BS4142 Noise Survey & Assessment: A Practical Guide to BS4142 Noise Assessments and Planning Permission
Posted in Acoustic Consultants News on Jan 09, 2020
What is BS4142?
The British Standard BS 4142: 2014 - Methods for rating and assessing industrial and commercial sound is used for the assessment of noise of a commercial and industrial nature. It provides methods for rating and assessing sound of an industrial and/or commercial nature, including:
- Sound from industrial and manufacturing processes
- Sound from fixed installations of mechanical and electrical plant and equipment; this commonly includes air conditioning units and extractions systems
- Sound from the loading and unloading of goods and materials at industrial and/or commercial premises
- Sound from mobile plant and vehicles that is an intrinsic part of the overall sound emanating from premises or processes, such as that from forklift trucks, or that from train or ship movements on or around an industrial and/or commercial site.
The assessment method in BS 4142 is based on the difference between the measured ‘background sound level’ without the influence of any industrial noise source, and the ‘rating level’ of the industrial source, at the receiver location. BS4142:2014 states: “The significance of sound of an industrial and/or commercial nature depends upon both the margin by which the rating level of the specific sound source exceeds the background sound level and the context in which the sound occurs”. An estimation of the impact of the specific sound can be obtained by the difference of the rating sound level and the background sound level and considering the following:
- “Typically, the greater this difference, the greater the magnitude of the impact.”
- “A difference of around +10dB or more is likely to be an indication of a significant adverse impact, depending on the context.”
- “A difference of around +5dB is likely to be an indication of an adverse impact, depending on the context.”
“The lower the rating level is relative to the measured background sound level, the less likely it is that the specific sound source will have an adverse impact or a significant adverse impact. Where the rating level does not exceed the background sound level, this is an indication of the specific sound source having a negligible impact, depending on the context.”
Why do you need a BS4142 noise assessment?
BS4142 noise surveys are conducted to assess the likely impact of industrial and commercial noise sources at noise sensitive premises. So, if you are installing external plant equipment, including air conditioning units, extractions systems or generators at your commercial premises. The Local Authority will request a BS4142 noise assessment to be undertaken to ensure the noise impact at the closest sensitive premises is kept to a minimum. BS4142 will also apply if you are developing new sensitive premises, including residential houses or flats, schools, healthcare or hotels, in close proximity to existing industrial or commercial noise sources.
A BS4142 noise report can be requested at the pre-application stage of planning permission, if the Local Authority considers noise to be a high enough risk to affect the likelihood of the planning application being accepted. Or it may be conditioned under the planning permission approval. The information submitted within a noise survey report allows the Planning and Environmental Health Departments to assess the level of noise impact expected from the development and ensure appropriate noise control measures are put in to place.
Ultimately, the purpose of the BS4142 noise survey is to ensure that the development is compliant with the National Planning and Policy Framework and Noise Policy Statement for England.
Typical Planning Conditions?
Here are some examples of typical planning conditions that relate to BS4142:2014:
Example 1: Prior to the first occupation of the Class A1/A2/A3/D1 floorspace within the development hereby permitted, details of all mechanical plant associated with the selected use, including the proposed location for installation and an assessment of associated noise impacts, shall be submitted to and approved in writing by the Local Planning Authority. The report shall clearly outline mitigation measures for the development to reduce these noise impacts to acceptable levels. It should include
all calculations and baseline data and be set out so that the Local Planning Authority can fully audit the report and critically analyse the contents andrecommendations. The development shall be implemented in accordance with the details as approved.
Example 2:“The rating level (LAeq,T) from all fixed plant and machinery associated with the development, when operating simultaneously, shall not exceed the background noise level (LA90,T) at any time when measured at the nearest noise sensitive premises. Noise measurements and assessments should be compliant with BS 4142:2014 "Rating industrial noise affecting mixed residential and industrial areas".
Typically, the Local Authority considers that new developments should contribute and enhance the area in which they are located, therefore the Local Authority will normally define the following criteria;
‘The development should be designed so as to achieve a rating level of 5dB (LAeq) below the typical background (LA90) level at the nearest noise sensitive location’.
How is a BS4142 noise survey conducted?
The aim of a BS4142 noise survey is to firstly gain a baseline measurement of the prevailing background noise. Secondly
- We will carry out an environmental noise measurement to assess the prevailing background sound level without the proposed industrial or commercial noise source in operation at the closest sensitive receptor
- An assessment of the noise emissions from the source of industrial noise under assessment is conducted. If the noise source is not yet operational, acoustic modelling will be undertaken to predict the level of noise emissions. If the noise source is operational noise measurements will be conducted at the closest sensitive receptor with the noise source active.
- The level of noise impact is analysed according to BS4142:2014 and the level in which the industrial noise exceeds the prevailing background sound level dictates the likely impact.
- We recommend and assess appropriate mitigation measures to protect the closest sensitive premises from noise.
- We will provide a technical report for submission to your local authority to support your planning application
What will be in the technical report?
The purpose of the technical report is to concisely outline to the Local Authority the level of noise impact expected from the proposals in accordance with BS4142:2014 and to ensure appropriate noise control measures are being installed. The noise survey report will outline the following:
- A statement outlining the purpose and objectives of the report
- A detailed review of the proposed development
- A description of the surrounding area and the noise sources that are being assessed
- The method that has been applied to assess the noise, including monitoring locations, the equipment used, calibration details, a weather summary and when the survey was conducted
- A summary of the results pertinent to the survey which typically include, LAeq,t, LAMax,T, LA90, LA10 and 1/3 octave LZeq,t.
- An assessment of the noise level results in accordance with BS4142:2014
- Recommendations and Mitigations measures required to protect the closest noise sensitive premises including calculations of the expected noise reduction from the noise control measures.
What Recommendations and Mitigations measures can be expected from your noise report?
The report will aim to apply all reasonable noise control measures to ensure the likely noise impact is minimised in accordance with the requirements of BS4142:2014. It is always preferable for noise to be controlled at source, however this is not always feasible. The following mitigations measures can be applied:
- Specifying Low Noise Equipment
- Distance Separation
- Screening and Acoustic Barriers
- Building Layout and Design
- Acoustic Enclosures
- Sound Insulation Schemes
- Acoustic Glazing and Doors
- Alternative Ventilation Strategies
What do you need to do?
Once you have had your BS4142 noise survey completed and received your technical report, you will need to review the recommendations and ensure any amendments to the design of the development are clearly outlined in your site layouts, detailed plans and any other supporting documents. The report will need to be sent to the council for approval, which should be received in writing.
Following this, the responsibility then falls on the developer to ensure all the recommendations and mitigations measures are installed. Quality control and workmanship can have a huge impact on the adequate performance of noise control measures, so it is imperative to have a high standard of workmanship to ensure the correct execution of the acoustic detailing recommended.
How can we help?
We listen to our clients’ needs and present them with practical, cost-effective solutions. This means that we offer a truly bespoke acoustic consultancy service for prices that are considered among the most competitive in the industry. NOVA Acoustics Ltd places a team of highly skilled, qualified and experienced acoustic consultants at our client’s full disposable; this is combined with the latest equipment, technological insights and expert guidance and recommendation, to ensure that clients are getting a guaranteed quality service every time they decide to get in touch.
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