# Compute Similarity between Fourier Transforms

I'm looking to compare the Fourier Transforms generated by accelerators and gyroscopes that collected data of people walking. I've looked to see if there is a standard form of comparison, but I have yet to find one.

Here's my specific use case: I'm looking to compare similarity between the dominant signals of two Fourier Transforms (i.e. how close are they to being the same frequency/magnitude). Is there a specific metric that would help identify that?

If not (or perhaps irrespective of my goal), what are some common ways of comparing two Fourier transforms? I've found surprisingly little on the subject.

• Are you comparing two single FFTs from a accel/gyro capture, or are you comparing 2 series of FFTs (over time, re: walking)? Have you narrowed down the most salient parts of spectrum that you are interested in? These questions can inform your choice of similarity metric. – ruoho ruotsi Mar 7 '15 at 4:34
• They would be from two different time periods (e.g. different days), certainly not the same sample. As far as limiting, yes, partially because we're using consumer-grade accelerometers and because walking data is not very likely to produce high frequency oscillations, unless you walk really really fast (</kidding>). – ahjohnston25 Mar 7 '15 at 4:37