I get this question a lot locally when people come with their Skoda Felicia to ask for my help. Frankly, to me they often sound similar, even when using a stethoscope. Sharing the same area, the noise travels through the engine block and timing cover resulting in deceiving conclusions.  You'll say that no matter what proves to be noisy, it's good practice to replace both. Yet my question is this: do you know any tips & tricks to tell for sure what part is noisy?

Take off the alternator's belt and start the engine again.If the noise continues that means is the chain , else is the  water pump.

Thank you, aggel! Well thought  Duh...