Test Overview
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 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.
Talk to your doctor about any concerns you have about the need for a
hearing test, its risks, how it will be done, or what the results will mean. To
help you understand the importance of this test, fill out the
medical test information form(What is a PDF document?).
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.
Results
A hearing test is part of an ear
examination that evaluates a person's ability to hear.
Hearing test results| Normal | - You are able to hear whispered speech
accurately.
- You can hear tones at equal loudness in both
ears.
- You are able to repeat 90% to 95% of the words in a word
recognition test.
- The microphone detects emissions from the inner
ear in otoacoustic emissions (OAE) testing.
- The values recorded on
the graph for auditory brain stem response (ABR) testing show that the nerves
in the brain responsible for hearing are working normally.
|
|---|
| Abnormal | - You are not able to hear the whispers
during a whispered speech test, or you are able to hear with one ear but not
with the other.
- You hear the tone more loudly in one ear than in
the other.
- You can only hear certain sounds at high decibel
levels.
- You can hear sounds but you cannot understand
words.
- No emissions are detected from the inner ear in otoacoustic
emissions (OAE) testing.
- The values recorded on the graph for
auditory brain stem response (ABR) testing show that nerves in the brain
responsible for hearing are not functioning normally.
|
|---|
Sound is described in terms of
frequency and intensity. Your hearing threshold is how loud the sound of a
certain frequency must be for you to hear it.
- Frequency, or pitch (whether a sound is low or
high), is measured in vibrations per second, or hertz (Hz). The human ear can
normally hear frequencies from a very low rumble of 16 Hz to a high-pitched
whine of 20,000 Hz. The frequencies of normal conversations in a quiet place
are 500 Hz to 2,000 Hz.
- Intensity, or loudness, is measured in
decibels (dB). The normal range (threshold or lower limit) of hearing is 0 dB to
25 dB. For children, the normal range is 0 dB to 15 dB. Normal results shows that
you hear within these ranges in both ears.
The following table relates how loud a sound must be for a
person to hear it (hearing thresholds) to the degree of hearing loss for
adults:
Hearing loss table| Hearing threshold in
decibels (dB) | Degree of hearing
loss | Ability to hear
speech |
|---|
0–25 dB | None | No significant
difficulty |
26–40 dB | Mild | Difficulty with faint or
distant speech |
41–55 dB | Moderate | Difficulty with conversational
speech |
56–70 dB | Moderate to
severe | Speech must be loud;
difficulty with group conversation |
71–90 dB | Severe | Difficulty with loud speech;
understands only shouted or amplified speech |
91+ dB | Profound | May not understand amplified
speech |
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.
References
Citations
- U.S. Preventive Services Task Force (2008). Universal
screening for hearing loss in newborns: U.S. Preventive Services Task Force
Recommendation Statement. Pediatrics, 122(1): 143–148.
Also available online:
http://www.uspreventiveservicestaskforce.org/uspstf/uspsnbhr.htm.
Other Works Consulted
- American Academy of Pediatrics (2008). Recommendations
for preventive pediatric health care. In Bright Futures: Guidelines for Health Supervision of Infants, Children, and Adolescents,
3rd ed., p. 591. Elk Grove Village, IL: American Academy of Pediatrics. Also
available online:
http://brightfutures.aap.org/pdfs/Guidelines_PDF/20-Appendices_PeriodicitySchedule.pdf.
Credits
| By | Healthwise Staff |
|---|
| Primary Medical Reviewer | Sarah Marshall, MD - Family Medicine |
|---|
| Specialist Medical Reviewer | Steven T. Kmucha, MD - Otolaryngology |
|---|
| Last Revised | October 25, 2011 |
|---|