Hearing and Hearing Test
Hearing is the ability to process sounds. For this function to work properly, the brain and the ears are required to work together. Hearing evaluations can help to determine if these two organs are functioning correctly for processing sounds. If a patient is having difficulty hearing, hearing evaluations can aid in verifying if the hearing loss is a permanent issue or if it is a medically treatable issue. To fully understand this process, it is important to understand how these organs interact for hearing.
Sound travels through the air in the form of sound waves. The ear is similar to a funnel which allows the sounds waves to travel through the ear canal and vibrate the eardrum. The middle ear bones, which are the smallest bones in the human body, are attached to the eardrum and will send these vibrations to the cochlea in the inner ear. The cochlea, which is fluid filled, is made up a two parts separated by an elastic membrane called the basilar membrane. The important structures for hearing called hair cells are housed on the basilar membrane. The sound wave vibrations from the middle ear bones will cause the fluid in the cochlea to move. This movement will cause a wavelike ripple along the basilar membrane causing the hair cells to move up and down. This movement of the hair cells will initiate a chemical reaction which creates an electrical signal. This electrical signal is then sent to the auditory nerve which then sends the signal to the brain. The brain then turns the electrical signal into sound that we can identify and understand.
The purpose of conducting a hearing test is to determine if a person has hearing loss. Most adults and children (over the age of three) can be evaluated using pure tone audiometry. This testing encompasses sitting inside a sound booth with foam inserts inserted into the patient’s ear canals. The patient will then press a button when they are able to hear a tone which is being presented by the doctor. The doctor will determine the lowest level of where the patient can hear the tone. The tones presented usually range from 250 Hz up to 8000 Hz. The doctor then plots the results on an audiogram. The testing should also include speech awareness testing and word recognition testing. This evaluates what sound level a person can understand speech and it also evaluates how well a person can understand speech without visual cues.
For younger children (under the age of three) behavioral hearing tests and tests of auditory function maybe recommended. This includes Behavioral Observation Audiometry (BOA), Visual Reinforcement Audiometry (VRA), and Conditioned Play Audiometry (CPA). Tests of auditory function may include otoacoustic emission (OAE) and Auditory Brainstem Response (ABR) testing.