Mic/Line In Static

[p3rcussion]

So, I just purchased a new mic and both it and the soundboard seem to be working fine. However, when it is connected to my computer's line in or its mic in, it just makes a loud hiss and seems to be mixing in other random signals. For example, I would move my mouse around the screen and it would make different noises. Even if I unplugged my mouse and turned it off, it proceeded to make the odd hissing noise. After messing with the settings, I was able to bring the noise down, but the loud hiss was still there. I then began playing music from my phone directly into the computer (without the soundboard) with a different cable and it seemed fine, so I paused the music for a second and I heard a pop in my headphones. When I pressed play again, it was playing out of my phone and was also playing a poor quality version of the song with lots of static through the computer. It would go back to normal when I unplugged and plugged it back into the computer. The same thing happened with both mic in jacks and the line in jack. Btw, I have an Asus Z170 AR. Does anyone know how I can fix this? Thanks.