If your System76 machine makes a clicking noise while sound is not playing, don't worry. It turns out it's an issue with power save in the Intel High Definition Audio drivers. What's worse, is that it's an issue that has affected some portable Intel HDA users for years.
Anyway, according to this post from three years ago, the easiest way to fix it is to simply turn off the power save function.
It's pretty simple to do:
To disable it immediately,
To disable it on every boot, add this above "exit 0" in /etc/rc.localCode:echo 0 | sudo tee /sys/module/snd_hda_intel/parameters/power_save
Code:echo 0 > /sys/module/snd_hda_intel/parameters/power_save