How to determine a frequency that contains 90% of the power of the signal?

So, I have a signal taken from an audio file and I want to determine the frequency below wich 90% of the power of the signal is contained. However, I cant think of a way to do it. Can anybody give me a guidance?

Many thanks.

Answer 1

[Daniel kiracofe]

1) create a power spectrum (i.e. using the results of fft()). I'm assuming you know how to do this, if not just ask

2) create cumulative power spectral using the cumsum() function. e.g. if vector P is your power spectrum, then CP = cumsum(P) is the cumulative spectrum.

3) normalize: e.g. NCP = CP / CP(end)

4) plot versus frequency and look for the 0.9 level.

[Arquelau]

Just perfect. Thank you so much!