I'm trying to transforming an already know signal from time domain to frequency domain using
fft function in MATLAB. And I got different values of amplitude when I change the value of length of signal $L$. I'm therefore wondering if there is a rule to choose the length of signal when calculating FFT.
I have an acoustic signal got from a sensor and need to analyze it (I have no idea about its frequency range, amplitude, and so on.) I want to transform it into frequency domain using
fft function in MATLAB. And I don't know how can I choose the length of signal.
Could somebody please help?