i rebuilded my cinewhoop on a new carbon baseplate, its exactly the same weight, 130g, but it seems like much louder on hoovering. 

the changes i did:
stiffer carbon baseplate 
from regular combination to pusher
from the new baseplate, there is shrinked motor distance, the rotorguards has no gap between anymore - there was about 7mm between them previous

 i didnt plan to make it  louder xD
i have no other idea than the distance between the motors as source for the louder sound

anyone experienced the same?
anyone another idea where it could come or the reason why a lower motor distance would result in more noise?

If you moved to a tighter build, most likely more of the airflow is blocked (intake or out) and also more turbulence compared to a wider more spacious setup where there are less parts in the airflow path and less interference between props, so I think it is normal for it to be noisier. Not sure about pusher vs puller though, if flipping the exact same setup over will change the noise profile.

i didnt noticed any increasement in noise by my other pusher builds, more the opposide; more silent.

de rotorguards are less aerodynamic shape onit as pusher. but i dont bwlieve they are realy areodynamic the otherway too xD

The stated benefit of pusher config is to give clear free unobstructed airflow down from props.

Your battery positioning stops this, and you will get a much more turbulent airflow, and so likely noise.

mounted the battery on top for a try, noise was exactly the same.

i dont like the idea of a quad with weight not balanced around the rotors - the common battery placement on top of pushers is a beginner mistake in my eyes xD