In the 15 years I lived in my 3-room HDB flat in Lorong Ah Soo, my family had to endure what sounded like marbles being dropped on the floor of the unit above mine. Strangely, this seemed to take place only at night, at times in the wee hours of the morning. Never one for confrontation, I did not speak to the occupants upstairs, and we lived with it.
We moved to Punggol 21 five years ago, and the sound of the marbles dropping in the wee hours of the morning seemed to have followed us. I once trotted upstairs to to see what sort of neighbors I have and the occupants were an elderly woman, her weak elderly husband and their domestic help. It is unlikely that they played with marbles, and certainly not in the wee hours of the morning.
From conversations with friends, I was astounded to learn that this sound of dropping marbles is a widespread phenomenon in Singapore. It seems it happens only in HDB flats. One of my friends suggested that it may be the way the HDB flats are built.
As a non-believer in the supernatnural, I am eager to understand this mystery that is fast becoming an urban legend. I may have legitimate reason to ask the HDB to explain it, since it seems to inflict flats built by it.