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BS 4142 Assessments

At JG Acoustics, we provide expert BS 4142 noise assessments for industrial and commercial type sound on nearby properties. Our detailed reports help developers, businesses, and planners meet local authority conditions, minimise noise complaints, and secure planning approvals with confidence.

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BS 4142 Noise Assessments – Minimising Impact

BS 4142:2014 describes methods for assessing the likelihood of adverse comment arising as a result of commercial or industrial type noise. The methodology requires the determination of the ‘noise rating level’ (or LAr,Tr) for the noise source(s) being assessed, which is the noise of the plant plus corrections for acoustic characteristics, e.g. tonality, impulsivity, intermittency. The noise rating level is then compared against the prevailing ’background sound level’ (or LA90,T) at the noise-sensitive receptor considering the following guidance: 

  • Typically, the greater the difference, the greater the magnitude of the impact;

  • A difference of around +10 dB or more is likely to be an indication of a significant adverse impact, depending on the context;

  • A difference of around +5 dB is likely to be an indication of an adverse impact, depending on the context; and

  • The lower the rating 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. When the rating level does not exceed the background sound level, this is an indication of the specific sound source having a low impact, depending on the context.
     

Local authorities may publish or specify their own requirements for a BS 4142 noise impact assessment as part of planning conditions. Often, these include stricter rating level limits, such as -5 dB or -10 dB below the representative background level, to minimise potential noise impact on surrounding properties. At JG Acoustics, we ensure any recommended mitigation aligns with these requirements, helping clients navigate the path to compliance and secure approvals.

BS 4142 Methodology
✅1 / Baseline Noise Survey

We attend site and install a class 1 noise monitoring system in a secure location. Often this will be left for a minimum of 24 hours under suitable weather conditions. 

✅2 / Source Measurements

We also conduct on-site measurements to assess noise sources in operation. If the noise source is not yet installed or operational, we will request manufacturer specifications for its Sound Power Level (Lw dB)—a fundamental rating before the noise becomes airborne. Using this data, we can calculate and predict the anticipated noise levels at the nearest receptors. Often this will involve the use of noise modelling software such as SoundPlan. Character corrections shall also be applied according to BS 4142 requirements.

✅3 / BS 4142 Report

The report will include a full site survey, assessment outcomes, and conclusions. Where practicable and required, it will also outline recommended mitigation measures to achieve compliance with local authorities conditions.

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Types of Noise Sources and Mitigation

While the scope of BS 4142 is limited to industrial and commercial noise, it is commonly used for air handling systems as part of building services, and external fixed plant and machinery. However, its application can be broader, covering more unusual cases such as playground noise, gymnasiums, dog kennels and field facilities. In the absence of a standardised approach for these noise sources, the suitability of BS 4142 can often be discussed with the local authority. At JG Acoustics, we have extensive experience collaborating with councils to establish appropriate methods and criteria, ensuring a practical and accepted assessment approach.​

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It is strongly recommended that any BS 4142 noise assessment is carried out at the planning stage to avoid costly mistakes and mitigation. We cannot stress this enough. Too often, we are contacted after installation, when a noise complaint has been served- most commonly for domestic air conditioning units. Early assessment ensures compliance, minimises risk, and prevents expensive mitigation action when options are more limited.

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Examples of Mitigation Measures

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Mitigation strategies we may specify include, but are not limited to:

  • Optimal siting of equipment, considering distance from noise receptors, avoiding reflections, and making use of existing acoustic features.

  • Alternative selection of equipment of a lower noise emissions value. 

  • Acoustically graded barriers or walls to reduce direct noise transmission.

  • Acoustic enclosures or louvres, either as standalone solutions or integrated into a plant room configuration.

  • Resilient/anti-vibration mounts to prevent structure-borne noise transmission.

  • In-line split attenuators and silencers within ducting to minimise airflow noise.

  • Directional exhausts to control and redirect noise emissions.

  • Landscaping and natural screening, where appropriate, to absorb or deflect noise.

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At JG Acoustics, we provide expert BS 4142 noise assessments and tailored mitigation strategies to help businesses, developers, and homeowners achieve compliance and avoid costly noise issues. Whether at the planning stage or in response to a noise complaint, our practical approach ensures effective solutions that meet local authority requirements. Get in touch today to discuss your project and find the best path to approval.​​​​​​

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