Professional tools
Occupational Noise Exposure
Computes a weighted exposure normalised to an 8-hour working day from exposure periods, and compares it to the table in the Second Schedule to the noise regulations.
What the tool does, and what it does not
- Computes a weighted exposure (LEX,8h) and a daily dose from the periods you enter.
- Compares the result to the table in the Second Schedule to the regulations, and shows the distance from the permitted value.
- It is not a sound level meter. The values are entered by hand and are not a measurement.
- It is not an occupational environmental test and does not replace a hygiene survey. Under the regulations, testing is carried out by an accredited laboratory tester.
- It determines nothing about hearing, health or medical fitness.
Exposure periods
Divide the working day into periods in which the level is roughly constant. A single period is fine.
- 1. Description
Periods left incomplete and excluded from the calculation: 1
Result
Enter a level and a duration for at least one period.
How it is calculated
LEX,8h = 10 · log₁₀ ( (1/480) · Σ tᵢ · 10^(Lᵢ/10) )
Each period is converted to acoustic energy, the energies are summed, and the total is normalised to a 480-minute working day. Because it is energy that is summed, doubling the time adds about 3 decibels — a property of sound, not of the regulations.
The permitted duration is taken from the schedule. For a level the schedule does not list, the exchange rate the schedule itself exhibits is applied. Below the lowest level in the schedule the regulations state no permitted duration, and the tool does not invent one.
Definitions from the regulations
The definitions are given as the regulations word them. Note the definition of continuous noise in particular: it requires a calibrated meter set to Leq and a measurement of at least 30 seconds.
Who measures, and how often
- Testing frequency
- At least once every two years, unless a regional labour inspector has directed otherwise
- Who carries out the test
- An accredited laboratory tester — an employee of a laboratory accredited by the Chief Labour Inspector to carry out occupational environmental testing of noise levels.
The source
Every numeric value in the tool comes from the Second Schedule to the regulations. Nothing here was written from memory.
- The regulations
- Safety at Work (Occupational Hygiene and Workers' Health in Noise) Regulations, 1984
- As amended to
- 2000-04-04
- Verified on
- 2026-08-22
What was not established: No evidence was found of an amendment to these regulations in 2022–2026, and no positive evidence of its absence either. The calculation is made against the text as amended to 2000.
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