\mbox{v} = \sqrt{\left( \frac{\partial p}{\partial \rho} \right)_S}

where

and the derivative is taken at constant entropy: .

It differs for p-wave and s-wave:

\mbox{v}_p = \sqrt{ \frac{K + \frac{4}{3} G}{\rho} }

\mbox{v}_s = \sqrt{ \frac{G}{\rho}}

where

See also