What is the ruling on someone who prays a silent prayer behind an Imam who is leading a loud prayer?

Scholars have differed on the ruling concerning a congregant's intention differing from that of the Imam. The fatwa adopted by us is that it is permissible. This includes one who prays a silent prayer behind one who prays an audible prayer, because silence and audibility are among the Sunnah and not among the Fara'id (obligatory acts).