What Is: Latency

What is Latency? Spearline explains how your calls could be affected by this issue.
On Thursday 27 February 2020 by Josh O'Farrell


1. What is Latency?

Latency is a major annoyance that can interrupt important conversations and cause irritation between callers. Latency, or more famously known as ‘lag’, is the time delay from when you speak to when the other person hears your voice. A common cause of poor VoIP (Voice over Internet Protocol) calls, high latency value can lead to great difficulty in conducting conversations and cause frustration. 

Phone calls are normally made between two remote locations, so there will always be some natural delay.  More extreme delays increase the conversational challenge. Latency can be caused by a number of factors in the call path, including the number of network hops and the chain of hardware components that ultimately link the call.


2. What are the effects of Latency?

High latency is a frequent cause of poor quality voice or video interaction across a network, and it can have a very significant impact on the effectiveness of communications. Workgroup collaboration and customer engagement can suffer and have a real impact on business. 

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.


3.How do you measure Latency?

Latency can be measured in one or both directions and is quantified in terms of milliseconds (ms). Latency is measured in two ways: 


  1. One-way latency is the time it takes for a data packet to travel in one direction only and it is generally used to diagnose network problems. 
  2. Two-way latency, also known as ‘round trip latency’, measures the round trip time and 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. But anything more than that, the quality and consistency of the call starts to decline. Latency is utterly unacceptable at 300 ms or greater. The International Telecoms Union (ITU) of the United Nations recommends (ITU-T G.114) 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. 


4.Latency testing explained

Voice is a realtime application and latency does impact human interaction.  With international call connections that do cross the globe, and do transit multiple networks, there are challenges, but tolerable latency that supports good conversation is possible.

Today’s users have very high expectations regarding the quality of phone calls, and there are many issues that can occur with a voice connection, including latency. Businesses depend on clear communication channels in their customer interactions and more and more are taking a truly proactive approach to audio quality management. 

By implementing the Spearline latency test you will be allowed to proactively measure any delay, and, with repeated testing, detect where there are variations over time. To find out more about our latency tests and how to set them up in your organization, please download our latency fact sheet.

Be sure to also download our Latency whitepaper today.

*For more, connect with Josh O'Farrell on LinkedIn here. 

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Spearline is a technology company that proactively tests toll and toll-free numbers for connectivity and audio quality globally. It enables organizations to provide uninterrupted services to customers around the world. For further information, or if you have any further questions please get in touch with us.


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