If the noise drives you crazy new spring loaded backdraft dampers 9 to 30 depending on the size should solve the problem.
Bathroom vent flap noise from wind.
If this noise is annoying the flaps can be replaced with ones that are electronically controlled.
With gusts of wind that causes air to actually move from the house out through this exhaust duct.
By replacing the old flap with one that is weighted or has a spring you can stop the wind from opening the vent flap.
There are a couple of things that can help to reduce the problem.
Four bolts were put through the flap towards the bottom to add weight to prevent flap from open so often and reduce the angle of swing and electrical tape was applied where the flap contacts the body of the vent to soften the noise.
Easier fix should not interrupt the air flow.
This pressurises the house a bit on one side and depressurises it on the side of the exhaust hood.
The flapper should have a thin piece 1 8 of foam stripping to sit on when closed this foam strip will stop the noise considerably.
Another step would be to alter the angle that the vent is installed.
Noise is often a problem unfortunately which is caused by the flaps that close the vent off when the fan is inactive.
Putting a magnet on may cause recir of the humidity from the vent.
This noise can get annoying but there is a remedy for it.
The flap still moved when the wind is blowing.
Either apply this thin foam strip to the flap disc or to the edge that the flapper rests on whichever is the easiest.
Sometimes wind and roof vents do not get along well.
This simulates the on state of the fan.
Same effect occurs when the shower curtain is drawn to you in the shower.
You are probably better of putting a stick on felt pad on the flap itself so that when it does bang it is more muffled.
Those others are roof attic vents.
If you hear a banging noise coming through your bathroom vent when it is windy chances are that the wind is picking up the vent flap and then letting it bang closed.
Hube nov 14 2007.
The noise is because the flapper is hitting on a metal to metal surface.
The vent hood ducts through a rigid or flexible pipe to a cap on the roof or side of your home.
Often a stiff wind will open vent dampers causing them to periodically clang shut.