Voice Quality Troubleshooting Tips
When you observe significant and persistent changes to metrics, use the following table for general
troubleshooting information.
Table 47: Changes to Voice Quality Metrics
ConditionMetric Change
Network impairment from packet loss or high jitter.Conceal Ratio and Conceal Seconds
increase significantly
•
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.
Conceal Ratio is near or at zero, but
the voice quality is poor.
Network impairment from packet loss or high jitter levels:
•
Average MOS LQK decreases may indicate widespread and
uniform impairment.
•
Individual MOS LQK decreases may indicate bursty impairment.
Cross-check the conceal ratio and conceal seconds for evidence of
packet loss and jitter.
MOS LQK scores decrease
significantly
•
Check to see if the phone is using a different codec than expected
(RxType and TxType).
•
Check to see if the MOS LQK version changed after a firmware
upgrade.
MOS LQK scores increase
significantly
Voice quality metrics do not account for noise or distortion, only frame loss.Note
Cisco IP Phone 8800 Series Administration Guide for Cisco Unified Communications Manager
259
Voice Quality Monitoring
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