If it's coming from the rear I found that it was the styrafoam inserts around the spare. Some well placed small towels eliminated it. Seemed to be caused by the mentioned rear air exhaust vents.
I have had the same issue with my BL. Every now and again it just stops working. I dont do anything and the next day or a day or two later it starts to work. Annoying. But sporadic so no point in taking it in to get it looked at as by the time you get an appointment it's okay. Sometimes it's the...
I had the same issue and found it to be the foam inserts around the spare tire was causing it. Used a cloth under the inserts sound gone.
I would be cautious removing the flaps as they are there to prevent critters getting into your car when its not moving.
Same noise I hear as well every time I park the Bronco and get out. Not really what I want to here but since its done it every time since new I figure its what it does. '22 Badlands.
6000km (~3730 miles) on a Badlands, average fuel usage a good mix of country roads, city driving and highway 8.6l/100km (32.8 imperial mpg or 27.3 US mpg). Not bad considering the 2l hp and vehicle shape/weight. My 2016 Forester is doing about 35mpg(imperial)/30mpg(US)