How to find Fourier Transform Peaks ?

Hi, I am a student in engineering and my project is about identifying frequencies corresponding to vibrations in internal combustion car engines. I have obtained the signal of the vibrations via accelerometer connected to laptop microphone and transformed it in frequency domain via FFT command.

My problem is that I cannot figure the way how to generate a code that would return me the frequencies that present some peak values of the spectrum. For example, my highest vibration is somewhere near to 30 Hz, but how can I instuct Matlab to automatically return precise values?

Does anyone knows codes and functions related to Fourier waveform processing?

Thank you in advance!

Answer 1

[Matt J]

Rather than using FFTs, I would do something like this

 peak = fminsearch(@(f) -abs(dot( exp(-2j*pi*f*yourTimes),yourSamples)),30);

where yourSamples are your time domain signal values and yourTimes are the times in seconds where the samples are recorded.