bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the Closed-Response Format on Modified Rhyme-Test Scores
Authors: Williams Carl E. , Woods B. , Hecker Michael H. L.
Published: September 2005

The Modified Rhyme Test (MRT) is generally more convenient to use than the Harvard PB-Word Test, but less capable of discriminating among highly intelligible communication systems. An experiment was performed to determine whether the higher scores typically obtained with the MRT can be attributed to the closed-response format of this test. The total MRT vocabulary, recorded by an adult male speaker, was repeatedly administered to three groups of listeners at two signal-to-noise ratios: the first group used an open-response (write-down) format, the second group used the regular closed-response (multiple-choice) format, and the third group first heard the same speaker read other speech material and then used the closed-response format. The results indicate that the scores finally obtained with the open-response format are not appreciably different from the scores initially obtained with the closed-response format, and that MRT scores do not rise as listening experience is acquired. [Work supported by Decision Sciences Laboratory, Electronic Systems Division, Air Force Systems Command, Bedford, Massachusetts.]
Frequency Dependence of Reverberation in the Ocean
Authors: Anderson Victor C.
Published: September 2005

Data collected at 12 stations in the Pacific Ocean of acoustic reverberation are presented to show gross characteristics of the volume reverberation as a function of depth at two frequencies, 10 and 25 kHz. The experimental equipment consisted of a cable-connected, horizontally directional, echo-ranging instrument package operating in conjunction with a shipboard digital data recorder. Of interest are the comparisons of relative scattering coefficients measured simultaneously at two frequencies. These comparisons indicate significant changes of scatterer composition with depth.
Ambient Sea Noise in the Deep and the Shallow Ocean
Authors: Arase Elizabeth M. , Arase T.
Published: September 2005

Simultaneous measurements of ambient sea noise in the frequency range 22–715 Hz were made with two identical hydrophones. One was located on a shallow bank in about 200 ft of water, the other at a depth of about 5000 ft, both near the ocean bottom. The data were correlated with simultaneous weather observations. The sea noise at the shallow hydrophone was in general found to be lower than at the deep one and to be more sensitive to variations in wind speed. [Hudson Laboratories of Columbia University Informal Documentation No. 113. Work supported by the U. S. Office of Naval Research.]
Some Factors Affecting the Measurements of Bottom Reflectivity
Authors: Menotti F. R. , Santaniello S. R.
Published: September 2005

Bottom-reflection measurements were made in four different geographically smooth, nonsloping bottom areas. Reflection coefficients were computed as a function of angle from data obtained at two single frequencies, two frequency bands, and several pulse lengths. The experimental design and first area results are discussed elsewhere [J. Acoust. Soc. Am. 38, 707–714 (1965)]. Vertical hydrophone arrays were used in three of the areas and it was possible to make comparisons based on hydrophone separation. Average values of reflectivity for data taken at the same angle but for different bottom-reflection points within a small area are observed to differ by as much as a factor of two. Cores taken within the same reflection areas as the observed acoustic results also showed variations in sediment properties. Results obtained at the four locations are presented to show the degree to which it is possible to characterize a large geographic area from measurements taken over a very small area within it.
Acoustic Backscattering from a Wind-Driven Water Surface
Authors: Pruitt R. A. , Goodman R. R. , Marshall S. W.
Published: September 2005

Since wind waves generated on a water surface are not symmetrical, radiation backscattered from this surface should exhibit asymmetry. A 40-ft wind-tunnel/water-flume provided a controlled surface that was ensonified from above at 160 kHz by pulses 30 μsec in duration (5 cycles). The scattered amplitude pulses were analyzed statistically as a function of the shear stress produced at the water surface. Depending on the angle between the transducer and the water surface, the statistical amplitude ratio of the backscattered wave viewed upwind to that viewed downwind varied between 2 and 10. [Work supported in part by the U. S. Office of Naval Research.]
Measurement of Dynamic Properties of Materials, Using a Transfer-Impedance Technique
Authors: Parsons Jerome S. , Yater Wallace , Schloss Fred
Published: September 2005

The application of mechanical-impedance techniques to the measurement of dynamic properties of materials is presented. The method is flexible in that it can be employed over a wide frequency range for a variety of materials (20–10 000 Hz for rubberlike compounds). The method has been used to determine the complex Young's modulus, propagation constants, characteristic impedance, loss factor, etc., of viscoelastic materials. The specimen is suspended vertically and blocked at the upper end by means of a stiff force gauge. A static tensile stress, which can be varied, assures proper vertical alignment for the axial excitation applied at the free end of the sample. The motion of the free end is measured with an accelerometer. Instrumentation has been developed to measure the phase angle between the two transducers to within 0.02° from 10 to 20000 Hz. A computer program has been written to expedite the analysis of the data. The method and computer program can also be applied to the measurements of dynamic shear and bulk properties.
Transmission Parameters of Thickness-Driven Piezoelectric Transducers Arranged in Multilayer Configurations
Authors: Sittig E. K.
Published: September 2005

The individual transducer or inactive layers of a sandwich structure affixed to an ultrasonic delay medium are described by the transformation matrix of their equivalent transmission-line circuit. The resulting simple expression and iterative procedures are well suited to digital computation. Computation reveals effects on input impedance, insertion loss, etc., of various arrangements of such layers, which may be qualitatively understood by visualizing separately the effects due to the mechanical-resonance behavior of the whole stack and then due to the arrangement of piezoelectric material with respect to the stress distribution in various parts of the stack. Illustrative examples are presented for CdS and ceramic transducers.
Microphone Rise-Time Response to a Progressive Shock Wave
Authors: Brown R. , Siddon T. E. , Van Houten John J.
Published: September 2005

The response limitations of microphones imposed by both finite size and sensing-element dynamics has been examined in order to assess the utility of transducers currently being used in the measuremert of sonic-boom phenomena, ballistic pressures, and shock-wave motion in aerodynamic flows. Experimentation includes the application of the expansion tunnel and shock-tube technology to generate “weak” progressive shock waves. Transducers are both flush mounted and subjected to normal incidence shock-wave motion in the expansion tunnel. The rise-time characteristic of the transducer is also measured with a simulated transient pressure generated by application of the electrostatic actuator. Experimentation utilizing these techniques provides a direct comparison of the finite-size effect and the basic limitations in transducer rise-time response contributed by the sensing-element dynamics. Anomalous behavior of nonflush diaphragms is demonstrated by the experiments as well as the effect on rise-time characteristics created by the microphone protecting grid. Analysis which complements this experimentation is reviewed in the material presented. [Work supported by the National Aeronautics and Space Administration, Langley Research Center.]
Technique to Predict Acoustic Distortion in Elastic-Walled Liquid Cylinders
Authors: Rivera Charles J.
Published: September 2005

When a piston sound source excites a fixed-length liquid cylinder above its lowest symmetrical cutoff frequency, the standing waves within the cylinder are distorted. Data acquisition then becomes extremely difficult when the liquid-cylinder lengths cannot be varied. Submarine and shipboard piping systems are typical examples. This paper describes a distortion that is produced below the lowest symmetrical cutoff frequency in elastic-walled liquid cylinders. It has been found that this distortion begins when nonlinear subharmonic frequencies appear in the system and the modified Bessel function=s argument (Kr), in the acoustic-pressure equation, obtains the imaginary zero value of 2.405.
Brillouin Scattering in Water: The Landau-Placzek Ratio
Authors: O'Connor C. Leonard , Schlupf Joseph P.
Published: September 2005

An experimental study of the ratio of intensities of the central line, in the molecular scattering of light, to the Brillouin components has been made in water over a temperature range from 0° to 50°C. A 75-mW He-Ne gas laser was used as a light source and the scattered radiation was analyzed by a Fabry-Perot interferometer (pressure scanning) in conjunction with a dry-ice-cooled phototube detector with recorder output. The ultrahigh-frequency sound velocity in water is compared with values obtained by using ultrasonic techniques. There is no evidence of relaxation effects in the frequency range studied. An analysis of the Landau-Placzek ratio is made for water considered as an ideal fluid. It is shown that the usual approximations used in deriving this ratio are not valid for water and the ratio (kt−ks)/ks does not go to zero at 4°C. The actual behavior of the Landau-Placzek ratio for water as a function of temperature can be explained in part when an exact solution is used.
Acoustic Ion Waves at Frequencies Comparable to the Ion-Plasma Frequency
Authors: Sessler G. M.
Published: September 2005

The phase velocity and the attenuation constant of acoustic-ion waves were measured in weakly ionized gases with charged-particle densities of about 109 cm−3, corresponding to ion-plasma frequencies ωi/2π of about 1 MHz. The waves were generated with a grid-excitation method [G. M. Sessler, Phys. Rev. Letters 17, 243 (1966)] over a frequency range extended up to 10 MHz. For ω smaller than ωi, the phase velocity corresponds to the Tonks-Langmuir speed while the attenuation is primarily determined by ion-neutral collisions, yielding collision cross sections that are in good agreement with those found by other methods. For ω larger than ωi, the phase velocity shows a slight increase with frequency, while the attenuation per wavelength is relatively frequency-independent and weak. In this frequency range, the propagation is determined primarily by the ionic-velocity distribution, particularly the high-velocity tail. It is found that the experimental data can not be explained by a Maxwellian distribution, which would lead to strong Landau damping. Better agreement with the data can be achieved by assuming distributions that decrease more rapidly at high velocities. Such distributions are actually expected in gas discharges.
Ultrasonic Absorption in Potassium
Authors: Natale Giovan G. , Wang Taylor G. J. , Stern Richard , Rudnick Isadore
Published: September 2005

Measurements of ultrasonic absorption have been made in potassium as a function of temperature from 2.5° to 77°K at various frequencies between 200 and 400 kcps. The samples are polycrystalline wires in which Young-modulus-type waves are propagated and the attenuation is measured using a standard pulse-echo or a resonance-decay technique. The results show the presence of a large component of attenuation, presumably due to dislocation motion, which has a broad amplitude maximum in the region between 25° and 40°K. At temperatures below 20°K, the attenuation due to electron-lattice interaction becomes dominant and its main features (amplitude, temperature, and frequency dependence) are discussed in relation to the values predicted by the free-electron theories. [Work supported by the U. S. Office of Naval Research.]
Superfluid Helmholtz Resonators
Authors: Kriss Michael A. , Shapiro Kenneth A. , Rudnick Isadore
Published: September 2005

The equations governing the resonances of a superfluid in a Helmholtz resonator have been developed. Four cases are considered: (1) when the entire resonator is packed with a superleak; (2) when only the neck is packed with superleak; (3) when only the volume is packed with the superleak; (4) when no superleak is present. The solutions for the first three cases are identical. The results give two resonant frequencies, one of which is zero. The zero-frequency mode corresponds to second sound, or entropy waves, that is unable to propagate due to the immobility of the normal fluid. The second resonant frequency is given by ω2=U42(A/Vl), where U4 is the velocity of fourth sound and where A, l, and V are the effective values of the cross-sectional area of the neck, the length of the neck, and volume of the resonator, respectively. The fourth case also gives two resonant frequencies. The first is the usual Helmholtz resonance for a pressure wave and is given by ω2=U12(A/Vl), where U1 is the velocity of first sound. The second resonant frequency corresponds to second sound and is given by ω2=U22(A/Vl), where U2 is the velocity of second sound. Experiments on first sound resonance give values of U1, which agree with other measurements.
Waveforms of Cavitation-Generated Sound
Authors: Batchelder Laurence
Published: September 2005

Oscillograms of the sound generated by the oscillating bubbles of sonically induced cavitation show how the oscillations develop as the bubbles grow through rectified diffusion, and die away after the excitation has stopped. The rate of decay indicates bubble Q's of at least 100. Surprisingly, bubbles of randomly different size continue during the decay to oscillate in harmony at the same fundamental frequency as the excitation. The well-known subharmonic sound occurs under strong excitation, seemingly as a distortion of the fundamental oscillation and not as a resonant oscillation at the subharmonic frequency. The oscillograms often illustrate the fortuitous nature of cavitation effects. [Work supported by U. S. Naval Ships Engineering Center, Norfolk Division (EMEC).]
Quality of Impedance Matching by the Middle Ear of Cats
Authors: Tonndorf Juergen , Khanna S. M.
Published: September 2005

In experiments on cats, the source impedance of the ear was varied by substituting the air between a sound source and the tympanic membrane by helium (Z=−4 dB re ZAIR) or by xenon (Z=−3.7 dB re ZAIR). Resulting middle-ear transmission changes were monitored by recording round-window cochlear microphonics. In a first series of animals, a small closed sound system was employed. In a second series, an “open” system was simulated by keeping the animal's head and the gas in a thin-walled plastic bag which was practically transparent for audiofrequencies. Although the induced impedance changes were small, both types of gas substitutions decreased middle-ear transmission slightly in the low frequencies, indicating that the impedance provided by the cat' middle ear when facing air is close to being optimal in that region. However, in the range from 500 to 1600 Hz, xenon substitution resulted in improvements of transmission of up to 15 dB, indicating that, apparently, in that range the cat's ear is slightly undermatched. [Work supported by grants from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Some Relations of the V Potential to Loudness and to Masking
Authors: Davis Hallowell , Bowers C. , Hirsh S. K.
Published: September 2005

Tone pips and tone bursts (rise time 20 msec) of different frequency and bursts of white noise that were judged equally loud all evoked slow V (vertex) potentials of approximately equal amplitude. For some subjects, however, the noise was clearly more effective than tone burst or pip and in general a fairly strong 4000-Hz burst (or 4800-Hz pip) was less effective than an equally loud one at 1000 (or 1200) or 250 (or 300) Hz. The rate of increase of V potential with the SPL (sound-pressure level) of tone bursts was very slow. The exponent of the power law was 0.15 at 250 Hz, 0.11 at 1000 Hz, and only 0.08 at 4000 Hz. Individual differences across subjects seem more important than the interval between stimuli (1 versus 3.2 sec). In the presence of appropriate bands of masking noise, the input-output curves rise abruptly to approach the unmasked amplitude at a level about 30 dB above the corresponding masked threshold. The effect resembles recruitment of loudness. [Work supported by the National Institute of Neurological Diseases and Blindness, National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Possible Mechanism for the Surface-Pressure Fluctuations beneath Turbulent Boundary Layers
Authors: Lowson Martin V.
Published: September 2005

It is suggested that the fluctuating surface pressure field beneath a turbulent boundary layer is substantially due to the laminar sublayer eruption observed by Einstein and Li and other workers. The eddy-convection-velocity characteristics observed in flow visualization studies of the eruption process are shown to agree reasonably well with those of the fluctuating pressure field. The mechanism suggests new theoretical models for the study of surface-pressure-fluctuation phenomena. [This work is an extension of that reported in NASA TN D3156; supported by the National Aeronautics and Space Administration.]
Flow-Noise Research Related to the Sonar Self-Noise Problem
Authors: Leehey Patrick
Published: September 2005

A sonar dome is excited into bending vibration by random pressure fluctuations of turbulent-boundary-layer flow over the dome. A reverberant acoustic field is set up within the dome. The field appears as an important source of self-noise in the sonar transducer at moderate to high ship speeds. Much of the research on the corresponding aerodynamic-noise problem is directly applicable to the study of this underwater-noise problem; in particular, work characterizing the random pressure field for subsonic boundary-layer flows may be carried over directly. Dome response and the consequent internal acoustic radiation, however, are severely influenced by internal and external water loading. In addition, hydrodynamic coincidence effects play a markedly different rôle in the underwater problem than in the aerodynamic problem. Those aspects of flow-noise research pertinent to the sonar self-noise problem are reviewed in this paper, and directions for further research upon the influence of water loading in the prediction of self-noise levels are pointed out.
Response of Flexible Panel to Turbulence
Authors: Maestrello Lucio
Published: September 2005

Using a relatively simple functional representation of space-time correlation of the wall pressure fluctuation and by the use of the Lyon-Dyer method, the motion of a simple supported panel can be predicted, and the results agree reasonably well with the author's experimental results. The most striking feature of the excitation mechanism is called coincidence. This is a condition under which the wavenumber and frequency spectrum coincide with the turbulence and panel spectra. The matching and mismatching in wavenumber and frequency scale clearly indicate that the mean-square displacement peaks corresponding to the various panel modes coincide with those of a pressure at a given frequency. The frequencies were chosen so that 2πf/K1* corresponds to the convection velocity, K1* being the wavenumber at the spectrum peak. If, for certain frequencies and wavenumbers, mismatch between panel spectrum and turbulence spectrum should occur, a reduction in panel-displacement amplitude is observed. Such a mismatch is also reflected in the acoustic power radiated where similar reduction is obtained.
Design and Construction of an Acoustics Laboratory for Exceptional Sound and Vibration Isolation
Authors: Ramer L. G.
Published: September 2005

The laboratory planning indicated desirability of locating it near to the general development laboratory and engineering offices. Evaluation of earth vibration at the proposed site and analysis of the earth characteristics indicated the degree of vibration isolation required. The normal outdoor noise and the indoor ambient desired were the factors controlling the construction of the basic building. Requirements for simultaneous sound measurements on 300-ton-capacity refrigeration compressors and 600-cfm fan-coil units required unusual isolation between test rooms. Three test rooms in line, each a complete unit, were individually spring supported. Each test room has an individual cooled-air supply with air drawn from and discharged into the general laboratory through sound traps. The sound-transmission-loss requirements were predicted with a possible building pink spectra over-all sound-pressure level (SPL) of 80 dB in the general laboratory area. The SPL's in the test rooms with the 80-dB SPL in the laboratory were to be about 5 dB lower than an NC20. Results of measurements of sound-transmission loss and background-sound levels are shown.
Reverberation-Room Acoustics. I: Effects of Absorptive Floor, Suspended Ceiling Panels, and Diffusers on Decay Curves
Authors: Knudsen V. O. , Delsasso L. P. , Leonard R. W.
Published: September 2005

This paper and a following one [Paper 5A5, this meeting] report our most recent findings in an investigation of the nature of reverberant sound in a rectangular reverberation room 19×30×24 ft as influenced by a 2-in. Fiberglas floor covering, 96 suspended panels of 1×3-ft×12-in. plywood (12 ft above floor), and various numbers of diffusive convex panels of 4×8-ft×316-in. hardboard. Decay curves from repeated pistol shots for the same room condition, with the shot and microphone kept at fixed positions, are remarkably identical, even in respect of fluctuations. But the decay curves for 12-oct bands centered at 250, 360, and 500 cps, if the floor is absorptive, are greatly altered by source and pickup locations, by the suspended panels, and especially by file diffusers; thus, with the pistol shots in the upper part of the room without diffusers, the decay rates (first 30 to 40 dB) are only about 8 dB/sec for most microphone positions (except near the floor), but, for shots less than about 8 ft above the floor, the early decay rates increase to as much as 20 dB/sec. The introduction of diffusers, as expected, greatly improved the uniformity of decay and also increased decay rates.
Reverberation-Room Acoustics. II: Effects of Absorptive Floor, Suspended Ceiling Panels, and Diffusers on Speech and Music
Authors: Delsasso L. P. , Leonard R. W. , Knudsen V. O.
Published: September 2005

The results of the preceding investigation [Paper 5A4, this meeting] indicated that, with the floor absorptive, the suspended panels and the diffusers (located in the space below the panels) would greatly affect the quality of music and the intelligibility of speech. Recordings of speech and music (a trumpet, a violin, and the Roth String Quartet) in the anechoic chamber, played back in the reverberation room, under conditions that we had previously investigated, revealed some interesting and probably useful results. For example, speech articulation and the quality of music were greatly improved by introducing diffusion in the lower space. even though the “reverberation time” (estimated by projecting linearly the early decay to 60 dB) was of the order of 3.0 sec. The results are demonstrated with tape recordings; they suggest that large diffusers may have a more useful effect on room acoustics, for speech as well as music, than we have generally supposed.
Effect of Array Form on the Measured Sound Absorption of Auditorium Chairs
Authors: Ostergaard Paul B.
Published: September 2005

The sound absorption of 16 chairs removed from Philharmonic Hall have been tested in the Cedar Knolls Acoustical Laboratories reverberation room for sound absorption. The measured sound absorption varies both with the number of chairs and the array shape and spacing. The variations are small on a per-chair basis; however, on an area basis, changes of over 30% result from changes in spacing.
Examples of Unusual Sound-Reinforcement Systems
Authors: Veneklasen Paul S.
Published: September 2005

Several examples are selected to illustrate solutions of unusual or extreme problems, such as excessive reverberation, high-level ambient noise, disproportioned theaters, large-group conference, indoors-to-outdoors, the large amphitheater. All solutions are devised to achieve high intelligibility, naturalness, and apparent source localization.
Acoustical Dispersive Delay Lines for Pulse Compression by Fluid Layered Media
Authors: Tournois Pierre
Published: September 2005

In the low-frequency sonar field, sometimes it is necessary to make linear FM pulse compression in bands of a width between 2 and 100 kcps. Generally, the metallic delay lines are not suitable because they have too high acoustical velocities. Here, two linearly dispersive acoustical delay lines are described. They use the propagation of a surface wave in fluid layered media. The first one, fitted to lower bandwidths, is made by two-layered gas—one is heavy, the other is light; in the presented design, a plane structure (SF6-air) is able to compress, for 1 m length, 4 msec of a linear FM pulse in a 2000 cps bandwidth. The second one, fitted for more important bandwidths, is made by two-layered liquids; in the presented design, a cylindrical structure (C⋅Cl4-water), is able to compress, for 1 m length, 0.4 msec of a linear FM pulse in a 100-kHz bandwidth. [Work supported in part by DRME.]
Acoustical Dispersive Delay Lines for Pulse Compression by Solid Layered Media
Authors: Tournois Pierre
Published: September 2005

Modern radars use linear FM pulse compression in more and more important swept bandwidths. To compress these pulses in a receiver, different kinds of dispersive delay lines have been proposed by Meeker (strip delay lines), Fitch (tapered-strip delay lines), and Coquin (perpendicular-diffraction delay lines). A new kind of line is presented here. It uses the dispersion curves relative to the propagation of the surface waves in the solid layered media. Particularly, a Love-wave delay line is described. It is constituted by a copper coating on a steel substratum, which provides easily a 3-Mcps swept bandwidth for a 5-Mcps center frequency. The same kind of line in fused silica is actually under investigation to have a 30-Mcps swept bandwidth. These delay lines have the following advantages: the relative available bandwidth is important (more than 50%), the center frequency is limited by the structure geometry but for very high frequencies; and, finally, these lines need but one accoustical transmitter and one acoustical receiver.
Acoustical Interferometer for Cryogenic Liquids
Authors: Leonard R. W. , Seguin H. , Imai J. S.
Published: September 2005

An acoustical interferometer for the measurement of velocity and attenuation at several frequencies up to 1 GHz is described. Because of the high frequencies and the short acoustical wavelengths, the displacement mechanism, displacement monitoring system, and method of the excitation of the liquid are of interest. The displacement mechanism consists of a system of piezoelectric bimorphs and levers. Such a system permits the selection of any specific displacement by simply dialing a dc voltage. The displacement monitor consists of a transistorized Klapp oscillator whose variable capacitor was machined integrally with the moveable transducer assembly. The oscillator output is displayed on a digital frequency counter and can resolve displacements of about 150 wavelength of sodium light. The liquid is excited by quartz crystals up to several hundred megahertz and by CdS thin films to 1 GHz. The CdS transducers are sputtered on gold evaporated on a quartz substrate. The CdS films were prepared by G. A. Rozgonye and B. Schwartz of Bell Telephone Laboratories.
Excess Acoustic Absorption in Closed Tubes as Compared to Identical Open Tubes
Authors: Winter T. G.
Published: September 2005

The principal method of investigating long relaxation times in gases involves confining sound in a tube and measuring the absorption as a function of frequency. A review of the work of many investigators shows that the Kirchoff formula correctly predicts the absorption due to tube walls for a traveling sound wave but that, if the tube ends are closed and the absorption measured by a standing wave resonance method, the measured absorption is 6%–40% higher. This excess absorption varies with (frequency/pressure)12 as does the Kirchoff-tube absorption. Some possible mechanisms of absorption due to reflection and due to the presence of the end plates are examined but without conclusive results.
Further Report on the Transient Solution for Sound in a Viscous Fluid
Authors: Blackstock David T.
Published: September 2005

In a previous paper [J. Acoust. Soc. Am. 38, 931(A) (1965)], a solution, including the transient as well as the steady state, of the viscous-wave equation νuxxT+c02 × uxx−uTT=0 was given for the radiation condition u(0,t)=u0H(t) sin ωt, where H(t) is the unit step function. Improvement and analysis of the transient solution is discussed in this paper. As distance from the source increases, there is a rather surprising growth of the transient relative to the steady-state signal. For example, at a distance such that the steady-state wave has decayed 20 dB, the transient amplitude is about 2.4 times that of the steady state. At this point, the transient signal extends for about a wavelength on either side of the position x=c0t. Implications with respect to sound-velocity measurements are raised. [Work supported by the Mechanics Division, U. S. Air Force of Scientific Research, Office of Aerospace Research.]
Lateral Acoustic Instability
Authors: Schulz Michael , Ingard Uno
Published: September 2005

An acoustic instability, first observed by Strickler and Stewart [Phys. Rev. Letters 11, 527 (1963)], in which the path of a constricted argon discharge develops regular kinks when the current is modulated at certain acoustic resonant frequencies, is discussed in terms of more-recent experiments. A semi-quantitative theoretical model for the effect is presented. [Work supported by the U. S. Navy, Office of Naval Research, and in part by the Joint Services Electronics Program.]
Ultrasonic Absorption and Velocity Dispersion in Diatomic Gases at High Temperature
Authors: Hill Garnett L. , Winter T. G.
Published: September 2005

Velocity and absorption measurements have been made on hydrogen, deuterium, nitrogen, and oxygen gases at frequencies from 0.5 to 40 MHz/atm. This frequency range encompasses the rotational relaxation of hydrogen and deuterium, but it is below the frequency of maximum absorption in nitrogen and oxygen. It was found that the frequency of maximum absorption always decreases with increasing temperature, as predicted by Parker (and just the opposite of vibrational relaxation behavior). Absorption measurements on hydrogen at 24°C nearly fit a single relaxation curve, but the 800°C data show that multiple relaxations must exist. The frequency of maximum absorption shifts from 13 MHz/atm at 24°C to 6 MHz/atm at 800°C in hydrogen and from 18 to 4 MHz/atm in deuterium. Single-relaxation theory applied to nitrogen gives collision numbers of 4, 7, and 10 at temperatures of 24°, 500° and 800°C. [Work supported in part by the U. S. Army Research Office and the Oklahoma State University Research Foundation.]
Tolerance of Glass for High-Level Noise Exposure
Authors: Christoff Jerry P. , Veneklasen Paul S. , Huh John
Published: September 2005

Experiments are described to determine the sound-tolerance limits of glass plates under resonant excitation. The tests were performed in relation to the problem of hazard to the public. Relations are given between sound-exposure levels, mode pattern, vibration, and dynamic stresses.
Transient Response of a Rectangular Plate Coupled with a Helmholtz Resonator
Authors: Whitehouse G. D. , Lowery Richard L.
Published: September 2005

The sonic-boom tests conducted in Oklahoma City in 1964 have given indications that various building enclosures can be excited as Helmholtz resonators. A question arises as to what effect these pressure oscillations can have upon the response of windows or other flexible panels mounted in the enclosure. The findings of an investigation of the transient response of a simply supported rectangular plate coupled with a Helmholtz resonator are presented. Experimental results, are discussed, as taken from a model mounted at the termination of an acoustic delay line and driven by an electronic-pulse-generator system. The experimental data are compared with theoretical predictions based on a lumped-parameter analysis. Representative experimental recordings are presented showing the relationship of the input pressure, the cavity pressure, and the strain of the plate.
Experimental Aids for Predicting Structural Response to Sonic Booms
Authors: Lowery Richard L.
Published: September 2005

The response of a given structure to sonic-boom excitation depends upon the natural frequencies of the roof, walls, windows, and other elements. The presence of acoustical networks within the building will also affect the response markedly. This paper presents experimental methods of determining the necessary natural frequencies and damping factors of structural elements. The instrumentation techniques developed are straight-forward and inexpensive. Field measurements of ceiling and window vibrations, as well as internal pressure oscillations, are given. Simple methods of exciting structures are discussed.
High-Frequency Response of Point-Excited, Submerged, Spherical Shells
Authors: Junger M. C.
Published: September 2005

The classical, modal formulation of the vibrations and radiation loading of submerged elastic shells [S. Hayek, J. Acoust. Soc. Am. 40, 342–348 (1966)] requires extensive calculations at high frequencies. An alternative formulation in terms of traveling waves familiar from studies of plane-wave scattering by elastic cylinders and spheres [see bibliography, Doolittle et al., J. Acoust. Soc. Am. 43, 1–14 (1968)] is applied to thin spherical shells excited by radial point forces. The response is expressed as the sum of (1) a primarily structure-borne field consisting of three modes, two of them rapidly attenuated, characterized, except for membrane effects, by the wave-numbers of point-excited flat plates in water; (2) a diffracted field, resembling “creeping waves” on “pressure-release” spheres. One structure-borne and two “creeping-wave” modes suitably represent shell response and surface pressures except in the immediate vicinity of the drive point. [Work sponsored by Office of Naval Research, Structural Mechanics Branch.]
Experimental Observation of Three Types of Circumferential Surface Waves on Aluminum Cylinders in Water Using Pulses
Authors: Neubauer W. G.
Published: September 2005

Three types of circumferential waves that contribute to the total diffracted acoustic field of an elastic cylinder are isolated by means of a short pulse emitted from a narrow-beam transducer. These waves are often called “creeping waves”; one called the “Franz type” is primarily related to the geometry of the diffracting body, whereas the other two are more related to the elastic properties of the cylinder. The wave velocities are determined from the pulses observed in the diffracted field of the cylinders whose size parameter ka=323. Schlieren photographs are presented showing the progression of the diffracted wavefronts that result from the boundary waves.
Scattering of Acoustic Pulses by Rigid Spheres
Authors: Rudgers Anthony J.
Published: September 2005

The scattered pressure field examined is that produced when a plane wave pulse is incident upon an ideally rigid sphere immersed in a fluid. The classical normal-mode series expresses the scattered field when a harmonic plane wave is incident upon the sphere. By using this series solution in conjunction with an incident pulse of known spectral content, it is possible, by numerical means, to synthesize exactly the resulting reflected pulse at an arbitrary field point. In the present instance, truncated sinusoidal incident pulses are considered, and scattered pulses are determined both at points close to the sphere and points distant from it. The time-varying amplitudes of these reflected pulses, thus rigorously calculated, are discussed in terms of a model based upon the existence of circumferential or “creeping” waves propagating along the periphery of the sphere. This model considers the reflected pulse to be composed from a specularly reflected replica of the incident pulse and attenuating pulses that travel along the periphery of the sphere from the boundary of the geometric shadow to the observation point.
Underwater Sound Diffraction around the Edge of a Shielding Baffle
Authors: Bell Thaddeus Gibson
Published: September 2005

The Fresnel-Kirchhoff theory for optical diffraction around the edge of a semi-infinite screen offers a means of estimating the diffraction leakage around the edge of an underwater-sound shielding baffle. To test the utility of the Fresnel-Kirchhoff theory for this application, experiments were conducted using a Laboratory tank and a frequency of 93 kHz. The baffle consisisted of a 116-in.-thick piece of closed-cell, cellular rubber bonded to a 116-in.-thick aluminum plate. To explore the sensitivity of the measured diffraction to experimental conditions, both straight- and curved-baffle edge geometries were used; various inclinations of the baffle to the sound field were also tried. It was concluded that the Fresnel-Kirchhoff theory offers an accurate prediction of diffraction leakage around an underwater-sound baffle, even though the actual baffle construction and geometry may vary somewhat from the ideal model for which the theory was developed.
Series Expansion Prediction of the Farfield from the Nearfield
Authors: Butler John L.
Published: September 2005

A series expansion method for determining the farfield from nearfield measurements of coherent and partially coherent sound fields is presented. Current investigations have generally been based on a Helmholtz integral or Green's-function approach, although one of the earliest methods for sinusoidal oscillation [J. Pachner, J. Acoust. Soc. Am. 28, 86–89 (1956)] was actually based on a series expansion of the nearfield solution in spherical wave-functions. By confining the measurements to a spherical surface, Pachner was able to evaluate the expansion coefficients through the orthogonality of the Legendre polynomials. However, in the method presented here, the expansion is truncated to include only the number of terms equal to the number of nearfield measuring points. In this way, the coefficients may be evaluated through a matrix inversion for nearfield measuring points at any location. A comparison of exact and predicted farfields is presented for some simple source distributions. The method has been extended for crosspower nearfield spectral measurements. [Work supported by the Office of Naval Research.]
Correlation Methods for Determining Transmission-Loss Characteristics of Plates
Authors: DuBack Earl
Published: September 2005

This paper introduces a method for measuring the transmission loss and phase distortion that an acoustic signal undergoes in passing through plates. The physical setup consisted of two hydrophones on either side of a 14-in. steel plate and an underwater speaker at a “quiet” test facility. Their “white-noise” signals were recorded simultaneously on an FM tape recorder. The tape recordings, filtered from 100 to 9000 Hz to avoid aliasing, were digitized at 18 000 samples/sec, introduced into a UNIVAC 1107 computer, and the cross-correlation functions obtained. The cross correlation between the speaker and hydrophone separates the signal coming along various paths according to their time of arrival. The section of the correlogram containing the incident signal is considered, while all other values are set to zero; then the power and phase associated with this section are determined. The section containing the transmitted signal is given similar consideration. The incident power minus the transmitted power gives the transmission loss. Mathematical description of the transmission loss is found to be in good agreement with these experimental results.
Relationships between Several Indices of Acoustic Reflex Function and Susceptibility to Temporary Threshold Shift Produced by Different Spacings of Impulsive Noise and by Continuous Noise
Authors: Fletcher John L. , Weiler Ernest M. , Loeb Michel
Published: September 2005

Temporary threshold shift (TTS) was measured following exposure, on separate days, to 110 dB thermal noise or to 20 successive 166-dB-peak, 58-μsec-duration, spark-gap-produced impulsive noises, spaced 0.2, 2.0, or 10.0 sec apart. Pearson correlations were calculated between these measures and estimates of acoustic intratympanic reflex thresholds, durations, rise times, and decay times, obtained with a Madsen impedance bridge and averaged over 10 trials at each of three eliciting frequencies on an averaging computer. There were indications of negative correlations of reflex duration and TTS and of positive correlations of reflex threshold and TTS, especially at the 2.0-sec impulse spacing.
TTS and PTS in Chinchillas
Authors: Ward W. Dixon , Nelson David A.
Published: September 2005

A group of 18 uniaural chinchillas was exposed for 2 h to a 2-oct-wide band of noise having an over-all SPL of 124 dB and band limits of 750 and 3000 cps. Most animals were untestable (i.e., had thresholds in excess of 110 dB SPL) at one or several test frequencies immediately after exposure. The median shift 1 day later was about 115 dB at 1, 2, 4, and 8 kc/sec, and recovery proceeded slowly for the following 3 mo., reaching a final permanent threshold shift (PTS) on the order of 50 dB. Correlations were calculated between these values of PTS and various tests of temporary threshold shift (TTS) performed on the animals before the high-intensity exposure. Implications of these results in regard to tests for susceptibility to noise-induced hearing loss in humans will be discussed. [Research supported by the U. S. Public Health Service.]
Repetition of Two Binaural Fatigue Experiments
Authors: Melnick William
Published: September 2005

Puzzling results from two previous studies of binaural fatigue, one involving dichotic exposure [W. D. Ward, J. Acoust. Soc. Am. 39, 1262(A) (1966)] and the other binaural phase effects [W. Melnick, J. Acoust. Soc. Am. 42, 179–184 (1967)] indicated a need for repetition. For the dichotic experiment, 24 listeners were exposed for 5 min to either 700 Hz at 115 dB SPL or 2.4–4.8-Hz noise at 112 dB monaurally and to both dichotically. Dichotic exposure produced a reduction in TTS at 4, 6, and 8 kHz for the ear exposed to the high-frequency noise similar to that seen in the earlier experiment. In the binaural phase experiment, 15 listeners tracked TTS for 6000 Hz following 2 min of exposure at 4000 Hz, 120 dB SPL in three sessions under three conditions: monaural, binaurally in phase, and binaurally 180° out of phase. In this experiment, contrary to the results reported earlier, no difference was observed for the three exposure conditions.
Recovery from Temporary Threshold Shifts as a Function of Test and Exposure Frequencies
Authors: Smith Richard P. , Loeb Michel
Published: September 2005

The purpose of these experiments was to test Ward's hypothesis that recovery time is a function of the initial loss and independent of test frequency and to extend his findings to higher test frequencies. Twenty-five subjects were exposed to 110-dB sinusoidal stimulation at 700, 2700, and 8000 Hz at varying durations so as to produce approximately equal (within-5-dB) losses (10–30 dB) at one of 13 test frequencies ranging from 250 to 12 000 Hz. Recovery was followed until thresholds had returned to within 5 dB of the pretest levels. The results indicated that subjects took significantly more time to recover from high-frequency than from low-frequency exposures. The analysis is still in progress, but these results suggest that recovery from high-frequency sinusoidal exposure is slower than recovery from low-frequency sinusoidal exposure.
Effects of Background Noise upon Perceived Noisiness
Authors: Parry Hugh J. , Nagel David C. , Parnell John E.
Published: September 2005

Cross-modality tests, matching the apparent intensity of a 100-Hz vibration to the noisiness of 13-oct bands of noise, have been conducted to measure the effects of background noise upon judged noisiness. The growth function for noisiness behaves like a modified power function of the form ψ = k(In − I0n), where ψ is noisiness, I is the intensity of the stimulus, I0 is the threshold intensity, and k and n are constants that depend upon frequency. A calculation scheme has been developed that reduces the sound-pressure level of each 13-oct band by an amount dependent upon the signal-noise/background-noise ratio. For signal-noise/back-ground noise band-level ratios of greater than 65 dB, the band correction is equal to 0. For realistic background spectra and signal-noise/background-noise over-all level ratios of 40 dB, the total correction is approximately 3 PNdB. [Research supported by the Federal Aviation Administration.]
Ultrasonic Instrumentation for Recording Lateral Pharyngeal Wall Motion
Authors: Kelsey Charles A. , Hixon Thomas J. , Minifie Fred D.
Published: September 2005

Pulsed ultrasound has been used to monitor and record the motion of the lateral pharyngeal wall during speech. A time-motion (T.M.) method of display was recorded on the screen of a storage oscilloscope. An audio signal was simultaneously displayed and permanent records were made by photographing the storage oscilloscope screen. Tests were conducted to insure that the recorded signals were produced by the motion of the lateral pharyngeal wall. Distance calibration was made using a known displacement in a water bath. The effect of different ultrasonic frequencies was investigated by making measurements with both 2.25- and 5-MHz ultrasound beams. The results of all the measurements are reported in the following paper. [This research was supported by the National Institutes of Health.]
Lateral Pharyngeal Wall Motion during Speech
Authors: Minifie Fred D. , Kelsey Charles A. , Hixon Thomas J.
Published: September 2005

Movement of the lateral pharyngeal wall during the production of selected VCVCV trisyllables and during connected discourse was monitored via a time—motion modification of ultrasonic echo ranging as described in preceding abstract. The data from three subjects indicate that pharyngeal-wall displacement patterns within the same phonetic context remain somewhat constant from trial to trial (the basic trends maintain even though the absolute magnitudes of displacement vary a little). The inward movements of the pharyngeal wall from a static or resting configuration appear to be dependent upon the vocalic elements, whereas the outward movements appear to be more associated with consonants. Low vowels appear to be accompanied by greater inward movement of the pharynx than do high vowels. [This research was supported by the National Institutes of Health.]