Australia Model Code of Practice Managing Noise and Preventing Hearing Loss at Work 2.4: Make sure warning signals can be heard above ambient noise: reversing alarms on mobile plant per ISO 9533 at least as loud as the engine at high idle, and other signals at least 65 dB(A) and more than 15 dB(A) above ambient at every reception point, assessed per ISO 7731

What does 2.4 require?

Safe work depends on hearing warning signals over everything else going on at the workplace. For reversing alarms on mobile plant, ISO 9533 is the reference: at the points where people need to hear the alarm it should be at least as loud as the engine running at high idle. In other situations the bar is higher, a minimum of 65 dB(A) and more than 15 dB(A) above the ambient level at every position where the signal has to be received; ISO 7731 gives detailed guidance on checking that danger signals can be heard.