What is the quietest range (cooker) hood?
One of the best ways to keep your hood quiet is to buy something that has adequate CFM ratings for your situation without being overkill.  A 900-CFM hood is probably never going to be as quiet as a 600-CFM hood and 600 CFMs is usually overkill for all but the most professional of range tops.  Also, if you can find a hood that has infinite fan speed like the Kenmore 50303, then you can select a speed that isn't as loud as High, but provides better ventilation than Low.  After you figure out how much CFM you really need, then you can start comparing Sone ratings (which is usually tested and reported on the highest setting).  As an additional tip, barrel-shaped centrifugal fans are usually quieter than standard blade fans that chop the air.