Why does my Audi 80's engine make a knocking noise when I accelerate?

I have noticed that when I accelerate in my Audi 80, there is a knocking sound coming from the engine. It seems to go away once I reach a certain speed. What could be causing this and how can I fix it?

Possible causes for a knocking noise in the engine could be worn-out engine bearings or a damaged piston. It is important to have a mechanic inspect and diagnose the issue to prevent further damage.