Buzz on my FTTC line

[#1]

Earlier this year I had a persistent buzz on the line.

Later on it disappeared, but now it is back.

Can any learned person suggest what would cause said buzz?

Please note.

1. the sub (24Mbs) not so super-fast broadband service has not changed, all parameters recorded 24/7 and logged into the database have not gone outside the norm for my rather long 1500m line. S/N typically 3-4 dB, Attn 32dB

2. No changes to any electrical equipment or wiring have been made.

3. No radio transmissions are made from the property apart from mobile phones.

4. The line is underground all the way to PCP, and the DSLAM is with 2m. 

5. Filter is OR Mk4 5C, problem persists with the supplied PN filter at the JOM socket.

[#2]

Any number of things can cause it, something going faulty, changes in the Weather, it's hard to say or narrow it down to what the actual cause could be.

But with any noise on the line it's best to get it seen to as whilst it may not be affecting the Broadband just yet there will be a time it does.  

[#3]

@Terranova667 

Thank you for your reply.

As the buzz is in the audio range, its impact on VDSL is not a factor, however its almost like a missing earth (but I do not think the wires are earthed).

I am very reluctant to call a fault in the current climate as a. OR will not come into the property, and b. it's working, the phone is  rarely used.

If it goes critical, ie the connection rate drops below the guaranteed rate then it will be faulted.