EAR CANAL REFLECTANCE IN THE PRESENCE OF SPONTANEOUS OTOACOUSTIC EMISSIONS - I - LIMIT-CYCLE OSCILLATOR MODEL

Alien et al. [Abstract in Eighteenth Midwinter Research Meeting of the Association for Research in Otolaryngology, Des Moines, IA (1995)] ha ve found that the ear canal reflectance passes through a minimum aroun d the frequency of a spontaneous otoacoustic emission (SOAE). They con sidered this result to constitute evidence against active nonlinear co chlear function as the basis for SOAEs. In order to investigate theore tically the expected behavior of ear canal reflectance in the neighbor hood of a SOAE associated with an active-nonlinear cochlea, we use a s implified model in which the ear drum end of the ear canal is effectiv ely terminated by a nonlinear-active element. Under the influence of a sinusoidal driver at the entrance of the ear canal, this element will , to a good approximation, either (1) oscillate at both the frequency of the driver (at which the reflectance is determined) and the SOAE (a t a suppressed level, corresponding to nonentrainment). or (2) be entr ained and only oscillate at the driving frequency. The magnitude of th e nonlinear ear canal reflectance is found to exceed unity only at suf ficiently low stimulus levels, and occurs under conditions of entrainm ent and nonentrainment of the spontaneous emission. Otherwise, the ref lectance is less than unity and, as a function of frequency, has a min imum around the SOAE frequency. (C) 1998 Acoustical Society of America .