[asterisk-users] SIP & Echo

[Dan Austin]

Alex wrote:
> I tried with the ping ... all of the phones respond 
> in ca. 0.3ms, so network seems to be OK. More than 
> 90% of CPU on * box is idle even in peak times, so 
> this shouldn't cause echoes either, right? Hmmm, so 
> handset could be an issue, but did anyone ever 
> experience any handset problems with Polycom IP 
> SoundPoint 430 :-) ?

> I will check the headsets and any possibilities of 
> acoustical echo. Besides that, if we rule out the 
> network, and the CPU on the * box, is there anything 
> else that could be causing echoes on internal SIP calls?

As others have pointed out it is highly unlikely that
a network issue is the source of the problem (unless
the phone's firmware has a MAJOR bug).

Acoustic issue is 99.9% likely to be the cause, but
is can be less than obvious why.  A certain vintage
of Cisco phone firmware would introduce echo when the
headset/handset/speaker volume was set above 65~75%.

I spent about 6 months chasing that one on and off.
After Cisco fixed that, then next two common causes
were:
   1.  Enclosed offices/conference rooms without
	acoustic treatment 
   2.  3rd party amplified headsets
      (Echo was only one symptom of this one and not
	a common one, but it did happen)

Some phones deal with item 1 better than others.
last ditch efforts to fixup a room that a phone
has problems with would include wall hangings, or
even a cloth place mat (don't use the wife's Holiday
mats) under the phone if the echo is most common on
speakerphone calls.  I've often wondered why phone
designers put the mic on the bottom front of so many
phones, where it is most likely to get acoustic reflection
off the table/desk surface...

Oh, one more cause that is a bear to correct.  After
first switching to the new system, my users felt the
need to yell at their phones.  Maybe a byproduct of 
poor experience with cell phones, which is how they
expected the new phones to work like.  Getting the
yellers and loud talkers to bring it down a notch also
helped.

Dan