- took to dealer and they can't figure it out

Hi - took to dealer and they can't figure it out. At low speeds you can hear a squeaking sound coming from the rear of my car. I put the drivers window down and sure enough, there it is. They rotated the tires w/ balance and alignment - they said they ck'd the CV joints etc. And found nothing. They said afterwards they drove it and didn't hear it. I pulled it out of my garage this morning to go to work, drivers window down, and it's still there. I'm not crazy! This noise just started like a week ago and concerns me due to long distances that I drive. Any suggestions anyone? Thank you in advance! :)