Quality of Voice
An important criteria for a reader is an understandable voice. This is particularly true for the reader recording my materials, but it applies to whomever I work with. Difficult accents, indistinct pronunciations, and quietness can, unfortunately, prove to be a barrier between me and information. Every person is different in what voices they can and can’t readily understand. Some accents are easy for me to understand and do not pose any problem whatsoever, while some accents are extremely difficult. I prefer readers who can speak quickly. It will be different for every visually-impaired student. In the end, the call should be made by the student rather than the disabilities office.
Reflecting Written Structure
Some people, when faced with a page of text and asked to read, will speak the whole thing in a steady stream as if it were one sentence. For me, it is much more difficult to track with content when things like paragraph breaks, commas, semi-colons, and even periods are not reflected in the recording. Punctuations marks exist visually for a reason: to provide clarity and display organization of thought.
I need to have the same clarity and organization reflected in the recordings I listen to. An excellent reader is set apart by their attention to the non-verbal parts of writing, namely, punctuation and structure. They have an understanding of the functions of different punctuation marks, and indicate them with appropriate pauses and pacing.
See Recording Method for some very specific guidelines I give readers about recording scientific articles.