http://harpers.org/archive/2003/02/0079475
 
When killing just won't do
From  "Nonlethal Weapons: Terms and References," a report published by the  United States Air Force Institute for National Security Studies.  According to the report's introduction, many of the weapons are still in  the proposal stage.
Acoustic
Acoustic Bullets: High-power, very low-frequency  waves emitted from one- to two-meter antenna dishes. Results in  blunt-object trauma. Effects range from discomfort to death.
Curdler Unit: A device that is plugged into a sound  system to produce a shrill, shrieking, blatting noise. It is used to  irritate and disperse rioters and has a decibel range just below that of  the danger level to the human ear. It is used in night operations to  produce a "voodoo" effect and breaks up chanting, singing, and clapping.