The van sustained a lot of front-end damage from a head-on collision a couple years ago. It has new Big-O tires from October. We drove 1000 miles for Christmas, had an oil change & tire rotation, and drove 1000 miles back home. I began noticing the whirring noise on the way home, but wasn't sure if it was just grooves in the road. It's very subtle, but after my wife had been driving it for a few days, I mentioned it and she had noticed the noise, too. It seems like the noise is related to the van speed and not the engine load/RPM. I visually inspected the tires and they all look fine to me.