In the U.S., OSHA has set regulations on worker noise exposure. The specific regulations are 29 CFR 1910.95 for industry and 29 CFR 1926.52 for construction. The usual measurement method is to use a portable noise dosimeter attached to a worker that measures noise exposure as the person moves about the work area. However, this does nothing to identify the source and location of the noise. It also does not address non-OSHA noise issues such as community noise, noise frequencies, or noise control. When conducing a noise survey, a noise map is the most useful means of identifying noise sources and where the noise exposure may be greatest.
The most useful starting point is a floor plan of the work space or the property where measurements are taken. Specific noise readings can be logged on the floor plan. Since few industrial settings have steady static noise, it is usually best to list both 1) the average noise level, and 2) the range from low to high. Make sure that the readings are in the same settings as the noise dosimeters—usually dB (A scale) slow response.
A noise map is valuable in that it both gives us the ability to identify the noise levels that contribute to a worker’s cumulative exposure AND it indicates where noise reduction efforts need to be focused to achieve OSHA compliance and reduce the possibility of work related hearing loss among employees. (The OSHA noise standard is 29 CFR 1910.95 for industry and 29 CFR 1926.52 for construction.)
During the noise survey, it may be necessary to gather additional details regarding noise such as octave band analysis to identify specific frequencies that are the noise contributors. This is important since most noise reduction methods and materials are frequency specific. This applies to both OSHA Noise Regulations issues and community noise.
If noise levels approach 85 dB-A on the noise map, it is strongly advised to have workers in that area be sampled with a noise dosimeter, actually worn by the worker, to get an accurate exposure level measurement.
I firmly believe that any Hearing Conservation effort in a commercial setting must include both noise dosimetry and noise mapping as the minimum effort to effectively control worker noise exposure. These efforts can be added to other hearing conservation activities such as audiometric testing/sampling, hearing protection, worker training and noise central engineering.