Qalqalah/Echo letters: the following five letters are Called Qalqalah 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.Qalqalah will be done when Qalqalah letter is Sakin. 2. The letter at the end when we make it sakin because of doing Stop on it.