I would tend to agree with OG’s analysis.
To confirm whether the buzzing sound is 50Hz mains hum – with the volume low, unplug the sound bar input from the satellite/cable box and hold the tip of the input jack with your finger. The sound bar amp will now be amplifying the 50Hz pick-up on your body. If you place one hand close to a mains cable, this will increase the 50Hz pick-up signal (and the output volume).
If it is 50Hz hum, the next thing to do is to connect the sound bar to an alternate signal source to see if the 50Hz hum is still present. If it is not present when using a signal from an alternate source, this suggests the fault lies with the satellite/cable box.
Be aware that many amplifiers automatically disconnect any input signal source not required, to minimise this type of problem. So when you pause the TV, it may be disconnecting the input signal (which has the mains borne hum). This mains borne hum signal might be due to a poorly screened audio cable connected somewhere in the system.