bluuebunny/crossref_metadata_2025 huggingface dataset:
Discriminability, response bias, and phoneme categories in discrimination of voice onset time
Authors: Wood Charles C.
Published: October 2005

The ’’phoneme-boundary effect’’ refers to the observation that discrimination of stop consonants across a boundary between phoneme categories is superior to discrimination of comparable stimulus differences within a phoneme category. The present experiment employed signal detection methodology (a) to distinguish between changes in discriminability and response bias; and (b) to reevaluate the role of phonetic categorization in the phoneme-boundary effect. A SAME–DIFFERENT discrimination task compared discrimination of 10− and 20−msec differences in voice onset time (VOT) in a synthetic stimulus continuum ranging from [ba] to [pa] (VOT’s from −50 to +70 msec). Both a clear increase in discriminability and a marked shift in response bias from SAME to DIFFERENT occurred near the voiced–voiceless boundary. When variations in VOT were isolated from syllable context so that they were not categorized as phonemes, discriminability increased near the voiced–voiceless boundary in a manner comparable to the full-syllable stimuli. These data suggest that the phoneme-boundary effect in VOT discrimination reflects a genuine increase in discriminability near the phoneme boundary. However, in agreement with the recent data of J. D. Miller and his colleagues, these results suggest further that the phoneme-boundary effect for VOT is not due exclusively to phonetic categorization but may instead reflect acoustic and auditory properties which are distinct from phonetic processing.

Subject Classification: [43]70.30; [43]65.75; [43]70.35..
Shear properties of mammalian tissues at low megahertz frequencies
Authors: Frizzell Leon A. , Carstensen Edwin L. , Dyro Joseph F.
Published: October 2005

Rough values for the transverse-wave specific acoustic impedance Zs=Rs+jXs, transverse velocity of sound cs, and transverse absorption coefficient αs have been measured for canine liver, kidney, muscle tissues, and for packed red blood cells in the frequency range from 2 to 14 MHz at 25°C. The ranges of the results are Rs=700–3000 Ωmech/cm2, Xs=400–4000 Ωmech/cm2, cs=900–10 000 cm/sec, and αs=2000–30 000 np/cm. The corresponding results for shear stiffness μ1 and viscosity μ2 are μ1<107 dyn/cm2 and μ2=4–30 centipoise. At these frequencies the viscosities are orders of magnitude less than those reported at 0.5–5 kHz by Oestreicher (1951). The low impedances (viscosities) correspond to low velocities and extremely high absorption coefficients for shear waves in tissue.

Subject Classification: [43]80.20, [43]80.30.
Fluid-loading influence coefficients for a finite cylindrical shell
Authors: Sandman B. E.
Published: October 2005

The fluid radiation loading exhibited by a finite cylindrical shell with rigid immovable end plates is investigated by implementing the methods of Fourier integral transforms. The solution is obtained for a generalized velocity distribution on the cylindrical surface. The numerical solution for a radially pulsating surface is utilized as the basis for comparison to previous investigations. In addition, the radiation loading displayed by the low-order modes of a simply supported shell section is obtained, and the relative effect of the imposed condition of an infinite cylindrical baffle embodying the shell is ascertained. It is shown that the classical solution for a vibrating band on an otherwise rigid surface offers a reasonable approximation in the determination of the fluid radiation loading imparted to a finite cylindrical shell with rigid end closures.

Subject Classification: [43]20.60.
Multiple scattering between a cylinder and a plane
Authors: Bertrand J. C. , Young J. W.
Published: October 2005

Experimental measurements of the backscattering of a plane acoustic wave by a rigid cylinder parallel to an elastic plate are compared with theoretical calculations. Two sets of calculations, one which includes the effects of multiple scattering between the cylinder and the plate abd one which ignores multiple scattering between the cylinder and the plate and one which ignores these effects, were performed. The measurements were done in fresh water these effects, were performed. The measurements were done in fresh water using a 5.08-cm-diam solid steel cylinder at various distances from a 0.635 cm-thick steel plate. The frequency of the incident wave was varied from 50 to 100 kHz. Comparisons between the theories and experiment were made both for the case of the cylinder in front of the plate and for the case of the cylinder behind the plate. The results confirm that multiple scattering effects should be included in these scattering calculations.

Subject Classification: [43]30.40; [43]20.30.
Frequency discrimination as a function of frequency and sensation level
Authors: Wier Craig C. , Jesteadt Walt , Green David M.
Published: October 2005

Frequency discrimination was measured for frequencies from 200 to 8000 Hz and for sensation levels from 5 to 80 dB using pulsed sinusoids as stimuli in an adaptive two-interval force-choice psychophysical procedure. An analysis of variance indicated significant effects of frequency and sensation level, and of the interaction between frequency and sensation level. The effect of sensation level is greatest at low frequencies and decreases at high frequenices, being quite small at 8000 Hz. The data are used to evaluate the predictions of current theoretical models.
Thermal effects and damping mechanisms in the forced radial oscillations of gas bubbles in liquids
Authors: Prosperetti Andrea
Published: October 2005

A linearized theory of the forced radial oscillations of a gas bubble in a liquid is presented. Particular attention is devoted to the thermal effects. It is shown that both the effective polytropic exponent and the thermal damping constant are strongly dependent on the driving frequency. This dependence is illustrated with the aid of graphs and numerical tables which are applicable to any noncondensing gas–liquid combination. The particular case of an air bubble in water is also considered in detail.
Interactions of backward and forward masking
Authors: Lynn Gerri K. , Small Arnold M.
Published: October 2005

The interaction between backward and forward masking was investigated for conditions in which a signal is presented in the same ear as the masker, monotically, or in the contralateral ear, dichotically. The SPL of a signal required for equal detectability was determined in both monotic and dichotic backward and forward masking paradigms and in paradigms that combined backward and forward masking. In most cases, the combination of the various masking conditions produced a greater effect than either masker alone. Further investigation of the interaction of monotic forward and dichotic backward masking was conducted. Within intermasker intervals of 15, 25, and 45 msec signal SPL’s for equal detectability were determined for different temporal placements of the signal. The results indicated that when a contralateral backward masker is added to a forward masking paradigm, the signal must be increased by a constant amount to remain equally detectable. However, this constant increase was larger for the 15-msec masker separation than either the 25- or 45-msec separations.
Lateralization of pulsed sinusoids based on interaural onset, ongoing, and offset temporal differences
Authors: Yost William A.
Published: October 2005

When pulsed sinusoids are presented to the ears with an interaural temporal difference but with no rise–decay time or filtering, three values of interaural time are present: onset, ongoing, and offset interaural differences. Lateral discrimination based on interaural temporal differences was studied for such stimuli. The sinusoids were either equal-energy or constant-intensity 65 dB SPL tones. The frequencies of the tones ranged from 150 to 4050 Hz and the durations covered a range of 2 msec–1 sec. The threshold value of interaural time obtained in the lateral discrimination task increased as a function of increasing frequency when intensity was maintained constant. When equal-energy signals were used, the change in lateralization as a function of changes in frequency depended on signal duration. All lateral discrimination thresholds were approximately the same when the onset and offset temporal differences were reduced or eliminated by applying a bandpass filter, high-pass filter, or a rise–decay time, or by presenting the signals with only an ongoing temporal difference. Low-pass filtering the 4050-Hz signals produced lateral discriminations approximately equal to those obtained with no filtering. These results suggest that low-frequency information is the crucial variable for lateralization sinusoidal stimuli presented with onset, ongoing, and offset interaural temporal differences.
Critical reflection of antisymmetric SH waves in an infinite piezoelectric plate
Authors: Kaul R. K.
Published: October 2005

It may ordinarily appear that at grazing incidence of an antisymmetric SH wave, the motion of an infinite piezoelectric plate is evanescent. It is shown, however, that in this critical situation the wave motion is purely torsional with very simple mechanical displacement.
Application of one-dimensional finite elements to normal mode analysis of ferroelectric cylindrical shells
Authors: Sabbagh Harold A. , Krile Thomas F.
Published: October 2005

System models consisting of linear partial differential equations which have been put into variational form, can be solved using the finite element method. The construction and use of a special class of one- dimensional finite elements, consisting of multiple convolutions of the unit pulse function, is described in this paper. As an example of how to use finite elements, the short circuit and open circuit normal modes of a radially polarized piezoelectric cylindrical shell are obtained. The computional procedures are shown, with special emphasis on how the system matrix equations can be constructed as well as solved by the computer. The finite element results are compared to exact values computed by classical methods. Convergence properties with respect to the order of finite elements used and the fineness of the grid structure are examined. Good results are observed for relatively coarse grids with second- or third-order elements.
Atmospheric attenuation of explosion waves
Authors: Reed Jack W.
Published: October 2005

Observations of sound attenuation in the out of doors have shown an attenuation factor approximately dependent on the five-fourths power of frequency, rather than the square. Both power laws have been applied to calculations of yield-scalable pressure signatures from explosions to allow comparison of results with measurements of explosion-wave compression rise times. It appears that the five-fourths law better explains the long rise times observed, but there are still serious underpredictions. Nevertheless, this model has been applied to the problem of determining the requirements for pressure-gauge frequency response. At the low overpressures of concern in environmental monitoring, it appears that a 1-kHz instrument response is more than adequate for recording explosion waves.
Analysis of scattering from large planar gratings of compliant cylindrical shells
Authors: Brigham Gerald A. , Libuha John J. , Radlinski Ronald P.
Published: October 2005

A two-dimensional mathematical model for estimating the scattering of plane acoustic waves from an infinite, uniform, plane grating of compliant, elliptically, cylindric shells is developed. Calculations from the model are found to be in good agreement with insertion loss measurements of experimental arrays. The array is shown to be analogous to a multituned acoustic-band rejection filter that has the shell’s fundamental flexural mode in the array for its center frequency. Low-frequency approximations are also included. Conditions for an ultrawide resonance bandwidth having very high array resonance reflectivity are considered and an alternative application for compliant tube gratings, as an acoustic window that provides mechanical shading for a sonar receiving array, is discussed.
Acoustic fluctuations using the parabolic profile
Authors: Ramsdale Dan J.
Published: October 2005

Calculations were performed using the normal-mode solutions for the parabolic profile to determine the behavior of the acoustic field when either the axial or maximum profile sound speed was altered slightly from an unperturbed value. It was found that incrementing either the axial or maximum profile speed by small amounts produced a change in the focal length of the parabolic profile, which in turn caused a range-dependent compression or expansion of the unperturbed acoustic field with no noticeable distortion for frequencies less than 400 Hz and range less than 550 km. Approximating the effect of the first-mode semidiurnal internal tide by appropriate variations in axial velocity, this fact was used to show that for cw propagation between fixed source and fixed receiver, the fluctuation in acoustic amplitude produced by the internal tide can be obtained by sampling the amplitude function for the unperturbed profile a distance Δr either side of the range in question, where Δr is the distance the unperturbed acoustic field is shifted due to the change in axial speed produced by the internal tide. For a moving source, a range-dependent critical source speed was determined such that for source speeds equal to or less than the critical speed, the effect of the internal tide predominates as a source of acoustic fluctuations, while for source speeds greater than this critical speed the effect of source motion is paramount.
Application of the subharmonic threshold to the measurement of the damping of oscillating gas bubbles
Authors: Prosperetti Andrea
Published: October 2005

It is suggested that the damping affecting the forced radial oscillations of gas bubbles can be determined very accurately through the measurement of the subharmonic threshold for the oscillations. The advantage of the method is that, while the subharmonic oscillations have a large amplitude and can be easily detected, the theory can be accurately based on a perturbation approach. The theoretical basis for the subharmonic generation is also reviewed and its results illustrated for the case of an air bubble in water.
A statistically based measure of the acoustic reflex and its relation to stimulus loudness
Authors: Block Michael G. , Wightman Frederic L.
Published: October 2005

To develop an objective statistic for quantifying acoustic-reflex magnitude, a computer sampled baseline and perstimulatory conductance and susceptance. For each component, the difference between baseline and perstimulatory means was divided by the pooled standard deviation of the samples yielding a statistic similar to d′. Component d′’s were combined by taking the square root of the sum of the squared d′s. The resultant d′ was used to represent acoustic-reflex magnitude in an objective, statistically based format. Stimulus level required to elicit reflexes of specific magnitudes was estimated using the PEST adaptive procedure. Magnitude-intensity functions were determined for a 1-kHz tone, 50- and 300-Hz wide noise bands, and white noise. Stimuli at estimated levels were then used as references in loudness balances among all stimulus pairs, yielding four equal-loudness contours. Equal-loudness and equal-reflex contours had similar shapes, suggesting a relationship between loudness and the acoustic reflex. The magnitude-intensity functions were quite steep, indicating that small intensity changes produced large changes in reflex magnitude. We concluded that the data do not permit rejection of the hypothesis that stimuli eliciting equal reflexes are equally loud. However, the quantification technique has value in that the notion of reflex ’’threshold’’ can be replaced with a mathematically rigorous measure of reflex magnitude. Experiments to refine this technique are in progress.
Numerical-perturbation technique for the transverse vibrations of highly prestressed plates
Authors: Nayfeh Ali H. , Kamat M. P.
Published: October 2005

Under the usual assumptions of small strains with moderately large rotations, the problem of the transverse vibrations of highly prestressed, nonuniform annular plates is reduced to the solution of the differential equation governing the transverse vibration of the corresponding prestressed membrane subject to modific boundary conditions that account for the effects of bending. The methods of matched asymptotic and/or composite expansions are used to determine these modified boundary conditions. The agreement of the results of both methods with known exact solutions for simple geometries demonstrates the efficiency of this technique when compared with other well-known numerical techniques.

Subject Classification: [43]40.24.
Combined psychophysical and electrophysiological study on the role of combination tones in the perception of phase changes
Authors: Buunen T. J. F. , Kate J. H. ten , Raatgever J. , Bilsen F. A.
Published: October 2005

It is a well-known psychophysical fact that phase changes in a three-component signal are audible provided that the frequency separation between the components does not exceed a critical value. A possible source of these effects is the phase-dependent level of the ’’internal components’’ caused by an interaction within the ear of acoustic frequency components and ’’combination tones’’ of the form (n+1) f1−nf2. The experiments described in this paper are intended to verify this hypothesis by both psychophysical and electrophysiological experiments. The level of the internal component as a function of phase was psychophysically estimated in a forward-masking experiment. Besides, single cell recordings in the cochlear nucleus of the cat were performed to investigate the phase dependence. It has been possible to demonstrate the interaction between acoustic components and combination tones for both experimental approaches. It can be described as a vector addition. Subsequent psychophysical and electrophysiological experiments on the detectability limits of combination tones have shown that these limits correspond to the maximum frequency separations for the audibility of phase changes.
Physics of the guitar at the Helmholtz and first top-plate resonances
Authors: Firth Ian M.
Published: October 2005

The action of the guitar has been studied in detail in the vicinity of the Helmholtz air resonance and the first resonance of the top plate. Measurements of the input mechanical admittance, the output sound pressure, and their phases suggest an analogous acoustical circuit for the guitar identical with that used to describe the action of a loudspeaker in a bass-reflex enclosure. Below the Helmholtz resonance sound radiated from the rose and from the top plate are out of phase. As a result sound radiated from the guitar is not enhanced by the rose. Above this resonance sound output from the rose and top plate are more nearly in phase with a resulting enhancement of radiated sound.
Voice onset time for voiceless stop consonants in the fluent reading of stutterers and nonstutterers
Authors: Hillman Robert E. , Gilbert Harvey R.
Published: October 2005

Ten stutterers and ten nonstutterers read ’’The Rainbow Passage.’’ Intervocalic voiceless stop consonant segments were selected and displayed on wide-band spectrograms. Results of VOT measurements obtained indicated that (1) the stutterers displayed longer VOT values than the nonstutterers, and (2) VOT values increased in duration as place of articulation moved back in the oral cavity.
Theory of the spherical, compliant-tube Luneburg lens
Authors: Boyles C. A.
Published: October 2005

This paper presents the theory of the spherical, compliant-tube Luneburg lens. Since a mixture of compliant tubes and water is dispersive, the compliant-tube lens is a Luneburg lens only at a single frequency. The wave equation for the pressure field is solved for plane wave incidence. This solution corresponds to measurements made with an omnidirectional hydrophone on the lens. The wave theory is further developed to include solutions corresponding to measurements made by a dipole and cardioid hydrophone. The intensity, which is not proportional to the pressure squared, is also calculated. Numerical evaluation of these solutions is performed for a 10-ft-diam lens over the frequency range 500–5000 Hz (D/λ=1 to D/λ=10). This particular lens was chosen for study since it corresponds to a lens built by the Autonetics Division of Rockwell International. This lens is a Luneburg lens at 5000 Hz and is not perfect focusing for frequencies below 5000 Hz. The on-axis gain, beam patterns, and directivity indices are calculated for the three sensors. In general, the on-axis gain and directivity index are different. A comparison is made between measured results and theoretical results. Finally, the compliant-tube lens is compared with a Luneburg lens (at all frequencies) and a liquid lens.
Approximate ray angle diagram
Authors: Cox Henry
Published: October 2005

The ray angle diagram presents loci as a function of depth of the angles which selected rays make with the horizontal as sound propagates in the ocean. It provides useful qualitative information about deep ocean propagation and the vertical distribution of signal and ambient noise power. The loci are based on Snell’s law. It is shown that an approximate ray angle diagram (ARAD) can be easily constructed directly from the sound-velocity profile since on an appropriate scale the loci of one minus the cosine of the ray angle versus depth are approximately mirror images of the sound-velocity profile. The approximations are shown to involve negligible errors for cases of interest in underwater acoustics. The use and construction of the ARAD are illustrated with examples. A simple graphical technique is presented for annotating the ARAD with range information from which rays may be plotted without the use of a computer.
Sonar cross section of a coated hollow cylinder in water
Authors: Gaunaurd G. C.
Published: October 2005

We study the acoustic scattering which occurs when a plane wave is incident on an infinite hollow elastic cylinder covered with an ideally bonded layer of viscoelastic and sound-absorbing material. The structure is immersed in water and it contains air in the cavity. The normal-mode solution is found in all four media and programmed for numerical evaluation in the exterior fluid. Series expressions for the differential and the sonar scattering cross sections are constructed and added by computer. Two size cylinders are investigated in a parametric study, and oscillations in the cross-sectional values due to resonances in the shell and coating materials are found and plotted for the basically low-frequency range k1c<20. The effect of a variable viscosity in the coating is analyzed, and as one would expect, progressively higher viscosity values damp out the rapid cross-sectional oscillations and reduce the amplitudes to smaller values, down to an optimum point, beyond which the reverse effect begins to take place. The way the oscillating cross-section peaks are shifted in frequency or damped out in amplitude by changing shell or coating sizes or materials, can be quantitatively used at one’s convenience for various design purposes.
The influence of range-dependent environments on low-frequency volume attenuation measurements in the sea
Authors: Hanna J. S. , Rost P. V.
Published: October 2005

Two measurements (for the Hudson Bay and Baffin Bay) performed by the Naval Underwater Systems Center to determine volume attenuation at low frequencies have been reanalyzed. The reanalysis gives substantial evidence that the attenuation coefficients previously inferred for these areas are dominated by the influence of range dependence in the respective environments. The previous analysis assumed cylindrical spreading for the long-range propagation loss, with departures ascribed to volume attenuation. The work here shows that such departures may be caused by range dependence of the environment for the Hudson and Baffin Bays. The conclusion is that no a priori assumption about the dependence of loss on range is defensible for the long ranges involved in these experiments and that careful concurrent environmental measurements are required for use in the data analysis.
Architectural acoustics in America to 1930
Authors: Shankland Robert S.
Published: October 2005

The beginning of architectural acoustics as an engineering science began with Joseph Henry, when he was requested by Congress to design a new lecture hall for the Smithsonian Institution in Washington. Henry’s preliminary investigations led him to the discovery of what is now known as the ’’precedence effect,’’ setting limits on the permissible time lags in successive acoustic signals before echoing is evident. Henry’s design of the lecture hall made skillful use of his discovery for the location and shape of wall and ceiling surfaces to produce much ’’early reflected sound’’ to enhance the direct impulses. The next great advance in architectural acoustics was made by Professor Wallace C. Sabine of Harvard in his quantitative studies of reverberation, and in his masterful use of these discoveries in the acoustical designs for many notable buildings especially Boston Symphony Hall—still considered one of the world’s finest. After Sabine’s untimely death in 1919 his work was extended and applied by many others in the next decade, notable, Dayton C. Miller, F. R. Watson, Paul E. Sabine, Carl Eyring, R. F. Norris, and Vern O. Knudsen. The early development and application of architectural acoustics as an exact science was primarily an achievement of the New World, and one of which we can be justly proud in the bicentennial year.
Building acoustics in America, 1920–1940
Authors: Sabine Hale J.
Published: October 2005

This paper reviews the progress in building acoustics in America between the two World Wars. Special emphasis is laid on the development of improved methods of measuring reverberation times, and the development of acoustical materials and methods of measuring their absorption coefficients. Reference is also made to normal-mode calculations, noise quieting applications, and transmission through walls.
Acoustical measurements and instrumentation
Authors: Miller Harry B.
Published: October 2005

A few selected topics will be discussed. Each had a major influence in setting a new trend. The discussion will include the significance of Wente’s condenser microphone in freeing acoustic measurements from the constraints of contemporary microphones; the effect of Maxfield and Harrison’s paper on the analysis and synthesis of acoustic devices; and the evolution of the reciprocity principle into a measurement tool.
Review of undersea acoustics to 1950
Authors: Lasky Marvin
Published: October 2005

For much of the first four decades of the twentieth century (with the exception of an impulse effort during World War I), undersea acoustics had limited financial support and a small number of practitioners. During 1940–1950 this situation changed. A massive effort funded by the U. S. Navy enabled a large multidisciplined group of civilian scientists to transform a previously relatively simple pragmatic ’’art’’ into an increasingly complex emerging science.
Amplitude and phase variation of a narrow inhomogeneous sound bundle reflected by the irregular sea surface
Authors: de Jong B.
Published: October 2005

A narrow bundle of monochromatic acoustic waves is reflected from an irregular sea surface. The elevations of the surface are normally distributed with a relatively narrow power spectrum. The characteristic width of the active scattering area is small as compared to the correlation distance of the irregular waves. A stochastic model is devised for the surface waves in which the amplitude and frequency of these waves vary linearly over the active scattering area. Starting from the Helmholtz equation and using the Kirchhoff approximation, first-order expressions are derived for the average amplitude and phase variation of the reflected waves. The expression for the average amplitude of the reflected waves depends on the width of the incoming sound bundle. However, for short waves this expression becomes independent of the width and reduces to the familiar result of Eckart when the angle of incidence is equal to the angle of observation. The phase variation is independent of the width of the scattering area and has its largest values when the inverse acoustic wave number has the same order of magnitude as the root-mean-square value of the surface-wave height.
Axisymmetric spherical radiator with mixed boundary conditions
Authors: Gerding Christopher C. , Thompson William
Published: October 2005

The acoustic radiation field of an axisymmetric spherical radiator with mixed surface boundary conditions is determined numerically. The general problem consists of a sphere comprised of a radially vibrating polar cap and a contiguous pressure release belt mounted on a rigid baffle (the remainder of the sphere). Two limiting cases, a vanishing belt or a vanishing baffle, are also considered. The radiation field is developed using both a least-mean-square-error method of analysis and a point matching or boundary collocation analysis. The radiation characteristics of the general problem are found to be intermediate between those of the two limiting cases.
Radiation coupling of a disk to a plane and back or a disk to a disk: An exact solution
Authors: Rhyne Theodore L.
Published: October 2005

The radiation coupling or coupling by propagating waves is solved for a disk in an infinite baffle to a plane and back or equivalently a disk to a disk both in infinite baffles. The radiation coupling is defined as a linear filter operating between lumped mechanical components which may be incorporated into transducer models. The impulse response of the radiation-coupling filter and the Fourier transfer function for the radiation-coupling filter are solved in closed form. The radiation-coupling gain (loss) is applicable to the correction of experimental data and to the absolute calibration of circular transducers by self-reciprocity measurements.
Sideband structure of sound from a harmonic point source scattered by a rough surface moving over an upward-refracting ocean
Authors: Labianca F. M. , Harper E. Y.
Published: October 2005

A normal-mode theory, for scattering of sound by the ocean surface in the presence of refraction, is reviewed. The theory is based on a perturbation expansion for small surface-wave heights. New results, based on this theory, are presented for the Doppler-shifted signal sidebands. These sidebands are the solution of the first-order perturbation problem and are represented exactly by a double normal-mode expansion with coefficients given by certain integral representations. The new results are derived by a saddle-point analysis of the integral representations, due account being taken of the presence of singularities. Specific numerical results for the case of upward refraction are shown to display considerably more structure than in the case of an isovelocity ocean. The increased structure is explained in terms of the effects of backscatter and focusing through the use of wave-number diagrams and ray-trajectory constructions.
Infrasonic flow-noise measurements using an H-58 omnidirectional cylindrical hydrophone
Authors: McGrath James R. , Griffin Owen M. , Finger Robert A.
Published: October 2005

Infrasonic and low-frequency flow-noise measurements were made during laboratory tests of an H-58 omnidirectional hydrophone. The hydrophone was tested in three configurations: bare, framed, and faired. The incident water speeds varied from 0.25 to 0.45 knot, which correspond to a Reynolds number range from 8800 to 16 000. The faired and framed configurations developed flow-noise levels lower than the bare hydrophone, and the latter configuration developed the highest noise levels at the lowest frequencies of the 1–50−Hz band. Hydrodynamic factors which influence the acoustic measurements made during this test are discussed, and the importance of hydrophone configuration during very low-frequency measurements is demonstrated.
Elimination of transducer bond corrections in accurate ultrasonic-wave velocity measurements by use of capacitive transducers
Authors: Cantrell John H. , Breazeale M. A.
Published: October 2005

A capacitive-driver–capacitive-detector system for generation and detection of ultrasonic waves has been developed. This eliminates the necessity of bonding piezoelectric transducers to solid samples. With the capacitive-driver–capacitive-detector system, free–free boundary conditions exist at the sample surfaces and longitudinal ultrasonic-wave velocities in solids can be measured accurately without correcting for ultrasonic-wave phase shifts due to sample-bonded transducer interfaces. The capacitive driver has a mica dielectric which increases the breakdown potential, but maintains the free–free boundary conditions at the solid specimen surfaces. This allows for a larger-amplitude ultrasonic signal to be generated in the sample than is possible with an air-gap capacitive driver. This improves the precision of the measurement. The accuracy of the method is comparable with that of bonded-transducer methods, after bond corrections are made.
Some theoretical aspects of the generation of surface ripples by parametric subharmonic resonance with sound waves
Authors: Hughes B.
Published: October 2005

An investigation is made of the dynamics of a liquid free surface in the presence of a reflecting sound field. A finite-amplitude surface standing wave is also specified and the resulting unbalanced vertical stress at the surface is equated to the acoustic pressure. Second- and third-order terms are retained in the surface-wave description (and fourth-order in the nonlinear interaction model). By further equating the viscous dissipation in the surface wave with the net upward acoustic energy flux, the surface-wave parameters are determined in terms of the acoustic-field parameters. Three major results are obtained: no surface waves can exist below an acoustic-intensity threshold (same value as predicted by using Mathieu’s differential equation), above the threshold the square of the surface-wave amplitude is linearly dependent on the acoustic-driving amplitude (for small surface-wave slopes), the sensitivity of the surface waves to driving amplitude is essentially independent of frequency except near the region of resonant gravity–capillary coupling. Comparisons are made with measurements (primarily at ultrasonic frequencies) and reasonable agreement is shown to exist.
Geometrical theory of diffraction for three-D elastodynamics
Authors: Achenbach J. D. , Gautesen A. K.
Published: October 2005

Keller’s geometrical theory of diffraction is applied to three-dimensional elastodynamics, in particularly to diffraction of longitudinal waves by a crack. The theory provides useful approximations for large frequencies and/or large distances from the edge of the crack. For the class of problems considered in this paper, the canonical solution is provided by the fields describing diffraction by a semi-infinite crack of a plane longitudinal wave which is incident under an arbitrary angle with the edge of the crack. The formal solution to the canonical problem is obtained by means of integral transform techniques in conjunction with an application of the Wiener–Hopf method to a set of coupled equations. The pertinent asymptotic expressions for the diffracted field are evaluated, and the diffraction coefficients which enter the geometrical theory are determined. As an example, the three-dimensional problem of diffraction of a point-source field by a semi-infinite crack is worked out in detail.
Equivalent electrical circuit of a multielectrode composite piezoceramic bar
Authors: Adelman N. T. , Stavsky Y.
Published: October 2005

An analysis is made for the longitudinal vibrations of a thin, multielectrode, piezoelectric bar composed of N ferroceramic materials. Resonant and antiresonant eigenfrequency equations are derived, and an equivalent electrical circuit of the transducer is developed from the admittance matrix. Numerical solutions are presented for the fundamental resonant frequencies and corresponding normalized frequency differences of a uniformly polarized, two-electrode, PZT-4 bar with nonzero interelectrode spacing.
Sound-power measurements on large machinery installed indoors: Two-surface method
Authors: Diehl George M.
Published: October 2005

Sound-power ratings of machinery are becoming more important for a number of reasons. Industrial installations must comply with recently enacted state and local noise control codes, and sound power ratings are needed to predict compliance. In addition to this, The Federal Noise Control Act of 1972 requires labeling of machinery to show maximum noise emission, and this, logically, may be in terms of sound power. There are several ways to determine the sound power of machinery under laboratory conditions, but these procedures are usually not applicable in industrial environments. The two-surface method offers the best practical approach to the problem of calculating sound power ratings of large machinery installed indoors, under actual operating conditions.
Laser interference microphone for ultrasonics and nonlinear acoustics
Authors: Smeets G.
Published: October 2005

A small part of a focused laser beam in a Mach–Zehnder arrangement is used for the detection of high-frequency pressure waves. The interferometer is stabilized on an interference slope by means of a simple electro-optical feedback system. The method introduces only little perturbation to the pressure field and yields the true pressure history p (t) with a submicrosecond time resolution. Several examples of registrations show the capability of this ideal microphone.
Effect of tone/noise combination on speech intelligibility
Authors: Pearsons Karl S.
Published: October 2005

Tests were conducted in an anechoic chamber to determine the effect of pure tones on speech intelligibility. The results indicate that in the presence of aircraft-type noise in which combinations of tones and noise are held at a constant A-level, intelligibility is either unaffected or actually increased by addition of tones in the 2–4-kHz range.
Bird song as music
Authors: Dobson Charles W. , Lemon Robert E.
Published: October 2005

From two to five frequency peaks, representing sustained portions of white-throated sparrow (Zonotrichia albicollis) song, were derived using a Ubiquitous Spectrum Analyzer for each of more than 300 recorded songs from 58 different birds. After conversion to cents, a logarithmic unit, each bird’s song data were averaged and placed into three distributions: largest interval in whole song, largest interval between adjacent notes in each song, and all intervals between adjacent frequency peaks in each song. These three distributions plus another from African shrike data previously published by Thorpe did not significantly correlate with a distribution derived from commonly used Western musical scales. It is therefore suggested that utilization of Western musical notation may lead one to overemphasize the ’’musical’’ quality of bird song.
The notebooks of Wallace C. Sabine
Authors: Beranek Leo L.
Published: October 2005

Generally believed lost, 12 of Wallace Clement Sabine’s notebooks have been offered by the Riverbank Laboratories, IITRI, of Geneva, Illinois, to Harvard’s rare books library for safekeeping. The Author has indexed the notebooks against Sabine’s published papers and has sought an answer to Sabine’s Silence in the 1900–1904 period following the opening of Boston Symphony Hall. The investigation reveals that all significant data recorded in the notebooks were either submitted for publication priuor to 1915 or were taken in 1915 just before Sabine became involved in World War I scientific service abroad. He died in January 1919. The excising of over 200 pages from his notebooks just after 1900 indicates that he may have been disappointed in his predictions of the reverberation times of Symphony Hall. This paper summarizes the contents of the notebooks and explains the reason for the discrepancy between his predictions and more recent measured reverberation times for Symphony Hall. It protrays the depth of Sabine’s experimentation, his influence on the growth of applied physics at Harvard, his extensive consultation with architects, and his service in the war effort.
Characteristics of a wake-vortex tracking system based on acoustic refractive scattering
Authors: Burnham David C.
Published: October 2005

The theory of acoustic-ray bending by aircraft-generated vortices is developed in a form convenient for application to a practical vortex tracking system. The maximum scattering angle ϑm is proportional to the vortex circulation divided by the average core radius. Since the circulation for commercial jet transports is roughly proportional to the wingspan, the value of ϑm depends little on aircraft size but strongly on the ratio of the core size to the wingspan. For landing aircraft ϑm varies from 0.5 to 1.4 rad depending upon the engine placement. A variety of vortex core models are considered which lead to values of ϑm between 0.2 and 0.9 rad. The capabilities of a pulsed acoustic vortex tracking system depend strongly upon ϑm and therefore upon aircraft type. The effects of timing errors, both vortex induced and random, on tracking accuracy are derived. The fundamental differences between refractive scattering and turbulence scattering techniques are described.
Gaussian quadrature ranges with observed sound-speed profiles
Authors: Floyd Edward R. , Pugh James D.
Published: October 2005

For observed sound-speed profiles, the range to a noise source in the first convergence zone is calculated numerically by applying Gaussian quadrature techniques of various orders to the ray-tracing range integral. The observed profile is tabulated for standard oceanographic depths. The tabulated profile is mapped into the sample set for Gaussian quadrature by cubic splines. We compare various strategies that divide the ray-tracing range integral into convenient intervals for evaluation by the appropriate Gaussian quadrature consistent with the singular points of the integrand.
Negative bottom loss, critical-angle shift, and the interpretation of the bottom reflection coefficient
Authors: Stickler D. C.
Published: October 2005

The determination of the acoustical properties of the ocean bottom is a formidable task. One method is the seismic reflection method. Some of the limitations inherent in the interpretation of the reflected field are described. These include the dependence of the measurement on the complete geometry of the experiment, the occurrence of negative bottom loss and the apparent shift in the critical angle.
Acoustically relevant statistics for stochastic internal-wave models
Authors: Watson J. G. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

A consistent hydrodynamic model is developed for the effects of a stochastic field of internal waves in the deep ocean on sound-speed and current fluctuations. A scaling is used which reflects the preponderance of energy contained in internal waves of long horizontal wavelengths and near-inertial periods. An approximate solution to the consistent boundary-value problem for vertical eigenfunctions is obtained by a WKB(J) expansion. Expressions are found for internal-wave fluctuations as superpositions of deterministic functions multiplied by random variables, for which particular probability distributions are not assumed. Using specific forms of Brunt–Vaisala frequency and internal-wave energy-density spectrum for illustration, formulas for covariances, variances, confidence intervals, correlation coefficients, and correlation scales are obtained for acoustically pertinent fluctuations. As a result of the consistent treatment of vertical variations throughout the model, many properties of the statistical quantities, such as vertical nonstationarity of the variances, upper and lower correlation depths, and horizontal correlation length, are demonstrated and physically interpreted.
Matrix formulation of multiple and partial coherence
Authors: Potter Ron
Published: October 2005

The conventional theory of coherence is essentially a scalar theory in the sense that coherence values are generally expressed as scalars obtained from the elements of various auto- and cross-spectral matrices. Furthermore, the theory is generally described for the single-output case, and for the case where only one undesired interfering input is assumed. In this paper, we present a general matrix formulation of coherence for the multiple-input and output case, including an arbitrary number of interfering inputs. We show that for n inputs, there are 2n−1 different output coherence matrices.
Two-tone suppression in a nonlinear model of the basilar membrane
Authors: Hall J. L.
Published: October 2005

Several aspects of two-tone suppression in auditory-nerve fibers have been reproduced in a nonlinear computational model for motion of the basilar membrane. In the model, a distinction is made between mechanical nonlinearity (related in the model to membrane velocity) and neural excitatory signal (related in the model to first or second spatial derivative of membrane displacement). For f1 (frequency of exciting tone) equal to CF (characteristic frequency), the model successfully reproduces the physiologically observed distinction between f2 (frequency of suppressing tone) greater than CF and f2<CF: For f2≳CF suppression is related to the intensity ratio of suppressor to excitor, while for f2<CF it is related approximately to suppressor intensity. The model exhibits nonmonotonic increase of response with intensity increase of a two-tone input. The results can be viewed in terms of an ’’attenuating power’’ for the suppressing tone. Extraction by Fourier series analysis of the f1 and f2 components of response to a two-tone input reveals features of the system that should be amenable to confirmation in future electrophysiological experiments.
Selective attention. I. Two-channel simultaneous frequency difference limen
Authors: Ahroon William A. , Pastore Richard E. , Wolz James P.
Published: October 2005

A set of experiments which assesses the ability of human observers to monitor two earphone channels for the purpose of performing one or two independent and simultaneous frequency difference-limen tasks is described. Performance (d′) was significantly poorer with dichotic stimulus presentation than with monaural, control conditions. Under dichotic presentation conditions, performance was equivalent whether the observers were instructed to listen to one or both channels. A detailed analysis of the data indicated that the observers could discriminate a change but seemed to have difficulty in identifying the channel in which the change occurred. Consistent with results reported in the simultaneous signal-detection literature using intensity detection or discriminations, we found that observers cannot successfully monitor more than one channel. It is suggested that when the dichotic stimulus presentation provides useful information which is not present during monaural tasks (i.e., lateralization cues), observers may be able, using this added information, to perform a divided attention task with little or no apparent performance decrement relative to single-channel tasks.
Discrimination of perceived movement velocity for fused auditory image in dichotic stimulation
Authors: Altman J. A. , Viskov O. V.
Published: October 2005

on four subjects, perception of the movement velocity of the fused auditory image (FI) was studied by means of click-train dichotic stimulation with gradually changing interaural time delays. With the signal used, the subjects were able to perceive differences in the velocities of FI movement. Absolute velocity difference limens (DL’s) were determined on the assumption that FI movements was uniform and that its trajectory might be approximated by an arc of a circle. The velocity DL’s were found to be nearly linearly related to the velocity of FI movement and increased from 14°/sec to 140°/sec.