3-12. PERSONAL PROTECTIVE MEASURES
a. Personal protective devices to lessen the risk of hearing loss consist of
earplugs and earmuffs (see Figures 3-6, 3-7, 3-8). Whichever device can be worn
comfortable and consistently by the exposed individuals is an important element in
selecting the device to be worn. In exposures to extremely high, steady state noise
levels (108 dB (A) and above), earplugs and earmuffs must be worn together.
Table 3-3 gives a list of earplugs and earmuffs available through medical and/or
regular supply channels.
b. Well-designed and properly fitted earplugs or earmuffs will lessen the noise
reaching the inner ear by 15 dB in the lower frequencies and by up to 35 dB in the
higher frequencies. Wearing earplugs and earmuffs together, however, does not
provide attenuation (weakening of the sound) equal to the arithmetic sum of the
individual attenuation of earplugs and earmuffs worn separately. The combination of
plugs and muffs provides from 35 to 40 dB noise attenuation at most frequencies.
Regular use of ear protective devices is mandatory for all individuals exposed to noise
in excess of 85 dB(A) or impulse noise in excess of 140 dB(P).
c. Persons with normal hearing will have little difficulty in understanding speech
when earplugs or muffs are worn if the speakers will raise their voices slightly above the
level of ordinary conversation. Actually it is easier for a person to hear and understand
auditory signals with them. A simple demonstration will be useful in illustrating this
conversation in a noisy room. You will note that the conversation can be more
Figure 3-6. Ear plugs and carrying case approved by The Surgeon General.