Acoustics – Sound Insulation for the Building Envelope
Dave Arden, Technical Services Manager for Building Envelope products at Tata Steel, discusses the various solutions available to optimise sound insulation for the Building Envelope…
Metal roofing systems can be used to improve the acoustic performance of any building.
The three main areas that you will probably be involved with are: –
- Sound insulation – Resisting the passage of airborne noise through a wall or roof construction. This could be required to contain a particularly noisy process or to prevent unwanted noise penetration into a dedicated “quiet” area.
- Rain noise – Resisting the passage of impact noise, typically rain through the roof of building.
- Sound absorption – Reducing the reflection of noise within a space, to improve the acoustic properties of the space and reduce overall noise levels
Acoustic requirements are covered in England and Wales by Approved Document E and in Scotland in section 5.
Today we are going to have a look at Sound insulation
The required sound reduction will be based on either statutory requirements, planning conditions or specific industry guidelines and so can vary considerably. When reading through acoustic survey reports you will come across many terms that are unfamiliar but they are all used to describe different conditions.
The reduction in airborne noise of a roof or wall construction is referred to as the sound reduction index SRI. The higher the sound reduction, the better the performance. The reduction in sound will vary dependant upon the sound frequency. The performance across a range of frequencies is often quoted as a single averaged figure Rw.
Another unfamiliar term would be LAeq.T . This is the A weighted equivalent continuous sound pressure level. Used often in measuring noise from factories, construction sites etc. where the noise level varies over a period of time, it can be thought of as the average noise over a given period of time. “A” weighting is used as a method of dealing with the varying frequency content of sound so that it gives weight to the frequencies in a similar way to the human ear.
Predicted Sound Reduction Index Values – Trisomet® 333, 120mm core
Weighted S.R.I Rw = 29.4
Predicted Sound Reduction Index Values – Trisobuild® RL32-120-19
Weighted S.R.I Rw = 36.5
The examples above show the sound reduction that can be achieved using a 120 mm thick Trisomet® 333 PIR insulated panel and a 120mm thick Trisobuild® system using LP1000 liner and glass fibre insulation. The insulated panel does not perform as well as the built up system due to the connected cells of the foam, which cause an acoustic bridge.
Generally, single skin constructions show the lowest reduction, foam insulated panels of all thicknesses have performances slightly better than single skin, mineral wool insulated panels have better performance, particularly at low frequency noise, due to the increased mass in the panel and built up systems generally have the best overall performance, which can be adjusted by the use of different amounts of acoustic insulation.
We can supply the full range of options above and can provide an unbiased view on selecting the correct system for your project needs. For further information on different metal cladding systems you can find literature downloads on our website or can request a CPD on ‘Steel cladding systems for the non-domestic building envelope’ .
Our technical department have a large library of test results and can offer specific advice on the various Tata Steel systems and also provide predicted sound reduction figures for various build-ups within our Trisobuild® range to ensure you meet your project specific requirements. If the project requires it these predictions can be verified with testing at approved UK laboratories.
Please contact us on 01244 892130 for further details