why does a humming sound come from the choke of a old tube light?

Answer 1

The old choke hums 'cos it doesn't know the words.

What you're hearing is the AC frequency of 50Hz (or 60Hz) in the US. Noise can also be an indication that the choke is about to fail. Chokes normally last 10-20 years, but often become noisy just before they fail. If the light goes out and then comes back on unexpectedly after initially operating for a while, it means that a thermal switch inside the choke has opened and closed - another indication that the choke is at its end-of-life.

Answer 2

when a choke is mad, a coil is wounded on the metal iron core,and varnish is spread,or the coil is dipped in the varnish.With the passage of time,the varnish gets burnt depending upon the factor that how much the heating had effected the choke, the varnish is used to stop noise, devloped in the coil, when the varnish is burnt the coil starts giving humming noise.