Hi all, recently, I've noticed a whine that tends to come and go while driving my brick. Sometimes it's really noticeable, other times, not at all. It's not really high pitched, like a belt squeal or brake squeal, but it's not really a groan or a grind either. The pitch raises with the speed of the car, and drops as I slow down. At steady speed, the pitch is steady. My best attempt at writing what it sounds like is that it sounds alot like a fire station siren, or a tornado siren, slowly ramps up with acceleration, holds steady, then slowly drops as I come to a stop. It seems like maybe it's coming from somewhere central to the car, like the driveshaft, or the differential, because if I drive with my windows down and go near a building it doesn't seem to be more prominent on one side or the other. I uderstand this is not the most exact method of troubleshooting. It is definitely not related to engine RPM. I'm thinking it's one of three things.

1) Drive shaft support bearing. I slid as far under the car as I could yesterday when I got home from work (after dealing with it the whole trip) and the bearing didn't feel warm at all. Would it if the bearing was going?

2) The rear end has an issue.

3) New tires that I recently put on the car, though I would think that it would happen all the time and not come and go like it does.