How do record Plex Knock monitor audio?

I am having a hard time hearing the difference between engine noise and knock at high rpm. I would like to record the knock audio so I can compare back to back runs. What is the best way to perform this. I tried to record audio into my laptop and the sound is very distorted. Thank you for your advise.

You can run the audio from the plex into a laptop and use a software package like goldwave to record and analyse the signal.

Maybe I will try purchasing the full version of gold wave. I tried using the demo to record and the sound quality is on playback is terrible(a lot of static/feedback). I will also try turning the volume down on the plex to see if it gets any better.