I have noticed a well tuned hum develop slowly over the last year or so and I believe it to be an exhaust vibration, I only notice it while I am turning the wheel (even very slight turns) and occasionally at highway speeds. So my question is what causes this and how do I fix it? is it just warn out exhaust hangers?

 

Check for metal to metal contact with the exhaust rubbing on something, or you could have a small hole in one of the components, or a leak where there is a joint. Good luck