My hearing tests suggest I have a dip at 4Khz (which isn't that uncommon anyway) but, using my test gear here, my loudest, most predominant tinnitus also sits at around 4Khz, so that might be right or purely coincidental.
Audiologists have in some cases found that using hearing aids that fill in what's missing from a sufferers hearing can help to alleviate the effects of Tinnitus. (That is, a hearing aid that only amplifies what the ear is having trouble hearing, normal ambient sounds can pass through the ear canal as normal). My last Audiologist used hearing aids for this very reason and was able to noticeably mask the tinnitus effects of his time shooting guns. *I hope my understanding is correct and it's a path I am going to follow to test the theory myself.