Internal microphone does not work due to phase inversion

[Chris Rainey]

PulseAudio detects internal microphone but cannot receive any sound from it.

WORK-AROUND:

Issue command: $ pactl set-source-volume 1 0% 100%

or

"Install the pavucontrol application, start it and go to the "Input Devices" tab. Unlock the channels (there is a keylock icon), then mute the right channel while keeping the left channel at the volume you want.
If the internal mic is now working correctly, you have an inverted internal mic, so that your right channel cancels out the left one."

source: https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1002978

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: pulseaudio 1:8.0-0ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-38.57-generic 4.4.19
Uname: Linux 4.4.0-38-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: chris 1737 F.... pulseaudio
                      chris 10382 F.... alsamixer
Date: Thu Oct 6 10:47:52 2016
InstallationDate: Installed on 2016-10-05 (1 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
SourcePackage: pulseaudio
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/15/2016
dmi.bios.vendor: LENOVO
dmi.bios.version: D5CN46WW
dmi.board.asset.tag: NO Asset Tag
dmi.board.name: VIUU4
dmi.board.vendor: LENOVO
dmi.board.version: SDK0J40700 WIN
dmi.chassis.asset.tag: NO Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Lenovo ideapad 300-17ISK
dmi.modalias: dmi:bvnLENOVO:bvrD5CN46WW:bd03/15/2016:svnLENOVO:pn80QH:pvrLenovoideapad300-17ISK:rvnLENOVO:rnVIUU4:rvrSDK0J40700WIN:cvnLENOVO:ct10:cvrLenovoideapad300-17ISK:
dmi.product.name: 80QH
dmi.product.version: Lenovo ideapad 300-17ISK
dmi.sys.vendor: LENOVO