MOS

Mean Opinion Score (MOS) is a standardized measure of voice call quality, rated on a scale from 1 (bad) to 5 (excellent). Originally based on human listener panels, MOS is now often calculated algorithmically using tools like PESQ or POLQA.

A MOS of 4.0+ is considered toll quality. Scores between 3.5 and 4.0 are acceptable for business use. Below 3.0, users typically perceive noticeable degradation. Factors affecting MOS include codec choice, jitter, latency, and packet loss.