Earmuffs are objects designed to cover a person's ears for protection. They consist of a thermoplastic or metal head-band, that fits over the top of the head, and a pad at each end, to cover the external ears.
Chester Greenwood invented the earmuff in 1873, at the age of 15.[1][2] He reportedly came up with the idea while ice skating, and had his grandmother sew tufts of fur between loops of wire.[3] He was awarded patent #188,292 on March 13, 1877. He manufactured these ear protectors, providing jobs for people in the Farmington Maine area, for nearly 60 years.[1][4]
Modern earmuffs come in two basic kinds:
Ear defenders protect the wearer from extreme noises. The head band and outer covering is usually made from a hard thermoplastic or metal. The protection usually comes from acoustic foam - this absorbs sound waves by increasing air resistance, thus reducing the amplitude of the waves. The energy is transformed into heat. Some ear defenders employ active sound protection, in which a microphone mounted in the headset picks up ambient sounds and transmits them through a dynamic range compression circuit to earphones inside. By virtue of the dynamic compression, the headset can be adjusted to allow the wearer to hear sounds at ordinary volumes normally, while attenuating louder sounds.
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If people are exposed to excessively loud environments (90 dB or more), hearing protectors are necessary to prevent ear damage. They should be worn whenever power tools, loud yard equipment, or unsuppressed firearms are used. The table below shows how easy it is to exceed the maximum exposure levels. Even at sound levels below the level of possible damage, hearing protection will reduce fatigue from frequent exposure to sound.
| Level of noise (dB(A)) | Maximum daily exposure time |
|---|---|
| 85 | 8 Hours |
| 91 | 2 Hours |
| 97 | 30 Minutes |
| 103 | 7 Minutes |