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# Hanning Window

Asked by Lisa Justin on 21 Feb 2012
Latest activity Edited by Matt J on 18 Oct 2013

Why is the Hanning window function best for random signal analysis?

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Answer by Wayne King on 21 Feb 2012

Hi Lisa, I don't whether I would say it's definitely "best". That is a hard thing to say, but the general rationale is that the Hanning, or Hann window is a good compromise between main lobe width, which determines frequency resolution, and side lobe level, which governs spectral leakage.

As you reduce the side lobe levels, you inevitably worsen frequency resolution by increasing the width of the main lobe.

Conversely, as you narrow the main lobe, you inevitably raise the side lobe level.

The Hann window is in a good middle ground on both measures among the commonly-used windows.

Lisa Justin on 21 Feb 2012

Do you advice that i use a hann window also for my periodic signal sinece it will give better freq. resolution with a little spectral loss.

Wayne King on 21 Feb 2012

I would. I don't know if I would use the term "spectral loss", leakage results in spurious energy showing up in your spectral estimate that is not the result of signal energy. It comes from the convolution of the signal's spectrum with that of the window.

Lisa Justin on 13 Mar 2012

what scaling do i use with hann window for my periodic signal?

Answer by Nicolas on 13 Mar 2012

Hello! Mainly, because it filters out with 42.3 dB all the freq. after the 3dB main lobe. It is easy to compute and gets really good results

## 1 Comment

Lisa Justin on 13 Mar 2012

xn=signal;%%%periodic signal
w=flattopwin(length(xn));
x=xn.*w;
sc=1/sum(w);%%%%scaling
y=(fft(x)).*sc

please how would i scale if i want to usse hann window instead. what would 'sc' be?