Venting [whoosh] noise

I've just set up my first indoor grow in a friends attic. I have two 300 CFM inline fans; one on the intake the other on the exhaust. The intake comes off of a rectangular tin vent thing, concealed by a vent covering as to be inconspicuous. It then travels 3 or 4 feet to my fan via insulated ducting The fan is suspended off the rafters with bungee cords. The fan is the connected to 3 or so feet of insulated ducting and comes into the bottom of my grow room through the panda plastic.



I then have my 400 hps light hung off the rafters with a carbon filter mounted behind it sucking the hot air off the lamp. The air then travels through 3 feet of ducting to my suspended fan. It then travels 3 feet to my exhaust which is configured the same as my intake.



I turned it on and everything looks good other than a profound sucking/blowing noise from my vents. This is in an attic so it is important that it be run at night, but as it is right next to my friends room the possibility of them sleeping is nil. The CFM of the fan is necessary because it is indeed in an attic and the air temp will not be optimal and fresh air exchange is important even if it isn't cold air.



Any ideas how to muffle the whooshing noise?

Extend the ducting? Try to remove all corners? :|

 

Exhaust mufflers are available at certain hydro stores.

 

Thanks meangreen; I was hoping you would be the one too reply.
I guess it comes down to either variable speed controllers or mufflers. As the speed controllers are half the price I assume I'll go with them.

I'm suprised more people don't have this problem.
Perhaps its the size of my fans. It's good to have more than less ventilation but perhaps the hydro store was just after my money. Thinking about it I think my fans are just shy of 400 CFM each.

Good news is they can be used on a 1000watt when space and location are more optimal. Something I'll be sure to utilize.

Thanks again bro,

 

Btw: here are some pictures of my last years outdoor grow. It was my first but I yeilded over 3 pounds! The grow was completely organic; I religiously made my tea's from fish emulsion, cattle feed, kelp, bone meal, compost for microbes etc. I experimented with tying down, mulches, trimming, everything. A very good learning experience.

I'm excited about indoor though; been absorbing all the information as of late. That's my nature; last year I spent a good 6 months researching outdoor. I'm addicted.

Here's a few photos of one of my plants called Magenta. I also grew some Texada Timewarp.

This following plant yeilded me 10 ounces, my 6'4 Texada yeilded 20! :O

 

Those outdoor ladies look good.I cannot understand how your inline fans produce that much noise.I use elicent centrifigals and I cannot here them when the room door is closed.They run 24/7 for with a carbone filter.What kind of fans did ya get?

 

Oh and by the way you can go to a home depot or what ever ya got there and get a fan speed control switch for $15.You will have to get a extension cord and wire it yourself.

 

It's not the inline fans themselves making the noise; it's the volume of air being sucked and exhausted. Makes almost a whistling/whooshing sound from the vent. The intake is right next to my buddies bed.

I think my fans are called tiger something? Pretty sure they're near 400 CFM each 6'.

Perhaps using 8 inch ducting would be more appropriate, or cutting off the tin duct conversion.

Is wiring a fan speed control very difficult? I'd hate to set my buddies house on fire!

 

They are designed for controling ceiling fan speeds.Basically they are the wall switch found in newer houses to control speed of.3 wires in and 3 out,consisting of a positive,negitive ,and a ground,as simple as it gets.Cut a extentsion cord in half and that gives ya a male and female end.

 

i had a similar problem once and tried everything. turned out it was the air moving past the slotted vent grate. i took it out and the noise drematically reduced.
peace