I've hooked it up to insulated ducting. It muffles it a little bit but not enough to allow me to sleep. I am thinking about a router speed controller. When the fan starts out, it isn't very loud until its fully charged, I'm thinking if I lower the RPM it could stay at that lower sound frequency. Has anyone personally used one and could confirm that with me? Thanks ahead.
I'm not sure if it would help but perhaps adding a duct muffler, in conjunction with the insulated ducting?
On it's own it would definitely cut down the noise, the reason insulated ducting isn't as good is that the sound isn't "captured" as the insulation isnt open to the flowing air.
insulated ducting is as follows : Larger ducting : padding : smaller ducting : airflow
This means none of the insulation can "capture" the sound, it simply blocks it out, whereas a duct muffler can "capture" the sound..
Duct mufflers are as follows : Large ducting : padding : chicken wire : airflow.
Here is a link to a DIY one :
International Cannagraphic Magazine Forums - DIY fan muffler (30% noise reduction) for $30
If it's the fan making noise you could always build a box, like with egg crate foam and place the fan inside it, with holes for the ducting
Hope this helps...
p.s. I could be wrong, but I'm just using logic..