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FFT and Third octave discrepancy - Sound and Vibration

Hello all, I need some help with a problem that Im having. Im currently analyzing a calibration signal and when I perform the FFT signal analysis I find a peak with amplitud 93.1dB @998,66Hz and 2 peak sides of aprox. 87dB (marked in the picture attached). Then i performed a Third octave analysis and I found that the Band related to 1000Hz has an amplitude of 93.1dB. My question is: just the sum of these 3 bins  gives me an amplitude of aprox 99dB, why the amplitude of the band is 93.1dB? What Im misunderstanding? Thank you so much for your help.

Regards,

Alan

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Hi alanesco

 

We are seeing that you posted the question in two different forums. To provide you a better support I´ll be closing this forum and we will work on the other one.

Other Forum

 

Have a great day!!!!

Juan Arguello Director Support Services @NI
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Yes I pressed the button 3 times because it was running slow and it published my post 3 times. Thanks.

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