How to detect overlapping peaks in FFT?

1. What is FFT overlap?
2. Why do we use overlap in FFT?
3. Why does FFT have two peaks?
4. Why are there multiple peaks in an FFT graph?

What is FFT overlap?

FFT convolution uses the overlap-add method together with the Fast Fourier Transform, allowing signals to be convolved by multiplying their frequency spectra. For filter kernels longer than about 64 points, FFT convolution is faster than standard convolution, while producing exactly the same result.

Why do we use overlap in FFT?

FFT processing can be particularly problematic when the signal consists of randomly occurring transients superimposed on a more continuous signal. Overlap processing is commonly used in this situation to improve the estimates.

Why does FFT have two peaks?

It's not two peaks, it's one peak, but an FFT is always mirror-symmetric. Only the first half is actually useful. Think of it this way: an FFT can't pick up signal data at more than half the sampling rate. When you try you get essentially garbage data that just so happens to be a mirrored refection of the "real" FFT.

Why are there multiple peaks in an FFT graph?

The height of the spike gives the amplitude. The figure below shows the FFT of a pure tone with frequency 5,000 Hz: Frequency plot for an simple vibration with a frequency of 5000 Hz. FFTs of complex vibrations have multiple peaks- one for each frequency present in the vibration.