Alleviating tinnitus, and the shape of the auditory phenomenological landscape
Tinnitus is a chronic condition where you hear a ringing in your ears - for acute sufferers it can be very loud and never stops. This is tortuously unpleasant.
I wonder if this has been tried - could you alleviate the symptoms of tinnitus by playing in a kind of psychologically out-of-phase sound, to cancel the ringing sound experienced? Of course, the normal physics of waves and phases won't hold true here, since the perceived sound isn't 'real' (i.e. external, based on moving currents of air).
However, I wonder if there might be psychological rules about sounds where some external sound of the right characteristics might cause a kind of neural interference, and disrupt the perception of the tinnitus sound.
One could imagine having a tinnitus subject navigate with gradient descent through a space of auditory parameters, rating the subjective intensity of the tinnitus sounds while listening to different external sounds. Eventually, you might find a point in the auditory parameter landscape where the tinnitus wasn't too annoying. With enough participants, you might learn something interesting about the shape of that landscape, and about the phenomenology (and neural representations) of audition.
In principle, I suppose, one could do this with non-tinnitus sufferers, but I'm assuming that the tinnitus sounds are constant and so would provide a fixed point of comparison.
UPDATE: hah! It looks like someone's trying to do something a little akin, though it uses a more physiological than phenomenological mechanism. I wonder what made them pick a low hum? See Teen inventors fight tinnitus