Built-in mic not working in Ubuntu 20.04

Solution 1:

No microphone input on Acer Aspire One and Lenovo Ideapad 310-15ISK/330-15ARR

Install pavucontrol, unlink the microphone channels and turn down the left one to 0.

Some applications (e.g. chromium) can change microphone levels causing the same issue, a workaround is to remap stereo input to mono and use the remapped device as default.

Another Possible Cause

Another possible cause is that your mic has two channels but only one channel can provide a valid sound signal. The solution is to remap the stereo input to a mono input:

1. Find your source name from the following command; mine is alsa_input.pci-0000_00_1f.3.analog-stereo

    pacmd list-sources | grep 'name:.*input'
   

2. Edit /etc/pulse/default.pa and add the following lines, where INPUT_NAME is name of the input source from above step:

   load-module module-remap-source source_name=record_mono master=INPUT_NAME master_channel_map=front-left channel_map=mono
   set-default-source record_mono
   

3. Restart PulseAudio:

   $ pulseaudio -k
   $ pulseaudio --start
   

Now record hopefully works. You may still need to change the RecordStream from setting to Remapped Built-in Audio Analog Stereo of a specific application in the Recording tab of pavucontrol.

for reference check this out:https://wiki.archlinux.org/index.php/PulseAudio/Troubleshooting#Another_Possible_Cause