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Nov 1990

Volume 88, Issue S1, pp. S1-S200

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back to top Session 8PA: Physical Acoustics: Ultrasonics and Sources of Sound
Contributed Papers
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Large amplitude radial pulsations of a single, driven gas bubble: Comparison between theory and experiment (A)

D. Felipe Gaitan, Lawrence A. Crum, Charles C. Church, and Ronald A. Roy

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S165-S165 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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In a previous paper [J. Acoust. Soc. Am. Suppl. 1 87, S141 (1990)], the observation of a single gas bubble pulsating radially and acoustically levitated in a stationary wave system at a pressure amplitude on the order of 1.5 bars with a relative pulsation amplitude Rmax/R0⩾3, was reported. This discovery was rather unexpected since the surface instability threshold under these conditions should have been on the order of 0.8 bars [S. Horsburgh, Ph.D. dissertation, University of Mississippi (1990)] and surface instabilities usually result in the break up of the bubble, preventing large radial pulsation amplitudes. The bubble was also observed to be undergoing sonoluminescence, a phenomenon in which light is emitted from the bubble, probably due to the high temperatures associated with the bubble collapse. In this paper, a comparison between the predicted and measured values of the pulsation amplitude, phase of collapse (radial minimum), and the number of radial minima per acoustic period will be presented. The theoretical calculations were made using three of the most current formulations of bubble dynamics, two of which include the energy and mass conservation equations of the gas inside the bubble to evaluate the dynamic temperatures and pressures. The experimental results have been used to test the applicability of these theories. In addition, the pressure amplitude threshold for light emission measured during the experiments has been used to determine the theoretical minimum temperature necessary to generate sonoluminescence. Comparison with previously measured temperatures inside cavitation bubbles during sonoluminescence activity will be made. [Work supported by ONR.]
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Long‐range detection and sizing of millimeter size bubbles (A)

G. George, D. Koller, Y. Li, P. M. Shankar, and V. L. Newhouse

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S165-S166 (1990); (2 pages)

Online Publication Date: 14 Aug 2005

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The sizing of mm size bubbles at ranges of 1–2 m using the double‐frequency technique [V. L. Newhouse and P.M. Shankar, J. Acoust. Soc. Am. 74, 1473–1477 (1984)] is described. The experiment was performed in a small swimming pool installed in the laboratory. Bubbles generated, using a number of pipettes connected to a compressed air supply, were insonified continuously by a pump field in the range of resonant frequency of the bubbles and an imaging field at 450 kHz. The imaging field was pulsed with a Gaussian envelope, generated using an IBM PC. The echo from the bubbles at the sum and difference frequency was received by a third transducer forming a crossed‐beam geometry and displayed on an HP 3585 spectrum analyzer. The sizes of the bubbles were obtained from the peaks at the sum and difference frequencies. The passive oscillations of the bubbles were also recorded at short ranges so that the size estimations can be compared. The double‐frequency technique was capable of measuring the sizes of bubbles with diameters 1 mm and above at ranges of up to 2 m. The sum and difference frequency signal that was used for the measurement was also demodulated using a 450‐kHz carrier, recovering the resonant pump signal. This signal recovery should be useful for off‐shore measurements of bubble sizes since it is easy to record and store low‐frequency information on tapes. [Work supported by ONR.]
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Cavitation from diagnostic ultrasound (A)

R. A. Roy, C. K. Holland, R. E. Apfel, and L. A. Crum

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S166-S166 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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The possibility of cavitation as a consequence of short‐pulse diagnostic ultrasound was predicted theoretically in 1982 by Apfel [R. E. Apfel, Br. J. Cancer 45 (Suppl. V), 140–146 (1982)] and Flynn [H. G. Flynn, J. Acoust. Soc. Am. 72, 1926–1932 (1982)]. Experiments were performed in ultraclean water to test this hypothesis under conditions comparable to those found in clinical ultrasound examinations. The development of an ultrasensitive acoustic backscattering technique that utilizes 30‐MHz pulsed ultrasound has made it possible to detect the presence of transient cavitation due to microsecond‐length pulses [R. A. Roy et al., J. Acoust. Soc. Am. 87, 2451–2458 (1990)]. This “active cavitation detector” has been employed in an in vitro study to probe the potential of cavitation production by a clinical ultrasound imaging system, specifically, an HP 77020A. Two calibrated, phased‐array HP imaging transducers with and 5.0‐MHz operating frequencies were driven in M‐mode (single cycle) and Doppler mode (4 cycles) by the HP imaging system. Hydrophobic polystyrene spheres with an average diameter of 0.245 μm served as potential cavitation nuclei. Cavitation was detected in the water at 2.5 MHz in both M‐mode and Doppler mode at a peak negative acoustic pressure of 1.1 MPa or greater. Insonfication at 5.0 MHz in either mode did not produce a detectable amount of cavitation, even with peak negative pressures as high as 1.2 MPa. [Work supported by the National Institutes of Health, Grant No. 5‐RO1‐CA‐39374‐05.]
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On initial stage of bubble cavitation zone dynamics in pulse rarefaction waves (A)

A. S. Besov, V. K. Kedrinskii, and Ye. I. Pal'chikov

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S166-S166 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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This paper presents experimental results of studying peculiarities of the initial stage of bubble cavitation evolution in liquid near a free surface when a microsecond duration shock wave reflects from it. Use of independent diffraction and electromagnetic techniques, as well as laser beam intensity variation, allowed the threshold effect evolution to be observed with an increase in the incident shock wave amplitude and solvability of these effects to be analyzed. Correlation of dynamics of the free surface and cavitation zone, predicted earlier on the basis of numerical studies performed [V. K. Kedrinskii and S. I. Plaksin, Proc. of the 11th ISNA (1984)], is confirmed experimentally. For the experiments, a transparent small hydrodynamic shock tube filled with distilled water was used. The shock wave was generated by a membrane occupying the central tube bottom part and excited by pulse magnetic field. The system geometry was chosen in order to exclude the effect of the tube walls on the wave field structure and cavitation evolution process. The experiments showed that, with the shock amplitude increase, the following effects can be observed: (1) the jump‐like increase in light intensity scattered on cavitation micronuclei, (2) considerable velocity retaining by the free surface for a long time after the rarefaction wave has passed, and (3) its complete absorption by developing cavitation zone. Attention is paid to hysteresis‐type effects of the free‐surface dynamics that can be due to both the structure of nuclei and peculiarities of their attaining the “visible” zone (zone of detection).
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The effect of extracorporeal shock wave lithotripsy (ESWL) on electrophysiological parameters across abdominal frog skin: Real time observations (A)

Mumtaz A. Dinno, Wendy Kennedy, Lawrence A. Crum, and Charles C. Church

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S166-S166 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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The side effects of ESWL, such as increased sodium excretion and proteinuria, may be explained by structural and functional changes that lead to an increase in permeability across the renal tubule. This preliminary study was undertaken to examine the feasibilty of such an explanation. Frog skin was used in this investigation, since sodium transport across it is similar to that of the distal convoluted tubule in the kidney. Exposure of the skin to a single shock at 20‐kV electrode voltage caused a significant but reversible decrease in transepithelial membrane potential, a decrease in ionic current (primarily sodium), and an increase in total ionic permeability. It is of interest to note here that these results are similar to those reported by Dinno et al. [Ultrasound Med. Biol. 15, 461–470 (1989)] on the effect of therapeutic ultrasound (1 MHz, 60–480 mW/cm2) on frog skin. Those similarities suggest a common mechanism. On the basis of this observation and other unpublished results, acoustic cavitation, and consequent free radical formation, seem to be an important factor contributing to the observed side effects. [Work supported by NIH under Grant No. 5‐RO1‐CA‐39374‐05. We gratefully acknowledge Dornier for making available their experimental lithotripter.]
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The effect of ultrasound on the ionic conductance across frog skin in the presence of free‐radical scavengers (A)

Mumtaz A. Dinno, Wendy Kennedy, Robert Ingraham, Beau Idom, and Lawrence Crum

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S166-S166 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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In a recent study, Dinno et al. [Ultrasound Meal. Biol. 15, 461–470 (1989).] reported that the increase in ionic conductance across frog skin is primarily due to effects of nonthermal origin. Cavitation was considered to be the major mechanism response for the change in the conductance. Since free radicals (FR), under certain conditions, are known to be generated during cavitation, it was decided to investigate the effect of ultrasound in the presence of free‐radical scavengers (FRS). It was found that the presence of 5 mM of either vitamin C or cysteamine caused a significant block to the increase of ionic conductance induced by ultrasound. On the other hand, cystamine, which does not permeate into the cell as readily as the other two FRS, did not interfere as strongly with the action of ultrasound. On the basis of these results, the following indications are suggested: (1) The increase in ionic conductance in the presence of ultrasound is triggered by FR produced by cavitation and (2) in some as‐yet‐unknown way, secondary effects of cavitation are triggered within the interior of the cell. [Work supported by the NIH under Grant No. 5‐RO1‐CA‐39374‐05.]
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Measurements of ultrasonic pulse arrival time differences produced by abdominal wall specimens (A)

Yoichi Sumino and Robert C. Waag

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S166-S167 (1990); (2 pages)

Online Publication Date: 14 Aug 2005

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The influence of propagation medium inhomogeneities on pulsatile ultrasonic fields has been investigated experimentally. The study employed a special curved transducer to produce a hemispherical wave pulse and a linear array to measure the resulting field along a line in a plane. Translation of the array in the elevation direction yielded data over a two‐dimensional aperture. Time delay across the aperture was calculated by adding delay differences obtained by crosscorrelating signals on adjacent elements and noting the position of the crosscorrelation peaks. Received waveforms were shifted an amount given by the difference between the actual arrival time and a calculated geometric delay to isolate arrival time differences due to propagation path inhomogeneities. Waveform and time delay difference plots, as well as histograms and statistics derived from them for propagation through a water path and for propagation through five specimens of human abdominal wall, indicate that arrival time fluctuations in the presence of human abdominal wall specimens are significantly greater than for a water path, and that degradation in focusing through human abdominal wall can be expected in ultrasonic imaging systems that operate in the low megahertz range and employ a relatively large aperture.
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Analysis of the ultrasonic beam produced by a wedge transducer (A)

M. A. Breazeale, G. Du, and D. Joharapurkar

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S167-S167 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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Recently, the wedge transducer has found application in ultrasonic microscopy (J. D. N. Cheeke and L. Germain, IEEE Ultrasonics Symposium, Montreal, 1989). Since the resonance frequency of the wedge transducer varies with position, it is possible to sweep the ultrasonic beam by changing the driving frequency. A theoretical analysis is given of the diffraction pattern produced at a single frequency by a one‐dimensional wedge transducer. The relation of resonance frequency with position is by no means linear, which means that the distribution of resonance frequency along the transducer is not symmetric about its center position. A linear relationship between beam frequency and position on the wedge is possible if one uses a curved back surface, however. The effect of the transducer edge on the diffraction pattern is noticeable even at frequencies at which the beam emerges near the center of the wedge. This result is confirmed by comparing with schlieren photographs. The implication of this observation for design of Gaussian transducers is considered. [Research supported by the Office of Naval Research.]
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Phase relations in ultrasonic light diffraction spectra (A)

A. Sliwinski

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S167-S167 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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In the phenomenon of light diffraction by ultrasound, the light intensity distribution in diffracted spectra depends on the power, frequency, and the width of the ultrasonic wave. It is known that, due to these dependences, the output light in given diffraction orders is modulated in phase. In the paper, some interesting relations are examined against ultrasonic power in the case of a single ultrasonic beam, as well as for two adjacent beams of various frequency ratios (in MHz range) that were experimentally observed and adequate numerical calculations were verified.
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Acoustical tweezers: Its principles and applications (A)

Junru Wu

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S167-S167 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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A stable force potential well was generated by two collimated focused ultrasonic (3.5‐MHz) beams propagating along opposite directions. Latex particles (270 μm in diameter) and clusters of frog eggs were trapped in the potential well. The trapped object can be moved axially or laterally by moving one of the PZT focusing transducers that generate the ultrasonic focused beams. The axial position of the trapped object can also be maneuvered by tuning the frequency of the electrical voltage applied on the transducers. [Work supported by NIH HL45161.]
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Transient response of the line parametric array with arbitrary taper (A)

Peter J. Westervelt

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S167-S167 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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The pressure impulse response of an array with arbitrary taper τ(y′) is shown to be P  =  βE(4πa)−1[ψeτ(x0 − R0)].00 in which ψc  =  a(x0 − x1)−1θ(x0 − R) [see Eq. (6), in P. J. Westervelt, Acta Phys. Pol. 27, 831–841 (1965)], β is the coefficient of nonlinearity, and E is the impulse energy. Applied to the truncated array of length L with a square wave input of duration T, it can be shown, by methods similar to those used by Westervelt [P. J. Westervelt, JETP Lett. 4, 225–228 (1965)], that the far‐field pressure is given by
math
, in which R0 is the length of the vector from the transducer to the field point, L is the length of the vector from the transducer to the absorber, ϕ is the angle between R0 and L, and E is the energy of the square wave.
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Noise generated by vortices over a cylindrical tube (A)

Timothy W. Lancey

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S167-S167 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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The sound field generated by a system of vortices, located near the outer boundary of a cylinder, with axes parallel with the cylinder's axis, was investigated. Analytical expressions for the near‐field sound and the far field were derived, following the developments of earlier researchers [A. T. Conlisk and Y. G. Guezennec, Nonlinear Interaction Effects and Chaotic Motions, edited by M. M. Reischman, M.P. Paidoussis, and R. J. Hansen (The American Society of Mechanical Engineers, New York, 1988), pp. 31–51]. A formulation with the inviscid Euler equation was employed, with the flow assumed irrotational and incompressible. From the complex potential describing the vortex array external to the cylinder, the complex velocity was derived, yielding the equations for the trajectories of the vortices. The sound field radiated was compared to that of the pulsating cylindrical source.
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Novel electromagnetic generation of subsonic waves on a membrane and a wave‐number‐selective differential optical detector (A)

Thomas J. Matula and Philip L. Marston

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S167-S168 (1990); (2 pages)

Online Publication Date: 14 Aug 2005

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Associated with a subsonic disturbance of a plane surface is an evanescent wave in the surrounding fluid. There has been interest in techniques for generating such disturbances [D. H. Trivett et al., J. Acoust. Soc. Am. 87, 2535<2540 (1990)]. An electromagnetic generator of subsonic waves on an electrically conducting layer is described. The method was used to generate waves having a velocity cm≈62 m/s on an aluminized Mylar membrane in air. A meander line (a serpentine coil) is driven by a tone burst of current. The plane of the meander line is parallel to that of the Mylar with a distance b between the center of adjacent lines. A spatially and temporally oscillating Lorentz force is generated on the membrane with the application of a current pulse across the aluminized Mylar simultaneous to the tone burst. Selection of the burst frequency f to be cm/2b, maximizes the amplitude of the tone burst launched on the membrane. Unlike conventional EMAT sources, no permanent magnets were used. The propagating membrane wave was detected by reflecting (off the membrane) a laser beam into a knife‐edge photodetector. A modified wave‐number‐selective knife‐edge detector was also demonstrated, which made use of a retroreflective prism. The modification is designed to reduce the sensitivity to background low‐frequency vibrations. [Work supported by ONR.]
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Studies of various electrode configurations for a plasma sound source (A)

Jeffrey A. Cook, Sirian Thepsoumane, Austin Gleeson, and Robert Rogers

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S168-S168 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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Several different types of electrode configurations, including gap, exploding‐wire, and various others, have been studied in an attempt to garner better understanding of the mechanisms by which acoustic pulses are generated. It is hoped that this research will allow the shaping of these acoustic pulses for specific applications and yield a repeatable broadband sound source. To this end, current, voltage, and acoustic data have been taken for each electrode firing, and a high‐speed photographic record made of selective firings to increase understanding of the hydrodynamical properties of the spark‐induced bubble. Relations have been studied between such parameters as breakdown time, energy at breakdown, and energy delivered in the acoustic pulse, in the hope of characterizing various electrode types by easily measured criteria.
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Computational studies of different laser intensity modulation techniques to generate underwater sound via thermal expansion (A)

Thomas C. Willett and Yves H. Berthelot

J. Acoust. Soc. Am. Volume 88, Issue S1, pp. S168-S168 (1990); (1 page)

Online Publication Date: 14 Aug 2005

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The thermalization of water, due to the absorption of laser radiation, offers a way to generate underwater sound from an airborne platform. However, the thermal expansion mechanism that produces sound is notoriously inefficient and the standard technique of amplitude modulation (AM) of the laser intensity is generally inadequate for practical applications such as bathymetry. With the advent of ultra‐high repetition rate pulsed lasers, it is now appropriate to take a fresh look at some alternative schemes for modulating the laser intensity. Computer simulations will be shown for three different modulation techniques in comparison with the standard AM technique. These modulation schemes are, respectively, frequency modulation (FM), pulse density modulation, and pulse amplitude modulation. In each case, the parameters controlling the far‐field acoustic pressure amplitude will be identified in an attempt to optimize the system. [Work supported by NSF.]
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