How long of a length of flex does it actually take to minimize noise?
Aston01
| Posted in Mechanicals on
I frequently hear that rigid duct offers the best efficiency, but utilizing a section of flex duct off the register can help minimize noise transmission.
That got me thinking though…how long of a section of flex do you actually need if the main reason for using it is noise minimization?
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Replies
Any disconnect between rigid duct will help. Just make sure that you use rigid for all corners and only replace straight sections of duct with flex.
It depends on the the type of flex duct you use. With standard duct 2'-3' will decouple the plenum from the register but will not do much for crosstalk between rooms.
If you go with one of the acouistical flex ducts that have decent absorption, something like 4' on a 6" duct will make a significant difference. If you can oversize the duct, having a bend in flex (which is terrible for air flow thus the larger size) does a good job of reducing crosstalk, common design detail for home theater rooms.
For ultra queit, you can get duct silencers (they look like car mufflers) that work extremely well.
These are a good read for noise control:
https://www.cedengineering.com/userfiles/HVAC%20Systems%20Noise%20Control.pdf
https://www.priceindustries.com/content/uploads/assets/literature/engineering-guides/silencers-panels-engineering-guide.pdf
That is exactly what I wanted to know. Thanks for your help.