You write youre an audio beginner but apologies if this is obvious, you have to keep in mind that simply buying a VMP and putting it on top of the camera isnt a magic key to good audio, audio is always about putting the right mic in the right place (most of the time as close as possible to what you want to record)..
(The silent room that you mentioned can also emphasise the hiss a lot more unless you have a strong source like a voice close to the camera)
(PS I have no experience of EM5, possibly there could be some extra noise related to the IBIS?)