Critical distance is computed from room constant and source directivity

Evidence

What is the critical distance for a freestanding, omnidirectional loudspeaker radiating into a room whose surface area is 75 m2 and whose average absorption coefficient is 0.2? What would be the effect of mounting the speaker into a wall? The speaker is omnidirectional, so the Q is equal to 1. The room constant R is the same as was found in the earlier example, 18.75 m2. Substituting both these values into Equation 6.11 gives: r RQ critical distance m cm = = × = 0 141 0 141 18 75 1 0 61 61 . — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1799

Categorization

• DEFINE: States the operative formula q = 0.141 sqrt(RQ), making the concept of critical distance numerically concrete.