The diagnostic order that finds it
VoIP carries voice as data, so voice quality is network quality. The culprits, in real-world order: WiFi handsets or apps — wireless jitter mangles voice; the first test is always 'does a wired phone do it too?' (usually not). No QoS — voice packets queueing behind someone's cloud backup causes the classic 3pm robot voice; business routers fix this with voice prioritisation, ISP freebies often can't. An overloaded or failing router — years-old ISP kit produces exactly these intermittent symptoms. The line itself — congested FTTC in the evening, or a genuine fault. One-way audio specifically — almost always a router NAT/SIP setting, maddening to users, minutes to fix for engineers who've seen it a thousand times.
The fixes, and who should own them
Wired connections for desk phones (or properly designed WiFi if wireless is unavoidable), a business-grade router with QoS shaping voice first, bandwidth sanity-checked against real needs, and monitoring that measures jitter and packet loss rather than guessing. The honest structural point: when one provider supplies both the connectivity and the phones, 'is it the internet or the phone system?' stops being a two-supplier blame loop and becomes one engineer's afternoon. That's not a sales line; it's why our quality tickets resolve in hours.
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Frequently asked questions
Why do calls sound fine in the morning and robotic at 3pm?
Congestion — voice queueing behind data at busy times. QoS prioritisation on a proper router fixes it; contended lines may also need upgrading.
Why can callers hear me but I can't hear them?
One-way audio is a router NAT/SIP configuration issue in almost every case — a known fix, minutes for the right engineer.
Is our internet 'too slow' for VoIP?
Almost never — calls use ~0.1 Mbps each. Stability and prioritisation matter, not headline speed. The diagnosis is about jitter, not megabits.