iPad speakers make static noise

I mostly hear crackling static noise from the speakers that are built into the iPad when I put the device into sleep mode. You need to place your ear up to the speaker. It seems a sound effect like a switch flipping, but unfortunately the noise I am referring to is not that.

When I open up mail or safari and then the keyboard pop up, it also has a faint hiss from the speaker. How to make the iPad speaker completely silent?

It is annoying. This issue happens when an app or native process is accessing the speaker device. It also happens with some Bluetooth headsets connected to your iPad.