hearing

balance

NIDCD Fact Sheet

Hearing Aids

U.S. DEPARTMENT OF HEALTH & HUMAN SERVICES ∙ NATIONAL INSTITUTES OF HEALTH ∙ NATIONAL INSTITUTE ON DEAFNESS AND OTHER COMMUNICATION DISORDERS

What is a hearing aid?

A hearing aid is a small electronic device that you 

wear in or behind your ear. It makes some sounds 

louder so that a person with hearing loss can listen, 

communicate, and participate more fully in daily 

activities. A hearing aid can help people hear more in 

both quiet and noisy situations. However, only about 

one out of five people who would benefit from a 

hearing aid actually uses one. 

A hearing aid has three basic parts: a microphone, 

amplifier, and speaker. The hearing aid receives sound 

through a microphone, which converts the sound 

waves to electrical signals and sends them to an 

amplifier. The amplifier increases the power of the 

signals and then sends them to the ear through a 

speaker.

How can hearing aids help?

Hearing aids are primarily useful in improving the 

hearing and speech comprehension of people who 

have hearing loss that results from damage to the 

small sensory cells in the inner ear, called hair cells. 

This type of hearing loss is called sensorineural hearing 

loss. The damage can occur as a result of disease, 

aging, or injury from noise or certain medicines. 

A hearing aid magnifies sound vibrations entering the 

ear. Surviving hair cells detect the larger vibrations and 

convert them into neural signals that are passed along 

to the brain. The greater the damage to a person’s hair 

cells, the more severe the hearing loss, and the greater 

the hearing aid amplification needed to make up the 

difference. However, there are practical limits to the 

amount of amplification a hearing aid can provide. In

addition, if the inner ear is too damaged, even large 

vibrations will not be converted into neural signals. In 

this situation, a hearing aid would be ineffective.

Styles of hearing aids

Behind-the-ear (BTE)

Receiver in ear canal

 “Mini” BTE

In-the-ear (ITE) In-the-canal (ITC)

Completely-in-canal 

(CIC)

Credit: NIH Medical Arts
How can I find out if I need a hearing 

aid?

If you think you might have hearing loss and could 

benefit from a hearing aid, visit your physician, who 

may refer you to an otolaryngologist or audiologist. 

An otolaryngologist is a physician who specializes in 

ear, nose, and throat disorders and will investigate the 

cause of the hearing loss. An audiologist is a hearing 

health professional who identifies and measures 

hearing loss and will perform a hearing test to assess 

the type and degree of loss. 

Are there different styles of hearing 

aids? 

There are three basic styles of hearing aids. The styles 

differ by size, their placement on or inside the ear, and 

the degree to which they amplify sound (see figure on 

page 1).

•	 Behind-the-ear (BTE) hearing aids consist of a hard 

plastic case worn behind the ear and connected 

to a plastic earmold that fits inside the outer ear. 

The electronic parts are held in the case behind the 

ear. Sound travels from the hearing aid through 

the earmold and into the ear. BTE aids are used by 

people of all ages for mild to profound hearing loss. 

A new kind of BTE aid is an open-fit hearing aid. 

Small, open-fit aids fit behind the ear completely, 

with only a narrow tube inserted into the ear canal, 

enabling the canal to remain open. For this reason, 

open-fit hearing aids may be a good choice for 

people who experience a buildup of earwax, since 

this type of aid is less likely to be damaged by such 

substances. In addition, some people may prefer 

the open-fit hearing aid because their perception of 

their voice does not sound “plugged up.”

• In-the-ear (ITE) hearing aids fit completely inside 

the outer ear and are used for mild to severe 

hearing loss. The case holding the electronic 

components is made of hard plastic. Some ITE 

aids may have certain added features installed, 

such as a telecoil. A telecoil is a small magnetic 

coil that allows users to receive sound through the 

circuitry of the hearing aid, rather than through 

its microphone. This makes it easier to hear 

conversations over the telephone. A telecoil also 

helps people hear in public facilities where a special 

sound system, called an induction loop system, 

has been installed. Induction loop systems can be 

found in many churches, schools, airports, and 

auditoriums. ITE aids usually are not worn by young 

children because the casings need to be replaced 

often as the ear grows. 

• Canal aids fit into the ear canal and are available 

in two styles. The in-the-canal (ITC) hearing aid is 

made to fit the size and shape of a person’s ear 

canal. A completely-in-canal (CIC) hearing aid is 

nearly hidden in the ear canal. Both types are used 

for mild to moderately severe hearing loss. 

Because they are small, canal aids may be difficult 

for a person to adjust and remove. In addition, 

canal aids have less space available for batteries 

and additional devices, such as a telecoil. They 

usually are not recommended for young children 

or for people with severe to profound hearing loss 

because their reduced size limits their power and 

volume. 

Do all hearing aids work the same way?

Hearing aids work differently depending on the 

electronics used. The two main types of electronics are 

analog and digital. 

Analog aids convert sound waves into electrical 

signals, which are amplified. Analog/adjustable hearing 

aids are custom built to meet the needs of each 

user. The aid is programmed by the manufacturer 

according to the specifications recommended by your 

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NIDCD Fact Sheet

Hearing Aids

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audiologist. Analog/programmable hearing aids have 

more than one program or setting. An audiologist 

can program the aid using a computer, and the 

user can change the program for different listening 

environments—from a small, quiet room to a crowded 

restaurant to large, open areas, such as a theater or 

stadium. Analog/programmable circuitry can be used 

in all types of hearing aids. Analog aids usually are less 

expensive than digital aids. 

Digital aids convert sound waves into numerical 

codes, similar to the binary code of a computer, before 

amplifying them. Because the code also includes 

information about a sound’s pitch or loudness, the 

aid can be specially programmed to amplify some 

frequencies more than others. Digital circuitry gives 

an audiologist more flexibility in adjusting the aid to 

a user’s needs and to certain listening environments. 

These aids also can be programmed to focus on 

sounds coming from a specific direction. Digital 

circuitry can be used in all types of hearing aids. 

Which hearing aid will work best for 

me?

The hearing aid that will work best for you depends on 

the kind and severity of your hearing loss. If you have 

a hearing loss in both of your ears, two hearing aids 

are generally recommended because two aids provide 

a more natural signal to the brain. Hearing in both ears 

also will help you understand speech and locate where 

the sound is coming from. 

You and your audiologist should select a hearing aid 

that best suits your needs and lifestyle. Price is also a 

key consideration because hearing aids range from 

hundreds to several thousand dollars. Similar to other 

equipment purchases, style and features affect cost. 

However, don’t use price alone to determine the best 

hearing aid for you. Just because one hearing aid is 

more expensive than another does not necessarily 

mean that it will better suit your needs.

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A hearing aid will not restore your normal hearing. 

With practice, however, a hearing aid will increase 

your awareness of sounds and their sources. You 

will want to wear your hearing aid regularly, so 

select one that is convenient and easy for you to 

use. Other features to consider include parts or 

services covered by the warranty, estimated schedule 

and costs for maintenance and repair, options and 

upgrade opportunities, and the hearing aid company’s 

reputation for quality and customer service. 

What questions should I ask before 

buying a hearing aid?

Before you buy a hearing aid, ask your audiologist 

these important questions: 

• What features would be most useful to me?

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•

•		

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What is the total cost of the hearing aid? Do the 

benefits of newer technologies outweigh the higher 

costs? 

Is there a trial period to test the hearing aids? 

(Most manufacturers allow a 30- to 60-day trial 

period during which aids can be returned for a 

refund.) What fees are nonrefundable if the aids are 

returned after the trial period?

How long is the warranty? Can it be extended? 

Does the warranty cover future maintenance and 

repairs? 

Can the audiologist make adjustments and provide 

servicing and minor repairs? Will loaner aids be 

provided when repairs are needed? 

What instruction does the audiologist provide?

How can I adjust to my hearing aid?

Hearing aids take time and patience to use successfully. Wearing your aids regularly will help you adjust 

to them.
Become familiar with your hearing aid’s features. 

With your audiologist present, practice putting in and 

taking out the aid, cleaning it, identifying right and 

left aids, and replacing the batteries. Ask how to test 

it in listening environments where you have problems 

with hearing. Learn to adjust the aid’s volume and to 

program it for sounds that are too loud or too soft. 

Work with your audiologist until you are comfortable 

and satisfied.

You may experience some of the following problems 

as you adjust to wearing your new aid.

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•

My hearing aid feels uncomfortable. Some 

individuals may find a hearing aid to be slightly 

uncomfortable at first. Ask your audiologist how 

long you should wear your hearing aid while you 

are adjusting to it.

My voice sounds too loud. The “plugged-up” 

sensation that causes a hearing aid user’s voice to 

sound louder inside the head is called the occlusion 

effect, and it is very common for new hearing 

aid users. Check with your audiologist to see if a 

correction is possible. Most individuals get used to 

this effect over time.

I get feedback from my hearing aid. A whistling 

sound can be caused by a hearing aid that does not 

fit or work well or is clogged by earwax or fluid. See 

your audiologist for adjustments. 

I hear background noise. A hearing aid does not 

completely separate the sounds you want to hear 

from the ones you do not want to hear. Sometimes, 

however, the hearing aid may need to be adjusted. 

Talk with your audiologist.

I hear a buzzing sound when I use my cell 

phone. Some people who wear hearing aids 

or have implanted hearing devices experience 

problems with the radio frequency interference 

caused by digital cell phones. Both hearing aids 

and cell phones are improving, however, so these 

problems are occurring less often. When you are 

being fitted for a new hearing aid, take your cell 

phone with you to see if it will work well with

the aid. 

How can I care for my hearing aid? 

Proper maintenance and care will extend the life of 

your hearing aid. Make it a habit to: 

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•

•

•

•

•

Keep hearing aids away from heat and moisture.

Clean hearing aids as instructed. Earwax and ear

drainage can damage a hearing aid.

Avoid using hairspray or other hair care products 

while wearing hearing aids.

Turn off hearing aids when they are not in use.

Replace dead batteries immediately.

Keep replacement batteries and small aids away 

from children and pets. 

Are new types of aids available?

Although they work differently than the hearing 

aids described above, implantable hearing aids are 

designed to help increase the transmission of sound 

vibrations entering the inner ear. A middle ear 

implant (MEI) is a small device attached to one of the 

bones of the middle ear. Rather than amplifying the 

sound traveling to the eardrum, an MEI moves these 

bones directly. Both techniques have the net result 

of strengthening sound vibrations entering the inner 

ear so that they can be detected by individuals with 

sensorineural hearing loss. 

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hearingbalance

NIDCD Fact Sheet

Hearing Aids
A bone-anchored hearing aid (BAHA) is a small device 

that attaches to the bone behind the ear. The device 

transmits sound vibrations directly to the inner ear 

through the skull, bypassing the middle ear. BAHAs are 

generally used by individuals with middle ear problems 

or deafness in one ear. Because surgery is required 

to implant either of these devices, many hearing 

specialists feel that the benefits may not outweigh

the risks.

Can I obtain financial assistance for a 

hearing aid?

Hearing aids are generally not covered by health 

insurance companies, although some do. For eligible 

children and young adults ages 21 and under, 

Medicaid will pay for the diagnosis and treatment of 

hearing loss, including hearing aids, under the Early 

and Periodic Screening, Diagnostic, and Treatment 

(EPSDT) service. Also, children may be covered by their 

state’s early intervention program or State Children’s 

Health Insurance Program (SCHIP).

Medicare does not cover hearing aids for adults; 

however, diagnostic evaluations are covered if they 

are ordered by a physician for the purpose of assisting 

the physician in developing a treatment plan. Since 

Medicare has declared the BAHA a prosthetic device 

and not a hearing aid, Medicare will cover the BAHA if 

other coverage policies are met. 

Some nonprofit organizations provide financial 

assistance for hearing aids, while others may help 

provide used or refurbished aids. Contact the National 

Institute on Deafness and Other Communication 

Disorders’ (NIDCD’s) Information Clearinghouse with 

questions about organizations that offer financial 

assistance for hearing aids.

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What research is being done on hearing 

aids?

Researchers are looking at ways to apply new signal 

processing strategies to the design of hearing aids. 

Signal processing is the method used to modify normal 

sound waves into amplified sound that is the best 

possible match to the remaining hearing for a hearing 

aid user. NIDCD-funded researchers also are studying 

how hearing aids can enhance speech signals to 

improve understanding. 

In addition, researchers are investigating the use 

of computer-aided technology to design and 

manufacture better hearing aids. Researchers also are 

seeking ways to improve sound transmission and to 

reduce noise interference, feedback, and the occlusion 

effect. Additional studies focus on the best ways to 

select and fit hearing aids in children and other groups 

whose hearing ability is hard to test. 

Another promising research focus is to use lessons 

learned from animal models to design better 

microphones for hearing aids. NIDCD-supported 

scientists are studying the tiny fly Ormia ochracea

because its ear structure allows the fly to determine 

the source of a sound easily. Scientists are using 

the fly’s ear structure as a model for designing 

miniature directional microphones for hearing aids. 

These microphones amplify the sound coming from 

a particular direction (usually the direction a person 

is facing), but not the sounds that arrive from other 

directions. Directional microphones hold great promise 

for making it easier for people to hear a single 

conversation, even when surrounded by other noises 

and voices. 
hearing, balance

smell, tastevoice, speech, language

NIDCD supports and conducts research and research training on the 

normal and disordered processes of hearing, balance, smell, taste, 

voice, speech, and language and provides health information, based 

upon scientific discovery, to the public.

Where can I find more information?

The NIDCD maintains a directory of organizations that 

provide information on the normal and disordered 

processes of hearing, balance, taste, smell, voice, 

speech, and language. Please see the list of 

organizations at www.nidcd.nih.gov/directory.

Use the following keywords to help you search for 

organizations that can answer questions and provide 

printed or electronic information on hearing aids:

•

•

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Hearing aids

Assistive listening device

Assistive technology

For more information, additional addresses and phone 

numbers, or a printed list of organizations, contact:

NIDCD Information Clearinghouse

1 Communication Avenue

Bethesda, MD 20892-3456

Toll-free Voice: (800) 241-1044

Toll-free TTY: (800) 241-1055

Fax: (301) 770-8977

E-mail: nidcdinfo@nidcd.nih.gov NIDCD Fact Sheet: Hearing Aids

NIH Publication No. 08-4340

Updated November 2008

For more information, contact:

NIDCD Information Clearinghouse

1 Communication Avenue

Bethesda, MD 20892-3456

Toll-free Voice: (800) 241-1044

Toll-free TTY: (800) 241-1055

Fax: (301) 770-8977

E-mail: nidcdinfo@nidcd.nih.gov

Internet: www.nidcd.nih.gov

The NIDCD Information Clearinghouse is a service of the 

National Institute on Deafness and Other Communication

Disorders, National Institutes of Health, U.S. Department 

of Health and Human Services.

NIH. . .Turning Discovery Into Health

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