Eardrum impedance and ear canal geometry

A consistent description of the human external ear must take into account a diversity of data concerning (a) the transformation of sound-pressure level from the free field to the eardrum, (b) the transfer functions from the ear-canal entrance and insert positions to the eardrum, (c) the pressure distributions in the ear canal and concha, (d) eardrum impedance, (e) insert earphone response. (f) ear-canal length and volume (directly measured), and (g) sex differences. A cylindrical canal 23 mm in length and 7.5 mm in diameter satisfies most of the data fairly well but places the primary resonance frequency of the complete external ear at a frequency 5%–7% higher than the observed value. The discrepancy is probably associated with the connection between the canal and the concha.