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Fast Fourier Transforms
Reference
FFT Time Domain Record
FFT Time Domain Record
After Windowing
FFT Window
FFT Frequency Domain Record
FFT
Xs
Figure 3-27: Windowing the FFT Time Domain Record
You can often determine the best window empirically by first using the window
with the most frequency resolution (rectangular), then proceeding toward that
window with the least (Blackman-Harris) until the frequencies merge. Use the
window just before the window that lets the frequencies merge for best com-
promise between resolution and amplitude accuracy.
NOTE
If the Hanning window merges the frequencies, try the Hamming
window before settling on the rectangular window. Depending on the
distance of the frequencies you are trying to measure from the
fundamental, the Hamming window sometimes resolves frequencies
better than the Hanning.