Wave Dynamics GuidesBS 4142 Explained
How BS 4142:2014+A1:2019 works: rating level, background sound, character corrections, context and what the results mean for planning.
In Short
BS 4142:2014+A1:2019 is the British Standard for rating and assessing sound from industrial and commercial sources, such as plant, factories and deliveries, at nearby homes. It compares the rating level of the specific sound, including penalties for tones, impulses or intermittency, with the existing background sound level.
- Compares rating level (LAr,Tr) with background sound (LA90).
- Adds character corrections for tonal, impulsive or intermittent sound.
- A difference of around +10 dB indicates a likely significant adverse impact; around +5 dB an adverse impact.
- Context must be considered before reaching a conclusion.
What BS 4142 Is Used For
BS 4142 is used in Ireland and the UK for new or existing industrial and commercial sound sources affecting residential receptors: air handling and refrigeration plant, data centre cooling and generators, energy storage, manufacturing, loading bays and similar. Planning authorities often name it in conditions.
The Method in Brief
- Background sound: measured as LA90 at or near the receptor during the periods when the source will operate.
- Specific sound: the LAeq of the source alone, measured or predicted, over 1 hour by day and 15 minutes at night.
- Rating level: the specific sound plus corrections for tonality (up to 6 dB), impulsivity (up to 9 dB), intermittency (3 dB) and other distinctive characteristics (3 dB).
- Initial estimate: rating level minus background sound.
Interpreting the Result
The greater the difference, the greater the likely impact. A difference of around +10 dB or more is likely to be an indication of a significant adverse impact, and around +5 dB of an adverse impact, depending on context. Where the rating level does not exceed the background sound level, that is an indication of a low impact.
Why Context Matters
The 2014 revision made context central. Absolute levels, the character of the existing area, the time of day and the sensitivity of the receptor can all change the conclusion. In very quiet areas, low absolute levels can be acceptable despite a high difference, and the reverse also applies.
Getting the Survey Right
The result depends heavily on the background level, so the survey must be representative: the right location, enough data, suitable weather and the right periods. That is where most BS 4142 disputes start.
Frequently Asked Questions
Is BS 4142 used in Ireland?
Yes. Irish planning authorities and the EPA regularly refer to BS 4142 for industrial and commercial sound, alongside EPA guidance such as NG4 for licensed sites.
Can BS 4142 be used for indoor noise?
No. It is intended for sound outside dwellings. Internal noise is assessed against guidance such as BS 8233.
This guide gives general information and is not a substitute for project-specific advice. Requirements change, so always check the current regulations, guidance and your planning conditions. Ask our team about your project.
Jon Maguire (BSc Hons MIOA) brings over 8 years of expertise in acoustic consultancy, specialising in environmental acoustics with a focus on 3D modelling, assessments, and detailed design for industrial, commercial, and energy projects. He has lead noise assessments for key clients while thriving in multidisciplinary environments. Jon’s diplomatic communication skills are ideal for stakeholder consultation.
Jack is a Field Engineer at Wave Dynamics, supporting the delivery of environmental monitoring and acoustic consultancy services through detailed on-site fieldwork. He has hands-on experience in noise monitoring, vibration monitoring, and dust monitoring across a variety of infrastructure, construction, and environmental projects. Jack is involved in the setup, operation, and maintenance of monitoring equipment, ensuring accurate data collection in line with relevant standards and project requirements. He works closely with consultants and project teams, providing reliable field support that underpins high-quality assessments and reporting.
Aidan is the Director for all U.K Operations and has worked in multiple industries including for clients in the UK and internationally operating in the residential, industry, healthcare, education, and construction sectors.
