quietening the exhaust

How can i quieten down the noise from my exhaust from my fan ?
Is it better having a shorter run of ducting or do i need to get the acustic stuff? seems these fans are generally to vent indoors from a tent but im going straight outside and it sounds like a tumble drier thats going for 18 hours

...here is one idea that lowers the noise. (fan inside box)

...also, here's a link to inline mufflers >>> http://www.discount-hydro.com/productdisp.php?pid=304&navid=29

A Carbon filter really deadens the sound if air gets pushed through it near the end of the ducting.

Thanks guys ,i do have a carbon filter at the end and it made no difference ,the noise is definatly the air being moved and not the fan so i dont think a box will help .It really is just the sound of gushing air which in the day is not too bad but in the night it sounds like a jet taking off

bifter said:

Thanks guys ,i do have a carbon filter at the end and it made no difference ,the noise is definatly the air being moved and not the fan so i dont think a box will help .It really is just the sound of gushing air which in the day is not too bad but in the night it sounds like a jet taking off

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You could use something like this to turn the fan speed down and cut some of the air flow. Achieving optimum air flow will reduce noise:

http://www.bustan.ca/product_detail.asp?menuID=1&SID=13&PID=1071

This article has some good suggestions about acoustic dampening:

http://www.brighthub.com/engineering/mechanical/articles/23271.aspx

Also... I read somewhere that air will make more noise the more it moves through bends in the duct work or through rough transitings between duct components. Straight and smooth runs are quieter.

do you have any ducting on the exhaust side of the fan. my fan is very loud as well but when I added about 5 feet of vent on the other end of the fan it really muffled the noise down.

put carbon filter right on the back of fan and eeverything else gets air pushed throw it very quite that way got 6 inch on full blast cant even tell its running also hang fan with bungie cords

If that doesn't work, insulated ducting might help. If its the fan that loud throw some towels over it and see if that helps...