Ã&©l#'!!! NOISE

Noise, often defined as unwanted sound, is one of the most widespread job hazards. Noise can cause temporary hearing loss and then permanent hearing loss. It can also cause blood vessels to constrict, as do other "danger" signals. Between October 1998 and September 1999, Federal OSHA cited violations of the noise standard (1019.95) in 743 different inspections. By contrast, violations of the air levels of all the chemicals included in 1910.1000 were cited in a total of 225 inspections, and asbestos in 118 inspections during the same time period. Noise is the most frequently cited exposure standard.

Sound is actually a wave traveling in air with pressure higher at the crest of the wave and lower in the trough. The ear is able to detect the frequency of these waves (translating into different pitches) and the amplitude (translating into softness and loudness).

Intensity or loudness of sound is measured in decibels (dB), a log scale, because the range is so large, from about 1 to about 1 billion, that it would be hard to use a regular linear scale. The usual dBA measurement scale incorporates a filter that is sensitive to different frequencies in much the same way as the human ear, more sensitive to high pitched noises, than low ones.

Typical Decibel Ratings in dBA

Threshold of hearing -acute	0	Busy street traffic	75
Threshold of hearing-average	15	Truck passing/heaving traffic	80-5
Rustle of leaves	20	Subway 20 feet away	90
Whisper at 5 feet	30	Many factories	80-99
Quiet office	40	Chain saw, idling	85
Average office	50	OSHA hearing conservation program	85
Average restaurant	55	OSHA 8 hr standard	90
Ordinary conversation	60	Chain saw, cutting	115
Loud office noise	70	Pneumatic rock drill	130

Our ears are capable of detecting a huge range of sounds, from very, very soft to extremely loud, from very very low pitched to extremely high frequency. We can hear very complex noises with many different waves.

The louder the nose and the longer the exposure, the more likely the damage to the inner ear that results in hearing loss. The first sign is usually a temporary threshold shift, or temporary hearing loss. Perhaps you have to turn up the car stereo on the way home from work, but in the morning after a quiet night, the radio seems to blast. The ear can recover from these shifts but with repeated exposure to noise, the ear will eventually loose its ability to recover.

Hearing loss usually progresses gradually. It may not be noticeable at first. Workplace noise usually affects the ability to hear high-pitched sounds, and causes sound to be distorted, and speech difficult to comprehend. This loss is not associated with physical pain, so it does not always strike the same fear into our hearts as substances that cause respiratory disease or cancer. But noise induced hearing loss makes communication difficult and cuts us off from other human beings. Helen Keller, who was deaf as well as blind, has said that of the two senses, hearing is the most valuable.

THERE IS AS YET NO CURE for noise-induced hearing loss. A hearing aid will make the sound louder but cannot correct the distortion and fuzziness.

Noise-induced hearing loss usually occurs first in higher frequencies, with the greatest loss usually at about 4000 hertz or cycles per second. This is why a number of different pure tones are used in a hearing test or audiogram. A typical audiogram showing baseline hearing and hearing after 25 years in a noisy environment may look like this:

Click here for a high-resolution image

WHAT ABOUT OSHA?

OSHA does have a standard covering noise exposure at work. It allows noise exposures up to 90 dBA as an 8-hour time weighted average. A worker is allowed to be exposed to 95 dBA for 4 hours, 100 dBA for 2 hours, 105 dBA for 1 hr, and no more than 115 dBA as a ceiling. If noise levels exceed these, the noise must be reduced! OSHA requires that all methods of reducing noise be tried even if workers are already wearing hearing protection.

At exposure levels above 85 dBA, workers must be enrolled in a hearing conservation program. This program includes training, a baseline as well as annual audiograms, training about noise and its effects, and hearing protection. Each workplace with noise exposures above 85 dBA must have a written program describing all aspects of their hearing conservation program, including workplace noise monitoring, provision of baseline and annual audiograms, follow-up to audiograms, the provision of choices of hearing protectors, and training in the all of these aspects. If you are exposed to noise levels averaging 85 dBA for an 8 hour period, you must be included in a hearing conservation program and be given the necessary knowledge to protect yourself.

Almost all noises can be reduced with the proper engineering controls. Noise is not "part of the job" Your employer can and must reduce noise levels about 90 dBA at work.

Make ãhearing healthä part of your lifestyle. Avoid excess noise whenever possible. Turn down the stereo volume and make sure noisy tools are equipped with sound controls.

When it is necessary to be around noise either at work or at play, use hearing protection. For home use, hearing protective devices are available in any pharmacy and hardware store. At work, your employer is required to provide a variety of types of hearing protectors for you to choose from. You can choose from a range of earplugs, earmuffs, or canal caps. Different brands offer different amounts of protection. Often the best model is one that you can wear comfortably and consistently. Keep your hearing protectors handy, clean, and in good condition.

Teach your family the importance of avoiding excessive noise and the correct use of hearing protection.

If you or someone in your family suspects you are developing hearing loss, have your hearing tested.

The Yale Occupational and Environmental Medicine Program where you can get hearing screening, noise exposure assessment as well as information on hearing protection, noise control and prevention, and further evaluation for hearing loss. Call 203-785-4197.

The National Institute for Occupational Safety and Health (NIOSH) and NIHâs National Institute on Deafness and Other Communication Disorders (NIDCD) are conducting a public awareness campaign on the causes and prevention of noise-induced hearing loss. NOISE also provides information on how to reduce the noise emitted from many specific industrial processes and machinery. NIOSH information number: 1-800-35-NIOSH or http://www.cdc.gov/niosh.

The League for the Hard of Hearing produces educational materials and programs about the noise hazards of toys and other common noise sources; 71 West 23rd Street, New York, NY 10010 212-255-1932.

The National Hearing Conservation Association is a membership organization of professionals working to prevent hearing loss due to noise, and also produces educational materials: contact NHCA 9101 E. Kenyon Avenue, Suite 3000 Denver, CO 80237. (303)-224-9022) .

The Sight and Hearing Association distributes educational materials on noise and hearing loss, including the ãKnow Noiseä video and curriculum for 3-6 graders. Contact SHA 674 Transfer Road St. Paul, MN 55114. (800) 645-2546.

ConnectiCOSH provides training on many workplace safety and health subjects. 203-549-1877.