Questions,
When did it start?
Is it the TV?
How old is the Unit that's making the noise?
Always start by checking the obvious, are the plugs in good condition, connections true and tight inside the plugs.
Tidy runs of cables, NOT running alongside speaker cables etc.
Is your 13A socket overloaded with too many things plugged into it, ditto the ring main.
PS Just got an E Mail from Russ Andrews today £50 for a Classic Powerkord special offer, might be just what you need.