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sayde_gw

Is there any way to make vent hood quieter?

sayde
12 years ago

We have the Prestige 1200 CFM blower motor installed in a custom hood. The 10 inch duct goes straight back into the garge and then straight up about 8 feet and out the garage roof. The fan works quite well but it is really noisy. Or so it seems to me.

Is there anything we can add to the system to make it quieter?

Comments (14)

  • davidro1
    12 years ago

    fantech.net sells silencers.

  • sayde
    Original Author
    12 years ago

    Thanks Trevor and David. I will look into these options.

  • kaseki
    12 years ago

    A silencer will not materially help when the fan is in the hood. The question is what is the source of noise. Duct rattle? Blade tip aero turbulence noise? Fan vibration noise? Hood vibration noise? Baffle turbulence noise?

    Hood vibration noise could be reduced using dampening material such as the stick-on weighted vinyl used in automobiles and available from auto parts stores that cater to body shops. Use on the outside of the hood liner, not the inside. This could also be used on the ducts for duct rattle.

    Baffle noise is probably not correctable except with different baffles. A silencer will handle blade tip noise well, but only when the fan is on the outdoors side of the silencer. Blade tip noise is a function of the blade design and speed.

    Fan motor vibration might be correctable to some degree. Trevor's suggestion will help with it propagating between the liner structure and the wood surround. Different motor mounts could be helpful, but that would be a problem for Prestige to address.

    kas

  • davidro1
    12 years ago

    when the fan is in the hood you cannot add a silencer.

  • asolo
    12 years ago

    Best solution is to have the fan itself outside at the tail end of the vent. Unfortunately, a pretty costly do-over.

  • live_wire_oak
    12 years ago

    You can insulate your duct run, and this should be done for other reasons as well. Hot moist air will condense against a cooler surface, and you can have problems with dripping back into your hood in winter unless the ducting is insulated. That means cutting a hole in the soffit encasing the ductwork in your garage and spray foaming it with the less expansive foam that won't blow your duct apart. Then you can repair the drywall. That can help with the noise issue, but it will depend greatly on where your noise is coming from. You're gonna have to sleuth that out yourself.

  • bernise6
    12 years ago

    Your best bet is to remove the indoor fan and go to an outdoor vent fan. After you have done that, the rest of the noise will be coming from the air moving through your custom hood. If you have the option of changing out the filters, you want to make the total area the air moves through as large as possible.

  • sayde
    Original Author
    12 years ago

    Thank you for all the suggestions. Knowing what we know now, we would have put in a remote blower. But at this point we are not considering replacing the in-hood unit. We're considering trying some insulation around the duct and around the blower unit inside the hood canopy. Thanks again!

  • davidro1
    12 years ago

    sayde if anything is loose and touching another thing, it might make a rattling noise that gets combined into all the other fuzz noise. Caulking might be your friend. The shape of hood you have might be acting like a drum instead of a funnel. Gluing a silicon pad to the inside of the big flat surface might help a lot.

  • _sophiewheeler
    12 years ago

    Start detective work. Begin with the fan motor itself. Is it balanced, or does it wobble? then look at the housing. Caulk and insulate anything that moves when it's not supposed to. Then the duct cover....and keep going. You may not eliminate noise, but if you eliminate every little bit of noise from every source, you end up making a big difference overall. One of the bigger possible culprits besides the motor itself is the duct run itself. It should be secured to studs and have rubber isolation strips between it and the studs. It should be joined together fully with mastic at every joint. It should have an insulation blanket around it, and it should be encased in a drywall chase which has either foam or blown in cellulose.

  • Kevin .Williams
    4 years ago

    My fan noise seems to emanate from the fan blade or the motor. I'll start there. Great advice a possible solutions. Thanks!

  • kaseki
    4 years ago

    Eliminate all the vibration and rattles, and the dominant noise will be from blade tip turbulence. This is not practical to reduce at the blower without essentially completely redesigning it into something that probably won't fit. Blade tip turbulence noise measured at the cook can be attenuated somewhat by using a remote blower, and attenuated further using an in-line silencer between blower and hood. After those changes, the dominant noise should be from hood baffle turbulence.

  • davoid_aus
    3 years ago
    last modified: 3 years ago

    All vent hood fans are noisy (range hoods in Australia). I'm talking the range hoods with the fan built-in to the hood. The more powerful the fan the noisier it is.

    My previous fan had 2 settings low (22 Watts), and high (35 Watts). My current one is low (48 Watts) ad high (65 Watts), and is much louder.

    The options are:

    1. replace the rangehood with one that has a less powerful motor.

    2. replace the rangehood with a type that has the fan in the ceiling.

    3. buy a step down motor device. I've seen these on eBay for about AUS$30. You plug the fan into the device and 'step down' the power so the fan runs slower and quieter.