For the next hour, the crowd moved up and down among Beaver, Broad, and William. Around 10 AM, still on Broad and Beaver, I heard a sound to my left like the alarm when someone opens an emergency subway exit. Turning, I saw a line of maybe twenty protesters, not two feet over, drop to the ground like puppets with their strings cut. This was the LRAD—a Long Range Acoustic Device, or sound cannon, that emits a high frequency pulse that rattles the skull—earplugs don’t help. First developed for use in faraway countries, it has finally found its way home.