As PJ said above, CFL and LED lighting generate enormous amounts of RF crud.
This will affect your WiFi at home ( try turning the lights off and compare signal strength and error rates etc)
Dimmers usually use triacs to control the voltage delivered to a bulb. Electronic dimmers for LED lighting often use more complex circuits that switch at high frequencies to achieve a cheap and compact build.
The cleanest sounding lighting is from low voltage DC lighting from a Battery supply (12V car battery for instance running a normal filament lamp) I have used this in a Faraday cage for sensitive RF measurements and for noise measurements on condenser microphones and tape machine reproduce circuits.It's the RF equivalent of an anechoic chamber.
The crud put out by LED lighting is so bad that the FCC is investigating problems caused by the Ernst & Young building in LA for cell phone carriers. The crud basically wipes out cells.
See here
http://www.pcworld.com/article/2095940/la-buildings-lights-interfere-with-cellular-network-fcc-says.htmlSimilar investigations are now occurring in Australia by the ACMA ( our FCC) because of interference to Digital TV and DAB+ reception ( DAB+ is our HD radio equivalent operating around 202 - 208 MHz using AAC+ encoding).
Dimmer wise, I use Tridonic electronic dimmers on halogen downlights in on-air studios with the dimmers mounted externally and long low voltage cabling to the lamps. They are expensive, around $70 each ,but can drive 3 x 50w lamps each. This is quiet enough to not be picked up on our Neumann Large diaphragm condenser mics.
