I need help with my sqeaky Yukon!

My husband and I own a 2002 Yukon XL with 142,000 miles on it. A few months ago it started making a sqeaking noise that seems to be coming fromt the drivers front end by the tire. It is a high pitched sqeak that sounds almost like a bird chirping. At times it is very loud (people on the sidewalk turn to look)and at other times very subtle. The sound only happens when the car is moving and does not speed up or slow down with accelration or braking etc. We have tried four mechanics. One couldn’t hear it. The second one could hear it but had no idea what it was. Same with the third guy. The fourth one replaced our back brakes and the left front wheel bearing. The sound is exactly as it was before and now he wants to replace the right front wheel bearing which he noticed was loose when he was replacing the left side. We do not think we are on the right track. Do you have any ideas? It seems like we are just throwing money at this and our mechanic doesn’t have any idea what this is.

Although your front brake components may not be worn out they may be the source of the noise.