Basically, a passive radiator is a reactionary device as the name suggests. When a driver (such as a subwoofer) is mounted to a sealed speaker box (enclosure), the physical forward/back movement of the speaker affects the internal air pressure of the enclosure.
Three landforms created by wind are; sand dunes, yardangs (half-teardrop shaped formations hill sized, and deflation hollows (wind swept depressions.
List of Landforms on Earth Types of Landforms and Definitions Alluvial fan: land formation that occurs when sedimentary materials such as rocks, gravel, and silt, are deposited onto land as a result of decreasing or stopped water flow from a river or stream source.