<p>This answer assumes language of FFT based processing (e.g. Spectrograms). For other type of processing language could be changed.</p>
<p>Assume you have a signal just between two FFT blocks. As the FFT assumes circular data, the signal constitutes a discontinuity that corrupts the spectrum. Yes this is spectral leakage, which is attenuated by a windowing function that reduces the influence of edge effects from spectrogram.</p>
<p>Windowing reduces in the assumed case the signal close to the edge. Consequently, if the next FFT is shifted by a complete window, the signal may be missed, but when shifted by 1/2 the window length, the signal will fully captured.</p>
<p>Overlapping windows by 50 % is standard for Hann, Hamming, and other standard window functions.</p>
<p>More overlap is useful when one wanted a smoother (higher correlated) spectrogram.</p>
<p>Note: to estimate power spectral density (PSD), window shape and overlap must be considered.</p>

CC BY-SA 4.0
2022-07-29T09:10:43.890Z
2022-07-29T09:10:43.890Z
WMXZ
<p>When reading the methods sections of bioacoustics papers, I often see a <strong>window length</strong> and <strong>% overlap</strong> reported in the description of how the spectral analysis was done.</p>
<ul>
<li>What is the purpose of this?</li>
<li>What factors inform what an appropriate
% of overlap between neighbouring windows should be?</li>
<li>Does it have anything to do with addressing 'spectral leakage'?</li>
</ul>
<p>Thanks in advance</p>

CC BY-SA 4.0
2022-07-29T09:28:22.273Z
Related post in the Signal Processing SE: [STFT: why overlapping the window](https://dsp.stackexchange.com/questions/19311/stft-why-overlapping-the-window)
Noil
CC BY-SA 4.0
2022-08-02T08:32:52.533Z
thanks @Noil - did not see this before
Chloe
CC BY-SA 4.0
2022-08-03T07:25:50.360Z
This paper gives recommended overlaps for all sorts of windows: https://holometer.fnal.gov/GH_FFT.pdf
From p. 28 on it's just windowing heaven!
Rasmus
<analysis><best-practice><processing><window>
What is the purpose of overlapping windows in acoustic signal processing?
# What is the purpose of overlapping windows in acoustic signal processing?

(Asked by: username_0 on 2022-07-29)

When reading the methods sections of bioacoustics papers, I often see a **window length** and **% overlap** reported in the description of how the spectral analysis was done.

* What is the purpose of this?
* What factors inform what an appropriate
  % of overlap between neighbouring windows should be?
* Does it have anything to do with addressing 'spectral leakage'?

Thanks in advance

**Tags:** analysis, best-practice, processing, window

> **Comments:**
> **username_1**: Related post in the Signal Processing SE: [STFT: why overlapping the window](https://dsp.stackexchange.com/questions/19311/stft-why-overlapping-the-window)  
> **username_0**: thanks @username_1 - did not see this before  
> **username_2**: This paper gives recommended overlaps for all sorts of windows: https://holometer.fnal.gov/GH_FFT.pdf From p. 28 on it's just windowing heaven!  

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## 1 answers

### Answer by username_3 on 2022-07-29. Score: 11 | Accepted answer

This answer assumes language of FFT based processing (e.g. Spectrograms). For other type of processing language could be changed.

Assume you have a signal just between two FFT blocks. As the FFT assumes circular data, the signal constitutes a discontinuity that corrupts the spectrum. Yes this is spectral leakage, which is attenuated by a windowing function that reduces the influence of edge effects from spectrogram.

Windowing reduces in the assumed case the signal close to the edge. Consequently, if the next FFT is shifted by a complete window, the signal may be missed, but when shifted by 1/2 the window length, the signal will fully captured.

Overlapping windows by 50 % is standard for Hann, Hamming, and other standard window functions.

More overlap is useful when one wanted a smoother (higher correlated) spectrogram.

Note: to estimate power spectral density (PSD), window shape and overlap must be considered.


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