Rectangular room modes

The calculation

f(n,m,p) = (c/2) × √[(n/L)² + (m/W)² + (p/H)²]
n, m, p are non-negative integers, not all zero
c = 343 m/s

Assumptions & limits

A rectangular room with rigid boundaries. Frequencies alone do not predict level, decay time or audibility at a listening position. Openings, non-rectangular shapes and flexible walls change the result.