I also notice wind noise. We haven't had ours long but I suspect it's the black exterior cover trim on the A pillars. I'm going to try some temporary remedies to see if I can isolate it. I know taking it to the dealership will be a waste of time.
Any chance you could share a picture of the hard foam or the fix itself? I think i might try it myself. we have 3 kids under two and cant really afford to leave the carnival at a dealer for a few a weeks.Had the car back out to the dealer regarding the wind noise. The observation was the driver side door was out of adjustment (is closer to the body, than sliding door) and did a minor adjustment. Do a quick observation of horizonal exterior trim to see if both are flush when doors closed. May help to run hand over it, as well. Check symmetry on both sides. He applied 2 pieces of hardened foam to the inside channel of the window weatherstip (which pushed the stripping more flush with the closed window.) It definitely stopped the "cracked window" noise, but regrettably, it is still pretty loud depending on your speed (over 50mph) and wind direction. Not sure if it in the aerodynamics or assembly, at this point? For now, it will hold me off but still think that is a bandaid. I'll see how other people are faring and solutions, but this is a start. Good luck!
It's been several months since I had my Carnival serviced for the wind noise issue. I wanted to wait and see if it was really fixed. I'm happy to say it's 90% better than before. The dealer replaced three different weather strips on the door and added some foam backing to the weather stripping that sits against the driver side window. See the pictures below.
Replaced three weather strips around the door.
View attachment 953 View attachment 954
Adding foam backing to this weather strip (so it seats more firmly against the window).
View attachment 955
This has mostly fixed the wind noise issue where it sounds like your window is slightly cracked. It's not 100% gone, but way better. Hope this helps.