Frequency spectrum in Doppler effect

[yulija]

Homework Statement

I have been investigating the Doppler effect in a circular motion with a stationary source and moving observer (however the main aim is to determine the speed of sound in the end). Using Vernier software - Logger Pro - I have obtained two graphs of the sound pressure against time.

I may also use FFT analysis and get a frequency spectrum but I am not sure what I can use it for. How can in help?

I tried two different frequencies:
f₁ = 3000Hz
f₂ = 1000Hz

And the radius of the circle was 40cm.

Homework Equations

observer moving towards the source

observer moving away from the source

 

[haruspex]

If your source is more-or-less a pure tone, I don't see how FFT will help. It will still be a single frequency received at any instant.
Was that your only question?