How to Measure Latency on a Call

The Importance of Measuring Latency

Does your organization know how to measure latency on a call?

A January 2021 survey by IDC stated that, “global business leaders rate latency a higher priority than speed.” In addition, the survey observed that “9 of 10 executives believe business success depends upon low latency.

Increased incidents of latency in call centres negatively impact call quality, frustrating both agents and customers.

In the gaming industry, latency isn’t just annoying, it affects the user’s experience and the perceived quality of the game.

What Is Latency?

Latency, also known as ‘lag’, is the time delay from when you speak to when the other person hears your voice. Basically, latency interrupts important conversations and causes irritation between callers. High latency values lead to great difficulty in conducting conversations.

Phone calls are usually made between two remote locations. This means there will always be some natural delay. However, more extreme delays increase the conversational challenge. There are a number of factors along the call path that cause latency.

These include the number of network hops, and the chain of hardware components that ultimately link the call.

What Are the Effects of Latency?

High latency is a cause of poor quality voice or video interaction across a network. Significantly, latency has a very notable impact on the effectiveness of communications. Workgroup collaboration and customer engagement suffers, which has a real impact on business operations.

Echo, overlapping noises, i.e. talking over one another, ‘slow calls’, interrupted calls, and disturbed synchronization between voice and video during conferencing are all common effects of poor latency.

How to Measure Latency?

You can measure latency in one or both directions. Milliseconds (ms) is the unit of measure.

There are two ways to measure:

1. One-way latency is the time it takes for a data packet to travel in one direction only. This is generally used to diagnose network problems.
2. Two-way latency, also known as ‘round trip latency’, measures the round trip time. This figure is used to calculate MOS (mean opinion scores).

For VoIP calls, a one-way latency of 20 ms is normal. A latency of even 150 ms is barely perceptible and thus acceptable. However, anything over that, the quality and consistency of the call starts to decline.

Latency is unacceptable at 300 ms or greater. The International Telecoms Union (ITU) recommends no more than 150ms latency (one-way) for voice calls.

Beyond 150ms (300ms round trip), call quality declines to the point of unacceptable and completely non-productive.

Voice is a real-time application and latency impacts human interaction. Certainly, with international call connections that cross the globe, and transit multiple networks, there are challenges. Despite this, tolerable latency that supports good conversation is possible.

Today’s users have very high expectations regarding the quality of phone calls. However, there are many issues that can occur with a voice connection, including latency.

Businesses depend on clear communication channels in their customer interactions. Increasingly, more organizations are taking a proactive approach to audio quality management.