Hamming-, Hanning-window

Several odier MA methods have been proposed in die literature, two of die best known being die Hanning window (named after Julius Von Hann) (which for 3 points has weights 0.25, 0.5 and 0.25), and the Hamming window (named after R. W. Hamming) (which for 5 points has weights 0.0357, 0.2411, 0.4464, 0.2411, 0.0357) - not to be confused in name but very similar in effects. These windows can be calculated for any size, but we recommend diese two filter sizes. 

Other window functions, such as triangular windows of variable widths, can also be used. In fact, there is a whole bevy of window functions available, often named after their originators or proponents, such as Bartlett, Hamming, Hanning, Parzen (for the triangular window), andWelch. Some of these are discussed in Section 12.7 of the book Numerical Recipes (W. H. Press etal., Cambridge University Press 1986). 

For standard analysis windows (e.g. Hanning, Hamming,) the cutoff frequency is inversely proportional to the window length, CO/, 4% IT. The first condition implies that T > 4A CO min The window must be longer than 4 times the period corresponding to the interval between the closest frequencies. The last constraint above implies R < 774, i.e. successive analysis windows must have a minimum overlap of 75%. The larger the cutoff frequency, the larger the minimum overlap between successive analysis windows. 

Savitsky-Golay Filters, Hanning and Hamming Windows... 

There are several other linear filters such as Hanning and Hamming windows which can be found in specialist spectroscopic texts. Often, for historic reasons, users of specific spectroscopic techniques have employed particular named filters. 

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