NOTE: THIS DOCUMENT IS OBSOLETE, PLEASE CHECK THE NEW VERSION: "Mathematics of the Discrete Fourier Transform (DFT), with Audio Applications --- Second Edition", by Julius O. Smith III, W3K Publishing, 2007, ISBN 978-0-9745607-4-8. - Copyright © 2017-09-28 by Julius O. Smith III - Center for Computer Research in Music and Acoustics (CCRMA), Stanford University
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Convolution
Definition: The convolution of two signals and in is denoted '''' and defined by
Note that this is cyclic or ''circular'' convolution.8.2 The importance of convolution in linear systems theory is discussed in §8.7Convolution is commutative, i.e.,
Proof:
where in the first step we made the change of summation variable , and in the second step, we made use of the fact that any sum over all terms is equivalent to a sum from to .
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