This is often a sign of some bad ground connection problem. Here is some points you can check yourselves :
1- Please check the input cable on your system. A bad cable with a poor connection can be the source.
2- This can come from another device. Please disconnect all the sound chain one by one to find where this noise comes from.
3- Disconnect your system from any external elements. If the buzzing sound is still present, the system can be defective and we advise you to contact the resale store where you bought it to ask for an ASS procedure.