Dimmer noise

When I use a dimmer to dim a light, it makes a light buzzing noise. Why does it make a noise?
In my experience this was a major problem with dimmers some years ago. New dimmers do not exhibit the problem. Try a new dimmer, and don't buy the cheapest one you can find.
When I bought my house, it had nothing but dimmer switches. I changed them all.
Try to avoid dimmers - nasty noise generators - also avoid energy saving lamps and fluorecents...

Virtually all dimmers are build around SCRs and Triacs and what they do, in effect, is turn the switch on and off really, really fast. Since conventional incandescent lights have a filament that doesn't respond that fast, the filament sort of averages the actual power its getting.

But, some other lights, like flourescents and halogens, don't like being switched on and off like that. I had a set of LV halogens on a dimmer in my dining room that made a huge racket when the dimmer was used. I replaced that dimmer with one meant to control halogens, and its been fine.

But, be aware that switching things on and off like that really fast really messes with the AC in your house. Most audiofools won't have a dimmer in the same circuit (even the same house) as a decent stereo. While newer dimmers may control noise coming from the switch somewhat, just be aware they are still (unless things have undergone some radical redesign I wasn't aware of) going to create ugly noise on your AC lines. You will hear that on your stereo.

Besides, dimmers don't work well with compact flourescents. You have changed to cheaper, more eco-friendly CFLs, right?
Edesilva...When I said that the new dimmers which I have bought are quiet I meant with respect to buzz on audio equipment. They must have done something to avoid noise getting on to the power lines.

Halogens are just a different kind of incandescent and there is no noise problem. The problem with using a dimmer with them is that they don't get really hot, which is what a halogen must do to burn off deposits that dim their light.

Some compact flourescents can be used with regular dimmers. However, they won't start with reduced voltage, so you need to turn the brightness up for a second when you turn them down. Once they are lit they dim just fine.

The eco-friendly bit really bugs me. They talk about the energy that is "wasted" making heat. But in my part of the country we need heat most of the year, at least at night when lights are on. If the light bulbs don't make heat my oil burner needs to run longer. They are only eco-friendly when your air conditioner is running.
I have a ton of dimmers in my house and am also obsesed with clean power.

I am a lighting guru and have several recessed lights and such throughout the house and was not going to change my lifestyle of nicely dimmed lights opposed to overly uncomfortable bright lights for an audio system-I found a way for them to exsist together.

One night I did an experiment to see if I could hear the effects of the dimmers on my system. In my home theater there are 11 seperate light throughout the room that are on a two way electronic dimmers. From my sitting spot I can turn on and off all the lights while still sitting in my seat. While the music was on I turned on and off the dimmers. Wow, what a difference. When all the lights where turned on with the dimmer it was like it took life out of the system...chocked it. It was very noticable.

Now, the dimmers don't effect the sound at all. I have bought so many parralel type conditioners that the dimmers dont effect things anymore. I think theres over forty different types ranging from noise harvestors, b86's to enacom ac cleaners and quantum . I have 2 richard grays and audioprism foundation 2 which are also paralel cleaners by themselfs which serve just to plug all these in. I have a BPT sig 3.5 for my source. I understand many don't and won't spend that kind of money, but my lighting in my house is too important for an audio system to dictate an important part of house design.

Another thing you can do thats free that will help with dimmers. In the circuit breaker box there are two hots that come into the house. My system is on one of the hot legs, and all the circuits with dimmers are on the other hot leg. With the ps noise harvester blinking in my systems circuit, I tried a dimmer that was turned on and put it on my systems hot and the other hot opposite the system. The noise harvesters showed that the dimmers on the other hot gave less blinking to it.
When you dim the lights the filament start to vibrate,causing the noise. try a GE ConstantColor lamp.
@Eldartford--I'd be interested to know which kind of dimmers you use. The ones I've seen have all relied on fast switching. There are those that tend to switch off on the downside of the AC waveform that are supposed to be friendlier to certain types of technology, but even those strike me as being pretty noisy.

With respect to the halogens, I think its an issue with the transformers for low voltage halogens--something in my lights audibly buzzed. Companies like Leviton actually make special dimmers for inductive loads designed to combat that--they run over $50 a piece. They do reduce transformer noise, but I still wouldn't put them in the same circuit as my stereo.

As far as the eco-friendly part, it was intended to be tongue in cheek. That said, I don't buy your argument. A CFL uses about 1/6th the energy of a standard incandescent. That represents energy savings for lighting--a bulb's principle purpose. Saying "yeah, but the energy of an incandescent turns into heat and I need heat" is a red herring--light bulbs are a hideously inefficient way to heat your house. The touted "heat replacement effect" has pretty much been discredited, as far as I know--in large part b/c incandescent bulbs don't distribute heat as well as a system designed as a heating system (this ignores higher efficiency heating systems as well). As I understand it, CFLs come out better in terms of overall energy consumption, cost, and CO2 emissions even considering heat replacement.
Edesilva...I don't know the particular brand of dimmer which works for me, but the package it comes in does talk about eliminating interference.

You are right about low voltage halogens. I am in the process of having such a system (cable lights) installed in an addition I am building onto my house. I did need to buy a special type of dimmer for this application, but the price was about $28 (not $50).

But you are wrong about the eco-friendly lights. A BTU is a BTU, and electric heat is 100% efficient. My oil burning furnace is about 87% just after it has been cleaned and adjusted, and starts to go downhill before the service man's truck is out of my driveway. Of course an electric BTU costs more than an oil BTU, but if the environmentalists would let us build some nuclear plants that would change.

BTW, I do have quite a few of the compact flourescents, but this is to avoid heat in some ceiling fixtures, to reduce load on some circuits, and to avoid frequent replacement in inaccessable locations.
Point taken, but its the distribution of the heat in a useful manner, not the production of the heat, that I believe accounts for the difference.

I'll have to look at dimmers again and shop around. Getting the LV halogen dimmer was a special order at the time--couple years ago--and the price shocked me. It would be great if they were more broadly available.
Edesilva...For a recessed ceiling fixture in a one story house the heat distribution would be poor indeed. But for table lamps and the like which are used right next to people the distribution is good. I once (50 years ago) worked in an architectural office doing HVAC design, and I remember at the time being amazed by how much of the heat load on an AC system is due to lights.
I wouldn't doubt it. But, I still feel like for the overwhelming majority of the US population, going CFL is appropriately "green." (As a side note, I gather Home Despot is giving CFLs away this w/e for earth day.)

I would further note that ultimately anything I say here is probably hypocritical. While I haven't claimed to heat my house using light bulbs, I have tried to justify my vacuum tubes on that basis. ;)
Just today I had to deal with this very issue. I have an HT with dedicated circuits for audio, separate from lights. One of my 2" halogen can light bulbs burnt out. I went to look for a replacement and with no sales, they were $10@! No way was I going to spend $10/bulb long term to keep light in the room. (When I had bought initially, the bulbs were on super-sale and I didn't realize the long term cost)
I decided to switch the intensities of the can bulbs and the wall sconce bulbs. So, I got lower lumen can bulbs and seemingly innocuous 100w regular bulbs for the sconces.

They buzzed. The sconces had an audible buzz all round the room (after reading this thread I agree that it was filament vibration). I had to go to halogen bulbs in the sconces to get rid of it.
In my experience, lower watt bulbs (i.e. 40-60w) give less issues with hum in dimmer installs, and halogens have been golden. Halogens are much more expensive, but I've not heard them buzz.
I have a Lutron "Spacer" remote lighting system, which was not cheap, and halogens work perfectly.
Now for my rant:
As for the "green" bulbs, I feel they, in a word, suck. I spent plenty to buy dozens of them three years ago thinking I'd see big savings over the advertised "seven years" of life. Bought a bunch on "sale", which meant sending in rediculous amounts of rebates, just to get them down to a "reasonable" price of between $1-2/bulb. What a pile of B.S.! We (wife and I) have had several bulbs that need replacing annually! For a bulb that gives flat, deathly light and costs five to ten times more? Forget it.
We've concluded that the ripoff on these bulbs are the starting units. If the lights are left on continually they'll do fine, but if you have them on/of in cycles several times a day, forget it about long life. I figure I've spent a lot more and had more hassles with them than regular bulbs. I've started to buy regular bulbs again, because I'm sick and tired of the poor light, the cost and LACK of long life! It's a situation similar to the stripped down cars that were getting bogus EPA milage ratings, sometimes off by rediculous amounts.
And you want to see one of these "green" bulbs go black really quick? Put one in your garrage in the winter. Cuts their lifetime to about 8 months, AND when it's really cold they either produce only half the lumens or don't turn on at all! Can you tell I'm not thrilled with them?
I'd love to save the earth by using a light bulb, but at this point they've proven a rip off in my use.
If I had the common sense to try one or two, but NO, I had to buy dozens (because they're supposed to be so pefect, economical, long lasting, blah blah...)so that I'd have plenty for years. Stupid! Classic case of Caveat Emptor.

Man, I've been waiting years to say that! Felt good! Rarely do I rage about a product, but rarely have I been so disappointed in what's supposed to be a no brainer upgrade. YMMV
With the 11 lights in my home theater, I switched to super low watt bulbs. I did have buzz with higher watt bulbs. The bulbs I bought range anywhere to just 7 1/2, 15, and 25 watt.

Very low watts but its way better on a bulb, cause your not holding back sooo much wattage.

It is true, that the lower the watt bulb the less buzz to no buzz there is.