bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Problems in the Measurement of Cochlear Distortion
Authors: Dallos P. , Schoeny Z. G. , Worthington D. W. , Cheatham M. A.
Published: October 2005

Proper specification of the magnitude and purity of the sound stimulus is of utmost importance in studies dealing with distortion processes in the ear. It is shown that, in general, sound pressure level (SPL) measurements in rigid-walled couplers do not provide adequate representation of sound levels observed at the experimental animal's eardrum. Similarly, the distortion generated by the experimental apparatus can be either over or underestimated if measured in couplers. It is shown that, in general, the absolute specification of tolerable distortion level created by the experimental apparatus is not possible, and that this level depends on various factors of the actual experiment. Finally, evidence is presented that favors the prosecution of studies on aural distortion with the auditory bulla closed.
Binaural Masking: Backward, Forward, and Simultaneous Effects
Authors: Deatherage Bruce H. , Evans Thomas R.
Published: October 2005

This study sought to examine the temporal relations of binaural masking as compared with monaural masking for conditions of forward, simultaneous, and backward masking. Five conditions of different signal-masker configurations and a number of temporal relations were examined to determine the masking effects on a tone by a tonal masker. The results indicate that forward, simultaneous, and backward masking are all the result of time-dependent properties of the neural mechanism, but the dependency for all three types of masking is wholly or in part mediated by the central nervous system. The concept of peripheral adaptation as an explanation for forward masking is not supported. A discussion of the various contralateral masking conditions is presented.
Intensity Perception. I. Preliminary Theory of Intensity Resolution
Authors: Durlach N. I. , Braida L. D.
Published: October 2005

An attempt is made to develop a quantitative theory of intensity resolution that is applicable to a wide variety of experiments on discrimination, identification, and scaling. The theory is composed of a Thurstonian decision model, which separates sensitivity from response bias, and an internal-noise model, which separates sensory limitations from memory limitations. It is assumed that the subject has two memory operating modes, a sensory-trace mode and a context-coding mode, and that the use of these two modes is determined by the characteristics of the experiment. In one-interval paradigms, it is assumed that the context-coding mode is used, and the theory relates resolution to the total range of intensities in the stimulus set. In two-interval paradigms, it is assumed that the two modes are combined, and the theory relates resolution to both the total intensity range and the duration between the two intervals. The theory provides, among other things, a new interpretation of the 7 ± 2 phenomenon.
Remote Masking for Listeners with Cochlear Impairment
Authors: Keith Robert W. , Anderson Charles V.
Published: October 2005

Remote masking in ears with cochlear impairment was investigated, According to one theory, remote masking results from unsymmetrical mechanical action in the inner ear that generates a broad-band noise within the inner ear. The broad-band noise is said to mask tones at frequencies remote from and below the narrow-band masker. A second theory proposes that remote masking is the result of attenuation provided by the acoustic reflex. Two noise bands were presented at three levels to a group of listeners with normal hearing and two groups with high-frequency hearing losses of presumed cochlear origin. From these results, it appears that, when a noise band is located at frequencies of hearing loss, listeners with presumed cochlear impairment require a higher level of noise for remote masking to occur than do normal-hearing listeners; and their remote masked thresholds are at a lower SPL and there is less remote masking than for normal-hearing listeners. It was observed that remote masking is not necessarily at a constant sensation level across frequency, with the greatest amount of remote masking occurring near 800 Hz. The similarities between results of this investigation and known parameters of the acoustic reflex lead us to the conclusion that a dual mechanism of middle-ear plus inner-ear activity is a more suitable explanation of remote masking than either theory alone.
Perstimulatory Tracking in Pitch Perception at Different Sensation Levels
Authors: Skinner Paul H. , Antinoro Frank
Published: October 2005

The pitch of a continuous fatiguing tone was tracked over time to study the effects of frequency and sensation level of the fatiguing stimulus on pitch perception. Perstimulatory tracking in pitch perception was done at the following frequencies: 500, 1500, 2500, and 4500 Hz; and at the following sensation levels: 20, 40, 60, 90, and 100 dB. The perstimulatory or continuous fatiguing signals were presented initially in the experiment for a duration of 3–8 min, depending on the frequency and intensity of the fatiguing stimulus. The pitch of the continuous tone was tracked constantly over that period. Immediately after cessation of the continuous tone, poststimulatory tracking was done at preexposure sensation levels of from 10 to 30 dB with pulsed tones alternating between ears. Perstimulatory pitch shifts were never apparent at the lowest frequency at any sensation level. Perstimulatory pitch shifts occurred commonly in the midfrequencies and were more prevalent at the higher sensation levels. Perstimulatory pitch shifts were observed at all of the experimental sessions at 4500 Hz regardless of sensation level. The direction of temporary pitch shift (TPS) was apparently related to sensation level of the fatiguing signal. The amount of TPS was significant and increased with in creasing frequency. Poststimulatory tracking revealed a very rapid recovery of TPS.
Temporal Summation of Loudness: An Analysis
Authors: Zwislocki J. J.
Published: October 2005

A quantitative psychophysiological theory is developed for loudness level and loudness as a function of stimulus duration. It is based on the psychophysical as well as neurophysiological evidence that the apparent temporal summation of acoustic energy is a result of neural summation at a high level of the auditory system. The theory shows how this can be achieved in spite of a nonlinear relationship between sound intensity and neural excitation. The temporal decay of neural firing preceding the final stage of temporal summation seems to be responsible for overcoming the nonlinearity.
Parallel Processing Techniques for Estimating Pitch Periods of Speech in the Time Domain
Authors: Gold B. , Rabiner L.
Published: October 2005

A computational algorithm for estimating pitch periods of speech in the time domain is presented, and two recent modifications of the algorithm are discussed in detail. The algorithm and its modifications have been found to be relatively accurate and efficient in tests on real and synthetic speech.
Radiation Pressure from Breathing and Heartbeat
Authors: Barnes Thomas G.
Published: October 2005

The approximate infrasonic source strength of a human's breathing and heartbeat is determined from pressure and frequency measurements made with the subject inside a sealed chamber of known volume. Theoretical free-field pressures are then computed for each source strength. Respiration pressure field is considered to be due to a dipole and a monopole source. By separately measuring each pole in the sealed chamber, the source strength was obtained for each pole of the dipole. The infrasonic pressure field due to respiration varied from individual to individual, but was of the order of magnitude of 10−4 μbar at 1 m in the direction of minimum field. The pressure field due to heartbeat was an order of magnitude lower.
Temporal Summation of Acoustic Signals by the Chinchilla
Authors: Henderson Donald
Published: October 2005

The auditory sensitivity of two chinchillas was measured by means of a conditioned-avoidance technique. The signals were 2000-Hz sinusoids of 25, 50, 100, 200, 400, and 750 msec. The data were similar to the familiar temporal integration curve that has been reported for human subjects. Subsequently, the chinchillas were exposed for three hours to a 105-dB SPL octave-band of noise centered at 2000 Hz. The pre- and postexposure thresholds were measured for signals of 25, 200, and 750 msec. After exposure, the thresholds for all three stimuli were elevated, and they recovered to normal in approximately two weeks. The preexposure difference of 12 dB between the 25- and 750-msec signals was reduced after the noise exposure. During the process of recovery, the difference gradually returned to the preexposure magnitude.
Intraoral Air Pressures for /p/ in Oral and Whispered Vowel Environments
Authors: Schwartz Martin F.
Published: October 2005

A study of the intraoral air pressures for /p/ in oral and whispered vowel environments revealed: (1) significantly lower air pressures for the whispered /p/ productions, and (2) a significant differential influence for high versus low vowel environments.
Near- and Farfields in a Marine Environment
Authors: Siler William
Published: October 2005

A particle velocity sound unit is introduced, the microvar, which equals 1/ρc cm sec. Approximate formulas for the nearfield and farfield are derived which indicate that in the farfield, velocity in microvars and pressure in microbars are equal; in the nearfield, the pressure-velocity ratio falls off at 6 dB per distance octave as the source is approached; and the crossover point between near- and farfields on the major vibration axis is distant from the source nλ, 2π, where n = 1 for a monopole, 2 for a dipole, and 3 for a quadrupole source. Off the major axis the crossover point moves farther away from the source. The approximate formulas are shown to be in reasonable agreement with theoretical values. It is concluded that the stimulus is present to permit a velocity displacement-sensitive organism to detect sound at any distance from a source of sufficient intensity.
Ultralow Frequency Waves Generated by the Saturn F-1 Engine
Authors: Fehr Uri , McGahan L. C.
Published: October 2005

The source characteristics of the Saturn F-1 engine in the infrasonic frequency range of 0.1–20 Hz and the seismic and magnetic fluctuations from 4 to 16 Hz have been ascertained. The acoustic signals have shown a characteristic ignition and cutoff pulse. The ignition signal shows a typical explosion signature (N-type wave), while the cutoff signal produces a bubble pulse-type effect, which might have resulted from an implosion structure. The engine run produces a steady state signal. However, its acoustic energy peak in the ultralow frequency range is a function of the engine-run duration. The power spectrum shows energy distribution in two regions, with a maxima at 4–8 Hz and at approximately 1.4 Hz, with energy extending to about 0.1 Hz. The lower frequency peak becomes more significant with the increase in the engine-run duration. The magnetic signals have shown a narrow-band signal between 8 and 12 Hz during the engine run and a high-intensity cutoff signal of a wider band. The cutoff signal resembles a pulse. The downward exhaust of the static running of a rocket motor is a source for ultralow frequency acoustic and magnetic waves. Similar conclusions are drawn for the behavior of an Atlas rocket during the first few kilometers of flight.
Influence of Diffraction on the Four-Pole Impedances of Electroacoustic Delay Lines with Circular or Rectangular Plane-Parallel Transducers
Authors: van der Pauw L. J.
Published: October 2005

In this paper, the influence of diffraction on the four-pole impedances of electroacoustic delay lines with circular or rectangular electrodes is investigated. In particular, it is shown that by means of a simple procedure the diffraction losses of an electroacoustic delay line with circular or rectangular plane-parallel transducers can be determined from a graphical plot. It is assumed that the transducers are of identical shape and located in opposition. The method applies in the nearfield region, the farfield region and the transition region; the only assumption being that the dimensions of the electrodes are large compared with the acoustical wavelength. The error made by the simplifications introduced is estimated and is typically of the order of 10% or less.
Effect of Pressure on Ultrasonic Absorption, Multistate Dissociation, and Chemical Equilibrium in MnSO4 Solutions
Authors: Fisher F. H. , Wright W. M.
Published: October 2005

Measurements were made on the effect of pressure on ultrasonic absorption in a 0.5M aqueous solution of manganese sulfate at 25°C. A cylindrical resonant cavity was used for obtaining absorption in the frequency regions of 300 and 500 kHz, at pressures up to 20 000 psi. Results are similar to those obtained for MgSO4, in that absorption decreases by a factor of about 3 for a pressure increase of 15 000 psi. Independent conductivity data show nearly the same behavior for MnSO4 as for MgSO4 solutions, namely, an increase of only about 14% in the concentration of dissociated ions for the same pressure increase. These results for MnSO4 appear to be inconsistent with the model used by Atkinson and Kor to analyze their data. The large effect of pressure on ultrasonic absorption is similar to that observed by Carnevale for 0.1M MnSO4 at 60°C from 9 to 75 MHz.
Pressure Waves in an Accelerated Sphere Filled with a Compressible Liquid
Authors: Ehlers F. Edward
Published: October 2005

The linearized equations for the flow of a compressible inviscid fluid in an accelerated sphere were solved for a constant step in the acceleration from a state of rest. Pressure waves whose maximum amplitude is nearly equal to the hydrostatic pressure from an equivalent steady gravitational field acting through the depth of the diameter are induced in the fluid. This maximum pressure occurs at the end of that diameter aligned in the direction of the acceleration. By means of the convolution integral, the pressure distribution on the inner surface of a sphere being accelerated sinusoidally was obtained and the reaction force resulting from the fluid motion was computed. The pressure oscillations build up in a resonant manner with amplitude linear with time when the driving-reduced frequency is equal to an eigenvalue of the problem.
Analysis of Acoustic Wave Scattering from a Rough Layer
Authors: Krishen Kumar , Koepsel W. W.
Published: October 2005

The theory of wave scattering from a rough surface has been used to calculate reflection from a rough layer. Mathematical expressions have been developed for the average value and the variance of the scattered power. These expressions take into account multiple reflections in the layer between the top and the bottom interfaces. The variance of the scattered power is expressed as a series. The terms of this series decrease rapidly.
Dispersion of Flexural Waves in Circular Bimaterial Cylinders—Theoretical Treatment
Authors: Reuter Robert C.
Published: October 2005

The general form for displacements and the frequency equation are obtained for the first mode of flexural wave propagation in an infinitely long circular bimaterial cylinder. Based on the equations of linear elasticity, the theory follows the technique developed by Pochhammer and Chree for elastic bars. Several first-branch dispersion curves for the first flexural mode are presented for various ratios of the constituent cylinder radii. Dispersion characteristics significantly different from those predicted by the theory for homogeneous cylinders are realized. Some implications in regard to equivalent properties are discussed.
Time-Domain Analysis of Broad-Band Refraction and Diffraction
Authors: Wright H. A.
Published: October 2005

The emissions from a broad-band impulsive point source are refracted by a spherically shaped interface between two fluids having different acoustic velocities. It is shown that, on axis, two disturbances are produced: The first is the waveform emitted by the source, and the second is its polarity inverse. As the observation point approaches the image point of the source, the waveform approaches the derivative of the waveform emitted by the source. Diffraction is a special case for which the acoustic velocities of the two fluids are equal. Two disturbances are produced: The first is the waveform emitted by the source, and the second is its inverse.
Free Vibrations of Circular Membranes under Arbitrary Tension by the Finite-Element Method
Authors: Mei Chuh
Published: October 2005

The method of finite elements is extended to problems of free vibrations of elastic homogeneous membranes of general shape under arbitrary tensile forces at the edge. Special consideration is given to drumhead-type structures that are basically circular thin elastic sheets fixed at the edge and subjected to nonuniform tension. Six different loading conditions, including the uniform case, are considered. Particular attention is given to the influence of various force systems on natural frequencies and normal modes of vibration. It is found that the lowest natural frequencies are virtually identical for the various edge loading conditions studied, and the corresponding vibration modes vary little from one another. However, for the higher modes, not only do the natural frequencies of vibration differ much, but some of the nodal patterns are distorted in a very fascinating fashion. For the case of uniform tension, a comparison of natural frequencies with known exact solutions shows that the method gives very good results.
Spherical Model of an Acoustical Wave Generated by Rapid Laser Heating in a Liquid
Authors: Hu Chia-Lun
Published: October 2005

A spherical model for the acoustic pressure-wave generated by the rapid thermal expansion owing to laser heating is analytically investigated. The physics of the wave generation is extensively discussed, and from this point of view the mathematical boundary value problem is formulated. A Laplace-transform-Green-function method is applied to solve this problem, and the resultant pressure wave is expressed as a function of time, space, and input parameters. The result shows that any point in the medium outside the laser focus experiences, first, a strong positive pressure pulse, and then, a strong tension (negative pressure) pulse. The shape of these two pulses is skew symmetric with respect to the central time between the two peaks of the pulses. These two peaks occur respectively at the retarded starting and extinguishing edges of the laser pulse. The magnitudes of these two peaks are equal. They are proportional to the laser intensity, and inversely proportional to the distance of observation. Numerical examples are given.
Relationships between Acoustic Backscatter and Geological Characteristics of the Deep Ocean Floor
Authors: Patterson R. B.
Published: October 2005

The ocean floor exhibits a wide variety of geological characteristics that can affect incident acoustic radiation. Therefore, in order fully to understand and use any acoustic-backscatter measurements, it is necessary to obtain as much information as possible about the characteristics at the location of the measurements. Measurements have been made of the acoustic backscatters as a function of grazing angle at a location on the Blake Plateau, using an acoustic frequency of 1.78 kHz. For grazing angles below 65°, the scattering strengths are significantly lower than some data previously obtained at the same site using a frequency of 19.5 kHz. A number of bottom photographs and a seismic-refraction profile were obtained in close proximity to the location of the acoustic measurements. A number of photographs and a bottom sample have also been obtained on Challenger Bank, the location of some 2.5-kHz backscatter measurements.
Cavitation Due to Shock Pulses Reflected from the Sea Surface
Authors: Wentzell R. A. , Scott H. D. , Chapman R. P.
Published: October 2005

Cavitation caused by shock pulses reflected from the sea surface is studied. A breaking pressure of zero is assumed and a model based on spalled layers is proposed to determine the prominent characteristics. These characteristics include the extent of cavitation, and a return pulse with an initial spike followed by an approximately rectangular pulse that, for larger charges fired near the sea surface, is very much longer than the incident pulse. Experiments using explosives to produce exponential shock pulses of various peak pressures and characteristic lengths verify the prominent features of the model. The acoustic effects indicate a breaking tension at least a factor of 10 smaller than that indicated by visible effects.
Signal Distortion in a Constant Gradient Medium is Continuous and Bounded
Authors: Wood D. H.
Published: October 2005

In an unbounded constant gradient medium, the distortion of an arbitrary signal φ is necessarily bounded and continuous, even when φ is unbounded and discontinuous. The distortion, which goes to zero as time goes to infinity, goes uniformly to zero as a parameter (gradient squared multiplied by travel time) goes to zero.
Direct Correlation of Fluctuating Lift with Radiated Sound for an Airfoil in Turbulent Flow
Authors: Clark P. J. F. , Ribner H. S.
Published: October 2005

An airfoil in turbulent flow is thought to radiate sound in consequence of its fluctuating lift. The instantaneous sound and lift should be connected by Curle's equation, which describes sound radiation from a rigid surface in contact with turbulent flow. It follows that the crosscorrelation of sound and lift should be related in a corresponding way to the lift autocorrelation. Such correlations were measured in the present investigation of an airfoil in a jet flow, and the Curle relationship was verified semiquantitatively. The predicted comparative shapes of the correlation curves were found; the comparative magnitudes showed a 27% (2.7-dB) discrepancy. This small discrepancy is attributed to model vibration, which falsely enhanced the lift signal via inertial loading. The work answers, in part, questions that have been raised as to the applicability of Curle's equation. Further, it confirms that a rigid surface in contact with a turbulent flow need not be inherently passive—a reflector of sound—but can be an active generator of sound.
Reply to “Comments on ‘Finite Radial Oscillations of a Spinning Thick-Walled Cylinder’” [S. Bharatha, J. Acoust. Soc. Amer. 46, 823(L) (1969)]
Authors: Nowinski J. L. , Wang S. D.
Published: October 2005

Attention is called to the fact that (a) the boundary conditions should be accounted for, and (b) more information is needed on mode separation.
Vibration of Inhomogeneous Circular Membranes
Authors: Frommf Joseph A.
Published: October 2005

Exact solutions are given for the free vibration of circular membranes when their density is an analytic function of the radial variable. Comparisons are made with recently published approximate solutions, and an error is found.
Displacement-Transducer Assembly Used in Studying the Parallel-Flow-Induced Vibration of Reactor Fuel Rods
Authors: Jendrzejczvk J. A. , Wambsganss M. W.
Published: October 2005

A displacement-transducer assembly used in measuring the vibration amplitude of simulated fuel rods in parallel coolant flow is discussed. The transducer assembly is built around a proximity sensor of the eddy-current type. Pickup coils are supported on a thin-walled small diameter tube that is concentrically mounted inside the tubular test element. A typical spectral-density response is presented along with displacement-time histories, which allow evaluation.
On the Vibration of a Thin Piezoelectric Disk with an Arbitrary Impedance on the Boundary
Authors: Nelson Ralph A. , Royster Larry H.
Published: October 2005

Expressions are developed for the electrical impedance, resonant frequencies, and dynamic electromechanical-coupling coefficient for an arbitrary impedance on the boundary of a thin piezoelectric disk. The equations are then specialized for the case of a springlike boundary condition.
Traveling-Wave Velocity in the Human Cochlea
Authors: Zerlin Stanley
Published: October 2005

When two equally loud tones of somewhat different frequency are simultaneously pulsed and presented, one to each ear, a single coherent tonal image can be heard lateralized toward the higher-frequency side. When the higher-frequency signal is delayed by an appropriate amount, the sound image is brought to the midline. According to place theory, the two different frequencies are now arriving simultaneously at their designated places on the cochlear partition. A number of such tonal pairs were used to determine traveling-wave velocity along various short segments of cochlear partition. Averaged estimates from three trained listeners showed wave velocity decreasing from about 30 m/sec on the higher-frequency portion of the partition to approximately 1.0 m/sec near the low-frequency end. Our results are compared with some psychophysical and electrophysiological findings.
Whither Speech Recognition?
Authors: Pierce J. R.
Published: October 2005

Speech recognition has glamour. Funds have been available. Results have been less glamorous. “When we listen to a person speaking much of what we think we hear is supplied from our memory. [W. James, Talks to Teachers on Psychology and to Students on Some of Life's Ideals (Holt, New York, 1889), p. 159]. General-purpose speech recognition seems far away Special-purpose speech recognition is severely limited. It would seem appropriate for people to ask themselves why they are working in the field and what they can expect to accomplish.
Alterations in the Duration, Pitch, and Intensity of Spoken Passages Successively Heard and Repeated Several Times
Authors: Werner Marlin Spike
Published: October 2005

The serial repetition of 10-syllable passage that are heard revealed a tendency for the duration of passage and duration of voicing to increase and for the range of pitch and the range of intensity to decrease. The disadvantages of the 10-syllable nonrhetorical passages are discussed.
Thresholds re Duration and Levels of a Continuous or Gated Masker
Authors: Campbell Richard A.
Published: October 2005

The importance of data regarding the effect of short signal durations on detection for gated- versus continuous-noise maskers and the theoretical implications of this data have been presented in recent papers by Jeffress, Tucker, and Williams. Masked thresholds for a 1000-Hz signal of 40-, 80, 160-, and 400-msec duration were determined in the presence of a narrow-band masking noise that was either continuously on or gated only during the two possible signal intervals, with the masker presented over a 90-dB range of levels. At the 400-msec duration, the continuous masker led to thresholds that were about 2 dB lower than did the gated masker at all but the lowest masker levels. At shorter durations, consistent continuous-gated differences in threshold were not found, indicating that, in addition to the experience of the listeners (as suggested by Tucker, Williams, and Jeffress), the level of the masker may also be a factor in the difference between continuous and gated masked thresholds or signal detectability.
Contralateral Remote Masking and the Aural Reflex
Authors: Gjaevenes Kjell , Gran Sverre , Rollag Öystein
Published: October 2005

The contralateral remote masking (CRM) caused by a high-frequency-band noise is determined in the frequency range 250–1200 cps. The threshold shift expected from the mechanical changes due to the aural reflex is calculated on the basis of measurements of the acoustic impedance at the ear drum. The two sets of measurements are performed on seven subjects. The results support the assumption that central factors predominate in the CRM and that the middle-ear muscles are responsible for a small part of the masking only.
Stimulus Level of Dichotically Presented Tones and Cat Superior Olive S-Segment Cell Discharge
Authors: Tsuchitani Chiyeko , Boudreau James C.
Published: October 2005

Knowledge of the frequency of the stimulus and existing interaural intensity differences are inadequate for predicting S-segment cell discharge rates. The stimulus level, re threshold, of dichotically delivered tones must also be known. At low stimulus levels the most active population of S-segment cells consists of cells whose CFs are tuned to the frequency of the stimulus tone. As stimulus levels of dichotically delivered tones increase above threshold, cells with CFs not tuned to the stimulus frequency, tend to discharge at rates higher than these of the cells initially responsive at low levels. The higher the stimulus level, the greater the discrepancy in frequency between the CFs of the most active cell population and the stimulus. Thus, the locus of maximum activity within the S-segment is dependent not only on the frequency of the dichotically delivered stimulus tone but also on its stimulus level.
First-Order Gradient Microphone Based on the Foil-Electret Principle: Discrimination against Air-Borne and Solid-Borne Noises
Authors: Sessler G. M. , West J. E.
Published: October 2005

Design and performance of a simple first-order pressure-gradient microphone based on the electrostatic principle using foil electrets are discussed. Such a microphone discriminates against air-borne noise as well as against solid-borne vibrations transmitted through the microphone case. For air-borne sound originating from a spherical sound source positioned close to the microphone, the frequency response is flat within ±3 dB in the frequency range 0.1 to 3 kHz with a sensitivity of about −50 dBV/μbar in the direction of the microphone axis. In a plane sound field, the microphone exhibits the typical first-order gradient behavior, i.e., its sensitivity rises proportional to frequency over most of the mentioned frequency range. At 0.1 and 1 kHz, the plane-wave sensitivity is 30 and 10 dB, respectively lower than the sensitivity to sound originating from a nearby source, making this microphone a noise-discriminating device for close-talking applications. Rejection of solid-borne vibrations is due to the lightness of the foil-electret diaphragm. Compared with electrodynamic and electromagnetic transducers, the foil-electret microphone responds 30 to 40 dB less to solid-borne vibrations, referred to equal output for air-borne sound.
Thickness-Twist Vibrations of a Piezoelectric Plate
Authors: Onoe Morio
Published: October 2005

The analysis of thickness-twist or SH waves in an infinite piezoelectric plate by Bleustein [J. Acoust. Soc. Amer. 45, 614–620 (1969)] is supplemented by a few figures that show effects of the electromechanical coupling factor, the mass of electrodes, and finite dielectric constants on dispersion curves.
Digital Beamforming in the Frequency Domain
Authors: Rudnick Philip
Published: October 2005

A recent proposal to use digital Fourier transformation in forming acoustic beams is discussed tutorially. Relations to other procedures for beamforming, and for spectral analysis, are given. Need is shown for a lower limit on the data batch size.
Ultrasonic Dispersion and Absorption in Freon 113
Authors: Eberhardt F. J.
Published: October 2005

Additional velocity measurements and first absorption measurements indicate a single relaxation process in freon 113. There is some discrepancy between the relaxation time calculated from velocity dispersion and that from absorption, but the absorption data fit theoretical calculations very well. Calculations indicate that the effect of rotational isomerism is too small to be measured in this vapor with present apparatus. The relaxation time measured in freon 113 at 53°C is 0.53 × 10−8 sec from absorption data.
High-Frequency Acoustical Interferometer
Authors: Imai J. S. , Rudnick I.
Published: October 2005

An acoustical interferometer that operates at 1 GHz at both room and cryogenic temperatures is described. The experimental system features a method yielding a direct measurement of the absolute attenuation.
Acoustic Decoupling Properties of Corprene DC-100
Authors: Higgs R. W. , Eriksson L. J.
Published: October 2005

The sound velocity and attenuation of Corprene DC-100, a polychloroprene-cork composite, were measured by means of impedance-tube techniques. The temperature was varied from 4°–30°C, frequency from 8–40 kHz, and pressure from 100–2000 psi. The density, modulus, and sound velocity were then modeled as a function of composition by using a series model for composite materials. From this, it was demonstrated that, as the pressure is increased, the Corprene changes nonlinearly from a cork-dominated to rubber-dominated material. It was also shown that this nonlinear change in the properties of Corprene leads to its failure to perform satisfactorily as an acoustic decoupling material.
Ray and Wave Invariants for SOFAR Channel Propagation
Authors: Milder D. Michael
Published: October 2005

Rays and waves propagating in the SOFAR channel and encountering changes in the vertical profile of sound velocity c(z) possess certain invariants, if the changes are sufficiently gradual (adiabatic). For rays, the invariant quantity is ∮(n2 − nm2)12dz, n = 1/c, where nm denotes the value of n at maximum ray excursion, and where the integral is taken over the full ray period. The wave invariants are the individual normal modes φα (z), α = 0,1,2, …, as defined at each point of the propagation path by the local form of c(z). Adiabatic invariance of the modes will be maintained if the gradient of n2 along the path ∂n2/∂x is sufficiently small, as expressed by the condition λ/X≫2πΔn2/n2, where λ is the sound wavelength and X is the ray period, and where Δn2 = X ∫φα(∂n2/∂x)φβdz between adjacent modes α, β. For actual gradients measured off the California coast, the above condition is, numerically, λ≫2.5 m, or f≪600 Hz.
A Cyclic Cavitation Process
Authors: Neppiras E. A. , Fill E. E.
Published: October 2005

A type of acoustic cavitation has been studied that occurs at the face of a vibrator with a small diameter. A gas bubble grows to near-resonant size by accumulation of microbubbles. The process then reverses and the parent bubble rapidly throws off a cloud of microbubbles. This phase is accompanied by severe surface distortion of the main bubble, with emission of strong harmonics and a good deal of white noise. Under suitable conditions, a cyclic process is set up at a very regular repetition rate that depends on the acoustic pressure and the physical properties of the liquid. Acoustic streaming has an important rôle in maintaining the cycle. High-speed movies have been taken, and these, along with measurements of the acoustic emission, show clearly the progress of the cycle. A technique is discussed for using this process to generate bubbles of defined size.
Azimuthal Dependence of Sound Backscattered from the Sea Surface
Authors: Reeves Jon , Igarashi Yoshiya , Beck Lloyd , Stern R.
Published: October 2005

The dependence on azimuthal angle of acoustic sea-surface reverberation is investigated at 60 kHz, utilizing a three-axis rotationally stabilized conical-beam transducer. Measurements of backscattering strength in the upwind and crosswind directions are compared for a range of grazing angles from 10° to 40°. Polar plots of scattering strength versus azimuthal angle are presented for wind speeds from 4 to 13 kt. An attempt is made to correlate the backscattering measurements with swell and local wind-driven waves by means of aerial sea-state photographs taken during the test. Data indicate that surface reverberation has a pronounced dependence on azimuthal angle at wind speeds below about 9 kt, but becomes independent of azimuthal angle at higher wind speeds.
Effects of Noninstantaneous Transducer Response on the Measurement of Turbulent Pressure
Authors: Strawderman Wayne A.
Published: October 2005

The temporal response characteristics of a transducer limits its ability to resolve the temporal (or frequency) characteristics of the turbulent pressure field, just as the finite size of a transducer limits the ability of a transducer to resolve the spatial details of the turbulent pressure field. The spatial effects have been treated previously under the assumption that the transducer responds instantaneously time. This analysis treats mathematically the ability of real transducers (i.e., transducers of finite size and noninstantaneous time response) to resolve the pressure statistics of the turbulent field. It is assumed that the spatial and temporal response characteristics of the transducers are known in the form of the impulse response kernel. Mathematical expressions relate the measured statistics of the turbulent pressure field to the actual statistics in terms of the impulse response kernel. It is shown that, where the impulse response kernel is separable in time and space, no temporal distortion of the turbulent pressure statistics occurs.
Velocity Profiles that Produce Acoustic Focal Points on an Axis of Minimum Velocity
Authors: White DeWayne
Published: October 2005

This theoretical paper develops the velocity-profile class that produces focal points for source and receiver on an axis of minimum velocity. For this class, all initially upgoing rays (or initially downgoing, or both), leaving an axial source, at least once again cross the axis at a common point, a focal point. The general mathematical solution expresses the depth as an explicit function of the velocity. This solution is the sum of an inverse hyperbolic-cosine function and any function satisfying two mild mathematical constraints. Physical reality imposes a further constraint that the velocity be single valued. Numerous examples (seven with ray diagrams) are presented as applied to the field of underwater sound. The classic hyperbolic cosine profile appears in the general solution as the only profile for which every axial crossing is a focal point.
Green's Functions for Unbounded Constant Gradient Media
Authors: Wood D. H.
Published: October 2005

Results of Pekeris and Goodman are used in a Fourier synthesis that gives the response to a signal φ(t) from a point source in an unbounded medium with constant sound-speed gradient. That response is φ(t)*(r coshγτ)−1{δ(t−τ)−γτH (t−τ)J1[γ(t2−τ2)12](t2−τ2)−12}, where * denotes convolution, H (t) is the unit step function, τ is the travel time between source and receiver, r is the distance from the source to the receiver, and γ is one-half the magnitude of the gradient. The quantity to the right of the * in the above expression is the Green's function for a point source. The Green's function for a plane source is 2πvH (t−τ)J0[γ(t2−τ2)12], where v is the geometric mean of the sound speeds at the source and receiver. The Green's function for a line source is approximately 2γH (t−τ) (sinh2γt−sinh2γτ)−12. As γ → 0, all intermediate and final results approach known results for an unbounded medium with uniform sound speed.
Propagation of Shear-Stress Waves in an Infinite Nonhomogeneous Elastic Medium with Cylindrical Cavity
Authors: Reddy Damoder P. , Marietta Melvin G.
Published: October 2005

The problem of the radial propagation of shear waves in a nonhomogeneous elastic medium with a cylindrical cavity is solved by the theory of propagating surfaces of discontinuity. Thus, numerical integration that is required in using method of characteristics is avoided. An analytical solution, in the form of a Taylor series expanded about the time of arrival of the wavefront, is obtained. Two numerical examples, which are shown to agree with previous results, are also presented.
Damping-Material Effectiveness Measured by the Geiger-Plate and Composite-Beam Tests
Authors: Dudek T. J.
Published: October 2005

The Geiger thick-plate test and the vibrating composite-beam test for the evaluation of vibration damping materials are briefly reviewed, and the advantages and disadvantages of both methods are analyzed. The results of damping tests conducted on composite (two-layered) -plate and -beam test samples coated with the same damping material LD501 are compared and shown to agree within about 20%. The composite-beam test method is shown to offer more advantages than the plate test method as it is now run, primarily because material parameters are obtained in the beam test that can be used to estimate the vibration properties of damping-material coated plates of arbitrary geometry.
Comments on “Propagating and Standing Sawtooth Waves” [S. Temkin, J. Acoust. Soc. Amer. 45, 224–227 (1969)]
Authors: Cruikshank Donald B.
Published: October 2005

It is suggested that the discrepancies between Temkin's results for mechanically or thermally driven resonant tubes and previous theoretical work can be eliminated through a more accurate assumption concerning the inviscid waveform.
Some Investigations on Output Level of Microphones in Air Streams
Authors: Nakamura Akira , Matsumoto Rimpey , Sugiyama Akira , Tanaka Tadami
Published: October 2005

Investigations were made of the relation between different physical properties of a microphone in an air-stream and the sound pressure and pressure fluctuations caused by turbulent flow. The theoretical formula for the turbulent fluctuated pressure is deduced by considering small variations of flow in a quasistationary flow tube under a low magnitude condition for percentage of turbulence. Measurements were made in a wind tunnel using condenser microphones and probe microphones of various diameters. One of the probe microphones produced an output level in good agreement with the theoretical value. Another probe microphone, which has four tiny holes located on the side wall of the tube, produced an output level 24 dB below the theoretical value. A convenient theoretical expression of the microphone output level in the airflow is obtained by assuming random incidence of the pressure fluctuation on the microphone diaphragm by an analogy with sound waves. The results obtained are in reasonable agreement with the experimental values.
Estimation of Periodic Signals in Noise
Authors: Kincaid Thomas G. , Scudder Henry J.
Published: October 2005

Two equivalent methods for the estimation of a periodic signal in additive noise are presented. Both assume that a finite time sample of the signal plus noise is available. Both minimize the mean-square error between the estimate and the sample. In the first method, estimates for the period of the signal and the complex amplitudes of its harmonics are derived. In the second method, estimates for the period of the signal and the waveform of one period are derived. The estimates for the period are found to be the same by both methods. The estimate is unbiased and has a variance inversely proportional to both the signal-to-noise ratio and the cube of the number of periods in the sample. The expected values of the waveform estimates are derived, and the estimates are found to be biased.
Relation between Sound Intensity and Amplitude of the AER at Different Stimulus Frequencies
Authors: Antinoro Frank , Skinner Paul H. , Jones Jacqueline J.
Published: October 2005

Summing computer technique was employed to study the relationship between sensation level and phons, and peak-to-peak (N2-P2) voltage of the auditory evoked response at different frequencies. The relationship of the frequencies 125, 500, 1000, 2000, 4000, and 8000 Hz was studied at five intensities (20, 40, 60, 80, and 100 dB) by sensation level and by phons. There has been some controversy as to whether the power law, a straight line in double logarithmic coordinates, is a better fit than a linear relation between the voltage of the N2-P2 peak amplitude and decibels (sensation level and phons). Our observations, however, led us to believe that the linear relation is the more accurate fit. The data also revealed a marked decrease in slope of the function from 500 to 8000 Hz. Slope ranged from 1.1 at 125 Hz to almost none (constant) at 8000 Hz. Peak-to-peak amplitude ranged from 3.8 μV at 20 dB to 8.9 μV at 100 dB for 500 Hz, to only 1.6 μV at 20 dB to 3.4 μV at 100 dB for 8000 Hz. The consistent growth in peak-to-peak amplitude with each increase in sound intensity at the low frequencies did not maintain above 2000 Hz. At 8000 Hz, for example, the average amplitude of N2-P2 was less at 100 dB than at 80 dB. As also reported in an earlier study, a consistent decrease in the peak-to-peak amplitude was observed under both conditions as the frequency was increased.
A Direct Comparison between Lateralization and Detection under Conditions of Antiphasic Masking
Authors: Hafter Ervin R. , Bourbon Walter T. , Blocker Anne S. , Tucker Ann
Published: October 2005

In order to compare lateralization and the detection of noise-masked signals under conditions of antiphasic masking, subjects were instructed to indicate the lateral displacement of signals presented at five levels of signal-to-noise ratio. The signals were 500-Hz 100-msec bursts of tone heard in a wide-band noise mask. A “likelihood ratio” analysis of lateralization data allowed a direct comparison between detection based on lateralized differences and detection obtained in a standard two-interval forced-choice detection experiment. It was found that the measure of detection based on lateralization is nearly the same as that actually obtained in the conventional detection experiment.
Interaural Intensity Difference for Intracranial Lateralization
Authors: Pinheiro Marilyn L. , Tobin Henry
Published: October 2005

The interaural intensity difference (IID) for intracranial lateralization of white-noise bursts was investigated in 17 normal subjects, in 17 subjects with high-frequency sensorineural hearing losses, and in 17 subjects with predominantly unilateral cerebral lesions. Broad-band- and low-pass filtered-noise bursts with durations of 76 msec and 506 msec and a fast rise time of 10 msec were used for the dichotic signals. These were presented relative to the hearing sensitivity in each ear. There were no statistically significant differences between normal and sensorineural subjects except for the filtered noise condition, which resulted in a slightly but significantly greater IID for subjects with hearing losses. In subjects with cerebral lesions, the IID for the ear contralateral to the lesion was much smaller than the IID for normal or sensorineural ears, while the IID for lateralization to the ear ipsilateral to the lesion was slightly larger than the normal IID. It was found that the model for neural interaction in stimulus lateralization that von Békésy developed on the surface of the skin could be applied to the auditory phenomenon of sound lateralization.
Relation between Critical Bands in Hearing and the Phase Characteristics of Cubic Difference Tones
Authors: Schroeder M. R.
Published: October 2005

The measured amplitude and phase characteristics of aural cubic difference tones are difficult to account for solely by known mechanical processes in the ear. The frequency selectivity implied by these characteristics considerably exceeds that of the middle and inner ears, even when the selectivity of the basilar membrane is augmented by a traveling-wave model for nonlinear distortion components. On the other hand, the frequency selectivity implied by the phase characteristics of the cubic difference tone is found to correspond closely to the well-known critical bandwidths of hearing. Thus, the sharpening mechanism responsible for the formation of the critical bands may also be responsible for the formation and perception of cubic difference tones. New phase measurements, with a well-defined phase reference, show that the auditory nonlinearity giving rise to cubic difference tones must be an amplitude-limiting nonlinearity if it occurs in an excitatory channel (or an amplitude-expanding one if it is located primarily in an inhibitory pathway).