Can't redirect microphone by rdp: No audio devices are installed
Solution 1:
Go to Administrative Tools / Server Manager / Roles / Add Roles. Add the Remote Desktop Services role. In the Role Services submenu add Remote Desktop Session Host. In the Client Experience submenu select "Audio and video playback" and "Audio recording redirection".
After installing this a Remote Audio device appears in the Recording tab.
Solution 2:
I ran into the same issue. In order for it to work I had to change the registry setting on the Remote Desktop Client, not the host machine.
The following registry subkey can disable the Audio Recording Redirection feature:
HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp
fDisableAudioCapture REG_DWORD 0 | 1
In Windows 7 Enterprise Edition, this registry subey is set to 1 by default. Therefore, Audio Recording Redirection is not available.
In this case it would not help to set the policy value to Enabled. Instead, you must set the subkey to 0.