Human middle ear sound transfer function and cochlear input impedance

Middle ear sound transfer function (METF) and acoustic input impedance of the cochlea (Z(c)) were measured in 12 fresh human temporal bones for the 0.05-10 kHz frequency range. METF was determined by two methods: middle ear sound pressure gain (GME) and the ear canal sound pressure to stapes footplate velocity transfer function (STF). The mean CME magnitude reached 23.5 dB at 1.2 kHz with a slope of approximately 6 dB/octave from 0.1-1.2 KHz and -6 dB/octave above 1.2 kHz. From 0.1-0.5 kHz, the mean GME phase angle was 51 degrees, rolling off at -78 degrees /octave above this frequency. The mean STF magnitude reached a maximum of 0.33 mms(.)s(-1)/Pa at 1.0 kHz with nearly the same shape in magnitude and phase angle as the mean GME. Direct measurement of Z(c) in human ears is reported here for the first time. The mean Z(c) was virtually flat with a value of 21.1 acoustic G Omega MKS between 0.1 and 5.0 kHz. Above 5 KHz, the mean Z increased to a maximum value of 49.9 G Omega at 6.7 kHz. The mean Z(c) angle was near 0 degrees from 0.5-5.0 kHz, decreasing below 0.5 kHz and above 5 kHz with peaks and valleys.