Whoa.. wait a second.
The tires on the front were worn very unevenly where the outsides were heavily worn while the middle and inside still had decent tread. I replaced those with no change in the road noise.
I took it to a local shop to get the alighnment checked. According to them, the alighnent in the back right wheel was a little off whereas the front there were worn tires and where it seemed like the noise was coming from was OK.
However, they did tell me that the front left strut was shot and recommend to replacing both up front struts. While they said that might explain the unevenly worn tires, they really couldn’t explain the noise.
I would be looking for a new alignment shop personally.
As to the humming…
I assume it changes pitch according to speed, if so.
First thing would be to get the frontend mechanics repaired and get a proper alignment.
If the humming continues …
Your dealing with a rotational issue.
Have to start looking at all things that spin.
Brake rotors / caliper
Wheel mounting .. free of rust and wheels fully seated, torqued and sitting flush.
CV shafts
Motor and transmission mounts
Might also look at the exhaust system for loose components and heat shields.
And just on the outside possibility, check for any loose exterior trim pieces that might produce wind noise or buzz