A mean opinion score averages many listeners’ ratings into one quality number.

Evidence

The absolute category-rating (ACR) test requires listeners to respond with a rating from the five-point ACR rating scale shown in Table 7.2. The results from all the listeners are averaged to provide a mean opinion score (MOS) for the signals being tested. Depending on the purpose of the test, it might be of more interest to present the results of the listening test in terms of the percentage of listeners that rated the presented sounds in one of the categories such as good or excellent or poor or bad. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2388

Categorization

• DEFINE: MOS is the single most widely used term in audio quality testing — worth having its construction spelled out.