Last week's police busts on Occupy camps around the United States saw one of the highest-profile deployments yet of high-tech crowd control: sound cannons, reports the Week. Designed to keep birds out of the way of planes at airports, the "long range acoustic device," or LRAD for short, blasts high-frequency sound waves over a 300-meter range, causing intense pain that can incapacitate people.
Military-grade versions on the LRAD can fire off sound waves north of 160 decibels, well above the point that can cause hearing loss; the model typically used by police has a maximum of just 149 decibels and is typically used around 110 decibels—akin to the noise at a rock concert. Although several media outlets have reported that police in New York and Oakland used the LRADs on protesters last week, the NYPD denies having used its LRAD as a sound cannon—instead, it insists it only used its LRAD as a "megaphone," to broadcast instructions to protesters. (Read more nonlethal weapons stories.)