Input RMS dB - RTA Measurement

[ivitish]

Hi everyone,

I am trying to figure out how the input RMS is calculated when an RTA Measurement is done.
I have tried to calculate it from the SPL of each frequency given by the FFT, also obtained with the RTA measurement, but I have never succeeded to find exactly the same answer as the one given by REW.
Does someone know how it is done?

Thanks a lot for your help.

 

[John Mulcahy]

You need to convert the dB values back to a linear representation and divide the magnitude squared sum by the noise bandwidth of the window being used before calculating the rms value.