fan mount for quiet sound help

Right now my fan is hard mounted to the top of the box, harmonics are to loud when I turn the fan speed up, so Iam going to remount the fan, hanging it with bungies seems out of the question because the bungies will stretch and allow the fan to hang several inches from the top of the box, will hanging the fan with plastic wire ties work, what can Iuse between the eye bolt on the fan to the eye bolt in the top of the box, that is short and stops the transfer sound?

Bicycle inner tube(s). That's what I use. Super strong, a little stretchy, works great. I cut the fill valve out, thread it through the eye bolts and clamp and/or tie it when I get it(the fan or whatever) where I want it. Let the tube hold the dead weight, then subtract a bit for some stretch.

You can cut and drill rubber bungees to be very short. Do that.

Sponges or the foam egg crate lookin shit helps muffle sound