Acoustic behavior of large encapsulated gas bubbles with resonance frequencies in the 50 to 100 Hz range
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A one-dimensional resonator technique was used to investigate the acoustic behavior of water containing large spherical and toroidal encapsulated air bubbles. Tethered balloons and inner tubes, respectively, were used to create the bubbles, which had effective spherical radii of approximately 5 cm. The number of balloons or inner tubes varied from 3 to 6, which resulted in void fractions from 1.5% to 5%. Effective mixture sound speeds for both shapes were inferred from the resonances of a water and bubble-filled waveguide 1.8 meters in length. For the spherical bubbles, the Commander and Prosperetti (CP) model [J. Acoust. Soc. Am. 85, 732-746 (1989)] quantitatively described the measured sound speed dispersion approaching the individual bubble resonance frequency, and qualitatively predicted the frequency range of high attenuation, even in this regime of high void fractions and discrete bubble distribution within the waveguide. Qualitative agreement was found between the CP model and the toroidal bubble measurements. Finite-element simulations of both experiments were performed, which help explain the discrepancy between the model and the spherical bubble measurements. © 2010 Acoustical Society of America.
author list (cited authors)
Wochner, M. S., Hinojosa, K. T., Lee, K., Argo, T. F., Wilson, P. S., & Mercier, R. S.