The car has 73k miles on it. Starting last fall, wife (primary driver) says she notices more "engine noise" on the highway. If she notices something, it usually is there, so I drive it, and yes, something has changed. In December I had it in to indepenent shop for timing belt and had them drive and see what they thought. Yes, a bit noisier than usual, but nothing wrong, yet. Wheels bearings believed to be OK, suspension tight.

The noise has steadily gotten louder. It is a low drone, steady pitch that does not vary with speed. First start to hear about 40mph, and at 60 is very noticable. At 70, it perhaps fades a bit. Tires (MXV4 w/20k) have been rotated and balanced regularly. Just did a 1,200 mile road trip in it and otherwise the car worked flawlessly. Just a lot of noise!

I'm about to take it back to the shop, but would like some ideas ahead of time as to probable causes or diagnostics I can do to rule out/in various solutions. Any ideas??????

thanks!