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Noise, Ears & Hearing
Some warning signs of dangerous noise levels are the need to shout over background noise to be heard, noise that hurts the ears, ringing in the ears or temporary hearing loss after exposure to noise. Continued exposure to loud noise can gradually damage your hearing as severely as a singe explosion close to the ear. Noise can accelerate the normal deterioration that occurs as you age. The best treatment for nerve damage is prevention. Earplugs can reduce sound intensity by 10 to 15 decibels. A good pair of earmuffs can reduce it by 20 to 30 decibels. Even though it may seem inconvenient to wear earplugs or earmuffs, these devices can protect your ears from noise pollution. They should be worn whenever you work with machinery, cut the grass or shoot a gun. The Occupational Safety and Health Administration (OSHA) strictly regulates the amount of noise exposure and the length of exposure allowed in the workplace. OSHA requires mandatory ear protection for employees exposed to noise above a certain level. If a person has already suffered permanent damage and hearing loss, hearing aids can be very helpful. Ringing in the ears can be caused by exposure to loud noises, but loud ringing in only one ear should be investigated by an ear specialist to rule out other causes, such as a benign growth on the hearing nerve. What is noise-induced hearing loss (NIHL)?Every day, we experience sound in our environment, such as the sounds from television and radio, household appliances, and traffic. Normally, we hear these sounds at safe levels that do not affect our hearing. However, when we are exposed to harmful noise—sounds that are too loud or loud sounds that last a long time—sensitive structures in our 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, our hair cells cannot grow back. What sounds cause 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. 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 approximately 60 decibels, and the noise from heavy city traffic can reach 85 decibels. Sources of noise that can cause NIHL 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. Sounds of less than 75 decibels, even after long exposure, are unlikely to cause hearing loss. Although being aware of decibel levels is an important factor in protecting one’s hearing, distance from the source of the sound and duration of exposure to the sound are equally important. A good rule of thumb is to avoid noises that are “too loud” and “too close” or that last “too long.” What are the effects of NIHL? Exposure to harmful sounds causes damage to the hair cells as well as the auditory, or hearing, nerve (see figure). 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, and tinnitus may continue constantly or occasionally throughout a lifetime. Continuous exposure to loud noise also can damage the structure of hair cells, resulting in hearing loss and tinnitus, although the process occurs more gradually than for impulse noise. Exposure to impulse and continuous noise may cause only a temporary hearing loss. If a person regains hearing, the temporary hearing loss is called a temporary threshold shift. The temporary threshold shift largely disappears 16 to 48 hours after exposure to loud noise. You can prevent NIHL from both impulse and continuous noise by regularly using hearing protectors such as earplugs or earmuffs. Scientists believe that, depending on the type of noise, the pure force of vibrations from the noise can cause hearing loss. Recent studies also show that exposure to harmful noise levels triggers the formation of molecules inside the ear that damage hair cells and result in NIHL. These destructive molecules play an important role in hearing loss in children and adults who listen to loud noise for too long. Who is affected by NIHL? 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 high frequency hearing loss that may have been caused by exposure to loud sounds or noise at work or in leisure activities. Recreational activities that can put someone at risk for NIHL include target shooting and hunting, snowmobile riding, woodworking and other hobbies, playing in a band, and attending rock concerts. Harmful noises at home may come from lawnmowers, leaf blowers, and shop tools. Other ENT Conditions
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Loud noises are a part of life. The sound level of heavy traffic or an alarm clock is about 80 decibels. A chain saw or pneumatic drill registers about 100 decibels. A rock concert, thunder clap, or rifle blast can generate sound ranging from 120 to 140 decibels.
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