bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Measurement of Nonlinear Magnetostrictive Parameters on Strip Specimens
Authors: Karplus Henry B.
Published: September 2005

The conventional, linear, thermodynamic interrelations of field induction stress and strain in a magnetostrictive material are valid only for small amplitudes. For large amplitudes, such as are needed in a high-power projector, the nonlinear interrelations must be measured. Apparatus is described in which stress, strain, or field is held constant while any two of the remaining parameters are displayed on a cathode-ray tube face. Measurements are made on a strip specimen of about 0.4 mm2 section. At constant strain, the sample is clamped. The clamp consists in part of a piezoelectric tube which also senses the stress. At constant stress the motion of the sample is sensed with a variable capacitance micrometer. The integrated difference of the output of a pair of pickup coils one of which surrounds the specimen yields the induction in the specimen. The field is supplied by 60 cps and superimposed direct current in a large external solenoid. Polarization and excitation fields may exceed 1000 oe. Optimum excitation and polarization fields are computed for strip specimens used as transducers. A peak dynamic stress of 8 × 107 dynes cm−2 and strain of 4 × 10−5 for “A” nickel are in good agreement with the literature. (This research was supported by the Office of Naval Research.)
On the “Psychophysical Law.”
Authors: Zwislocki J. , Hellman R.
Published: September 2005

In recent years, S. S. Stevens revitalized the discussion concerning the growth of sensation as a function of stimulus intensity by showing that the relationship can be described more adequately in terms of a power function suggested by Plateau than in terms of a logarithmic function derived by Fechner. The power function applied by Stevens to various sense modalities holds at medium and high sensation levels. At near threshold intensities, it appears to deviate from empirical data. Attempts have been made to correct the discrepancy by adding a constant in the intensity domain. It is shown that such a correction is inadequate and that an additive constant on the sensation continuum produces a better approximation of the experimental data. The derivation of the mathematical expression is followed by examples in which experimental and theoretical data obtained under various psychophysical conditions are compared. (Work supported by a contract between the Office of Naval Research and Syracuse University.)
Subjective Scale of Tonal Volume
Authors: Terrace H. S. , Stevens S. S.
Published: September 2005

Tonal volume is defined as the apparent size or space-filling attribute of a sound. In six experiments, groups of 10 subjects estimated the magnitude of the apparent volume of tones selected from the equal-volume contours previously determined by G. J. Thomas. For each experiment, two cuts, widely spaced, were made across each of five contours. These cuts defined a set of ten tones, each of a different frequency and intensity. In order to check the reliability of the magnitude estimations of volume, the tones from each cut were used in at least two experiments. In each experiment, one of the two tones from the middle contour served as a modulus (standard) whose value was called 10. The data from all six experiments confirm the general shape of Thomas' equal-volume contours. Magnitude estimations of volume had nearly identical values for all tones taken from the same contour. The averaged values from the six experiments indicate that the subjective magnitude associated with each of Thomas' equal-volume contours is approximately twice that of the next smallest contour. From these contour values it follows that volume grows as a power function of sound pressure, but that the exponent increases markedly with frequency.
Studies of Subjective and Objective Measures of Loudness
Authors: Kryter K. D. , Williams Carl
Published: September 2005

To compute or estimate the subjective loudness of a complex sound from physical measures, one must take into account both the position of its components on the frequency scale and the total bandwidth of the sound. To this end, Stevens and later Zwicker have proposed methods that take into account the presumed role these two prime factors play in the determination of loudness. Kryter found that Stevens' loudness method did not predict accurately the judgments people made of the relative “noisiness” of aircraft sounds, and he proposed a new unit (PNdb), based on Stevens' methodological concepts, for predictive purposes. However, loudness as calculated by Zwicker's method agreed well with the judged “noisiness” of the aircraft sounds. Recent calculations we have made indicate that loudness judgments of complex sounds obtained by Quietsch and Wiese, in Germany, and Copeland et al., in England, are in closer agreement with their PNdb values than with Phons determined either by Zwicker's or Stevens' methods. Data will be presented on the accuracies of various calculation and sound level meter measuring schemes for predicting the loudness and noisiness of complex sounds as previously reported by several investigators and as determined in experiments just completed in this laboratory.
Differential Pitch Threshold Shift Associated with Moderately High-Level Background Noise
Authors: Voots R. J.
Published: September 2005

Normal ears are known to exhibit a distortion of the normal loudness growth function (pseudo-recruitment) in the presence of threshold shifting levels of thermal noise. A deterioration of the pitch discrimination function has often been associated with loudness recruitment in abnormal ears. This study involves the determination of differential pitch thresholds (DPT) for normals in the presence of 50- to 70-db threshold shifting levels of thermal noise for comparison with determinations in quiet. Testing for DPT was done with an automated instrument using a modified method of constant stimuli. Frequencies tested were 500, 1000, 2000, and 4000 cps at 50-db SL. Levels in the noise situation were equated to the quiet SL using a loudness balancing method. Maximum shifts in the DPT were found at the highest frequency though most subjects showed noticeable shifts at the other frequencies, also. As might be expected, some increase in variability is also evident in the data obtained in noise. (This work supported in part by a Public Health Service grant.)
Influence of Simulated Feedback and Time on Task on Responding to Simple Auditory Stimuli
Authors: Loeb Michel , Schmidt E. Allyn
Published: September 2005

It has been suggested that individuals responding to infrequent “randomly” occurring inconspicuous auditory stimuli should not exhibit a progressive decrement in performance over time comparable to that noted with certain visual stimuli. It has been found, when visual stimuli are employed, that knowledge of results enhances performance, and this effect is commonly described as being due to “feedback” to the organism. In the present experiments subjects were required to respond rapidly to intermittently occurring low-frequency tones during four 50-min sessions. In half the sessions the SL of the tones was 10 db; in half, 60 db. In half the sessions at each SL, O was supposedly told after each response whether he responded more slowly or more quickly than on the previous response. Actually the information given was randomly determined and unrelated to performance. Analysis of the data indicated that median response time increased significantly with time on task, except in the session where simulated feedback was given after the 60-db stimuli. Failures to respond were unrelated to time on task. RT was significantly smaller and failures to respond significantly fewer at 10 db when simulated feedback was given. Implications of the findings are discussed.
Ray-Theory Intensity Oscillations
Authors: Klerer Melvin
Published: September 2005

The intensity pattern vs range for a CW point source in a model of the deep ocean has been computed using an IBM 650 digital computer. The model chosen assumed a flat bottom over a liquid stratum and a range independent linearly segmented velocity profile. The intensity pattern was obtained by coherent addition of the various multipath arrivals including phase shifts due to Rayleigh reflection. It is indicated that these methods can be used routinely on a digital computer even for the case of irregular boundaries. (This work was supported by the Office of Naval Research.)
Optimum Frequencies for Active Sonar
Authors: Stewart J. L. , Westerfield E. C. , Brandon M. K.
Published: September 2005

The method of determination of the optimum frequencies for active sonar without knowledge of the absolute values of the sonar set parameters, but only of their frequency dependence, appears to have been originated by J. W. Horton in about 1945 and is to be found in his recent text [J. W. Horton, Fundamentals of Sonar (United States Naval Institute, 1957), pp. 317–324, 344–352]. This theory has been simplified and extended to include search rate and the ratio of echo to noise plus reverberation. The inclusion of search and reverberation only slightly modifies the results obtained by maximizing echo-to-noise ratio alone because of the dominating effect of the frequency dependence of the exponential attenuation term in the transmission loss. The exact frequency dependence of the attenuation is critical as a result of this dominance. The slope of the optimum frequency vs range curve on a log-log plot is the negative of the reciprocal of the frequency exponent of the attenuation.
Digital Computer Simulation Program for Studying Undersea Acoustic Detection Techniques
Authors: Drinan J. D. , Heart F. E. , Mathiasen A. A. , Ornstein S. M.
Published: September 2005

A digital computer simulation program system has been constructed to permit controlled experiments with detection techniques for underwater acoustic arrays. The first part of the system consists of a generator program to which one may specify, within broad limits, the positions and acoustic spectra of sound sources, the background noise level and transmission characteristics of the medium, and the positions and response characteristics of the detectors. For a particular test configuration the program generates samples of the amplitude of the resultant acoustic energy at each detector. By using a sample rate of 1200 samples per second, it is feasible to generate several seconds, or possibly minutes, of data. The second part of the system is a “pluggable unit” consisting of a processing program which embodies the particular detection logic to be investigated. One such processor, based on standard correlation techniques, is now being used to evaluate the system. This simulation system appears useful in three ways: first. it permits an examination of the performance of a particular signal detection method against a variety of inputs; second, it permits comparison of different signal detection techniques against typical inputs; finally, it represents an approach which may find application to other problems of acoustic detection. (The research in this document was supported jointly by the Army, Navy, and Air Force under contract with the Massachusetts Institute of Technology.)
Instrumentation for Deep Ocean Acoustic Research
Authors: Blickley L. F.
Published: September 2005

In response to the need for direct measurements of sound propagation phenomena at great ocean depths, a Government-Industry team built and tested in 1959 a medium-power transducer for use in deep ocean acoustic research. During the experiments (1} an instrument package weighing over one-half a ton was lowered by cable to depths greater than 10 000 ft and (2} the transducer was operated at great depths. The deep-sea instrument pack age consists of an acoustic projector mounted on a pressure hull which contained control instrumentation. This unit was suspended from a specially designed ship by a double armored cable. The complete underwater unit, designed to operate to depths of 3000 fathoms, weighs 1600 lb. The projector, which is resonant at 2700 cps, has an acoustic power output of several kilowatts. The instrumentation inside the pressure hull permits the transducer to be used both as a projector and a receiver. The high-power electronic driver and recording instrumentation is located on the research vessel. A total of 100 hr of operating time has accumulated on this equipment. The purpose of this paper is to make available to those interested in deep-sea research the data on equipment performance collected during the operation.
Determining the Direction of a Sound Wave by Using a Scanned-Line Array
Authors: Pigott M. T. , Whitmarsh D. C.
Published: September 2005

An attempt is being made to employ independent hydrophone elements uniformly spaced along a straight line to deduce the bearing of an incoming plane sound wave. Upon sampling the outputs of the hydrophone elements in succession, one simulates a single hydrophone moving relative to the sound wave. The signal measured in such a case would have a frequency of f = f0 (1 − α cos θ) where f0 is the frequency of the sound, α is the ratio of the scanning speed to the sound speed. and θ is the bearing angle to be deduced from a measurement of f. If two mutually orthogonal lines of hydrophones are used in the horizontal plane, the azimuth of the incoming sound wave can be determined uniquely, and the elevation angle can be found with “up vs down” ambiguity present. Calculations show that the limit of solid angle resolution is determined by the ratio of the wavelength to hydrophone array length. The solid angle resolution is calculated from the bearing resolution Δθ = π N for a single line hydrophone where N is a number > 1. The necessary minimum number of hydrophones per unit length depends upon the arbitrary choice of α and the Shannon Sampling Theorem. The signal-to-noise ratio improves with increasing resolution, the improvement being proportional to N.
Combined Effects of Sonic and Gamma Irradiation
Authors: Benson R. W.
Published: September 2005

The combined effects of sonic and gamma energy were studied to determine if chemical reactions may be produced which are different from those reactions initiated by either type of these energies alone. Both gamma and ultrasonic irradiations can cause changes in many systems. The mechanisms responsible for these reactions are, in general, different. Consequently, it is expected that the combined use of these two types of energy sources probably will not result in a linear addition relationship. The degradation of polystyrene in carbon tetrachloride solution was investigated since this reaction is known to be initiated efficiently by both ultrasonic and gamma radiations. (This research was supported by Armour Research Foundation.)
Ultrasonic Relaxation in Dichloroethane and Dibromoethane Solutions
Authors: Piercy J. E.
Published: September 2005

The ultrasonic absorption of liquid 1:2 dichloro- and 1:2 dibromo-ethane has been found by previous investigators to have an anomalous negative temperature coefficient for temperatures near the freezing point, namely −35 and +10°C, respectively, and a number of molecular mechanisms have been proposed for this anomaly. The absorption of solutions of these substances in acetone, ether, and n-hexane has now been measured in the frequency region around 40 Mc/sec at temperatures down to −90° C. A relaxation is found in all solutions with a characteristic frequency of 40 Mc/sec at approximately −70°C for dichloroethane solutions and −60°C for dibromoethane solutions, the negative temperature coefficient of absorption in the pure liquid at higher temperatures being caused by this same relaxation with a characteristic frequency then much higher than measurement frequencies. The behavior of the relaxation with changes in concentration and solvent is consistent with its molecular origin, being the interconversion of gauche and trans molecular isomers by the sound wave. Present measurements indicate an activation energy of about 3 kcal/mole for dilute solutions of dichloroethane in ether and 4 kcal/mole for dilute solutions of dibromoethane in acetone.
Ultrasonic Propagation in Water Vapor and Other Gases
Authors: Ener C. , Herbjørnsen O. , Fujii Y. , Nyborg Wesley L.
Published: September 2005

A system has been devised for measurement of sound absorption and velocity in gases and vapors at pressures less than atmospheric down to pressures of about 2 mm Hg. Sound pulses (65 kc) propagate from source to receiver, whose separation r is variable up to about 60 cm; the geometry is such that the received amplitude varies as (r−1 e−ατ). The experimental tank is of stainless steel; its fittings and parts are designed to minimize condensation and adsorption at walls, corners, cracks, etc. The tank is completely surrounded by a water bath, permitting control of temperature up to 90°C. Absorption and velocity measurements in A, Ne, O2, and N2 yield results in good agreement with classical theory, in the case of A and Ne, and with recent results of others in the case of N2, O2, Measurements were made in water vapor at 40°C and at pressures from 2 to 45 mm Hg (about 1–25 Mc/atm). The sound velocity agrees well with the classical value while the absorption exceeds the classical by a constant percentage of about 50%. Attributing this excess to rotational relaxation. we find that for our conditions the frequency for vibrational relaxation must be less than about 100 kc/atm. Reasons are yet to be found for the discrepancy of this result with findings of others. (Supported in part by the Office of Naval Research.)
High-Amplitude Internal Friction and Its Relation to Fatigue in Metals
Authors: Mason Warren P.
Published: September 2005

By using a barium titanate transducer coupled to two brass exponential horns, in one of which a sample of metal is mounted, it has been possible to measure the internal friction of the sample up to strains of 5×10−3. There are four strain regions for which different internal friction behavior is observed and where presumably different dislocation mechanisms are operating. The final phase is marked by a rapidly rising internal friction and a rapidly failing elastic modulus. In this region fatigue of the sample can occur for a large number of cycles for stresses no larger than twice that at the initiation of this phase. A discussion is given of possible dislocation models for the last two phases, and evidence is presented that they are connected with the multiplication of dislocations by the Frank-Read mechanism. Fatigue appears to result from the large number of vacancies produced when dislocation jogs are dragged through the material. It is shown that fatigue stresses can be increased if peak length dislocation loops can be made shorter. This can be done by several metallurgical processes.
Sonic Fatigue Testing of Flight Vehicle Structures—Facilities and Techniques
Authors: Spice Bernard J.
Published: September 2005

The structural fatigue problems caused by engine noise and aerodynamic boundary layer turbulence necessitate the laboratory testing of specimens that are typical of the flight vehicle's structure. Generally, specimens of panel configuration are tested to facilitate a comparison of the test results. The present noise source in the laboratory that is capable of generating the required sound pressure levels for such testing is the discrete frequency siren. This may employ either the normal or grazing incidence technique. The siren discussed herein uses the grazing incidence, plane-wave tube principle. Specimens of up to 14 ft long and 4 ft wide can be accommodated and tested to sound pressure levels of 170 db (re 0.0002 microbar) at frequencies between 50 cps and 1000 cps. A siren plenum chamber of 6-ft diameter with a rotor of 3-ft diameter is utilized to obtain these sound pressure levels. The testing techniques used in the operation of this facility are described.
Use of the Fourier Series Bandlimitation Assumption in the Analysis of Psycho-physical Data
Authors: Tanner Wilson P.
Published: September 2005

Whenever a general model is to be applied to a particular problem, it is necessary to make specializing assumptions to tailor the model to fit the particular application. In order to make quantitative statements of upper bounds of performance in detection tasks, an assumption that both the noise waveforms and the signal plus noise waveforms are Fourier series bandlimited in the same way is made. This assumption permits an analysis in terms of 2WT discrete values. A detailed discussion of the assumptions involved and why each is made is presented. The problem of the influence of approximations to the assumptions on the results is considered. It is argued that, for an analysis based on the assumptions to be used, it is only necessary for the physical conditions to be of such a nature that the analysis applies. It is not necessary either that the physical conditions agree precisely with the assumptions or that they approximate them. A set of realizable laboratory conditions are described such that the analysis employing the 2WT discrete samples is judged to apply. It is contended that the agreement between the laboratory conditions and the analysis is adequate to satisfy the purposes for which the analysis is employed.
Further Results on the Detectability of Known Signals in Gaussian Noise
Authors: Martel H. C. , Mathews Max V.
Published: September 2005

In a previous paper Mathews and David pointed out that the theoretical detectability of a known signal in noise, whose power spectrum is bandlimited, may be larger than 2E/N0. However, their results showed only a small improvement over 2E/N0, and nothing was said concerning noise with a rational power spectrum. For the case of a known signal in noise of rational power spectrum, a test statistic which maximizes (in a certain sense) the detectability has been derived. By using this test statistic the detectability can be calculated. For a signal which is a constant in noise whose power spectrum has only poles, the detectability increases as the number of poles is increased to make the noise more nearly bandlimited. The results for the rational power spectrum case suggested measuring derivatives as a test statistic for the bandlimited noise case. By using only derivatives for the statistic, the detectability of a known signal in bandlimited noise is shown to be proportional to the number of derivatives measured. Thus, examples are presented in which theoretical detectability increases without bound either as a rational noise approaches a bandlimited noise or as more derivatives of a bandlimited noise are measured. We feel these results have very little to do with subjective signal perception.
Amplitude Discrimination as a Function of Three Variables
Authors: Clarke Frank R.
Published: September 2005

Two alternative forced-choice experiments were conducted in which the observers were required to report which of two sinusoidal signals had the larger amplitude. Three variables were systematically studied: (1) the level of the background noise; (2) the level of the base carrier; and (3) the energy of the difference signal. Data are reported for four observers. These data are fit by equations of the form (d′)2 = η2E/−(N0 + kVB2), where E is the energy of the difference signal, VB2 is proportional to the power of the base carrier, and N0 is the noise power per unit bandwidth. Both η and k are parameters describing the individual observers. Although these studies were analyzed in the framework of the theory of signal detectability, results are reported using the traditional percent of correct responses as a dependent variable. (The study upon which this paper is based was sponsored by the U. S. Air Force Office of Scientific Research.)
Patient Reactions to Hospital Noises
Authors: Cardinell Richmond L. , Goodfriend Lewis S.
Published: September 2005

During a comprehensive study of hospital noise made in eight hospitals, patient reactions were determined through questionnaires and voluntary comments. A total of 61 annoying sounds were tabulated and scored on the basis of annoyance. These sounds have been arranged in rank order for each of the institutions and in order of prevalence in a majority of the hospitals. (This work supported by the U. S. Public Health Service.)
Wind Tunnel Noise Measurements
Authors: Galloway William J.
Published: September 2005

Measurements have been made of the noise produced by two blow-down wind tunnels. One tunnel, having a 1-ft × 1-ft test section, was operating at test section Mach numbers from 0.2 to 3.5. The second tunnel, having a 4-ft × 4-ft test section, was operated with test section Mach numbers of 1.2 and 4.0. Measurements were made in the exhaust plena of both tunnels to evaluate noise associated with a normal shock system. Measurements also were made in the vicinity of the control valves to evaluate their noise characteristics. Acoustic data are presented for cases where the tunnel operating parameters were varied to obtain the individual effects on noise of valve pressure ratio, test section Mach number, and air weight flow. These data have been used to obtain relationships between tunnel operating parameters and the efficiency of conversion of mechanical stream power to acoustic power. Comparisons are made to previous results of H. Medwin, A. C. Pietrasanta, and I. Dyer [J. Acoust. Soc. Am. 27, 1015 (1955)].
Fundamental Notions Concerning Convection of Aerodynamic Noise Generators
Authors: Powell Alan
Published: September 2005

Some new ideas are presented concerning the resolution of Lighthills paradox: “The feature … which is the hardest of all to explain … is the accuracy with which the acoustic power output [of turbulent jets] varies with U8” since convection effects necessary to account for the characteristic sound pattern result in the index greatly exceeding eight, together with an excessive frequency rise. It is argued that, because acoustic quadrupoles have a very local near field, the full effect of convection according to Lighthills' concept should not be applied to generators too far from the jet boundary (in terms of local frequency and sound speed). Some simple and plausible assumptions then lead to an explanation of the empirical U8, the slow frequency rise, a basis for its empirical scale fD/aj, and the absence of changes due to Doppler effects, yet maintaining the proper directional characteristics, including that of the preferred direction of the higher frequencies lying further from the jet axis. With such encouragement, it is hoped to place such reasoning in a mathematical framework so that such radical ideas may be put to crucial quantitative test. (This work has been supported partially by the Office of Naval Research, U. S. Navy.)
Measured Noise in Space Vehicles
Authors: Hilton David A. , Mayes William H.
Published: September 2005

Measured internal-noise time histories from on-board tape recordings are presented for three different ground-launched rocket-powered space vehicles. Surface-pressure measurements for one of these vehicles are also included. For the vehicles measured, noise of aerodynamic origin was noted to have higher levels and to persist for a longer time than noise from other sources. Particular attention is given to the aerodynamic noise during the exit phase of the flights for which sound pressure levels and spectra are presented over a wide range of Mach numbers and dynamic pressures and for different aerodynamic shapes. The vehicles used in these investigations were launched by the NASA in connection with the development program of Project Mercury.
Heat Flow and Sonic Microstreaming
Authors: Gould R. K. , Nyborg Wesley L.
Published: September 2005

Measurements are being made to determine solid-to-liquid heat flow in the presence of sonically induced microstreaming near the interface. The microstreaming is induced by an air bubble vibrating near the region of heat flow. The air bubble is placed by means of a micropipette on the bottom of a clear plastic chamber containing the liquid. A 2-kc piston vibrator operated at low amplitudes a few centimeters above the bubble causes the bubble to become a strong source of sonic microstreaming. Imbedded in the plastic on which the bubble sits, and concentric with the bubble, is a thin multilayered annulus, the top of which is flush with the surface of the plastic. For a typical annulus the too layer is copper foil, the second is constantan; the bottom layer is a thermistor wafer through which current can be sent to produce a desired amount of heating. The thermal emf developed at the copper-constantan junction can be measured. Thus we have a source of known heat flow and known surface temperature. Investigations have been carried out in which heat flow was measured as a function of sonic amplitude, the surface temperature of the annulus being kept constant. The results indicate that, when the sonic amplitude A is small, the heat flow H varies linearly with A. This linear relationship between H and A is in agreement with the predictions of a simplified theory. At higher amplitudes the bubble may move about erratically, so that consistent readings are difficult to obtain. (Supported in part by the U. S. Air Force Office of Scientific Research.)
Measurement of the Nonlinearity Parameter in Water and Xylene
Authors: Adler Laszlo
Published: September 2005

The rate at which the second harmonic is developed during the propagation of an initially sinusoidal ultrasonic wave depends on the nonlinearity of the liquid. A stainless steel plate is used to filter out the first or second harmonic, respectively. The rate of growth of the second harmonic, as a function of distance and pressure, is measured by means of the diffraction pattern produced by this wave. From the result of this measurement the parameter B/A (describing nonlinearity) is calculated. (This work was supported by the Office of Ordnance Research, U. S. Army.)
Propagation of Finite Amplitude Sound in a Relaxing Medium
Authors: Attanasio C. R. , Beyer R. T.
Published: September 2005

The harmonic content of a finite-amplitude sound wave of moderate intensity has been examined in terms of the method developed by C. Eckart [Phys. Rev. 73, 68 (1948)]. In particular, the analysis indicates a considerable reduction in the growth rate of the second harmonic relative to the corresponding rate for a nonrelaxing medium. The results of the calculation agree qualitatively with the small amount of data available. (Work supported in part by the Office of Naval Research.)
A Case in Which the Small-Signal Approximation Is Not Applicable to Sound Waves of Small Amplitude
Authors: Blackstock David T.
Published: September 2005

According to small-signal theory, when a step-wave of small amplitude is propagated in a viscous gas, the waveform never reaches a stable configuration. The steepness of the step is continually reduced as the wave propagates. According to shock-wave theory, however, the step-wave of small amplitude does most certainly attain a stable configuration, namely that of the steady weak shock. The contradiction between the predictions of the two theories will be explored. An improved “small-signal” wave equation, applicable for low-intensity sounds in a viscous gas, will be presented and a solution given for the case of a step-wave. Finally, the effect of thermal conduction in the gas will be indicated. (This work was supported in part by the Office of Naval Research.)
Nonlinear Acoustic Properties of Screens
Authors: Westervelt Peter J. , Allen Clayton H. , Lansil Richard S.
Published: September 2005

As part of a fundamental study on the nonlinear behavior of acoustical materials at high sound intensities, we have examined a fine-wire screen. The theoretical analysis has been based on considering the screen to be an assemblage of noninteracting orifices. On this basis, a formula for the specific nonlinear resistance, valid at low frequencies, has been found which agrees quite well with static flow measurements. Criteria have been established for the onset of nonlinear behavior. These criteria are valid over a wide range of frequencies. (This effort has been supported by Nobs 77075.)
Experimental Investigation of a Parametric End Array
Authors: Bellin J. L. S. , Westervelt Peter J. , Beyer R. T.
Published: September 2005

To obtain experimental verification of the expression for an acoustic end-fire array derived by Westervelt a 13.4-Mc crystal, mounted inside a water-filled tank, was driven simultaneously by 13-Mc and 14-Mc transmitters. A small barium titanate probe, free to rotate in the horizontal plane, was used to detect the 1 Mc difference frequency radiated by the interacting carrier beams. This transducer was connected in turn with a sensitive calibrated receiver. The entire system permits a determination of the directivity pattern and the absolute magnitude of the radiated 1-Mc signal. The results of experiments using this arrangement, as well as of trials with both higher and lower difference frequencies, are in good agreement with the theoretical expression mentioned above.
Research Problems and Progress in Musical Acoustics
Authors: Martin Daniel W.
Published: September 2005

The status of knowledge in the field of musical acoustics is surveyed. An analysis of research needs is attempted in a general way, and several specific examples of basic unsolved problems are outlined.
Lateralization vs Localization
Authors: Jeffress Lloyd A. , Taylor Robert W.
Published: September 2005

As we all know, sounds heard through earphones appear to be inside our head instead of “out there.” Because of this, many investigators use the term “lateralization” for the spatial aspects of such sounds and reserve “localization” for sounds from external sources. The present study finds the distinction unnecessary. Subjects listening to bursts of wide-band noise through earphones were asked to indicate where the sound would have come from if its source were external. To aid him in this judgment, small lamps were placed at 15° intervals in the horizontal plane around the subject. He was provided with a switch with which he could light any one of the lamps which then flashed in synchronism with the sound. His task was to select the lamp which most nearly represented the direction of the imaginary sound source. Interaural time differences appropriate to the various directions were provided by a delay line. The results show that subjects can make this judgment from the start with little difficulty, that their performances compare favorably with localization judgments based on sound from external sources, and that practice and prompting do not improve their accuracy. (This work was partially supported by the Bureau of Ships.)
Lateralization of Acoustic Transients
Authors: Teas Don C.
Published: September 2005

Acoustic transients were presented binaurally to observers via earphones. The intensities at the two ears for all stimuli were equal. The dependent variable was the interaural time difference set by the observer for one pair of clicks which remained constant with respect to the other variables throughout the experiment. The independent variables, frequency content and level, were altered in a second pair of clicks, while the parameter over which these effects were assessed was the interaural time difference of the second pair. For a given frequency content and level, the experimenter fixed the interaural time difference of the second pair of clicks at either 0, 400, or 700 μsec. The observer listened alternately to one of the two click pairs and, by changing the interaural time difference of the first pair, matched the two for intracranial position. When the two click pairs were the same in frequency content and level, the interaural time difference set by the observer for one pair was the same as that set by the experimenter for the other, giving a slope of 1.0 to the curve relating the two interaural time differences for the two pairs of clicks. When the two pairs were different in frequency content or level, the slope of this matching curve departed from 1.0. It follows, therefore, that the relation between interaural time and position is not unique but varies with frequency content and level. These and related observations suggest that a cross-correlation function of the stimuli at the two ears or of the N1 responses alone is insufficient to account for the location of a click in phenomenal space.
Models for Approximating Basilar Membrane Displacement
Authors: Flanagan J. L.
Published: September 2005

Three analytical models are developed for estimating the displacement of the basilar membrane in the human ear when the sound pressure at the eardrum is known. Frequency-domain data, derived experimentally by Bekesy, are Fourier transformed to examine the impulse response of the membrane. Time-domain and frequency-domain responses of the models are compared with the experimental data. Excitation of the models by periodic impulses is considered. Calculations of membrane displacement are made for excitation by positive pulses and by alternately positive and negative pulses. Applicability of the results to the perception of pitch is indicated.
Factor Analysis of Absolute Auditory Thresholds
Authors: O'Hare John J.
Published: September 2005

Graphic recordings were obtained of the absolute thresholds to a series of twenty (20) pure tones, in equal-mel steps from 200 to 6000 cps, in steps of 1 db. Each tone was pulsed on a 0.50 duty cycle with a 500-msec duration for a period of 30 sec. The equipment was carefully calibrated to yield thresholds in db SPL. Fifty-seven young male adults with normal (plus or minus 15-db) hearing served as the observers. The data were normalized, a product-moment correlation applied, and the correlation matrix factored according to the complete centroid technique. Three significant oblique factors were obtained. The first had high loadings in the 200 to 1000-cps range, the second loaded high from 2200–6000 cps, and the third yielded high loadings in the 1200 to 2000-cps interval. Results are discussed in relation to Wever's theory of audibility.
Measurement of Auditory Adaptation
Authors: Wright H. N.
Published: September 2005

One estimate of perstimulatory auditory adaptation to a tone sustained in an experimental ear has been the decrease in intensity in the contralateral control ear required to maintain the median plane localization of successive 15-sec comparison stimuli. Use of such a measure assumes that only a negligible amount of adaptation occurs in the control ear during this 15 sec. The results of the present investigation show that this assumption is not tenable by demonstrating that the amount of measured adaptation to a tone sustained in the experimental ear is dependent upon the duration of the comparison stimulus to the control ear. Adaptation in the control ear may be demonstrated easily by first sustaining a tone in the experimental ear until it has reached an asymptotic level of adaptation and then also sustaining the comparison stimulus at a constant intensity in the contralateral control ear. As the control ear adapts, the phantom sound image accompanying the tones in both ears moves toward the experimental ear. The time for this moving phantom sound to reach the median plane depends upon the intensity of the comparison tone as well as on the frequency and intensity of the tone to the originally adapted experimental ear. [This study was supported by a grant from the National Institutes of Health (NINDB).]
Light Diffraction by Progressive Ultrasonic Waves in Plexiglas
Authors: Mayer Walter G.
Published: September 2005

The optical grating produced by a progressive ultrasonic wave in Plexiglas is used to verify directly the Raman-Nath theory for solids after it is shown that no finite amplitude distortion of the waveform is present. The absorption coefficient is determined by evaluating the diffraction pattern. (This work was supported by the Office of Naval Research, U. S. Navy, and by a National Science Foundation grant.)
Effect of Surface Reflections on Directive Sound Sources
Authors: Thompson W. , Junger M. C.
Published: September 2005

Reflections from the sea surface affect the acoustic power radiated by sound sources located at shallow depths. Furthermore, these surface reflections produce propagation anomalies characterized by a pattern of interference fringes and, at larger range, by abnormally high spreading losses known as the acoustic Lloyd mirror effect. Both phenomena are well known for simple, nondirectional sources. They are studied here for directive sources whose directivity patterns have a horizontal or tilted main lobe. Directive sources differ from simple sources in that the surface-reflected and direct rays are of different intensity. This causes a marked blurring of the interference fringe pattern, but has a negligible effect on the propagation anomaly at the long ranges where the Lloyd mirror effect holds. The effect on power output of phase cancellations and reinforcements by surface-reflected sound waves is generally less marked than for a simple source. (This work was sponsored by the Office of Naval Research.)
Experimental Determination of the Depth of Focus of Transducers Using Elliptical and Modified Parabolic Reflector Systems
Authors: Jones J. D. , Wallace R. H.
Published: September 2005

When operating in the near zone of a large aperture transducer, one must use a focusing technique to realize the far-field resolving power of the aperture. For many applications the depth of focus is an important consideration. Experimental data will be presented showing the beam width, minor-lobe suppression, and sensitivity as a function of range near the far focus of an elliptic reflector. Data for similar conditions will also be presented for parabolic reflectors with the focal element shifted to obtain optimum directivity conditions. (This work is supported by the Bureau of Ships.)
Computation of the Directivity Pattern and Source Level of a Transducer from Near-Field Measurements
Authors: Baker D. D.
Published: September 2005

Kirchhoff's formula is used to compute the directivity pattern and the source level of a large cylindrical transducer from measurements made near the transducer. Directivity patterns are computed for a plane normal to the axis of the cylinder and a plane which contains the axis of the cylinder. The normal pressure gradient required in the formula is obtained by a simple approximation, and the computations are carried out by means of a numerical integration over the surface of a circular cylinder of finite length. Data have been taken by making various numbers of passes around the transducer at different positions along the axis with a probe hydrophone, or by making one pass with a line hydrophone. There is good agreement between measured and computed patterns and source levels. (This work is supported by the Bureau of Ships.)
Composite Spherical Sonar Transducers
Authors: Green Charles E.
Published: September 2005

This paper describes the construction of and behavior of a large spherical transducer formed as a mosaic of ceramic elements with no inactive material Formulas are shown that describe the several elements which form the building block of the assembly. The developed techniques indicate spheres up to 30 in. in diameter can be easily constructed and a modification of the basic element will permit much larger spheres to be built. Complete evaluation of a 10-in.-diam sphere is shown with efficiencies approaching 100%. Correlation between its evaluation and the theoretical report of S. Hanish at NRL is shown. Behavior in water indicates a good acoustic loading and wide-band operation.
Some Acoustic Characteristics of Underwater Explosions of Hydrogen-Oxygen Mixture
Authors: Leroy C. C. , Parkes D. J. , Sirovich E. M.
Published: September 2005

To meet the requirement for the simple high-powered sound sources necessary in studies of underwater acoustic propagation and geophysical exploration various substitutes for solid explosives such as TNT have, from time to time, been investigated. This experimental study of the acoustic characteristics of explosions of hydrogen-oxygen mixtures represents a systematic attempt to achieve a simple acoustic pulse free from the complicating bubble oscillations that have often discouraged previous investigators. Experimental data are shown relating the intensity and character of the acoustic signal produced to the proportions and amount of gas mixture; to point of ignition; to hydrostatic pressure; to length-to-diameter ratios of chambers and to various chamber appendages and terminations. It is shown that for certain conditions it is possible, almost completely, to suppress or dissipate the bubble pulse. Some information is given about the experimental techniques used and the difficulties which may be associated with the realization of a practical device.
Backward Scattering of Short Pulses from Cylinders in Water
Authors: Diercks K. J. , King W. R. , Horton C. W.
Published: September 2005

The echo structure of backward scattered acoustic energy from hollow air-filled metal cylinders in water was investigated experimentally using pulses which were small compared to the physical dimensions of the cylinders. This is a continuation of the work reported by Barnard and McKinney [J. Acoust. Soc. Am. 33, 226–238 (1961)]. Pulses of 25 and 50μ sec duration at the frequencies 125, 290, and 470 kc were employed. True backscattering was accomplished through the use of a single transducer for transmitting and receiving. For a single transmitted pulse multiple periodic echo pulses were received. The time between the echo pulses and their rate of decay were measured. A periodic circular path about the cylinders was assumed and velocities computed and compared to the longitudinal velocity in infinite plates. Two sets of cylinders, one with constant outside diameter and four wall thicknesses and another having constant wall thickness and four different outside diameters were chosen to represent both thin and thick shells over a wide range of ka values. (This work is supported by the Office of Naval Research.)
Attenuation of Pipe-Organ Tone by Swell Shutters
Authors: Meyer Albert , Wayne William C.
Published: September 2005

The attenuation-frequency characteristic of typical pipe-organ swell shutters was measured, using pipe tones as the source of signal. For shutters fully closed, relative to fully open, the average response shows a uniform negative slope. Several “swell shutter volume control” circuits have been synthesized to achieve this response.
Supplementary Sound for Opera
Authors: Yannopoulos Dino , Martin Daniel W. , Martin David W.
Published: September 2005

A supplementary sound system was one of the technical innovations of the 1961 summer season of grand opera at the Cincinnati Zoo Pavilion, a covered but unenclosed area seating 2500 people. Neither the 85-piece orchestra nor the Metropolitan and European soloists and the chorus required or were provided sound re-enforcement. The versatile, flexible sound-amplification and reproduction system was intended and used instead for a variety of supplementary purposes as follows: (a) auditory relocation of individual instruments or groups from the orchestra pit (actual) to backstage or on-stage (apparent) positions, to fulfill dramatic requirements; (b) solo voice modification and motion, when “supernatural” timbre or spatial effects were appropriate; (c) sound effects which were difficult for the orchestra percussionists to produce as realistically or dramatically as desired; (d) electronic musical instruments. Microphones in the orchestra pit and backstage, stereo tape playback, and a Baldwin electronic organ were the program sources. Sound effects filters, artificial reverberation, and a Choratone (for organ) were available for modification effects. In addition to patch panel interconnection, a keyboard of variable resistance switches provided rapid, smooth transitions among the seven amplification channels leading to different loudspeaker locations (e.g., backstage, on stage, proscenium, ceiling, and rear).