About BS 4142:1997 Noise Assessments
BS4142 Noise assessments are normally requested by a Planning Officer or E.H.O (Environmental Health Officer) due to concerns of increased noise from proposed mechanical noise e.g. Fans, Air Conditioning Systems, Generators etc. applied for in a planning application to the local authority (Council).
Background noise levels should be measured as broadband dB LA90, with the specific (mechanical/commercial) noise measured as an LAeq.
The British Standard BS4142 describes methods for determining at the outside of a building:
- Noise levels from factories, industrial premises or fixed installations or sources of an industrial nature in commercial premises
- Background noise level
The standard also describes a method for assessing whether the noise referred to in a. above is likely to give rise to complaints from people residing in the building. The method is NOT suitable for assessing the noise measured inside buildings or when the background and rating levels are very low.
It is usually accepted that a 10dB excess (specific noise over background noise) will create a situation where complaints are likely.
Measurement positions.
Chosen measurement positions are outside buildings and representative of the specific noise level and background noise level at the buildings where people are likely to be affected. To minimize the influence of reflections the measurements are taken at least 3.5m from any reflecting surface other than the ground. The preferred measurement height is between 1.2 to 1.5m above the ground.
Noise Assessment – Process
A class 1 (or Type 1) Sound Level Meter and environmental kit is positioned on site.
Broadband background noise levels (LA90) are monitored and recorded.
The specific noise (LAeq) (the new noise source) is measured (if already commissioned) or calculated if in the planning stage.
Specific levels are compared to background noise levels in accordance with BS4142: 1997 or relevant local authority UDP (Unitory Development Policy).
For more information, please call 01366 387354