Deep metallic noise from accessory belt

[Randall0208]

When my 2005 volvo v50 is running theres a deep metallic noise from the serpentine belt. I'm guessing it's a bearing on one of the accessories or something and I'd have to look a little further into it. Tomorrow I may try and take the belt off and spin all the pulleys and find the source of the noise. If anyone has had this happen to them before or knows what it may be any help or information would be appreciated.