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Reference.org
Short-time Fourier transform
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<p>The short-time Fourier transform (STFT) is a <a href="/facts/List_of_Fourier-related_transforms/omM5lS1k">Fourier-related transform</a> used to determine the sinusoidal frequency and phase content of local sections of a signal as it changes over time. In practice, the procedure for computing STFTs is to divide a longer time signal into shorter segments of equal length and then compute the Fourier transform separately on each shorter segment. This reveals the Fourier spectrum on each shorter segment. One then usually plots the changing spectra as a function of time, known as a <a href="/facts/Spectrogram/Jt8zHI0H">spectrogram</a> or <a href="/facts/Waterfall_plot/100UHwhv">waterfall plot</a>, such as commonly used in <a href="/facts/Software_Defined_Radio/k7qLq1mu">software defined radio</a> (SDR) based spectrum displays. Full bandwidth displays covering the whole range of an SDR commonly use fast Fourier transforms (FFTs) with 2^24 points on desktop computers. </p>