Variations of amplitude and frequency according to timeare commonly visualised through a time × frequency × amplitude density plot, named the spectrogram. The theory of the short-time discrete Fourier transform (and its inverse function), which is behind the spectrogram output, is introduced with a particular attention paid to the uncertainty principle. Practical solutions are given to display, tune, decorate, annotate, describe, animate, and print a 2D/3D spectrogram. The realization of a mean spectrum and a soundscape spectrum, which are computed on the short-time Fourier transform, is also introduced.
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