I have experienced the exact same thing, normally on start up after turning on lights and putting the electrical system under load. A load squealing noise which eventually goes after one or two minutes. My belts have not been touched since I bought the car a year ago!
Hi, inside the back of the car behind the rear shelf cover are securing clips, spaced out around the edge (these secure the back of the hood to the body). If you unclip these clips you can lift the back of the hood up. If there is something there that its fouling, you can remove it and refit the clips to secure the back down again. It's only a ten minute job, but if the back of the hood has not been moved for some time it may be a little stiff!
My exhaust has the actuator on the off side outlet, when the revs reach about 2000rpm it opens to allow full flow! It does make the exhaust more throaty! But as it works fine so I haven't touched it.
If you can't see or hear a blow, I wouldn't worry to much. The giveaway for a blowing exhaust (if you can't see any obvious holes) would be soot or exhaust residue around joints, best checked when the exhaust is at working temperature (ie after a drive) as then metal will have expanded causing any obvious leaks to become apparent.