Noise from the left front wheel
 

There is some little noise from the left front wheel of my X.
The noise happens when the car is at low speed (<60km/h)
At high speed, there is no noise.

I check the front axle, nothing is loose. However, the exterior CV rubber boot is cracked.

Does anyone has any clue on this problem?

Drive over various surfaces and see if the noise changes or goes away. Nice new asphalt is the quietest, at least on CA roads. My X has annoying tire noise and it always seems like it is coming from the L/F.

If the sound goes away or changes on different roads, then it is the tires. Bearings or CV joints will make noise on any surface, depending on on turning angles.

the noise happens on bumpy surfaces at the front left wheel regardless of turning angles. But the wheel is free and smooth.

Is your "rough" road bumpy, where the wheel bounces up and down, or rough like old asphalt where the little rocks stick up out of the tar, or concrete that has been brushed or textured? This I would call a "course" surface.

The sounds made when the tire bounces up and down, clicking noises, would indicate a problem with mechanical parts like bearings, etc. Tire noise would be constant and louder on a road with a course surface, then quieter when going over a new section of road that would be smooth feeling if you rubbed your hand over it.

Hope that makes sense. Another test would be to ride in the passenger seat and see if the sound is equal on both sides. If it is, tire noise might be the problem because it is unlikely that both sides would have the same mechanical problem at the same time.