the responses to be uncorrelated is obtained from the autocorrelation function of the room response, which can be obtained from the decay time of the room. The number of sidebands at which the responses are uncorrelated, rather than the number of sidebands having appreciable power, is the determining factor. Experimental results are presented which bear out the theoretical predictions. [Work supported by the U. S. Office of Naval Research.]
Shock-Tube Techniques for Pressure Calibration of Microphones
Authors: Dahlke H. E. , Robinson D. A. , Van Houten John J.
Published: September 2005

Measurement of boundary-layer noise, shock-wave phenomena, and ballistic pressures are interpreted in terms of the pressure response of a microphone. These measurements require a flush-mounted transducer capable of providing accurate information well above audio frequencies. Current methods of microphone pressure calibration are inadequate above frequencies of the order of 20 kc/sec. A useful approach to microphone calibration is to determine the microphone's steady-state response from its transient response to an appropriate pressure input. The shock tube has been used to provide a “step-function” pressure input simulating sound-pressure levels in excess of 180 dB. The microphone response to this “step function” provides a measure of high-frequency resonance characteristics, damping, and an absolute measure of sensitivity. The technique provides a practical method of microphone pressure calibration approaching a frequency of 1 Mc/sec. The difficulty in this approach lies in interpreting transient-response characteristics in terms of the desired steady-state response of the microphone. This paper discusses various shock-tube techniques and methods for determining steady-state response from transient response.