Planning conditions for all new developments, especially residential, schools and healthcare, require a noise impact assessment. A Noise impact assessment involves comparing the predicted noise levels from the proposed development against the prevailing background noise levels.
By measuring existing noise levels in an area, we can establish an appropriate noise level for new noise sources to avoid disturbance and ‘noise creep’. We also calibrate noise maps (see below) to show how sound propagates across a built up area.
Noise surveys are used to assess the impact of environmental noise on a new development, particularly residential developments, where they allow us to establish the acoustic strategy for ventilations and facades (BS 8233 assessment).
Where new noise sources will be introduced, noise surveys are the basis for a BS 4142 assessment (see below) to establish the level of disturbance occasioned to surrounding premises.
BS 4142 is the standard used to assess the potential for disturbance arising from industrial and commercial noise sources. In a BS 4142 assessment, the noise from an existing or future noise source is compared against the existing background sound level. Penalties are applied for acoustically distinctive characteristics such as intermittency or tonality. Based on the difference between the ‘rating level’ and background and considering the acoustic context of the area, the likelihood of disturbance to surrounding areas can be predicted.
A BS 4142 assessment is usually required at the planning stage for new industrial and commercial noise sources. It can also be carried out where noise complaints are received to investigate whether there is a basis for the complaints.
For complex sites, noise modelling is a great way to investigate how new noise sources will affect the surrounding area. Models allow us to consider factors such as the landscape, screening from buildings and the location of new noise sources.
We calibrate models using the data gathered from noise surveys, which means multiple noise sources in an area (e.g. roads, industry, rail) can be accurately represented. Models also allow us to optimise mitigation measures such as bunding and noise barriers, saving money for the client while making sure the surrounding area is appropriately protected from noise.
During 2021, an industrial facility at Trafford Park, Manchester contacted dBx Acoustics to assist them with the investigation and resolution of noise complaints received from residents a new build development who had also involved the Environment Agency.
dBx carried out a night-time noise survey at the affected properties, which were 500 metres away from the client’s premises, to identify and quantify the noise reported by the residents. As our client’s premises was in the middle of a large industrial site with other noise generating operations in the area, our remit was to identify whether (a) the noise was emanating from our client’s site and (b) whether the problematic noise existed prior to the residential development and therefore arguably should have been mitigated for in the residential design.
Our extensive measurements established the source of the noise was a specific item of equipment on the client’s site.
We then carried out a detailed review of the planning documentation associated with the residential development. The documentation included multiple noise assessments by different consultants, with disagreement between them as to the impact of industrial noise on the proposed residential properties and the mitigation measures required. Our review found the planning noise impact assessments had only focused on the impact of noise during the day from a scrapyard adjacent to the residential development and had not included overnight noise measurements to assess more distant industrial noise.
We then analysed historic noise data and together with our own measurements we were able to demonstrate there had been no change in the industrial noise levels affecting the residential development since planning permission was granted. An assessment of the mitigation measures included within the planning noise impact assessments identified that these should be appropriate to control noise affecting residents to within acceptable limits.
The Environment Agency’s permit relating to the industrial site requires activities at the site ‘shall be free from noise and vibration levels likely to cause pollution outside the site’. A BS4142 assessment was carried out based on the noise levels measured by dBx Acoustics which identified the industrial noise would not be expected to adversely affect residential amenity.
The noise levels measured at the residential properties were found to be compliant with the Local Authority’s requirements for noise levels affecting residential amenity.
It was concluded our client was compliant with all relevant permits and legislation, and no further action by the Environment Agency was required.