To mute all participants in the meeting, open the Participants panel and then click Participant Actions. Select Mute Audience. All attendees’ lines in the meeting are muted.
Note: Any dial-in attendee can press *6 to mute or unmute their own line.
Unmute the audience
To unmute everyone, click Participant Actions and then click Unmute Audience. Everyone hears a message that the audience is unmuted, followed by another message that says, "Mute on." In Skype, when you unmute the audience, you are giving participants control over their mics again, not unmuting them. Each participant can unmute their own mic using their participant controls.