It's obviously a stealth indicator. Probably try a different video format maybe? Takes a little bit to load for 55 secs. Not a whole lot there. But very good potential all together. Your isometric people could use some work. I suggest look at some of eboy.com stuff for reference. I think youtube has some isometric tutorials as well.
For those of you curious about the pseudo-3D motion of bits when the turret explodes, I just submitted an article describing how to code 3D projectile motion in isometric perspective. Check it out.
As for the sound meter, yes it is a stealth indicator. It shows how much noise you're making. The louder you are, the further away enemies can hear you.
I should get around to posting a debug-mode vid soon, where you'll be able to actually see how noises are handled, as well as bullet paths and enemy sight cones, etc.