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a means of personal protection from the harmful effects of noise; such devices fall under the classification of protective clothing and equipment. Two types of ear defenders are distinguished: the internal type, which is inserted into the outer ear canal, and the external type, which covers the entire outer ear. Internal ear defenders are plugs made of special fabric, extremely fine glass wool, ordinary cotton wadding and gauze, rubber, or plastic. External ear defenders may be in the form of a helmet liner, used to protect aviators’ hearing, or protective cups, similar in appearance to headphones, consisting of two shells or cups linked to one another. The shells are made of several layers of sound-absorbing materials, such as thick felt, cardboard, rubber, or vinyl chloride, with fillers between them, such as oakum or slag wool.
The use of ear defenders reduces the effective noise level at least 20-30 decibels. The noise spectrum is also less harmful because high-frequency sounds are attenuated.