Yesterday I received my Silver Bullet earphones and after a couple of calls people told me that they could hear some serious background noise. After some testing with a recording app, I realized that this noise occurs only when the screen is on (see attachments).

This happens on latest CyanogenOS 12 and on cm12.1 nightlies

I also tested on Oxygen OS and it's not happening there.

I've issued a bug report on jira, please upvote if you have the same issue!
https://jira.cyanogenmod.org/browse/BACON-3699