Noise Assessment Calculator

There is no single legal limit, but local authorities typically set daytime limits of 65-75 dB(A) LAeq at the nearest noise-sensitive receiver. BS 5228 provides guidance values: 65 dB for low ambient areas, 70 dB for suburban, and 75 dB for urban/industrial areas. Work outside permitted hours (usually 08:00-18:00 Mon-Fri, 08:00-13:00 Sat) is generally not allowed.

For a point source, noise decreases by approximately 6 dB for every doubling of distance. So if a concrete breaker is 95 dB at 10m, it will be approximately 89 dB at 20m, 83 dB at 40m, and 77 dB at 80m. This is the inverse-square law. Line sources (e.g., traffic) decrease by only 3 dB per doubling of distance.

A solid construction site barrier (2.4m high hoarding) typically reduces noise by 5-15 dB depending on its height relative to the line of sight between source and receiver. A barrier that just breaks the line of sight gives about 5 dB reduction. Higher barriers or earth bunds can achieve 10-15 dB. The barrier must have no gaps to be effective.

Under Section 61 of the Control of Pollution Act 1974, a contractor can apply to the local authority for prior consent for construction works. This sets agreed noise levels, working hours, and best practicable means (BPM) of noise control. Having Section 61 consent provides a defence against prosecution under Section 60 noise nuisance notices.

On-time percentage is the proportion of the daytime assessment period during which the plant actually operates. For example, a concrete breaker running 5 hours in a 10-hour day is 50% on-time. Because the percentage is already defined relative to the assessment period, BS 5228 applies a single correction of 10 × log10(on-time/100) to convert the level-while-operating into the period LAeq — so 50% on-time lowers the LAeq by 3 dB versus continuous running. There is no separate adjustment for the length of the working day; the working-hours figure here is descriptive only.