http://blogs.technet.com/b/lystavlen/archive/2012/08/23/silence-in-your-microsoft-lync-online-conference.aspxIf you are using an Audio Conference Provider (ACP) - and you experienced the following: after you dial in to a Microsoft Lync Online conference by using your ACP access number, you cannot hear other users who are connected to the Lync Online conferenceen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)