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Does the length of a Fourier Transform affect the ability to discern a small event in the data?

This is a tricky question to ask, let me clarify. I don't care about when the event happened and I don't care about the resolution of the event (it doesn't have to be some precise measurement) but I want to SEE the event. I realize short events/pulses will affect the results in a weird ways, but it doesn't matter, I just want to know some event/pulse happened. Will the length of an FFT affect how long this event/pulse needs to be before I become aware of it?

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I assume that "small event" means "short (in time) event". Fourier transforms are not good instruments for detecting short events. You would be better off looking for such events in the time domain, or with a wavelet transform, perhaps, that is set up specifically to detect the events you are interested in.

That being said, if for some reason the events have to be detected in the frequency domain then I would keep the transforms short. The reason for this is if the event is short with respect to the transform length it will look like a non-ideal impulse, which basically just creates a lot of high frequency content. Because of the small amount of energy (due to the short time) it will probably be difficult to pick the signal out of the noise.

If the transform is short, on the other hand, then its energy is a significant part of the total transform energy. That will make it possible to pick the signal out of the noise, or even enable detection by measuring the total energy.

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  • $\begingroup$ I am going to mark this as the answer for two reasons, from my knowledge of transforms, this answer makes sense and I am impatient. Yes, small events were referring to short time events, and yes I can only consider the frequency domain. I simply have too much data to consider performing the transform and performing other analysis methods(80 MS). $\endgroup$ – Andrew Mar 21 '13 at 22:56

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