What a listener hears depends on the position of the source of the sound.
The diagrams show a source of sound when it is placed
• in front of the listener
• to the left of the listener.
The sound waves from the source in front of the listener arrive at each ear at the same time.
The sound waves from the source to the left of the listener arrive at the left ear first.
The sound waves then reach the right ear by diffraction.