the million dollar question: how many times is the 'beep' sound played to announce the closing of MRT doors? I'm referring to this announcement in north south line (red) and east west line (green): "doors are closing.. beep beep beep beep...."

I counted the beeping sound a long time back, satisfied and convinced with the result. asked my friend this afternoon, he was adamant in his belief that it beeps 10 times. I asked him to count again when he's inside the train. he texted me saying that it's actually 5.. then soon after he texted again saying that it's 9...

I'm still convinced by my own count, though.. there are 13 beeps. what say you?