Why is media captioning an essential part of universal design? Look at who benefits:
The Described and Captioned Media Program (DCMP) produces the DCMP Captioning Key, known to many professionals the holy grail of captioning best practices.
According to the DCMP's philosophy, to fulfill their intended purpose media captions must be:
1. Synchronized: appearing at approximately the same time as the audio is delivered
2. Accurate: equivalent in content and meaning to that of the audio, including speaker identification and relevant sound effects
3. Available: consistently accessible to those who need or want them
How Do I Make Multimedia Accessible? - University of Washington DO-IT Center
Captions, Transcripts, and Audio Descriptions - WebAIM Techniques
Multimedia Best Practices - Accessibility at Penn State University
Video below: "Captions: Improving Access to Postsecondary Education," from The UW DO-IT Center.