Presumably, a sound at the resonant frequency
of the human colon
, about 11 Hz
. When played at high volume
, it can act as a kind of bowel disruptor
. The french police
looked into making a riot control weapon
out of one of these in the late 1960s. I suspect that even if it worked, it didn't take on because
- There is no easy way to guarantee that only the mob and not other police will be affected.
- Colons probably differ enough from person to person for this device to be very selective.
May be an urban legend.