Maximum length sequences and Volterra series in the analysis of transient evoked otoacoustic emissions

Previous work from this group (IHR, Southampton) has shown the feasibility of using maximum length sequence (MLS) stimulation to obtain evoked otoacoustic emissions (OAE). Because an MLS is one of a set of inputs that enables the Volterra series to be computed, we investigated its use with OAE. We wanted to see if the Volterra series could model the system and if we could extract the higher order kernels. In order to realise a practicable MLS system, a variant of the MLS has been used which permits real time recovery of the response and so enables the rejection of noisy epochs. This paper shows that the MLS used does enable the higher order kernels to be measured. The problems of selecting the correct sequences are discussed and the necessary system checks described.