Microwave Hood Duct


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Old 12-19-14, 06:43 AM
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Microwave Hood Duct

I've installed many Hood Combos, but I never had anyone ask me to insulate the duct (inside upper cabinet). Customer wants me to place insulation around the 7" round duct, thinking it will reduce noise. I'm not sure if it will but I need to try.

Any ideas of what I can use that may be in direct contact and wrapped around ductwork?

Thanks,
Brian
 
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Old 12-19-14, 07:35 AM
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I have had good luck with the sound insulation used in cars. There is one product that has a tar like substance with an aluminum backing. It's adhesive and just stick it on the outside. It works if there is a rattle or rumble in the duct itself but it does nothing for the fan noise.
 
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Old 12-19-14, 09:00 AM
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The product Dane is referring to is produced by Dynamat. Dynamat | Dynaliner Brand


I would severly doubt it would reduce any noise in your situation.
 
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Old 12-19-14, 12:26 PM
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Yes, Dynamat is the popular brand name one. I use FatMat. It's the same/similar but less expensive and both are available from retailers like Amazon as well as many car audio suppliers.
 
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Old 12-19-14, 02:47 PM
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Thanks guys,
I doubt if it will reduce the noise also. The noise is not a rattle, it's simply the air flow. But I need to show her it can't be done.

I'm sure the blower on a combo is as quiet as any, I think it's the way air is channeled through the unit that makes it loud, especially at high speeds. Anybody with me on that?
I've installed hundreds and never seen a quiet one at level 5.
 
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Old 12-19-14, 03:23 PM
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You're talking about the split units.... with the blower outside ?
Those things roar on high. They'll suck the coating right off the fried chicken.
 
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Old 12-19-14, 05:25 PM
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My MIL has a commercial split unit. You're ears will pop if you don't open a window when turning it on high.

Air flow noise is tough to control at high flow velocity. It can be done but but stuff like elbows and other fittings end up disturbing the flow and make noise. I think the cheapest and most practical thing you can do is go to the largest duct size possible to reduce the flow velocity.
 
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Old 12-19-14, 05:29 PM
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Don't know if they still make them, but at my last home I had the fan on the outside of the house - about six feet above and twenty feet south of the hood. That's about as quiet as you can get.
 
 

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