In short: BT Cloud Voice call quality problems often start on the local network or internet connection: not enough upload bandwidth, jitter or packet loss, weak Wi-Fi, SIP ALG left on, a wrong NAT timer or competing traffic. Match the symptom to the likely cause, test with BT's network assessment, then fix the router, LAN or connection.
Match the symptom to the likely cause
| What you hear or see | Most likely causes | First things to try |
|---|---|---|
| Choppy, robotic or breaking-up audio | Packet loss, not enough upload bandwidth, weak Wi-Fi | Stop large uploads, use a wired connection, check bandwidth |
| Echo or distorted voice | Jitter on the connection, speakerphone or headset problems | Run the network assessment, try a different headset |
| Long pauses, people talking over each other | High round trip time (delay) | Check for a congested connection, and whether voice is being sent through a VPN |
| One-way audio | SIP ALG on, packet acceleration, firewall rules | Turn off SIP ALG and packet acceleration, check outbound rules |
| Calls cut off after about five minutes | NAT refresh (UDP timeout) not set correctly, SIP ALG | Set NAT refresh to 300 seconds, as BT's guide asks |
| Phone shows no service or will not register | Firewall blocking, SIP ALG, DNS or time not reachable, cabling | Turn the phone off for a minute, check the cable, PoE and router port, check firewall rules |
| Silent calls or sudden poor quality | A phone or cordless base station that needs restarting | Unplug it for one minute, plug it back in and test, as BT suggests |
| Problems only at home or on the app | Home broadband or Wi-Fi, mobile signal | Move closer to the router, use a cable, try mobile data |
BT's network assessment test measures the same things as this table: jitter (which BT says may cause echo or voice distortion), packet loss (which makes calls break up and sound choppy), round trip time (high RTT causes gaps in the conversation) and a mean opinion score for overall voice quality. Re-running it is the quickest way to see whether the connection has changed since you went live. See internet connection requirements.
Bandwidth and a busy connection
A common cause of poor calls is the connection being full at the moment the call is made, and upload bandwidth is usually the limit. BT points out that the more devices share the connection, the less bandwidth is left, and that streaming and downloading use a lot of it. Cloud backups, large file uploads, video meetings and software updates can all push the line to its limit for minutes at a time.
- Check what else was happening when the bad call happened; problems at the same time each day often match a backup job
- Use quality of service so voice goes first (see our LAN and firewall guide)
- Schedule backups and updates out of hours
- Use no more than 80% of the connection for voice and data, as BT recommends
- If you have added users since go-live, check the bandwidth again; BT asks you to tell it about changes that use more bandwidth
If the line is simply too small for your team, an upgrade to business full fibre or a leased line fixes the root cause.
Router, firewall and LAN problems
The second big group of problems is inside the building:
- SIP ALG left on. It can stop phones registering, break incoming and internal calls and cause poor audio. BT's Business Hub 5 and Smart Hubs have it off, but resetting the hub switches it back on.
- NAT timers. BT asks for a NAT refresh (UDP timeout) of 300 seconds. If it is wrong, calls can fail or cut off after five minutes.
- A busy or faulty LAN. BT warns that any problem with your internal network can affect voice quality. A failing switch or a damaged patch lead can sound just like poor broadband.
- PCs plugged in through the phone. Heavy PC traffic on the same port can affect the phone if quality of service is not set.
- VPNs. Sending voice through a VPN adds an extra hop for every call. Ask your IT provider whether calls can go direct to BT.
- The wrong router port. On a BT Business Hub, phones and cordless bases must use a numbered Ethernet port, not the red WAN port.
If you use a non-BT connection, BT asks you to check that your access, routers, firewalls and LAN are working correctly before reporting a call quality fault. BT says that if it finds the fault is in your own equipment, it might charge you, which is another reason to check these first.
Wi-Fi, apps and home working
Wi-Fi is fine for voice when the signal is strong and the network is not overloaded, but it is where many intermittent problems come from.
- Wi-Fi desk phones need a good to excellent signal where they sit, as BT recommends. Walls, lifts and metal shelving all cut the signal.
- The BT Cloud Voice app on a laptop works best on a cable at the office, or close to the router at home.
- The app on a mobile can use Wi-Fi or mobile data. If calls are poor on one, try the other.
- Home broadband is shared with the rest of the household. Streaming and gaming at home affect work calls.
- Headsets matter. A worn cable or a low-quality headset can sound like a network fault. See BT Cloud Voice headsets.
Read more about the BT Cloud Voice app and cordless DECT phones, which avoid Wi-Fi altogether for staff who move around a site.
Emergency calls and resilience
BT says the ability to make 999 and 112 calls depends on the adequacy and resilience of your LAN, internet connection and power. You might not be able to make emergency calls during a power or network failure, or when using the service through an app on a mobile device. Keep a mobile phone or another way of calling the emergency services available, especially on sites with lone workers.
To keep calls flowing when something fails, set a Not Reachable divert to a mobile or another site (see how to divert calls), and consider backup power for routers and switches.
Reporting a call quality problem to us
If the steps above do not fix it, raise it with Forever Communications Limited through our contact form. The more detail you give, the faster it can be traced:
- The date and time of the affected calls, and roughly how long they lasted
- The numbers involved, and whether the calls were inbound, outbound or internal
- The device used: desk phone, cordless phone, the app on a computer or the app on a mobile
- What you heard: choppy, echo, one-way, delay or a dropped call
- Whether it affects one person, one site or everyone, and anything that changed recently, such as a new router
We check the network side with you and raise it with BT where needed. Contact us to report a problem, or see BT Cloud Voice help and support.
Why buy BT Cloud Voice from Forever Communications Limited
Forever Communications Limited is part of Forever Group and a BT Business Partner. We supply, set up and support BT Cloud Voice for UK businesses, schools, charities and public sector organisations, from a handful of users to multi-site teams.
- A named partner who plans your numbers, call flows, user feature packs and handsets with you
- Number porting managed for you, timed to avoid downtime
- Connectivity checked first, so call quality is right from day one, with BT business broadband and BTnet available if you need it
- Help with the digital switchover, including alarms, lifts, card terminals and other analogue lines
- Training and ongoing support for the apps, Microsoft Teams integration, moves, adds, changes and faults
BT Cloud Voice is a business service. We do not sell consumer or home phone products.
Want a BT Cloud Voice quote for your business?
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Contact usFrequently asked questions
Why are my BT Cloud Voice calls choppy?
Choppy or robotic audio usually means packet loss or not enough upload bandwidth at that moment, often because of backups, uploads or weak Wi-Fi. Use a wired connection, prioritise voice with quality of service and re-run BT's network assessment test.
What causes one-way audio on BT Cloud Voice?
One-way audio usually comes from the router or firewall: SIP ALG left on, packet acceleration, or outbound rules that block call audio. BT's guidance is to switch off SIP ALG and, if needed, packet acceleration.
Why do BT Cloud Voice calls keep dropping?
Calls that cut off after about five minutes point to the router's NAT refresh (UDP timeout), which BT asks you to set to 300 seconds, or to SIP ALG. Random drops are more often Wi-Fi signal, mobile signal or a congested connection.
Is poor call quality BT's fault or my network?
It can be either, but the local network and internet connection are common causes. BT asks non-BT access customers to check their routers, firewalls and LAN first, and may charge if the fault is in your equipment. We help trace anything left with BT.
Can I call 999 on BT Cloud Voice?
Yes, but BT says 999 and 112 calls depend on your network and power, and may not work during a power or network failure or over an app on a mobile. Keep another way to reach the emergency services.