Transient evoked otoacoustic emission with unexpectedly short latency

Two alternative approaches for studying short-latency click-evoked otoacoustic emission (OAE) in normal-hearing subjects were employed. Growth of a click-evoked "ear canal response" with stimulus increase became progressively more non-linear and saturated when the latency of the analyzed segment of response increased. This relation between latency and shape of the response input/output function was observed even after linear component cancellation, indicating that it could be an intrinsic property of OAE. Hence, the existence of an essentially linear short-latency OAE component which is probably eliminated by commonly used artifact cancellation technique is suggested. Taking into account the fact that transient evoked otoacoustic emission (TEOAE) may be completely suppressed by simultaneously presented noise, a "true" artifact cancellation was performed by subtracting the ear canal response in the presence of a masker from the conventional click-evoked OAE recording. An additional TEOAE component with a latency of 2.5-5 ms was found. Its growth with stimulus intensity was indeed more linear than that of later components. However, latency and frequency of this TEOAE component, being specific for each subject, can hardly be explained by both a commonly assumed latency-frequency relationship of TEOAE and a generally used estimation of TEOAE latency as the sum of the forward and backward traveling wave propagation times.