The acoustic short circuit occurs when two equal sound waves but reversed phase overlap canceling each other.
This phenomenon occurs in the loudspeakers, the loudspeaker membrane emits two opposite waves on each side, while the front "pushes" by pressing the air, the back "pulls" leaving a depression, if these waves are found, the movement is annulled, disappearing the bass which are the waves that produce more air movement and leaving a very poor sound.
To avoid this effect, the back of the loudspeaker is isolated by means of a flat baffle or inside a sound box whose walls absorb the rear waves, preventing them from overlapping those that are emitted from the front.
wiki
