Public bug reported:
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.
** Affects: pulseaudio (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug trusty xenial
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https://bugs.launchpad.net/bugs/1580394
Title:
Analog Loopback Static in Headphones while on Dell Latitude 3340
Battery Power
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