Windows Server 2008 R2 : Audio Over VM (Hyper-v)/RD Server

Windows Server 2008 R2:

1. Open the Remote Desktop Session Host Configuration MMC (Start -> Remote Desktop Services -> Remote Desktop Session Host Configuration).
2. Double-click RDP-Tcp in the Connections panel.
3. Click Client Settings, clear the “Audio and video playback” and “Audio recording” checkbox.

Source: https://social.technet.microsoft.com/wiki/contents/articles/731.hyper-v-troubleshooting-enabling-audio-over-rdp.aspx