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 agents of erosion are gravity, ice, water, and wind. Erosion is sometimes restricted to transportation, excluding weathering.So as rock is eroded away by one force or another, the landscape changes. If enough sediment is eroded away in one place, it can begin to form erosional landforms.