How to get the input unit back with the spectrogram function
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Hello,
I have a signal (acceleration) in witch I want to know how much of a certain frequency is excited. For that I use spectrogram and I want to extract, at a point in time and frequency, the level of excitation in acceleration unit.
If I take sig as a signal then abs( fft(sig) )*2/window gives me the rigth amplitude (window is the size of the window). I tested it with sig = 300*cos(2*pi*f*t) and it indeed gave me 300 at the frequency f. So it works fine with fft.
But when I use it on the 's' output of spectrogram it dont give me that at all.
Any ideas to recover my acceleration unit from the spectrogram ?
Thx
2 commentaires
Mathieu NOE
le 11 Mai 2021
hello
sometimes it's not so easy to understand how things are scaled inside matlab's functions
that's why I ended up rebuilding the spectrogram with fft so I know the amplitude of the spectrum matches the input signal
FYI I use hanning window and the corresponding corrrection factor
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