Submitted on June 30, 2003
Accepted on August 16, 2003
Otoacoustic emissions at different click intensities: invariant and subject dependent features
Giovanna Zimatore1, Alessandro Giuliani2, Stavros Hatzopoulos3, Alessandro Martini3, and Alfredo Colosimo1*
1 Department of Human Physiology and Pharmacology, University of Rome, Rome, Italy
2 T.C.E. Laboratory, Istituto Superiore di Sanita', Rome, Italy
3 Audiology Department and Center of Bioacoustics, University of Ferrara, Ferrara, Italy
* To whom correspondence should be addressed. E-mail: a.colosimo{at}caspur.it.
A study of Click Evoked Otoacoustic Emissions (CEOAEs) elicited at stimulation intensities from 35 to over 80 dB was carried out by Recurrence Quantification Analysis (RQA) on signals from both normal and hearing impaired subjects. In normal subjects, a clear scaling of determinism with increasing stimulation intensity was observed in the click intensity range from 41 to 59 dB. Outside that range and, in particular, above its upper end, subject-dependent features appeared in the form of different maximal levels of determinism. A comparative analysis of responses from hearing impaired subjects with conductive hearing losses and sensorineural hearing losses suggested that the principal contributor to this behavior is the middle ear and allowed to discriminate the two pathologies solely on the basis of CEOAEs. These observations are consistent with a simple phenomenological model of the auditory periphery in which different functional modules are sequentially recruited at increasing stimulus intensities, with a consequent rise in CEOAEs coherence.
