Introduction

When you speak to someone over a VoIP line, you can instantly feel whether the sound is good or not. Sometimes the voice is clear and pleasant, other times it breaks or lags. The MOS score is a way to express that real listening experience in a single number. It shows how the call actually sounds to a person, not to a machine. That is why it is still one of the most trusted indicators of call quality.

What Is a VoIP MOS Score

MOS is a rating from 1 to 5 that reflects the quality of a voice call. A score close to 5 means the voice sounds natural and easy to understand. A score near 3 or lower means the call has problems that any listener will notice.

In VoIP, MOS helps evaluate how clear the voice is, whether the sound is delayed, whether there is echo, and how comfortable the call feels for the person listening. Because VoIP works through the internet, the MOS score also reflects the condition of the network. Issues such as jitter, packet loss and latency will quickly lower the score.

How MOS Is Calculated

Years ago, MOS was calculated by asking people to listen to call samples and rate them. Today the process is automated, but the idea is the same. Modern systems use algorithms that analyse the codec, packet delivery, delays and audio clarity. These tools try to predict how a real listener would judge the sound.

A score between 4.3 and 5 is considered excellent and feels very close to a normal face to face conversation. Scores between 4 and 4.3 are good and easy to listen to. Scores below 3.5 have noticeable issues and anything under 3 is considered poor quality.

Using MOS in Business

For many companies phone calls are an essential part of daily work. When sound quality drops customers can feel it right away. That is why businesses use the MOS score to monitor call quality, compare VoIP providers and identify network issues before they affect conversations.

A call center might notice that customers complain about delays. When they check their statistics, the MOS score has dropped. After adjusting their network settings the score improves and the complaints disappear.

Remote workers often face the same issue. If their Wi Fi is unstable the voice may sound robotic or broken. Their MOS score will be low. Switching to a wired connection usually improves the score and the call becomes clear again.

FAQ

What is MOS in VoIP

It is a simple rating from 1 to 5 that shows how good a VoIP call sounds to the listener.

How is MOS calculated

VoIP systems analyse clarity, delay, jitter, packet loss and codec performance. Based on this they calculate a score that reflects what a person would likely hear.

What MOS score is considered good

A score of 4 or higher is considered good. Scores above 4.3 are excellent.

What affects the MOS score

The most common reasons include unstable Wi Fi, limited bandwidth, high network load, latency, jitter and packet loss. Some codecs such as G729 also reduce quality due to heavy compression.

How can I improve MOS

You can switch to a wired connection, use a higher quality codec such as G711, enable QoS on your router, reduce overall network load and choose a stable SIP trunk provider. A cloud PBX with voice prioritization can also help.

In simple terms

MOS is a single number that shows how good your call sounds. If it is high, the sound is clear. If it is low, something in your network needs attention.