Noise Impact Assessments & BS 4142
Why do I need one?
A noise impact assessment is required whenever a development has the potential to affect its neighbours by way of noise emission. For example, a restaurant might want to install some kitchen extract plant, a supermarket might want to receive deliveries at night, or perhaps a company would like to build a new factory near a residential area. All of these situations would need planning permission from the local planning authority (LPA), and part of that application would require a noise impact assessment.
The noise impact assessment needs to demonstrate that either the proposals won’t adversely affect the neighbours, or that the applicant is prepared to adapt their proposals, in order to cut down the noise emissions sufficiently.
What’s involved?
The process involves comparing the noise emission of the proposed development to the existing soundscape of the area. In simple terms, if the noise from the development is too loud, it’s likely to cause problems.
To assess how likely this is, an environmental noise survey is carried out to measure the existing sound levels. Then, using information about the proposed development, calculations are made to work out how loud it will be. By comparing the ‘before’ and ‘after’ situations, it’s possible to estimate the level of impact.
The noise survey is carried out outdoors, and usually involves a set of specialist measurement equipment being left on site over a number of days. Very often, additional short-term measurements are required alongside this. It all depends on the context of the site and what’s proposed.
What do we offer?
Firstly, we will discuss your project with you to establish your individual needs. We’ll need details about what it is you’re planning, where it’s situated, what times it might be in use, and whereabouts the nearest neighbours are.
Following that, we’ll visit the site to do our measurements. We’ll use our state-of-the-art calibrated meters to measure the current sound levels, and we’ll also use the most sophisticated sound-sensitive devices of all – our ears! While numbers can tell us a great deal about a soundscape, they only paint half the picture – the subjective impression is just as important.
Next, we’ll crunch the numbers. Using the data we’ve measured on site, plus details about the noise emission from your proposed development, we’ll carefully compare the ‘before’ and ‘after’ scenarios. We usually do this using dedicated noise mapping software.
If your plans need to be adapted in any way so that the noise output is reduced, we’ll work closely with you to advise on potential measures you can take.
Once we’re happy with the proposals, we produce a professional noise impact assessment report which can be submitted to the local authority as part of the planning application. In the vast majority of cases, this results in a successful application. If for any reason the local authority object to the proposals on grounds of noise, we can work with them to find a suitable solution.
BS 4142 – what is it?
British Standard 4142 is the benchmark guidance document for all noise impact assessments when it comes to any type of commercial or industrial noise. It has its origins back in the 1960s, when a government report investigated the increasing levels of noise in the UK. The current version was published in 2014 and revised in 2019.
BS 4142 prescribes a very specific procedure for assessing the likely impact of noise on nearby dwellings and other noise-sensitive places. It’s a very robust methodology which has evolved over time and applies the ‘agent of change’ principle, e.g. that the existing residents should not be adversely affected by any new noise source.
Almost all noise impact assessments for industrial or commercial developments in the UK are assessed against BS 4142, because it provides a framework which is both understood by everyone concerned and also extremely reliable.
Example: kitchen extract plant
Say someone wants to open a restaurant in a town centre. The unit they’d like to use sits in a row of shops on the high street, and there are flats above them.
Once we have all the details of the project, we would go down to the site and carry out an environmental noise survey. In this case, this would probably involve installing a microphone and a sound level meter close to the flat above the vacant shop unit.
With the data from site, and information about the extraction equipment, we can model the noise emission from the proposed development, and compare this with the existing soundscape. Using the methodology of BS 4142, we might find that there’s a likelihood of an adverse impact on the nearby residents.
To overcome this, we might find an alternative set of extraction equipment, or suggest attenuators that could be fitted to the ductwork, so that the sound level is reduced. This would then be detailed in our report before submission to the local authority.