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I've been doing FFT's (on sound) for a while and usually use the highest intensity or the ones above average to get the spikes in an FFT result.

What would be a good method to get all the 'spikes' in an FFT. I can't use averages or peaks because the frequency response drops off. Visually its quite obvious there is a spike but I can't get a way extract the frequency from the spike.

Low frequencies always tend to have a higher itensity than higher ones but don't necessarily have any spikes in them.

Are there any good reliable techniques for this?

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  • $\begingroup$ may be check the difference between the intensity at the current frequency and the one just before that? If the difference is above a certain threshold then consider it a spike, otherwise not. $\endgroup$
    – user13267
    Commented Sep 30, 2013 at 7:54
  • $\begingroup$ Thanks @user13267 it sounds like a good idea, I'll give it a try why not add this as an answer? $\endgroup$
    – Akshat K
    Commented Sep 30, 2013 at 8:00
  • $\begingroup$ @user13267 I have a bit of trouble with aliasing, I do apply the window but its there in small amounts how do you think I can account this in? $\endgroup$
    – Akshat K
    Commented Sep 30, 2013 at 9:47

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A statistical test might be appropriate. For instance, if you assume the noise floor is Gaussian, then you could compute the standard deviation in any particular octave (or other appropriate sub-band), and look for maxima that are whatever multiple of standard deviations above the local average that you might consider to be statistically significant for your application.

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