Strange rolling/popping noise from passenger area

[Pim]

I have the same problem since today. It's a popping noise like a little stone hitting the undersite of the car. But if you turn of the music and drive like zigzag you can hear something rolling from one to the other side and it stops with that "ponk"-noise till you turn your steering wheel in the other direction, rolling and then again "ponk". It is comming from the passenger/floor area. Don't know what it is....
Anyone with that same problem ??