MOS (Mean Opinion Score) is the foundational measure of perceived audio quality: a panel of listeners rates samples on a five-point scale (1 bad, 5 excellent) and the scores are averaged. It is subjective by design and therefore the ground truth that every objective metric — PESQ, POLQA, ViSQOL — is built to predict. MOS appears throughout codec evaluation, VoIP monitoring, and standards work, often via specific test methodologies like ACR (absolute category rating). Its weaknesses are cost, time, and variability — results depend on the listeners, the content, and the test conditions — which is exactly why automated estimators exist. When you see a single quality number for a codec or a call, it is usually a MOS, measured or predicted.
The book · Volume 5 of 7
Audio for Video: A Complete Guide to Sound in Video Products: From Jitter Buffers and Lip Sync to Atmos, Quality Metrics, and Neural Codecs
MOS is the score stakeholders ask for, yet a MOS without a proper test design says little about real users. This volume covers MOS in depth with subjective test methods such as MUSHRA and ABX, plus the PESQ, POLQA and ViSQOL metrics that predict it, so your quality numbers stand up to scrutiny. Written by Nikolay Sapunov, CEO at Fora Soft.
Need a credible MOS for your voice or audio quality before a launch or tender?
Tell us what you need to prove and we will design a MOS test, run objective metrics alongside it and deliver a report you can share. 250+ video products shipped since 2005.
