Lots of noise on Librem mini's microphone

I get a lot of noise when recording audio via a microphone in headset plugged into the 2.5mm jack. The very same headset gave me much less noise when used in my old Thinkpad laptop (with literally the same software since I just transferred the SSD from the Thinkpad to the Librem mini) and in my tablet.

Has anyone noticed a similar problem? Any idea how to reduce that noise?

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Maybe it needs a microphone windscreen? (You know, like those big “fuzzballs” on news reporter’s microphones.)

No, no, the problem appears with all microphones, and shows much more noise then when the same microphone is connected to another machine. It really looks like a problem within the Libre mini itself.

What do you hear without any microphone whatsoever?

here are two recordings done with:

arecord -f S16_LE -r 48000  -d 5 foo.wav
ffmpeg -i foo.wav foo.ogg

The first (http://www.iro.umontreal.ca/~monnier/nomic.ogg) was done with nothing plugged into the 2.5mm jack at all.

The second (http://www.iro.umontreal.ca/~monnier/withmic.ogg) is done with the mic plugged in and me saying “hello”.

In both cases the gain is set to 45% in pavucontrol.

FWIW, while I have no idea where this noise comes from (seems to be due to faulty (or maybe badly initialized) hardware), I did find a partial workaround. I added the following lines to my /etc/pulse/default.pa:

### Load echo cancellation module
load-module module-echo-cancel source_name=echosource aec_method=webrtc
set-default-source echosource

and after rebooting, I now have an additional audio input which has some kind of echo cancelling, and that seems to help. I’ll see if my students also think the result is now acceptable (it clearly wasn’t before).

To me it sounds exactly like a noise cancellation issue. I can only say that while your software is the same, your hardware is not. It is possible that your thinkpad had hardware geared towards noise cancellation or the mic wasn’t as sensitive, etc, that your mini does not.

Although to be honest, I wouldn’t be using the base mic to begin with. I’d probably look at a USB solution in conjunction with a webcam. That might be a quicker solution.

I still think it’s a problem in the Librem mini: that very same microphone connected in the same way and used at the exact same place gives perfectly acceptable results when connected to my Android tablet as well as either of the laptops (Thinkpad X201 and Thinkpad T61) with which I tried (all 3 non-Android machines running the same Debian testing).

That is what I was saying as well. Your hardware is the only variable that is different. Circuits are specific things. They behave exactly the way they are designed. If the tolerances for noise in the mic circuitry on the mini are different than those on your thinkpads (each designed specifically with conferencing in mind) then you will notice audible differences. This is to be expected.

What you are hearing here as noise, is most likely the differences in the designs of those circuits. Fortunately dsp has come along way and most circuitry failings can be overcome in software.

Now whether your device is faulty, I can’t say. I would suggest contact Purism directly for support.

if you’re looking for an immediate solution i found that using an external usb-DAC/AMP with Analog to Digital Input conversion for your microphone will render the BEST results … onboard audio-processing circuitry is less ideal on such congested hardware like the Librem-Mini’s motherboard (too cramped inside due to so little room for a quality implementation)
see > Audiophile question

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I’m not looking for “the BEST results”. I’m just looking for a comparable quality to what I get on all my other devices. IOW “good enough”.

Sadly, his explanation may be the road to good enough you are looking for. IE: if it is a hardware issue, software might help mitigate it, but the hardware wont be improved.

I have no Librem Mini, but you could maybe use the pulse audio echo reduction module: https://askubuntu.com/questions/18958/realtime-noise-removal-with-pulseaudio

Or you could try out this GUI for another module for noise reduction: https://github.com/josh-richardson/cadmus

Thanks @johndoe, that’s what I’ve been using since (I’m now pretty sure it’s a hardware fault in my Librem mini, but it was not important enough to send it back and wait for a replacement).
But now the GNU/Linux world is moving to Pipewire. Do you happen to know how to configure the same kind of noise reduction in Pipewire?

I have the same problem with 2.5mm jack in mini v2. It gives distorted sound most likely due to a hardware issue but not sure. Another issue is windows also shows the computer has a microphone connected when it isn’t.

I’m able to use USB headsets and mics just fine.