DICTATION 1

Human beings can locate sound sources by comparing in the brain the sounds which arrive at each ear. Try a simple experiment: ask a friend to sit in a chair and to close his eyes. Tell him to sit facing in one direction and not to move his head. Make a sharp sound, for example, by clicking the fingers, blowing a whistle or striking a piece of metal, about two meters away from him. Get your friend to point to the source of the sound. Now make the sound at different places around him, still about two meters away. See how good he is at locating the sounds. Make sure that the room is almost silent and do not distract the subject by other noises. Note carefully his performance with sounds in the medial plane. The result will probably show one important factor in location: it is not very accurate when the sound source is at points of equal distance from the two ears.