To begin to understand hearing loss, it is first necessary to have a basic understanding of how we hear. There are two pathways by which sound waves produce the sensation of hearing:
Air Conduction - Sound waves collected by the outer ear move down the ear canal and hit the eardrum causing it to vibrate. The three bones in
the midlle ear (malleus, incus and stapes) are moved and the incus pumps in and out of the fluid in the inner ear or cochlea. This results in a fluid wave that corresponds to the sound wave
originally collected by the outer ear. The cochlea contains thousands of hair cells which are moved by the wave and when they are stimulated sufficiently a nerve impulse is created. This is
transported to the brain via the auditory nerve where it is interpreted as sound.
Bone Conduction - This occurs when a sound wave or other source of vibration cuses the bones of the skull to vibrate. These vibrations are
transmitted to the fluid in the cochlea and a wave is created which results in hearing.