Hanning Window
The Hanning window, also called "Hanning weighting", is a digital manipulation of the sampled signal in an FFT analyzer which forces the beginning and end of the time record to zero amplitude. This compensates for an inherent error in the FFT algorithm that would cause the energy at specific frequencies to be spread out rather than well-defined in frequency. The Hanning window causes a distortion of the waveform used by the analyzer to calculate the spectrum resulting in the measured levels being too low. When processing continuous data, this effect is compensated for, but an error is introduced if the Hanning window is used for transient data.
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