When the daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each. Cn indicates the total time of exposure at a specified noise level, and Tn indicates the total time of exposure permitted at that level. Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level. Engineering controls are most effective. Basically, all we're talking about is attempting to eliminate or reduce the noise level by redesigning, replacing or enclosing noisy equipment.
Administrative controls attempt to limit exposure by reducing the duration of exposure to the noise.
If you have questions about administering the hearing conservation program itself, you can attend our workshop on that subject, or call one of our health consultants who can answer your specific questions. As you're probably well aware, there are basically four types of hearing protectors. They are available in a variety of shapes and sizes and are usually characterized by one or more ribs or contours. Custom molded plugs are generally made of plastic and are designed from a molded wax insert of the wearer's ears. They are considered multiple use but cannot be switched ear to ear.