Quiet doesn't climb with price
KitchenAid rates the five picks at 47, 41, 44, 44 and 44 dBA, so the 324 is quieter than the 424, 624 and 724. Every 3 dBA doubles sound power, so the 224's 47 is about four times the 324's 41. KitchenAid's quietest model, the flush KDTF924 at 39 dBA, is shown as unavailable at Abt in stainless. If your kitchen opens onto the living room, start with the 324.
KitchenAid All Dishwashers at Abt