When sound waves reach the ear, they are gathered by the funnel-shaped outer ear and are channeled into the middle ear. At the entrance to the middle ear, sound waves hit the tympanic membrane, or eardrum. The resultant vibrations then travel through the middle ear and into the fluid filled inner ear where they are converted to signals that are sent to the brain. In order to test a person's hearing, an audiologist, or hearing specialist, will perform a series of hearing tests. Today these tests are often performed by using a combination of electronic equipment and a tuning fork. A tuning fork is a fork-like instrument made of aluminum or metal that makes a musical note when struck. The hearing test where a tuning fork is used is called a Rinne test. During this test, the tuning fork is struck and is held close to the ear but without touching the head. This tests whether sound waves are able to enter the ear and travel through the middle ear to reach the cochlea via air conduction, which is normal hearing. Next, the tuning fork will be struck and then held against the skull behind the ear. This test bypasses the conduction of sound through the outer and middle ear and focuses on the reception of vibrations by the cochlea via bone conduction. Through the use of this test combined with speech testing, an audiologist can determine whether a hearing impairment exists and what the cause may be.
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