It turns out that after some automatic updates, the microphone device was replaced by a "Stereo Mix" device, which was disabled.
Updating the Conexant SmartAudio HD driver did nothing.
Deleting the Audio input and output devices (Speakers, and Stereo Mix) and rebooting did nothing.
However, when looking down the list in the Device Manager, I found a "Sound, video and game controllers" section with a device called: "Conexant SmartAudio HD".
By deleting this device, all the Audio input and output devices were deleted.
Then, after a reboot, the Audio input and output devices showed:
- Microphone Array (Conexant SmartAudio HD)
- Speakers (Conexant SmartAudio HD)
