I've moved into an apartment. I noticed that whenever I switched on my fluorescence light and when my neighbor switches on his light, my fluorescence light would produce a 'rrrrr' or 'mmm' sound which sometimes can be loud and irritating. I have tried changing the light bulb and even the ballast but the situation remains. My light does not produce these sounds when my neighbor does not switch on his light. Appreciate if somebody could tell me what is wrong - is there an open connection between the circuit of my home and that of my neighbor? If so, my neighbor could take the advantage of connecting other devices to my circuit and use the electricity which I'll be paying or even do some other weird things, e.g.. controlling usage of my own electrical system. Thanks.

I highly doubt there is any connection after the meters. However, his light could be sending something back through the line. I am sure you are fairly closely connected before the meter. I will leave the details of just what is going on to the more knowledgeable.

One reason may be due to all ballasts emit RF frequencies, or radio waves, and can be affected by them. Perhaps your neighbor ballast is defective and emitting a larger amount of RF than normal.

There is a slim chance that there is a loose neutral connection in the main equipment, but this would cause other symptoms in your apartment.If this is true , only a qualified electrician would be capable of troubleshooting this and repairing.

As far as sharing power, the best way to find out if there is any sharing, is to shut off the main for one unit, and see if there is any effect in the live apartment.

Dear labman,
TQ for your response. I was wondering why is it that the volume sound produced by my own lighting (when my neighbor switches his light on) can be 'controlled' by neighbor - it can really be very irritating since the sound could grow very loud (deafening) when I am taking a bath but when I finish my bath, the sound tend to be lower in volume. I noticed that when my neighbor is out, little or no sound is produced when I switch on the lights and take a bath.
When my neighbor is in, even my fridge and washing machine would give a loud sound when I switch them on but the sound would be normal when he's not around.
Sometimes I feel that my devices (lights, fridge, washing machine, etc) are 'fighting' for electricity when I switch them on (when my neighbor is in); perhaps that's why all these loud sounds come about. Furthermore,
I always feel as if he's always waiting for me to switch on something in my apartment. Could he be using some device which requires extra electricity and that extra has been 'configured' to come from my apartment?
I have tried to get electricians to check but they will do a simple check and that's it. Of course, that way I know they would not find anything and my neighbor would be smart enough not to use whatever device he has when these people came over. Any suggestions or explanations? Would appreciate very much. Thanks.

You can pick up a cheap multimeter for $5-$10. Put it on AC volts, and just stick the probes in any unused outlet when you neighbor isn't around. It should read at least 110, and maybe as high as 125. Then wait until your neighbor is there, and try again. If the power is much less, especially if it is below 110, you have a problem. It should be 115-120. Electricity will draw from what ever it is connected to. If your neighbor is using excessive amounts, your apartment would only be affected more if where they branch off is closer than to other apartments. Is this a large building with many apartments? The noise is a problem. Have you complained to the landlord? Be a little more gentle toward your neighbor. He may neither know of the problem, or be intentionally causing it. He may have even complaind about his light, and not gotten anything done about it.