To some people, recorded material in your documents or presentation is totally meaningless. They can't hear it.
When you create any sound materials, ask yourself the following:
Does this make sense without the audio material?
If not, do I provide a text equivalent of the audio material?
With these two questions you will make sure people with hearing impairment will be able to equally enjoy what you have to show them.
Hat Tip: Tom Babinski http://www.evengrounds.com/