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== <div style="font-weight:bold; color:blue; font-size:10pt;">Symptoms</div> ==
<p>Users of SoundPoint IP phones experience echo issues. The echo is most
noticeable when making calls to a party located outside your organization’s
network when a gateway is part of the overall connection.<br/>
Possible issues include:</p>
<ul>
<li>Echo on external calls through a gateway. The user, calling an outside
number through a gateway, may hear echo on all terminations (handset,
headset, handsfree) that persists during the call.</li>
<li>Internal calls (no gateway), handsfree echo. User "A" talks to user "B",
where "B" is using a SoundPoint IP phone in handsfree mode. User "A"
may hear echo at the start of a call that trains away, but it can recur during
the call.</li>
<li>Internal calls (no gateway), handset/headset to handset/headset echo.
For handset/headset to handset/headset calls, echo is heard if both users
have the volume set very high.</li>
</ul>
== <div style="font-weight:bold; color:blue; font-size:10pt;">Causes</div> ==
<p>On SoundPoint IP phones, certain audio and echo issues can be traced back to
different sources:</p>
<ul>
<li>Gateways. Incorrect settings for CISCO’s echo canceller and certain
CISCO gateways configured with “CISCO Trust” enabled (sends
messages that are only relevant to a CISCO phone) may lead to echo issues
for SoundPoint IP phones. Handsfree echo is due to the adaptive echo
canceller taking a few seconds to train.
The echo heard during gateway calls is the result of the line echo canceller
in the gateway failing to adequately cancel echo generated by analog
4-wire to 2-wire converters or acoustic coupling in the equipment on the
PSTN side of the gateway.</li>
<li>Incorrect Configuration Files. A mismatch between application version
and configuration files can lead to numerous audio problems including
echo, static, and ‘squeal’ if the DSP code and/or audio gains have
changed. There are also configuration parameters for acoustic echo
cancellation and suppression.</li>
<li>Environmental. Low-level background noise—for example, a server or
music from PC speakers— can cause echo and/or distortion in
speakerphone audio, as can something as simple as shuffling a pile of
papers too closely to the phone.</li>
<li>Hardware. In rare cases, a hardware issue can cause echo, for example,
acoustic, mechanical or electrical coupling.</li>
<li>User. If users turn up the volume on the phone to the maximum level, they
will experience echo issues.</li>
<li>Room Acoustics. Large rooms or rooms with a great quantity of glass or
metal can cause echo issues.</li>
</ul>
== <div style="font-weight:bold; color:blue; font-size:10pt;">Resolutions</div> ==
<p>The phones are designed for use under ‘normal’ circumstances— for example,
the handset used a reasonable distance from the user’s mouth and speaking at
a ‘normal’ volume into the speakerphone at a ‘normal’ distance from the
microphone. Excessive variations in these conditions can cause echo or
garbled audio.</p>
<p>Packet captures can be used to identify the echo source. Taking captures right
at the phone at each end of the conversation, and on either side of the gateway
will go a long way to narrowing down the element causing the echo. For
example, if the far end complains of echo, but the near end phone audio is
clear, the problem is almost certainly network-related.</p>
<p>Another troubleshooting method would be to place an IP-to-IP call between
two phones that are experiencing echo—if the echo persists, then there is likely
a configuration (or possibly hardware) issue in one or both phones. If the echo
goes away, that is another indicator that the echo is likely being caused by the
network and you have no control over it.<br/>
The recommended solutions include:</p>
<ol>
<li>Upgrade Software<br/>
Upgrade your SoundPoint IP phones to the latest SIP application. Refer to
the VoIP SIP Software Release matrix on the Polycom Customer Support
web site at
http://downloads.polycom.com/voice/voip/sip_sw_releases_matrix.html .<br/>
Ensure you are using the default configuation files, especially the default
audio parameters.</li>
<li> Reduce Tx Signal Level<br/>
For handset issues:
<ul>
<li>In the sip.cfg configuration file, reduce the value of
voice.gain.tx.analog.handset by 6. As of SIP 3.0,
voice.gain.tx.analog.handset is set to 6.</li>
</ul>
For headset issues:
<ul>
<li>In the sip.cfg configuration file, reduce the value of
voice.gain.tx.analog.headset by 3. As of SIP 3.0,
voice.gain.tx.analog.headset is set to 3.</li>
</ul>
<li> Enable Echo Cancellation<br/>
For handset issues:
<ul>
<li>In the sip.cfg configuration file, set voice.aec.hs.enable and
voice.aes.hs.enable to 1.</li>
For headset issues:
<li>In the sip.cfg configuration file, set voice.aec.hd.enable and
voice.aes.hd.enable to 1.</li>
</ul>
<li>Gateway Settings<br/>
There is a default CISCO gateway setting, “echo canceller coverage”.
The default setting for this parameter is 64ms. In some cases, it may have been
modified (as low as 24ms) for performance-related reasons. Polycom
recommends that “echo canceller coverage” be set to 64ms when SoundPoint
IP phones are in use. For information about your specific CISCO gateway,
refer to your gateway documentation or contact your CISCO vendor.
Different tuning parameters (for example, non-linear processor enabled or
disabled, and impedance) may be required. The software running on the
gateway may need to be upgraded.</li>
<li>SLR (Send Loudness Rating)<br/>
Handset: The TIA 810 standard specifies an SLR of 8 +/- 4.<br/>
Handsfree: The TIA 810 standard specifies an SLR of 13 +/- 4.<br/>
The handsfree echo has been reduced as much as possible by tuning the
parameters that are sent to the DSP code running in the SoundPoint IP phones.</li>
</ol><br/>
Link to the original '''pdf''':
http://support.polycom.com/global/documents/support/technical/products/voice/Troubleshooting_Echo_issues_TB16249.pdf
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[[Category:Audio Issues]][[Category:Troubleshooting]]