bang their door
and put some smelly rubbish at their doorstep with warning notes...
"Learn to respect others or you'll be in trouble the next day!!!!"

hehehe....
no larr...
i've faced the same problem some years ago...
what i did? i went to talk to the occupants...
unfortunately...
they are Cambodian and Myanmarian....
worked at factory nearby...
dunno how to speak Malay or English....
so i just use the "shut up" sign...shhhhhhhhh!
and indicate that i'm the one who stays below their unit....

fortunately....
its not that they keep silent the following months...
but i've heard that police and relevant authorities did raid their premise...
together with other premises...
where those immigrants are found guilty for not having proper legal documents working in our country....

lucky me then...