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 3 middle ear bones (the malleus, incus, and stapes) and transmit that sound into the fluid filled inner ear where they stimulate tiny hair cells, causing them to bend. The hair cells create signals that are sent to the brain to be interpreted as sound. In order to test a person’s hearing, an audiologist, or hearing specialist, will perform a series of hearing tests. Today these tests are performed with a machine called an audiometer. The audiometer delivers sounds at various, exactly measured frequencies, and at varying loudness levels. An audiogram is a figure showing the lowest levels that a person can hear sounds at each frequency tested. People are also often tested to determine how well the eardrum moves to conduct sound (tympanometry), the quietest sound that can trigger a reflex of the middle ear bones in order to hear (acoustic reflex testing), how flexible the hair cells in the inner ear are (otoacoustic emissions), and how well they can understand spoken words (speech audiometry). The results of these tests will help your audiologist determine the presence and severity of possible hearing loss.