TRANSIENT EVOKED OTOACOUSTIC EMISSION WITH UNEXPECTEDLY SHORT-LATENCY

Two alternative approaches for studying short-latency click-evoked oto acoustic emission (OAE) in normal-hearing subjects were employed. Grow th of a click-evoked ''ear canal response'' with stimulus increase bec ame progressively more non-linear and saturated when the latency of th e analyzed segment of response increased. This relation between latenc y and shape of the response input/output function was observed even af ter linear component cancellation, indicating that it could be an intr insic property of OAE. Hence, the existence of an essentially linear s hort-latency OAE component which is probably eliminated by commonly us ed artifact cancellation technique is suggested. Taking into account t he fact that transient evoked otoacoustic emission (TEOAE) may be comp letely suppressed by simultaneously presented noise, a ''true'' artifa ct cancellation was performed by subtracting the ear canal response in the presence of a masker from the conventional click-evoked OAE recor ding. An additional TEOAE component with a latency of 2.5-5 ms was fou nd. Its growth with stimulus intensity was indeed more linear than tha t of later components. However, latency and frequency of this TEOAE co mponent, being specific for each subject, can hardly be explained by b oth a commonly assumed latency-frequency relationship of TEOAE and a g enerally used estimation of TEOAE latency as the sum of the forward an d backward traveling wave propagation times.