In ultrasonics, a longitudinal wave can be converted to transverse when interacting with a physical boundary, similarly, transverse can be mode converted to longitudinal. The phenomenon is well understood when referring to a planar reflector. However, what about non planar reflectors such as a side drilled hole? Is there any equation that shows the amount of mode conversion depending on the variables such as angle of incidence, size of reflector, velocity of the sound wave etc..