Light Fitting Resonance!

[JohnW2]

So, had a little play today and found that with one particular fitting (chosen at random), if I removed the lamp then the sound started (in that fitting - buzzing sound). Replace the lamp (I tried two and it made no difference which one I used) and the sound stopped. Not sure if I would have achieved the same if result if I had chosen another fitting. It's not very consistent!

Still very odd! I presume you're not saying that it makes the noise without any lamps in it at all - or are you?

Kind Regards, John

 

[craig1234]

Hello John.
No, must have at least one lamp in to make a noise. It's definitely resonance of some sort I'm sure. What I don't understand is the inconsistency.

 

[JohnW2]

Hello John. No, must have at least one lamp in to make a noise. It's definitely resonance of some sort I'm sure. What I don't understand is the inconsistency.

I don't really know what you mean by "resonance" - what do you think might be resonating with what?

Kind Regards, John

 

[craig1234]

I might have used the wrong term with resonance - possibly inductance. It is a large metal light so the metal may be picking up the mains (from memory I think the live is switched within the ceiling rose) and causing the fitting to vibrate/hum.

 

[JohnW2]

I might have used the wrong term with resonance - possibly inductance. It is a large metal light so the metal may be picking up the mains (from memory I think the live is switched within the ceiling rose) and causing the fitting to vibrate/hum.

That would seem extremely improbable, but the whole thing is so mysterious that I would be hesitant to rule anything out

Kind Regards, John

 

[FrodoOne]

That which you call a "resonance" others might call a "buzzing sound" (50Hz ?)
Is it a 50Hz "Buzz" or some higher frequency?

From where (exactly) is it emanating?
You may need a stethoscope (or similar device) to determine this.

 

[craig1234]

Apologies for the delay - am abroad at the moment.
Difficult to say exactly but I would say it is probably a 50Hz frequency. The sound appears to be emanating from inside the fitting. It's not really a problem as it is fairly quiet and now I have found a way to silence it by moving the lamps round. I was more curious as to its cause than anything.

 

[FrodoOne]

A 50 Hz "buzz" is most likely to be a poor/loose connection across which arcing (and heating) is taking place.
You could have a significant problem with contact heating which (eventually) may overheat and produce fire.

 

[craig1234]

I understand what you are saying but the "buzz" moves from lamp holder to lamp holder and disappears if all lamps are removed. It's also much quieter than a "normal" arcing sound.