Larry - I got rid of the Chevy several years ago. But I disagree completely with your statement. I think my new one is somewhat quieter but not all that much. I still shut it down every time I go through a Mcdonalds drive-through.
I'm really just comparing the technology that first came about with the introduction of the first Duramax in 2001 (I think)- the changed injection system vs. what was then used by the older GMs, Fords, and Dodges. THAT reduction in noise was on the order of 100 times. Nobody, and I mean NOBODY, would believe I was driving a diesel back then.