normal high mileage engine sound?
 

At constant idle:
Rhut, rhut, rhut, rhut, rhut, rhat
Rhut, rhut, rhut, rhut, rhut, rhat
Rhut, rhut, rhut, rhut, rhut, rhat

Not sure if this is any different than normal as far as sound. just seems louder than usual. It jumped out at me when i was paying a toll and with the echo effect and window down it was very clear. My exhaust is loud so its hard to hear sometimes.

At idle mine sounds like a sewing machine. Very clean, smooth, no odd knocks or tapping. Idle is rock steady.