The best way of reducing exposure is by controlling the noise at source.
Where a risk assessment identifies that individuals are exposed to hazardous noise levels at work, employers need to introduce measures to control the associated risks. These measures usually involve a combination of methods, such as controlling the noise at source, redesigning the layout of workstations and re-organising the work processes. Noise transmission pathways and personal hearing protection will also need to be considered.
Hierarchy of noise control
OSH professionals use the hierarchy of control to determine how to implement practical and effective risk management programmes to tackle noise-related issues in the workplace. The hierarchy of noise control includes elimination or substitution of noise sources, collective control measures through engineering and work organisation, and personal protective equipment.
Hierarchy of controls
There are several ways in which noise can be controlled, which can vary from one workplace to another. There’s no standard single technique or solution that is appropriate for every situation. Good understanding of plant operations and work processes is necessary to determine the most effective method of eliminating, minimising or controlling the noise.
Factors the employers should consider include:
- the scale of the noise problem and its impact on the business (including workers)
- cost and effort required to reduce noise exposure
- effectiveness of planned control measures
- the number of individuals who would benefit from those control measures.
An essential outcome of noise risk assessment is identifying and prioritising measures to control the risks. Employers can use the findings of the risk assessment to formalise an action plan for controlling noise. The key actions will include:
- prioritising and tackling the immediate risks
- identifying possible methods that can be used to control noise
- assessing the reduction levels that can be achieved by introducing cumulative controls
- assigning responsibilities
- monitoring controls and performance.
Noise can be controlled by using the following hierarchy of controls.
Elimination is a process that eradicates the noise source it is the most effective way to prevent risks to workers and should always be considered when introducing a new work process, selecting new work equipment and designing the layout of the workstations. Examples of noise elimination will include avoiding the use of noisy processes or machinery, elimination of impacts between hard objects or surfaces, outsourcing the noisy work processes and moving the noisy operations away from other work activities.
Advance planning and introducing a suitable purchasing or hire policy are essential to reducing the level of noise at work. Considering at an early stage how the new work process or new machinery would work without exposing the workers to excessive noise is the most cost-effective and long-term measure businesses can take to reduce overall noise levels. Before acquiring new machinery, its noise levels should be considered this can be achieved by liaising with and obtaining information from the manufacturer or supplier of the plant or machinery. This may include installation instructions, maintenance arrangements and likely noise levels under the specific conditions in which the machinery will be operated. The UK Health and Safety Executive’s ‘Buy quiet’ guide for purchasing quieter equipment provides further advice.
Substitution is a process of replacing noisy machinery or equipment with quieter alternatives. When elimination is not possible, substitution of the noisy machinery or equipment for quieter ones may be the next-best alternative to protect workers from exposure to noise.
Employers should always consider alternative equipment and work processes which would make the job less noisy. It’s also important to keep up-to-date with the applicable standards and industry good practice. Performing a task differently can also protect the workers from noise exposure for example, the use of welded instead of riveted construction in fabrications and the use of hydraulic processes to bend material produces less noise than hammering.
This table provides some exemplar substitution methods that can be adopted to reduce the level of noise in a workplace.
Engineering controls are all about making changes to processes, machinery or equipment so that the workers are exposed to less noise. For example, using screens, barriers, enclosures and absorbent materials help to reduce workers’ noise exposure.
Some engineering measures that may be considered include:
- separating the noisy area from other workspaces by a sound-reducing partition
- enclosure of noisy machinery with sound-absorbing material (effect may be limited unless total enclosure is achieved)
- avoiding metal-to-metal contact by using plastic bumpers
- using absorbent lining on surfaces to cushion the fall or impact of objects
- fitting sound-absorbing materials to hard reflective surfaces
- using conveyor belts rather than rollers
- using acoustical silencers in intake and exhaust systems
- using rubber mounts to isolate vibrating noise source to separate it from the surface it’s mounted to
- vmaintaining optimum speed of machinery or its particular components
- repairing and replacing loose rotating parts, worn bearings and gears
- using sound-absorbing material on walls, ceiling and floors to reduce the noise level due to reverberation
- undertaking regular maintenance on equipment (very effective in reducing noise emission if carried out regularly).
Administrative controls are the way work is organised to reduce either the number of workers who are exposed or the length of time they are exposed to noise. Administrative controls should be used when it is not possible to reduce noise exposure through elimination, substitution or engineering noise control measures.
Some administrative measures include:
- identifying hearing protection zones and clearly sign-posting noisy areas
- increasing the distance between noise sources and workers the further away the noise source is, the less harmful its effect on workers will be
- organising schedules so that noisy tasks are performed when as few people as possible are present
- minimising the number of individuals working in a noisy area keeping individuals out of the area if their job does not require them to be there
- limiting the time workers spend in noisy areas by job design and job rotation
- providing rest breaks in areas away from a noisy work environment
- providing sufficient information, instructions and training to the workers for the proper use of work equipment.
Personal protective equipment
Personal protective equipment protects the users from any adverse effects on hearing caused by exposure to high levels of noise. It is the last option in the hierarchy of control and should be used as a last resort after all efforts to eliminate or reduce the noise levels have been exhausted through technical and organisational means.
All hearing protection must be capable of reducing the noise exposure to the safe exposure levels and should be made available for workers to use. It is important to make sure that the hearing protection chosen to protect the workers is suitable for individuals working environment and compatible with other personal protective equipment being used, for example hard hats, dust masks, eye protection etc. It is good practice to offer different types of protectors so that workers can choose ones which suit them better.
Its important to remember that if the protection provided (attenuation) by hearing protection is too high, communication becomes difficult and individuals can end up working in isolation.
Selecting the hearing protection device
There is no single ideal type of hearing protection for all individuals and situations. No matter how good the hearing protection is, its not the best control as its effectiveness is reliant on its correct use, condition and whether it fits correctly.
To choose the correct type of hearing protection, employers must use the results from their noise assessment and the information from hearing protection suppliers.
The following factors play an important role in the selection of suitable hearing protection device(s):
- attenuation offered by the hearing protection device
- compatibility with other personal protective equipment
- comfortability to the wearer (pre-existing medical condition of user)
- impairment of important sounds (warning signals)
- costs of maintenance and replacement
- user preference
- ease of fitting and monitoring
- suitability for work environment (heat, humidity, dust, etc).
Hearing protection must be inspected periodically for any damage and replaced if its not of a disposable nature. Employers should make sure that hearing protection is available and well maintained, while employees are responsible for reporting any damage, defects or loss.
British Standard BS EN 458:2016 - Hearing protectors. Recommendations for selection, use, care and maintenance provides further guidance on hearing protection devices.
Fact sheet: The main types of hearing protection
Reviewing control measures
Implemented noise control measures should be reviewed regularly and if necessary revised, to make sure they work as planned. Employers should make sure that:
- all noise-related hazards have been identified, assessed and controlled
- control measures introduced are working effectively
- control measures introduced have not created any new problems
- the engineering controls put in place have made the job safer
- safety procedures are being followed adequately by the workers
- training and instruction provided to workers on how to work safely has been successful
- workers are raising health and safety concerns and reporting problems promptly
- frequency and severity of health and safety incidents are reducing over time.
If the control measures are not working effectively, employers should review their noise risk management programme and make further improvements in noise risk controls.