Audio issue - static buzzing when nothing is playing

Issue description:

• Using a 3.5mm jack cable, I have an external audio system connected to my DELL Vostro laptop.
  Everything works fine when sound is playing but when I stop playing any sound, it starts buzzing after a while. If I play a sound again, the buzzing stops, if I stop playing the sound, the buzzing returns.

I tried:

• Uninstalling the sound driver and installing the latest driver from the DELL website - that didn't help.
• Reinstalling Windows - that didn't help.
• Replacing the 3.5mm jack cable - that didn't help.

My environment:

• DELL Vostro 15 5510
  
• Windows 10 21H2 (latest update)

Additional notes:

• This is not a problem with my external audio system as everything works fine when connected to another computer (not DELL)
• SupportAssist does not see any missing drivers
  
• The command "sfc /scannow" does not return any corrupt files / errors