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Noise Induced Hearing Loss (NIHL): Causes & Prevention


  • Published: 2016-02-15 (Revised/Updated 2016-10-11) : Author: Thomas C. Weiss : Contact: Disabled World
  • Synopsis: Long lasting and loud sounds can damage sensitive structures in the inner ear and cause noise induced hearing loss (NIHL).

Each day, people experience sound in their environments such as the sound from radio and television, traffic and home appliances. Usually, these sound are at safe levels that do not damage a person's hearing. Yet sound may be harmful when they are too loud - even for a short period of time, or when they are both long-lasting and loud. The sounds might damage sensitive structures in a person's inner ear and cause noise induced hearing loss (NIHL).

Noise-induced hearing loss (NIHL) is defined as a hearing impairment resulting from exposure to high decibel sound that may exhibit as loss of a narrow range of frequencies, impaired cognitive perception of sound or other impairment, including hyperacusis or tinnitus. Long term exposure to sound levels over 80 dB can cause permanent hearing loss. Once lost, hearing cannot currently be restored in humans.

NIHL can be immediate, or it can take a long time before a person notices it. It may be temporary or permanent and it may affect one or both of a person's ears. Even if someone cannot tell that you are damaging your hearing, you might have difficulties with hearing in the future, such as an inability to understand other people when they speak; particularly in a noisy room or on the telephone. Despite the way it may affect someone one thing is for sure, noise induced hearing loss is something a person can prevent.

Exposure to harmful noise can happen at any age.

People of all ages - to include children, adolescents, young adults and seniors can develop NIHL. Around fifteen percent of people in America between the ages of twenty and sixty-nine, or twenty-six million Americans, experience hearing loss that might have been caused by exposure to noise either at work or during leisure activities. As many as sixteen percent of teenagers between the ages of twelve and nineteen have reported some level of hearing loss that may have been caused by loud noise according to a report from 2010 by the Centers for Disease Control and Prevention (CDC).

Causes of NIHL

NIHL can be caused by a one-time exposure to an intense impulse sound such as an explosion, or through continuous exposure to loud sounds over a long period of time, such as noise generated in a steel mill. Recreational activities that may place a person at risk for NIHL include:

Harmful noises at home might come from sources such as leaf blowers, lawnmowers and the use of power tools.

Sound is measured in units called, 'decibels.' Sounds of less than seventy-five decibels - even following long exposure, are not likely to cause hearing loss. Long or repeated exposure to sounds at or above eighty-five decibels; however, might cause hearing loss. The louder the sound, the shorter period of time it takes for a person to experience NIHL. What follows are the average decibel ratings of sounds that are familiar:

A person's distance from the source of the sound, as well as the length of time they are exposed to the sound, are also important factors in protecting their hearing. A good rule is to avoid noises that are too close, too loud, or which last too long.

How Noise Can Damage Your Hearing

In order to understand how loud noises may damage a person's hearing, we need to understand how people 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 person's brain via a complex series of steps which include:

The majority of NIHL is caused by the damage and eventual death of these hair cells. Unlike amphibian and bird hair cells - human hair cells do not grow back; they are gone for good.

Effects and Signs of NIHL

When a person is exposed to loud noise over an extended period of time, they might slowly begin to lose their hearing. Due to the damage from noise exposure being gradual the person may not notice it, or they may ignore the signs of hearing loss until they become more pronounced. Over a period of time, sounds might become muffled or distorted and the affected person may find it hard to understand what others are saying when they speak, or have to turn up the volume on their television. The damage from NIHL - in combination with the person's age, may lead to hearing loss severe enough that the person needs hearing aids to magnify the sounds around them and help them hear, communicate and participate more fully in everyday activities.

NIHL may also be caused by very loud bursts of sound, such as explosions or gunfire, which can rupture the person's eardrum or damage the bones in the person's middle ear. This kind of NIHL may be immediate and permanent. Exposure to loud noise may also cause tinnitus, which is a buzzing, ringing or roaring in the person's ears or head. Tinnitus may subside over time, although it may at times continue occasionally or constantly throughout the person's lifetime. Hearing loss and tinnitus can happen in one or both of a person's ears.

Sometimes, exposure to impulse or continuous loud noises causes a temporary hearing loss that disappears sixteen to forty-eight hours later. Recent research suggests; however, that even though the loss of hearing seems to disappear, there might be residual long-term damage to a person's hearing.

Preventing NIHL

NIHL is the only type of hearing loss that is entirely preventable. If people understand the hazards of noise and how to practice good hearing health, they can protect their hearing for life; here is how:

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