mel
n. a unit designed to measure the subjective extent of pitch. By definition, the pitch of a 1000 Hz tone presented at 40 dB SPL (40 phons) is 1000 mels. A tone whose frequency is judged to produce a pitch twice that of a 1000 mel tone has a pitch of 2000 mels, and so on. Across the range of orchestral instruments, the mel scale corresponds closely to the basic unit of the musical scale, the octave, so that doubling the frequency of a tone approximately doubles the number of mels.
