Noise Pollution and Hearing Loss
Exposed to endless music issuing from shopping malls, supermarkets, and elevators, sounds of vehicles on the streets or overhead aircraft, construction, seasonal ouoor home maintenance, and basement workshops, we live in a world where it is difficult to avoid noise, the most prevalent type of air pollution.
Hearing can be damaged by a one-time exposure to an intense "impulse" sound, such as a gunshot, explosion (think Baghdad), or by continuous exposure to loud sounds over an extended period of time, for example, in the workplace, a long motorcycle ride, and especially the "sound of mucous" in the form of MP3 players like iPods, TV, radio, and concerts-especially the rock variety. Here are some striking statistics:
- Three out of 4 children have an ear infection, by the time they are 3 years old. An unknown number of these result in hearing loss.
- Almost 10% of Americans, 30 million people have hearing impairment. Of these, 10 million Americans have suffered irreversible noise-induced hearing loss, and 30 million more are exposed to dangerous noise levels each day.
- 30% of people over 65 and 40% of those over 75 have hearing loss.
- At least 12 million Americans have tinnitus (ringing, buzzing, or roaring in one or both ears; it can also be a high pitched whining, hissing, humming, whistling sound, or a "whooshing" sound). usually the result of temporary or permanent hearing damage from excessive exposure to loud sound. Of these, at least 1 million experience it so severely that it interferes with their daily activities.
- Only 1 out of 5 people who could benefit from a hearing aid actually wears one.
The loudness of sound is measured in units called decibels, written "dB." Decibels are tricky to understand unless you know a bit about logarithms and acoustical physics. It turns out that a 5 dB noise reduction is about 30% quieter and represents a 50% decrease in the risk of hearing loss! Decibel examples: rustling leaves, 20 dB, humming of a refrigerator, 45 dB, normal conversation, 60 dB, busy traffic 75dB-85 dB, noisy restaurant, 80 dB- all with no time limit of exposure. But for average factory noise, 85 dB, it takes only 8 hours for noise-induced hearing loss (NIHL-this can can be temporary or permanent).
Other excess levels include: passing motorcycle, 90 dB-8 hours exposure for NIHL, subway train or diesel truck, 100 dB-2 hours exposure , helicopter and power mower 105 dB 1 hour, and, ranking with auto horn, propeller aircraft, and air raid siren, live rock music 90-130 dB 20 minutes to 8 hours. THRESHOLD OF PAIN is 140 dB, the danger level, from a jet engine. A rocket launching is 180 dB. 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. A good rule of thumb is to avoid noises that are "too loud" and "too close" or that last "too long."
Noise-induced hearing loss from impulse sound and loud continuous noise occurs primarily because of damage to the hair cells of the ear as well as the auditory, or hearing, nerve. This hearing loss can be temporary and disappear in 16 to 48 hours; it is often accompanied by tinnitus (see above). However, this so-called "temporary threshhold shift" is a serious warning sign and may lead to permanent increase in threshhold, i.e. long-lasting hearing damage. As the NIH reports, 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, leafblowers, and shop tools. As the NIH further states, noise-induced hearing loss (NIHL) is 100 percent preventable. To protect your hearing:
- Know which noises can cause damage (those at or above 85 decibels).
- Wear earplugs or other hearing protective devices when involved in a loud activity (special earplugs and earmuffs are available at hardware and sporting goods stores).
- Be alert to hazardous noise in the environment.
- Protect the ears of children who are too young to protect their own.
An excellent discussion on the subject of hearing can be seen at this web site by "Abelard" from which I quote a few pearls about listening to music:"The big culprits arenít the devices themselves [iPods and MP3 players], but the tiny "ear bud" style headphones that the music players use. The earbuds are even more likely to cause hearing loss than the muff-type earphones that were used on Walkman and portable CD players. ...On average, the smaller [the headphones] were, the higher their output levels at any given volume-control setting. [Harvard Medical School study] ...Tiny phones inserted into the ears are not as efficient at blocking outside sounds as the cushioned headsets, users tend to crank up the volume to compensate. A quarter of iPod users between 18 and 54 years of age listened at volumes sufficient to cause hearing damage." [Australian research]
"As one researcher found was often the case, listening to music/muzak at 110 to 120 decibels damages hearing in less than an hour and a half. Thus, the "longer-lasting batteries and more storage capacity encourages people with portable players to listen longer, not giving the ears a chance to recover."
I constantly worry about how many millions of our younger generation will add to the growing population of hearing-impaired over the next decades.
Martin F. Sturman, MD, FACP
Copyright 2007, Mathemedics, Inc.
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