Acoustic impedance measurement on normal ears of children.

Abstract

In order to provide the fundamental knowledge on outer and middle ear of children, acoustic impedance measurements were performed on 205 subjects. They ranged from 3 years old to 11 years old and had normal hearing. We utilized the acoustic inverse method for reconstruction of the ear canal area functions. The results show (a) the children have smaller ear canal radius than the adults and (b) the ear canal volume and the ear canal radius increase as a function of the age. The acoustic impedance at the eardrum were calculated from the reconstructed area function of the ear canals and the measured reflection data. It is shown that (c) mean resistance of the eardrum impedance remains between 300 and 350 cgs acoustic ohms above 2 kHz, and the value is not so much different from the reported data on the adults. On the other hand, (d) middle ear of the children has small compliance and its values approach to the adults data as the age increases. This is evident in lower frequencies below 1 kHz.