This compares different sources of interference (12)
I believe the answer is:
atmospherics
'sources of interference' is the definition.
(electrical interferences with phone signals)
'this compares different' is the wordplay.
'different' indicates an anagram.
'this'+'compares'='thiscompares'
'thiscompares' is an anagram of 'ATMOSPHERICS'.
(Other definitions for atmospherics that I've seen before include "Interference" , "Electrical disturbances" .)