[Latitude 3340, Realtek ALC3234] MATE - Headphone Static on Battery Power

[Wes]

I have noticed that when I am on battery power on a Dell Latitude 3340 laptop with headphones plugged in , and there is no audio playing on the computer, there is a consistent static sound that comes through the headphones at a constant volume that is not affected by changing the volume level. I think it may be picking up some kind of analog loopback signal because keyboard presses and disk activity seem to influence the noise. When I plug the power cable into the laptop , the static immediately goes away.

I reported this earlier to the upstream Linux Kernel bug tracker, but it seems to be fixed in any distro running a 4.4 kernel or greater that I have tested , Except for Ubuntu MATE 16.04 LTS 64-bit. This make me think it is not a kernel level issue and is found somewhere either in the audio settings on Ubuntu MATE or a pulseaudio bug. I cannot reproduce it on any other 16.04 distro version, but it also affects all the 14.04.4 distros as well.

Running amixer -c 1 set "Loopback Mixing" "Disabled" does not prevent the static.

The BIOS Firmware version is up to date.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: pulseaudio 1:8.0-0ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: ubuntu-mate 1718 F.... pulseaudio
 /dev/snd/controlC0: ubuntu-mate 1718 F.... pulseaudio
CasperVersion: 1.376
CurrentDesktop: MATE
Date: Wed May 11 00:43:52 2016
LiveMediaBuild: Ubuntu-MATE 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: pulseaudio
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/04/2015
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A10
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA10:bd11/04/2015:svnDellInc.:pnLatitude3340:pvr00:rvnDellInc.:rn:rvr:cvnDellInc.:ct9:cvr:
dmi.product.name: Latitude 3340
dmi.product.version: 00
dmi.sys.vendor: Dell Inc.

[Wes (wesinator)]

Still present in Ubuntu MATE 16.04.2 LTS 64-bit, not reproducible in any other Xenial variant.

Similar to the issue described at https://askubuntu.com/questions/457910/strange-noise-in-headphones-when-no-sound-is-played

[Wes (wesinator)]

Possible duplicate of https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1547024