Room Constant

The room constant (R) is a measure of a room’s total effective absorption that accounts for multiple reflections, used in calculating sound pressure levels in enclosed spaces. It is related to the total absorption area (A) by the formula R = A/(1 − ᾱ), where ᾱ is the average absorption coefficient. In rooms with low absorption, R is approximately equal to A; in highly absorptive rooms, R is significantly larger than A because each unit of absorption is more effective when the remaining surfaces are also absorptive. The room constant appears in the classic room acoustics equation for predicting SPL from a source: SPL = SWL + 10×log(Q/4πr² + 4/R). It determines the reverberant field level and the critical distance. Increasing the room constant through absorption treatment reduces the reverberant sound level and extends the critical distance, improving both noise control and speech intelligibility.