I heard some cracky sound in my Steering wheel. Even when the road is smooth, I still here that sound randomly.

Steering Wheel Noise

When you hear a new noise in your car it is a good idea to turn down the radio and continue driving normally to try and determine where the noise is coming from, when it occurs, and how to describe it to your mechanic.  Since the steering system in your car is connected to so many things, steering wheel noise can come from lots of different places.  To allow your front wheels to carry the weight of your car, turn, travel with your suspension and deliver power to the ground, there are lots of links and joints that can make noise.

Crunching

If you hear crunching from just behind your steering wheel you probably have a bad clock spring.  The clock spring in your car is an electrical connection that maintains contact even if one side is rotated.  It consists of a round contact pad on the steering column and a small spring on your steering wheel that makes contact.  If that spring is broken or damage it will crunch as it travels in a circle and should be replaced.

Reference: https://gobdp.com/blog/steering-wheel-noise/