Wet the stone with water and use your hands to rub it evenly over the surface. The best effect is achieved with hands that are free of oil. 

Rubbing on the stone causes a vibration that creates a sound. A similar phenomenon is known from glasses, which can be made to create a sound by wetting the rim with water and rubbing it with the finger.

The sound of the stone is full and deep and the mass of the stone causes the special effect to continue for a while.