greatal - I am not sure if tinnitus in itself is an issue, but I understand that it may indicate some hearing loss has occurred. You have to either live with it, or....... That includes obviously everything you do, work, play, whatever.
andy148 - the hearing thresholds are based on not using a hearing aid. Once you have a Class One, the limits lower and if below those then a hearing test in an a/craft can be undertaken. I think hearing aids pick up additional noises that you wouldn't want to hear on the flight deck but technology may be moving on in that respect. A good quality ANR headset is probably better.
As with all things medical, get a Class One before pursing things too far. There is no need to 'volunteer' any problems unless you are specifically asked.