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The Short Time Fourier Transform (STFT)
is a function
of both time (frame number
) and frequency (
).
It is therefore an example of a timefrequency distribution.
Others include
 ConstantQ STFTs [#!JOSNSF!#]
 Dyadic Wavelet Filterbank (§11.9.1) [#!Vaidyanathan93!#]
 Wigner Distribution [#!Cohen95!#]
The uniform and rectangular nature of the STFT timefrequency tiling
is illustrated in Fig.7.1. The window length is proportional
to the resolution cell in time, indicated by the vertical lines
in Fig.7.1. The width of the mainlobe of the
windowtransform is proportional to the resolution cell in
frequency, indicated by the horizontal lines in Fig.7.1. As
detailed in Chapter 3, choosing a window length
and window
type (Hamming, Blackman, etc.) chooses the ``aspect ratio'' and total
area of the timefrequency resolution cells (rectangles
in Fig.7.1). For an example of a nonuniform timefrequency
tiling, see Fig.10.14.
Figure:
Example timefrequency tiling
for the STFT. Vertical line spacing indicates time resolution, and
horizontal line spacing indicates frequency resolution (both fixed
by window length and type). The area of the rectangular cells are
bounded below by the minimum timebandwidth product (see
§B.17.1 for one definition).

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