Why does my Audi A2 make a strange noise when I turn on the air conditioning?

I've noticed that when I turn on my Audi A2's air conditioning, there's a weird humming or clicking noise coming from the engine area. It only happens when the AC is on, and sometimes it goes away after a few minutes. Is this normal, or is there a problem?

This could be due to a faulty AC compressor or a loose belt. It's best to get it checked by a mechanic to ensure it doesn't cause further damage to your car.