Hearing Impaired is information you usually get in video files.
There are several ways to make videos and clips accessible for people with a hearing disability. Sometimes, a person using sign language is used, yet the most common practice is using a subtitle stream specifically designed for deaf people. But even people that have not lost all of their hearing ability greatly benefit from such subtitles since they don’t have to turn up the volume of a video unbearably high to understand the content.
A video containing information about Hearing Impaired thus very likely contains or at one time contained captions or subtitles for people with such a disability.