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Fast Fourier Transforms
Reference
3Ć50
FFT Time Domain Record
FFT Time Domain Record
After Windowing
FFT Window
FFT Frequency Domain Record
FFT
Xs
Figure 3Ć27:ăWindowing 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 (BlackmanĆHarris) until the frequencies
merge. Use the window just before the window that lets the frequencies
merge for best compromise 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 frequenĆ
cies better than the Hanning.