Sound deadening material behind painting

I've tried this. It depends on the canvas and how well treated and how much paint is on it. If the paint is very thick it doesn't work very well. I used loose unprimed duck canvas and used Acrylic paint that was fairly thin--almost like water colors, with a few exceptions. Behind the canvas was Sonex--not the typical thick stuff, but the thinnest pyramid shaped stuff. Audio Advisor sells this stuff. It worked well for high frequency 1st reflections off the side wall. I have not tried it with acoustic tile, but hopefully my experience will help.

Yes, I have done this behind my couch. You can use some cheap foam from a hardware store to get an idea, the use something like sonex to hit the right frequencies when you are ready to do it...

Wow ... you guys can afford this hobby AND paintings with real paint? The only ones that I own with paint on them are the felt Elvis ones. Not bad for attenuating highs, though.

I gotta get a better job.