Shared Walls? Soundproof Your Apartment with MLV and Felt Panels

A client in a well built tower once told us she could follow the plot of her neighbour's serial without turning her own television on. Not the words, exactly, but enough of the rhythm, the laugh track and the bass of the title music to know which episode it was. The wall between them was a full block wall, plastered on both faces, built to code and passed by the consultant. Nothing was wrong with it. It simply was not designed for what she wanted from it.

This is the ordinary situation in apartments. Shared walls transmit loud televisions, conversation, kitchen clatter and footfall, and the standard brick, gypsum or block partition typically rates STC 35 to 40. That is enough to make a neighbour unintelligible some of the time. It is not enough to make them absent, and residents of premium apartments increasingly expect absence.

What are you actually hearing through the party wall?

Spend a minute identifying the character of the sound before buying anything. If you hear consonants, the intelligible edges of speech, the leak is usually airborne and often through a gap rather than the wall itself. If you hear a muffled murmur with no words, the wall is doing its job and simply lacks mass. If you feel more than you hear, a thud in the chest from music or a washing machine, the path is structural and needs a different remedy.

The first two are what a layered treatment solves, and it solves them with two products doing two different jobs. One blocks. One absorbs. Confusing the two is why so many DIY attempts with foam stuck to a shared wall change nothing at all.

Why mass, and why it has to be limp

A partition blocks sound roughly in proportion to how heavy it is and how little it wants to vibrate. You can add weight by building a second block wall, which costs you 150 mm of room, or you can add a dense, flexible membrane that carries weight without stiffness. SoundBlanket Mass Loaded Vinyl is the second option. At 2100 kg/m³ it is dense enough to matter and limp enough not to resonate, which is the property that separates it from a sheet of ply of the same weight.

It arrives in 32 x 4 ft rolls (10 m x 1.2 m), is ASTM, EN and ISO certified, and carries a Class A fire rating, which is the first thing a facility manager asks about in a residential tower.

Getting the barrier in without losing the room

The objection we hear most often is floor area. In a city apartment, a bedroom wall that grows by 100 mm is a real loss. The MLV route is deliberately thin: mounted directly behind gypsum or plasterboard, the whole barrier adds roughly 4 to 8 mm. The work is sequential, and skipping a stage is where installations go wrong.

1. Strip back and check the substrate

   Open up to a sound surface and look for the service chases, back boxes and any hollow behind the existing plaster. Everything you find now is something you would otherwise have sealed a barrier over.

2. Hang and lap the membrane

   Fix the MLV across the full wall face, floor slab to soffit, not just to the ceiling line. Lap the seams and seal them. An airtight, continuous membrane is the whole point; a barrier with a 10 mm open joint at the skirting performs like a barrier with a window in it.

3. Close the board over it

   Gypsum or plasterboard goes back over the membrane, with the perimeter sealed rather than left open for the skirting to hide. Only then does the assembly behave as designed.

Done properly, the wall moves from around STC 35 to STC 55 and above, which is the band written into hotel specifications.

Why finish with felt rather than paint?

Blocking the neighbour solves half the problem. The other half is that a sealed, hard-surfaced bedroom sounds tight and reflective, and every sound made inside it lingers. That is what Echsorbix PET felt panels are for. They run NRC 0.30 at 9 mm to 0.60 at 24 mm, absorbing the mid and high frequencies that make a room feel hard, and they come in 9 mm, 12 mm, 18 mm and 24 mm. Across a treated room, internal absorption reaches up to NRC 0.90.

They also solve the aesthetic argument, which in a bedroom is not a minor one.

• ColourMute: solid shades for modern interiors, the safe choice behind a bed or a sofa.
• Mirage: PET U-V groove designs with textured patterns, where the wall is meant to be a feature.
• Canvas Prints: custom graphic or printed designs when the client wants artwork rather than acoustics.
• Pinboard use: the panels take pins directly, which is why they work so well in a work-from-home corner or a child's study area.

When is bass the real complaint?

If the neighbour's subwoofer, a treadmill or an appliance is what wakes you, mass alone will disappoint. Low frequencies carry structural energy and need an absorber tuned lower than felt. In that case BassBloc at 20 mm, NRC 0.85, goes in behind the MLV. It is an addition, not a substitute, and on a wall where the complaint is only television and conversation it is usually unnecessary.

What changed in a Bangalore apartment?

A recent premium apartment project in Bangalore had the classic version of this problem: a shared bedroom wall carrying a neighbour's television at volume every evening. We installed SoundBlanket MLV at 4 mm (STC 34) behind new drywall and finished the face with Echsorbix ColourMute panels in Ash Grey, rated NRC 0.30 to 0.60 by thickness.

Audible noise dropped by roughly 15 dB. The owners described the change less in numbers than in behaviour: they stopped noticing when the neighbours came home.

Which gaps are left when the wall is done?

A finished wall exposes the paths you were not listening to before. Three are worth closing in the same visit.

• Electrical outlets: noise leaks straight through the back box into the cavity. Acoustic putty pads seal them.
• The entrance door: corridor noise arrives around the whole leaf. EPDM perimeter seals and bottom sweeps close it.
• Road-facing windows: soundproof curtains at 4500 GSM, STC 30 and NRC 0.20 add useful insulation where the glazing cannot be changed.

What should you do first?

Diagnose before you buy. Establish whether the complaint is speech, general noise or bass, and whether it arrives through the wall or around the door, because the three call for different money. If it is airborne noise through the party wall, plan a single opening of that wall and do the MLV, the sealing and the board in one visit. Then treat the room face with felt, and leave BassBloc as a decision you make only if the low end survives. Ask for the test reports before ordering: on a certified product they exist, and they are the only reason to trust the numbers on this page.