In the past, workers accepted partial hearing loss as a cost of working in a noisy plant or on a production line. New workers were told by oldtimers that they would soon get used to the noise. But times have changed. Noise is now recognized as an occupational hazard that can cause temporary or permanent hearing loss, stress and other physical problems.

WHERE ARE THE REGULATIONS?
Regulations governing the allowable levels of noise and hearing protection requirements for companies to provide employees have been issued by the Occupational Safety and Health Administration (OSHA). The regulations can be found in the Code of Federal Regulations, CFR Title 29, Part 1910.95.

WHAT IS NOISE?
One definition describes noise as unwanted or unpleasant sound. We're all exposed to noise every day at home, at work and in traffic. However, a clear definition of noise is hard to pin down. How you're affected by sound depends on several things--- loudness and frequency of the sound, length of exposure and even your age and health. A temporary hearing loss can occur from short exposure to loud sounds, but your hearing soon recovers when the noise stops. Despite this factor, one fact about noise is very clear. If the level is high enough for long enough; it can cause health problems--- including permanent hearing loss. How do we hear sounds? A sound source sends out vibrations in the air. These vibrations are called sound waves. The ear changes the energy in sound waves into nerve impulses, which travel to the brain and are then interpreted.

Sound is measured by its frequency and intensity. Frequency is the pitch (high or low) of a sound. High-frequency sound can be more damaging to your hearing than low-frequency sound. Intensity is the loudness of a sound. Loudness is measured in decibels (dB), named for Alexander Graham Bell. Intensity that exceeds an average of 85 dB over an eight-hour day may cause hearing loss. According to OSHA standards workers may not be exposed to more than an average of 85 dB over an eight-hour period without hearing protection being provided.

DIFFERENT KINDS OF NOISE
But noise is just noise, right? And too much of it is bad for your ears. It would be nice if the picture was that simple, but it's not. In general, there are three types of noise: Wide band is noise that is distributed over a wide range of frequencies. Examples are the noise produced in most manufacturing settings and by the operation of most internal combustion engines.

Narrow band noise is restricted to a narrow range of frequencies. Examples include noise from various kinds of power tools, circular saws, fans and planers.

Impulse noise is composed of temporary "beats" that can occur in - and - off repeating patterns. A jack hammer is a good example of impulse noise.


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