Weird sound captured from Stereo Mix

Hi

I'm trying to record sound directly from the sound card, in the Hardware options I changed the recording input to Stereo Mix.

So when the sound starts, there's always some waves that appear in the timeline, even if I'm not hearing anything or the sound is too low, they just appear. I attach an image of this issue. At the top, the waves from the original sound, at the bottom, mi issue.

It's a sound that I found on the web, and I just tried to record it, and the parts where the sound is gone, it seems like there's a sound in my recording.

I tried to hear what it was using Hard limiter, and it's kind of a static sound, like some sort of electricity, and without Hard limiter the sound isn't noticeable.

I've checked my connections and it even happens when using only battery and without speakers connected. It's kinda weird, I've disabled all enhancements from the Devices properties, disabled any other software related to audio, and this keeps happening.

I'd appreciate if somebody knows why is this happening.

Thank you.