Removing noise from PCM file I want to implement basic noise reduction. I'm recording audio using a microphone mounted on a drone. I would like to filter the audio file from drone noise.
What's the best way to do it ?

My first idea is to first record sound that is emitted by a drone only and convert it using fourier transform to see which frequency has the most energy.
Then I could do the same thing with audio file with drone noise.

My question is how to cancel this drone noise ?

This is the spectrum of the sound emitted by propellers:


Most of its power is in the low frequencies.

Edit.
Community noise, including aircraft and motor vehicles, typically ranges between 50 Hz and 5,000 Hz. So basically if I filter noise from propellers I might also filter sound from vehicles?
It really depends on the purpose of your project. If you want to do it from scratches, it will not be easy. However, if you want to do it for just one file, and the goal is to suppress the noise of the drone on that file, I recommend you to download free processing tool: audacity: http://www.audacityteam.org/download/, and use their feature where you can pick a period with a typical noise, analyze it and remove so analyzed noise from the whole file. I think that you may find their source code as well for free, which may include the implementation of the feature as well.
However, if you want to do it from scratches, there is a whole nice theory how to do it, but it is not easy.