320d noise diagnosis please

Hi guys

I tried to explain this noise to the dealer the last time the car was booked in. They said afterwards that it is nothing to worry about but I am not convinced.

The noise I refer to is the high pitched noise, almost like a small bell being striked very quickly.

Please look at the link below and share your ideas.

https://www.youtube.com/watch?v=w87qRiJN...data_playe

Thanks