Octave
Interval between two frequencies, one of which is twice as large as the other (for example 250 Hz and 500 Hz).

Ossicles
Three small bones of the middle ear (i.e., malleus, incus, and stapes).

Ossicle Chain
Three small connected bones in the middle ear.

Otoacoustic Emissions (OAE)
A hearing test which measures acoustic emissions (sounds) that are generated in the cochlea and reflected back through the middle ear to the external ear. This tests the functioning of the cochlea.

Otitis Media
Fluid or an infection in the middle ear.

Otolaryngologist
Physician who is knowledgeable in diseases of the ear, nose, and throat (ENT).

Otologist
Physician who specializes in the anatomy, physiology, and pathology of the ear.

Otosclerosis
a disease affecting the middle ear capsule, specifically the movement of the stapes.

Otoscopy
Inspection of the ear.

Outer Ear
Also known as the auricle or pinna; includes the ear flap and the ear canal; Gathers and enhances sound and channels it to the middle ear.

Oval Window
Opening between the middle and the inner ear.

Oxotoxic Drugs
Drugs that can damage the cochlea of an unborn child.