When do you hear the noise - you might need to do a little experimentation:
1) When the vehicle is moving slowly, but the steering is NOT being adjusted
2) The vehicle is NOT moving but the steering is being turned
3) The vehicle is moving across an uneven surface
4) On wet grass, put the vehicle into 4WD and try the above.
What size tyres are you using?
Do you have a suspension/body lift and how high did you go?
Worst case it could be a front axle that's broken.
Is the sound like:
a) a ticking sound, like a small stone being thrown onto a tiled floor?
b) a tapping sound, like a hammer hitting a vice?
c) a cracking sound, like a potato chip packet?
It could also be a cracked disc brake rotor, failed shock absorber ... who knows, yet!