silencer

My current set up is filter to 8" hyperfan connected directly to a 90 elbow that is attached directly to a back draft dampener that exhausts directly into my attic. My question is can I attach a silencer after the backdraft dampener? I need more airflow but can't adjust the fan higher then...

Has anyone here used or heard of the Phresh Stealth fan? there seems to be very little coverage of it anywhere on google. I came across one product review and someone said the built in muffler created 'oscillating sounds' due to its bulld but nothing else on it hardly. The stealth is supposed...