Of course the other thing to remember is that testing "by ear" doesn't tell you which is quietest it only tells you what does or doesn't suit your ear
and your ear can be as fussy with mods as your eye can be with scopes.

You also get different results depending where you test, stand in the middle of an open field & you get a different sound to having trees, hedges or walls nearby, because the sound will echo back to you.