Yell into the hole “anybody there?” Then after 2 or 3 seconds bulldoze both ends shut.
“would be ineffective”
Hilarious. The border is lined with acoustic detectors and sonars to find just this. The footings of the Wall will cause even more grief for them.
On and On: Ju cannot stop us! Eeet Eees Eeempossible! Give up! Surrender! Ju cannot win!
More noise from the loser side trying to con us into surrendering.