Other possible Echo Cause

[Paul]

I made the switch to SHR to test out how things are.  The echo problem
is resolved with the following patch

http://lists.openmoko.org/nabble.html#nabble-td1486414|a1518726

Now there was the annoying buzz to rectify.  This worked perfectly for me.

http://www.mail-archive.com/support@lists.openmoko.org/msg00564.html

On Mon, Dec 15, 2008 at 12:21 PM, Al Johnson
<openmoko at mazikeen.demon.co.uk> wrote:
> On Monday 15 December 2008, Paul wrote:
>> > It's possible, but the buzz is within the voice frequency range. If we
>> > could characterise the buzz sufficiently it may be possible to remove it
>> > by applying a suitable digital filter in the CPU, but a hardware fix is
>> > certainly preferable.
>>
>> I was thinking a software noise gate would be preferable since it
>> requires less computing.  Also, anyone tried sound proofing the mic
>> with sound insulating foam to prevent the sound from traveling through
>> the phone?
>
> There's a noise gate in the Wolfson chip, but I never managed to get it
> working. The functions in the GSM chipset sound like a noise gate in
> operation too. A better low-computing method might be to monitor the GSM
> output and mute the mic if there is significant signal there. This approach
> is used by some VoIP handsets ad is very effective at preventing echo, but
> can be awkward as the other end can't hear when you interrupt them ;-)
>
> The mic has rubber around it which seals the gap between the mic and the case.
> I haven't tried modifying this.
>
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-- 
Paul
Email - paultsai at gmail.com

There were moments when he looked on evil simply as a mode through
which he could realize his conception of the beautiful.
Oscar Wilde - The Picture of Dorian Gray