Noise Impact Assessment

BS4142:2014+A1:2019 is the British Standard for rating and assessing industrial and commercial sound. It applies when a proposed development will introduce specific sound sources — such as plant equipment, extraction systems, or industrial processes — near existing noise-sensitive receptors. It compares the rating level of the specific sound source (including any corrections for tonal, impulsive, or intermittent characteristics) with the background sound level at the nearest sensitive receptor.

ProPG: Planning and Noise is professional practice guidance published in 2017 for the planning of new residential development in areas affected by noise from transport sources (roads, railways, aircraft). It provides a staged approach: an initial noise risk assessment, a detailed appraisal if needed, and an assessment of good acoustic design. It is the primary guidance document for residential schemes near busy roads or railway lines and is widely referenced by planning authorities across England.

The duration depends on the purpose. For assessing road traffic noise at a proposed residential site, a minimum 24-hour continuous measurement is typically sufficient. For BS4142 assessments, measurements of the background sound level are needed during the periods when the noise source will operate — often requiring separate daytime and night-time surveys. Where noise conditions vary significantly (for example, near a venue that only operates at weekends), the survey should capture representative worst-case conditions.

BS8233:2014 recommends internal ambient noise levels of 35 dB LAeq,16hr in living rooms during the daytime and 30 dB LAeq,8hr in bedrooms at night. Individual noise events at night should not normally exceed 45 dB LAmax more than 10-15 times per night. These are design targets, and the acoustic glazing and ventilation strategy for new dwellings should be specified to achieve them. ProPG provides additional guidance where transport noise is the dominant source.

Yes. The NPPF states that planning decisions should avoid noise giving rise to significant adverse impacts on health and quality of life, and should mitigate and reduce noise impacts to a minimum. Where the noise assessment demonstrates that adverse effects cannot be adequately mitigated — for example, where even with the best available glazing, garden noise levels would be unacceptable — the planning authority may refuse permission. Noise is a material consideration that carries significant weight.

LAeq is the equivalent continuous A-weighted sound pressure level — essentially the average noise level over a measurement period. It is the primary metric for assessing transport noise exposure. LA90 is the level exceeded for 90% of the measurement period, representing the background noise level without the influence of individual noise events. LA90 is the key parameter in BS4142 assessments, as it establishes the background against which a new noise source is compared.

Very likely, yes. Restaurant and takeaway applications near residential properties almost always require a noise assessment covering plant and extraction equipment, customer noise, delivery and waste collection noise, and operating hours. The assessment may need to demonstrate compliance with BS4142 criteria for plant noise and address the potential for disturbance from patrons entering and leaving the premises, particularly in the evening and at night.

A noise mitigation scheme is a package of measures designed to reduce noise impacts to acceptable levels. For residential development near roads, this typically includes enhanced acoustic glazing, alternative ventilation systems (so windows can remain closed), and careful site layout with buildings screening outdoor amenity areas. For commercial developments, mitigation might include acoustic enclosures for plant, anti-vibration mounts, silencers on extraction systems, and restrictions on delivery hours.

Turnaround depends on the survey requirements. If baseline monitoring is needed, the survey itself takes at least 24 hours and often longer. Some consultancies offer expedited services where the survey and report can be completed within 2 weeks at a premium. However, rushing a noise assessment risks undermining its conclusions — if the survey period is not representative of typical conditions, the planning authority or their environmental health officer may reject it.

The council's Environmental Health Officer (EHO) is the primary technical consultee for noise matters in planning. They will review your Noise Impact Assessment and advise the planning case officer on whether the methodology is appropriate, whether the conclusions are sound, and what conditions should be attached to any permission. Building a good working relationship with the EHO early in the process — ideally through pre-application discussions — can help avoid surprises later.