Editing Cochlea (section)

===Hair cell amplification===
Not only does the cochlea "receive" sound, a healthy cochlea ''generates'' and amplifies sound when necessary.  Where the organism needs a mechanism to hear very faint sounds, the cochlea amplifies by the reverse [[Transduction (physiology)|transduction]] of the OHCs, converting electrical signals back to mechanical in a positive-feedback configuration.  The OHCs have a protein motor called [[prestin]] on their outer membranes; it generates additional movement that couples back to the fluid–membrane wave. This "active amplifier" is essential in the ear's ability to amplify weak sounds.<ref>{{Cite journal|last=Ashmore|first=Jonathan Felix|author-link=Jonathan Ashmore|year=1987|title=A fast motile response in guinea-pig outer hair cells: the cellular basis of the cochlear amplifier|journal=[[The Journal of Physiology]]|language=en|volume=388|issue=1|pages=323–347|doi=10.1113/jphysiol.1987.sp016617|issn=1469-7793|pmid=3656195 |pmc=1192551}} {{open access}}</ref><ref>{{Cite journal|last=Ashmore|first=Jonathan|s2cid=17722638|author-link=Jonathan Ashmore|date=2008|title=Cochlear Outer Hair Cell Motility|journal=[[Physiological Reviews]]|language=en|volume=88|issue=1|pages=173–210|doi=10.1152/physrev.00044.2006|issn=0031-9333|pmid= 18195086}} {{open access}}</ref>

The active amplifier also leads to the phenomenon of soundwave vibrations being emitted from the cochlea back into the ear canal through the middle ear (otoacoustic emissions).