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.
A fluvioglacial landform created by both erosion and deposition by melt water is a Sandur or outwash plain that often has braided streams. Outwash plains are areas that may have been glaciated by ice sheets and then affected by melt water or they may be areas in front of the snout.