Noise at work: a manufacturer's guide to engineering controls
The Control of Noise at Work Regulations 2005 requires employers to control noise exposure through engineering controls before relying on hearing protection. This guide explains what the regulations require, what qualifies as an engineering control, and how to choose the right solution for your production environment.
What the Control of Noise at Work Regulations 2005 require
The Control of Noise at Work Regulations 2005 came into force on 6 April 2006 and replaced the earlier Noise at Work Regulations 1989. They apply to all employers in Great Britain whose workers are exposed to noise at work, with specific duties that increase as exposure levels rise.
The regulations establish three exposure values that define what action is required.
Lower exposure action value — 80 dB(A)
At this level or above, employers must:
- carry out a risk assessment
- provide workers with information, instruction and training on noise risks and controls
- make hearing protection available to any worker who requests it
Upper exposure action value — 85 dB(A)
At this level or above, employers must:
- implement a programme to reduce noise exposure, prioritising engineering controls
- provide hearing protection and ensure it is worn
- designate hearing protection zones and mark them with signs
- introduce health surveillance
Exposure limit value — 87 dB(A)
This is the absolute ceiling. Employers must ensure this level is never exceeded, even taking into account the attenuation provided by hearing protection. Where a worker’s exposure reaches the limit value, work must stop immediately, the cause identified and controls put in place before it resumes.
The values above refer to daily personal noise exposure averaged over an eight-hour working day. The regulations also set equivalent values for peak sound pressure: 135 dB(C) at the lower action value, 137 dB(C) at the upper action value and 140 dB(C) at the limit value. Peak values are relevant for impact noise such as hammering, pressing and stamping operations.
The hierarchy of controls: why engineering comes before PPE
The regulations are explicit about the order in which controls must be applied. This is known as the hierarchy of controls, and it is not a suggestion. Where a higher-level control is reasonably practicable, the employer must apply it before moving to a lower-level control.
- Elimination. Remove the noise source entirely. This is the most effective control and should always be considered first. In practice it may mean replacing a noisy process with a quieter one, or redesigning a production step to remove the operation that generates excessive noise.
- Substitution. Replace the noisy equipment or process with a quieter alternative. Examples include replacing pneumatic tools with electric equivalents, or replacing impact processes with pressing or bonding.
- Engineering controls. Modify the equipment, environment or work process to reduce noise transmission. This is the most commonly applicable level for production and manufacturing environments and includes acoustic enclosures, barriers, damping, isolation and silencers.
- Administrative controls. Reduce exposure by limiting the time workers spend in noisy areas, rotating jobs, or scheduling noisy work for periods when fewer workers are present.
- Personal protective equipment (PPE). Hearing protection is the last resort. It must be provided and must be worn where exposure cannot be adequately reduced by other means. It does not remove the obligation to apply higher-level controls where they are reasonably practicable.
Employers who issue hearing protection and consider the matter closed are not controlling a noise problem. They are managing the symptom of one. Where engineering controls are reasonably practicable and have not been implemented, PPE does not provide a legal defence.
What counts as an engineering control for noise at work
Engineering controls are physical modifications to equipment, layout or structure that reduce the level of noise at source or at the point of transmission. The HSE recognises several categories.
Acoustic enclosures
An acoustic enclosure is a structure built around a noise source to contain the sound it generates. It is the most effective engineering control for machinery and production equipment that cannot be substituted or redesigned.
A well-designed enclosure reduces the noise level in the surrounding work area by absorbing sound within the enclosure walls and preventing transmission outward. The degree of reduction depends on the construction, the materials used and how well the enclosure seals around the equipment, including access panels, ventilation openings and service penetrations.
OTTOKIND modular acoustic cabins are steel-framed enclosures with Class A sound absorption panels. They are designed to be fitted around existing machinery without requiring structural alterations or planning permission.
Acoustic partition walls and screens
Where a full enclosure is not practicable, acoustic partition walls and screens can be used to reduce the transmission of noise from a noisy area to adjacent work areas. They do not eliminate the noise at source but they reduce the ambient level in the surrounding environment.
Vibration damping and isolation mounts
Many noise problems in manufacturing arise from vibration transmitted through machinery frames, floors and structures. Anti-vibration mounts placed beneath machinery isolate the vibration at source, reducing both the airborne noise generated by the equipment and the structure-borne noise transmitted through the building fabric.
Silencers and exhaust treatment
Pneumatic equipment generates significant noise at its exhaust point. Silencers fitted to exhaust ports can reduce exhaust noise substantially without affecting equipment performance.
Acoustic booths for operators
Where a noise source cannot be enclosed, an acoustic booth or acoustic control room provides a quiet refuge from which operators can monitor the process. This approach is used where the equipment is too large or too complex to enclose, or where the process requires close monitoring but not continuous proximity.
How to choose the right engineering control for your situation
The right control depends on the nature of the noise source, the layout of your production environment, the access requirements of the equipment and the level of reduction required to bring exposure below the action values.
| Situation | Recommended control |
|---|---|
| Single machine generating noise above 85 dB(A), good access around it | Full acoustic enclosure |
| Noisy process area adjacent to quieter work area | Acoustic partition wall or barrier |
| Large machinery that cannot be enclosed | Acoustic operator booth or cabin |
| Noise from pneumatic tools and exhaust points | Exhaust silencers, plus enclosure if levels remain high |
| Noise transmitted through floor or structure from machinery | Anti-vibration isolation mounts, damping treatment on panels |
| Multiple noise sources across a production floor | Combination of enclosures for highest-output sources plus partitioning for adjacent areas |
In practice, most production environments require a combination of controls rather than a single solution. The noise risk assessment should identify all significant sources and specify the control hierarchy for each.
How acoustic enclosures reduce noise levels
When sound waves generated by a machine strike the walls of an acoustic enclosure, three things happen. Some sound is reflected back into the enclosure. Some is absorbed by the lining material. A small amount is transmitted through the wall to the outside. The ratio of these three outcomes determines the effectiveness of the enclosure.
The key performance indicators for an acoustic enclosure are:
- Insertion loss: the reduction in sound pressure level at a given point outside the enclosure, compared with the level without the enclosure in place. A well-designed enclosure for a single machine can achieve 15 to 30 dB of insertion loss.
- Sound absorption rating: the ability of the internal lining to absorb sound energy rather than reflecting it back. Rated from Class A (highest) to Class E. Class A absorption minimises reverberant energy build-up inside the enclosure.
- Flanking paths: routes by which sound bypasses the enclosure walls, typically through gaps around access panels, ventilation openings or service penetrations. Poorly sealed flanking paths are the most common reason an enclosure underperforms.
A 10 dB reduction in noise level corresponds to a halving of perceived loudness. A 20 dB reduction is perceived as a quarter of the original loudness. At 30 dB of insertion loss, a machine operating at 98 dB(A) would produce an ambient level of approximately 68 dB(A) outside the enclosure — well below both action values.
What “reasonably practicable” means for engineering controls
The phrase “reasonably practicable” appears throughout the regulations. It means the duty to implement a control is not absolute — it is qualified by whether the cost and effort involved is proportionate to the risk and the benefit achieved. However, the bar is set high, and employers who believe a control is not reasonably practicable must be able to demonstrate why.
The HSE’s approach to reasonably practicable for engineering controls takes into account:
- The level of noise exposure and the number of workers affected.
- Whether a suitable engineering control exists and is commercially available.
- The cost of the control relative to the reduction in risk it achieves.
- Any technical constraints that would prevent the control from working in the specific environment.
For modular acoustic enclosures, the reasonably practicable argument is usually straightforward. The products are commercially available, the technology is proven, they can be fitted around existing equipment without structural work, and their cost is substantially lower than a noise-induced hearing loss claim or a prosecution following a notice.
The cost of not acting: fines, claims and health surveillance
The financial case for engineering controls is clearer than it might initially appear. There are several categories of cost that flow from inadequate noise control.
HSE enforcement and prosecution
The HSE actively prosecutes employers who fail to control noise exposure. Published cases include a £50,000 fine against a UK manufacturer in 2019 where workers suffered noise-induced hearing loss and the company had relied on hearing protection without implementing engineering controls. Unlimited fines are available in the Crown Court.
Civil liability for noise-induced hearing loss
Noise-induced hearing loss (NIHL) claims are among the most common occupational health claims brought against UK manufacturers. A single successful claim can cost £20,000 to £50,000 in compensation and legal fees. Where multiple workers are affected and the employer cannot demonstrate adequate controls, group claims are common.
Health surveillance costs
Where noise levels are above the upper exposure action value and engineering controls are not in place, health surveillance must be provided to all exposed workers. Audiometric testing, medical review and record-keeping carry an ongoing cost that is removed once engineering controls bring exposure below the threshold.
The Annual Investment Allowance
OTTOKIND acoustic systems qualify as plant and machinery under the Annual Investment Allowance (AIA). This means 100% of the purchase cost is deductible from taxable profits in the year of purchase. For a business on 25% corporation tax, the effective cost after tax relief is 75% of the purchase price. The AIA limit is £1 million per year.
OTTOKIND modular acoustic systems: the engineering solution
OTTOKIND manufactures modular acoustic enclosures, partition walls and operator cabins for industrial and manufacturing environments. The systems are designed to be fitted around existing production equipment without structural building work, planning permission or production downtime.
- Modular steel construction — panels are assembled on site and can be reconfigured as your layout changes
- Class A sound absorption — the highest absorption rating, minimising reverberant build-up inside the enclosure
- Integrated access doors — full-width doors with acoustic seals for maintenance and material transfer
- Viewing windows — double-glazed acoustic windows for process monitoring without opening the enclosure
- Ventilation — attenuated ventilation openings maintain airflow without creating flanking paths
- TUV certified, manufactured in Germany — independently verified performance to European standards
- UK supply from DRH KIND — specification support, installation guidance and ongoing service from the UK
One installation in a European manufacturing facility achieved a 97% reduction in acoustic energy, bringing the working environment from above the upper exposure action value to well below the lower exposure action value.
Book a free 15-minute noise compliance review
If your production environment has areas operating above 80 dB(A) and you are not certain your controls meet the requirements of the Control of Noise at Work Regulations 2005, a free 15-minute review by phone or Teams will help you understand where you stand.
In that call we will:
- discuss the noise levels, equipment and layout of the areas you are concerned about
- identify whether an acoustic enclosure, partition system or cabin is the appropriate solution
- give you a clear sense of what is involved and a budget indication
There is no site visit required at the initial stage and no obligation to proceed.