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Discussion Starter · #1 ·
There are so many threads on noise reduction and insulation on this forum and I've learned a lot. However, the HVAC problem doesn't get much attention. What good is the best insulation if the sound is propagated through the conduit system into the rest of the house? But even more importantly, how do you minimize incoming noise from the HVAC itself to keep the Noise level low. This might be interesting to everyone here thus I hope for great posts. As an example, the HVAC in my rental apartment produces easily 50 db C-weighted and the fridge does, too.


In the new place I'll move to in December, the Ht will be in a fully insulated garage and get its own HVAC system so sound propagation is not an issue. I just want to avoid the rattling blower noise and the wind noise. So here are the questions:


1. Which HVAC brand and model is particularly quiet? I've heard scroll compressors at low speed are quieter than piston compressors.


2. How to avoid the HVAC machine noise from coming out of your vent?

I've heard plastic flex duct is quieter but not as efficient as metal duct. Same for making some turns in the ductwork.


3. Do exhaust pipe style noise reducers work in flex duct and how well? There are some models on the net but I don't know anything about those and whether they are worth the investment.


4. How do low noise outlets and intakes look? How much are they? How much is the noise reduction?


5. For all those who already have an AC, how do you get it quiet aftermarket?


If it weren't for the AC I am pretty sure I could easily get the room to the recommended 20-30db noise level, certainly with an A-weighting and maybe even with a C-weighting.


Thanks for all your posts. Let's make this the reference thread on the question for I've found no other so far.


Till
 

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In constructing my HT, which is part of an overall basement finishing, we have a standard Carrier single-speed blower/furnace/ac to which we added an Arzel zoning system which allows 8 separately controlled zones throughout the home. The HT is one of the zones, it is supplied by (2) 6" flex ducts which are each to be attached to 4 ft. long, 3 slot linear diffusers. These are commercial grade diffusers specifically rated for highly adjustable flow pattern control and very low noise, mine are rated for
 

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Discussion Starter · #3 ·
Thanks a lot for your post. For me upgrading the main unit to a stronger one wasn't possible and I think it is preferable to have a separate unit in my case. I wonder, did you ever measure the noise level in your HT with music turned off so you only see what the ambiance noise is?


I also wonder how one would do that with a radioshack meter that only goes down to 50 Hz anyway.


1300$ for inline silencers are definitely over my budget.


Who else has experience with quieting their AC system?


Till
 

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You have three sources of noise in an HVAC system:

(1) sound from the air handler itself, (2) sound from other rooms, and, (3) the sound resulting from air movement in the ducts and through the diffusors.


1. Use oversized diffusors (reduce air velocity) and/or linear diffusors (aka "slotted")

2. Use oversized ducts (again to reduce air velocity, not volume)

3. Use insulated flex duct (if metal ducts are used, they must be lined) and have "S" curves or turns between the diffusor and the air handler.

4. Any duct servicing the theater should not be on a trunk servicing any other room. If this cannot be avoided, the ducts (and trunk) to the other room(s) should be insulated flex duct or lined duct with multiple turns between diffusors.
 

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Discussion Starter · #5 ·
Dennis,


thanks for the excellent advice that should be easy and not too costly to follow. Very much appreciated. Otherwise, sorry I forgot the "e" on Erskine in another post. I am reading all you posting with great attention though.


Would you know which brand of HVAC is recommended or has a good reputation for reliable and quiet units?


Thanks and greetings,


Till
 

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I work for a plumbing, htg and air conditioner company. On and off for 9 years now. As far as the equipment with the absolute lowest noise level........... American Standard is on top of the list. Trane would be next.........however, it doesn't make a whole lot of sense that they would be number 2, since American Standard owns Trane. Go find a dealer that has American Standard on display and hooked up in the showroom and you will see what I mean by quiet. My theater has a Ducane. noisy furnace. hate it. But it was free. Have a Bryant condenser for the theater and it is mediocre at best. Carrier and Bryant are the same thing. But the condenser was also free so I guess I can't whine too much. My ducane is an 80% with a combustion blower which also is louder than I would like. The american standard ones are super quiet. For one thing the Am stand uses a heavier gauge metal for the chassis than most other furnace companies.

http://www.amstd-comfort.com/Glossar...ion=homeOwners
 

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Discussion Starter · #8 ·
Cool! No pun intended but it's not a bad one. Thanks so much for your recommendation of a good, quiet AC brand. I shall check out their prices and hope they are within my reach. Thank you also for the link with the HVAC glossary and FAQ. That is certainly useful for all of us non-experts.


Do you have any idea how much a 1 ton unit might cost?


Till
 

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I have read a lot of posts on quieting the HVAC when it is blowing into the room. Does anyone have any good creative solutions for quieting a cold air return vent? My furnace room is located kiddy corner to the theater and the cold air return in the theater is only about 12 duct feet away from the furnace. Any help would be much appreciated.


Thanks
 

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Discussion Starter · #11 ·
I have learned something interesting from a forum called hvac-talk. There are made to measure sound covers costing around 80$ that one puts directly over the compressor itself. While this might not make a big difference for the AC noise in your room it will make a difference for you in your garden and for the neighbors. Nice idea I think.


Probably in order to quiet the air handler (blower) one would have to put it on a sound absorbing mat to reduce vibrations. Inline silencers might be nice but are very expensive.


Best,


Till
 

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Quote:
Originally posted by Till
I have learned something interesting from a forum called hvac-talk.

Till
Just when I think I saw everything on the internet, there's www.hvac-talk.com.


Thanks Till. I too have had questions about hvac.
 
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