MOS stands for Mean Opinion Score. MOS is a process by which the quality of a phone call is measured and scored between 1 and 5 — with 5 being the highest quality score. MOS is a mathematical approach to call quality, and in the past was performed using human assessors seated in a quiet room. n VoIP, it can be performed algorithmically with various codecs. G7.11u has received a 4.4 maximum score in the MOS scale, which is an “Excellent” rating, and is the baseline for Non-HD quality calls.