noise?

hey guys, just wanted to know why my car is doing something weird. i gotta 2001 honda accord and when im going around 75 and giving gas steadily, i hear this humming sound...its like either from my front tires or the engine...i have no clue what it is... and also when i break somewhat hard, i hear my brakes not sqeek, but sounds like its metal to metal, but i had my brakes checked and i still had 45% brake pad left. any one have any ideas whats going on??? and what are good brake pads to get as a replacement for hard braking??