So what happens when two frequencies in the megahertz range are within beating distance? They behave in exactly the same manner as two strings. The periodicity of the beating generates a fundamental that occurs within hearing range. Noise is a cloud of frequencies. As a result there are myriad frequencies interacting, generating a myriad of audible fundamentals. Joe Cohen of the Lotus Group presents his explanation of how overtones / harmonics affects a manufacturer's design decisions.