Loud footsteps

I have been hearing noticeable footsteps above me for about the past 12 months or so. I have lived here for about 5 years. I am on the lowest level of apartments (there is a car park only below me on street level). The block itself is about 10 years old and in very good condition. I hear the footsteps often and but was not aware of any noise of this type from above for the first three years or so I was here. I believe that a floating floor has been installed (without approval), in the apartment three floors directly above me, and a floating floor (with approval) in the apartment five floors above me but no one has ever complained to the EC about either of them or mentioned any apparent noise to me.

1) Could the noise I’m hearing be coming from three floors above me? Would it travel that far, through two other occupied units? 

2) It could be that the people directly above me, who are the same owners as far as I know the whole time and is supposed to be owner occupied, have changed their flooring and installed something unsatisfactory, such as a different carpet with poor quality underlay or floating floors.  If that is the case, then I can take some action under our by-laws which are pretty much the relevant model ones but at least give me some grounds. 

But, how do I found out if they have changed the flooring? As I understand it, no one has the right to access their unit (and no one has the key anyway).  I have rarely ever seen the owner, only occasionally having contact in summer when I have to yell from my balcony at 2am to ask them to please go inside so I can sleep. 

It’s all very well to say that if people have installed the inappropriate flooring without permission, then these are the steps…  But how do you find out in the first place???

I don’t want to accuse someone of something if it isn’t true. How do I verify whether they are the problem in the first place?

Please help if you can