COMPREHENSIVE SURVEYS OF AREA NOISE LEVELS AND EMPLOYEE NOISE EXPOSURES

The survey of equipment and area noise levels throughout a department, and often the total plant site, involves measurement of the A-weighted sound level (expressed in units of dBA) at specific locations near equipment and employee work areas. These data may then be plotted on a floor plan (i.e., an AutoCad or other electronic file) to generate a noise contour map, as illustrated in the drawing above. This information is useful toward identifying areas in need of engineering noise controls, where hearing protection is necessary, and to educate and train employees as to the extent of the potential noise hazard throughout their department or plant.

Next, to supplement the equipment or area noise level measurements, a noise exposure survey is often conducted to determine the time-weighted average (TWA), or daily exposure for each employee. For the most past, the exposure assessment is typically conducted using noise dosimeters. These devices, which are worn by employees, consist of a miniature microphone connected to a small microprocessor-based sound level meter, which automatically records the data. Noise dosimeters continuously measure and process A-weighted sound levels obtained near a person's ear (i.e., hearing zone), then produces an average level of noise exposure that occurred throughout the individual's workday. Under some circumstances, we may also use an exposure profiling technique that combines area sound levels with durations of exposure, all of which are entered into a data base for computerized processing and calculation of the TWAs. It is important to note that the survey protocol is designed to satisfy the needs of the client with the highest degree of scientific accuracy. The TWA or noise exposure data is then used to assist the client with making informed decisions regarding protection of employee hearing and establishment or maintenance of an effective hearing conservation program.