Definetely sounds like a tire pressure issue to me. Sometimes i hear people that sound like they have a flat tire (almost the same humming sound as a mud tire would make), when they are really driving with one tire somewhere between 1/2 and 3/4 recommended tire pressure.
Your wheel bearing is going. It will make the car sound like it has mudders on it. Take for another drive and start turning the wheel one way then the other way and it should get louder one way than the other.
Silly Ricers Useless Wings Are For Penguins.
yes, smallblockfreak makes a good point, could most definantly be the wheel bearings, another way that may help diagnose if its this is when you hit a small bump or anything like that if you can hear like a small clanging noise... id check the wheel pressure first to make sure its correct, i keep mine about 32lbs, then if they are good, i would go ahead and pull the tire off and check everything else...
also, if it pulls to the right... could mean your right caliper could be sticking which could make a small roaring noise... but if its not pulling to one side or the other, i wouldnt worry about the braking system