Kia Rondo

My wife and I recently bought a brand new Kia Rondo with 18 miles on it. We paid cash for the vehicle in order to avoid expenssive interest payments. While driving the car home for the first time my wife noticed that the windows make a whistleing noise like the window is cracked open. Any time the vehicle is driven over 30 mph the noise can be heard. The very next day my wife made an appointment to have it looked at. The dealership couldn't tell what was wrong with it so they opened a case with Kia. After 3 months of going back and forth with the dealership and Kia they told us that the noise wasn't a defect but part a characterstic of the model and that it is not a substantial impairment to the value, safety, or use. The brochure on the Rondo claims that the Rondo "is equipped with a range of structural and technological refinements that reduce cabin noise and road vibration to deliver a quiet ride." I can hear the wind noise over the radio. Needless to say my wife and I are very upset. My wife hates the car that we bought for her to drive. We are concerned because they can't determine what is causing the noise. We also have two childeren under two and the recent link between Autism and white noise makes us fearful of placing them in the car. What can we do? Thank you for your time,Eric Bither