There are two icons on your video sources: a microphone and a speaker. These new buttons allow you to mute or unmute audio on stream as well as monitor your sources.
The Microphone Button
In the lower-right corner of your video sources is a small microphone button. Clicking this button toggles muting and unmuting the audio source for that camera.
When the microphone button is white, the audio is live (unmuted). When the microphone button is red and crossed out, the audio is muted and cannot be heard on stream.
The Speaker Button
Next to the microphone button in the lower-right corner of your video sources is a speaker button. This button controls what audio is monitored, or what you hear in Vidpresso.
When the speaker button is white, audio from that video source will be heard on the monitor (as long as that video source is not also muted (microphone button red and crossed out )). When the speaker button is red and crossed out, audio from that video source will not be heard on the monitor.
Be aware that if the microphone button is white but the speaker button is red and crossed out that audio from that source is still being heard on the stream even though you are not hearing it through the monitor.
By default local audio sources are muted in the monitor, this prevents feedback.