How tare the words audience and auditorium related?

They are related through the ''audi'' prefix, which refers to audio.

Explanation:

Both words are related with the word ''audio'', which refer to sound. Now, audience is people who listen some exposition, and auditorium is the place where is placed the expositor and the audience. So, that's it, people and place, for the same matter.

The auditorium is associated with the area where an audience assembles to watch or listen to the public event, such as a play, movie, concert, etc and the area is known as "auditorium"

An audience is a group of listeners or viewers gathered at the public events such as a plays, comedy, performance, or meeting.

An auditorium is a massive room where the spectator sits to view performances and other events. Sometimes the word is used to apply to a whole building utilized for public events.