Hi Bill Kuck, Paul Bruno, ... When I was a student the bel was an absolute measure of sound intensity that progressed as log to the base 10 (=Log) of intensity. Let u be the absolute unit of intensity. 1 u = 0 bel (inaudible) 10 u = 1 bel (inaudible) 10^2 u = 2 bel (inaudible) 10^3 u = 3 bel (watch ticking at 1 meter) 10^4 u = 4 bel (murmur) 10^5 u = 5 bel (human talk) ... 10^13 u = 13 bel (ear damaging sound) The sound intensity unit u was arbitrarily chosen to be 2*(10^-4)dynes per square centimeter. A dyne is the force that accellerates a 1 gram mass 1cm per second per second. Maybe nowadays a bel is just Log of just about any 'linear' measure used in accoustics (?) (like the output/input ratio of an amplifier). Cheers Laurent S PS. 3 bel = 30 decibel etc.