Soundproofing Walls

NOVA Acoustics Ltd deals with builders, architects, developers and specifiers on a day to day basis and the challenges behind soundproofing walls are very apparent. It is really important to not only understand the target levels for wall soundproofing but also a few of the basic principles that will help you achieve a great sound test result.

1. Decoupling

We’ve all been in homes or flats where you can hear a person walking across the floor in the room directly above. This is particularly noticeable in buildings which have hardwood or marble floors and apartment buildings which have not been converted to a particularly high standard.

One of the best ways to reduce the sound of people walking on the floor above is to decouple the ceiling structure from the floor joists. This can be done using a Mute Clip System, a Resilient Bar System, A suspended MF Ceiling or an Independent Ceiling to decouple of the SoundBloc plasterboard linings from the joists above. Second to this decoupling the floor and creating a floating floor creates a suspension in the floor and decouples the cosmetic floor finish from the sub floor and minimise impact noise transference.
The same kind of system can also be used on the walls by creating a staggered or double stud wall which helps to reduce the spread of sound waves and vibration through the partition wall. Ideally, two layers of studwork should be installed with a good quality and high density acoustic mineral wool between the studs to reduce sound transmission even further.

2. Acoustic Mineral Wool

To ensure your partition floor or wall achieves a good degree of acoustic insulation, you will need to install a good quality mineral wool between the joists or studwork. This needs to be tightly fitted between the framework to ensure a ‘snug’ fit and not have any gaps or voids. ALOT of soundproofing and building supplies companies will call any mineral wool ‘Acoustic Mineral Wool’ but to ensure you are getting the best product there is one simple rule. If it comes in a roll it is not acoustic! (Even if its got acoustic written on it!). We specify good quality Acoustic Slab Insulation, such as Rockwool RW45, Rockwool Flexi or Rockwool RW3. These mineral wool products come in varying slab sizes and whilst having a higher mass per cubic metre, improving the acoustic insulation, they are also easy to install and sit snuggly between you joists or studwork.

3. Mass

One of the key ways to improve the acoustic insulation of a party floor or wall is to ensure there is adequate mass, this can be done by using one of the higher mass mineral wool products mentioned above. There are also a number of Mass Loaded Vinyl products which can be used to apply to floors or walls. Finally, using SoundBloc, Duraline or SoundPlank ensures that your plasterboard linings also have the optimum mass. It is very challenging to achieve the requirements of Part E of the Building Regulations when using standard 12.5mm plasterboard on your ceiling.
For sound to travel through a wall, it actually has to move, hence the vibration. By making the walls heavy and a lot more rigid, they become harder to move, meaning the vibrations will be reduced. Some cost-effective choices for making walls heavier include plywood, OSB, and cement board. Though a heavy wall will still vibrate somewhat and you will still hear low frequencies, the sound will be reduced dramatically.

4. Air Tight Seal

One of the key areas to guarantee the acoustic insulation performance you are aiming for is by achieving an air tight seal. Air is like water, if there is any gaps, holes or cracks it will find a way through. Poor sealing is one of the most common reason for Sound Test Failures and is so easy to overcome.

For example, with a timber floor construction take the following steps:

• Insulate between the joists with Rockwool RW45 and ensure this is tightly fitted between the timbers. Cut the insulation slightly proud of the joist spacing so that it holds itself in place.
• Ensure you leave an air cavity of 25 – 50% of the joist, this significantly improves the floors performance, never overfill with mineral wool and NEVER use Kingspan.
• On the underside of the ceiling, Install your ceiling system, Resilient Bars or Mute Clips. When installing your first layer of SoundBloc plasterboard affix this to the Resilient Bar or Furring Channel with no mechanical fixings (screws) to the joists. Finish the plasterboard with a 3mm gap around the perimeter. At this stage silicone the perimeter and joints. Now apply your second layer of SoundBloc plasterboard, stagger the joints, and follow the same process of finishing with a 3mm gap and silicone the perimeter and joints.
• From above apply your subfloor layer of 22mm Chipboard, if you are wanting a higher performing floor use a Cement Particle Board, this layer will need to be screwed into the joists. At this stage seal the perimeter and junctions within the room to ensure there are no gaps or holes.
• Finally lay your Composite rubber floor layer, Mutemat 2, over the top.

5. Add Damping

Finally adding damping to your wall and ceiling can help to dissipate the vibrations caused by sound waves. One of the easiest ways to add damping is to apply a layer of Tecsound between the plasterboard layers. Damping can be applied to all of the above soundproofing methods so long as two layers of board or drywall are being installed. When combined with a hot or resilient channel this results in a particularly effective soundproofing method.