I'd say absolutely get new tires. Just yesterday I had a tire that had great tread, but some cracks that I thought nothing of go out on me. Tires can do way more things than just explode and you never know if an internal part is worse than how it looks on the outside. For example, the steel belt(s)/strap went out on my tire. It held air but it was as if my round tire suddenly became square while doing 80. I got real lucky it didn't blow before I pulled over. But yeah, of all things that can decide to stop working while operating your vehicle, tires are probably the most deadly. I know, brakes/steering and what not can do, but that isn't extremely common. But yeah, a lot of us still ride on shitty tires cause we're cheap.
Ok, off the soap box =P. I don't know the exact sound, but tires are surely capable of making humming sounds at higher speeds. One or more could be off balance(sounds like what it is to me), slightly warped or have a bent rim. Maybe a weight fell off your rim?
Another suggestion is to mark both sides of your rotor with a crayon or chalk, drive 20 ft or w/e without hitting the brakes. Get out and see if any of the marking is gone. Should be none unless you have brand new pads.
Just to be sure, I'd make sure that plate is still bent back pretty good. When mine was rubbing, I didn't bend the shield back far enough the first time and the sound came back after about a week. Sorry if I'm smothering you with random BS, just trying to help. GL.