Political activists planning protest rallies at the upcoming Democratic Convention in Denver have their stomachs in knots over a rumor about a crowd control weapon - known as the “crap cannon” - that might be unleashed against them.

Also called “Brown Note,” it is believed to be an infrasound frequency that debilitates a person by making them defecate involuntarily.

Mark Cohen, co-founder of Re-create 68, an alliance of local activists working for the protection of first amendment rights, said he believes this could be deployed at the convention in August to subdue crowds.

“We know this weapon and weapons like it have been used at other large protests before,” he said.

Cohen, who described Brown Note as a “sonic weapon used to disrupt people’s equilibrium,” cited eyewitness accounts of its use during free-trade agreement protests in Miami in 2003.