[asterisk-users] Audio feedback - where to troubleshoot?

[Matthew J. Roth]

Justin Sherrill wrote:

> We occasionally get a sort of feedback/echo noise on our phones
> here.  (Polycom IP550 / Asterisk 1.8).  It lasts for about a second,
> and it's described by users as 'jingle bells'.

That's very appropriate for the season.  I just hope they're not
Todash Chimes.  ; )

> It happens when people are using the speakerphone, especially when
> it's on both ends.  It happens on internal calls, so it's not
> something from the PSTN.
> 
> My theory is that the very sensitive speakerphone microphones in
> those models are picking up small noises, and then picking up their
> own playback of the noise, which leads to the feedback sound.  It
> repeats, which is why it sounds like an echo.

Your theory sounds correct to me.  You've described acoustic echo and
that is the most prevalent type for internal VoIP calls.

> I think turning rxgain/txgain down may make a difference, but I
> haven't tried it yet.  Has anyone else experienced something
> similar?  

I believe rxgain and txgain only apply to DAHDI channels.  The first
thing I would try is reducing the speakerphone volume settings on the
Polycom IP550s.

Regards,

Matthew Roth
InterMedia Marketing Solutions
Software Engineer and Systems Developer