I went for a short test-drive with no turbo or exhaust. It's deafening.
But with a turbo and no muffler, I don't know. I suspect it's the sort of thing 18 year olds would love. I'm running a 2.25" system with one muffler, which is quiet. It'll be replaced with a mostly 3" system and straight through muffler at some stage.
One interesting point, when I was tuning my boost compensator I did some driving with the waste-gate popped so boost was zero. At 100km/h I had exhaust drone that I could easily hear inside with the windows up. With the turbo working even with the windows down you hear the exhaust.

