A periodic signal has a harmonic spectrum. In the extreme case, a click train signal has a comb spectrum: Figure 1: A click train (left), and its corresponding comb spectrum (right). But why? After all, a solitary click has a uniform spectrum. So why should the sum of multiple clicks have a non-uniform spectrum? Figure 2: A click (left), and its corresponding spectrum (right). The answer exposes a lot of detail of how spectra work, and gives us a glimpse into the inner workings of spectral ph...
