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.
By P Tiwari Geomorphology. The landforms created as a result of degradational action (erosion) or aggradation work (deposition) of running water is called fluvial landforms. These landforms result from the action of surface flow/run-off or stream flow (water flowing through a channel under the influence of gravity).