Scipy : fourier transform of a few selected frequencies

Question

I am using scipy.fft on a signal, with a moving window to plot the amplitudes of frequencies changing with time (here is an example, time is on X, frequency on Y, a

Answer 1

You're really looking to use the Goertzel Algorithm: http://en.wikipedia.org/wiki/Goertzel_algorithm. Basically, it's an FFT at a single point, and efficient if you only need a limited number of frequencies in a signal. If you have trouble pulling apart the algorithm from Wikipedia, ping back, and I'll help you. Also if you google a few resources, there exist DTMF decoders (touch tone phone decoders) written in python. You could check out how they do it.