Update: It is still an issue & the same fix in ubuntu 18.04 unfortunately.

A while ago I upgrade from Ubuntu 14.10 to 16.04. Afterwards, my laptop’s internal microphone started to become massively distorted to the point that people on the other end of skype or hangouts calls couldn’t understand me at all.

Looking in the ALSA settings I noticed that the “Internal Mic Boost” was constantly being set to 100% and when I dropped this down to 0% everything went well. It seems on my laptop at least to be coupled with the “Mic Boost” which boosts both but without quite so much distortion, ie the “Internal Mic Boost” is a boost on top of the “Mic Boost” which is obviously a problem.

I couldn’t find much detail about how to configure this properly, so after some hacking around I was able to come up with the following solution. Go through every file in /usr/share/pulseaudio/alsa-mixer/paths, look for the section “[Element Internal Mic Boost]” if it is there. You should see a setting under that section like “volume = merge“. Turn that into “volume = off“. For me the files are analog-input-internal-mic.conf and analog-input-internal-mic-always.conf

To prevent it being changed later when ALSA is updated, you can run:

chattr +i /usr/share/pulseaudio/alsa-mixer/paths

I’d love to hear if there is a simpler way to work around this issue, but it works for me at least!