Fix microphone on Lenovo IdeaPad 320 on Ubuntu 18.04

fix_mic_lenovo320.md

In /usr/share/pulseaudio/alsa-mixer/paths/analog-input-internal-mic.conf and /usr/share/pulseaudio/alsa-mixer/paths/analog-input-mic.conf:

• Under [Element Internal Mic Boost] set volume to zero.
• Under [Element Int Mic Boost] set volume to zero.
• Under [Element Mic Boost] set volume to zero

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'

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`

Then restart PulseAudio:

  $ pulseaudio -k
  $ pulseaudio --start

This procedure worked for my Acer Aspire 5 A515-44-R2SA laptop running Xubuntu 22.04 up-to-date with these audio characteristics:
Device-1: AMD Renoir Radeon High Definition Audio driver: snd_hda_intel
Device-2: AMD Raven/Raven2/FireFlight/Renoir Audio Processor driver: N/A
Device-3: AMD Family 17h HD Audio driver: snd_hda_intel
Sound Server-1: ALSA v: k6.5.0-14-generic running: yes
Sound Server-2: PulseAudio v: 15.99.1 running: yes
Sound Server-3: PipeWire v: 0.3.48 running: yes

I suspect that a recent Ubuntu base update mangled my analog-input-internal-mic.conf file.