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: ''This article is about earmuffs that covers a person's ear. “Earmuffs” may also refer to the “earmuff convention” in Common Lisp.'' Earmuffs are objects designed to cover a person's ears for protection. They consist of a thermoplastic or blametal head-band, that fits over the top or back of the head, and a pad at each end, to cover the external ears. == Varieties == Modern earmuffs come in two basic kinds: *Thermal earmuffs, worn in cold environments to keep a person's ears warm with pads of cloth or fur. *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 music, communication or other audio source and also enjoy protection or isolation from ambient noise. For extra sound attenuation, earplugs can also be used in conjunction with earmuffs. 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. Similar active earplugs also exist, primarily aimed at musicians. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「earmuffs」の詳細全文を読む スポンサード リンク
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