Made so that sound cannot pass through; or to make something so sound cannot enter or escape.
From 'sound' (noise) plus 'proof' (resistant to). Created as a word in the early 1900s when noise control became an urban concern with traffic and industry.
Recording studios use layers of different materials to soundproof because sound travels in multiple ways—as vibrations through air, through walls, and through the ground, so you need multiple barriers working together.
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