Due to the positioning of the two ears on humans, sounds has to travel different distances to reach either ear. Similar to the process of depth perception, the body analyses the slight differences in time and is able to detect from that what direction the sound has travelled from. Also if a sound is coming from the right, the right ear will hear the sound first and the head will block the left yeah from hearing the sounds or will interfere with the transition of the sound to the left ear. This is another way in which the ear is able to detect the direction of a sound in relation to the individual.

Aubusson, Eileen Kennedy Peter. Biology in Context: the Spectrum of Life. Victoria : Oxford Uni. Press., 2001. Print.
"HSC Online." NSW HSC Online. N.p., n.d. Web. 25 June 2010. <http://www.hsc.csu.edu.au/biology/options/communication/2952/CommPart4.html#1>.