User's Manual Part 1

Nomad User’s Manual Chapter 7 – Monitoring a Test in Progress

7.4 Interpreting MOS Results (Voice Quality Testing)

Nomad provides audio quality scores using either PESQ P862.1 MOS or POLQA P.863 MOS as

selected by the user

. Both standardized models for predictive speech quality utilize speech signals

that are subjected to the communications link under test and compare the degraded speech to the

original speech. Both models provide speech quality on a 5-point scale:

Score

Quality of Speech

Excellent

Good

Fair

Poor

Bad

See Appendix E for an introduction to POLQA including a comparison between PESQ and POLQA.

When interpreting results during live collection or in a summary report (see Section 8.1), the

highest MOS values represent the best quality of speech. Although the determination of

“acceptable” or “poor” scores is somewhat subjective, the following guidelines represent a general

rule of thumb:

 A MOS value of 4.5 or higher represents virtually perfect audio.

 A MOS value of 3.500 or higher generally indicates good voice quality.

 A MOS value of 3.000 or higher generally indicates poor voice quality with degradation

audible to the end user.

POLQA scoring is available as an optional upgrade. Please contact your Spirent Communications

representative for more information about this option.