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.
Something that prevents sound from traveling through it, such as is put on walls so adjacent areas are not disturbed by noise.
Until the soundproofing is installed, I don't think I'll be able to get to sleep here.
The act of installing material to dampen sound.
The soundproofing will take place today.