I have a Dell OptiPlex 3060 Micro running KDE neon 5.18 and use the Anker SoundCore Mini speaker with a 3,5 mm aux cable.

After boot, the speakers emit a very loud static for about 20 minutes (± 10 minutes), thereafter the static disappears completely. The static is independent of any played sound on the system.

More about the systen and audio hardware:

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$ lspci  | grep Audio
00:1f.3 Audio device: Intel Corporation Cannon Lake PCH cAVS (rev 10)
$ cat /etc/issue.net
KDE neon 5.18
$ uname -a
Linux <hostname> 5.3.0-40-generic #32~18.04.1-Ubuntu SMP Mon Feb 3 14:05:59 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

Alsamixer lists the sound card as:

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HDA Intel PCH

I've already tried the following approaches, but none worked for me so far:

• Add

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  options snd-hda-intel power_save=0 power_save_controller=N

  to

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  /etc/modprobe.d/alsa-base.conf.

  
  
• Create a service, which does
  
  

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  echo 0 | sudo tee sys/module/snd_hda_intel/parameters/power_save

  
  on boot.

In alsamixer:

• Disable loopback
• Lower/Zero headphone mic boost
• Mic mute on/off
• Auto-mute off/lineout+speaker/speaker only
• Mute headset-mic
• Zero headset-mic boost

I have also tried using different aux cables, without difference, but the static varies in loudness and frequency when plugging in and out the aux cable.

I'm slowly getting desperate. None of the solutions I found so far worked for me. I've started booting the system and leaving the room, about 30 minutes before actually using it, so I don't have to deal with the static.

How can I prevent the static from the speakers?

I've identified the issue.

The speakers emit the static when they are charging! After a while the battery was full and therefore the static stopped. If they're operated solely on battery, the static never starts.

I've not expected this at all, but this seems to be the solution.

EDIT: The issue only occurs, if the speaker is powered via USB on the Optiplex. With an external power supply it's fine.