Human middle-ear sound transfer function and cochlear input impedance

Abstract

The middle-ear pressure gain, defined as the ear canal sound pressure to cochlear vestibule pressure gain, GME, and the ear canal sound pressure to stapes footplate velocity transfer function, SVTF, simultaneously measured in 12 fresh human temporal bones for the 0.05 to 10 kHz frequency range are reported. The mean GME magnitude reached 23.5 dB at 1.2 kHz with a slope of approximately 6 dB/octave from 0.1 to 1.2 kHz and -6 dB/octave above 1.2 kHz. From 0.1 to 0.5 kHz, the mean GME phase angle was 51 degrees, rolling off at -78 degrees /octave above this frequency. The mean SVTF magnitude reached a maximum of 0.33 mm s(-1)/Pa at 1.0 kHz with nearly the same shape in magnitude and phase angle as the mean GME. The ratio of GME and SVTF provide the first direct measurements of Z(c) in human ears. The mean Z(c) was virtually flat with a value of 21.1 acoustic GOmega MKS between 0.1 and 5.0 kHz. Above 5 kHz, the mean Z(c) increased to a maximum value of 49.9 GOmega at 6.7 kHz. The mean Z(c) angle was near 0 degrees from 0.5 to 5.0 kHz, decreasing below 0.5 kHz and above 5 kHz with peaks and valleys.