I see this is a reply to Jilio, but just want to add something here, so excuse me.
Interpreters was brought to us by deaf people, not hearings. I am not sure what you mean with "various forms of sign", but if we are talking sign language/ASL, it was invented by deaf people, not hearing people. Sign language grows naturally where deaf people are. Closed captioning is also something that deaf people have demanded. Hearing aids was brought to us by old deafened scientist who wantet to hear more. You would maybe find some books on deaf history interesting if you want to know more. Gallaudet Press have some.
But CI... that is a bit different. No deaf people have been involved with that, or asked for it. Another interesting thing, is that I have asked various deaf people if they could choose between a goverment/healtcare/insurance sponsed CI implant, and the cash it takes to do the implant. Almost everyone says CASH thank you.. This is a clear example of wrongly spent money and ethnocentrical aid. I am willing to bet 1 million dollars with you, that NAD would spend the money the society uses on CI now, on something totally different if they could choose. And that is not because they are scared of CI beeing so powerful it can annihilate ASL, but due to it beeing of so little practical use.
The main reason CI is so widespread, is that parents choose to implant their kids, and kids cannot make this choice.
What is the "various forms of sign" anyway? Curious.