Reference: Sharh ‘Umdatil-Fiqh – Tape No.8, Question No.13
Question: Sometimes I hear the adhaan from the Haram via radio, and it is live. [Bearing in mind] I am in Riyadh and we have already prayed, if I was to repeat [the adhaan] after [the mu.adhdhin] will I be rewarded for that?
Response: Yes, because it is a remembrance of Allaah (‘Azza wa Jall), so you should repeat it along with him when you hear it – even if you have already prayed.