Have tried to get the internal microphone working on my Fujitsu T4220 convertible laptop since I purchased it three or four years ago. Running Debian Linux the past 2-3 years.
Have fussed with ALSA and read numerous webpages about configuring ALSA to do so.
(Have also heard that internal laptop microphones are problematic.)
The sound card is an Intel 9 series card.
Today, I took another look and saw this thread. Noticed the comment about configuring using the alsactl init command, and one respondent saying that it worked.
Tried it just now and for the first time, with no other adjustments, the internal microphone works.
I launched alsamixer and noted that it seemed to have fewer settings than before I issued the command. (On boot today, I realized that there is a long string of alsactl error messages about not finding files; not sure if that is part of the problem, or that my previous manipulations caused problems or that alsa can't find the files until after the system is fully booted up.)
Anyhow, thanks much craig(-notso-)evil, for the HOWTO.
I will see if the microphone works after rebooting and if not, if repeating the alsactl init command restores it to working order and if my memory allows, I will report back.