The US company, "Scientific Applications and Research Associates" (SARA) Inc, has developed crowd-dispersal weapons for the US military that generate high-intensity sound waves. Sound levels of 120 to 130 decibels cause pain and blurred vision; above 140 decibels, sound produces profound discomfort throughout the body. Ear plugs are no protection. These acoustic systems have a directed beam, projecting the sound in a narrow fan. They include high-intensity sound generators with power levels of up to 60 kilowatts and are combustion driven, using a series of small explosions to create a noise or drive a siren or whistle.