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When exposure should be assessed
The answer depends on how loud the noise is and how long people are exposed to it. As a simple guide, you will probably need to act on noise if any of the following applies.
- The noise is intrusive for most of the working day, like a busy street, a vacuum cleaner or a crowded restaurant.
- Employees have to raise their voices to hold a normal conversation about 2 m apart for at least part of the day.
- Employees use noisy powered tools or machinery for more than half an hour a day.
- Employees complain of ringing or humming in the ears when they leave work.
- Employees complain of temporary hearing loss when they leave work.
- The business is in a noisy industry, such as construction, demolition or road repair, woodworking, plastics processing, engineering, textile manufacture, general fabrication, forging, pressing or stamping, paper or board making, canning or bottling, or foundries.
- The work involves impact noises such as hammering, drop forging or pneumatic impact tools, or explosive sources such as cartridge-operated tools, detonators or guns.
If the answer to any of these is yes, you need to assess the risks to decide whether more action is required, and plan how to do it.
There are two kinds of assessment.
Preliminary noise survey. An overview of noise exposure, in the form of a walk-through of the site with a sound level meter. It allows for variations in noise caused by shift changes and by the running of noisy equipment.
Detailed noise survey. Carried out when the preliminary survey shows that more specific monitoring is needed. The detailed survey will:
- use appropriate sound-level measurements or personal dosimetry to estimate representative worker exposure across the tasks performed
- evaluate each employee's exposure averaged over an 8-hour working day
- define the areas that should be designated as noise hazard areas where hearing protection is required
For US federal general industry, OSHA 29 CFR 1910.95 uses a 90 dBA eight-hour permissible exposure limit and an 85 dBA eight-hour hearing-conservation action level. Other sectors and jurisdictions can have different requirements and assessment methods. These figures are not interchangeable with the British system below.
In Great Britain, the Control of Noise at Work Regulations 2005 use the values below. Compare representative daily exposure and relevant peaks; weekly averaging is permitted only under specified conditions. Hearing-protector attenuation is considered for the exposure limit, not when deciding whether action values are exceeded. The listed duties are a summary, not the complete regulations.
| Level | Daily or weekly exposure | Peak sound pressure | What the employer must do |
|---|---|---|---|
| Lower exposure action value | 80 dB(A) | 135 dB(C) | Assess and control risk, provide information/training and make suitable hearing protection available on request |
| Upper exposure action value | 85 dB(A) | 137 dB(C) | Implement a noise-reduction programme; ensure suitable hearing protection is worn, designate zones where required and provide risk-based hearing surveillance |
| Exposure limit value | 87 dB(A) | 140 dB(C) | Must not be exceeded, with the effect of hearing protection taken into account |
Summary notes for Element 5 · Cheat sheet · Glossary. A study aid, not published or endorsed by NEBOSH.