Welcome to the site.
I would reccomend checking out the "forced induction" portion of this forum. Also, visit
www.howstuffworks.com and click on the turbocharger link. It will fill you in on the basics.
As I'm bored, I'll tell you what a BOV does: when you are on the throttle in a turbo'd car, you are creating boost, or more pressure into the throttle body. When you lift your foot, there is still boost in the pipes, so to speak. The BOV gives that pressure somewhere to go. If it didn't have that exit, it would go backwards and damage the turbo.
There is really no way you can get a blow-off sound without having a turbo. A new intake will give you a nice *chut* sound when you stom on the gas, though.