I have a 2004 4 door, 3rd seat Explorer and ever since I got it it sounds as though the rear window is open. It has been checked by the dealer and I've been told that it is just the standard road noise. It is very annoying and can be heard in both the front and middle seats. Any idea what's causing it and if so, how can it be fixed? Also, my Explorer has started an occasional (every 3-5 mins)chirp. I have noticed it just recently and it may be associated with the a/c.