any ideas why this happens?

[#1]

A spanner for you, I had a engineer out today to fix a noisy line.  He relied on his machine to Listen for faults and was about to leave when he did a 17070/2 test and heard the noise, he was going to leave and get me or PN billed for it.
The fancy blue tooth test box failed to register the fault on mine and also failed in January when I had them out before for the same problem.  So push for the engineer to check from your cabinet to the exchange.  He finally found that the line from the cabinet to exchange was giving higher readings than it should, which was suppose to be shown with his tester.  He moved my phone line to a new line from cabinet too the exchange and all is better now.

[#2]

Thanks Gus. 
1st engineer did a few tests, and remade a joint on the line...  This as Ok for a couple of days.  2nd engineer did some tests from a box, and stated NFF.  He never listened to the phone with everything attached, just via the test socket, with his equipment.
Last major fault I had was something like this.. Ended up being a line card at the exchange that a lift and shift cured, after 8 engineer vists......
Currently going through the fault checks for plusnet.  Using another microfilter at the min, no appreciable noise on the line, but running some margin graphs, as comparisons, that I will post up later on.

[#3]

noise Margin graphs from tonight, with a new microfilter...
There is no noise on the line now, with and without router attached. Still not happy with the upstream graphing.
ideas... Surely i cant be that unlucky to get a filtered faceplate going faulty, and then use a dodgy microfilter...

[#4]

Line has now been stable with the other microfilter.  only had 1 line drop, when  plusnet did another line test, but upstream margins are still erratic.  the drop on the graph below for upstream is due to a call to us, and then a call from the phone.  Margin goes back up after the call.  There is no noise on the line at all now.  Could the erratic upstream margins be due to the ADSL2+ frequencys, and does anyone think I may be better going to ADSL1 over 21CN?? Even so, I need a new filtered faceplate obviously.  What are peoples opinions on the newer VDSL faceplate, is it better quality than the XTE5 from adslnation.  The one I have now, is an old BT supplied one, but I am surprised its gone faulty....

[#5]

update for anyone whos interested......
Line still stable, however still get bursts of noise on the phone, although these are much reduced from before. no resyncs, that cannot be attributed to line tests from plusnet.
Just a couple of questions if anyone from the DCT reads this....
1.. Would a change of profile cause a drop of the PPP link?  Had a drop Sunday morning at 1min past midnight, but line did not retrain, or if it did, it resynced at exactly the same figures.....
2.. Although line stable, still get erratic SNR graphing, and SNTM does drop by at least 5dB when phone handset picked up, or receiving a call.  ??any ideas?
3.. From what I understand from the ticket, I appear to be on up to 24M with interleaving on downstream, with a margin of 9dB, but unsure as to what the upstream is actually set to.  As we would prefer stability to speed, can I have the upload recapped, if not already capped.  unsure as the upload is sat at 440, with a margin of around 22dB.
Thanks....

[#6]

Hi Penfold,
If your profile was to update then and you are connected then yes you would see a PPP disconnection. There was no change in your profile at that time though.
Your upload is currently capped at 448kbp/s, it would probably make more sense to uncap your upstream for better performance.
Regarding the noise on the line, It would be making sure that nothing is interfering internally. Is there other electrical device at all that is switched on when you experience a spike in noise?

[#7]

Thanks chris. Had a few resyncs today. Wife also noted phone crackly during calls... Checked, and phone line crackly. Immediately pulled everything from test socket, and put phone directly into test socket, and there was hisding and crackling, on a quiet line test. Dialled the csc, but before i got through noise went, and has stayed quiet...  Will update the ticket later. There is nothing i can track down that could be causing spurious noise on the line. I an a little stumped to be honest...

[#8]

Hi, sorry to see this is still ongoing. As you know you just have to checking until you can catch it persisting for long enough, it's a bad joint somewhere or an intermittent break in the o/h cable.

[#9]

Thanks anotherone.  Yeah, I am just gong to have to wait it out, until it goes badly wrong enough.  It seems to be worse as the weather drys out.  I suppose thats when the dodgy connections would start to oxydise, and create noise etc.
@Chris.....  Can we keep my upstream capped for the min.  It would be more stable in the short term till we finally get to the bottom of this.  Even though its capped at 448, seems to always resync at 440????

[#10]

That's fine, I will leave your upload capped at 448kbp/s. Upstream sync can depend again on noise on your line. I'll have a look at your next couple of upstream syncs and work it out from there.

[#11]

Just a final post on this....  
line has now been stable for over 160hrs, and to be honest no appreciable noise on the line, except for the occasional crackle, which will probably never be traced....
Just fitted a brand new XTE-2005 faceplate to replace the aging BT supplied V1.0 faceplate.  The background hiss on the line has noticeably decreased, and have not heard any noise at all.  Noise margin graphs still a little erratic upstream, but as the BB is now stable, I dont think there is any simple fix to this, BT certainly wont have an inclanation to investigate this further.  I have noticed many openreach vans around the estate, particularly around the corner from me, who I am presuming are on the same CAB.  Things have improved, so maybe they have also fixed my fault at the same time.
Margin graphing from after the new faceplate attached.  Red line indicate a quiet line test start and finish.
Seems to indicate there is still some issue somewhere. Weather around here just constant rain and thunderstorms at the min....
Thanks to all who have offered advice here...