Annoying whitenoise sound coming from snd_hda enabled chipset

[Ben Kaduk]

On Sat, Feb 21, 2009 at 8:06 AM, Alexander Motin <mav at freebsd.org> wrote:
> Garrett Cooper wrote:
>>
>>    I don't know how else to describe it, but when I turn up my
>> speakers enough (50%+) and don't have any sound playing, I hear a
>> whitenoise hiss coming out of them. When I change webpages (nvidia
>> driver is GIANT locked) or do something else kernel intensive it stops
>> for a brief second, but apart from that it's an annoying trill sound
>> almost like a mosquito humming around me waiting to be swatted.
>
> I think it may be radio interference with disconnected microphone inputs.
> Try to set all unneeded mixer volumes to 0, especially mic, monitor, speaker
> and mix. Inputs often have too sensitive 20-30dB pre-amplifiers. Some codecs
> have them on all inputs.

It's hard to be sure, since I'm not sure that I could describe what I
hear any better than Garret did, but I think I'm seeing the same sort
of thing on my work desktop.  I'll try setting unneeded volumes to
zero the next time I'm in, and see if that helps.

dmesg and pciconf are available here:
http://stuff.mit.edu/afs/sipb.mit.edu/user/kaduk/freebsd/periphrasis/

-Ben Kaduk