This is a common sense issue. I think the CFR 1910.178 is where you should look
Some warehouses or factory floors are so noisy you need to wear earplugs Some are not. rock and hard spot issue. Make everybody mad when they are allowed to listen to their tunes ;or when somebody gets hurts and sues because they could not hear the motion sensors. I think crown has a really loud motion alarms in their parts system, plus when they install them you have a little more piece of mind. Shakesphere once said kill all the layers
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