How to troubleshoot engine noise on my Audi A4?

I have been hearing a strange noise coming from my engine on my Audi A4. It seems to be getting louder and more frequent. What could be causing this and what steps should I take to resolve it?

First, it's important to diagnose the source of the noise. It could be a number of things, such as a loose fan belt, worn bearings, or a problem with the exhaust system. If you aren't comfortable doing this yourself, it's best to take it to a reputable mechanic who has experience with Audi vehicles.