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Help! Quieting a return grill register
pizza on Fri, 05/13/2005 - 01:58
Hi. I recently bought a larger return grill to try and solve a sound issue with my existing air conditioning return grille. The one they installed with the air conditioning system made a lot of noise like a wind whistling out side the window in the winter. I think they sized their return grill too small so I bought a 12 x 12 grill today to see if the larger openings would solve this problem.
When I removed the return grill they installed with the system I discovered that some of the slot openings were actually blocked by the drywall (which was painted black) and I calculated that it reduced the throat area of the grill by 17 percent.
As close as I can determine and measure, I think the openings in the new 12x12 grill total up to around 118 square inches of total air way passage. The return ducting behind the grill is 12" diameter which calculates to around 113 square inches of opening or throat.
They originally placed a grille that measures overall 9.75" x 17.75" over a hole in the wall that measures 9" x 13" . And its' very noisy when the air is being sucked back to the a/c unit. As soon as I remove the grill entirely it, of course, quiets down immensely.
So I figured if I could get a return grill that had the same throat as the ducting, the noise should quiet down. Does anyone think that if I open the hole in the wall to accept this new grill that the noise should then be reduced. It also sounds like a tuning fork at times when it hits its resonating frequency and its very annoying to try and watch TV with that going on. This register is in my living room.
Also I have another return grill up stairs, which doesn't make as much noise. Appreciate any suggestions. Thanks in advance. One last question, do you think the angle of the bent sheet metal fins in the grill is a large factor?