Mass Loaded Vinyl (MLV)

How MLV works — the physics in one paragraph

Sound crossing a wall vibrates the wall as a giant loudspeaker cone. The wall's mass determines how easily it moves. Add heavy limp mass to the wall (that's MLV) and the wall vibrates less for the same sound input — less energy passes through, less sound reaches the room next door. It's called the "mass law": every doubling of wall mass adds ~6 dB of transmission loss. MLV is the highest-mass-per-thickness option available; nothing else adds this much STC in this little wall depth.

Where MLV goes in a wall assembly

The classic assembly: drywall + MLV + drywall on stud partitions. Sandwiching MLV between drywall layers is more effective than exposed MLV because the drywall layers add rigidity and damping to the whole assembly. STC 55+ is achievable with 2 MM MLV; 60+ with 5 MM MLV in a well-sealed installation.

For ceiling isolation (upstairs footfall noise into a home theatre below), MLV between joists or above the ceiling drywall. Combined with resilient channels the isolation improvement is dramatic — the ceiling stops functioning as a giant amplifier for footsteps.

Choosing thickness — 2 MM, 3 MM, or 5 MM?

2 MM MLV is the sweet spot for most residential and studio applications. It weighs about 4.5 kg/m², adds ~8 dB STC on standard walls, and is the least expensive per square metre. Standard for home theatres, podcast rooms, hotel guest-room partitions.

3 MM MLV steps up to ~6 kg/m² for slightly better isolation. Used when you need to hit STC 55 without a mass-air-mass wall.

5 MM MLV weighs 10+ kg/m² and delivers isolation on par with a lightweight concrete wall. Reserved for broadcast studios, machinery enclosures, and cinema inter-hall walls where STC 60+ is non-negotiable.

The critical detail — sealing every seam

MLV is limp and flexible — it seals well against irregular substrates. But the wall's isolation is only as good as the weakest gap in it. Seal every seam with acoustic sealant (Green Glue, or equivalent butyl caulk). Overlap MLV sheets by 5 cm at joints. Seal around electrical boxes, HVAC penetrations, and door frames.

A single unsealed electrical box can leak 6–8 dB of isolation from an otherwise well-built MLV wall. This is where amateur installations go wrong: they buy expensive MLV, install it well, and forget to seal one penetration. Send us the drawing; we'll flag the seams.

Common misconceptions about MLV

"Foam is soundproofing." No — foam absorbs sound already in the room. MLV blocks sound moving between rooms. They're different problems with different materials. Most projects need both.

"Thicker MLV is always better." Diminishing returns kick in past 5 MM. For most residential and studio applications, 2 MM in a well-sealed assembly beats 5 MM in a poorly-sealed one.

"MLV under a rug soundproofs a floor." Partially — it damps impact noise significantly. But airborne noise (voices from the room below) needs MLV inside the ceiling assembly, not on the floor.

MLV order sizing for common projects

Home theatre (15×20 ft, walls + ceiling): plan on 500 sq ft of MLV coverage — two 12 SQM rolls of 2 MM.

Podcast studio (10×12 ft, walls only): plan on 300 sq ft — one 12 SQM roll of 2 MM covers with waste.

Cinema inter-hall partition: 5 MM MLV, calculated per wall area. Bulk quoting standard on this segment.