Extraction of cochlear non-linearities with the bispectral analysis-An application to TEOAEs in styrene-exposed workers

Objectives: Transient Otoacoustic emission (TEOAEs) are low intensity sounds generated by active mechanisms in the cochlea and elicited by broadband and short acoustic stimuli. TEOAEs are a quick, non-invasive, and very reliable measure to objectively assess the peripheral auditory system. In the current study, we present a recent technique to extract and evaluate non-linearities in TEOAEs, and apply it for the preliminary analysis of TEOAE recordings of a group of worker of a fiberglass manufacturing facility exposed to styrene solvent. Methods: Bispectral analysis was applied to TEOAEs to extract the quadratic frequency couplings (QFCs) in TEOAEs. Amplitude of QFCs was calculated in a group of 7 styreneexposed workers (14 ears) and compared with normative results obtained on normal hearing young adults. Results: Difference in amplitude of QFCs were found between workers and controls. In workers, TEOAE non-linear components were found in the 1.5 - 4 kHz frequency range, whereas in control subjects they were found in a lower frequency region, ranging from 1 to 3 kHz. Conclusion: The amplitude of QFCs highlighted differences in TEOAEs recorded among workers and controls.