I have noticed that when certain tube-lights are switched 'ON' , they make certain noise corresponding to their "blinking".
In blinking, there are alternate periods of the tube lighting up and then going out. The "sound" is heard at the instant the tube lights up.
I can not properly describe the "noise" or the "sound" I'm referring to, but it seems as if the tube-light is struck gently with something. It feels as if the gas molecules inside the tube-light are striking its inner surface.
Can anybody explain this ?