  The human ear canal couples the external sound field to the eardrum and the
solid parts of the middle ear. Therefore, knowledge of the acoustic impedance
of the human ear is widely used in the industry to develop audio devices such
as smartphones, headsets, and hearing aids. In this study acoustic impedance
measurements in the human ear canal of 32 adult subjects is presented. Wideband
measurement techniques developed specifically for this purpose enable impedance
measurement to be obtained in the full audio band up to 20kHz. Full ear canal
geometries of all subjects are also available from the first of its kind in
vivo based magnetic resonance imaging study of the human outer ear. These ear
canal geometries are used to obtain individual ear moulds of all subjects and
to process the data. By utilizing a theoretical Webster's horn description, the
measured impedance is propagated in each ear canal to a common theoretical
reference plane across all subjects. At this plane the mean human impedance and
standard deviation of the population is found. The results are further
demographically divided by gender and age and compared to a widely used ear
simulator (the IEC711 coupler).
