Basic Idea

The basic idea is to partition FFT bins into the desired nonuniform bands, and perform smaller inverse FFTs on each subband to synthesize downsampled time-domain signals in each band. A simple example for a length 8 FFT octave filter bank is shown in Fig.10.30. We'll next extend this example to a practically useful level via a series of tutorially oriented matlab examples.

Figure: FFT implementation of one frame of the simple octave filter bank shown in Fig.10.31. Successive frames are non-overlapping (rectangular window advances its full length each frame).

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Summing STFT Bins
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Audio Filter Banks