Noise from rear end (bearings/tires)?

OK, I have a 92LS-L, no fluid leaks. No weird behavior. Lately I think I'm hearing a subtle increase in noise coming from the back. It definitely increases in rate (not volume) as the speed increases. Like a tire whine would... It's just that the car seems a tad noisier while cruising along. I'm not sure if it's a tire noise, bearings or what... We've had a ton of snow, so I've driven through a lot of slush/road salt this past winter. I can say that while driving through a tunnel and rolling down a window, you can't hear anything unusual at all. You just hear it from inside the car, but again it's subtle. My tires are about 7months old (TOYO Proxes FZ4) I was thinking it's maybe because the tires are colder, due to low temps, but I don't know if that's even relevant. Perhaps something that's just starting to go? Any thoughts?