Posted: 22nd April 2022
When applying to your Local Authority for planning consent for a pub, restaurant, factory or any other type of industrial and commercial development, it is common for the Environmental Health Officer (EHO) to request that a BS 4142 noise impact assessment report is submitted with the application. So, what is a BS 4142 assessment?
The scope to BS 4142:2014+A1:2019 Methods for rating and assessing industrial and commercial sound advises that it provides a method to assess the potential effects of noise of an industrial or commercial nature to outside residential dwellings. Typical examples given include:
The standard can be used to consider complaints about existing industrial noise or to assess potential impacts from proposed new developments.
An important first step is for the assessor to fully understand the situation which is being assessed. BS 4142 describes this as the ‘context’. Some acoustic consultants or other people following the BS 4142 assessment method miss out this vital step which can render the entire outcome meaningless.
Once the context has been established and appropriate measurements/receptor positions identified, a background sound level survey is carried out. The survey should be carried out using a sound level meter which confirms to BS EN 61672-1 Class 1. All of ACA Acoustics’ sound level meters conform to this standard.
It’s important that the survey is conducted during appropriate weather conditions. We discuss the impact that weather conditions can have on the results of a sound level survey on a previous blog.
The commercial noise is then measured. For a source with a constant level, such as a fan, this may only need a single short measurement. Other sources, such as a large industrial facility, may require a number of different measurements, surveys over a number of days, measurements with different wind directions, or even surveys at different times of the year.
When a new source is being proposed noise levels are calculated. It’s important that accurate calculation methods are used, for example following British or International Standards.
Corrections are applied to the industrial noise level to account for characteristics which might make the noise more noticeable or disturbing. This corrected sound level is called the ‘rating level’.
The rating level is compared to the background sound level. The higher the rating level is above the background sound level the more likely that there will be an adverse impact on residents. If the rating level is equal to or below the background sound level, BS 4142 advises the commercial noise source will have a low impact.
The context of the assessment is considered along with the numerical result to determine the final assessment outcome.
BS 4142 is a very useful assessment method, when used in the way it is intended. The problem is that some Environmental Health Officers – and some other acoustic consultants – try and use the assessment method in situations where it is not suitable.
Section 1.3 of BS 4142 confirms that vehicles on public roads and railways should not be considered industrial or commercial noise and use of the standard is not suitable. It also confirms the method is not suitable when assessing sound to inside a property.
Other areas explicitly excluded by the standard are:
We have seen many situations where an EHO or other acoustic consultants have used BS 4142 where the standard should not be used. These include assessing outdoor dining areas to restaurants, music from bars, and dogs barking.
One example included a planning application for an outdoor seating area to a bar. Another acoustic consultant used BS 4142 to assess noise from people on the terrace and recommended a 3m high fence at the residential boundary. Planning permission was refused because of the height of the proposed fence. The client contacted ACA Acoustics for a second opinion. We confirmed that BS 4142 was not appropriate and quickly determined that when assessed correctly the fence was not necessary,
A BS 4142 assessment should be conducted by an acoustic professional with sufficient training and direct experience. The assessor must fully understand the context of the assessment. As part of that ACA Acoustics can advise when BS 4142 is not appropriate and agree an alternative and more suitable methodology with the EHO on your behalf.
Using the correct assessment method can have a significant impact on the required sound levels and could save ££££’s on unnecessary noise control measures.
To discuss your project and find out more about our acoustic consultancy services please contact our qualified acoustic consultants today.