bluuebunny/crossref_metadata_2025 huggingface dataset:
Coherent modes and boundary waves in a rough-walled acoustic waveguide
Authors: Tolstoy I.
Published: October 2005

The theory of Biot scatter was generalized to acoustically rough interfaces between fluids of differing densities and sound velocities by Tolstoy [J. Acoust. Soc. Am. 72, 960–972 (1982)] for the case kh≤1, k being the wavenumber and h the mean spacing between roughness elements. The present paper applies this approach to a harmonic point acoustic source in a fluid layer of thickness H and sound velocity c1, with: (1) a rigid floor with hard pebbles and (2) a soft floor of sound velocity c2≥c1 (Pekeris waveguide) with a monolayer of hard pebbles at the interface. For a ratio H/h=102 it is shown that: (a) pebbles have a marked influence on the usual coherent acoustic waveguide modes. This effect is best understood in terms of an alteration of the smooth-walled phase shift suffered by sound totally reflected from the bottom. This is particularly obvious for the Pekeris waveguide, for which the net effect on individual modes, for tightly packed spherical pebbles and for typical bottom acoustic parameters, is to increase their excitation amplitudes by factors approaching 2 near the limit of validity of the scatter theory (kh=1). (b) Pebbles may bring about the existence of a subsonic branch of the lowest mode, corresponding to a wall roughness boundary mode carried by the rough boundary. In the hard-bottomed model this branch always exists for k≥(εH)−1/2, where ε is a scattering parameter determined by the shape and volume per unit area of the scatterers. When combined with the criterion kh≤1 this condition yields a definite boundary wave passband. In the case of the Pekeris waveguide the passband is quite restrictive, being very sensitive to the ratio c2/c1; the boundary mode exists only for c2/c1≂1+δ, where δ≲0.008. For the special case c2=c1 the boundary wave is strongest and allows for an entirely subsonic mode having no analog in the smooth-walled model. The c2/c1 restriction being fairly stringent one must expect the chief practical effect of this kind of bottom roughness to be of the type (a).
Oboe normal mode adjustment via reed and staple proportioning
Authors: Benade A. H. , Richards W. Bruce
Published: October 2005

We have analyzed a simple theoretical model of an oboe, having a truncated conical air column of variable length and a reed assembly consisting of a tapered neck leading to a closed, cylindrical cavity. Proportions are chosen for this assembly so that its input admittance at the bottom of the neck is very closely the same function of frequency as the admittance of the missing conical segment at the apex of the air column for frequencies below the tone-hole cutoff. The most important requirements are that the reed assembly by itself possess the same volume and lowest-mode frequency as the missing apex. The intervals between the first-mode frequency and the below-cutoff frequencies of the second, third, and fourth modes of the model instrument can be made harmonic to within five cents as the length of the air column is varied to sweep the first mode through an octave range. We have investigated the effects of small variations in the proportions of the reed assembly on the natural frequencies of the model instrument. The results provide practical guidance for adjustment of the reed structure of a real oboe to special features of its own not-quite-conical acoustical behavior.
Effect of the branch-cut on the transformation between modes and rays
Authors: Gao Tain-Fu , Shang Er-Chang
Published: October 2005

In this paper the effect of the branch-cut on the transformation between the modes and rays is discussed. Characteristics of the bottom reflection coefficient on the ζ plane were analyzed in detail and a certain branch-cut was taken. Once the integral path of the generalized ray is deformed to the real axis of the ζ plane, the ray representation consists of ‘‘canonical’’ generalized ray and a ‘‘lateral term.’’ The mode representation and the ray representation are given as follows: Mode representation=∑∞nφn(r,z,z0) +∮b. Ray representation =∑∞lBl(r,z,z0) +𝒥∞l∮bl. It was found that the ‘‘canonical’’ generalized ray Bl and the normal mode φn were still connected by the Poisson summation relation strictly, as proved by our previous paper [Gao and Shang, J. Sound Vib. 80, 105–115 (1982)]. The sum of the ‘‘lateral term’’ of the ‘‘canonical’’ generalized ray was exactly equal to the part of the ‘‘lateral’’ wave in the mode representation:∮b=∑∞l∮bl.
Ultrasonic signal distortion and its effects on velocity measurements in dispersive constant-group-velocity media
Authors: Edwards P. L.
Published: October 2005

Results are presented of calculations made of distortion experienced by ultrasonic pulses in transmission through dispersive constant-group-velocity media, and the effects that it may have on velocity measurements. Three types of pulses were considered: a pulsed sine wave of constant amplitude, a pulsed sine wave with amplitude varying as sine-squared, and a rectangular pulse. It is shown that the individual waves in the pulsed sine waves move with the phase velocity of a continuous wave, and the envelope moves with the group velocity. It was also found that a pulsed sine wave in going a certain distance in a constant-group-velocity medium repeats itself, and midway between these distances is the negative of the values at the repetition distances. Because of this repetition phenomenon it is seen that the pulses propagating through the constant-group-velocity dispersive media do not spread as is normally the case in dispersive media. The envelopes of the propagated waves were also calculated, and in agreement with Brillouin’s results [Wave Propagation and Group Velocity (Academic, New York, 1960)] it was found that if the envelope contains negligible frequency components above the carrier frequency, then the envelope is not distorted in passing through a dispersive constant-group-velocity medium.
Glory- and rainbow-enhanced acoustic backscattering from fluid spheres: Models for diffracted axial focusing
Authors: Marston Philip L. , Langley Dean S.
Published: October 2005

Transmitted-wave contributions to backscattering from large spheres are calculated. Amplitudes due to glory rays are enhanced, relative to those of axial reflections, because of focusing. The glory pressure amplitudes are proportional to a(ka)1/2, where a is the sphere’s radius and k is the wavenumber. The model, though similar in form to one for optical scattering from air bubbles [D. S. Langley and P. L. Marston, Phys. Rev. Lett. 47, 913–916 (1981)], contains new features to facilitate the summing of amplitudes in a range of angles. An additional enhancement due to rainbow focusing is modeled for certain sound velocity ratios M; for these M the backscattered amplitude is proportional to a(ka)2/3. Major features of the exact scattering are reproduced by these models when ka=1000 and (with defects) ka=100. The enhancements are not intrinsically due to resonance. Applications to the design of passive sonar targets are noted.
Harmonics of S motion on bowed strings
Authors: Lawergren Bo
Published: October 2005

Lossless bowed strings have usually been thought to possess a motion discovered by Helmholtz in 1863. However, it was shown [Acustica 44, 194–206 (1980)] by the author that a more complicated standing wave motion, the S motion, exists on such strings provided both the bowing distance and bowing force are above certain minimum values. This paper explores S-motion harmonics which give arise to waveforms of considerable complexity on very thin strings. Equations are found which describe the experimentally determined waveforms as a function of bow position, bow velocity, and observation point. In the special case of square velocity waves at the bow point, the equations give quantized values for the bow/string sticking duration. That result agrees with Raman’s [Proc. Ind. Assoc. Adv. Sci. 15, 1–158 (1918)] prediction. In general, however, the waveforms have rounded corners.
Acoustic ground impedance meter
Authors: Zuckerwar Allan J.
Published: October 2005

A compact, portable instrument has been developed to measure the acoustic impedance of the ground, or other surfaces, by direct pressure-volume velocity measurement. A Helmholtz resonator, constructed of heavy-walled stainless steel but open at the bottom, is positioned over the surface having the unknown impedance. The sound source, a cam-driven piston of known stroke and thus known volume velocity, is located in the neck of the resonator. The cam speed is variable up to a maximum 3600 rpm, and since the cam has five lobes, the maximum acoustic frequency is 300 Hz. The sound pressure at the test surface is measured by means of a microphone flush mounted in the wall of the chamber. An optical monitor of the piston displacement permits measurement of the phase angle between the volume velocity and the sound pressure, from which the real and imaginary parts of the impedance can be evaluated. The prototype instrument can measure specific ground impedance at normal incidence up to 50 times the specific impedance of air. Detailed design criteria and results of measurements on an uncultivated grass field are presented.
Bottom reverberation in the oceans
Authors: Mackenzie Kenneth V.
Published: October 2005

The location of reverberation measurements have been declassified and are now identified.
Advantage of speaker as listener in a vowel identification task
Authors: Carney Arlene Earley , Edman Thomas , Strange Winifred , Jenkins James J.
Published: October 2005

Six talkers (two men, two women, and two children) listened to recordings of their own vowels, and to vowels produced by five other speakers both in isolation and pVp contexts. On the whole, subjects perceived their own vowel productions more accurately than those of the other speakers. Further, they perceived vowel tokens in a pVp context more accurately than in isolation even when they were presented with their own vowel tokens. Thus both speaker normalization and formant-transition information can be considered important variables in determining vowel identification.
Experience with new auditorium acoustic measurements
Authors: Bradley J. S.
Published: October 2005

As the inadequacy of reverberation time as a predictor of the acoustical quality of auditoria has been recognized, many new measures have been proposed. Of these, early-to-late sound ratios and interaural cross correlations are generally accepted as correlates of two major aspects of acoustical quality. Accordingly, the present work includes a large number of measurements of these quantities in halls ranging from 200 to 2500 seats. The purpose of the work was to improve familiarity with the newer measures, to provide more published data, and to explore the dependence of these measures on other quantities. Variations of the new measures were examined within and among halls. Halls that are apparently similar in terms of reverberation times showed clearly identifiable differences when early-to-late sound ratios were considered.
Two-tone suppression in auditory nerve fibers of the green treefrog (H
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Authors: Ehret Günter , Moffat Anne J. M. , Capranica Robert R.
Published: October 2005

The phenomenon of two-tone suppression was studied quantitatively in the peripheral auditory system of the green treefrog (Hyla cinerea). Linear relationships were found between best excitatory and best suppressor frequency, between response thresholds at these frequencies, between Q10dB-values of excitatory and suppressor tuning curves and best excitatory frequency, and between both Q10dB- values.
A new higher order dynamic theory for thermoelastic bars. I: General theory
Authors: Mengi Yalçin , Akkaş Nuri
Published: October 2005

A dynamic approximate theory capable of predicting high-frequency behavior of cylindrical thermoelastic bars is developed using a new theory. The cross section of the bar has an arbitrary shape and contains an arbitrary number of holes. The approximate theory is valid for all of the deformation modes such as flexural, longitudinal, torsional, etc. The use of the new method permits one to eliminate any inconsistency which may occur between lateral boundary conditions and the distributions of displacements or temperature assumed over the cross section of the bar. Accordingly, the method enables one to correctly describe the reflections of the waves propagating along the bar. This, in turn, makes the dispersive characteristics of waves in bars predicted by the approximate theory agree with those obtained from the exact theory without having to introduce any matching coefficients into the approximate theory.
Lingual vibrotactile sensation magnitudes: Comparison of suprathreshold responses for the tongue and hand
Authors: Fucci Donald , Petrosino Linda
Published: October 2005

The psychophysical method of magnitude production was used to obtain suprathreshold vibratory sensation magnitude functions from a group of ten young adult subjects. The test frequency was 250 Hz, and the body sites tested were the anterior midline section of the dorsum of the tongue, the thenar eminence of the right hand, and the distal pad of the middle finger of the right hand. Results showed that the mechanoreceptive mechanisms located within these three body locations can produce suprathreshold magnitude functions that are compatible with each other as well as with those described in the literature.
A note on the effect of velocity errors in computerized acoustic focusing techniques
Authors: de Vries D. , Berkhout A. J.
Published: October 2005

In computerized acoustic focusing procedures, the values of the propagation velocities of the media between (secondary) sources and registration area must be inserted into the wave-field extrapolation operator. These values are often only approximately known. In this discussion, the effect of velocity errors will be evaluated for several acoustic focusing techniques, active as well as passive.
Measurement of the acoustic internal source impedance of an internal combustion engine
Authors: Ross David F. , Crocker Malcolm J.
Published: October 2005

The standing wave tube technique has been adapted to measure the acoustic internal source impedance of an internal combustion engine. In order to implement this technique an extensive experimental facility was designed and constructed and simple test cases were evaluated for validity. In addition an adaptation of the standing wave tube method incorporating a random signal as the external driver sound source and digital data analysis techniques were introduced to reduce the experimental difficulty and time consumption. Normalized specific acoustic impedance data at a constant engine speed of 2200 rpm show little change with varying engine load conditions. Similar data at a constant engine load condition of 254-mm Hg exhibit more significant dependence on engine speed.
Effect of pressure on sound absorption in synthetic seawater and in aqueous solutions of MgSO4
Authors: Hsu C. C. , Fisher F. H.
Published: October 2005

Measurements have been made, at 25 °C, of the effect of pressure on sound absorption in Lyman and Fleming (LF) synthetic seawater from 30–300 kHz up to 307 atm. Similar measurements were made in 0.02M MgSO4 solution in a 0.02M MgSO4–0.6M NaCl solution. The decrease with pressure of absorption per wavelength (αλ) in LF seawater differs substantially from those reported by other investigators. The relaxation frequency, within experimental error, was found to be independent of pressure. For LF seawater, increasing pressure to 307 atm reduced absorption by 26.3%, very nearly the same as was observed previously (28.2%) for 0.5M MgSO4 solutions. The addition of 0.6M NaCl to the 0.02M MgSO4 solution decreased the absorption by a factor of 4 and the effect of pressure was found to be independent of the NaCl concentration. The Eigen and Tamm multistate dissociation parameters which best describe the pressure dependence of sound absorption and electrical conductance in a 0.02M MgSO4 solution predict a 21.4% decrease in absorption at 307 atm compared with the observed 19.6% decrease. However, these parameters yield an equilibrium constant which differs from the conductance derived value by a factor of 3.
Coarticulation in sequences of two nonhomorganic stop consonants: Perceptual and acoustic evidence
Authors: Repp Bruno H.
Published: October 2005

This study investigated whether any perceptually useful coarticulatory information is carried by the release burst of the first of two successive, nonhomorganic stop consonants. The CV portions of natural VCCV utterances were replaced with matched synthetic stimuli from a continuum spanning the three places of stop articulation. There was a sizable effect of coarticulatory cues in the natural-speech portion on the perception of the second stop consonant. Moreover, when the natural VC portions including the final release burst were presented in isolation, listeners were significantly better than chance at guessing the identity of the following, ‘‘missing’’ syllable-initial stop. The hypothesis that the release burst of a syllable-final stop contains significant coarticulatory information about the place of articulation of a following, nonhomorganic stop was further confirmed in acoustic analyses which revealed significant effects of CV context on the spectral properties of the release bursts. The relationship between acoustic stimulus properties and listeners’ perceptual responses was not straightforward, however.
Continuum approach to electroacoustic echoes in piezoelectric powders
Authors: Pouget J. , Maugin G. A.
Published: October 2005

Based on an oriented continuum model, a continuum approach for powders made of piezoelectric grains proposed in a previous work is applied to the study of electroacoustic echoes in resonant piezoelectric powders. The nonlinear equations obtained through this approach govern the piezoelectric oscillations and microgyration motion of each grain, as well as the global behavior of the powder and lead to the echo formation. The evaluations of the dynamical echo at 2τ and the memory echo at T+τ are presented. A memory phenomenon lying in the reorientation of grains due to a ponderomotive couple inside the powder sample is placed in evidence. The global response of the sample consists in summing up all the elementary electric polarizations associated with the piezoelectric oscillations of grains. Then the echoes are caused not only by the nonlinear interaction effects between the deformation of grains and the electric field, but also by a refocalization of collective oscillations which, after a complete dephasing period, gives a coherent signal through the inversion of the phase evolution. This continuum approach presents definite advantages over previous ones. Typical numerical values of parameters involved in this phenomenon as well as physical interpretations are given.
Experimental studies of low-frequency waterborne and sediment-borne acoustic wave propagation on a continental shelf
Authors: Brocher Thomas M. , Iwatake Brian T. , Lindwall Dennis A.
Published: October 2005

The loss rates for propagation of 5- to 40-Hz acoustic normal modes recorded on a shallow, sandy bottom off Nova Scotia were found to be strongly dependent on the azimuth and range of propagation. Beyond a certain range the propagation loss rates for signals just below the nominal cutoff frequency (calculated assuming a range-independent acoustic medium) differed only insignificantly from those just above the nominal cutoff, suggesting that propagation of signals at long ranges below cutoff may not be less efficient than those slightly above cutoff. Although it is commonly thought that scattering, conversion to shear waves, and surface wave generation are important causes of acoustic wave attenuation at low frequencies, our data indicate that nearly all loss arises from sediment attenuation. These results are of general interest because the near seafloor geology of many continental shelves is similar. We are less certain of the reasons for the lack of success in modeling the observed propagation loss using the parabolic approximation for frequencies well above the cutoff frequency. We do know that the spatial variation of the sound velocity, density, and thickness of the water column was not measured in sufficient detail during the experiment. More reasonable fits to the observed propagation loss at lower frequencies suggest that the parabolic approximation was not the major source of modeling error.
Investigation of chemical sound absorption in sea water. Part IV
Authors: Mellen R. H. , Browning D. G. , Simmons V. P.
Published: October 2005

The low-frequency boric acid relaxation mechanism in seawater has been identified as an acid-base exchange between the B(OH)3/B(OH)−4 and HCO−3/CO2−3 equilibria. Ion pairing with Ca2+ is also involved and a coupled-system model is proposed. Supporting experimental data for the CO2 exchange mechanism are presented. Similar exchanges with ammonia and silicic acid are also investigated.
Some simple expressions for the beamforming properties of focused high-resolution circular arrays, with applications to refocusing systems
Authors: Lynch James F.
Published: October 2005

Some simple analytical expressions for two important optical characteristics of focused high-resolution circular arrays are derived, specifically those for beam patterns and depths of field. The expressions generated, in addition to providing simple estimational tools for array design purposes, also lend themselves to straightforward interpretation in terms of the Fourier (farfield) and Fresnel (nearfield) kernels. Applications to refocusing arrays are discussed, as well as similarities and differences between such (sonar oriented) systems and radar and optical systems.
Optimum SNR enhancement of narrow-band signals in surface reverberation
Authors: Symons Frank W.
Published: October 2005

Theoretical performance capabilities of the optimum filter for maximization of signal-to-noise ratio (SNR) and a suboptimum approximation, easy to realize in practice, are compared to the conventional matched filter (designed for white noise only) in the case of low Doppler signals masked by surface reverberation. Spectrum models for surface backscattering as a function of local environmental parameters are based on recent results describing scattering from a subsurface bubble layer. Significant improvements in SNR in the low Doppler region as well as a dramatic dependence of performance on windspeed and direction, and the ratio of reverberation to uncorrelated noise power are predicted. Results serve as average performance limits to be compared to those obtained by algorithmic implementations of optimum and adaptive filters.
On the application of coherence techniques for source identification in a multiple noise source environment
Authors: Wang M. E. , Crocker Malcolm J.
Published: October 2005

Two approaches for noise source identification based on theory for multiple-input systems have been investigated. The concepts of the frequency response function and the coherent residual spectral density function were used to estimate the spectra of the noise sources that were accounted for in the multiple-input model. The key factors which determine the applicability of the techniques for noise source identification are found to be the degrees of coherence between the measured inputs. The experimental results showed that, for a noise system with multiple sources which were slightly coherent to each other, the techniques presented might be able to estimate the spectra of the noise sources, provided there was only modest measurement contamination.
Spatial coherence in semicircular noise fields
Authors: Sloboda Ronald S. , Manness Michael A.
Published: October 2005

An expression for the spatial coherence in a semicircular noise field is obtained which involves the function J0(x) and a single integral that can be evaluated by Gaussian quadrature. The semicircular noise model is motivated by an idealized representation of ship traffic plying a well-defined sea lane. The model coherence is characterized by a marked dependence on sensor orientation relative to the sea lane. An extension of the single lane model to the case of multiple parallel lanes yields a coherence expression which involves the weighted sum of J0(x) and the previously derived coherence function for a single lane. For this general situation the weighting factors depend on the relative power distribution among the lanes. Model calculations show good qualitative agreement with coherence estimates for d/λ≤1 which were computed from acoustic data for sensor orientations both parallel and perpendicular to known shipping lanes.
Linguistic modality effects on fundamental frequency in speech
Authors: O’Shaughnessy Douglas , Allen Jonathan
Published: October 2005

This paper examines the effects on fundamental frequency (F0) patterns of modality operators, such as sentential adverbs, modals, negatives, and quantifiers. These words form inherently contrastive classes which have varying tendencies to produce emphasis deviations in F0 contours. Three speakers read a set of 186 sentences and three paragraphs to provide data for F0 analysis. The important words in each sentence were marked intonationally with rises or sharp falls in F0, compared to gradually falling F0 in unemphasized words. These emphasis deviations were measured in terms of F0 variations from the norm; they were larger toward the beginning of sentences, in longer sentences, on syllables surrounded by unemphasized syllables, and in contrastive contexts. Other results showed that embedded clauses tended to have lower F0, and negative contractions were emphasized on their first syllables. Individual speakers differed in overall F0 levels, while using roughly similar emphasis strategies. F0 levels changed in paragraphs, with emphasis going to contextually new information.
Temporal integration, frequency resolution, and off-frequency listening in normal-hearing and cochlear-impaired listeners
Authors: Hall Joseph W. , Fernandes Mariano A.
Published: October 2005

Temporal integration for a 1000-Hz signal was determined for normal-hearing and cochlear hearing-impaired listeners in quiet and in masking noise of variable bandwidth. Critical ratio and 3-dB critical band measures of frequency resolution were derived from the masking data. Temporal integration for the normal-hearing listeners was markedly reduced in narrow-band noise, when contrasted with temporal integration in quiet or in wideband noise. The effect of noise bandwidth on temporal integration was smaller for the hearing-impaired group. Hearing-impaired subjects showed both reduced temporal integration and reduced frequency resolution for the 200-ms signal. However, a direct relation between temporal integration and frequency resolution was not indicated. Frequency resolution for the normal-hearing listeners did not differ from that of the hearing-impaired listeners for the 20-ms signal. It was suggested that some of the frequency resolution and temporal integration differences between normal-hearing and hearing-impaired listeners could be accounted for by off-frequency listening.
Upward shifts in the masking pattern with increasing masker intensity
Authors: McFadden Dennis , Yama Mark F.
Published: October 2005

Masking patterns obtained with forward-masking paradigms and relatively intense maskers sometimes have their peaks at the masker frequency and sometimes at a frequency well above it. Here it is shown that which outcome is obtained depends upon certain temporal parameters of the procedure. Specifically, the masking pattern for a 2000-Hz tone showed a gradual shift toward higher frequencies as masker intensity was increased from 65 to 95 dB SPL when long signals (about 50 ms) and long masker-to-signal intervals (about 50 ms) were used, but the effect was absent or smaller when the signals and intervals were short. This shift did not occur with a 750-Hz masker. Upward shifts in the masking pattern with increasing masker intensity are in accord with the view that the peak of displacement of the traveling-wave envelope migrates basally with increasing intensity—an idea that has frequently been suggested as an explanation of the so-called half-octave shift so routinely seen in auditory fatigue experiments.
P waves transient scattering by 2-D penetrable targets: A direct solution
Authors: Lesselier D.
Published: October 2005

The scattering of a transient acoustic P wave by a two-dimensional inhomogeneous fluid target is studied. An exact time-domain formulation of the pressure is introduced and discretized. Discrete pressures are then computed by marching on in time and space. The convergence of this step by step procedure is examined numerically. Comparisons are made in the frequency domain with results obtained by another method. Influence of the size and of the sound velocity of a circular target is investigated.
A model relating ultrasonic scattering measurements through liquid–solid interfaces to unbounded medium scattering amplitudes
Authors: Thompson R. B. , Gray T. A.
Published: October 2005

The relationship between scattering data obtained from ultrasonic experiments, in which the waves are excited and detected in a finite measurement geometry, and unbounded medium, farfield scattering amplitudes is considered. For a scatterer in a single fluid medium, a Green’s function approach is used to develop an approximate, but absolute, relationship between these experimental and theoretical cases. Electromechanical reciprocity relationships are then employed to generalize to a two medium case in which the scatterer is located in an elastic solid which, along with the ultrasonic transducer, is immersed in a fluid medium. The case explicitly considered is one in which the incident waves are quasiplanar over the volume of the flaw and the scattering amplitudes are slowly varying over the range of angles subtended by the receiving transducer. Analytic approximations are developed for the absolute relationship of the received transducer signal to the unbounded medium scattering amplitudes, and formal expressions for the error terms are presented. Preliminary experimental confirmation is reported for the cases of (1) L→L and T→T pulse–echo scattering from oblate spheroidal voids and (2) both pulse–echo and pitch–catch L→L scattering from spherical inclusions. With no adjustable parameters, good agreement for both the phase and absolute amplitude response is observed.
Acoustic intensity in the nearfield of two interfering monopoles
Authors: Krishnappa G.
Published: October 2005

The expressions for acoustic intensity in the nearfield of two interfering monopoles are derived. Both harmonic and random monopoles are considered in the present study. Based on a few sample calculations, the effect of different variables on nearfield acoustic intensity are illustrated. The expressions are similar for the two cases except the expression for the random monopoles contains an additional factor, coherence function relating the source strengths of the two monopoles.
Bone-conduction measurement and calibration using the cancellation method
Authors: Kapteyn T. S. , Boezeman E. H. J. F. , Snel A. M.
Published: October 2005

We have demonstrated that the cancellation method can be used for calibrating the bone-conduction vibrator in relation to the headphone of the audiometer and for an accurate measurement of a maximum bilateral conductive hearing loss. It is discussed how the correctness of the adjustment for the cancellation can be verified by recording brainstem auditory evoked potentials.
Authors’ reply to ‘‘Comments on ‘Precise model measurements versus theoretical prediction of barrier insertion loss in presence of the ground’ ’’
Authors: Nicolas J. , Embleton T. F. W. , Piercy J. E.
Published: October 2005

It is explained, through quotations from several previously published papers, that the deviations of several curves in the cited paper are due to the elimination of one of two partially compensating theoretical approximations.
Acoustic propagation in resonant axisymmetric cavities enclosing an inhomogeneous medium. Part II: Cavity with center body
Authors: El-Raheb Michael , Wagner Paul
Published: October 2005

Analysis of acoustic propagation of standing waves in rigid axisymmetric cavities enclosing an inhomogeneous medium is extended to cavities with concentric center bodies. An approximation is adopted to study the problem parametrically. Results from this analysis are checked against a more accurate numerical model which relies on surface elements and a Green’s function modified to account for medium inhomogeneity. The center body may enhance the transfer of energy through the c gradient in the case of transverse waves corresponding to the lowest radial harmonic.
Estimation of mutual information from limited experimental data
Authors: Houtsma Adrianus J. M.
Published: October 2005

To obtain an unbiased estimate of mutual information from an experimental confusion matrix, one needs a minimum number of trials of about five times the number of cells in the matrix. This study presents a computer-simulated approach to derive unbiased estimates of mutual information from samples of considerably fewer data.
Beam splitting at the reflection of elastic waves by a periodic surface profile
Authors: Roberts Ronald , Achenbach Jan D. , Ko Ray-Tse , Adler Laszlo , Jungman Alain , Quentin Gerard
Published: October 2005

Theoretical and experimental results are presented which exhibit the splitting of a beam of elastic waves into two beams, on reflection at a traction-free surface of periodic profile. The beam splitting is more pronounced for a narrower incident beam and for frequencies close to a resonance frequency of the profile.
Author’s comments on the comments of Sidhu and Singh on the paper ‘‘Reflection of elastic waves under initial stress at a free surface: P and S
V motion’’ [J. Acoust. Soc. Am. 7
2, 255–263 (1982)]
Authors: Chakraborty M.
Published: October 2005

The author replies to the comments by Sidhu and Singh [J. Acoust. Soc. Am. 74, 1640–1642 (1983)] and by Norris [J. Acoust. Soc. Am. 74, 1642–1643 (1983)].
Ring model of railroad wheel vibrations
Authors: Haran Shivan , Finch R. D.
Published: October 2005

This paper presents a model for prediction of the vibration characteristics of railroad wheels. Earlier workers showed that the ring theory gave a good explanation of the ratio of resonant frequencies in the railroad wheel, assuming flexural modes are excited in the rim. In the present work, the wheel is modeled by taking the flange, the rim, and the plate as a series of elastically connected rings. The differential equations governing the normal mode flexural vibrations are developed for such a system. The free vibration of the system with displacement out of the plane of the wheel was studied. Modifications were made to include wear on the flange and tread. Hoop stress in the rim was also modeled. The results agree well with those from other theoretical models and also with experimental values.
Measurements of transmission fluctuations at three ranges for refracted paths through the deep ocean
Authors: DeFerrari H. A. , Davis R. I. , Nguyen H. , Tusting R. F. , Williams N. J.
Published: October 2005

Fluctuations of acoustic transmission were measured for resolved refracted–refracted ray paths at three long ranges in the deep ocean (258, 410, 560 km). A moored broadband source with center frequency of 460 Hz transmitted continuously for a period of several days from each range. Received signals were processed to give time histories of complex pulse response. Fluctuation statistics are computed for the carrier line, the combined multipath signal and for time gated arrivals associated with predicted paths. Refracted arrivals are identified by ray models and statistics are computed for resolved paths, unresolved doublets of upgoing and downgoing rays and the combined multipath. A second mooring was used to measure temperature fluctuations associated with internal waves and for estimating the magnitude and vertical coherence of sound-speed fluctuations during the acoustic experiments. We report statistics of fluctuations and compare measurement with predictions of A Theory of Sound Transmission Through a Fluctuating Ocean, edited by Flatté (Cambridge U.P., Cambridge, 1979). Λ and Φ parameters of the theory are computed numerically using environmental measurements of sound-speed fluctuations as input. Estimates of the mean square phase fluctuations using the Φ parameter are in agreement with measurements for all three ranges. Most paths at all ranges exhibit regular fading characteristics of time varying multipath interferance. Some paths at the shorter range exhibit more rapid fading and have decorrelation times, moments, and pulse spreading more characteristic of full saturation than paths of the longer ranges. Neither variations of environment fluctuations, details of the ray geometry nor computed Λ–Φ values explain these short-range results.
Intensity fluctuations. Part II: Comparison with the Cobb experiment
Authors: Ewart T. E. , Macaskill C. , Uscinski B. J.
Published: October 2005

The intensity fluctuations measured at 4 and 8 kHz in the Cobb experiment have been available for nearly 10 years and in that time have not successfully been predicted theoretically. We show that multiple scatter effects must be considered, and that neither the Born nor the Rytov approximation to the scattering formulation is appropriate. A companion paper [J. Acoust. Soc. Am. 74, 1474–14832  (1983)] provides the theoretical background for this work by presenting a general form of the analytical solution to the fourth moment equation in two dimensions for a point source transmission. We use the parameters of the Garrett–Munk model of the internal wave field appropriate to the Cobb experiment oceanographic regime to obtain the correlation functions of the acoustic refractive index field, and then predict the intensity fluctuations. We discuss corrections to the predicted spectrum that are due to fine structure effects and tidal motions. We include a discussion of the scattering parameters Γ and X, which are the scattering and range scaling parameters of the moment equation formulation, and the parameters of the path integral formulation, Γ and Φ. We present a discussion of the measured correlation functions taken during a more recent experiment at Cobb seamount and indicate the directions we need to take to bring the scattering predictions based on internal waves and finestructure into closer agreement with experiment.
Effect of vibrational relaxation on rise times of shock waves in the atmosphere
Authors: Bass Henry E. , Ezell Jean , Raspet Richard
Published: October 2005

The effect of atmospheric absorption including vibrational relaxation absorption of N2 and O2 on shock wave rise times was presented in an earlier paper [J. Acoust. Soc. Am. 64, 1208–1210 (1978)]. In this paper, velocity dispersion due to these same relaxation mechanisms is included. The added effect of dispersion is to lengthen predicted rise times except for large amplitude (peak pressure greater than 100 Pa) shocks. The rise times computed with both absorption and dispersion are in excellent agreement with experimental data. This finding suggests that atmospheric turbulence has little or no effect on measured rise times.
Acoustic wave propagation in randomly distributed spherical particles
Authors: Machado João Carlos , Sigelmann Rubens A. , Ishimaru Akira
Published: October 2005

An experimental study has been conducted on the propagation of ultrasound at 1 and 5 MHz in a random medium consisting of a suspension of polystyrene spheres (mean diameter 0.589 mm, standard deviation 0.666 mm) in a solution of water and sugar. A burst of sine waves with repetition frequency of 200 Hz and pulse width of 15–20 μs was transmitted to the random medium. The experimental results for the attenuation and pulse broadening for the transmission and backscattering plus attenuation as a function of the receiving angle for transmission at different frequencies and particle concentrations are presented in this paper. Comparisons are given with some theoretical calculations.
Intensity discrimination as a function of level and frequency and its relation to high-frequency hearing
Authors: Florentine Mary
Published: October 2005

This paper examines how intensity discrimination depends on the test frequency, the level, and the subjects’s high-frequency hearing. Three experiments were performed. In the first experiment, intensity discrimination of pulsed tones was measured as a function of level at 1 and 14 kHz in five listeners. Results show less deviation from Weber’s law at 14 kHz than at 1 kHz. In the second experiment, intensity discrimination was measured for a 1-kHz tone at 90-dB SPL as a function of the cutoff frequency of a high-pass masking noise in two listeners. Results show that the audibility of very high frequencies is important for frequency discrimination at 1 kHz. The DL increased by a factor between 1.5 and 2.0 as the cutoff frequency of the noise was lowered from 19 to 6 kHz. In the third experiment, thresholds from 6 to 20 kHz and intensity discrimination for a 1-kHz tone was measured in 12 listeners. Results show that the DLs at 80-dB SPL are correlated with the ability to hear very high frequencies. Results of all three experiments are consistent with the multiband version of the excitation-pattern model for intensity discrimination [Florentine and Buus, J. Acoust. Soc. Am. 70, 1646–1654 (1981)].
Signal detection in nearly Gaussian skewed noise
Authors: Huang Y. F. , Thomas J. B.
Published: October 2005

The problem of detecting a constant signal in nearly Gaussian skewed noise is studied in this paper. Sensitivity of both the linear detector and the sign detector are examined. It is shown that the performance of the linear detector deteriorates when the noise distribution becomes skewed. On the other hand, the sign detector appears to be less sensitive to the noise skewness. Furthermore, a modification of the linear detector is proposed. This modified scheme, when the noise skewness measure is small, will behave almost like the linear detector in Gaussian noise.
Thermoviscous effects on acoustic scattering by thermoelastic solid cylinders and spheres
Authors: Lin Wen H. , Raptis A.C.
Published: October 2005

This paper presents analytic solutions and numerical results of the scattering of plane sound waves from a thermoelastic circular cylinder and from a thermoelastic sphere in an infinite, thermoviscous fluid medium. The thermoelastic properties of the cylinder and the sphere and the viscosity and thermal conductivity of the surrounding fluid are taken into consideration in the solutions of the acoustic-scattering problems. We started with examining the acoustic field equations in thermoviscous fluids and in thermoelastic solids from the standpoints of continuum mechanics and thermodynamics, and then presented the normal-mode solutions to, and numerical examples of, the acoustic scattering by a single cylinder and a sphere. The acoustic parameters of interest are the farfield scattering pattern, the acoustic-radiation force, and the absorption and scattering cross sections. These parameters were first derived in closed forms and then evaluated numerically for a given set of material properties.
The scattering integral equation for surfaces containing curvature discontinuities
Authors: Bojarski Norbert N.
Published: October 2005

The conventional formulations of the acoustic and electromagnetic scattering integral equations, which are valid only for surfaces with continuous and differentiable curvature, are generalized to surfaces containing curvature discontinuities. It is argued that these generalizations are essentially a generalization of the 1859 and 1882 Kirchhoff integration of the scalar and vector wave equations, respectively, as well as a generalization of the 1938 Stratton–Chu integration of Maxwell’s equations.
The reduction of blast noise with aqueous foam
Authors: Raspet Richard , Griffiths S. K.
Published: October 2005

Experiments were performed to investigate the potential of water-based foams to reduce the farfield noise levels produced by demolitions activity. Measurements of the noise reductions in flat-weighted sound exposure level (FSEL), C-weighted sound exposure level (CSEL), and peak level were made for a variety of charge masses, foam depths, and foam densities (250:1 and 30:1 expansion ratio foams). Scaling laws were developed to relate the foam depth, foam density, and charge mass to noise reductions. These laws provide consistent results for reductions in the peak level, FSEL and CSEL up to a dimensionless foam depth of 2.5. A two part model for the mechanisms of sound level reductions by foam is suggested.
Experimental investigation on the effect of some temporal factors of nonsteady noise on annoyance
Authors: Hiramatsu Kozo , Takagi Koichi , Yamamoto Takeo
Published: October 2005

The effects of some temporal factors of nonsteady noise on annoyance was investigated by means of six experiments. The factors are rising speed, fluctuation speed, fluctuation frequency, and fluctuation deviation. The results show that the ratio of annoyance and the rising speed are in linear relation in log–log coordinates and the annoyance increase with the increase of rising speed from 25 to 1000 dB/s corresponds to the increase of sound pressure level of 2.6 dB. The fluctuation speed, the fluctuation frequency, and the fluctuation deviation have little effect on annoyance provided the equivalent sound level (Leq) is constant. The validity of some rating scales of fluctuating noise is discussed on the basis of the present experimental results.
A comparison of two techniques for measured iodine release as an indicator of acoustic cavitation
Authors: Ciaravino Victor , Miller Morton W.
Published: October 2005

A spectrophotometric and a radioactive-label technique were used to assess for acoustically induced iodine release from sodium iodide. For both techniques there was a dose-dependent relationship between the percentage of iodine released and the ultrasound intensity (1 MHz, ISP to 30 W/cm2, continuous wave for 1 min). Iodine release decreased with increased atmospheric pressure or increased concentrations of the radical scavenger cysteamine, thus confirming that the release was related to cavitational processes.
Pulsed spectrophone measurements of vibrational energy transfer in CO2
Authors: Bass Henry E. , Yan Hai-Xing
Published: October 2005

A pulsed spectrophone has been developed to study vibrational energy transfer processes in gases. CO2 was chosen as the test gas to allow comparisons with other methods. The spectrophone proves to be a powerful tool to measure relaxation rates and study relaxation pathways when coupled with other measurement techniques. All the micro- and macroscopic processes which affect the spectrophone response must be considered simultaneously in order to interpret the measured temporal evolution of pressure following excitation. Formulas which include a generalized treatment of multilevel systems and important macroscopic processes are presented. The experimental data are represented in terms of characteristic times of the pressure waveform and amplitudes of pressure changes. At intermediate (20 Torr and above) pressures, collisional energy transfer rates and mechanisms have the greatest influence on computed waveforms. Spontaneous emission has an obvious effect on the zero pressure intercept of the characteristic times. Acoustic propagation and thermal conduction determine the rate at which the gas, once perturbed, returns to equilibrium; at intermediate and higher pressures, acoustic propagation is found to be most important. The assumed rates of energy transfer and the relaxation mechanisms are varied to give computed pressure waveforms which agree with the measured spectrophone response (characteristic times and amplitudes), and which are simultaneously consistent with measurements using other techniques. This process indicates that the path of energy transferred from CO2 (001) to CO2 (040) is consistent with all experimental observations.