Overall sound pressure level (or pressure)

Dear,

I have a problem to calculate "overall" pressure in ray acoustics module.

I know equation for real overall (with diferent frequencys or bands), but in ray acoustics module we have direct and reflected rays on single frequency (on the microphone position in Small_Concert_Hall_Analyzer for example..).

How to sum all ray (direct and reflected) on the microphone position in single number ("overall" or some type of "total" pressure or SPL)?

With respect
Marko Jankovic