Otoacoustic Emissions:

In the ear there is a mechanism called the Cochlear Amplifier, which acts to amplify auditory signals received by the outer hair cells. However, the same mechanism that amplifies auditory responses can also generate noises of its own, known as Otoacoustic Emissions.

The Cochlear Amplifier produces Otoacoustic Emissions by essentially working in reverse. When a sound enters the cochlea, it also generates an echo, which moves back through the cochlear fluids and membranes, which in turn vibrates the oval window and ossicles, and finally vibrates the tympanic membrane (ear drum) to create a sound in the outside the ear.

Generally these Otoacoustic Emissions go unnoticed because they are very small in intensity. However, damaged regions of the cochlea, caused by exposure to loud noises, can produce these Otoacoustic Emissions spontaneously, creating ringing in the ears- a disorder called tinnitus. In mild cases, the auditory cortex can recognize these unwanted, spontaneous emissions and suppress our perception of them, but, as a result, we experience a slight loss of hearing.

(Sorry, I've been studying for a neural science exam.)


Here's a goofy picture of a woman getting her Otoacoustic Emissions checked: