ABSTRACT
This chapter introduces the mathematical basis of Fourier analysis and describes some qualitative patterns of amplitude and phase. Fourier analysis provides a mathematical technique for decomposing signals that extend over time and/or space into a sum of sinusoidal components. The shape of a Fourier spectrum can also provide some indication of the relative complexity of a signal. Fourier transforms also provide mathematical ease in calculating the response of linear dynamic systems in a manner similar to Laplace transforms. The time history for the healthy individual exhibits a relatively complex temporal structure, and the Fourier spectrum decreases inversely with frequency. In summary, Fourier analysis provides an alternative representation of time histories in terms of an additive combination of sinusoidal components. The patterns revealed in the Fourier spectra often provide additional insight into the structure of the underlying process.
