What I'm doing is that I send an audio signal consisting of a single frequency into a resonator. To check whether and how the signal has changed I perform a QAM demodulation.
I do not need intend to recover the signal or something like that, I'm just interested in the magnitude of the change/modulation of the input signal.
In the next step I would like to use multiple frequencies simultaneously and analysed how the amplitude of each signal has changed.
Is there a different/better way than just analysing the signal by Fourier transform?