title: Distortion product otoacoustic emission generation mechanisms and their dependence on stimulus level and primary frequency ratio.
abstract: In this study, a systematic analysis of the dependence on stimulus level and primary frequency ratio r of the different components of human distortion product otoacoustic emissions has been performed, to check the validity of theoretical models of their generation, as regards the localization of the sources and the relative weight of distortion and reflection generation mechanisms. 2f1 - f2 and 2f2 - f1 distortion product otoacoustic emissions of 12 normal hearing ears from six human subjects have been measured at four different levels, in the range [35, 65] dB sound pressure level, at eight different ratios, in the range [1.1, 1.45]. Time-frequency filtering was used to separate distortion and reflection components. Numerical simulations have also been performed using an active nonlinear cochlear model. Both in the experiment and in the simulations, the behavior of the 2f1 - f2 distortion and reflection components was in agreement with previous measurements and with the predictions of the two-source model. The 2f2 - f1 response showed a rotating-phase component only, whose behavior was in general agreement with that predicted for a component generated and reflected within a region basal to the characteristic place of frequency 2f2 - f1, although alternative interpretations, which are also discussed, cannot be ruled out.
authors.affiliation: Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL Research, Via Fontana Candida, 1, 00040 Monte Porzio Catone, Rome, Italy.
authors.forename: Teresa
authors.initials: T
authors.lastname: Botti
authors.affiliation: Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL Research, Via Fontana Candida, 1, 00040 Monte Porzio Catone, Rome, Italy.
authors.forename: Renata
authors.initials: R
authors.lastname: Sisto
authors.affiliation: Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL Research, Via Fontana Candida, 1, 00040 Monte Porzio Catone, Rome, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Sanjust
authors.affiliation: Physics Department, University of Roma Tor Vergata, Via della Ricerca Scientifica, 1, 00133 Roma, Italy.
authors.forename: Arturo
authors.initials: A
authors.lastname: Moleti
authors.affiliation: Physics Department, University of Roma Tor Vergata, Via della Ricerca Scientifica, 1, 00133 Roma, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: D'Amato
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000162:Acoustics; D001309:Auditory Threshold; D003051:Cochlea / Q000502:physiology; D003198:Computer Simulation; D064368:Healthy Volunteers; D017711:Nonlinear Dynamics; D009716:Numerical Analysis, Computer-Assisted; D017084:Otoacoustic Emissions, Spontaneous; D013018:Sound Spectrography; D058067:Wavelet Analysis; D006801:Humans