Otoacoustic emissions, travelling waves and cochlear mechanisms.

The phenomenon of otoacoustic emissions is discussed in relation to the question--is the cochlear travelling wave actively enhanced? Distinctions are made between active loss reduction and true amplification, and between different types of emission source. The dynamic control exercised by the cochlea over the level of mechanical activity is analysed. An adaptive mechanism, capable of oscillatory transient behaviour is found both acoustically and psychophysically in response to strong low frequency stimulation. A feedback model is presented and used to predict aspects of emission behaviour.