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The Mean Opinion Score (MOS) is an industry standard method for gauging call quality. MOS is an estimation of how impairments to a voice signal affect listener perception of call quality. The MOS scale ranges from 5.0 to 1.0.
The MOS provided in UC Monitor reports is an average that is derived from multiple samples, unless otherwise specified.
The G.107 standard provides a scale that relates MOS values to user satisfaction:
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MOS Range |
Likely User Opinion of Call Quality |
|---|---|
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4.3-5.0 |
Users are very satisfied |
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4.0-4.3 |
Users are satisfied |
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3.6-4.0 |
Some users are dissatisfied |
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3.1-3.6 |
Many users are dissatisfied |
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2.6-3.1 |
Nearly all users are dissatisfied |
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1.0-2.6 |
Not recommended |
The MOS value for a VoIP call leg partly depends on the codec that is used to packetize the audio signal. Different codecs advertise different theoretical maximum MOS values, which are the highest possible score they can achieve in the absence of other impediments.
In UC Monitor reports, the calculations for MOS values in a Cisco or Avaya environment differ from the calculations in a Microsoft environment.
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