I am studying wave propagation in combustion chamber and looking for free codes for solving inhomogeneous wave equation. P

The algorithm for solving inhomegeneous wave equation can be found in computational electromagnetics books if you plan to use finite difference time domain method.

I want to have good review with the application of acoustics. P

I would suggest going through the archives of journal of computational physics. They have pretty good papers which might help you. If you want to look for a book have a look at numerical partial differential equation by ames if you want to use a finite difference scheme or volume.Have a look at any standard FEM book if you are interested in that method.

First order wave equation represents an important challenge for natural self-adjoint methods such as FEM, or Finite Difference Methods. I suggest that you take a look into the Least Squares-FEM. A good reference is The least-squares FEM Bo-nan Jiang.