Scraping/grinding noise

We have a 2006 Acura MDX, 96K miles, well maintained. It has started making a disturbing scraping/grinding/humming noise from under the car, driver’s side. It’s random, sporadic, usually for 3 to 5 seconds; doesn’t seem to be related to speed, braking or turning; sometimes barely perceptible, sometimes very loud. It drives fine. Wheel bearing maybe?

Might check the engine shroud to make sure it has not lost any of its fasteners.