Hearing Loss Overview

To understand hearing loss it is important to understand how normal hearing takes place. There are 2 different pathways by which sound waves produce the sensation of hearing: air conduction and bone conduction.

• In air conduction, sound waves move through the air in the external auditory canal (the "ear canal" between the outside air and your eardrum). The sound waves hit the tympanic membrane (eardrum) and cause the tympanic membrane to move.

• The bones in the middle ear are connected to the tympanic membrane. When the tympanic membrane moves, this movement is transmitted to the bones. These 3 bones are called the malleus, the incus, and the stapes. Movement of the stapes causes pressure waves in the fluid-filled inner ear.

• The cochlea is an inner ear structure surrounded by fluid. It contains multiple small hairs. Pressure waves in the fluid cause the hairs to move. This movement stimulates the auditory nerve. Different frequencies of noises stimulate different hairs on the cochlea, which translate to the sensation of sounds of different pitch. 

• Hearing by bone conduction occurs when a sound wave or other source of vibration causes the bones of the skull to vibrate. These vibrations are transmitted to the fluid surrounding the cochlea and hearing results.