You have not to repeat the mantra, you have to understand its meaning and let that meaning sink into you. Sitting silently, be utterly quiet, unmoving. Watch your mind. A few thoughts will be there, but as you become silent those thoughts will disappear, and suddenly you hear a humming sound all around you.That humming sound is not made by you.
It is at the very center of existence.
It is the sound of the skies.
It is the sound of space.
It is the sound of the universe; it is its indication of aliveness. It is vibrating with dance and music.
This OM is perhaps the greatest symbol in the whole world.
~ OSHO – Om Mani Padme Hum, Ch 1, Q 1