There are many product and service providers in the audio accessibility arena. I have listed a few to get you started.
Audio Captions; Descriptions; Subtitles; Translations
3PlayMedia, Captions Plugin: http://www.3playmedia.com/services-features/plugins
Audio Eyes: http://www.audioeyes.com
Caption and Description Editing Tool (CADET): http://ncam.wgbh.org/invent_build/web_multimedia/cadet
Recite me: http://www.reciteme.com
Video Description Research and Development Center (VDRDC): http://www.vdrdc.org/resources
How to meet Success Criterion 1.2.5 Audio Description, W3C WCAG 2.0
Terrill Thompson’s My Audio Description Talk @ CSUN (March 10, 2017): http://terrillthompson.com/blog/813
The Audio Description Project: http://www.acb.org/adp/services.html
How to Provide Meaningful Descriptions
Description Key: http://www.descriptionkey.org/quality_description.html
Accurate: There must be no errors in word selection, pronunciation, diction, or enunciation.
Prioritized: Content essential to the intended learning and enjoyment outcomes is of primary importance.
Consistent: Both the description content and the voicing should match the style, tone, and pace of the program.
Appropriate: Consider the intended audience, be objective, and seek simplicity and succinctness.
Equal: Equal access requires that the meaning and intention of the program be conveyed.