bluuebunny/crossref_metadata_2025 huggingface dataset:
Skipping stones along the boundary between marine mammal acoustics and acoustical oceanography.
Authors: Thode Aaron M.
Published: July 2011

Reductions in the power consumption and cost of underwater acoustic data acquisition systems have created profound changes in how acoustic oceanography, particularly bioacoustics, is conducted. Swarms of autonomous bioacoustic recorders can now be deployed across regions formerly too isolated to be reliably monitored. The consequent flood of acoustic data has made automated detection and classification systems an essential tool in current research. This presentation reviews three recent efforts that exemplify these trends. The first focuses on gray whales in San Ignacio Lagoon, Baja, CA, where interesting relationships are being uncovered between visual census counts and background calling rates. The second concerns sperm whale depredation of longline fishing gear in Southeast Alaska, where acoustic tools have helped reveal how animals locate fishing activity, and how depredation success might be remotely monitored. The final effort involves large-scale acoustic research conducted in the Arctic Ocean by Shell Oil to monitor the fall migration of bowhead whales through regions subject to seismic airgun exploration activity. The development of large-scale automated processing methods was required to process millions of bowhead whale sounds collected on multichannel sensors and vertical arrays. All three projects illustrate the intimate connections between marine mammal acoustic behavior and the background noise environment.
The quality of histotripsy produced tissue lesions can be remarkably insensitive to strong acoustic aberrations: Role of nonlinear phenomena.
Authors: Cain Charles , Kim Yohan , Wang Tzu-Yin , Xu Zhen
Published: July 2011

Cavitation induced by short high intensity pulses can produce confined lesions with remarkably narrow transition zones (often bisecting individual cells). This process (histotripsy) is a nonlinear phenomenon wherein energetic bubble clouds are produced only when the incident ultrasound beam is above the cavitation threshold. It has been shown that acoustic aberrations in the path of an acoustic beam tend to rob energy from the main lobe raising surrounding side-lobes, sometimes significantly. However, in many cases, the shape of the main lobe, while diminished in amplitude, retains its original confined Gaussian-shaped cross-section. If the transducer-driving electronics has sufficient head-room, the main lobe can be boosted to preaberration above-threshold levels while maintaining the original main lobe profile. If the boosted main lobe amplitude is above the side-lobe levels, the lesion producing bubble clouds often are indistinguishable from the nonaberration case thus producing a clean confined lesion with little collateral damage even in the presence of strong aberrations. Confirmation of this strategy with porcine and polymer rib aberration phantoms is presented with a study of lesion shape as well as collateral damage with and without aberrations. Boosted intensities can be kept below thermally significant levels by adjusting pulse repetition frequency and pulse width.
A method of mechanical emulsification in a bulk tissue using shock wave heating and millisecond boiling.
Authors: Khokhlova Vera A. , Canney Michael S. , Bailey Michael R. , Hwang Joo Ha , Khokhlova Tatiana D. , Kreider Wayne , Wang Yak-Nam , Simon Julianna C. , Zhou Yufeng , Sapozhnikov Oleg A. , Crum Lawrence A.
Published: July 2011

Recent studies in high intensity focused ultrasound (HIFU) have shown significant interest in generating purely mechanical damage of tissue without thermal coagulation. Here, an approach using millisecond bursts of ultrasound shock waves and repeated localized boiling is presented. In HIFU fields, nonlinear propagation effects lead to formation of shocks only in a small focal region. Significant enhancement of heating due to absorption at the shocks leads to boiling temperatures in tissue in milliseconds as calculated based on weak shock theory. The heated and potentially necrotized region of tissue is small compared to the volume occupied by the mm-sized boiling bubble it creates. If the HIFU pulse is only slightly longer than the time-to-boil, thermal injury is negligible compared to the mechanical injury caused by the exploding boiling bubble and its further interaction with shocks. Experiments performed in transparent gels and various ex vivo and in vivo tissues have confirmed the effectiveness of this emulsification method. In addition, since mm-sized boiling bubbles are highly echogenic, tissue emulsification can be easily monitored in real-time using B-mode ultrasound imaging. [Work supported by NIH EB007643, RFBR 09-02-01530, and NSBRI through NASA NCC 9-58].
The application of kilohertz-frequency ultrasound energy in performing advanced clinical procedures.
Authors: Makin Inder Raj S.
Published: July 2011

The use of ultrasound energy for therapeutic applications is an ever-increasing option for the medical professional in managing clinical disease states. Ultrasound therapies in medicine are generally delineated based on frequency regimes, namely, kilohertz and megahertz. Based on the relatively long wavelengths in tissue (several millimeters), and the small size of the radiator source (1–4 mm), with respect to the wavelength, kilohertz-frequency medical devices generally rely on biophysical effects such as rapid frictional heating, cavitation, streaming, and mechanical disruption, in very close proximity to the ultrasound sources. These devices are therefore inserted intra-corporeally to achieve tissue cutting, hemostasis, thrombolysis, or lipid-based tissue emulsification. The bioeffects resulting from the use of kilohertz-frequency based devices are much more controlled compared to their counterparts such as radiofrequency, lasers, and microwave devices. This talk will provide an overview of the kilohertz-frequency techniques used in the areas of vascular (angioplasty) advanced surgical (ultrasonic scalpel), as well as cosmetic (lipolysis) procedures. Numerical simulation, experimental, as well as some clinical examples will be presented to illustrate various biophysical mechanisms that form the basis of different systems.
Focused destruction of renal tissue by a narrow focal width lithotripter.
Authors: McAteer James A. , Evan Andrew P. , Connors Bret A. , Blomgren Philip M.
Published: July 2011

Although lithotripters can differ substantially in acoustic output, renal response to SWs has been thoroughly characterized for only one type of lithotripter (moderate-pressure ∼40 MPa, intermediate-focal-width 8–9 mm, Dornier-HM3). Therefore, we assessed injury using a high-pressure (∼85 MPa), narrow-focal-width (3–4 mm) device (Storz-SLX). SWs were administered to the lower renal pole of pigs (15 kg) (PL-9, 2000 or 4000 SWs at 120 SWs/min; or 2000SWs at 60 SW/min) followed by serial sectioning to quantify lesion. Tissue damage with the SLX showed an abrupt transition between injured and unaffected tissue. Core of lesion was typically devoid of recognizable structure, with renal tubules, glomeruli, vessels essentially eliminated. The lesion extended from cortex to medulla, and in some kidneys homogenized tissue could be tracked across full thickness of the kidney. In comparison, the lesion using HM3 was not as severe with only focal spots of hemorrhage and no areas of complete tissue destruction. Doubling the SW-dose with SLX did not increase lesion volume as occurred with HM3. Also, slowing the SW-rate of the SLX to 60 SW/min did not have a protective effect as observed with other lithotripters. These findings suggest that lithotripters having different acoustic characteristics are capable of producing different forms of tissue damage. [Work supported by NIH-DK43881.]
Models for cavitation-induced displacement, stress, and strain in tissue.
Authors: Hamilton Mark F. , Hay Todd A. , Ilinskii Yurii A. , Zabolotskaya Evgenia A.
Published: July 2011

Cavitation activity near tissue interfaces may cause the tissue to deform, inducing stresses and strains of sufficient magnitude to cause damage. Understanding the interaction between bubbles and the surrounding tissue is therefore critical in therapeutic ultrasound. Since interacting bubble clusters are often responsible for bio-effects, both bubble-bubble and bubble-tissue interactions should be considered. In this presentation, simulation results from models describing the dynamics of single bubbles and bubble pairs immersed in a viscous liquid near tissue interfaces will be presented for two geometries. The first geometry is that of a bubble pair positioned between parallel tissue layers, and the second is for a bubble in a viscoelastic cylindrical tube. Tissue displacements caused by the motion of the bubbles may be estimated via models derived using Green’s function and Lagrangian mechanics approaches. The Green’s function approach further permits estimation of the time-varying strain and stress fields in the tissue, including effects of viscoelasticity. Aspherical bubble deformation and the onset of jetting due to bubble-bubble or bubble-tissue interaction is modeled using the Lagrangian mechanics approach. Simulations illustrating the dynamics of the bubbles and tissue for clinically relevant parameters will be presented. [Work supported by NIH Grant Nos. DK070618 and EB011603.]
Ultrasonic atomization on the tissue-bubble interface as a possible mechanism of tissue erosion in histotripsy.
Authors: Sapozhnikov Oleg A. , Khokhlova Vera A. , Bailey Michael R.
Published: July 2011

When an intense ultrasound beam is directed at a free surface of a liquid, an acoustic fountain is produced that is typically accompanied by ejection of tiny droplets, i.e., liquid atomization. This phenomenon is usually attributed to instability of cavitation-produced capillary waves on the surface. In addition to capillary effects, a process called spallation may also contribute. Although the acoustic fountain is typically observed at a flat liquid surface, nothing prohibits the atomization from occurring at a curved surface. This brings about the possibility to create an acoustic fountain and droplet emission at the surface of a gas cavity in liquid or, similarly, in the bulk of soft biological tissue. The appropriate condition occurs when high-intensity ultrasound is focused in tissue and creates large (0.1–1 mm in diameter) bubbles due to acoustic cavitation or rapid boiling. To test this hypothesis, acoustic pressure distribution and the corresponding radiation force on the empty spherical cavity were calculated using finite difference modeling and spherical harmonic expansion. It is shown that in histotripsy regimes appropriate conditions appear for the atomization, which may be considered as a possible mechanism of tissue erosion. [Work supported by NIH EB007643, RFBR, and NSBRI through NASA NCC 9-58.]
Ultrasound-induced fragmentation of connective tissue guided by passive acoustic mapping.
Authors: Molinari M. B. , Arora M. , Urban J. P. G. , Coussios C. C.
Published: July 2011

To date, studies on the mechanical bio-effects of acoustic cavitation have been confined to soft tissues such as the liver or prostate. In the present work, acoustic cavitation caused by high intensity focused ultrasound (HIFU) is used to disrupt the highly collagenous, acellular connective tissue of the intervertebral disk (IVD). The IVD is comprised of three regions: a highly hydrated, amorphous nucleus pulposus (NP) enclosed circumferentially by the lamellar structure of the annulus fibrosus, and capped by cartilaginous endplates. In experiments using ex vivo bovine coccygeal disks as a model, two confocally-aligned HIFU transducers were positioned with their focus inside the disk, and driven at 500 kHz. Cavitation activity was localized and monitored using both a 3.5 MHz PCD and a 2-D passive mapping array and was found to be confined to the NP. Treatment parameters were optimized to minimize treatment time and thermal damage to adjacent tissue. Disruption of the tissue after treatment was determined visually and suggests that it should be possible to remove disrupted tissue through a small gauge needle, thus enabling several proposed treatments for disk degeneration.
Time-domain simulations of outdoor sound propagation in presence of a complex topography.
Authors: Blanc-Benon Philippe , Dragna Didier , Poisson Franck
Published: July 2011

For transportation noise applications, the description of the environment, as well as the description of acoustic sources, is complex; and finite-difference time-domain methods have proved their capability to take into account both atmospheric effects and topography. Recently, a time-domain boundary condition has been proposed [Cotté et al., AIAA J. 47, 23912403 (2009)] and implemented in a solver using methods developed in the computational aeroacoustics community [Bogey and Bailly, J. Comput. Phys. 194, 194214 (2004)]. First, propagation of an initial pulse over a distance of 500 m in a two-dimensional geometry is considered in a frequency band up to 1200 Hz. Ground effects are discussed depending on the impedance of the ground, and results are compared with available analytical data. Surface waves, which propagate close to the ground, are exhibited. Then, acoustic scattering by an impedance cylinder in a two-dimensional geometry is considered as a test case to validate the boundary conditions in the presence of an acoustic shadow zone. Comparisons are realized with conformal mapping numerical predictions. At last, a three-dimensional geometry of a railway track is considered to highlight the effects of topography on measurements of railway noise. [This work was performed using HPC resources from GENCI-IDRIS Grant No. 2010-022203.]
Prediction of urban sound propagation via adaptive beam tracing.
Authors: Hart Carl R. , Lau Siu-Kit
Published: July 2011

Prediction of urban sound propagation is an integral part for the assessment of noise levels in cities. Several propagation modeling methods exist to predict sound propagation in city environments including parabolic equation, diffusion equation, radiosity, ray tracing, image source, modal analysis, and transmission line matrix methods. For this study, adaptive beam tracing as a geometrical acoustic prediction method is applied in the context of predicting sound propagation in complex urban environments. Adaptive beam tracing is advantageous compared to the ray tracing and image source methods by eliminating aliasing errors and spurious image sources, respectively. A model of diffraction [Svensson et al., J. Acoust. Soc. Am. 106, 2331–2344 (1999)] is integrated with the adaptive beam tracing algorithm in order to enhance the prediction capability of the proposed method. The effects of facade roughness, street canyon shielding, and building spacing are investigated. Comparison of the proposed method is made with a ray tracing method. Computation times, as well as various geometric configurations, are compared between the proposed method and the ray tracing method.
An ex vivo study on targeted cell surgery.
Authors: Wang Zhi Biao , Fang Liao Qiong , Wang Hua , Li Fa Qi , Wu Junru
Published: July 2011

High intensity focused ultrasound (HIFU) has become a new noninvasive surgical modality in medicine. It was shown by ex vivo experiments that the dimensions of the tissue which experiences CN can be as small as 50 × 250 × 250 μm3 after 1 s exposure of ultrasonic pulse [the spatial and pulse average acoustic power is on the order of tens of watts and the local acoustic spatial and temporal pulse averaged intensity is on the order of 30 thousands per square meter generated by a 1.6 MHz HIFU transducer of 12 cm diameter and 11 cm geometric focal length (f-number = 0.92)]. The numbers of cells which suffered CN were estimated to be on the order of 40. This result suggests that HIFU is able to interact with tens of cells at/near its focal zone while keeping the neighboring cells minimally affected, and thus the targeted cell surgery may be achievable. [It was funded by National Basic Research Program of China (No. 2011CB707902) and Key Program of National Natural Science Fund by the Chinese National Science Foundation (No. 30830040). J. W. was supported by the HAS fund at University of Vermont.]
Nonlinearly torsional vibrations in acoustic friction force microscope.
Authors: Zhang Hui , Zhang Shu-yi , Fan Li
Published: July 2011

The tip motion in the acoustic friction force microscope shows the stick-slip behavior for a large displacement in the tip-sample contact, in which the tip begins to slide on the sample when the lateral force is larger than the threshold lateral friction. To investigate the torsional vibrations of the cantilever in the microscope, the ratio of the threshold lateral friction to the product of the lateral contact stiffness and the vibration amplitude is an important parameter. When the ratio tends to 0, the tip purely slips on the sample. When the ratio is equal to or larger than 1, the stick appears, in which the lateral force can be regarded as a linear force applied to the tip. If the ratio changes from 0 to 1, the stick-slip motions of the tip exist, in which the lateral friction is nonlinear and induces a complex torsional vibration of the cantilever. The vibration can be described by a transition state from the pure stick to the pure slip, which is determined by the tribological characterization of the interface of the tip-sample. [This work is supported by NNSF of China (11004099 and 10774074), and supported by State Key Laboratory of Acoustics, CAS.]
A binaural model to simulate the precedence effect with adaptive stages to compensate for head movements.
Authors: Braasch Jonas , Parks Anthony , Xiang Ning
Published: July 2011

Several models exist to simulate localization dominance, the ability of the auditory system to disregard room reflections when determining the location of a sound source. Psychoacoustic experiments have shown that the suppression of a reflection can improve over time, an effect known as the build up of the precedence effect. A recently introduced binaural model [Braasch, J. Acoust. Soc. Am. 124, 2494] is an ideal candidate to simulate this buildup effect. The model estimates the optimal parameters to inhibit a reflection using an autocorrelation algorithm, and thus the buildup can be understood as a learning process to tune these parameters optimally. The question of how the auditory system adapts to stimuli changes when the listener changes position, however, has not been addressed adequately. An initial attempt to simulate this condition is made here by combining the aforementioned binaural model with one that compensates for head movements, which is achieved by rotating the binaural activity pattern in the opposite direction, but with the same magnitude, of the head movements [Braasch et al., J. Acoust. Soc. Am. 127, 1886]. This way, the precedence effect model is able to adapt to the new situation without having to relearn the configuration of direct sound and reflection.
Binaural beat rate discrimination.
Authors: Grose John H. , Buss Emily , Hall Joseph W.
Published: July 2011

Rate discrimination for binaural beats was measured for standard rates of 4, 8, 16, and 32 Hz in normal-hearing adults. Binaural beats were generated by presenting pairs of 1250-ms tones dichotically at a level of 65 dB sand pressure level (SPL) through insert earphones. This duration allowed for 5 cycles of the lowest (4 Hz) modulation. Tone frequency was roved between 400 and 500 Hz on a presentation-by-presentation basis to avoid monaural place cues for discrimination; starting phase was random. The ratio of a just-discriminable increase in rate relative to a standard rate was fairly constant across the four beat frequencies. The salience of the beat percept was matched to that of sinusoidal amplitude modulation (SAM) by varying the depth of modulation of a diotic SAM tone having the same rate as a given standard beat. Rate discrimination for this salience-matched SAM tone was then measured, again with frequency rove keeping all components within the 400–500 Hz region. Whereas rate discrimination for the salience-matched SAM tone tended to be poorer than that of binaural beat discrimination, rate discrimination for a 100% modulated SAM tone tended to be better. The implication of these results for binaural sluggishness will be discussed. [Work supported by NIH NIDCD Grant No. 5R01DC001507.]
Surface decomposition method for near-field acoustic holography.
Authors: Valdivia Nicolas P.
Published: July 2011

Near-field acoustic holography reconstruction of the acoustic field at the surface of an arbitrarily shaped radiating structure from pressure measurements at a nearby conformal surface is obtained from the solution of a boundary integral equation. This integral equation is discretized using the equivalent source method to be transformed into a matrix system that can be solved using iterative regularization methods that counteract the effect of noise on the measurements. This work considers the case when the resultant matrix system is so large that it cannot be explicitly formed and iterative methods of solution cannot be directly implemented. In this case the method of surface decomposition is proposed, where the measurement surface is divided into smaller nonoverlapping subsurfaces. Each subsurface is used to form a smaller matrix system that will be solved and the result joined together to generate a global solution to the original matrix system. We use numerically generated data to study the use of subsurface extensions to increase the continuity of the global solution, the size of the subsurfaces, and the distance of the measurement surface from the surface of the vibrating surface. Finally a vibrating ship hull structure is considered as a physical example to apply and validate our results.
Transmission loss measurements using a scanned array nearfield acoustical holography system in an anechoic/reverberation facility. Part II. Comparison of transmission loss methods.
Authors: Sklanka Bernard J. , Tuss Joel R.
Published: July 2011

Transmission loss is an important metric used to assist in the selection of materials for noise control and design. In order to assess and improve the performance of transmission loss measurements, two different techniques were compared: traditional microphone and/or matched pair microphone intensity anechoic chamber-side techniques, and nearfield acoustical holography techniques. Intensity and sound power measurements using traditional methods were made on a test panel installed in an anechoic-reverb facility transmission loss window, then repeated using a conformal nearfield microphone array and nearfield acoustical holography processing techniques. The full vectored intensity components were used to assess the radiation characteristics of the test panel. This assessment quantifies the acoustics as panel radiation, flanking path contamination, and boundary effects. Data are presented to qualify the best estimate for transmission loss by rejecting contamination. Also, the dynamic range of the transmission loss measurement is compared between traditional and nearfield acoustical holography techniques with high transmission loss panel samples.
Hierarchical autoregressive error models in trans-dimensional matched-field geoacoustic inversion.
Authors: Dettmer Jan , Dosso Stan E.
Published: July 2011

This paper applies a general trans-dimensional matched-field inversion algorithm to data with strongly correlated errors, which are addressed by augmenting the forward model with a hierarchical autoregressive error model. This approach accounts for the limited knowledge of the optimal seabed parametrization and of the data-error statistics in the resulting geoacoustic parameter uncertainties. The assumed seabed parametrization influences estimates of parameter values and uncertainties since different parametrizations lead to different ranges of data predictions. The data support for a particular model is often non-unique and trans-dimensional formulations account for this by including an unknown model indexing parameter to consider groups of models (indexed by this parameter) in the posterior results. The hierarchical autoregressive error model accounts for a wide range of possible error correlations with few parameters, with no requirement to explicitly specify a covariance matrix (for which an inverse and determinant must be computed) at every Markov chain step, thereby increasing efficiency. This approach is particularly useful for trans-dimensional inversion since point estimates may not be representative of the state space which spans multiple subspaces of different dimensionalities. The order of the autoregressive process required by the data is determined here by posterior residual-sample examination. [Work supported by ONR.]
Estimating the acoustic impact of a tidal energy project.
Authors: Bassett Christopher , Thomson Jim , Polagye Brian
Published: July 2011

A pilot-scale tidal hydrokinetic energy project is proposed for Admiralty Inlet, Puget Sound, WA (United States). Quantifying the potential impact on the underwater acoustic environment requires knowledge of pre-installation ambient noise levels, sound production characteristics of tidal turbines, periods for turbine operation, transmission losses in the complex coastal environment, and the response of marine species to received sound levels. Acoustics data obtained during six 3-month deployments at the proposed site are used to characterize ambient noise levels at the site between 20 Hz and 30 kHz. Ancillary data sets reveal shipping and ferry traffic to be the most important sources of anthropogenic noise, and these sources are used to estimate (empirically) transmission losses in the project area. During strong currents, pseudosound from turbulent pressure fluctuations can mask ambient noise at low frequencies while increases in background noise levels at higher frequencies are consistent with bedload transport. Ambient noise due to natural physical processes such as rain, breaking waves, and surf noise are identifiable but secondary to anthropogenic sources. The intensity, frequency, and duration of turbine noise are discussed in the context of existing ambient noise and provide an initial estimate of the impact of the underwater acoustic environment.
Airborne noise contributions to the underwater noise sound field.
Authors: Dall’Osto David R. , Dahl Peter H.
Published: July 2011

Contributions of airborne noise sources to the underwater noise field are the result of two acoustic fields: the transmitted and evanescent. The transmitted field can be represented by only those rays confined to a small cone (about 26 deg) where the reflection coefficient is real-valued. The evanescent field, which arises when rays are totally reflected from the surface, can also contribute to the underwater noise field. Unlike the transmitted field, the evanescent field does not propagate and decays exponentially with depth with a decay rate as a function of frequency. Determining the individual contribution of these two fields to the overall sound field is experimentally difficult to observe. One situation where these two fields can be observed individually occurs when an airplane flies overhead. The Doppler shift associated with tonal propeller noise is dependent on the acoustic path. The frequency separation of the two fields allows for separate analysis of the two fields. Measurements from aircraft (altitude 1000 ft) passing over a buoy equipped with a microphone 3 m above the surface and a hydrophone 2.5 m below the surface will be presented. Numerical simulations are presented along with the experimental observations. [Research supported by the Washington Sea Grant and the U.S. Office of Naval Research.]
Is mixing the source of diffusion?
Authors: Polack Jean-Dominique
Published: July 2011

In a recent Ph.D. thesis, Defrance attempted to attain the essence of diffusion by tracking the so-called mixing time, that is, the time after which sound fields are homogeneous and isotropic. What he achieved, though, was only sparking a discussion between acousticians and physicists on the nature of mixing. Traditionally, mixing is defined in dynamics theory as the process that randomizes the positions of particles after they have been launched in a restricted area of the space phase. Thus, the process should be statistical, and evenly distributed through space: random distribution should be achieved everywhere at the same time. However, the data of Defrance do not confirm this theory. They show that impulse responses become random shortly after the arrival of the direct sound. In other words, the randomization process is position dependent, which is not compatible with mixing. This confirms a recent declaration by Cédric Villani, Field Medal 2010, that mixing cannot explain diffusion, because it is too slow a process. This paper closes with a review of several other mechanisms contending for solving the diffusion puzzle.
A multi-faceted study of sound diffusing elements in an auditorium.
Authors: Gulsrud Timothy , Van der Harten Arthur , Kiel Andrew , Kirkegaard Larry
Published: July 2011

Sound diffusing elements are often provided in auditoria as a means of providing diffuse sound reflections intended to improve listening conditions. Some recent consulting experience, however, has revealed that sound diffusing elements can sometimes have unintended consequences that detract from, rather than improve, listening conditions in an auditorium. This paper discusses a specific example from Hamer Hall at the Arts Centre, Melbourne, Australia. The influence of large scale sound diffusing elements along the upper sidewalls and ceiling of this hall has been studied subjectively and objectively through critical listening, in situ measurements, computer modeling, and scale model measurements. We review the results of this multifaceted study, and discuss the delicate balance between positive and negative impacts of sound diffusion in auditoria.
Impacts of architectural design variables to diffusion in room acoustics.
Authors: Utami Sentagi S. , Navvab Mojtaba
Published: July 2011

The claim on the importance of having diffusive surfaces as a room acoustics design solution is based on the arising demand of architectural spaces requiring need of reducing echoes and maintaining sound energy. Realization of the design goal is commonly by introducing diffuser panels as architectural elements. In practice, implementing this design variable alone may not be the solution. This study demonstrates the use of integrated methods to better understand the impact of architectural design variables to room acoustics diffusion. Impacts are characterized by evaluating the relationship of the degree of diffuseness indicated by the coherence of impulse response, room acoustics parameters, and the auditory perception. A system of multi-microphones arrays based on beam forming with acoustical imaging algorithms is utilized for in-situ measurements along with computer simulation of recording studio, classrooms, auditoriums, large multi-purpose halls, and arenas. The results of selected scenes are visualized with current computer simulation capabilities for subjective evaluation to obtain real time spatial experience given the auralization capabilities. The integrated method applied in this study and the relationships of indices help in decision making as to what extent the variation of design variables is required to create diffusion that fulfills the expected room acoustics quality.
Why do Weddell seals shout?
Authors: Terhune Jack
Published: July 2011

Source levels (SLs) of Weddell seal (Leptonychotes weddellii) underwater calls near Mawson, Antarctica, were determined using a two hydrophone array. SLs were 161 ± 10 dB re 1 μPa m (range 135–179, n = 280). SLs from 0.1–6 kHz varied little with frequency (r2 = 0.02, t = −2.46, P = 0.01, n = 251). One-sixth octave ambient noise levels (ANLs) from 0.1–6 kHz were measured on low (n = 1), medium (n = 7), and high (n = 7) noise level days. The ANLs were flat (0.1–6 kHz) and the mean 1/6 octave ANLs were 77 ± 2.8, 96 ± 6.5, and 110 ± 6.1 dB re 1 μPa. SLs were randomly paired against ANLs in a Monte Carlo (n = 100 000) model to calculate the seal communication ranges (m), assuming spherical spreading and received levels 20 dB above threshold. The mean communication ranges for low, medium, and high ANLs were 2806 ± 2718, 428 ± 662, and 83 ± 124 m, respectively (median distances were 2006, 205, and 43m). The distributions were highly skewed toward the shorter distances. The high amplitude calls of Weddell seals may have evolved to facilitate local communication under noisy conditions rather than for very long range purposes.
Automatic localization of individual Hawaiian minke whales from boing vocalizations.
Authors: Martin Stephen W. , Norris Tom , Nosal Eva-Marie , Mellinger David K. , Morrissey Ronald P. , Jarvis Susan
Published: July 2011

A method is described to automatically localize Hawaiian minke whales from their boing vocalizations. Recorded passive acoustic data from 15 deep water seafloor mounted hydrophones at the Pacific Missile Range Facility is utilized. A critical step is the automatic association of the same vocalization as received by the widely spaced hydrophones. The peak frequency of the vocalization in the detection bandwidth is shown to aid in the association process. Temporal integration of standard time difference of arrival localizations reduces erroneous automatic localizations, which occur for a variety of reasons. A case study of a 2009 minke visual sighting by a field team, which was facilitated by radioing near real-time location information from shore is described. The peak frequency feature (PFF) has unexpectedly been observed to be very stable for what is believed to be the sighted individual over a 6 hour time period (n = 57, PF¯F=1384.0 Hz, σ = 1.78 Hz). When the minke ceased vocalizing at 13:44 HST, no vocalizations at this frequency were again observed until 18:30 HST. This suggests a possible acoustic feature unique to individual animals with potential anatomical relationship with the sound production mechanism.
Shape space analysis of structures in bat biosonar.
Authors: Müller Rolf , Cai Lvyin , Grimm Cindy , Mio Washington
Published: July 2011

Sound diffracting shapes such as the noseleaves and outer ears are prominent features of the biosonar systems in bats. Across different bat species, a remarkable diversity exists in the shapes of these structures. Interspecific differences between shapes are found in global shape properties such as size and aspect ratio as well as in local features such as flaps, ridges, and grooves. Because of the irregular shapes of these biological structures, the relationship between physical shape and acoustic function across all their different shapes is difficult to comprehend. As a first step to address this problem, an attempt is made to describe the different pinna geometries in a shape space intended to capture the salient trends in biological variability. Descriptions of variability require an alignment of shapes. This can be achieved by virtue of invariant features within a low spatial frequency band. Here, modal analysis is used for this purpose. The shapes can be transformed by mapping each point into a new space defined by the amplitudes of the shape’s vibration eigenmodes. The acoustic properties of the shapes can be changed significantly by local features. Hence, local shape descriptors are used to quantify these features and establish correspondences across different species.
Acoustic analysis of bat eigenears.
Authors: Ma Jianguo , Feng Lin , Müller Rolf
Published: July 2011

The shape diversity in bat pinnae can be explored using principal component analysis. For this purpose, a vector-space description of the shapes is obtained by transforming the positions on the inner and outer pinna surfaces into cylindrical coordinates. This yields two functions of two independent variables: inner and outer surface radius as a function of angle and height. Pinnae from different species were aligned at the centers of gravity of these functions. The domain of the two functions can be discretized and the corresponding function values arranged to form a vector. In order to explore the acoustic properties of the resulting eigenvectors (“eigenears”), the center of the eigenear coordinate system was positioned at the average pinna, which is similar to an obliquely truncated cone and has a simple beampattern dominated by a single, upward-pointing mainlobe. The first eigenear is similar in shape to the average ear, subtracting or adding it to the first eigenear results in a wider or narrower cone. In the vicinity of the average ear, this operation will likewise result in a wider or narrower mainlobe. The second eigenear has a symmetry-breaking effect on both the pinna shape and its beampattern. Higher eigenears will also be explored.
Study of underwater sound propagation in the continental shelf of the Mid Atlantic Bight with integrated physical oceanographic and acoustic models.
Authors: Lin Ying-Tsong , Zhang Weifeng Gordon , Duda Timothy F. , Lynch James F. , Newhall Arthur E.
Published: July 2011

Underwater sound propagation in continental shelf regions is influenced by many physical oceanographic and geological features. With a data-assimilated ocean model, the physical oceanographic (PO) influences can be taken into account in a sound propagation model. This talk presents an integrated modeling framework with the regional ocean modeling system (ROMS) and parabolic-equation (PE) based sound propagation models. Technical issues on the model integration will be addressed, and the final product is implemented in the continental shelf of the Mid Atlantic Bight. The water column variability caused by shelfbreak fronts and linear internal waves is captured in the ocean model and directed into the acoustic model. The sound propagation effects by realistic shelfbreak fronts, frontal intrusions, and linear internal waves can be studied. In considering the geological influences on both PO and acoustic fields, this integrated model is implemented over the Hudson Canyon area. Three dimensional sound focusing due to the canyon topography is observed, and the temporal variability of such focusing patterns caused by the changes in the PO field is also quantified. In conclusion, by combining the state-of-the-art ocean and acoustic models, numerical simulations of underwater sound propagation are moving forward and toward more reality.
Validation of ice-ocean models using acoustic measurements.
Authors: Sagen Hanne , Bertino Laurent , Sakov Pavel , Sandven Stein , Haugen Svein Arild
Published: July 2011

The Fram Strait is the main passage through which the ocean mass and heat exchange between the Atlantic and Arctic Oceans take place. On the eastern side of the strait the northbound West Spitzbergen Current transports Atlantic water to the Arctic Ocean, whereas on the western side the southbound East Greenland Current transports sea ice and polar water from the Arctic Ocean to the Nordic Seas and the Atlantic Ocean. The currents in the Fram Strait are characterized by significant recirculation and numerous propagating mesoscale eddies. Under the EU project DAMOCLES single-track acoustic travel time measurements were carried out for a year. Acoustic travel time pattern is modeled by feeding oceanographic fields from ice-ocean models into acoustic propagation models. By comparing modeled travel times to accurate acoustic observations we can validate the ocean models. Two different ice-ocean models are considered: a single member high-resolution model and a multi member ice-ocean model system at coarser resolution. This validation approach is complementary to the use of point measurements or single profiles form oceanographic moorings and can provide new insight to the ocean model performance and assess feasibility of assimilating acoustic travel times in ocean models.
Reconstruction of reverberation levels based on measured surface roughness: Theory and experiment.
Authors: Salin Boris M. , Salin Mikhail B. , Spindel Robert C.
Published: July 2011

This presentation is devoted to the investigation of sound scattering by wind waves in case of propagation in shallow water (∼20 m) at distances of 100–1000 m and frequencies of 1–5 kHz. We consider several models and direct numerical calculation based on small perturbation theory that allows reconstruction of the reverberation levels when given knowledge of the wind-driven rough surface displacement spectrum. Some data were obtained in an experiment where simultaneous acoustic and surface roughness measurements were made. We also describe a new optical method to measure the surface roughness in detail. The technique uses a video recording of the surface over an area about 10 × 10 wavelengths (the most energetic surface waves) and a zoomed-in video recording of a spar buoy located within this area. Processing the entire image gives a distribution of brightness as a function of time and horizontal coordinates. Processing the buoy’s video allows one to obtain a record of surface displacement at that point. The distribution of brightness of the entire area can then be calibrated and recalculated to yield the 2-D (x and y) elevation as a function of time and thus the 3-D surface spectrum. [B.M.S. and M.B.S. acknowledge the support of ONRG.]
Comparing the Marmottant model for ultrasound contrast agents with experimental postexcitation signals.
Authors: King Daniel A. , O’Brien William D.
Published: July 2011

When insonified with sufficiently large rarefactional pressures, single unconstrained ultrasound contrast agents undergo inertial collapse with postexcitation emissions. Experimental measurements of postexcitation signal data for Definity microbubbles are compared with the Marmottant theoretical model for large amplitude oscillations of ultrasound contrast agents (UCAs). After taking into account the insonifying pulse characteristics, microbubble properties, and size distribution of the population of UCAs, a good comparison between simulated results and experimental data is obtained by determining a threshold maximum radial expansion (Rmax) to indicate the onset of postexcitation activity. Though this threshold Rmax is found to vary depending on insonification frequency, the values obtained are well above the typical free bubble inertial cavitation threshold commonly chosen at 2R0. The close agreement between the experiment and models suggests that lipid shelled UCAs behave as unshelled bubbles during most of a large amplitude cavitation cycle, as proposed in the Marmottant equation. [NIH Grant No. R37EB002641.]
On the dissolution of microbubble contrast agents in an ultrasound field.
Authors: O'Brien Jean-Pierre , Stride Eleanor , Ovenden Nick
Published: July 2011

Accurate understanding of the behavior of ultrasound contrast particles driven by an external sound source is crucial to enabling the development of better therapeutic and imaging techniques. Unfortunately current models are unable to fully explain, amongst other factors, changes in bubble characteristics following pulsed excitation. One aspect that has hitherto received little attention is the time dependent nature of the microbubble coating, specifically its gas permeability and variable surface tension. We show initially through nonlinear numerical simulations that acoustically driven microbubbles can dissolve more rapidly than stationary bubbles. However, the increased rate observed seems insufficient to account for the significant changes in bubble response over a few pulse cycles observed experimentally. Then, in an attempt to explain this continued discrepancy between models and experiments, we consider the impact of changes in surfactant concentration on the bubble behavior and gas diffusion. In particular, a model of surfactant mass transfer, including shedding, between the surface of the bubble and the bulk liquid is developed and subsequently coupled to a nonlinear bubble equation. Results from this model are presented that can replicate and potentially explain bubble response changes which may occur, leading to improvements in propagation modeling and quantitative imaging software.
Effects of ultrasound on osteoblast proliferation in presence of encapsulated contrast microbubbles.
Authors: Katiyar Amit , Sarkar Kausik , Duncan Randall
Published: July 2011

The actual mechanism behind the observed accelerated healing of fractures triggered by application of low-intensity pulsed ultrasound is not known. To understand it, the effects of ultrasound on osteoblast cells are studied in vitro. Cell proliferation showed significant increase under pulsed ultrasound excitation (0.5–5 MHz, 1–500 mW/cm2, 200 μs, and 1 kHz PRF) for a duration of 5–30 min daily for the intensity variation of 1–100 mW/cm2. Intracellular calcium storage and its flux through cellular membrane are believed to play a critical role in cell response to mechanical stimuli. In this study, encapsulated microbubbles are introduced during sonicaton. The bubbles trigger streaming against cell layer and their oscillation may concentrate mechanical forcing on the cell wall. Such activities have been shown to cause sonoporation and enhanced calcium transport. The results of variation in bubble type, concentration, and other excitation parameters such as duration, frequency, and intensity will be presented.
Synthetic aperture sonars for imaging of marine geology and buried objects.
Authors: Schock Steven G. , Ringle Victoria
Published: July 2011

Large acoustic apertures are necessary for generating high quality imagery of marine sediments and objects buried beneath the seafloor. These aperture sizes are usually much larger than the widths and lengths of small underwater vehicles. A large aperture is formed along the track of the vehicle by utilization of synthetic aperture processing. Vehicle wings, containing hydrophone arrays that are extended after vehicle submergence, are used to form a large across vehicle track aperture. Imagery of sediment layering is formed by time domain focusing on planar surfaces. However, buried object images are formed by time domain focusing at subsurface focal points. Images of sediments and buried objects are used to measure the performance of these techniques.
Talking to journalists: And knowing they never get it right!.
Authors: Crum Lawrence A.
Published: July 2011

Communicating with journalists poses a major dilemma: We have an obligation to explain science to the public because there are so many voices that denigrate scientists and their work; yet, in order for the journalists to effectively communicate, they often dumb it down so much that they get it wrong, and then we are embarrassed in front of our scientific colleagues. This dilemma can be mitigated somewhat by speaking only to those journalists who understand the science and to whom will allow you to edit their work. Of course, it is often difficult to determine, in the middle of an interview, the scientific capability of an interviewer, and often journalists do not like to have their work edited. In the end, a greater understanding of science by the general public is in our best interests and interviews with journalists should (nearly) always be granted. Some reflections on my experiences with such interviews will be given.