Noise on the line
Noise on the line can cause problems with your broadband connection such as intermittent connections and packet loss.
Disconnect the modem/router and filter from the phone socket and plug the telephone in to the socket on its own, is the noise still apparent? If yes call BT on 0800800150 to have the line tested.
If there is no noise when the router is unplugged from the socket it is likely that the micro filter is faulty. After testing an alternative filter if there is no change please contact the Support Team for further assistance.