Microphone recording problem

[Nathan Aubrey]

On Wednesday 27 December 2006 10:55, Alan Dayley wrote:
> I got a new headset with a microphone for Christmas.  I want to record
> audio and use VOIP applications, etc.  However, I have a very
> pronounced, high pitched screeching or squealing in the recording no
> matter what ALSA settings I attempt.  I'd like some ideas on how to
> proceed with figuring out the problem.
>
> Here are some facts and things I have found or tried:
> - The computer has a built-in microphone and an external microphone jack.
> - alsamixer and KMix show only one "capture" control and one "mic" input.
> - Background noise is present when using either the built-in microphone
> or the external.
> - KRecord's level meter set to the "log" scale is constantly bouncing
> from 39 to 43 or so dBs.
> - KRecord's frequency meter shows the background screech all the time.
>
> Big Hint:
> By closing X and getting to a text only terminal, I can use the "rec"
> and "play" command line programs to record and play back a .WAV file.
> In this environment the recording is *clean* with either the built in
> mic or the external mic.

Try doing exactley this from a command line while in X and report back what 
happens. 
Try killing artsd completely and recording.
I had similar problems but fixed it by disabling the mic boost option and 
lowering the speaker output volume. I got rid of it completely later on, by 
replacing the microphone. If it does not do it while X is shutdown, I almost 
want to say the processor is creating interference while in X, like it is 
running to high or something. What kind of sound card is it? Maybe it 
requires the processor to handle the DSP as it doesn't have a dedicated DSP 
on it's own and shutting down X gives the DSP better access to the processor?
In which, try rebuilding your kernel using different preemptions or timer 
frequency?

nathan

>
> Based on the clean results from the command line, I'm thinking KDE is
> aRTs fighting with ALSA or something of that nature is going on when in
> the GUI environment.
>
> I am running:
> Linux 2.6.18.2-34-default i686
> openSUSE 10.2 (i586)
> KDE:  3.5.5 "release 45"
>
> It was very late last night when I got to this point and had to stop the
> effort.  So, in anticipation of taking this up again this evening, I
> thought someone on the list may have ideas about what to look at next or
> any online resources to check.
>
> Alan
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