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
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
The ducts are not the problem I found when building my room ( see http://www.angelfire.com/mn2/mzn50/ and click on the CAD) you will see that I have installed insullated ends, like mufflers, they do a great job and my room is dead silent.

Good luck
Matt
I have returned to re-read this thread after so much time has elapsed. The comments have been right on point. Thank you. It is the return system which has caused the problem. I have a dedicated 2.5 ton hvac system with hydroair heat directly below the green marble shelf. The returns which draw air across the amps produce 50db at 25hz.

The initial attempt to baffle them in the return boxes, each of which has it's own 12" round duct to the blower unit reduced the volume but did not eliminate it.

I have been advised to have the ducts interrupted by making a horizontal turn, then a downward turn, then a horizontal turn, then an upward turn and tie on back to the system. Each leg to be treated similarly and each duct lined with hospital grade accoustical liner and wrapped with fiberglass insulation.

Your thoughts please?

Bill E
Problem Solved!...
build an earthship. We have NO need for heating or cooling year round - not even a crackling fire ;-)
http://www.ranchocalypso.com/

then again solar electric power and tube amps can be a problem.
???

Gardengirl must have taken lessons from my wife. I don't understand a thing she says either.

Bill E.