The Uncertainty Principle - Signals, Processes, and Systems - page 69

Illustration 54: Overview of the most important "window types"
Here you see the most important examples of window types. With the exception of the triangular type and
the "rounded rectangular window" they all look very similar and their spectrum hardly differs. With a
duration of roughly 1 s they generate a frequency uncertainty of only roughly 1 Hz. The „rippled curves“
in the frequency domain derive from the worst windows - triangle and "rounded rectangle".
"Windowing" always involves a compromise. As it is a very important process, a great
deal of thought has been given to the ideal form of a time window. In principle they all
do the same thing and with few exceptions resemble the GAUSS-function. They begin
gently and end gently. The most important types of window are presented in Illustration
54 and their frequency-based effects are compared with each other. The worst is the
triangular window, of course, as it displays fluctuations at the beginning, in the middle
and at the end. The other windows are scarcely different from each other so that we shall
continue to use the GAUSSian-window.
In the frequency-based analysis of long-lasting non-periodic
signals - e.g. speech - these are divided up into several segments.
The frequency-based analysis is then carried out for each
individual segment.