The Mean Opinion Score (MOS) has been a commonly-used metric to measure the overall voice call quality for decades. MOS score is a rating from 1 to 5 of the perceived quality of a voice call, 1 being the lowest score and 5 the highest for excellent quality. It has been standardized by the International Telecommunications Union.
We select the Call Quality in the App based on the MOS Score. The following table lists the different qualities and the lower MOS limit for each of them. The limit values are from the ITU-T standards.
perl voip_mos.pl 8.8.8.8