bluuebunny/crossref_metadata_2025 huggingface dataset:
Examination of attenuation at very low frequencies using the deep-water ambient noise field
Authors: Kibblewhite A. C. , Shooter J. A. , Watkins S. L.
Published: October 2005

In a recent experiment employing a number of hydrophone systems deployed at various positions in the Northeast Pacific Ocean, several operational periods were dedicated to an ambient sea-noise study. Signals received at hydrophones distributed at various depths throughout the water column were analyzed to characterize the noise field at each site. The results obtained revealed a noise-level dependence on frequency, hydrophone depth, and sound velocity profile. The general features of the noise field could be interpreted in terms of distant shipping and local wind effects, the two major directional noise sources believed to be dominant in the deep ocean. This paper discusses some specific features of the noise field and examines the implication of these to the anomalously high attenuations reported so often at frequencies below 100 Hz.

Subject Classification: [43]30.20, [43]30.70.
Shock spectrum of a two-degree-of-freedom nonlinear vibratory system
Authors: Root R. M. , Cunniff P. F.
Published: October 2005

The shock spectrum of the foundation or isolator mass of a two-degree-of-freedom vibratory system was studied. The system had a cubic hardening elastic nonlinearity in the foundation or isolator restoring force. The system was impulsively shocked, and analytical, experimental, and numerical methods used to determine the resulting shock spectrum. The system was studied theoretically in two ways. An analytic solution was developed using a perturbation expansion of the nonlinear equations of motion, combined with an analytic solution for the shock spectrum due to the motion. A numerical solution to the nonlinear equations of motion was developed and used to verify the range of validity of the solution developed from the perturbation expansion. The nondimensional parameter of the perturbation expansion was found to be directly dependent on the coefficient of the cubic hardening spring and the square of the initial velocity of the foundation or isolator mass, and inversely dependent on the generalized mass and the fourth power of the natural frequency of each linear mode. The numerical solutions of the equations of motion verified that variations in this parameter defined the degree to which the behavior of the nonlinear system departed from the behavior of the linear system. The theoretical studies predicted that the cubic hardening spring would cause the peaks in the shock spectrum corresponding to the linear natural frequencies to be shifted to higher frequencies, and that significant additional peaks would be introduced at combinations of the shifted frequencies. An experimental study of a two-degree-of-freedom system with a cubic hardening spring was undertaken. The experimental results verified shifting of the frequencies of the peaks and introduction of additional peaks in the shock spectrum.

Subject Classification: [43]40.40, [43]40.30, [43]40.60.
Correlation of nonlinear orifice impedance
Authors: Panton Ronald L. , Goldman Allen L.
Published: October 2005

Dimensional analysis of the orifice impedance problem produces several sets of nondimensional variables which may be used to correlate nonlinear orifice behavior. Published experimental data on thin orifices were examined and it was found that tests with oil, water, and air can be correlated. Graphs of orifice resistance are given in nondimensional forms that are useful over a wide range of conditions. The form for resistance is R/ρ (νω)1/2 as a function of an aspect ratio parameter l/d, an orifice velocity parameter V/(νω)1/2, and a diameter-viscous parameter d/(ν/ω)1/2. For thin orifices the resistance is independent of d/(ν/ω)1/2 when this parameter is greater than 10. Nonlinear effects begin when V/(ν/ω)1/2=3. This parameter compares the displacement amplitude to the viscous diffusion length. The reactance end correction δ was normalized by the Rayliegh value of 8d/3π and correlated using the variables l/d, V/ωd, and d/(ν/ω)1/2. Again thin orifices show no dependence on d/(ν/ω)1/2 for values greater than 20 and the nonlinear reactance region begins at V/ωd=0.1. Thus, different parameters govern the onset of nonlinear resistance and reactance.

Subject Classification: [43]85.20, [43]85.50; [43]28.60.
Measurement of the acoustic impedance of an orifice under a turbulent boundary layer
Authors: Goldman A. L. , Panton Ronald L.
Published: October 2005

The acoustic impedance of an orifice under a turbulent boundary layer was measured. A single orifice, 0.508 cm in diameter and 0.32 cm thick, was tested in a wind tunnel where the velocity was varied from 16 to 30 m/sec. An impedance tube mounted behind the orifice was operated at frequencies from 250 to 2200 Hz with sound pressure levels from 85 to 140 dB. It was found that the resistance and reactance end correction could be nondimensionalized as R/ρ (νω)1/2 and δ/δeo, respectively, and correlated as functions of l/d, ωd2/ν, u*d/ν, and V/u*. The symbols are R resistance, ρ density, ν kinematic viscosity, ω frequency, δ end correction, δeo linear end correction without flow, l orifice thickness, d diameter, u* boundary layer friction velocity, and V acoustic velocity amplitude. Nonlinear behavior occurred when V/u* was greater than three. Amplitudes greater than three were only obtained in the 250-Hz tests, however, at this frequency the V/u*≳3 criteria was independent of u*d/ν. In the linear range R/ρ (νω)1/2 versus ωd2/ν produced U shaped curves parametrically dependent on u*d/ν. When u*d/ν was greater than 250 the resistance with flow was greater than the no flow for all frequencies. If u*d/ν was less than 250 there was a frequency range where the resistance with flow was less than the no-flow resistance. The reactance end correction as a function of these same variables gave an inverted U shape. Above u*d/ν=250, the reactance decreases with flow for all frequencies, while below 250 there is a frequency range in which the reactance increases over the no-flow reactance.

Subject Classification: [43]85.20; [43]28.60.
Multipath acoustic propagation with a moving source in a bounded deep ocean channel
Authors: Clark J. G. , Flanagan R. P. , Weinberg N. L.
Published: October 2005

An analysis is presented for coherent multipath propagation between a moving source and a fixed receiver. The major mulitpath effects of source motion are frequency spreading range or emission-coordinate spreading, and travel-time spreading of the multipath arrival set. These are analytically related to the signal propgation as functions of time and velocity. Computer simulations with a shallow moving source and a fixed receiver below the SOFAR channel are presented which clearly illustrate the contributions of source motion developed in the analysis.

Subject Classification: [43]30.20 [43]20.20..
Coupled power equations for cylindrically spreading waves
Authors: McDaniel Suzanne
Published: October 2005

Equations are derived for the power transferred between normal modes due to scattering from weak, random variations in the horizontal strati- fication of the ocean. Perturbation theory is used to obtain results for a horizontally isotropic medium. The validity of these results is discussed for the case of dorward scattering. The modal power transfer given by two- dimensional model will, in many cases, suffice to estimate modal power transfer.

Subject Classification: [43]30.20; [43]20.15.
Transient response of laminated composite plates subjected to transverse dynamic loading
Authors: Whitney James M. , Sun Chang-Tsan
Published: October 2005

Transient solutions are presented for an infinitely long simply supported composite plate subjected to either a uniform or line concentrated dynamic pressure at the upper surface of the plate. A rectangular pulse, triangular pulse, and sinusoidal pulse are considered and dynamic load factors determined for maximum values of deflection, bending stress, and interlaminar shear stress as a function of pulse dwell time. Effect of pulse shape on deflection and stresses is also considered. These numerical results are obtained for graphite/epoxy symmetric angle-ply laminates.
Middle ear transmission in cats with experimentally induced tympanic membrane perforations
Authors: Kruger Barbara , Tonndorf Juergen
Published: October 2005

A small perforation (2 mm2) was placed in the posterosuperior quadrant of the feline tympanic membrane (TM). Sound pressures (amplitudes and phases) required for a 10-μV round window cochlear microphonic (CM) output were measured at third-octave intervals from 200 to 4000 Hz (a) in front and behind the TM, (b) in open and closed sound systems, and (c) before and after perforation, as were the corresponding voltages across the transducer. Sound pressure (SP) changes in front of the TM after perforation revealed low-frequency losses, identical in shape and magnitude for both open and closed sound systems, that vary inversely with frequency at a rate of 12 dB/octave below 1600 Hz. The transducer voltage changes, concomitant with SP’s in front of the TM necessary to produce the criterion CM, paralleled the SP changes only in the open system. However, considerably larger voltage changes were found in the closed system, especially between 630 and 2000 Hz. Furthermore, from the SP’s measured on both sides of the TM, the mean effective sound pressure (SPeff) acting on the TM was calculated. The changes in SPeff, taken in reference to a constant CM output, demonstrate that a small TM perforation produces a 10-dB frequency-independent loss in transmission.
Subjective duration and temporal masking patterns of broadband noise impulses
Authors: Fastl Hugo
Published: October 2005

Subjective duration of broadband noise impulses is investigated. At equal subjective duration, the physical durations of impulses may differe by up to 10%, the accruacy of duration measurements. For impulses shorter than 500 msec, subjective doubling of duration requires a ratio of physical durations larger than two, typically 2.6. This result is achieved by the method of constant stimuli. The subjective duration of impulses can be traced back to the corresponding temporal masking patterns. A model of subjective duration is proposed as follows: Whenever the sound pressure level of the temporal masking pattern reaches a critical value, marks are set. The temporal distance between these marks corresponds to the subjective duration of the sound. Applying the model, subjective doubling of impulse durations can be predicted from temporal masking patterns with an accuracy of typically 10%.
Integrated acousto-optical effect produced by pulsed sound fields
Authors: Cook Bill D.
Published: October 2005

Precision acousto-optic transducer calibration requires an understanding of the influence of the nearfield of a transducer on the integrated optical effect. This influence has previously been studied theoretically for continuous waves from circular and rectangular plane piston transducers [F. Ingenito and B. Cook, J. Acoust. Soc. Am. 45, 572–577 (1969)]. For pulsed ultrasonic transducers, the nearfield can be considerably different than for continuous waves. The influence of the differences on the integrated acousto-optic effect is analyzed by linear superposition. For a circular transducer with piston motion, it is possible to reduce the formulation with appropriate approximations and restrictions to a universal form. For long pulses, i.e., greater than ten wavelengths, the integrated acousto-optic effect is the same as for continuous waves. For shorter pulses, the nearfield can influence the pulse shape, but not substantially. This influence is dependent on field position and can be minimized.
Natural frequencies of elastically supported orthotropic reactangular plates
Authors: Magrab Edward B.
Published: October 2005

An expression is derived from which the natural frequencies of a rectangular orthotropic plate, under any combination of simply supported, elastically supported, or clamped boundary conditions, can be obtained. The Mindlin–Timoshenko theory, which includes the effects of transverse shear and rotary inertia, is used to describe the plate motion. The solution is obtained with a previously developed extension of the Galerkin technique. Comparison of results with the limited results of previous investigations is very good. New results are presented for the fundamental frequencies of rectangular and square plates for boundary conditions on all four edges that vary continuously from simply supported to clamped, and for various combinations of length-to-thickness ratios and material constants. Additional results are presented for orthotropic plates simply supported and clamped on all four edges.
Response of fluid-filled porous media to a transient input
Authors: Mengi Yalcin , McNiven Hugh D.
Published: October 2005

The theory predicting the dynamic behavior of fluid-filled porous media is due to Biot. In the theory he accounts for the relationship between the friction force between the two phases, solid and fluid, and the average relative fluid velocity by means of what he calls a viscodynamic operator. Recognizing that the operator makes the solution of the equations difficult, he presents an asymptotic approximation of the operator and introduces it into the equations for linear momentum, which results in an approximate theory which can be used to study wave propagation in the media. Study of the approximation shows that it is particularly suitable when the velocity of the fluid relative to the solid varies gradually with time. This raises the suspicion that the theory may not predict accurately the behavior of transient waves, especially near the head of the pulse. Accordingly, in this paper another approximate theory is developed, following the lead of Biot, this one appropriate when the relative velocity varies abruptly with time. A problem involving transient responses in a fluid-filled porous half-space is solved and the responses predicted by the ’’gradual’’ and ’’abrupt’’ theories are compared. The uneasiness concerning the appropriateness of the Boit theory for transient-wave-propagation problems proves to be without foundation.
Moving-load stability of a circular plate on a floating central collar
Authors: Mote C. D.
Published: October 2005

The eigenvalue problem and transverse response of a circular plate, that is free at the periphery and that slides freely along the axis of symmetry without bending rotation, are theoretically analyzed. The occurance of eigenvalues in the boundary conditions is accounted for with an extended operator definition in the equation of transverse motion. The stability of these plates under concentrated loads moving at uniform speed is analyzed for (i) harmonic transverse loading and (ii) loading proportional to transverse displacement and velocity. The harmonic loading case leads to a classical, critical-speed analysis. The proportional loading case represents the excitation of the plate by transverse position guides. The number, orientation, and mechanical properties of the guides determine the transverse stability of the plate-guide dynamic system.
Qualification procedures for free-field conditions for sound-power determination of sound sources and methods for the determination of the appropriate environmental correction
Authors: Hübner Gerhard
Published: October 2005

For determination of sound power of sources by the ’’method of enveloping measurement surfaces,’’ the test environment should provide a measurement surface which lies (1) outside the nearfield of the sound source under test and (2) inside a sound field free of undesired sound reflections from room boundaries or reflecting objects near the source. Methods to check the free-field conditions and to qualify a given measurement surface for an actual source under test are (1) the absolute comparison test using a (small) calibrated reference sound source, (2) the relative comparison test using a small test sound source which radiates broadband noise that remains essentially constant during the measurement, and (3) the reverberant test, which requires measurement of reverberation time. Method 3 is only applicable in closed spaces (rooms). Methods 1 and 2 may be used in rooms and outdoors. Methods 1 and 2 require replacing the source under test by the reference sound source or test sound source in the test site. If the source under test cannot be removed, methods 1 and 2 still allow qualification for free-field conditions, with less accuracy. This paper deals mainly with the relative comparison test (method 2) and gives information about the accuracy of the determination of the environmental corrections factor K under different field conditions.
Improving the acoustic environment for i
n s
i
t
u noise measurements
Authors: Angevine O. L.
Published: October 2005

When using in situ measurements to characterize the noise of a machine in other installations, the measurement space must meet certain qualifications, as outlined by Hübner. In cases where nearby walls and other reflective surfaces interfere, such surfaces may be given a temporary sound-absorptive treatment. If the machine is symmetrical, measurements on an unobstructed side can be accepted as typical of both sides. Temporary barriers may be used to shield measuring microphones from the direct noise of other nearby noise sources which cannot be turned off. While some installations are hopelessly unsuitable for measurements of typical machine noise, such methods can often make an installation acceptable. Similar approaches can be applied to special-purpose facilities used for noise measurements of machines and engines. An effective facility can be developed at minimum cost for making free-field measurements above a reflecting plane to distances of at least 5 ft. A recently developed facility of this type in a vacant automotive collision shop was made by covering less than 50% of the hard walls and ceiling with panels of acoustic absorption. Nearly spherical speading (4–6 dB per distance doubling) was obtained out to 24 ft for frequencies above 250 Hz.
Theory of binaural interaction based on auditory-nerve data. II. Detection of tones in noise
Authors: Colburn H. Steven
Published: October 2005

A binaural interaction model is described in which the peripheral transduction from acoustical waveforms to firing patterns on the auditory nerves is included explicitly. Quantitative predictions are compared with available data on the binaural detection of low-frequency tones masked by Gaussian noise. The model describes the parametric dependence of masking-level differences in almost all available data.
Role of dynamic cues in monaural and binaural signal detection
Authors: Grantham D. Wesley , Robinson Donald E.
Published: October 2005

Three experiments were carried out to investigate the importance of dynamic cues in monaural and binaural detection tasks. All experiments employed a two-interval forced-choice procedure, in which the signal, a 500-Hz tone, 128 msec in duration, was added to the masker prior to gating in one of the two intervals. Both monaural (signal and masker diotic: M0–S0) and binaural (diotic masker, signal phase-reversed in one ear relative to the other: M0–Sπ) conditions were investigated. The masker (70 dB SPL) was either a tone of 500 Hz (Experiment 1), a 500-Hz carrier tone modulated by a 50-Hz tone (Experiment 2), or a 500-Hz carrier tone modulated by a band-pass noise centered at 60 Hz (Experiment 3). The angle of addition of the signal to the masker (α) was either 0°, 45°, 90° or 135°. In general, for all values of α, S0 thresholds increased from Experiment 1 to Experiment 3, indicating that monaural signal detection is more difficult in a dynamic than in a static environment. Sπ thresholds did not change significantly from Experiment 1 to Experiment 2, thus giving no support to the notion that detection of regularly varying interaural cues (at a modulation frequency of 50 Hz) is easier than detection of static cues. However, Sπ thresholds in Experiment 3 were slightly higher than in Experiment 2, indicating that detection of randomly fluctuating interaural cues is more difficult than detection of regularly fluctuating cues.
On detecting nasals in continuous speech
Authors: Mermelstein Paul
Published: October 2005

The acoustic manifestation of nasal murmurs is significantly context dependent. To what extent can the class of nasals be automatically detected without prior detailed knowledge of the segmental context? This contribution reports on the characterization of the spectral change accompanying the transition between vowel and nasal for the purpose of automatic detection of nasal murmurs. The speech is first segmented into syllable-sized units, the voiced sonorant region within the syllable is delimited, and the points of maximal spectral change on either side of the syllabic peak are hypothesized to be potential nasal transitions. Four simply extractible acoustic parameters, the relative energy change in the frequency bands 0–1, 1–2, and 2–5 kHz, and the frequency centroid of the 0–500-Hz band at four points in time spaced 12.8 msec apart are used to represent the dynamic transition. Categorization of the transitions using multivariate statistics on some 524 transition segments from data of two speakers resulted in a 91% correct nasal/non-nasal decision rate.
Calculation of shading effect in the nearfield by ring-function method
Authors: Hasegawa Takahi
Published: October 2005

This article presents a nonconventional way using the ring-function method for the analysis of the nearfield of a circular piston in an infinite baffle for the case where the velocity distribution across the face of the piston has a parabolic profile.
Nearfield axial levels of exponentially shaded end-fire arrays
Authors: Mellen Robert H.
Published: October 2005

The contour integration method is used to compute nearfield axial levels for two exponentially shaded end-fire arrays of finite cross section: a plane-collimated cylindrical array and a spherically divergent conical array. The results are of interest in modeling parameteric virtual arrays.
Closure and constriction duration for alveolar consonants during voiced and whispered speaking conditions
Authors: Parnell Martha , Amerman James D. , Wells G. Beverly
Published: October 2005

Ten normal adult speakers produced the alveolar consonants /t, d, n, s, z/ in VCV bisyllables embedded in a carrier sentence. The stimulus consonants were produced in the symmetrical contexts /j/ and /a/ under voiced and whispered speaking conditions. Spectrographic analysis of steady-state portions of vowels and closure and constriction durations for consonants revealed significant durational differences associated with speaking conditions for /t, d, s, z, i, a/. Durational effects for /n/ were nonsignificant. Implications with regard to the Schwartz hypothesis [J. Acoust. Soc. Am. 51, 2025–2029 (1972)] that individuals prolong air-arresting articulatory gestures in whispered speech are discussed.
Psychological and physiological acoustics: 1920–1942
Authors: Davis Hallowell
Published: October 2005

This article is a review of important developments in psychological and physiological acoustics, primarily in the United States in the period 1920–1942. It includes a reference to the early work of Harvey Fletcher and his co-workers at the Bell Telephone Laboratories on the psychoacoustics of speech and hearing, leading to the definitive exploration of the ’’auditory area’’ and the development of the audiometer. The replacement of the Weber–Fechner psychophysical law by the Stevens power law is mentioned. In the domain of physiological acoustics the importance of the investigations of Békésy, Wever and Bray, and Galambos on acoustical nerve transmission is emphasized.
Electroacoustics to 1940
Authors: Hilliard John K.
Published: October 2005

The historical context of acoustical and motional impedance was conceived and applied on a large scale before the Acoustical Society was founded in 1929. It seems appropriate at this time to review for the Society some of the people and their devleopments which contributed to the advancement of transducers by application of the impedance concept.
Sound scattering from a fluid sphere revisited
Authors: Johnson Richard K.
Published: October 2005

The backscattering frequency responses for euphausiids and copepods are predicted using a fluid-sphere model and measured physical properties for the zooplankters. The fluid-sphere model is also compared with the resonant gas bubble equation.
Higher-order effects of initial deformation on the vibrations of crystal plates
Authors: Markenscoff Xanthippi
Published: October 2005

A system of plate equations for the thickness-shear and flexural vibrations superposed on large initial deflection due to bending is derived; in the stress–strain relations the terms associated with the fourth-order elastic stiffness coefficients are retained. An explicit formula for the change in the fundamental cutoff thickness shear frequency is obtained and the effects of the terms associated with the fourth-order constrants appear to be significant for large gradients of the rotation angles.
Diffraction of a spherical wave by an absorbing plane
Authors: Briquet Martine , Filippi Paul
Published: October 2005

A solution is presented for the problem of the diffraction of a constant-frequency spherical wave by a plane surface with constant normal specific acoustic admittance. By the use of a bidimensional Fourier transform, the transformed solution, obtained in the classical manner, is decomposed into a sum of products of functions, each of which is the Fourier image of a known function. The recognition of this enables one to readily invert the transform and, in this manner, a new representation of the exact solution is obtained. The particular case of grazing waves (source and receiver on the plane) is examined and asymptotic farfield expressions are derived. Comparison with experiments indicates that, if the plane-wave admittance for normal incidence is used in the theory, the farfield sound-pressure level can be predicted to within ±1.5 dB or better.
Sound propagation above a layer with a large refraction index
Authors: Thomasson Sven-Ingvar
Published: October 2005

This study treats the solution of the wave field produced by a point source in the presence of a layered medium on an acoustically hard backing. It is shown that if the refraction index of the layer is sufficiently large, the solution may be brought back to the problem of propagation above a boundary of local reaction. The point impedance of the surface is expressed in terms of known functions by assuming that the layer is porous, which also makes it possible to obtain an approximate solution of high accuracy. Comparisons are made to similar approximate solutions by Ingard and Lawhead-Rudnick. A new method of measuring the ground impedance as a function of frequency by estimating four constants is suggested. Finally, experiments are added, supporting the theory that the acoustical properties of ground could be physically described by some kind of porous layer and acoustically described by a point impedance. ’’Surface waves’’ are experimentally verified in terms of the suggested theory.
Variability of low-frequency sound absorption in the ocean: pH dependence
Authors: Mellen Robert H. , Browning David G.
Published: October 2005

Experimental measurements of the excess sound absorption in sea water below 1 kHz show a marked regional dependence. For example, the excess in the North Pacific Ocean is found to be only half that in the North Atlantic Ocean. Recent laboratory measurements have demonstrated that the absorption mechanism is a boric acid–borate relaxation. Since this reaction is also a buffer in sea water, the equilibrium and, consequently, the absorption coefficient should depend strongly on pH. A pH correction factor for Thorp’s formula is proposed. Over the range of pH values encountered in the oceans (7.5–8.2), the predicted absorption is, approximately, an exponentially increasing function of pH with a range of values of about 5 to 1. Comparison of experimental absorption coefficients with predictions based on reported local pH values shows reasonably good agreement.
Monitoring sound pressures within the ear: Application to noise exposure
Authors: Brammer A. J. , Piercy J. E.
Published: October 2005

A technique for monitoring sound pressures within the ear, particularly suited to studies of exposure to noise, has been developed based on a miniature microphone located in the cavum of the concha, and a calibrated, cassette tape recorder. By applying a frequency-dependent pressure transformation during playback of data recorded at the concha, typical sound pressures at the center-head position are recovered for comparison with accepted standards for hearing conservation, including those permitting increased exposure to interrupted noise. As an application of the technique, the sound levels experienced by forest workers operating timber skidders have been studied. It is found that near-daily exposure to the noise of a typical harvesting operation will result in significant loss of hearing. The consequences of changing the sequence of work, and the noise of the machine, are discussed, as well as the wearing of ear protectors.
Simple model for simulating traffic noise spectra
Authors: Cornillon Peter C. , Keane Martin A.
Published: October 2005

A comparatively simple six-parameter model has been developed which fits quite well the underlying power spectra of most vehicular traffic noise samples which we have examined. The six free parameters of the model define a system which can easily be represented in either electronic or digital form. In such a form the system can then be used to generate a time series which has the same underlying, or average, power spectrum as the traffic noise which it represents. It does not however incorporate the characteristics noises of motorcycles, trucks, buses, etc. The model can be used as a laboratory tool for identifying the annoying characteristics of traffic noise or for evaluating proposed automobile and truck noise standards. As such it is much more flexible than current methods which use actual traffic noise recordings. It may also be possible to extract from the parameters of the model a more sensitive measure of traffic noise annoyance than is now available. The techniques used in fitting the model to the power spectrum are applicable not only to traffic noise but may be applied in many other areas as well.
Adaptive optimum array processing
Authors: Hodgkiss W. S. , Nolte L. W.
Published: October 2005

A global approach to the processing of information from an array of sensors when uncertain parameters exist is proposed. Although an ad hoc estimate and plug structure is appealing due to its explicit adaptive characteristics, it is shown that the Bayes optimal array processor exhibits natural learning or adaptive features when implemented sequentially.
Difference thresholds for interaural intensity
Authors: Hafter Ervin R. , Dye Raymond H. , Neutzel John M. , Aronow Howard
Published: October 2005

In an earlier paper, wqe examined the distribution of binaural resolvins power by measuring threshold increments of interaural delay as a function of overall dealy [E. R. Hafter and J. Demaio, J. Acoust. Soc. Am. 57, 181–187 (1975)]. In the current study, similar measures were made for interaural increments of intensity. As before, the stimuli were bandpass clicks of either low (0. 1–2 kHz) or hish (3–4 kHz) frequency. For overall interaural differences as sreat as 24 dB, it seems that performance was based on the interaural differences, and not on the monaural increments/decrements that are concommitant with a binaural change in level. As was the case with time, sensitivity to interaural intensity was reasonably constant across the range tested, indicating that, unlike the case for vision, spatial resolution in the auditory system is not concentrated in the center. A simple binaural trading ratio which converts intensity time can be shown to fit the data for low-frequency clicks quite well. However, the fit to high frequencies is so poor as to suggest that separate mechanisms were used for detecting time and intensity.Finally, a number like the binaural masking-level difference (MLD) was computed for the two kines of clicks. Suprisingly, the MLD’s for low and high frequencies were a similar 7.2 and 8.0 dB.
Studies on the perception of place and manner of articulation: A comparison of the labial-alveolar and nasal-stop distinctions
Authors: Miller Joanne L. , Eimas Peter D.
Published: October 2005

Three experiments were conducted in order to compare the perception of the phonetic features of place and manner of articulation, specifically, the labial-alveolar and the nasal-stop distinctions. The results of experiment 1 showed that both features are perceived in a nearly categorical manner, with within-category discrimination performance being quite poor compared to cross-category performance in each case. Experiment 2, which used a selective adaptation paradigm, indicated that for each of these features there exist channels of analysis that are sensitive to the critical information specifying the contrast and that these channels operate in a context- conditioned fashion. Finally, in experiment 3, a right-ear advantage was obtained for both place and manner, implicating the left hemisphere in the processing of each of these features. Taken together, the results of the three studies provide strong support for the claim that the place and manner features undergo similar forms of processing, even though they are specified by very different acoustic parameters.
Computer-controlled method for measuring articulatory activities
Authors: van der Giet G.
Published: October 2005

A computer on-line method for measuring articulatory activities is presented. Small receivers are attached to articulatory organs, recording their motion via electric voltages induced by external inhomogeneous electromagnetic fields. The signals, which are the electrical equivalents of the motion relative to a coordinate system, are subjected to automatic computer analysis. First, experiments have been performed and the results for some utterances are shown, demonstrating the abilities of the system. Moreover, as an example of automatic performance, lip-opening data are deduced.
Computer-aided signal handling for speech research
Authors: Nakatani Lloyd H.
Published: October 2005

Of the total time and effort expended on an experiment in speech research, a significant fraction is usually spent on signal-handling tasks such as collecting and inspecting speech tokens, and making test tapes. Such tasks can be done more quickly, easily, precisely, and reliably with the aid of an interactive signal-handling program implemented on a laboratory computer. This paper describes how Editor, a versatile yet easy-to-use signal-handling program at Bell Laboratories, is used to cope with a variety of signal-handling tasks in speech research. The paper seeks to create an awareness of the scope and power of computer-aided signal handling by describing Editor as a working model. The description emphasizes concepts relevant to the design and implementation of any system for handling signals with the aid of computers.
Reciprocity relations for scattering of plane, elastic waves
Authors: Tan T. H.
Published: October 2005

The reciprocity relations that apply to the scattering of plane, elastic waves that are incident upon an obstacle of finite extent are investigated. In these relations, the particle-displacement radiation characteristics of the scattered waves occur. The elastic medium outside the obstacle is assumed to be homogeneous, isotropic, and perfectly elastic. Hence, two kinds of acoustic waves can propagate in it, viz., irrotational, compressional or P waves and solenoidal, shear or S waves; each of these two waves has its own radiation characteristic. It is shown that the far-zone scattered wave due to an incident wave propagating in the direction ? and observed in the direction −? is related to the far-zone scattered wave due to an incident wave propagating in the direction ? and observed in the direction −?. This reciprocity property is next applied to two incident P waves, two incident S waves, and an incident P wave and an incident S wave. The resulting reciprocity relations hold under the assumption that the scattering obstacle is linear and reciprocal in its elastic behavior.
Amplitude and phase fluctuation periods for long-range propagation in the ocean
Authors: Dyer Ira , Shepard George W.
Published: October 2005

It is commonly observed in long-range propagation that the phase fluctuation period is longer than that of the amplitude. A phase-random multipath model, used previously to explain amplitude statistics [I. Dyer, J. Acoust. Soc. Am. 48, 337–345 (1970)], is now applied to the joint problem of amplitude and phase. The ratio of phase period to amplitude period is found to be proportional to a Rayleigh probability density, with a peak value of about three. This result is supported by data acquired by the Woods Hole Oceanographic Institution and analyzed by us, for a 300-km propagation path extending approximately northeast from Eleuthera.
Temporal light modulation in thick-screen diffraction by ultrasound beam plus amplitude grating
Authors: Calligaris F. , Ciuti P. , Gabrielli I.
Published: October 2005

Temporal modulation of light obtained by a diffraction device consisting of an ultrasonic beam and an optical grating has been theoretically described under the hypotheses of diffraction effects not superposed (thick-screen treatment). In comparison with any thin-screen theory considering spatially superposed effects, the present thick-screen treatment is in better agreement with the experimental results.
Wave propagation along a sapphire rod
Authors: Wilson Lynn O.
Published: October 2005

We consider the propagation of elastic waves along a circular rod composed of sapphire or of another material with the same elastic symmetry. We obtain an analytical description of the modes by making an infinite-series perturbation expansion about an expression which describes waves along a transversely isotropic rod.
Monostatic and bistatic cross sections of a large (capped) sphere partially insonified at a circular spot
Authors: Gaunaurd G. C.
Published: October 2005

The physical-optics (Kirchhoff) method is used to determine the differential scattering cross section and the sonar cross section of a sphere partially insonified by a beam intersecting the surface of the sphere at a circular spot. The sphere is first assumed bare and then partially covered with a raised, centered cap which is smaller than the beam spot. A procedure to make the Kirchhoff method yield directly the bistatic cross section is extended to account for partial insonification and for the cap’s presence. We show that partial insonifcation alone can enhance the normalized sonar cross section up to four times the geometrical acoustics value, and with the additional introduction of a moderately thin and small cap, the enhancement goes beyond an order of magnitude. Quantitative plots of the cross sections are displayed and the general results are seen to reduce properly to, and in one instance, correct, particular cases available in the literature.
Attenuation of the coherent component of sound propagating in shallow water with rough boundaries
Authors: Kuperman W. A. , Ingenito F.
Published: October 2005

Attenuation of the coherent component of sound propagating in shallow water with rough boundaries is studied. Normal-mode theory is used in conjunction with a boundary perturbation method. The inclusion of surface and bottom scattering cause the eigenvalues to become complex and explicit mathematical expressions for the imaginary parts of these eigenvalues are derived. These expressions correspond to the individual normal-mode attenuation coefficients due to scattering. Numerical results are presented for sample shallow-water environments with depth-dependent sound-speed profiles and lossy bottom sediments. The profile structure and the acoustic properties of the bottom sediment have a significant effect on the total attenuation due to scattering.
Frequency-frequency correlations of ocean ambient noise levels
Authors: Nichols R. H. , Sayer C. E.
Published: October 2005

The correlation of ambient noise fluctuations in each of seven frequency bands at frequencies f1 with those in other bands (f2) was investigated for a 4 1/2−d period in February 1976 with a hydrophone laid on the bottom in deep water. The bandwidth was generally 6 Hz; band center frequencies ranged from 5 to l50 Hz. A total of 572 consecutive samples, 640 sec each, was taken concurrently in each frequency band. The average level for each sample was used in the computation of correlation coefficient. Tonal line components were excluded. The correlation coefficients between f1 and f2 generally fell off with increasing frequency spacing between f1 and f2, but the patterns differed with different values of f1. Day-to-day processing showed very high variability, due perhaps to changing weather.
Loudness perception of signals of monotonically changing sound pressure
Authors: Small Arnold M.
Published: October 2005

Listeners were required to judge whether a 500-Hz stimulus, whose SPL was monotonically changing, was increasing or decreasing in loudness over its 2-sec duration. Performance was best when single stimuli were presented in isolation. Providing a second, fixed SPL stimulus for use as a reference generally resulted in poorer performance especially as the initial SPL of the changing stimulus departed from that of the reference. It made little difference whether the variable was presented before or after the reference stimulus. Under optimal conditions listeners could discern changes as small as 0.25 dB/sec 75% of the time. The traditional differential threshold for stimuli whose SPL was not changing was 0.37 dB, a value similar to that reported by other investigators. The question as to whether judgments were being made on the basis of the rate of change of sound pressure per se, or the range over which SPL changed was not directly addressed by this experiment and was therefore not resolved.
Acoustic estimation of scattering-layer composition
Authors: Johnson Richard K.
Published: October 2005

A method is presented for the estimation of the abundances of scatterers from their backscattering spectra. It uses constrained steepest descent and gives optimal estimates in the least-squares sense. The population distributions of fish with gas-filled swim bladders, calculated from a set of backscattering measurements taken in the ocean near Oregon, are generally consistent with midwater-trawl samples in the same area.
Evaluation of an integral occurring in spatial-correlation theory
Authors: Mohnkern Gerald L.
Published: October 2005

The equation for the correlation of a pair of arbitrarily positioned sensors in a noise field produced by a uniform distribution of independent dipole noise sources on a distant surface results in a pair of integrals. It is shown here that one of these integrals can be evaluated analytically to obtain a closed-form result.
Comparison of monaural and binaural discrimination of intensity and frequency
Authors: Jesteadt Walt , Wier Craig C.
Published: October 2005

Intensity and frequency discrimination were measured at three signal frequencies for stimuli presented (1) binaurally, in phase, (2) monaurally, to the left ear, and (3) monaurally, to the right ear. The binaural difference limens (DL’s) are uniformly smaller than the monaural DL’s for both intensity and frequency discrimination at all frequencies. The size of the effect is within the range that is predicted by either an information-integration or an independent-threshold model.
Calibration of ultrasonic fields from acousto-optic data using Fourier-transform techniques: Theory
Authors: Cook Bill D. , Berlinghieri Joel C.
Published: October 2005

The local variations of acoustical-field quantities, in the nearfield of an ultrasonic transducer, influence most calibration techniques including the optical methods. A mathematical formulation is presented which accounts for these local variations and, in fact, allows the mapping of these quantities from conventional ultrasonic light-diffraction measurements. This analysis requires acquiring considerable amount of data and reducing it in the spatial Fourier domain for mapping pressure, particle velocity, and intensity distributions. However, simpler procedures are developed for the determination of radiated power and intensity along the primary beam. An important attribute of this technique is that modeling of the field is not necessary; optical measurements can be taken as close to the transducer as is convenient, and the method is not restricted to transducers with simple geometries. However, theory is developed within the constraints of linear acoustics.
Fluid-loaded vibration of an elastic plate carrying a concentrated mass
Authors: Sandman B. E.
Published: October 2005

The vibration of a simply supported rectangular plate with a discretely attached mass and fluid radiation loading is considered. The equations of motion are solved by utilizing the in vacuo eigenfunctions of a homogeneous panel as the basis for Fourier decomposition of both the fluid loading and attached mass loading. A modal matrix equation is established for the interactive system which includes the cross-modal coupling induced by the discrete mass and acoustic fluid. The solution is exemplified by the numerical investigation of a centrally excited plate with a concentrated mass at center and off-center locations. The influence of mass attachment upon both the plate response and radiated pressure is illustrated.
Bearing estimation using a perturbed linear array
Authors: Hinich Melvin J.
Published: October 2005

A linear hydrophone array which is towed in the ocean is subject to snakelike bending. If the array is processed as if it was truly linear, the author has shown that the bending causes a deflection of the measured bearing of a fixed source from its true bearing relative to the array. This deflection results from patterned perturbations in the true sensor positions along the nominal array axis. As the perturbation pattern changes with the flexing of the array, the source appears to move around. A probability model of the perturbations is used in order to develop a theoretical solution to the question of how the space–time information gathered by the array is best used to measure source bearing. The method which is used to reduce the bending perturbation deflection of the bearing is to group the sensors into adjacent subarrays, process these arrays over short time slices, average the subarray bearings for each time period, and then to average the average over time. This averaging method significantly improves the bearing accuracy of the source when the array is bent according to the model.
Gradient hydrophone flow noise
Authors: Keller Bruce D.
Published: October 2005

The flow-noise response of two types of gradient hydrophones is investigated by comparing models. Several effects are given detailed investigation, such as differentiating between noise conducted directly from the flow and noise caused by case acceleration. Models are used to predict the operational effects of several types of flow screens.
Two-tone suppression in backward masking
Authors: Tyler Richard S. , Small Arnold M.
Published: October 2005

Nonsimultaneous masking experiments (forward masking, pulsation threshold), using a two-tone masker, have shown effects similar to two-tone inhibition in auditory-nerve fibers. In the present experiment, backward masking was examined with five subjects where the masker contained a 1000-Hz, 40-dB SPL masker and a second tone of variable frequency at 70 dB SPL, called the suppressor. The test signal was 1000 Hz. For certain suppressor frequencies, the masker suppressor combinations produced less masking than the 40-dB SPL masker alone.