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02-14-2017 11:25 AM

How does LMS Test.Lab calculate RMS level for a sound power spectrum derived using the SOUNDPOWER function? I tried using the procedure in this link (https://community.plm.automation.siemens.com/t5/Testing-Forum/RMS-Calculation/m-p/382342#U382342). I found the calculation works for a sound pressure spectra, but not a sound power spectra. My guess is it has something to do with a linear spectrum vs. a power spectrum.

Thanks in advance.

Solved! Go to Solution.

3 REPLIES

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02-14-2017 02:07 PM - edited 02-14-2017 02:08 PM

Hello,

We have an FAQ on the RMS calcualtions in the Solution Center area of the Global Technical Assistance Center (GTAC) site http://www.plm.automation.siemens.com/en_us/support/gtac/. FAQ is at https://solutions.industrysoftware.automation.siemens.com/view.php?sort=desc&p=1&q=RMS+calc&file_typ... but you will need your webkey login and password. Here is some information from that FAQ related to power functions:

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02-14-2017 04:20 PM

Kevin,

Thanks for the reply. For the RMS scaling equation you show to provide the same answer in Excel as the cursor RMS calculation in LMS Test.Lab, I needed to multiple the amplitudes by the __square__ of the energy and amplitude correction factors . . . . (1.633/2)^2.

Does this make sense when the spectrum format is power?

Greg

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02-14-2017 04:55 PM

Greg,

If you used a Hanning Window for the Power function then yes, the correct from Amplitude correction to Energy correction woul be be to (1.63/2)^2.

Kevin

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