Noise is all around you, from televisions and radios to lawn mowers and washing machines. Normally, you hear these sounds at safe levels that don't affect hearing. But sounds that are too loud or loud sounds over a long time are harmful. They can damage sensitive structures of the inner ear and cause noise-induced hearing loss.

More than 30 million Americans are exposed to hazardous sound levels on a regular basis. Hazardous sound levels are louder than 80 decibels. That's not as loud as traffic on a busy street. Listening to loud music, especially on headphones, is a common cause of noise-induced hearing loss. You can protect your hearing by

• Keeping the volume down when listening to music
• Wearing earplugs when using loud equipment

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.

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.

It's frustrating to be unable to hear well enough to enjoy talking with friends or family. Hearing disorders make it hard, but not impossible, to hear. They can often be helped. Deafness can keep you from hearing sound at all.

What causes hearing loss? Some possibilities are

• Heredity
• Diseases such as ear infections and meningitis
• Trauma
• Certain medicines
• Long-term exposure to loud noise
• Aging

There are two main types of hearing loss. One happens when your inner ear or auditory nerve is damaged. This type is usually permanent. The other kind happens when sound waves cannot reach your inner ear. Earwax build-up, fluid, or a punctured eardrum can cause it. Treatment or surgery can often reverse this kind of hearing loss.

Untreated, hearing problems can get worse. If you have trouble hearing, you can get help. Possible treatments include hearing aids, cochlear implants, special training, certain medicines, and surgery.

Occupational hearing loss may result from an acute traumatic injury, but it is far more likely to develop gradually as a result of chronic exposure to ototraumatic (damaging to the ear or hearing process) agents. Noise is the most important occupational cause of hearing loss, but solvents, metals, asphyxiants, and heat may also play a role. Exposure to noise combined with other agents can result in hearing losses greater than those resulting from exposure to noise or other agents alone. Research is needed to define further the causal contributions of these hazards (alone or in combination) and to implement and evaluate methods for early detection and hearing conservation programs.

Occupational hearing loss is the most common occupational disease in the United States: it is so common that it is often accepted as a normal consequence of employment. More than 30 million workers are exposed to hazardous noise, and an additional 9 million are at risk from other ototraumatic agents. Occupational hearing loss knows no boundaries with respect to industries. Any worker, young or old, male or female, risks hearing loss when exposed to ototraumatic agents. Once the loss is acquired, it is irreversible.

Although noise-induced occupational hearing loss is the most common occupational disease and is the second most self-reported occupational illness or injury, it has not been possible to create a sense of urgency about this problem. Efforts to prevent occupational hearing loss have been hindered because the problem is insidious and occurs without pain or obvious physical abnormalities in affected workers.

Problems created by occupational hearing loss include the following: (1) reduced quality of life because of social isolation and unrelenting tinnitus (ringing in the ears), (2) impaired communication with family members, the public, and coworkers, (3) diminished ability to monitor the work environment (warning signals, equipment sounds, etc.), (4) lost productivity and increased accidents resulting from impaired communication and isolation, and (5) expenses for workers’ compensation and hearing aids.

Because no national surveillance or injury-reporting system exists, no generalizable data are available regarding the economic impact of occupational hearing loss.

Occupational health problems occur at work or because of the kind of work you do. These problems can include

• Cuts, broken bones, sprains, and strains
• Loss of limbs
• Repetitive motion disorders
• Hearing problems caused by exposure to noise
• Vision problems
• Illness caused by breathing, touching, or swallowing unsafe substances
• Illness caused by exposure to radiation
• Exposure to germs in health care settings

Good job safety and prevention practices can reduce your risk of these problems. Try to stay fit, reduce stress, set up your work area properly, and use the right equipment and gear.

What is Noise Pollution?

The traditional definition of noise is “unwanted or disturbing sound”. Sound becomes unwanted when it either interferes with normal activities such as sleeping, conversation, or disrupts or diminishes one’s quality of life. The fact that you can’t see, taste or smell it may help explain why it has not received as much attention as other types of pollution, such as air pollution, or water pollution. The air around us is constantly filled with sounds, yet most of us would probably not say we are surrounded by noise. Though for some, the persistent and escalating sources of sound can often be considered an annoyance. This “annoyance” can have major consequences, primarily to one’s overall health.

Health Effects

Noise pollution adversely affects the lives of millions of people. Studies have shown that there are direct links between noise and health. Problems related to noise include stress related illnesses, high blood pressure, speech interference, hearing loss, sleep disruption, and lost productivity. Noise Induced Hearing Loss (NIHL) is the most common and often discussed health effect, but research has shown that exposure to constant or high levels of noise can cause countless adverse health affects.

Protection from Noise

Individuals can take many steps to protect themselves from the harmful effects of noise pollution. If people must be around loud sounds, they can protect their ears with hearing protection (e.g., ear plugs or ear muffs). There are various strategies for combating noise in your home, school, workplace, and the community.