Does DeSmuME support the microphone?
Yes, but only on the Windows and GNU/Linux ports. You do need to have an actual microphone attached to your PC, though. In 0.9.2 the microphone in Windows really only works for noise, but this was fixed in 0.9.4; it was fixed even further in 0.9.5. Linux support will exist in 0.9.5+ — please note that it requires libasound. When in windows, if it seems that the microphone is not working, bear in mind that it has no idea what kind of how many microphones you have. You will need to use the windows control panel to specify the correct microphone as the default audio input device, and then make sure in the recording level properties (volume control) that it is selected and at an appropriate volume.