Effect of middle ear on otoacoustic emissions.

Otoacoustic emissions (OAEs) are believed to originate from outer hair cell movement and are considered to be transmitted to the external auditory meatus through the middle ear in a retrograde fashion. Therefore, the effect of the middle-ear on OAEs seems to be large. However, few investigations of middle-ear effects on OAEs have been published because no apparatus that can measure the middle-ear dynamic characteristics is easily available except a conventional impedance meter. We developed a sweep frequency impedance meter (SFI) which gives us much more information on middle-ear dynamic characteristics than a conventional impedance meter. In this paper, applying SFI and 3 OAE measuring apparatuses, middle-ear dynamic characteristics and different sorts of OAEs of human subjects and guinea pigs were measured, and an attempt was made to examine the relationship between OAEs and middle-ear dynamic characteristics from various aspects. It is concluded that frequency characteristics of OAEs correlate well with middle-ear frequency characteristics; and middle-ear effect on OAEs must be taken into account when OAE data are analyzed.