The contestant was placed in a soundproof booth so he could not receive help from the audience.

The electrical activity of the subject's cerebral cortex was recorded in a state of relative rest, after a 5 min adaptation of the subject to a dark soundproof chamber. The biopote…

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.

We soundproofed the room so we couldn't hear the road noises; unfortunately we couldn't hear the fire alarm either.