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I am using Ubuntu 18.04 with unity-desktop on a Thinkpad T480s. I noticed today (can't really say if it was the same before and I had never noticed, or if it started now) that my laptop's speakers emit a constant low hissing noise when they are unmuted and the laptop is plugged to its AC adapter. The only thing I did today was to install pavucontrol and switch configuration, as yesterday I had plugged my laptop to HDMI to stream onto a TV and the sound had remained muted after unplugging (it probably kept the wrong profile, also after reboot). I did recheck all configurations on pavucontrol, to no avail, the hissing is still there. It seems to me that there's no hissing through the headphones. The hissing dies off after a couple of seconds if I unplug the power cord. I am 100% sure it comes from the speakers and not from the power adapter: when I mute the sound, the hissing is also muted. Any idea how to solve this? Here's the output of sudo aplay -l:

**** List of PLAYBACK Hardware Devices ****
Home directory not accessible: Permission denied
card 0: PCH [HDA Intel PCH], device 0: ALC257 Analog [ALC257 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 9: HDMI 3 [HDMI 3]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 10: HDMI 4 [HDMI 4]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

I read somewhere that disabling loopback in alsamixer would solve this, but there is no such channel for me.

EDIT: I already tried muting the microphone in alsamixer, which had no effect at all. It doesn't seem related to that.

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  • It sounds like your Mic is feeding back through your speakers. Can you please go back into Alsa and either disable the Mic or reduce your Mic boost to zero and also anything else related to the Mic. Try that and report back. Some people also had luck adjusting th eMic boost just above zero, but try zero first and then try just turning it off.
    – jwcooper
    Apr 23, 2019 at 20:20
  • Nope, I had tried that already to no avail. It seems unrelated to what I do with the microphone (at least from the alsamixer point of view). Only disabling either Speaker or Master removes the noise (as well as any other sound, though).
    – elgicse
    Apr 26, 2019 at 17:31
  • So I just googled your laptop model and "speaker hissing" and apparently a lot of people are having this problem regardless of OS. Here's a Reddit link: reddit.com/r/thinkpad/comments/93x6yi/… And heres one from someone who claims to have fixed it, but I'm skeptical if this will work for everyone: reddit.com/r/thinkpad/comments/a5jaov/… I'll keep digging around and see if I can find a solution though.
    – jwcooper
    Apr 26, 2019 at 19:35
  • thank you for the hints. My laptop is actually a T480s (thinner than a T480), and I am not really keen on opening the laptop/trimming stuff as this could invalidate warranty. The buzzing is not easy to hear when playing videos or music, it is mostly annoying when the laptop is not making any sound but it is unmuted. Also, I am rather confident that this problem was not there before I tried to fix the fact that the output mode was tuck on HDMI. I am continuing researching this too, but so far nothing has worked for me.
    – elgicse
    Apr 29, 2019 at 8:59
  • Understood. Unfortunately, i cant seem to find anything concrete regarding a solution. I'm still looking, but if you come up with anything please post the answer back here for everyone to see.
    – jwcooper
    Apr 30, 2019 at 1:19

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