What is the role of chokes and starter in tube lights? Why do they make noise?

            Tube lights are discharge lamps. To initiate a discharge, it requires a high voltage (about 1000 Volts) several times the mains voltage (about 220 V). To sustain a discharge it requires only about 100 V.

A choke is an inductance. When current through an inductance is abruptly interrupted it includes a high voltage. The interruption is done by the starter which works like a switch. The high voltage strikes an arc between the filaments at the ends of the tube light. Once an arc has struck, the choke takes half of the mains voltage and leaves the rest to maintain the arc.

The choke has a core made of thin laminated silicon steel sheets. When the sheets vibrate with the power frequency (50 Hz) or its harmonics it generates noise.

A starter is made of two electrodes one of them is a bimetallic strip. When a tube light is switched on, the voltage between the two electrodes produces a spark. 

This heats the bimetallic strip, forcing it to stretch and bridge the gap.  This in turn stops the sparking and cools the strip. The strip comes back to its initial position. This process interrupts the current in the choke.

When the discharge is established the starter will be in parallel (electrically) to the tube and gets only half the mains voltage which is insufficient to initiate a spark. The starter will now idle. If the tube fails to sustain the arc the starter will repeat the job. The job of the starter can be done manually by a switch.