Silencer placement

[Ouch420]

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 lowest setting because it gets too loud. Don't have room to mount inside room

 

[Gardenseed]

Any pictures of the situation would help.

 

[Ouch420]

Sorry just at work so can't take a photo now
Black is the filter
Red is hyperfan
Light gray is the 90
Orange is dampner
Dark gray is the ceiling