I have had a Kobe Kobe RA0230SQB-1 range hood (now seems to be discontinued) for several years and was really unhappy with the noise. We have a TV in the kitchen and would have to turn it up really loud to hear when cooking. I really love this hood and chose it because of the simplicity with old school power knobs, no circuit boards or fancy displays, and commercial style grease baffles. The hood is rated at 760 CFM, connected to 6" round duct, and its over a GE CAFE gas range. I measured several points and calculated the air flow at 353/521/685 CFM for Low/Med/ high speeds and metered 65-78 decibels (low to high) standing in front of the range. Although 65 decibels is supposed to be quiet, its not really quiet enough to not raise your voice when having a conversation...

I removed the squirrel cage blower inside of the hood and connected a new Fantech FKD 8" inline fan rated at 836. I kept a short 18" section of 6" due to east of installation in the attic then transition to 8" to the roof vent with 90 and a 45 degree elbows. Probably 5' of total ductwork. I replaced old 3 position the fan switch with a Fantech WC on/off variable speed switch in the same position and using the old knob to match. New CFM was measured at 460/563/754 CFM (Low/Med/High) and the decibels were metered at 60-73 decibels standing at the range. A 5 decible drop.

It is hard to describe the sound but prior was super noisy with the squirrel cage blower inside the hood. The sound now from the hood with the remote blower is kinda like air moving in a tin can. It is definitely quieter and this it was worth the effort. I think maybe if I brought an 8" duct down into hood it may have reduced the air in a tin can sound; or possibly trying insulating the duct.