Voice Quality Monitoring; Voice Quality Troubleshooting Tips - Cisco 7800 Series Administration Manual

Voice Quality Monitoring

Voice Quality Monitoring
To measure the voice quality of calls that are sent and received within the network, Cisco IP Phones use these
statistical metrics that are based on concealment events. The DSP plays concealment frames to mask frame
loss in the voice packet stream.
• Concealment Ratio metrics—Show the ratio of concealment frames over total speech frames. An interval
• Concealed Second metrics—Show the number of seconds in which the DSP plays concealment frames
Note Concealment ratio and concealment seconds are primary measurements based on frame loss. A Conceal Ratio
of zero indicates that the IP network is delivering frames and packets on time with no loss.
You can access voice quality metrics from the Cisco IP Phone using the Call Statistics screen or remotely by
using Streaming Statistics.

Voice Quality Troubleshooting Tips

When you observe significant and persistent changes to metrics, use the following table for general
troubleshooting information.
Table 40: Changes to Voice Quality Metrics
Metric Change
Conceal Ratio and Conceal Seconds increase
significantly
Conceal Ratio is near or at zero, but the voice quality
is poor.
Note Voice quality metrics do not account for noise or distortion, only frame loss.
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conceal ratio is calculated every 3 seconds.
due to lost frames. A severely "concealed second" is a second in which the DSP plays more than five
percent concealment frames.
Cisco IP Phone Troubleshooting
Condition
Network impairment from packet loss or high jitter.
• Noise or distortion in the audio channel such as
echo or audio levels.
• Tandem calls that undergo multiple
encode/decode such as calls to a cellular network
or calling card network.
• Acoustic problems coming from a speakerphone,
handsfree cellular phone or wireless headset.
Check packet transmit (TxCnt) and packet receive
(RxCnt) counters to verify that voice packets are
flowing.