How We Hear : Summary
There are three main parts of the ear involved in the hearing process: the outer ear, the middle ear and the inner ear.

The hearing process begins when sound waves enter the outer ear and travel through the ear canal to the ear drum, causing it to vibrate. These vibrations travel through three tiny bones in the middle ear, called the ossicles. The ossicles cause the sound to be amplified before it enters the inner ear. The inner ear contains a fluid-filled cochlea that is lined with thousands of tiny hair cells. The fluid moves in waves along the entire length of the cochlea. As the fluid moves, approximately 12,000 hair cells bend. The frequency and intensity of the sound is determined by which hair cells bend. The action causes nerve impulses to travel up the auditory nerve to the brain for processing. These nerve impulses are the "language" that the brain can understand and convert into meaningful sounds.