I would bet that it is a feature of Airbus aircraft that this chime occurs. It is to signify that wheels are up and is part of a system of chimes to signify this followed by passing through 10,000 feet and the no smoking lights from going out. The chime can be stopped from occuring by the pilots, but it is the default setting.

Now, what are the little black triangles for that are above the windows at row 12 or 13????