A FIELD EVALUATION OF MUFF-TYPE HEARING PROTECTION DEVICES

In many noisy environments it is necessary to provide the work force with hearing protection. These protectors are subjectively tested under laboratory conditions, and numerous procedures have been developed for predicting their effectiveness in actual service from the resultant data. Little work has, however, been done in determining the actual noise reduction achieved by means of measurements made under actual working conditions. This article reports the results of tests in which sound levels were recorded simultaneously through one microphone placed inside the cup of a muff-type protector and a second microphone placed on the subject's shoulder during exposure to typical noisy conditions in the proximity of mining machinery. A series of such measurements indicated that the reduction in sound level achieved is less than the laboratory tests would indicate.