# How to calculate the energy of a mechanically produced wave?

I have a situation in mind, where at a number of points there is placed a material that positively strains in response to a stimuli, like pictured below,

This is to produce a Rayleigh or surface acoustic wave (SAW) that propagates along the surface. Using the material properties and strains of actuation material, I can work out the stress placed along the substrate layer.

However, I am not sure how to go about moving this forward into a calculation of energy of the wave produced. Which is what I am interested in finding out.

I have come across how the energy is proportional to the amplitude of the wave squared. I am not sure how or if I could work out an amplitude of this and what other factors I would need to consider.

Any suggestions as to how I might approach this, would be appreciated.

• Strain energy = the integral of the strain energy density = $\displaystyle \int_V \sigma \cdot \epsilon\,dV$ (summed over all the nonzero components of $\sigma$ and $\epsilon$.) – alephzero Sep 16 '19 at 14:09
• You could compute the flux of the elastodynamic Poynting vector (radiated power) across a well-chosen surface. – user8736288 Sep 16 '19 at 15:15