Noise exposure calculator Add each noisy task and how long one person spends on it to see their daily exposure against the 80 and 85 dB(A) action values, and the time left.

What is daily noise exposure (LEP,d)?

It is one person’s noise dose for the day, given as the steady level that would deliver the same dose over eight hours. Loudness and time both count. Every 3 dB doubles the sound energy, so at 88 dB(A) the eight-hour allowance for 85 is used up in four hours, and at 91 in two.

HSE’s worked example has three tasks. 80 dB(A) for 5 hours is 20 points, 86 dB(A) for 2 hours is 31, and 95 dB(A) for 45 minutes is 94. That makes 145 points, a daily exposure of 86.6 dB(A). The 45 minutes at 95 give 65% of the points, so that is the task to quieten first.

The formula is in Schedule 1 of the Control of Noise at Work Regulations 2005. HSE’s points system is in Appendix 3 of L108, Controlling noise at work.

What are the noise action values?

• From 80 dB(A) assess the risk, make hearing protection available to anyone who asks, and give information and training.
• From 85 dB(A) cut the noise by means other than ear defenders, provide hearing protection and make sure it is worn, and sign the hearing protection zones.
• 87 dB(A) is the limit at the ear, with hearing protection taken into account. Nobody may be exposed above it.

The values are in regulation 4. The duties are in regulations 5 to 10, explained in L108.

How long can you be exposed to 85, 90 or 100 dB?

Each time is for that noise alone, from the Schedule 1 formula. Anything else loud that day uses up the same allowance, so two hours at 91 dB(A) leaves no time for any other noise before 85.

How do HSE noise exposure points work?

Decibels cannot simply be added, so HSE turns each task into points that can. 100 points in a day is 85 dB(A) and 32 points is 80.

An hour at 80 dB(A) is 4 points, at 86 it is 16, and at 95 it is 125. So 45 minutes at 95 dB(A) gives more points than a whole eight-hour day at 80.

The points system is in Appendix 3 of L108.

When can you use weekly exposure instead of daily?

Only where exposure varies markedly from day to day (regulation 4). L108 says that is only likely to fit one or two days at least 5 dB louder than the rest, or three or fewer noisy days in the week. Consult the workers first, and never use it to cover a very loud day without hearing protection.

The week is always divided by five, however many days are worked. Seven days at 85 dB(A) come to 86 dB(A) for the week, not 85.

Does hearing protection count?

Only against the 87 dB(A) limit, at the ear. The 80 and 85 action values are always judged without ear defenders (regulation 4).

For the level at the ear, take the task’s C-weighted level, subtract the protector’s SNR and add 4 dB, because ear defenders on site do less than in the test. A task at 100 dB(C) with ear defenders rated SNR 25 gives 79 dB(A) at the ear. L108 says to aim for 70 to 80. Below 70 is too much, and people stop hearing warnings and traffic.

HSE’s hearing protection guide gives this as a rough guide. It does not suit low-frequency noise such as generators or plant rooms.

Where do I get the noise level for a tool?

A noise survey of the work gives the best figure, the LAeq. Failing that, the tool’s manual gives the sound pressure level at the operator (LpA), which manufacturers must declare above 70 dB(A). It is for the machine alone, so on site the level can be higher. The sound power level (LWA) in the same manual is a different, bigger number. Phone apps can be more than 10 dB out (L108).

HSE’s quick test needs no meter. If the noise is intrusive but you can still talk normally 2 m apart, it is probably 80 dB or more. If you have to shout to someone 2 m away for more than about two hours a day, it is probably 85 or more.

HSE’s typical construction figures are whole-day exposures, not task levels, and HSE warns they can vary a lot.

Enter one of these on the week tab as a day’s figure, not as a task level.

How do I use a dosemeter reading?

A dose in Pa²h or a percentage turns straight into points. If the dosemeter ran for only part of the time in the noise, the points are scaled up by time exposed over time measured. Choose “I have a dosemeter reading” on a task. If it gives an LAeq instead, enter that as a normal task.

The calculator uses the exact conversion, where about 1.01 Pa²h is 100 points. L108 rounds it to 100 points per Pa²h, so its example of 1.3 Pa²h over 2.5 hours, scaled to 6, gives 312 points where the calculator gives 308. Both come to 90 dB(A).