I recently got a new dishwasher, and in addition to actually getting the dishes clean, a key factor was doing so quietly. This is a big selling point of many models, though manufacturers lover to talk in marketing terms like “QuietSeries 300″ instead of giving you a decibel (dB). Number you could make an useful comparison with.
One notable exception was GE, who is apparently letting engineers write their e-commerce site. Not only do they spec a dB number for noise, you can download a full, exploded parts diagram in the standard CAD DWG format! I ended up buying a Maytag that was a slightly better value on clearance, but we’ll assume they get about the same level being in the same price range: a claimed 57 dB. According to the Wikipedia link above, that’s quieter than normal conversation.
Being an audio geek, I naturally have a sound pressure meter for setting up speakers, and decided to compare the old and new dishwashers. My old one hit about 70 dB, equivalent to loud traffic and certainly enough to keep you from watching TV or talking on the phone while nearby. The new one measures about 58 dB, less than one-tenth the noise on the logarithmic dB scale! It’s quiet enough to be unobtrusive, and goes unnoticed once you leave the room.
As I was installing it, I studied the sound isolation. The tub is solidly constructed and covered with a thin heat and sound insulation blanket. There are seals for the door, and harder seals where it connects to the counter and cabinets. The kick panel was also insulated, and came with weatherstripping for the bottom and two side baffles to close any gap. That seemed to be the common theme of all the additional sound proofing parts: block any air movement between the noisy workings of the dishwasher and the room.
It makes perfect sense, since sound is simply a pressure wave moving through the air. In fact, I found that the most noise after installing it came from the gap at the back of the counter and between the one side of the dishwasher and the wall. Stuffing both the these with foam insulation should block some of the remaining noise. Though I’m sure the machine also uses quitter pumps and motors, it’s likely you can get good noise reduction with any dishwasher by tightly sealing the edges with weatherstripping products and isolating it from the room.