There is no audio when listening on Mozilla Firefox's browser.

The RealPlayer functionality, Downloading & Recording, has compatibility issues with Flash Player 11.3. If RealPlayer is installed, Flash Player content does not appear. YouTube provides an error message when you try to watch a video.

As a workaround, do the following:

1. Start RealPlayer.

2. Click the RealPlayer icon in the upper-left corner and select Preferences.

3. Select Download & Recording in the left menu and deselect Enable Web Download & Recording for These Installed Browsers option.

4. Click OK and restart Mozilla Firefox.

Help information originated from Adobe's website:
http://helpx.adobe.com/flash-player/kb/flash-player-113-crash-mozilla.html