Cochlea 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. 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). Otoacoustic emissions are due to a wave exiting the cochlea via the oval window, and propagating back through the middle ear to the eardrum, and out the ear canal, where it can be picked up by a microphone. Otoacoustic emissions
Traditional Chinese medicines derived from the human body story, it would seem that those 'who go down to the silkworm room' [who are administratively sentenced to castration] should not be ignorant of this method, so I append it here." In some "Bencao gangmu" contexts concerning human drugs, Li Shizhen would accept the traditional theory but deny the contemporary practice. Under the human breath or "qi" section (52.23, tr. Luo 2003: 4176), Li says a "very effective" method for treating an elderly person who is suffering from cold and deficiency in the lower body is to have a boy or girl blow air through a cloth into the navel.