Hi
Are you sure it is comming form the screen frame? The frame should be snug against the back wall when mounted correctly.If it is comming from the screen you can try using rope calk.
Rope calk is available at Home Depot.A 15' roll is about $3 Tear small
peices of the rope calk off the roll roll it up in your hand to make a ball
Make several balls then place them in various locations on the back of the frame.Re install the screen and press against the frame so the ball of rope calk makes contact with the wall and squishes out.
This will isolate vibration from the wall transmitted to the frame.Be carfull
when working around your screen material.You can use rope calk for isolating rattles,keeping pictures straight and securing bookshelf speaker to there stands Its also good for loading the back of a horn lense on horn speakers
not a bad product to have around the HT for $3
Happy Listening
Ray