Speaker background noise problem on android phone

I have just noticed there is a background noise in all unity applications running on android, even when there isn’t any AudioSource in the scene.

I tried setting AudioListener static variables:

AudioListener.pause = true;

AudioListener.volume = 0.0f;

on empty project. It doesn’t help. Also I tried to disable listener as well.

Do you have any idea why this happens. How we can get rid of it?

p.s. With Simcity Buildit, you can see the same problem. When you turn off music and sound from settings, the noise disappears.

If you don’t use any audio source, try set the ‘Disable Unity Audio’ checked in Audio Settings, this will definitely work… I’ve encountered same problem recently and solved by this method … Well, I think it might a bug of Unity =.=