This paper introduces the major phenomena of binaural hearing. The sounds arriving at the two ears are rarely the same: usually one ear will be partially shadowed from the sound source by the head, and the sound will also have to travel further to get to that ear. The resulting differences in interaural level and time can be detected by the auditory system and can be used to determine the direction of the source of sound. They also facilitate improvements in the detectability of a target sound masked by some other sound from some other direction. In many circumstances there is a special emphasis to the onset of a sound, which helps to perceptually suppress the complex patterns of reflections and reverberations that are present in most listening environments; yet, the auditory system is often insensitive to-and cannot take advantage of-fast dynamic changes within a sound.