Acoustical waves with frequency content below the frequency range of the human ear, typically below 20 Hz. Infrasound can often be felt, or sensed as a vibration, and can induce motion sickness and other disturbances, and even kill. The level of infrasound in a modern industrial environment is quite high, with common sources of infrasound being automotive traffic, railroads, buildings, bridges, wind noise, and thunder. Infrasound is used by the military to detect explosions. When an explosion occurs, low frequency acoustic signals are emitted. Infrasound sensors can detect these signals. An Infrasound system may be employed to detect and identify atmospheric, shallow buried or moderately shielded explosions. It has sensors either buried underground or underwater to monitor the atmosphere for low frequency acoustic signals resulting from explosions. Usually, an infrasound system can detect kiloton-type explosions up to a distance of 3000 to 5000 km. In the U.S., the Department of Energy (DOE) conducts Infrasound Monitoring Research to improve the government's capability to detect explosions. The primary DOE laboratory involved in infrasonic monitoring research is the Los Alamos National Laboratory.