soundproof

Etymology

sound + -proof

adj

1. Not allowing sound through.
   The contestant was placed in a soundproof booth so he could not receive help from the audience.

verb

1. To make resistant to transmitting sound.
   We soundproofed the room so we couldn't hear the road noises; unfortunately we couldn't hear the fire alarm either.
   It almost goes without saying that the train is fully soundproofed, with double-glazed windows and highly efficient air-conditioning by the British firm of J. Stone. 1960 March, G. Freeman Allen, “Europe's most luxurious express - the "Settebello"”, in Trains Illustrated, page 141
   Soundproofing a room may be as simple as sealing gaps around a door, or it may require rebuilding an entire wall or lowering a ceiling. 1980, Robert M. Jones, editor, Walls and Ceilings, Time-Life Books, page 114