The Monday call starts fine. Three minutes in, the customer's voice turns into clipped syllables — every third word missing — and then the line drops. You call back on your mobile and it's perfect. Nobody can explain why the office phones sound like a walkie-talkie in a stairwell.
Bad VoIP audio is not mysterious. Each symptom points at a specific part of your setup, and most of the fixes are settings, not hardware. Work through this and you'll either fix the calls or walk away with evidence your provider cannot shrug off.
What the symptom is telling you
A VoIP call slices your voice into tiny packets and fires them across the internet dozens of times a second. How a call fails tells you where that journey is breaking down.
- Choppy, robotic, words dropping out. Packets are going missing (packet loss) or arriving in uneven clumps (jitter), so the phone briefly has nothing to play. A network problem — yours, your provider's, or the line between.
- Echo. You hear your own voice a beat later. Almost never the network — it is a device and acoustics problem, covered below.
- One-way audio. You hear them, they can't hear you, or the reverse. The classic router failure: the call setup and the audio itself travel separately, and your router or firewall lets one through while blocking the other.
- Calls that drop at the same minute mark. A router feature is timing out or rewriting the connection mid-call — see SIP ALG below.
The bandwidth myth
The first instinct is a faster internet plan. It almost never helps, because a call uses a fraction of the bandwidth of one video stream. What voice needs is not volume but consistency — small packets arriving on time, every time. A download doesn't care if its data arrives in bursts; a call cannot wait — a late packet belongs to a moment that has already been played. That variation in arrival time is jitter, and it is why a fast connection can carry terrible calls while a modest one sounds fine.
It is also why calls collapse at predictable times. Someone starts a cloud backup or a screen-share, the upload side of your connection — nearly always the narrow direction — fills, and voice packets queue behind the bulk traffic. The speed test you run afterwards looks great — it measures the size of the pipe, not whether your packets kept their appointments.
The fixes that clear most cases
Turn off SIP ALG first
Most routers ship with a feature called SIP ALG switched on. It was meant to help phone traffic through the router by rewriting it in flight, and in practice it is the classic villain of VoIP: one-way audio, phones that unregister at random, calls that drop at the same minute mark. Nearly every provider tells you to disable it. Look in the router's settings for SIP ALG, SIP Helper or SIP Transformations, switch it off, and reboot the phones. If the router's menus defeat you, a technician on Koadi can find the setting over a screen-share in a few minutes.
Get the phones onto cables
Wi-Fi and voice are a bad marriage. Wireless links quietly lose and resend small amounts of data all day; a laptop never notices, but a call cannot replay a moment that has passed. Desk phones that do business all day belong on cables. Softphones over Wi-Fi are fine for occasional use; when quality matters, the cable wins. If the wireless itself is flaky, that is its own repair: see Wi-Fi keeps disconnecting.
Give voice its own lane
Quality of Service — QoS — is a router rule that lets phone traffic jump the queue. Think of your connection as a road: QoS paints a bus lane on it, and the phones are the buses. When the office is uploading backups and running video meetings, voice goes first — voice packets are tiny and impatient, and everything else can afford to wait a few milliseconds. Most business-grade routers do this well; consumer routers range from decent to decorative.
Treat echo as a device problem
Ask which side hears the echo, because the side that hears it is usually not the side causing it — your voice comes out of their speaker, into their microphone, and back to you. The fixes, in order: turn the speakerphone volume down, switch to a handset or headset, move the microphone away from the speakers. Echo on every call, whoever is on the other end, points at your own equipment — a worn headset, an old analog adapter, or outdated handset firmware.
Build evidence your provider will respect
“Calls are bad sometimes” gets you sympathy and a suggestion to reboot the router. A pattern gets you an engineer. For one week, log every bad call:
- Date and time to the minute — providers can pull the statistics for an exact call
- Which extension or user, and whether the call was inbound or outbound
- What failed, and in which direction — they couldn't hear you, you couldn't hear them, or both sides broke up
- Wired or Wi-Fi, and what else the office was doing — a backup, a video meeting, lunchtime streaming
The direction column does diagnostic work on its own. One-way failures point at your router; both directions turning to gravel at the same hour every day points at congestion — often a scheduled task eating your upload.
Working out whose fault it is
Before you argue with anyone, split the problem in half.
- Move one phone to a different network. Run a handset or softphone at home or on a mobile hotspot. Still bad means the provider or your account's configuration; suddenly fine means the trouble lives in your building.
- Bypass your own equipment. Plug one phone straight into the router, skipping any switches. If it becomes reliable, a switch or cable in the middle is the suspect.
- Watch the rest of the traffic. If video meetings freeze at the same moments calls break up, the line or the ISP is struggling. If only the phones suffer while everything else hums, the cause is phone-specific: SIP ALG, missing QoS, or the provider.
If the provider stays guilty on a clean network after a support ticket, the fix may be a different provider — RingCentral vs Nextiva vs a managed VoIP install compares the realistic options.
When the network needs designing, not tweaking
Past a handful of handsets, call quality stops being a settings problem and becomes an architecture problem. An office that runs on the phone wants voice on its own VLAN, QoS enforced end to end — on the switches, not just the router — power-over-Ethernet feeding the handsets, and an internet connection sized for its upload rather than its download. That is a design job — the same job as building the network right in the first place: small office network setup covers what belongs in it. If you're moving to VoIP now, start with switching your business to VoIP and skip inheriting these problems.
If you'd rather someone else chased the packets
Koadi installs and supports VoIP phone systems — handsets, SIP trunks, call flows, number porting — and builds office networks with QoS designed in, so voice gets its lane from the handset to the internet. For a one-off fix, post the problem free with the symptom and what you've tried. Vetted technicians pick it up; you set a fixed price or take bids, and payment sits in escrow until you approve the result. Most call-quality work — SIP ALG, QoS, router configuration — happens over a remote session, anywhere in the US, with on-site visits through local technicians when someone needs to touch the cabling.