an annoying sound comes from the speakers

[sakissim]

hallo when the unit turn on i am always listening an annoying static sound only if i mute the sound stop its very annoying there is any firmware update for this problem? or its a hardware problem? thank you
i bought this unit from amazon.de

order number: 304-5169009-5145952

[Limses]

I've got the same problem. And it's the second unit I've ordered.
I think it's a hardware problem. I've also changed the audio cables and the speakers... If the audio is comming from an external device or if I activate Bluetooth the annoying sound is getting even louder... I think something in the radio isn't shieldet correctly.