Like scathing said, N/A is actually generally louder with the same exhaust, as the turbo muffles the sound as it comes out of the headers.
My N/A skyline was freaking loud when I got it... had a 3" straight-through exhaust, one small resonator and twin cannons on the back. Got done for EPA, got a decent 2.5" system made up with a decent resonator and a proper muffler at the back, brought it down to a nice legal volume.
On an N/A, you actually need a little bit of backpressure... 3" was too big... it moved the power (lol if you can call it that on an N/A) too high up the rev range to be useable... with the 2.5" setup the car became much more driveable (i.e. torque down low where you needed it, rather than having to slip the clutch all the time to take off).
So yeah, a loud exhaust (esp. on an N/A) isn't always a good thing!