[cisco-voip] 7911s and Echo Troubleshooting

Jeff Ruttman ruttmanj at carewisc.org
Tue Feb 24 16:31:41 EST 2009



We're getting a small but increasing number of complaints about echo
where the talker hears him/herself.  In pursuing this doc:



about echo, I'm wondering about 7911s.  Virtually all complaints have
come from people with 7911s, and the doc states this:  "Currently,
available load IDs only include echo cancellation on the speaker phone."
So ASSUMING (which I'm not as yet) the gateway is doing echo cancelling
properly, are my 7911 users doomed with no firmware with echo
cancellation?  I'm searching but can't find an answer.


So far as doing some troubleshooting on our gateways, it appears we
don't fall into any of the known bug categories with IOS and DSPWare, so
I want to do this as recommended by the doc:

Troubleshoot Echo Problems with these DSP Voice Quality Metrics 

*         Check the delay (DSP/DL) and R-factor (DSP/RF) statistics. You
can potentially find perceptible delay between when the originating
signal is transmitted and when the echo returns. In most telephones,
sidetone helps mask some of the echo. Echos must be delayed by at least
20 milliseconds in order to be perceived. 

*         Check the level (DSP/LE) statitstic for sufficient echo
amplitude. If the amplitude of the echo is low, it can go unnoticed. 

Unfortunately I don't know how to do this.  Is it way involved or can
someone get me started?







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