How We Hear

The fascinating conversion of waves of sound pressure into voices, music and other everyday noises all occurs in our ears and brain. There are three components of our ears each with very basic purposes and functions:

• Outer Ear - This area acts as a funnel directing the sounds to the ear drum.
• Middle Ear - Here sound is changed from sound pressure waves to mechanical energy through the vibrating of the ear drum. The tiny bones attached to the ear drum then send it on to the...
• Inner Ear - It is in the fluid-filled labyrinth of the inner ear that electrical nerve impulses send sounds to the brain for interpretation.

Sound is transformed into mechanical energy by the tympanic membrane. It is then transmitted through the ossicles to the inner ear where it is changed again into hydraulic energy for transmission through the fluid-filled cochlea. The cochlea's hair cells are stimulated by the fluid waves and a neurochemical event takes place that excites the nerves of hearing. The physical characteristics of the original sound are preserved at every energy change along the way until this code becomes one the brain can recognize and process.

Hearing loss misleads our brain with a loss of audibility and introduces distortion into the message that reaches the brain. Changes in the effectiveness of the brain to process stimuli, from head trauma, disease, or from aging, can result in symptoms that mimic hearing loss. The ears and the brain combine in a remarkable way to process neural events into the sense of hearing. Perhaps it's fair to say that we "hear" with our brain, not with our ears!

In general terms, there are two types of hearing loss, conductive and sensorineural. A combination of both is also seen as a mixed hearing loss.