To physically check what is there, you would need access to the shower valve and pipes, which often means taking surrounding tiles off the wall! (Unless there is access from behind). I guess that may not be an attractive proposition.
You could try removing the cover/escutcheon plate to see how much of the shower valve and pipes you could get at.
If you could find out the make and model of the shower valve, and find the technical information/ installation instructions, you could see if check valves are part of the shower unit. Even if they are, they may not be easily accessible.
In my experience check valves do make noise when the water is throttled, and the noise tends to diminish with more flow.
Would I be right in thinking your noise quietens or stops with the tap full on - is it still excessively noisy when taking a shower?
I don't have any suggestions as to how to stop it without getting at the whole shower valve assembly, no doubt others on the forum will.