Click-evoked Otoacoustic Emissions for the As- Sessment of Auditory Filter Tuning at Supra- Threshold Levels

Reliable estimates of supra-threshold (60-80 dB SPL) filter tuning are necessary to understand auditory processing of speech. However, existing approaches suffer from methodological limitations that require high suppressor tone levels (psychoacoustics) or an assumption of linearity (otoacoustic emission group delay) to estimate human auditory filter tuning at higher stimulus levels. We propose a method based on temporal suppression (or, forward masking) of click-evoked otoacoustic emissions (CEOAE) to assess human supra-threshold filter tuning, with the underlying thought that the basilar-membrane impulse-response duration can be estimated from the spectral peaks in an individual’s CEOAE spectrum and how they interact with the forward masker. We derived tuning values for 11 subjects, recorded at 65 dB peSPL, and observed a clear frequency-dependence of tuning that resembles that of near-threshold otoacoustic emission tuning estimates. The mean Q values were 8.4 at 1 kHz, and sharpened to 12.1 at 4 kHz. We compared our method to psychoacoustic tuning curves (PTC) measured in the same subjects at equivalent levels, and found that PTC tuning was generally sharper than that obtained using the OAE methods.