[Asterisk-Users] Local Echo

[Noah Silverman]

Jeff,

Thanks for the help. Your explanation of an "echo" makes perfect sense.

Here are some notes on our system that might help:

1) The echo occurs on EVERY call either inbound or outbound, local or ld.
2) We don't use any VOIP services, just PTSN lines from the phone company
3) Our system is like this:  SIP phone <-> Asterisk box <-> TDM400 card
with FXO <-> Telco Pots line
4) I hear my own voice echo.  The other party sounds fine to me, and I
sound fine to them.
5) The phones are on a very small LAN in our office with almost no traffic.
6) Our phones are Polycom IP500
7) I have the codec set to ulaw


Thanks!!!

-N

Jeff Heath wrote:

>On Tue, 2005-04-12 at 15:28, Noah Silverman wrote:
>  
>
>>Hi,
>>
>>I tried, and still get an echo.
>>I don't think the problem is with the zap interface.  It must be on the
>>asterisk or phone side.
>>
>>-N
>>
>>    
>>
>
>Echo requires 2 phenomena:  1) reflected energy  2) enough delay that it
>is discernable.   That you are hearing echo means that something at the
>far end is reflecting the electrical or accoustical energy of your
>voice.
>
>Echo cancellation should be done as close to the source of unwanted
>reflected energy as possible.  The fact that you're hearing echo means
>that the echo cancelers at the far end either a) don't exist or b)
>didn't work.  It will be very difficult to cancel reflected energy
>coming back at you from the "other side" of the network. 
>
>Tell me more about the phone call where you experienced the echo and I
>_might_ be able to help.  Specifically,
>
>- was the phone at the other end a speaker phone and if so, was it an
>expensive Polycom phone that's designed to be a speaker phone or a cheap
>Walmart phone that happens to have speaker capability?
>
>- was it a local call or a long distance call
>
>- what codecs are in use?
>
>- what's your best guess at the round trip delay (i.e. what networks had
>to be traversed and what is the jitter buffer set for?)
>
>
>
>  
>
>>Rich Adamson wrote:
>>
>>    
>>
>>>>I have a strange echo problem.
>>>>
>>>>When speaking on the phone with someone, I hear MY OWN voice with a
>>>>sever echo.  The other party sounds perfect, and they can hear me
>>>>perfectly.  It is as if only the sidetone has an echo.
>>>>
>>>>I'm running * on a dedicated box, small LAN, and am using 4 FXO cards to
>>>>connect the box to PTSN lines.  My phones are Polycom IP500 SIP phones.
>>>>
>>>>The only echo cancellation stuff that I can find relates to cancelling
>>>>echo between my system and the PTSN lines.  Since the call is "perfect",
>>>>I don't see how this would apply.
>>>>
>>>>Any suggestions??
>>>>   
>>>>
>>>>        
>>>>
>>>Try these parameters for each zap channel:
>>>echotraining=800
>>>echocancel=yes
>>>echocancelwhenbridged=yes
>>>
>>>Don't forget you have to stop and restart asterisk. a reload will not work.
>>>
>>>
>>>_______________________________________________
>>>Asterisk-Users mailing list
>>>Asterisk-Users at lists.digium.com
>>>http://lists.digium.com/mailman/listinfo/asterisk-users
>>>To UNSUBSCRIBE or update options visit:
>>>  http://lists.digium.com/mailman/listinfo/asterisk-users
>>>
>>> 
>>>
>>>      
>>>
>>_______________________________________________
>>Asterisk-Users mailing list
>>Asterisk-Users at lists.digium.com
>>http://lists.digium.com/mailman/listinfo/asterisk-users
>>To UNSUBSCRIBE or update options visit:
>>   http://lists.digium.com/mailman/listinfo/asterisk-users
>>    
>>
>
>_______________________________________________
>Asterisk-Users mailing list
>Asterisk-Users at lists.digium.com
>http://lists.digium.com/mailman/listinfo/asterisk-users
>To UNSUBSCRIBE or update options visit:
>   http://lists.digium.com/mailman/listinfo/asterisk-users
>
>  
>