"Wave" as defined by wave intensity analysis

The propagation of waves in the arteries is generally described using Fourier analysis in terms of periodic wavetrains formed by the superposition of a mean value and sinusoidal waves at the fundamental frequency (defined by the heart rate) and its harmonics. There is, however, an alternative way to describe waves in the vasculature based upon the method-of-characteristics solution of 1-D conservation laws. This method, wave intensity analysis (WIA), can be used to describe periodic waves but can also be used to describe the propagation of non-periodic waves that cannot be practically described in terms of sinusoidal wavetrains. As a means of demonstrating how WIA defines a wave, we used data gathered in a simple bench-top experiment where a single disturbance propagated along a single elastic tube and was reflected and re-reflected between a closed and a relatively open end. Results demonstrate that forward- and backward-travelling peaks of intensity usefully define wave interactions.