"Mental pan" of the sound source.
 

• The spectator will mentally place a voice as coming from off screen left, in tandem with visual indications about the person speaking, even through in an monaural movie theater the sound really emanates from a speaker behind the center of the screen 

• If a character is walking across the screen, the sound of the footsteps seems to follow his image, even though in real space, they continue to issue from the same stationary loudspeaker.

• Sounds of loudspeakers located somewhere in the room will be perceived as coming from the TV-screen 

Magnetization happens in spite of the evidence of our own senses. 
The spectator perceive that a sound source is in space of the image, 
no matter what the real point of origin of the sound.