[Clinical investigation of individual differences in evoked otoacoustic emission]

Factors causing individual differences in evoked otoacoustic emission (e-OAE) were investigated in 223 ears of 159 persons with normal hearing. After recording e-OAE to click by using ILO88, the relation between the intensity of e-OAE and factors such as age, sex, small differences in hearing, volume of the external auditory canal, static compliance, developmental extent of the mastoid cavity and presence or absence of spontaneous otoacoustic emission (s-OAE) were studied. The volume of the external auditory canal and static compliance were estimated from a tympanogram measured by Teledyne TA-2C and the developmental extent of the mastoid cavity was measured with a Schüller X-ray film. A correlation was found between the intensity of e-OAE and two factors, the age and the s-OAE, but not between the intensity of e-OAE and other factors. From the fact that the percentage of s-OAE present declines with aging, the presence or absence and the characteristics of s-OAE were considered to be a factor causing individual differences in e-OAE.