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.
1 Dune ridges:- In areas of large-scale dune activity, certain types of dunes result in sand ridges. 2  Moraines and eskers:- Glacial activity may leave ridges in the form of moraines and eskers. 3  An arete arÃªte is a thin ridge of rock that is formed by glacial.  erosionidges are usually termed hills or mountains as well, depending on size. There are several main types of ridges:-. 1  Dendritic ridge:- In typical dissected plateau terrain, the stream drainage valleys will leave intervening ridges.