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Message 1 of 8

Digital Voice - intermittent noise and distortion

Hi -
BT Full Fibre 100 Broadband (FTTP) installed ten days ago. Reported line speed: 144 Mb/s down, 29 Mb/s Up.

Fairly standard installation - with corded analogue phones - read on even if you're using DECT handsets....
Incoming fibre to Openreach Optical Network Terminator (ONT)
ONT connected to WAN port on BT Smart Hub 2
Hub LAN port connected to Gigabit Ethernet Switch and then to wired ethernet sockets
Original analogue phone wiring (all CAT5E) connected directly to green analogue telephone port on Hub

It was found that up to four corded analogue phones (BT Viscount) would ring OK from this port.
There are currently only two Viscount phones connected to the wired phone sockets.
I found Viscount phones to have better reliability than many other BT offerings - they are now 30 years old!

The Digital Voice service is fine for short calls, in or outgoing. There is a low-level background noise - hiss and slight buzzing - less than with the previous FTTC / ADSL service - so not quite as 'crystal-clear' as advertised by BT. This noise is the same level whether the analogue phone is connected directly to the Smart Hub, or via the phone wiring.

For long calls (in or out) there is intermittent crackling / buzzing / 'squeaky' distortion on the line, nearly severe enough to make speech unintelligible. This is of fairly short duration - maybe a second or two, and occurs fairly infrequently, maybe every 5 to 15 minutes during a call - if it continues, I will make an audio recording.

A characteristic of digital telephony is the 'saving' of digital bandwidth 'on the fly' - if one of the people on the line stops talking for a short time - the line goes quiet.
This can be disconcerting at first (if you're used to a 'dedicated' copper conection) - you think that the call has disconnected.

Commercial users of digital telephones usually have much better 'kit' than a BT Smart Hub - this 'kit' reserves digital bandwidth specifically for many simultaneous telephone calls. This function is called 'Quality of Service' (QoS) and it maintains 'crystal-clear digital communication' (BT advertising 'speak').

Reported 'defects' of an inadequate QoS service (and hence inadequate bandwidth for the voice 'channel') include distortion, echo and noise on the line.

I seem to have these - but only very occasional echo - which I put down to the called party's 'end'.

Since....
I am not using DECT (but the DECT 'base station' in the Smart Hub is still active - and no way to shut it down*), and....
There was previously no DECT 'presence' in the house, and....
My phone wiring is not subject to interference pick-up (at least it wasn't when the service was FTTC)....

* I may try 'screening' the Hub.

I am thinking that the problem may stem from....
DECT base station interference pick-up, or....
Inadequate QoS** - poor bandwidth / bandwidth changes actioned by 'bandwidth-saving' software, or....
Another unknown 'system' shortcoming....

** This would appear unlikely, given the large bandwidth available - but bandwidth restrictions may apply on the way to the 'other end' of the call - it may be possible to disprove with a 'load test' - a big, fast download and a simultaneous telephone call.

If this is so, it would affect all handsets - digital, analogue, corded or 'walk-about'.

Has anyone else noticed any of the above symptoms?

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7 REPLIES 7
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Message 2 of 8

Re: Digital Voice - intermittent noise and distortion

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Message 3 of 8

Re: Digital Voice - intermittent noise and distortion

No

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Message 4 of 8

Re: Digital Voice - intermittent noise and distortion

I will use the system for a month or two - I will report if there is any repeat.

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3,117 Views
Message 5 of 8

Re: Digital Voice - intermittent noise and distortion

Hi @Robin1952 

Yes, I have experienced the symptoms you describe, on some calls to or from people who have changed to the

"crystal clear" smart hub2.  I am still on copper analogue and just 100m from PSTN village exchange, fault free.

Calls from PSTN and mobile networks are clear. 

Maybe the poor quality is originating from the far end and there is nothing wrong with your equipment.

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3,110 Views
Message 6 of 8

Re: Digital Voice - intermittent noise and distortion

I think you will find that the "crystal clear" quality that BT are referring to, only applies when using the BT Digital phones that connect directly to the Smart Hub 2 using DECT.  I believe they have more audio bandwidth allocated, possibly 128Kbs instead of the 64Kbs allocated to the internal ATA interface, and the DV adapters.

This was the case with the old BT Broadband Talk service which also had special phones connected by DECT, and also an ATA interface on the back of the original home hubs 1, 1.5, and 2. Those phones could use the full 128Kbs allocation.

This service was the forerunner to the current BT Digital Voice service. 

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3,079 Views
Message 7 of 8

Re: Digital Voice - intermittent noise and distortion

Thank you for your replies - with more than one provider potentially involved in the two 'ends' (and the 'middle') of a call there are plenty of variables! Maybe the best we can do is to report any occurences and see if a pattern emerges.

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Message 8 of 8

Re: Digital Voice - intermittent noise and distortion

Hi @Robin1952 

It used to be said that HD quality was only available when connecting to a BT/EE number, but I can no longer find that information.  That said, I've had digital voice for around 3 years and I've never experienced  the problems that you've encountered. I've always used the BT supplied DV handsets and when they display 'HD' on a call it is crystal clear, when it shows non HD then the call quality is 'normal'.

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