Geophony, from the Greek prefix, geo, meaning earth-related, and phon, meaning sound, is one of three components of the soundscape that relates to the naturally occurring non-biological audio signal sources coming from different types of habitats, whether marine or terrestrial. Typically, these refer to wild, relatively undisturbed habitats. But geophony is not limited to that narrow definition since these audio sources can be experienced nearly everywhere the effects of wind and water are expressed. The term was first used by Drs. Stuart Gage and Bernie Krause to describe certain soundscape phenomena recorded as part of a bioacoustic study in 2001–2002 commissioned by the National Park Service, and done in Sequoia/King's Canyon National Park. Geophony is one of three terms used to define the general sources of sound that occur within a soundscape. The other two are biophony, and anthropophony.