Bearing vs Belt noise



Well recently when idling I hear a little squeeking noise from the engine. ONLY when idling, it dooesnt get louder when revving.

The belts were changed about 30 000KM ago.

How do I diagnose if its a belt or if its a bearing/pulley/tensioner?

As extra info, the last service the car went in, they did mention that some bearing was worn, they oiled it temporarily but I havent really heard about a bearing or pulley squeeking when its worn.

Ive got a drive up to swakopmund planned soon, is it something I should adress before the drive?