bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive beamforming techniques for bottom-loss estimation using marine ambient noise.
Authors: Muzi Lanfranco , Siderius Martin
Published: July 2011

Previous studies in underwater acoustics have shown that conventional beamforming of ocean noise with a vertical line array of hydrophones can be used to estimate the bottom loss (BL) as a function of frequency and grazing angle. The BL estimate is obtained by comparing the output power of beams steered toward the sea surface with that of beams reflected off the seabed. In practice, the finite aperture of arrays causes the beamwidths to be frequency dependent, and wider beams decrease the resolution of the BL estimate, blurring the interference patterns caused by seabed layering, and other distinct features such as the critical angle transition. This effect increases as frequency decreases and eventually sets the low-frequency limit on BL estimation for this technique. To minimize these effects, high-resolution adaptive beamforming techniques were applied to both measured and simulated ambient noise data. The results in this presentation show that some ABF techniques (e.g., the white-noise-gain-constraint beamformer) are better suited for this particular application, whereas others can sometimes have surprisingly poor performance. [Work sponsored by the Office of Naval Research.]
Estimation of geophysical parameters from ambient noise correlation.
Authors: Traer James , Gerstoft Peter
Published: July 2011

The passive fathometer correlates the ambient noise recorded by elements of an array to infer the depth of seabed reflecting layers. This includes two distinct processes: the cross-correlation of two elements separated by a finite distance and the autocorrelation of a single element. A model is presented for the correlation of ambient noise in the presence of reflecting boundaries with one sensor, a pair of sensors, and an array of sensors. The results obtained from experimental data from pressure and particle-velocity (vector) sensors are presented. The presence and location of reflecting boundaries can be inferred when the amplitude of the incident noise field varies smoothly across all directions of incidence. In the presence of discontinuities in the incident noise field, spurious peaks appear in the noise correlation which can be attenuated relative to the reflection peaks with use of adaptive array processing (minimum variance distortionless response). The reflection coefficient of the reflecting boundary affects the height of the reflection peaks in the noise correlation and in the ocean this can be used to infer seabed properties such as density and sound speed.
Bayesian inversion of seabed scattering data.
Authors: Steininger Gavin , Dosso Stan E. , Holland Charles W. , Dettmer Jan
Published: July 2011

Reverberation modeling and sonar performance predictions in shallow water require good estimates of seabed scattering and reflection as well as an understanding of scattering processes in a particular region. This talk considers the ability to resolve scattering parameters (e.g., scattering strength and roughness) and geoacoustic parameters (layer thicknesses, sound speed, density, and attenuation) using Bayesian inversion and a forward model based on first-order perturbation scattering theory and multilayer reflection coefficients. Results are considered in terms of marginal posterior probability distributions, which quantify the effective data information content to resolve scattering/geoacoustic parameters. Inversions are applied to synthetic data and to direct-path scattering measurements from shallow-water test beds. These measurements probe the seabed on an intermediate spatial scale (patch-size radius of ∼500 m for both reflection and scattering), which reduces the effects of ocean variability (associated with sound speed profile, seabed, and biologics) and uncertainty relative to long-range reverberation measurements. [This work is supported by the ONR.]
An under-ice Arctic geophysical exploration sonar system concept to resolve international territorial claims.
Authors: Arvelo Juan I.
Published: July 2011

A consequence of the shrinking polar ice cap is the increased interest in commercial shipping. Therefore, several nations are surveying the continental slopes and Arctic basin to better define the political boundaries. Under Article 76 of the United Nations Convention on the Law of the Sea (UNCLOS), the boundary between territorial and international waters is defined where the sub-bottom basement extends l km from the seafloor. Therefore, icebreakers and air guns are currently implemented for deep sub-bottom profiling. However, there still remains older and thicker ice that leads to inaccessible areas for geophysical surveys from surface ships. Submarines can easily navigate below the Arctic ice, but a safer sound source must be identified to avoid air guns or explosives. An analytic formulation was developed to predict the maximum basement detection depth of an under-ice sound source. This formulation was implemented to compare candidate underwater transducers and impulsive sound sources. Results from this study will be presented with discussions on additional constraints affecting the selection process. A workable submarine system for defining territorial boundaries would also help increase our understanding of the Arctic environment and facilitate exploration for potential natural resources. [Funding provided via UAF sub-award under NOAA Grant No. NA09NOS4000262.]
Measurement of the underwater noise levels generated from marine piling associated with the installation of offshore wind turbines.
Authors: Theobald Pete D. , Robinson Stephen P. , Ainslie Michael A. , de Jong Christ A. F. , Lepper Paul A.
Published: July 2011

Marine piling is the most commonly used method for the installation of offshore wind turbines in the shallow coastal waters in the UK and consists of steel mono-piles being driven into the seabed using powerful hydraulic hammers. This is a source of impulsive sound, of potentially high level, that can travel a considerable distance in the water column and has the potential for impact on marine life. This presentation describes methodologies developed for measurement of marine piling and for the estimation of the energy source level. Measurements are presented for piles of typically 5 m in diameter driven by hammers with typical strike energies of 1000 kJ. Data were recorded as a function of range from the source using vessel-deployed hydrophones, and using fixed acoustic buoys that recorded the entire piling sequence, including soft start. The methodology of measurement is described along with the method of estimation of the energy source level. Limitations and knowledge gaps are discussed.
Pile driving noise: Source level and sound generation mechanisms.
Authors: de Jong Christ A. F. , Zampolli Mario , Ainslie Michael A. , Jansen Erwin W. , Fillinger Laurent , Middeldorp Fred M. , Hazelwood Richard A. , Robinson Stephen P. , Jung Bob
Published: July 2011

Offshore percussive pile driving generates loud impulsive sounds in the marine environment, sometimes characterized in terms of their “source level,” a measure of acoustic pressure in the far field of its source. Special difficulties with the definition of source level for this application are described. Environmental assessment of future building projects requires a proper understanding of the sound generation mechanisms and their dependence on the various parameters (e.g., hammer type, stroke energy, pile construction, and sediment properties). Progress is reported on a combined numerical and experimental approach to modeling the sound generation and propagation through the medium. The acoustic response of the pile and its near field in fluid and sediment are calculated with a finite element model. The far field is obtained by coupling the acoustic field near the pile, from the finite element model, to a horizontal wavenumber integration model. Measurements carried out on a test pile in shallow water at IHC Hydrohammer in Kinderdijk are presented. Synchronous recording of hammer sensor data, pile vibrations, sound pressure, and sediment surface vibrations, close to the pile and at larger distance from the pile, enable a better understanding of the mechanisms and make it possible to check the model results.
The Newman medal and architectural acoustics at the University of Florida.
Authors: Siebein Gary W. , Kinzey Bertram Y.
Published: July 2011

The architectural acoustics program at the University of Florida was heavily influenced by the Newman medal program as well as the life and work of Robert B. Newman. Bertram Y. Kinzey, Jr., the founder of the program, had the pleasure of attending one of Bob Newman’s seminars and brought much of Bob’s enthusiasm for the subject to all of his students. Four principles that organize the program were influenced by the life and work of Bob Newman. The program is based in architecture as the fundamental discipline from which to approach architectural acoustics. The creative application of acoustical design principles in buildings is the focus of study. The exploration of acoustics in actual buildings becomes a thrust for research in the field. The program teaches future architects about acoustics in the built environment. A fifth principle that introduces a strong research component is necessary in a modern university. We are extremely grateful for the recognition for excellence in the study of architectural acoustics that we have been able to extend to our students as a result of the Newman Award program.
The dolphin's mental representation during echolocation: Ron Schusterman and the email debate between the “seeing through sound” and “associative learning” hypotheses.
Authors: Branstetter Brian K. , Mulsow Jason
Published: July 2011

[Evidence suggests that detection, discrimination, and recognition abilities of dolphin echolocation are related to perceived differences in time, frequency, and amplitude information from received echoes. Although an acoustic analysis has proven successful for explaining simple experimental paradigms, no similar analysis has successfully accounted for the findings from a series of cross-modal matching experiments. In cross-modal “identity” matching, the dolphin is first presented with a sample object to either vision or echolocation only. The dolphin must then select a matching object from a number of nonmatching alternative objects presented to the opposite sensory modality. The “seeing through sound” hypothesis claims that immediate (i.e., first-trial) cross-modal matching is evidence that dolphins perceive object shape through echolocation while an alternative hypothesis states that successful performance is the result of the animal’s “associative learning” history. Evidence against, or in support, of both alternative hypotheses is critically examined and the dolphin’s mental representation during echolocation is discussed.
Dolphin response time in vocal reporting of echolocation targets.
Authors: Sam Ridgway , Elsberry Wesley , Blackwood Diane , Kamolnick T. , Todd Mark , Carder Don , Cranford Ted
Published: July 2011

To study response time in echolocation, dolphins were trained to wear opaque suction cups over their eyes and to station on an underwater apparatus behind and acoustically opaque door. This put the dolphins in a known position and orientation. When the door opened, the dolphin produced clicks to identify the presence or absence of targets. Dolphin S emitted a whistle if the target was a 7.5 cm water filled sphere, she made a pulse burst if the target was a rock, and she remained quiet if there were no target present. Dolphin B whistled for the sphere but remained quiet for rock and for no target. Thus, S had to choose between three different responses, whistle, pulse burst, or remain quiet. B had to choose between two different responses, whistle or remain quiet. S gave correct vocal responses averaging 114 ms after her last echolocation click (range 18 ms before and 219 ms after the last click). Average response for B was 21 ms before her last echolocation click (range 250 ms before and 95 ms after the last click in the train). More often than not, B began her whistle response before her echolocation train ended.
Behavioral and evoked potential audiograms for goldfish.
Authors: Fay Richard
Published: July 2011

Twelve recently determined evoked potential (EP) audiograms were compared to six behavioral (BEH) audiograms for the goldfish. There are no theories possible on the relationships between these two very different measurements of auditory response; nevertheless many workers desire to know how they compare so that the EP audiograms can possibly “stand in” for the BEH measures. The data from the many audiograms indicate that they are only very roughly similar in terms of sensitivity (variation ranging from 45 to 60 dB) and best frequency (variation ranging from 300 to 1500 Hz). This variation among audiograms, within and between measurement methods used, is discomforting. There are no trends indicating that this variation is due to a single factor such as near field acoustics (all audiograms were determined in the near field of the sound source), threshold definition, ambient noise levels, conditioning method, or type of sound source. The averaged audiograms differ in best frequency (EP=525 Hz; BEH=725 Hz) and best sensitivity (EP=72 dB; BEH=63 dB). Thus, the EP method results in audiograms that are roughly comparable to the BEH audiograms, except at frequencies higher than the best frequency where the EP method appears to overestimate sensitivity.
The effects of sex and reproductive condition on auditory evoked responses in the round goby, Neogobius melanostomus.
Authors: Zeyl Jeffrey N. , Higgs Dennis M.
Published: July 2011

Effectively receiving and responding to mating signals is critically important in acoustically communicating vertebrate species, particularly for individuals that are reproductively mature. Behavioral responses to mating and advertisement signals in these individuals are often more intense than in their non-reproductive counterparts, which might be explained in part by changes in the response properties of the auditory system. The current study examined the potential for auditory plasticity of hearing sensitivity in relation to reproductive state in the round goby. This fish breeds in high density aggregations, with males guarding nests and producing low frequency (150–180 Hz dominant frequency) vocalizations that both males and females can localize. Auditory sensitivities in both sexes were assessed in reproductive and non-reproductive individuals using auditory evoked responses to tone pips that ranged from 100 to 600 Hz. Females were more sensitive than males across their hearing range. When assessed based on reproductive status, reproductive females were more sensitive than non-reproductive females and males at 100 Hz. Thresholds in males were similar between reproductive and non-reproductive individuals. These results suggest that hearing sensitivity in the round goby is sexually dimorphic at selected frequencies and is enhanced with reproductive maturity in females. [Work supported by NSERC.]
Seasonal plasticity of saccular sensitivity in the type II sneaker-male plainfin midshipman fish (Porichthys notatus).
Authors: Whitchurch Elizabeth A. , Sisneros Joseph A.
Published: July 2011

Acoustic communication is essential to the reproductive success of the nocturnally breeding plainfin midshipman fish (Porichthys notatus). During the summer breeding season, type I singing-males excavate nests in the Pacific intertidal zone and vocalize a multiharmonic “advertisement hum” to attract potential mates. Summer reproductive females are more sensitive to the dominant frequencies that comprise the hum than winter nonreproductive females. Type II or “sneaker” males employ alternative mating strategies that do not require nest construction or hum production but instead involve satellite and/or sneak spawning strategies. These strategies require nocturnal nest selection and localization. Because sneaker-males must rely on their auditory system to find the nests of singing males just as females must, we hypothesized that the saccular sensitivity of the reproductive sneaker-males would be most like that of reproductive females. Here we measured the evoked saccular potentials of reproductive and nonreproductive sneaker-males to tones of various sound pressure levels, and determined saccular thresholds for frequencies from 65 to 505 Hz. As predicted, thresholds measured in reproductive sneaker-males very closely matched those reported for reproductive females. Future studies will investigate the effects of gonadal steroids on hearing in sneaker-male midshipman fish. [Work supported by NIH NIDCD Grant No. 2T32DC005361-06.]
Mysterious magno.
Authors: Edds-Walton Peggy L. , Rivera-Matos Solymar , Fay Richard R.
Published: July 2011

Fish have three otolithic endorgans that may be involved in auditory processing: saccule, lagena, and utricle. One or more of those endorgans may serve a vestibular (tilt) function. In general, vestibular inputs are distributed more ventrally than auditory inputs in the medulla of teleost fishes, but there are zones of overlap with the more dorsal auditory sites. The octaval nucleus magnocellularis (Magno) receives overlapping input from all three endorgans, but Magno is not part of the ascending auditory circuit in the oyster toadfish, Opsanus tau, and the sensory role of this nucleus is unknown. Extracellular recordings were conducted in Magno and neurobiotin was injected at successful recording sites to confirm location and label local cell types. Sinusoidal particle motion stimuli (50–303 Hz) were presented at multiple stimulus levels to assess relative sensitivity. The data indicate that some cells in Magno respond to auditory frequencies at biologically relevant levels. While these results are suggestive, many attempts to record auditory responses in the divisions of Magno were negative, indicating that only a subset of cells is auditory.
Vibration of otolithlike scatterers due to low frequency harmonic wave excitation in water.
Authors: Schilt Carl R. , Cranford Ted W. , Krysl Petr , Hawkins Anthony D.
Published: July 2011

Otoliths may be approximated as hard objects moving in an acoustic medium in response to arriving sounds. We modeled how parameters of sound such as frequency and direction could be encoded from the motion of the otoliths. Prior numerical models predicted harmonic oscillation (rocking) of scatterers suspended in an acoustic medium when exposed to planar harmonic waves. Because of the potential for the angular oscillation to produce additional information about the sound source, the simulated rocking motions were studied using an additional numerical model. The number of scatterers, their spatial arrangements, shapes, and the characteristics of the incident sound waves were varied. The results were analyzed and will be presented. [Work supported by the Office Naval Research.]
Ontogeny of early audition in the plainfin midshipman, Porichthys notatus.
Authors: Alderks Peter W. , Sisneros Joseph A.
Published: July 2011

Early development is a time of great organizational activity. As sensory systems become functionally active, they often undergo a period of ontogenetic plasticity. The early ontogeny of the auditory system of the plainfin midshipman is of particular interest. During early ontogeny, the fertilized eggs of the midshipman are attached to the underside of rocks guarded by nesting (type I) males. These nesting males often guard multiple clutches of eggs while actively calling to attract additional mates. The males’ advertisement call is high intensity (approximately 145 dB re 1 μPa at the source) and long duration (minutes to hours). During nest incubation, the auditory system of the developing embryos becomes active. We previously showed that when juveniles leave the nest, the auditory sensitivity of their saccule closely resembles that of nonreproductive adults. Here, we investigate auditory sensitivity from the time the auditory system becomes functional until the juvenile midshipman is free swimming using an acoustic startlelike response to broadband clicks. We characterize the startlelike response in embryos and juveniles and use this behavior as a measure to determine when the midshipman auditory system becomes functional. We also present physiology data on evoked saccular potentials during this developmental window.
Mechanisms of action for ultrasound surgical instruments.
Authors: Schafer Mark E.
Published: July 2011

Ultrasound devices operating at kilohertz frequencies have been used in surgery for over 40 years. Examples range from cataract removal (phacoemulsification) to adipocyte extraction (ultrasound assisted liposuction). These devices make direct contact to erode tissue and work via a number of mechanisms including cavitation (both inertial and stable) and acoustic (micro)streaming. This talk will describe recent research into various factors which affect the mechanisms of tissue erosion. While all these devices operate in the frequency range of 23 to about 43 kHz, the exact combination of frequency, vibration amplitude and mode, and tip configuration creates a range of acoustic source strengths and thus acoustic outputs. Some devices work principally through inertial cavitation action, and experiments to demonstrate this will be reviewed. Other systems tend to favor stable cavitation, permitting, for example, the extraction of viable fat cells which can be re-implanted or harvested for other purposes, such as adipose-derived regenerative (stem) cells. Still other devices rely mostly on acoustic microstreaming and physical macromotion to dissolve blood clots. The range of device types and mechanisms creates difficulties in making direct comparisons between systems, even between those with similar overall design and clinical purpose. Potential solutions to this issue will also be presented.
Histological and biochemical analysis of emulsified lesions in tissue induced by high intensity focused ultrasound.
Authors: Wang Yak-Nam , Khokhlova Tatiana D. , Canney Mike S. , Khokhlova Vera A. , Crum Lawrence A. , Bailey Mike R.
Published: July 2011

As recently shown, shock wave heating and millisecond boiling can be used to obtain mechanical emulsification of tissue with or without evident thermal damage, which can be controlled by varying the parameters of the high intensity focused ultrasound exposure. The goal of this work was to examine these bioeffects using histological and biochemical analysis. Lesions were created in ex vivo bovine heart and liver using a 2-MHz transducer and pulsing scheme with 71 MPa in situ shock amplitude, 0.01 duty factor, and 5–500 ms pulse duration. Mechanical tissue damage and viability of cells in the lesions were evaluated histologically using conventional staining techniques (H&E and NADH-diaphorase). Thermal effects were quantified by measuring denaturation of salt soluble proteins in the treated area and confirmed by histology. By visual observation, the liquefied lesions obtained with shorter pulses (< 15 ms) did not show any thermal damage that correlated well with the results of both histology and protein analysis. Increasing the pulse duration resulted in an increase in thermal damage; both protein analysis and NADH-diaphorase staining showed denaturation that was visually observed as whitening of the lesion content. [Work supported by NSBRI through NASA NCC 9-58, NIH EB007643 and DK007742.]
Models for coupled bubble dynamics between parallel elastic layers.
Authors: Hay Todd A. , Ilinskii Yurii A. , Zabolotskaya Evgenia A. , Hamilton Mark F.
Published: July 2011

Recent photographs of microbubbles driven by high-amplitude pulses in ex vivo blood vessels have provided quantitative measurements of coupled bubble dynamics near tissue [Chen et al., J. Acoust. Soc. Am. 126, 2175 (2009)]. There is also interest in exploiting bubble-bubble interaction to aid sonoporation of an adjacent cell membrane [Sankin et al., Phys. Rev. Lett. 105, 078101 (2010)]. These observations have motivated the development of models describing the dynamics of coupled bubbles near compliant interfaces. Two models describing the dynamics of a bubble pair positioned between parallel tissue layers immersed in a viscous liquid will be presented. One model is based on Lagrangian mechanics and incorporates bubble shape deformation accounting for the onset of jetting, but is limited to an orientation in which the axis connecting the bubbles is perpendicular to the tissue layers. The second model, which makes use of Green’s function, accounts for fluid compressibility and tissue viscoelasticity, but is limited to spherical bubbles. Expressions for the displacement, strain, and stress fields in the tissue are derived. Simulations will be presented to illustrate the influence of bubble-tissue and bubble-bubble interaction, for a variety of clinically relevant parameters. [Work supported by NIH Grant Nos. DK070618 and EB011603.]
Miniature acoustic fountain mechanism for tissue emulsification during millisecond boiling in high intensity focused ultrasound fields.
Authors: Simon Julianna C. , Sapozhnikov Oleg A. , Khokhlova Vera A. , Khokhlova Tatiana D. , Bailey Michael R. , Crum Lawrence A.
Published: July 2011

Feasibility of soft tissue emulsification using shock wave heating and millisecond boiling induced by high intensity focused ultrasound was demonstrated recently. However, the mechanism by which the bubbles emulsify tissue is not well understood. High-speed photography of such exposures in transparent gel phantoms shows a milimeter-sized boiling bubble, and histological analysis in tissue samples reveals sub-micron-sized fragments. Here, a novel mechanism of tissue emulsification by the formation of a miniature acoustic fountain within the boiling bubble is tested experimentally using a 2 MHz transducer generating up to 70 MPa positive and 15 MPa negative peak pressures at the focus. The focus was positioned at or 1–2 mm off the plane interface between air and various materials including degassed water, transparent gel, thin sliced muscle tissue phantom, and ex-vivo tissue. Pulsing schemes with duty factors 0.001–0.1, and pulse durations 0.05–500 ms were used. Violent removal of micron-sized fragments and substantial displacement of the phantom surface were observed through high-speed filming. At the end of each exposure, the resulting erosion of the phantom surface and subsurface area was photographed and related to the exposure parameters. Work supported by NIH (DK43881, DK070618, EB007643, and DK007742) and NSBRI through NASA NCC 9-58.
Modeling single-bubble dynamics in histotripsy.
Authors: Hua Chengyun , Johnsen Eric
Published: July 2011

In several therapeutic ultrasound applications such as histotripsy, cavitation bubbles are generated in tissue by high-intensity ultrasound pulses. In order to understand bubble dynamics in human tissue related to histotripsy, the model of Yang and Church (2005) for spherical bubble dynamics in a compressible and viscoelastic medium is extended to include variations in the liquid density and non-spherical perturbations in viscoelastic media based on the stability analysis by Prosperetti (1977). Both continuous symmetric pulses and asymmetric pulses representative of histotripsy are considered. The bubble exhibits a strongly nonlinear response to the asymmetric pulses but recovers rapidly thereafter. Density variations in the liquid lead to a larger amplitude response of the bubble radius after the first cycle. The pressure and strain in the surrounding material are determined both analytically and numerically, thus providing estimates for potential damage away from the bubble. The violent bubble collapse leads to high local pressures at the bubble location and significant strains are achieved away from the bubble during the expansion. The effects of nonlinearity, amplitude, and frequency of the asymmetric pulses will be considered and more sophisticated viscoelastic models will be applied.
Use of meteorological classes for simplifying forecasts of outdoor sound propagation.
Authors: White Michael J. , Swearingen Michelle E.
Published: July 2011

The detailed and variable atmospheric condition is mostly undersampled but certainly important for making accurate predictions of sound propagation. While prediction accuracy suffers due to incomplete knowledge of the current atmosphere, the benefit of coarse classification has not been fully explored. We use measured wind and temperature values from a 30 m tower to infer the nearest stability class and wind speed and to develop statistics for measurements of tones propagated from the tower to 1.6 km distance. The measured statistics for the classes are reinforced with computational modeling.
Investigations of environmental and terrain effects on the propagation of freeway noise.
Authors: Ovenden Nick C. , Shaffer Stephen R. , Fernando Harindra J. S.
Published: July 2011

Noise caused by freeway traffic is a serious environmental concern in major urban areas. This study examines the impact of meteorological conditions and terrain features on the propagation of traffic noise from urban freeways. Meteorological and sound-level measurements were taken at freeway sites in Phoenix, AZ, and an analytical Green’s function solution was used to produce a sound field in the neighborhood of the freeway that replicates the sound levels measured. A parabolic equation model for sound propagation is then coupled to this Green’s function solution of the source field to compute the refracted sound field out to a range of half a mile from the freeway to predict the noise exposure in residential areas. The model demonstrates that atmospheric effects can raise sound levels by 10–20 dB at significant distances away from the highway, causing violations of acceptable limits imposed by the Federal Highway Administration in residential areas that are normally in compliance. A generalized terrain parabolic equation model is also extended to account for coupled two-way sound propagation, enabling the study of backscatter from certain terrain features. Terrain examples incorporating noise barriers and freeway canyons will be presented. [Work supported by Arizona Dept. of Transportation.]
Sound field of a fast moving source in a horizontally stratified medium above an impedance plane.
Authors: Tong Bao , Li Kai Ming
Published: July 2011

A continuous source motion model is developed for computing the sound fields of a uniformly moving monopole source in a horizontally stratified atmosphere. The numerical model is based on the Lorentz transformation and the one-dimensional fast field formulation. The global matrix method and a bounded Green’s function solution expressed in the wavenumber domain is used in the numerical implementation. The solution is then expressed in the Lorentz frame. A transformation is performed to map the spatial Lorentz frame quantities into a reception time history in the stationary frame. Numerical results for an elevated source in a downward refracting atmosphere demonstrates the importance of a continuous source motion model especially at high Mach numbers in the presence of sound speed gradients where the pseudo-stationary source approximation becomes questionable. Coupled with the convective effects of continuous source motion and a frequency dependent ground impedance model, the resulting sound fields are significantly different from those predicted due to a pseudo-stationary source. Fluctuations on the order of 20 dB are predicted in the interference pattern in the far-field. A shift of the interference onset time to lower values is predicted when the source Mach number and/or sound speed gradient is increased.
Improving the efficiency of mean sound level calculations through importance sampling.
Authors: Wilson D. Keith , Pettit Chris L.
Published: July 2011

Outdoor sound levels vary in space and time due to randomness in acoustic source emissions and environmental effects on wave propagation. Sound levels may also appropriately be viewed as random due to uncertainties in the modeling process. To assess the impact of the randomness on sound level predictions, Monte Carlo sampling of the model input space can be used; that is, equally likely sets of model inputs are generated, to which a sound propagation model is applied repeatedly. To improve the efficiency of the calculations, it is highly desirable to sample primarily the acoustical frequency bands and environmental conditions (such as downwind propagation and hard ground surfaces) contributing most strongly to the sound level. Importance sampling techniques, which adaptively focus sampling effort on the most important parts of the input parameter space, can be used for this purpose. This paper explores application of importance sampling to prediction of sound level statistics. The technique is found to be particularly valuable in limiting the calculation effort at high frequencies, where most computational methods are highly inefficient and propagation effects are most unpredictable.
Parabolic equation approach for modeling atmospheric noise propagation.
Authors: Lingevitch Joseph F. , Fialkowski Laurie T.
Published: July 2011

A wide-angle parabolic equation (PE) model for propagating atmospheric noise from a directional source is developed. The directivity pattern of a compact directional source is modeled with a vertical distribution of phased sources and the effects of atmospheric attenuation, sound speed and wind profiles, and range-dependent terrain are incorporated into the marching algorithm. The PE approach includes the effects of diffraction by terrain features using a piecewise linear terrain-flattening transformation to simplify the implementation of the impedance boundary condition at the ground. Comparisons with image, ray-based, and finite element solutions are shown to validate the model. [Work supported by the ONR.].
Response of infrasonic microphone field array to a controlled source.
Authors: Shams Qamar A , Zuckerwar Allan J. , Weistroffer George R.
Published: July 2011

A field test on a three-microphone array at NASA Langley Research Center was conducted using a mobile controlled infrasonic source. A Helmholtz resonator, used to provide a simulated point source for infrasonic propagation studies, had an output SPL of 99 dB (at 1 m) at its resonance frequency of 9.45 Hz. The three-microphone array was arranged as an equilateral triangle with microphone spacing of 30.48 m (100 ft) and at a distance of more than 85.3 m (280 ft) from the source. The signal level was 40 dB above the background noise in a 1-Hz band. Measurements of the acoustical response for each of the array microphones were recorded, and the received signal was measured at the nearest microphone to be 60 dB (6 dB per doubling of distance).
Scale model investigation of factors affecting the performance of roadside noise barriers.
Authors: Daltrop Shira , Hodgson Murray , Wakefield Clair
Published: July 2011

Besides numerical models, another way to model complex environments is using physical reduced-scale models. This project used scale models to study several factors which may influence the performance of roadside noise barriers. One is the barrier absorption. Making the barrier sound absorptive decreases reflections and may decrease amplification between parallel barriers. The other is tree foliage growing near the barrier. Tree foliage may scatter sound into the shadow zone behind the barrier, increasing noise levels and decreasing the insertion loss. Tree foliage may also attenuate sound that would normally be diffracted into the shadow zone, actually increasing the insertion loss. A 1:31.5 scale model was created in an anechoic chamber to test the effects of these two factors. Excess attenuation measurements were performed to choose scale model materials, which accurately represent full scale surfaces. Parallel barriers were modeled with a reflective surface and their IL's were measured for different configurations of absorptive covering. IL's of single barriers were measured both with and without scale model trees placed either in front or behind them. The results are compared to previously performed field test measurements.
Moments to cherish in his life: Our father Rongjue Wei.
Authors: Wei Yihua , Wei Lanhua
Published: July 2011

We would like to take this opportunity to celebrate the life of our father, Prof. R. J. Wei, who devoted his life and passion to physics and acoustics. We would like to share some of the precious moments in his life: from the time early in his career when he came to America to find his dream; to the time he went back to China to establish the first acoustics science and education foundation in the country; to the time he fought even bravely after the national disaster of the cultural revolution to catch up to the world’s advances in science; to the time later in life, even though with failing memory, he still cared with all his heart about the scientific progress of his institute and university. Throughout it all, he was a loving father, a respectful advisor, and a good friend to his family, his colleagues, and his students some of whom were a couple of generations younger than he.
Dislodgement and removal of dust-particles from a surface relevant to NASA project by vibration and acoustic levitation.
Authors: Wu Junru , Chen Di
Published: July 2011

There are many fine particles on the moon and on Mars, which may cause risk for the success of a long-term project for NASA. These dust-particles might cover the solar panels making them fail to generate electricity. The particles would be hazardous to human health if they were inhaled. Development of robust dust mitigation technology is needed for the viable long-term exploration and habilitation of either the moon or Mars. We report here a feasibility study to develop a dust removal technique, which may be used in space-stations or other enclosures for habitation. It is shown that the acoustic levitating radiation force produced by a 13.8 kHz 128 dB sound-level standing wave between a 3 cm-aperture tweeter and a reflector separated by 9 cm is strong enough to overcome the van der Waals adhesive force between the dust-particles and the reflector-surface. Thus the majority of fine particles (greater than 2 μm diameter) on a reflector surface can be dislodged and removed by a technique combining acoustic levitation and airflow methods. The removal efficiency deteriorates for particles less than 2 μm in size. [This work was partially supported by NASA under Cooperative Agreement No. NNX08AZ07A.]
Transmission characteristics of double negativity acoustic metamaterials studied with fluid impedance theory.
Authors: Fan Li , Zhang Shu-yi , Zhang Hui
Published: July 2011

Input acoustic impedances and transmission coefficients of acoustic metamaterials composed of double negativity structures, i.e., periodic membranes (negative density) and side holes (negative modulus) set along pipes, are studied with the fluid impedance theory, by which the performances of the pipy metamaterials can be studied at any frequency, and the mechanisms of forbidden bands are presented with the theory of acoustic impedance match. In the type of pipy metamaterials, a forbidden band and a pass band successively occur from zero to the upper cut-off frequency of the double negativity. Then, another forbidden band occurs in the frequency range of the single negativity structure formed by the membranes or side holes. Meanwhile, it is found that the input acoustic resistance of the metamaterial is zero in the forbidden bands. Furthermore, other high-frequency forbidden bands caused by the Bragg scattering can be found. All the forbidden bands result from the acoustic impedance mismatch at the positions of the membranes and/or side holes. Finally, the influences of the structural parameters of the metamaterials on transmission coefficients, forbidden and pass band widths, fluctuations in pass bands, etc., are evaluated. [This work is supported by the National Natural Science Foundation of China Nos. 10904067 and 11074125, and Ph.D. Programs Foundation of Education Ministry of China No. 20090091120050.]
Late studies in Nanjing on dynamic behavior of nonpropagating solitons in Faraday wave experiment.
Authors: Zhang Likun
Published: July 2011

The standing solitons [Wu et al., Phys. Rev. Lett. 52, 1421–1424 (1984)] in Faraday wave experiment with a vertically driven rectangular water tank manifest wide nonlinear phenomena [R. Wei, J. Acoust. Soc. Am. 97, 3376 (1995)]. In this talk, we will briefly review the history, and then report some relatively recent studies in Nanjing on the dynamic behavior of such solitons, especially on the soliton’s creation, temporal modulation, spatial rocking, and the possible route from solitary waves to chaos via spatiotemporal bifurcations and mode competition [Zhang et al., Phys. Rev. E 75, 036602 (2007)]. Possible mechanisms for the spatial symmetry breaking and head rocking of a solitary wave will be discussed.
Nonlinear vibrations and heating phenomena of cracks in metal plates excited by intensive ultrasonic pulses.
Authors: Zhang Shu-yi , Chen Zhao-jiang , Zheng Kai , Mi Xiao-bing , Zheng Jiang
Published: July 2011

When thin metal plates are excited by intensive ultrasonic pulses, nonlinear vibration phenomena are observed in experiments. As the plates contain cracks, the frictional heating of both faces of the crack appears under the excitation of the ultrasonic pulses. Based on the experimental conditions, a finite element modeling is established and transient dynamic analyzes are performed to explore the generation mechanism of the nonlinear vibrations including superharmonics, subharmonics, and chaotics, as well as the heating phenomena of the cracks. A piezoelectric-thermal analogy method is used to simulate the high-power ultrasonic transducer excitation, and a contact-impact algorithm is used to simulate the dynamical interaction between the ultrasonic horn and plate as well as between both sides of the cracks. By analyzing the vibration velocity waveforms, vibration frequency spectra, and contact force waveform, it can be found that the waveform distortion of the intermittent contact forces between the horn tip and the plate is the main reason for generating the nonlinear vibrations. Meanwhile, the intermittent contacts and frictions between both faces of the crack induce heating the area. The numerical simulations show that the acoustic nonlinearities greatly enhance the heating. Generally, the theoretical results agree well with that of the experiments.
Threshold of the precedence effect in the presence of interfering noise.
Authors: Freyman Richard L. , Griffin Amanda M. , Zurek Patrick M.
Published: July 2011

Recent work suggests that the precedence effect involves three distinct phenomena: (1) a transient onset that enhances early spatial cues relative to those arriving shortly after; (2) the Franssen effect, in which localization/lateralization estimates established at onset are maintained throughout a long-duration stimulus; and (3) an ongoing precedence effect, in which leading cues throughout a long stimulus determine localization and lateralization. The goal of the present study was to determine whether the three phenomena are influenced to differing degrees by interference from other sources. Brief and longer trains of noise bursts that alternated between 0- and 500-μs interaural time delays were created to elicit the three types of phenomena. Masked thresholds for the stimuli beginning with 0-μs interaural delays were nearly identical to those beginning with 500 μs across the different types, indicating no precedence effect for detection threshold. Listeners’ ability to discriminate the 0-μs-leading and 500-μs-leading stimuli did not reach threshold performance until at least 12 dB above masked threshold, indicating that none of the three types of precedence effects is strong near detection threshold. However, the threshold of the Franssen effect was substantially higher than that of the other two phenomena. [Work supported by NIDCD Grant No. DC01625.]
Perceptual constancy for real-room reverberation in loudness judgements and the effects of interstimulus interval.
Authors: Raimond Andrew P. , Watkins Anthony J.
Published: July 2011

Narrowband stimuli shaped with fast-onset and slow-offset temporal envelopes are judged to be less loud than their reversed counterparts, particularly when preceded by a slow-offset standard. It has been suggested that a “perceptual constancy” may be responsible for this “loudness context effect.” The idea is that when a slow-offset “tail” is at the end of a sound it is largely attributed to listening-environment reflections and is discounted in the listener’s loudness judgment. Previous experiments have shown that this effect is even bigger when real-room reflection-patterns are used. The present experiments varied the interval between the standard and comparison tones (ISI) to investigate the contribution of time-order effects to these loudness judgements. Such effects might arise as the peak-to-peak interval between sounds changes with reversal of the standard, thereby confounding the duration of this interval with the presence of a “tail” in the standard. Results show that the loudness context effect reported earlier remains prominent across a range of ISI times and that the influence of any time-order effects is relatively weak. Consequently, these findings remain consistent with the idea that the context effect arises through a perceptual constancy. [Work supported by EPSRC.]
Auditory and visual distance estimation.
Authors: Anderson Paul W. , Zahorik Pavel
Published: July 2011

Past research has shown auditory distance estimation improves when listeners are given the opportunity to see all possible sound sources when compared to no visual input. It has also been established that distance perception is more accurate for visual stimuli than auditory stimuli. The present study investigates the degree to which auditory distance perception is improved when matched with a congruent visual stimulus. Virtual sound sources based on impulse response measurements made from distances ranging between 0.3038 and 9.7536 m in a concert hall were used as auditory stimuli. Visual stimuli were photographs taken from the listener’s perspective at each distance in the impulse response measurement setup presented on a large HDTV monitor. Listeners were asked to estimate egocentric distance to the sound source in each of three conditions: (A) auditory only, (V) visual only, and (A+V) congruent auditory/visual stimuli. Each condition was presented within its own block. Distance estimates from both V and A+V conditions were found to be considerably more accurate and less variable than estimates from the A condition. These results are consistent with visual capture phenomena that have been demonstrated in other spatial tasks with input from both auditory and visual modalities.
Adaptation to room acoustics using the modified rhyme test.
Authors: Brandewie Eugene J. , Zahorik Pavel
Published: July 2011

The negative effect of reverberant sound energy on speech intelligibility is well documented. Recently, however, prior exposure to room acoustics has been shown to increase intelligibility for a number of listeners in simulated room environments. This room adaptation effect, a possible extension of dynamic echo suppression, has been shown to be specific to reverberant rooms and requires binaural input. Because this effect has been demonstrated only using the coordinated response measure (CRM) corpus it is important to determine whether the increase in intelligibility scores reported previously was due to the specific nature of the CRM task. Here a comparable room-acoustic effect was demonstrated using the modified rhyme test corpus in multiple room environments. The results are consistent with the idea that the room adaptation effect is a natural phenomenon of listening in reverberant environments.