Soundproofing Ductwork Video

Discussion in 'Studio Construction & Acoustics Forum' started by dvdhawk, Jan 4, 2010.

  1. dvdhawk

    dvdhawk

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    What do you experts make of this how-to-video on preventing sound from passing through ducts?

    http://www.ehow.com/video_4971322_soundproofing-ventilation.html

    This is the first time I've heard [or read] anyone suggesting sticking multiple 4ft. long fiberglass ductboard panels lengthwise into straight ducts - rotated at different angles as baffles to keep sound from traveling through round ductwork.

    Seems plausible, but you guys are the experts...


    << The author's homepage >>

    http://www.acousticsciences.com/

    Any of you Pacific Northwesterners familiar with the company, studio designs, or the author?


    Thanks!
     
  2. camsr

    camsr

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    I thought they just use the 1/2 inch baffle stuff.
     
  3. dvdhawk

    dvdhawk

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    The video instructor is showing a 2" rigid fiberglass duct board - with beveled leading edges. (foil removed, eventually wrapped in an approved HVAC fabric)

    Here's what I'm getting from his video instruction:

    [​IMG]
    3D View

    [​IMG]
    2D END VIEW

    Interesting concept I haven't seen anywhere else before.
    I can see how it might inhibit some sound, but I wonder how much it constricts the air flow.


    Thanks all.
     
  4. Thomas W. Bethel

    Thomas W. Bethel

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    ART Noxon is the President of the Company. He and I go back a long way. They are the originators of the Tube Traps that many here use. He really knows his stuff. If he says it works it works....
     
  5. camsr

    camsr

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    It should work as far as my knowledge goes. It's also a quick and easy retrofit to an existing duct.
     
  6. Space

    Space Moderator

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    Wouldn't you have to, in a retrofit, resize the duct to not burden the system with restricted air flow?
     
  7. PITA

    PITA

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    The thing that makes the ducts noisy "outside of the fan and motor and radiated/transmitted noise" is duct air turbulence. Turbulent air is noisy. Find a way to make the air laminar and it stops making noise.

    There is a great product called Hexcell that works really good for creating quiet laminar airflow. Just a though. That won't adress sound transmission however but it will kill turbulent blowing noise.
     
    Last edited: Jan 8, 2010
  8. MadMax

    MadMax

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    All I can tell you is that I don't have them in my system, and you CANNOT hear my HVAC run... period. So, I know that a properly designed and executed HVAC system does not require them.

    Just sumpin' to ponder, while you got nuttin' else to do, right?
     
  9. dvdhawk

    dvdhawk

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    My HVAC contractor is the one who found that particular video. I've seen countless projects here at RO and on the JL Sayers site that build their own rectangular silencers and we've always planned on using them. This was the first time I've seen this particular round-duct approach. This has got to be one of the more wallet-friendly approaches, if you're in a position to try it.

    Thomas' endorsement of Mr. Noxon's credentials goes a long way. The inter-web has so much conflicting information from people who mis-represent themselves as experts in the field. It helps to have someone like Thomas say, "He and I go back a long way..... He really knows his stuff. If he says it works it works.... "

    Mr. Noxon seems to be a bonafide professional and we may employ a combination of techniques on site to get the results we want. Currently we're planning for several big S bends with lined flexible duct in the AC supply and returns, along with several of the more common lined plenum silencers. If we have any straight sections we might use this method too. My HVAC guy believes the oversized variable speed fan we're using will be more than able to compensate for any restrictions to the airflow cause by any of these silencers, since we've sized the ducts up so much.

    With the air-tightness of the ICF building our goal is to keep the air circulating slowly even when it's not being cooled - so that we can keep the fresh-air circulated and control the humidity. Heat as needed will come from the radiant heat in the floor.

    So far, I like where my HVAC contractor is going with the design. But I'd like to see more of this kind of discussion if it would give him more ammunition in doing the design.

    Thanks to all involved so far.
     
    Last edited: Jan 9, 2010
  10. Space

    Space Moderator

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    Engineering legend Bruce Swedien has shown his love for ART Noxon's Tube traps. The circle and or round appliances seem to be favored by Mr. Noxon and seem to agree with his certain way of approaching acoustics.
     
  11. Thomas W. Bethel

    Thomas W. Bethel

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  12. Rod Gervais

    Rod Gervais Moderator

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    I see nothing wrong with this approach - assuming that the ducts are increased in size to compensate for the flow restriction........

    Simply setting the shiv on the fan to increase it's velocity is not going to help - the problem here is 2 fold - the first is creating a properly sized duct assembly to maintain a large volume low velocity system - this takes care of turbulance - the 2nd is to determine a method of silencing the noises that want to travel through the duct into the space.

    I (for one) would be very nervous about intalling these on any existing system due to the reduction in flow that would take place - or (if the fan could overcome the added static presure) the increase in velocity and he noise it bould bring at the final enrance to the space.

    I designed Max's system using standard construction techniques and materials for quiet operations - nothing special - and he can use his fans 24 hours a day 7 days a week and no-one will ever hear a thing, and no mic will ever pick up even a hint of system operations..
     

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