Rank: Super forum user 
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Noise level definitions
I have been reviewing some equipment recently and noticed that they are quoting two sound levels Power and Pressure both in units of dBA. My question is if I wanted to compare against an existing piece of equipment to see if it is worth changing or investigate a potential new set up of equipment which figure should I use in the HSE calculator?
Yes, I know real life readings will be required, but would like a view before spending money.
I know Lp is Sound Pressure Level and Lw is Sound Power Level and that the Sound Pressure Level is the sound at the operator’s ears, where the Sound Power Level is the noise energy produced by the machine. Which would make it reasonable to use the Pressure level that the person will (theoretically) be exposed to at ears. However, the HSE calculator asks for LAeq which is an 8 hour time A weighted average (equivalent continuous sound level) of Sound energy for that period, which I would equate energy to Power, not Pressure ( but could easily be wrong here).
If there are there any noise experts willing to help clarify for me I would be grateful.
Chris
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Rank: Super forum user 
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As a matter of pure physics, energy and power are not the same thing at all and are measured in different physical units. So there's no reason to equate them.
The HSE calculator is designed to output the overall exposure to an individual so the inputs also have to be individual exposures.
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 2 users thanked Kate for this useful post.
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Rank: Forum user 
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Originally Posted by: Kate  As a matter of pure physics, energy and power are not the same thing at all and are measured in different physical units. So there's no reason to equate them.
The HSE calculator is designed to output the overall exposure to an individual so the inputs also have to be individual exposures.
Correct, power is the rate at which energy is used. I just thought I'd add that in case anyone was still wondering.
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1 user thanked DavidGault for this useful post.
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Rank: Super forum user
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Thanks both for the reply, to be honest I wasn’t really expecting the answer to my question.
Yes I think my head was fried by the time I came to write the question. I was thinking about the rate at which energy is used as David notes and so felt they went together better, but as I said fried brain by that time.
I have found my answer separately and it appears to be the Sound Pressure Level you should use in the calc, which was more explicit on the old HSE calculation table I found. It also agrees with what you are saying.
Classic case of doubting myself and then muddling myself up. I used to understand all this better, time for some CPD and a refresh I think.
Again thanks
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