A different approach to over-the-horizon radar is to use creeping waves or electromagnetic surface waves at much lower frequencies. Creeping waves are the scattering into the rear of an object due to diffraction, which is the reason both ears can hear a sound on one side of the head, for instance, and was how early communication and broadcast radio was accomplished. In the radar role, the creeping waves in question are diffracting around the Earth, although processing the returned signal is difficult.