Passive protective earmuffs and earplugs.

Passive

— passive headphones do not use electronic components, but provide hearing protection only due to the physical properties of the materials from which they are made. The ear pads of over-ear headphones are made of sound-absorbing foam, plastic or rubber. Passive earplugs are ordinary earplugs. Note that to achieve the maximum degree of noise insulation, passive earplugs can be used in conjunction with over-ear headphones.