It is basic science. Turbos work by taking energy out of the exhaust stream and use it to compress intake air. Less exhaust energy = less exciting / neutered sound. Just ask Ferrari enthusiasts what they think of the new V8 turbo's sound as compared to the N/A V8s.
v8 turbos still sound good. they just dont sound like an intense NA cammed straight pipe v8. it sounds like a turbo v8, which still sounds good.
v6 all cammed out, on straight pipes sounds like shit lol. its less bad with turbas, but still sounds like shit.