The quick answer
BassBloc is a high-density absorber rated NRC 0.90 under ASTM C423, made to deal with the low frequencies that ordinary acoustic foam cannot touch. It is the middle layer of a soundproofing build, not a barrier on its own. Put it over MLV, cover it with a finish panel, and it stops walls resonating.
Low-frequency noise is the hardest kind to deal with. Long wavelengths carry more energy, pass through ordinary partitions with little loss, and are barely affected by thin absorbers. Bass is why a neighbour's television is audible as a thud when the words are not, and why a subwoofer two rooms away still finds you. BassBloc exists for that problem.
01 /What BassBloc actually is
BassBloc is a high-density acoustic foam made from recycled acoustic foam, pressed to 100 kg per cubic metre. That density is the whole point. Standard studio foam is a fraction of that and works on mid and high frequencies, which is why a room covered in pyramid foam still booms.
- Sheet size 6x3 ft, in 20mm and 40mm, with a 5 per cent size tolerance.
- Weight roughly 3.6 kg per 20mm sheet and 7.2 kg per 40mm sheet.
- Rated NRC 0.90 under ASTM C423 at both thicknesses.
- Fixing with SR Adhesive, ordered as an add-on or supplied separately.
02 /Absorbing is not blocking
This distinction decides whether your project works. Blocking sound needs mass, and mass is what MLV provides. Absorbing sound needs an open, porous structure, which is what BassBloc provides. A wall with only mass rings like a drum. A wall with only absorption lets everything through.
| Layer | Job | Rating | Alone? |
|---|---|---|---|
| SoundBlanket MLV | Blocks airborne sound with mass | STC 30 at 2.5mm, STC 34 at 4mm | Wall resonates |
| BassBloc | Absorbs vibration and low frequency | NRC 0.90 | Nothing is blocked |
| Finish panel | Covers, protects, finishes the room | Varies by material | Decorative only |
| All three together | Block, damp and finish | Full build-up | This is the system |
03 /Which thickness
- 20mm for bedrooms, offices, hotels and general wall build-ups where room depth matters and the noise is mostly speech and television.
- 40mm for studios, home theatres and anywhere a subwoofer is involved. The extra depth works further down the frequency range, which is where theatre and music problems live.
04 /Where it is used
Walls, ceilings and floors, in recording studios, home theatres, jamming rooms, apartments with shared walls, offices and any space where machinery or bass is the complaint. On walls it goes over the MLV and under the finish. On ceilings the same order applies. On floors it sits beneath the flooring build-up.
Related reading: how effective is MLV, and BassBloc compared with rockwool.
05 /Frequently asked questions
How effective is BassBloc?
BassBloc is rated NRC 0.90 under ASTM C423, which is high for an absorber. Its density of 100 kg per cubic metre is what lets it work at low frequencies where ordinary studio foam does very little. It is most effective as the damping layer over an MLV barrier rather than used on its own.
Can BassBloc block noise by itself?
No. Blocking sound requires mass, and BassBloc is an absorber. Used alone it will improve how a room sounds but will not stop noise passing through a wall. Pair it with SoundBlanket MLV, which is the blocking layer.
What is the difference between BassBloc and acoustic foam?
Density and purpose. Standard acoustic foam is light and shaped to scatter and absorb mid and high frequencies on a visible wall surface. BassBloc is 100 kg per cubic metre, goes inside the build-up, and targets low frequencies and structural vibration.
Does BassBloc need to be covered?
Yes, always. Cover it fully with felt panels, wooden slats, gypsum or HDHMR. It is a technical layer within the wall build-up and is not intended as a visible finish.
Sonit writes about practical soundproofing for Indian homes and workplaces, with a focus on what delivers measurable results at sensible cost.
