Change privacy settings on Hangouts Hangouts shows a green phone icon when someone is on a voice call.

Is it possible to hide this indicator to other users so nobody knows if I'm on a call?
Yes, press the 3 bars on top left, choose Settings, under Account Settings select your username (username@gmail.com), select "Share your status" and uncheck Device

Keep in mind, this will remove the little mobile icon when you're chatting as well. I have found that some of my friends message me more if they think I'm on my computer.