bluuebunny/crossref_metadata_2025 huggingface dataset:
A three-dimensional model of tongue movement based on ultrasound and x-ray microbeam data
Authors: Stone Maureen
Published: October 2005

Point-tracking techniques provide timing information about structural movements of the tongue. Imaging techniques provide information about cross-sectional and pharyngeal tongue shape and movement. This study joined these techniques in a single subject. Five pellets on the tongue surface were tracked using x-ray microbeam, and the midsagittal and coronal planes of the tongue were imaged using real-time ultrasound. The speech materials were the consonants [s] and [l] and the vowels [i], [a], and [o] combined in VCVC E utterances. Analyses concentrated on the difference in tongue movements related to the two consonants. A model of tongue movement was developed, in which critical features of consonant shape and position dominated the tongue opening movement. In this model, the tongue is divided into subdivisions termed ‘‘functional segments’’ in both the sagittal and coronal planes. Movements of the functional segments created observable opening movement patterns.
The influence of variations in biophysical conditions on hemolysis near ultrasonically activated gas-filled micropores
Authors: Miller Douglas L. , Thomas Ronald M.
Published: October 2005

Hemolysis induced by 1.9-MHz ultrasound in 0.5% suspensions of canine erythrocytes with 3.7-μm-diam micropore-trapped gas bodies was investigated for a variety of biophysical conditions. For isotonic media, hemolysis increased with exposure duration (4–64 min) but did not greatly change with exposure temperature (15, 25, 37, and 48 °C), or prior heat treatment (48 or 50 °C for 30 min). The temperature results were especially interesting because increased temperatures might have been expected to increase the sensitivity of the cells to the ultrasonically activated gas bodies. Variations in osmolarity (180, 290, or 580 mOsm) had little influence on the results. Increasing the viscosity (0.7, 2.2, 2.3, or 4.2 cP) of the medium decreased the effect, and this did not seem to depend on the molecular weight of the dextran additive (9400 or 250 000). A medium with elevated mass density (1.12 g/cm3 ) seemed to increase the effectiveness of the exposures. This condition eliminated the density difference between the cells and the medium, and might have been expected to reduce the effectiveness of the exposures, because the radiation force, which theoretically gathers cells to the gas bodies, is minimized for such conditions. This information should aid in developing refinements to the theoretical understanding of low-intensity ultrasonic bioeffects.
Comparison of effective medium and multiple-scattering theories of predicting the ultrasonic properties of dispersions: A reexamination of results
Authors: Gaunaurd G. C. , Wertman W.
Published: October 2005

Quantities such as a complex compressibility and a complex density introduced for suspensions in recent work are studied [viz., McClements et al., J. Acoust. Soc. Am. 87, XXX–XXX (1990)]. (a) While it is true that analytic expressions for these quantities coincide if one uses the effective medium theory (EMT) or the Waterman and Truell (WT) approaches to derive them, these expressions lack physical significance. (b) The derivation presented in the same letter, although of limited applicability in view of the nonphysical nature of the quantities involved, seems to fail for suspensions as claimed. (c) The analytic machinery of the EMT is shown to already contain those expressions, which have never been used in any practical case. (d) The claim that ‘‘the analytic differences between the EMT and WT approach (in the case of suspensions, in which they are still significant) have been accounted for,’’ is neither true, nor has it yet been carried out anywhere.
Comments on ‘‘Broadband repetition pitch: Spectral dominance or pitch averaging?’’ [J. Acoust. Soc. Am. 8
4, 2058–2062 (1988)]
Authors: Bilsen Frans A.
Published: October 2005

The article ‘‘Broadband repetition pitch: Spectral dominance or pitch averaging?’’ by R. M. Warren and J. A. Bashford, Jr. [J. Acoust. Soc. Am. 84, 2058–2062 (1988)] calls for some remarks and clarifications concerning current views on the perception of pitch and repetition pitch, in particular.
Cavity resonance in the violin: Network representation and the effect of damped and undamped rib holes
Authors: Shaw E. A. G.
Published: October 2005

The upper and lower volumes of the violin cavity are treated as acoustical capacitances coupled by an internal inertance. This leads to the development of a simple acoustical network that takes into account the noncentral position of the f-hole system and has two degrees of freedom representing the Helmholtz mode A0 and the primary longitudinal mode A1. The initial choice of values for the network elements is based in part on wave-acoustical considerations. These values are then adjusted under the guidance of new experimental data. In particular, when the violin is operating in the A0 mode, it is found that the acoustic pressure in the upper volume is 30% greater than that in the lower volume. The presence of rib holes around the upper and lower volumes is represented by additional network elements shunting the acoustical capacitances. The characteristics of the modified instrument, with and without rib-hole damping, are presented in terms of the calculated values of the resonance frequencies ν0 and ν1 , the Q factors, and the volume velocity ratios (φ) of the A0 and A1 modes as functions of the number of rib holes. (The parameter φ provides an indication of the volume velocity passing through the rib holes in comparison with that associated with the f-hole system.) The calculated values are compared with experimental data for the special instrument known as ‘‘Le Gruyère’’ [C.M. Hutchins, J. Acoust. Soc. Am. Suppl. 1 73, S84(1983); 87, XXX–XXX (1990)].
Underwater audiogram of a Hawaiian monk seal (M
o
n
a
c
h
u
s s
c
h
a
u
i
n
s
l
a
n
d
i)
Authors: Thomas Jeanette , Moore Patrick , Withrow Reid , Stoermer Mark
Published: October 2005

Underwater audiograms are available for a few pinnipeds from the families otariidae and phocidae, but little is known about hearing abilities in the monachid seals. A young male Hawaiian monk seal (Monachus schauinslandi) was trained at Sea Life Park on Oahu, Hawaii for an underwater hearing test using a go/no-go response paradigm. Over a 6-month period, auditory thresholds from 2 to 48 kHz were measured using an up/down staircase psychometric technique. The resulting audiogram shows a somewhat narrower hearing range than for other pinnipeds. The monk seal’s hearing was most sensitive (20 dB above maximum sensitivity) between 12 and 28 kHz. Below 8 kHz, the Hawaiian monk seal’s hearing was less sensitive than other pinnipeds measured. High-frequency sensitivity dropped off sharply above 30 kHz, as has been reported for other otariids, Callorhinus and Zalophus. Phocid seals, Phoca hispida, P. groenlandica, and P. vitulina, have a broader hearing range with the upper limit near 60 kHz.
Response to ‘‘Comments on ‘The growth of and recovery from TTS in human subjects exposed to impact noise’ ’’ [J. Acoust. Soc. Am. 8
6, 2020–2021 (1989)]
Authors: Laroche Chantal , Hétu Raymond
Published: October 2005

In this letter, the authors reply to comments written by W. D. Ward [J. Acoust. Soc. Am. 86, 2020–2021 (1989)] on an earlier article by Laroche et al. [J. Acoust. Soc. Am. 85, 1681–1690 (1989)].
Theory of symmetric multilayer structures as layer replacements for Chebyshev acoustic antireflection coatings
Authors: Martin B. G. , Cheng Z. Y. , Lee C. C.
Published: October 2005

Chebyshev filter theory can be applied to the design of wideband acoustic multilayer antireflection (ar) coatings. However, in many cases the acoustic impedance required for a particular layer is not readily available among common materials. In such cases, this study shows that the Chebyshev layer can be replaced by an acoustic symmetric multilayer (ASM) with the prescribed impedance. On the other hand, ASMs are dispersive, i.e., their reflection properties are a function of frequency. Consequently, the ASM replacement will somewhat degrade the performance of the resulting Chebyshev ar coating. In this study, theoretical results are obtained for a number of ASM replacement designs. For each design, normal-incidence reflection coefficient versus frequency is calculated. It is concluded that the performance of a Chebyshev ar coating is only slightly degraded by the use of ASM replacements, provided that the ASM dispersion is kept as small as possible. Accordingly, the ASM technique offers a useful means for the practical design of acoustic Chebyshev ar coatings.
A theoretical model of acoustoelectric transducer with a nonuniform distribution of piezoelectric coefficient: Application to transducer optimization
Authors: Chapeau-Blondeau François , Greenleaf James F.
Published: October 2005

A general equation is derived that describes the behavior of a piezoelectric transducer with a nonuniform distribution of piezoelectric coefficient within its bulk, when submitted to an arbitrary distribution of acoustic pressure. Based on this equation, an expression for the receiving transfer function of the transducer is calculated. The results demonstrate the dependence of the transfer function on the distribution of piezoelectric coefficient, and that it is possible to benefit from a nonuniform distribution to optimize the transfer function. The general equation also describes the influence of the external electric circuit loading the transducer, which leads to another independent means of optimizing the transfer function. The proposed model combines effects of piezoelectric material characteristics, acoustic backing, and electric loading, without resorting to Mason or other equivalent circuits for the transducer.
Dynamical behavior of middle ear: Theoretical study corresponding to measurement results obtained by a newly developed measuring apparatus
Authors: Wada Hiroshi , Kobayashi Toshimitsu
Published: October 2005

An attempt is made to develop a new measuring apparatus, and the dynamical characteristics of the middle ear of normal subjects and patients are measured with this apparatus. Applying the impedance theory of the tube to the external auditory canal, the aditus and the tympanic and mastoid cavities, and applying the energy method to the eardrum and the ossicular chain, the equation of the middle ear, corresponding to the output of the apparatus and including the pressure difference effect upon the eardrum is obtained. The numerical results are compared with the measurement results, and the effects of each part of the middle ear upon its dynamical characteristics are clarified. The great dependence of the dynamical characteristics of the middle ear upon the external auditory canal pressure is mainly caused by the pressure-dependent ossicular chain angular stiffness. The clearly different measurement results of the ossicular chain disorder patients from those of the normal subjects are obtainable by this apparatus, and these characteristics can be explained theoretically.
Multiple scattering by finite regular arrays of resonators
Authors: Twersky Victor
Published: October 2005

Earlier results for multiple scattering by arbitrary configurations of N obstacles are applied to seven regular arrays of two to six monopole resonators (with radius a, maximum scattering cross section σc, and normalized resonance frequency xc=kca). The arrays involve m=1, 2, or 3 different values of the separations of monopole centers, with d as the smallest. For each array, the corresponding scattering amplitude reduces to a sum of m+1 collective oscillator modes Fn (orthogonal in the same sense as the spherical harmonics). The doublet, triangular, and tetrahedral arrays are specified by two modes, F0 and F1; the square, pentagonal, and octahedral arrays require a third, F2; and the hexagonal array also requires a fourth, F3. The scattering cross section S of each array is less than 2Nσc, with maximum at a frequency ka=x near xc for relatively large kd=y=x/p≫x. If y>2x is small, the Fn reduce to simple multipoles in terms of spherical harmonics and elementary functions of x, p, and xc. Then S has narrow resonance peaks Sn=O(σc) at frequencies xn relatively far from xc (with x0xc); the averages over orientation S̄n add up to Nσc (an average oscillator-strength sum rule). The separations of the resonance frequencies xn and the fineness of the peaks Sn (nonoverlapping at half-power) provide distinctive signatures for diagnostic and related applications.
Temporal integration of trains of tone pulses by normal and by cochlearly impaired listeners
Authors: Carlyon Robert P. , Buus So/ren , Florentine Mary
Published: October 2005

Two experiments investigated the temporal integration of trains of tone pulses by normal and by cochlearly impaired listeners. In the first experiment, thresholds were measured for a single 5-ms, 4-kHz tone pulse, and for ten such tone pulses as a function of interpulse interval (Δt). For normal listeners, temporal integration, defined as the threshold difference between one and ten pulses, was about 8 dB for Δt<20 ms, and about 5 dB at longer Δt’s. For impaired listeners, temporal integration was only about 2–3 dB across the range of Δt’s (5–160 ms) studied. A second experiment measured psychometric functions (log d′ versus log signal power) for a single pulse and for ten pulses with Δt’s of 5 ms and 80 ms. The normal listeners’ functions had slopes close to unity in all three conditions, with a few exceptions. The impaired listeners’ functions had slopes close to unity for ten pulses with Δt=5 ms, but had slopes significantly greater than unity for Δt=80 ms, and for a single pulse. At Δt=80 ms, the increase in d′ relative to the condition with a single tone was similar (a factor of (10)1/2) for both impaired and normal listeners, but the threshold difference was smaller for the impaired listeners due to their steeper psychometric functions. For impaired listeners, then, temporal integration at Δt=80 ms was normal in terms of a change in d′, but abnormal when measured as a threshold difference. Impaired listeners’ functions for ten pulses at Δt=5 m were shallower than for a single pulse, so temporal integration at this Δt depended on the point on the psychometric function at which it was measured. The results of both experiments are discussed in relation to various hypotheses proposed to account for the reduced temporal integration in impaired ears.
Effects of flanking band proximity, number, and modulation pattern on comodulation masking release
Authors: Hall Joseph W. , Grose John H. , Haggard Mark P.
Published: October 2005

Comodulation masking release for a 700-Hz pure-tone signal was investigated as a function of the number and spectral positions of 20-Hz-wide comodulated flanking bands. In the first experiment, all stimuli were presented diotically. CMR was examined as a function of the number of flanking bands present, in conditions where the bands were arranged symmetrically around the signal frequency, were below the signal frequency, or were above the signal frequency. The number of flanking bands ranged from one to eight, and the magnitude of the diotic CMR ranged from approximately 5–16 dB. The results indicated: (1) bands closer to the signal resulted in larger masking release, and (2) more bands gave rise to larger CMR (but with diminishing returns above two flanking bands).

Two additional sets of diotic conditions were examined and compared to the condition where all eight comodulated flanking bands were present: In one set of conditions, two of the eight flanking bands were removed; in the other set of conditions, two of the eight flanking bands were replaced with bands (termed ‘‘deviant’’ bands) that were not comodulated with respect to the other bands.

There was very little effect of reducing eight bands to six, even when the removed bands were relatively near the signal frequency; however, CMR was substantially reduced when deviant bands were introduced, particularly when the deviant bands were placed relatively near the signal frequency. These reductions in CMR were slightly greater when each of the deviant bands had a unique modulation pattern (bideviant bands) than when the two deviant bands themselves shared the same modulation pattern (codeviant bands). In the second experiment, dichotic conditions were examined where the number and spectral positions of the flanking bands in the nonsignal ear were varied (the signal ear received only a 20-Hz-wide noise band centered on the signal frequency).

The magnitude of the dichotic CMR ranged from approximately 2–10 dB, depending on condition. Effects of proximity and the number of flanking bands were similar to the effects obtained in diotic conditions. For both the diotic and the dichotic data, the effects of proximity were more consistent with an interpretation based upon across-channel processing than upon a within-channel interaction. The results obtained using deviant bands indicate that it is difficult for the auditory system to disregard the modulation pattern of flanking bands that differ from the modulation pattern of the on-signal band, particularly if such bands are proximal to the signal frequency.
Experimental measurements of three-dimensional propagation in a wedge-shaped ocean with pressure-release boundary conditions
Authors: Glegg Stewart A. L. , Yoon Jong R.
Published: October 2005

The theoretical solution for three-dimensional acoustic propagation in a wedge-shaped ocean with ideal pressure-release boundaries predicts a well-defined beam in the down-slope direction that diverges as the energy propagates out towards deep water. Outside of the beam, shadow zones are formed, and its spatial extent is determined by the lowest mode of propagation. The purpose of the experimental results presented here is to check the theoretical analyses, as part of an ongoing investigation into three-dimensional propagation in the ocean environment. The wedge model in this experiment has a pressure-release bottom and a slope that is around 20 deg. For convenience of analysis, only the lowest mode is excited by locating a source near the cutoff range. It has been found that for down-slope propagation, the spatial characteristics of the field in a direction parallel to the shore line are in good agreement with the theoretical solution, and the azimuthal extent of the beam depends on the wedge angle. In addition to the evaluation of the exact theory, measurements have been made of acoustic pulse propagation and distortion in the wedge.
Free oscillations of near-surface bubbles as a source of the underwater noise of rain
Authors: Pumphrey Hugh C. , Crum L. A.
Published: October 2005

A bubble that is oscillating with a small amplitude may be thought of as a damped, undriven harmonic oscillator. If the bubble is near a free surface, it may be considered as a simple acoustic source close to a pressure release boundary and will therefore radiate as a dipole. It has been shown in a previous paper [Pumphrey et al., J. Acoust. Soc. Am. 85, 1518–1526 (1989)] that this mechanism is the major cause of the sound produced by rain and probably makes a contribution to the Knudsen spectrum of ambient noise in the ocean. Experimental results are presented for such freely oscillating bubbles, mostly entrained by drop impacts, which show that they have the resonance frequencies and damping constants predicted by theory. The presence of the free surface affects these values to a certain extent. The radiation pattern was measured and was shown to be a dipole, as predicted. Calculations of the amplitude of the bubble oscillation indicate that it is small, confirming that the linear approximation is valid. The spectrum level caused by a rain shower was calculated and compared with field measurements.
Seabed generation of ambient noise
Authors: Thorne Peter D.
Published: October 2005

Although the seabed has not generally been noted as an active originator of underwater sound, it can in some circumstances behave as an acoustic source, and contribute to marine ambient noise conditions. This arises when near-bed current flow, induced by tides and waves, exerts sufficient shear stress at the bottom boundary to cause the bedload transport of sediments. Interparticle collisions of this mobile material occur and sound is generated by particle impacts. To understand this addition to ambient noise, an examination of this source of sound generation has been conducted in the laboratory and at sea. The laboratory observations were taken using colliding sediments covering size fractions from medium sand to large cobbles. The marine records of ambient noise conditions were obtained over a mobile shingle bed. Comparison of predictions based on rigid body radiation theory with the data has been carried out and similar results obtained.
A subarray approach to matched-field processing
Authors: Cox Henry , Zeskind Robert M. , Myers Matthew
Published: October 2005

A simplified approach is presented for matched-field processing of large vertical arrays in typical ocean environments. The large array is divided into subarrays such that a plane-wave decomposition of the signal field is a good approximation over each subarray. A simple rule, based on the sound-speed profile, is presented for subarray sizing. Plane-wave beamforming is then performed to provide multiple beams from each subarray. For long-range situations, only those beams need to be formed that are steered to receive rays that are not strongly bottom interacting. When elements are spaced at one-half wavelength, the typical result of considering only these beams is a significant reduction in the size of the problem with far fewer beams required than elements. This first step is very robust and does not require a detailed knowledge of the signal field, or an assumption of signal coherence across the full array aperture. Beam outputs can then be combined to achieve full matched-field processing. The relative performance of suboptimal approaches such as incoherent combination of beam outputs or simply choosing the best beam is also examined. It is shown that full optimum coherent matched-field processing in spatially white noise yields an output signal-to-noise ratio that depends only on the total signal power intercepted by the aperture, and not on the details of the signal field. For an array that spans the full water column, this can be estimated simply on the basis of cylindrical power flow and falls off as the reciprocal of range. Detailed results are presented for a Pacific winter profile at three widely separated ranges. A small percentage of the beams is found to contain almost all of the signal power. The ray angle diagram (RAD) is used to relate rays, normal modes, and subarray beams, providing insight into the underlying principles. It is shown that the signal field has a fixed number of degrees of freedom and can be represented by that number of beams or normal modes.
A variational principle for the scattered wave
Authors: Freund D. E. , Farrell R. A.
Published: October 2005

A Schwinger-type variational principle is presented for the scattered field in the case of scalar wave scattering with an arbitrary field incident on an object of arbitrary shape with homogeneous Dirichlet boundary conditions. The result is variationally invariant at field points ranging from the surface of the scatterer to the farfield and is an important extension of the usual Schwinger variational principle for the scattering amplitude, which is a farfield quantity. Also, a generic procedure, physically motivated by the general principles of boundary conditions and shadowing, is presented for constructing simple trial functions to approximate the fields. The variational principle and the trial function design are tested for the special case of a spherical scatterer and accurate answers are found over the entire frequency range.
Analysis of echoes from a cylinder that includes the directivity of the transmitter and receiver
Authors: Li Tai-bao , Ueda Mitsuhiro
Published: October 2005

Analysis of an echo from a solid elastic cylinder had been limited to the case of a plane incident wave so far. Recently, plane wave theory was modified to the case of a spherically incident wave. In this paper an arbitrary ultrasonic transmitter and receiver are considered as a set of point sources and point receivers, respectively. The analysis is modified to the practical case, that is, the cylinder is placed so that its axis coincides with the central line of curvature of a cylindrical shell transducer. The dependence of the echo from the cylinder on the cylinder material is examined. These results are compared with those experimentally obtained using metal and plastic cylinders and they show very good agreement.
Influence of anisotropy on the dispersion characteristics of guided ultrasonic plate modes
Authors: Li Yan , Thompson R. Bruce
Published: October 2005

Dispersion curves are developed for elastic wave propagation in an anisotropic plate of monoclinic or higher symmetry. Emphasis is placed on analytic expressions for various features. Generalization of the isotropic Rayleigh–Lamb dispersion relations are derived for the cases of (a) propagation along a material symmetry axis and (b) propagation in a general direction. Examination of the high-frequency limit of the lowest symmetric and antisymmetric mode dispersion curves yields expressions for the half-space surface or Rayleigh wave velocity. It is shown that the dispersion curves for these modes can exhibit multiple crossings in approaching this limit, and an analytic solution is presented for the constant crossing interval that occurs for propagation along symmetry directions. The analytic results are illustrated by extensive numerical calculations for a variety of degrees of anisotropy with emphasis placed on the relationship between the slowness curves governing partial wave propagation and various features of the dispersion curves.
Coupled finite element/boundary element approach for fluid–structure interaction
Authors: Everstine Gordon C. , Henderson Francis M.
Published: October 2005

A new computational capability is described for calculating the sound-pressure field radiated or scattered by a harmonically excited, submerged, arbitrary, three-dimensional elastic structure. This approach, called nashua, couples a nastran finite element model of the structure with a boundary element model of the surrounding fluid. The surface fluid pressures and normal velocities are first calculated by coupling the finite element model of the structure with a discretized form of the Helmholtz surface integral equation for the exterior fluid. After generation of the fluid matrices, most of the required matrix operations are performed using the general matrix manipulation package available in nastran. Farfield radiated pressures are then calculated from the surface solution using the Helmholtz exterior integral equation. The overall capability is very general, highly automated, and requires no independent specification of the fluid mesh. An efficient, new, out-of-core block equation solver was written so that very large problems could be solved. The use of nastran as the structural analyzer permits a variety of graphical displays of results, including computer animation of the dynamic response. The overall approach is illustrated and validated using known analytic solutions for submerged spherical shells subjected to both incident pressure and uniform and nonuniform applied mechanical loads.
Modal contributions of a finite plate to power spectra
Authors: Ko Sung H.
Published: October 2005

An investigation is made of the modal contribution of a finite elastic plate, simply supported at both ends, to the power spectrum. Theoretical calculations were made for a finite steel plate submerged in a fluid and excited by two types of forcing functions: (1) a line force and (2) a statistically uniform force. Numerical results calculated for transfer functions and power spectra were presented. A comparison of power spectra calculated for different loading conditions is presented.
Comparison between two approaches for solving nonlinear radiations from a bubble in a liquid
Authors: Du Gonghuan , Wu Junru
Published: October 2005

Two different approaches have been used in the literature to discuss the nonlinearity of the scattered wave from a pulsating bubble in a liquid: The radial displacement approach and the volume displacement approach. These two treatments have been compared and it has been pointed out that there is no theoretical basis for the conclusion reached from the volume displacement approach that the second-harmonic amplitude of the sound emission is zero at a specific frequency.
Application of the SAFARI model to sound propagation in the atmosphere
Authors: Güdesen Alwin
Published: October 2005

The SAFARI (seismo acoustic fast-field algorithm for range-independent environments) wave propagation model is applied for the first time to low-frequency atmospheric sound propagation and tested by means of synthetic and real-world data. Problems experienced with the use of SAFARI are discussed in detail. Good agreement of the model output with theoretical predictions is achieved for two half-spaces (air/ground). Available meteorological data up to 5 000-m height are applied to the model in the next step in order to compute sound transmission loss versus range and receiver height. Results are given in transmission loss contour plots covering a field of 1 000 m in height and 30 000 m in range. The influence of typical sound velocity profiles including strong gradients close to the ground is investigated. It turns out that knowledge of meteorological data is most relevant for heights of up to about 200 m for sound propagation modeling within a field of interest as above. SAFARI is finally compared with a fast-field program developed at the U.S. Army Construction Engineering Laboratory. This test yields very good agreement between both model predictions on a test case in which a real-world sound profile is used. It has to be emphasized that all results are for very low frequencies where finite impedance ground effects are minimal. One would expect to see differences at higher frequencies. These encouraging results give rise to recommending the use of the models in a number of interesting applications such as various types of acoustic detection system and civil noise control.
Ground characterization by short-range propagation measurements
Authors: Hess H. M. , Attenborough K. , Heap N. W.
Published: October 2005

In recent years, short-range measurements of excess attenuation from a point source have been used together with semiempirical formulas for frequency dependence of impedance to enable the acoustical characterization of ground surfaces, including snow, in terms of a single parameter. This has then been advocated as a basis for predicting ground and propagation effects at longer ranges. An alternative method is described for determining acoustical properties of ground surfaces including sands, soils, and snow from iterative least-squares fitting of the level difference spectrum obtained between a pair of vertically separated microphones within 2 m of a broadband point source. The method is based on a three-parameter model for the surface normal impedance as a function of frequency, together with well-established formulations for propagation from a point source above either local or extended reaction surfaces. The three parameters are porosity, effective flow resistivity, and tortuosity. Independent (nonacoustic) measurements of porosity compare tolerably well with the acoustically determined values for soils that are homogeneous to several centimeters depth. For such soils, fitting comparisons reveal the superiority of the three-parameter impedance model to the single-parameter semiempirical model. Where there are obvious surface crusts, a double-layer model based upon a two-parameter approximation for the characteristic impedance of each layer is found to give better agreement with short-range propagation measurements than the three-parameter homogeneous approximation.
Ocean-bottom ultralow-frequency (ULF) seismo-acoustic ambient noise: 0.002 to 0.4 Hz
Authors: Sutton George H. , Barstow Noël
Published: October 2005

Observed spatial and temporal characteristics of ultralow-frequency (ULF) ocean-bottom seismo-acoustic ambient noise are required in order to construct realistic quantitative predictive models of the phenomena involved. Few such data exist or have been studied, especially for frequencies below about 0.1 Hz. Analysis of noise data is presented in the band 0.002 to 0.4 Hz from a 2-week period, 11/28–12/12/67, recorded from long-period, three-component seismometers and a hydrophone of the Columbia-Point Arena ocean-bottom seismic station (OBSS, 38° 09.2′N–124° 54.4′W, 3903-m depth). Two intense NE Pacific storms with hurricane force winds occurred during the emphasized time period. Time variations of spectra and of amplitude and phase coherencies of the four-component OBSS data are related to the storm histories and to local weather/wave conditions and are used to identify motion (seismic wave) types and directions of propagation.
Fine-scale measurements of the vertical ambient noise field
Authors: Sotirin B. J. , Hodgkiss W. S.
Published: October 2005

The fine-scale structure of the directional ambient noise field is investigated utilizing a large-aperture (900-m) vertical array. Frequency and directional spectral estimates are calculated during the passage of a local storm, providing a detailed study of the ambient noise field temporal and spatial characteristics at low frequencies (15–130 Hz) as wind speed increases from 2 to 12 m/s over a 21-h period. Spectral levels of horizontal beams reflect the variability of discrete distant sources. Spectral levels of beams directed toward the surface and the bottom display a threshold-type behavior, suggesting the abrupt onset of a source mechanism such as breaking waves.
Identification of liquid mixtures for ultrasonic applications
Authors: Bonney Rob , Davis Christopher C.
Published: October 2005

Liquid mixtures and solutions are sought that exhibit improved properties for ultrasonic applications such as acoustic microscopy and stimulated Brillouin scattering. Both these applications require liquid media with low acoustic velocity and attenuation. A thermodynamic theory is used to predict the acoustic velocity of a mixture from the heat of mixing; consulting a table of heats of mixing then provides a way of identifying candidate liquid mixtures. Acoustic attenuation is not predicted and must be found experimentally. The method works well for liquid solutes, but is shown to be ineffective for solid solutes since the lattice energy of the solute dominates the heat of mixing. An optical heterodyne technique was used to measure the acoustic properties of candidate mixtures in the frequency range 0.2–1.2 GHz. New acoustic data are reported for these mixtures: aqueous cetyl pyridinium chloride (a detergent solid), aqueous ethylene carbonate, and ethyl acetate in carbon disulphide. No mixtures were found with superior properties for ultrasonic applications.
Click rates from sperm whales
Authors: Whitehead Hal , Weilgart Linda
Published: October 2005

The rate of production of clicks by groups of (mainly female) sperm whales off the Galápagos Islands was dependent on two principal factors: the number of whales present and the behavioral state of the group. When the whales were in their principal (occupying about 80% of their time) behavioral state, diving deep for prolonged periods and usually being seen at the surface singly or in pairs, each whale made trains of clicks with an interclick interval of about 0.5 s about 70% of the time. About 10% of the time, the groups remained at or near the surface, with individual members forming clusters containing greater than five individuals, and being generally silent. Group behavior was sometimes intermediate between these extremes, with some whales silent at the surface in medium-sized clusters, and others clicking at depth. Click rate can be used as an indicator of the behavior of sperm whales, the size of a group, and/or the number of groups present. In our studies, groups associated often, and more frequently in 1985 than in 1987, perhaps because of changes in oceanographic conditions. The overall click rate, needed to calibrate acoustic censuses, was estimated to be 1.22 clicks s−1/animal.
Diffraction of Lamb waves at the end section of a plate
Authors: Luppé F. , Chatelets B. Gilles , Maze G.
Published: October 2005

An experimental study is presented of the diffraction of Lamb waves at the end section of a plate imbedded in water. The amplitude of the diffracted wave is plotted versus angle of diffraction for different Lamb modes. The S modes have maxima of diffraction in their direction of propagation, as opposed to A modes that are associated with minima of diffraction in their direction of propagation. For all modes, the diffraction pattern is symmetric about the direction of propagation of the incident (Lamb) wave, and the peaks associated with maxima of the diffracted amplitude widen as the angle of observation increases. Those results are in good agreement with those obtained by a simple calculation of interferences between two sources, the relative phases of which are determined by the type (A or S) of diffracting Lamb wave.
Identification of the acoustic ocean transfer function in the Tyrrhenian Sea. II: Physical considerations
Authors: Fradkin Larissa Ju.
Published: October 2005

In the process of statistical analysis of signature/response pairs collected in the Tyrrhenian Sea during the Napoli 85 Trial, a novel deconvolution method has been developed for identifying the ocean transfer function (OTF) when its bandwidth is larger than the bandwidth of the emitted pulse. The analysis itself is described in the preceding paper [L. Ju. Fradkin, J. Acoust. Soc. Am. 87, XXXX (1990)]. Here, the underlying convolution formula relating the received signal to the signature as well as other important physical constraints are derived under the assumptions (reasonable in the analyzed case) that the emitted pulse contains no low frequencies, and that it travels along the paths none of which reverses the phase (i.e., no reflections or caustics are involved). The results of processing a representative signature/response pair with the proposed method are discussed briefly. It is shown that for the given source/receiver configuration at least two deep sea (and hence non-phase-reversing) paths exist. It is also shown that the ‘‘internal waves’’ model, rejected by other investigators in the course of their analysis of the environmental data, would not allow for existence of the second macropath. It is concluded that in certain circumstances, the proposed deconvolution method could be used to assess models of medium fluctuations.
Brain-stem auditory-evoked reponses elicited by maximum length sequences: Effect of simultaneous masking noise
Authors: Burkard Robert , Shi Ying , Hecox Kurt W.
Published: October 2005

The effects of masking noise on wave V of the brain-stem auditory-evoked response (BAER) obtained to pseudorandom pulse sequences are evaluated in two experiments. In the first experiment, the level of broadband noise was covaried with minimim pulse interval (rate) using maximum length sequence analysis (MLSA). Both increasing noise level and decreasing minimum pulse interval decrease wave V amplitude and increase wave V latency. A nonadditivity of rate and noise level was observed such that, at the shortest interpulse intervals, simultaneous background noise produced virtually no latency change and minimal amplitude change, for the noise levels tested. In a second experiment, high-pass masking was performed to assess the feasibility of derived-band techniques using maximum length sequence analysis (MLSA) and to compare the frequency regions responsible for the BAER using MLSA versus conventional averaging. Results of experiment 2 showed that reliable responses across high-pass masker cutoff frequency could be obtained in normal-hearing listeners. The frequency specificity of the MLSA-based responses was nearly identical to that obtained by conventional averaging, although both amplitude and latency of wave V were affected by the high-pass masker cutoff and minimum pulse interval values. These studies suggest that the neuronal populations and frequency regions responsible for the BAER are virtually the same for MLSA and conventional averaging.
Across-channel masking and comodulation masking release
Authors: Moore Brian C. J. , Glasberg Brian R. , Schooneveldt Gregory P.
Published: October 2005

These experiments on across-channel masking (ACM) and comodulation masking release (CMR) were designed to extend the work of Grose and Hall [J. Acoust. Soc. Am. 85, 1276–1284 (1989)] on CMR. They investigated the effect of the temporal position of a brief 700-Hz signal relative to the modulation cycle of a 700-Hz masker 100% sinusoidally amplitude modulated (SAM) at a 10-Hz rate, which was either presented alone (reference masker) or formed part of a masker consisting of the 3rd to 11th harmonics of a 100-Hz fundamental. In the harmonic maskers, each harmonic was either SAM with the same 10-Hz modulator phase (comodulated masker) or with a shift in modulator phase of 90° for each successive harmonic (phase-incoherent masker). When the signal was presented at the dips of the envelope of the 700-Hz component, the comodulated masker gave lower thresholds than the reference masker, while the phase-incoherent masker gave higher thresholds, i.e., a CMR was observed. No CMR was found when the signal was presented at the peaks of the envelope. In experiment 1, we replicated the experiment of Grose and Hall, but with an additional condition in which the 600- and 800-Hz components were removed from the masker, in order to investigate the role of within-channel masking effects. The results were similar to those of Grose and Hall. In experiment 2, the signal was added at the peaks of the envelope of the 700-Hz component, but in antiphase to the carrier of that component and at a level chosen to transform the peaks into dips. No CMR was found. Rather, performance was worse for both the comodulated and phase-incoherent maskers than for the reference masker. This was true even when the flanking components in the maskers were all remote in frequency from 700 Hz. In experiment 3, the masker components were all 50% SAM and the signal was added in antiphase at a dip of the envelope of the 700-Hz component, thus making the dip deeper. Performance was worse for the phase-incoherent than for the reference masker and was worse still for the comodulated masker. The results of all three experiments indicate strong ACM effects. CMR was found only when the signal was placed in the dips of the masker envelope and when it produced an increase in level relative to that in adjacent bands.
Perception of temporal patterns defined by tonal sequences
Authors: Sorkin Robert D.
Published: October 2005

This experiment tested how listeners discriminate between the temporal patterns defined by two sequences of tones. Two arrhythmic sequences of n tones were played successively (n=8, 12, or 16, tone duration=35 ms, frequency=1000 Hz), and the listener reported whether the sequences had the same or different temporal patterns. In the first sequence, the durations of the intertone gaps were chosen at random; in the second sequence, the gaps were either (a) the same as the first sequence or (b) chosen at random. Discrimination performance increased with the variability of the gap sequences and decreased with the size of the correlation between the sequences. A discrimination model based on computation of the sample correlation between the sequences of gaps, but limited by an internal variability of approximately 15 ms, described observer performance in a variety of conditions.
The effect of pitch-related changes on the perception of sung vowels
Authors: Benolken Martha S. , Swanson Charles E.
Published: October 2005

Vowel discrimination and perception were studied for a soprano singing on a fundamental frequency between 262 and 1047 Hz. The vowels were identified by 28 listeners as 1 of 12 American English vowels. As expected, both the singer’s apparent first formant and the difficulty in vowel recognition increased as the fundamental frequency increased. Although some formant frequency shift can be tolerated without changing vowel perception, the greater shifts that occurred here contributed to the difficulty in understanding in a roughly predictable way.
Ultrasonic propagation properties of articular cartilage at 100 MHz
Authors: Agemura Diane H. , O’Brien William D. , Olerud John E. , Chun Lawrence E. , Eyre David E.
Published: October 2005

A pilot study on articular cartilage assessed the contributions of individual matrix components to ultrasound propagation. The influence of collagen fibril orientation and collagen cross linking was also assessed. Sections of adult bovine articular cartilage cut both parallel and perpendicular to the articular surface were examined using the scanning laser acoustic microscope (SLAM) operating at an ultrasonic frequency of 100 MHz. A set of samples was evaluated that had been sequentially treated by enzymes to (1) remove 85% of the chondroitin sulfate; (2) remove remaining glycosaminoglycans, glycoproteins, and other noncollagen proteins, leaving only the collagen fibril network; and (3) disrupt the collagen intermolecular cross links. Two striking observations were made: a profound effect of the ‘‘preferred’’ collagen fibril orientation on ultrasonic speed and a marked increase in attenuation coefficient when intermolecular cross links were broken in the collagen.
Analysis and synthesis of backscattering from a circular cylindrical shell
Authors: Veksler N. D. , Korsunskii V. M.
Published: October 2005

The farfield backscattered form function is examined for the problem of plane acoustic pressure wave scattering by an empty elastic circular cylindrical shell. The analysis of the exactly computed total form function has been carried out. The approach of finding the contribution introduced by two peripheral Lamb-type waves—the zero-order symmetric S0 and the zero-order antisymmetric A0—is outlined. An approximate description of these contributions is used to synthesize the backscattered form function. The presentation is developed using the case of an Armco iron shell with moderate thickness, immersed in water.
A hybrid (boundary elements)-(finite elements)-ray-mode method for wave scattering by inhomogeneous scatterers in a waveguide
Authors: Lu I-Tai , Jung H. K.
Published: October 2005

Wave scattering by inhomogeneous scatterers in a waveguide is studied using a new method that combines the hybrid ray-mode, boundary element, and finite element methods systematically in a single framework. This is a generalization of the previous work [I. T. Lu, ‘‘Analysis of acoustic wave scattering by scatterers in layered media using the hybrid ray-mode-(boundary integral equation) method,’’ J. Acoust. Soc. Am. 86, 1136-1141 (1989)]. The boundary element method is employed to model the interaction among scatterers and the coupling between interior and exterior of scatterers, the finite element method to formulate the interior responses of the scatterers, and the ray-mode method to provide Green’s function of the waveguide. This hybrid combination optimizes the advantages of each method and hence, provides physical insights and numerical efficiency and accuracy. To further improve the computational efficiency, the Jacobi’s iteration solution is employed.