Found out the stock tires are Michelins. He has them rotated every 5k miles. I don't think the noise changed with the last rotation.

 

*Update* I drove his car today and now it's shaking or shuttering when accelerating from a stop or during low speeds. Something's definitely not right. I brought this up to him and he said it's been doing it since the noise started. Why he didn't mention this until now, I don't know. But now it's time to take it back to the dealer again. This can't be good and could be related to the noise. If something is truly wrong mechanically, I now question how it was not appearant to both dealers who have already checked the car over (if they even did).
FWIW, the tires are Michelin Latitudes.