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RMS Calculation for Sound Power Spectrum

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.

 

 

3 REPLIES
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Solution
Accepted by topic author Greg_H
‎02-15-2017 07:24 AM

Re: RMS Calculation for Sound Power Spectrum

[ Edited ]

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:

 

2-14-2017 1-57-19 PM.jpg

 

 

2-14-2017 2-05-30 PM.jpg

 

 

Re: RMS Calculation for Sound Power Spectrum

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

Re: RMS Calculation for Sound Power Spectrum

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