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High Velocity HVAC noise

post #1 of 11
Thread Starter 
I have a basement room that is conditioned with a Unico high velocity HVAC system. It is noisy, and i am wondering if i should consider ripping out the ceiling and adding inline mufflers . Do they work? Other options?
Thanks
post #2 of 11
I doubt the mufflers will help. The issue is the "high velocity" which creates turbulence which creates noise. About all you can do is decrease the velocity by using larger ducts and larger diffusors OR more (meaning lots more) small ones.

Now to my soap box ....

I have a potential client that is very focused on specifying duct size, diffusor size, etc. Here's how it works when you're dealing with other trades (such as HVAC contractors). If your objective is to have a duct of size "x", then specify "x" if that's what is important to you. I'd suggest, that duct size is of no importance to you in an acoustic application. What is important is noise levels, etc. So if the noise level of the air leaving a diffusor is important to you then specify (as an example), the Noise Rating (or Noise Criteria) shall be not more than 21 when measured .5 meter from any diffusor.

Another example ... are you concerned that the HVAC will provide 18,000 BTU's of cooling. I'd suggest that's not what you're really interested in. Here's a better way: "The system shall maintain 70 degrees with an outside temperature range from -30 degrees to 110 degrees, humidity shall not be less than 25% nor greater than 35%...."

Let me explain one (not all) of the reasons for this. If you tell your HVAC contractor that he must meet a given temperature, humidity and NR, then if you don't get that, it is his problem to fix, at his expense, at his potential loss of license. On the other hand, if you tell him you want 10" dia. ducts, and he gives you 10" dia ducts but the air noise is outrageous and the room will get no cooler than 85, it's your problem, not his.

Think about it.
post #3 of 11
Good soapbox. +1.
post #4 of 11
Quote:
Originally Posted by Dennis Erskine View Post

Now to my soap box ....

Classic Erskine
post #5 of 11
This is why he's the man
post #6 of 11
What Dennis doesn't know is that I designed that soapbox and rigged it to cave in at the touch of a button...he he he!
post #7 of 11
What you're really saying is you designed that soap box and it was so flimsy it caved in ... so you called it a feature not a bug.
post #8 of 11
I can only say it is a reflection of the way I was raised in such a cruel design world.
post #9 of 11
Thread Starter 
Ah yes, little did i know when i put in high velocity ducts that these systems dont cool/heat as effectively and are noisy. So i am bringing in some HVAC contractors, but each one gives me a different solution. Once i get all of them to give me an opinion i will post here.
post #10 of 11
Quote:
Originally Posted by Lic265 View Post

Ah yes, little did i know when i put in high velocity ducts that these systems dont cool/heat as effectively and are noisy. So i am bringing in some HVAC contractors, but each one gives me a different solution. Once i get all of them to give me an opinion i will post here.

This should be interesting. I doubt if Dennis and I will disagree. There are only a handful of correct solutions, and they pretty much all involve making more or larger vents.
post #11 of 11
Thread Starter 
Update : 2 HVAC contractors to the house. Basically they both said that the current high velocity setup will be noisy. Not too much can be improved with mufflers placed inline.
However, since the room above is the kitchen, and there is not enough cooling, one option is to take the excess capacity and put it into this space. I would then use a split unit in the medial room as a separete zone.

Not sure of the cost yet, but it does solve 2 issues - better cooling in kitchen and quieter ventilation in media room
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