bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for heritability and prenatal masculinization of cochlear mechanisms from measures of otoacoustic emissions
Authors: McFadden Dennis , Loehlin John C.
Published: October 2005

Spontaneous and click-evoked otoacoustic emissions (SOAEs and CEOAEs) were measured in twin pairs of various sorts—monozygotic (MZ), same-sex dizygotic (SSDZ), and opposite-sex dizygotic (OSDZ)—as well as in nontwins. Comparison of the number of SOAEs exhibited by MZ and SSDZ twin pairs previously led to the conclusion that about 75% of the individual variation in SOAE expression can be attributed to genes. Parallel calculations will be shown for the CEOAE data. In accord with past surveys, females generally exhibited more SOAEs than males; however, OSDZ females exhibited, on average, less than half as many SOAEs as other females, and thus were comparable to males on this measure. Similarly, the strength of the CEOAEs was generally greater in females than in males, but not in OSDZ females. The interpretation is that the cochleas of OSDZ females have been masculinized by exposure to the high levels of androgens produced prenatally by their male co-twins. (Prenatal masculinizing effects are well known in other mammals.) If correct, the genes apparently lay a groundwork for the expression of emissions—and, correspondingly, good hearing sensitivity—and prenatal exposure to androgens operates to reduce both emission strength and sensitivity. [Work supported by NIDCD.]
Differential sensitivity to increases and decreases in tempo: Evidence for an entrainment model
Authors: McAuley J. Devin , Kidd Gary R.
Published: October 2005

Listeners’ abilities to detect changes in tempo were investigated with two- and four-tone isochronous sequences with interonset intervals (IOI) of 100, 400, 700, and 1000 ms. Separate thresholds were measured for increases and decreases in tempo using an adaptive-tracking procedure. On each trial a standard pattern was followed by two comparison patterns, one of which was faster or slower than the standard. Listeners judged which comparison pattern was different from the standard. Consistent with previous studies of tempo discrimination, thresholds were found to be lower with four-tone sequences than with two-tone sequences, especially at the faster tempos. However, at the fastest tempos, listeners showed greater sensitivity to increases than to decreases in tempo, while the reverse was true at the slower tempos. The crossover point occurred at an IOI between 400 and 700 ms. The findings are consistent with the predictions of an entrainment model [J. D. McAuley, J. Acoust. Soc. Am. 95, 2966 (A) (1994)] in which tempo sensitivity is reflected by the degree to which a system of adaptive oscillators is entrained by the rhythm of a stimulus pattern. [Work supported by NIMH and NIDCD.]
A novel architecture for rhythmic pattern recognition
Authors: Cummins Fred
Published: October 2005

The problem of pattern recognition in time is usually addressed by buffering, which converts time into a spatial dimension, and allows the application of standard pattern recognition methods. But buffering of high bandwidth sensory input is implausible and problematical. An architecture based on the adaptive oscillator model [J. D. McAuley, J. Acoust. Soc. Am. 95, 2966 (A) (1994)] is presented which generates a spatial pattern from the rhythmic content of the acoustic input. The acoustic signal is passed through a bank of gammatone filters, each channel is half-wave rectified and down sampled, allowing a simple differencing procedure to identify onsets, which serve as inputs to a 2-D array of oscillators organized by frequency channel and by intrinsic period. Each oscillator adjusts its intrinsic period to match periodic onsets present in the signal. Only those oscillators that succeed in synchronizing their activity to a period in the input signal produce persistant output. After synchronization, the output distribution produces a stable spatial pattern over the 2-D array. The procedure allows treatment of pattern distributed in time without recourse to sensory buffering. Output patterns for a variety of stimuli, including animal gaits, musical rhythms, and prosodic structure will be presented. [This project was supported by ONR.]
Effects of rise/fall time on masked detection thresholds and temporal integration for noise band signals
Authors: Heinz M. G. , Formby C. , Mortimer K. L.
Published: October 2005

Formby etal. [J. Acoust. Soc. Am. 96, 102–114 (1994)] noted that masked detection thresholds (MDT) and temporal integration (TI) for brief noise band signals may be influenced by the rise/fall time (RFT) used to gate the signals. Also, the definition of signal duration (T), defined (1) exclusive of RFT or (2) inclusive of RFT, affected time constant (τ) estimates for TI. In this study, the role of RFT was evaluated systematically for signal bandwidth (W=62–6000 Hz) and masker conditions reported by Formby etal. The MDTs were measured for a range of rise/fall time (RFT=1–40 ms) and plateau (P=1–20 ms) values to extend Formby etal.’s original durations (T=P=10–480 ms). In general, for a given W and P condition, MDT decreased and became asymptotic with increasing RFT. For a given W, the effect of RFT increased as P decreased, and the effect was greatest for small W. For P≥10 ms and RFT≥1 ms, MDTs were independent of RFT for all W. For T defined exclusive of RFT (i.e., T=P), τ was inversely proportional to RFT for W≤1000 Hz and invariant with RFT for W≳1000 Hz. For T defined inclusive of RFT (i.e., T=2*RFT+P), τ increased monotonically with RFT for all W. [Research supported by NIH.]
Compressibility in bubble dynamics and scattering
Authors: Barbone Paul E. , Nadim Ali , Goldman Daniel
Published: October 2005

The Rayleigh–Plesset equation describes the oscillations of a spherical bubble wall under the assumption that the fluid surrounding the bubble is incompressible. Many modifications of this equation have been proposed to incorporate slight fluid compressibility, and though different in form, they are asymptotically equivalent. The different forms of the equations, however, reveal remarkably different properties. In some forms of the modified Rayleigh–Plesset equation, for example, spurious unstable solutions are present while in other cases they are not. Here, physically motivated restrictions on the form of the modified Rayleigh–Plesset equation are discussed. These restrictions are discussed in the context of causality requirements and higher-order corrections to the modified Rayleigh–Plesset equation.
Active structural vibration control via sliding modes: Links to Lyapunov design
Authors: Burke Shawn E. , Meyer John E.
Published: October 2005

A nonlinear active vibration control design method is developed based upon an extension of variable structure control (VSC) techniques, in particular sliding mode control, to distributed parameter systems. The temporal compensator design utilizes a generalized wave equation representation of the plant. The control is implemented via a series of decentralized single-input/single-output (SISO) local loops around collocated transducers. No apriori knowledge of the temporal plant model is assumed, hence the resulting designs are insensitive to variations in the plant modal frequencies. The equivalent control reduces to output velocity feedback, a known stabilizing control. Active damping performance is enhanced through the introduction of an additive nonlinear term which selectively increases the velocity feedback control with a constrained nonlinear gain profile away from the zero-velocity phase plane origin. Stability constraints are discussed. For simple structural components such as beams and plates, the design method yields controllers identical to those derived using Lyapunov’s direct method, which extremize total system energy. Example controllers for beams and plates are presented. In order to demonstrate the application of the nonlinear control, closed-loop vibration control experiments on a 56- ×59-in. nine-bay aluminum grillage are summarized.
Experiments on active control of wave propagation in fluid-filled elastic cylindrical shells
Authors: Brévart Bertrand J. , Fuller Chris R.
Published: October 2005

Experimental results of studies on active vibration control in fluid-filled piping systems are presented. Reductions of the total power flow, i.e., the power flow in the shell wall and the power flow in the fluid field, have been achieved by means of external radial forces applied to the structure. Axisymmetric wave propagation was first considered, using PVDF cables both as actuators and sensors. The shell radial displacement beyond the control discontinuity was reduced by 7 to 20 dB in a large frequency range. In addition, the internal pressure field was globally attenuated by the external forces. Considering a point force disturbance at low frequencies, attenuations of the shell motion associated with higher-order modes (n=1,2) have been achieved, by means of shaped PVDF films as error sensors and point forces as structural control inputs. [Work supported by ONR.]
Normal-mode description of reverberation with a finite area bottom patch average
Authors: LeMond J.
Published: October 2005

A normal-mode reverberation model is presented that includes the effects of modal interference among spatially correlated fields scattered within a patch of (nearby) bottom locations. At each frequency the integrated scattered field from a bottom patch as a function of patch size is calculated from an explicit normal-mode expression. The time integrated reverberation level at each frequency is computed by squaring this contribution from each patch and summing over bottom patches. As a function of source/receiver separation, the time integrated reverberation levels computed with the finite patch description oscillate about a mean that is consistently lower than the levels obtained in the zero patch area limit. Results from a study of the dependence of the level differences and oscillation magnitudes on environment, frequency and patch area are presented. [Work supported by the Advanced Surveillance and Prediction System (ASAPS) Program of the Space and Naval Warfare Systems Command (SPAWAR, PMW 183-32).]
‘‘...through the glass darkly...’’ or designing for the needs of traveling groups in a multipurpose performing arts facility
Authors: Hougland Dana S. , Logsdon Edward L.
Published: October 2005

Predicting and designing for the everchanging acoustic and electroacoustic needs of a traveling show utilizing multipurpose performing arts facilities is an ongoing challenge. Most communities cannot afford the luxury of building and maintaining single-purpose performing arts facilities. There is a need to accommodate a variety of local or resident performing arts groups, as well as traveling shows. Shows may range from simple lectures to Broadway show productions, as well as the everincreasing number of multimedia performances. Measures to facilitate the traveling show performances must be simultaneously unobtrusive when not in use, and readily accessible to the crew of each traveling show. The successes and failures of various techniques are presented and critiqued.
Acoustics of large homes
Authors: Bruce James E. , Moritz Charles T. , Bruce Robert D.
Published: October 2005

Many large houses (in excess of 5000 square feet) have recently been built in the Houston, TX area. Some of these houses are constructed on speculation by builders and some are designed and built for specific individuals. This paper summarizes the results of a survey of the builders of both types of homes. Since many individuals who build their own homes design into their spaces features that reflect their personality and needs, it was thought that it would be interesting to investigate if ‘‘good acoustics’’ were one of these features. In addition, measurements of background noise, reverberation time, noise reduction between critical spaces, and the noise reduction from outside sources will be discussed. Finally, suggestions for improving the acoustics of large homes will be presented.
A review of the effects of sound on cetaceans
Authors: Frankel Adam S. , Clark Christopher W.
Published: October 2005

Studies to determine the effects of various acoustic stimuli on whales are reviewed, with an emphasis on those studies that quantified sound level. Most of these studies have tested the effects of anthropogenic sound on bowhead and gray whales, with some work on other species. The variables used to measure the whales’ response to sound typically include course deviations and changes in rates of respiration and other behaviors. Examples include the relationship of received level with the probability of avoidance of the sound source [Malme etal., MMS Rep. (1983, 1984)] and changes in respiration rate after the beginning of a sound playback [Richardson etal., Mar. Environ. Res. 29, 135–160 (1990)]. Response thresholds for continuous sounds have typically been measured at 110–124 dB, with responses to orca ‘‘screams’’ near 0 dB S/N ratio [Malme etal., MMS Rep. (1983)]. These studies have led to the use of the 120-dB level as a regulatory criterion for cetacean disturbance. The results of these studies will be presented considering which variables may be important for determining or predicting a whale’s response to sound.
MMATS: Acoustic localization of whales in real time over large areas
Authors: Clark David S. , Flattery John , Gisiner R. , Griffith L. , Schilling J. , Sledzinksi T. , Trueblood R.
Published: October 2005

The marine mammal acoustic tracking system (MMATS) provides real-time display and signal processing of ten channels of acoustic data. In this study analog signal data from ten sonobuoys were radioed to a circling aircraft carrying the MMATS hardware; the data were transformed into an intensity/time/frequency display scrolling in real time. Whale species were determined from the signal characteristics; the system includes a neural network for automated detection. Arrival time delays of a signal at three or more sites were used to localize the whale. Acoustic identification and localization of the whales were visually confirmed by observers making an independent visual survey of the area at the same time. Acoustic monitoring capabilities of the type provided by MMATS can significantly reduce the number of whales missed by traditional visual-only monitoring and provides a means of calibrating both methods, reducing the statistical uncertainty of population estimates made using either technique alone. Because MMATS can monitor large areas for long periods of time, it is well suited to monitoring the effects of manmade noise on the activities of whales.
Acoustic detection and location of blue whales (Balaenoptera
musculus) from SOSUS data by matched filtering
Authors: Stafford Kathleen M. , Fox Christopher G. , Mate Bruce R.
Published: October 2005

Blue whale calls were recorded off central California in the Fall of 1993. These calls were characterized as to duration, frequency downsweep, intercall interval, and sound-pressure level. Average values were determined from 303 calls, including up to three harmonics (fundamental downsweep from 18.9 to 17.2 Hz over 16 s). These frequency-domain characterizations were then used to develop numerical time series (kernels) that, when convolved with the original time series, produce correlation peaks indicating the presence of blue whale calls (matched filter). When harmonics were present in the data, a combined kernel, including the fundamental frequency and first harmonic, improved the signal to noise ratio over use of the fundamental kernel alone. These matched filters were able to detect blue whale calls even in very ‘‘noisy’’ time series. When applied to hydrophone recordings from three U.S. Navy SOSUS (SOund SUrveillance System) arrays, it is possible to produce locations for blue whale calls by timing the arrival of individual calls and applying least-squares techniques. This information can be used to increase our knowledge of blue whale distribution in the northeast Pacific. The methods described here may also be extended to other species that employ low-frequency vocalizations or to other ocean areas.
Temporal and spatial distribution of whale calls off Monterey, California
Authors: Lashkari Khosrow
Published: October 2005

Twenty-seven hours of acoustic data were recorded from a horizontal array in deep waters off the central coast of California. These data were analyzed to determine the characteristics of diverse underwater acoustic sources. Some of the identified sources were: moored RAFOS sources at ranges of 150–1000 km, low-frequency ship and machinery noise, and sounds of biological origin. Over 400 whale calls were identified and analyzed to determine the distribution of these calls in both time and azimuth. Spectral analysis of the vocalizations indicate that most of the calls were from humpback whales. [Work supported by the United States Navy, Naval Postgraduate School, and Monterey Bay Aquarium Research Institute.]
Acoustical properties of undisturbed sands from the West Florida sand sheet
Authors: Brandes Horst G. , Silva Armand J.
Published: October 2005

Eight undisturbed large-diameter (10.1-cm) gravity cores, ranging in length from 13.5 to 50.5 cm, were collected at the CBBL-SRP study site southeast of Panama City, FL. The recovered sediments varied from coarse sand and shell fragments near the surface to fine/medium sand at depth. The Multi Sensor Core Logger was used to measure compressional wave velocity, density, and attenuation as a function of depth in each of the unsplit cores in two mutually perpendicular directions. Two spring-loaded compressional wave transducers operating at 500 kHz, mounted on the outside of the liner, were used to measure velocity and attenuation, and a Cs-137 gamma ray source with scintillation counter were used to measure bulk density. In the longest of the cores, PC-GC-623, compressional wave velocity varied between 1700 and 1730 m/s in the upper 10 cm and between 1650 and 1700 m/s below that depth. Attenuation decreased slightly with depth, with most values falling between 0.3 and 0.5 dB/kHz/m (with reference to core liner filled with water). Density was relatively depth-independent and ranged between 1.8 and 1.9 g/cm3.
Optimizing finite difference schemes for wave propagation in high-loss viscoelastic materials
Authors: Hayner Mark A. , Fricke J. Robert
Published: October 2005

An optimization technique is discussed which improves the numerical efficiency of the finite difference method with memory variables used to analyze wave propagation in high-loss materials [η=O(1)] [Blanch etal., ‘‘Viscoelastic finite difference modeling,’’ Rice University Tech. Rep. TR93-04 (1993)]. With the conventional use of memory variables, the relaxation function of a viscoelastic material is modeled with a series of decaying exponential functions. The amplitudes and relaxation times of these exponentials are then matched, as closely as possible, to the behavior of the viscoelastic material. Using the new optimization technique, the error of the finite difference method, which is completely predictable using the von Neuman method, is accounted for during the matching process reducing the total error. For narrow-band models, the reoptimization process can reduce run times and memory requirements for 2-D models by about 8X and 4X, respectively. The usefulness and accuracy of this technique versus analytic methods are demonstrated.
The effects of a thin slow sediment layer on shallow water acoustic field
Authors: Shang E. C. , Wang Y. Y.
Published: October 2005

The seabottom often has a thin layer on its top and the sound speed in this thin layer is less than in water. It has been found that this thin layer can significantly affect the acoustic field in water column. First, it changes the bottom reflection character, and, on the other hand, it changes the modal wave-number difference: Dmn=2π(km−kn)−1. Those two factors determine the basic features of the acoustic field—the modal interference pattern and the modal attenuation rate. Based upon the sensitivity analysis, bottom parameter estimation scheme is proposed.
Boundary conditions and the theory of acoustic attenuation in lossy fluid seabeds
Authors: Deane Grant B.
Published: October 2005

During the last decade the traditional view that acoustic attenuation in marine sediments is linear in frequency from seismic to ultrasonic frequencies has been re-examined [A. C. Kibblewhite, J. Acoust. Soc. Am. 86, 716–738 (1989)]. In particular, there is a growing body of evidence from the ocean acoustic and marine seismology communities that the characteristics of attenuation in marine sediments are compatible with the Biot–Stoll theory for porous media. The Biot–Stoll formulation predicts a range of frequency dependencies, according to which of a number of attenuation mechanisms, including viscous dissipation, is dominant. The question of how different attenuation mechanisms can be accounted for in a fluid description of sediments will be examined. The convention of complex sound speed does not account for all the effects of absorption due to viscous dissipation when quantities involving both the pressure and velocity field are considered. An example of such a problem is the Pekeris waveguide with a lossy basement. The effect of viscous dissipation can be accounted for by adopting a convention that amounts to introducing a complex quiescent density.
The influence of acoustic signals on a juvenile gray whale
Authors: Rovero Peter J. , Keolian Robert M. , Miller James H.
Published: October 2005

In May 1994, a juvenile gray whale, Eschrichtiusglaucus, entered the Petaluma River, which empties into the north end of San Francisco Bay, CA. The Marine Mammal Center of Sausalito, CA, coordinated a rescue and asked us to lure the whale to deeper water with sound. The Petaluma River is muddy and brackish, 20 km long, and generally 75 m wide and 3 to 4 m deep. Recorded gray whale calls and synthetic signals in the range of 100–900 Hz were broadcast with a J-9 acoustic transducer providing a source level of 153 dB re: 1 μPa at 1 m. Over several hours, the whale, who surfaced for air every 140 s, seemed to be attracted to these sounds as we traveled at a few knots down river, our sound boat typically 50 m ahead of the whale. The whale appeared to lose interest in the sound boat much beyond 100 m. A split step parabolic equation model of acoustic propagation in the river suggests that the sound level was 123 dB near the river bottom at a range of 50 m and 120 dB at 200 m. On one occasion the whale approached to within 3 m of the active source. The sound level at this distance would be about 144 dB.
A procedure for the calculation of the noise impacts from a spatially stochastic source
Authors: Arrieta Rodolfo T.
Published: October 2005

There is growing concern over the impact of human intrusion into the habitat of certain wild animal species. A major part of this intrusion is in the form of noise from moving vehicles. The level on the ground or underwater caused by moving noise sources has been dealt with as single-event intrusions that may cause startle and associated physiological responses, and as cumulative noise exposures. The later approach allows correlation between the cumulative noise exposure of the whole animal population, and the change in population numbers and overall health. Currently, the most difficult part of this analysis lies in determining the sound exposure of the population since both the animals and the noise sources are spatially and temporally varying. There is a certain amount of knowledge about the movement of both the noise sources and the population; this knowledge can be used to create a kinematic simulation of the motions of both entities. Such a simulation has been used to yield long-term spatial probability distributions of noise sources that can then be superimposed over similarly obtained distributions of the population. This superimposition yields the required estimates of the total noise exposure of the population.
Behavioral response of migrating gray whales (Eschrichtius robustus) to acoustic stimuli along the central California coast
Authors: Angiel Nicole M.
Published: October 2005

The gray whale (Eschrichtiusrobustus) migrates close to shore along the central California coast, and is easily observable from land. The objective of this study is to determine the effects of low-frequency sounds on gray whale behavior. A J-15 transducer will be used to project tones of varying low frequencies and intensities from a vessel platform located off the coast of central California. Gray whales will be observed from shore during the south and northbound migrations past this region, in the presence and absence of sound production. Observed behaviors will then be compared and any disturbance due to sound will be determined. Results of this experiment will be important in regulating future sound-producing activities along the gray whale migration route. This study will also help resolve some of the controversy over another experiment known as the acoustic thermometry of ocean climate (ATOC). The ATOC program involves the projection of low-frequency sounds at higher intensities to measure changes in the ocean temperature over extended time periods. One of the sound projectors for ATOC is proposed to be placed off the central California coast and within the auditory range of migrating gray whales.
Transient, high-pressure solidification associated with cavitation in water
Authors: Hickling Robert
Published: October 2005

The very high pressures (≳1 GPa) that occur during the final stages of collapse of a cavitation bubble force the water in the vicinity of the bubble wall briefly (∼1 ns) into a metastable state of subcooling, relative to the equilibrium phase diagram. Estimates show that the subcooling can fall below the critical temperature for homogeneous nucleation of freezing and that high-pressure ice particles form at a sufficient rate to affect the collapse. Because of the greater density of high-pressure ice, a sudden drop in pressure occurs that triggers a shock wave that converges at the center of the compressed gas in the bubble. Such microshocks are believed to be the cause of the extremely short duration of the flashes of sonoluminescence (<50 ps) that have been observed from single cavitation bubbles. The occurrence of transient, high-pressure solidification can explain different phenomena associated with cavitation, specifically the decrease in cavitation erosion and the increase in sonoluminescence as the overall water temperature approaches 0 °C, together with the nucleation of freezing by cavitation in subcooled liquids. A single explanation for such diverse effects provides strong support for the solidification hypothesis.
Comparisons between multibubble and single-bubble sonoluminescence
Authors: Matula Thomas J. , McNamara William B. , Mourad Pierre D. , Roy Ron A. , Suslick Kenneth S.
Published: October 2005

Recent advances in the use of single bubble cavitation [D. F. Gaitan etal., J. Acoust. Soc. Am. 91, 3166 (1992)] have made it possible to examine both the temporal and spectral characteristics of sonoluminescence [B. P. Barber etal., J. Acoust. Soc. Am. 91, 3061 (1992)]. Direct comparison of the spectra of single-bubble sonoluminescence to multibubble sonoluminescence has proved difficult, however, due to differences in experimental conditions. Examination has begun of both single-bubble and multibubble sonoluminescence spectra of various aqueous solutions under closely similar conditions, where, in a systematic way, a variety of dissolved gases, volatile organic liquids, and involatile inorganic salts have been introduced. Qualitative comparisons of these spectra will be discussed. [Work supported by ONR and NSF.]
Numerical simulations of single bubble sonoluminescence
Authors: Mourad Pierre D. , Marcus Daniel L. , Roy Ron A. , Matula Thomas J.
Published: October 2005

A higher-order Godunov method is used to solve the spherically symmetric, compressible Euler equations with an ideal gas equation of state as a model for single bubble sonoluminescence. Basic shock physics is discussed in this context, exploring how modeled variations of the bubble interior support or suppress the generation and propagation of shock waves within the bubble as well as the interaction of a shock with the bubble interface. [Work supported by ONR through the ONR/ARL program.]
Probing the unknowns of sonoluminescence
Authors: Barber Bradley P. , Hiller Robert , Löfstedt Ritva , Weninger Keith , Putterman Seth
Published: October 2005

The mechanism whereby a bubble transduces sound into a clocklike stream of picosecond flashes of ultraviolet light is robust, complex, and unknown. A theoretical understanding of the key bubble parameter, its ambient radius, is lacking. An explanation as to why this phenomenon has so far only been seen in water is elusive. In addition, we do not understand why cooling the water dramatically increases the light output or why sonoluminescence is so sensitive to doping with a noble gas. Experimentally, the spectrum has been unable to be followed past 7 electron volts and so the limits of energy concentration which can be achieved with sonoluminescence from a single bubble are not yet measured. In addition to yielding clues experiments in progress will most likely serve to deepen the mystery! [Work supported by the US DOE Division of Advanced Energy Projects; RL is an AT&T Fellow.]
Picosecond sonoluminescence from macroscopic to microscopic models
Authors: Lepoint T. , Mullie F. , Lambillotte Y. , Goldman M. , Goldman A. , Tardiveau P.
Published: October 2005

The discovery of stable ‘‘picosecond’’ sonoluminescence (SL) has stimulated a great deal of theoretical effort aimed at explaining this striking result. Instead of assuming a perfectly smooth spherical bubble (as in the hot-spot theory, the converging shock-wave model or the Casimir effect model), our model is based on bubble deformation and the subsequent disruption of the interface toward the end of the collapse. The formation of an intracavity spray via the Taylor (hydrodynamic) or the Rayleigh (electrohydrodynamic) instabilities and the electrification of the tiny droplets due to the disturbances of the interfacial electrical double layer during the spraying process are described. The high electrical field (E≂109 Vm−1) characterizing a small area of a droplet surface is considered to be responsible for the field emission process. The formation and expansion of a dense microplasma inside the cavity as a consequence of the emission of electrons is proposed to be the origin of picosecond sonoluminescence. By means of this model, which is based both on hydrodynamics and on the microstructure of the bubble interface, the main experimental observations (SL flash temporal localization and duration, shape of the SL spectrum) can be explained.
Spherical shocks in a van der Waals gas and their stability
Authors: Wu C. C. , Roberts P. H.
Published: October 2005

A theory of sonoluminescence has been developed based on the compression and eventual ionization of air in a bubble by the converging shock waves generated by the applied acoustic radiation. The air is compressed to such high densities that departures from the ideal gas law become very significant. An extension to the van der Waals gas has been made to the similarity theory of Guderley for the structure of spherical shocks in an ideal gas. The linear stability of these shocks has also been examined.
On the scattering cross section of bodies in inhomogeneous medium
Authors: Guo Yueping
Published: October 2005

A theorem is proven that relates the scattering cross section of arbitrarily shaped scatterers to the scattered far field in one or two particular directions. This can be regarded as a generalization of the classical optical theorem (also known as the extinction theorem) for homogeneous medium of infinite extent. In that case, the scattering cross section is given by the far field in the forward scattering direction. For a half-space with a bounding surface of arbitrary mechanical properties, it is shown that the scattering cross section is given by the scattered far field in the specular reflection direction. For an inhomogeneous medium with abrupt density and sound-speed change at an interface, the scattering cross section is given by the far field in both the specular reflection direction and the transmission direction that obeys the Snell’s law. [Work supported by ONR.]
Forward scattering from hemispherically end-capped cylindrical shell in shallow water
Authors: Sarkissian Angie
Published: October 2005

When measuring the scattered field from a target in the exact forward direction, the presence of a significantly stronger indicident field makes the extraction of the scattered field difficult because the two signals arrive almost simultaneously. As the position of the target changes, the two signals arrive at distinct times to make the scattered field easier to extract. In a bounded medium, multipath arrivals produce additional complications by increasing the duration of the incident field. Frequency and time domain computations are made for the scattered field from a hemispherically end-capped cylindrical shell placed in a bounded medium where the geometry consists of a fixed source, a fixed receiver, and a target placed in between. The location of the target is varied, to compare the incident field to the scattered field in both intensity and arrival times.
Analytical numerical matching for efficient calculation of acoustic scattering from cylindrical shells
Authors: Loftman Richard C. , Bliss Donald B.
Published: October 2005

Structural discontinuities in highly coupled fluid/structure systems are modeled by a novel approach called analytical numerical matching (ANM). ANM separates the low-resolution global influence of a discontinuity from the relatively high-resolution local effects. A continuous, smoothed replacement for a fundamental structural discontinuity is constructed so that the system is identically unchanged beyond a small smoothing region. Simultaneously, the precise local effect of smoothing the discontinuity is retained in analytical form. The smoothed problem is solved by numerical techniques, with rapid convergence and reduced computational cost. The original discontinuous character is restored, using the analytical expression for the local difference between the smoothed and the original problems. ANM has been successfully applied to acoustic scattering from a thin, infinitely long cylindrical shell, with multiple structural discontinuities. Local solutions for line discontinuities with radial, tangential, and rotational constraints have been formulated using ANM. Line constrained scattering problems, as well as line driven problems, are investigated. The ability of analytic numerical matching to replace a discontinuous physical problem by a well-behaved continuous one for numerical evaluation, while ultimately retaining the original geometry and physical behavior, is illustrated. [Work supported by ONR.]
Reciprocity relations for endcap scattering of natural waves on a fluid-loaded cylindrical shell
Authors: Smith P. W. , LePage Kevin D. , McDaniel J. Gregory
Published: October 2005

The response field on a finite axisymmetric elastic shell is approximated by a limited set of lightly damped natural waves which are coupled to each other and to far-field sound by the scattering process at the endcaps. In this talk the constraints upon the scattering functions that are a consequence of the principle of reciprocity are obtained through analysis. Results show that the reciprocity constraints predicted for a thin shell example agree well with the observed behavior of natural wave scattering as predicted by SARA 2D finite-element methods. [Work supported by ONR.]
Experimental investigation of backscatter from an internally loaded cylindrical shell with a constrained layer damping treatment
Authors: Klausbruckner Michael , Conti Matthew , Dyer Ira , Fricke J. Robert
Published: October 2005

Previous investigations have examined the backscatter from empty and internally loaded shells with no damping treatment, demonstrating the primary importance of helical shear waves. The helical waves contribute to large backscatter for aspect angles within 30 deg of normal for the empty shell. The region increases to 45 deg of normal for the internally loaded shells. A constrained layer was applied to the cylindrical section of an internally loaded shell to damp the helical waves while decoupling them from the internal structures. The intended effect was to lower the backscatter levels and reduce the angular width of strong backscatter to within 30 deg of normal. This preliminary investigation demonstrates the achievement of each of these goals. In addition, the importance of direct acoustic backscatter from the attachment locations of the internal rings was highlighted. The bistatic measurements were conducted over a frequency range of 2.5<ka<10, corresponding to 3/4 to 3 times the ring frequency of the shells. [The authors acknowledge the assistance of NRI for acquisition of data. Work supported by ONR.]
Point-matching technique for scattering of Stokesian flows around axisymmetric bodies
Authors: Wymer Scott A. , Engel Renata S. , Lakhtakia Akhlesh
Published: October 2005

In solving for velocity and pressure fields in a slow, viscous, incompressible fluid, frequency-domain scattering techniques can be brought into action by taking the Fourier transform of the equations describing Stokesian flows. This is exemplified by considering the scattering of a transverse plane wave by an impenetrable axisymmetric body immersed in a fluid modeled by the unsteady Stoke’s equation, the wave number in the ambient Stoke’s fluid being necessarily complex. The pressure and velocity phasors satisfy the Laplace and the Helmholtz equations, respectively, and are written as sums of incident and scattered components. These components are then expanded in terms of spherical harmonic functions. The point-matching technique is used to satisfy boundary conditions on a discrete set of points on the surface of the scattering body. Convergence of the resulting series solutions is studied for spheroids of different aspect ratios and for varying wave numbers.
Acoustics wave diffraction on a cylindrical shell with two local masses
Authors: Dudnik Rostislav A. , Kolpakov Andrei B.
Published: October 2005

The diffraction of a plane sound wave on a thin cylindrical shell having inhomogeneity presented by two identical inertia masses fastened symmetrically on its surface is considered. It is shown that the field scattered by such a shell presents a superposition of the fields radiated by both the symmetrical and antisymmetrical low-frequency azimuth modes excited depending on the direction of initial wave propagation toward the vertical plane of the shell symmetry (Φ=0; Φ=180). In support of the existence of corresponding nonsingular normal velocity distributions, a specialized experimental investigation was carried out for the force-excited shell models. The experimental investigation of near as well as far acoustical fields of these shell was executed also. The calculation results of frequency responses and directionality diagrams of the field scattered by the shell with two masses fastened diametrically opposed at the initial only symmetrical oscillations are presented. These results are compared with analogous results for the shell having one inertia mass (at Φ=180). It was found that the radiation level control is possible for the investigated oscillation structure by such division of a unit inhomogeneity in certain frequency ranges.
Scattering of sound by a free-flooded cylindrical shell
Authors: Kim K. Steven
Published: October 2005

Scattered acoustic pressure fields are obtained when a free-flooded cylindrical shell of finite length is subjected to plane waves incident obliquely to the axis of the cylindrical shell. Integral equations are formulated for the cases of a rigid thin shell and a elastic thin shell with simply supported boundary condition at both ends. Equations are solved by a Rayleigh–Ritz type approach. Near-field and far-field acoustic pressures of the scattered sound are calculated. Scattered far-field acoustic pressures for a short shell and a long shell are discussed.
Enhanced backscatter in finite reverberant systems
Authors: Weaver Richard L.
Published: October 2005

Enhanced backscatter, in which reverberant signal levels at the position of a transient source are greater than mean reverberant signal levels elsewhere, is studied analytically and numerically. Popular weak localization arguments, in which descriptions of responses in terms of incoherent rays are modified to include some effects of coherent interference, indicate that the mean-square response at the source should be twice as large as it is at other points. A modal analysis, however, shows that the actual ratio should be three. A more detailed theory shows that the enhanced return factor is 2 at moderate times, but 3 at late times comparable to the modal density. The theory indicates that the factor of 2 is achieved only if the eigenfrequency statistics have the spectral rigidity predicted by random matrix theory. Thus a connection between spectral rigidity and weak localization is hinted at. Numerical solutions in model undamped two-dimensional reverberation rooms are found to agree with the theory. The effect of damping on these results is also investigated.
Microphone systems and signal processing: New opportunities in sound capture
Authors: Flanagan J. L. , Silverman H. F.
Published: October 2005

Over the recent past, advances in two technical areas have opened new opportunities for sophisticated sound capture at distances. High-quality low-cost acoustic sensors, primarily in the form of electret microphones, are plentiful and can be used in large numbers. Continued progress in microelectronics now provides enormous amounts of economical computation. These incentives have stimulated research in new techniques for sound capture in practical acoustic environments—such as conference halls, noisy computer rooms, teleconferencing facilities, and mobile communication. Recent research has embraced the design of large-scale two- and three-dimensional arrays of microphones, and the implementation of algorithms for automatic sound source location. This report reviews the status of research in these areas. It also highlights the emerging applications of distant-talking sound capture for hands-free operation of communications equipment such as automatic speech recognizers. [This research is supported by the National Science Foundation under Contract ♯MIP 9314625.]
Legal frame of environmental noise in México
Authors: Trovamala Landa Rafael
Published: October 2005

The regulations, accepted methods of measurement, and standards used in México related to the determination of noise in environmental and labor environments, as well as the maximum allowable values in contrast with their equivalents used in the United States and Canada, are reviewed.
Modeling the near-bottom seafloor
Authors: Stoll Robert D.
Published: October 2005

In mine counter measures work and other seafloor engineering applications, there are two distinctly different classes of sediment properties that play important roles in object detection and sonar performance—those that determine if an object will sink into the bottom or stay fully or partially exposed and those that control the penetration of high-frequency sonar signals into the bottom. The ability of the seafloor to support an object depends largely on shearing strength which is a nonlinear, large-strain property associated with plastic deformation and complete disruption of the in-situ structure. In contrast, the complex velocity (speed and attenuation) of low-amplitude geoacoustic signals is a small-strain property that can be treated to a good approximation using linear theories. Both classes of response and their interaction are discussed using insights gained from the Biot–Gassmann theory. This theory allows extrapolation from low- to high-frequency response and examination of the effects of various parameters such as gas content and low overburden pressure. In particular the effect of recently measured high attenuation and velocity gradients is discussed and a correlation between shear strength and shear-wave velocity is shown. [Work supported by NRL, CBBLSRP.]
A propagation model for wave motion in saturated granular sediments
Authors: Sadd M. H. , Gautam A. , Silva A. J. , Veyera G. E.
Published: October 2005

Wave propagation in saturated granular sediments is modeled through discrete element simulation. The sediments under study are assumed to be primarily sandy, and are thus modeled as cohesionless granular material saturated with pore fluid. Numerical simulation is based on the discreteelementmethod, a numerical scheme employing a modeling strategy to determine the translational and rotational motion of all particles in model material assemblies. For application to wave propagation, the movements of individual particles are a result of the propagation of disturbances through the media. Contact laws between adjacent particles are constructed using elastohydrodynamic lubrication theory, and these relations determine the contact force as a function of the relative displacement and relative velocity between neighboring particles. Using these new contact laws, wave motion simulations of one- and two-dimensional computer-generated model assemblies have been conducted. Results indicate that the wave speed and amplitude attenuation are functions of the physical microstructure or fabric of the discrete medium. Wave speed is inversely related to the porosity of the solid phase, while attenuation studies indicate that a branch vector distribution correlates with interparticle force transmission. Model development and simulation results will be presented.
Estimation of Arctic ice thickness from ambient noise
Authors: Chernets Olga , Fricke J. Robert
Published: October 2005

An estimate of total ice mass in the Arctic is an important parameter for global climate studies, but there are no direct means for providing this information. A surrogate measurement, spatial integration of ice thickness, is being pursued by several groups using active acoustic and electromagnetic methods. As a complement to these efforts, the passive estimation of ice thickness using ambient noise caused by thermal and mechanical stress cracks in the ice sheet is focused on. The acoustic signal received from propagating stress cracks is the convolution of an elemental fracture source function and the spatial distribution function (array) of the propagating crack. This analytic result predicts a tonal spectral component of O(1 kHz) that relates directly to ice thickness. Experimental data collected in the Beaufort Sea during the spring of 1994 demonstrates the presence of this spectral peak, which correlates well with the measured ice thickness at the site.
Shallow-water ambient noise due to surf
Authors: Stewart Marc , Wilson O. B. , Wilson J. H. , Bourke R. H.
Published: October 2005

Forecasting levels and directionality of ambient noise in the littoral environment is important for predicting performance of acoustic sensor systems and developing naval warfare tactics for that environment. Noise due to waves breaking at the beach contributes significantly to the low-frequency ambient noise in shallow water, as shown by the observations of O. B. Wilson, S. N. Wolf, and F. Ingenito [J. Acoust. Soc. Am. 78, 190–195 (1985)]. At some geographic points worldwide, unique geoacoustic features contribute to the detectability of ‘‘surf point noise’’ (a term coined by submariners) dozens of kilometers out to sea. The objective of this work is to apply more recently developed and powerful shallow-water propagation loss models and the increased knowledge of the geoacoustic properties of the seabed to obtain a quantitative understanding of observations reported by O. B. Wilson etal., and to make possible the prediction of the noise fields from surf in other locations. The results of the use of the SNAP programs applied to the Monterey Bay environment will be presented.