How many of you have any of them?  What brands?  I'd like to get my hands on one again for sound recording purposes.  I miss that noise!!  Always remember the noise from fixtures in my dad and Grandpa's old workshops and at various Gym's we would go to to work out at.

got one in my old car storage barn.maybe i can stick a microphone in one of the knockouts and record with my netbook.its as old,worn,and buzzy as a preheat ballast comes.rusty too.
late season bonus!wasps coming and going during the test.always get a nest inside the thing.every year.but it keeps on working.have threatened to take it down and restore it but why change its charecter by removing the "patina" ROFLOL!

I have some by various Israeli manufacturers - Eltam, Shingot, and i have some more 60's ballasts that i can't identify as the label (it was a paper label) fell off them

You can try to make many magnetic ballasts buzz by leaning loosely a part of sheet metal (same as what the noisy fixtures were made of) on the ballast's core from various directions / edges (need some play, be carefull to not stick it accidentally in the windings - you'll get a dangerous shock and damage the ballast). Other times, the noise of the ballast is coming from a plate near the end of the core that cracked apart from the others (there is sime tiny crack in the paint that sticks it to the others). Here too you can probably play with the sound by leaning some more metal on the loose plate

At one point I had a GE 2x F40T12 rapid-start ballast that buzzed fairly loud...

Somewhere I've got a 2' preheat fixture that has a fairly noisy ballast LOL I recorded some of its sounds one time

I have one very noisy ballast in a row of lights in my shop.  It is an old General Electric "Tulamp" that probably had a tube/starter left in place @ EOL.  Much of the tar cooked out of it before I got the fixture.  It still works perfectly and only one tube causes the "buzz".  I don't use that row of lights as regularly as some of the others, but always love listening to that thing buzz.  It gets louder as it gets warm and would be fun to play with, using a near EOL tube.
Of the newer ballasts, I have some of those Advance HF instant start in a fixture in my bathroom with four 32 watt tubes.  They buzz with the mains, just like good ole magnetic preheat and rapid start ballasts.

I have one Lithonia 2F40T12 fixture in the garage that has an Advance HPF ballast that buzzes angrily when cold.  I have one lithonia strip light in the kitchen and one in the bathroom that are single lamp F40T12 with universal HPF ballasts that also buzz pretty good.

late season bonus!wasps coming and going during the test.always get a nest inside the thing.every year.

LOL the wasps probably think the buzzing is other wasps welcoming them in!

My experience is, than the ballasts are buzzing, because something is not OK with them. And the same "something" make them to run hotter. And iot is the higher temperature, what attract the insects...

There are different buzzes depending on what's rattling and the acoustics of the fixture. For instance, I have some ballasts that hum because of parts of the transformer rattling (coils vibrating, laminations vibrating). Then I have some that the tar has dried up and is rattling inside. They make more of a raspy buzz than a hum.

Lights also make a difference. Some lights are somewhat insulated (either by design or by how they are installed). Others, like my shoplight over my workbench, seem to have acoustics that makes the hum sound louder!

If I have a chance, I'll try to record some of the hums.

As far as i seen, ballasts noise is hum with shorted starter and buzz with lamp working. I think it is to do with perfect sine waveform when preheating vs non sine waveform when in series with discharge lamp

Some ballasts especially of this construction have their own sound (when in series with discarge) that isn't even exactly a buzz

Newer ballasts with closed magnetic circuit (where the flux does not go through air) and most importantly vacuum soaked with polyester resin, are silent. Though they can often emit some "bumps" when the starter is opening and closing

In old (open core) ballasts the noise is partly from the mounting in the fixture and partly from the ballast itself. In newer mostly from the mounting. There should be somewhere 2 parts of metal which are loosely touching that make the buzz (as magnetic field escaping from the ballast separates them and snaps them back together at 50/60/100/120 Hz)

Intrigued by the idea, I decided to go out and record two of my noisier lights.

Here is the sound of my Curtis 3' preheat fixture on startup. You can hear the starter close and open only once (it starts perfectly almost every time):
Preheat starting mp3

This light also has a bit of a rattle between the tube and starter, and with a different microphone placement, it is heard here:
Preheat rattle mp3

Yet another placement shows its warmer hum a little better:
Preheat hum mp3

Note that for these two sound files (rattle and hum), I isolated one cycle of sound in Audacity and repeated it for a better sounding, consistent hum.


Here is a noisier, raspier hum from an 8' instant start slimline fixture (with a nice "bang" at startup):
Slimline starting mp3
The uneven "wobbling" sound (and raspiness) is likely due to loose fixture cover mounting.

Lastly, here is a different take on the slimline rattle:
Slimline rattle mp3


If anyone is interested in using these files in any way, feel free. These are public domain as far as I'm concerned.


To the OP, some ballasts are worse than others. The best bet is to find a few larger (for 4' lamps or better) ballasts, hook them up, and see what they sound like. Even new off-the-shelf magnetic ballasts can hum sometimes.

Wow that's a deep sounding buzz, the ones I am more accustom to are a bit higher pitched. 

higher pitched low frequency buzz = maybe result of 50 vs 60 Hz difference ?

I was told one way to rectify noise in ballasts was to remove it from the fixture, put it on a hard surface and hit it with a hammer a couple of times. When re-installed it should be quiet again. Has anyone tried this?

I think it would get it more noisy by cracking more of the potting resin. Besides making it more vulnerable to corrosion, and if you hit hard enough then just break it. Totally dont recommend it

However try something else :

Put the ballast out of the fixture on a non magnetic surface, and try powering it up with a lamp. Some ballasts will be still noisy, but most will be silent as the noise is the result of it being in the fixture and moving it with its magnetic field

So if thats the case, install it in the fixture with longer bolts (and few more nuts) that will make an air distance of 10mm or more between the ballast and any parts of the fixture metal