Author Topic: Traffic noise/exhaust fan duct  (Read 8062 times)

drblanke

  • Guest
Traffic noise/exhaust fan duct
« on: July 25, 2008, 04:48:19 PM »
Our bedroom faces a moderately busy 2 lane state highway. I installed laminated glass windows and doors to help stop the noise through the existing double pane and sliding glass doors. After a lot of calking, I'm happy to say that has stopped 50% of the noise. The rest seems to mainly be coming in via the bathroom on the other side of the bedroom towards the rear of the house, via the bathroom exhaust air duct that was run out to the front of the house facing traffic. The wall vent is located inside the floor of a deck so I can't get a good look at it, but our builder says it is just an open pipe. So the traffic noise is being carried through this duct, through the ceiling of our bedroom, and then into the bathroom via the exhaust fans. Does anyone have any ideas for stopping this noise transmission? I looked at duct silencers, but those are probably more suited to extreme noise situations that just traffic wooshing by? Simple passive dampers opened by airflow probably just keep out mice and not sound? It may already have one of those anyway. Maybe some way to control an electronic vent cover that opens only when the fan is on (snaking the wire from the exhaust fans through the ductwork to the outside)?  Any solution would need to deal with lots of moisture from the bathroom exhaust. Thanks!

johnbergstromslc

  • Guest
Re: Traffic noise/exhaust fan duct
« Reply #1 on: July 26, 2008, 10:11:33 PM »
Couldn't you just shut the bathroom door?

drblanke

  • Guest
Re: Traffic noise/exhaust fan duct
« Reply #2 on: July 27, 2008, 04:30:31 PM »
That is what we do currently, and it helps--some. That's how we know most of the noise is coming through the air duct (that and all the reverb). BUT we can also hear it in the ceiling where the duct is located, and of course through the bathroom door. I guess I could buy a better bathroom door, seal it super tight, tear down the ceiling and spray insulation on the duct as it goes through the bedroom ceiling. However, wouldn't it be best to stop the noise at it's source by dealing with the exhaust wall vent before it ever enters the house? Impossible to do?

johnbergstromslc

  • Guest
Re: Traffic noise/exhaust fan duct
« Reply #3 on: July 31, 2008, 02:03:00 AM »
It would be difficult with all the moisture in the duct.  I've never dealt with that kind of problem and wouldn't contemplate using fiberglass or even a mineral wool duct liner.  Not sure what would work, really....

It might be cheaper to install perimeter seals and a sweep on the bathroom door. 

joel

  • Guest
Re: Traffic noise/exhaust fan duct
« Reply #4 on: August 22, 2008, 04:16:45 PM »
The best duct liner is our Super Soundproofing foam mat.  Thousands and thousands of feet of asbestos duct linings have been replaced with this material.  It is a closed cell, vinyl nitrile foam that is fiber free, mold resistent, and water-based adhesives compatible.  This material both absorbs and blocks sound (has both NRC and STC).  For info and pricing see the first product discussed/shown at http://www.soundproofing.org/sales/prices.html  I would recommend at least 1" thick.