electrical wiring,Whining and buzzing noise coming from head unit

In my Lexus LX450 I hooked up my Alpine 9883 head unit in the sound system. The position of the head unit is the problem for me. I hear whinney buzzing noises when the head unit is positioned at a certain angle. To loosen the head unit’s grip with the dash, I loosened the screws and then the whinney buzzing sound disappeared. However, after two hours the sound returned. I am thinking that it returned due to gravity repositioning the head unit. I wrapped the screws with electrical tape so the electrical conductivity would be insulated. I need your advice on how to fix this. Thank you.