Dutch_12078 wrote:
Comparing a DP to a front engine gasser is "apples and oranges". Try comparing a rear engine gasser to a DP and a front engine diesel (FRED) to a front engine gasser for noise levels.
Then compare specific engines. 
For example I drive Ford with diesels for a decade. 
When I drove 7.3l, going to customers, they already waited in front of the house since they could hear me 3 blocks away. 
The 6l I drive now is relatively quiet, while 6.7l truck I am considering is quieter than my DP
Multi-injection in digital diesels made whole World of difference.