Troubleshooting VoIP Call Quality Issues

Unfortunately, you do sometimes encounter issues with VoIP. If you’re reading this blog post, it’s safe to assume that you’re having issues at the moment. VoIP call quality can drop for numerous reasons, so I’ll cover all the potential issues in this blog post.

Here are the typical VoIP call quality issues. Click the issue that you’re having to be taken to the resolution.

If you don’t see your issue above, please leave a comment at the end of this blog post. I’m happy to advise on how you can resolve your issue. For now, I’m going to explain these call quality issues in more detail, talk through what could be causing them, and detail how you can fix them.

Choppy Audio With Lag on VoIP Calls

We’ve all experienced those poor phone calls where choppy audio results in you missing some really important information. And there are fewer things more uncomfortable than waiting on the person on the other end of the phone to answer you because you’re experiencing lag. So what causes this issue and how can you resolve it?

This issue can be caused in numerous ways. The primary reason for choppy audio with lag is your bandwidth capacity. If you don’t have enough upload or download capacity, this can cause choppy audio with lag for one or both parties. The only problem is determining whether it’s your upload or your download bandwidth that’s causing the issue. So here’s how to determine what the problem is.

In most cases, the following will be true:

  • If you are hearing the other person cut out and their audio is lagging, it means your download bandwidth is the issue.
  • If the person you’re calling says your audio is choppy and lagging, it means your upload bandwidth is the issue.

If you’re experiencing both of the above, you’re going to need a new internet connection altogether. I wrote a blog post entitled How Much Bandwidth Do I Need For VoIP? Which, surprisingly, explains how much bandwidth you need for VoIP. It’s well worth a read if you’re unsure on whether your connection is suitable for Voice over IP. But there are some other causes of choppy audio with lag to be aware of too.

For example, I’ve seen scenarios in the past where provider’s introducing new features has caused call issues. But the most likely reason for choppy audio with lag is lack of bandwidth, either up or down.

It’s not difficult to determine how you resolve this issue. One easy resolution would be upgrading your internet connection. However, that’s not always a possibility. Another possibility is changing to a different codec that requires less bandwidth to work. You wouldn’t personally be able to make this change unless you manage your telephone system yourself. However, your provider can make the change for you and you might see a difference in call quality. To find out more about what codecs are and how they work, I’ll refer you to my blog post What Is A VoIP Codec? In this blog post, I explain what a VoIP codec is, discuss the codecs that are available, and explain how much bandwidth each codec needs. It’s well worth a read if you think your broadband is the issue here.

Low-Quality Audio on VoIP Calls

Low-quality audio is very frustrating. Again, having to ask the person on the other end of the phone to repeat themselves time and time again is awkward. Frankly, it isn’t very professional and shines a bad light on your business if there’s something wrong with your telephone system. So, what typically causes issues with low-quality audio and how do your resolve it?

Yet again, this is likely to be a bandwidth issue. If your connection doesn’t have any bandwidth available, audio quality is going to be very poor. This might be an issue on your end or an issue on the end of the person you’re talking to. There are typically multiple ways to get around this issue.

First and foremost, you might want to consider upgrading your internet connection. If you’ve noticed that your network performance is very poor in general, upgrading your connection could help. Alternatively, there might be some optimisations possible to save yourself spending money on upgrading your connection.

For example, is your VoIP telephone system currently on its own VLAN? By placing your VoIP phones on their own VLAN, you’ll separate all VoIP traffic from the rest of your traffic. An optimisation such as this enables you to prioritise VoIP traffic over anything else, hopefully preventing low-quality audio calls in the future. If you look after your network yourself, this is a quick change to enact. If a business or a member of your team is responsible for looking after your network, find out if your VoIP is on its own VLAN.

The Call Connects With No Sound on VoIP

Are you having an issue where calls connect with no sound? Again, this is another thing that can make you sound daft. The last thing you want is to be shouting, “can you hear me?” down the phone at a customer! Fortunately, there’s one issue that typically causes this: your firewall blocking RTP packets.

This isn’t a particularly rare issue and it all comes to:

  • The type of firewall you’re using
  • The way your firewall is configured

RTP stands for Real-time Transport Protocol. RTP is one of the technical foundations of VoIP, along with protocols such as UDP and SIP. RTP is responsible to carrying media streams (in this case, audio). As you can imagine, having a firewall that stops RTP packets from flowing can be very problematic. And that’s likely what’s causing the issue with the call connecting but you being unable to hear audio.

Fortunately, this problem is easily resolved and won’t cause your business too much of a problem. It’s sometimes as simple as opening a port on your firewall to allow RTP packets to flow without interruption.

Calls Regularly Dropping VoIP

Calls frequently dropping is one of the most frustrating VoIP issues that you can come across. Again, this is another issue that’s so frustrating and can make your business look bad.

There are several issues that could be the cause of your calls regularly dropping, such as:

  • Bandwidth limitations: Is this Déjà vu? It might feel like it because bandwidth limitations is the cause of so many VoIP problems. Bandwidth limitations can cause your calls to drop suddenly, particularly if your VoIP traffic isn’t segregated from the rest of your network traffic using a VLAN.
  • Incorrectly configured QoS settings: QoS, which means Quality of Service, is a term that covers settings that enable you to prioritise voice traffic over any other type of traffic at router-level. If you haven’t configured your Quality of Service settings, or you’re not using them at all, this could be another reason for VoIP calls regularly dropping.
  • Defective devices: If you know that bandwidth limitations and incorrectly configured QoS settings aren’t causing your calls to drop, it could be a fault with the device you’re using to make calls. Unfortunately, it’s not unusual for IP phones to develop issues over time; this is a particular consideration if you’re using cheap devices, actually. Test out a new device and see if the issue is still occurring. If it is, consider the reasons I’ve given above. If not, you know that your device is faulty.

Calls Immediately Going To Voicemail VoIP

Are all your calls going straight to voicemail? This is obviously a big issue, as it might result in you letting down customers and missing out on new business. If calls to your phone number are immediately going to voicemail, there are a few variables that could be causing the problem.

  • You have call forwarding set up: This is a simple thing that you can quickly fix, fortunately. If all calls to your main office number or DDI are going straight to voicemail, it’s possible that you have call forwarding set up. You can set up call forwarding up at device-level or on the interface you use to manage your system, so check both. It’s possible that call forwarding has been set up on your line without you being aware, so it’s well worth checking.
  • Your phone’s set to DND: Is it only calls to your phone specifically that are going straight to voicemail? The problem could be as simple as you having the DND feature on your phone switched on. On IP phones, this will stop you from receiving any calls and send all callers to voicemail, depending on how your system is configured. The fix for this is simple: turn off the Do Not Disturb setting!
  • Unregistered device: If your phone is no longer registered with your VoIP provider, this would cause all calls to your device to go straight to voicemail. A glitch could cause your device to become unregistered, so it’s not beyond the realms of possibility. When you log into the interface that you use to manage your VoIP system, you’ll likely get some kind of notification or warning if your device isn’t registered anymore.

Jack Mitchell

Jack Mitchell has been the Operations manager at telecoms and MSP Optionbox for more than 4 years. He has played a crucial role in the company, from marketing to helpdesk, and ensures that the IT requirements of over 300 clients are continuously met. With his innate passion for technology and troubleshooting and a particular interest in Apple products, Jack now delivers the most comprehensive tech guides to make your life easier. You can connect with Jack on LinkedIn.

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