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Controlling Noise on Site: Practical Steps Beyond Hearing Protection

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Noise induced hearing loss is one of the most common occupational diseases in Australia, and Safe Work Australia reports that close to 30,000 workers' compensation claims for hearing loss have been lodged since 2015. It is also entirely preventable, and the controls that prevent it are well understood and readily available.

Earplugs and eardefenders have a place, but they cannot protect the person who is not wearing them, the person who takes them out to have a conversation, or the person who has been issued the wrong class. The most effective noise control happens before the sound reaches anyone's ears.

This guide takes you through a practical noise control programme, in the order you would actually do it.

• What the exposure standard requires, with the regulation numbers
• How to reduce noise at the source
• How to isolate what you cannot quieten
• Where administrative controls and hearing protection fit
• Measure and prove the controls are working

Step 1. Know what the exposure standard requires

Part 4.1 of the model WHS Regulations sets the noise exposure standard in two parts. Regulation 56 defines it as an eight hour equivalent continuous A weighted sound pressure level of 85 dB(A), and a C weighted peak level of 140 dB(C).

The first figure is calculated as time average. It is the average over eight hours, which means a shorter exposure at a higher level carries the same risk. Two hours at 91 dB(A) is the same dose as eight hours at 85 dB(A). Every three decibel increase halves the time you can be exposed.

The second figure is an instant. A single impact above 140 dB(C), a sledgehammer strike or a nail gun, can cause immediate and permanent damage regardless of how quiet the rest of the shift was.

Regulation 57 requires the risk of hearing loss to be managed, and regulation 58 requires audiometric testing where workers frequently need personal hearing protection to keep them under the standard. That last point is worth noting. If you are relying on hearing protection to achieve compliance, you have also triggered a health monitoring duty.

The Code of Practice also notes that the standard protects most people, not all. Levels below 75 dB(A) over eight hours are unlikely to cause hearing loss, so where it is reasonably practicable to get well below 85, that is the better target.

Step 2. Identify where the noise dose is coming from

You cannot prioritise noise controls without knowing where the noise dose comes from, and estimating from experience is unreliable.A useful first pass is to identify the areas and tasks where conversation at a metre is difficult. That is a rough indicator of 85 dB(A) and above, and it tells you where to measure properly.

Personal dosimetry worn for a full shift tells you what an individual actually receives across all tasks. Area measurement tells you which machine or operation is driving the level. Boundary monitoring tells you what the neighbours receive against the consent condition. Sites that measure only one of these are regularly caught out by the other.

Step 3. Control the noise at the source

The most effective controls change the machine or the process, not the person.

• Buy and hire quiet. The Code of Practice calls a purchasing and hiring policy one of the most cost effective long term noise controls available. Sound power data is available from manufacturers and suppliers, so the quietest suitable plant can be specified at the point of hire. It costs nothing at the point of decision and removes the noise for the whole life of the hire.
• Maintain the plant. Worn bearings, loose panels, unbalanced fans and blunt blades all add noise. A machine that has got louder is usually telling you something about its condition.
• Fit silencers and damping. Exhaust silencers on engines and compressors, absorptive lining in duct runs, damping applied to panels and chutes that ring. Vibration isolation mounts stop a machine driving structural noise through a floor.
• Change the method. Hydraulic breaking instead of percussive breaking where the geometry allows. Crimping or bolting instead of hammering. Rubber lined chutes and skips instead of steel on steel. Lowering material rather than dropping it.

Step 4. Isolate what you cannot quieten

Where the source cannot be reduced far enough, put something between it and the people.

Acoustic screening around a noise source such as a generator, compressor or cutting station gives a substantial reduction and, unlike hearing protection, protects everyone in the area at once. Screens work best when positioned close to the source and tight to the ground, because sound leaks through gaps (just like water would). If it is possible to source a noise enclosure to fully surround plant or machinery, that is often the best option.

Distance is free and often overlooked. Sound pressure falls the further it is away from the source, so positioning noisy plant away from high traffic areas, will reduce the risk of exposure.

Screening also matters at the boundary. Most urban projects carry noise conditions in their development consent, set by the consent authority rather than the safety regulator. Those are the conditions a neighbour will report, and acoustic screening is usually the control that keeps you inside them.

Step 5. Use administrative controls to limit who is exposed

Rotating workers through a noisy task limits any one person's dose. Programming the loudest operations for periods when fewest people are present reduces the number exposed. Restricted access zones keep people out of the areas where levels are highest.

These are real controls. They depend on being followed every day, which is why they sit below engineering controls and why they need supervision rather than a signature.

Step 6. Provide hearing protection for the residual risk

Under regulation 36 personal protective equipment sits at the bottom of the hierarchy of control, and noise shows exactly why.

Protection depends on fit, and real world attenuation is routinely well below the laboratory rating. It depends on continuous wear, and a hearing protector removed for ten minutes in a 100 dB(A) environment loses most of its daily benefit. It protects the wearer only, so everyone else in the area is still exposed. It fails silently, with no signal that it has stopped working. And over protection has its own cost, because a worker who cannot hear a reversing alarm or a shouted warning has traded one risk for another.

None of that makes hearing protection wrong. Issue correctly specified, fit checked hearing protection for the residual risk once the steps above have been applied, and put audiometric testing in place where protection is relied on.

Step 7. Measure and prove the controls are working

Measurement also does the important job of proving a control worked. Use the same measurement point in comparable conditions, before and after the screen goes up, and you have evidence rather than an assumption.

Review the controls whenever the plant, the task or the site layout changes, because a screen positioned for last month's layout may be protecting nobody today.

Getting it right on your site

Noise control is a specification exercise. The right screen in the wrong position achieves very little, and the quietest machine in the catalogue is no help if it cannot do the job.

RVT Group Australia supplies noise control equipment on hire across construction, infrastructure and industrial projects, from acoustic screening and enclosures through to noise monitoring that shows whether the controls are working. Every hire starts with a site assessment, so the solution is built around your source, your site layout and your consent conditions.

Next Steps

Book a free site assessment or call the team on 1300 086 248.

Download our Noise Control Poster to raise awareness of the dangers of uncontrolled noise and how to protect people.

*The model WHS laws created by Safe Work Australia have been implemented by all jurisdictions except Victoria. Victoria is governed by the state-specific Occupational Health and Safety Act 2004 and its own set of occupational health and safety regulations. Western Australia adopted the model laws with its own regulation numbering, so confirm local references before publication.