Mel
From ExoDictionary
Mel
A unit of acoustic pitch. By definition, a simple tone of frequency 1000 cycles per second, 40 decibels above a listener's threshold, produces a pitch of 1000 mels. The pitch of any sound that is judged by the listener to be n times that of a 1-mel tone is n mels.
References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
