Hi Vikki .....
I did not have radiosurgery, but I developed hyperacusis after the surgical removal of my AN three years ago. I, also, am a singer and this has been most frustrating for me.
Two things: 1) My audiologist fit me with a musicians' earplug (see
http://www.etymotic.com/ephp/erme.aspx) that I carry with me at all times to use in my good ear in noisy environments (movies, restaurants, concerts, etc.) 2) it does get better over time ..... or my brain has made some compensations so that I can now sing, albeit not like before.
I have about 20% hearing in my AN ear, 100% in my good ear. I wear a Widex digital hearing aid in my AN ear, which is a big improvement but, of course, not normal hearing as before. I no longer feel comfortable singing solos and I find that when singing in choral groups I have to position myself very carefully so a very loud singer is not on my "good" side.
I have not tried the white noise generators, but using the hearing aid definitely helps equalize incoming sounds.
Hope that helps. Clarice