I bought an audio interface and connected it to my laptop. I use a display via HDMI. But when I connect my laptop with the audio interface to the display a weird cracking noise is coming out of the KRK's. The audio interface is working fine when I do not connect my laptop to the display via HDMI. How can I fix this?
Going from the comments you added to your original posting: you are using powered speakers that have balanced TRS inputs, an audio interface that has balanced TRS outputs, and you connect them with unbalanced TS-to-RCA cables?
The powered speakers, for better or worse, will have some relation to the ground at least via some capacitance, and they have separate power supplies. That means that you have a ground loop that is susceptible to magnetic interference. It's the same with 3.5mm unbalanced jacks.
So connect your speakers with balanced TRS cables to your soundcard: that gives you a much better chance at taking "ground out of the loop", likely also mitigating your HDMI interference problem.