Deafdude,
I understand you are trying to really understand what level of hearing ability someone with a CI has. This is the only way to make an educated decission. Have you spoken with an audiologist who programs CI's and is familiar with the programming options? Have you attended any CI meeting in your area either associated with a University or one of the CI manufacturers?
There are two meetings this weekend in my area. One by Cochlear in Ann Arbor MI on Saturday and the Hearing Loss Association of America Michigan Cochlear Implant Chapter in Grand Rapids, MI on Sunday. These meetings are where I learned a lot about what CI's are capable of and was able to speak with other users regarding their experience. I still go to the meetings to share my experiences.
In regards to hearing at 0db. I asked the question of my Audiologist during my Friday mapping session and was told that some centers adjust the audiogram 25db to reflect a 0db "normal" audiogram appearance. We looked at the programming and the lowest db that the CI will start sending stimulation for and found it to be 24db. Both mine are set at 25db. The loud sounds around 75db and above start compressing above that level so it does not get painfully loud but still alows me to distinguish between the volume. Sounds like air compressors, air nailers, gun shots, clapping, drag cars for CI users may not get the extreme loud shock as someone with normal hearing may experience since the CI just won't send that level of stimulation. Basically a concert at 120db may sound like 85db for a CI user. Still plenty loud. At least this is my experience and it all depends on the T and C levels set during the mapping session. If you set them to high, there may be times where hearing is uncomfortable.
Regarding HA, it has been a while since I used mine, but also know I was just trying to get it set so I could hear speech as clearly as possible. I really wasn't worried about hearing everything.
As far as my ability to hear sounds today, my audiologist tested my speech understanding on my bilateral CI (activated January 2009) on Friday and scored 97%. My first CI (activated January 2007) scored 100% when it was tested I think between month 2 and 3 so March-April 2007 but that was my only option to hear so my brain worked that CI exclusively. My bilateral CI activation has taken longer which has been expected but after this last appointment, it is a LOT nicer. Easier to listen to, better sound, easier to understand speech, more comfortable. I can also say that I can use the various speeds almost seamlessly unlike my first one. I currently have 900, 1200, 2400 and 3500. The only difference is how I have the "equilizer" set by modifing the T and C levels. Some programs have more low or high frequency gain. I tried this as a test.
Ultimately, I'm still learning to use my bilateral CI with my first one but so far, it has been great.
Again, I hope you are able to find the information you need.
BTW, I have tried to find my audiograms to share and have been unable to locate them. I have another appointment in early June and hope to remember to ask for them for you. Sorry I forgot.
Steve