We took our first road trip in the C-max to see my parents. Along the way I noticed this intermittent sound that sounds like when you blow across the top of a glass jug to make a low woooooooooooo. I noticed that I could reproduce the sound by maintaining a steady speed with the engine on. When the vehicle ran in EV mode, I did not notice the sound. At first I thought it might be a bad bearing in the eCVT. Later I noticed that I could make the sound quit by turning off the recirculating air function in climate control. I could swear I heard it one time at 40 mph with the recirc off, but I'd have to do more testing to be sure.
The sound was very loud, reverberating throughout the cabin of the car. It was louder than a normal speaking voice, so over 85 db. Does anyone know if this is a sign of not having a cabin air filter perhaps? I will check that as soon as I can tomorrow. I feel certain that there is something amiss in the cabin air intake system, but I'm unfamiliar with the vehicle. It could also have something to do with the tube that pipes air intake sounds into the cabin if this vehicle has one of those.
Has anyone experienced anything like this?