As per some of the comments above, firstly ensure your installation is correctly filtered, if so, then determine if the same conditions exist at the test socket of the NTE5 (Master Socket).
Once you have proved the fault to be present at the test socket, then you are well within your rights to request an engineering visit.
Now for the tricky bit. This kind of fault is
definitely a miniscule HR (High Resistance) causing the hissing noise. The problem is, they are usually so small that even our on-site testers fail to spot most of them, let alone the remote test systems our front desks utilise. As such, the chances are that when you try and raise a fault the subsequent test the advisor will run will return a LTOK (Line Tests OK). They may even run a higher-grade CIDT test (Copper Integrated Digital Test), but again, I would suggest that this too will return a LTOK.
Next, it depends on what type of fault is built (Network or Broadband) and the skill level of the engineer. I'll leave it to others to enlighten you on this hot potato.
![Grin ;D](https://forum.kitz.co.uk/Smileys/kitzemotes/grin.gif)
But IMO, you need a
broadband engineer, as this type of fault usually requires network intervention (PCP, DP), with both the tester connected in DSL mode and listening for the 'hiss' with our 'Tappers'. A non-broadband engineer would not be able to simulate this scenario.
Good luck.