A head shadow is a region of reduced amplitude of a sound because it is obstructed by the head. Sound may have to travel though and around the head in order to reach an ear. The obstruction caused by the head can account for a significant attenuation (reduced amplitude) of overall intensity as well as cause a filtering effect. The filtering effects of head shadowing cause one to have perception problems with linear distance and direction of a sound source.
The head shadow causes particular difficulty in sound localisation in people suffering from unilateral hearing loss.