When comparing sound levels of Bosch and Miele dishwashers, Miele model G5915SCI is quietest, with a 37 decibel rating, according to Yale Appliance. The loudest is Bosch model SHE3ARL2UC, listed at 50 decibels. Many dishwashers by both brands range from 42 to 46 decibels.
As decibel ratings increase slightly, the noise level increases dramatically. A one-decibel boost raises the sound of the dishwasher by 30 percent. Dishwashers rated from 41 to 50 decibels are considered quiet. By comparison, a whisper is 15 decibels, while standard conversation volume is 60 decibels. Features that affect dishwasher noise level include type of insulation, use of exterior sound dampening material, composition of the tub and presence of a disposal.