How to analyse the sound of Motor I have a motor, that I want to analyse, using its sound, so I can  its 'character' I was using the the simple fft, and figured out, that it wouldn't help, so I tried the order analysis, at least I incremented the speed of the motor and I can say it in spectrogram like here:



My question isn't about codes but about theory, what are the methods that I can use to analyse the sound of motor? 
Thanks for any help ! 
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In my opinion, using the STFT (or spectrogram) as you already did is a good start. Try to change the parameters of your STFT, i.e. window size and frame shift until you are able to detect certain frequencies and their repetitions.

This is an example for a decelerating car on the highway. The inertial sensor (not a microphone) was placed at the axle: