Ears capable of detecting airborne sound have arisen repeatedly and independently in the five major tetrapod groups – the anurans, turtles, lizards and snakes, archosaurs (birds and crocodiles) and mammals. All use a major cue for localization, the arrival time information from each ear. In birds, arrival time difference processing is mediated by neural circuits which form maps of sound location in the CNS. In the mammals, however, confirmation of a map is lacking. Instead, recent work in small mammals suggests that sound source location might be encoded by activity in two broad, hemispheric spatial channels. I will discuss the evolution of neural codes for computing sound location in birds, alligators, lizards and mammals.