Delay Parameter $M$

A delay of $M = f_s/(2f_0)$ samples in the comb filter will yield a notch (complete cancelation) at

$$f_0 = \frac{f_s}{2M}$$    Hz$$,$$

as well as notches at odd harmonics of $f_0$.

Figure 18: Destructive interference occurs at odd harmonics of the fundamental frequency.