Accurate noise measurements can be informative, although to truly appreciate the difference between jet powered flight and piston powered aircraft, vibration needs to be considered as well. The difference between the two is nothing short of dramatic.
My family belonged to a flying club and as a child I got to experience a few trips in a Martin 404 and an L749 Connie. The vibration was exciting and noise tremendous on both aircraft. We would have to raise our voices almost to a yell in order to be heard across the aisle on the Constellation. I would guess the difference must have surely been north of 20db at cruise.