W204 rattle or buzz near seat belt top anchor

[philnewmerc]

I wonder if anyone else has come across this issue or can link to a potential fix? Basically I have noticed (having rainman senses when it comes to rattles) that on certain roads, where the tarmac is very coarse, there is a faint buzzing coming out of the B pillor seat belt area next to my right ear. When I tense/lock the seatbelt it stops though, so I assume it is something to do with the seatbelt real... Any ideas on the issue or a link to a fix?

My next car will be a bloody Lexus and be quiet

Thanks in advance