Fluorescent lights sometimes buzz, flicker or hum. This is not something that has to stay the same or be replaced with a whole new light or with a phone call to an electrician. It just means being careful and finding out what the source of trouble is.
Buzzing in fluorescent lights is caused by the ballast, also known as the transformer, in the lighting fixture. Most residential fixtures use magnetic ballasts that operate at 60 hertz, which creates audible humming and flickering. Your solution is to replace the magnetic ballast with electronic ballast, which operates at 20,000 to 40,000 hertz, essentially continuously. This completely eliminates humming and flickering.
The electronic ballasts only work with the new thinner diameter fluorescent tubes, called T-8s. If you convert your fixture to electronic ballasts and T-8 lamps, you will notice a huge improvement in quality. No more humming and flickering—and much better color rendition from the higher quality T-8s.
Flickering fluorescent lights are caused by the starter not being able to fire gas into the tubes. You will need to remove the bulb to get to the starter, which is a round plug sticking out through a hole. It’s either been unseated, or it’s defective. If the first, it will need to be clicked back into place to start working properly again. Otherwise, you need to have it replaced. You can take it to a hardware store and get the exact match in amps.
Humming occurs when the prongs of the bulb get dirty or misaligned. To fix this, you will need to remove the bulb and clean the prongs. Also check to make sure that they’re not curved or otherwise not straight by using pliers to straighten them. If it’s still humming, try switching the ends to see if that fixes the problem. Otherwise you will need to remove the end casings and the starter and replace it or replace the ballast.