Comparative influence of repeated measurement and of attention on evoked otoacoustic emissions.

This study compared the influence of an auditory attention task and of repetitive measures on the peripheral auditory system, using evoked otoacoustic emissions (EOAEs). The experimental task protocol comprised three sessions (pre-control, attention and post-control conditions) with, in each session, six measurements of EOAEs, at intervals of about 60 seconds, while the other ear was receiving two pure tones of 2,500 and 750 Hz, with a probability of appearance of 20% and 80%, respectively. In the contralateral attention condition, the subject had to count the number of the less frequent high pitched sounds. A long duration protocol (20 min for the total experiment) was used in order to examine a possible time-effect on EOAEs. An increase in EOAE amplitude during the second and third sessions, with linear saturation around the last measurements, was observed. While no attention effect could be identified, a time-effect seemed to be present. Possible explanations for the influence of repeated measurements on EOAEs are discussed. Moreover, EOAE amplitudes of subjects presenting spontaneous otoacoustic emissions were compared to those of subjects without SOAEs: significant differences were found, showing the particularity of cochleas emitting SOAEs.