The outer ear directs sound waves (changes in air pressure) to the external auditory canal where they are funneled to the tympanic membrane (eardrum). The tympanic membrane is the structure that marks the beginning of the middle ear. When the air pressure hits the eardrum, it converts sound waves into mechanical energy, and causes the three tiny bones that are attached to the eardrums (also called ossicles: malleus, incus and stapes) to move back and forth. The stapes is attached to the oval window, which is the beginning structure of the inner ear. When the stapes moves, it creates waves of pressure within the fluid-filled cochlea.