Spontaneous otoacoustic emissions (SOAE) were recorded from normal hearing subjects using a sensitive microphone in the external ear canal. SOAE were recorded in 33% of 45 subjects, 24% of 90 ears tested. SOAE showed a higher incidence in female than in male. Its frequency was within 3000Hz.
Patients with tinnitus also showed a tendency for a higher incidence of the presence of SOAE, but their SOAE frequency differed from that obtained from pitch-match technique. In our study, it seemed that there was few interrelations between SOAE and tinnitus.
External puretone suppressed SOAE with nonlinear input-output function. We discovered that in the range of steep slope of input-output function a combination tone appeared with SOAE and a suppressor tone.
Our observation indicated that there was an active nonlinear process in the cochlea.