Bispectral Analysis of Transient Evoked Otoacoustic Emissions to Study Factors Influencing Cochlear Non-Linearities: Normative Data in Young Adults

Influences of different factors on non-linear interaction mechanisms in the cochlea, as evaluated in transient evoked otoacoustic emissions (TEOAEs), are investigated. The bispectral approach is applied to TEOAEs recorded in normal hearing young adults to extract non-linearities, with three main goals: (i) to obtain normative data; (ii) to evaluate test-retest repeatability of non-linear interaction mechanisms; and (iii) to investigate the influence of stimulus intensity on non-linear interaction mechanisms. Results revealed that most of the energy of non-linear components is located in the 1-4 kHz range and that the test-retest repeatability of non-linear interaction mechanisms is high. The factor that most affects non-linearities is stimulus intensity. The findings in this work could help in reaching a characterization of non-linear characteristics of TEOAEs in normal hearing subjects, contributing in creating normative data, that would be useful to identify possible subclinical dysfunctions.