Ignorance of taking action on multiple notices of faulty electrical items which creates noise.

Our apartment on 7th floor. The apartment below us (6th floor), master bed room fan, creates some special machine like noise which is very evident in the night time. And increases as time pass on. We have brought this to their notice and have requested to swap MBR fan with hall/dining to find out if this is fan issue or something else, as their hall/dining fans are not making such noise. On this simple request, his co-operation is zero. We have requested them to visit our place in night but for that too they are ignorant. Now that sound is unbearable as we are loosing our sleep. The electrician checked only their fans and said there is no noise in their apartment but never came to our apartment to check what we are complaining about. I need suggestions. I have reported to association and they said it is personal matter ca they can not pitch in. Builder says until owner permits, they can not force them to swap fans, even though currently apartments are under their maintenance period. What next can be done ?