Noise control: what I wish employers knew before making the big spend

Before the big spend: start with condition and maintenance

One of the most common patterns I see, once noise becomes a priority, is organisations moving quickly towards visible, high-cost solutions without first stepping back to assess whether noise levels have increased due to changes in equipment condition, rather than the process itself.

In many workplaces, elevated noise levels are not solely a function of design or duty, but the result of wear, poor adjustment or gradual deterioration of plant, equipment and machines over time. These issues are often addressable through maintenance and basic engineering attention, yet they are frequently overlooked when pressure mounts to ‘do something’ about noise.

Gill Cussons: "Employers often spend significant sums attempting to reduce noise levels from plant and machinery without first considering lower cost, but often more effective approaches."

Guards, covers and access panels are a typical example: as fixings degrade over time, panels can begin to rattle during operation, contributing unnecessarily to overall noise levels. This additional noise is a consequence of poor mechanical condition rather than the process itself, yet it is often accepted as unavoidable once it becomes part of the background.

Mechanical condition is another major contributor. Inadequate lubrication and worn bearings can significantly increase noise and vibration as friction rises. Fans associated with pumps and motors may also become partially blocked with dust, debris or product build-up, causing them to work harder and run hotter. As temperatures rise, lubrication degrades more rapidly, accelerating wear and noise generation. Because these changes tend to occur gradually, rising noise levels often go unnoticed until they are already problematic.

Compressed air systems are another frequently overlooked contributor. Leaking air from pneumatic pipework, fittings or couplings can generate continuous, high-frequency broadband noise. Because this noise is often localised and blends easily into busy production environments, it may not be recognised as a significant contributor to overall exposure. Multiple small leaks can accumulate across a site, increasing background noise while also driving unnecessary energy use, to the point where they are simply accepted as ‘normal’.

High-hygiene environments introduce additional challenges. While regular washdown regimes are essential, they can unintentionally shorten component life if not carefully controlled. High-pressure water directed at bearings, seals or isolation mounts can strip lubrication and introduce moisture into components, increasing the risk of premature wear and associated noise escalation.

Photograph: Shutterstock

The condition of existing noise control features is also frequently overlooked. Silencers may be missing, blocked or partially clogged, and vibration isolation mounts can harden or degrade over time, allowing structure-borne vibration to transmit more readily into surrounding structures.

None of these issues are complex, and none require redesign or new control measures. However, if they are not identified early, organisations can find themselves investing in large-scale interventions to compensate for problems that arise simply because equipment is no longer operating as intended.

Before committing to major expenditure, it is worth asking a basic but often overlooked question: has the noise increased because of the process, or because the equipment has drifted away from its original condition?

Trust the 3 dB rule and set expectations accordingly

Another thing I wish employers understood before committing to major noise control spend is how the 3 dB rule should shape expectations and priorities. When this is misunderstood, large budgets are often directed at highly visible but less effective changes, rather than at the dominant noise sources that would deliver the greatest reduction.

Decibels behave in a logarithmic, not linear, way, which means large physical changes do not always translate into equally large numerical reductions. In simple terms, halving sound energy only reduces the overall level by around 3 dB. This is a fundamental property of sound, not a limitation of measurement.

This becomes particularly relevant when organisations make sensible decisions such as removing a machine or shutting down one of two similar production lines operating in the same area. There is often an expectation that removing an entire machine will result in a dramatic drop in noise levels. In reality, if the two sources were contributing broadly equally, removing one halves the sound energy and delivers a reduction of approximately 3 dB in the overall level.

From a technical standpoint, this outcome is entirely predictable. From a business perspective, it can feel disappointing when the scale of the intervention appears significant. Without an appreciation of how sound energy combines, it is easy to conclude that the change ‘hasn’t worked’, when in fact it has performed exactly as expected.

This highlights an important principle that is worth understanding early, before budgets are committed and expectations are set: to achieve meaningful reductions in workplace noise, effort must be focused on the dominant source first.

An analogy I often use is lighting. If you wanted to make a room darker and it contained a ceiling light, table lamps and candles, you would not start by extinguishing the candles. You would turn off the main ceiling light first. Only once the dominant source has been addressed do smaller changes begin to make a noticeable difference.

Noise behaves in much the same way. Reducing lower-level contributors will have little impact if a dominant source remains untreated. Understanding this relationship before making large investments helps organisations prioritise effort more effectively and avoid spending significant sums on changes that were never going to deliver the reductions hoped for on their own.

Acoustic absorbent: what it can – and can’t – do

Another area where I regularly see significant sums spent with disappointing results is the use of acoustic absorbent materials.

This idea is often rooted in familiar imagery from films, rehearsal rooms or home studios where egg boxes are shown as a way of reducing noise, and it continues to influence how acoustic treatment is understood in workplaces.

In reality, acoustic absorbent is not primarily intended to stop sound travelling through walls. Its main function is to reduce reverberation by absorbing sound that would otherwise reflect back into the room. Used appropriately, this can make a space feel less harsh or echoic. Used without a clear purpose, it can make very little difference to the noise levels that actually matter.

A common misunderstanding is the expectation that lining walls or ceilings will significantly reduce the noise experienced by someone working close to a noisy machine. In practice, most of what the operator hears comes directly from the machine itself, so treating the room often has little effect on their exposure.

An analogy I often use is local exhaust ventilation (LEV). If someone is working at a bench with a grinder, placing the LEV system behind them would do very little to control what they are breathing in. The same principle applies to noise: treating the space does not address the dominant sound travelling directly from the machine to the person.

This does not mean acoustic absorbent has no place in noise control. It can be very effective where reverberation is genuinely contributing to overall noise levels. However, without a clear understanding of what problem is being addressed, organisations can spend considerable sums lining spaces and still find that measured noise levels – and operator exposure – remain largely unchanged.

For more information see:
uk-nvs.com
linkedin.com/company/noise-vibration-solutions

Gill Cussons is an Associate member of the UK Hearing Conservation Association (UKHCA). See:
hearingconservation.org.uk/at-work