John Major

I have a 99 E320 with 122k on it. I noticed a while ago that is was making a humming noise that you can feel in the pedal when traveling at about 40 miles an hour and up. At first I thought it was the tires. Got new tires, problem still there. I do know my cat converter on the driver's side needs to be replaced but I don't see why i should get this noise from that. It gives a buzzing feeling in the pedal. Really weird. I tried driving hwy speeds and putting it in neutral but I could still feel it. What could this be folks? Please help, i don't know if something's going bad in the car.