Loud Medium hum sound
So, I have been driving my truck for a while with this loud, medium hum sound that sounds like it is coming from the front or middle of the truck and only starts at about 40 and gets really loud about 60 but then seems like it goes away about 75. I thought it was my wheel bearing so I replaced one of my front wheel bearings. Still there. The other wheel bearing is still good. Any ideas on what I should be looking for? It isn't the tires because I just had them replaced and it is the same sound. It is loud at 60 and never really feel safe driving it. Any advice would help.