Apparently, there is a limit to the maximum sound amplitude that depends on the medium in which the sound in question travels. In the atmosphere, the limit is supposedly around 194 Db, arising from the fact that in sound above this level, the pressure throughs would exceed atmospheric pressure and there can be no negative absolute pressure, so the throughs would be cut-off, which means the pressure waves would no longer have sinusoid waveform (I guess it could be argued that they are still sound). What I am wondering about is if there is a limit on the other end of the scale (if so, it would probably also be medium dependent) and if so, what is it and why is it there? Young children can supposedly hear up to -5 Db or even -10 Db at certain frequencies and some animals can apparently beat even that (my internet searches yielded -10 Db, -15 Db or even close to - 20 Db peak sensitivity for cats), so if there is a lower limit it must lie somewhere below that. One source had some owl hearing sensitivity pegged at between -90 and -100 Db, but I found no other source to corroborate it and other sources yielded owl sensitivities somewhere in the cat range I described above. Unfortunately, I did not manage to find the lowest sound recorded by human-made equipment, so that yielded no clues at all. I would presume that below some amplitude of vibration, the air molecules no longer reach each other to propagate the sound, so that would provide some sort of lower limit and random effects might drown out any sound before that, but that is just my speculation and I don't know what decibel limits (assuming my speculation is even correct) this would impose in the atmosphere. Anyway, I have been wondering about this for a while and have finally decided to ask some experts, so I registered here and voila this is my first post. I am hoping somebody here can shed some light on the matter. Thanks!