I'm interested in what it says about the cause of tinnitus, since I know someone who suffers from it -- I've experienced ringing in my ears after deep breathing and it was a kind of spiritual thing, sounded like those singing bowls used in buddhism, lots of harmonics and tremolo. As I understand it, the tinnitus caused by hearing damage is not nearly so pleasant..

But if it can be activated by changing your O2/CO2 levels, maybe it could be deadened by some change as well?