Sound is a vibration. Sound waves travel through oscillating molecules in a medium like air or water.

Light reaches the human retina within the 180-degrees forward-facing field of view. Sound reaches the ears from all directions at all times. Artist Christian Marcly once commented:

“I think it is in sound’s nature to be free and uncontrollable and to go through the cracks and to go places where it’s not supposed to go.”

The eye can shut out external stimuli with the aid of an eye-lid, while the ear remains in a state of permanent receptivity.