Tag Archives: call quality MOS

Mean Opinion Score and V1 VoIP Quality

The Mean Opinion Score (MOS) is a test that has been used for decades in telephony networks to obtain the human user’s experience of the quality of a phone call. This measurement is the result of underlying network attributes that act upon data flow and is useful in predicting call quality and is a good VoIP test tool in determining issues that can affect your VoIP quality and your conversations.

Testing the quality of VoIP has become easier which has furthered the advancement in the quality of services has helped increase the number of VoIP subscribers, but occasionally issues affecting voice quality do arise and being able to test your VoIP and identify these instances can be helpful in addressing them. The MOS is assigned by a group of listeners using a scale of 1 to 5 with

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: Not great.
2: Very annoying. Nearly impossible to communicate.
1: Impossible to communicate

By its very name “Opinion”, the MOS, Mean Opinion Score was a subjective measurement used to test the listener’s perception of the voice quality, and clarity of the communication. The test was performed in a ‘quiet room’ meeting specific size and noise requirements, in which listeners would receive and score calls on the quality as they perceived it. VoIP MOS score measurements, on the other hand, is usually more objective, the score providing a measure of the network over which it is carried.

Having a metric to measure changes or degradation in the quality of the voice/VoIP connection after testing can help identify problems. VoIP calls often are in the 3.5 to 4.2 MOS range. MOS is a relative scale and is built upon many factors which can affect voice quality. Real voice signals are used to test clarity, delay, packet loss, jitter and determine a probable MOS score. Yes, this is an estimate to the human based MOS score, but it is more practical and scalable. MOS takes into account factors including listening quality, transmission quality, and conversational quality.

To learn more about what your MOS score is and how you can improve it with V1 VoIP, contact us today.

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