Frequency and temporal analysis of contralateral acoustic stimulation on evoked otoacoustic emissions in humans

Previous studies have shown that the effect of contralateral acoustic stimu lation (CAS) on ipsilateral evoked otoacoustic emissions (EOAE) depends som ewhat upon the spectrum of the eliciting stimulus. The latency of the EOAE, however, is itself frequency-dependent. Consequently, two general ways of analyzing the effects of CAS may be considered: by frequency band or by tem poral segment. In this study, we analyzed the effects of CAS both ways in t he same subjects, essentially simultaneously. The frequency analysis of the EOAE derived from the wavelet transform (WT). The WT is known to provide a robust approach to the analysis of non-stationary signals and was anticipa ted to avoid possible time-frequency confounds of the cochlear mechanical s ystem. For comparison, a more basic analysis - using a temporal moving wind ow - was employed. The results largely support earlier findings and confirm that in humans the greatest suppression of EOAEs by CAS is obtained for lo wer frequency and/or longer latency EOAE components. Despite expectations f or the WT analysis, the more basic, temporal, analysis tended to yield the clearer results. (C) 2000 Elsevier Science B.V. All rights reserved.