Alsamixer - strange speaker noise when microphone is unmuted

Aere Greenway Aere at
Mon Feb 17 18:45:06 UTC 2014


I noticed what appears to be a similar problem reported on the 
Fluidsynth (fluid-dev) e-mail list.  I have copied the text from that 
e-mail here:

    When I start fluidsynth for the first time, after a boot up, or a
    log on, fluidsynth sounds fuzzy.  And when I quit my application,
    which is using alsa as a audio driver, and then start up the
    application again, all is fine- normal timbres.  Is there a way
    around this?  Is this a bug?

    I am using ubuntu 13.10.

Perhaps it is the same problem.

- Aere

On 02/16/2014 03:57 PM, Netrick wrote:
> I found a very strange bug in Lubuntu 13.10. When I open alsamixer and 
> unmute the microphone and increase its volume, my speakers start to 
> constantly give some noise. When I enable microphone boost, the noise 
> gets even louder. When I mute microphone, the noise disappers.
> The speaker noise happens with and without microphone plugged. Please 
> note that this is noise from speakers and has nothing to do with 
> recording noise. The speaker noise starts just when I boot Lubuntu and 
> it is present all the time after, even if I'm not logged in (just 
> sitting on the login screen after boot is enough to hear the noise 
> which is audible all the time when Lubuntu is working).
> I tested it on different PCs with different soundcards - Realtek ALC 
> 892, Audigy 1 Gold, Sound Blaster and the noise appeared on every PC.
> The workaround I found is installing PulseAudio and pavucontrol, then 
> muting microphone in alsamixer and then enabling microphone in 
> pavucontrol, after that when I use PulseAudio for audio output and 
> input there is no noise in speakers, so PulseAudio somehow fixes it.
> Is it a known bug in ALSA? Maybe it's a bug in how Lubuntu uses ALSA? 
> Maybe it's a bug in alsamixer and not ALSA? I have no idea where I 
> should report it. I really want to get it fixed as it is very annoying 
> in my favourite distro. And I have no clue what and where I should report.
> I don't want to use PulseAudio workaround as PulseAudio still has some 
> outstanding issues in Wine in 2014 and I think the bug in ALSA should 
> be fixed as Lubuntu is just ALSA-only distro and probably it will stay 
> that way. And well, ALSA should be reliable with microphone input.
> Of course, despite the noise, sound works allright, I can listen to 
> the music or record using the microphone etc. It's just the noise is 
> "added" to speakers all the time when microphone is unmuted.
> Thanks!


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