When you receive a video or audio volley, it is automatically transcribed. To see the closed captions of that while listening to that volley, click the "cc" icon in the lower right-hand corner of the volley. 

On a desktop, the closed caption is automatically enabled when you watch the video or audio volley. To disable closed captioning, click on the "cc" icon in the lower right-hand corner. 

You can also view the transcript* of the entire conversation by navigating to the Transcript view in the upper right-hand corner.

*Interactive transcripts are available for Volley Pro Spaces