Wiktionary
n. 1 Something that prevents sound from traveling through it, such as is put on walls so adjacent areas are not disturbed by noise. 2 The act of installing material to dampen sound. vb. (present participle of soundproof English)
Wikipedia
Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles, or using active antinoise sound generators.
Two distinct soundproofing problems may need to be considered when designing acoustic treatments - to improve the sound within a room (See anechoic chamber), and reduce sound leakage to/from adjacent rooms or outdoors. Acoustic quieting, noise mitigation, and noise control can be used to limit unwanted noise. Soundproofing can suppress unwanted indirect sound waves such as reflections that cause echoes and resonances that cause reverberation. Soundproofing can reduce the transmission of unwanted direct sound waves from the source to an involuntary listener through the use of distance and intervening objects in the sound path.
Usage examples of "soundproofing".
The absolute silence told her the building had excellent soundproofing, or everyone in the place was dead.
Even through the soundproofing I heard her pounding at the door, asking if I was okay.
His 9mm sounded like a cannon compared to the silenced weapon, and his bullets punched much larger holes through the hardboard and soundproofing material.
A car horn sounded close by, insinuating itself like a knife through the window's soundproofing, and she started.
His office had soundproofing on the ceiling, a gray steel desk with two matching chairs, a gray dictating machine on a gray stand, a telephone and pen set of the same color as the walls and floor.
An HG-2 hasn't got room for soundproofing, which was fine with meit added a bit to the effect.
The smell of sweet, burned human flesh filled his nasal cavities as he leaned up against the door, and through the thick soundproofing of the metal he could just about discern some quiet whimpering and shuffling.
He wasn't going to let this opportunity slip by, soundproofing or no soundproofing.
The soundproofing cones in the walls and ceiling sublimed and drifted as black cobwebs in fierce air currents.