How to objectively measure audio quality in a telecoms network.

Poor audio quality often means a customer can’t complete the objective of their call. It has a negative effect on average call duration, customer experience and call abandonment rates for contact centres and UC providers. Audio quality can be lost for all sorts of reasons. One of the most common situations is where your telephone provider is working with multiple partners (downstream carriers) and one or more is compressing files to save bandwidth (transcoding).


How can I measure audio quality in a telecoms network? 

The only way to truly test the audio quality your customer is experiencing (and hence their perception of your brand when they call you) is to dial your numbers from the same country and same telephone lines as them. This gives you the outside-in view of your customers’ experience, and can alert you to customer-impacting issues that you would otherwise be completely unaware of.


What is PESQ?

Spearline relies on an objective, recognised industry standard audio quality measure called PESQ (Perceptual Evaluation of Speech Quality) in our global in-country number testing. PESQ is an ITU (International Telecommunication Union) standard for measuring audio quality and it takes into consideration characteristics such as:

  • Audio sharpness
  • Call volume
  • Background noise
  • Variable latency or lag in audio
  • Clipping
  • Audio interference

With PESQ, audio quality on phone calls – mobile or fixed-lines; toll and toll-free services, VoIP or PSTN – can be assessed to an agreed international standard. There’s no ambiguity, so you know exactly how your phone services are performing.


Spearline’s audio quality test

Our audio quality test is used to proactively monitor the availability, and quality, of your global toll and toll-free numbers. It is used to gain real-time alerts on customer-impacting issues and to hold carriers to SLAs. In many cases, it is also used to demonstrate your quality standards to your customers using independent and objective measures.


How does the audio quality test work?

The test compares an audio output (at the phone line’s ‘listener’ end) to the original voice file (played on the ‘talker’ side) to create a fully unbiased and objective indicator of the actual audio being heard. This is more accurate than other methods of audio quality measurement which often rely on audio quality predictions based on network performance. PESQ returns a score from -0.5 to 4.5, with higher scores indicating better quality.

The CDR (call details record) information we provide, along with the objective PESQ score allows our customers to more effectively manage SLA’s with carriers and make key routing decisions for infrastructure. Audio quality performance can also be benchmarked on a per country basis using Spearline data. This allows organizations to view telephony performance in the context of the industry average.

These insights are invaluable to organizations as they:

  • Are based on real audio samples instead of just looking at the internal network.
  • Confirm that audio quality is performing at the highest standard for your business critical numbers.
  • Identify connection or audio quality issues, with clear steps to resolution, before they can significantly affect your customers’ experience.
  • Allow you to make more informed call-routing, and carrier-sourcing decisions.

Here’s a brief outline of how the test works:

  • Spearline in-country server dials your toll/toll-free contact number. We use standard phone lines with ISDN signaling to replicate your customers’ experience.
  • Spearline server sends a DTMF tone which your IVR is configured to recognise (eg ‘9-8-7-5-7’)
  • IVR connects the test call to a pre-loaded audio (WAV) file. The WAV file is played back over the line, recorded on the Spearline server and then analyzed to generate an audio quality score.

What does the Spearline audio quality test measure?

Spearline’s audio quality test presents data on several key metrics, including:

  • Connection success or failure
  • Post dial delay (the time between the number being dialled, and the call being answered)
  • DTMF (touch tone) functionality
  • IVR response
  • Audio quality


Find out more

Please check out our test types page if you would like to find out more about the Spearline audio quality test and how your organization can benefit. Alternatively, if you are an existing Spearline customer, and you would like to add the audio quality test to your existing portfolio, please do not hesitate to contact your Customer Engagement Mananager or our 24/7 Support team at who will be more than happy to assist.


New to Spearline?

Spearline proactively tests and monitors toll and toll-free numbers for connectivity, audio quality and other telecoms aspects, globally. Our SaaS-based platform ensures an organization’s telecommunication infrastructure is performing to its highest standards, as it gives peace of mind that numbers are performing as they should be, and dramatically reduces the time spent troubleshooting. If you are interested in benefiting from our platform, please get in touch with us.

Customer Contact Central

Spearline provides first rate audio quality testing tools that allow us to enhance our customers’ experience. I cannot overstate the value of their solutions.

Rosie Scott,
PGI Director of Vendor Management – EMEA PGI

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