Embedded audio and video
Both audio and video within PowerPoint should be accompanied with captions to aid people who can't hear the content. Depending on your PowerPoint installation, there is built in functionality for adding .vtt subtitle files to videos. If they are your own content, you can upload and caption on YouTube and download the .vtt from there to use in PowerPoint. Otherwise, you may need to find other ways of creating a caption file.
For audio, if you have PowerPoint 2010, 2013, or 2016, you can use an external plugin to add captions to the audio file.
For more detailed instructions on captioning both audio and video, visit Microsoft - Add closed captions or subtitles to media in PowerPoint.
Alternatives
If your software is not compatible with the methods detailed on the Microsoft website, there are a couple less effective alternatives available. For audio, you could record a video of the PowerPoint that contains the audio being played, and then caption the video to provide in addition to the PowerPoint. Alternatively, you could provide an audio transcript in addition to the PowerPoint. These are discouraged because of the way they split the content across two files, but if no other options are available, they're better than nothing. For video, it's probably best to link to an external video that has been captioned, either in YouTube or in Amara.