Ear damage from noise is easily avoided

Waimarino Bulletin, Volume 6, Issue 270, 17 January 1989, Page 7

Ear damage from noise is easily avoided

Noise induced hearing loss is the damage to hearing caused by being exposed to too much noise for too long.

It is a serious incurable disease that causes isolation from family and friends and mars the enjoyment of life. The sad thing about it is that this condition is so readily preventable. Noise can be found in any area where people live, work or play. Many machines produce high noise levels. Power lawnmowers can reach a sound level of 110 decibels (dBA), a chainsaw and a farm tractor 100 dBA, inside the cab of a heavy truck about 90 dBA and shouting children 95 dBA. Noise and Hearing Acoustic trauma is the physical damage of the ear from a single exposure to very high sound levels. Damage is immediate and usually results in some permanent hearing loss. Even brief exposure to loud noise causes a short lived hearing loss and may cause a "ringing" in the ear, making speech sound muffled and resulting in an inability to hear high pitched sounds. This usually disappears about i6 hours after exposure. If noise is very loud or exposure is long, temporary deafness may not disappear. The result is permanent hearing loss in both ears. There is no pain or bleeding, but normal hearing does not return because hearing cells have been irrevocably destroyed, and the damage is permanent. How long a worker stays in a noisy place is just as important as how loud the noise is. The following figures show the time it takes

at various noise levels to cause damage. Duration per day - Sound Level: 8hr - 85 dBA, 4hr - 88 dBA, 2hr - 91 dBA, lhr - 94 dBA, 30min - 97 dBA, 15min - 100 dBA, 8min - 103 dBA, 4min - 106 dBA, 2min - 109 dBA, lmin - 112 dBA, 30sec - 115 dBA.

No one should be exposed to sound levels above 115 dBA for any time at all unless wearing suitable hearing protection. The louder the noise level the less time it takes for damage to occur. Noise is probably too loud when: You have trouble talking to someone one metre

away because of noise; your ears ring after being in a noisy place; speech and other sounds seem muffled after you've been in a noisy place. A workers exposure to noise can be reduced in two ways. Reduction at source. Many loud noises can be controlled at their source by good manufacturing design, engineering controls and maintaining the equipment properly.

Wearing Hearing Protection Devices they block the sound at the entrance of the ear and so protect the delicate hearing organ in the inner ear. If noise cannot be reduced below 85 dBA suitable hearing protection must be worn. Hearing conservation Hearing conservation involves noise measurement, hearing testing "at risk" workers, noise reduction - reducing the amount of noise reaching the ears if there is a risk of damaging hearing and

hearing protection - shield the machine to cut down the noise, or wear protection devices. Industrial deafness doesn't develop at an equal rate during a worker's career. Much of the damage to hearing occurs in the first two or three years. Industrial deafness is commonly accompanied by tinnitus (ringing or humming in the ears). Often it is continuously present, causing effects from mild annoyance to des-

peration. If tinnitus is noticed after noise exposure, hearing damage has occurred. The consistent use of personal hearing protectors will prevent industrial deafness. Remember that a lawnmower or chainsaw is just as much a noise hazard as a factory machine, so protect your hearing at home too. About 350,000 New Zealanders have significant hearing loss. It is estimated that 20 per cent are attributable to excessive noise.

Helen

Pocknall

PHN