Scheme of a parallelepipedic caivty (or room) of dimensions $a\times b \times h$ m3.
The expression for the frequency of m,n,p th mode (or resonance) in a parallelepidic air-filled cavity of dimensions $a\times b \times h$ m3 is:
where $c_{0}$ is the speed of sound in air at temperature and pressure conditions in the cavity (or room) and $m,n,p \in \mathbb{N}$.