TEOAE recording protocols revised: Data from adult subjects

The objective of this study was the experimental re-evaluation of the current clinical transiently evoked otoacoustic emission (TEOAE) protocols, based on linear and non-linear protocol paradigms from a population of 42 adult subjects serving as a normative database. The linear and non-linear TEOAE responses were elicited by clicks with average intensities of 72 and 84 dB p.e. SPL respectively. An initial comparison between nonprocessed non-linear and linear recordings, at early recording segments from 3.2 to 5.2 ms, showed that the responses had highly similar contours and no statistically significant mean differences. The stimulus-induced artefact in the linear TEOAE responses was suppressed by postprocessing the data with a window function (3.8-13.8 ms) and by a high-pass filter at 830 Hz. A repeated-measures model was used to evaluate the differences between post-processed linear and non-linear responses across clinical variables of interest (such as TEOAE response, noise, correlation, and signal-to-noise ratios (SNRs) at 1.0-5.0 kHz). The data indicated that the linear recordings demonstrate significantly lower levels of noise (and thus superior SNRs) and higher values of reproducibility. Normative adult scoring criteria were calculated from free distribution tolerance intervals for the TEOAE correlation and the SNRs at 2.0 and 3.0 kHz.