Hi, I am aware of the hissing sound when half-pressing the shutter button, that is caused by the IBIS. What I have noticed is that there is also a background hissing sound always present (without half-pressing the shutter button). It is audible only in complete silence, it is lower in volume than the IBIS and it sounds a bit like a small fan. Is it something you are experiencing as well?
This seems to be normal, my EM10 also makes the hissing sound. I think it is some "standby" mode where the sensor is kept still but no stabilisation is performed. When you turn the camera off the sensor is "parked" and can be heard shaking in the camera. When on and shaken you will hear nothing.
The sensor still has to be held centrally, ready for action, so yes you'll hear sound from the voice-coil magnets, unless the camera is off completely.
