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Introduction and Overview

The ear is a kind of Fourier analyzer. That is, sound is spread out along the inner ear according to frequency, much like a prism separates light into various colors. As a result, hearing in the brain is based on a kind of ``short term spectrum analysis'' of sound. This is useful for a variety reasons:

As another example of the utility of spectrum analysis, the fields of chemistry, physics, astronomy, and cosmology were all advanced profoundly by the study of light spectra. To cite just one of many, many examples, the ``red shift'' (downward Doppler frequency-shift) of light coming from stars led Edwin Hubble (in 1929) to conclude that the Universe was expanding according to the Big Bang theory of cosmology (the farther apart two stars are, the faster they are racing away from each other).

In summary, spectrum analysis provides a wealth of information about signals that can be used for detection, classification, and discrimination tasks. Since hearing is based on a spectral decomposition, spectrum analysis provides an important foundation for many audio signal processing applications.

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``Spectral Audio Signal Processing'', by Julius O. Smith III, W3K Publishing, 2011, ISBN 978-0-9745607-3-1.
Copyright © 2022-02-28 by Julius O. Smith III
Center for Computer Research in Music and Acoustics (CCRMA),   Stanford University