I thought I noticed this a couple months ago on my wife's 2008 Odyssey Touring but really noticed it on a recent trip.
Notice this the most when driving slowly in enclosed areas like our garage but can hear it on and off driving around town.
The engine area seems to make a whining sound. Somewhat like a high pitched sewing machine or even a Porsche engine
It seems to waver up and down with the RPM. Maybe it's alternator, drive belt, water pump or even transmission?
Any ideas what it could be?