The Noise at Work Regulations, explained.

Regulation 4 of the Noise at Work Regulations sets three pairs of figures. Each pair has an A-weighted value for personal noise exposure, daily (the dose over a working day normalised to eight hours) or weekly (normalised to five eight-hour days), and a C-weighted peak value for sudden impulsive sounds such as hammering, cartridge tools or pressing.

The action values take no account of hearing protection. They describe the noise arriving at the person, and they trigger duties. The limit values take the attenuation of any protection worn into account, so they describe what reaches the ear, and they must never be exceeded. Properly worn protectors can keep someone exposed to 95 dB(A) all shift inside the limit, but every duty attached to the upper action value still applies. The limit is a backstop, not a target.

Daily personal noise exposure, written LEP,d, is an energy average. Every 3 dB increase doubles the sound energy and halves the time it takes to reach the same dose. An exposure of 85 dB(A) for eight hours is the same dose as 88 dB(A) for four, 91 dB(A) for two, or 94 dB(A) for one. Weekly exposure, LEP,w, may be used instead where exposure varies markedly from day to day: a fitter who spends one day a week grinding, for example. It is not a way of diluting a consistently noisy job.

Regulation 5 requires a suitable and sufficient assessment of the risk wherever employees are liable to be exposed at or above a lower exposure action value. A sheet of meter readings is not an assessment, and neither is a generic document that does not name the jobs on this site. The assessment has to identify who is at risk, estimate their exposure well enough to say which action values are likely to be reached, and record what is being done about it. The Regulations list what it must take into account, and how it is recorded and kept current.

The Regulations do not prescribe a measurement method. L108 sets out the principles, and BS EN ISO 9612 gives the engineering method that workplace measurement is normally carried out to. BS EN ISO 9612 describes measurement strategies that build the day from individual tasks, sample across a group doing the same job, or cover the whole working day, usually with dosimeters. A good survey often mixes them.

Instruments are specified by class. L108 says sound level meters should be integrating-averaging meters of Class 1 or Class 2, and that personal sound exposure meters, usually called dosimeters, should meet their own instrument standard. Class 2 instruments are acceptable for noise at work measurement. Our sound level meters are Class 1, holding current traceable laboratory calibration certificates and field-checked before and after each deployment. Whatever the class, the meter is checked with an acoustic calibrator before and after each series of measurements, and the readings are discarded if the two checks disagree by more than the tolerance BS EN ISO 9612 allows.

With a hand-held meter the microphone is held close to the ear, on the side of the noisier ear. A dosimeter microphone is mounted on top of the shoulder on the same side, clear of clothing and the wearer's own voice. Dosimeter time histories are inspected and knocks or interference removed rather than averaged in. Every exposure figure carries an uncertainty, and it should be reported with the result.

Regulation 6 is the one that gets forgotten. The risk from exposure must be eliminated at source or, where that is not reasonably practicable, reduced to as low a level as is reasonably practicable. Where the upper exposure action value is likely to be reached, the employer must put in place a programme of organisational and technical measures to reduce exposure, and hearing protectors are specifically excluded from that programme. Earplugs are the last line, not the plan.

Hearing protection is governed by Regulation 7. Any area where people are likely to be exposed at or above the upper exposure action value must be designated a hearing protection zone and marked with the standard ear protection sign. Access must be restricted where that is practicable and the risk justifies it. The employer must ensure, so far as is reasonably practicable, that no employee enters without protection. The boundary is drawn from measured levels, not from the edge of the machine. At or above the lower action value, protectors must be made available to any employee who asks. At or above the upper action value they must be provided wherever exposure cannot be brought below that value by other means, and Regulation 8 requires the employer to ensure, so far as is practicable, that they are properly worn.

L108 says protectors must at least bring exposure below the limit values and advises aiming for a level at the ear between 70 and 80 dB(A), avoiding anything below 70 dB(A): over-protection isolates people, hides warning signals and gets protectors taken off. It also advises subtracting 4 dB from the manufacturer's attenuation figure to allow for how protectors are actually worn.

Regulation 9 requires health surveillance wherever the risk assessment shows a risk to health. L108 reads that as everyone likely to be regularly and frequently exposed at or above the upper exposure action value, and anyone exposed between the two action values who is at particular risk. For noise that means audiometry: L108 describes a baseline test, ideally before exposure begins, then annual tests for the first two years and three-yearly tests after that, more often if a change is found. Employees are told their own results, and the employer keeps a health record for each person under surveillance, containing no confidential medical detail. Where a test shows hearing damage, the employer must have the employee examined by a doctor. If the doctor considers the damage likely to be the result of noise exposure, the employer must make sure the employee is told, review the assessment and the controls, consider moving the employee to work with no risk from further exposure, and keep up surveillance while reviewing the health of everyone else similarly exposed.

An inspector checking compliance with the Noise at Work Regulations on a noisy site is likely to start with the noise risk assessment, and the questions that follow are easy to anticipate. Who did it, and were they competent? Does it describe the plant running today? Which action values are reached, and what controls followed? Is the hearing protection adequate, and is it worn? Who is under health surveillance, and what have the results shown?

An improvement notice needs only a breach, not an injury. The gaps that invite one are no assessment at all, an assessment years out of date, exposures above the upper action value with protection as the only control, and no health surveillance where it is plainly required. Each of those is visible in the paperwork before an inspector takes a single reading. The same document is what an insurer asks for when a hearing loss claim arrives.

A workplace noise survey starts with a work analysis: the processes, the job roles, the shift pattern and what a normal day looks like, because a survey measured on an unrepresentative day describes nobody's exposure. The work analysis then sets the strategy for each job: task-based measurement with a hand-held meter where the day breaks into clear tasks, dosimeters where people move between areas or the pattern is unpredictable. Levels are measured at operator positions, task durations are observed rather than estimated, and peaks are taken wherever impact noise is present. The calculation gives an LEP,d for each job role, with its uncertainty, set against the action and limit values. Our noise at work service page sets out how that assessment is scoped and delivered.

Assessments we are asked to review fail in the same few ways.