Magazine article Occupational Hazards

Solving Noise Problems

Magazine article Occupational Hazards

Solving Noise Problems

Article excerpt

Professionals use sophisticated equipment and expertise to identify and control noise.

A line of machines in a footwear manufacturing plant in Mississippi generated over 90 decibels (dB) of noise. Adding to the problem was a very smooth concrete wall located just behind the line of machines. Sound bounced off the wall, causing workers who were over 20 feet away to be exposed to excessive noise.

Mosely and Associates Inc., Nashville, Tenn., an industrial and environmental safety company specializing in noise control services, visited the facility, analyzed the situation and came up with a solution. They determined that a rubber-backed carpet hung two inches from the smooth wall would absorb the noise and stop reverberation. This simple engineering control helped to reduce the exposure to excessive noise for over half of the workers in that area.

So, how did Mosely and Associates know they could reduce the noise level simply by hanging a carpet two inches from the wall? Ralph Mosely, consultant and president of the company, attributes it to experience, sophisticated measuring devices and an extensive noise evaluation process. "When you solve as many noise problems as we have, then you know almost immediately what is going to work and what won't," said Mosely.

To engineer a quieter environment for your workplace, you first need to determine if your company has a problem with excessive noise. If so, then a noise evaluation, including monitoring and discussions with employees, is needed. Finally, controls to reduce or eliminate noise need to be introduced into the work place. These controls do not need to be expensive or high-tech to be effective.

Does Your Company Have a Problem?

The action level for noise, according to OSHA regulations, is a time-weighted average of 85 dB in an eight-hour shift. When noise levels reach that level, then a hearing conservation program, including engineering controls where feasible, is required. If the controls do not completely solve the problem, then employees must be issued hearing protection.

"If you thought before that the noise levels were low in your plant and people didn't need proper protection or training and then you find the levels are high, the thing to do first is to bring your people into the hearing conservation program, because your highest priority is to protect your employees," said Mosely.

Once the hearing conservation program has been initiated, the next step is a noise evaluation process to identify the sources of noise.

Noise Evaluation

Consultants agreed that talking with those most involved with the problem is the next step in evaluating noise sources.

"The employees are the ones who are there all day. If a machine is making noise, we always ask the employee working on that machine where he thinks the noise is coming from, said Mosely.

Bill Gastmeier, MASc, PEng, consultant with Howe Gastmeier Chapnik (HGC) Ltd., a consulting firm in Mississauga, Ontario, said his firm begins every evaluation with a plant walkthrough. "We try to get some idea of what the noisiest sources are so we can devote the most time to those areas," said Gastmeier.

The human ear is not direction specific, so simply relying on it to hear where a noise is coming from will not do the trick. The best way to evaluate noise at the source is through the use of technical measuring instruments. There are three types of instruments consultants typically use to measure noise sources: a sound level meter, an integrating sound level meter and an octave band frequency analyzer.

The choice of which instrument to use depends on the type of noise, the work environment and the personal preference of the professionals conducting the monitoring. The goal is to discover the amount and frequency distribution of noise emitted by a source, using one or more of these instruments. These results are matched with the proper type of control. …

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