Does acoustic plasterboard actually work?
What the dense board really does, why it disappoints people who fit it on its own, and the three things that matter more than the board choice.
- Difficulty
- intermediate
- Time
- 10 min
- Read
- 5 min
Short answer
Yes, but only as one part of a system. Acoustic plasterboard is denser than standard board and denser board blocks more sound — that is real physics. What defeats it is that sound also travels through every air gap and through the structure itself, so a denser board on a wall with a gap under the door, a shared joist, or back-to-back sockets changes very little. Seal, decouple, add mass, in that order.
People fit acoustic board expecting a transformation and frequently get a modest improvement, then conclude the product does not work. The product works exactly as specified. What has usually happened is that the wall was never the weakest path the sound was taking.
Step by step
- Understand what the board does.Acoustic plasterboard has a denser core than standard board, so a sheet of it has more mass per square metre. Sound transmission through a barrier falls as its mass rises — this is the mass law, and it is the whole mechanism. More mass, less sound through it.
- Understand the diminishing return.Because the relationship is logarithmic, doubling the mass of a partition gives a useful but not dramatic improvement. Swapping one layer of standard board for one layer of acoustic board gives less than doubling, so expect an improvement you can hear rather than a transformation.
- Find the actual weakest path first.Sound takes the easiest route. A gap under a door, an unsealed hole where a pipe passes through, a shared ceiling void, back-to-back socket boxes in the same stud bay, or a suspended floor whose joists run through into the next room — any of these will dominate, and no board choice fixes them.
- Seal every air gap before you spend anything.Sound travels through air. Perimeter gaps, service penetrations, the gap at the floor, the gap round a door. Acoustic sealant at every junction and a decent door seal often produce a bigger improvement than a board upgrade and cost a fraction as much.
- Then think about decoupling.The single biggest gain in a partition comes from making the two faces structurally independent — resilient bars, a staggered stud wall, or an independent stud frame. A rigid connection between the two faces conducts sound straight through however heavy the board is.
- Then add mass, and add it properly.Two layers of board with staggered joints, or acoustic board rather than standard, or both. Two layers of standard board is often cheaper than one layer of acoustic and performs comparably, so compare on cost per unit of performance.
- Fill the cavity with a mineral wool quilt.Insulation in a stud cavity absorbs sound within the cavity and stops it resonating. It is inexpensive, it is easy while the wall is open, and it is a meaningful part of any acoustic partition.
- Follow a system rather than assembling parts.Manufacturers publish tested wall and ceiling constructions with measured performance figures. Following one of those, exactly, gets you the number they measured. Substituting one component changes the result in ways that are not predictable from the parts.
- Be realistic about impact noise.Footsteps, doors banging and a washing machine on spin are structure-borne, not airborne, and mass on a wall does very little about them. Impact noise needs decoupling and resilient layers at the source, usually in the floor.
Tips
- In a flat or a terraced house, the party wall is usually not the only path. Sound flanks round through the floor joists, the ceiling void and the external wall, and treating only the party wall gives a disappointing result.
- Never fit sockets back to back in the same stud bay on a partition you care about. Offset them by at least one bay and seal the boxes.
- Acoustic board is heavier than standard board of the same thickness — noticeably so for handling and for the fixings. Check the fixing spec and get help lifting it.
- Acoustic foam panels on a wall reduce echo within a room and do essentially nothing about sound passing through it. They solve a different problem entirely.
Common mistakes
- Fitting acoustic board and leaving the gaps unsealed — A small unsealed gap transmits a surprising amount of sound and will dominate the performance of the whole wall. Sealing is the cheapest and highest-value step and it must come first.
- Expecting a board upgrade to fix noise from a neighbour's floor — Impact noise travels through the structure. A denser wall board does not intercept it. That problem is solved at the floor, usually on the neighbour's side.
- Screwing new board rigidly through to the existing wall — A rigid mechanical connection conducts sound straight through the new layer and undoes much of the benefit. Resilient bars or an independent frame are what break that path.
- Comparing products on the board's own figure — Board specifications are measured in specific tested constructions. A number quoted for a board only means anything in the wall it was measured in, so compare complete systems rather than components.
Questions people ask
Is two layers of standard board as good as one layer of acoustic?
Often comparable and sometimes better, because two layers with staggered joints add more total mass and break the joint lines. It is also usually cheaper. Where a specification names acoustic board in a tested system, use what the system says; where you are simply trying to improve a wall, compare the two on cost and mass.
Will it stop me hearing my neighbours' television?
It will reduce it. Whether it reduces it enough depends far more on the flanking paths and the air gaps than on the board. Realistically, a well-executed decoupled and sealed partition with mass makes normal conversation and television much quieter; nothing short of major structural work makes a party wall silent.
What about acoustic board on a ceiling?
It helps with airborne sound from above and does much less about footsteps, which is what people usually want fixed. An independent or resiliently mounted ceiling with a cavity quilt does far more, at the cost of ceiling height.