The reason why this tipped me off is that I hear the ringing happening sometimes when I pause the music. It's also significantly louder on the left cup than the right cup.
So... what exactly do I do if I want to have these looked at?
Probably start by emailing Chan at firstname.lastname@example.org or Massdrop, if you purchased through them. If that doesn't work, you might start asking around for a DIY'er around these parts.