Employers Guide to Managing Noise in the Workplace
Posted in General on Feb 18, 2019
Design and lay out the workplace for reduced noise exposure
When considering a new workplace or modifying an existing one, noise emissions and noise exposure can be limited by careful choice of design, layout and the construction materials used for the building. For example, the appropriate use of absorption materials within the building can reduce or limit the effects of reflected sound (specialist help will be needed to put this into effect).
Noise risk management is a lot easier if you limit the number of employees exposed. Careful planning could segregate noisy machines from other areas where quiet operations are carried out, reducing the need for noise control after the workplace is in operation (see also the section on screens and barriers). The number of employees working in noisy areas should be kept to a minimum.
Use of absorption
When considering using noise-absorbing materials to change the acoustic characteristics of a work area remember:
- environmental and workplace factors: absorption materials are available in forms which are designed to withstand physical impacts, and can be adapted to hygienic environments or where absorption of oil, water etc may be a problem;
- there may be a reduction in the natural light if absorption is placed in the roof;
- adding absorbent materials to walls and ceiling areas will only affect the reflected, reverberant sound – not the direct path of sound.
Screens and barriers - placing an obstacle between the noise source and the people
Screens, barriers or walls can be placed between the source of the noise and the people to stop or reduce the direct sound. Barriers should be constructed from a dense material, eg brick or sheet steel, although chipboard and plasterboard can be used.
Screens and barriers work best when they are placed close to the noise source or close to the people you are trying to protect. The higher and wider they are, the more effective they are likely to be. They work best in rooms with either high or sound-absorbent ceilings.
Covering the barrier or screen with noise-absorbing material on the side facing the noise source will have the added advantage of reducing the sound reflected back into that area containing the noise source. Those workplaces which have already been treated with sound-absorbing material will help to create conditions which will allow the screen or barrier to perform to its maximum potential, since in these cases the direct noise is likely to be the dominant source.
CAUTION: Be aware of the following when using screens or barriers:
- Screens and barriers may not work well for low frequencies.
- They are best at reducing the direct noise, and may not affect reflected noise.
- Always place the screen or barrier as close to the noise source or employee position as possible.
- The screen or barrier should be made of a dense material, and should be lined with absorptive material facing the noise source.
- Always consider other health and safety risks, such as safe movement of people and vehicles, when placing barriers in the workplace.
Refuges - noise-reduced enclosures for people
Noise refuges can be a practical solution in situations where noise control is very difficult, or where only occasional attendance in noisy areas is necessary. The design of refuges will be similar to that of acoustic enclosures, although since the purpose is to keep noise out rather than in, lining the inner surfaces with acoustic absorbent material will not be necessary.
If machine controls are brought into the refuge, and thought is given to allowing remote monitoring or viewing of machinery and processes, it should be possible to minimise the amount of time that workers have to spend outside the refuge – so maximising the benefit of having the refuge. For example, a refuge that is used for only half a shift will achieve no more than 3 dB reduction in noise exposure.
Refuges must be acceptable to employees. This means they must be of a reasonable size, well lit and ventilated and have good ergonomic seating.
CAUTION: Check your refuge design for:
- adequate ventilation;
- good door and window seals;
- self-closing doors;
- dense construction materials, with plenty of acoustically double-glazed windows;
- isolation from the floor to reduce structure vibrations;
- size – is it large enough?
Distance - increase the distance between the source of the noise and the people
Increasing the distance between a person and the noise source can reduce noise exposure considerably. Some examples of this are:
- direct the discharge from exhausts well away from workers, eg by fitting a flexible hose to discharge exhaust several metres away from the operator. Similarly, on a mobile machine powered by an internal combustion engine the exhaust can be kept well away from the driving position;
- use remote control or automated equipment to avoid the need for workers to spend long periods near to machines;
- separate noisy processes to restrict the number of people exposed to high levels of noise, eg test engines in test cells which need to be entered only occasionally, make arrangements for quiet inspection tasks to be carried out away from noisy manufacturing areas, and locate unattended air compressors and refrigeration plant in separate rooms.
Protectors that reduce the level at the ear to below 70 dB should be avoided, since this over-protection may cause difficulties with communication and hearing warning signals. Users may become isolated from their environment, leading to safety risks, and generally may have a tendency to remove the hearing protection and therefore risk damage to their hearing.
The table below gives an indication of the protector factor that is likely to be suitable for different levels of noise (the noise level during a particular work task, not the daily personal noise exposure). It is based on the single number rating (SNR) value provided with a hearing protection device. The information is intended as a guide rather than a substitute for using one of the standardised methods for calculating hearing protection performance, and in particular will not be appropriate if there are significant low-frequency components to the noise in question. Examples of noise environments which may contain significant low-frequency components, and for which this table is not suitable, include press shops, generators and generator test bays, plant rooms, boiler houses, concrete shaker tables, moulding presses and punch presses.
Advice on issuing hearing protection
When issuing hearing protectors you will need to consider regulations 7 (hearing protection), 8 (Maintenance and use of equipment) and 10 (Information, instruction and training) of the Control of Noise Regulations at Work Regulations 2005 and take account of the points below.
You should provide your employees with information on:
- why you are issuing hearing protectors;
- where they must be used;
- how they can obtain replacements or new protectors; and
- how they should wear them properly and look after them.
You should ensure that employees can readily obtain hearing protectors and replacements when they need them. This might include personal issue to individual employees. Alternatively, you might wish to install dispensers from which employees can take disposable hearing protectors as they need them. Locate the dispensers at or near to the entrances to areas where hearing protectors are required, in a place where your employees can conveniently use them. Make sure you keep the dispensers topped up.
Personal issue and visitors
People should not pass earplugs to one another. Preferably, a set of earmuffs should be used by one individual only. Where earmuffs are kept for the use of visitors, they should be hygienically cleaned for each new wearer. Alternatively, disposable covers may be used.
Training and effective use
Hearing protection will only provide good protection when used properly and fitted correctly. Users must be instructed in its correct fitting and use, including: how to avoid the potential interference of long hair, spectacles and earrings on the effectiveness of their hearing protection; how to wear their hearing protection in combination with other personal protection; the importance of wearing their hearing protection at all times in a noisy environment (removing it for only a few minutes in a shift will lower the protection to the wearer considerably); how to store their hearing protection correctly; how to care for and to check their hearing protection at frequent intervals; where to report damage to their hearing protection.
Low noise machines
The Control of Noise Regulations 2005 requires that the actions taken by an employer in controlling noise risks and noise exposure should include consideration of the choice of appropriate work equipment emitting the least possible noise.
For many types of equipment there will be models designed to be less noisy. Noise-reduction programmes are only likely to be effective if they include a positive purchasing policy which makes sure you take noise into account when selecting machinery. When buying, hiring or replacing equipment the employer should ask potential suppliers for information on the noise emission of machines under the conditions of intended use, and use that information to compare machines.
Where it is found to be necessary to purchase machinery which causes workers to be exposed over the action levels of the above regulations, keeping a record of the reasons for the decision will help guide future action, eg by providing those responsible for future machine specifications with information on improvements that are needed. Part 4 of L108 has more information on the selection of quieter tools and machinery, including the use and limitations of manufacturers’ noise data.
Selection of low-noise tools and machinery through a positive purchasing and hire policy can avoid the need to apply retrofit noise control. This could be the single most cost effective, long-term measure an employer can take to reduce Noise.
A positive noise-reduction purchasing policy could involve:
- preparing a machine specification. Draw suppliers’ attention to the requirements of the Supply of Machinery (Safety) Regulations 2008 (see Part 4 of L108). Introduce a company noise limit, ie a realistic low-noise emission level that the company is prepared to accept from incoming plant and equipment given the circumstances and planned machine use;
- comparing the noise information declared by the manufacturer to identify low-noise machines;
- requiring a statement from all companies who are tendering or supplying, saying if their machinery will meet the company noise limit specification;
- discussing noise issues with the supplier of the machine. This may influence the design of future low-noise machines;
- where it is necessary to purchase noisy machinery, keeping a record of the reasons for decisions made to help with the preparation of future machine specifications with information on where improvements are necessary;
- using an agreed format for the presentation of results by suppliers;
- discussing machinery needs and noise emission levels with safety or employee representative(s).