Choppy or Robotic Audio on VoIP Calls

When Your Phones Sound Bad: Part 1 of 12

Choppy audio is probably the most common VoIP complaint there is. The person on the other end sounds like they're talking through a fan, or their words are breaking up into fragments, or the audio has a stuttering, robotic quality that makes it hard to follow the conversation. It might happen on every call or just some calls. It might last for the entire conversation or come and go in waves.

The frustrating thing about choppy audio is that it has multiple possible causes, and those causes can live in different parts of the chain. But the list of likely culprits is actually shorter than most people think, and you can work through them systematically.

What's actually happening

When audio sounds choppy or robotic, what you're hearing is the result of one of two things: packets arriving late (jitter) or packets not arriving at all (packet loss). Sometimes both.

VoIP calls work by breaking audio into small chunks, typically 20 milliseconds each, packaging each chunk into a data packet, and sending those packets across the network. On the receiving end, the phone collects those packets and plays them back in sequence to reconstruct the audio. If a packet arrives late or doesn't arrive at all, the phone has to either skip that chunk of audio or try to guess what the missing audio sounded like. Neither option sounds good. Skipped chunks produce gaps and choppiness. Bad guesses produce that distinctive robotic or warbling quality.

Check 1: Is it happening on all calls or just some?

This is the first question to ask because it immediately narrows the investigation.

If every call sounds choppy, the problem is almost certainly on your end. Something in your local network, your internet connection, or your phone equipment is consistently degrading the audio. This is actually the easier scenario to troubleshoot because the problem is reproducible and within your control.

If only some calls are choppy, the pattern matters. Calls to a specific person or number might indicate a problem on the far end. Calls that are fine in the morning but bad in the afternoon might indicate ISP congestion during peak hours. Calls that are choppy only when certain other activities are happening (large file transfers, cloud backups, video streaming) point to bandwidth saturation on your network.

Check 2: WiFi

If the phone experiencing choppy audio is connected over WiFi, that's the first thing to address. WiFi and VoIP are a bad combination, and this is the single most common cause of choppy audio in offices that use wireless phones, softphones on laptops, or desktop phones connected through WiFi adapters.

WiFi introduces jitter because the wireless medium is shared and contended. Your phone's packets have to compete with every other device on the same WiFi network for airtime. When the access point is busy serving other clients, your phone's packets wait in a queue. That waiting introduces variable delay, which is jitter by definition. WiFi also retransmits packets that get corrupted by interference, which adds more variable delay.

The fix is simple in concept: use a wired Ethernet connection for any device that carries voice. Plug the phone into a switch port with a cable. If the phone is a softphone on a laptop, connect the laptop to Ethernet when making calls. This single change eliminates WiFi as a variable and resolves the problem in a remarkable number of cases.

If wired connections aren't practical (some office layouts make it genuinely difficult), you can improve WiFi performance for voice by ensuring the access points support band steering to 5 GHz, reducing the number of clients per access point, enabling WMM (WiFi Multimedia) QoS on the access points, and placing access points close enough that signal strength is strong throughout the office. But a wired connection will always be more consistent than WiFi for voice traffic.

Check 3: Bandwidth saturation

Your internet connection has a limited amount of capacity, and when that capacity is fully used, new packets get delayed or dropped. This affects everything on the network, but voice traffic shows the symptoms first because it's the most sensitive to delays and losses.

The direction that matters most for voice is upload. When you're on a call, your outbound audio is traveling on your upload bandwidth. If your upload is saturated by other traffic, your voice packets get queued behind everything else, or they get dropped entirely.

This is especially common on connections with asymmetric speeds, which includes most cable and DSL connections. A cable plan might give you 300 Mbps download and 20 Mbps upload. The download is rarely the problem. But 20 Mbps of upload can get saturated faster than you'd expect when you add up VoIP calls, video conferences, cloud backups, file uploads, email attachments, and all the other outbound traffic from your office.

To check for this, run a speed test during the times when choppy audio is occurring. Pay attention to the upload speed specifically. Compare it to what you're paying for. If the upload speed is significantly lower than expected, your connection may be congested. If the speed looks normal on the test, try running the test while the problem is actively happening, because a speed test taken during a quiet moment won't show congestion that only occurs during busy periods.

Also check whether any scheduled tasks are consuming upload bandwidth during business hours. Cloud backup services, file sync applications, software update distribution, and security camera footage uploads are common culprits. These can often be scheduled for off hours or throttled during business hours.

Check 4: QoS (Quality of Service) configuration

QoS is a feature on routers and managed switches that prioritizes certain types of traffic over others. When QoS is configured for VoIP, the router identifies voice packets and gives them priority over other traffic. This means that even when the connection is busy, voice packets get through without waiting in line.

If your router supports QoS and it's not configured, voice packets are treated the same as everything else. During periods of congestion, voice packets get delayed right alongside file downloads and web browsing. Configuring QoS to prioritize voice traffic can make a significant difference on connections that are anywhere near their capacity limits.

Most business routers support some form of QoS. The implementation varies by manufacturer, but the general concept is the same: you define a rule that identifies VoIP traffic (usually by port range, DSCP marking, or the IP address of the phone system) and assign it to a high priority queue. The router then ensures that high priority traffic is sent before lower priority traffic when there's contention for bandwidth.

If your PBX or phones tag voice packets with DSCP markings (most do by default, using EF, Expedited Forwarding, which is DSCP value 46), your router needs to be configured to honor those markings and prioritize accordingly. If the router ignores DSCP markings, the tagging is meaningless.

Check 5: Local network issues

Problems inside your office network can cause choppy audio even when your internet connection is fine. The chain between your phone and your router includes Ethernet cables, switches, and potentially other network equipment, and any of these can introduce problems.

Bad cables. An Ethernet cable with a damaged connector, a kink, or internal wire damage can cause packet loss and errors that affect voice quality. These problems can be intermittent, showing up when the cable is moved or when temperature changes cause slight expansion and contraction. If choppy audio is isolated to a specific phone, try replacing the Ethernet cable.

Overloaded switches. Cheap, unmanaged consumer switches don't handle traffic prioritization. If a switch is handling traffic from a busy computer and a phone at the same time, the phone's packets can be delayed. Business grade managed switches support VLANs and QoS, which allow you to separate voice traffic onto its own virtual network segment with priority handling. If you're running phones and computers through the same consumer switch, upgrading to a managed switch with VLAN support is one of the more effective improvements you can make.

Duplex mismatches. If a switch port is running in half duplex mode (which can happen when auto negotiation fails), the port can only send or receive at any given moment, not both simultaneously. This causes collisions and retransmissions that introduce jitter. Check that all switch ports connected to phones are negotiating full duplex at 100 Mbps or 1 Gbps.

Check 6: The phone itself

Sometimes the phone hardware is the issue. A phone with a failing network interface can cause packet loss at the device level. A phone that's overheating (placed on top of a warm docking station or in direct sunlight) can behave erratically. A phone with outdated firmware might have known bugs that affect audio processing.

Check whether the phone manufacturer has released firmware updates. VoIP phone manufacturers regularly release updates that fix audio processing bugs, improve jitter buffer algorithms, and address codec issues. Running old firmware means running known problems that have already been fixed.

Check 7: Your internet connection

If you've checked everything on the local side and the problem persists, the issue may be with the internet connection itself. As covered in the Getting the Internet Right series, not all internet connections are equally suitable for voice traffic.

Cable connections can experience congestion during peak hours because of their shared bandwidth nature. DSL connections can develop intermittent issues from degraded copper. Even fiber connections can have problems if there's an issue with the handoff equipment or the provider's backbone.

Run an extended ping test to a reliable external host (your VoIP provider's server address is ideal) and look at the results over a period of minutes. Better yet, run our VoIP quality test, which sends traffic that matches actual voice patterns rather than ICMP pings. If you see latency spikes above 100 milliseconds, jitter exceeding 20 to 30 milliseconds, or packet loss above 0.5%, your internet connection is likely contributing to the problem.

If the connection consistently shows poor metrics during business hours but looks fine at night, that's a congestion pattern and it points to either your ISP's infrastructure being overloaded or your own outbound traffic saturating the upload.

Working through it systematically

The key to solving choppy audio is working through these checks in order rather than guessing. Start with WiFi (because it's the most common cause and the easiest to test by plugging in a cable). Move to bandwidth and QoS. Then check local network equipment. Then look at the phone hardware and firmware. Then evaluate the internet connection.

Each check is a process of elimination. When you eliminate a possible cause, you've narrowed the problem. When you find something that's clearly wrong, fix it and test again before continuing down the list. Many choppy audio issues have more than one contributing factor, and sometimes fixing the biggest one is enough even if a smaller issue remains.

Next up: One Way Audio: I Can Hear Them But They Can't Hear Me, the second most common VoIP complaint and the specific causes behind it.