bluuebunny/crossref_metadata_2025 huggingface dataset:
Comments on “Effect of Air Bubbles in the External Auditory Meatus on Underwater Hearing Thresholds” [H. Hollien and J. F. Brandt, J. Acoust. Soc. Amer. 46, 384–387 (1969)]
Authors: Bauer Benjamin B.
Published: October 2005

The loss in acuity which occurs when ears are submerged underwater has been computed using equivalent circuit analysis for the completely filled ear canal and for the canal containing a trapped air bubble at the eardrum. Contrary to popular misconception, the bubble is, if anything, beneficial, not detrimental. This may explain the recent findings of Hollien and Brandt [J. Acoust. Soc. Amer. 46, 384–387 (1969)], who measured no significant difference in underwater thresholds with and without bubble and regarded this as evidence that the middle-ear mechanism is not functionally operative in underwater hearing. Their contention is not supported by the present analysis. The computed differential loss between aerial and underwater tympanic transmission shows a frequency-dependent function, which resembles Hollien's measurements, but with 10–15-dB smaller magnitudes. Various hypotheses relating to this difference still need to be investigated; however, the predicted frequency dependence of the loss lends strength to previous observation [B. B. Bauer and E. L. Torick, J. Acoust. Soc. Amer. 39, 35–39 (1966)] that a rising pressure-frequency response near the external auditory meatus is needed to produce a normal-sounding underwater earphone.
Peripheral Inhibition in Auditory Fibers in the Frog
Authors: Liff Harold J. , Goldstein Moise H.
Published: October 2005

Two-tone interactions in complex units in bullfrogs and leopard frogs were studied. The discharges of a complex unit in response to a tone at its best excitatory frequency (BEF) could be suppressed by addition of a second, higher-frequency tone. The best inhibitory frequency (BIF) was that for which the least intense tone totally suppressed the response to a BEF tone. Between BEF and BIF, there was a frequency range in which tones had both excitatory and inhibitory effects. We call this range the “gray region.” During prolonged continuous presentation of a high-level inhibiting tone, the inhibitory effect showed no adaptation. A rebound in firing rate occurred when a unit, which had been previously adapted and then inhibited, was released from the inhibition by terminating the inhibitory tone. The level of an inhibitory tone necessary for total inhibition depended on excitor level, even for levels at which the spike rate in response to the excitor alone had saturated. Results are discussed with regard to the stage in the process leading to neuronal excitation at which inhibition occurs, and two-tone interactions in frog complex units are compared with those in mammalian first-order units.
Whither Speech Recognition?—II
Authors: Pierce J. R.
Published: October 2005

Mr. Pierce does not recant.
Long-Range Infrasound from Rockets
Authors: Kaschak George , Donn William L. , Fehr Uri
Published: October 2005

Long-range infrasound from large rockets launched at Cape Kennedy have been recorded and studied since 1957 by a variety of low-frequency acoustic sensors. Dominant energy ranges from 0.1 to 2 Hz. Signals can be grouped into early (apparently supersonic) arrivals, normal acoustic arrivals, and late (apparently subsonic) arrivals. The normal acoustic signals detected in the eastern United States from rockets launched in the northeast quadrant from Cape Kennedy show two prominent wave groups generated by the launch and first-stage reentry. The origin of this long-range infrasound is shown to be acoustic energy radiated from the cone of shock waves. The data of early arrivals (supersonic waves) suggests an origin from coupling between normal acoustic waves and those in a higher-speed region. Late arrivals having apparently subsonic velocities are also detected less frequently than the supersonic arrivals.
Vibrations of Rib-Stiffened Elliptical and Circular Plates
Authors: Desiderati Frank W. , Laura Patricio A.
Published: October 2005

This investigation deals with the determination of the fundamental frequency of vibration of simply supported and clamped rib-stiffened plates of elliptical boundary. It is assumed that the stiffeners are closely spaced and that their height is moderate when compared with the thickness of the plate. Variational techniques are used to determine the fundamental frequencies. The values compare reasonably well with other results available in the literature. This same straightforward approach can be used for other boundary shapes; experimental determination of the coefficients of the orthotropic biharmonic operator is not required.
Transient Fields of Acoustic Radiators
Authors: Freedman A.
Published: October 2005

A set of short sketches is presented, giving an overview, unobscured by mathematical detail, of the literature on transient fields of acoustic radiators. Related papers are grouped together and interrelationships between results emphasized.
Transient Flexural Vibrations of Ship-Like Structures Exposed to Underwater Explosions
Authors: Chertock George
Published: October 2005

The flexural vibrations of ship-like structures are easily excited by underwater explosions, particularly if the explosion bubble period approximately synchronizes with a period of flexural vibration. A summary of the theoretical analysis shows how the transient motions are related to the principal vibration modes of the structure, and to the distribution and history of the applied pressures. The latter depend on the size, depth, and relative position of the explosive. Experiments on small idealized ship and submarine models are described which vary the weight, depth, and position of the explosive, and which measure the instantaneous deformations of the structure with strain gauges connected into special bridge circuits to yield the normal coordinates associated with the principal flexural vibration modes. Comparison of the theory and experiments verify the theory as applied to the fundamental flexural mode, and with less precision, as applied to the higher flexural modes. The principal mode patterns and the history of the explosion bubble are verified by independent experiments.
Motion of Bubbles in a Stationary Sound Field
Authors: Crum Lawrence A. , Eller Anthony I.
Published: October 2005

Small air bubbles can be propelled through a liquid by a sound field. This paper presents observed and calculated values of the translational velocities at which bubbles smaller than resonance size are propelled through a standing acoustic wave in water and isopropyl alcohol. Bubble radii ranged from 29 to 149 μ, acoustic-pressure amplitudes ranged up to 1.1 bar, and the frequencies ranged from 23.6 to 28.3 kHz. The resulting bubble velocities, ranging to 23 cm/sec, were measured by photographing a moving bubble under stroboscopic illumination. Experiment and theory are in agreement as long as the bubble translation is rectilinear. Experimental results also indicate that the bubble translation becomes erratic when the pressure amplitude exceeds a threshold value. This threshold appears to be identical to the threshold for a similar onset of erratic dancing by bubbles that are trapped without translational motion in the sound field.
Third-Order Elastic Constants of Al2O3
Authors: Hankey Robert E. , Schuele Donald E.
Published: October 2005

By use of the pulse-echo technique, the hydrostatic pressure and uniaxial stress dependence of the ultrasonic wave velocities in single-crystal Al2O3 have been measured, and the values of the 14 independent third-order elastic stiffnesses were determined using a least-squares fit to 31 different experimental measurements. A generalized Gruneisen theory was used in the quasiharmonic approximation to calculate the high- and low-temperature limits for the two coefficients of linear thermal expansion. A numerical integration over 171 directions in the crystal was used for these calculations. The low-temperature limit does not compare well with the available thermal data; however, measurements of thermal expansion below 100°K, which are needed for a realistic comparison, are not presently available.
Nonlinear Effects in Microwave Acoustic LiNbO3 Surface-Wave Delay Lines
Authors: Slobodnik A. J.
Published: October 2005

Nonlinear effects have been observed in LiNbO3 acoustic surface-wave delay lines operating at a fundamental frequency of 905 MHz. Second-, third-, and fourth-harmonic generation, and their buildup and subsequent decay with distance, have been measured using laser-light deflection. The acoustic power entering these harmonics can be made comparable to that in the fundamental, since surface-wave attenuation has been seen to be dependent on input power. In fact, under certain conditions harmonic power is returned to the fundamental causing a region of negative attenuation or “gain.” Similar effects have been observed for the sum and difference frequencies (mixing) when two input frequencies are used. For linear operation at 905 MHz, surface-wave devices using Y-cut Z-propagating LiNbO3 should be limited to power densities of 10 mW/mm.
Effects of Winds on the Dispersion of Acoustic-Gravity Waves
Authors: Balachandran Nambath K.
Published: October 2005

The influence of winds at various levels in the atmosphere on the propagation of acoustic-gravity waves is studied theoretically using dispersion curves for various atmospheric models. It is found that short-period waves (periods less than about 400 sec) are influenced mainly by winds close to the ground, whereas long-period waves (periods more than about 400 sec) are influenced by high-altitude as well as low-altitude winds. Strong winds at altitudes near 100 km in the direction of propagation of the waves and winds near the ground blowing in a direction opposite to that of the waves are found to be favorable for inverse dispersion in group velocities at long periods. Exactly opposite wind conditions favor normal dispersion at all periods.
Sound Field of Plane or Gently Curved Pulsed Radiators
Authors: Freedman Albert
Published: October 2005

When a single pulse is applied to a plane radiator in a large rigid baffle or to a convexly curved baffled radiator having dimensions and radii of curvature large compared with the relevant wavelengths, the pressure at a field point is shown theoretically to consist, generally, of a sequence of pulses, each of which is, approximately, a scaled replica of the applied pulse. The number of pulses and their relative size and spacing are functions of position of the field point. In the direction of the main beam, if the radiating surface is plane, these pulses are not resolved and a single nearly undistorted pulse is obtained. A form of reciprocity is shown to exist between the structure of the acoustic signal at a point in the field of a pulsed transducer when transmitting and the structure of the electrical signal when the same transducer receives an acoustic pulse. Simple relationships are presented between the formulas for pulsed radiation, reception, and backscattering from a plane surface.
Scattering of Waves by a Cylindrical Piezoelectric Inclusion
Authors: Moon F. C.
Published: October 2005

The general problem of the scattering of waves from a transversely isotropic piezoelectric cylinder is examined. The solution for the interaction of an electromagnetic wave with a circular piezoelectric cylinder or antenna is presented. Solutions for the scattering of axial shear and compressional elastic waves by a piezo-electric circular cylinder embedded in an elastic medium are also presented. A few numerical results are presented for barium titanate.
Effect of Diffraction on Stress-Wave Measurement and a Concept for an Omnidirectional-Dynamic-Stress Gauge
Authors: Moon F. C. , Mow C. C.
Published: October 2005

This paper presents an analysis of the transient response of the pressure in an embedded elastic inclusion due to an incident compressional wave. It is found that the pressure or mean stress at the center of the inclusion is insensitive to the curvature of the incident wave. An early time analysis reveals that internal reflections in the inclusion can be minimized by matching the acoustic impedance of the inclusion with that of the matrix. An estimate is made of the time taken for these reflections to decay due to radiation damping. The method makes use of the calculus of residues and the high-frequency response to sum the resulting infinite series. The inverse problem is solved exactly; i.e., the incident-wave pressure is found in terms of the inclusion pressure. A design for an omnidirectional-pressure transducer is also discussed.
An Active Transducer as a Characteristic Impedance of an Acoustic Transmission Line
Authors: Bobber R. J.
Published: October 2005

The behavior of an electroacoustic transducer driven simultaneously by an acoustic pressure and an electronic generator has been analyzed and the conditions of voltage, pressure, and impedances for which the transducer functions as the characteristic impedance of an acoustic transmission line have been identified. The electronic generator serves largely as a means of canceling the internal acoustic reactance of the transducer. The energy, in a typical case, is absorbed largely in the transducer's internal acoustic resistance. In some cases, the electronic generator may load the transducer with a negative resistance. Control of the electronic generator is not critical. The blocked impedance of the transducer is not significant.
Solution of Acoustical-Radiation Problems by Boundary Collocation
Authors: Butler John L.
Published: October 2005

A boundary-collocation method for the solution of acoustical-radiation problems is presented. In this method, a wave function expansion is truncated to include only the number of terms equal to the number of specified boundary or field values. The expansion coefficients may be evaluated through a matrix inversion, and the solution improves as the number of terms increases. The method is general and is applied here to the radiation from the ends of a finite cylinder, a vibrating piston on a soft sphere, and the prediction of the farfield from measurements made in the nearfield of a coherent and a partially coherent source. It is shown that the method is simple and easily applied to otherwise complicated acoustical-radiation problems.
Statistics of Sound Propagation in the Ocean
Authors: Dyer Ira
Published: October 2005

The statistics of transmission fluctuations in the ocean are examined theoretically for both multipath and scattering processes. It is shown that, when both are present, multipath propagation dominates the fluctuations and leads to quite broad statistical distributions. In such cases, the mean and standard deviation for logarithmic measures such as transmission loss differ considerably from corresponding mean-square measures. Results for a single tone have been generalized to include multitones, as a model of ambient noise. Statistics of a signal combined with such noise have been derived; the standard deviation of the combination may be several decibels higher than the 5.6 dB of signal alone. The distributions of logarithmic quantities are generally found to be log transformations and combinations of chi-square distributions, and not log-normal distributions as commonly supposed.
Infinite Arrays with Nonrigid Interstices
Authors: Mangulis V.
Published: October 2005

The radiation from an infinite phased planar array of rectangular pistons (all with the same velocity magnitude) in a nonrigid baffle is evaluated. The nonrigid interstices between the array elements are approximated by equivalent undriven pistons with some internal impedance. When the dimensions of the pistons are small as compared to a wavelength, simple approximations are obtained for the radiation impedance of an array element and for the loss in source level due to the effect of the interstices. The source level is multiplied by the factor 1/|1 + (ΔA/ZI cosθ)|2, where ΔA is the fraction of the array area occupied by interstices, θ is the angle between the normal to the array and the direction to which the array is phased, and ZI is the interstitial impedance per unit area divided by ρc (ρ is the density of water; c, the velocity of sound in water).
Acoustic Propagation in an Isospeed Channel with Uniform Tidal Current and Depth Change
Authors: Stallworth L. A. , Jacobson M. J.
Published: October 2005

Ray geometry, spreading loss, boundary effects, and travel time of individual CW arrivals are examined in a uniformly moving acoustic channel with horizontal boundaries and a constant sound speed. The properties of corresponding arrivals at a fixed receiving point are compared for the cases of a stationary channel, a uniformly moving channel, and a channel with slowly time-varying current. The total field at a fixed receiving point is examined and it is shown that, under rather general conditions, the amplitude is virtually independent of current changes while the phase can vary significantly. The effects on the total field of spatially uniform, tidally related depth variations are then investigated. For a channel with large range-to-depth ratio, it is found that changes in tidal current cause most of the phase variation while amplitude variation is more dependent upon depth changes. Depth changes are shown to generate the phase offset-amplitude fade phenomenon described in earlier investigations. Phase variations associated with current changes are computed for a 33-km×40-m channel and compared with experimental data. Close agreement between theory and experiment is obtained.
Reverberation-Derived Scattering Strength of the Shallow Sea Bed
Authors: Urick R. J.
Published: October 2005

Measurements of explosive reverberation level and transmission loss have been made at a location off the west coast of Florida in water 200 ft deep. The measurements were reduced to scattering strength by means of a simple formula that ignores the details of the propagation paths to and from the scatterers. These reverberation-derived scattering strengths are found to be comparable to those previously measured for the deep sea bed. In addition, the reverberation tails of offset sources, displaced by distances up to 5 miles from the receiving hydrophone, are found to be identical to the reverberation tail of a nearby source when time shifted by the travel time from source to hydrophone. Although no direct scattering measurements on the shallow sea bed were made, the agreement of the reverberation-derived scattering strengths with the known scattering strength of the deep sea bed suggests the validity of the simplified model and its possible value for reverberation prediction, so as to make it analogous to the various existing prediction models for shallow-water transmission.
Scattering of Sound by Sound
Authors: Jones Joie Pierce , Beyer Robert T.
Published: October 2005

Following recent theoretical work, another attempt has been made to seek evidence of scattering resulting from the nonlinear interaction of two finite-amplitude sources operating in water. Experiments were performed using two perpendicularly intersecting pulsed sound beams having frequencies of 7 and 5 MHz. These beams produced pressure amplitudes of 4.5 and 1.8 atm, respectively, at the center of the interaction region. A receiver tuned to the summation frequency (12 MHz) was swept about the interaction region to investigate the scattered field. Various theoretical descriptions of this experiment have predicted for the scattered wave maximum pressure amplitudes ranging between 2.40×104 and 5.07 dyn/cm2. Although pressure levels of 0.07 dyn/cm2 could be measured with a 10-dB signal-to-noise ratio, no scattered wave was found. The lack of scattering outside the interaction region is in agreement with the theoretical considerations of Westervelt, but contrary to the predictions of Ingard and Pridmore-Brown, Dean, and Berktay and Al-Temimi.
Mean-Square Responses in Structural Systems
Authors: Gersch Will
Published: October 2005

The zero-lag state covariance matrix of a mechanical system subject to white-noise excitation is computed by algebraic techniques. This matrix is of interest because it is the solution to the familiar mean-square response computations. The problem is to determine the solution of the matrix equation AP+PA′= −G for P given A, an n×n nonsingular (structural system) matrix, and G, a symmetric, positive, semidefinite, input covariance matrix. P is the covariance matrix in question. This problem is the stochastic dual of the direct method of Lyapounov in the study of the stability of linear systems. The equation is solved in two ways. The direct solution involves inversion of a matrix whose order increases as the square of the number of degrees-of-freedom (df). Another solution is accomplished by a decomposition in which the input excitation is separated into stochastically independent components. In that case, for each input, G has rank 1 and the solution is readily computable upon transformation to a convenient form by a technique introduced by Kryloff in 1937. In the vernacular of contemporary control theory, the problem solution employs canonical transformations and the concept of a controllability matrix introduced and exploited by Kalman in 1960. The second solution of the equation requires inversion of a matrix whose order increases linearly with the number of degrees-of-freedom. The algebraic techniques discussed here are simpler to use than the “classical,” complex, variable-residue-theory techniques. More important, and in contrast with the classical techniques, the procedures described here are applicable to systems with an arbitrarily large number of degrees of freedom and may also be used to compute mean-square responses for systems with a vector of inputs. Explicit computational formulas for mean-square responses computed by the direct method are given for the general 1-, 2-, and 3-df systems. Numerical and graphical examples illustrate the procedure. Computational results, procedures, and formulas for the alternate “indirect” method are also worked for the 1-, 2-, and 3-df systems. Machine computations on a 2-df system illustrate the details for the practical computational use of the procedure.
Target Strength of a Single Fish
Authors: Diercks K. J. , Goldsberry T. G.
Published: October 2005

Measurements of the target strength of a single fish, species Ictiobus bubalus, over the frequency range from 50 to 470 kHz are presented and compared with estimated values calculated using an empirical relation recently derived by Love. The present measurements reveal an optimum frequency for detecting this fish. The measured target strength at this frequency is 17 dB greater than the value estimated using Love's equation.
METHOD AND CONTROL OF LARYNGEAL EMG ELECTRODE PLACEMENT IN MAN
Authors: Shipp Thomas , Fishman Barbara V. , Morrissey Philip , McGlone Robert E.
Published: October 2005

An EMG procedure has been devised for sampling the intrinsic laryngeal muscles during phonation. Problems regarding subject medication, selection, and construction of electrodes, and method and verification of electrode placement are discussed.
Effect of Noise Bandwidth on the Loudness of a 1000-Hz Tone
Authors: Hellman Rhona P.
Published: October 2005

The loudness of a 1000-Hz tone was measured by the method of adjustment in the presence of bands of white noise that varied in width from critical to very broad. Comparisons were made between the effects on loudness of noise bands set at nearly the same over-all sound-pressure level (SPL) and between the effects of those adjusted to produce the same amount of masking at threshold. The results suggest that, as long as the threshold shift is maintained constant, the loudness of the tone below an SPL of about 30 dB is reduced equally by narrow- and wide-band noise. At higher SPLs, the loudness of the tone tends to grow more rapidly in the presence of a narrow-band noise than in the presence of a wide-band noise. The magnitude of the effect depends on the width of the noise band.
Audibility Curve of the Chinchilla
Authors: Miller James D.
Published: October 2005

The audibility curve of the chinchilla was measured by behavioral audiometry. The animals were trained to respond to tones by the method of instrumental avoidance conditioning. Threshold tests were conducted in a sound-treated quiet room, with the loudspeaker located over the chinchilla's head. Thirty-six chinchillas were made monaural by surgical destruction of the left cochleas. Their auditory sensitivity was measured for tones spaced at equal logarithmic intervals over the range from 0.09 to 22.8 kHz. In addition, a few animals were tested at 32.0 kHz. For tones between 0.62 and 6.0 kHz, the chinchilla's threshold is about 2.4 dB sound-pressure level (SPL). For low frequencies, sensitivity declines about 5 dB/oct from 0.62 to 0.19 kHz, and about 17 dB/oct from 0.19 to 0.09 kHz. For high frequencies, sensitivity declines about 7 dB/oct from 6.0 to 16.0 kHz, and about 22 dB/oct from 16.0 to 22.8 kHz. Similar measurements were made for 10 binaural chinchillas. On the average, the binaural animals are 2.0–8.0 dB more sensitive than monaural animals. Two old chinchillas, 12 and 14 years of age, were found to have nearly normal thresholds, but abnormal inner ears.
Temporary Threshold Shift and Damage-Risk Criteria for Intermittent Noise Exposures
Authors: Ward W. Dixon
Published: October 2005

Twelve normal-hearing students were exposed for up to 8 h to steady and intermittent noises that, according to the CHABA damage-risk criteria (DRC) proposed in 1966, should produce an average TTS2 (temporary threshold shift measured 2 min after exposure) no greater than 10 dB at 1 kHz or below, 15 dB at 2 kHz, or 20 dB at 3 kHz or above. This objective appears to have been attained for single uninterrupted exposures and for intermittent exposures involving short (below 3–5 min) noise bursts and recovery periods. However, the cited limits of TTS2 tend to be exceeded when the noise bursts are quite long (10 min or more), owing to an erroneous previous assumption about the course of recovery during the quieter intervals between successive bursts. Modification of the DRC is therefore indicated. However, a more vexing finding is that intermittent exposures to high-frequency high-energy noise—either long bursts or short—often produce a delayed recovery; that is, more than 16 h of rest is required to restore the initial sensitivity. Thus, in an industrial situation, some workers in such a noise may in essence have a chronic TTS. In case such a chronic auditory fatigue may lead to permanent damage, extreme caution should be exercised in exposing men to levels above 100 dB in the 1500-Hz range or higher, even when the ratio of noise duration to pause duration is quite small. It is proposed that limiting values of TTS30 or TTS1000 rather than TTS2 might be more valid indicators of relative noxiousness of various exposure patterns. Alternate DRC presently under consideration are also discussed.
Pitch of Noise Bands Reconsidered
Authors: Lovell John D. , Madigan Robert J. , Carterette Edward C.
Published: October 2005

An explanation is given for the difficulty of Small and Daniloff's observers [“Pitch of Noise Bands,” J. Acoust. Soc. Amer. 41, 506–512 (1967)] in making octave judgments relative to the cutoff frequency of high-pass white noise. It is suggested that pink noise is a more appropriate psychoacoustic stimuli than white noise both in this case in general.
Comment on “Waveform Preservation in the Cochlea” [J. O. Nordmark, T. J. Glattke, and E. D. Schubert, J. Acoust. Soc. Amer. 46, 1587–1588 (1969)]
Authors: Tonndorf Juergen
Published: October 2005

Nordmark, et al. (1969), using cochlear-microphonic recordings from differential electrodes as indicator, showed that between Turns I and III there are no relative phase shifts for the components of a complex signal, as long as frequencies are not higher than the cutoff frequency of the Turn III location. The present communication argues that the relative phase shifts they had found for higher frequencies may be due to a recording artifact. Dallos (1969) demonstrated that for frequencies higher than their respective cutoff point upper-turn electrodes do not register local responses, but rather potentials that were generated at more basal locations.
Plastic Flow in Acoustically and Statically Loaded Nickel
Authors: Lester William W. , Whymark Roy R.
Published: October 2005

The plastic-flow threshold in pure nickel is measured under the combined action of various ultrasonic and static loadings. It is found that the ultrasonic vibrations, and combinations with static loading, are much more effective in producing flow than is static loading alone. The modulus and Q of nickel samples are measured in a cold-drawn, annealed, and plastically flowed state. It is found that a certain amount of annealing appears to take place after plastic flow over a period of hours or days at room temperature.
Stress Amplitudes of Long Waves in Filamentary Composites
Authors: Behrens Ernst
Published: October 2005

A theory for calculating distributions of stress-wave amplitudes in filamentary composites is presented. Plane waves with long wavelengths are classified in six different modes that can be compared with static strain conditions. For each wave mode, stress distributions in the elementary cell are calculated and plotted.
Radiation from the Forced Harmonic Vibrations of a Clamped Circular Plate in an Acoustic Fluid
Authors: Alper Stanley , Magrab Edward B.
Published: October 2005

The forced harmonic vibrations of a solid circular plate clamped to a rigid infinite baffle and bounded on one side of an inviscid fluid of infinite extent is considered. The motion in the plate is described by the Mindlin-Timoshenko theory, which includes the effects of transverse shear and rotatory inertia. The external force, which is applied from the in vacuo side of the plate, can have any spatial distribution. The solution is obtained with the use of orthogonal functions which result from transforming the polar cylindrical coordinates describing the fluid motion into oblate spheroidal coordinates and the solution to the in vacuo vibrations of the clamped plate. This method of solution removes all previous restrictions regarding the solution of this problem, namely, boundary conditions of the plate, symmetry of loading, applicable frequency range, and extensive numerical calculations for the determination of the complete nearfield pressure. Expressions are obtained for the near- and farfield pressure in the fluid and the radiated power from the plate-fluid surface. A numerical case for a concentrated load at the center of the plate is presented.
Experimental and Analytical Study of Vibrating Stiffened Rectangular Plates Subjected to In-Plane Loading
Authors: Smith G. A. , Laura P. A. , Matis M.
Published: October 2005

This study deals with vibrating rib-stiffened and unstiffened clamped plates. The effects of point masses and in-plane loading are studied analytically and experimentally. The agreement between calculated and measured frequencies is good in spite of the fact that some of the assumptions regarding the nature of the stress distribution connected with the in-plane loading are rather gross. Mode shapes of the first nine modes of vibration of a square plate stiffened in one direction are presented.
Standard Probe Hydrophone for Acoustic Measurements from 10 Hz to 200 kHz
Authors: Groves Ivor D. , Tims Allan C.
Published: October 2005

Smooth response, omnidirectionality, and wide dynamic range are features of a new reference standard probe hydrophone for the frequency range 10 Hz 200 kHz at hydrostatic pressure to 1000 psig and temperature from 5° to 35°C. The nominal end-of cable sensitivity is −116.9 dB re 1 V μbar from 10 Hz to 60 kHz.
Use of Splines and Numerical Integration in Geometrical Acoustics
Authors: Moler Cleve B. , Solomon Louis P.
Published: October 2005

Two contributions are made to ray theoretic techniques for propagation through continuously stratified media. The first makes use of spline polynomials to approximate speed-of-sound profiles smoothly. The second eliminates the singularity occuring in the usual range integral. A versatile automatic numerical procedure for solving a wide variety of acoustic propagation problems results.
Transmission Characteristics of the SOFAR Channel
Authors: Webb D. C. , Tucker M. J.
Published: October 2005

The transmission of long single-frequency pulses of sound in the deep sound channel is described. Pulses of 2-sec duration and 778-Hz carrier frequency were transmitted for ranges up to 270 km in the area south of Bermuda. The measurements include the attenuation coefficient, transition range, and horizontal small-scale spatial variation. The transmission measurements were made to evaluate the feasibility of a freely drifting Swallow float able to signal for extended periods to land-based receiving stations.
Interactions between High-Frequency Acoustical Waves in Lithium Niobate
Authors: Thery Pierre , Bridoux Edouard , Moriamez Michel
Published: October 2005

We have studied the interaction between two colinear longitudinal acoustical waves of frequencies 930 MHz and 2770 MHz simultaneously excited in LiNbO3 (cut 001). The acoustical waves were produced by placing a crystal in an intense electric field of a cavity resonating with two distinct frequencies. The waves thereby produced interact at the surface of the crystal (when the acoustical waves are produced) and in the volume when the waves are propagated, forming harmonies and waves of mixed frequencies mF1±nF2 (F1 and F2 are frequencies of the fundamental waves, m and n are integers). We have detected waves of frequencies 2F1 and F2 − F1 in the second end of the crystal. The deformation amplitudes detected at these frequencies depend on the length of the crystal studied. The interaction observed, along the direction [001] of LiNbO3, depends then on the interaction length between waves in the crystal and has been interpreted by considering only the nonlinear effects in the propagation of the acoustical waves.
On the Depth Variation in the Energy Spectra of Underwater Explosive Charges
Authors: Turner R. G. , Scrimger J. A.
Published: October 2005

Measurements were made of the energy per unit area spectrum level of charges exploded underwater in the depth range from near the surface to about 2000 ft. Two charge types were used—a 1-lb Pentolite charge and a Seismocap (Canadian Industries Ltd., TNT equivalent: 0.00146 lb). The frequency range covered was 0.02–10.24 kHz for the 1-lb charges and 0.08–10.24 kHz for the Seismocaps. The spectrum-level values obtained are compared with Christian's “consistent family” of energy-spectrum curves for the various explosion depths [E. A. Christian, J. Acoust. Soc. Amer. 36, 2418(L) (1964)].
Structural and Environmental Studies of Acoustical Duct-Lining Materials
Authors: Watson Herschel A.
Published: October 2005

This paper is a review of the structural aspects of current turbofan noise-suppression designs presented in conjunction with a summary of the environmental conditions, which determine the design criteria of duct-lining acoustical materials. The subject is confined to structural and environmental studies of acoustical materials and to the analyses, tests, and design criteria necessary to provide a certifiable noise-suppression system for commercial aircraft. The paper parallels, but updates, similar paper presented by the author to the October 1968 Conference on Progress of NASA Research Relating to Noise Alleviation of Large Subsonic Jet Aircraft [R. A. Mangiarotty, A. H. Marsh, and E. Feder, NASA SP-189 (1968)]. Studies related to the structure and environment of duct-lining acoustical materials proposed for use in the noise-suppression systems of turbofan aircraft may be more clearly understood when preceded by: (1) an indication of where the systems are used within a power plant nacelle, (2) a complete definition of the environmental conditions under which the systems are expected to function, (3) an explanation of the basic acoustical function of the materials, and (4) a detailed description of typical duct-lining configurations.
Parametric Studies of the Acoustic Behavior of Duct-Lining Materials
Authors: Atvars J. , Mangiarotty R. A.
Published: October 2005

Fan noise radiated from the engine inlet and fan discharge of current fan jet airplanes during landing makes the largest contribution to perceived noise. This noise can be reduced by lining the engine inlet and duct walls with sound-absorbing materials. Because of the scarcity of analytical lining design methods which include duct airflow effects, an experimental program was conducted to investigate the influence of acoustic and geometric duct-lining parameters on fan-noise attenuation. The significant parameters were found to be the acoustic impedance, treatment length, depth, core-cell dimensions, channel width, number of walls lined, number of layers in the linings, air velocity, and direction of flow with reference to sound propagation. The influence of these parameters is discussed. For simple single-layer linings a design technology has been developed by means of empirical equations. Experimental results show that this technology is valid, for duct sizes from 4 to 12 in., lining depths of 14 to 1 in., and duct airflow Mach numbers from −0.4 to 0.4.
Bat Signals as Optimally Doppler Tolerant Waveforms
Authors: Altes R. A. , Titlebaum E. L.
Published: October 2005

Wide-band ambiguity function analysis is combined with techniques of variational calculus to find optimally Doppler tolerant waveforms, i.e., signals such that magnitude of correlator output is relatively unaffected by target velocity. With appropriate constraints, these signals are found to be very similar to those used by Myotis lucifugus.
The Pattern of Stapedial Vibration
Authors: Dankbaar W. A.
Published: October 2005

Experiments are performed on human temporal bones to investigate the mode of vibration of the stapes. The results support the assumption that the stapes generally moves pistonlike.
Effects of Interaural Frequency Differences on the Lateralization Function
Authors: Perrott David R. , Williams Kendrick N.
Published: October 2005

Lateralization thresholds were determined under conditions of interaural frequency disparity. The lateralization function was independent of the interaural frequency differences employed. Implications for a model of binaural interaction were discussed.
Fixed-Scale Mechanism of Absolute Pitch
Authors: Brady Paul T.
Published: October 2005

With intensive training, the author, who had no previous ability in identification of randomly presented tones from the 12-tone musical scale, achieved performance level of 65% exactly correct and 97% correct within ±1 half-step (semitone). The training task consisted of spending many hours hearing and identifying randomly presented tones with feedback on the judgments. Successful acquisition of absolute-tone identification contributes to the evidence that an adult can learn this task, but apparently only with great effort. It is suggested that naturally occurring absolute pitch is not an innate ability. Rather, this skill results from perceiving only one musical scale (for example, C-major), and if music is played in a different scale, the notes retain their C-major perceptual values. This mechanism, which is probably acquired in early childhood, can account for much of the introspective and performance data from possessors and nonpossessors of absolute pitch.
Discrimination of Transient Signals Having Identical Energy Spectra
Authors: Patterson James H. , Green David M.
Published: October 2005

Pairs of waveforms having identical energy spectra were generated using a technique developed by Huffman [IRE Trans. IT8, S10–S16 (1962)]. A pair of such waveforms differ only in their phase spectra. The discriminability of such waveforms was measured under various conditions. The total duration of the waveforms was varied as well as the nature of the differences in their phase spectra. The results of these experiments suggest that the ear can discriminate differences in temporal order as small as 2.5 msec. In later experiments this discriminability among pairs was studied when both waveforms were partially masked by noise. Some pairs can be discriminated when only 6 dB above their masked threshold.
Depth of Sequential Auditory Information Processing: II
Authors: Pollack Irwin
Published: October 2005

Folded Markov sequences provide a tool for the examination of the depth of processing sequential information. The effect of diffusing random sequences within folded Markov sequences was studied for finite-state interval-coded auditory pulse trains. Random sequences actively interfere with the discrimination of folded Markov sequences: Their effect is greater than simply deleting an equivalent number of intervals from the folded Markov sequence, or of extending the equivalent depth of folding. Random sequences provide effective interference, primarily because they fail to provide differential information for discrimination. Nondifferential nonrandom sequences also produce interference. In addition, it is shown that discrimination of folded Markov sequences is nearly independent of the number of possible states of the sequence under conditions of equivalent uncertainty. The apparent depth of sequential processing is virtually unlimited; the necessary condition is that each depth of folding be represented by about five samples.
Effects of Electric Stimulation of the Crossed Olivocochlear Bundle on Single Auditory-Nerve Fibers in the Cat
Authors: Wiederhold M. L. , Kiang N. Y. S.
Published: October 2005

The activity of single auditory-nerve fibers was examined with and without electric stimulation of the crossed olivocochlear bundle (COCB). In the presence of tones at the characteristic frequencies (CF) of the fibers, the effect of COCB stimulation is, in general, to reduce the spike-discharge rate. The time characteristics of the effect were studied for several parameters of the electric shocks, acoustic stimuli, and fiber characteristics. Some effects of COCB stimulation on “spontaneous” and acoustically generated activity are discussed with reference to cochlear mechanisms.
Transmission Loss of Multiple Uncoupled Panels
Authors: Salmon Vincent
Published: October 2005

The transmission loss of n multiple limp nonreflecting panels whose mechanical or air-cushion coupling is negligible is approximated by L = nL1−20 n logn, where L1 is the transmission loss of a single limp panel of the same total mass per unit area.
Visualization of Plane-Strain Vibration Modes of a Long Cylinder Capable of Producing Sound Radiation
Authors: Sittig E. K. , Coquin G. A.
Published: October 2005

This paper points out that a class of plane-strain vibration modes in an isotropic solid cylinder has properties suitable for interaction with a sound field in a fluid medium surrounding the cylinder. A resonance-type theory of such modes is presented. Experimental verification of this theory is obtained by observing stress birefringence patterns of resonating glass cylinders. The circumferential waves arising from these modes are likely to play a part in the scattering phenomena occurring in the medium surrounding the cylinder.
Harmonic Nonaxisymmetric Waves with Short Wavelengths Propagating in Composite Rods
Authors: Armenàkas Anthony E. , Keck Henry E.
Published: October 2005

The asymptotic phase velocities, at very large wavenumbers, of nonaxisymmetric waves traveling in composite rods are established analytically. Frequency spectra and mode shapes of composite rods are presented and compared with those of simple (made of one material) rods.
The Role of Impurities in Cavitation-Threshold Determination
Authors: Apfel Robert E.
Published: October 2005

We have extended the theoretical work of Harvey et al. [J. Cellular Comp. Physiol. 24, 1–22 (1944)] and Strasberg [J. Acoust. Soc. Amer. 31, 163–176 (1959)] in order to consider the conditions that must exist in a liquid for a vapor cavity to be nucleated from an imperfectly wetted solid impurity (mote) in the liquid. It is found that, for sufficiently small and readily wetted motes, the tensile stress required for nucleation increases with increasing surface tension and decreasing mote size but is almost independent of the gas content and history of the liquid. On the other hand, for sufficiently large and imperfectly wetted motes, the gas content of the liquid and its history are crucial, whereas the mote size and the liquid-vapor surface tension play no role in determining the conditions for nucleation. The qualitative predictions of this theory of moted-induced nucleation bring some semblance of order to a wide variety of observations of statically induced cavitation and low-frequency acoustic cavitation reported in the literature.
Measurement of the Effect of Air Bubbles on the Speed of Sound in Water
Authors: Gibson Frederick W.
Published: October 2005

A simple technique for measuring the effect of air bubbles on the speed of sound in water, and hence on the attenuation of pressure pulses in water, has been developed. The good agreement of the experimental data with computed values indicates the adequacy of the experimental method.
Closed-Form Solution of Forced Vibrations of Spherical Shells with Attachments
Authors: Junger Miguel C.
Published: October 2005

An asymptotic high-frequency closed-form solution of the point-excited spherical shell [D. Feit et al., J. Appl. Mech. 36, 859 (1969)] is extended here to nonaxisymmetrically point-excited shells with point attachments characterized by an arbitrary impedance. The structure-borne sound field near the attachment displays the characteristics of the diffracted acoustic field near an infinite cylinder. A dashpot located diametrically opposite the drive point drastically reduces the shell response if its impedance is matched to the drive-point impedance of the shell.
MEASUREMENT OF ULTRASONIC VELOCITIES IN SOLIDS UNDER HYDROSTATIC PRESSURE
Authors: Peselnick L.
Published: October 2005

An ultrasonic method for determining velocity has been developed that is independent of phase-change errors due to reflection of specimen waves from coupling films. The method also eliminates the possibility of error due to conditions of nonhydrostatic stress at a specimen-transducer or specimen-delay line interface. Preliminary data are given for Alcoa 2024-T4 aluminum and are compared with results using the phase-comparison method.
EFFECT OF EXHAUST-NOZZLE SHAPE ON JET NOISE
Authors: Tirumalesa Duvvuri
Published: October 2005

Some salient results of an analysis based on Ribner's jet-noise model of experimental studies of the noise field of full-scale fitted with conical and eight-lobed daisy nozzles are presented in this note. The results show the effect of the exhaust-nozzle shape on the shear noise component of Ribner's model and importance of the noise contribution from the transitional region of the jet on the perceived noise levels (PNL).
A Model for Two-Tone Inhibition of Single Cochlear-Nerve Fibers
Authors: Pfeiffer Russell R.
Published: October 2005

An analog model by Engebretson and Eldredge accounts for nonlinear properties of the cochlear microphonic (CM) in response to single- and two-tone stimulation. Recent evidence that shows strong similarities between CM and spike-discharge patterns of single cochlear-nerve fibers has prompted an association of two-tone interaction of CM with two-tone inhibition of nerve fibers, leading to a modification of the model for CM so as to make it applicable to cochlear-nerve fibers. The result is a model that has clear two-tone inhibition properties similar to those observed experimentally. Mathematical analysis applied to the model shows that the “inhibition” is easily explained by signal suppressions inherent to bandpass nonlinearities.