EDIT: Scratch this whole thread, i'm a moron, I had a bunch of spare change under the floormat in the rear and a monkey wrench was vibrating against the change....... facepalm of the year award..
When the tob starts to go it produces a "squeeling" or "screeching" sound. A vid would probably give a us all a better clue as to pin pointing the possible cause and issue. These cars make so many funny noises over time depending on what's going bad.
The good thing about it being a tob issue is that it will just get progressively louder and more embarassing at lights as it will start to get real loud just idling.