Why is an FM signal less susceptible to noise than an AM signal?

FM receivers have "limiters", which remove pulse-type noise and amplitude variations from the signal. Broadcast FM occupies a much wider bandwidth than AM, which accounts for its improved fidelity, and its ability to carry stereo, subcarriers, and digital. The wide-bandwidth is not required for AM noise immunity.

AM (or Amplitude Modulation) and FM (or Frequency Modulation) are ways of broadcasting radio signals. Both transmit the information in the form of electromagnetic waves. AM works by modulating (varying) the amplitude of the signal or carrier transmitted according to the information being sent, while the frequency remains constant. This differs from FM technology in which information (sound) is encoded by varying the frequency of the wave and the amplitude is kept constant.