VoIP call quality problems: causes and fixes

Start here: which problem do you have?

Most VoIP problems fall into one of five patterns, and each has a different cause. Identify yours first — it saves a lot of guessing.

• Choppy, robotic or breaking-up audio → network congestion, jitter or weak Wi-Fi.
• Echo → usually the handset, headset or speakerphone volume, sometimes the far end.
• One-way or no audio → router or firewall blocking the audio stream (often SIP ALG).
• Calls dropping → at a regular time: a router or firewall timeout. At random: an unstable connection.
• Delay — people talking over each other → high latency, often from a congested connection or a VPN.

1. Choppy or robotic audio

Voice is sent in a steady stream of small packets. If some arrive late or not at all, you hear gaps and a metallic sound. The usual causes:

• Someone is using the whole connection — a large upload, cloud backup or video stream. Upload is often the bottleneck on business NBN plans.
• Weak or crowded Wi-Fi — desk phones and laptops on Wi-Fi are far more sensitive than cabled ones.
• No voice priority — the router treats a phone call the same as a file download.

Fixes: plug desk phones into a network cable where you can, turn on QoS (traffic priority) for voice on your router, schedule big backups out of hours, and check that your plan’s upload speed suits the number of people working at once.

2. Echo

If you hear your own voice, the echo is usually coming from the other person’s device — a speakerphone or a handset turned right up. If they hear themselves, check your end: lower the speakerphone volume, try the handset or a headset, and make sure a headset isn’t sitting too close to its microphone.

3. One-way audio or no audio

The call connects, but sound only goes one way. This is nearly always the router or firewall:

• SIP ALG — a router feature meant to help VoIP that often breaks it. Turning it off is the single most common fix.
• Firewall rules — a strict firewall can block the audio ports while still letting the call set up.
• Two routers in a row — a modem doing routing behind another router can confuse the traffic. Put one into bridge mode.

4. Calls dropping

Note when the calls drop. Regular drops (always around the same length of call) usually mean a router or firewall is closing the connection after a set time — a configuration change fixes it. Random drops point to the connection itself: check for internet dropouts, a failing cable, or Wi-Fi roaming between access points mid-call.

5. Delay and people talking over each other

A noticeable lag usually comes from a congested connection, a VPN routing calls through another location, or Wi-Fi interference. Calls hosted in Australian data centres keep the distance short; the remaining delay is almost always local.

A quick checklist before you call for help

• Does it happen on every phone, or one? (One phone → that device, cable or Wi-Fi spot.)
• Does it happen at certain times of day? (Busy times → congestion.)
• Is the phone on Wi-Fi or a cable? Try a cable.
• Has anything changed recently — a new router, NBN plan or firewall?
• Restart the phone and the router, then test again.

Related: why is my business internet slow? and what happens to your phones during an outage.