Otoacoustic Emissions

n this chapter, we present a very special kind of acoustic emissions, coming from inside the cochlea and generated along the basilar membrane by the electro-motile (active) vibrations of outer hair cells of the organ of Corti. They are called OtoAcoustic Emissions (OAE) and are detected in the ear canal by means of microphones which are usually assembled as part of earphone-like probes. Since their discovery by Kemp [1], the study of otoacoustic emissions has become an hot topic both in basic and clinical research, due to OAE unique feature to inform directly about the normal and pathological functions of the cochlear receptors mecha‐-nisms, thus like the efficiency of the middle ear transmission chain.
From the signal point of view, the most interesting characteristics of OAE is their broad band frequency spectrum so rousing also a new interest for broad band ear immittance measurements and interpretation [2]. In this respect, this chapter will focus the reader’s attention on two very innovative topics to improve objective and non-invasive audiological tests: the potentiality of Transient-Evoked otoacoustic emissions (TEOAE) to detect hearing impairment and the availability of a new microprobe able to capture directly both the pressure and velocity acoustic signals in the ear canal so allowing the direct measurement of ear immittance.