HVAC Sound Proofing

Started by MusicmanY2K on 9 June 2008. 5 replies.

Originally posted at johnlsayers.com, topic 10710.

MusicmanY2K9 June 2008#1

Quick one! What is the cheapest way to deaden to vibration for my HVAC ducts. They are 6" DIA. and 22'long. I will be using Rock wool for Installation(between the truss), Sound board, then RC, and finally Dry wall. Will common R-13 insulation wrapped around the piping be efficient for the job? Thanks in advance, Rick

rod gervais9 June 2008#2

the first question is - why are they vibrating? If the vibration is mechanical in nature (i.e.: the fan motor is vibrating the duct) then they need to be decoupled from the fan through the use of a canvas connector. If they are vibrating due to velocity - then they really should be larger duct - You will not stop duct noise by applying insulation on the outside of the duct. Rod

MusicmanY2K9 June 2008#3

Thanks Rod Sorry for the lack of detail. I'm planning to minimize the sound level by the means of insulation, sound boards and RC setup along with the finer details to make an air tight room (good enough to lower the sound level so the family can watch TV above without turning the TV all the way up). However, have a concern with noise transiting through the ducts from a live jam session. I have reviewed some other builds and have seen ideas for mounting the inlet air vents (which I will use), but looking for some options to deaden the sound that travels thought the ductwork. Or will this not be an issue after all other materials in place? Not an issue with noise coming from the HVAC unit. Thanks, Rick

doublehelix9 June 2008#4

Hey Rick: Search for "silencers", this should help you find something. There are several folks around here that have built silencers... Here is a design that http://www.johnlsayers.com/phpBB2/viewtopic.php?t=10328 one user built, but I know there are several others. Good luck!

MusicmanY2K9 June 2008#5

Thanks, James! Excellent ideas and one that will be easy for me to apply. One questions that I haven't found an answer for. Is it necessary to wrap some sort of insulation around the tube to reduce the vibration, or will just filling in the joist and building the surface with the attended method (Rock wool, soundboard, RC and Drywall) work? Other alterative, Replace all the metal ductwork with the insulated flex tubing? Is there a sticky note for this topic? Thanks again. Rick

AVare9 June 2008#6

MusicmanY2K wrote:
One questions that I haven't found an answer for. Is it necessary to wrap some sort of insulation around the tube to reduce the vibration...?

You are asking about SOUND traveling through the duct, right? For that you need line the inside of the ducts. Andre