I bought an LG Intellowasher DD for two reasons:-
(a) it was one of the quietest I could find at the time to buy (it lives in my kitchen where I also have a dining table) and
(b) it was a huge (7.5kg) drum capacity - so I could wash my duvets in it
I think the Hotpoint BS1400UK is the quietest on the market at the moment - more info
here
Here's the four quietest listed on that site:-
Hotpoint BS1400UK 39dB �564 - �720
Miele W2888WPS 44dB �1,130
AEG-Electrolux Lavamat 1800 46dB �557
Bosch WFXI 2840 48 dB �719 - �757