Asking this for a friend

Has anyone here know of a way to quiet down a portable dyno?

He wants to be able to do dyno runs not only at shows but at his home, so noise is a concern

You're kidding, right? I dont know what kind of loud dyno your friend has, but it's usually the motorcycle that's noisey.

Hmmm, out of luck here Brian. Most of the portable units are very loud (most of the trailers they are in even seem to amplify it a bit more.

Might do a bit with standing partitions covered in acoustic foam to attempt to dedden some of the noise, but I do not think it will reduce it enough to run at a persons house w/o complaints.