InterAction of Bath - Specialists in Noise Assessments

InterAction of Bath Ltd

Our services include:

  • Noise measurement across all or selected frequency ranges
  • Measurement of speech interference levels and related indices
  • Advice on limiting noise by a variety of methods, including modification of work process and machinery
  • Advice on suitable hearing protectors
  • Before and after studies to validate interventions

The following sections discuss the measurement of noise and the legal responsibilities incumbent on employers to limit noise to safe levels.

Prevalence of noise-related injury

A Medical Research Council survey for 1997 to 1998 suggested that over half a million workers in the UK suffer some level of work-related hearing damage - a surprisingly high proportion of the workforce. Yet work-related hearing damage is entirely avoidable.

Noise measurement

Noise is measured in decibels, usually weighted for the sensitivity of the human ear, abbreviated to dB(A). The faintest audible sounds are 0dB(A); loud conversation is around 60dB(A); and a road drill delivers around 100dB(A). You can find a few other examples below.

Typical noise levels
Equipment dB(A)
Power drill 90-100
Tractor cab 80-85
Lawn Mower 88-94
Air Compressor 90-93
Leaf Blower 95-105
Circular Saw 100-104

A more useful measure of noise is called a noise exposure value, which averages all noise levels experienced by a particular person across a specified time period, usually a working day or week. Respectively, it is often referred to as LEP,d or LEP,w. For brief loud noises, such as a gunshot, the peak sound pressure of the noise is more relevant, and in this case the unit is dB(C).

Responsibilities of employers

The Control of Noise at Work Regulations 2005 set the legal requirements for limiting work-related noise risks in the UK. The Regulations came into force on the 6th April this year, tightening up parts of the Noise at Work Regulations 1989. Perhaps most importantly they define three noise levels, as shown in the table. The actions required of the employer at each level will be explained in a moment.

The limits imposed by the Control of Noise at Work Regulations 2005
Name Value Measured where?
Lower exposure action value 80dB(A) daily or weekly exposure level
135dB(C)peak sound pressure
At source
Upper exposure action value 85dB(A) daily or weekly exposure level
137dB(C) peak sound pressure
At source
Exposure limit value 87dB(A) daily or weekly exposure level
140dB(C) peak sound pressure
Inside hearing protection

The Regulations also state the actions that employers must take to reduce the risks posed by noise. The process is actually quite simple:

Step 1: Begin with a risk assessment. List all the jobs that are noisy and then estimate their noise level in decibels. Ideally you would measure the noise with a noise meter, but as a last resort you could make estimates using the examples given earlier. Be pessimistic with your judgements of noise to allow a margin of safety. Make sure your risk assessment is contained in a document that can be stored, either as a hardcopy or on computer.

Step 2: Calculate the daily or weekly noise exposure by entering the noise levels and their durations into the noise exposure calculator at the HSE web page - it's very simple to use. The calculator takes account of the time you or your staff spend with different pieces of equipment.

Step 3: Having calculated the noise exposure values, you must take measures to reduce noise exposure if you or any of your staff are likely to exceed the action values or the limit value. The Regulations describe clearly what you need to do. It's useful to consider remedial actions in terms of four main areas: hearing protection, training, reducing noise, and health surveillance.

When noise levels equal or exceed the lower exposure action value:

Hearing protection: Employers must make hearing protection available and advise on its effective use. It need not be worn, but it must be made available.

Training: Staff should be told about (a) the risks posed by noise, (b) the action levels and the exposure limit value, (c) the results of the noise risk assessments, (d) the availability and provision of personal hearing protection, and (e) safe working practices to minimise exposure to noise.

Health surveillance: Staff should know about (a) how to detect and report signs of hearing damage and (b) their entitlement to health surveillance and its purposes.

At or above the upper exposure action value stricter requirements apply:

Hearing protection: This is compulsory and the employer must use signs to designate the zones where it is required.

Reducing noise: Noise must be reduced as far as reasonably practicable by (a) adopting different work methods, (b) buying quieter equipment or using noise insulation, (c) improving the design and layout of workplaces, (d) adopting appropriate maintenance programmes for work equipment, the workplace and work systems, and (e) imposing limits on the duration and intensity of noise exposure

Training: Suitable and sufficient training must inform employees how to minimise their exposure to noise. Employees should be advised how to use hearing protection effectively.

Health surveillance: A comprehensive screening programme is necessary, including a means for staff to report high noise levels and hearing damage, and a method of monitoring the hearing of staff.

As for the exposure limit value, this is an area into which noise levels must never stray - avoid it at all costs!

Step 4: Next develop a plan of action and check periodically that it is being followed. Hold onto the risk assessment and the action plan. You might need to revisit them when work arrangements change. For example, new equipment might be used or perhaps some of your staff will shortly work on a new site.

These steps will be the basis for managing the risks of noise at your work place.


For more information have a look at the free HSE leaflet called Noise at Work: Guidance for Employers on the Control of Noise at Work Regulations 2005, available at, and Protect your hearing or lose it!, available at Both leaflets are also available by post from the HSE on request.

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