Who has solved the HVAC air noise problem?


I am in the redesign stage of a totally dedicated listening room which will inlcude tube amp, pre-amp and cd player. The reconstruction will include a flat ceiling and tons of sound isolation and insulation. The central air system for the house with constant air flow produces way too much background noise and hum through the vents. I want to add a separate dedicated a/c system for just this room (25Lx15W x 9.5H). I am looking for the advice of those who have managed to baffle internally in the ducts sufficiently to eliminate the air flow noise and machine hum, while still having an effective a/c system. I want an invisable a/c system with five overhead vents. Duct size should not be a problem as the walls will be at least 12" thick at one end. I presume that fiberglass or lined/insulated sheet metal with all surfaces covered are the way to go. BUT, I really don't know. What I know is that I want to be able to never hear the environment, only the music.

All thoughts welcome including my obvious need for more therapy.

Bill E.
lakefrontroad

Showing 2 responses by rogereckert

Bill
The first thing you need to know is the cooling BTU requirement for the room. From that number total cfm
can be calculated.CFM will dictate the number and sizes of
ducts. To reduce vent noise you can go with larger ducts and registers and fewer of them. Use insulated flex duct. If you have room to snake the duct around instead of running it straight you can reduce noise further. Don't forget to install returns. You can use ductboard or flexduct for this to reduce noise further. Finally, have canvas vibration joints installed at the blower housing if any sheet metal ducts are used.
How will you heat this room?
Sincerely,
Roger
A.A.S. in HVAC
B.A. in Management
M.S.Ed. in Counseling
If my suggestions aren't enough, we'll look at therapy
:)
For return ducting, internally lined sheet metal ductwork would be my first choice for noise reduction, followed by ductboard. By the way, ductboard IS code approved for residential and commercial HVAC systems. I'm not crazy about the fiber from ductboard either. Internal insulation lining is MUCH better. Wrapping the outside of metal ductwork with insulation is done primarily to prevent condensation and avoid energy losses through the duct walls. In my experience wrapping the outside of metal ductwork with insulation does little to reduce or dampen air noise inside the ducts-which is what Bill wants to accomplish.
Make sure any metal ductwork is heavy gauge. This will help prevent ductwork noise often experienced when the blower first comes on and pressurizes the duct system.
As to filtration, an Aprilaire Space Gaurd media type filter installed by the blower does a great job and adds to noise reduction due to its thickness and composition. Some electronic air filters will marginally outperform the Space Gaurd but require maintainance and make some noise.
Hope this helps.
Roger