We have a 46dB Dishwasher (Bosch) and its very quiet - much quieter than the one it
replaced - this was also a Bosch
but 20 years older (never went wrong) and we gave to a friend 30 months ago, who still
runs it twice a day in a B and B !!
(its well shagged though now !)

46dB is quiet enough to have a normal conversation 4 feet away in a quiet room and only
notice its on when someone
points out it is on - not even obtrusive - it was selected for its quietness as its in
the kitchen / diner where the family
seem to spend most of their time !!

Hope that helps...

Nick