The guests feel the wind from the air cannon, and hear the ghosts pass by. The show could be extended to include another air cannon at the end of the hallway. Spider webbing, cheescloth, shredded cloth, etc. could be used to give visual effect to the air movement. Add fog to the air cannon and use a blacklight to ehnance the puff. He may be contacted at his e-mail address for more information.
Smoke is injected into the hole before testing.
The secret is in how the 'thump' is produced. Just the same as whacking a membrane. What this does is push air out the hole, then air is sucked back in immediately as the speaker cone moves back. The only reasonable explanation I can come up with is that on the 'push' stroke, there is a much higher air pressure along the edges of the hole than in the center of the hole due to the restriction. This higher air pressure moves the 'edge' air out much faster than the center air.