I remembered this particular night, I had difficulty sleeping. I tossed and turned but I still could not sleep. All of a sudden, I heard this 'PSST' sound. It happened every 8-10 minutes. Though I was scared, I went to check out the noise. Turns out to be my air refresher.. Silly, but it scared me. (Memory collected at the Central Public Library during the "irememberGhost stories" campaign from 27 Sep to 30 Nov 2012)