It's difficult to say why it doesn't play sound. Usually because of missing codecs, but I don't know exactly.
Could you try the newer (preview) version http://iptvtalk.org/showthread.php?16376-IPTV-STB-Emulator-v0-8-preview&p=127749&viewfull=1#post127749
It has a newer version of Exo player (and Ijk) so it may work on your device.
You may install both release and preview versions, just save your settings in release version (Common settings->Save and restore settings) and restore them in preview version.
Could you try the newer (preview) version http://iptvtalk.org/showthread.php?16376-IPTV-STB-Emulator-v0-8-preview&p=127749&viewfull=1#post127749
It has a newer version of Exo player (and Ijk) so it may work on your device.
You may install both release and preview versions, just save your settings in release version (Common settings->Save and restore settings) and restore them in preview version.