I arrived in Saint-Etienne at the beginning of July. The summer months see people moving out of the cities and into the holiday locations for their annual vacations. As a result, the city seems deserted. I spent the first two months in this new city seeing on an average one person every five minutes when I was outside on the streets.
Thus, when September began and the schools opened, more importantly the primary school just across the road from my house, it took me some time to get accustomed to all the noise every morning. It was during the first week of September that something very interesting happened, and this is the story of that very event.
I wake up at 6:40 every morning and by 8:25 I leave my apartment to go to work. Since the first week of September, every morning sometime between 8:15 and 8:17, I hear a child singing in the corridor just outside my door for a few seconds. Just about a second later, I hear a sound as if someone were asking the child to be quiet. It sounds like "Shh!" The child does not stop. Around two seconds later, there is a second "Shh!" and the child becomes silent.
When I heard this the first time, I did not attach much importance to it. However, the next day, the exact same sequence of events followed. This is when my curiosity was piqued.
The first day when I heard the child, I had formed the following story in my mind. I had assumed that the child was going to school accompanied by a parent. As the child sang, the parent said "Shh!" to ask the child to be quiet. The child did not listen and continues to sing until the parent says "Shh!" again. However, I asked myself the following question: "Why is it that everyday the child becomes quiet only after the second time the "Shh!" is said?"
I could have just looked out the door the next day, but I thought it to be a nice challenge to be able to figure it out on my own. Therefore, later that day, I examined the corridor. Standing at my door, there are two elevators straight ahead. The inner doors of the elevator are sliding doors while the outer doors, which open on each floor are of the swinging type. To the right of the elevators is the door of the only other apartment on my floor, which is the ground floor. An old couple lives in this apartment and they have no small children in their house. To the left of the elevators is the security door which has heavy glass panes and leads to the exterieur of the building. Thus, anyone wishing to enter or leave the building must pass through this door.
Having seen this I thought about the events and arrived at a solution. I verified it the next day and was delighted to see that I was correct. If you wish to solve the problem yourself, I suggest you stop reading here because I will describe my solution in the remaining part of the text.
I first brought to mind the fact that I had seen nothing, but only heard. Therefore assuming that the sound of "Shh!" was made by a person is pure speculation. The sound the child made was definitely beyond doubt that of a child. This led me to the following solution to the problem. The child goes to school every morning around 8:15. He descends using the elevator and is in the habit of singing or making some sound as he walks out. The first sound of "Shh!" is not made by a person, but by the closing of the swinging door of the elevator. Of course, this does stop the child from singing. In order to exit the building, the child now moves to the security door and opens it. All this time, he continues his song. As he leaves the building by the security door, it is the door that makes the second "Shh!" sound. After the door closes, the thick glass prevents the transmission of sound. Therefore, I do not hear the child any more, even though he may as well still be singing outside.
