Every word originates from sound and each sound has its echo. So a devotee should practise chanting so fervently that the echo of naam jap/mantra begins to be heard from inside while he is silent outwardly. This is called ajpa- jap i.e. continuous chanting through our sub conscious mind. It happens with the grace of God only but firstly the seeker needs to be desperate for Him. Then only our chants can bring the desired result.