# Duct unit noise



## Rinusverbeke (6 d ago)

Hi all

I have a duct unit installed in the ceiling of my living room. The supply vent is directly behind the unit and there is no return vent because I in the ceiling are a lot of gaps where air gets in the ceiling into the duct unit. But the unit is quit noisy, it’s the Movement of air that’s making noise.what is the best way to reduce that noise ? The outlet en inlet of the duct unit is 200mm high and 750mm wide. The picture u can see is the supply vent that is directly installed behind the duct unit.In other words, I have no duct channels…


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## jfont (Feb 1, 2009)

Your best option is to reduce the speed of air in the duct and the outlet grid. Air movement noise decreases a lot with decreasing air speed; decreasing air speed by half will reduce the noise by about 14 dB. The first option I would try would be reducing the fan speed; most air conditioner units have fan motors with various windings that allow adjusting the speed. If that solution is not available or acceptable (you may need to keep the current room cooling or heating capacity), you can check if the noise is caused by turbulence in the grid louvers, by temporarily removing it. If you get a significant improvement then you might consider not using a grid, or increasing the vent area to about twice the current area with a gradual enlargement and a larger grid (or a second grid next to the one you already have). How this helps.


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## Da Wiz (May 8, 2019)

There are ducts manufactured with fiberglass INSIDE the duct. That reduces noise considerably. You can replace the entire duct-run with the fiberglass ducting, or you might replace just the last 10 feet before the outlet. Either option should make a significant improvement in the noise levels in your room.


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