Earmuffs

Earmuffs are objects designed to cover a person's ears for hearing protection or for warmth. They consist of a thermoplastic or metal head-band, that fits over the top or back of the head, and a cushion or cup at each end, to cover the external ears. This article primarly focuses on the earmuffs for hearing protection. The difference between passsive and active earmuffs is discussed, as well as a brief history of earmuffs. Finally, principals of hearing protection are introduced and the effectiveness of earmuffs for protecting against noise-induced hearing loss is dicussed.

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. Similar active earplugs also exist, primarily aimed at musicians.

There are two different types of earmuffs used to protect the user from loud sounds based on the acoustical properties and materials used to create them: passively attenuating and actively attenuating earmuffs.

The ability of a passive earmuff to attenuate a signal is based on the materials used. Materials, such as a cupped foam coated in hard plastic, will block sound due to the thick and dampening properties of the foam.

Some passive earmuffs have an electronic component and microphones that allow the user to control their access to communication while attenuating background noise. When in loud, hazardous settings, the wearer may still be required to listen to outside sources, such as machinery work, their supervisor's commands, or talk to their colleagues. While the material and design of the muff allows for a reasonable attenuation (roughly 22 dBNRR), the user has the option to allow some sounds in that are necessary for their job. These earmuffs incorporate a volume control to increase and decrease the attenuation.

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