bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic properties of tendon: Velocity, attenuation, and backscattering in equine digital flexor tendons
Authors: Miles Christopher A.
Published: October 2005

Ultrasound velocity, attenuation, and backscattering were measured in vitro in samples of equine digital flexor tendon sandwiched between plane, parallel rexolite buffer rods. The buffer rods were coupled to transmitting and receiving transducers (nominally 10 MHz) mounted in-line and facing one another on the jaws of a digital caliper. Six superficial digital flexor (SDF) tendons and six deep digital flexor (DDF) tendons were measured in three orthogonal directions: along the long axis of the tendon (D), and across the tendon in the dorsal-volar (C), and lateral (L) directions. Substantial anisotropy was apparent in all the measured properties. The velocity data, which in both tendons showed a higher velocity along the fibers than across (e.g., in the DDF tendon at 0 °C: 1713±9 m/s in the D direction compared with 1650±5 m/s in the C direction), were consistent with a composite comprising stiff fibers embedded in a less stiff medium of lower speed. The apparent backscattering coefficient adjusted for the tissue’s frequency-dependent attenuation (e.g., in the C direction of the DDF tendon at 0 °C: 7.4×10−3 cm−1 sr−1), was independent of frequency in both transverse directions and larger than that measured along the long axis of the tendon (e.g., in DDF tendon at 0 °C: 1.2×10−3 cm−1 sr−1 at 7 MHz) in which direction the apparent backscattering coefficient increased with frequency as f4.0±1.2. The frequency-independent backscattering was thought to be due to specular reflection from the boundaries between the fascicles, i.e., the bundles of fibers making up the tendon, while backscattering along the axis was due to structures of unknown origin, but of a size much smaller than 45 μm. Attenuation of ultrasound directed along the fibers was higher than that across (at 7 MHz in DDF tendon at 0 °C: 58 dB/cm in the D direction compared with 11.3 dB/cm in the C direction). Calculations indicated that the attenuation was primarily caused by absorption rather than scattering.
A spherical basis function neural network for approximating acoustic scatter
Authors: Jenison Rick L.
Published: October 2005

This paper describes a neural network for approximation problems on the sphere. The von Mises basis function is introduced, whose response depends on polar rather than Cartesian input coordinates. The architecture of the von Mises basis function (VMBF) neural network is presented along with the corresponding gradient descent learning rules. The VMBF neural network is used to solve a specific benchmark spherical problem of approximating a known function, the reflection factor of a plane wave scattering at a rigid sphere.
Ultrasound pulse reflection mode measurement of nonlinearity parameter B/A and attenuation coefficient
Authors: Fukukita Hiroshi , Ueno Shin-ichiro , Yano Tsutomu
Published: October 2005

A new method for obtaining depth distribution of the nonlinearity parameter B/A and the frequency-dependent attenuation coefficient is outlined. In this method, the higher frequency probe pulse wave, superposed coaxially on the lower frequency pump pulse wave, is modulated nonlinearly due to their propagation, and is received as an echo signal. The relationship between these acoustic parameters and the modulation characteristics of the probe pulse wave is derived by the division of the spectra of modulated echo signals with each other. The possibility of canceling out of error factors, such as the frequency-dependent acoustic reflection coefficient of random scattering medium, in the above division process is discussed. A preliminary evaluation of this method is made by using an experimental system. B/A values are obtained for various kinds of sponge test targets immersed in water, n-propyl alcohol, isopropyl alcohol, ethylene glycol, or diethylene glycol; and for agar graphite phantom.
Low-frequency coupling between eardrum and manubrium in a finite-element model
Authors: Funnell W. Robert J.
Published: October 2005

The mechanical coupling between the eardrum and the manubrium was studied by means of a finite-element model of the cat eardrum. Previous calculations of the effect of varying the eardrum curvature were extended, demonstrating the critical role of curvature in the behavior of the eardrum. A new procedure was developed for directly studying the coupling of forces from different points on the eardrum to the manubrium, and the distribution of load-coupling values over the eardrum surface was calculated. A geometrically simplified eardrum with a circular outline was also studied. It was found that certain regions of the eardrum are more effective in driving the manubrium than can be explained on the basis of their distance from the axis of rotation. This enhanced coupling depends on the curvature of the eardrum but, unlike the mechanism hypothesized by Helmholtz, requires neither tension nor anisotropy.
Determination of velocity and attenuation of shear waves using ultrasonic spectroscopy
Authors: Wu Junru
Published: October 2005

The ultrasonic spectroscopy (broadband pulse) technique was applied to simultaneously measure phase velocity and attenuation coefficient of shear waves in a solid at frequencies ranging from 2.2 to 7.6 MHz. This technique is an extension of the ultrasonic spectropy technique currently used in determining dispersion of longitudinal waves.
Lexical familiarity and English-language experience affect Japanese adults’ perception of /ɹ/ and /l/
Authors: Flege James Emil , Takagi Naoyuki , Mann Virginia
Published: October 2005

This study assessed the influence of subjective lexical familiarity and English-language experience on Japanese adults’ accuracy in identifying singleton word-initial tokens of English /ɹ/ and /l/. The inexperienced Japanese (IJ) subjects had lived in the U.S. for 2 years, whereas the experienced Japanese (EJ) subjects had lived there for 21 years, on average. The native Japanese subjects correctly identified English /in r/ and /l/ tokens less often than did a group of native English (NE) subjects, but they did not differ from the NE subjects in identifying the control consonants /w/ and /d/. The NE subjects, who were at ceiling, showed no effect of subjective lexical familiarity. However, the EJ and IJ subjects correctly identified /in r/ and /l/ tokens more often in words that were more familiar than their minimal pairs than in words that were less familiar than their minimal pairs. The EJ subjects identified liquids more often than did the IJ subjects, but usually less often than the NE subjects. However, the EJ subjects managed to identify /in r/ tokens at rates comparable to the NE subjects’ rates in words that were matched in subjective familiarity to their minimal pair (experiment 1), and when identifying /in r/ tokens that had been edited out of their original word or nonword context (experiment 2).
Applicability of the Leq as a damage-risk criterion: An animal experiment
Authors: Lataye Robert , Campo Pierre
Published: October 2005

Within the European communities, the Leq8h is used as a damage-risk criterion (DRC) for hearing protection. The use of such a DRC supposes that sound exposures with equal energy imply equal risk for noise-induced hearing loss (NIHL). The aim of the present study, carried out with guinea pigs, was to test the applicability of the Leq8h for estimating the hazard of different noises having the same spectrum and acoustic energy. Therefore, only the temporal structure of noises was a variable (continuous, intermittent, or impulsive) and each noise had a Leq8h of 92 dB. The results indicate the Leq8h is not an accurate DRC. It overestimates the NIHL for intermittent and short-continuous noises, whereas it seems to be useful for moderate-intensity noises (95 dB) and for the impulse noise (101 dB). Furthermore, the data point out the notion of ‘‘critical intensity’’ which seems to play a determining role in the transition between metabolic and mechanical mechanisms involved in the acoustic trauma. Since the critical intensity and the existence of two mechanisms are parameters that the Leq8h cannot take into consideration, recommendations on the safety program of hearing loss prevention are discussed.
A space-time finite element method for the exterior acoustics problem
Authors: Thompson Lonny L. , Pinsky Peter M.
Published: October 2005

In this paper, the development of a space-time finite element method for the solution of the transient acoustics problem in exterior domains is discussed. The space-time formulation for the exterior acoustics problem is obtained from a time-discontinuous Galerkin variational equation for coupled structural acoustics, specialized to the case of zero normal velocities on the wet surface, i.e., a rigid scatterer. The formulation employs a finite computational acoustic domain surrounding the scatterer and incorporates high-order time-dependent nonreflecting (radiation) boundary conditions on the fluid truncation boundary as ‘‘natural’’ boundary conditions in the space-time variational equation, i.e., they are enforced weakly in both space and time. The result is an algorithm for direct transient analysis of acoustic radiation and scattering with the desired combination of good stability and high accuracy. The method is especially useful for the application of adaptive solution strategies for transient acoustics in which unstructured space-time meshes are used to track wavefronts propagating along space-time characteristics. Optimal stability estimates and convergence rates are reported together with two representative numerical examples involving transient radiation and scattering which illustrate the high-order accuracy achieved by the method for the exterior acoustics problem.
A renormalization method for nonlinear pulsed sound beams
Authors: Fro/ysa Kjell-Eivind , Coulouvrat François
Published: October 2005

An analytical, approximate solution of the inviscid KZK equation, for a finite amplitude pulsed sound beam radiated by a Gaussian source, is obtained by means of the renormalization method. The method involves two main steps. First, the transient quasilinear field is obtained under an integral form. However, this weakly nonlinear approximation breaks down with increasing nonlinear effects. Its validity is then extended by inserting into it a nonlinear coordinate transform, so as to counterbalance nonuniform terms. The choice of the renormalization is made so as to handle, as best as possible, the formation of shock waves. Comparisons with the results of a finite-differences scheme (‘‘Bergen code’’) show that, both on and off axis, for short and long pulses, the method is able to describe accurately the nonlinear distortion of the wave profile, the formation of shock waves, and their early evolution.
Influence of phase between original frequencies on the nonlinear generation of new harmonics. Examples of application from nonlinear acoustics
Authors: Hedberg Claes M.
Published: October 2005

It is assumed that the solution to a problem is given in the form of a complex multiple Fourier series infinite in each of the original frequencies. In this paper a simple theorem shows that the absolute values of the individual frequency coefficients in the series are independent of the phase relation between the original frequencies. But the coefficient’s division into real and imaginary parts is phase dependent. When the ratios between the frequencies are not irrational numbers there exist in the sum several coefficients giving the same frequency, and hence, the total amplitude for a specific frequency depends on the phase. An example of application shows results from nonlinear acoustics where, e.g., the importance of original phase for parametric arrays can be estimated.
Elastic pulsed wave propagation in media with second- or higher-order nonlinearity. Part I. Theoretical framework
Authors: Van Den Abeele Koen E-A
Published: October 2005

A theoretical model is presented that describes the interaction of frequency components in arbitrary pulsed elastic waves during one-dimensional propagation in an infinite medium with extreme nonlinear response. The model is based on one-dimensional Green’s function theory in combination with a perturbation method, as has been developed for a general source function by McCall [J. Geophys. Res. 99 (B2), 2591–2600 (Feb. 1994)]. A polynomial expansion of the equation of state is used in which four orders of nonlinearity in the moduli are accounted for. The nonlinear wave equation is solved for the displacement field at distance x from a symmetric ‘‘breathing’’ source with arbitrary Fourier spectrum imbedded in an infinite medium. The perturbation expression corresponds to a higher-order equivalent of the Burgers’ equation solution for velocity fields in solids. The solution is implemented numerically in an iterative procedure which allows one to include an arbitrary attenuation function. Energy conservation is investigated in the absence of (linear) attenuation, and the notion of a hybrid (linear and nonlinear) dissipation is illustrated. Examples are provided showing the effect of each term in the perturbation solution on the spectral content of the waveform. Finally, the possibility of creating a parametric array for seismic exploration is briefly considered from a theoretical point of view.
The propagation of elastic waves through a layered poroelastic medium
Authors: Baird Gordon E. , Thomas Paul D. , Sang Gabriella
Published: October 2005

A matrix formalism developed by Thomson and Haskell to study the transmission of plane elastic waves through a system of parallel, homogeneous, isotropic layers is extended to the case of parallel poroelastic layers. In a poroelastic medium, there are two dilatation waves and one rotational wave contrasted with one rotational wave and only a single dilatation wave for ordinary elastic media. Formal matrices are obtained which allow the systematic computation of transmission of these waves through layered poroelastic media.
A computational model for tympanometry
Authors: Chen Lin , Shen Yun-Hua
Published: October 2005

A computational model for tympanometry was developed by describing the ear canal with the impedance theory of a tube and by representing the middle ear with the Zwislocki electroacoustic analog. Changes in ear-canal length and acoustic properties of the middle ear with ear-canal pressures during a tympanometric procedure were mimicked by manipulating relevant model parameters. Tympanograms of different patterns of the normal ear and the ear with a disarticulation of the ossicular chain were reproduced with the model and were in agreement with experimental observations reported by other investigators. The model demonstrated the relationship between various patterns of admittance tympanograms and middle ear impedance predicted by the Vanhuyse theory. The effects of the ear canal on the estimates of middle ear admittance using compensation procedures for ear-canal volume were also predicted with the model. The model can provide a better understanding of the mechanism of tympanometry and a framework for further modeling study.
Responses of ventral cochlear nucleus units in the chinchilla to amplitude modulation by low-frequency, two-tone complexes
Authors: Shofner William P. , Sheft Stanley , Guzman Sandra J.
Published: October 2005

For a tone that is amplitude modulated by two tones (fmod1 and fmod2), neither the stimulus waveform nor the half-wave rectified waveform has spectral energy at the envelope beat frequency (fmod2−fmod1). The responses of ventral cochlear nucleus units in the chinchilla were recorded for best frequency tones that were amplitude modulated by low-frequency, two-tone complexes. Fourier analysis of poststimulus time histograms shows spectral peaks at fmod2−fmod1 in addition to the peaks at fmod1 and fmod2. The peaks in the neural spectra arise from compressive nonlinearities in the auditory system. The magnitudes of these spectral peaks are measures of synchrony at each frequency component. For all units, synchrony at fmod1 and fmod2 is greater than the synchrony at fmod2−fmod1. For a given unit, synchrony at fmod1 and fmod2 remains relatively constant as a function of overall level, whereas synchrony at fmod2−fmod1 decreases as the level increases. Synchrony was quantified in terms of the Rayleigh statistic (z), which is a measure of the statistical significance of the phase locking. In terms of z, phase locking at fmod1 and fmod2 is largest in chopper units, whereas onset-chopper units and primarylike units having sloping saturation in their rate-level functions show the smallest amount of phase locking. Phase locking at fmod2−fmod1 is also largest in chopper units, and smallest in onset-chopper units and primarylike units with sloping saturation.
Acoustic elements of speechlike stimuli are reflected in surface recorded responses over the guinea pig temporal lobe
Authors: McGee Therese , Kraus Nina , King Cynthia , Nicol Trent , Carrell Thomas D.
Published: October 2005

Auditory evoked potentials measured from the guinea pig temporal lobe surface reflect acoustic elements of synthesized speech syllables. Eliciting stimuli included a four formant anchor stimulus /ba/, with a 40-ms formant transition duration. The other stimuli differed from /ba/ along simple acoustic dimensions. The /pa/ stimuli differed on a VOT continuum; /da/ stimuli had higher frequency F2 onset; /wa/ had a longer (80 ms) formant transition duration; and /bi/ differed in three vowel formant frequencies. The /ba/ and /da/ onset response latencies decreased systematically with increasing F2 onset frequency. The response to the /pa/ voicing increased in latency with increasing VOT and showed a physiologic discontinuity at VOT of 15–20 ms. Responses to /ba/ and /wa/ showed similar onset morphology but significant amplitude differences at latencies corresponding to vowel onset. Significant amplitude differences in /ba/ and /bi/ responses corresponded in latency to both consonant and vowel portions of the syllables. Similar to previous reports in the awake monkey for VOT, these results demonstrate in the anesthetized guinea pig that acoustic elements essential to speech perception are reflected in aggregate response of ensembles of cortical neurons.
Extents of laterality and binaural interference effects
Authors: Heller Laurie M. , Trahiotis Constantine
Published: October 2005

Extents of laterality produced by ongoing interaural time delays (ITDs) within high-frequency sinusoidally amplitude-modulated (SAM) target tones were measured in the presence or absence of a second, spectrally remote, diotic, SAM tone. The spectrally remote SAM tones had recently been shown to reduce sensitivity to ITDs conveyed by a 4-kHz SAM tone in a previous experiment employing the same listeners [L. M. Heller and C. Trahiotis, J. Acoust. Soc. Am. 97, 1808–1816 (1995)]. All SAM tones were 100% modulated at 250 Hz and were presented at 77 dB SPL for a duration of 250 ms. The SAM target tone was centered at 4 kHz and the lower-frequency SAM tones were centered at either 500 Hz, 1 kHz, or 2 kHz. The data indicate that spectrally remote, diotic, SAM tones ‘‘pull’’ the lateral position of a 4-kHz SAM tone toward the midline, even when the 4-kHz SAM tone contains an ITD of up to 400 or 600 μs. This means that effects of spectrally remote information are not confined to tasks which require that listeners detect, or discriminate between, threshold amounts of ITD. Analyses revealed that changes in lateral position, as measured by an acoustic pointing task, cannot in and of themselves account for the interference effects found in discrimination tasks with similar stimuli. It was found, however, that Buell and Hafter’s [J. Acoust. Soc. Am. 90, 1894–1900 (1991)] weighted-combination model, when augmented to include measures of laterality as well as measures of discriminability, could provide reasonably accurate predictions of the amounts of interference obtained in the discrimination task.
Cues for discrimination of envelopes
Authors: Strickland Elizabeth A. , Viemeister Neal F.
Published: October 2005

Thresholds for detection of sinusoidal amplitude modulation at a signal modulation frequency were measured in the presence of a masker modulation frequency, with broadband noise carriers. Broad tuning for modulation frequency was observed. For maskers half or twice the signal frequency, thresholds depended on the relative phases of the signal and masker. These results were used to determine what aspects of envelopes listeners might be using in making decisions. Simulations were performed using an envelope detector model, consisting of bandpass filtering, half-wave rectification, and low-pass filtering. Decisions were based on envelope statistics that have been used to predict other data. These statistics were (1) rms power, (2) ratio of maximum to minimum amplitude (max/min), (3) crest factor, (4) fourth moment, and (5) average slope. The max/min statistic was successful at predicting the major trends in the data, without requiring the presence of channels tuned to modulation frequency.
Spread of excitation produced by maskers with damped and ramped envelopes
Authors: Carlyon Robert P.
Published: October 2005

Three experiments compared the ability of pairs of modulated narrow-band sounds with identical power spectra to mask signals above, below, and at their center frequency. In the first experiment, forward-masked psychophysical tuning curves (PTCs) were measured using a 1600-Hz 10-ms signal and 400-ms ‘‘damped’’ and ‘‘ramped’’ sinusoidal maskers. The damped maskers were produced by repeating a 25-ms sinusoid which had been shaped by an exponentially decaying function with a half-life of 4 ms. The ramped maskers were simply time reversals of the damped maskers. When the masker frequency was below that of the signal, ramped maskers were more effective than damped maskers, whereas the reverse was true for maskers above the signal. Experiment 2 measured thresholds for a 400-ms 1000-Hz damped or ramped sinusoidal signal, in the presence of a simultaneous masker with the same envelope shape, as a function of the masker frequency. Again, ramped maskers were more effective below the signal frequency, and damped maskers more effective above it. Experiment 3 was similar to experiment 2 except that the masker was a damped or ramped narrow-band noise, and the signal was an unmodulated sinusoid. The pattern of results was generally similar to that obtained in experiments 1 and 2. The results of all three experiments are inconsistent with the ‘‘traditional’’ method of calculating excitation patterns, which is based on the power spectrum of the stimulus, and also differ from the predictions of a recent model of auditory processing [R. D. Patterson, J. Acoust. Soc. Am. 96, 1409–1418 (1994)]. It is suggested that changes to the peripheral filtering stage of Patterson’s model may provide a useful first step toward accounting for the data.
Detection of decrements and increments in sinusoids at high overall levels
Authors: Moore Brian C. J. , Peters Robert W. , Glasberg Brian R.
Published: October 2005

Thresholds for the detection of decrements in level of sinusoidal signals were measured as a function of duration (2, 4, 6, 10, and 14 ms), level (70, 80, and 90 dB SPL) and frequency (250, 500, 1000, 2000, and 4000 Hz). Seven normally hearing listeners were tested at each frequency (with different subjects for each frequency). Thresholds for detecting a 10-ms increment in level were also measured. The sinusoids were presented in a background noise low-pass filtered at 5 kHz, which was intended to mask spectral splatter associated with the decrement or increment. Performance improved with increasing frequency for all decrement and increment durations. Performance also tended to improve with increasing level at 2000 and 4000 Hz. The results were analyzed using a four-stage model consisting of an auditory filter centered on the signal frequency, a compressive nonlinearity, a sliding temporal integrator and a decision mechanism. The analysis indicated that the improved performance with increasing frequency and increasing level could be attributed partly to off-frequency listening; for the two highest center frequencies, subjects probably made use of the output of an auditory filter centered above the signal frequency, where changes in excitation level associated with an increment or decrement were magnified. The measurements at 4000 Hz were repeated using a broadband background noise (15-kHz bandwidth), which would prevent the use of information from auditory filters centered far above the signal frequency. Performance was poorer than when low-pass noise was used, but still improved somewhat with increasing level. The slight improvement in performance with increasing level can be accounted for by a reduced compressive linearity at high levels. A good fit to the data could be obtained by assuming that the equivalent rectangular duration (ERD) of the temporal integrator was invariant with level, but that the compressive nonlinearity varied with level in a similar way to basilar-membrane input–output functions. The nonlinearity appears to be somewhat less compressive at 250 Hz than at higher center frequencies. The ERD is about 7 ms regardless of center frequency.
On the externalization of sound images
Authors: Hartmann William M. , Wittenberg Andrew
Published: October 2005

Listeners perceive the sounds of the real world to be externalized. The sound images are compact and correctly located in space. The experiments reported in this article attempted to determine the characteristics of signals appearing in the ear canals that are responsible for the perception of externalization. The experiments used headphones to gain experimental control, and they employed a psychophysical method whereby the measurement of externalization was reduced to discrimination. When the headphone signals were synthesized to best resemble real-world signals (the baseline synthesis) listeners could not distinguish between the virtual image created by the headphones and the real source. Externalization was then studied, using both discrimination and listener rating, by systematically modifying the baseline synthesis. It was found that externalization depends on the interaural phases of low-frequency components but not high-frequency components, as defined by a boundary near 1 kHz. By contrast, interaural level differences in all frequency ranges appear to be about equally important. Other experiments showed that externalization requires realistic spectral profiles in both ears; maintaining only the interaural difference spectrum is inadequate. It was also found that externalization does not depend on dispersion around the head; an optimum interaural time difference proved to be an adequate phase relationship.
Influence of mean flow on boundary layer generated interior noise
Authors: Howe M. S. , Shah P. L.
Published: October 2005

An analysis is made of the ‘‘interior noise’’ produced by high, subsonic turbulent flow over a thin elastic plate partitioned into ‘‘panels’’ by straight edges transverse to the mean flow direction. This configuration models a section of an aircraft fuselage that may be regarded as locally flat. The analytical problem can be solved in closed form to represent the acoustic radiation in terms of prescribed turbulent boundary layer pressure fluctuations. Two cases are considered: (i) the production of sound at an isolated panel edge (i.e., in the approximation in which the correlation between sound and vibrations generated at neighboring edges is neglected), and (ii) the sound generated by a periodic arrangement of identical panels. The latter problem is amenable to exact analytical treatment provided the panel edge conditions are the same for all panels. Detailed predictions of the interior noise depend on a knowledge of the turbulent boundary layer wall pressure spectrum, and are given here in terms of an empirical spectrum proposed by Laganelli and Wolfe. It is expected that these analytical representations of the sound generated by simplified models of fluid–structure interactions can used to validate more general numerical schemes.
Predicting ultrasonic grain noise in polycrystals: A Monte Carlo model
Authors: Yalda Isaac , Margetan Frank J. , Thompson R. Bruce
Published: October 2005

A Monte Carlo technique is described for predicting the ultrasonic noise backscattered from the microstructure of polycrystalline materials in a pulse/echo immersion inspection. Explicit results are presented for equiaxed, randomly oriented aggregates of either cubic or hexagonal crystallites. The model is then tested using measured noise signals. Average and peak noise levels and the distribution of the noise voltages are studied as the density of grains changes.
The processing of duration and intensity cues to prominence
Authors: Turk Alice E. , Sawusch James R.
Published: October 2005

This paper presents results from two experiments designed to show how duration and intensity are processed during speech perception. Duration and intensity are two physical dimensions which are known to interact psychoacoustically in the perception of both length (a term that will be used for perceived duration) and loudness. The first experiment, a selective attention task, shows that length and loudness are processed as a unit [integrally, in the terms of Garner, The Processing of Information and Structure (Erlbaum, Potomac, MD, 1974)], but that the integrality is asymmetric: Extracting length information appears to be easier than extracting loudness information. The results of the first experiment make the prediction that listeners would not use loudness by itself in making prominence judgments, since the extraction of loudness in the presence of duration variation appears to require a (relatively) high processing load. The second experiment, a traditional trading relation experiment in which duration and intensity were varied orthogonally, appears to bear out this prediction. Listeners’ responses were predicted from computed measures of length and loudness in a linear multiple regression analysis. Results show a negligible independent contribution of loudness to listeners’ responses. Listeners’ behavior is best predicted by computed measures of length.
On the ‘‘bubble grapes’’ induced by a sound field
Authors: Doinikov A. A. , Zavtrak S. T.
Published: October 2005

A suggestion is advanced that the stable bubble clusters observed by Marston et al. [Bubble Dynamics and Interface Phenomena, edited by J. R. Blake et al. (Kluwer Academic, Dordrecht, 1994), pp. 343–353] in an ultrasonic field are due to the radiative interaction forces of the bubbles, which change from attraction to repulsion when the distances between the bubbles become comparable with their sizes. This reversal is predicted by a theory developed in a previous paper by the authors [Phys. Fluids 7, 1923–1930 (1995)].
Acoustic radiation from the monopole resonance of a bubble excited in a dielectrophoretic levitator by oscillating electric fields.
Authors: Marston Philip L. , Hicks Nathaniel K. , Thiessen David B.
Published: October 2005

Dielectrophoretic levitation of bubbles in an insulating liquid appears to be a novel way of studying acoustic radiation from transient bubble volume pulsations. Single bubbles were trapped in a spatially varying dc electric field designed to give stable levitation. A few cycles of a weaker oscillating field were superposed on the levitation field. When the modulation frequency was adjusted for the electric field to excite the monopole resonance, a transient acoustic signature was detected by an electrically shielded hydrophone in the surrounding oil bath. One mechanism for monopole excitation is that the energy of the bubble is increased by the electric field giving a positive electric pressure contribution proportional to the square of the field [P. L. Marston and R. E. Apfel, Phys. Lett. 60A, 225–226 (1977)]. The same result follows from a surface average of the Maxwell stress using the Minkowski form of the stress tensor. Additional monopole coupling mechanisms may include a Helmholtz dielectric stress contribution (mitigated by the electrostrictive liquid response) and vertical oscillations of the bubble’s centroid in the hydrostatic pressure field. [Work supported by the Office of Naval Research.]
The shape stability and interaction of millimeter-size gas bubbles trapped in an ultrasonic standing wave.
Authors: Trinh Eugene H.
Published: October 2005

A three-dimensional standing wave in a resonant liquid-filled cavity allows the trapping of multiple millimeter-size air bubbles. The coupling of the radiation pressure stresses to the bubble interfaces induces a net downward force counteracting gravity, a steady-state shape deformation, and it also drives natural shape oscillations of large amplitude under certain circumstances. The parameter space for the shape stability of trapped bubbles in ultrasonic fields having a frequency between 45 and 65 kHz has been experimentally determined in pure distilled water as well as in aqueous solutions containing surfactants. The variable parameters are the sound pressure, the sound wavelength, and the bubble equilibrium radius. The effects of the sound field intensity on the interaction of contacting and noncontacting neighboring bubbles are also experimentally investigated. In particular, a preliminary study of the impact of the sound intensity on the coalescence efficiency of contacting bubbles is conducted in pure water and in aqueous surfactant solutions. [Work funded by NASA.]
Collinear ultrasonic four-wave mixing in suspensions of particles and bubbles.
Authors: Kwiatkowski Christopher S. , Marston Philip L.
Published: October 2005

The interaction of sound with sound in a suspension can be mediated by the suspension’s response to acoustic radiation pressure [H.J. Simpson and P.L. Marston, J. Acoust. Soc. Am. 98, 1731–1741 (1995)]. Four wave mixing mediated by a suspension with collinear pump and probe waves is investigated. Radiation pressure from counter propagating pump beams induces a periodic grating in the number density of hollow glass microspheres suspended in a water/sugar mixture designed to make the particles neutrally buoyant. The Bragg scattering amplitude was measured using a single PVDF transducer as both the probe source and receiver that is parallel with the standing pump wave nodal planes. Reflection coefficients are calculated by comparing the reflected and transmitted waves. By increasing the particle concentration, total Bragg reflectivities from the established grating reaching 20% have been seen, which is still in the region of agreement between the Born approximation and transfer matrix theory. The dynamics of both the grating formation and dissolution have been studied, leading to the conclusion that grating dissolution is not dominated by diffusion alone. Bragg scattering by gratings of gas bubbles caused by cavitation was detected. [Work supported by the Office of Naval Research.]

All posters will be on display from 1:00 to 5:00 p.m. To allow contributors an opportunity to see other posters, contributors of odd-numbered papers will be at their posters from 1:00 to 3:00 p.m. and contributors of even-numbered papers will be at their posters from 3:00 to 5:00 p.m.
Temporal integration as a function of masker bandwidth.
Authors: Oxenham Andrew J.
Published: October 2005

Thresholds were measured for a 6-kHz sinusoid, temporally centered in a 500-ms masker which was either a bandpass Gaussian noise (20 dB SPL spectrum level) or a 6-kHz sinusoid (40 dB SPL). A notched noise centered on 6 kHz prevented the use of off-frequency cues. The signal, gated with 2-ms ramps, ranged in half-amplitude duration from 2 to 300 ms. The noise bandwidth was arithmetically centered on 6 kHz and was varied from 60 Hz to 12 kHz. For masker bandwidths below 300 Hz, the slope of integration for signal durations between 2 and 20 ms decreased with decreasing masker bandwidth. For the tonal masker, increasing signal duration from 2 to 20 ms had no effect on threshold. These results cannot be accounted for by lowpass-filter or temporal-window models of temporal integration or resolution. Instead, it is proposed that the auditory system performs a spectral analysis of the stimulus envelope, so that the rapid fluctuations (high modulation frequencies) introduced by gating the signal can be used as a cue for brief signals in narrowband noise and tones. For broadband maskers, this cue is not available due to the masker’s inherent rapid envelope fluctuations. [Work supported by the Wellcome Trust.]
Sinusoidal amplitude modulation thresholds as a function of carrier frequency and level.
Authors: Fassel Ralf , Kohlrausch Armin
Published: October 2005

Modulation detection thresholds for sinusoidal carriers were obtained for a wide range of modulation rates (10–1600 Hz) as a function of carrier frequency (1, 3, 5, 8, and 10 kHz) and carrier level (30, 45, 60, and 75 dB SPL). At low modulation rates, between 10 and about 100 Hz, thresholds were roughly constant. For higher modulation rates, thresholds were dependent on carrier frequency. For the lowest carrier frequency (1 kHz), the modulation sidebands were already spectrally resolved at a modulation rate of 100 Hz and thus thresholds decreased with increasing modulation rate. For the higher carrier frequencies, the sidebands were resolved only at higher modulation rates, due to the increasing auditory-filter bandwidth. In these cases, thresholds initially increased with increasing modulation rate with a slope of about 8 dB/oct. The threshold curves show a different shape than those obtained with broadband noise carriers. In general, thresholds decreased with increasing carrier level at any given carrier frequency up to at least 60 dB SPL. For one subject a saturation of thresholds at medium carrier levels was observed. At very low carrier levels of 20 dB SL, thresholds tended to increase with increasing modulation rate already below 100 Hz.
Cylindrical bubble evolution and acoustic signature through the arc phase of an electrical discharge.
Authors: Fisher David L. , Rogers Robert L.
Published: October 2005

The arc phase of an electrical discharge in salt water is investigated using a 1-D nonlinear fluid model in cylindrical (r) coordinates. For most electrode geometries, the arc phase is more accurately modeled using a cylindrical geometry compared to the usual and simpler to implement spherical model. This is due to the fact that until the bubble radius is comparable to the distance between electrodes, the preferred geometry is cylindrical. Both the bubbles external (water) and internal (dissociated water and plasma) are discretized and modeled with nonlinear fluid equations. The model includes the energy flow from the capacitor, into the plasma arc through its resistivity, and then finally into the hydroacoustic pulse. Simulation results will be compared to experiments. Also the efficiency of various electrode configurations will be investigated. [Work supported by the Office of Naval Research.]
USAF monitors for recording aircraft noise received by animals.
Authors: Carter Michael , Kull Robert
Published: October 2005

Although researchers have studied the effects of aircraft noise on wild and domestic animals for many years, accurate descriptions of the noise levels received by the animals in many of the studies was not verified. Recent technology has allowed for the miniaturization of much of the hardware for noise monitoring devices, making it feasible to build a noise monitor small enough to fit on a large animal collar. An animal noise monitor (ANM) was designed and built to capture A- and C-weighted noise levels above a programmable threshold, distinguishing aircraft noise from other sound sources. The device, weighing only 350 g, also captures onset rate, Leq, and gross movements of the animal via accelerometers after a noise event, while fitting on a large animal collar. The ANMs were also designed to function as stand-alone, weatherproof units for up to 6 months. The ANMs have already been field tested under natural weather conditions at stationary locations by Peregrine Falcon aeries around Fairbanks, Alaska. The ANMs will be tested on penned animals to determine their reliability and accuracy.
Design and effectiveness of in-line tuning cables for quieting hydraulic power units.
Authors: Dodson John M. , Dowling David R. , Grosh Karl
Published: October 2005

The use of hydraulic units to power tools, lifts, and other industrial equipment in both indoor and outdoor settings is widespread. The noise radiated by these units and the hydraulic lines used to convey the fluid continues to be a problem. The dominant noise components arise from pressure fluctuations in the hydraulic fluid ocurring at harmonics of the pump vane or piston passage frequency. In this study, the effectiveness of in-line tuning cables (after a patent by Klees 1967) for quieting the harmonic noise from these hydraulic lines is determined. This approach, which combines ease of installation with relative economy, amounts to the insertion of a quarter-wavelength side branch into the acoustical circuit. Critical to effective design is the determination of the wave speeds in the flexible hosing. Theoretical predictions and measurements are applied to determine the wave speeds in the fluid-loaded hydraulic line. Multiple PVDF sensors measure wave speeds and the wave amplitude insertion loss achieved by the device. Experiments performed on a full-scale 60 h.p., 1500 p.s.i. unit will be compared to the theory. Sound pressure levels determine design effectiveness.
The determination of physical properties at high pressure using a high-temperature database from resonant ultrasound spectroscopy (RUS) measurements.
Authors: Anderson Orson L. , Cynn Hyunchae , Isaak Donald G.
Published: October 2005

Using the RUS technique called rectangular parallelepiped resonance, a large database on elastic constants and associated thermoelastic parameters extending from 300 K up to as high as 1800 K (P=0) has been established at UCLA. Temperature derivatives of the Cij’s have been determined with considerable precision. It has been shown how the pressure derivatives of elastic constants (∂Cij/∂P)T can be approximated from (∂Cij/∂T)P. Agreement with experiment is quite good in some cases. Extending this method to high pressure (≳3 GPa) requires evaluation of the volume dependence of the parameter, (∂P/∂T)V=αKT, where α is thermal expansivity and KT is the isothermal bulk modulus. Again, this is done from temperature Cij data, but it requires one datum on pressure, K0′=(∂KT/∂P)T (P=0). From the data, the temperature at which αKT becomes independent of volume was predicted. The theory agrees well with experiment for all solids tested (NaCl, MgO, Al2O3, Mg2SiO4, CaO).
Resonant ultrasound spectroscopy and Raman measurements to examine cation order–disorder.
Authors: Cynn Hyunchae , Anderson Orson L. , Isaak Donald G.
Published: October 2005

The elastic constants of natural MgAl2O4 spinel have been measured using resonant ultrasound spectroscopy at high temperature. Below 1000 K, the ultrasonic resonant frequencies of an ordered natural spinel change significantly after heat treatment. The Raman spectra for ordered natural and disordered spinels also differ below 1000 K but are similar at higher temperatures and after cooling to ambient temperature. These changes in ultrasonic resonance and Raman spectra of spinel can be associated with cation disordering at high temperature that may be quenched by cooling. The estimated inversion parameters from the relative intensities of the two A1g Raman modes are in very good agreement with estimates from other measurements. It is found that C11 and C12 decrease by 4% and 8%, respectively, with 20% inversion in spinel; C44 is less sensitive to cation disorder. These results imply that previous measurements of the adiabatic elastic constants of spinels at ambient conditions have been affected by the state of cation disorder of the specimen.
An application of resonant-ultrasound spectroscopy using a discrete-layer continuum theory.
Authors: Heyliger Paul R. , Ledbetter Hassel , Kim Sudook
Published: October 2005

The majority of analysis methods for the computation of natural frequencies required by ultrasonic resonance spectroscopy is based on variational methods of approximation that incorporate basis functions with C−1 continuity at every point within the domain. When used for laminated materials of different constitution, the continuous strain field implied by such approximations cannot represent true behavior at an interface between the materials. A discrete-layer theory is developed in this study which introduces piecewise approximations in the layered direction of the solid, allowing for a more accurate portrayal of the strain field. The vibrational modes can be grouped into four groups rather than the eight that are typical for an orthorhombic material. The model is used to study a seven-layer laminate composed of layers of aluminum and aramid/epoxy. Two geometries are considered: a plate and a parallelepiped. The frequencies predicted by the discrete-layer theory are compared with measurements and frequencies found using a more conventional Ritz method with the effective properties of the material. The discrete-layer frequencies tend to be slightly larger than those computed using the Ritz method for the plate and slightly lower for the parallelepiped. Implications for the use of this theory are discussed.
Otoacoustic emissions as tools to probe cochlear function.
Authors: Long Glenis R. , Talmadge Carrick L. , Tubis Arnold
Published: October 2005

Otoacoustic emissions (acoustic signals originating in the cochlea) can be noninvasively evaluated by placing a sensitive microphone in the ear canal and extracting the emissions from the noise by signal analysis. Since first reported (Kemp, 1978), otoacoustic emissions have been developed into a very useful experimental tool for probing cochlear function. A research overview will give special attention to the existence of a strong periodicity in the frequency domain in all human otoacoustic emissions. This periodicity will be related to maxima and minima seen in hearing threshold measurements. Discussion will focus on the hypothesis that the basis for the pseudoperiodic nature of the emissions is the coherent scattering from cochlear irregularities within the tall and broad peak of the traveling wave [cf. Shera and Zweig, J. Acoust. Soc. Am. 98, 2018–2047 (1995)]. This scattering gives rise to a reflection of the cochlear wave towards the base, whose effects are detectable in the ear canal signal. The pseudoperiodic properties of emissions are governed by the nearly linear frequency dependence of the phase of the cochlear traveling wave ratio, which is mainly determined by the complex wavelength of the traveling wave in the peak region. [Work supported by NIDCD.]
Structural acoustic energy finite element method.
Authors: Bitsie Fernando , Bernhard Robert J.
Published: October 2005

A new numerical method, referred to as the energy finite element method, had been previously developed to predict the high-frequency response of built-up structural acoustic systems consisting of subsystems such as rods, beams, plates, and acoustic spaces. The methodology for prediction of behavior in the subsystems is based on a diffuse energy field approximation. Subsystems are coupled together using net energy flow and energy superposition principles. In this paper, the structural acoustic coupling relationship for energy flow analysis of coupled plates and acoustical spaces is shown. The coupling approach chosen for structural acoustic radiation uses plate radiation efficiency. The approach has been implemented into an energy finite element model. The energy finite element predictions will be compared to measured results for an acoustical enclosure with one flexible wall.