[Aspire 5735, Realtek ALC268, Mic, Internal] Background noise and low volume

[bastet]

There is a high background sound covering voice when using internal mic, making it unusable.
If I reduce the mic volume, the problem is the same. It is worse when using amplification.
I haven't this problem withe usb mic.

Evrything was working properly before upgrading to Xenial.

The distribution I'm using is:
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=16.04
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION="Ubuntu 16.04.1 LTS
uname -a
Linux cb-Aspire-5735 4.4.0-31-generic #50-Ubuntu SMP Wed Jul 13 00:07:12 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

My computer is Acer Aspire 5735

The sound card is 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03).

The shipset is realtek alc268:
cat /proc/asound/pcm
00-00: ALC268 Analog : ALC268 Analog : playback 1 : capture 1

My version Alsa is
cat /proc/asound/version
Advanced Linux Sound Architecture Driver Version k4.4.0-31-generic.

I have edited the file /etc/pulse/default.pa and modified line ; "load-module module-udev-detect" by " load-module module-udev-detect tsched=0" as suggested here https://forum.ubuntu-fr.org/viewtopic.php?id=511551Description: Ubuntu 16.04.1 LTS
Release: 16.04

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: alsa-base 1.0.25+dfsg-0ubuntu5
ProcVersionSignature: Ubuntu 4.4.0-34.53-generic 4.4.15
Uname: Linux 4.4.0-34-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/pcmC0D0c: cb 3322 F...m pulseaudio
 /dev/snd/controlC0: cb 3322 F.... pulseaudio
 /dev/snd/timer: cb 3322 f.... pulseaudio
CurrentDesktop: Unity
Date: Fri Aug 26 15:17:23 2016
InstallationDate: Installed on 2016-05-31 (86 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
JournalErrors:
 Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] failed with exit code 1: Hint: You are currently not seeing messages from other users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=fr_LU:fr
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fr_LU.UTF-8
 SHELL=/bin/bash
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaRecordingTest: ALSA recording test through plughw:Intel successful
Symptom_Card: Audio interne - HDA Intel
Symptom_Jack: Mic, Internal
Symptom_PulseAudioRecordingTest: PulseAudio recording test through plughw:Intel successful
Symptom_Type: High background noise, or volume is too low
Title: [Aspire 5735, Realtek ALC268, Mic, Internal] Background noise or low volume
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/10/2008
dmi.bios.vendor: Phoenix Technologies LTD
dmi.bios.version: V1.08
dmi.board.name: CathedralPeak
dmi.board.vendor: Acer
dmi.board.version: Rev
dmi.chassis.type: 10
dmi.chassis.vendor: Acer
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnPhoenixTechnologiesLTD:bvrV1.08:bd09/10/2008:svnAcer:pnAspire5735:pvr0100:rvnAcer:rnCathedralPeak:rvrRev:cvnAcer:ct10:cvrN/A:
dmi.product.name: Aspire 5735
dmi.product.version: 0100
dmi.sys.vendor: Acer