reducer causing extra noise?

[ShOrTbUs]

i'm running a 6" 400+ cfm inline fan. but the duct running out of the room into the ceiling is only 4" so put in a 6"-4" reducer. is that causing extra noise inside my room?

 

[The Hemp Goddess]

It may. Have you considered using 4" ducting all the way from the light? I use a 6-4" reducer, however, I have mine right at the light and I do not experience much fan noise out of my room at all.

 

[ShOrTbUs]

my fan is 6" though so i would have to use 3 reducers to make the whole setup 4"...i'm thinking of picking up a fan speed controller. i think 435cfm is more then i need for such a small run

 

[The Hemp Goddess]

So you are going 6" to 4" and back to 6"? I would get my ducting all the same size, or go from smaller to larger. When a 6" duct hits a restriction like reducing from 6" to 4", 1/2 the cross sectional area (a 6" duct is twice as large as a 4" one), I expect some noise.

You absolutely need a speed controller. I wouldn't order a fan without ordering a speed controller at the same time.

 

[ShOrTbUs]

yeah its on the way overnight delivery. i've already decided to just take out all the 4" in the ceiling and replace it with insulated 6" duct. its only a 20' straight run with easy access. should only take me a few hours this weekend to replace it