I can offer little commentary about Braille, but as far as audio formats are concerned, I can say that the visually impaired persons I have known who listen to substantial amounts of text often listen to it at substantially faster-than-intended speeds, and some do some other transformations on the audio to help them better catch meaning at these high speeds. Such things seem to be idiosyncratic to the individual listener. A fairly 'raw' format, such as .wav, would I think be useful to such users, but lossy compression formats have been engineered around assumptions about listening conditions that simply aren't true for the practices of those who listen to recorded speech as a way of life, and may be of little practical value. -- RS