Whenever I light up a tube-light it makes 'ting' 'ting' sound every-time it blinks.
I am talking about this tube-light
Why is it so?
I think its because of sparking(inside glass tube)
similar sound in the 6th box hover and listen here
This sound is most likely caused by the choke coil which is inside the lamps housing.
It is needed for lamp starting and operation. Starting works like this: After initially the starter circuit allows for current flow through the heaters in the tube, it interrupts the the current after an initial period. This causes a high voltage impulse to be created by the choke coil, which is needed to start the light generation (i.e. current flow through the tube).
During operation, the choke coil acts as a impedance element with the purpose to limit limit the current flow.
You most likely hear the abrupt change in mechanical forces (due to abrupt current changes) in this choke coil during the starting procedure.
Also note, that in flourescent tubes which have an electronic starter circuit (e.g. energy saving lamp) you dont hear this sound.
Depending on the bulb, the bulb has two circuits. The first circuit (across the two posts at either end) heats a filament at either end to vaporize mercury from an amalgam pellet reservoir behind a small metal shield under the filament. The second circuit is through the tube, the mercury vapor discharge with negative resistance, regulated by the ballast.
Each filament is connected to its posts by a bimetallic strip. After the tube lights, the higher temperature disconnects the filaments by flexing the bimetallic strip. When it cools, that reverses. If this sources the sound, it should "ting" once at each end when it lights and the heating circuit breaks.
Light is composed of zillions of photons, elementary particles which even though have zero mass carry momentum.
In the link you gave one sees that the ping sound comes at a delta function in time of a lot of light.
My first guess is that the photons of these impinge on the glass cage and transfer their energy to the glass, creating vibrations of the glass on impact due to their large number. In the quiet phases it is seen that only after a certain intensity a sound is heard.
My second guess is that even though the pressure of the gas in the tubes is fairly low, 0.3% of atmospheric pressure, the gas might vibrate during the excess light,the vibrations may even be the cause of the excess,and part of the vibration is transferred to the glass tube . The gas vibrations might arise because of the boundary conditions of voltage and geometry of the tube and transient variations in the voltage imposed, which have to exceed some value in order to set up a resonance with the glass.
Edit : A third possibility is if the excess light is due to sparking, as you suggest. In that case it will be the vibrations induced in the anode and cathode by the spark that will dominate, transferred to the whole tube .
An experiment would solve the problem, and it probably has been done, but I have not found it by googling.