MLV Soundproofing Panels: When Mass Loaded Vinyl Works

MLV soundproofing panels are sheets of heavy, limp vinyl that block sound with mass. A 1 lb/sq ft sheet rates STC 26 on its own in Johns Manville's lab test (opens in a new tab). Here's the catch: it only earns that number when it's built into a sealed layer, under drywall or wrapped around a duct. Hang mass loaded vinyl loose on a wall with the edges open and sound just leaks around the sides. It won't change much.

What mass loaded vinyl soundproofing panels are

Mass loaded vinyl is a flexible vinyl sheet packed with a dense mineral. It's sold by weight per square foot. 1 lb is the standard, and there are 1.5 and 2 lb versions if you want more blocking. Johns Manville's 1 lb sheet is 0.100 in. thick and has no lead in it. Kinetics loads its KNM barrier with barium sulfate (Kinetics (opens in a new tab)).

• 1 lb/sq ft

  STC 26

  The usual weight for walls and ceilings. About 0.1 in. thick.

• 1.5 lb/sq ft

  STC 29

  The in-between option. Johns Manville quotes roll sizes on request.

• 2 lb/sq ft

  STC 31

  Twice the weight for 5 more points. Heavier rolls to hang.

Those ratings are Johns Manville's ASTM E90 results for the sheet by itself. Most MLV ships in rolls, not rigid panels, and the best mass loaded vinyl compares brands and weights.

Why MLV blocks sound when foam panels don't

MLV blocks sound because it's heavy for how thin it is: 1 lb/sq ft in 0.1 in., while a 2 in. fiberglass acoustic panel weighs 0.5 lb/sq ft. For a single layer, every time you double the weight you get about 6 dB more blocking. That's the mass law in NRC Canada's CBD-239 (opens in a new tab).

Being floppy helps too. Stiff boards lose blocking at a "coincidence" dip that "often leads to a reduced STC rating," while very limp materials like sheet lead "effectively do not show coincidence dips," the same digest says. MLV is limp, so it blocks close to what its weight says it should.

Where MLV works

MLV works in four places, and they're all sealed: inside a new wall or ceiling, between two layers of drywall, wrapped around ducts and pipes, and lining machine enclosures.

• Inside new walls and ceilings: fasten it across the studs with cap washers and leave it "relaxed" or "limp" between studs. Lap the seams at least 1 in. and seal them, then cover with 5/8 in. or thicker drywall (Acoustiblok wall instructions (opens in a new tab)).
• Over existing drywall: screw it through the old drywall into the studs and put a new layer over it. Can you put MLV directly on drywall has the steps and the caveats.
• Ducts and pipes: Kinetics' MLV over a 2 in. fiberglass board cut duct noise by 27 dB at 500 Hz, compared with 18 dB when it was wrapped right on the duct (KNM-100ALQ data sheet (opens in a new tab)). The soft layer added 9 to 11 dB at 500 and 1,000 Hz.
• Machine enclosures: Johns Manville rates its vinyl for applying straight onto a noise source or the enclosure around it.

Where MLV is wasted

MLV is wasted anywhere sound can get around it: hung like a tapestry, pinned up as separate squares, or left with gaps at the floor and ceiling. Sound is like water. It takes the leak every time. In PABCO's example (opens in a new tab) one unsealed 1/8 in. gap 1 ft long drops a wall from STC 46 to 36.

The other way to waste it is buying MLV for a wall that's leaking somewhere else. Seal the door, the outlets and the wall base first. Does mass loaded vinyl work lays out what to expect from it on a typical wall.

Soundproof barrier panels: MLV plus an absorber

Soundproof barrier panels bond MLV to a layer of foam or fiberglass, so one product both blocks and absorbs. Johns Manville says its vinyl can be combined with acoustic foams and mineral or glass fiber wool to make light composites, and Kinetics' KNM-100ALQ pairs 1 lb MLV with 1 in. quilted fiberglass (STC 28 hanging free).

These composites are built for ducts, machinery and equipment enclosures. Put a barrier panel on a living room wall and it still needs sealed edges and full coverage to block anything. The soundproof panels guide explains why surface panels rarely pull that off.

What MLV costs and weighs

Auralex lists its SheetBlok MLV rolls (opens in a new tab) at $223.99 to $329.99 (list price as of October 2026), but the listing doesn't give roll sizes. Divide any roll's price by its square footage before you compare. Weight matters as much as price, because somebody has to lift every roll onto the wall.

Area is width in feet times length (35.5 ÷ 12 × 36 = 106.5), and roll weight is area times weight per square foot, using the sizes on the Johns Manville (opens in a new tab) and Kinetics (opens in a new tab) pages. A 12 ft wall 8 ft high is 96 sq ft, so one Johns Manville roll covers it with about 10 sq ft left over for laps.