Welcome to Beoworld, its good to have you on-board..
When you say you "Suddenly experience noise when the speakers are on" what kind of noise ?
- Is it a hum at low volume ?
- A buzz all the time which can be heard over what you are playing ?
- Or some other kind of noise ?
If you are getting hum at low volume Hum from loudspeaker which can often be caused by the Switch Mode Power Supply generating teh noise.
To reduce this noise it is important to use the original Power Link cables. You should use Power Link Mark III (with the triangle symbol on the plugs), or fully mounted Power Link cables (cable with all pins connected)
There was also a shield introduced and the changing of two components because of mains noise from the bridge-rectifier which was reflected into the low frequency circuit
Unless you are a technical person with some knowledge in this area, you will most likely have to get a B&O dealer to resolve this latter issue if that is your problem.