Sound proofing in high impact areas

A first request for an answer to a problem. This one comes from a community centre in Cardiff and refers to how to help sound proof a community hall but also to keep a surface that will take the knocks and scrapes associated with playing games etc.

There are a couple of issues here and actually a common solution can be found that will help both.

Sound really comes in two main forms, ambient and impact. Ambient sounds are background mid range noises like talking, general hubbub etc, whilst impact noises are lower frequency and tend to be louder. To reduce sound transmission one requires a variety of material types that will affect different frequencies. Having heavy weight dense materials mixed with lighter weight ones and also ones that have a cushioning affect mean that the different frequencies of sound can all be reduced.

If we look at recording studios for example they use a range of techniques like having a ‘floating room’ where rubber is placed between structures to absorb sound and so isolate the sound studio. They also use angled glass of differing thicknesses to deflect sound and to reduce sound transmission across a greater range of frequencies. The room is also sealed so that there are no sound leakages, so a constant seal is important. Care is taken to ensure that rooms do not set up their own resonances because of having parallel walls, so walls are made to be angled and have ‘rougher’ edges as this disperses the sound in a less echo-ey manner.

So when looking at a community centre one can see that it is possible to use an internal system to reduce the noise transmission just by having an internal wall made of different materials with different densities, mass, resonance frequencies and also potentially with varying surfaces / angles.

There are also specialist materials like very heavy rubber sheeting that can be used to provide even more mass in a structure, e.g. acoustiblok.

So a make up that would have dramatic effect on the sound proofing of a wall would be:

Existing wall

Rubber strip attached to a 100mm stud wall frame

Higher density 75mm insulation(there are a range of ‘acoustic insulations’ available from virtually all the manufacturers)

Acoustiblok sheet (optional)

Heavy weight boards (here we would not recommend plasterboard as it can make sound worse by its resonance), so a product like a 25mm or 50mm woodwool board. These are incredibly strong and can easily take being basked around by footballs etc

Lime plaster / render with an embedded mesh

Silicate paint finish

By having a mix of heavy weight, fluffy and absorbent materials the vast majority of aural frequencies will be radically reduced. Care needs to be taken to ensure that all gaps are sealed up so that leakage is kept to a minimum. All doors and windows will also have to be checked to make sure that they are either double or preferably triple glazed and that there are draught-proof seals in place.

Similar structures can be used in a ceiling, but here there is a additional opportunity to put in different angles and shapes into the structure to reduce the possibility of resonance problems.

So the more mass, the more different types of material and the more deflective the design the better for acoustics.