Setting Noise Limits and Thresholds for UK construction Sites – Including ABC Method
BS 5228-1: 2009 Code of Practice for noise and vibration control on construction and open sites
BS 5228-1 code of practice is the guidance to which UK professional manage noise related to construction projects.
Setting the noise limits and thresholds requires some judgement and these levels are primarily dependant on the location of the construction project and the existing noise conditions. Sites with low ambient noise are likely to be more adversely affected than sites with higher ambient noise. BS 5228-1 gives some guidance on this topic in Annex E and it states noise assessments and thresholds are needed for 3 main reasons:
For EIA (Environmental Impact Assessments) - major schemes, possible compensation could be required for rehousing or noise insulation
For developments that do not require EIA but could still be required to advise on the likely effects that might arise.
Control of Pollution Act (CoPA) 1974, Section 61. These are applications for prior consent for work on construction sites. This is deemed to be desirable for all parties and they would include details of the works and methods and proposed steps to minimise noise resulting from the works. This application can include noise thresholds. It is recommended to use noise prediction software such as CadnaA as part of the application. By gaining consent under section 61 the contractor gains protection from stop/ enforcement notices under section 60 of the CoPA
Fixed limits are given in the standard but not often used now as they give no consideration to the site location and current noise levels. This older and more simplistic approach dates back to the 1963 Wilson report. It gives the following basic guidance:
Between 7am and 7pm – Levels outside the nearest window of the occupied room closest to the site boundary:
70 dBA in areas away from main roads and heavy industry
75 dBA in areas close to main roads and heavy industry
E 3.2 Method 1 - The ABC method
This is the most popular method and it takes account of the ambient conditions when setting noise thresholds
To summarise
Requires background/ ambient noise measurements prior to construction works.
Measure dBA LAeq which is the A weighted (adjusted for human hearing) equivalent sound energy which will be measured by your noise monitor/ Sound Level Meter.
Measurements should be of significant duration - normally from 08.00 to 18.00 Monday to Friday and 08.00 to 13.00 on Saturdays.
Measurements should be of more than one period. You should measure over several days where possible.
Process:
Round your LAeq dBA measurements to the nearest 5d. If your rounded value:
is less than the levels in category A then you should use category A as your thresholds
is the same as Category A values then you should use Category B thresholds
is more than category A then use category C thresholds
is higher than the values in the table see NOTE 2
Example calculation
E 3.3 Method 2 – 5dB(A) change
Noise limits from construction activities are deemed to be significant if:
Construction (including the ambient) noise is 5dB or more than the ambient noise pre-construction.
Lower cut-off values of 65dB, 55dB and 45dB for day, evening and night. i.e you do not need to set threshold values lower than these.
Thresholds and Monitoring Locations
It is often not possible to place noise monitors at the nearest dwelling for practical reasons such as power and security against theft. For this reason, monitors are often located on the perimeter of the site, and on these occasions, you may need to adjust the threshold values for monitors to reflect the distance they are located from the nearest dwelling.
Figure F2 & F4 in BS 5228-1 gives typical distance corrections, or you can use noise prediction software such as CadnaA to make these adjustments more accurately.
For doubling of distance from the noise source to the noise receptor there is a 6dB correction, as seen in the annotated diagram below.
For more details on construction noise monitoring please visit: https://www.campbell-associates.co.uk/construction
John Campbell MIOA