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.
The arena of erosion caused by overland flow is a whole slope. The eroded material. moves down the slope. Gullies can form in the middle or lower parts of a slope if the topography favors the. concentration of overland flow and small streams.