ERB scale

It appeared that the critical bandwidth, or the ERB of the human auditory filter, corresponds to a constant distance along the basilar membrane (Moore 1986).

The ERB scale is often used in intonation research where a perceptual scaling is needed to weigh the perceptual importance of differences in fundamental frequency. Another perceptual scale used in intonation research is the semitone scale.
The following conversion transforms frequency values (F in Hz) into ERBs:
ERB=16.6*log(1+(F/165.4))

Link

Utrecht Lexicon of Linguistics

References

• Moore, B.C.J. 1986. Parallels between frequency selectivity measured physophysically and in cochlear mechanics, Scandinavian Audiology, Supplement. 25, 139-152