Well, if you have a cliff roll-off at 2200 Hz, that is going to be a difficult thing to overcome - which is probably no news to you. The hairs that would have been killed are in the cochlea, on the basilar membrane. It's confusing that it happened in a frequency selective way. If you unroll the cochlea, there's a place to frequency transform that happens along the length. Why the chemo would just stop killing hairs at a certain distance along the membrane is curious.

Here's hoping that Marshall has some encouraging words...
-Scott