観客 and 聴衆: spectators and listeners
Distinguish an audience viewed as watching from one viewed as listening.
An audience watching a performance
観客 (かんきゃく) means spectators or an audience watching a performance or match. 「観客が拍手しました」 says the audience applauded.
「観客席に座りました」 means sitting in the audience seating. It does not mean performing on stage.
An audience listening
聴衆 (ちょうしゅう) refers to listeners at a lecture, music performance, or similar event. 「聴衆に質問しました」 means asking the audience a question.
「聴衆から質問が出ました」 says a question came from the audience. に and から change the question's direction.
Perspectives may overlap
People at a music performance can be called 観客 or 聴衆 in context. These do not classify watching and listening as mutually exclusive activities.
「観客の一部が立ち上がりました」 says part of the audience stood up. Do not expand 一部 to everyone.
Who asked the question in 「聴衆から質問が出ました」?
Show the answer and why
Someone on the audience side. This reverses the direction of 「聴衆に質問しました」, asking the audience.