I was thinking about audio compression (namely mp3), that "filters" out sound that we would not likely hear.
The MP3 lossy audio data compression algorithm takes advantage of a perceptual limitation of human hearing called auditory masking. from: http://en.wikipedia.org/wiki/MP3
I've also checked the wiki entry for auditory masking, and found this:
If two sounds of two different frequencies are played at the same time, two separate sounds can often be heard rather than a combination tone. The ability to hear frequencies separately is known as frequency resolution or frequency selectivity. When signals are perceived as a combination tone, they are said to reside in the same critical bandwidth.
My question is how much is this critical bandwidth or what's the smallest frequency difference we can perceive as two different tones, if you wish. Let's assume that both tones are equally loud, are coming from the same direction and distance and we are in a quiet room - so basically we eliminate as much noise and affecting phenomenons as possible.
As @ sanchises pointed out (thank you again!) in the comment section the frequency resolution is 3.6Hz between 1 and 2kHz. But since perception threshold is a function of the pitch of the sound I'd assume that the ability to resolve two tones would change with pitch too. Does anybody have any data on that? For example resolution X pitch graph.