VoIP call quality explained

The four factors that determine call quality

A VoIP call travels as a stream of small data packets across the internet. The quality of what you hear depends on how reliably those packets arrive. Four network measurements describe that reliability, and understanding each one tells you both what can go wrong and how to prevent it.

Bandwidth: rarely the problem you think it is

Bandwidth is the factor most people worry about first, and it is almost never the real issue. A single VoIP call uses roughly 100 kbps each way. Five simultaneous calls need around 0.5 Mbps. Even a basic business broadband line at 20 Mbps has capacity for dozens of calls with bandwidth to spare. Our guide on internet speed for VoIP goes into the numbers in detail.

The one way bandwidth does cause problems is saturation. If someone on your network starts a large file upload or a video streaming session, it can eat a significant portion of your available connection and cause everything else, including calls, to fight for what is left. The solution is not necessarily more bandwidth: it is ensuring voice traffic is not competing with bulk data at the same time. That is what QoS is for.

Latency: the delay in the conversation

Latency is the round-trip time for data between you and the person you are calling. On a good broadband connection, this is typically 20 to 50 milliseconds, which is imperceptible. Problems start when latency rises above roughly 150 milliseconds one-way. At that point there is a noticeable pause between you speaking and the other person hearing you, and conversations start to feel awkward as people talk over each other because neither side can tell when the other has finished.

Most broadband connections have low latency by default. The exceptions are older ADSL lines, congested networks, and satellite broadband. If you are on a fibre connection and experiencing high latency, the cause is usually within your own local network rather than in the broadband itself: a router that is overloaded, a switch with a configuration problem, or a device generating traffic that pushes everything else to the back of the queue.

Jitter: the main cause of choppy audio

Jitter is variation in how long packets take to arrive. Imagine speaking in a steady rhythm but the packets carrying your voice arriving unevenly: some come quickly, some are delayed, some arrive out of order. The phone system reassembles them as best it can using a jitter buffer, which deliberately holds packets for a brief moment to smooth out the gaps. When jitter is mild, this is transparent. When it is severe, the buffer cannot keep up, and the audio on the receiving end becomes choppy, robotic or distorted.

Jitter is almost always a local network problem. Wi-Fi is the most common culprit: a wireless channel shared with many devices, or with interference from a neighbouring office's network, introduces the kind of inconsistency that makes calls sound poor. Switching from Wi-Fi to a wired connection frequently resolves jitter problems immediately. A business-grade router also helps, because consumer routers can struggle under load and introduce their own latency spikes when multiple devices are active at the same time.

Packet loss: dropouts and missing words

Packet loss is the most directly damaging quality problem. Unlike jitter, which can be softened, a lost packet is simply gone, and the audio that should have been in it disappears. Even a loss rate of 1% is noticeable on a call. At 5%, conversations become difficult to follow.

Good-quality broadband has very low packet loss, often below 0.1%. Problems arise on congested connections, faulty network equipment, or poor Wi-Fi coverage. If you are experiencing dropouts on calls, the first thing to check is whether the problem is on Wi-Fi: move to a wired connection and see if it resolves. If packet loss persists on a wired connection, it is worth checking whether the issue is on the line itself, which your broadband provider can test, or within your router and local network hardware.

Practical steps to keep calls clear

The good news is that most call quality problems are fixable, and the fixes do not require specialist equipment or expensive upgrades. The following steps address the most common causes.

Use a wired connection for desk phones. A network cable eliminates the jitter and packet loss that Wi-Fi can introduce. For a phone on a fixed desk, there is no practical reason to use wireless. IP desk phones plug directly into a network switch or into the spare port on a PoE switch that also powers the phone.

Choose a good router. A consumer router bought with a home broadband package is often not designed to handle business-level traffic loads. A business-grade router manages traffic more predictably under load, which means lower jitter and fewer packet spikes when several people are using the network at once.

Enable QoS where you can. Quality of Service is a setting that tells your router to give voice traffic priority over other data. When someone starts uploading a large file or streaming a video, QoS ensures that call packets still get through on time. Many business routers include QoS settings; the exact configuration depends on your router model.

Avoid saturating the line during calls. Large uploads are the most common culprit. If your team regularly uploads large files to cloud storage or transfers video, scheduling those transfers outside core calling hours is a simple way to protect call quality without any technical changes.

Use a decent headset. The network delivers clear audio to your device, but a poor microphone or speaker sends back distorted or noisy audio to the other person. A headset with a quality microphone removes ambient noise and echo at the source. This is one of the cheapest and most effective improvements available.

For most businesses on modern broadband, following these steps is enough to make calls sound consistently clear. If problems persist after checking the local network, the next step is to ask your broadband provider to run a line test, or to speak to your phone system provider about the specific symptoms you are seeing. VoIP quality issues are diagnosable: there is almost always a clear cause and a clear fix.

Where Voxora fits

Voxora's cloud phone system uses modern voice codecs and routes calls through resilient infrastructure, so the system itself is not a quality bottleneck. If you do experience call quality problems, the cause will be on the path between your device and the internet, and the steps above are where to look first.

You do not need an engineer on site to set up Voxora or to change your call routing. Everything is managed from the browser, and real UK support is available if you need help diagnosing a quality issue.