A device that covers the ear and provides noise reduction is known as what?

The term that accurately describes a device designed to cover the ears and reduce noise is "ear muffs." Ear muffs are specifically designed to fit over the ears to provide protection from harmful noise levels, making them essential for individuals working in loud environments or engaging in activities where noise exposure could lead to hearing loss. They work by encompassing the entire outer ear, using various materials that insulate against sound, effectively dampening noise.

Other terms mentioned do not serve the same function. Hearing aids are designed to amplify sound for individuals with hearing impairment, thus increasing sound exposure rather than reducing it. A sound barrier typically refers to a physical barrier that blocks sound, rather than a device worn on the body. An acoustic shield generally pertains to materials or setups that minimize noise in a broader context, not specifically worn to reduce sound exposure like ear muffs.