Australia Model Code of Practice Managing Noise and Preventing Hearing Loss at Work 5.1-HIER: In consultation with workers and HSRs, eliminate noise risk so far as is reasonably practicable, otherwise minimise it through the hierarchy: substitute quieter plant, processes and non-ototoxic substances with a buy-quiet purchasing and hiring policy based on supplier emission data, change the way the job is done, isolate sources by distance, barriers, enclosures, absorbent surfaces and remote operation, and apply engineering controls at the source before administrative controls and PPE

What does 5.1-HIER require?

After consulting workers and their HSRs, the PCBU removes the risk from hazardous noise as far as is reasonably practicable and, where removal is not reasonably practicable, reduces it as far as is reasonably practicable; where noise is managed as a psychosocial risk, its duration, frequency and severity must be weighed. The hierarchy runs from the most protective and dependable controls to the least. Elimination comes first: stop using the noisy machine, change the work so the noise is never made, or keep the hazard out of the workplace altogether. Failing that, reduce the risk by substitution (quieter plant or processes, less harmful products in place of ototoxic ones), by isolation (distance, barriers, enclosures and sound-absorbing surfaces, soundproof covers, screens across the direct sound path, moving sources further from workers, remote controls) and by engineering changes to plant and process; whatever risk remains is reduced by administrative controls and finally by PPE, both of which depend on behaviour and supervision rather than acting at the source. A policy of buying or hiring the quietest plant for the job is among the cheapest and most durable measures: collect emission data (sound power, or sound pressure at the operator's position) from makers, importers and suppliers, ask each supplier the same question about emission under your real operating conditions as well as test conditions so answers compare, treat sound power figures as a guide only, and deal only with suppliers who can show low-noise design with noise control built in rather than sold as an extra. Often a different method gives the same result far more quietly (bending in a vice or press instead of hammering, welding instead of riveting, gluing instead of nailing, clipping instead of stapling, lowering materials instead of dropping them), and noisy outdoor work should keep away from reverberant spots. In the open, sound drops roughly 6 dB each time the distance from the source doubles; indoors it drops less. Engineering measures include cushioning or separating impacting parts, lowering drop heights and angles, absorbent linings where objects land, exhaust mufflers on engines and silencers on compressed air exhausts and nozzles, better-meshing gears, damping or stiffening of panels, absorbent material on hard reflective surfaces, altered fan or component speeds, quieter materials such as plastic in place of metal, tyres suited to the surface, and vibration-reducing seats on mobile plant (more in Appendix F).