For any network engineer, tackling poor voice quality on a VoIP network is something that can become a nightmare.  The aim of this article is to provide a guide that will help troubleshooters to promptly diagnose the problem, discover its cause, and to resolve the issue as quickly and efficiently as possible.

Poor voice quality can be problematic

Intermittent network problems like poor voice quality are almost always more difficult to deal with because of their unpredictable nature.  It is much easier to diagnose and resolve a complete loss of connectivity rather than intermittent network communication.  There are several reasons for this and it’s important to understand them to more efficiently troubleshoot such issues.

User experience is subjective

Most problems involving poor voice quality are reported by the users themselves.  This can be problematic because the user’s experience is subjective.  People tend to use simplistic all-encompassing wording such as “my phone doesn’t work” to describe their problem, which isn’t very useful for the troubleshooter.  Even if they’re more detailed, most users simply don’t know how to describe the problem they are experiencing in a way that will be helpful to you to resolve the problem.  

Intermittent problems often have multiple possible causes

Unlike a complete communication failure, poor voice quality can be caused by a whole series of sources.  Network congestion, codec incompatibility, overtaxed VoIP server resources, and the use of network services such as network address translation or a firewall can adversely affect what a caller may experience.  This variety of possible causes can overwhelm a troubleshooter and adversely delay the resolution of the problem.

Troubleshooting steps

When a report of poor voice quality comes in, inexperienced troubleshooters will understandably feel overwhelmed asking a question like “what do I do now”?  This is to be expected, as there is no readily recognizable first step to take in such a situation.  For this reason, we’ve put together a series of actions you can initiate that will help you zero in on the cause and resolve it within a reasonable amount of time.

This procedure is by no means a “one solution fits all” resolution to every problem, but it will give you a starting point from which you can develop a solution strategy.  As you gain more experience, many of these procedures become second nature, as your own critical thinking kicks in.

Understand the problem

The most crucial first step is to understand the problem.  You must be able to cut through the subjective report of the user and reach a more objective understanding of what is going on.  There are two primary ways to do this:

  • Lead the user to provide the essential information by asking them pertinent questions. The best troubleshooters ask a minimal number of questions to obtain a maximum amount of information.  Keep in mind that this skill is honed with practice.
  • Experience the problem for yourself.  If possible, ask the user to reproduce the problem and be on hand to hear what the user hears.  Experiencing firsthand goes a long way in understanding the problem.

Determine the scope of the problem

It’s one thing for a single user to be experiencing poor voice quality and another if this is happening to tens or even hundreds of users.  This distinction is not only an indication of the ultimate cause of the problem, but it also affects the urgency of resolving it.   This is why determining the scope of the problem is so important.

By asking additional questions, determine if the problem is limited to a single user, to a small number of localized users, or to all users on the network.  Also, determine if the problem is observed on all calls, or only on a particular kind of calls, such as internal calls, or calls to the PSTN.  You may need to perform some experimentation yourself to determine this.

This will also depend on the type of service that you are provided with.  If using a service such as Ooma, you may find that problems exist only on calls to remote users, or just for calls terminating on physical SIP-based phones.

What’s the next step?

Once you have obtained a clear understanding of the problem and the scope of users it affects, it’s a good idea to make a written record of what you find.  Nothing official, just jot down a brief description.  

The next steps will help you to zero in on the source of the problem.  Typically, poor voice quality involves one of the following two categories:

  1. Phone model and software – If you are using a physical IP phone, it could be a hardware-related issue.  If you’re using a softphone app on a mobile device or computer, it may be related to the software version being used.
  2. Network related – This category includes problems occurring on the network infrastructure involving things like excessive jitter, packet loss, and latency.

Categorizing the problem

After going through the procedure of questioning users, experiencing the problem for yourself, and determining its scope, you’re probably already in a good position to accurately identify which category the problem belongs to.  In general, you will find the following:

Phone model and software related issues:

  • Quality degradation manifests itself in the same way on multiple devices of the same type and/or of the same software type and version
  • For hardware devices, white noise or static may indicate a problem with a headset or a handset cable
  • The scope of such problems is usually limited to a single individual or a few users

Network related voice quality issues:

  • Strange voice timbre including a metallic-sounding voice
  • Intermittent gaps in the voice
  • Voice is heard in only one direction of a conversation
  • Poor quality only on certain types of calls, such as those to the PSTN
  • Typically not isolated to a single user, but involves groups of people with similar network characteristics such as remote users, or those connected to the same network segment within an enterprise

Dealing with phone model and software related problems

How you deal with such problems depends upon whether you are using a physical IP phone on a desk, or if you are using a cloud-based service such as Aircall, which leverages smartphones, desktops, and laptops.  If you’re using physical IP phones, an indicative list of steps you could take is as follows:

  • Attempt to replicate the problematic behavior on other phones of the same model and firmware version.  If it can be replicated, it is likely a firmware or hardware problem.  If not, then it may not be a problem with the particular type of phone.
  • If you’ve ruled out firmware or hardware, determine if the problem is related to the headset, handset, or network cabling.  Attempt to replace cables to see if this affects the quality.
  • If the problem persists, then as a last resort, it may also be helpful to reach out to your hardware vendor, to determine if there is a hardware fault in your device.

If you’re using a software-based system like Freshcaller, then it would be a good idea to consult their online knowledge base to see if similar problems have been faced and resolved by other users.  As a second step, approaching the service provider’s helpdesk staff can also be helpful and may deliver a quick fix to any issues you may be facing.

Dealing with network-related problems

If you’ve ruled out software or hardware-related issues, then the next step is to examine your network.  Device and software issues are troubleshot at the devices themselves, whereas network issues must be examined in relation to the network being used.  Some steps that will help in your investigation include:

  • If the problem persists for remote users, verify that these people have enough bandwidth to ensure a steady flow of voice traffic.  
  • If the problem is concentrated among internal users of the enterprise network, the network should be examined for bottlenecks and congestion.  Use network monitoring tools to examine if phenomena such as jitter, latency, and packet loss are being experienced.  If this is the case, it may be beneficial to employ Quality of Service mechanisms on the network infrastructure.
  • If the problem is isolated to particular types of calls, such as those to the PSTN, then an examination of the network where the calls reach the outside world is probably necessary.


Troubleshooting problematic voice is never easy.  However, having a starting point from which to begin your diagnosis is very comforting, and can ease your mind by quickly putting you onto the path of resolving problems that arise.  And, as with most things in life, the more often you do it, the more proficient you become.