Viscoelastic bubbly media and ultrasonic shear-mode effects

Here we show that in ultrasonic fields the phenomenon of reconversion of shear-modes into an effective compressional wave has a significant effect for bubbles in a medium viscosity liquid or weak gel. We present the consequent extra terms in the effective wavenumber and find the changes in sound velocity for different bubble radii. At high concentrations of bubbles the inclusion of shear-mode effects in the multiple-scattering model can help identify bubble sizes where additional resonance signatures emerge.