How can we tell sounds that come from the directly in front of us, above or below?
The human outer ear, i.e. the structures of the pinna and the external ear canal, form direction-selective filters (which allows us to discriminate from up and down)
Depending on the sound input direction in the median plane creates-different patterns or bands of frequency are produced. We adapt to the shape of our pinna so if we change the shape of the pinna we adapt and respond to the real position of the source.
Direction-selective reflections at the the pinna, head, shoulders and torso, from the shape of the outer ear we get information about the location on the median plane.