Properties of the generator of stimulated acoustic emissions.

In Part I, the sound emitting properties of the peripheral auditory system are briefly reviewed and links with other literature are cited. (Summary of Symposium section introduction). In Part II, the stimulation of acoustic emissions by clicks is examined experimentally and analytically, in order to specify the physical qualities and parameters of the unknown generator which may be considered as driving the ear drum. Special attention is paid to absolute magnitudes to the qualitative interpretation of the generator's nonlinear properties and to the extent of inter-stimulus interactions in the time and frequency domains. New transient suppression results are presented. From the observations made, and without reference to the likely cochlear origin of the phenomenon, it is deduced that the generator is a multiple channel system, with each channel consisting of at least a steep-sloped narrow band filter followed by a fast acting compressive nonlinearity. A secondary nonlinearity seems also to be present, of a form which requires the filter itself to be nonlinear. The maximum power output of the generator is of the order 0.26 X 10(-12) W.