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OnSafeLines Free Advice on Noise at Work Health Risks and Management to Help You Manage Health and Safety Responsibilities
What about Multiple sound sources
Q. Would two machines be twice as loud as one?
A. The two machines will be producing twice as much sound energy, but because of the way the ear responds this doubling of energy will only just be noticeable (3 dB).
Q. How much louder is the noise of ten identical machines than that of just one?
A. The ten machines will be perceived as twice as loud as one machine, i.e., 10 dB louder
In terms of changes in sound level, the human ear can just about detect a sound level change of 3 decibels, and perceives an increase or decrease of 10 decibels as a doubling or halving of 'the loudness'.
The Noise Regulations require you to take specific action at certain action values.
These relate to:
* the levels of exposure to noise of your employees averaged over a working day or week; and
* the maximum noise (peak sound pressure) to which employees are exposed in a working day.
The two methods of measurement of noise levels are, 1. 'A' weighting, written as 'dB(A), for average noise, and 2. 'C' weighting, written as 'dB(C)', for peak, impact or explosive noises,.
The values are:
* for the lower exposure action values:
- daily or weekly exposure of 80 dB (A - weighted);
- peak sound pressure of 135 dB (C - weighted);
* for the upper exposure action values:
- daily or weekly exposure of 85 dB (A - weighted);
- peak sound pressure of 137 dB (C - weighted);
There are also levels of noise exposure which must not be exceeded:
* exposure limit values:
- daily or weekly exposure of 87 dB (A - weighted);
- peak sound pressure of 140 dB (C - weighted);
Remember, these exposure limit values take account of any reduction in exposure provided by hearing protection.
To assist in meeting the requirements of The Control of Noise at Work Regs 2005 further guidance can be found in the following publications.
- L108 - Guidance on The Control of Noise at Work Regulations 2005.
- INDG362 - Noise at Work - Guidance for employers on the Control of Noise at Work Regs 2005
- INDG363 - Protect your hearing or lose it!
- HSE - Free Leaflets - Noise
One point to remember is that often noise and vibration go together and the requirements of the Control of Vibration at Work Regulations 2005 may well need to be considered. Guidance on the requirements of this legislation can be found in the HSE ACOP L140 which deals with hand-arm vibration.
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Noise at Work
