I have recently purchased a Sony Xperia Z3. There seems to be a strange problem with the Sony Z3 top speaker. Most of the time it produces a static background noise when I run any applications that has sound. The noise can still be heard even if I have muted the media volume. But there are occasions where the noise does not occur.
I searched online and found out this a common problem for Sony Z3, the solutions they suggested on the forums(tuning the equalizer settings) did not help me. I have also contacted Sony customer service and they responded that “It happens when you use applications that access Internet.” That seems logical enough first but I soon realized that sometimes the noise does not occur even when I am using the applications that access Internet.
When I tracked down the cases where the noise did not occur, I found out the root cause of it: The Alarm Volume.
Alarm volume setting in Sony Z3 sound and notification setting
This is totally strange but it is indeed the cause of the noise. Whenever I lower the alarm volume to below about 60% and reopen the applications, the noise disappears. The alarm volume is not supposed to be related to the sound inside the applications but it seems that Sony Z3 has a software bug that caused them to be linked.
Also note that the global alarm volume in the sound settings will be overwritten by individual alarm volumes that you set in the alarm application.
Alarm volume setting in Sony Z3 Alarm app
So in order to make sure the noise does not come back, you need to set both the global alarm volume and individual alarm volumes to below about 60%.