Just please cover any material which is flammable that you add to your walls. In RI an entire night club burned to the ground in 10 minutes and over 100 people lost their lives. The reason was foam applied to the walls for the bands to play.
Foam burns fast, ever seen a couch burn...it's gone in 1 minute.
Just playin the fire marshall on this one.
You could add blue board insulation and sheetrock over it.
Or install some ear plugs into the the ol' ears.