I had this problem and it was driving me crazy. It was a loud chirping up front after hitting a bump. It got more noticeable as time went on... and the louder it got, the crazier it made me. I could turn the radio up, but I knew it was still there.
I read all the posts about everything from bad bearings, driveshafts, shocks, bushings, etc.. basically anything in the front of the Jeep that was going to be expensive. I could reproduce the problem by giving the front tires a good kick so I was hoping it may just be something loose in the front suspension/drive. Got my tools and planned on spending hours looking around and tightening any bolt I could find.
I saw no sign of any slack in any bushing, bolt or connection. Cables, pipes and tubes all routed fine from what I could see. Nothing. I was pissed that I was going to need to bring this is to the shop for a little noise. I gave the wheel another good kick while I was under the Jeep and I realized it was coming from up top somewhere. I opened the hood and looked around up there. Another kick and no noise. !!??. I closed the hood and latched it. Kicked again and the sound was back.
I put some oil on the small piece of rubber that the hood rests on next to the latches and the sound is gone. It has not returned.