mel

   a unit of perceived musical pitch, originally defined by Stevens, Volkmann, and Newmann in 1937. Our perception of musical pitch is complex. Although tones of higher frequency are perceived as being higher in pitch, tones separated by equal intervals (frequency ratios), such as octaves, will not be perceived as being equally spaced in pitch. A pure tone of frequency 1000 hertz, at a sound level 40 decibels above the faintest sound a listener can hear, is defined to have a pitch of 1000 mels, and tones perceived as being equally spaced in pitch are separated by an equal number of mels. Because perceptions of pitch depend on a number of factors other than frequency, it is not possible to give a straightforward conversion between hertz and mels. For tones above 1000 hertz the perceived pitch in mels is lower than the frequency in hertz; a 10-kilohertz tone is perceived at around 3000 mels. For tones lower than 1000 hertz the perceived pitch is a little higher than the frequency in hertz.