Noise exposure calculator

How daily noise exposure (LEP,d) works

The Control of Noise at Work Regulations 2005 measure noise as a daily personal exposure averaged over an eight-hour day, written LEP,d and given in dB(A). Because decibels are logarithmic, a short burst of very loud work can dominate the whole day — and you cannot simply add the numbers together. This calculator combines tasks by their sound energy, which is what the Regulations require:

LEP,d = 10 × log₁₀( Σ (tᵢ / 8) × 10^(Lᵢ / 10) )

where tᵢ is hours spent at level Lᵢ dB(A), normalised to an 8-hour reference day.

The three values and the duties they trigger

• Lower exposure action value — 80 dB(A) LEP,d. At or above this you must assess the risk, make hearing protection available on request, and provide information and training.
• Upper exposure action value — 85 dB(A) LEP,d. At or above this you must reduce exposure as low as reasonably practicable using organisational and technical measures (not just PPE), set up mandatory hearing protection zones with hearing protection worn, and provide health surveillance (audiometry) for those regularly exposed.
• Exposure limit value — 87 dB(A) LEP,d. This must not be exceeded. Crucially, the limit value takes the attenuation of hearing protectors into account, so simply issuing ear defenders does not bring you into compliance — the working arrangement itself has to change.

There are also peak sound pressure values for sudden, impulsive noise (135, 137 and 140 dB(C)) — for cartridge tools, piling and similar work, check those separately.

Getting the inputs right

• Use the time actually spent on the task, not the length of the working day. Several short noisy jobs across a shift are entered separately; the calculator normalises them to the 8-hour reference day for you.
• The +3 dB doubling rule. Every 3 dB(A) is a doubling of sound energy — so it halves the time you can spend at that level for the same daily dose. That is why a single loud half-hour can outweigh hours of quieter work.
• Indicative levels are estimates only. The presets here are typical operator-position figures to get you started. A real assessment should use measured levels or manufacturer in-use data for the specific equipment, working method and environment — HSE expects this where the lower action value may be reached.

This calculator gives an indicative LEP,d to help you judge whether a noise assessment is needed and what duties apply. It informs the decision — a competent person assessing the actual work makes it. See HSE's noise pages (hse.gov.uk/noise) and the Control of Noise at Work Regulations 2005.