Soundproofing & Acoustic Insulation Calculator

Cavity insulation like mineral wool kills the resonance inside a wall and typically adds 4 to 6 STC points. Big gains come from mass (a second layer of drywall) and decoupling (resilient channel or clips).

Treating 15 to 25% of the wall surface handles most rooms. Studios go to 35%. Start with first reflection points and the wall behind you.

It absorbs airborne sound within the cavity, which helps, but it does not stop sound transmitting through the structure. A wall's sound rating depends far more on mass, decoupling and airtightness than on what is in the bays. Insulation alone typically moves a wall a few STC points — real improvement needs the assembly changed, not just filled.

Soundproofing stops sound passing from one space to another; absorption reduces reflections within a space. Foam panels on a wall make a room sound less echoey — that is absorption — and do essentially nothing for the neighbour hearing you. Confusing the two is the single most common reason a soundproofing project disappoints.

Slightly, at typical densities, and it is easier to friction-fit tightly which matters because gaps leak sound. The difference between the two is small compared with the difference made by decoupling the drywall or adding a second layer with damping compound. Choose on price and handling unless the rest of the assembly is already done properly.