Noise at work

This talk is about noise that can damage hearing. It is not the vibration talk, though the same tools often do both. The Control of Noise at Work Regulations 2005 require employers to prevent or reduce risks from noise at work. Employees have duties too. HSE's list for employers is: assess the risks, take action to reduce the exposure, provide hearing protection if other methods cannot reduce it enough, make sure the legal limits are not exceeded, give information, instruction and training, and carry out health surveillance where there is a risk to health. Low-level noise that is only a nuisance, and does not risk hearing damage, is outside those regulations.

The action values are daily or weekly averages, plus a peak. HSE's employers page sets the lower exposure action values at a daily or weekly exposure of 80 dB(A), and a peak sound pressure of 135 dB(C). The upper exposure action values are 85 dB(A), and a peak of 137 dB(C). The exposure limit values, which must not be exceeded, are 87 dB(A) and a peak of 140 dB(C). HSE's book L108 says you must not permit exposure above those limit values at the ear, so the reduction from hearing protection can be taken into account there, and that if a limit is exceeded you must act immediately to get the exposure at the ear back below it. You cannot hear the difference between 80 and 85 and call it a measurement. These are not numbers you guess from how annoying a saw sounds.

On a construction site, HSE says you will probably have to do something about noise if people have to raise their voices to talk while about 2 metres apart, for at least part of the day, or if they use noisy powered tools or machinery for more than half an hour a day, or if they are exposed to regular impacts such as pneumatic drills, or to explosive sources such as cartridge-operated tools. A separate rule of thumb on HSE's assessing page says the level is probably 80 dB or more if the noise is intrusive but normal conversation is still possible between people 2 metres apart, and probably 85 dB or more if you have to shout to talk to someone 2 metres away for more than about two hours in total. Those are prompts to assess, not a certificate that a quieter spell was safe. Enclosed spaces reflect noise back and can raise the exposure. Give particular attention to anyone who already has a hearing problem.

HSE names the kit that puts people at higher risk if they use it regularly, or work near it: concrete breakers, pokers and compactors, sanders, grinders, disc cutters, hammer drills, chipping hammers, cartridge-operated tools, scabblers and needle guns, and heavy plant. The first control is to make less noise. Eliminate the noisy task at the design stage where you can. HSE's examples of a quieter process are a block splitter instead of a cut-off saw, bursting or crushing instead of pneumatic drilling, and boring instead of pile driving. Limit reversing, because reversing alarms add to the noise. Isolate people by keeping cab doors and windows closed, or by using remote-controlled equipment. Shut plant down when it is not in use.

If noisy work remains, HSE says select low-noise tools, fit mufflers, silencers and sound panels, use barriers or existing cabins to stop noise travelling, keep people out of noisy areas, put stationary plant far from the work, and move walkways away from it. Rotate people, and use quiet days, so the exposure is managed. Weekly averaging is allowed as a way to manage exposures. Hearing protection comes after that. HSE's construction noise page and the noise FAQ both say you should not rely on hearing protection as the only control. It fails and it gets misused. Too much protection is also a problem, because people on a site need to hear what is happening and need to talk.

The hearing protection page says what the law then requires. Provide protectors if an employee asks and their exposure is between the lower and upper action values. Provide them, and make sure they are used properly, when exposure exceeds the upper action values. Identify hearing protection zones, where use is compulsory, and mark them with signs. Train people how to use and care for them. Aim at least to get below 85 dB at the ear. Avoid protectors that reduce the level at the ear to below 70 dB, because that over-protection can isolate people and lead them to take the protection off. HSE gives a guide, not a substitute for a proper calculation, based on the single number rating of the protector and the noise level of the task: 20 or less for 85 to 90 dB, 20 to 30 for 90 to 95, 25 to 35 for 95 to 100, and 30 or more for 100 to 105. That table is not for noise with a lot of low frequency, and HSE lists press shops, generators, plant rooms and boiler houses among the places it does not fit. Do not make hearing protection compulsory where the law does not require it, and do not have a blanket rule that ignores the task.

Protection only works when it is worn and fitted. Taking it off for a few minutes in the noise considerably lowers the protection. Long hair, woolly hats, spectacles and earrings can spoil the fit. So can a hard hat, a dust mask or eye protection, if the combination was not thought through. Check that earmuff seals are undamaged, that the headband still has its tension, that nobody has modified the protector, and that compressible plugs are soft, clean and pliable. Provide a range so people can find one that suits them. Health surveillance, meaning hearing checks, is needed if people are frequently exposed above the upper action value, or if they are at risk for another reason, such as already having hearing loss. If a check finds a problem, review the controls and act to prevent further harm.

HSE is plain about the harm. Noise can seriously damage hearing. Some people get a ringing in the ears, tinnitus, which can become permanent. Once hearing has gone, it will not come back. There is no cure. Hearing aids cannot fully compensate. The damage can make it harder to hear warnings, which is how a hearing problem becomes an accident. If today's job needs a shout at two metres, we look for a quieter way before we reach for the defenders. If the defenders are the control, they stay on for the whole noisy spell, and they are the pair that fits with the hat.