Microphone always picks up sound and routes it to speakers

Question

I've started running into a kind of strange problem on my laptop, and Google hasn't proved to be very helpful so far.

Essentially, at seemingly random times, my microphone will start sending output directly to my speakers/headphones and I cannot disable it. Going through the Gnome GUI and muting my microphone doesn't stop the sound, and disabling the capture channel in alsamixer doesn't help either. For that matter, I can set every channel to a level of "0" in alsamixer, but if I unmute the master I'll still hear microphone input.

So far the only thing that solves the issue is rebooting my system, but that's clearly an inconvenient "workaround" for the problem. If I was on a desktop this might not bother me much, but my mic is integrated into my laptop so my typing and touchpad clicks get picked up and amplified right through my headphones (which is incredibly annoying, obviously).

This is on a fairly fresh Fedora 14 install, but the problem started on 13. lspci and alsa-info report my sound card as:

00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03)

and lsmod notes that the snd_hda_intel module is loaded.

Has anybody experienced this before? Any helpful hints? It might very well be a simple solution, but I just can't seem to figure out what it is.

Answer 1

Well I've fixed this for myself, though I'm unsure of the exact cause still.

I have Pandora One installed on my machine, and I noticed last week that it was running at startup/login. I generally dislike having applications run at startup unless they're actually necessary for general functionality, so I took it out of my startup lists. Since then, this problem has stopped occurring.

My guess is that either Pandora or Adobe AIR as a whole was grabbing my sound card at startup and locking it full on, then not resetting the levels/releasing it after exiting. Why it would be doing this, I have no idea, but that's the best I can come up with at this point. I did install Pandora before I went from F13 to F14, so that would explain why the problem persisted across versions/installs. This is just a guess, though, so if anyone can provide a legitimate explanation then I'm all ears.

Answer 2

As a last resort, you could disconnect the microphone from the board...