The finding of active function by the outer hair cells for sound processing prior to neural transduction in the inner hair cells represents the basic mechanism for the generation of Otoacoustic Emissions in the cochlea. Among them the so-called Distortion Product Otoacoustic Emissions represent a tool for an in depth knowledge of the Organ of Corti micromechanics, more advantageous than others, based on their properties, that makes possible an objective frequency-specific study: The response in a group of normally hearing subjects is presented and characterized to ascertain the basic features to be used in further testing of deaf people.