Improving Floor Sound Insulation Performance

As mentioned in the title, two key areas need to be looked at when improving a floor construction: the airborne aspect (tv noise, music, speech etc.) is typically dealt with by applying ceiling treatments and mass to the system and the impact (footfall etc.) performance is increased by the used of resilience and isolation of layers.

Let's look at how to deal with airborne sound insulation in the first instance and then detail the steps to improve the absorption of impact noise (although, as you will see, there is an overlap between the two topics).

Airborne noise soundproofing

In existing dwellings (taking the typical example of a house converted into two flats, ground and first floor), the separating floor construction typically consists of the following layers, from top to bottom:

• Existing floorboards

• Timber joists

• Plasterboard ceiling directly fixed to the joists

As you can probably imagine, this minimal construction is not adequate to separate two dwellings, being an internal partition originally. This system would typically achieve a sound insulation performance of 35dB Dntw + Ctr, way below the 43dB minimum requirement (see sound testing explained for more details).

So, what treatments are necessary to achieve adequate airborne performance?

Several simple and not extremely onerous additions should be made to drastically improve the soundproofing of this typical floor.

First and foremost, any debris ac

umulated between the joists should be removed. For 150mm (6 inch) or thicker joists, we would recommend the insertion of medium to high density (around 40kg/m3) mineral wool between the joists. This will help in absorbing medium to high frequencies, converting the sound energy into heat.

Practical Acoustics is a leading acoustic consultant specialising in Sound testing and Noise Surveys.