Is a dimmer noisy when it's turned OFF?

I think the poster meant do dimmers make noise when switched off. They shouldn't make any electrical noise when switched off because the SCR circuitry should be depowered. Now, if the dimmer is only turned down to minimum and not actually switched off, that may be a different matter. The SCR circuitry would still be powered and might generate some RF noise. The typical household dimmer is a low cost appliance using a switching device that reduces the average voltage to the light bulb. That's why they do not usually work with fluorescent or LED type bulbs because they need a minimum voltage level to turn on. They generate gobs of RF noise just like when you break/make an electrical circuit. My old ARC SP-6b preamp that I had a couple of decades ago was sensitive to dimmer noise. I banned all dimmers from our house back then. Simple solution.

Oh, and also, you can dampen out the RF noise using an R/C circuit. (Resistor/Capacitor) that is the solution used on DC motors. DC motors use brushes that are rapidly making/breaking the electrical connection. A choke coil and capacitor kill the noise. All the DC motors in your car have that so your radio doesn't buzz and also not to interfere with other electronics.