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I had some strange issues with the built-in microphone on a Lenovo IdeaPad 310-15IKB laptop under Linux Mint 19.1. For example, it was not working with Skype, but was working with Gnome Sound Recorder. The microphone input volume indicator in Sound configuration window was also acting strangely and seemed mostly insensitive to sounds (but reacted to tapping on the microphone opening).

I could fix the issue by using PulseAudio Volume Control and disabling one of the two microphone "channels" as suggested in Ubuntu Help wiki or elsewhere:

Volume Control screenshot

I believe that the built-in microphone is mono because it has only one opening (on the top of the laptop screen, to the left from the camera), so I would like to configure it as mono and not to have to manually disable one of the two "input channels." Moreover, changing the input volume in system's Sound configuration window breaks this workaround, and one of the "channels" has to be disabled again through the PulseAudio Volume Control.

Even if for some strange reason this microphone is stereo despite having only one opening, I imaging it will be better to configure it to work as mono.

If setting up the microphone as mono properly is too complicated, is there any clean workaround with .asoundrc?

More links

Alexey
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  • Interesting. I own an ideapad and also have noticed FreeBSD defaults to mono, but thought it was an incorrect default configuration...will check it out later on to confirm this. – Rui F Ribeiro Dec 26 '18 at 14:14
  • My built-in microphone has only one opening, so i suppose it should be mono, but i could not find any official technical specifications of the microphone. – Alexey Dec 26 '18 at 14:25
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    cnet and ebay selling pages mention it being stereo, but they are not a trustworthy reference. The other pages, include Lenovo only mention "microphone". – Rui F Ribeiro Dec 26 '18 at 14:36
  • @K7AAY, i've added details. – Alexey Dec 26 '18 at 22:17
  • Note that the headphones are stereo and still have only one jack socket. Mono and stereo jack sockets are unfortunately impossible to tell based on the external appearance (the plug can be recognized by the second isolator band). – Jan Hudec Dec 26 '18 at 22:33
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    @JanHudec, i am not talking about a jack, i am talking about the built-in microphone. – Alexey Dec 26 '18 at 22:40
  • Check ALSA settings with `amixer` or `alsamixer` and see if you can switch it to mono. Guess: The culprit is wrong BIOS data for the Intel HDA codec (happens frequently with laptops ...). You can try `hdajackretask` to fix that, though I don't know if it supports mono/stereo settings. If none of this works, you'll need complicated Pulseaudio settings. – dirkt Jul 01 '20 at 09:08
  • @dirkt, thanks for the indications. Could you explain what exactly to look for in the output of `amixer` and how "switching to mono" could be done? Do you have any links to the relevant documentation? Do you know by any chance if [`.asoundrc`](https://alsa.opensrc.org/Asoundrc) could be used for a clean workaround? – Alexey Jul 05 '20 at 12:09
  • P.S. I do not have this machine with me now, someone else is using it. – Alexey Jul 05 '20 at 12:09
  • 1) I don't know what to look for, because I have no idea what your hardware looks like. Do `amixer -D card_name control`, go through all the settings, see if something stands out. 2) Nothing beyond `man amixer`. 3) You can use .asoundrc with a route plugin etc., but that works only in ALSA, and getting that to work with Pulseaudio will be probably be difficult (though I never tried). – dirkt Jul 05 '20 at 15:46

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