I keep getting a ringing noise, not from engine only when moving forward not speed related except it only starts at 15mph,sounds like a quiet cow bell, audible with windows open, seems to be coming from offside rear. Any ideas

 

Not had car long, anyone know how to activate the passenger airbag,also one of the air vents dosnt open auto, it makes a slight movement but dosnt open, cant see any screws to have a look, it opens manually and air flow fine, its the one nearest drivers door

 

Not sure to which model of XF you are referring, but my 2010 X250 XF Premium had a "tinkling" sound when I was driving at any speed above 15 to 20 mph. Sounds something like the noise you are talking about here. It seemed to come from the front left side and was just audible inside the cabin. I asked the dealer to look into it but never found it and it continued to the day we parted company (3 1/2 years later). Never seemed to do any harm. Not sure if this helps, but it may ease your mind (at least until something drops off :-) )