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Anyone have a slick fix for air noise (humming) through a return air grill aside from increasing size. Depending on speed of variable fan, humming can get pretty loud.
 

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Add another return, the current one is apparently not large enough.

You can try bending the louver further open. But the grille and most likely the duct are still too small, and making that VS motor work harder then it should have to.
 

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ive had great success with opening the louvers a little on the return air grill as a simple quick fix.:yes:
While that does/can work to get the noise done, or stop the noise. the grille still has a air velocity of more then 500FPM going through it, which still makes it and probably the duct under sized.
 

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Not sure if it is a filter grille or not, but try finding a grille with more free area. A grille like a cube core has straight blades as opposed to angled ones. If it is a filter grille, try adding a thin carbon filter/pre filter material. If the grille itself is resting on the filter it may help stop the harmonics.
 
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