TEOAE amplitude growth, detectability, and response threshold in linear and nonlinear mode and in different time windows.

ABSTRACT

Transitory evoked otoacoustic emissions (TEOAE) have been recorded in 60 ears of 31 adult volunteers with nearly normal hearing at stimulus levels ranging from 83 dB SPL peak equivalent down to the individual response threshold using linear and nonlinear recording mode. The stimulus level dependence of response incidence and amplitude has been analysed for the integral response and in time windows selecting response components of limited latency ranges. At stimulus levels above 70 dB SPL peak equivalent the TEOAE records received in linear mode are contaminated with stimulus artifacts. At moderate stimulus levels the TEOAE amplitude differs only to a small extent between the two recording modes. At low levels the linear mode turns out to be better suited for signal detection due to its inherent lower noise level. The response threshold, defined as the highest stimulus level yielding a reproducibility of at least 60%, is significantly correlated to hearing threshold. The consideration of time windowed responses yields best results with respect to incidence and threshold of responses in the latency range between 5 and 10 ms, but it does not enhance frequency specificity.