I found what it cause buzzing noise to my brand new charge 4 It was small hole that should be covered from rubber pad,but it was poorly made. So: 1.Turn of your speaker 2.Push the both radiators at the same time and check if air is leaking 3.If there is sound from leaking air ,you must open the speaker and locate it(charge 4 have tiny circle left from the driver speaker) i covered it with electric tape and now is perfect! It was very simple solution for me and i hope it work for you guys!