  Equations of radial motion of a gas bubble in a compressible viscous liquid
have been modified to account for compressibility at the bubble boundary. A new
bubble boundary equation has been derived, including a new term resulted from
liquid compressibility. The influence of this term has been numerically
investigated using isothermal-adiabatic model for the gas inside the bubble.
The results clearly indicate that, at the end of the collapse, the new term has
a very significant role and its consideration dramatically changes the bubble
characteristics. Moreover, the more intense the collapse is, the more
significant the effect of the new term is. Also, it has been reasoned out that,
the influence of the new term will be established even when the effects of mass
(water vapor) exchange, chemical reactions, and gas dynamics inside the bubble
are taken into account.
