bluuebunny/crossref_metadata_2025 huggingface dataset:
Shallow surface-wave simulator for the study of jet-noise sources
Authors: Colwill W. H. , Reethof G.
Published: October 2005

A shallow liquid surface-wave analogy to turbulence-induced sound was utilized to investigate the mechanisms of noise generation and propagation in jets. Theoretical analysis was used to determine the wave-power dependence on Mach number and to derive the relationship between wave and turbulence spectra. The experimental investigation utilized a 24 ft2 mercury ripple tank. The waves were produced by the turbulence in a mercury jet exhausting into the tank. The results substantiate the validity of the surface-wave analogy as a jet-noise simulator. Measurement of mean and turbulent velocity profiles proved that the jet development was similar to the theoretical plane-free jet. Farfield measurements of wave power, directivity, and spectra compared favorably with the acoustic case. However, the wave spectra showed little of the higher-frequency content found with the turbulence spectra. This difference was attributed to the vertical spatial integration of the turbulence-source terms, which is not found in jet noise.
Stable arrays of resonant bubbles in a 1-MHz standing-wave acoustic field
Authors: Miller Douglas L.
Published: October 2005

As observed microscopically, bubbles in a standing-wave acoustic field move to the pressure nulls and oscillate, in elliptical orbits, about a common axis. The orbits of individual bubbles are equally spaced about 100 μm apart along the axis, forming a linear array. These arrays form in tap water for peak pressure amplitudes of 10–20 bar, but persist at levels as low as 1.5 bar. The 7-μm diameter of the bubbles is approximately the theoretical size for resonant air bubbles in water driven at the 986 kHz frequency of the field. The radius of the orbits is approximately inversely proportional to the pressure gradient at the pressure null, with proportionality constant 0.25 bar. In a simplified model of the orbit phenomenon the expected proportionality constant is given by (2)1/2ps, where ps is the threshold pressure amplitude for rectified diffusion and has the value 0.18 bar. Calculations of ps, based on current theories for rectified diffusion, are in substantial agreement with the this value. The period of the orbital motion is about 1 msec for an orbit radius B of 35 μm, and increases to about 6.5 msec for B=100 μm. Two adjacent bubbles are synchronized in their orbits approximately 90° out of phase, as required for stability of the arrays under Bjerknes forces.
Frequency selectivity of single auditory-nerve fibers in response to broadband noise stimuli
Authors: Mo/ller Aage R.
Published: October 2005

The tuning of single auditory nerve fibers in the rat in response to broadband noise was studied in a large sound intensity range. Pseudorandom noise was used as stimuli and the cross spectrum between a period histogram of the noise and a period of the noise was used as an approximation of the transfer function from sound to the modulation of the neural discharge rate. In units with a CF higher than 1000 Hz, the width of the cross spectra (at 10-dB points) invariably increased as the stimulus intensity increased and the center frequency decreased. The few units studied with CF below 1000 Hz seemed to undergo somewhat less of a change in width. The cross correlograms of all fibers with a characteristic frequency (CF) below 5 kHz showed a damped oscillation the duration of which decreased as stimulus intensity was increased. The similarity between the nonlinearity shown here and that shown in measurements of basilar membrane motion using the Mössbauer effect is discussed.
Psychophysical structure of eight complex underwater sounds
Authors: Howard James H.
Published: October 2005

The potential usefulness of multidimensional scaling techniques in the perceptual analysis of ’’real world’’ underwater sounds was demonstrated. Nineteen observers (nine with musical training, ten without) used a five-point scale to judge the similarity of all possible pairs of eight passive sonar recordings. The eight s signals were selected to represent a range of common natural and man-made underwater sounds. These data were analyzed using the INDSCAL multidimensonal scaling model, revealing an interpretable two-dimensional psychological space. One of the psychological dimensions was interpreted as reflecting the overall shape of the 1/3-octave spectra of the eight signals, while the second was seen to reflect the prominence of a low-frequency periodicity present in some signals. Individual observer analysis revealed substantial differences between the musically trained and musically inexperienced observers in the relative importance or salience of the two dimensions. The relation of these findings to earlier work was discussed.
Numerical technique for computing the wide-angle acoustic field in an ocean with range-dependent velocity profiles
Authors: Estes L. E. , Fain G.
Published: October 2005

A numerical technique for the propagation of sound in the ocean where velocity is a function of both range and depth has been developed. The technique is not restricted to the narrow-angle (parabolic) approximation and it reduces to an exact solution for a homogeneous media. The given field is transformed into a sum of plane waves via an FFT. This transformed field is propagated without approximation through a homogeneous space represented by an average wave number for that space. Updating the average wave number provides for Snell’s law bending in range. The variations from the average velocity are accounted for by summing deviations from the nominal phase to develop a group of direction-sensitive phase correction masks. A weighted group of plane waves centered about each direction are inverse transformed for multiplication by the phase mask with the results summed. The choice of overlapping weights in the transformed space provides an approximate continuous phase correction mask for all directions. The functional relationship of range-step size to frequency, angular spectrum, and velocity profiles are developed. Several results for a 1500-m channel are shown.
Acoustic radiation from point excited rib-reinforced plate
Authors: Lin Gau F. , Hayek Sabih I.
Published: October 2005

An analytic solution for the acoustic radiation from a rib-reinforced infinite elastic plate which is excited by a point force located on the rib was obtained. The solution exhibits a new coincidence angle, where the radiated pressure peaks, which depends on the relative stiffness and mass of the attached beam. An expression for the radiated power was also obtained which shows the general reduction of radiated power explicitly as a function of the mass and stiffness of the attached beam. Approximate formulas for the complex interaction between the beam and the plate were developed for frequencies above and below the coincidence frequency. Approximate expressions for the radiated power were obtained from simplified physical models.
Perceptual evaluations of synthesized musical instrument tones
Authors: Grey John M. , Moorer James A.
Published: October 2005

An analysis-based synthesis technique for the computer generation of musical instrument tones was perpetually evaluated in terms of the discriminability of 16 original and resynthesized tones taken from a wide class of orchestral instruments having quasiharmonic series. The analysis technique used was the heterodyne filter—which produced a set of intermediate data for additive synthesis, consisting of time-varying amplitude and frequency functions for the set of partials of each tone. Three successive levels of data reduction were applied to this intermediate data, producing types of simplified signals that were also compared with the original and resynthesized tones. The results of this study, in which all combinations of signals were compared, demonstrated the perceptual closeness of the original and directly resynthesized tones. An orderly relationship was found between the form of data reduction incurred by the signals and their relative discriminability, measured by a modified AAAB discrimination procedure. Direct judgments of the relative sizes of the differences between the tones agreed with these results; multidimensional scaling of the latter data provided a visual display of the relationships among the different forms of tones and pointed out the importance of certain small details existing in the attack segments of tones. Of the three forms of simplification attempted with the tones, the most successful was a line-segment approximation to time-varying amplitude and frequency functions for the partials. The pronounced success of this modification strongly suggests that many of the microfluctuations usually found in the analyzed physical attributes of music instrument tones have little perceptual significance.
Effects of temperature microstructure on low-frequency propagation in the South Tasman Sea
Authors: Kibblewhite A. C. , Shirtcliffe T. G. , Stanton B. R.
Published: October 2005

The attenuation of underwater sound at very low frequencies exceeds the values expected on the basis of the variation observed at higher frequencies, and this excess attenuation exhibits a regional dependence. Two theoretical models have been proposed to account for the effect observed. Temperature soundings made along a Tasmania-Antartica section have revealed variations of fine structure which an be correlated with variations in acoustical transmission properties and provide a test for the two theoretical models.
Experimental agreement of stochastic ray-theory relations
Authors: Neubert Jerome A.
Published: October 2005

The ray-theory intensity relation has been modified to allow consideration of the effects of medium randomness. This study compares the theoretical model with actual sea data. It also investigates the theoretical relations for the standard deviation and the coefficient of intensity fluctuation in a variable and random ocean. In all cases, good agreement is found within the sampling limitations imposed by the sea data. In addition, the higher-order statistical quantities are remarkably well behaved even beyond the predictions of the model.
Sound propagation in reacting systems
Authors: Ellis Robert J. , Gilbert Robert G.
Published: October 2005

Numerical solutions are given for the set of coupled differential equations describing the dynamic interaction of sound with an arbitrary number of gas phase reactions, for several systems, both near and far from equilibrium. Acoustic response is assumed linear and adiabatic. Absorption by relaxation is included. Results for simple combustion systems indicate that transient effects can result in appreciable amplification of low sound frequencies.
Reflection of finite-amplitude waves in a parametric array
Authors: Muir T. G. , Mellenbruch L. L. , Lockwood) J. C.
Published: October 2005

The effect of a pressure-release reflector on the parametric interaction process is examined theoretically and experimentally. It is shown that the 180° phase change upon reflection instigates a reversal of the finite-amplitude distortion process in the primary radiation. Although energy then passes from the harmonics to the fundamental components of the primaries, the difference frequency component suffers a phase interference effect that leads to its partial annihilation.
Tube method of sound-absorption measurement extended to frequencies far above cutoff
Authors: Shields F. Douglas , Bass H. E. , Bolen L. N.
Published: October 2005

Equipment had been constructed for measuring sound absorption in the frequency range from 4 to 100 kHz in a large tube 25.4 cm in diameter and 4.8-m long. The technique employs a large, moveable, solid-dielectric capacitance transducer that completely fills the tube cross section and generates pulses of plane waves. An identical transducer terminates the other end of the tube and serves as a microphone to detect and reflect the sound pulses. Measurements in argon, nitrogen, and air indicate that the attenuation of the sound pulses differs by less than 1% from values calculated for the zero-order mode for frequencies up to 44 times the cutoff frequency for the first ’’nonplane’’ mode. Above that frequency, the measured values are less than those predicted by theory by an amount that is approximately proportional to the wavelength to the −3.1 power. In a smaller tube (5.72-cm inside diameter) of similar construction, the high-frequency deviation from theory is absent. The equipment has been used to measure absorption in moist air at relative humidities from 0% to 100%, and at temperatures from 0° to 100° F. The results of these measurements will be reported in a later paper.
Evaluation of C-weighted L
d
n for assessment of impulse noise
Authors: Schomer Paul D.
Published: October 2005

Community response to impulsive noise, such as sonic boom, artillery fire, and other military ordinance, and quarry and mining operations, is currently a matter of great public interest. Recently, the EPA has proposed the of the C-weighted day–night level to estimate community response to large amplitude single-event impulsive noise. This measurement and its associated exposure criteria have been derived largely on the basis of existing community response to sonic boom data. Recent laboratory measurements of human reaction to artillery-type noise, reported on herein, strongly support this C-weighted measure.
Peripheral and central processes in selective adaptation of place of articulation in stop consonants
Authors: Sawusch James R.
Published: October 2005

Recent accounts of selective adaptation in speech perceptin have proposed that either one or two leves of processing are adapted. Most of the previous experimental results can, however, be accounted for by either type of model. In the present experiments, two aspects of the selective adaptation paradigm were manipulated. The spectral (frequency) overlap between adapting and test syllables was manipulated along with differences in interaural presentation (adapting in one ear, testing in the other). The results indicated that the adapting syllables drawn from the test series and adaptors with no spectral overlap with the test series both produced significant changes in subjects ratings of the test stimuli. However, the identical adaptors caused significantly more adaptation than the nonoverlapping adaptors. Moreover, the nonoverlapping adaptors produced 100% interaural transfer of adaptation, indicating a central locus of this effect. The identical adaptors drawn from the test series showed approximately 50% interaural transfer. Taken together, these results strongly suggest that two levels of processing are involved in selective adaptation to place of articulation in stop consonants. One is a peripheral level that is relatively frequency specific and the other is a central level that integrates information over a wider frequency (spectral) range.
Measurement of the acoustical impedance of a black box at low frequencies using a shorter impedance tube
Authors: Kathuriya M. L. , Munjal M. L.
Published: October 2005

For the experimental evaluation of the acoustical impedance of a termination by the impedance-tube method at low frequencies, the length of the impedance tube is a problem. In the present paper, the method of exact analysis of standing waves developed by the authors for the stationary medium as well as for mean flow, has been extended for measurement of the acoustical impedance of a termination at low frequencies. The values of the tube attenuation factor and the wave number at the low frequency of interest are established from the experiment conducted, with the given impedance tube, at a higher frequency. Then, exciting the tube at the desired low frequency it is sufficient to measure sound pressure at three differenct locations (not necessarily the minima) in order to evaluate reflection coefficient and hence the impedance of the termination at that frequency.
Improvement and evaluation of the vibration pick-up-type ear microphone and two-way communication device
Authors: Ono Hiroshi
Published: October 2005

A vibration pick-up-type ear microphone was developed as an alternative to the conventional sound-pressure-type ear microphone. It was evaluated and compared to other conventional microphones with the following results: It is possible to obtain remarkable sensibility without closing the ear canal and to obtain speech intelligibility scores of over 95%. There was no significant difference between voice intelligibility with a mask and without a mask. Speech intelligibility of the vibration pick-up-type ear microphone in high ambient noise is much higher (110 dB—96%, 125 dB—84%) than that of a noise canceling microphone (110 dB—87%, 125 dB—77%) and of a sound-pressure-type ear microphone with ear muff (110 dB—85%, 125 dB—68%). By using the two-way communication device it is possible to talk and to listen simultaneously since the ear canal is not obstructed. The vibration pick-up-type ear-insert microphone can be used (1) for voice communication in high ambient noise, (2) in a mask, (3) for hands-free operations, and (4) it will not howl due to excessive feedback. Communication systems using the vibration pick-up-type ear microphone have been evaluated in various environments.
Electroacoustic sensitivity of ceramic cylinders
Authors: Wilder William Doug
Published: October 2005

The low-frequency voltage–pressure sensitivity of piezoelectric right circular cylinders is derived for three common polarization schemes. The acoustic pressure on the three major surfaces is considered variable, thereby allowing for any configuration of shielding. Derived sensitivities are illustrated for a common piezoelectric ceramic material (Clevite PZT 4).
Addendum: ’’Huygens’ principle, radiation conditions, and integral formulas for the scattering of elastic waves’’ [J. Acoust. Soc. Am. 59, 1361–1370 (1976)]
Authors: Pao Yih-Hsing , Varadan-Varatharajulu Vasundara V.
Published: October 2005

This is an addendum to an already published article [J. Acoust. Soc. Am. 59, 1361–1370 (1976)].
’’Suppression’’ effects in forward masking
Authors: Terry Mark , Moore Brian C. J.
Published: October 2005

Two experiments on forward masking are described. Probe threshold were measured using a two-interval forced-choice technique. In experiment I the masked threshold for a 1-kHz probe was measured as a function of masker level for three maskers; a 1-kHz tone, a 1/3-, and a 1/1-octave noise band centered at 1 kHz. At medium and high masker levels, maskers equated for energy in the critical band around 1 kHz did not produce equal amounts of masking. The tone was the most effective masker, and the 1/1-octave noise the least. In experiment II the threshold for a 1-kHz probe was measured for a 1-kHz masker at levels ranging from 26 to 76 dB SPL, and for maskers ranging from 800 to 1100 Hz at levels of either 76 or 61 dB SPL. The effect of adding to each of these a 1.2-kHz tone at 81 dB SPL was also determined. The 1.2-kHz tone produced a significant reduction in probe threshold for masker frequencies within 50 Hz of that of the probe, but had little effect for maskers outside this range. The results are discussed in relation both to lateral suppression and to cues arising from qualitative differences between masker and probe.
Fundamental frequency contours at syntactic boundaries
Authors: Cooper William E. , Sorensen John M.
Published: October 2005

A series of experiments was conducted to determine the extent to which speakers’ syntactic coding influences fundamental frequency (F0) contours in the region of syntactic boundaries. F0 measurements were obtained for groups of nine and ten speakers by computer using a parallel processing algorithm. Measurements were obtained for key word segments at syntactic boundaries in sentences matched for surrounding phonetic environment and stress pattern. In experiment I, statistically significant fall–rise patterns of F0 were obtained at the boundaries between main conjoined clauses and at the boundaries between main and embedded clauses. The fall–rise pattern was somewhat more pronounced at the boundaries between two conjoined clauses. The results with main-embedded clause boundaries provided the basis for experiment II, in which contours were studied at the boundaries between main and embedded clauses for which the location of the boundaries is controversial on linguistic grounds. In experiment III, the study of fall–rise patterns was extended to major phrase boundaries in sentences having subject-verb-object word order and in sentences for which such order was violated by the fronting of a constituent to the beginning of the sentence. The results showed more pronounced postboundary rises in F0 after the fronted constituents. The results for experiments I and III suggested that the fall–rise patterns observed at clause and phrase boundaries typically represented local effects rather than the resetting of the speakers’ declination line. Finally, separate analyses of data for male and female speakers showed that F0 values for females were approximately 1.8 times those of males at each measured point in the F0 contours for all three experiments, suggesting the presence of a single male–female scaling factor for F0.
Sound-tube measurements of the relaxation frequency of moist nitrogen
Authors: Chang Dan , Shields F. D. , Bass H. E.
Published: October 2005

At audible frequencies, the vibrational relaxation of nitrogen contributes significantly to the absorption of sound in still air. The accurate measurement of the humidity dependence of the relaxation frequency of nitrogen, as yet, has eluded careful measurement due to the difficulty in measuring small absorption at low frequencies. Recently, equipment has been constructed for measuring sound absorption in air as a function of humidity over the frequency range from 4 to 100 kHz. In the experiment described here, the temperature and humidity range of this equipment has been extended so that it can be used to study the relaxation absorption in nitrogen at temperatures from 311° K to 418° K. The results indicate that, over this temperature range, the frequency of maximum absorption in moist nitrogen, fr,n, can be given by fr,n/P=260×h, Hz/atm, where h is the percent mole fraction of water, and P is the pressure in atm. To the accuracy of the measurements reported here, fr,n is independent of temperature over the range of temperatures at which the measurements were made.
Vibration of tubes conveying fluids
Authors: Svetlitsky V. A.
Published: October 2005

General, nonlinear equations are derived for the vibration of rectilinear tubes conveying incompressible fluid. From these equations are obtained the equations for small vibrations. If values of tube frequencies and critical flow parameters are to be predicted accurately, the initial state of stress must be taken into account. A numerical example is considered.
Effects of signal intensity and noise on the pitch mixture of dichotic chords
Authors: Efron R. , Tanis D. C. , Yund E. W.
Published: October 2005

The relative salience of the two pitch components (the pitch mixture) of a two-tone dichotic chord (one tone to each ear via earphones) has been shown to be invariant with respect to the interaural intensity difference (ΔI) over a wide range of ΔI [Efron and Yund, J. Acoust. Soc. Am. 59, 889–898 (1976)]. This range of invariance of the pitch mixture was systematically studied as a function of absolute signal level and signal-to-noise ratio. Results indicate that a decrease in the signal-to-noise ratio and a decrease in the sound-pressure level both served to decrease the range of interaural intensity differences over which the invariance occurs. However, while a decrease in both parameters decreased the range of intensity independence, there was a strong interaction between these parameters: The addition of noise eliminated the effect of sound-pressure levels. These findings are discussed in the context of the model described in the companion paper [Yund and Efron, J. Acoust. Soc. Am. 62, XXX–XXX(1977)].
Ear dominance in dichotic chords and ear superiority in frequency discrimination
Authors: Divenyi Pierre L. , Efron Robert , Yund E. William
Published: October 2005

Frequency-discrimination thresholds were determined for pure tones presented either to the right or to the left ear of experienced listeners. In some conditions the stimulus was monaural, whereas in others a tone of fixed, different frequency was simultaneoulsy present in the contralateral ear. Center frequencies of 1.2, 1.7, and 3.2 kHz were investigated. Results reveal a small but reliable discrepancy between just noticeable frequency differences obtained for the right and for the left ear, both in the monaural and in the dichotic conditions. Furthermore, the direction and the degree of asymmetry with respect to the frequency resolving power of the two ears showed a correlation with the direction and the degree of ear dominance for the pitch of dichotic two-tone complexes. [See Efron and Yund, J. Acoust. Soc. Am. 59, 889–898 (1976).] Implications of the relationship between the two types of functional asymmetry of the auditory system are discussed.
Lateralization model and the role of time-intensity tradings in binaural masking: Can the data be explained by a time-only hypothesis?
Authors: Hafter Ervin R.
Published: October 2005

In an earlier paper [J. Acoust. Soc. Am. 50, 1116–1122 (1971)] I presented a lateralization model of binaural masking-level differences (MLD’s), according to which detection under conditions which produce an MLD is based on the average value of an interaural parameter, Δ. This factor is made up of interaural time (Δt) plus interaural intensity (ΔI) weighted by a binaural trading ratio (TR). Two figures in that paper depicted application of the model to MLD’s found as a function of frequency [(Hirch and Burgeat, J. Acoust. Soc. Am. 30, 827–832 (1958)]; those figures are partially incorrect. They show the lateralization equation with a time-intensity trading ratio of 20 μsec/dB to be the best fit, when in fact, the fit to TR=0 μsec/dB is excellent. The lateralization model with a trading ratio of 0 is very much like the vector model of Webster [J. Acoust. Soc. Am. 23, 452– 462 (1951)] and Jeffress et al. [J. Acoust. Soc. Am. 28, 416–426 (1956)]. It is suggested here that variability in the noise process may be significant factor, allowing binaural neurons tuned to high frequencies to recover and then respond again to interaural differences of time.
Propagation of audible sound through air-water fogs
Authors: Davidson G. A.
Published: October 2005

The propagation of audible sound through air-water fogs is studied theoretically using a generalized Burgers’ equation applicable to media exhibiting relaxational as well as classical thermoviscous absorption. The effects of vibrational and rotational relaxation of the gas molecules, and of polydisperse water droplet relaxation due to mass, momentum, and heat exchange with the gas are included in the formulation. Analytic expressions showing the dependence of dispersion and attenuation parameters on gas and droplet properties and on sound frequency are derived. Agreement between theoretical predictions and available experimental measurements is good. The results clarify those conditions under which sound propagation in fogs is significantly different from propagation through humid air containing no suspended droplets.
High-frequency acoustic scattering from submerged cylindrical shells coated with viscoelastic absorbing layers
Authors: Gaunaurd G. C.
Published: October 2005

We analyze the high-frequency scattering of a plane-wave incident on a submerged air-filled cylindrical steel shell coated with a viscoelastic layer. The scattered pressure field consists of a geometrical acoustic contribution and another part due to creeping waves. We analyze the resulting generalized reflection coefficient as a function of azimuthal angle, for two shell sizes and various viscosity levels of the coating. We also obtain the locations of roots of the 10×10 characteristic determinant in the complex ν-plane for the two shell sizes of interest. These zeroes are compared to the zeroes of rigid and soft cylinders and to the roots of a simpler 3×3 determinant corresponding to the case of a solid sound-absorbing cylinder of the same size. The results show that the region in the ν-plane where many of the roots are usually concentrated for bare structures, contain no roots after the absorbing layer is bonded to the steel shell. All the above information is then used to compare the normal-mode solution for the sonar cross section of the coated cylindrical shell found in an earlier study of ours (and extended here to higher k1c values), and the corresponding expression obtained to lowest order from an application of the Watson–Sommerfeld transformation. This comparison, as exhibited in various graphs, is found to be very favorable. It verifies that the lowest-order term in the Watson–Sommerfeld transformed solution is capable of accurately reproducing the exact scattering solution at high frequencies for the cylindrical coated target considered here.
Finite-amplitude saturation of plane sound waves in air
Authors: Webster Don A. , Blackstock David T.
Published: October 2005

When the received level of a transmitted acoustic wave reaches an upper limit that cannot be exceeded regardless of how much acoustic power is radiated by the source, the wave is said to have saturated. Experiments on saturation of plane waves in air are reported in this paper. The measured quantity is the pressure amplitude p1 of the fundamental. To obtain a theoretical prediction that is valid close to and including saturation, we assume the decay rate of the fundamental is the sum of the sawtooth and ordinary absorption decay rates (Rudnick’s assumption). Solution of the assumed equation gives p1=2p10e−αx/[1+(1−e−αx)/α?], where p10 is the source amplitude, α is the ordinary (small-signal) attenuation coefficient, and ? (proportional to 1/p10) is the shock formation distance. The saturation amplitude is found by letting p10→∞. The experiments were done in a plane-wave tube over a frequency range of 0.5 to 4 kHz at source levels up to 163 dB (re 0.0002 μbar). Qualitatively, saturation is evident in the waveforms and the amplitude response (input–output) curves. Quantitatively, the data confirm the theoretical prediction. Dispersion, which is caused by tube-wall boundary layer effects, causes asymmetry of the waveforms but apparently has little effect on the fundamental amplitude.
Modifying the sound-speed profile to improve the accuracy of the parabolic-equation technique
Authors: Brock H. K. , Buchal R. N. , Spofford C. W.
Published: October 2005

The parabolic-equation technique has received considerable attention since its introduction to the underwater-sound community by Tappert and Hardin three years ago. The technique relies upon removing the primary radial dependence of the acoustic field from the elliptic wave equation, and approximating the resulting equation with a parabolic (or Schroedinger) equation which may then be rapidly solved on digital computers. The parabolic approximation has been shown for layered media to result in an error in the phase velocity of the normal modes. In underwater-sound propagation the phase-velocity error can cause substantial shifts in the range of convergence zones. A significant reduction in this error appears achievable by a simple modification to the refractive-index profile n (z) which transforms the (n,z) pairs of points into a new set of points (?,?). Within the accuracy of the WKB approximation, the normal modes for this new environment have the same phase velocities as the equivalent wave-equation modes in the original environment. The z to ? mapping indicates the correspondence between field points in the old and new environments. This mapping is designed to approximately map turning point into turning point. Comparisons with normal-mode solutions of the full elliptic wave equation are presented to illustrate the improvement in accuracy of the parabolic results under this transformation. A ray comparison is also given. Problems associated with extending the technique to a range-dependent environment are discussed and in limited testing have been found to be minimal.
Electronic models to simulate the effect of sensory distortions on speech perception by the deaf
Authors: Villchur Edgar
Published: October 2005

Electronic models that process signals to simulate omissions and distortions in perception by the deaf are useful analytical tools. These models can help in determining the degree to which the represented loss and/or distortion of acoustic speech cues, isolated from any central pathology, affects speech intelligibility. They can also help in evaluating the potential effectiveness of different modes of compensatory signal processing. Three examples of such models, designed on the basis of measured characteristics of the deaf subjects’ residual hearing, are described. A model of recruitment combined with accentuated high-frequency loss is used to study speech perception in noise. It suggests an explanation for the previously reported ability of sensorineurals to tolerate the masking of speech by white noise at least as well as normals do, and for the special vulnerability of the speech perception of such deaf subjects to masking signals that have the spectral distribution of speech. A second model, that simulates the severely restricted dynamic range of hearing in profound deafness, predicts that this one factor can destroy the intelligibilty of amplified speech by making the perceived sound drop out at frequent intervals. Finally, a model that simulates reduced frequency-discriminating ability is described, as an example of a model that deals with aspects of perception other than loudness.
Study of variations in the male and female glottal wave
Authors: Monsen Randall B. , Engebretson A. Maynard
Published: October 2005

A reflectionless metal tube which can act as a pseudoinfinite termination of the vocal tract was used to collect glottal volume-velocity waveforms produced by 10 male and female adult subjects. From each subject, glottal volume-velocity samples were collected of normal, loud, and soft voice; falsetto and creaky voice; monosyllables with rising and falling intonation; and three-syllable utterances containing primary lexical stress on one of the three syllables. Analysis of the data indicates a wide variation of the glottal waveform shape, its rms intensity and fundamental frequency, phase spectrum, and intensity spectrum. It is observed that as the fundamental frequency changes over time, the glottal source varies in one of two different ways. In one type of change, the harmonic relations in the glottal spectrum become steeper as fundamental frequency rises. In a different type of glottal-wave change, relations between harmonics tend to remain the same despite a change in the fundamental frequency; the source spectrum in this case is simply shifted along the frequency and amplitude axes as a function of fundamental frequency. To account for these variations in the glottal source, at least three factors must be known: the sex of the speaker, the voice register in which he phonates, and the linguistic context in which the phonation occurs.
Control of vocal-tract length in speech
Authors: Riordan Carol J.
Published: October 2005

Essential for the correct production of vowels is the accurate control of vocal-tract length. Perkell [Psychology of Speech Production (MIT, Cambridge, MA, 1969)] has suggested that two important determinants of vocal-tract length are vertical larynx position and lip spreading/protrusion, often acting together. The present study was designed to determine whether constraining lip spreading/protrusion induces compensatory vertical larynx displacements, particularly on rounded vowels. Upper lip and larynx movement were monitored photoelectrically while French and Mandarin native speakers produced the vowels /i,y,u/ first under normal-speech conditions and then with lip activity constrained. Significant differences were found in upper-lip protrusion and larynx position depending on the vowel uttered. Moreover, the generally low-larynx position of rounded vowels became even lower when lip protrusion was constrained. These results imply that compensatory articulations contribute to a contrast-preserving strategy in speech production.
Reverberation and noise levels in sports areas
Authors: Penman Kenneth A. , Englund James S. , Stanier Norman
Published: October 2005

Seven indoor sports spaces at Washington State University were measured for sound reverberation and noise levels. The areas included two gynmasia, three aquatics areas, handball–racquetball courts, and a fieldhouse. Reverberation rates ranged from 2.0 to 8.5 sec. Sounds levels generated during typical classes averaged between 52 and 90 dB and frequently exceeded 100 dB.
Excess sound propagation loss in a stochastic environment
Authors: Schneider Hans G.
Published: October 2005

A general scheme is outlined to explain excess propagation loss in sound channels in which the stochastic variability of the environment is combined with the usual deterministic effects on propagation loss. As a result, the excess loss in a shallow-water sound channel is a function of both the bottom loss and the stochastic variability of the environment. A method, previously reported by the author [Acustica 35, 18 (1976)], to ’’handle’’ stochastic sound-speed variations in ray-tracing routines is applied to model the excess propagation loss for the Hudson Bay data. The model results are in excellent agreement with the experimental data without fitting the parameters and exhibit the dependence predicted above. Additional results show that difficulties usually inherent in deterministic ray tracing as, for example, the focusing of energy at the source depth and sharp caustics may easily be overcome by using a stochastic ray-tracing approach.
Acoustic focusing device with an interdigital transducer
Authors: Toda Kohji , Murata Yohji
Published: October 2005

We have devised a new type of simple acoustic focusing device with an interdigital transducer in which all radiation from each section of the transducer constructively interferes at a focal point in water. The position of the focal point of the device is variable by changing the carrier frequency of an electrical signal applied to the transducer. The device is applicable to the acoustic imaging in both transmitting and reflecting modes. This paper reports basic design considerations for the transducer and discusses operational performance.
Attenuation of surface-generated noise received deep in the ocean
Authors: Bradner Hugh , Parvulescu Antares
Published: October 2005

Theoretical curves are presented for attenuation of surface-generated noise versus frequency in the range of 15–50 kHz, and depth in the range of 200 m–5 km. These curves are used to predict surface-generated contribution to deep-ocean high-frequency acoustic background. The strongest surface-generated sound at frequencies above 40 kHz should be reduced to thermal noise level at 4-km depth.
Changes in ground noise levels of general aviation aircraft derived from changes in cockpit noise levels
Authors: Curtis George D.
Published: October 2005

Minimal data are available on the noise levels associated with various power settings of general aviation aircraft in their operations about an airport. Ample sound levels are available for most types, however, under a standard 1000-ft, high-power condition. It is suggested that these reference levels can be adjusted to climb, cruise, and other conditions by relative measurements made inside the cockpit.
Multimicrophone signal-processing technique to remove room reverberation from speech signals
Authors: Allen J. B. , Berkley D. A. , Blauert J.
Published: October 2005

It is well known that room reverberation can significantly impair one’s perception of sounds recorded by a microphone in that room. Acoustic recordings produced in untreated rooms are characterized by a hollow echolike quality resulting from not locating the microphone close to the source. In this paper we discuss a multimicrophone digital processing scheme for removing much of the degrading distortion. To accomplish this the individual microphone signals are divided into frequency bands whose corresponding outputs are cophased (delay differences are compensated) and added. Then the gain of each resulting band is set based on the cross correlation between corresponding microphone signals in that band. The reconstructed broadband speech is perceived with considerably reduced reverberation.
Variance bounds for passively locating an acoustic source with a symmetric line array
Authors: Carter G. Clifford
Published: October 2005

The maximum-likelihood (ML) processor is presented for passively estimating range and bearing to an acoustic source. The source signal is observed for a finite-time duration at several sensors in the presence of uncorrelated noise. When the speed of sound in an isovelocity medium and the sensor positions are known, the ML estimator for position constrains the source to sensor delays to be focused into a point corresponding to a hypothesized source location. The variances of the range error and bearing error are presented for the optimum processor. It is shown that for bearing and range estimation, different sensor configurations are desirable. However, if the area of uncertainty is to be minimized, then the sensors should be divided into equal groups with one-third of the sensors in each group.
Optical farfield method for studying the temperature dependence of ultrasound induced optical birefringence in liquids
Authors: Riley Ward A.
Published: October 2005

An optical farfield method is described for studying the temperature dependence of ultrasound induced optical birefringence in liquids. It requires fewer experimental measurements and assumptions than the more commonly used optical nearfield method and permits a more direct evaluation of theoretical parameters describing the effect. Experimental results are given for castor oil to illustrate the general nature of the results which can be obtained. The method can be extended to a wide range of acoustic frequencies and applied to various interaction mechanisms with only slight modification.
Influence of the thickness of tabs on the resonating properties of a quartz crystal
Authors: van Ballegooijen E. C. , Boersma F. , van der Steen C.
Published: October 2005

The behavior of the resonant frequencies of a quartz crystal, coated with electrodes and tabs of the same material, is investigated both theoretically and experimentally. It is pointed out that, when the thicknesses of the tab exceeds the sum of the thickness of the electrodes, the tab behaves like a resonator acting independently of the resonator determined by the conventional electrodes. In the model, which describes this phenomenon, use is made of trapped energy theory on thickness-twist modes. The results of numerical calculations on the theoretical model developed in this paper are in excellent agreement with the results obtained form the experiments. The additional resonant frequencies created by the presence of the tab together with the resonant frequencies related to the electrodes could possibly be used in the field of simultaneous mass and temperature determination. The principle of such a method is given in the paper.
Wave propagation in cylindrical shells with finite regions of structural discontinuity
Authors: Harari A.
Published: October 2005

Transmission loss in cylindrical shells due to a finite region of discontinuities is considered. The analysis considers a free traveling wave encountering finite number of stiffeners. The material and geometric properties of the stiffeners and the spacing may vary. Numerical examples are presented. The transmission efficiency and the reflection efficiencey are found for two cases of interest.
Comparison of signal-processing methods for obtaining images from arrays of sonar transducers
Authors: Jones C. H. , Kesner J. W.
Published: October 2005

This study was made to compare a variety of signal-processing methods that can be used with arrays of sonic or ultrasonic transducers to produce images. Four types of holographic methods are compared with conjugate or beam-scanned systems. Effects of amplitude quantization, phase quantization, uncorrelated noise, element spacing, and shading are illustrated. Signal-processing comparisions in the literature often consider only a single point source or a pair of equal strength sources. The authors used a line array of hydrophones 30 wavelengths long to image a set of 10 point sources of varying amplitudes and phases. The composite signal received on each element of the array was calculated. Computer-generated plots of signal level in decibels versus pattern angle are given for each processing method. The different processing techniques are evaluated on the basis of the range of target signal strengths that could be successfully imaged. Holographic processing requires twice as many transducers to obtain the same quality of image as conjugate processing. Amplitude or phase quantization makes it difficult to detect weak targets in the presence of strong signals.
Intensity perception. VIII. Loudness comparisons between different types of stimuli
Authors: Lim J. S. , Rabinowitz W. M. , Braida L. D. , Durlach N. I.
Published: October 2005

In this paper, we describe an extension of our preliminary theory of intensity resolution [Durlach and Braida, J. Acoust. Soc. Am. 46, 372–383 (1969)] to include loudness comparisons among different types of stimuli. The extended theory relates mean loudness matches to discrimination and provides a framework for the interpretation of results on the intrasubject variability of loudness comparisons. The predicted relation between mean loudness matches and discrimination is essentially the same as that proposed by Riesz [J. Acoust. Soc. Am. 5, 211–216 (1933)]. With regard to the variability of loudness comparisons, the extended model is essentially the same as the preliminary model except that a new term is included in the trace-mode memory variance to account for the dissimilarity of the stimuli being compared. The model is compared to some published data on loudness matching and discrimination and to some new data of our own on the variability of loudness comparisons obtained in a two-interval, roving-level, loudness-discrimination experiment.
Acoustic backscattering from thin air-filled spherical shells in water
Authors: Hunter J. L. , Layton M. R. , Fisch M. R.
Published: October 2005

Air-filled spherical shells in water have been insonified by a pulsed sinusoidal beam with a carrier frequency of 2 MHz. Experimental ka values ranged from 47 to 550. The bulk of the investigation was directed toward the spheres with the larger ka values; and for these, experimental results are compared with computations made for the intensity distribution in reflection from a perfectly reflecting spherical surface. It is found that the agreement is good if the thickness of the shell is less than 1/10 wavelength, but that marked departures occur for shells of appreciable thickness (of the order of a sound wavelength in the shell material).