The world is a noisy place and our ears sometimes pay the price. Normally, we hear sounds, such as sounds from television and radio, household appliances, and traffic, at safe levels that do not affect our hearing. However, when exposed to harmful noise—sounds that are too loud or loud sounds that last a long time—sensitive structures in the inner ear can be damaged, causing noise-induced hearing loss (NIHL).

These sensitive structures, called hair cells, are small sensory cells that convert sound energy into electrical signals that travel to the brain. Once damaged, hair cells cannot grow back.

26 million American adults have permanently damaged their hearing due to exposure to loud noise at work or in leisure activities. Some examples are people who have worked a lifetime in a loud factory, served in a war, or listen to iPods turned up to high volume.

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What Sounds Cause Hearing Loss?

Noise induced hearing loss 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.

Sound is measured in units called decibels. On the decibel scale, an increase of 10 means that a sound is 10 times more intense, or powerful. To your ears, it sounds twice as loud. The humming of a refrigerator is 45 decibels, normal conversation is 60 decibels, and noise from city traffic can reach 85 decibels. Sources of noise that can cause hearing loss include motorcycles, firecrackers, and small firearms, all emitting sounds from 120 to 150 decibels. Long or repeated exposure to sounds at or above 85 decibels can cause hearing loss. The louder the sound, the shorter the time period before NIHL can occur.

Exposure to Loud Noise

Exposure to harmful sounds causes damage to the hair cells, auditory nerves. Impulse sound can result in immediate hearing loss that may be permanent. This kind of hearing loss may be accompanied by tinnitus—a ringing, buzzing, or roaring in the ears or head—which may subside over time. Hearing loss and tinnitus may be experienced in one or both ears.

What are the Symptoms?

When a person is exposed to loud noise over a long period of time, symptoms of hearing loss will increase gradually. Over time, the sounds a person hears may become distorted or muffled, and it may be difficult to understand speech.

If you suspect your loved has experienced hearing loss that is affecting their quality of life, have a medical examination by an otolaryngologist and a hearing test by an audiologist.

The National Institute on Deafness and Other Communication Disorders (NIDCD) is one of the Institutes that comprise the National Institutes of Health (NIH) and focuses on the prevention, detection, diagnosis and treatment of hearing loss and deafness.