bluuebunny/crossref_metadata_2025 huggingface dataset:
Audiometer-Earphone Mounting to Improve Intersubject and Cushion-Fit Reliability
Authors: Villchur Edgar
Published: October 2005

The range of combined intersubject and cushion-fit variation in the response of the TDH-39 audiometer earphone in an MX41/AR cushion, reported in the literature and confirmed in these measurements, is of the order of 25 dB at 100 Hz, 6 dB at 1 kHz, and 15 dB at 5 kHz. The performance of this earphone system is further impaired by cushion-induced physiological noise that masks low-frequency thresholds, typically by 6 dB in normal-hearing subjects. An experimental mounting for the TDH-39 is described and analyzed; it is a circumaural device designed to keep the earphone-ear acoustical system as near constant as possible with successive fittings and different subjects, and to reduce physiological noise. The performance of the TDH-39 in this mounting, compared to performance in an MX41/AR cushion, showed a substantial reduction in cushion-fit and intersubject response variation, and masking by physiological noise was largely eliminated in the subjects tested. The mounting has an optional cup for reducing the transmission of external noise, but this reduction is at the expense of a partial return of physiological noise masking. Average midrange sensitivity was reduced 5–6 dB. Response measurements were made with a free-field reference method, using a probe microphone at the subject's eardrum.
Formant Concentration Positions in the Speech of Children at Two Levels of Linguistic Development
Authors: Gilbert John H.
Published: October 2005

This investigation was concerned with acoustic measurements of the first two formants in four sustained vowels—/i/, /æ/, /a/, and /u/—produced by children at two different levels of linguistic development. The object of the investigation was to determine whether children of the same chronological age but at a different level of language development would exhibit significant differences of formant frequencies. Acoustic measurements of formants 1 and 2 of the four sustained vowels /i/,/æ/,/a/, and /u/ showed no statistically significant differences when produced by two groups of children at two levels of linguistic development. In each group, differences among formant measurements, for the four vowels, were significantly different.
Aids in Ultrasonic Diagnosis
Authors: Baum G.
Published: October 2005

This paper describes three new types of displays for use in medical ultrasonography. These are video inversion, scanned deflection modulation, and scanned deflection-intensity modulation. Video inversion is a B-mode display in which the ultrasonographic data is presented as a radar and TV display on alternate scans. This display makes it possible to use the steep slope of the gray scale on the face of the cathode-ray tube to display small changes in amplitude in both the very loud and weak ends of the acoustic spectrum. Scanned deflection modulation or scanning A-mode restores anatomical orientation. This type of display greatly facilitates interpretation of medical ultrasonograms. Scanned deflection modulation has been combined with intensity modulation to produce scanned deflection-intensity modulated ultrasonograms. This form of ultrasonographic data displays greatly facilitates ultrasonographic localization.
Sound Conduction in the Dolphin Ear
Authors: McCormick Jamers G. , Wever Ernest Glen , Palin Jerry , Ridgway Sam H.
Published: October 2005

By use of the electrical potentials of the cochlea, the pathway of sound conduction to the ear was investigated in two species of dolphins, Tursiops truncatus and Lagenorkynchus obliquidens. The observations show that the external auditory meatus is vestigial and that neither this meatus nor the tympanic membrane plays any part in sound reception. The ossicular chain has an essential function, though the outermost ossicle, the malleus, can be removed without seriously affecting the conductive process. It is concluded that auditory stimulation in the dolphin occurs by bone conduction. Acoustic vibrations in the water reach the ear through the tissues of the head, and set up differential motions between the stapes and the cochlear capsule. These differential motions involve the cochlear fluids, which are given mobility by the presence of gas in the region of the round window. The vibrations of the basilar membrane and stimulation of the hair cells of the organ of Corti then follow in the usual way.
Using a Computer Display to Model a Complex Vibrating Surface
Authors: Lee Robert M.
Published: October 2005

Vibration waveforms are taken at several points on a vibrating surface and then combined, using a computer with a cathode-ray-tube display, to produce several representations of the movement of the surface. An important advantage of this method is that the forms of the data and representations lend themselves readily to manipulation by the computer. A noncontact vibration pickup, developed especially for this application, is briefly described.
Propagation Constant and Specific Impedance of Airborne Sound in Metal Wool
Authors: Burns Stephen H.
Published: October 2005

This is a study of the acoustic properties of various grades (0000, 00, 1, and 3) and densities (0.0046–0.22 g/cm2) of steel wool. A theory that accounts for momentum and heat transfer from the acoustic wave to the wool is presented. Experimental evidence, obtained at frequencies of 173, 480, and 1440 Hz, confirms the theory to the expected accuracy.
Desk-Top Model of Harbor Resonators
Authors: James W.
Published: October 2005

A simple small-scale model of a generalized harbor entrance with rectangular resonators was set up. Using simple electronic equipment and sound waves of the order of 1000 cycles, the geometry for resonance was determined. The results are compared with those obtained from a hydraulic model, using gravity waves of similar wavelength. It was found that the results were not influenced by imperfect boundaries or reasonable changes in frequency. It is concluded that the results are sufficiently accurate to warrant further development of the method as an aid for harbor design, particularly in view of the simplicity and size of the equipment.
Power Output of a Point Source Exciting a Single Cartesian Mode
Authors: Waterhouse Richard
Published: October 2005

When a point source radiates steadily in a rectangular enclosure and excites one mode only, its power output W depends strongly on its position. Distribution functions for W are found when the source is positioned randomly, and an axial, tangential, or oblique mode is excited. The functions for these three cases form a consistent family of curves, whose shapes are controlled by the mode shapes. The space-averaged value of W, i.e., the average for all source positions in the enclosure, does not equal the free-field value W0, but depends on the modal damping. The value of W0 can be derived from sound-pressure measurements, however. The results are derived theoretically, and checked by a Monte Carlo procedure. Some experimental data which confirm the theoretical results are given for a small source driving an axial mode in a reverberation chamber. The work has application to standard methods of measuring the sound power output of a source.
Spectral Analysis of Cavitation Noise in Cryogenic Liquids
Authors: Mosse A. , Finch R. D.
Published: October 2005

Spectra of ultrasonic cavitation noise were obtained in liquid helium and liquid nitrogen. A subharmonic response at half the driving frequency was found to be present at all times. In the case of liquid helium, the relative intensity of this subharmonic showed a peak at the λ point. The background noise intensity was also higher in helium II. A tendency for the half-order subharmonic to increase with static pressure was also found both for helium I and nitrogen. A correlation between the onset of the subharmonic audible-frequency noise and the white-noise background was also found. The variation of the intensity of the first overtone with increasing driving voltage was found to be different in helium II than in other liquids. It is argued that many of these phenomena arise from the effect on bubble dynamics of the efficient heat transport in helium II.
Effects of Input Amplitude Profile upon Diffraction Loss and Phase Change in a Pulse-Echo System
Authors: Papadakis Emmanuel P.
Published: October 2005

The particle velocity profile V (ρ) across the face of a transmitting transducer is shown to have large effects upon the diffraction loss and phase change in the ultrasonic field of the transducer. Various functions V (ρ), monotonic decreasing from the center to the rim of a circular transducer, were employed. The pulse-echo response of the transducer was calculated by numerical integration on an electronic computer. It was found that the functions V (ρ) chosen caused the diffraction-loss and phase-change curves to be smoother than in the piston case and caused the respective peaks and plateaus to shift with distance in the Fresnel region.
Scattering of Acoustic Waves by a Periodic Thermal Field
Authors: Salant Richard F.
Published: October 2005

One-dimensional scattering of acoustic waves by the thermal field produced by a sinusoidal spatial distribution of heat sources in a perfect gas is examined analytically. The scattered field is found to consist of a transmitted acoustic wave, a reflected wave, and an entropy wave. When the thermal-field wavenumber is near the entropy wavenumber or twice the acoustic wavenumber, resonance-like phenomenon occurs, resulting in large-amplitude scattered waves.
On the Acoustic Study of Nucleation by Energetic Particles in Fluids
Authors: Coacci R. , Marietti P. , Sette D. , Wanderlingh F.
Published: October 2005

The absorption of a small-amplitude sound wave in a liquid can furnish a method for studying the size distribution of microcavities produced by energetic particles. In contrast to ultrasonic cavitation, this method is nondestructive and therefore allows the following of time variations of the distributions. The method has been improved to detect cavities of radii of the order of 2 μm, such as those created in water by fast neutrons.
On Arrays with Nonrigid Interstices
Authors: Mangulis V.
Published: October 2005

The radiation from an infinite phased planar array of rectangular pistons with nonrigid interstices is considered. Numerical calculations for exact equations are compared with a simple approximation, derived for small pistons close together. The comparisons show that the approximate expressions agree well with the exact results even for pistons of practical size, if (1) the array is steered to an angle near broadside, (2) the interstitial impedance is not very low, and (3) the interstices occupy a small fraction of the total array area.
Dynamic Interaction between an Elastic Cylindrical Shell Subjected to Point Loadings and an Acoustic Medium
Authors: Wang Y. F. , Berger B. S.
Published: October 2005

This investigation is concerned with the three-dimensional interaction between an infinitely long elastic circular cylindrical shell, subjected to point loading and an acoustic medium. The formal solution to the problem was obtained by solving the governing field equations of the shell and the acoustic medium through the application of integral-transform and series-solution techniques. The resulting Fourier Laplace inversion integral was evaluated by means of numerical-inversion methods. Detailed numerical results are presented for the dynamic response of a steel shell immersed in water when it is subjected to a point loading having the form of a step function of finite duration. Since there are no approximate relations introduced in the fluid-shell phenomena, the result obtained from this investigation is the exact solution to the problem within the scope of linear-acoustic and thin-shell theory, and the approximation errors introduced by the numerical techniques.
Response of a Nonlinear Form of the Mathieu Equation
Authors: Boston J. R.
Published: October 2005

This communication presents the results of an investigation of the response of a nonlinear form of the Mathieu equation in the first unstable region. The equation of interest is a Mathieu equation plus a cubic nonlinearity. The response consists of a modulated one-half subharmonic of the parametric-excitation frequency. The envelope of the subharmonic is approximately a sinusoid. The magnitude and frequency of this sinusoid are determined by the method of harmonic balance. The results are compared with the results of computer simulation.
Theoretical Study of Finite-Amplitude Traveling Waves in Rigid-Walled Ducts: Behavior for Strengths Precluding Shock Formation
Authors: Coppens Alan B.
Published: October 2005

This paper presents three different solutions to a one-dimensional model of the propagation of finite-amplitude traveling waves in rigid-walled ducts. The first two solutions, in the nature of perturbation solutions, provide useful information for relatively weak waves; the distances for which the solutions are valid range from α1x≪1 to α1x< ∞, depending on the strength of the waveform and the particular solution considered. The third solution is based on a set of first-order coupled nonlinear differential equations with one independent and two dependent variables. This solution is useful for all values of α1x for strengths up to those necessary for shock formation. Results include graphs of relative harmonic distortion, predictions of waveform profiles, and representative graphs illustrating the dispersive behavior of the phase speeds of the individual harmonics.
Calculation of Second-Harmonic Generation in a Piston Beam
Authors: Ingenito F. , Williams A. O.
Published: October 2005

We discuss the nonlinear generation of a second-harmonic component in the first-harmonic beam from a circular plane piston, radiating into a fluid. First-order perturbation theory is used; higher harmonics, absorption, and depletion of each harmonic are ignored, although a partial correction for the last two effects is applied later. The ratio of piston diameter to first-harmonic acoustic wavelength is assumed to be about 30 or greater. In particular, the axial behavior of the second harmonic, which has marked structure, is found to agree well with experimental results in water. Also, the average value of the second-harmonic field is calculated over a circle coaxial with the source, parallel to it, and of the same size. This average differs considerably from the result of an oversimplification that treats the first-harmonic beam as cylindrically collimated plane waves. When compared with measurements in water, the average agrees well at a source pressure of 3 atm but progressively less well at 5 and at 6 atm. It is suggested that both theory and experiment contribute to the discrepancies.
Natural Frequencies of Simply Supported Arcs
Authors: Chang Tish-Chun , Volterra Enrico
Published: October 2005

Natural frequencies of simply supported elastic arcs vibrating in the plane perpendicular to the plane of initial curvature are obtained by applying a method previously used by the authors to determine upper- and lower-bounds frequencies of curved beams. This method, based on the theory of adjoint operators, was originally proposed by Lehmann, Maehly, and Kato. The centerlines of the arcs are in the forms of circles, cycloids, catenaries, and parabolas. The numerical results obtained are plotted graphically.
Vibrations of Systems of Elastically Coupled Concentric Rings
Authors: Kirkhope J.
Published: October 2005

The flexural vibration of thin rings and systems of elastically coupled rings is examined using the concept of dynamic stiffness. A dynamic stiffness matrix is derived for a single ring which incorporates coupling between in-plane and out-of-plane motion. The method of coupling in-plane motions of a system of concentric rings is presented and shown to reduce to a previously obtained result for a system of two rings.
Propagation of Sound in a Shallow Bay
Authors: Banner Arnold
Published: October 2005

Acoustic pressures and particle velocities were measured at several distances from both pulsed multipole and continuous monopole broad-band sound sources, in a shallow bay. Pressure attenuation was less for pulsed than for continuous signals in the range of 80 to 640 Hz. Relationships of particle velocity to pressure amplitudes were determined, using a reference level common to both. The ratios of these parameters were found to remain constant for all distances beyond 1 m from the sources for frequencies from 20 to 640 Hz. These ratios were also valid for ambient noise measured at this location. Particle motion appeared to be primarily vertical and to attenuate at the same rate as pressure once this ratio bad been attained. Shallow-water marine organisms may thus receive nearfield stimuli at relatively great distances from sources.
Comments on “Time Autocorrelation of Sonic Pulses” [S. J. Campanella and A. G. Favret, J. Acoust. Soc. Amer. 46, 1234–1245 (1969)]
Authors: Kennedy Robert M.
Published: October 2005

In the subject paper, the match between experiment and the theoretical findings of Mintzner [J. Acoust. Soc. Amer. 25, 922–927, 1107–1111 (1953); 26, 186–190 (1954)] and Bergmann [Phys. Rev. 70, 486–492 1946)] was not particularly good. It is suggested that the theory of Chernov [Wave Propagation in a Random Medium (McGraw-Hill, New York, 1960)] offers a better fit.
Early History of Riverbank Acoustical Laboratories
Authors: Kranz Fred W.
Published: October 2005

The establishment of the Riverbank Acoustical Laboratories in Geneva, Illinois, had its origin in the interest of Colonel George Fabyan in an acoustic device purportedly described by Francis Bacon in a secret cipher embodied in the printed First Folio (1623) of the works of William Shakespeare, and the resulting acquaintance of Fabyan with Professor Wallace Sabine of Harvard University.
Effect of Cavity Absorption on the Sound Transmission Loss of Steel-Stud Gypsum Wallboard Partitions
Authors: Loney Wayne
Published: October 2005

Sound-transmission-loss tests were conducted using steel-stud drywall partitions with a single layer of 12-in. wallboard on each side to study the effect on acoustical performance due to the physical properties of cavity fill. These tests also compared the results using mineral wool and glass fiber and using studs of different widths. All tests were conducted in accordance with ASTM E90-66T. The transmission loss and sound-transmission class (STC) were found to be related directly to the thickness of fibrous absorbing material when used in the full cross area of the stud cavities. The increase in STC due to increasing thickness of the cavity fill is not a linear relationship, since the first inch has the greatest effect. When the absorbing material is placed in less than the full cross area of the stud cavities, the gain in acoustical performance is governed by the volume of the absorption material. The low-density glass fiber performed as well as high-density mineral wool except in the middle portion of the curve, where the transmission loss averaged 1 dB less. Increasing the stud size increases the transmission loss. This gain is limited to the lower frequencies when cavity absorption is present.
Precision Electrical Techniques in Condenser Microphone Reciprocity Calibration
Authors: Corney Andrew C.
Published: October 2005

Stray admittance and lead effects may be eliminated from the calibration of a condenser microphone by use of three-terminal measurement techniques. Modern ac-bridge null-balance methods applied to the measurement of electrical transfer impedance between two condenser microphones, cavity coupled for reciprocity calibration, result in a significantly higher accuracy than attainable by currently used deflection-comparison methods, and yield phase in addition to amplitude information. Using the bridge described reduces the uncertainty arising from all electrical measurements in the reciprocity determination of condenser microphone pressure response to less than ±0.006 dB from 400 Hz to 600 Hz, ±0.004 dB from 600 Hz to 1000 Hz, and ±0.01 dB at 10 kHz.
Observations on the Effect of Pressure Ratio and Upstream Flow Configuration on the Acoustical Response of Closed Pipes
Authors: Smetana F. O. , Daggerhart J. A.
Published: October 2005

The frequency response of a closed flue pipe as a function of blowing pressure is examined. It is hypothesized that the turbulence level in the air jet is the controlling factor in fixing the frequency of oscillation. Modifications are made in the flue pipe to reduce turbulence in order to test the hypothesis. Consequences of the turbulence-driven oscillation with regard to the use of such oscillators as temperature sensors are discussed.
Theory of Temporary Threshold Shift
Authors: Botsford James H.
Published: October 2005

Temporary threshold shift (TTS) is generally believed to grow during noise exposure and recover afterwards in proportion to the logarithm of time. However, these logarithmic laws of TTS disagree with experimental observations made very early or very late in these processes. Better agreement with experiment is obtained if TTS is regarded as the sum of two components that vary exponentially with time. Published information on TTS was analyzed to determine the properties of these two components. Only one of the components is believed to be associated with permanent hearing loss resulting from noise exposure, and its simple electrical analog makes possible the construction of a TTS meter for appraising noise hazard. The analysis also revealed two other components of TTS that account for the “bounce” sometimes observed very early in the recovery process. Additional studies are needed to refine the theory and improve understanding of the auditory process.
Auditory Memory for One and Two Tones
Authors: Elliott Lois L.
Published: October 2005

Pitch memory for one and for two successive tones was examined in two experiments which employed a method of adjustment procedure (Expt. I) and a recognition (four-alternative-forced choice) task (Expt. II). Frequency ratio of the two-tone targets was either simple (a musical third or fifth) or complex. Time between target and comparison tone(s) was either silent or filled with two intervening tones. The memory difference limen (DL) for each of two tones is about 1.5 to 2.0 times larger than the DL for one tone. The DL for pairs of tones with complex frequency ratios is, under some circumstances, larger than for pairs of tones with simple ratios. For “good pitch discriminators,” the task must become more difficult before ratio complexity affects performance than is true for “poor pitch discriminators.” At least two skill components, frequency analyzing power and memory, are present in these tasks, and consistent individual differences occur for both.
Determination of Microphonic Generator Transfer Characteristic from Modulation Data
Authors: Nieder P. , Nieder I.
Published: October 2005

Two methods are described for determination of the microphonic generator transfer characteristic using data from bitonal stimulation experiments. In one method, the filtered high-frequency microphonic output component is measured at the extreme points of the modulation envelope for a sequence of intensity levels of the lower-frequency component. This method is applied to data derived from a modulation test procedure making use of a wide range of test intensities for both the high- and low-frequency components and also to data generated in a test using a single sequence of stimuli with increasing intensity of the lower frequency. In a second method, the modulation envelope of the higher-frequency microphonic response to a bifrequency acoustic stimulus is used to determine a segment of the generator transfer characteristic. The results of a sequence of determinations for different lower-frequency intensities show good agreement with each other and with the transfer characteristic derived by the first method. However, the second method shows that there is an appreciable level-dependent hysteresis, the mechanism for which has not been determined. The transfer characteristics determined would give rise to a pronounced dc rectification component in the direction of positive summating potential.
Loudness-Intensity Relations under Various Levels of Contralateral Noise
Authors: Rowley Rodney R. , Studebaker Gerald A.
Published: October 2005

This study investigated the effects of four levels of broad-band noise [40-, 60-, 80-, and 100-dB sensation level (SL)], presented to the contralateral ear, on the loudness of a monaurally presented 1000-Hz pure tone. Loudness functions were obtained with the method of numerical magnitude balance. The findings indicate that when monaural loudness functions for a 1000-Hz pure tone, obtained with contralateral noise present, are compared with monaural loudness functions for a 1000-Hz pure tone, presented in quiet, there is a loss of loudness at low sensation levels, a loudness increase of as much as threefold at moderate SLs, and approximately equal loudness at high SLs. The loudness at lower SLs appears to be inversely related to the intensity of the broad-band contralateral noise, and the loudness at moderate SLs appears to be directly related to the intensity of the broad-band contralateral noise.
Harmonic Generation in the Trumpet
Authors: Backus John , Hundley T. C.
Published: October 2005

Various possible mechanisms for the generation of harmonics in the tone of the trumpet were investigated. By sounding the trumpet with a mechanical valve utilizing a sinusoidally varying opening, it was shown that nonsinusoidal motion of the player's lips is not an important mechanism for harmonic generation. Nonlinear behavior of the air column of the instrument due to high sound pressures was also shown not to be important by four different methods: (1) by a theoretical estimate of the amount of second-harmonic distortion to be expected; (2) by measuring the input resistance of the trumpet at resonance frequencies and finding that it did not vary significantly with sound pressure in the air column; (3) by measuring the intermodulation distortion produced when the air column was excited at two resonance frequencies simultaneously; and (4) by direct measurement of harmonic distortion produced in the trumpet output by different levels of excitation at the mouthpiece. It was found that the mechanism primarily responsible for harmonic generation is the relationship between the input impedance of the trumpet and the time-varying impedance of the player's lip opening during a cycle. Curves of mouthpiece pressure calculated on this basis showed good agreement with observed waveforms.
Phonological Oppositions in Children: A Perceptual Study
Authors: Graham Louella W. , House Arthur S.
Published: October 2005

The relationship between the development of a phonological system and auditory perception was studied by examining children's errors in discriminating among a group of English consonants. The perceptual equivalence and additivity of linguistic features were studied. A nonmetric multidimensional analysis procedure was used in an attempt to specify the number of processes by which children made decisions, and speculations about the nature of these processes were made. The discrimination errors of the children were similar to those of adults, except that the children produced more errors. The results failed to show that current linguistic descriptions identify the perceptual parameters children use in categorizing speech sounds.
Speech-Synchronized versus Periodic Interaural Switching of Speech
Authors: Rupf J. A. , Hughes G. W. , House A. S.
Published: October 2005

The ability of subjects to “shadow” speech switched between the ears periodically was compared to that for speech switched in syllable and phoneme units. Shadowing performance, expressed in terms of incorrectly articulated words, was not significantly different for the two conditions under test.
Natural Resonant Frequency of a Prolate Acoustical Resonator
Authors: Chang Christopher T. M.
Published: October 2005

Natural resonant frequencies of prolate acoustical resonators with either perfectly soft or perfectly rigid boundaries are calculated by locating the zeros of Rmn(1) (h,ξ) and Rmn(1)′ (h,ξ). These resonances are normalized to those of the corresponding modes in a spherical cavity with the same volume and are presented for various ratios of major to minor axes.
Development of an Underwater Acoustics Laboratory Course
Authors: Weinberg N. L. , Grantham W. G.
Published: October 2005

An underwater acoustics laboratory course has been instituted at the University of Miami using a natural body of water as the experimental medium. The experiments are conducted in Bear Cut, which connects Biscayne Bay to the Straits of Florida. The 600-ft acoustic range from the Institute of Marine Sciences pier to an instrument tower in Bear Cut is an almost flat channel with an average depth of about 13 ft. The majority of the equipment employed by the students consisted of piezoelectric projectors and hydrophones, and standard electronic laboratory apparatus such as oscillators, oscilloscopes, power amplifiers, filters, etc. The sequence of the experiments were planned for equipment familiarization and results needed for future tests. During the initial offering of this course in the Spring 1970 semester, experiments were conducted on the measurement of a piezoelectric transducer equivalent circuit, ambient-noise spectrum, spreading loss for several distances, reciprocity calibration, and waveguide effect. For the next offering, additional experiments are planned on arrays including shading and electrical steering, pulse modulation transmission, reflection, sound-velocity measurement, and longer range propagation. The laboratory's facilities are also available for student research.
Ultrasonic Measurement in Liquid Alkali Metals
Authors: Kim M. G. , Kemp K. A. , Letcher S. V.
Published: October 2005

Ultrasonic absorption and velocity measurements have been made in high-purity liquid sodium, potassium, rubidium, and cesium at temperatures from their melting points to 250°C. Corresponding classical absorption values have also been computed over these ranges of temperature. It has been found that the measured absorption values exceed the classical values by 3%–30%. These excess absorptions are attributed to structural relaxation. The ratio of bulk viscosity to shear viscosity was found to be approximately 2.3 in sodium and potassium, 3.4 in rubidium, and 4 in cesium. Sound velocities are presented as linear functions of temperature. Both observed and classical absorptions are given as quadratic functions of temperature.
A Water Immersion Technique for Measuring Attenuation and Phase Velocity of Longitudinal Waves in Plastics
Authors: McSkimin H. J. , Andreatch P.
Published: October 2005

The complex transmission coefficient for a plastic specimen immersed in water (or other suitable liquid) is determined through use of a phase meter and a calibrated attenuator. Heterodyning the received rf pulses directly to video signals with a 10-Hz beat frequency makes possible (1) the use of a commercial low-frequency phase meter, and (2) an increase in signal-to-noise ratio of approximately 20 dB [H. J. McSkimin and T. B. Bateman, J. Acoust. Soc. Amer. 45, 852–858 (1969)]. By way of illustration, measurements for attenuation and phase velocity are listed for a number of specimens, including Plexiglas (acrylate and methacrylate resin), Epon adhesive, epoxy foam, and several composite structures. The frequency and temperature ranges covered were 0.4–1.1 MHz and 20°–60°C, respectively.
Formalism of Geometrical Optics for Flexure Waves
Authors: Germogenova O. A.
Published: October 2005

The equations of geometrical optics governing the ray shape and the energy transport along the rays are obtained for flexure waves propagating on an inhomogeneous finite weight plate. Krasil'nikov's results for the energy flux vector and the amplitude relations along the rays are generalized both in the absence and in the presence of liquid loading.
Application of Conformal Mapping and Variational Method to the Study of Natural Frequencies of Polygonal Plates
Authors: Yu James C. M.
Published: October 2005

The stationary value problem of the dynamic action for the determination of the natural frequencies of the polygonal plates is transformed by a holomorphic function into an equivalent problem of another plate with a circular boundary. The equivalent problem is then solved by the Rayleigh-Ritz method. Since the selected coordinate functions are independent of the actual shape of a plate, the formulation is valid for one plate and for all others with boundaries which are the conformal images of a unit circle. The numerical results for the fundamental natural frequencies of plates of various shapes are calculated and compared with the available data in good agreement.
Attenuation of Low-Frequency Sound Waves in Sediments
Authors: Anderson Rockne S. , Blackman Abner
Published: October 2005

Magnetic tape recordings of seismic profiler signals were made across an acoustically transparent wedge of sediments varying from 80 to 500 m in thickness on the flanks of Bermuda. The data were processed using 13-oct bandwidth filters. The average attenuation coefficient of the sediment, α, was determined from the equation d (y)/d (z) =α, where y is the ratio expressed in decibels of the peak pressure amplitude of the bottom to the peak pressure amplitude of the subbottom returns, and z is twice the sediment thickness. Possible errors resulting from spreading losses and changes in subbottom reflectivity due to increasing velocity and density with depth were considered and appropriate corrections made to the computed attenuation coefficients. For filters centered at 200, 250, and 315 Hz the average attenuation coefficients for the sediment were found to be 0.0031, 0.0069, and 0.0126 dB/m, respectively. For a filter centered at 400 Hz, the minimum value of the attenuation coefficient is 0.0110 dB/m. Outside this frequency range, the attenuation is too high or too low to be determined by this method. With attenuation expressed as being proportional to the frequency raised to the power n, the value of n is close to 3 for the frequency range 200–400 Hz. This high value of n is attributed to the effect of intermediate reflecting layers.
Dorsal-Aspect Target Strength of an Individual Fish
Authors: Love Richard H.
Published: October 2005

Experiments are described in which the dorsal-aspect target strengths of a number of individual teleostean fishes of eight species were measured at various frequencies. The results of these experiments indicate that the variations of target strength with frequency are different for fishes in two major teleostean groups, the malacopterygians and the acanthopterygians. These results are combined with results from eight other sources and an empirical equation approximating the dorsal-aspect target strength of an individual fish determined for 0.7⩽L/λ⩽90, where L is the fish length and λ is the incident acoustic wavelength. The combined results are compared to similar results for the maximum side-aspect target strength of an individual fish, and curves showing the trend of dorsal-aspect and maximum side-aspect acoustic cross sections of an individual swimbladder-bearing fish are presented for all L/λ⩽90.
Effects of Humidity on the Velocity of Sound in Air
Authors: Harris Cyril M.
Published: October 2005

Measurements have been made of the effects of humidity on the velocity of sound in air at 20.00°C and normal atmospheric pressure in the audio frequency range. The velocity of sound was determined from measurements of the frequency of the decay of normal frequencies of a spherical chamber of very high Q. Contrary to the often-made assumption that the addition of moisture increases the velocity of sound in air, these results show that as moisture is added to dry air the velocity of sound at first decreases. The velocity is minimum at a relative humidity (RH) of about 14%; then it rises. Above about 30% RH, the velocity increases linearly with increasing moisture content.
Acoustic Field in a Cylindrical Fluid Luneberg Lens—A Short Sequel
Authors: Lord Gary E.
Published: October 2005

A cylindrical fluid acoustic Luneberg lens has been subjected to a wave analysis in a manner similar to that previously used for the corresponding spherical lens. The cylindrical Luneberg lens exhibits, as does its spherical counterpart, characteristic asymptotic focal properties that are fairly well established for wavenumber-aperture products of about 20.
Velocity Hydrophone Calibration
Authors: Hebert Harris J. , Paine Ward L.
Published: October 2005

Measurements show that the standard 10-dB maximum correction factor for particle velocity augmentation in a spherically divergent sound field can safely be increased to 25 dB.
A Discussion of the Physical Basis of Brillouin Scattering
Authors: Piercy J. E. , Hanes G. R.
Published: October 2005

Formulas for the spectrum of light scattered by the fluctuations of density and temperature, or pressure and entropy, in a thermally conducting viscous fluid are derived by applying the fluctuation-dissipation theorem directly to the scattering configuration. The language of simple circuits and familiar logic of Nyquist are used, and particular attention is paid to the phasing between the fluctuations of different variables. Spectral profiles and the correlation between the fluctuations of the variables indicated by these rather complicated formulas are also discussed in terms of physical concepts (normal modes, degrees of freedom, and the relaxation due to thermal conduction). Contact is made in this way with both classical and recent theories of light scattering. Limitations in these other theories due to inadequate phasing of fluctuations are described and extensions are proposed. It is established that different sets of approximate normal coordinates are required for an adequate simple description of spectra, depending on the ratio of the frequencies of relaxation and acoustic resonance. It is also shown that the traditional neglect of the contributions of temperature fluctuations may lead to serious error in the analysis of Brillouin spectra of scattered light. The extension of the new theory to fluids with relaxing heat capacity and compressibility or a different structure factor is sketched briefly.
Brillouin-Scattering Studies of the Acoustoelectric Effect
Authors: Zucker J. , Zemon S.
Published: October 2005

Brillouin-scattering studies of acoustoelectric interactions CdS and ZnO are reviewed. The important characteristics of amplified acoustic shear-wave noise as determined by Brillouin scattering is summarized. Data on acoustic parametric amplification is also given.
A New Acoustic Phonon Spectrometer
Authors: Anderson C. H. , Sabisky E. S.
Published: October 2005

Paramagnetic spins, which interact primarily with the resonant phonons in a dielectric crystal and show large magneto-optical properties, can be used as a tunable and sensitive probe of acoustic waves and phonons in a dielectric crystal. The technique works at a few degrees Kelvin and at frequencies from 10 to 300 GHz or more. A variety of experiments demonstrating uses of the spectrometer are discussed.
Brillouin Effect in Liquids in the Prelaser Era
Authors: Rank D. H.
Published: October 2005

The history of the theoretical discovery of the Brillouin effect is presented along with the experimental discovery of this phenomenon many years after the theoretical prediction. A fairly complete resume of the work accomplished on the Brillouin effect in liquids in the era prior to the invention of the laser is given in outline.
Low-Temperature Measurement of the Hypersonic Absorption in Fused Quartz by Stimulated Brillouin Scattering
Authors: Heinicke W. , Winterling G. , Dransfeld K.
Published: October 2005

By making use of stimulated Brillouin scattering, hypersonic absorption and velocity measurements in quartz glass were carried out at 24 GHz. Absorption data for longitudinal sound waves are presented below 8°K and velocity data between 4° and 300°K. The hypersonic absorption is observed to decrease strongly on cooling corresponding to a mean free path of the hypersonic phonons larger than 2 mm below 3.5°K. This value exceeds the mean free path calculated from heat conductivity data at 1.5°K for thermal phonons of similar energy by three orders of magnitude. The absorption data are discussed in connection with previous lower-frequency measurements.
Quantitative Investigations of Stimulated Brillouin Scattering
Authors: Kaiser W.
Published: October 2005

Intense stimulated Brillouin scattering produced by high-power (greater than 107 W/cm2) light beams is discussed in this paper. It is shown theoretically that the Brillouin intensity increases exponentially with the incident light intensity, with the interaction length, and with a gain factor depending on the medium properties. Quantitative estimates of the stimulated Brillouin scattering have been obtained from experiments using traveling waves and amplifying systems.
Laser Excitation of Microwave Sound in Solids
Authors: Cachier G.
Published: October 2005

Two methods are presented for generating sound at microwave frequencies with a Q-switched ruby laser. They are based on the modulation of the laser due to its mode structure and on the nonlinear properties of the solid. Sound is created at the laser modulation frequency. (1) Electrostrictive mixing in a LiNbO3 crystal, using a forward Brillouin scattering geometry, produces sound pulses at 800 MHz inside the crystal. Acoustic power densities were around 0.1 mW/mm2. (2) We then used surface heating of a metal film deposited on the surface of a dielectric crystal. At microwave frequencies, good efficiencies can be achieved; at 840 MHz, we generated in a gold film nearly 10 mW/mm2 of sound in 30-nsec pulses.
An Array Processor Optimum Subject to a Constraint
Authors: Fenwick A.
Published: October 2005

A problem of interest in signal processing using arrays is to design a processor that steers a null in one direction while steering a main lobe in another. In this paper, a solution to this problem for a monochromatic plane-wave signal is found by first transforming the gain equation and then choosing a particular basis for K-dimensional complex vector spaces. Other problems where the principle may be applied are mentioned.
Travel Time in the Cochlea and Its Determination from Cochlear-Microphonic Data
Authors: Dallos Peter , Cheatham Mary Ann
Published: October 2005

A correlation between the behavior of the interscala cochlear-microphonic phase and the absolute phase shift between microphonic and sound at the eardrum is presented. It is shown that absolute phase can be interpreted with confidence over a limited frequency region for a given electrode location. Within this region the travel time in the cochlea, as manifested by microphonic measurements, is frequency independent.
On the Limitations of Cochlear-Microphonic Measurements
Authors: Dallos Peter , Schoeny Zahrl G. , Cheatham Mary Ann
Published: October 2005

The interelectrode phase and the relative microphonic magnitude have been measured from electrodes placed in scalae vestibuli and tympani of the first three turns of the guinea pig cochlea. The relative phase difference between two electrodes in a given turn appears to be a sensitive indicator of the contributions to the recorded microphonics of local and remote potential generators. It is suggested that in the guinea pig, local responses can be measured up to 10 000 Hz in the first turn, up to 3000 Hz in the second turn, and only up to 500 Hz in the third turn. The results of interaction between local and remote activity, as manifested in amplitude and phase patterns of the microphonic, are demonstrated in detail and the influence of stimulus intensity is treated. Attention is called to some of the pitfalls that result from drawing inferences from data that are obtained in a frequency region where the response is dominated by remote components. Finally, for comparison, interelectrode phase data are given for the first turn of the cat's cochlea, and the problems of recording from the round-window region are considered for both cat and guinea pig.
Audibility of High Harmonics in a Periodic Pulse. II. Time Effect
Authors: Duifhuis H.
Published: October 2005

In a previous paper the audibility has been reported of high harmonics which had been eliminated from the spectrum of a periodic pulse. The present paper gives evidence that this phenomenon can be ascribed to an analysis of the time pattern of the stimulus. This time analysis is thought to occur after a frequency analysis with limited resolving power, such as is carried out at the basilar membrane. Evidence for this idea is provided by a scanning experiment. The response to a periodic pulse is scanned with a periodic sine-wave train as a probe. The data show a distinct time effect. A simple model of the peripheral auditory system (a bank of bandpass filters followed by time selective energy detectors) is shown to describe the data qualitatively. A quantative description requires additional specifications of the filter and detector characteristics. This allows an estimation of the frequency resolving power of the peripheral auditory system. For the quality factor Q, we thus estimated a value greater than 7.
Interaural Correlation Detection for Auditory Pulse Trains
Authors: Pollack Irwin
Published: October 2005

Interaural correlation discrimination thresholds were obtained for auditory pulse trains. Pulse trains of random polarity or of random pulse occurrence were delivered to the two ears. The interaural correlation is defined by the pulse-by-pulse agreement between the ears. Coding by pulse occurrence and coding by pulse polarity are about equally effective, except for larger thresholds for polarity at low pulse frequencies. Thresholds for the discrimination of changes in positive interaural correlations are smaller than corresponding thresholds for negative correlations. Interaural correlation discrimination thresholds for pulse trains are comparable to those obtained with wide-band continuous noise.
Forward and Backward Masking: Interactions and Additivity
Authors: Wilson Richard H. , Carhart Raymond
Published: October 2005

Monaural masked thresholds for clicks were established on three listeners. Masking functions across selected Δt's (the time disparities between the masker and click) were determined for four masking conditions in which the 70 dB SPL masker was a 500-msec burst of random noise. These four conditions were (1) simultaneous masking, (2) forward masking (FM) at Δt's from 1 to 250 msec, (3) backward masking (BM) at Δt's from −1 to −250 msec, and (4) forward-backward masking at selected Δt's between two 500-msec noise bursts. In this last instance, the interval between bursts was varied to achieve seven interburst intervals (IBIs) ranging from 25 to 500 msec. Simultaneous masking was 3–5 dB less at the boundaries of the noise burst than it was in the middle of the noise burst. The functions for FM and for BM were not inversely symmetrical with one another, although both showed less threshold shift (TS) the further displaced in time the click was from the masker. The masking that appeared when the click was presented between two noise bursts was greater immediately adjacent to a noise burst than near the center of the IBI. During the longer IBIs (500–300 msec), the configuration of masking was equivalent to that of FM followed by BM, with slight excess appearing only in the interval 20–40 msec before the second noise burst. The configurations of FM and BM were preserved during the shorter IBIs (200–50 msec), but the TSs were greater than either type would have produced if operating alone. These TSs became larger as the IBI was shortened, so that the brief IBIs were permeated with large amounts of masking even in the middle of the IBI. This cumulation of masking was so great when the IBI was reduced to 25 msec that the masking function lost the configuration characterizing the longer IBIs. The TSs during shorter IBIs exceeded the sum of the residual effective powers of FM and BM.