Earmuffs
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 area, for nearly 60 years.[1][4]
Modern earmuffs come in two basic kinds:
- Thermal earmuffs, worn in cold environments to keep a person's ears warm.
- Acoustic earmuffs, also known as ear defenders: cups lined with sound-deadening material, like thermal earmuffs and headphones in appearance, which are worn as hearing protection. These may be carried on a head-band or clipped onto the sides of a hard hat, for use on construction sites. Some manufacturers combine headphones with ear defenders, allowing the wearer to listen to a music, communication or other audio source and also enjoy protection or isolation from ambient noise. They are not commonly worn by people who have sideburns or glasses, who find earmuffs to be uncomfortable.[5]
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.
Hearing Protection
When should I wear hearing protection? If you are exposed to excessively noisy environments (80 dB or more), you should wear hearing protectors. You should also wear them when you are using power tools, noisy yard equipment, or firearms. The table below shows how easy it is to exceed maximum exposure levels.
| Level of noise in dB(A) | Maximum daily exposure time |
|---|---|
| 85 | 8 Hours |
| 91 | 2 Hours |
| 97 | 30 Minutes |
| 103 | 7 Minutes |
See also
References
- ^ a b Maine Secretary of State Kid's Page - Famous People
- ^ Chester Greenwood - Earmuffs
- ^ Dec. 4, 1858: It Was Very Cold the Day Chester Greenwood Was Born
- ^ Earmuff History - Invention of Earmuffs
- ^ Stephenson, Carol Merry. "Choosing the Hearing Protection That's Right For You". Retrieved 2009-07-30.
External links
