You are on the right track with the fans and noise reduction. A higher CFM fan dialed down will be quieter than lower CFM fan running at top speed. Also, noise can be greatly reduced simply by up sizing the ducts. So if it's a 6" duct, taper it up to 10" south of the fan and you will see considerable reduction in noise. I would do that before doing any experiments. That is essentially what a DIY duct muffler does anyway. See link in my signature for good info on fan sizing.
bigsby Reviewed by bigsby on . Static Pressure Question - Ducts and Carbon scrubbers Hello friends, I am in the process of designing a 400 watt grow cabinet, and I've got a couple questions. I am planning to use an Elicent inline fan to suck through a DIY carbon filter, through a 6" (probably Hydrofarm) cool tube, and blow out of the cabinet. I found the spec table for the Elicent fans. It gives flow rate (in m3/hr) versus pressure (in pa). This information would be priceless if I only knew how much static pressure would be generated by my DIY carbon scrubber... The Rating: 5