My opinion of MOS score testing is divided. When MOS score testing first came into existence, it was done by old fashioned human being. Now I’m using tools from companies such as VisualWare (which is very good by the way & what I use today in production). MOS scoring is only ever theoretical, and the amount of true auditing needed to be done on the network cant be simplified to a simple score. Surely?
What is MOS Score’ing?
In voice and video communication, quality usually dictates whether the experience is a good or bad one. Besides the qualitative description we hear, like ‘quite good’ or ‘very bad’, there is a numerical method of expressing voice and video quality. It is called Mean Opinion Score (MOS). MOS gives a numerical indication of the perceived quality of the media received after being transmitted and eventually compressed using codecs.
MOS is expressed in one number, from 1 to 5, 1 being the worst and 5 the best. MOS is quite subjective, as it is based figures that result from what is perceived by people during tests. However, there are software applications that measure MOS on networks, as we see below.
The Mean Opinion Score Values
Taken in whole numbers, the numbers are quite easy to grade.
- 5 – Perfect. Like face-to-face conversation or radio reception.
- 4 – Fair. Imperfections can be perceived, but sound still clear. This is (supposedly) the range for cell phones.
- 3 – Annoying.
- 2 – Very annoying. Nearly impossible to communicate.
- 1 – Impossible to communicate
The values do not need to be whole numbers. Certain thresholds and limits are often expressed in decimal values from this MOS spectrum. For instance, a value of 4.0 to 4.5 is referred to as toll-quality and causes complete satisfaction. This is the normal value of PSTN and many VoIP services aim at it, often with success. Values dropping below 3.5 are termed unacceptable by many users.
My speed test, which although I’m meant to be on a 10mb connection, is more like 2mb – oh well, overall voice quality should still be good. My MOS score results (below) are also pretty good, with minimal jitter so hopefully I’ll be able to make some decent quality calls