Results of modifying Input Gain, Output Attenuation

Discussion in 'VOIP' started by TexasMirty@gmail.com, May 18, 2006.

  1. Guest

    We are trying to fine-tune our voice port to minimize echo. Cisco techs
    have been working with us, but it seems to come down to trial and
    error. We have a Cisco 2851 router running CME (CallManager Express).

    These are settings we have tried and the results. Any audio engineers
    out there care to venture a suggestion? Thank you.

    Input Gain Output Attenuation Result
    -3......................3.....................Echo, loud and delayed
    -4......................4.....................Improved, some echo
    -5..................... 6.....................Worse, more echo
    -4......................5.....................Improved, still some echo

    Current Voice Port Echo settings:

    In Gain is Set to -4 dB
    Out Attenuation is Set to 5 dB
    Echo Cancellation is enabled
    Echo Cancellation NLP mute is disabled
    Echo Cancellation NLP threshold is -21 dB
    Echo Cancel Coverage is set to 64 ms
    Echo Cancel worst case ERL is set to 6 dB
     
    , May 18, 2006
    #1
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  2. Zeng Guest

    On 18 May 2006 08:43:11 -0700, ""
    <> wrote:

    >We are trying to fine-tune our voice port to minimize echo. Cisco techs
    >have been working with us, but it seems to come down to trial and
    >error. We have a Cisco 2851 router running CME (CallManager Express).
    >
    >These are settings we have tried and the results. Any audio engineers
    >out there care to venture a suggestion? Thank you.
    >
    >Input Gain Output Attenuation Result
    >-3......................3.....................Echo, loud and delayed
    >-4......................4.....................Improved, some echo
    >-5..................... 6.....................Worse, more echo
    >-4......................5.....................Improved, still some echo
    >
    >Current Voice Port Echo settings:
    >
    >In Gain is Set to -4 dB
    >Out Attenuation is Set to 5 dB
    >Echo Cancellation is enabled
    >Echo Cancellation NLP mute is disabled
    >Echo Cancellation NLP threshold is -21 dB
    >Echo Cancel Coverage is set to 64 ms
    >Echo Cancel worst case ERL is set to 6 dB


    TexasMirty,
    You started out with 0 db attenuation on the output side in your first
    posting (subj. hdr: Voice Port echo 5/2/06). You're actually adding a
    lot of gain by setting it to +5db. I'd kick that back down to 0db.
    Keep the input gain at -3db for now.

    Tell us a little about how the call gets to the destinations
    experiencing these calls. Are these over an IXC (LD carrier)? If
    you're still having problems with the -3 in, 0 out, then I'd start
    looking elsewhere as a source of trouble. For example, are these
    leased-lines (T-1s) that were ordered-up between distant offices?
    They may have been ordered w/o echo cancellation treatment, for
    example. If you're running both data and voice like on a West to East
    Coast PRI or T-1, then you'd have to understand how it's provisioned
    from the carrier.
    Zeng
     
    Zeng, May 19, 2006
    #2
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