[Asterisk-Users] Is this echo problem down to IP Phone hardware?

[Peter Svensson]

On Sat, 6 Aug 2005, Angus Comber wrote:

> >> I have a Grandstream GXP2000 with latest firmware.  When I use it holding 
> >> the handpiece I don't hear any echo - neither does other end.  However, 
> >> if I use it handsfree, the other end notices echo when they speak - ie 
> >> their voice is echoy.  I hear their voice being a bit echoy.
> >>
> > The Grandstreams are much maligned, but they actually do a better job in 
> > this area than most products. As said above, if you are using this in a 
> > large space the echo canceller in the phone may not cancel a long enough 
> > echo to be very effective. If it fails to kill the echo in a small room 
> > something is wrong.
> 
> * The room is 15 foot by 22 foot.  Not massive.  When you say something is 
> wrong, what should I be looking at?  I will buy a Cisco 7940 as suggested 
> previously to see if the handset does make a difference.

Grandstream claims to be working on integrating code to cancel acoustic 
echo from the speaker phone. For the handset the echo is not canceled but 
rather minimized through good handset design with a very small acoustic 
coupling from the earpiece to the microphone.

The major problem for the Grandstream GXP2000 is the acoustic coupling 
from the internal speaker to the internal microphone, not the room echo. 
This is a complicated problem since the speaker is much more powerful then 
the handset earpiece and at the same time the microphone needs to pick up 
a weaker signal. Fortunatly the coupling parameters for such internal 
coupling are more or less constant and with a short delay, making it 
easier to cancel.

Peter