I have a Blitz DD and running betwwen 5-10 psi right now. It sounds nice not to loud like the Type XS but louder thn the Apexi. You can definaltey hear it when it vents and it's not that annoying high pitch either like some.
My turbo spools quicker when shifting also, plus it looks bad *** in my engine bay
I highly recomend it. Mine is right off the stock intercooler pipe I connected it with some heater hose (nylon covered stuff really strong), only about 3 inches worth, it looks good.

 

If you want to hear different ones go to blowoffvalve.com they have lots of audio clips.

 

Im looking for a video/audio clip of the Greddy Type R BOV,they didn't have it.

 

I think the type r is the same as the type s but for much higher boost applications, you don't need type s.