A measure of consonance. I'll test it later. (Consonance is not a measurement of how good pitches sound, but instead how long two waves of different periods must be propagated in order to have them sync back up. Like setting two toy trains moving the same velocity on two circular tracks of differing circumferences and timing how long it takes the trains on the short track to catch up with the train on the longer track.)

Sounds that take longer are regarded as more distinct because they literally just don't pair up often.