This example studies the resonance frequencies of an empty room by
for the time-harmonic pressure field
$$ \Delta p + k^2 p = 0 $$
The resulting eigenmodes can be compared to and validated against the
analytical solution for the resonance frequencies of a boxed
enclosure, that is f = c/2*√( (i/lx)2 +
(j/ly)2 + (k/lz)2 ) where i, j, and k
are integer permutations 0 … n for the various modes.
This model is available as an automated tutorial by selecting Model
Examples and Tutorials… > Classic PDE > Resonance
Frequencies of a Room from the File menu. Or alternatively,
follow the linked step-by-step instructions.