Quietest I thing I’ve had was the 1957 283. It idled at 450 rpm through a small exhaust, a small carb, and an oil filled air cleaner. Under light driving, all you heard was the air cleaner sucking air.
i think the mopar 3.3 and 3.8 I had were quiet, and well the mopar 3.7.
the ford 2.7 was silent new, but it’s wearing in to some noise.
all our Hondas have sounded like sewing machines with happy little valves mouse-tapping away. Now their injectors get louder.