It has always been a wish of military designers to hide the sound of the equipment they build to insure its survivability on or above the battlefield. In fact even animals of prey try to stay as silent as possible when hunting as to better their chances for a kill.

But can we figure out a way to cloak our selves and our equipment from making noise? I think we can and have come up with several such ideas, some military in nature and others simply to help with a better lifestyle.

http://worldthinktank.net/wttbbs/index.php?s
=4f7b99bf761a25bc15bbd441d199844d&act=ST&f=223&t=891

And we must remember what causes sound from aircraft? Engines noise and sound barrier breaking. Well we know all about sound barrier breaking and its affect and how to minimize it too. Specially built designs can prevent sonic booms and or you can modify the medium you fly thru. Like a torpedo blowing bubbles traveling in a tube of air within its own boundary level, or using static air from the friction to scramble or re-align molecules of air around an aircrafts airfoils or fuselage. There are ways to control acoustics and well we have some smart cookies working on all this stuff and they