U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES ∙ National Institutes of Health 

NIDCD Fact Sheet | Hearing and Balance 

Noise-Induced Hearing Loss 

What is noise-induced hearing loss? 

Every day, we experience sound in our environment, 

such as the sounds from television and radio, household 

appliances, and traffic. Normally, these sounds are at safe 

levels that don’t damage our hearing. But sounds can be 

harmful when they are too loud, even for a brief time, or 

when they are both loud and long-lasting. These sounds 

can damage sensitive structures in the inner ear and cause 

noise-induced hearing loss (NIHL). 

NIHL can be immediate or it can take a long time to be 

noticeable. It can be temporary or permanent, and it can 

affect one ear or both ears. Even if you can’t tell that you are 

damaging your hearing, you could have trouble hearing 

in the future, such as not being able to understand other 

people when they talk, especially on the phone or in a 

noisy room. Regardless of how it might affect you, one 

thing is certain: noise-induced hearing loss is something 

you can prevent. 

Who is affected by NIHL? 

Exposure to harmful noise can happen at any age. People 

of all ages, including children, teens, young adults, and 

older people, can develop NIHL. Approximately 15 percent 

of Americans between the ages of 20 and 69—or 26 

million Americans—have hearing loss that may have 

been caused by exposure to noise at work or in leisure 

activities. As many as 16 percent of teens (ages 12 to 19) 

have reported some hearing loss that could have been 

caused by loud noise, according to a 2010 report based 

on a survey from the Centers for Disease Control and 

Prevention (CDC). 

What causes NIHL? 

NIHL can be caused by a one-time exposure to an intense 

“impulse” sound, such as an explosion, or by continuous 

exposure to loud sounds over an extended period of time, 

such as noise generated in a woodworking shop. 

Recreational activities that can put you at risk for NIHL 

include target shooting and hunting, snowmobile riding, 

listening to MP3 players at high volume through earbuds 

or headphones, playing in a band, and attending loud 

concerts. Harmful noises at home may come from 

sources including lawnmowers, leaf blowers, and 

woodworking tools. 

Sound is measured in units called decibels. Sounds of less 

than 75 decibels, even after long exposure, are unlikely to 

cause hearing loss. However, long or repeated exposure 

to sounds at or above 85 decibels can cause hearing loss. 

The louder the sound, the shorter the amount of time it 

takes for NIHL to happen. 

Here are the average decibel ratings of some familiar 

sounds: 

} The humming of a refrigerator 45 decibels 

} Normal conversation 60 decibels 

} Noise from heavy city traffic 85 decibels 

} Motorcyles 95 decibels 

} An MP3 player at maximum volume 105 decibels 

} Siren 120 decibels 

} Firecrackers and guns 150 decibels 

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Your distance from the source of the sound and the 

length of time you are exposed to the sound are also 

important factors in protecting your hearing. A good rule 

of thumb is to avoid noises that are too loud, too close, or 

last too long. 

How can noise damage our hearing? 

Parts of the inner ear 

Credit: NIH Medical Arts 

To understand how loud noises can damage our hearing, 

we have to understand how we hear. Hearing depends 

on a series of events that change sound waves in the air 

into electrical signals. Our auditory nerve then carries these 

signals to the brain through a complex series of steps. 

1.	 Sound waves enter the outer ear and travel through 

a narrow passageway called the ear canal, which 

leads to the eardrum. 

2.	 The eardrum vibrates from the incoming sound 

waves and sends these vibrations to three tiny 

bones in the middle ear. These bones are called the 

malleus, incus, and stapes. 

3.	 The bones in the middle ear couple the sound 


vibrations from the air to fluid vibrations in the 


cochlea of the inner ear, which is shaped like a snail 

and filled with fluid. An elastic partition runs from 

the beginning to the end of the cochlea, splitting it 

into an upper and lower part. This partition is called 

the basilar membrane because it serves as the base, 

or ground floor, on which key hearing structures sit. 

4.	 Once the vibrations cause the fluid inside the 

cochlea to ripple, a traveling wave forms along the 

basilar membrane. Hair cells—sensory cells sitting on 

top of the basilar membrane—ride the wave. 

5.	 As the hair cells move up and down, microscopic 

hair-like projections (known as stereocilia) that perch 

on top of the hair cells bump against an overlying 

structure and bend. Bending causes pore-like 

channels, which are at the tips of the stereocilia, to 

open up. When that happens, chemicals rush into 

the cell, creating an electrical signal. 

6.	 The auditory nerve carries this electrical signal to 

the brain, which translates it into a sound that we 

recognize and understand. 

Stereocilia perch atop sensory hair cells in the inner ear. 

Credit: Yoshiyuki Kawashima 

Most NIHL is caused by the damage and eventual death 

of these hair cells. Unlike bird and amphibian hair cells, 

human hair cells don’t grow back. They are gone 

for good. 

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What are the effects and signs 

of NIHL? 

When you are exposed to loud noise over a long period of 

time, you may slowly start to lose your hearing. Because 

the damage from noise exposure is usually gradual, you 

might not notice it, or you might ignore the signs of 

hearing loss until they become more pronounced. Over 

time, sounds may become distorted or muffled, and you 

might find it difficult to understand other people when 

they talk or have to turn up the volume on the television. 

The damage from NIHL, combined with aging, can lead 

to hearing loss severe enough that you need hearing 

aids to magnify the sounds around you to help you hear, 

communicate, and participate more fully in daily activities. 

NIHL can also be caused by extremely loud bursts of 

sound, such as gunshots or explosions, which can rupture 

the eardrum or damage the bones in the middle ear. This 

kind of NIHL can be immediate and permanent. 

Loud noise exposure can also cause tinnitus—a ringing, 

buzzing, or roaring in the ears or head. Tinnitus may 

subside over time, but can sometimes continue constantly 

or occasionally throughout a person’s life. Hearing loss 

and tinnitus can occur in one or both ears. 

Sometimes exposure to impulse or continuous loud noise 

causes a temporary hearing loss that disappears 16 to 

48 hours later. Recent research suggests, however, that 

although the loss of hearing seems to disappear, there 

may be residual long-term damage to your hearing. 

Can NIHL be prevented? 

NIHL is the only type of hearing loss that is completely 

preventable. If you understand the hazards of noise and 

how to practice good hearing health, you can protect 

your hearing for life. Here’s how: 

} Know which noises can cause damage (those at or 

above 85 decibels). 

} Wear earplugs or other protective devices when involved 

in a loud activity (activity-specific earplugs and earmuffs 

are available at hardware and sporting goods stores). 

} If you can’t reduce the noise or protect yourself from it, 

move away from it. 

} Be alert to hazardous noises in the environment. 

} Protect the ears of children who are too young to 

protect their own. 

} Make family, friends, and colleagues aware of the 

hazards of noise. 

} Have your hearing tested if you think you might have 

hearing loss. 

What research is being done on NIHL? 

The National Institute on Deafness and Other 

Communication Disorders (NIDCD) supports research 

on the causes, diagnosis, treatment, and prevention of 

hearing loss. NIDCD-supported researchers have helped 

to identify some of the many genes important for hair-cell 

development and function and are using this knowledge 

to explore new treatments for hearing loss. 

Researchers are also looking at the protective properties 

of supporting cells in the inner ear, which appear to be 

capable of lessening the damage to sensory hair cells 

upon exposure to noise. 

The NIDCD sponsors It’s a Noisy Planet. Protect Their 

Hearing®, a national public education campaign to 

increase awareness among parents of preteens about 

the causes and prevention of NIHL. Armed with this 

information, parents, teachers, school nurses, and other 

adults can encourage children to adopt healthy 

hearing habits. 

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Where can I find additional 

information about noise-induced 

hearing loss? 

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. Visit the NIDCD website at 

http://www.nidcd.nih.gov to search the directory. 

Use the following keywords to help you find 

organizations that can answer questions and provide 

printed or electronic information on NIHL: 

} Noise-induced hearing loss 

} Hard of hearing 

} Tinnitus 

More NIDCD fact sheets on Hearing and Balance: 

} Age-Related Hearing Loss 

} How Loud Is Too Loud? How Long Is Too Long? 

} Otosclerosis 

} Ten Ways to Recognize Hearing Loss 

} Tinnitus 

Visit the NIDCD website at http://www.nidcd.nih.gov 

to read, print, or download fact sheets. 

For more information, additional addresses and phone 

numbers, or a printed list of organizations, contact us at: 

The 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 

Email: nidcdinfo@nidcd.nih.gov 

http://www.nidcd.nih.gov

 Follow the NIDCD on Twitter at @NIDCD 

The NIDCD supports and conducts research and 

research training on the normal and disordered 

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

speech, and language and provides health information, 

based upon scientific discovery, to the public. 

Noise-Induced Hearing Loss 

NIH Pub. No. 14-4233 

Updated March 2014 

NIH...Turning Discovery Into Health®