In music, if a note has frequency 
, integer multiples of that frequency, 
and so on, are known as harmonics. As a result,
the mathematical study of overlapping waves is called harmonic analysis.
Harmonic analysis is a diverse field including such branches as Fourier series, isospectral manifolds (hearing the shape of a drum), and topological groups. Signal processing, medical imaging, and quantum mechanics are three of the fields that use harmonic analysis extensively.
