# LEDs and humming sound in 2015



## smc733 (Mar 5, 2015)

Hi Everyone,

I'm a semi long term reader, first poster. I recently bought a house, and one of my first orders of business was to replace nearly every bulb in the house with LEDs. So far, 7 enclosed fixtures are signing happily with a mix of Cree 4flow and regular 60w bulbs.

For the bathrooms, closets and kitchen, I went with GE, for one fixture which used A15s, and also because I think they look better when uncovered with the diffuser/frosted globe. I've noticed they have a buzz (all of them) whether they're connected to a dimmer or not. So here's where I stand with buzzing:

Cree 60w & 60w 4Flow: No buzzing, except dining room with Lutron CL dimmer (buzz is inaudible behind the enclosed fixture in which the bulbs are located)
GE 40w: No buzz
GE 40w A15: No buzz
GE 60w: Buzz (all 6 of them, none on dimmers)
GE 60w Reveal: Buzz (all 4, 2 in ceiling fan with dimmer worse)  Disappointed because I love the light quality
GE 65w Reveal BR30: All 10 buzz (at varying levels of sound), connected to Lutron CL (Skylark Contour). Again, extremely disappointed given how highly this bulb was reviewed, and given I got them on sale at the orange store for $8 subsidized by the local energy companies.

My questions are these:
1. Has anyone else used GE LEDs and noticed this awful buzzing? I can hear it a few feet away in a silent room. The Reveal A19s seem to get worse the longer they're on/hotter they get. Is there anything I can do to stop this (I am assuming no, its the electronics)? I like the light these bulbs put out, and I like the way they look in my bathroom fixture, but that buzzing can get very irritating.
2. Is there a BR30 which is known to be silent with dimmers? The dimmer I have is listed as "compatible" for nearly every BR30 I find, but I'm learning that doesn't mean much.

I've been happy with the Cree bulbs, and my gut is to replace the Reveals in the bedroom with them, I just dislike the way they look when exposed (dark spot). I'm reading there may be no good solution for the BR30s, either, as I hear the Crees also buzz. Are Philips any good?

Thanks!


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## Str8stroke (Mar 5, 2015)

I have Samsung bulbs BR40's in my cans. The ones on dimmer circuit do buzz. Especially when you attenuate the voltage down.


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## Anders Hoveland (Mar 5, 2015)

Sometimes the buzzing sound can vary between individual LED bulbs, even though it is the exact same type of bulb. I have two 18 watt LED flood bulbs, both exactly the same model, and one of them makes a buzzing sound while the other one does not. Actually, if you put your ear very close to the quiet bulb while it is on you can hear a very soft buzzing sound, but it is virtually quiet for all practical purposes. The one that makes the buzzing sound, it is not too loud, but it does get a little annoying if you are standing right next to it for any length of time. They also have slightly different color tints (even though they are the same color temperature), the one that makes the buzzing sound is just a little more greenish tinted, whereas the color of light from the quiet one is just a little purple-tinted and off. I wonder if they came from different production runs.


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## SemiMan (Mar 7, 2015)

Likely nothing that can be done. Inductors are "singing" and in some cases transformers. With dimmers its primarily drum core inductors inexpensively made and driven past saturation at triac turn on. Cheap transformers will buzz a bit too. If magnetics are up against the case it is louder. Potting in them will reduce noise.

Posted by really crappy Tapatalk app that is questionable wrt respect of personal data.


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## JSTFLK (Mar 11, 2015)

A lot of current drivers (especially cheap or high efficiency units) will limit themselves to a range of PWM that reduces losses. 

So for instance, suppose at 0.95 duty cycle, the driver is 90% efficient, at the desired load is .60 duty cycle, the driver will run in bursts of 0.90 duty cycle at 100kHz and then switch completely on and off at 1000Hz to avoid running in an inefficient mode. 

My experience has been that the PWM will be at 40-180kHz (WELL beyond hearing range) but that the cycling of the fast pulses will be at 500-1500Hz depending on load. You can easily test this by dimming the light and seeing if the pitch of the buzzing rises and falls with the voltage being fed to the unit. 

The bad part though is that if a particular led chip has a characteristic that puts the driver into pulsed mode, or if the driver is from a differently designed lot, there probably isn't much to be done. :/


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## SemiMan (Mar 11, 2015)

JSTFLK ... What you stated is for the most part completely inapplicable to phase cut dimming bulbs. The buzzing is slamming of the emi inductor and transformer when the dimmer turns on. Burst mode would rarely (ever?) be applicable to a bulb power supply off AC.


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