Do NOT put a studor vent/ air admittance valve inside of a wall, unless you also install an access panel.
Just my personal professional opinion, but I shy away from AAV's whenever possible. They are a check valve, so they can't relieve positive pressure in the plumbing system, only negative pressure. Also, they are a mechanical device, which means that they can and do fail.
Lake County, Florida plumber
Springtime Plumbing Services