Audio Knock Detection

Hi guys,

I'm here to ask about the audio that we listened in the lessons.

I'm not understanding clearly what type of difference i need to hear between the 2 audios, the one with "normal operating Engine" and the other 2 audios with Knock occurring.

The only difference to me is just a little increase of croak in the audio when knock is occuring.. Is that one the sound that knock monitor gives?

Can you guys also recomend some knock monitors like the one that Andre used for the video?

Thank you,

Anyone?