bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical modeling of nonlinear acoustic waves containing shocks
Authors: Khokhlova Vera
Published: October 2013

Theoretical models and corresponding numerical algorithms for the description of propagation of nonlinear acoustic waves containing shocks are presented. Plane waves and high intensity acoustic beams are considered. Various time and frequency domain numerical schemes that include numerical or artificial smoothening of the shocks and their specific features and artifacts are discussed. A modified spectral approach for the description of nonlinear waves containing discontinuous shocks is described. The method utilizes an analytical high frequency asymptote of the abrupt shock, which is used in the numerical algorithm to model sawtooth-like waves with a relatively few number of harmonics. Further generalizations of the method are discussed, in particular, to account for the discontinuity in the first derivative at the shock front, typical for the shock pulses; and for the finite thickness of the shock. The results of modeling of nonlinear waves containing shocks are presented: the effect of saturation in focused acoustic beams, double shock formation in a nearfield of a piston source, saturation of nonlinear waves in active media, the effect of various frequency dependent absorption on nonlinear interactions, and stationary and quasi-stationary solutions of the Burgers-type equations with the high order derivative absorption term. [Work supported by ONRIFO, CRDF, and RFBR.]
Regulatory standards and calibration procedures for shock wave devices
Authors: Schafer Mark E.
Published: October 2013

In order to bring any shock wave device into commercial use, i.e., clinical practice, it must receive regulatory approval from either the U.S Food and Drug Administration (FDA) or the appropriate national agency. A key part of this process involves the complete temporal and spatial description of the shock wave field. This device characterization presents a number of formidable measurement challenges, principally due to the destructive effects of shock waves on the measurement sensor, and shock wave variability (especially for electrohydraulic systems). This presentation reviews the measurement and regulatory approaches used for characterizing shock wave devices, including FDA and international measurement standards. The current approach is a compromise between the desire for a complete characterization of all possible parameters, and the realities of making the measurements. The complete measurement process will be described, including equipment, procedures and pitfalls. Polyvinylidene Fluoride (PVDF) membrane hydrophones have been the key enabling technology, providing sufficient temporal bandwidth and minimal effective sensor area, all at reasonable cost. Other types of sensors, both good and bad, have been used for these measurements. The talk will also present case studies of measurements of several lithotripters measured over the last 15 years.
Innovations in shock wave lithotripsy technology
Authors: Zhong Pei , Zhou Yufeng , Zhu Songlin , Cocks Franklin , Preminger Glenn
Published: October 2013

Since its introduction in early 1980s, shock wave lithotripsy (SWL) has been used widely in clinic for the treatment of kidney and upper urinary stones. Although a variety of methods have been developed for shock wave generation, coupling, and focusing, the core of SWL technology has not changed significantly. In this talk, we will present a summary of our research efforts, aiming to provide innovations in SWL technology. Our strategy is to first better understand the mechanisms by which stone comminution and tissue injury are produced in SWL using various experimental and theoretical techniques. Based on this knowledge, we then developed novel techniques that can optimize the effect of cavitation in SWL via modification of the waveform profile, pressure distribution, and pulse sequence of lithotripter-generated shock waves. These new techniques were upgraded on a Dornier HM-3 lithotripter, the gold standard in SWL. Both in vitro phantom and in vivo animal experiments were carried out which demonstrated that the performance and safety of the upgraded HM-3 lithotripter is superior to the original HM-3 lithotripter. Finally, strategies to improve stone comminution efficiency while reducing tissue injury in SWL will be presented. [Work supported by NIH DK52985 and DK58266.]
Perceptual evaluation and acoustical analyses of 6 kinds of electrolarynges
Authors: Sugimori Noriyo , Fuyuki Hiroyoshi , Kobayashi Noriko , Horiguchi Satoshi , Koike Minako , Hirose Hajime
Published: October 2013

Six different kinds of electrolarynges, which were commercially available in Japan, were compared with regard to the listeners preference and the acoustical characteristics. Listeners were 4 speech therapists who were familiar with electrolarynx speech and 15 university students who had little experience with the device. Sound samples were obtained for each E1 under two conditions: the original sound and the sustained vowels produced by two skilled E1 users with larynges. Perceptual evaluations were performed using Visual Analogue Scale (VAS) on intelligibility, acceptability, noisiness, and naturalness. Speech therapists perceived unnaturalness for an E1 with peculiar F0 declination while naive listeners did not. The lower the perceptual evaluations, the higher the mechanical noise level was found by acoustical analyses. High levels of higher harmonic components were found for the E1’s which had lower perceptual evaluation due to the noise disturbance. Although naive listeners tended to despise E1s with rich higher harmonic components in general, speech therapists did not perceive this as noisiness. Various factors seemed to exist for the listeners preference of E1s. [Work supported by Grant-in-Aid for Scientific Research on Priority Areas (B) Prosody and Speech Processing, Ministry of Education and Sciences.]
Applications of the continuous wavelet transform to architectural acoustics
Authors: Belanger Zackery B.
Published: October 2013

Wavelet analysis, which utilizes waveforms of limited duration, can reveal a signals time and frequency information without the resolution tradeoff that is typical of the sinusoid-based Fourier analysis. The continuous wavelet transform is an effective tool in the analysis of impulse responses from both in situ and scale model measurements. Simultaneous time and frequency information in architectural acoustics allows both beneficial and problematic reflections to be located and analyzed. A brief conceptual overview of wavelets is given, followed by general application to architectural acoustics and specific application to a few projects.
Spatial nonuniformity of noise measurements in the Gulf of Mexico LADC test area
Authors: Eller Anthony I. , Ioup George E. , Ioup Juliette W. , Larue James P.
Published: October 2013

Long-term, omnidirectional underwater acoustic noise was measured by three buoys in the northeastern Gulf of Mexico during the summer of 2001 as part of the Littoral Acoustic Demonstration Center project, Phase I. The buoys were placed over the coastal slope above the 600-, 800- and 1000-m contours, approximately in a straight line, 18 km from the first to the last. Initial looks at the noise time series, processed in standard one-third-octave bands from 10 to 5000 Hz, show noise levels in close agreement at each buoy except in the lowest bands (roughly 25 Hz and lower) where the noise levels grow higher at the shallower sites. Results presented here address buoy-to-buoy comparisons of long-term temporal variability and the cross-spectral density of fluctuations across the frequency spectrum. [Research supported by ONR.]
Analysis of the near field acoustic signature from subsonic high-speed projectiles in an acoustic test tank
Authors: Carroll Sam , Hu James , Stepanishen Peter , Kuklinski Robert
Published: October 2013

A series of tests to obtain the near field acoustic signature from subsonic high-speed supercavitating projectiles in an underwater acoustic test tank at NUWC/NPT have been recently obtained. The projectiles are approximately 0.1 meters in length and 0.02 meters in diameter and travel at speeds up to 900 m/s in the test tank. Underwater acoustic near field transient pressure data has been obtained with several sensors and a preliminary analysis of the data is reported. Possible noise source mechanisms which have been investigated include the radiated noise of the launcher, the near field hydrodynamic pressure field associated with the motion and shape of the projectile, acoustic multipath contributions from the walls of the tank, oscillations of the trailing cavity convected with the projectile and the collapse of bubbles from the aft end of the cavity. The data has been analyzed using an empirical mode decomposition/Hilbert–Huang transform (EMD/HHT) method and hybrid methods of EMD/ordinary spectral analysis, EMD/wavelet analysis, and EMD/short time Fourier transform (STFT) methods to obtain frequency–time information. Preliminary results for the relative importance of the launcher noise, hydrodynamic component and the bubble collapse are presented and discussed. [Work supported by ONR.]
Acoustic near field pressures from subsonic high-speed projectiles
Authors: Kuklinski Robert , Gieseke Thomas , Carroll Sam , Stepanishen Peter , Hu James
Published: October 2013

Preliminary experiments performed to measure the radiated noise from subsonic high-speed underwater projectiles indicated the presence of a characteristic disturbance in the mean pressure field during the approach of the projectile to the location of the sensing hydrophone in the test tank. A numerical model based on the potential flow field surrounding the projectile was developed to explain this behavior. A series of 10 projectile shots were fired at speeds ranging from 700–900 m/s to investigate this phenomenon. The underwater range in the tank was instrumented with 5 PCB narrow span pressure transducers. The transducer pressure ranges and locations in the tank were selected using the potential flow model predictions. Results from these experiments are presented. The mean pressure field disturbances show steep cross range gradients. Passage of the projectile at a fixed location in the tank was determined by observing self-similar features of the pressure field at different transducer locations. Projectile velocity estimates were determined from time delays between transducers and are compared with break screen data. The cross range gradients and velocity measurement techniques will be used to develop an open range system to track underwater projectiles. [Work supported by ONR.]
3D visualization of marine organism distribution and movement in water column using virtual reality techniques
Authors: Moszynski Marek , Stepnowski Andrzej , Bikonis Krzysztof
Published: October 2013

Virtual reality techniques mainly developed for computer graphics had found numerous applications in various scientific areas like chemistry, astronomy, geography, etc. The paper proposes application of the virtual reality techniques in hydroacoustics for 3D visualization of data acquired by split-beam or multi-beam echosounders. Both types of echosounders allow for nonambiguous localization of targets in the water column and their imaging. As the multi-beam systems also delivers bathymetric information, in addition to imaging of the spatial distribution, it is possible to create complete virtual scene of sampled volume. Using builtin properties of Virtual Reality Modeling Language (VRML) it was possible to animate movement of fishes and other marine organisms in the water column. As the language is supported by Internet technology, its textlike description allows for easy rendering by most popular WWW browsers.
Space–time variations of the acoustic field scattered from a penetrable isovelocity wedge
Authors: Feuillade C. , Chu D. , Clay C. S.
Published: October 2013

The formalism of D. Chu [J. Acoust. Soc. Am. 86, 1883–1896 (1989)] is used to perform an investigation of the spatial and time domain variations of the scattered field of a penetrable isovelocity wedge. The direct, reflected, and diffracted field components are considered, and the relationships between them are investigated. The density contrast surface is an appropriate model for many water–seafloor interfaces and, since diffractions often dominate scattering from rough surfaces, an emphasis is placed on achieving an improved description and understanding of these waves. Particular emphasis is placed on a detailed study of the wave phenomena and transition behavior around the forward scattering shadow boundary, where the causal relationship between the direct incident field and the diffracted field is specifically examined. At the apex the two fields coincide, and their propagational effects here, and also above and below the geometrical shadow zone, lead to complicated temporal and azimuthal variations of the field. The origin and behavior of diffractions associated with specular reflections of the source in the faces of the wedge is also studied. [Work supported by ONR.]
Measurement of speech privacy in closed offices
Authors: Roy Kenneth P.
Published: October 2013

Two closed offices of different sizes were constructed using a demountable wall system as a mockup for a planned new courthouse facility. The occupants of the existing fixed construction facility were concerned about the possible impact of the new wall system on the speech privacy performance. Field measurements were made to determine the speech privacy performance in terms of the PI rating. Issues relating to the application of ASTM E 1130 for closed office measurements will be discussed.
Frequency response and systematic errors in STI measurements
Authors: Mapp Peter
Published: October 2013

The paper examines two fundamental problems when measuring and verifying the STI of sound systems. These relate to the overall accuracy of the measurement platform in use and the fact that STI does not correctly account for system frequency response and spectral aberrations under certain conditions. As has previously been reported by the author, STI appears to significantly overestimate the intelligibility of limited bandwith sound systems under reverberant, high S/N ratio conditions. Further evidence and word score comparisons for a number of different frequency response conditions, measured under several reverberant situations are presented. The results indicate that errors of up to 30 comparisons with low-reverberant field and anechoic conditions are also made. It is also shown that the measurement platform itself and sound source characteristics can affect the resultant error. Tests, carried out under highly controlled conditions, are reported that enable the causes of the potential errors to be established. The implications of reported limitations in STI and STIPa, when assessing the potential intelligibility of a sound system or acoustics of a space, are discussed.
A new measure for assessment of architectural speech security
Authors: Gover Bradford N. , Bradley John S.
Published: October 2013

A new measure has been developed to indicate the audibility and intelligibility of speech transmitted through walls from adjacent rooms. The new measure is a frequency-weighted signal-to-noise ratio. It is shown to be a more accurate predictor of subjective ratings than the Articulation Index, the Speech Intelligibility Index, and simple A-weighted signal-to-noise ratios. Listening tests using English sentences were conducted to measure the fraction of words intelligible to acute-hearing, native-English-speaking listeners under a range of acoustical conditions. Each subject listened to 500 sentences, each of which had been filtered to represent passage through some type of wall construction. The level of the speech, as well as the level and spectrum of background ventilation-type noise was varied. The conditions in the test ranged from those where all subjects were able to correctly identify all the words in a sentence (i.e., very poor security), through to those where all subjects were unable to even recognize the presence of a speaking voice (i.e., excellent security). The tests, analysis, and derivation of the measure will be discussed, as will the directions of ongoing work in the area.
Acoustics textbooks of the future
Authors: Ayers R. Dean
Published: October 2013

There is likely to be a time when electronic textbooks will have become the norm. If these are essentially free, there will be some distinct advantages for both students and teachers. (Imagine a truly free marketplace of ideas, unaffected by the ploys of textbook publishers.) Electronic resources provide flexibility for adaptation to the organization and level of treatment suitable for particular groups of students. Internal links can be used to remove digressions, fine details, and advanced treatments from the direct line of sight of unsophisticated readers, making it easier to focus on the main ideas. Background materials can be linked to highlighted words, for the benefit of both the students who need them and those who do not. Links among chapters and sections could encourage encyclopedic browsing and the development of a cross-linked structure of understanding. Multimedia resources have an obvious relevance to acoustics in the form of audio examples. Kinetic, interactive figures could play an important role by encouraging the development of graphical literacy, coupled with the more widely recognized verbal and mathematical literacies needed for scientific work. MERLOT and other existing models for the development of electronic textbooks will be discussed. [Work supported by the Paul S. Veneklasen Research Foundation.]
Rough surface scattering from an elastic scale model of an ocean bottom
Authors: Soukup Raymond J. , Gragg Robert F. , Wiley Robert W. , Inanli Burcin
Published: October 2013

Monostatic and bistatic scattering strength measurements with a rough PVC surface were collected during two experiments in an acoustic tank facility at the Allied Geophysical Laboratories in the University of Houston. The PVC surface was analogous to limestone ocean bottoms in its two-dimensional power-law roughness spectrum and its large dependence of scattering strength on the roughness parameters. The experiments represent an initial effort to use physical models with ground-truth measurements of roughness and compressional/shear speeds and attenuations to verify the predicted effects of interface scattering models, e.g., the small-slope model developed at the Naval Research Laboratory for elastic bottoms. Comparisons between the small-slope model, perturbation theory, and the observed data are shown for the various geometries using acoustic transmissions in the 100–400 kHz band. The success in obtaining a good model-data fit is shown to be directly related to the ensonification of an area that represents a sufficient statistical sample of the roughness. Plans for a series of tank experiments with physical models for verifying predictions of rough surface scattering theories and elastic PE are described. [Work supported by ONR.]
Experimental demonstration of adaptive reverberation nulling using a time reversal mirror
Authors: Song H. C. , Kuperman W. A. , Hodgkiss W. S. , Roux P. , Akal T. , Stevenson M.
Published: October 2013

Boundary reverberation (e.g., due to bottom roughness) can serve as a surrogate probe source in time reversal. A time-gated portion of the reverberation is then refocused to the bottom interface at the corresponding range [Lingevitch et al., J. Acoust. Soc. Am. 111, 2609–2614 (2002)]. In this paper, reverberation nulling is investigated to enhance active target detection. The basic idea is to minimize the acoustic energy incident on the corresponding interface by applying a weight vector on the time reversal mirror which is in the orthogonal subspace to the focusing vector. The feasibility of the reverberation nulling is demonstrated in a recent time reversal experiment at 850 and 3500 Hz.
Automated buried object classification with a broadband autonomous underwater vehicle sonar system
Authors: Montanari Monica , Edwards Joseph R. , Schmidt Henrik
Published: October 2013

The classification of buried objects in the littoral ocean is a challenging task for the underwater community. The high attenuation rate of the seabed imposes the use of a low frequency sonar system, which leads to an increased aperture length requirement to achieve high resolution. A simple classification algorithm is proposed in which a broadband source insonifies the target area while multiple receiver vehicles process the target scattering strengths over various bistatic angles to reconstruct a planar cut of the scattered field of the target. The advantages of this technique are the low rate of information exchange between vehicles, the simplicity of the processing algorithm, and less demanding processing requirements compared to the image-based techniques. The algorithm is based on multistatic measurements of the target spatial acoustic signatures, which permits a parameterization of the identification problem to a decreased number of degrees of freedom, with the consequence of decreased processing and implementation difficulty. The use of a broadband sonar system splits the processing in parallel tasks, leading to an overall classification improvement. The GOATS experiment series is used to demonstrate the classification performance of the algorithm for various targets and conditions. The results compare favorably with the state-of-the-art imaging techniques.
Maximum performance synergy: A new approach to recording studio control room design
Authors: Szymanski Jeff D.
Published: October 2013

Popular recording studio control room designs include LEDE(tm), RFZ(tm), and nonenvironment rooms. The common goal of all of these is to create an accurate acoustical environment that does not distort or otherwise color audio reproduction. Also common to these designs is the frequent need to have multiple ancillary recording rooms, often adjacent to the main control room, where group members perform. This approach, where group members are physically separated from one another, can lead to lack of ensemble in the finished recordings. New twists on old acoustical treatment techniques have been implemented at a studio in Nashville, Tennessee, which minimize the need for multiple ancillary recording rooms, thus creating an environment where talent, producer and recording professionals can all occupy the same space for maximum performance synergy. Semi-separated performance areas are designed around a central, critical listening area. The techniques and equipment required to achieve this separation are reviewed, as are advantages and disadvantages to this new control room design approach.
Variable acoustics in small rooms for music
Authors: Shimizu Yasushi
Published: October 2013

Small rooms for music are frequently discussed to consider variable acoustics with different program in practice room, rehearsal room as well as audio listening room. In practice room major criteria in acoustics is usually discussed how to determine reverberation with less than 1.0 s. RT for different use such as practice for different musical instrument. And on audio listening room, acoustical effect on sound reproduced by speakers is important especially for reproducibility of 3D audio representation and usually surface material behind stereophonic speakers gave significant effect on the accuracy of sound localization with the sound played by speakers. Rehearsal room acoustics is always discussed compared to the stage acoustics in primary concert hall and some electro-acoustic technique is discussed how to simulate stage acoustics. This paper presents examples of acoustical design for different practice rooms, rehearsal room and audio listening room. A different RT setting for each room with different program is discussed as well as different configuration of surface material especially in audio listening room. Finally rehearsal room with electro-acoustics system to reproduce stage acoustics of specific concert hall is discussed and measurement result is presented.
Acoustical evaluation of preschool classrooms
Authors: Yang Wonyoung , Hodgson Murray
Published: October 2013

An investigation was made of the acoustical environments in the Berwick Preschool, Vancouver, in response to complaints by the teachers. Reverberation times (RT), background noise levels (BNL), and in-class sound levels (Leq) were measured for acoustical evaluation in the classrooms. With respect to the measured RT and BNL, none of the classrooms in the preschool were acceptable according to the criteria relevant to this study. A questionnaire was administered to the teachers to assess their subjective responses to the acoustical and nonacoustical environments of the classrooms. Teachers agreed that the nonacoustical environments in the classrooms were fair, but that the acoustical environments had problems. Eight different classroom configurations were simulated to improve the acoustical environments, using the CATT room acoustical simulation program. When the surface absorption was increased, both the RT and speech levels decreased. RASTI was dependent on the volumes of the classrooms when the background noise levels were high; however, it depended on the total absorption of the classrooms when the background noise levels were low. Ceiling heights are critical as well. It is recommended that decreasing the volume of the classrooms is effective. Sound absorptive materials should be added to the walls or ceiling.
Frequency-dependent acoustic properties of gassy marine sediments
Authors: Best Angus I. , Tuffin Michael D. J. , Dix Justin K. , Bull Jonathan M.
Published: October 2013

Acoustic velocity and attenuation were measured during two in-situ experiments in gassy intertidal muds in Southampton Water, United Kingdom. The horizontal transmission results gave frequency-independent velocity (1431 m/s) and attenuation (4 dB/m) over the frequency range 600 to 3000 Hz, representative of the soft (non-gassy) muds shallower than about 1 m. The results from a vertical transmission experiment straddling the top of the gassy zone (about 1 m depth) showed strong frequency-dependent velocity and attenuation over 600 to 3000 Hz. They showed velocity and attenuation maxima predicted by the Anderson and Hampton model, associated with gas bubble resonance. Moreover, attenuation maxima shifted in frequency with water depth over a tidal cycle that was monitored, suggesting variations in gas bubble size with hydrostatic pressure. X-ray CT images on a sealed core from the site revealed vertically-aligned, centimeter-scale, gas-filled cracks in the muddy sediments. Ultrasonic (300 to 700 kHz) velocities and attenuations were higher in the gassy zone than in the nongassy parts of the core. Overall, the results give a fascinating insight into the acoustical behavior of gassy sediments that could be used to extract sediment physical properties information from seabed acoustic reflection data. [Work supported by NERC].
Determining gas bubble morphology and size distribution in mud using CT imagery
Authors: Briggs Kevin B. , Reed Allen H.
Published: October 2013

Sampling for the measurement and description of methane gas bubbles in situ was accomplished using the method of Abegg and Anderson [Mar. Geol. 137, 137–147 (1997)]. Sediment cores from East Bay, off the mouth of the Mississippi River, were collected by divers and placed into aluminum pressure transfer chambers while on the seafloor. With the cores at seafloor pressure within the chambers, they were transferred to an x-ray computed tomography (CT) scanner where high-resolution images were made of the sediment within the cores. Data, in the format of series of cross-sectional images of x-ray attenuation reconstructed in 3-D, were evaluated in terms of spatial distribution, sizes, and shapes of bubbles. CT imagery was obtained from a GE LS medical CT scanner at a local hospital and the Naval Research Laboratory’s new HD-500 industrial CT scanner specifically designed for core sample imaging. The medical scanner provided images of stationary cores at 625-μm intervals with a rotating x-ray source and was able to resolve bubbles down to 625 μm in diameter. The industrial scanner provided images of rotating cores at 25-μm intervals with a stationary source and was able to resolve bubbles down to 10 μm in diameter.
Methods for blood flow measurements using ultrasound contrast agents
Authors: Fowlkes J. Brian
Published: October 2013

Blood flow measurements using ultrasound contrast agents are being investigated for myocardial perfusion and more recently in other organ systems. The methods are based largely on the relative increase in echogenicity due to the concentration of bubbles present in the ultrasound beam. In the simplest form, regional differences in blood volume can be inferred but the possibility exists to extract perfusion from the transit of contrast agent through tissue. Perfusion measurements rely on determining the flux of blood through a tissue volume and as such require knowledge of the fractional blood volume (FBV), i.e., ml blood/g tissue and the rate of exchange, commonly measured as the mean transit time (MTT). This presentation will discuss methods of determining each of these values and their combination to estimate tissue perfusion. Underlying principles of indicator-dilution theory will be provided in the context of ultrasound contrast agents. Current methods for determining MTT will include imaging of the intravenous bolus, in-plane contrast disruption with interval and real-time contrast recovery imaging, and control of contrast agent flow using arterial disruption (contrast interruption). The advantages and limitations of the methods will be examined along with current applications. [Work supported in part by NIH.]
Acoustical and optical monitoring of contrast microbubbles
Authors: Guan Jingfeng , Chen Wen-shiang , Matula Thomas
Published: October 2013

We have undertaken a series of studies to better understand the response of ultrasound contrast microbubbles to pulsed ultrasound. Toward this end we have used acoustical and optical scattering techniques. The acoustic interrogation of shell-disrupted microbubbles immediately following HIFU was used to monitor microbubble (or fragmented daughter) dissolution. Results were compared to calculations, assuming a simple Gaussian distribution of fragmented microbubbles and the dissolution characteristics of a mixed-gas system (such as a perfluorocarbon gas bubble in air-saturated water). Good results were obtained by considering a multi-modal bubble size distribution. That is, the HIFU pulse created a distribution of smaller bubbles. In order to follow the instantaneous motion of a single microbubble during pulsed ultrasound, light scattering was employed. For this experiment, a diagnostic ultrasound system was used to force the microbubble into oscillation. Light scattered off the microbubble was collected by a photodetector. A simple bubble dynamics model was used to fit the data. At low pressures, consecutive data segments were averaged to increase the signal/noise. At higher pressures, the bubble (size or shell) properties required systematic adjustment in order to obtain a good fit, suggesting that the bubble evolved with each pulse.
Ultrasound contrast agents and their use in monitoring therapy
Authors: Ferrara Katherine , Dayton Paul , Shortencarrier Michaelann , Kruse Dustin
Published: October 2013

The shell of ultrasound contrast agents can be modified to include a molecular targeting ligand, and the properties of the agent with and without molecular targeting can be used to monitor changes produced by a therapy. We have investigated the use of ligands targeted to an integrin expressed in cancer, whose expression correlates with tumor grade. Acoustic studies illustrate a 3- to 20-fold increase in echo amplitude from integrin-expressing cells exposed to the targeted contrast agent, as compared to controls, and depending on cell type, stimulation, and targeting ligand. Changes in integrin expression with therapy may be important in future studies. We have also developed a system to quantify small changes in vascular parameters due to effects of new anti-angiogenic drugs using the intrinsic properties of contrast agents. Regions containing intravascular contrast agents are identified using a strategy that combines subharmonic and phase inversion imaging. As predicted by a Rayleigh–Plesset analysis, this strategy can successfully detect flow over a range of transmission frequencies from 4–6 MHz. We demonstrate that regions of viable tumor as small as 1 mm, as verified by histology, can be detected and show similar morphology to images acquired with computed tomography (CT).
Effect of contrast agent on the incidence of ultrasound-induced lung hemorrhage in rats
Authors: O’Brien William D. , Simpson Douglas G. , Frizzell Leon A. , Zachary James F.
Published: October 2013

The objective is to test further the hypothesis that if inertial cavitation in the vasculature of the lung is the physical mechanism responsible for ultrasound-induced lung hemorrhage, then the addition of cavitation nuclei to the blood will enhance the occurrence of lung hemorrhage. A factorial design was used to study the effects of two types of injected agents (IA; 0.25 mL per rat of saline or Optison given intravenously) and two levels of pulsed ultrasound exposure (UE; in situ peak rarefactional pressures of 2.74 and 5.86 MPa) on the incidence and size of lung lesions. Ten 10-to-11-week-old Sprague–Dawley rats were exposed at each of the four combinations of IA and UE at 3.1 MHz for 10 s (1-kHz PRF, 1.2-microns PD). Rats administered contrast agent prior to exposure did not have an increase in lesion occurrence or size compared to rats that received saline with no contrast agent. These results provide further evidence that the mechanism of lung hemorrhage is not inertial cavitation. These findings are consistent with another group’s results from another species (mouse) showing no increase in the area of lung hemorrhage using a different contrast agent (Albunex) when exposed to pulsed ultrasound. [Work supported by NIH Grant No. R01EB02641.]
Regenerator-based thermoacoustic refrigerator for ice cream storage applications
Authors: Poese Matthew E. , Smith Robert W. M. , Garrett Steven L.
Published: October 2013

A regenerator-based chiller has been built in the ‘‘bellows bounce’’ style [J. Acoust. Soc. Am. 112, 15 (2002)] to replace the vapor compression system in an ice cream sales cabinet. It utilizes a 6-in.-diam metal bellows to form a compliant cavity that contains the dynamic pressure oscillation (>50 kPa). The stiffness of the gas trapped in the bellows is resonated against the mass of the bellows-cap and the mass of a moving-magnet linear motor which is capable of high (>85%) electro-acoustic efficiency. A second resonator, operated well below its natural frequency, uses the gas stiffness of a 1-l volume nested within the bellows and the inertia of an ordinary loudspeaker cone to create the pressure difference across the regenerator that drives gas flow that is in-phase with pressure. The mass of the cone can be adjusted to vary the multiplication factor that is typically 5%–10% greater than the dynamic pressure within the bellows. The loudspeaker cone suffers none of the hydrodynamic losses associated with an acoustic inertance and eliminates problems with dc gas flow in the energy feedback path. The cold heat exchanger forms one surface of the pressure vessel permitting direct contact with any thermal load. [Work supported by Ben and Jerry’s Homemade.]
Integration versus optimization in self-noise geoacoustic inversion
Authors: Battle David J. , Gerstoft Peter , Kuperman William A. , Hodgkiss William S. , Siderius Martin
Published: October 2013

Self-noise geoacoustic inversion involves the estimation of bottom parameters such as sound speeds and densities by analyzing towed-array signals whose origin is the tow platform itself. As well as feeding into more detailed assessments of seabed geology, these parameters enable performance predictions for sonar systems operating in shallow water. In this presentation, the use of the Gibbs sampler to obtain complete probability distributions of seabed parameters is discussed. This contrasts with conventional maximum likelihood inversion, in which only the best fitting model is identified. Advantages of viewing parameter estimation problems from such a probabilistic perspective are discussed in relation to the MAPEX 2000 self-noise data, which have previously been subjected to maximum-likelihood inversion via genetic algorithm optimization.
Propagation and attenuation of sound in a canonical model of shallow water with a thermocline and with a Biot sediment in the bottom
Authors: Pierce Allan D. , Carey William C. , Lynch James F.
Published: October 2013

Objective is benchmark solution, analytic in internal detail, for testing geoacoustic inversion methods. The water column has two isovelocity layers separated by a narrow thermocline. The bottom is a porous (Biot model) sediment, with an elastic matrix coexisting with a fluid filling the pores; coefficients are frequency independent, slowly varying with depth, and analogous to those in works by Stoll, Badiey, and Chotiros. Source and receiver are in the middle region of the water column. Constant frequency problem formulation has field expressed as a Fourier integral over horizontal coordinates, with a z-dependent kernel having discontinuous slope at source depth. Equations for the bottom region yield ratio of derivative to kernel amplitude at bottom interface, this being a complex function of wave number and frequency. Singularities in kernel at discrete complex values of k correspond to the natural modes, imaginary parts of k are attenuation constants. Simplifying approximations, especially those of perturbation theory, are guided by order of magnitude estimates of dimensionless groups, with the suppositions that the orders of magnitude of propagation frequency, water depth, and propagation distance are 100 Hz, 100 m, and from 2 to 100 km, and that Biot model parameter magnitudes are comparable to known measured values.
The characterization of the lesion growth in time
Authors: Nakazawa Marie , Reed Justin A. , Bailey Michael R. , Kim Yongmin
Published: October 2013

Thermal heating effects of high intensity focused ultrasound (HIFU) on the dynamics of lesion formation were characterized automatically to assess the role of vapor bubbles in distorting the shape. Tissue mimicking phantom was used in experiments by a 4.2 MHz curve-linear transducer with 44 mm diameter and 44 mm radius of curvature. A variety of HIFU intensities were produced by different amplitudes. Images were acquired by a CCD camera and HDI-1000 ultrasound imager, recorded to VHS, and digitized to measure lesion size and shape. Each image was subtracted with noise reduction in order to detect the HIFU on time and to segment the boundaries of the lesions performed by Matlab programming. Area, length, width, and ratio of lesion area proximal to center line over area distal to center line were calculated along HIFU exposure time. Slight increase in HIFU intensity, means hyperecho forms earlier, and lesion shape change. The data supported the hypothesis that lesion dramatically distorts well after hyperecho with only small increase in HIFU intensity. [Work supported by National Space and Biomedical Research Institute.]
Where they are now: An overview
Authors: Cottingham James P.
Published: October 2013

Since 1997 there have been fifteen award winners in the Best Student Paper competition in Musical Acoustics. Although some of the award winners are still active in musical acoustics, others are now active in other areas of acoustics or in fields outside acoustics altogether. A brief statistical overview will be presented of the history of the competition and past and current interests of those who have been the award winners. Capsule updates on several award winners who are unable to participate in the session will be presented.
Three-dimensional sound signals and their relevance to wave energy quantities and sound interference products
Authors: Vassilakis Pantelis
Published: October 2013

Signals are graphic representations of vibrations/waves and, like every representation, capture only selected attributes of the phenomenon they are meant to represent. The often assumed equivalence between signals and sound waves obscures the fact that two-dimensional signals are not fit to (a) represent wave-energy quantities consistently across frequencies, (b) account for the alternating positive/negative amplitude values of modulated waves with AM-depth>100%, and (c) represent the energy content of interference. An alternative sound-signal representation is proposed, based on the complex equation of motion describing a wave. It results in spiral sine signals and twisted-spiral complex signals, similar to complex analytic signals. Spiral sine signals offer a consistent measure of sine-wave energy across frequencies, while twisted spiral complex signals account for the negative amplitudes observed in modulated signals and map the modulation parameters onto the twisting parameters. In terms of interference, 3-D signals illustrate that amplitude fluctuations and the signal envelopes that describe them are not just boundary curves but waves that trace changes in the total instantaneous energy of a signal over time, representing the oscillation between potential and kinetic energies within a wave. Examples of 3-D animations illustrating the proposed signals are presented. a)Work completed while at the Department of Ethnomusicology, University of California, Los Angeles.
Methodology for quantifying the tonal prominence of frequency modulated tones
Authors: Lee Kyoung Hoon , Davies Patricia , Surprenant Aimee
Published: October 2013

The paper is focused on research conducted to develop a metric to quantify the tonal prominence of frequency modulated tones in noise. Frequency modulated tones are commonly encountered in machinery noise because of RPM variations caused by changing loads and poor control in timing and repeatability of combustion events in engines, particularly diesel engines. When tonal components are noticeable they increase annoyance; thus it is important to quantify both their strength and the resulting contribution to annoyance. In preliminary work on tones with randomly varying frequencies, it was found that it is possible to remove the trackable portion of the frequency variation and use established tonal prominence metrics (Aures’ Tonality and Tone-to-Noise Ratio) on the modified signal to predict the perceived tonalness of the sounds (Lee, Hastings, Davies and Surprenant, Internoise 2003). The work presented is an extension of this earlier work: deterministic frequency variations are studied along with different levels of background noise. Modifications to the procedure to determine the strength of the tonal feature are described, as well as the issues that must be addressed before using this approach to analyze more complex machinery sounds. [Work sponsored by Caterpillar Inc.]
Directional measurements in sound fields using a spherical microphone array
Authors: Gover Bradford N.
Published: October 2013

A 32-element spherical array of microphones has been used to perform directional analysis of sound at a point. Optimized filter-and-sum beamforming is used to generate a highly directional beam over a broad frequency range. The beam can be steered in any three-dimensional direction, enabling angular discrimination of sound at a listening point. The directional responses can also be analyzed temporally, giving the directionality of the sound field at any time instant, or over any desired time range. By establishing a sound field with a test signal such as MLS or a sine sweep, the omnidirectional impulse response at each array microphone can be determined. Subsequent beamforming results in a set of directional impulse responses, which enables isolation of individual arrivals, or analysis in terms of early/late sound, for example. Various measurements made with the spherical array system will be presented and discussed.
Classification of binaural-activity patterns
Authors: Hess Wolfgang , Blauert Jens
Published: October 2013

The three-dimensional, time-variant output of a computational model of the human auditory system was investigated with the aim of extracting perceptually patterns as relevant to spatial impression. To this end, the same stimuli with which the model was excited were also presented to human listeners which evaluated (i) the auditory source width (ASW), i.e., the horizontal extent of the auditory event, and (ii) the listener envelopment (LEV), i.e., the amount of envelopment by the auditory event. The listeners had to be trained beforehand as the discrimination of source- and room-related parameters of auditory events is not a common task to them. To allow for natural localization and to enable interactive listening, the stimuli were presented through head-tracked headphones. Trained listeners appeared to produce consistent results when depicting auditory objects on a compass-rose-shaped plane, where they had to mark the position and broadening of the auditory event(s) by the position(s) and length(s) of straight lines, and the envelopment by the position and size of an ellipse.
Auditory and visual spatial impression: Recent studies of three auditoria
Authors: Nguyen Andy , Cabrera Densil
Published: October 2013

Auditory spatial impression is widely studied for its contribution to auditorium acoustical quality. By contrast, visual spatial impression in auditoria has received relatively little attention in formal studies. This paper reports results from a series of experiments investigating the auditory and visual spatial impression of concert auditoria. For auditory stimuli, a fragment of an anechoic recording of orchestral music was convolved with calibrated binaural impulse responses, which had been made with the dummy head microphone at a wide range of positions in three auditoria and the sound source on the stage. For visual stimuli, greyscale photographs were used, taken at the same positions in the three auditoria, with a visual target on the stage. Subjective experiments were conducted with auditory stimuli alone, visual stimuli alone, and visual and auditory stimuli combined. In these experiments, subjects rated apparent source width, listener envelopment, intimacy and source distance (auditory stimuli), and spaciousness, envelopment, stage dominance, intimacy and target distance (visual stimuli). Results show target distance to be of primary importance in auditory and visual spatial impression—thereby providing a basis for covariance between some attributes of auditory and visual spatial impression. Nevertheless, some attributes of spatial impression diverge between the senses.