Any faulty equipment including telephones connected as part of your broadband set up can certainly cause an issue such as the one you are experiencing. I suggest removing your handset from the telephone socket for 24 hours and see if your connection remains stable during this time.
From there, look into replacing your Handset as it is likely at fault. Try a second handset and see if the noise still persists on your line. If it does then please read on,
Other things that can cause issues such as this are SKY TV boxes, Redcare Alarm Systems, Fax Machines or anything of this nature.
If you have nothing like the above connected, ensure that you are trying to test socket on your NTE5 with nothing but a filter & a telephone connected, no extensions of any kind.
A question I have for you is, do you hear any noise on your line when your broadband equipment is disconnected?
If so there may be a problem with your PSTN line, if Orange are your landline provider call from your mobile and ask to speak to the 'home phone faults' team, have them run a test, they will be able to determine this.
But from what you've posted, It is highly likely that your issue is related to your telephone handset. If you require any further support call 0844 874 8586 or 150 from an Orange mobile.
Edited by Ascension (Fri 29-Jun-12 12:04:51)