VoIPexaminer reports both Packetloss and MOS values as an indication of voice call quality.

This article explains the relationship between both.

The actual measurement in the system is the packetloss value as experienced and reported by the MTA for each voice call in the network. Therefore, packetloss values are the best way to assess the quality of your network.

Because voice quality is often expressed as MOS (Mean Opinion Score), VoIPexaminer also provides the possibility to display the quality as MOS.

We use the E-model as defined by the ITU in G.107 to translate the packetloss values to a MOS score. Of the many parameters defined by the E-model, the Random Packet-loss Probability (Plp) is the only variable parameter. Other parameters are left to sensible defaults (e.g. concealment algorithm defining the Packet-loss Robustness Factor Bpl). The Equipment Impairment factor (Ie) is chosen such that the maximum attainable MOS score is 4.15 (in case of 0% packetloss).

Use MOS scores with care. Don't compare VoIPexaminer MOS scores with MOS scores calculated by different systems, and be aware of the limits: it's a mere translation of packetloss values: the MOS score indicates the network quality, and doesn't include e.g. quality experienced by the customer due to the type of phone used.