I have looked into the Broan Allure series which claim to be quiet (1 sone). However on closer inspection, the claimed sound level is only for the lowest setting. The highest setting is 4 sones (4 times louder). Is this something with no workaround or are there quiet models out there.
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.
Pulling from this site: http://www.appliance.com/editorial.php?article=1249&zone=1000&first=61
Some of the most powerful, but quietest range hoods are made by Abbaka, which offers units that have a blower capacity of 1,400 cfms and a 3 sone noise level. For example, the Imperial Wall Canopy Series has 1,330 cfms and a 4.6 sone rating for $1,893-$2,336. The Sirius Modular Island Style, which has lower cfms-600-but has a 3.9 sone rating, and retails for about $2,143. In the lower price ranges, the Broan-Nutone Allure series is also known to be particularly quiet (4.5 sones for the 400 cfm unit) at a reasonable price range of $242-$341.
So, there are quieter models available, but they will cost you much more money.