George , Yes -- and no! There certainly may be activities that DO require the use of (for example) hearing. But there are a lot of activities that are generally done by hearing that could be done equally well through another channel (using signage, the written word, sign language, and so on. We have to be careful to separate out what is USUALLY done through vision, hearing, reaching, etc., from what MUST be done in that way alone. Dr. Jane Jarrow