Florescent light

Why Florescent light circuit gives hum. I belive it is due to faulty ballast (choke coil) or coil not properly mounted.

Please correct me if I am wrong.

Many thanks.

Because inside the f-tube working a gas-discharge with mains frequency, the electromagnetic hum coming also from tube. The switchmode dimmable "ballasts" probably wronger: almost impossible the shortwawe receive... The magnetostrictive hum coming only from choke.(sound)

Sebi is correct, and I would add that a faulty ballast can produce mains frequency mechanical hum, as can a loosely mounted one. Often they are only attached at one end with a screw, on the other end part of the ballast case is notched into the reflector housing metal work. Sometimes the reflector itself will resonate with the ballast, making the hum sound louder. Try tightening the ballast mounting screws first. If the ballast is extremely hot, or shows signs of the internal potting compound ( often pitch or tar ) leaking out, it is probably due to be replaced.

Thanks for the suggesstions.

There are several f-lightings in the house. One or two producing those hum. Others are OK. I too belive it is a loose mounting. If not I will replace ballast.