Qalqalah/Echo letters: the following five letters are Called Qalqala or Echo letters. 
when these letters are Sakin, we make a little lighter echo sound while pronouncing them and we pronounce them with more force, when they are Mushaddad. 1. Qalqala will be done when Qalqala letter is Sakin. 2. The letter at the end when we make it sakin because of doing Stop on it. 
Listen to Surah and know how Qalqala is done, the mark words become Sakin when Stop occurs on it as you have learnt up
