Resonance Apparatus Wooden Plank To determine the velocity of sound , it consists of a vertical wooden plank which carries a wooden scale at one side, a brass tube on another and a transparent tube in between. The lower end of brass tube carries a two way nozzle. The vertical end of the nozzle is connected to the transparent tube and the horizontal end is connected to the transparent tube and the horizontal end is connected to a reservoir through rubber tubing , the wooden plank is supported on a heavy base with levelling screws , supplied without rubber tubing.