Handbook for Sound Engineers

Small Room Acoustics 137

by the first mode on the low end of the spectrum and f at
the high end, where f| 3 C/RSD (rooms smallest dimen-

sion). In this region where the room modes dominate the
acoustical performance, wave behavior is the best model
and some forms of bass absorption can work well.

Region 3 spans from f to roughly four times f. This
region is dominated by diffraction and diffusion. The
final region is where the wavelengths are generally small

relative to the dimensions of the room. In this region, one

can use a ray acoustics approach as we are dealing with

specular reflections.

The discussion of how to quantify the decay of

sound in small rooms continues. Most recording

studios, control rooms, and listening rooms are too

small to have a completely diffuse sound field, espe-

cially at the lower frequencies. In small, acoustically

dead rooms the only frequencies that have any signifi-

cant decay are those that are at or very near to the

natural resonances of the room. This decay time is,

Figure 6-12. Enlargement of the first 500 ms of Fig. 6-11.

Figure 6-13. Schroeder integration of Fig. 6-11.