Clap in a cathedral and the sound hangs for seconds; clap in a padded room and it dies at once. Wallace Sabine turned that into the first law of architectural acoustics: the reverberation time depends only on the room’s VOLUME and how much its surfaces DRINK the sound. Slide the absorption and hear the room close in.
Sabine’s formula (1898): the time for sound to fall by 60 dB is RT60 = 0.161 · V / A, with V the room volume in cubic metres and A the total absorption (surface area × absorption coefficient, in sabins). More soft material = larger A = shorter reverberation; a bigger room = longer. The instrument runs a real 60-dB decay for the chosen A. A fail-loud self-check throws unless RT60 falls as absorption rises and equals 0.161V/A exactly (V=200, A=20 gives 1.61 s).
Sabine assumes a diffuse field and evenly-spread absorption; very dead or oddly-shaped rooms need Eyring’s correction. The 0.161V/A relation and the 60-dB decay are exact for this model.