Hearing Tests

 A hearing (audiometric) test is part of an ear examination that evaluates a person's ability to hear by measuring the ability of sound to reach the brain.

The sounds we hear start as vibrations of air, fluid, and solid materials in our environment. The vibrations produce sound waves, which vibrate at a certain speed (frequency) and have a certain height (amplitude). The vibration speed of a sound wave determines how high or low a sound is (pitch). The height of the sound wave determines how loud the sound is (volume).

Hearing happens when these sound waves travel through the ear and are turned into nerve impulses. These nerve impulses are sent to the brain, which "hears" them.

    Sound waves enter the ear camera through the ear canal (external ear) and strike the eardrum (tympanic membrane), which separates the ear canal and the middle ear.
    The eardrum vibrates, and the vibrations move to the bones of the middle ear. In response, the bones of the middle ear vibrate, magnifying the sound and sending it to the inner ear.
    The fluid-filled, curved space of the inner ear, sometimes called the labyrinth, contains the main sensory organ of hearing, the cochlea. Sound vibrations cause the fluid in the inner ear to move, which bends tiny hair cells (cilia) in the cochlea. The movement of the hair cells creates nerve impulses, which travel along the cochlear (auditory, or eighth cranial) nerve to the brain and are interpreted as sound.

Hearing tests help determine what kind of hearing loss you have by measuring your ability to hear sounds that reach the inner ear through the ear canal (air-conducted sounds) and sounds transmitted through the skull (bone-conducted sounds).

Most hearing tests ask you to respond to a series of tones or words. But there are some hearing tests that do not require a response.

Why It Is Done

Hearing tests may be done:

    To screen babies and young children for hearing problems that might interfere with their ability to learn, speak, or understand language. The United States Preventive Services Task Force recommends that all newborns be screened for hearing loss.1 All 50 states require newborn hearing tests for all babies born in hospitals. Also, many health organizations and doctors' groups recommend routine screening. Talk to your doctor about whether your child has been or should be tested.
    To screen children and teens for hearing loss. Hearing should be checked by a doctor at each well-child visit. In children, normal hearing is important for proper language development. Some speech, behavior, and learning problems in children can be related to problems with hearing. For this reason, many schools routinely provide hearing tests when children first begin school. The American Academy of Pediatrics recommends a formal hearing test at ages 4, 5, 6, 8, and 10 years.
    As part of a routine physical exam. In general, unless hearing loss is suspected, only a simple whispered speech test is done during a routine physical exam.
    To evaluate possible hearing loss in anyone who has noticed a persistent hearing problem in one or both ears or has had difficulty understanding words in conversation.
    To screen for hearing problems in older adults. Hearing loss in older adults is often mistaken for diminished mental capacity (for instance, if the person does not seem to listen or respond to conversation).
    To screen for hearing loss in people who are repeatedly exposed to loud noises or who are taking certain antibiotics, such as gentamicin.
    To find out the type and amount of hearing loss (conductive, sensorineural, or both). In conductive hearing loss, the movement of sound (conduction) is blocked or does not pass into the inner ear. In sensorineural hearing loss, sound reaches the inner ear, but a problem in the nerves of the ear or, in rare cases, the brain itself prevents proper hearing.

How To Prepare

Tell your doctor if you:

    Have recently been exposed to any painfully loud noise or to a noise that made your ears ring. Avoid loud noises for 16 hours prior to having a thorough hearing test.
    Are taking or have taken antibiotics that can damage hearing, such as gentamicin.
    Have had any problems hearing normal conversations or noticed any other signs of possible hearing loss.
    Have recently had a cold or ear infection.

Before beginning any hearing tests, the health professional may check your ear canals for earwax and remove any hardened wax, which can interfere with your ability to hear the tones or words during testing.

For tests in which you wear headphones, you will need to remove eyeglasses, earrings, or hair clips that interfere with the placement of the headphones. The health professional will press on each ear to find out whether the pressure from the headphones on your outer ear will cause the ear canal to close. If so, a thin plastic tube may be placed in the ear canal before the testing to keep your ear canal open. The headphones are then placed on your head and adjusted to fit.

If you are wearing hearing aids, you may be asked to remove them for some of the tests. You may be asked to shampoo your hair before you have auditory brain stem response (ABR) testing.

How It Is Done

Hearing tests can be done in an audiometry laboratory by a hearing specialist (audiologist) or in a doctor's office, a school, or the workplace by a nurse, health professional, psychologist, speech therapist, or audiometric technician.

Whispered speech test

In a whispered speech test, the health professional will ask you to cover the opening of one ear with your finger. The health professional will stand 1 ft (0.3 m) to 2 ft (0.6 m) behind you and whisper a series of words. You will repeat the words that you hear. If you cannot hear the words at a soft whisper, the health professional will keep saying the words more loudly until you can hear them. Each ear is tested separately.

Pure tone audiometry

Pure tone audiometry uses a machine called an audiometer to play a series of tones through headphones. The tones vary in pitch (frequency, measured in hertz) and loudness (intensity, measured in decibels). The health professional will control the volume of a tone and reduce its loudness until you can no longer hear it. Then the tone will get louder until you can hear it again. You signal by raising your hand or pressing a button every time you hear a tone, even if the tone you hear is very faint. The health professional will then repeat the test several times, using a higher-pitched tone each time. Each ear is tested separately. The headphones will then be removed, and a special vibrating device will be placed on the bone behind your ear. Again, you will signal each time you hear a tone.

Tuning fork tests

A tuning fork is a metal, two-pronged device that produces a tone when it vibrates. The health professional strikes the tuning fork to make it vibrate and produce a tone. These tests assess how well sound moves through your ear. Sometimes the tuning fork will be placed on your head or behind your ear. Depending on how you hear the sound, your health professional can tell if there is a problem with the nerves themselves or with sound getting to nerves.
Speech reception and word recognition tests

Speech reception and word recognition tests measure your ability to hear and understand normal conversation. In these tests, you are asked to repeat a series of simple words spoken with different degrees of loudness. A test called the spondee threshold test determines the level at which you can repeat at least half of a list of familiar two-syllable words (spondees).
Otoacoustic emissions (OAE) testing

Otoacoustic emissions (OAE) testing is often used to screen newborns for hearing problems. In this test, a small, soft microphone is placed in the baby's ear canal. Sound is then introduced through a small flexible probe inserted in the baby's ear. The microphone detects the inner's ear's response to the sound. This test cannot distinguish between conductive and sensorineural hearing loss.
Auditory brain stem response (ABR) testing

Auditory brain stem response (ABR) testing detects sensorineural hearing loss. In this test, electrodes are placed on your scalp and on each earlobe. Clicking noises are then sent through earphones. The electrodes monitor your brain's response to the clicking noises and record the response on a graph. This test is also called brain stem auditory evoked response (BAER) testing or auditory brain stem evoked potential (ABEP) testing.
How It Feels

There is normally no discomfort involved with a hearing test.
Risks

There are no risks associated with hearing tests.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

    Being unable to cooperate, follow directions, and understand speech well enough to respond during most tests. It may be difficult to conduct hearing tests on young children or on people who have physical or mental disabilities.
    Equipment problems, such as cracked or poorly fitting headphones or an uncalibrated audiometer, or background noise.
    Difficulty speaking or understanding the language of the tester.
    A recent cold or ear infection.
    Being around loud noises within 16 hours before the test.

What To Think About

    Other types of tests may be used to evaluate hearing. These tests include:
        Acoustic immitance testing (tympanometry and acoustic reflex testing). This 2- to 3-minute test measures how well the eardrum moves in response to sound. The soft tip of a small instrument is inserted into the ear canal and adjusted to achieve a tight seal. Sound and air pressure are then directed toward the eardrum. The test is not painful, but slight changes in pressure may be felt or the tone may be heard.
        Vestibular tests (falling and past-pointing tests). These tests can detect problems with areas of the inner ear that help control balance and coordination. During these tests, the person tries to maintain balance and coordination while moving the arms and legs in certain ways, standing on one foot, standing heel-to-toe, and performing other maneuvers with the eyes open and closed. The health professional will protect the person from falling, and no special preparation is needed.