long-range acoustic device (LRAD)

A loudspeaker system that projects sound, including clear speech, in a narrow beam over long distances, so that people in its path hear it clearly while people beside it hear far less. LRAD is the brand name of devices made by Genasys (formerly LRAD Corporation) of San Diego, and is often used for the whole category.

Navies and ships use them to hail and warn other vessels, a use that grew after the attack on the USS Cole in 2000. Police use them for announcements and crowd control; the first widely reported use against protesters in the United States was at the 2009 G20 summit in Pittsburgh. At high volume the alert tone can cause pain and hearing damage, and in 2018 a federal appeals court held that police use of the device against protesters can amount to excessive force (Edrei v. Maguire).

Related terms: parametric array, Mosquito device, structure-borne audio, directed energy