Does adding sound-absorbing material to the surface of a wall or a floor significantly increase the sound insulation?
The addition of a typical sound-absorbing material to the surface of a wall may change the high frequency transmission losses. This is where common sound-absorbing materials are most effective. However, the sound transmission class does not usually change, or only changes by one or two decibels. This is because the low frequency transmission is not changed by the addition of typical absorptive materials on walls. The addition of a carpet to a floor, will certainly increase impact insulation ratings, but usually does not change the sound transmission class. Many people believe that adding sound-absorptive material to walls or doors will improve sound isolation between apartments. On the receiving room side, if enough absorptive material is added, the room will be less reverberant and intrusive noise levels will be slightly reduced; the reduction can be as much as 3 dB if the amount of absorption in the room is doubled. The room will also feel ‘dead’ acoustically, so there is a perceptio
