Interrelations between psychoacoustical tuning curves and spontaneous and evoked otoacoustic emissions

With the hypothesis that cochlear active mechanisms are the origin of otoacoustic emissions (OAEs) and of the high frequency selectivity exhibited by the ear, psychoacoustical tuning curves (PTCs), transiently evoked otoacoustic emissions (TEOAEs), and spontaneous otoacoustic emissions (SOAEs) have been examined in 50 normal hearing subjects. Using a clinical simplified method, PTCs were successively assessed at three frequencies--1, 2 and 4 kHz--in each subject. The results showed the existence of significant differences in the quality of tuning (Q10dB) of the PTCs between, first, subjects having SOAEs and subjects having no SOAEs (Student's t-test; p < 0.05; df = 35) and, second, subjects having large TEOAEs and subjects having small TEOAEs (Student's t-test; p < 0.05; df = 14). Nevertheless, these significant differences did not appear for all the frequencies studied: the frequency selective relationship between PTCs and OAEs mainly involved the 2 kHz zone. Such results are discussed according to the specificities of the clinical method used for PTC measurement as well as to the spectral characteristics of OAEs.