To isolate vibrations, engineers must first identify their sources,
including machinery that may not even be in the same room. In
addition, environmental vibrations, such as seismic activity or from a
nearby highway, create low-frequency disturbances that are
transmitted through a building structure (usually 5 to 15 Hz). In
multilevel buildings, the structure itself will sometimes sway at a very
low frequency (<2 Hz). Damping this motion requires a pendulum
isolation system, which will allow greater freedom in the horizontal
plane.