bluuebunny/crossref_metadata_2025 huggingface dataset:
Ray calculations with beam displacement
Authors: Tindle C. T.
Published: October 2005

Ray theory with beam displacement is used to calculate the sound field in shallow water as a function of range. Results for the Pekeris model are compared with normal mode calculations and agreement is good even when the water depth is only a few wavelengths. The inclusion of beam displacement leads to the formation of ray caustics. Caustics are important at all ranges and occur even in isovelocity layers. Eventual failure of the ray method at short ranges and very low frequencies is traced to difficulties with the approximate evaluation of integrals by the method of stationary phase.
Mesoscale variability of SOFAR group velocity in the northwest Pacific
Authors: Shockley R. C. , Montoya S. M.
Published: October 2005

We present a ray-trace numerical study of the effects of mesoscale structure on the group velocity (defined as the average horizontal ray speed) of deep-refracted acoustic signals using data from a large-scale, near synoptic survey of the thermal structure in the upper 800 m of the Northwest Pacific ocean reported by Emery et al. [W. J. Emery, T. J. Reid, J. A. de Santo, R. N. Baer, and J. P. Dugan, J. Acoust. Soc. Am. 66, 831–841 (1979)]. A representative sample of twelve sound speed profiles (SSPs) from the survey show maximum variation of 10 m/s in the group velocity of a ray with a given J value, J being the phase integral, and illustrate how particular features in the SSPs cause local maxima in the group velocity as a function of J.
Time-of-day corrections in measures of aircraft noise exposure
Authors: Bullen Robert B. , Hede Andrew J.
Published: October 2005

Results of a socio-acoustic study of human reaction to aircraft noise around Australian airports are described. The relative importance of night, evening, and daytime operations in determining overall reaction is assessed using a correlation analysis procedure. The results indicate that night-time weightings used in most existing noise exposure indices including NEF and DNL, are too large. However, other evidence suggests that both night and evening weightings should be greater than 0 dB. The optimal weightings found were about 3 dB for night-time operations and 9 dB for evening operations. However, other considerations indicate that in a practical noise index it may be more reasonable to apply a weighting of about 6 dB during both night and evening hours.
Detection performance characteristics for a system with quantizers, OR-ing, and accumulator
Authors: Nuttall Albert H.
Published: October 2005

The false alarm and detection probabilities of an N-channel system subject to L+1 level quantization, OR-ing, and accumulation of M time samples, are evaluated exactly, with no Gaussian assumptions, for arbitrary values of N, L, M, and for a quantizer with arbitrary breakpoint locations. The channel noises are independent but can have arbitrary statistics. The signal occupies one unknown (possibly changing) channel, if present. Two FFTs suffice to sweep out a complete detection probability versus threshold curve. The optimum placement of quantizer breakpoints, for a fixed total number of levels, L+1, is a subtle one and shown to depend on N, M, and the desired level of performance; a simple rule-of-thumb is presented which yields near-optimum capability over the useful range of the operating characteristics.
A finite-difference treatment of interface conditions for the parabolic wave equation: The irregular interface
Authors: Lee Ding , McDaniel Suzanne T.
Published: October 2005

A finite-difference solution to the parabolic wave equation is extended to treat an irregular interface. Interface conditions are developed to preserve continuity of pressure and continuity of the normal component of particle velocity at the boundary between media having different sound speeds and densities. A complete mathematical treatment for the case of an irregular interface is presented. To demonstrate the method, numerical results are obtained for sound propagation from deep to shallow water.
Low-frequency acoustic diffraction by a soft elliptic disk
Authors: Roy Arabinda , Sabina Federico J.
Published: October 2005

The problem of the diffraction of an arbitrary incident plane sound wave by a soft-sound elliptic disk is studied. A Fredholm integral equation of the first class is posed and solved explicitly in the low-frequency limit up to terms of O(κ2), κ being the wavenumber, though higher order terms could be found in a similar fashion without much difficulty. The solution is new and expressions for the farfield amplitude (which are also believed to be new) and the scattering cross section are obtained to the same order. The limiting values when the ellipse degenerates into a circle agree with those of a circular disk found using other methods. Also the scattering cross section agrees with expressions obtained using alternative methods.
A laser study of multiple reflections within parallel noise barriers
Authors: Hutchins D. A. , Pitcarn D.
Published: October 2005

A laser has been used to determine acoustic wave paths from a source, located between parallel noise barriers, to the top of each barrier. Various barrier designs have been studied, and conclusions drawn on the likely effect of parallel siting on sound levels at a protected receiver for a typical traffic noise geometry.
Normal-mode propagation in deep-ocean sediment channels: A sequel
Authors: Williams A. O.
Published: October 2005

The present writer has discussed various aspects of propagation in sediment channels [J. Acoust.Soc. Am. 70, 820–824 (1981)]. A simplifying assumption was that cw, the speed of sound in the water, is constant everywhere. In this sequel it is more realistically assumed that cw decreases slowly and linearly with height above the water–sediment interface. Consequently an acoustic barrier exists from the interface to, typically, 100–200 m above it. Acoustic energy in a signal traveling along the sediment channel can tunnel upward through the barrier, thereby causing a ‘‘leakage’’ attenuation along the channel. Equations are derived to describe the acoustic field both in and above the barrier, and a long-known method yields the amplitude attenuation factor caused by leakage. Using numerical examples from the 1981 article, we find that the leakage factor is a negligible 1% of the factor caused by absorption in the sediment. In this case, the approximation of constant cw was justified, but for a normal mode nearer cutoff the leakage would increase considerably.
On the three-dimensional vibrations of the cantilevered rectangular parallelepiped
Authors: Leissa Arthur , Zhang Zhong-ding
Published: October 2005

A solution is presented for the three-dimensional problem of determining the free vibration frequencies and mode shapes for a rectangular parallelepiped which is completely fixed on one face and free on the other five faces. This problem apparently is previously unsolved in the published literature. The Ritz method is used, with displacements assumed in the form of algebraic polynomials. Convergence is studied. Numerical results are given for the first five frequencies of each of the four symmetry classes of vibration, for five thick parallelepiped configurations, including the cube. Contour plots are exhibited for the modal displacements of the cube. The effects of varying Poisson’s ratio are also observed.
Presbycusis, sociocusis and nosocusis
Authors: Kryter Karl D.
Published: October 2005

Data and idealized curves are presented for a number of surveys on the threshold of hearing of persons who were not exposed, by and large, to intense workplace noise. From these results, and on the basis of certain assumptions, new generalized functions are presented to show pure presbycusis (aging) and sociocusis (non-work-noise-induced hearing loss); typical presbycusis; typical sociocusis; and typical presbycusis-plus-sociocusis. Hearing level surveys, conducted in industrialized societies to reveal presbycusis, appear to reflect the joint effects of presbycusis and sociocusis, especially in males, and factory workers may suffer more sociocusis and a greater degree of presumably non-noise-related otological disorders (nosocusis) than are found in the general population.
Field of a parametric focusing source
Authors: Lucas Bernard G. , Tjo/tta Jacqueline Naze , Muir Thomas G.
Published: October 2005

An analytical description for the field of a parametric focusing source is derived. It is valid for spherically concave sources with small aperture angle and high ka, under conditions of quasilinear interaction (strong shocks precluded). The solution furnishes computations on the phase and amplitude of difference frequency sound along the axis and in the focal plane, as well as on the width of the radiation lobe in the focal region. Underwater experiments conducted with an f/2 lens coupled to a dual, interleaved primary array are discussed. The results support the utility and validity of the analytical model for describing the distribution of sound along the acoustic axis and across the focal plane. The difference frequency radiation was found to be effectively focused, in that the width of the beam became quite narrow in the focal plane.
Susceptibility to intraspeech spread of masking in listeners with sensorineural hearing loss
Authors: Hannley Maureen , Dorman Michael F.
Published: October 2005

Previous research with speechlike signals has suggested that upward spread of masking from the first formant (F1) may interfere with the identification of place of articulation information signaled by changes in the upper formants. This suggestion was tested by presenting two-formant stop consonant–vowel syllables varying along a /ba/–/da/–/ga/ continuum to hearing-impaired listeners grouped according to etiological basis of the disorder. The syllables were presented monaurally at 80 and 100 dB SPL when formant amplitudes were equal and when F1 amplitude was reduced by 6, 12, and 18 dB. Noise-on-tone masking patterns were also generated using narrow bands of noise at 80 and 100 dB SPL to assess the extent of upward spread of masking. Upward spread of masking could be demonstrated in both speech and nonspeech tasks, irrespective of the subject’s age, audiometric configuration, or etiology of hearing impairment. Attenuation of F1 had different effects on phonetic identification in different subject groups: While listeners with noise-induced hearing loss showed substantial improvement in identifying place of articulation, upward spread of masking did not consistently account for poor place identification in other types of sensorineural hearing impairment.
Spectro-Temporal Modulation Transfer Function (STMTF) for various types of temporal modulation and a peak distance of 200 Hz
Authors: van Zanten G. A. , Senten C. J. J.
Published: October 2005

For noise which is spectrally modulated (ripple noise) as well as temporally modulated (the ripples move), the Spectro-Temporal Modulation Transfer Function (STMTF) is defined as the curve relating modulation threshold to temporal modulation frequency with ripple spacing as a parameter. A white noise stimulus was spectro-temporally modulated in the 0.2- to 1.0-kHz region with a spectral modulation frequency (peak distance) of 0.2 kHz. Three types of temporal modulation were applied: the ripples rolled upward, downward, or the peaks and troughs interchanged periodically. It is shown that the STMTFs for these types are equal. So, for a ripple spacing of 0.2 kHz the spectro-temporal modulation thresholds are independent of the type of temporal modulation. These STMTFs appeared to be low-pass functions, no minimum was found. Their plateaus were at the same modulation depth as the modulation thresholds found by previous investigators who employed stationary ripple noise.
Level and phase of the (2f1–f2)-cancellation tone expressed in vector diagrams
Authors: Zwicker Eberhard
Published: October 2005

Sets of level and phase data of the (2f1–f2)-cancellation tone were measured with the same fit of the earphone. The results obtained were transferred into vector diagrams as x-y representations. Characteristic rules for the development of the cancellation tone can be extracted from a detailed analysis of such diagrams.
Multiple scale analysis of the spirally coiled cochlea
Authors: Loh Chee Hoong
Published: October 2005

The method of multiple scales is applied to the analysis of a curved box model of the spirally coiled cochlea. The fluid motion is fully three-dimensional and the basilar membrane movement is represented by a single mode of deflection. Coiling parameters for the human cochlea are determined from the experimental data of von Békésy [Experiments in Hearing (McGraw-Hill, New York, 1960)]. The approximate solution is numerically calculated to yield comparisons with the uncoiled case. It is found that the coiling effects are long-wave in character and the results do not differ significantly from the corresponding straight box model.
Numerical evaluation of the radiation from unbaffled, finite plates using the FFT
Authors: Williams Earl G.
Published: October 2005

An iteration technique is described which numerically evaluates the acoustic pressure and velocity on and near unbaffled, finite, thin plates vibrating in air. The technique is based on Rayleigh’s integral formula and its inverse. These formulas are written in their angular spectrum form so that the fast Fourier transform (FFT) algorithm may be used to evaluate them. As an example of the technique the pressure on the surface of a vibrating, unbaffled disk is computed and shown to be in excellent agreement with the exact solution using oblate spheroidal functions. Furthermore, the computed velocity field outside the disk shows the well-known singularity at the rim of the disk. The radiated fields from unbaffled flat sources of any geometry with prescribed surface velocity may be evaluated using this technique. The use of the FFT to perform the integrations in Rayleigh’s formulas provides a great savings in computation time compared with standard integration algorithms, especially when an array processor can be used to implement the FFT.
Effects of eddy currents on the magnetomechanical coupling of conducting piezomagnetic rods
Authors: Hill J. Clifton , Meeks Steven W.
Published: October 2005

An equivalent circuit model for a piezomagnetic transducer has been used to predict the effect of eddy currents on a widely used method of determining the magnetomechanical coupling coefficient. Results show that the changes in the impedance loop diagram are sensitive clues to eddy current effects on the accuracy of the measured keff.
Model validation of the geometric dispersion of acoustic signals propagated in a deep ocean channel
Authors: Flowers K. D. , Gerlach A. A.
Published: October 2005

In this paper we report the results of an experiment designed to measure the effects of geometric dispersion on acoustic cw signals propagated to long ranges in a deep ocean channel. The experimental results are shown to compare favorably with model calculations using a standard normal mode model. It is concluded that the effects of dispersion can be successfully simulated for a wide range of frequencies, frequency ratios, and signal-to-noise ratios.
Normal mode scaling and phase change at the boundary
Authors: Yang T. C.
Published: October 2005

The group velocities of normal modes are not independent but are related to each other by a scaling law. The scaling law relates the frequencies of any two modes received at a particular time (associated with a particular group velocity) by a scaling parameter. The scaling parameter is a constant for mode energies fully contained in the water column; in the ray picture, this corresponds to refracted only, and refracted and surface reflected rays. Experimental data will be analyzed to see how well the ‘‘constant’’ behaves for a variety of frequencies and modes. For bottom-limited acoustic propagation, the scaling parameter for the normal modes may not be a constant. For this case we can use the theory to deduce the phase change of reflection at the boundary from the measured scaling parameter data. The phase change for bottom reflection is deduced from shallow water shot data for grazing angles from 9° to 10.4° and is used to probe the sound speed in the bottom. This proves to be a useful technique since direct measurement of phase change is extremely difficult by other experimental techniques.
Sound propagation in the surface layer of the atmosphere
Authors: Wessels Herman R. A. , Velds Carel A.
Published: October 2005

Quantitative climatological data with regard to sound propagation have been obtained from routinely measured temperature and wind profiles along a meteorological tower. The results are presented in terms of the percentage of nights during one year, on which sound rays bend over barriers, as a function of distance from the barrier and wind direction. The vertical sound velocity gradient has been expressed in terms of atmospheric surface layer scaling factors for temperature and wind speed. A nomogram is presented for rapid estimation of the curvature of sound rays as a function of these generalized meteorological parameters. Apart from the estimation of acoustic behavior from available tower measurements, the method can also be used to forecast sound propagation from readily available meteorological data.
Parameters influencing the sonic velocity in compact calcified tissues of various species
Authors: Lees S. , Ahern J. M. , Leonard M.
Published: October 2005

Compact calcified tissues from a wide variety of species were used in a study of the dependence of sonic plesio-velocity on physical parameters. A linear dependence of velocity on wet density has been found for each of three categories of wet mineralized tissue: compact long bone measured in the axial direction, compact long bone measured in the radial direction, and hyperpycnotic mineralized tissues. A similar linear dependency was found for dry calcified tissue using the dry density. In addition to these three parameters (density, orientation, and water content) two other factors were identified. The bone fibers in long bone matrix are ordered with respect to the bone axis and the anisotropy of long bone matches that of its matrix. There is no corresponding order to the fibers in hyperpycnotic tissue matrix. The fifth parameter is believed to be the porosity. Fish bone is much more porous than other compact bone from long bone and the sonic velocity in fish bone is much lower than for other bone. These parameters are not independent.
Effects of crossed-olivocochlear-bundle stimulation on cat auditory nerve fiber responses to tones
Authors: Gifford Margaret L. , Guinan John J.
Published: October 2005

Phase, synchronization index, and average firing rate were calculated from period histograms of tone burst responses obtained from sound level series with and without electrical stimulation of the cross-olivocochlear-bundle (COCB). For most fibers, at low sound levels, COCB stimulation shifted the rate and synochronization index level functions up in sound level but did not shift the phase-level function in the same way. These effects can be accounted for if the stage at which the COCB acts precedes the stage at which analog signals are changed into neural firing patterns with a given rate and synchronization index, but does not precede the stage at which the level dependence of phase is introduced. Some level series show an abrupt phase change and ‘‘dips’’ in rate and synchronization-index level functions at high sound levels. COCB stimulation shifted these abrupt phase changes and dips down in sound level and usually had little effect at sound levels above these abrupt phase changes and dips. The following explanatory hypothesis is developed: excitation of an auditory-nerve fiber is the result of two factors which are out of phase and have different growth functions. The two factors cancel when they are equal in amplitude producing the dips and phase changes. COCB stimulation reduces the more sensitive factor but does not change the other factor so the two factors cancel at a lower sound level with COCB stimulation.
Optimum and sub-optimum source localization with sensors subject to random motion
Authors: Schultheiss Peter M. , Ashok Erramilli , Ianniello John P.
Published: October 2005

When an array is used to estimate source location, random motion of the receiving sensors can seriously limit performance. This paper models sensor motion as a flat, bandlimited Gaussian process independent from sensor to sensor. Cramer–Rao bounds on errors in time delay estimates are derived and these are converted to bounds on range and bearing errors. The validity of the bandlimited model is examined, and the performance of conventional and optimal processors compared. It is shown that conventional processors can achieve near-optimal performance if the post processing signal-to-noise ratio is sufficiently large and the motion of the sensors sufficiently slow. For short observation times T, the optimum and conventional processors have the same errors due to sensor motion; for longer observation times the incremental errors decrease as T−1.
Asymmetric light diffraction by pulsed ultrasonic waves
Authors: Neighbors Thomas H. , Mayer Walter G.
Published: October 2005

Low-MHz, continuous ultrasonic waves traveling in a transparent medium cause light to be diffracted into discrete diffraction orders when light and sound propagation directions are normal to each other. When pulsed ultrasonic waves are used the diffraction orders split into secondary orders which are asymmetric with respect to the central diffraction order. This splitting is derived and a general expression provided for the intensity as a function of the ultrasonic pulse Fourier spectra. Examples are provided which demonstrate the degree of asymmetry for an exponential driving pulse and the convergence to the classic Raman–Nath results when the pulse approaches a continuous wave.
Formant frequencies, bandwidths, and Qs in helium speech
Authors: Belcher Edward O. , Hatlestad Steinar
Published: October 2005

We used linear prediction analysis to estimate a diver’s vocal tract response for isolated vowels spoken in air at 1 atm and in heliox at simulated depths of 54-, 120-, 300-, and 500-m seawater. We specifically measured formant frequency, bandwidth, and Q changes as a function of environment. The formant frequencies shifted upward nonlinearly in helium speech. The formant bandwidths in helium speech increased as much as 14 times their corresponding bandwidths in normal speech. The ratios of formant Qs (helium speech to normal speech) ranges from 0.3 (low formants) to 2 (high formants).
Wave propagation through a slender curved tube
Authors: Ting Lu , Miksis Michael J.
Published: October 2005

The transmission of an acoustic wave through a slender three-dimensional tubular region is investigated. The ratio of the reference length a of a cross section of the tube to the reference curvature of the center line of the tube is assumed to be small. The analysis is carried out for wavelengths ranging from the order of the reference curvature of the center line of the tube to wavelengths much smaller than the reference length of the cross-sectional area. It is shown that the leading solution inside the tube is governed by the same equation as for an equivalent straight tube except for the case where the wavelength is much smaller than the reference length a. For the latter the leading solution is governed by a partial differential equation in the cross section of the tube. The radius of curvature of the center line enters only into the amplitude of the leading order solution of the short waves.
A note on acoustic wave propagation in periodically stratified media
Authors: Maewal A.
Published: October 2005

This Letter has been motivated by a recent paper [Schoenberg and Sen, J. Acoust. Soc. Am. 73, 61 (1983)] on perusal of which it occurred to the author that it should be possible to derive the macroscopic acoustic properties of a medium with periodic microstructure by utilizing the same analytical methods that have been useful for the problem of heat conduction in such media.
Theoretical foundations of urban noise control
Authors: Makarewicz Rufin
Published: October 2005

Traffic noise propagating within an urban area of any configuration is considered. A street and a single building being a part of a ‘‘loose urban area’’ are examined closely. Final results allow one to determine any composite index (based upon equivalent level—Leq) of noise penetrating into a building, i.e., a room. These results are a synthesis of a study of such phenomena as: propagation of noise over a flat surface, specular reflection and scattering by the walls of buildings, and transmission through a barrier, e.g., a window.
Multifrequency remote acoustic sensing of suspended materials in water
Authors: Ma Y. , Varadan V. K. , Varadan V. V. , Bedford K. W.
Published: October 2005

A multifrequency acoustic technique is employed as an oceanographic tool to infer the characteristic information, e.g., concentration, size distribution, and mean size, about suspended materials in the deep ocean environment. The technique employs the single scattering theory which is valid for a sparse distribution of scatterers in water. Theoretical results are presented as the acoustic response versus frequencies for different size distributions.
Discrimination of speech processed by low-pass filtering and pitch-invariant frequency lowering
Authors: Reed Charlotte M. , Hicks Bruce L. , Braida Louis D. , Durlach Nathaniel I.
Published: October 2005

Consonant discriminability by normal-hearing listeners was studied for monosyllables processed using frequency lowering with either uniform (linear) or nonuniform (warped) compression of the frequency axis. The bandwidth of the compressed signal was either 2500 or 1250 Hz and five compression characteristics were studied, in addition to low-pass filtering, for each of the two bandwidths. Stimuli were 24 consonant–vowel syllables made up of 24 consonants and three vowels, recorded three times by each of two male and female speakers. A ‘‘roving-speaker, roving-vowel, roving-utterance,’’ two-interval, forced-choiced procedure with feedback was employed. As expected, performance for the 2500-Hz bandwidth was superior to that for the 1250-Hz bandwidth. For each bandwidth, compression schemes which accomplished greater lowering of the high frequencies relative to the low frequencies resulted in the highest performance. Overall performance for the best frequency-lowering system studied, however, was roughly comparable to that obtained for low-pass filtering. Patterns of performance over articulatory features were different for frequency lowering and filtering. In general, lowering was superior to filtering for contrasts of fricative sounds but inferior for contrasts of nasals and semivowels.
Stress and vowel duration effects on syllable recognition
Authors: Marshall Charles W. , Nye Patrick W.
Published: October 2005

Systems designed to recognize continuous speech must be able to adapt to many types of acoustic variation, including variations in stress. A speaker-dependent recognition study was conducted on a group of stressed and destressed syllables. These syllables, some containing the short vowel /I/ and others the long vowel /1/, were excised from continuous speech and transformed into arrays of cepstral coefficients at two levels of precision. From these data, four types of template dictionaries varying in size and stress composition were formed by a time-warping procedure. Recognition performance data were gathered from listeners and from a computer recognition algorithm that also employed warping. It was found that for a significant portion of the data base, stressed and destressed versions of the same syllable are sufficiently different from one another as to justify the use of separate dictionary templates. Second, destressed syllables exhibit roughly the same acoustic variance as their stressed counterparts. Third, long vowels tend to be involved in proportionally fewer cross-vowel errors but tend to diminish the warping algorithm’s ability to discriminate consonantal information. Finally, the pattern of consonant errors that listeners make as a function of vowel length shows significant differences from that produced by the computer.
Intense sounds may alter the mechanical properties of the cochlear partition
Authors: McFadden Dennis
Published: October 2005

Morphological and structural changes have been observed in various cochlear elements following exposure to intense sounds. Whether these changes are sufficient to locally alter the mechanical properties of the cochlear partition is unknown. Here a psychophysical test for mechanical changes in the partition is developed and applied. Monaural exposures to an intense 1700-Hz tone were preceded and followed by a binaural task in which the subject adjusted the interaural time difference of a 250-Hz tone in order to perceive it as centered inside his head. If the local gradients of mass, stiffness, and/or coupling were altered by the exposure, then the post-exposure settings should contain a time lead toward one ear or the other, depending upon the direction of the mechanical changes. Following exposure to an intense tone, the maximum temporary threshold shift (TTS) is often displaced upward in frequency from the exposure stimulus—an effect widely known as the half-octave shift in TTS. Time leads toward the nonexposed ear in the post-exposure centering task would be in accord with a mechanical-change explanation of the half-octave shift. Settings in this direction were observed with the most intense and longest durations of exposure used, but with less intense or shorter exposures, the post-exposure settings were initially toward the exposed ear. Thus, the psychophysical evidence reported here supports the idea that exposure to intense sounds does produce temporary, local changes in cochlear mechanics, but it fails to provide a simple confirmation of the possibility that these mechanical changes underlie the half-octave shift in TTS.
Ultrasonic flow metering based on transit time differentials which are insensitive to flow profile
Authors: Lechner Hubert
Published: October 2005

This paper describes a theoretical study of the performance of a transit time ultrasonic flowmeter which uses a flow tube to contain the interaction between the flow and the ultrasonic wave field. The flow tube is treated as an acoustic waveguide and it is seen that the transit time differentials of the higher order acoustic modes are affected by the type of flow profile encountered, resulting in errors in the volume throughput measurement. Nevertheless these errors can be minimized by an appropriate choice of transducer separation.
Suppression in simultaneous masking
Authors: Fastl Hugo , Bechly Matthias
Published: October 2005

Suppression, i.e., the decrease of masked threshold caused by the addition of a second masker M2 to a first masker M1, is measured for the case of simultaneous masking. The magnitude of suppression decreases with increasing test tone duration; pulsed maskers elicit somewhat more suppression than continuous maskers. In comparison to suppression effects obtained in nonsimultaneous masking (post-masking, pulsation threshold) suppression in simultaneous masking is considerably smaller and was found only at the lower slopes of the two maskers. Suppression in simultaneous masking would not be predicted by those models of suppression which require nonsimultaneous presentation of maskers and test sound.
Time course of adaptation and recovery of channels selectively sensitive to frequency and amplitude modulation
Authors: Tansley B. W. , Suffield J. B.
Published: October 2005

In a series of experiments we investigated the time course of adaptation and recovery of channels in the human auditory system selectively sensitive to frequency and amplitude modulation (FM and AM). We determined the rate of loss of sensitivity to modulation using sinusoidal frequency or amplitude modulation (SFM or SAM) of a 50 dB SL, 500-Hz pure tone carrier over a 30-min period. Adaptation stimuli were modulated at ten times the preadaptation modulation detection threshold, as determined immediately before the 30-min adaptation session. Modulation rates investigated were 2, 4, 8, 16, and 32 Hz. Long exposure to SFM always elevated thresholds for detection of SFM more than this exposure elevated thresholds for detection of SAM. Similarly, adapting to SAM always elevated SAM detection thresholds more than SFM thresholds. Loss of sensitivity during adaptation was relatively slow; asymptotic loss of modulation sensitivity took 20 to 30 min. The recovery of modulation sensitivity after cessation of the modulation component of the adapting stimulus was determined in a second experiment. Recovery was found to be rapid; most of the recovery occurred within the first 60 sec. Our evidence suggests that there exist two types of modulation-sensitive channels in the human auditory system—one selectively sensitive to amplitude modulation and the other to frequency modulation. They appear to have similar time courses for adaptation and for recovery.
Equivalent bandwidth of a general class of polynomial smoothers
Authors: Ng Lawrence C. , LaTourette Robert A.
Published: October 2005

This paper presents a detailed investigation of the properties of a general class of least-mean-square-fit (LMSF) smoothers in the presence of a white or colored input sequence. The results of the investigation show that the LMSF can be described as a low-pass filter whose frequency response characteristics can be calculated exactly. A particularly useful result derived from the frequency response characteristics is the LMSF equivalent bandwidth. It was shown that knowledge of LMSF bandwidth, plus knowledge of the input bandwidth, provides the second-order statistical description of the LMSF output noise process. Results of the analysis are verified by extensive computer simulation.
Nonstationarity in acoustic fields
Authors: Tsao Y. H. , Hammond J. K.
Published: October 2005

Acoustic pressure fields measured by an observer when the source or observer or both are moving is a nonstationary random process even if the source generates a random process which is stationary in the reference frame of the source. The causes of nonstationarity are classified as being due to wave expansion, directivity, and Doppler shift. This paper is concerned with developing two-dimensional (frequency–time) spectral descriptions for the processes by constraining the processes to fit within the framework of the ‘‘evolutionary spectral density.’’ Earlier literature has described how evolutionary spectra may be estimated from single sample realizations. Spectral representation forms for free-field acoustic processes produced by moving monopole and dipole excitations are derived from the fundamental wave equations.
High-frequency acoustic properties of a fluid/porous solid interface. I. New surface mode
Authors: Feng Shechao , Johnson David Linton
Published: October 2005

We use Biot’s theory to search numerically for the velocities of the various surface waves, both the true slow surface wave and the pseudosurface waves, at an interface between a fluid half-space and a half-space of a fluid-saturated porous medium. We focus on the high-frequency range where the Biot–Plona slow wave is propagatory. We find that for an open-pore surface situation, the true surface mode exists for a limited range of material parameters and changes continuously into a slightly leaky pseudo-Stoneley mode as the mode speed increases past the slowest bulk wave speed; for the sealed pore situation there exist simultaneously a true surface mode (for all values of material parameters) and a pseudo-Stoneley mode. The pseudo-Rayleigh mode has features similar to those of the pseudo-Rayleigh mode for a fluid/nonporous solid case.
Single and multiple scattering of elastic waves in two dimensions
Authors: Shah A. H. , Wong K. C. , Datta S. K.
Published: October 2005

In this paper a combined analytical and finite element method is presented for studying diffraction of elastic waves by cylindrical cavities in two dimensions. The method consists of dividing the infinite space into two regions: an interior bounded region containing the cavities and an exterior unbounded region. The interior region is represented by finite elements and wavefunction expansions are used to represent the field in the exterior homogeneous isotropic medium. Numerical results obtained by this method for scattering of plane longitudinal ( P) and shear (SV) waves by a circular cylindrical cavity are shown to be in agreement with the exact solution. The method is then applied to problems of single scattering by triangular and square shaped cavities. Finally, multiple scattering by two circular, and one circular and one square shaped cavity are solved.
Fluctuations of sound propagating vertically through the ocean
Authors: Desaubies Yves
Published: October 2005

Fluctuations of sound propagating vertically through the ocean are considered. Expressions are derived for the acoustic phase structure function and spectra. As an application, the errors incurred by systems based on travel time measurements (depth sounding and tracking systems) are estimated. They are found to be generally negligible.
Deep-ocean ray transmissions over convergent and divergent sloping bottoms
Authors: Itzikowitz S. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

Surface-reflected/bottom-reflected transmissions over a slowly sloping bottom in a deep ocean are investigated using ray theory. For convenience, sound speed is taken to be bilinear with depth in the water, while the bottom structure is assumed to be uniform. The sound source and receiver are located on or near the ocean boundaries, and the effects of bottom slope on ray geometry, per-ray travel time, and incoherent total-field amplitude are examined. For transmission ranges of tens of km, and for typical deep-ocean slope inclinations, travel time may change by about 1.0 s, relative to its value for a horizontal bottom. The time difference between ray arrivals decreases (increases) in the divergent (convergent) channel. Principal effects of bottom slope on total-field amplitude arise primarily through bottom-loss modifications, rather than through spreading loss. An inclination-angle magnitude of only 0.25° is shown to cause a decrease of about 8 dB (increase of about 4 dB) in the incoherent amplitude in the convergent (divergent) channel, for ranges of about 100 km. Changing bottomed receiver location in a convergent channel, in order to improve source detectability, is shown in an example to be much more effective than in the case of a horizontal bottom. In a corresponding divergent channel, however, the strength of the acoustic reception is much less sensitive to variations in receiver location.
Complete solutions of the transient behavior of a transmitting thickness-mode piezoelectric transducer and their physical interpretations
Authors: Zhang H. L. , Li M. X. , Ying C. F.
Published: October 2005

Full analytic solutions of the internal stress field and the radiated ultrasonic wave are obtained for a thickness-mode piezoelectric transducer excited by a pulse voltage source, having or not having an internal resistance. Two mechanisms of transduction as well as the effect of the internal resistance on these are drawn from the complete solutions. The negative capacitance in the Mason equivalent circuit is interpreted in terms of the identified mechanism of the acoustoelectrical regenerative vibration.
The intelligibility of sentences in quiet and in noise in aged listeners
Authors: Duquesnoy A. J.
Published: October 2005

The monaural speech-reception threshold (SRT) for sentences was investigated in quiet and under four noise conditions for 80 male subjects (age 60–90) and 30 female subjects (age 71–89). The noise levels used were 28, 43, 58, and 73 dBA. The noise had the long-term average spectrum of speech. It is shown that a model developed by Plomp [J. Acoust. Soc. Am. 63, 533–549 (1978)], which interprets any hearing loss for speech (SHL) as a combination of a loss of class A (attenuation of both speech and noise) and a loss of class D (distortion of the sound signals), enables one to make an accurate description of the SRT values measured. Fitting this model, for each individual, to the SRT data yielded values for SHL in quiet (= A+D) and in noise (= D). These individual SHL values were studied in relation to one another and in relation to such parameters as the pure-tone average (PTA), the Fletcher Index (FI), and the increment in intelligibility score per dB near SRT. It was found that (1) subjects with the same SHL in quiet may differ considerably in their SHL in noise; (2) for an individual, PTA and FI are inaccurate measures for predicting SHL in quiet and in noise, and (3) the higher an individual’s SHL in noise, the lower is the increase per dB of the intelligibility score for sentences in noise.
Adaptive computation of articulatory parameters from the speech signal
Authors: Levinson S. E. , Schmidt C. E.
Published: October 2005

An unconstrained optimization technique is used to find the values of parameters, of a combination of an articulatory and a vocal tract model, that minimize the difference between model spectra and natural speech spectra. The articulatory model is anatomically realistic and the vocal tract model is a ‘‘lossy’’ Webster equation for which a method of solution is given. For English vowels in the steady state, anatomically reasonable articulatory configurations whose corresponding spectra match those of human speech to within 2 dB have been computed in fewer than ten iterations. Results are also given which demonstrate a limited ability of the system to track the articulatory dynamics of voiced speech.
Characterization of volume scattering power spectra in isotropic media from power spectra of scattering by planes
Authors: Waag R. C. , Nilsson J. O. , Astheimer J. P.
Published: October 2005

Relations between the power spectrum of scattering by a plane and by a volume of a statistically isotropic random medium are developed from two basic expressions. One gives the power spectrum of scattering by an n-dimensional isotropic medium as a one-dimensional transform of a rotationally symmetric correlation function of medium variations. The other describes the power spectrum of scattering by an (n-k)-dimensional cross section as a projection of the power spectrum in n-dimensional space. The results are used to determine the power spectrum of scattering by a volume from the power spectrum of scattering by a plane within the volume and also to relate the moments of power scattered in spaces of various dimensions. To illustrate the relations, calculations of power spectra and selected moments for volume scattering are made from power spectra having analytic forms as well as form power spectra computed in two dimensions from images of closely packed spheres and of pig liver sections. Numerical results obtained by processing power spectra having closed form expressions for volume scattering are in close agreement with theoretical values. Calculations for packed spheres show general concentrations of power explained by theory but required substantial smoothing of data in two dimensions to obtain consistent results because the images were not true cross sections. Results from sections of pig liver agree wth expected relationships. The theoretical expressions and numerical data indicate how quantitative information about the three-dimensional structure can be obtained from two-dimensional sections when the basic isotropy conditions are satisfied.
Acoustic propagation in resonant axisymmetric cavities enclosing an inhomogeneous medium. Part I: Hollow cavity
Authors: El-Raheb Michael , Wagner Paul
Published: October 2005

Longitudinal and transverse standing waves in rigid cylindrical and conical cavities enclosing an inhomogeneous medium are studied. First, the inhomogeneity in speed of sound c is analyzed in terms of c gradient location, intensity, and shape. The energy transmission of longitudinal waves is optimum when the c gradient is located at pressure nodes. The energy transmission efficiency of transverse waves improves when a cone connects c1 and c2 regions of different cross section. The inhomogeneity in both density and speed of sound is then considered and differences between the two types of inhomogeneity are explained.
Geometrical aspects of acoustic radiation from a shallow spherical cap
Authors: Krenk Steen
Published: October 2005

Geometrical properties are used to obtain the acoustic field from harmonic and pulse excitation of a shallow spherical cap in a baffle. The axial field from harmonic oscillation is obtained by observing the equivalence with the field from oscillation of a suitably chosen full sphere. This defines a convenient Legendre polynomial expansion of the velocity on the cap and leads to an axial field in the form of a series of products of spherical Bessel and Hankel functions. Each term corresponds to a Bessel function variation of the potential in the focal plane. The full solution for a uniform pulse excitation is obtained from the geometry of intersecting spheres. The simplicity and finite duration of the pulse solution suggests its use as convolution kernel for general time dependence of the excitation.
Magnetic boundary conditions for metallic–glass piezomagnetic transducers
Authors: Meeks Steven W. , Hill J. Clifton
Published: October 2005

It has been shown by comparison of theory and experiment that metallic–glass piezomagnetic ribbons can have boundary conditions intermediate to constant B or constant H. It is argued that this intermediate boundary condition is due to partial rotation of the transverse magnetization at very low fields in the 2605SC alloy. An empirical relation for k33 has been derived for metallic–glass alloys with intermediate boundary conditions.
Comments on ‘‘A general Chebyshev complex function approximation procedure and an application to beamforming’’[J. Acoust. Soc. Am.7
2, 181–190 (1982)]
Authors: Wilson Geoffrey L.
Published: October 2005

Streit and Nuttall [J. Acoust. Soc. Am. 72, 181–190 (1982)] have described a numerical procedure for beamforming in which they minimize the possible error from the desired response function in several directions in the complex plane. By use of a vector diagram it is possible to estimate how many such directions ought to be chosen to achieve a given accuracy.
Comments on ‘‘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: Sidhu R. S. , Singh Sarva Jit
Published: October 2005

In the paper under discussion, Chattopadhyay et al. [J. Acoust. Soc. Am. 72, 255–263 (1982)] studied the problem of the reflection of elastic waves at the plane free boundary of an initially stressed sandy medium. The authors effected the decoupling of the P and SV motion for waves propagating in the horizontal and vertical directions which are the principal directions of the initial stress tensor considered. However, while discussing the reflection of P and SV waves, the authors use the above decoupling for waves propagating in an arbitrary direction. In fact, the expressions for the displacement potentials assumed by the authors do not satisfy the equations of motion. Consequently, most of the equations and results of the subject paper are either irrelevant or incorrect. Similarly, the results obtained by the authors for Rayleigh waves in an initially stressed sandy medium are also wrong.
An experimental study of signal-to-noise ratio losses due to OR-ing
Authors: Struzinski William A. , Bloom Jerrold C.
Published: October 2005

OR-ing experiments have been conducted on the Naval Underwater Systems Center Acoustic Display Research Facility. The objective of the experiments is to determine the signal-to-noise ratio loss when OR-ing N bins of data and to compare these results with some of the recently published theoretically derived losses. This paper discusses the details of the OR-ing experiment hardware and software, as well as the results obtained to date.