1. Mechanism of Noise Induced Hearing Loss
Noise induced hearing loss (NIHL) is also referred to as sensorineural hearing loss. It happens in response to loud noise. It can occur suddenly or over time. Researchers now believe that the body forms free radicals in response to noise. Free radicals are harmful molecules that promote inflammation and damage to cells and blood vessels. Harmful sound can also damage the auditory nerve, leading to sensorineural hearing loss. The result can be permanent or temporary.
2. How We Process Sound
Sound enters the ear through the ear canal. Noise vibrates the eardrum, then the tiny bones of the middle ear (malleus, incus and stapes), rippling to the cochlea where the sound amplifies. The cochlea is a tiny bone in the inner ear that contains fluid. It allows vibration to travel like a wave through the ear. Tiny hair cells sit on top of a thin membrane in the cochlea. The cells open up in reaction to vibration carrying electrical signals to the auditory nerve, then to the brain for processing. The location of the hair cells, or cilia, identifies pitch and tone. Hair cells in the center of the ear detect low pitch sound, while those at the base of the cochlear membrane sense high-pitched sound.
3. We Are All at Risk for Noise Induced Hearing Loss
People of all ages can suffer from noise induced hearing loss. According to the National Institute on Deafness and Other Communication Disorders (NIDCD), twenty two million Americans may already have some form of permanent hearing loss. Chronic exposure to noise over 85 decibels can cause permanent hearing loss. Most people speak at about 60 decibels. Truck traffic, shop tools and lawnmowers generate about 90 decibels. Exposure to 90 decibels, longer than 8 hours a day, is considered harmful. When sound increases to 100 decibels, exposure for more than two hours can be damaging. Examples include chainsaws, snowmobiles and pneumatic drills.
Fifteen minutes of exposure to a 115-decibel rock concert is the maximum amount of noise your ear can safely handle. Exposure to a gun muzzle blast or jet engine requires protection, at 140 decibels. Firecrackers generate a noisy 180 decibels and your car stereo can crank out 154 decibels. The noise at your health club exposes you to approximately 120 decibels. A one-time sound, such as an explosion can cause hearing loss.
Exposure to over 100 decibels, over a period of five, twenty and forty years can reduce hearing by five, fourteen and nineteen decibels respectively. It may be difficult to determine who in the workplace is at risk for noise induced hearing loss. Some individuals are more sensitive than others. Noise may not be continuous. Many individuals move from one work area to another, reducing, then increasing noise exposure. Detailed standards have been set by the American National Standards Institute and the International Organization for Standards for the measurement of occupational noise.
The good news is that noise induced hearing loss is completely preventable.
4. Prevention and Treatment of Noise Induced Hearing Loss
Familiarize yourself with activities that lead to hearing loss. According to the NIDCD, it is a good idea to "avoid noises that are too loud and too close or that last too long."
Remain alert to the possibilities. Buy earplugs and use them when you are mowing the lawn, using power tools or engaging in activities that are known to cause hearing loss. Musicians and drummers can purchase special earplugs. Avoidance is the best means of protection. Teach your family and friends about the hazards of noise exposure.
Several organizations are actively working to get rid of unnecessary noise that not only impacts hearing, but possibly cardovascular health. The Noise Pollution Clearinghouse is an organization whose goal is to educate the public about the effects of noise pollution, and encourage stronger laws to help restore a more natural, healthy environment.
Hearing aids can be set to provide protection against additional hearing loss. Depending on the degree of hearing loss, medical treatment or surgery can be pursued. With patience, and professional guidance you and your family can learn to minimize the effects of noise induced hearing loss.
Studies are ongoing to find ways to minimize the effects of sudden noise exposure. Scientific advances recognize the potential of gene therapy to restore noise induced hearing loss. Gene therapy studies on animals have proven successful.
5. Symptoms and Diagnosis
You may not even be aware that you are experiencing a hearing problem. Symptoms can develop over time. Sounds become distorted. Eventually it is difficult to understand specific words. A hearing test will provide a diagnosis
