The belt itself squeaks? Or, your holster/belt combination squeaks? Seems hard to believe that a belt just wrapped around your waist is going to be rubbing against anything such that it would be noisy.
Or, perhaps, if really speaking of the holster/gun combination, could it be that this new belt is so much stiffer than your prior belt that it has contorted the holster sufficiently to cause the different pieces of the holster to start rubbing against one another despite the stitching? If this is true, then the solution should include investment in a better holster.
Data point: I've never had any belt squeak like that on its own. I've had a few holsters do so, and one low-end, badly-sewn holster tug at itself while strapped onto an uber-stiff Kramer belt. Other than a couple of new-holster blues where they squeaked until they broke in properly, I've never been able to trace it down to the belt doing the squeaking, and this is through a half dozen belts and a few dozen holsters over 20+ years.