  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.
