The noise started yesterday while driving and is consistent; it doesn't get any louder/slower with RPM's, heater, A/C or any other accessories on or off. I bought the car a month ago and had it inspected by a mechanic who said the only repairs needed on the car were front wheel bearings and tie rods - the bearings are humming, not squeaking - he said nothing about needed to replace belts. The intake, thermostat, head gaskets and control arm bushings had been replaced before I bought it. I'm thinking tensioner or bearings?? How do I diagnose?