The quick answer
Mass Loaded Vinyl blocks airborne sound by adding dense, limp mass to a surface. SoundBlanket 2.5mm is rated STC 30 and 4mm is rated STC 34. It is the only layer in a typical build that actually blocks noise, and it must always be covered by a finish layer.
Most soundproofing failures come from using an absorber where a barrier was needed. MLV is the barrier. It is thin, heavy and flexible, and it works on a simple principle: heavier surfaces are harder for sound to pass through. Everything else in a wall build-up supports it.
01 /Why mass is what blocks sound
Airborne sound transmission is governed largely by mass law: the heavier a partition, the more sound energy it takes to make it vibrate, and the less passes through. MLV is engineered to be as heavy as possible while staying thin and limp enough to conform to curves, corners and irregular surfaces.
Limpness matters as much as weight. A stiff panel resonates and lets specific frequencies through. A limp one does not, which is why MLV outperforms rigid boards of similar weight.
02 /The two grades
| Product | Rating | Sheet sizes | Best for |
|---|---|---|---|
| SoundBlanket 2.5mm | STC 30 | 8x4 ft at 22 kg, 16x4 ft at 35 kg | Bedrooms, offices, general walls and ceilings |
| SoundBlanket 4mm | STC 34 | 8x4 ft at 28 kg, 16x4 ft at 55 kg | Studios, home theatres, shared walls |
The 8x4 ft sheet covers 32 sq ft and the 16x4 ft covers 64 sq ft. Both ship rolled. Where low frequencies are involved, the extra mass of the 4mm earns its cost.
03 /Where it goes
- Walls. Directly onto the existing surface as the first layer, then BassBloc, then a finish panel.
- Ceilings. Same order. Essential in apartments and duplexes where the neighbour above is the problem.
- Floors. As an underlayment beneath the flooring build-up, often with acoustic carpet tiles over the top.
- Around services. Wrapped over pipes and ducts to deal with plumbing and HVAC noise at source.
Fix with SR Adhesive or nails. Sheets can be cut, trimmed and overlapped, and seams should be sealed rather than left open, since a gap in a barrier behaves like a hole.
04 /Always cover it
MLV is a technical layer and is not a finish. Cover it fully with gypsum, wooden panelling, felt acoustic panels or HDHMR. Leaving it exposed is neither durable nor the intended installation, and an uncovered barrier tends to get damaged and lose its seal.
Related reading: how effective is BassBloc, and how to soundproof a wall.
05 /Frequently asked questions
How effective is MLV for soundproofing?
Very, for airborne noise. SoundBlanket 2.5mm is rated STC 30 and the 4mm is STC 34. Because it works by mass rather than absorption, it blocks speech, television and traffic noise passing through a partition, which no amount of foam will do.
Which MLV thickness should I choose?
Use 2.5mm for bedrooms, offices and general walls where speech and television are the issue. Use 4mm for studios, home theatres and shared walls, where the extra mass matters at the low frequencies that cause most complaints.
Does MLV reduce echo inside a room?
No. MLV is a barrier, not an absorber. It stops sound crossing a partition but does nothing about reflections inside the room. For echo and reverberation you need acoustic panels or foam on the visible surface.
Can MLV be left exposed?
No. Always cover it with gypsum, wooden panelling, felt panels or HDHMR. It is a technical layer within the build-up, and an exposed barrier is vulnerable to damage that breaks its seal.
How is MLV installed?
With SR Adhesive or nails, directly onto the existing surface. It cuts and trims easily and conforms to curves and corners. Overlap and seal the seams, because an open joint in a barrier lets sound straight through.
Sonit writes about practical soundproofing for Indian homes and workplaces, with a focus on what delivers measurable results at sensible cost.
