Acoustical room transfer functions without using Green´s functions

Acoustical room transfer functions are obtained for rooms with soft boundaries, i.e., taking wall damping into account. The transfer functions derived are well-known but all the known derivations make use of Green´s functions. In this paper a derivation, starting from fundamentals, is given which doesn´t use Green´s functions. This makes the derivation straightforward and can be understood easily by researchers without acoustics background. This has obvious use for control engineers who are drawn in large numbers to the active noise control research. It is shown that under certain conditions the room transfer functions are a weighted sum of damped second order transfer functions