SNR Noise (dB) lowers by itself over time? Is this okay?

[Sinuous]

I had an engineer visit us last month to solve a noise problem that was caused by a tree, and we were given a new line. When the router reboots, it corrects itself to the 6.0(dB) noise margin, but over time, it slowly starts to reduce my Max Rate(kbps) and also lowers my SNR Margin(dB) as well, yet my upload appears to always be the same. Are these line stats okay? I ended up rebooting my router when the SNR Margin(dB) went as low as 2.8dB before I rebooted. I did not notice any issues at all with the stability of my internet, but I wanted to be sure.

These are my current line stats on my TP-Link.

  Upstream Downstream

Current Rate(kbps)	6718	41570
Max Rate(kbps)	7465	44348
SNR Margin(dB)	6.7	4.3
Line Attenuation(dB)	33	16.5
Errors(pkts)	1	2043

[imjolly]

Many people now run with a noise margin of about 3db when the DLM activates G.INP giving the lower noise margin and slightly better down speed

low noise margin can also be a sign of line problem. Have you tried quiet line test. Dial 17070 option 2 should be quiet and best with corded phone

[Sinuous]

No crackling or anything like that, but I always hear a vrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr sort of sound when a call is active. It is constant. But, besides that, nothing else, no. I also called our own house on the phone and the "vibration noise" is always present. Not sure if we've always had that though. Voice quality is flawless as you'd expect.

[imjolly]

There should be no noise on quiet line test and any noise needs to be reported as a phone fault to 151. 

You could try using the test socket with a filter and check quiet line test again to see if the noise is still there before reporting the fault

[Sinuous · Accepted solution]

That's impossible I'm afraid. I was given a new faceplate and it's called Master Socket 5C. I opened the back and... there's no test socket? In fact, the original socket it was put in is the only socket that exists. It of course, disconnected my internet and reconnected with the following line stats:

Upstream Downstream

Current Rate(kbps)	7111	41157
Max Rate(kbps)	7392	47779
SNR Margin(dB)	6.2	6
Line Attenuation(dB)	33	16.5
Errors(pkts)	1	7852

The added packet errors was caused by me disconnecting the router without actually turning it off, hence why it now says 7852. Over time, the SNR Margin for my downstream will go down. But, like I mentioned, my internet is not unstable at all. No problems whatsoever.

EDIT :: Just tried a different phone and there's NO NOISE AT ALL! None. Zero. Nada. It was due to my phone, but still, that doesn't really explain why my noise margin and max speed decreases over time. DLM bug?

[imjolly]

you do have a test socket with new 5c as shown here https://www.openreach.co.uk/orpg/home/helpandsupport/how-toguides/howtoguides/downloads/NTE5C_Instru...

the front just unclips and the test socket is visible as shown by above link

if your line is stable then the DLM may reduce noise margin down to 3db and activate G.INP which will give a slightly better conenction speed due to the lower noise margin